diff --git a/.mailmap b/.mailmap
index da8044de405a6..9587aaab35945 100644
--- a/.mailmap
+++ b/.mailmap
@@ -184,6 +184,7 @@ Neil Pankey <npankey@gmail.com> <neil@wire.im>
 Nick Platt <platt.nicholas@gmail.com>
 Nicole Mazzuca <npmazzuca@gmail.com>
 Nif Ward <nif.ward@gmail.com>
+Oliver Middleton <olliemail27@gmail.com> <ollie27@users.noreply.github.com>
 Oliver Scherer <oliver.schneider@kit.edu> <git-spam-no-reply9815368754983@oli-obk.de>
 Oliver Scherer <oliver.schneider@kit.edu> <git-spam9815368754983@oli-obk.de>
 Oliver Scherer <oliver.schneider@kit.edu> <github333195615777966@oli-obk.de>
diff --git a/Cargo.lock b/Cargo.lock
index 243a326646c38..f52e9738da8f9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -109,9 +109,9 @@ dependencies = [
 
 [[package]]
 name = "backtrace"
-version = "0.3.35"
+version = "0.3.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1371048253fa3bac6704bfd6bbfc922ee9bdcee8881330d40f308b81cc5adc55"
+checksum = "5180c5a20655b14a819b652fd2378fa5f1697b6c9ddad3e695c2f9cedf6df4e2"
 dependencies = [
  "backtrace-sys",
  "cfg-if",
@@ -223,18 +223,18 @@ checksum = "560c32574a12a89ecd91f5e742165893f86e3ab98d21f8ea548658eb9eef5f40"
 
 [[package]]
 name = "bytecount"
-version = "0.5.1"
+version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be0fdd54b507df8f22012890aadd099979befdba27713c767993f8380112ca7c"
+checksum = "b0017894339f586ccb943b01b9555de56770c11cda818e7e3d8bd93f4ed7f46e"
 dependencies = [
  "packed_simd",
 ]
 
 [[package]]
 name = "byteorder"
-version = "1.2.7"
+version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94f88df23a25417badc922ab0f5716cc1330e87f71ddd9203b3a3ccd9cedf75d"
+checksum = "a7c3dd8985a7111efc5c80b44e23ecdd8c007de8ade3b96595387e812b957cf5"
 
 [[package]]
 name = "bytes"
@@ -270,6 +270,7 @@ dependencies = [
  "atty",
  "bytesize",
  "cargo-test-macro",
+ "cargo-test-support",
  "clap",
  "core-foundation",
  "crates-io",
@@ -277,7 +278,7 @@ dependencies = [
  "crypto-hash",
  "curl",
  "curl-sys",
- "env_logger 0.6.0",
+ "env_logger",
  "failure",
  "filetime",
  "flate2",
@@ -286,8 +287,9 @@ dependencies = [
  "git2",
  "git2-curl",
  "glob",
- "hex",
- "home 0.5.0",
+ "hex 0.4.0",
+ "home",
+ "humantime",
  "ignore",
  "im-rc",
  "jobserver",
@@ -309,7 +311,7 @@ dependencies = [
  "same-file",
  "semver",
  "serde",
- "serde_ignored 0.1.0",
+ "serde_ignored",
  "serde_json",
  "shell-escape",
  "strip-ansi-escapes",
@@ -327,6 +329,23 @@ dependencies = [
 name = "cargo-test-macro"
 version = "0.1.0"
 
+[[package]]
+name = "cargo-test-support"
+version = "0.1.0"
+dependencies = [
+ "cargo",
+ "cargo-test-macro",
+ "filetime",
+ "flate2",
+ "git2",
+ "glob",
+ "lazy_static 1.3.0",
+ "remove_dir_all",
+ "serde_json",
+ "tar",
+ "url 2.1.0",
+]
+
 [[package]]
 name = "cargo_metadata"
 version = "0.8.0"
@@ -392,9 +411,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "2.32.0"
+version = "2.33.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b957d88f4b6a63b9d70d5f454ac8011819c6efa7727858f458ab71c756ce2d3e"
+checksum = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
 dependencies = [
  "ansi_term",
  "atty",
@@ -507,7 +526,7 @@ name = "compiletest"
 version = "0.0.0"
 dependencies = [
  "diff",
- "env_logger 0.5.13",
+ "env_logger",
  "getopts",
  "lazy_static 1.3.0",
  "libc",
@@ -698,7 +717,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09de9ee0fc255ace04c7fa0763c9395a945c37c8292bb554f8d48361d1dcf1b4"
 dependencies = [
  "commoncrypto",
- "hex",
+ "hex 0.3.2",
  "openssl",
  "winapi 0.3.6",
 ]
@@ -753,9 +772,9 @@ checksum = "d2a368589465391e127e10c9e3a08efc8df66fd49b87dc8524c764bbe7f2ef82"
 dependencies = [
  "fnv",
  "ident_case",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -765,8 +784,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "244e8987bd4e174385240cde20a3657f607fb0797563c28255c353b5819a07b1"
 dependencies = [
  "darling_core",
- "quote",
- "syn",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -781,9 +800,9 @@ version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6ca414e896ae072546f4d789f452daaecf60ddee4c9df5dc6d5936d769e3d87c"
 dependencies = [
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -792,10 +811,10 @@ version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f57d78cf3bd45270dad4e70c21ec77a960b36c7a841ff9db76aaa775a8fb871"
 dependencies = [
- "proc-macro2",
- "quote",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
  "rustc_version",
- "syn",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -909,21 +928,9 @@ dependencies = [
 
 [[package]]
 name = "env_logger"
-version = "0.5.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "15b0a4d2e39f8420210be8b27eeda28029729e2fd4291019455016c348240c38"
-dependencies = [
- "atty",
- "humantime",
- "log",
- "termcolor",
-]
-
-[[package]]
-name = "env_logger"
-version = "0.6.0"
+version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "afb070faf94c85d17d50ca44f6ad076bce18ae92f0037d350947240a36e9d42e"
+checksum = "aafcde04e90a5226a6443b7aabdb016ba2f8307c847d524724bd9b346dd1a2d3"
 dependencies = [
  "atty",
  "humantime",
@@ -965,9 +972,9 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea1063915fd7ef4309e222a5a07cf9c319fb9c7836b1f89b85458672dbb127e1"
 dependencies = [
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
  "synstructure",
 ]
 
@@ -1151,12 +1158,13 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.1.8"
+version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34f33de6f0ae7c9cb5e574502a562e2b512799e32abb801cd1e79ad952b62b49"
+checksum = "473a1265acc8ff1e808cd0a1af8cee3c2ee5200916058a2ca113c29f2d903571"
 dependencies = [
  "cfg-if",
  "libc",
+ "wasi",
 ]
 
 [[package]]
@@ -1272,14 +1280,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "805026a5d0141ffc30abb3be3173848ad46a1b1664fe632428479619a3644d77"
 
 [[package]]
-name = "home"
-version = "0.3.3"
+name = "hex"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "80dff82fb58cfbbc617fb9a9184b010be0529201553cda50ad04372bc2333aff"
-dependencies = [
- "scopeguard 0.3.3",
- "winapi 0.3.6",
-]
+checksum = "023b39be39e3a2da62a94feb433e91e8bcd37676fbc8bea371daf52b7a769a3e"
 
 [[package]]
 name = "home"
@@ -1300,9 +1304,9 @@ dependencies = [
  "log",
  "mac",
  "markup5ever",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -1540,11 +1544,30 @@ version = "0.11.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9ad0485404155f45cce53a40d4b2d6ac356418300daed05273d9e26f91c390be"
 
+[[package]]
+name = "jsonrpc-client-transports"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39577db48b004cffb4c5b8e5c9b993c177c52599ecbee88711e815acf65144db"
+dependencies = [
+ "failure",
+ "futures",
+ "jsonrpc-core",
+ "jsonrpc-pubsub",
+ "jsonrpc-server-utils",
+ "log",
+ "parity-tokio-ipc",
+ "serde",
+ "serde_json",
+ "tokio",
+ "url 1.7.2",
+]
+
 [[package]]
 name = "jsonrpc-core"
-version = "12.0.0"
+version = "13.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "288dca7f9713710a29e485076b9340156cb701edb46a881f5d0c31aa4f5b9143"
+checksum = "dd42951eb35079520ee29b7efbac654d85821b397ef88c8151600ef7e2d00217"
 dependencies = [
  "futures",
  "log",
@@ -1553,6 +1576,70 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "jsonrpc-core-client"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f047c10738edee7c3c6acf5241a0ce33df32ef9230c1a7fb03e4a77ee72c992f"
+dependencies = [
+ "jsonrpc-client-transports",
+]
+
+[[package]]
+name = "jsonrpc-derive"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29f9149f785deaae92a4c834a9a1a83a4313b8cfedccf15362cd4cf039a64501"
+dependencies = [
+ "proc-macro-crate",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
+]
+
+[[package]]
+name = "jsonrpc-ipc-server"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "256c5e4292c17b4c2ecdf542299dc8e9d6b3939c075c54825570ad9317fe5751"
+dependencies = [
+ "jsonrpc-core",
+ "jsonrpc-server-utils",
+ "log",
+ "parity-tokio-ipc",
+ "parking_lot 0.9.0",
+ "tokio-service",
+]
+
+[[package]]
+name = "jsonrpc-pubsub"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2c08b444cc0ed70263798834343d0ac875e664257df8079160f23ac1ea79446"
+dependencies = [
+ "jsonrpc-core",
+ "log",
+ "parking_lot 0.9.0",
+ "serde",
+]
+
+[[package]]
+name = "jsonrpc-server-utils"
+version = "13.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44561bfdd31401bad790527f1e951dde144f2341ddc3e1b859d32945e1a34eff"
+dependencies = [
+ "bytes",
+ "globset",
+ "jsonrpc-core",
+ "lazy_static 1.3.0",
+ "log",
+ "num_cpus",
+ "tokio",
+ "tokio-codec",
+ "unicase 2.4.0",
+]
+
 [[package]]
 name = "kernel32-sys"
 version = "0.2.2"
@@ -1583,9 +1670,9 @@ checksum = "b294d6fa9ee409a054354afc4352b0b9ef7ca222c69b8812cbea9e7d2bf3783f"
 
 [[package]]
 name = "libc"
-version = "0.2.61"
+version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c665266eb592905e8503ba3403020f4b8794d26263f412ca33171600eca9a6fa"
+checksum = "34fcd2c08d2f832f376f4173a231990fa5aef4e99fb569867318a227ef4c06ba"
 dependencies = [
  "rustc-std-workspace-core",
 ]
@@ -1667,6 +1754,15 @@ dependencies = [
  "scopeguard 0.3.3",
 ]
 
+[[package]]
+name = "lock_api"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8912e782533a93a167888781b836336a6ca5da6175c05944c86cf28c31104dc"
+dependencies = [
+ "scopeguard 1.0.0",
+]
+
 [[package]]
 name = "log"
 version = "0.4.8"
@@ -1698,18 +1794,15 @@ dependencies = [
 
 [[package]]
 name = "lsp-types"
-version = "0.57.2"
+version = "0.60.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b62b77309737b1e262b3bbf37ff8faa740562c633b14702afe9be85dbcb6f88a"
+checksum = "fe3edefcd66dde1f7f1df706f46520a3c93adc5ca4bc5747da6621195e894efd"
 dependencies = [
  "bitflags",
- "num-derive",
- "num-traits",
  "serde",
- "serde_derive",
  "serde_json",
- "url 1.7.2",
- "url_serde",
+ "serde_repr",
+ "url 2.1.0",
 ]
 
 [[package]]
@@ -1774,7 +1867,7 @@ dependencies = [
  "chrono",
  "clap",
  "elasticlunr-rs",
- "env_logger 0.6.0",
+ "env_logger",
  "error-chain",
  "handlebars",
  "itertools 0.8.0",
@@ -1799,7 +1892,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77d1f0ba4d1e6b86fa18e8853d026d7d76a97eb7eb5eb052ed80901e43b7fc10"
 dependencies = [
- "env_logger 0.6.0",
+ "env_logger",
  "failure",
  "log",
  "mdbook",
@@ -1812,7 +1905,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "serde_json",
- "structopt",
+ "structopt 0.2.18",
  "url 1.7.2",
 ]
 
@@ -1992,12 +2085,12 @@ dependencies = [
  "colored",
  "compiletest_rs",
  "directories",
- "env_logger 0.6.0",
+ "env_logger",
  "getrandom",
- "hex",
+ "hex 0.3.2",
  "log",
  "num-traits",
- "rand 0.6.1",
+ "rand 0.7.0",
  "rustc-workspace-hack",
  "rustc_version",
  "shell-escape",
@@ -2045,18 +2138,6 @@ version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a2228dca57108069a5262f2ed8bd2e82496d2e074a06d1ccc7ce1687b6ae0a2"
 
-[[package]]
-name = "num-derive"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8af1847c907c2f04d7bfd572fb25bbb4385c637fe5be163cf2f8c5d778fe1e7d"
-dependencies = [
- "num-traits",
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "num-integer"
 version = "0.1.39"
@@ -2081,6 +2162,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6a04cb71e910d0034815600180f62a95bf6e67942d7ab52a166a68c7d7e9cd0"
+
 [[package]]
 name = "open"
 version = "1.2.1"
@@ -2118,9 +2205,9 @@ checksum = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
 
 [[package]]
 name = "openssl-src"
-version = "111.3.0+1.1.1c"
+version = "111.6.0+1.1.1d"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "53ed5f31d294bdf5f7a4ba0a206c2754b0f60e9a63b7e3076babc5317873c797"
+checksum = "b9c2da1de8a7a3f860919c01540b03a6db16de042405a8a07a5e9d0b4b825d9c"
 dependencies = [
  "cc",
 ]
@@ -2190,14 +2277,43 @@ dependencies = [
  "unwind",
 ]
 
+[[package]]
+name = "parity-tokio-ipc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8281bf4f1d6429573f89589bf68d89451c46750977a8264f8ea3edbabeba7947"
+dependencies = [
+ "bytes",
+ "futures",
+ "log",
+ "mio-named-pipes",
+ "miow 0.3.3",
+ "rand 0.7.0",
+ "tokio",
+ "tokio-named-pipes",
+ "tokio-uds",
+ "winapi 0.3.6",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ab41b4aed082705d1056416ae4468b6ea99d52599ecf3169b00088d43113e337"
 dependencies = [
- "lock_api",
- "parking_lot_core",
+ "lock_api 0.1.3",
+ "parking_lot_core 0.4.0",
+]
+
+[[package]]
+name = "parking_lot"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
+dependencies = [
+ "lock_api 0.3.1",
+ "parking_lot_core 0.6.2",
+ "rustc_version",
 ]
 
 [[package]]
@@ -2213,6 +2329,21 @@ dependencies = [
  "winapi 0.3.6",
 ]
 
+[[package]]
+name = "parking_lot_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
+dependencies = [
+ "cfg-if",
+ "cloudabi",
+ "libc",
+ "redox_syscall",
+ "rustc_version",
+ "smallvec",
+ "winapi 0.3.6",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "1.0.1"
@@ -2252,9 +2383,9 @@ checksum = "63120576c4efd69615b5537d3d052257328a4ca82876771d6944424ccfd9f646"
 dependencies = [
  "pest",
  "pest_meta",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -2363,10 +2494,30 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "df8b3f4e0475def7d9c2e5de8e5a1306949849761e107b360d03e98eafaffd61"
 dependencies = [
  "chrono",
- "env_logger 0.6.0",
+ "env_logger",
  "log",
 ]
 
+[[package]]
+name = "proc-macro-crate"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e10d4b51f154c8a7fb96fd6dad097cb74b863943ec010ac94b9fd1be8861fe1e"
+dependencies = [
+ "toml",
+]
+
+[[package]]
+name = "proc-macro-error"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aeccfe4d5d8ea175d5f0e4a2ad0637e0f4121d63bd99d356fb1f39ab2e7c6097"
+dependencies = [
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.5",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "0.4.30"
@@ -2376,6 +2527,15 @@ dependencies = [
  "unicode-xid 0.1.0",
 ]
 
+[[package]]
+name = "proc-macro2"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e98a83a9f9b331f54b924e68a66acb1bb35cb01fb0a23645139967abefb697e8"
+dependencies = [
+ "unicode-xid 0.2.0",
+]
+
 [[package]]
 name = "proc_macro"
 version = "0.0.0"
@@ -2428,19 +2588,28 @@ version = "0.6.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "faf4799c5d274f3868a4aae320a0a182cbd2baee377b378f080e16a23e9d80db"
 dependencies = [
- "proc-macro2",
+ "proc-macro2 0.4.30",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
+dependencies = [
+ "proc-macro2 1.0.3",
 ]
 
 [[package]]
 name = "racer"
-version = "2.1.25"
+version = "2.1.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0727b9d7baaf9e42851145545d7b980b5c1752bd16a4c77c925c5e573d0069d9"
+checksum = "dde22b84ab75220015cbd91240222402bf885cbe3a5dc856475771abb82533ae"
 dependencies = [
  "bitflags",
  "clap",
  "derive_more",
- "env_logger 0.6.0",
+ "env_logger",
  "humantime",
  "lazy_static 1.3.0",
  "log",
@@ -2727,18 +2896,18 @@ checksum = "cabe4fa914dec5870285fa7f71f602645da47c486e68486d2b4ceb4a343e90ac"
 
 [[package]]
 name = "rls"
-version = "1.38.0"
+version = "1.39.0"
 dependencies = [
  "cargo",
  "cargo_metadata",
  "clippy_lints",
  "crossbeam-channel",
  "difference",
- "env_logger 0.6.0",
+ "env_logger",
  "failure",
  "futures",
  "heck",
- "home 0.3.3",
+ "home",
  "itertools 0.8.0",
  "jsonrpc-core",
  "lazy_static 1.3.0",
@@ -2753,6 +2922,7 @@ dependencies = [
  "regex",
  "rls-analysis",
  "rls-data",
+ "rls-ipc",
  "rls-rustc",
  "rls-span",
  "rls-vfs",
@@ -2762,14 +2932,14 @@ dependencies = [
  "rustfmt-nightly",
  "serde",
  "serde_derive",
- "serde_ignored 0.0.4",
+ "serde_ignored",
  "serde_json",
  "tempfile",
  "tokio",
  "tokio-process",
  "tokio-timer",
  "toml",
- "url 1.7.2",
+ "url 2.1.0",
  "walkdir",
 ]
 
@@ -2800,9 +2970,33 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "rls-ipc"
+version = "0.1.0"
+dependencies = [
+ "jsonrpc-core",
+ "jsonrpc-core-client",
+ "jsonrpc-derive",
+ "jsonrpc-ipc-server",
+ "rls-data",
+ "serde",
+]
+
 [[package]]
 name = "rls-rustc"
 version = "0.6.0"
+dependencies = [
+ "clippy_lints",
+ "env_logger",
+ "failure",
+ "futures",
+ "log",
+ "rand 0.6.1",
+ "rls-data",
+ "rls-ipc",
+ "serde",
+ "tokio",
+]
 
 [[package]]
 name = "rls-span"
@@ -2845,11 +3039,10 @@ dependencies = [
  "fmt_macros",
  "graphviz",
  "jobserver",
- "lazy_static 1.3.0",
  "log",
  "measureme",
  "num_cpus",
- "parking_lot",
+ "parking_lot 0.9.0",
  "polonius-engine",
  "rustc-rayon",
  "rustc-rayon-core",
@@ -2868,9 +3061,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-arena"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4dc2e1e68b64268c543bfa6e63e3c0d9ea58074c71396f42f76931f35a9287f9"
+checksum = "f59b76d334bd533f3fdc5c651c27678c5e80fac67c6f7da22ba21a58878c55f5"
 dependencies = [
  "rustc-ap-rustc_data_structures",
  "smallvec",
@@ -2878,15 +3071,15 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-graphviz"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c108d647ce0dd46477b048eafff5a6273b5652e02d47424b0cd684147379c811"
+checksum = "3e632ef08ca17458acfd46d2ead3d541a1c249586cd5329f5fe333dacfab6142"
 
 [[package]]
 name = "rustc-ap-rustc_data_structures"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "656771744e0783cb8e4481e3b8b1f975687610aaf18833b898018111a0e0e582"
+checksum = "e89e2c7be68185418f3cd56af3df8b29007a59a1cebefa63612d055f9bcb1a36"
 dependencies = [
  "cfg-if",
  "crossbeam-utils 0.6.5",
@@ -2895,7 +3088,7 @@ dependencies = [
  "jobserver",
  "lazy_static 1.3.0",
  "log",
- "parking_lot",
+ "parking_lot 0.7.1",
  "rustc-ap-graphviz",
  "rustc-ap-serialize",
  "rustc-hash",
@@ -2907,9 +3100,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-rustc_errors"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e37064f6624bc799bfaa2968b61ee6880926dea2a8bba69f18aef6c8e69c9604"
+checksum = "1e47cb380abeb72b01e42b2342d592f7eeea7d536c2f1f0d0e550dc509e46333"
 dependencies = [
  "annotate-snippets",
  "atty",
@@ -2917,34 +3110,38 @@ dependencies = [
  "rustc-ap-rustc_data_structures",
  "rustc-ap-serialize",
  "rustc-ap-syntax_pos",
+ "term_size",
  "termcolor",
  "unicode-width",
 ]
 
 [[package]]
 name = "rustc-ap-rustc_lexer"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef5bc0a971823637ea23a857f0ef1467f44b1e05d71968821f83a0abe53e0fe3"
+checksum = "494cfaf67f49217d67d0774eeecbba61ac89acf478db97ef11f113ed8a959305"
+dependencies = [
+ "unicode-xid 0.2.0",
+]
 
 [[package]]
 name = "rustc-ap-rustc_macros"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b90037e3336fe8835f468db44d0848ae10d9cc8533ae89b55828883f905b7e80"
+checksum = "e2e5d36becc59b4497f9cbd3ae0610081de0207a1d0e95c066369167b14f486f"
 dependencies = [
  "itertools 0.8.0",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
  "synstructure",
 ]
 
 [[package]]
 name = "rustc-ap-rustc_target"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cadf9ca07315eab3a7a21f63872f9cc81e250fd6ede0419c24f8926ade73a45d"
+checksum = "a7bfc5f96dfc3b9f8d5b57884f7f37467ecff6776cd4b8b491a7daece6fdd7c2"
 dependencies = [
  "bitflags",
  "log",
@@ -2955,9 +3152,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-serialize"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "61673783f2089e01033ffa82d1988f55175402071b31253a358292e1624d4602"
+checksum = "2bb9ee231cf79eded39c56647499f83d6136ff5c8c0baaa9e21b6febee00f4f6"
 dependencies = [
  "indexmap",
  "smallvec",
@@ -2965,9 +3162,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-syntax"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28f3dd1346d5b0269c07a4a78855e309a298ab569c9c1302d4d4f57f8eee4e84"
+checksum = "b3827fc208814efbde82d613e31d11b4250ce9e8cf8afe4a4d47bbbd099632c9"
 dependencies = [
  "bitflags",
  "lazy_static 1.3.0",
@@ -2985,9 +3182,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-syntax_pos"
-version = "546.0.0"
+version = "583.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "45e67b526dbda3a0c7dab91c8947d43685e7697f52686a4949da3c179cd7c979"
+checksum = "930ed81c34f325e512cc315c04d676fa84a373879d5c43bb54054a0522b05213"
 dependencies = [
  "cfg-if",
  "rustc-ap-arena",
@@ -3058,21 +3255,21 @@ checksum = "dcf128d1287d2ea9d80910b5f1120d0b8eede3fbf1abe91c40d39ea7d51e6fda"
 
 [[package]]
 name = "rustc-std-workspace-alloc"
-version = "1.0.0"
+version = "1.99.0"
 dependencies = [
  "alloc",
 ]
 
 [[package]]
 name = "rustc-std-workspace-core"
-version = "1.0.0"
+version = "1.99.0"
 dependencies = [
  "core",
 ]
 
 [[package]]
 name = "rustc-std-workspace-std"
-version = "1.0.0"
+version = "1.99.0"
 dependencies = [
  "std",
 ]
@@ -3081,15 +3278,11 @@ dependencies = [
 name = "rustc-workspace-hack"
 version = "1.0.0"
 dependencies = [
- "byteorder",
  "crossbeam-utils 0.6.5",
- "parking_lot",
- "rand 0.6.1",
- "scopeguard 0.3.3",
  "serde",
  "serde_json",
  "smallvec",
- "syn",
+ "url 2.1.0",
  "winapi 0.3.6",
 ]
 
@@ -3129,11 +3322,7 @@ dependencies = [
 name = "rustc_codegen_llvm"
 version = "0.0.0"
 dependencies = [
- "cc",
- "memmap",
- "num_cpus",
  "rustc_llvm",
- "tempfile",
 ]
 
 [[package]]
@@ -3147,7 +3336,7 @@ dependencies = [
  "log",
  "memmap",
  "num_cpus",
- "parking_lot",
+ "parking_lot 0.9.0",
  "rustc",
  "rustc_apfloat",
  "rustc_codegen_utils",
@@ -3190,7 +3379,7 @@ dependencies = [
  "jobserver",
  "lazy_static 1.3.0",
  "log",
- "parking_lot",
+ "parking_lot 0.9.0",
  "rustc-hash",
  "rustc-rayon",
  "rustc-rayon-core",
@@ -3203,8 +3392,9 @@ dependencies = [
 name = "rustc_driver"
 version = "0.0.0"
 dependencies = [
- "env_logger 0.5.13",
+ "env_logger",
  "graphviz",
+ "lazy_static 1.3.0",
  "log",
  "rustc",
  "rustc_ast_borrowck",
@@ -3248,7 +3438,7 @@ version = "0.0.0"
 dependencies = [
  "graphviz",
  "log",
- "rand 0.6.1",
+ "rand 0.7.0",
  "rustc",
  "rustc_data_structures",
  "rustc_fs_util",
@@ -3262,6 +3452,7 @@ name = "rustc_interface"
 version = "0.0.0"
 dependencies = [
  "log",
+ "once_cell",
  "rustc",
  "rustc-rayon",
  "rustc_ast_borrowck",
@@ -3330,9 +3521,9 @@ name = "rustc_macros"
 version = "0.1.0"
 dependencies = [
  "itertools 0.8.0",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
  "synstructure",
 ]
 
@@ -3571,26 +3762,25 @@ dependencies = [
 
 [[package]]
 name = "rustfmt-config_proc_macro"
-version = "0.1.2"
+version = "0.2.0"
 dependencies = [
- "proc-macro2",
- "quote",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
  "serde",
- "syn",
+ "syn 1.0.5",
 ]
 
 [[package]]
 name = "rustfmt-nightly"
-version = "1.4.6"
+version = "1.4.8"
 dependencies = [
  "annotate-snippets",
- "atty",
  "bytecount",
  "cargo_metadata",
  "derive-new",
  "diff",
  "dirs",
- "env_logger 0.6.0",
+ "env_logger",
  "failure",
  "getopts",
  "ignore",
@@ -3605,7 +3795,7 @@ dependencies = [
  "rustfmt-config_proc_macro",
  "serde",
  "serde_json",
- "structopt",
+ "structopt 0.3.1",
  "term 0.6.0",
  "toml",
  "unicode-segmentation",
@@ -3714,18 +3904,9 @@ version = "1.0.81"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "477b13b646f5b5b56fc95bedfc3b550d12141ce84f466f6c44b9a17589923885"
 dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "serde_ignored"
-version = "0.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "190e9765dcedb56be63b6e0993a006c7e3b071a016a304736e4a315dc01fb142"
-dependencies = [
- "serde",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -3748,6 +3929,17 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_repr"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd02c7587ec314570041b2754829f84d873ced14a96d1fd1823531e11db40573"
+dependencies = [
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.5",
+]
+
 [[package]]
 name = "serde_urlencoded"
 version = "0.5.5"
@@ -3864,12 +4056,13 @@ dependencies = [
  "panic_abort",
  "panic_unwind",
  "profiler_builtins",
- "rand 0.6.1",
+ "rand 0.7.0",
  "rustc_asan",
  "rustc_lsan",
  "rustc_msan",
  "rustc_tsan",
  "unwind",
+ "wasi",
 ]
 
 [[package]]
@@ -3904,8 +4097,8 @@ checksum = "1eea1eee654ef80933142157fdad9dd8bc43cf7c74e999e369263496f04ff4da"
 dependencies = [
  "phf_generator",
  "phf_shared",
- "proc-macro2",
- "quote",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
  "string_cache_shared",
 ]
 
@@ -3926,9 +4119,9 @@ dependencies = [
 
 [[package]]
 name = "strsim"
-version = "0.7.0"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb4f380125926a99e52bc279241539c018323fab05ad6368b56f93d9369ff550"
+checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
 
 [[package]]
 name = "structopt"
@@ -3937,7 +4130,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "16c2cdbf9cc375f15d1b4141bc48aeef444806655cd0e904207edc8d68d86ed7"
 dependencies = [
  "clap",
- "structopt-derive",
+ "structopt-derive 0.2.18",
+]
+
+[[package]]
+name = "structopt"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ac9d6e93dd792b217bf89cda5c14566e3043960c6f9da890c2ba5d09d07804c"
+dependencies = [
+ "clap",
+ "structopt-derive 0.3.1",
 ]
 
 [[package]]
@@ -3947,9 +4150,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53010261a84b37689f9ed7d395165029f9cc7abb9f56bbfe86bee2597ed25107"
 dependencies = [
  "heck",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
+]
+
+[[package]]
+name = "structopt-derive"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ae9e5165d463a0dea76967d021f8d0f9316057bf5163aa2a4843790e842ff37"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.5",
 ]
 
 [[package]]
@@ -3965,9 +4181,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8baacebd7b7c9b864d83a6ba7a246232983e277b86fa5cdec77f565715a4b136"
 dependencies = [
  "heck",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -3976,20 +4192,31 @@ version = "0.15.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "641e117d55514d6d918490e47102f7e08d096fdde360247e4a10f7a91a8478d3"
 dependencies = [
- "proc-macro2",
- "quote",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
  "unicode-xid 0.1.0",
 ]
 
+[[package]]
+name = "syn"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "66850e97125af79138385e9b88339cbcd037e3f28ceab8c5ad98e64f0f1f80bf"
+dependencies = [
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "unicode-xid 0.2.0",
+]
+
 [[package]]
 name = "synstructure"
 version = "0.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "02353edf96d6e4dc81aea2d8490a7e9db177bf8acb0e951c24940bf866cb313f"
 dependencies = [
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 0.4.30",
+ "quote 0.6.12",
+ "syn 0.15.35",
  "unicode-xid 0.1.0",
 ]
 
@@ -4059,13 +4286,13 @@ dependencies = [
 
 [[package]]
 name = "tempfile"
-version = "3.0.5"
+version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7e91405c14320e5c79b3d148e1c86f40749a36e490642202a31689cb1a3452b2"
+checksum = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 dependencies = [
  "cfg-if",
  "libc",
- "rand 0.6.1",
+ "rand 0.7.0",
  "redox_syscall",
  "remove_dir_all",
  "winapi 0.3.6",
@@ -4169,9 +4396,9 @@ dependencies = [
 
 [[package]]
 name = "textwrap"
-version = "0.10.0"
+version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "307686869c93e71f94da64286f9a9524c0f308a9e1c87a583de8e9c9039ad3f6"
+checksum = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
 dependencies = [
  "unicode-width",
 ]
@@ -4294,6 +4521,19 @@ dependencies = [
  "log",
 ]
 
+[[package]]
+name = "tokio-named-pipes"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d282d483052288b2308ba5ee795f5673b159c9bdf63c385a05609da782a5eae"
+dependencies = [
+ "bytes",
+ "futures",
+ "mio",
+ "mio-named-pipes",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-process"
 version = "0.2.3"
@@ -4322,12 +4562,21 @@ dependencies = [
  "log",
  "mio",
  "num_cpus",
- "parking_lot",
+ "parking_lot 0.7.1",
  "slab",
  "tokio-executor",
  "tokio-io",
 ]
 
+[[package]]
+name = "tokio-service"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "24da22d077e0f15f55162bdbdc661228c1581892f52074fb242678d015b45162"
+dependencies = [
+ "futures",
+]
+
 [[package]]
 name = "tokio-signal"
 version = "0.2.7"
@@ -4451,8 +4700,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c99ca245ec273c7e75c8ee58f47b882d0146f3c2c8495158082c6671e8b5335"
 dependencies = [
  "darling",
- "quote",
- "syn",
+ "quote 0.6.12",
+ "syn 0.15.35",
 ]
 
 [[package]]
@@ -4589,16 +4838,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "url_serde"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74e7d099f1ee52f823d4bdd60c93c3602043c728f5db3b97bdb548467f7bddea"
-dependencies = [
- "serde",
- "url 1.7.2",
-]
-
 [[package]]
 name = "utf-8"
 version = "0.7.2"
@@ -4686,6 +4925,17 @@ dependencies = [
  "try-lock",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b89c3ce4ce14bdc6fb6beaf9ec7928ca331de5df7e5ea278375642a2f478570d"
+dependencies = [
+ "compiler_builtins",
+ "rustc-std-workspace-alloc",
+ "rustc-std-workspace-core",
+]
+
 [[package]]
 name = "winapi"
 version = "0.2.8"
diff --git a/README.md b/README.md
index 724bc36ecc6fb..96d7e938be2f2 100644
--- a/README.md
+++ b/README.md
@@ -26,12 +26,13 @@ or reading the [rustc guide][rustcguidebuild].
 ### Building on *nix
 1. Make sure you have installed the dependencies:
 
-   * `g++` 4.7 or later or `clang++` 3.x or later
+   * `g++` 5.1 or later or `clang++` 3.5 or later
    * `python` 2.7 (but not 3.x)
    * GNU `make` 3.81 or later
    * `cmake` 3.4.3 or later
    * `curl`
    * `git`
+   * `ssl` which comes in `libssl-dev` or `openssl-devel`
 
 2. Clone the [source] with `git`:
 
@@ -56,6 +57,8 @@ or reading the [rustc guide][rustcguidebuild].
     an installation (using `./x.py install`) that you set the `prefix` value
     in the `[install]` section to a directory that you have write permissions.
 
+    Create install directory if you are not installing in default directory
+
 4. Build and install:
 
     ```sh
@@ -148,6 +151,17 @@ by manually calling the appropriate vcvars file before running the bootstrap.
 > python x.py build
 ```
 
+### Building rustc with older host toolchains
+It is still possible to build Rust with the older toolchain versions listed below, but only if the
+LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN option is set to true in the config.toml file.
+
+* Clang 3.1
+* Apple Clang 3.1
+* GCC 4.8
+* Visual Studio 2015 (Update 3)
+
+Toolchain versions older than what is listed above cannot be used to build rustc.
+
 #### Specifying an ABI
 
 Each specific ABI can also be used from either environment (for example, using
diff --git a/RELEASES.md b/RELEASES.md
index f26f6e6c888ed..d634feba33ac5 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,3 +1,108 @@
+Version 1.38.0 (2019-09-26)
+==========================
+
+Language
+--------
+- [The `#[global_allocator]` attribute can now be used in submodules.][62735]
+- [The `#[deprecated]` attribute can now be used on macros.][62042]
+
+Compiler
+--------
+- [Added pipelined compilation support to `rustc`.][62766] This will
+  improve compilation times in some cases. For further information please refer
+  to the [_"Evaluating pipelined rustc compilation"_][pipeline-internals] thread.
+- [Added tier 3\* support for the `aarch64-uwp-windows-msvc`, `i686-uwp-windows-gnu`,
+  `i686-uwp-windows-msvc`, `x86_64-uwp-windows-gnu`, and
+  `x86_64-uwp-windows-msvc` targets.][60260]
+- [Added tier 3 support for the `armv7-unknown-linux-gnueabi` and
+  `armv7-unknown-linux-musleabi` targets.][63107]
+- [Added tier 3 support for the `hexagon-unknown-linux-musl` target.][62814]
+- [Added tier 3 support for the `riscv32i-unknown-none-elf` target.][62784]
+
+\* Refer to Rust's [platform support page][forge-platform-support] for more
+information on Rust's tiered platform support.
+
+Libraries
+---------
+- [`ascii::EscapeDefault` now implements `Clone` and `Display`.][63421]
+- [Derive macros for prelude traits (e.g. `Clone`, `Debug`, `Hash`) are now
+  available at the same path as the trait.][63056] (e.g. The `Clone` derive macro
+  is available at `std::clone::Clone`). This also makes all built-in macros
+  available in `std`/`core` root. e.g. `std::include_bytes!`.
+- [`str::Chars` now implements `Debug`.][63000]
+- [`slice::{concat, connect, join}` now accepts `&[T]` in addition to `&T`.][62528]
+- [`*const T` and `*mut T` now implement `marker::Unpin`.][62583]
+- [`Arc<[T]>` and `Rc<[T]>` now implement `FromIterator<T>`.][61953]
+- [Added euclidean remainder and division operations (`div_euclid`,
+  `rem_euclid`) to all numeric primitives.][61884] Additionally `checked`,
+  `overflowing`, and `wrapping` versions are available for all
+  integer primitives.
+- [`thread::AccessError` now implements `Clone`, `Copy`, `Eq`, `Error`, and
+  `PartialEq`.][61491]
+- [`iter::{StepBy, Peekable, Take}` now implement `DoubleEndedIterator`.][61457]
+
+Stabilized APIs
+---------------
+- [`<*const T>::cast`]
+- [`<*mut T>::cast`]
+- [`Duration::as_secs_f32`]
+- [`Duration::as_secs_f64`]
+- [`Duration::div_duration_f32`]
+- [`Duration::div_duration_f64`]
+- [`Duration::div_f32`]
+- [`Duration::div_f64`]
+- [`Duration::from_secs_f32`]
+- [`Duration::from_secs_f64`]
+- [`Duration::mul_f32`]
+- [`Duration::mul_f64`]
+- [`any::type_name`]
+
+Cargo
+-----
+- [Added pipelined compilation support to `cargo`.][cargo/7143]
+- [You can now pass the `--features` option multiple times to enable
+  multiple features.][cargo/7084]
+
+Misc
+----
+- [`rustc` will now warn about some incorrect uses of
+  `mem::{uninitialized, zeroed}` that are known to cause undefined behaviour.][63346]
+
+[60260]: https://github.com/rust-lang/rust/pull/60260/
+[61457]: https://github.com/rust-lang/rust/pull/61457/
+[61491]: https://github.com/rust-lang/rust/pull/61491/
+[61884]: https://github.com/rust-lang/rust/pull/61884/
+[61953]: https://github.com/rust-lang/rust/pull/61953/
+[62042]: https://github.com/rust-lang/rust/pull/62042/
+[62528]: https://github.com/rust-lang/rust/pull/62528/
+[62583]: https://github.com/rust-lang/rust/pull/62583/
+[62735]: https://github.com/rust-lang/rust/pull/62735/
+[62766]: https://github.com/rust-lang/rust/pull/62766/
+[62784]: https://github.com/rust-lang/rust/pull/62784/
+[62814]: https://github.com/rust-lang/rust/pull/62814/
+[63000]: https://github.com/rust-lang/rust/pull/63000/
+[63056]: https://github.com/rust-lang/rust/pull/63056/
+[63107]: https://github.com/rust-lang/rust/pull/63107/
+[63346]: https://github.com/rust-lang/rust/pull/63346/
+[63421]: https://github.com/rust-lang/rust/pull/63421/
+[cargo/7084]: https://github.com/rust-lang/cargo/pull/7084/
+[cargo/7143]: https://github.com/rust-lang/cargo/pull/7143/
+[`<*const T>::cast`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.cast
+[`<*mut T>::cast`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.cast
+[`Duration::as_secs_f32`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_secs_f32
+[`Duration::as_secs_f64`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_secs_f64
+[`Duration::div_duration_f32`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.div_duration_f32
+[`Duration::div_duration_f64`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.div_duration_f64
+[`Duration::div_f32`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.div_f32
+[`Duration::div_f64`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.div_f64
+[`Duration::from_secs_f32`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.from_secs_f32
+[`Duration::from_secs_f64`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.from_secs_f64
+[`Duration::mul_f32`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.mul_f32
+[`Duration::mul_f64`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.mul_f64
+[`any::type_name`]: https://doc.rust-lang.org/std/any/fn.type_name.html
+[forge-platform-support]: https://forge.rust-lang.org/platform-support.html
+[pipeline-internals]: https://internals.rust-lang.org/t/evaluating-pipelined-rustc-compilation/10199
+
 Version 1.37.0 (2019-08-15)
 ==========================
 
diff --git a/config.toml.example b/config.toml.example
index 30e2ee1b9babf..848147c2974c1 100644
--- a/config.toml.example
+++ b/config.toml.example
@@ -184,7 +184,7 @@
 # default.
 #extended = false
 
-# Installs chosen set of extended tools if enables. By default builds all.
+# Installs chosen set of extended tools if enabled. By default builds all.
 # If chosen tool failed to build the installation fails.
 #tools = ["cargo", "rls", "clippy", "rustfmt", "analysis", "src"]
 
diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 8cb48df14bfef..84415baa3a140 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -119,17 +119,18 @@ fn main() {
         cmd.arg(format!("-Cdebuginfo={}", debuginfo_level));
     }
 
-    if env::var_os("RUSTC_DENY_WARNINGS").is_some() &&
-       env::var_os("RUSTC_EXTERNAL_TOOL").is_none() {
+    if env::var_os("RUSTC_EXTERNAL_TOOL").is_none() {
         // When extending this list, add the new lints to the RUSTFLAGS of the
         // build_bootstrap function of src/bootstrap/bootstrap.py as well as
         // some code doesn't go through this `rustc` wrapper.
-        cmd.arg("-Dwarnings");
-        cmd.arg("-Drust_2018_idioms");
-        cmd.arg("-Dunused_lifetimes");
+        cmd.arg("-Wrust_2018_idioms");
+        cmd.arg("-Wunused_lifetimes");
         if use_internal_lints(crate_name) {
             cmd.arg("-Zunstable-options");
-            cmd.arg("-Drustc::internal");
+            cmd.arg("-Wrustc::internal");
+        }
+        if env::var_os("RUSTC_DENY_WARNINGS").is_some() {
+            cmd.arg("-Dwarnings");
         }
     }
 
diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 4162fe1df5086..65129eeeec504 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -523,6 +523,10 @@ def get_toml(self, key, section=None):
         'value2'
         >>> rb.get_toml('key', 'c') is None
         True
+
+        >>> rb.config_toml = 'key1 = true'
+        >>> rb.get_toml("key1")
+        'true'
         """
 
         cur_section = None
@@ -571,6 +575,12 @@ def get_string(line):
 
         >>> RustBuild.get_string('    "devel"   ')
         'devel'
+        >>> RustBuild.get_string("    'devel'   ")
+        'devel'
+        >>> RustBuild.get_string('devel') is None
+        True
+        >>> RustBuild.get_string('    "devel   ')
+        ''
         """
         start = line.find('"')
         if start != -1:
@@ -631,8 +641,9 @@ def build_bootstrap(self):
         target_linker = self.get_toml("linker", build_section)
         if target_linker is not None:
             env["RUSTFLAGS"] += "-C linker=" + target_linker + " "
+        env["RUSTFLAGS"] += " -Wrust_2018_idioms -Wunused_lifetimes "
         if self.get_toml("deny-warnings", "rust") != "false":
-            env["RUSTFLAGS"] += "-Dwarnings -Drust_2018_idioms -Dunused_lifetimes "
+            env["RUSTFLAGS"] += "-Dwarnings "
 
         env["PATH"] = os.path.join(self.bin_root(), "bin") + \
             os.pathsep + env["PATH"]
@@ -668,7 +679,7 @@ def check_submodule(self, module, slow_submodules):
     def update_submodule(self, module, checked_out, recorded_submodules):
         module_path = os.path.join(self.rust_root, module)
 
-        if checked_out != None:
+        if checked_out is not None:
             default_encoding = sys.getdefaultencoding()
             checked_out = checked_out.communicate()[0].decode(default_encoding).strip()
             if recorded_submodules[module] == checked_out:
@@ -697,6 +708,14 @@ def update_submodules(self):
         if (not os.path.exists(os.path.join(self.rust_root, ".git"))) or \
                 self.get_toml('submodules') == "false":
             return
+
+        # check the existence of 'git' command
+        try:
+            subprocess.check_output(['git', '--version'])
+        except (subprocess.CalledProcessError, OSError):
+            print("error: `git` is not found, please make sure it's installed and in the path.")
+            sys.exit(1)
+
         slow_submodules = self.get_toml('fast-submodules') == "false"
         start_time = time()
         if slow_submodules:
@@ -821,13 +840,13 @@ def bootstrap(help_triggered):
     except (OSError, IOError):
         pass
 
-    match = re.search(r'\nverbose = (\d+)', build.config_toml)
-    if match is not None:
-        build.verbose = max(build.verbose, int(match.group(1)))
+    config_verbose = build.get_toml('verbose', 'build')
+    if config_verbose is not None:
+        build.verbose = max(build.verbose, int(config_verbose))
 
-    build.use_vendored_sources = '\nvendor = true' in build.config_toml
+    build.use_vendored_sources = build.get_toml('vendor', 'build') == 'true'
 
-    build.use_locked_deps = '\nlocked-deps = true' in build.config_toml
+    build.use_locked_deps = build.get_toml('locked-deps', 'build') == 'true'
 
     build.check_vendored_status()
 
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 4f5de1ecd2b44..b7873fd1d3581 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1167,6 +1167,8 @@ impl<'a> Builder<'a> {
             cargo.arg("--frozen");
         }
 
+        cargo.env("RUSTC_INSTALL_BINDIR", &self.config.bindir);
+
         self.ci_env.force_coloring_in_ci(&mut cargo);
 
         cargo
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 9d57a4f00d780..9a964457ef285 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -212,6 +212,7 @@ pub fn std_cargo(builder: &Builder<'_>,
                 emscripten: false,
             });
             cargo.env("LLVM_CONFIG", llvm_config);
+            cargo.env("RUSTC_BUILD_SANITIZERS", "1");
         }
 
         cargo.arg("--features").arg(features)
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 43d9264eaca92..52b5cd888df9c 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -137,7 +137,7 @@ pub struct Config {
     pub sysconfdir: Option<PathBuf>,
     pub datadir: Option<PathBuf>,
     pub docdir: Option<PathBuf>,
-    pub bindir: Option<PathBuf>,
+    pub bindir: PathBuf,
     pub libdir: Option<PathBuf>,
     pub mandir: Option<PathBuf>,
     pub codegen_tests: bool,
@@ -400,6 +400,7 @@ impl Config {
         config.incremental = flags.incremental;
         config.dry_run = flags.dry_run;
         config.keep_stage = flags.keep_stage;
+        config.bindir = "bin".into(); // default
         if let Some(value) = flags.deny_warnings {
             config.deny_warnings = value;
         }
@@ -482,7 +483,7 @@ impl Config {
             config.sysconfdir = install.sysconfdir.clone().map(PathBuf::from);
             config.datadir = install.datadir.clone().map(PathBuf::from);
             config.docdir = install.docdir.clone().map(PathBuf::from);
-            config.bindir = install.bindir.clone().map(PathBuf::from);
+            set(&mut config.bindir, install.bindir.clone().map(PathBuf::from));
             config.libdir = install.libdir.clone().map(PathBuf::from);
             config.mandir = install.mandir.clone().map(PathBuf::from);
         }
diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index 0f4ac63651ca9..e27a6bf7da0ac 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -762,7 +762,7 @@ impl Step for Analysis {
             return distdir(builder).join(format!("{}-{}.tar.gz", name, target));
         }
 
-        builder.ensure(Std { compiler, target });
+        builder.ensure(compile::Std { compiler, target });
 
         let image = tmpdir(builder).join(format!("{}-{}-image", name, target));
 
@@ -808,6 +808,7 @@ fn copy_src_dirs(builder: &Builder<'_>, src_dirs: &[&str], exclude_dirs: &[&str]
             "llvm-project/lld", "llvm-project\\lld",
             "llvm-project/lldb", "llvm-project\\lldb",
             "llvm-project/llvm", "llvm-project\\llvm",
+            "llvm-project/compiler-rt", "llvm-project\\compiler-rt",
         ];
         if spath.contains("llvm-project") && !spath.ends_with("llvm-project")
             && !LLVM_PROJECTS.iter().any(|path| spath.contains(path))
@@ -1999,6 +2000,8 @@ impl Step for HashSign {
     }
 
     fn run(self, builder: &Builder<'_>) {
+        // This gets called by `promote-release`
+        // (https://github.com/rust-lang/rust-central-station/tree/master/promote-release).
         let mut cmd = builder.tool_cmd(Tool::BuildManifest);
         if builder.config.dry_run {
             return;
@@ -2009,10 +2012,14 @@ impl Step for HashSign {
         let addr = builder.config.dist_upload_addr.as_ref().unwrap_or_else(|| {
             panic!("\n\nfailed to specify `dist.upload-addr` in `config.toml`\n\n")
         });
-        let file = builder.config.dist_gpg_password_file.as_ref().unwrap_or_else(|| {
-            panic!("\n\nfailed to specify `dist.gpg-password-file` in `config.toml`\n\n")
-        });
-        let pass = t!(fs::read_to_string(&file));
+        let pass = if env::var("BUILD_MANIFEST_DISABLE_SIGNING").is_err() {
+            let file = builder.config.dist_gpg_password_file.as_ref().unwrap_or_else(|| {
+                panic!("\n\nfailed to specify `dist.gpg-password-file` in `config.toml`\n\n")
+            });
+            t!(fs::read_to_string(&file))
+        } else {
+            String::new()
+        };
 
         let today = output(Command::new("date").arg("+%Y-%m-%d"));
 
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 6faedc80ad3f5..873a3c31d1535 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -476,11 +476,11 @@ impl Step for Std {
                  .arg("--index-page").arg(&builder.src.join("src/doc/index.md"));
 
             builder.run(&mut cargo);
-            builder.cp_r(&my_out, &out);
         };
         for krate in &["alloc", "core", "std", "proc_macro", "test"] {
             run_cargo_rustdoc_for(krate);
         }
+        builder.cp_r(&my_out, &out);
     }
 }
 
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index 828865f10ffba..d9580b598155e 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -36,7 +36,7 @@ pub struct Flags {
     // This overrides the deny-warnings configuation option,
     // which passes -Dwarnings to the compiler invocations.
     //
-    // true => deny, false => allow
+    // true => deny, false => warn
     pub deny_warnings: Option<bool>,
 }
 
@@ -556,10 +556,10 @@ fn split(s: &[String]) -> Vec<String> {
 fn parse_deny_warnings(matches: &getopts::Matches) -> Option<bool> {
     match matches.opt_str("warnings").as_ref().map(|v| v.as_str()) {
         Some("deny") => Some(true),
-        Some("allow") => Some(false),
+        Some("warn") => Some(false),
         Some(value) => {
             eprintln!(
-                r#"invalid value for --warnings: {:?}, expected "allow" or "deny""#,
+                r#"invalid value for --warnings: {:?}, expected "warn" or "deny""#,
                 value,
                 );
             process::exit(1);
diff --git a/src/bootstrap/install.rs b/src/bootstrap/install.rs
index 557586709c612..384219c38fd04 100644
--- a/src/bootstrap/install.rs
+++ b/src/bootstrap/install.rs
@@ -67,7 +67,6 @@ fn install_sh(
     let sysconfdir_default = PathBuf::from("/etc");
     let datadir_default = PathBuf::from("share");
     let docdir_default = datadir_default.join("doc/rust");
-    let bindir_default = PathBuf::from("bin");
     let libdir_default = PathBuf::from("lib");
     let mandir_default = datadir_default.join("man");
     let prefix = builder.config.prefix.as_ref().map_or(prefix_default, |p| {
@@ -76,7 +75,7 @@ fn install_sh(
     let sysconfdir = builder.config.sysconfdir.as_ref().unwrap_or(&sysconfdir_default);
     let datadir = builder.config.datadir.as_ref().unwrap_or(&datadir_default);
     let docdir = builder.config.docdir.as_ref().unwrap_or(&docdir_default);
-    let bindir = builder.config.bindir.as_ref().unwrap_or(&bindir_default);
+    let bindir = &builder.config.bindir;
     let libdir = builder.config.libdir.as_ref().unwrap_or(&libdir_default);
     let mandir = builder.config.mandir.as_ref().unwrap_or(&mandir_default);
 
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index f02def3e1b05d..7bf9ea2688f4c 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -81,26 +81,29 @@ impl Step for Llvm {
             (info, "src/llvm-project/llvm", builder.llvm_out(target), dir.join("bin"))
         };
 
-        if !llvm_info.is_git() {
-            println!(
-                "git could not determine the LLVM submodule commit hash. \
-                Assuming that an LLVM build is necessary.",
-            );
-        }
-
         let build_llvm_config = llvm_config_ret_dir
             .join(exe("llvm-config", &*builder.config.build));
         let done_stamp = out_dir.join("llvm-finished-building");
 
-        if let Some(llvm_commit) = llvm_info.sha() {
-            if done_stamp.exists() {
+        if done_stamp.exists() {
+            if let Some(llvm_commit) = llvm_info.sha() {
                 let done_contents = t!(fs::read(&done_stamp));
 
                 // If LLVM was already built previously and the submodule's commit didn't change
                 // from the previous build, then no action is required.
                 if done_contents == llvm_commit.as_bytes() {
-                    return build_llvm_config
+                    return build_llvm_config;
                 }
+            } else {
+                builder.info(
+                    "Could not determine the LLVM submodule commit hash. \
+                     Assuming that an LLVM rebuild is not necessary.",
+                );
+                builder.info(&format!(
+                    "To force LLVM to rebuild, remove the file `{}`",
+                    done_stamp.display()
+                ));
+                return build_llvm_config;
             }
         }
 
@@ -303,9 +306,7 @@ impl Step for Llvm {
 
         cfg.build();
 
-        if let Some(llvm_commit) = llvm_info.sha() {
-            t!(fs::write(&done_stamp, llvm_commit));
-        }
+        t!(fs::write(&done_stamp, llvm_info.sha().unwrap_or("")));
 
         build_llvm_config
     }
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 97b28ed9e96c8..00d87f3841cff 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1327,7 +1327,10 @@ impl Step for Compiletest {
             cmd.env("RUSTC_PROFILER_SUPPORT", "1");
         }
 
-        cmd.env("RUST_TEST_TMPDIR", builder.out.join("tmp"));
+        let tmp = builder.out.join("tmp");
+        std::fs::create_dir_all(&tmp).unwrap();
+        cmd.env("RUST_TEST_TMPDIR", tmp);
+
 
         cmd.arg("--adb-path").arg("adb");
         cmd.arg("--adb-test-dir").arg(ADB_TEST_DIR);
diff --git a/src/ci/azure-pipelines/auto.yml b/src/ci/azure-pipelines/auto.yml
index 77c9cda58b8e6..5f7761297095c 100644
--- a/src/ci/azure-pipelines/auto.yml
+++ b/src/ci/azure-pipelines/auto.yml
@@ -7,7 +7,7 @@ trigger:
   - auto
 
 variables:
-- group: real-prod-credentials
+- group: prod-credentials
 
 jobs:
 - job: Linux
@@ -236,10 +236,16 @@ jobs:
         MSYS_BITS: 32
         RUST_CONFIGURE_ARGS: --build=i686-pc-windows-msvc
         SCRIPT: make ci-subset-1
+        # FIXME(#59637)
+        NO_DEBUG_ASSERTIONS: 1
+        NO_LLVM_ASSERTIONS: 1
       i686-msvc-2:
         MSYS_BITS: 32
         RUST_CONFIGURE_ARGS: --build=i686-pc-windows-msvc
         SCRIPT: make ci-subset-2
+        # FIXME(#59637)
+        NO_DEBUG_ASSERTIONS: 1
+        NO_LLVM_ASSERTIONS: 1
       # MSVC aux tests
       x86_64-msvc-aux:
         MSYS_BITS: 64
@@ -250,6 +256,9 @@ jobs:
         SCRIPT: python x.py test src/tools/cargotest src/tools/cargo
         RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-msvc
         VCVARS_BAT: vcvars64.bat
+        # FIXME(#59637)
+        NO_DEBUG_ASSERTIONS: 1
+        NO_LLVM_ASSERTIONS: 1
       # MSVC tools tests
       x86_64-msvc-tools:
         MSYS_BITS: 64
diff --git a/src/ci/azure-pipelines/master.yml b/src/ci/azure-pipelines/master.yml
index 9742c71965851..e2baa923d99f7 100644
--- a/src/ci/azure-pipelines/master.yml
+++ b/src/ci/azure-pipelines/master.yml
@@ -7,7 +7,7 @@ trigger:
   - master
 
 variables:
-- group: real-prod-credentials
+- group: prod-credentials
 
 pool:
   vmImage: ubuntu-16.04
diff --git a/src/ci/azure-pipelines/steps/install-windows-build-deps.yml b/src/ci/azure-pipelines/steps/install-windows-build-deps.yml
index 9aaeb4b79d634..bd4f1ed0cea43 100644
--- a/src/ci/azure-pipelines/steps/install-windows-build-deps.yml
+++ b/src/ci/azure-pipelines/steps/install-windows-build-deps.yml
@@ -18,9 +18,9 @@ steps:
 # one is MSI installers and one is EXE, but they're not used so frequently at
 # this point anyway so perhaps it's a wash!
 - script: |
-    powershell -Command "$ProgressPreference = 'SilentlyContinue'; iwr -outf is-install.exe https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/2017-08-22-is.exe"
-    is-install.exe /VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP-
     echo ##vso[task.prependpath]C:\Program Files (x86)\Inno Setup 5
+    curl.exe -o is-install.exe https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/2017-08-22-is.exe
+    is-install.exe /VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP-
   displayName: Install InnoSetup
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
 
@@ -43,24 +43,18 @@ steps:
 # FIXME: we should probe the default azure image and see if we can use the MSYS2
 # toolchain there. (if there's even one there). For now though this gets the job
 # done.
-- script: |
-    set MSYS_PATH=%CD%\citools\msys64
-    choco install msys2 --params="/InstallDir:%MSYS_PATH% /NoPath" -y
-    set PATH=%MSYS_PATH%\usr\bin;%PATH%
-    pacman -S --noconfirm --needed base-devel ca-certificates make diffutils tar
-    IF "%MINGW_URL%"=="" (
-      IF "%MSYS_BITS%"=="32" pacman -S --noconfirm --needed mingw-w64-i686-toolchain mingw-w64-i686-cmake mingw-w64-i686-gcc mingw-w64-i686-python2
-      IF "%MSYS_BITS%"=="64" pacman -S --noconfirm --needed mingw-w64-x86_64-toolchain mingw-w64-x86_64-cmake mingw-w64-x86_64-gcc mingw-w64-x86_64-python2
-    )
-    where rev
-    rev --help
-    where make
-
-    echo ##vso[task.setvariable variable=MSYS_PATH]%MSYS_PATH%
-    echo ##vso[task.prependpath]%MSYS_PATH%\usr\bin
+- bash: |
+    set -e
+    choco install msys2 --params="/InstallDir:$(System.Workfolder)/msys2 /NoPath" -y --no-progress
+    echo "##vso[task.prependpath]$(System.Workfolder)/msys2/usr/bin"
+    mkdir -p "$(System.Workfolder)/msys2/home/$USERNAME"
   displayName: Install msys2
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
 
+- bash: pacman -S --noconfirm --needed base-devel ca-certificates make diffutils tar
+  displayName: Install msys2 base deps
+  condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
+
 # If we need to download a custom MinGW, do so here and set the path
 # appropriately.
 #
@@ -81,39 +75,46 @@ steps:
 #
 # Note that we don't literally overwrite the gdb.exe binary because it appears
 # to just use gdborig.exe, so that's the binary we deal with instead.
-- script: |
-    powershell -Command "$ProgressPreference = 'SilentlyContinue'; iwr -outf %MINGW_ARCHIVE% %MINGW_URL%/%MINGW_ARCHIVE%"
-    7z x -y %MINGW_ARCHIVE% > nul
-    powershell -Command "$ProgressPreference = 'SilentlyContinue'; iwr -outf 2017-04-20-%MSYS_BITS%bit-gdborig.exe %MINGW_URL%/2017-04-20-%MSYS_BITS%bit-gdborig.exe"
-    mv 2017-04-20-%MSYS_BITS%bit-gdborig.exe %MINGW_DIR%\bin\gdborig.exe
-    echo ##vso[task.prependpath]%CD%\%MINGW_DIR%\bin
+- bash: |
+    set -e
+    curl -o mingw.7z $MINGW_URL/$MINGW_ARCHIVE
+    7z x -y mingw.7z > /dev/null
+    curl -o $MINGW_DIR/bin/gdborig.exe $MINGW_URL/2017-04-20-${MSYS_BITS}bit-gdborig.exe
+    echo "##vso[task.prependpath]`pwd`/$MINGW_DIR/bin"
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'), ne(variables['MINGW_URL'],''))
   displayName: Download custom MinGW
 
-# Otherwise pull in the MinGW installed on appveyor
-- script: |
-    echo ##vso[task.prependpath]%MSYS_PATH%\mingw%MSYS_BITS%\bin
+# Otherwise install MinGW through `pacman`
+- bash: |
+    set -e
+    arch=i686
+    if [ "$MSYS_BITS" = "64" ]; then
+      arch=x86_64
+    fi
+    pacman -S --noconfirm --needed mingw-w64-$arch-toolchain mingw-w64-$arch-cmake mingw-w64-$arch-gcc mingw-w64-$arch-python2
+    echo "##vso[task.prependpath]$(System.Workfolder)/msys2/mingw$MSYS_BITS/bin"
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'), eq(variables['MINGW_URL'],''))
-  displayName: Add MinGW to path
+  displayName: Download standard MinGW
 
 # Make sure we use the native python interpreter instead of some msys equivalent
 # one way or another. The msys interpreters seem to have weird path conversions
 # baked in which break LLVM's build system one way or another, so let's use the
 # native version which keeps everything as native as possible.
-- script: |
-    copy C:\Python27amd64\python.exe C:\Python27amd64\python2.7.exe
-    echo ##vso[task.prependpath]C:\Python27amd64
+- bash: |
+    set -e
+    cp C:/Python27amd64/python.exe C:/Python27amd64/python2.7.exe
+    echo "##vso[task.prependpath]C:/Python27amd64"
   displayName: Prefer the "native" Python as LLVM has trouble building with MSYS sometimes
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
 
 # Note that this is originally from the github releases patch of Ninja
-- script: |
-    md ninja
-    powershell -Command "$ProgressPreference = 'SilentlyContinue'; iwr -outf 2017-03-15-ninja-win.zip https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/2017-03-15-ninja-win.zip"
-    7z x -oninja 2017-03-15-ninja-win.zip
-    del 2017-03-15-ninja-win.zip
-    set RUST_CONFIGURE_ARGS=%RUST_CONFIGURE_ARGS% --enable-ninja
-    echo ##vso[task.setvariable variable=RUST_CONFIGURE_ARGS]%RUST_CONFIGURE_ARGS%
-    echo ##vso[task.prependpath]%CD%\ninja
+- bash: |
+    set -e
+    mkdir ninja
+    curl -o ninja.zip https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/2017-03-15-ninja-win.zip
+    7z x -oninja ninja.zip
+    rm ninja.zip
+    echo "##vso[task.setvariable variable=RUST_CONFIGURE_ARGS]$RUST_CONFIGURE_ARGS --enable-ninja"
+    echo "##vso[task.prependpath]`pwd`/ninja"
   displayName: Download and install ninja
   condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
diff --git a/src/ci/azure-pipelines/steps/run.yml b/src/ci/azure-pipelines/steps/run.yml
index ac6b344a45e66..15a2499e4609e 100644
--- a/src/ci/azure-pipelines/steps/run.yml
+++ b/src/ci/azure-pipelines/steps/run.yml
@@ -147,8 +147,15 @@ steps:
     git clone --depth=1 https://github.com/rust-lang-nursery/rust-toolstate.git
     cd rust-toolstate
     python2.7 "$BUILD_SOURCESDIRECTORY/src/tools/publish_toolstate.py" "$(git rev-parse HEAD)" "$(git log --format=%s -n1 HEAD)" "" ""
+    # Only check maintainers if this build is supposed to publish toolstate.
+    # Builds that are not supposed to publish don't have the access token.
+    if [ -n "${TOOLSTATE_PUBLISH+is_set}" ]; then
+      TOOLSTATE_VALIDATE_MAINTAINERS_REPO=rust-lang/rust python2.7 "${BUILD_SOURCESDIRECTORY}/src/tools/publish_toolstate.py"
+    fi
     cd ..
     rm -rf rust-toolstate
+  env:
+    TOOLSTATE_REPO_ACCESS_TOKEN: $(TOOLSTATE_REPO_ACCESS_TOKEN)
   condition: and(succeeded(), not(variables.SKIP_JOB), eq(variables['IMAGE'], 'mingw-check'))
   displayName: Verify the publish_toolstate script works
 
@@ -168,7 +175,8 @@ steps:
   env:
     CI: true
     SRC: .
-    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
+    AWS_ACCESS_KEY_ID: $(SCCACHE_AWS_ACCESS_KEY_ID)
+    AWS_SECRET_ACCESS_KEY: $(SCCACHE_AWS_SECRET_ACCESS_KEY)
     TOOLSTATE_REPO_ACCESS_TOKEN: $(TOOLSTATE_REPO_ACCESS_TOKEN)
   condition: and(succeeded(), not(variables.SKIP_JOB))
   displayName: Run build
@@ -192,7 +200,8 @@ steps:
     fi
     retry aws s3 cp --no-progress --recursive --acl public-read ./$upload_dir s3://$DEPLOY_BUCKET/$deploy_dir/$BUILD_SOURCEVERSION
   env:
-    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
+    AWS_ACCESS_KEY_ID: $(UPLOAD_AWS_ACCESS_KEY_ID)
+    AWS_SECRET_ACCESS_KEY: $(UPLOAD_AWS_SECRET_ACCESS_KEY)
   condition: and(succeeded(), not(variables.SKIP_JOB), or(eq(variables.DEPLOY, '1'), eq(variables.DEPLOY_ALT, '1')))
   displayName: Upload artifacts
 
@@ -201,7 +210,8 @@ steps:
 # errors here ever fail the build since this is just informational.
 - bash: aws s3 cp --acl public-read cpu-usage.csv s3://$DEPLOY_BUCKET/rustc-builds/$BUILD_SOURCEVERSION/cpu-$CI_JOB_NAME.csv
   env:
-    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
-  condition: variables['AWS_SECRET_ACCESS_KEY']
+    AWS_ACCESS_KEY_ID: $(UPLOAD_AWS_ACCESS_KEY_ID)
+    AWS_SECRET_ACCESS_KEY: $(UPLOAD_AWS_SECRET_ACCESS_KEY)
+  condition: variables['UPLOAD_AWS_SECRET_ACCESS_KEY']
   continueOnError: true
   displayName: Upload CPU usage statistics
diff --git a/src/ci/azure-pipelines/try.yml b/src/ci/azure-pipelines/try.yml
index 0df6c6c951f24..c919b1023a0eb 100644
--- a/src/ci/azure-pipelines/try.yml
+++ b/src/ci/azure-pipelines/try.yml
@@ -3,7 +3,7 @@ trigger:
 - try
 
 variables:
-- group: real-prod-credentials
+- group: prod-credentials
 
 jobs:
 - job: Linux
diff --git a/src/ci/docker/i686-gnu-nopt/Dockerfile b/src/ci/docker/i686-gnu-nopt/Dockerfile
index 2041ba50bc9a0..517b59c38dcb0 100644
--- a/src/ci/docker/i686-gnu-nopt/Dockerfile
+++ b/src/ci/docker/i686-gnu-nopt/Dockerfile
@@ -19,3 +19,6 @@ RUN sh /scripts/sccache.sh
 
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu --disable-optimize-tests
 ENV SCRIPT python2.7 ../x.py test
+
+# FIXME(#59637) takes too long on CI right now
+ENV NO_LLVM_ASSERTIONS=1 NO_DEBUG_ASSERTIONS=1
diff --git a/src/ci/docker/i686-gnu/Dockerfile b/src/ci/docker/i686-gnu/Dockerfile
index 17441ddb4546b..03db3ba0995d6 100644
--- a/src/ci/docker/i686-gnu/Dockerfile
+++ b/src/ci/docker/i686-gnu/Dockerfile
@@ -25,3 +25,6 @@ ENV SCRIPT python2.7 ../x.py test \
   --exclude src/test/rustdoc-js \
   --exclude src/tools/error_index_generator \
   --exclude src/tools/linkchecker
+
+# FIXME(#59637) takes too long on CI right now
+ENV NO_LLVM_ASSERTIONS=1 NO_DEBUG_ASSERTIONS=1
diff --git a/src/doc/book b/src/doc/book
index 7ddc46460f09a..871416b85c1a7 160000
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit 7ddc46460f09a5cd9bd2a620565bdc20b3315ea9
+Subproject commit 871416b85c1a73717d65d6f4a9ea29e5aef3db0e
diff --git a/src/doc/nomicon b/src/doc/nomicon
index 38b9a76bc8b59..4374786f0b4bf 160000
--- a/src/doc/nomicon
+++ b/src/doc/nomicon
@@ -1 +1 @@
-Subproject commit 38b9a76bc8b59ac862663807fc51c9b757337fd6
+Subproject commit 4374786f0b4bf0606b35d5c30a9681f342e5707b
diff --git a/src/doc/reference b/src/doc/reference
index 090c015f79396..fa5dfb832ef8a 160000
--- a/src/doc/reference
+++ b/src/doc/reference
@@ -1 +1 @@
-Subproject commit 090c015f7939665866432c334957bd536c811870
+Subproject commit fa5dfb832ef8a7568e17dabf612f486d641ff4ac
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
index e76be6b2dc84c..67cfbf31df880 160000
--- a/src/doc/rust-by-example
+++ b/src/doc/rust-by-example
@@ -1 +1 @@
-Subproject commit e76be6b2dc84c6a992e186157efe29d625e29b94
+Subproject commit 67cfbf31df880728dcf7cb35b15b028ec92caf31
diff --git a/src/doc/rustc-guide b/src/doc/rustc-guide
index 6e25a3d0d3573..941968db2fd9c 160000
--- a/src/doc/rustc-guide
+++ b/src/doc/rustc-guide
@@ -1 +1 @@
-Subproject commit 6e25a3d0d3573eb42b2e2339f1219e969d1b3dee
+Subproject commit 941968db2fd9c85788a4f971c8e425d46b4cb734
diff --git a/src/doc/rustdoc/src/unstable-features.md b/src/doc/rustdoc/src/unstable-features.md
index 993fc8412836e..49d05b5038df7 100644
--- a/src/doc/rustdoc/src/unstable-features.md
+++ b/src/doc/rustdoc/src/unstable-features.md
@@ -471,3 +471,53 @@ Some methodology notes about what rustdoc counts in this metric:
 
 Public items that are not documented can be seen with the built-in `missing_docs` lint. Private
 items that are not documented can be seen with Clippy's `missing_docs_in_private_items` lint.
+
+### `--enable-per-target-ignores`: allow `ignore-foo` style filters for doctests
+
+Using this flag looks like this:
+
+```bash
+$ rustdoc src/lib.rs -Z unstable-options --enable-per-target-ignores
+```
+
+This flag allows you to tag doctests with compiltest style `ignore-foo` filters that prevent
+rustdoc from running that test if the target triple string contains foo. For example:
+
+```rust
+///```ignore-foo,ignore-bar
+///assert!(2 == 2);
+///```
+struct Foo;
+```
+
+This will not be run when the build target is `super-awesome-foo` or `less-bar-awesome`.
+If the flag is not enabled, then rustdoc will consume the filter, but do nothing with it, and
+the above example will be run for all targets.
+If you want to preserve backwards compatibility for older versions of rustdoc, you can use
+
+```rust
+///```ignore,ignore-foo
+///assert!(2 == 2);
+///```
+struct Foo;
+```
+
+In older versions, this will be ignored on all targets, but on newer versions `ignore-gnu` will
+override `ignore`.
+
+### `--runtool`, `--runtool-arg`: program to run tests with; args to pass to it
+
+Using thses options looks like this:
+
+```bash
+$ rustdoc src/lib.rs -Z unstable-options --runtool runner --runtool-arg --do-thing --runtool-arg --do-other-thing
+```
+
+These options can be used to run the doctest under a program, and also pass arguments to
+that program. For example, if you want to run your doctests under valgrind you might run
+
+```bash
+$ rustdoc src/lib.rs -Z unstable-options --runtool valgrind
+```
+
+Another use case would be to run a test inside an emulator, or through a Virtual Machine.
diff --git a/src/etc/lldb_batchmode.py b/src/etc/lldb_batchmode.py
index 537b419b3279f..7c2e91474c1f1 100644
--- a/src/etc/lldb_batchmode.py
+++ b/src/etc/lldb_batchmode.py
@@ -45,7 +45,10 @@ def normalize_whitespace(s):
 
 def breakpoint_callback(frame, bp_loc, dict):
     """This callback is registered with every breakpoint and makes sure that the
-    frame containing the breakpoint location is selected"""
+    frame containing the breakpoint location is selected """
+
+    # HACK(eddyb) print a newline to avoid continuing an unfinished line.
+    print("")
     print("Hit breakpoint " + str(bp_loc))
 
     # Select the frame and the thread containing it
diff --git a/src/liballoc/collections/btree/set.rs b/src/liballoc/collections/btree/set.rs
index d3af910a82c27..0cb91ba4c81da 100644
--- a/src/liballoc/collections/btree/set.rs
+++ b/src/liballoc/collections/btree/set.rs
@@ -3,7 +3,7 @@
 
 use core::borrow::Borrow;
 use core::cmp::Ordering::{self, Less, Greater, Equal};
-use core::cmp::max;
+use core::cmp::{max, min};
 use core::fmt::{self, Debug};
 use core::iter::{Peekable, FromIterator, FusedIterator};
 use core::ops::{BitOr, BitAnd, BitXor, Sub, RangeBounds};
@@ -187,8 +187,8 @@ pub struct Intersection<'a, T: 'a> {
 }
 enum IntersectionInner<'a, T: 'a> {
     Stitch {
-        small_iter: Iter<'a, T>, // for size_hint, should be the smaller of the sets
-        other_iter: Iter<'a, T>,
+        a: Iter<'a, T>,
+        b: Iter<'a, T>,
     },
     Search {
         small_iter: Iter<'a, T>,
@@ -201,12 +201,12 @@ impl<T: fmt::Debug> fmt::Debug for Intersection<'_, T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.inner {
             IntersectionInner::Stitch {
-                small_iter,
-                other_iter,
+                a,
+                b,
             } => f
                 .debug_tuple("Intersection")
-                .field(&small_iter)
-                .field(&other_iter)
+                .field(&a)
+                .field(&b)
                 .finish(),
             IntersectionInner::Search {
                 small_iter,
@@ -397,8 +397,8 @@ impl<T: Ord> BTreeSet<T> {
             // Iterate both sets jointly, spotting matches along the way.
             Intersection {
                 inner: IntersectionInner::Stitch {
-                    small_iter: small.iter(),
-                    other_iter: other.iter(),
+                    a: small.iter(),
+                    b: other.iter(),
                 },
             }
         } else {
@@ -1221,11 +1221,11 @@ impl<T> Clone for Intersection<'_, T> {
         Intersection {
             inner: match &self.inner {
                 IntersectionInner::Stitch {
-                    small_iter,
-                    other_iter,
+                    a,
+                    b,
                 } => IntersectionInner::Stitch {
-                    small_iter: small_iter.clone(),
-                    other_iter: other_iter.clone(),
+                    a: a.clone(),
+                    b: b.clone(),
                 },
                 IntersectionInner::Search {
                     small_iter,
@@ -1245,16 +1245,16 @@ impl<'a, T: Ord> Iterator for Intersection<'a, T> {
     fn next(&mut self) -> Option<&'a T> {
         match &mut self.inner {
             IntersectionInner::Stitch {
-                small_iter,
-                other_iter,
+                a,
+                b,
             } => {
-                let mut small_next = small_iter.next()?;
-                let mut other_next = other_iter.next()?;
+                let mut a_next = a.next()?;
+                let mut b_next = b.next()?;
                 loop {
-                    match Ord::cmp(small_next, other_next) {
-                        Less => small_next = small_iter.next()?,
-                        Greater => other_next = other_iter.next()?,
-                        Equal => return Some(small_next),
+                    match Ord::cmp(a_next, b_next) {
+                        Less => a_next = a.next()?,
+                        Greater => b_next = b.next()?,
+                        Equal => return Some(a_next),
                     }
                 }
             }
@@ -1272,7 +1272,7 @@ impl<'a, T: Ord> Iterator for Intersection<'a, T> {
 
     fn size_hint(&self) -> (usize, Option<usize>) {
         let min_len = match &self.inner {
-            IntersectionInner::Stitch { small_iter, .. } => small_iter.len(),
+            IntersectionInner::Stitch { a, b } => min(a.len(), b.len()),
             IntersectionInner::Search { small_iter, .. } => small_iter.len(),
         };
         (0, Some(min_len))
diff --git a/src/liballoc/collections/linked_list/tests.rs b/src/liballoc/collections/linked_list/tests.rs
index 9a6c57d286970..ecb5948f11b36 100644
--- a/src/liballoc/collections/linked_list/tests.rs
+++ b/src/liballoc/collections/linked_list/tests.rs
@@ -102,8 +102,8 @@ fn test_append() {
         assert_eq!(m.pop_front(), Some(elt))
     }
     assert_eq!(n.len(), 0);
-    // let's make sure it's working properly, since we
-    // did some direct changes to private members
+    // Let's make sure it's working properly, since we
+    // did some direct changes to private members.
     n.push_back(3);
     assert_eq!(n.len(), 1);
     assert_eq!(n.pop_front(), Some(3));
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 4a48945adc37a..9e6ed92ffb567 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -117,7 +117,7 @@
 #![feature(allocator_internals)]
 #![feature(on_unimplemented)]
 #![feature(rustc_const_unstable)]
-#![feature(const_vec_new)]
+#![cfg_attr(bootstrap, feature(const_vec_new))]
 #![feature(slice_partition_dedup)]
 #![feature(maybe_uninit_extra, maybe_uninit_slice)]
 #![feature(alloc_layout_extra)]
@@ -171,3 +171,9 @@ pub mod vec;
 mod std {
     pub use core::ops; // RangeFull
 }
+
+#[doc(hidden)]
+#[unstable(feature = "liballoc_internals", issue = "0", reason = "implementation detail")]
+pub mod __export {
+    pub use core::format_args;
+}
diff --git a/src/liballoc/macros.rs b/src/liballoc/macros.rs
index 0b5e186d4c77b..2f2cdc39c633d 100644
--- a/src/liballoc/macros.rs
+++ b/src/liballoc/macros.rs
@@ -98,5 +98,5 @@ macro_rules! vec {
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
 macro_rules! format {
-    ($($arg:tt)*) => ($crate::fmt::format(::core::format_args!($($arg)*)))
+    ($($arg:tt)*) => ($crate::fmt::format($crate::__export::format_args!($($arg)*)))
 }
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index bc8a38f6b3aad..ee75fc288fee5 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -19,26 +19,26 @@ mod tests;
 /// involved. This type is excellent for building your own data structures like Vec and VecDeque.
 /// In particular:
 ///
-/// * Produces Unique::empty() on zero-sized types
-/// * Produces Unique::empty() on zero-length allocations
-/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics)
-/// * Guards against 32-bit systems allocating more than isize::MAX bytes
-/// * Guards against overflowing your length
-/// * Aborts on OOM or calls handle_alloc_error as applicable
-/// * Avoids freeing Unique::empty()
-/// * Contains a ptr::Unique and thus endows the user with all related benefits
+/// * Produces `Unique::empty()` on zero-sized types.
+/// * Produces `Unique::empty()` on zero-length allocations.
+/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics).
+/// * Guards against 32-bit systems allocating more than isize::MAX bytes.
+/// * Guards against overflowing your length.
+/// * Aborts on OOM or calls `handle_alloc_error` as applicable.
+/// * Avoids freeing `Unique::empty()`.
+/// * Contains a `ptr::Unique` and thus endows the user with all related benefits.
 ///
 /// This type does not in anyway inspect the memory that it manages. When dropped it *will*
-/// free its memory, but it *won't* try to Drop its contents. It is up to the user of RawVec
-/// to handle the actual things *stored* inside of a RawVec.
+/// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec`
+/// to handle the actual things *stored* inside of a `RawVec`.
 ///
-/// Note that a RawVec always forces its capacity to be usize::MAX for zero-sized types.
-/// This enables you to use capacity growing logic catch the overflows in your length
+/// Note that a `RawVec` always forces its capacity to be `usize::MAX` for zero-sized types.
+/// This enables you to use capacity-growing logic catch the overflows in your length
 /// that might occur with zero-sized types.
 ///
-/// However this means that you need to be careful when round-tripping this type
-/// with a `Box<[T]>`: `capacity()` won't yield the len. However `with_capacity`,
-/// `shrink_to_fit`, and `from_box` will actually set RawVec's private capacity
+/// The above means that you need to be careful when round-tripping this type with a
+/// `Box<[T]>`, since `capacity()` won't yield the length. However, `with_capacity`,
+/// `shrink_to_fit`, and `from_box` will actually set `RawVec`'s private capacity
 /// field. This allows zero-sized types to not be special-cased by consumers of
 /// this type.
 #[allow(missing_debug_implementations)]
@@ -49,14 +49,14 @@ pub struct RawVec<T, A: Alloc = Global> {
 }
 
 impl<T, A: Alloc> RawVec<T, A> {
-    /// Like `new` but parameterized over the choice of allocator for
-    /// the returned RawVec.
+    /// Like `new`, but parameterized over the choice of allocator for
+    /// the returned `RawVec`.
     pub const fn new_in(a: A) -> Self {
-        // !0 is usize::MAX. This branch should be stripped at compile time.
-        // FIXME(mark-i-m): use this line when `if`s are allowed in `const`
+        // `!0` is `usize::MAX`. This branch should be stripped at compile time.
+        // FIXME(mark-i-m): use this line when `if`s are allowed in `const`:
         //let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
 
-        // Unique::empty() doubles as "unallocated" and "zero-sized allocation"
+        // `Unique::empty()` doubles as "unallocated" and "zero-sized allocation".
         RawVec {
             ptr: Unique::empty(),
             // FIXME(mark-i-m): use `cap` when ifs are allowed in const
@@ -65,15 +65,15 @@ impl<T, A: Alloc> RawVec<T, A> {
         }
     }
 
-    /// Like `with_capacity` but parameterized over the choice of
-    /// allocator for the returned RawVec.
+    /// Like `with_capacity`, but parameterized over the choice of
+    /// allocator for the returned `RawVec`.
     #[inline]
     pub fn with_capacity_in(capacity: usize, a: A) -> Self {
         RawVec::allocate_in(capacity, false, a)
     }
 
-    /// Like `with_capacity_zeroed` but parameterized over the choice
-    /// of allocator for the returned RawVec.
+    /// Like `with_capacity_zeroed`, but parameterized over the choice
+    /// of allocator for the returned `RawVec`.
     #[inline]
     pub fn with_capacity_zeroed_in(capacity: usize, a: A) -> Self {
         RawVec::allocate_in(capacity, true, a)
@@ -86,7 +86,7 @@ impl<T, A: Alloc> RawVec<T, A> {
             let alloc_size = capacity.checked_mul(elem_size).unwrap_or_else(|| capacity_overflow());
             alloc_guard(alloc_size).unwrap_or_else(|_| capacity_overflow());
 
-            // handles ZSTs and `capacity = 0` alike
+            // Handles ZSTs and `capacity == 0` alike.
             let ptr = if alloc_size == 0 {
                 NonNull::<T>::dangling()
             } else {
@@ -113,20 +113,45 @@ impl<T, A: Alloc> RawVec<T, A> {
 }
 
 impl<T> RawVec<T, Global> {
-    /// Creates the biggest possible RawVec (on the system heap)
-    /// without allocating. If T has positive size, then this makes a
-    /// RawVec with capacity 0. If T has 0 size, then it makes a
-    /// RawVec with capacity `usize::MAX`. Useful for implementing
+    /// HACK(Centril): This exists because `#[unstable]` `const fn`s needn't conform
+    /// to `min_const_fn` and so they cannot be called in `min_const_fn`s either.
+    ///
+    /// If you change `RawVec<T>::new` or dependencies, please take care to not
+    /// introduce anything that would truly violate `min_const_fn`.
+    ///
+    /// NOTE: We could avoid this hack and check conformance with some
+    /// `#[rustc_force_min_const_fn]` attribute which requires conformance
+    /// with `min_const_fn` but does not necessarily allow calling it in
+    /// `stable(...) const fn` / user code not enabling `foo` when
+    /// `#[rustc_const_unstable(feature = "foo", ..)]` is present.
+    pub const NEW: Self = Self::new();
+
+    /// Creates the biggest possible `RawVec` (on the system heap)
+    /// without allocating. If `T` has positive size, then this makes a
+    /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
+    /// `RawVec` with capacity `usize::MAX`. Useful for implementing
     /// delayed allocation.
     pub const fn new() -> Self {
-        Self::new_in(Global)
+        // FIXME(Centril): Reintegrate this with `fn new_in` when we can.
+
+        // `!0` is `usize::MAX`. This branch should be stripped at compile time.
+        // FIXME(mark-i-m): use this line when `if`s are allowed in `const`:
+        //let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
+
+        // `Unique::empty()` doubles as "unallocated" and "zero-sized allocation".
+        RawVec {
+            ptr: Unique::empty(),
+            // FIXME(mark-i-m): use `cap` when ifs are allowed in const
+            cap: [0, !0][(mem::size_of::<T>() == 0) as usize],
+            a: Global,
+        }
     }
 
-    /// Creates a RawVec (on the system heap) with exactly the
+    /// Creates a `RawVec` (on the system heap) with exactly the
     /// capacity and alignment requirements for a `[T; capacity]`. This is
-    /// equivalent to calling RawVec::new when `capacity` is 0 or T is
+    /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is
     /// zero-sized. Note that if `T` is zero-sized this means you will
-    /// *not* get a RawVec with the requested capacity!
+    /// *not* get a `RawVec` with the requested capacity.
     ///
     /// # Panics
     ///
@@ -136,13 +161,13 @@ impl<T> RawVec<T, Global> {
     ///
     /// # Aborts
     ///
-    /// Aborts on OOM
+    /// Aborts on OOM.
     #[inline]
     pub fn with_capacity(capacity: usize) -> Self {
         RawVec::allocate_in(capacity, false, Global)
     }
 
-    /// Like `with_capacity` but guarantees the buffer is zeroed.
+    /// Like `with_capacity`, but guarantees the buffer is zeroed.
     #[inline]
     pub fn with_capacity_zeroed(capacity: usize) -> Self {
         RawVec::allocate_in(capacity, true, Global)
@@ -150,13 +175,13 @@ impl<T> RawVec<T, Global> {
 }
 
 impl<T, A: Alloc> RawVec<T, A> {
-    /// Reconstitutes a RawVec from a pointer, capacity, and allocator.
+    /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
     ///
     /// # Undefined Behavior
     ///
-    /// The ptr must be allocated (via the given allocator `a`), and with the given capacity. The
-    /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems).
-    /// If the ptr and capacity come from a RawVec created via `a`, then this is guaranteed.
+    /// The `ptr` must be allocated (via the given allocator `a`), and with the given `capacity`.
+    /// The `capacity` cannot exceed `isize::MAX` (only a concern on 32-bit systems).
+    /// If the `ptr` and `capacity` come from a `RawVec` created via `a`, then this is guaranteed.
     pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, a: A) -> Self {
         RawVec {
             ptr: Unique::new_unchecked(ptr),
@@ -167,13 +192,13 @@ impl<T, A: Alloc> RawVec<T, A> {
 }
 
 impl<T> RawVec<T, Global> {
-    /// Reconstitutes a RawVec from a pointer, capacity.
+    /// Reconstitutes a `RawVec` from a pointer and capacity.
     ///
     /// # Undefined Behavior
     ///
-    /// The ptr must be allocated (on the system heap), and with the given capacity. The
-    /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems).
-    /// If the ptr and capacity come from a RawVec, then this is guaranteed.
+    /// The `ptr` must be allocated (on the system heap), and with the given `capacity`.
+    /// The `capacity` cannot exceed `isize::MAX` (only a concern on 32-bit systems).
+    /// If the `ptr` and `capacity` come from a `RawVec`, then this is guaranteed.
     pub unsafe fn from_raw_parts(ptr: *mut T, capacity: usize) -> Self {
         RawVec {
             ptr: Unique::new_unchecked(ptr),
@@ -194,7 +219,7 @@ impl<T> RawVec<T, Global> {
 
 impl<T, A: Alloc> RawVec<T, A> {
     /// Gets a raw pointer to the start of the allocation. Note that this is
-    /// Unique::empty() if `capacity = 0` or T is zero-sized. In the former case, you must
+    /// `Unique::empty()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
     /// be careful.
     pub fn ptr(&self) -> *mut T {
         self.ptr.as_ptr()
@@ -212,12 +237,12 @@ impl<T, A: Alloc> RawVec<T, A> {
         }
     }
 
-    /// Returns a shared reference to the allocator backing this RawVec.
+    /// Returns a shared reference to the allocator backing this `RawVec`.
     pub fn alloc(&self) -> &A {
         &self.a
     }
 
-    /// Returns a mutable reference to the allocator backing this RawVec.
+    /// Returns a mutable reference to the allocator backing this `RawVec`.
     pub fn alloc_mut(&mut self) -> &mut A {
         &mut self.a
     }
@@ -247,7 +272,7 @@ impl<T, A: Alloc> RawVec<T, A> {
     ///
     /// # Panics
     ///
-    /// * Panics if T is zero-sized on the assumption that you managed to exhaust
+    /// * Panics if `T` is zero-sized on the assumption that you managed to exhaust
     ///   all `usize::MAX` slots in your imaginary buffer.
     /// * Panics on 32-bit platforms if the requested capacity exceeds
     ///   `isize::MAX` bytes.
@@ -290,20 +315,20 @@ impl<T, A: Alloc> RawVec<T, A> {
         unsafe {
             let elem_size = mem::size_of::<T>();
 
-            // since we set the capacity to usize::MAX when elem_size is
-            // 0, getting to here necessarily means the RawVec is overfull.
+            // Since we set the capacity to `usize::MAX` when `elem_size` is
+            // 0, getting to here necessarily means the `RawVec` is overfull.
             assert!(elem_size != 0, "capacity overflow");
 
             let (new_cap, uniq) = match self.current_layout() {
                 Some(cur) => {
                     // Since we guarantee that we never allocate more than
-                    // isize::MAX bytes, `elem_size * self.cap <= isize::MAX` as
+                    // `isize::MAX` bytes, `elem_size * self.cap <= isize::MAX` as
                     // a precondition, so this can't overflow. Additionally the
                     // alignment will never be too large as to "not be
                     // satisfiable", so `Layout::from_size_align` will always
                     // return `Some`.
                     //
-                    // tl;dr; we bypass runtime checks due to dynamic assertions
+                    // TL;DR, we bypass runtime checks due to dynamic assertions
                     // in this module, allowing us to use
                     // `from_size_align_unchecked`.
                     let new_cap = 2 * self.cap;
@@ -320,8 +345,8 @@ impl<T, A: Alloc> RawVec<T, A> {
                     }
                 }
                 None => {
-                    // skip to 4 because tiny Vec's are dumb; but not if that
-                    // would cause overflow
+                    // Skip to 4 because tiny `Vec`'s are dumb; but not if that
+                    // would cause overflow.
                     let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 };
                     match self.a.alloc_array::<T>(new_cap) {
                         Ok(ptr) => (new_cap, ptr.into()),
@@ -342,7 +367,7 @@ impl<T, A: Alloc> RawVec<T, A> {
     ///
     /// # Panics
     ///
-    /// * Panics if T is zero-sized on the assumption that you managed to exhaust
+    /// * Panics if `T` is zero-sized on the assumption that you managed to exhaust
     ///   all `usize::MAX` slots in your imaginary buffer.
     /// * Panics on 32-bit platforms if the requested capacity exceeds
     ///   `isize::MAX` bytes.
@@ -356,15 +381,15 @@ impl<T, A: Alloc> RawVec<T, A> {
                 None => return false, // nothing to double
             };
 
-            // since we set the capacity to usize::MAX when elem_size is
-            // 0, getting to here necessarily means the RawVec is overfull.
+            // Since we set the capacity to `usize::MAX` when `elem_size` is
+            // 0, getting to here necessarily means the `RawVec` is overfull.
             assert!(elem_size != 0, "capacity overflow");
 
-            // Since we guarantee that we never allocate more than isize::MAX
+            // Since we guarantee that we never allocate more than `isize::MAX`
             // bytes, `elem_size * self.cap <= isize::MAX` as a precondition, so
             // this can't overflow.
             //
-            // Similarly like with `double` above we can go straight to
+            // Similarly to with `double` above, we can go straight to
             // `Layout::from_size_align_unchecked` as we know this won't
             // overflow and the alignment is sufficiently small.
             let new_cap = 2 * self.cap;
@@ -409,7 +434,7 @@ impl<T, A: Alloc> RawVec<T, A> {
     ///
     /// # Aborts
     ///
-    /// Aborts on OOM
+    /// Aborts on OOM.
     pub fn reserve_exact(&mut self, used_capacity: usize, needed_extra_capacity: usize) {
         match self.reserve_internal(used_capacity, needed_extra_capacity, Infallible, Exact) {
             Err(CapacityOverflow) => capacity_overflow(),
@@ -424,7 +449,7 @@ impl<T, A: Alloc> RawVec<T, A> {
     fn amortized_new_size(&self, used_capacity: usize, needed_extra_capacity: usize)
         -> Result<usize, TryReserveError> {
 
-        // Nothing we can really do about these checks :(
+        // Nothing we can really do about these checks, sadly.
         let required_cap = used_capacity.checked_add(needed_extra_capacity)
             .ok_or(CapacityOverflow)?;
         // Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`.
@@ -459,7 +484,7 @@ impl<T, A: Alloc> RawVec<T, A> {
     ///
     /// # Aborts
     ///
-    /// Aborts on OOM
+    /// Aborts on OOM.
     ///
     /// # Examples
     ///
@@ -538,7 +563,7 @@ impl<T, A: Alloc> RawVec<T, A> {
 
             // Here, `cap < used_capacity + needed_extra_capacity <= new_cap`
             // (regardless of whether `self.cap - used_capacity` wrapped).
-            // Therefore we can safely call grow_in_place.
+            // Therefore, we can safely call `grow_in_place`.
 
             let new_layout = Layout::new::<T>().repeat(new_cap).unwrap().0;
             // FIXME: may crash and burn on over-reserve
@@ -576,14 +601,14 @@ impl<T, A: Alloc> RawVec<T, A> {
             return;
         }
 
-        // This check is my waterloo; it's the only thing Vec wouldn't have to do.
+        // This check is my waterloo; it's the only thing `Vec` wouldn't have to do.
         assert!(self.cap >= amount, "Tried to shrink to a larger capacity");
 
         if amount == 0 {
             // We want to create a new zero-length vector within the
-            // same allocator.  We use ptr::write to avoid an
+            // same allocator. We use `ptr::write` to avoid an
             // erroneous attempt to drop the contents, and we use
-            // ptr::read to sidestep condition against destructuring
+            // `ptr::read` to sidestep condition against destructuring
             // types that implement Drop.
 
             unsafe {
@@ -600,7 +625,7 @@ impl<T, A: Alloc> RawVec<T, A> {
                 //
                 // We also know that `self.cap` is greater than `amount`, and
                 // consequently we don't need runtime checks for creating either
-                // layout
+                // layout.
                 let old_size = elem_size * self.cap;
                 let new_size = elem_size * amount;
                 let align = mem::align_of::<T>();
@@ -653,7 +678,7 @@ impl<T, A: Alloc> RawVec<T, A> {
                 return Ok(());
             }
 
-            // Nothing we can really do about these checks :(
+            // Nothing we can really do about these checks, sadly.
             let new_cap = match strategy {
                 Exact => used_capacity.checked_add(needed_extra_capacity).ok_or(CapacityOverflow)?,
                 Amortized => self.amortized_new_size(used_capacity, needed_extra_capacity)?,
@@ -692,7 +717,7 @@ impl<T> RawVec<T, Global> {
     /// Converts the entire buffer into `Box<[T]>`.
     ///
     /// Note that this will correctly reconstitute any `cap` changes
-    /// that may have been performed. (see description of type for details)
+    /// that may have been performed. (See description of type for details.)
     ///
     /// # Undefined Behavior
     ///
@@ -700,7 +725,7 @@ impl<T> RawVec<T, Global> {
     /// the rules around uninitialized boxed values are not finalized yet,
     /// but until they are, it is advisable to avoid them.
     pub unsafe fn into_box(self) -> Box<[T]> {
-        // NOTE: not calling `capacity()` here, actually using the real `cap` field!
+        // NOTE: not calling `capacity()` here; actually using the real `cap` field!
         let slice = slice::from_raw_parts_mut(self.ptr(), self.cap);
         let output: Box<[T]> = Box::from_raw(slice);
         mem::forget(self);
@@ -709,7 +734,7 @@ impl<T> RawVec<T, Global> {
 }
 
 impl<T, A: Alloc> RawVec<T, A> {
-    /// Frees the memory owned by the RawVec *without* trying to Drop its contents.
+    /// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
     pub unsafe fn dealloc_buffer(&mut self) {
         let elem_size = mem::size_of::<T>();
         if elem_size != 0 {
@@ -721,22 +746,20 @@ impl<T, A: Alloc> RawVec<T, A> {
 }
 
 unsafe impl<#[may_dangle] T, A: Alloc> Drop for RawVec<T, A> {
-    /// Frees the memory owned by the RawVec *without* trying to Drop its contents.
+    /// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
     fn drop(&mut self) {
         unsafe { self.dealloc_buffer(); }
     }
 }
 
-
-
 // We need to guarantee the following:
-// * We don't ever allocate `> isize::MAX` byte-size objects
-// * We don't overflow `usize::MAX` and actually allocate too little
+// * We don't ever allocate `> isize::MAX` byte-size objects.
+// * We don't overflow `usize::MAX` and actually allocate too little.
 //
 // On 64-bit we just need to check for overflow since trying to allocate
 // `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
 // an extra guard for this in case we're running on a platform which can use
-// all 4GB in user-space. e.g., PAE or x32
+// all 4GB in user-space, e.g., PAE or x32.
 
 #[inline]
 fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
@@ -751,5 +774,5 @@ fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
 // ensure that the code generation related to these panics is minimal as there's
 // only one location which panics rather than a bunch throughout the module.
 fn capacity_overflow() -> ! {
-    panic!("capacity overflow")
+    panic!("capacity overflow");
 }
diff --git a/src/liballoc/raw_vec/tests.rs b/src/liballoc/raw_vec/tests.rs
index c389898d1ef04..d35b62fc1ef15 100644
--- a/src/liballoc/raw_vec/tests.rs
+++ b/src/liballoc/raw_vec/tests.rs
@@ -5,12 +5,12 @@ fn allocator_param() {
     use crate::alloc::AllocErr;
 
     // Writing a test of integration between third-party
-    // allocators and RawVec is a little tricky because the RawVec
+    // allocators and `RawVec` is a little tricky because the `RawVec`
     // API does not expose fallible allocation methods, so we
     // cannot check what happens when allocator is exhausted
     // (beyond detecting a panic).
     //
-    // Instead, this just checks that the RawVec methods do at
+    // Instead, this just checks that the `RawVec` methods do at
     // least go through the Allocator API when it reserves
     // storage.
 
@@ -44,7 +44,7 @@ fn allocator_param() {
 fn reserve_does_not_overallocate() {
     {
         let mut v: RawVec<u32> = RawVec::new();
-        // First `reserve` allocates like `reserve_exact`
+        // First, `reserve` allocates like `reserve_exact`.
         v.reserve(0, 9);
         assert_eq!(9, v.capacity());
     }
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 2b222caf13f3d..f234ac5ebe51b 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -567,7 +567,7 @@ impl<T: ?Sized> Rc<T> {
     ///     let x = Rc::from_raw(x_ptr);
     ///     assert_eq!(&*x, "hello");
     ///
-    ///     // Further calls to `Rc::from_raw(x_ptr)` would be memory unsafe.
+    ///     // Further calls to `Rc::from_raw(x_ptr)` would be memory-unsafe.
     /// }
     ///
     /// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
@@ -1832,8 +1832,9 @@ impl<T: ?Sized> Weak<T> {
         }
     }
 
-    /// Returns `true` if the two `Weak`s point to the same value (not just values
-    /// that compare as equal).
+    /// Returns `true` if the two `Weak`s point to the same value (not just
+    /// values that compare as equal), or if both don't point to any value
+    /// (because they were created with `Weak::new()`).
     ///
     /// # Notes
     ///
@@ -1843,7 +1844,6 @@ impl<T: ?Sized> Weak<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::rc::Rc;
     ///
     /// let first_rc = Rc::new(5);
@@ -1861,7 +1861,6 @@ impl<T: ?Sized> Weak<T> {
     /// Comparing `Weak::new`.
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::rc::{Rc, Weak};
     ///
     /// let first = Weak::new();
@@ -1873,7 +1872,7 @@ impl<T: ?Sized> Weak<T> {
     /// assert!(!first.ptr_eq(&third));
     /// ```
     #[inline]
-    #[unstable(feature = "weak_ptr_eq", issue = "55981")]
+    #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
         self.ptr.as_ptr() == other.ptr.as_ptr()
     }
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index b65f191836e9d..1166e7b5df295 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -369,7 +369,7 @@ impl String {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_string_new")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_string_new"))]
     pub const fn new() -> String {
         String { vec: Vec::new() }
     }
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 9ffc1673e5ab8..45f98162e4cd5 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -547,7 +547,7 @@ impl<T: ?Sized> Arc<T> {
     ///     let x = Arc::from_raw(x_ptr);
     ///     assert_eq!(&*x, "hello");
     ///
-    ///     // Further calls to `Arc::from_raw(x_ptr)` would be memory unsafe.
+    ///     // Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
     /// }
     ///
     /// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
@@ -1550,19 +1550,18 @@ impl<T: ?Sized> Weak<T> {
         }
     }
 
-    /// Returns `true` if the two `Weak`s point to the same value (not just values
-    /// that compare as equal).
+    /// Returns `true` if the two `Weak`s point to the same value (not just
+    /// values that compare as equal), or if both don't point to any value
+    /// (because they were created with `Weak::new()`).
     ///
     /// # Notes
     ///
     /// Since this compares pointers it means that `Weak::new()` will equal each
     /// other, even though they don't point to any value.
     ///
-    ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::sync::Arc;
     ///
     /// let first_rc = Arc::new(5);
@@ -1580,7 +1579,6 @@ impl<T: ?Sized> Weak<T> {
     /// Comparing `Weak::new`.
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::sync::{Arc, Weak};
     ///
     /// let first = Weak::new();
@@ -1592,7 +1590,7 @@ impl<T: ?Sized> Weak<T> {
     /// assert!(!first.ptr_eq(&third));
     /// ```
     #[inline]
-    #[unstable(feature = "weak_ptr_eq", issue = "55981")]
+    #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
         self.ptr.as_ptr() == other.ptr.as_ptr()
     }
diff --git a/src/liballoc/tests/btree/set.rs b/src/liballoc/tests/btree/set.rs
index 62ccb53fcea18..35db18c39c83a 100644
--- a/src/liballoc/tests/btree/set.rs
+++ b/src/liballoc/tests/btree/set.rs
@@ -90,6 +90,17 @@ fn test_intersection() {
                        &[1, 3, 11, 77, 103]);
 }
 
+#[test]
+fn test_intersection_size_hint() {
+    let x: BTreeSet<i32> = [3, 4].iter().copied().collect();
+    let y: BTreeSet<i32> = [1, 2, 3].iter().copied().collect();
+    let mut iter = x.intersection(&y);
+    assert_eq!(iter.size_hint(), (0, Some(2)));
+    assert_eq!(iter.next(), Some(&3));
+    assert_eq!(iter.size_hint(), (0, Some(0)));
+    assert_eq!(iter.next(), None);
+}
+
 #[test]
 fn test_difference() {
     fn check_difference(a: &[i32], b: &[i32], expected: &[i32]) {
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index d5dc2d4b8688d..405969a550b88 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -314,10 +314,10 @@ impl<T> Vec<T> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_vec_new")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_vec_new"))]
     pub const fn new() -> Vec<T> {
         Vec {
-            buf: RawVec::new(),
+            buf: RawVec::NEW,
             len: 0,
         }
     }
@@ -685,21 +685,25 @@ impl<T> Vec<T> {
     /// [`drain`]: #method.drain
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn truncate(&mut self, len: usize) {
-        let current_len = self.len;
-        unsafe {
-            let mut ptr = self.as_mut_ptr().add(self.len);
-            // Set the final length at the end, keeping in mind that
-            // dropping an element might panic. Works around a missed
-            // optimization, as seen in the following issue:
-            // https://github.com/rust-lang/rust/issues/51802
-            let mut local_len = SetLenOnDrop::new(&mut self.len);
+        if mem::needs_drop::<T>() {
+            let current_len = self.len;
+            unsafe {
+                let mut ptr = self.as_mut_ptr().add(self.len);
+                // Set the final length at the end, keeping in mind that
+                // dropping an element might panic. Works around a missed
+                // optimization, as seen in the following issue:
+                // https://github.com/rust-lang/rust/issues/51802
+                let mut local_len = SetLenOnDrop::new(&mut self.len);
 
-            // drop any extra elements
-            for _ in len..current_len {
-                local_len.decrement_len(1);
-                ptr = ptr.offset(-1);
-                ptr::drop_in_place(ptr);
+                // drop any extra elements
+                for _ in len..current_len {
+                    local_len.decrement_len(1);
+                    ptr = ptr.offset(-1);
+                    ptr::drop_in_place(ptr);
+                }
             }
+        } else if len <= self.len {
+            self.len = len;
         }
     }
 
diff --git a/src/libcore/any.rs b/src/libcore/any.rs
index e8a0a88f12a7e..0afbf4f134679 100644
--- a/src/libcore/any.rs
+++ b/src/libcore/any.rs
@@ -153,13 +153,13 @@ impl dyn Any {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is<T: Any>(&self) -> bool {
-        // Get TypeId of the type this function is instantiated with
+        // Get `TypeId` of the type this function is instantiated with.
         let t = TypeId::of::<T>();
 
-        // Get TypeId of the type in the trait object
+        // Get `TypeId` of the type in the trait object.
         let concrete = self.type_id();
 
-        // Compare both TypeIds on equality
+        // Compare both `TypeId`s on equality.
         t == concrete
     }
 
diff --git a/src/libcore/bool.rs b/src/libcore/bool.rs
new file mode 100644
index 0000000000000..32ec26975e375
--- /dev/null
+++ b/src/libcore/bool.rs
@@ -0,0 +1,45 @@
+//! impl bool {}
+
+#[cfg(not(boostrap_stdarch_ignore_this))]
+#[lang = "bool"]
+impl bool {
+    /// Returns `Some(t)` if the `bool` is `true`, or `None` otherwise.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(bool_to_option)]
+    ///
+    /// assert_eq!(false.then(0), None);
+    /// assert_eq!(true.then(0), Some(0));
+    /// ```
+    #[unstable(feature = "bool_to_option", issue = "64260")]
+    #[inline]
+    pub fn then<T>(self, t: T) -> Option<T> {
+        if self {
+            Some(t)
+        } else {
+            None
+        }
+    }
+
+    /// Returns `Some(f())` if the `bool` is `true`, or `None` otherwise.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(bool_to_option)]
+    ///
+    /// assert_eq!(false.then_with(|| 0), None);
+    /// assert_eq!(true.then_with(|| 0), Some(0));
+    /// ```
+    #[unstable(feature = "bool_to_option", issue = "64260")]
+    #[inline]
+    pub fn then_with<T, F: FnOnce() -> T>(self, f: F) -> Option<T> {
+        if self {
+            Some(f())
+        } else {
+            None
+        }
+    }
+}
diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs
index 402a7b2c95a46..06f2b7bab12eb 100644
--- a/src/libcore/convert.rs
+++ b/src/libcore/convert.rs
@@ -42,11 +42,11 @@
 
 use crate::fmt;
 
-/// An identity function.
+/// The identity function.
 ///
 /// Two things are important to note about this function:
 ///
-/// - It is not always equivalent to a closure like `|x| x` since the
+/// - It is not always equivalent to a closure like `|x| x`, since the
 ///   closure may coerce `x` into a different type.
 ///
 /// - It moves the input `x` passed to the function.
@@ -56,31 +56,32 @@ use crate::fmt;
 ///
 /// # Examples
 ///
-/// Using `identity` to do nothing among other interesting functions:
+/// Using `identity` to do nothing in a sequence of other, interesting,
+/// functions:
 ///
 /// ```rust
 /// use std::convert::identity;
 ///
 /// fn manipulation(x: u32) -> u32 {
-///     // Let's assume that this function does something interesting.
+///     // Let's pretend that adding one is an interesting function.
 ///     x + 1
 /// }
 ///
 /// let _arr = &[identity, manipulation];
 /// ```
 ///
-/// Using `identity` to get a function that changes nothing in a conditional:
+/// Using `identity` as a "do nothing" base case in a conditional:
 ///
 /// ```rust
 /// use std::convert::identity;
 ///
 /// # let condition = true;
-///
+/// #
 /// # fn manipulation(x: u32) -> u32 { x + 1 }
-///
+/// #
 /// let do_stuff = if condition { manipulation } else { identity };
 ///
-/// // do more interesting stuff..
+/// // Do more interesting stuff...
 ///
 /// let _results = do_stuff(42);
 /// ```
diff --git a/src/libcore/hint.rs b/src/libcore/hint.rs
index 6439fa0e0c8b8..ee4be6c915119 100644
--- a/src/libcore/hint.rs
+++ b/src/libcore/hint.rs
@@ -49,28 +49,16 @@ pub unsafe fn unreachable_unchecked() -> ! {
     intrinsics::unreachable()
 }
 
-/// Signals the processor that it is entering a busy-wait spin-loop.
+/// Emits a machine instruction hinting to the processor that it is running in busy-wait
+/// spin-loop ("spin lock").
 ///
-/// Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving
-/// power or switching hyper-threads.
-///
-/// This function is different than [`std::thread::yield_now`] which directly yields to the
-/// system's scheduler, whereas `spin_loop` only signals the processor that it is entering a
-/// busy-wait spin-loop without yielding control to the system's scheduler.
-///
-/// Using a busy-wait spin-loop with `spin_loop` is ideally used in situations where a
-/// contended lock is held by another thread executed on a different CPU and where the waiting
-/// times are relatively small. Because entering busy-wait spin-loop does not trigger the system's
-/// scheduler, no overhead for switching threads occurs. However, if the thread holding the
-/// contended lock is running on the same CPU, the spin-loop is likely to occupy an entire CPU slice
-/// before switching to the thread that holds the lock. If the contending lock is held by a thread
-/// on the same CPU or if the waiting times for acquiring the lock are longer, it is often better to
-/// use [`std::thread::yield_now`].
+/// For a discussion of different locking strategies and their trade-offs, see
+/// [`core::sync::atomic::spin_loop_hint`].
 ///
 /// **Note**: On platforms that do not support receiving spin-loop hints this function does not
 /// do anything at all.
 ///
-/// [`std::thread::yield_now`]: ../../std/thread/fn.yield_now.html
+/// [`core::sync::atomic::spin_loop_hint`]: ../sync/atomic/fn.spin_loop_hint.html
 #[inline]
 #[unstable(feature = "renamed_spin_loop", issue = "55002")]
 pub fn spin_loop() {
diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index d145f2212f93a..ecff40a75978d 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -845,21 +845,26 @@ extern "rust-intrinsic" {
     ///
     /// ```
     /// let store = [0, 1, 2, 3];
-    /// let mut v_orig = store.iter().collect::<Vec<&i32>>();
+    /// let v_orig = store.iter().collect::<Vec<&i32>>();
+    ///
+    /// // clone the vector as we will reuse them later
+    /// let v_clone = v_orig.clone();
     ///
     /// // Using transmute: this is Undefined Behavior, and a bad idea.
     /// // However, it is no-copy.
     /// let v_transmuted = unsafe {
-    ///     std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(
-    ///         v_orig.clone())
+    ///     std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(v_clone)
     /// };
     ///
+    /// let v_clone = v_orig.clone();
+    ///
     /// // This is the suggested, safe way.
     /// // It does copy the entire vector, though, into a new array.
-    /// let v_collected = v_orig.clone()
-    ///                         .into_iter()
-    ///                         .map(|r| Some(r))
-    ///                         .collect::<Vec<Option<&i32>>>();
+    /// let v_collected = v_clone.into_iter()
+    ///                          .map(Some)
+    ///                          .collect::<Vec<Option<&i32>>>();
+    ///
+    /// let v_clone = v_orig.clone();
     ///
     /// // The no-copy, unsafe way, still using transmute, but not UB.
     /// // This is equivalent to the original, but safer, and reuses the
@@ -869,11 +874,12 @@ extern "rust-intrinsic" {
     /// // the original inner type (`&i32`) to the converted inner type
     /// // (`Option<&i32>`), so read the nomicon pages linked above.
     /// let v_from_raw = unsafe {
-    ///     Vec::from_raw_parts(v_orig.as_mut_ptr() as *mut Option<&i32>,
-    ///                         v_orig.len(),
-    ///                         v_orig.capacity())
+    ///     // Ensure the original vector is not dropped.
+    ///     let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
+    ///     Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,
+    ///                         v_clone.len(),
+    ///                         v_clone.capacity())
     /// };
-    /// std::mem::forget(v_orig);
     /// ```
     ///
     /// Implementing `split_at_mut`:
diff --git a/src/libcore/iter/adapters/mod.rs b/src/libcore/iter/adapters/mod.rs
index 8e1ac6082c8a8..3b8edc2ad6177 100644
--- a/src/libcore/iter/adapters/mod.rs
+++ b/src/libcore/iter/adapters/mod.rs
@@ -5,7 +5,7 @@ use crate::usize;
 use crate::intrinsics;
 
 use super::{Iterator, DoubleEndedIterator, ExactSizeIterator, FusedIterator, TrustedLen};
-use super::LoopState;
+use super::{LoopState, from_fn};
 
 mod chain;
 mod flatten;
@@ -534,6 +534,26 @@ impl<I> Iterator for StepBy<I> where I: Iterator {
             self.iter.nth(nth - 1);
         }
     }
+
+    fn try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
+    where
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Ok = Acc>,
+    {
+        #[inline]
+        fn nth<I: Iterator>(iter: &mut I, step: usize) -> impl FnMut() -> Option<I::Item> + '_ {
+            move || iter.nth(step)
+        }
+
+        if self.first_take {
+            self.first_take = false;
+            match self.iter.next() {
+                None => return Try::from_ok(acc),
+                Some(x) => acc = f(acc, x)?,
+            }
+        }
+        from_fn(nth(&mut self.iter, self.step)).try_fold(acc, f)
+    }
 }
 
 impl<I> StepBy<I> where I: ExactSizeIterator {
@@ -567,6 +587,28 @@ impl<I> DoubleEndedIterator for StepBy<I> where I: DoubleEndedIterator + ExactSi
             .saturating_add(self.next_back_index());
         self.iter.nth_back(n)
     }
+
+    fn try_rfold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
+    where
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Ok = Acc>,
+    {
+        #[inline]
+        fn nth_back<I: DoubleEndedIterator>(
+            iter: &mut I,
+            step: usize,
+        ) -> impl FnMut() -> Option<I::Item> + '_ {
+            move || iter.nth_back(step)
+        }
+
+        match self.next_back() {
+            None => Try::from_ok(init),
+            Some(x) => {
+                let acc = f(init, x)?;
+                from_fn(nth_back(&mut self.iter, self.step)).try_fold(acc, f)
+            }
+        }
+    }
 }
 
 // StepBy can only make the iterator shorter, so the len will still fit.
diff --git a/src/libcore/iter/traits/iterator.rs b/src/libcore/iter/traits/iterator.rs
index d644787d2c462..c09df3f7f22cb 100644
--- a/src/libcore/iter/traits/iterator.rs
+++ b/src/libcore/iter/traits/iterator.rs
@@ -2546,11 +2546,51 @@ pub trait Iterator {
 
     /// Lexicographically compares the elements of this `Iterator` with those
     /// of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::cmp::Ordering;
+    ///
+    /// assert_eq!([1].iter().cmp([1].iter()), Ordering::Equal);
+    /// assert_eq!([1].iter().cmp([1, 2].iter()), Ordering::Less);
+    /// assert_eq!([1, 2].iter().cmp([1].iter()), Ordering::Greater);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
-    fn cmp<I>(mut self, other: I) -> Ordering where
+    fn cmp<I>(self, other: I) -> Ordering
+    where
         I: IntoIterator<Item = Self::Item>,
         Self::Item: Ord,
         Self: Sized,
+    {
+        self.cmp_by(other, |x, y| x.cmp(&y))
+    }
+
+    /// Lexicographically compares the elements of this `Iterator` with those
+    /// of another with respect to the specified comparison function.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(iter_order_by)]
+    ///
+    /// use std::cmp::Ordering;
+    ///
+    /// let xs = [1, 2, 3, 4];
+    /// let ys = [1, 4, 9, 16];
+    ///
+    /// assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| x.cmp(&y)), Ordering::Less);
+    /// assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| (x * x).cmp(&y)), Ordering::Equal);
+    /// assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| (2 * x).cmp(&y)), Ordering::Greater);
+    /// ```
+    #[unstable(feature = "iter_order_by", issue = "0")]
+    fn cmp_by<I, F>(mut self, other: I, mut cmp: F) -> Ordering
+    where
+        Self: Sized,
+        I: IntoIterator,
+        F: FnMut(Self::Item, I::Item) -> Ordering,
     {
         let mut other = other.into_iter();
 
@@ -2569,7 +2609,7 @@ pub trait Iterator {
                 Some(val) => val,
             };
 
-            match x.cmp(&y) {
+            match cmp(x, y) {
                 Ordering::Equal => (),
                 non_eq => return non_eq,
             }
@@ -2578,11 +2618,62 @@ pub trait Iterator {
 
     /// Lexicographically compares the elements of this `Iterator` with those
     /// of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::cmp::Ordering;
+    ///
+    /// assert_eq!([1.].iter().partial_cmp([1.].iter()), Some(Ordering::Equal));
+    /// assert_eq!([1.].iter().partial_cmp([1., 2.].iter()), Some(Ordering::Less));
+    /// assert_eq!([1., 2.].iter().partial_cmp([1.].iter()), Some(Ordering::Greater));
+    ///
+    /// assert_eq!([std::f64::NAN].iter().partial_cmp([1.].iter()), None);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
-    fn partial_cmp<I>(mut self, other: I) -> Option<Ordering> where
+    fn partial_cmp<I>(self, other: I) -> Option<Ordering>
+    where
         I: IntoIterator,
         Self::Item: PartialOrd<I::Item>,
         Self: Sized,
+    {
+        self.partial_cmp_by(other, |x, y| x.partial_cmp(&y))
+    }
+
+    /// Lexicographically compares the elements of this `Iterator` with those
+    /// of another with respect to the specified comparison function.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(iter_order_by)]
+    ///
+    /// use std::cmp::Ordering;
+    ///
+    /// let xs = [1.0, 2.0, 3.0, 4.0];
+    /// let ys = [1.0, 4.0, 9.0, 16.0];
+    ///
+    /// assert_eq!(
+    ///     xs.iter().partial_cmp_by(&ys, |&x, &y| x.partial_cmp(&y)),
+    ///     Some(Ordering::Less)
+    /// );
+    /// assert_eq!(
+    ///     xs.iter().partial_cmp_by(&ys, |&x, &y| (x * x).partial_cmp(&y)),
+    ///     Some(Ordering::Equal)
+    /// );
+    /// assert_eq!(
+    ///     xs.iter().partial_cmp_by(&ys, |&x, &y| (2.0 * x).partial_cmp(&y)),
+    ///     Some(Ordering::Greater)
+    /// );
+    /// ```
+    #[unstable(feature = "iter_order_by", issue = "0")]
+    fn partial_cmp_by<I, F>(mut self, other: I, mut partial_cmp: F) -> Option<Ordering>
+    where
+        Self: Sized,
+        I: IntoIterator,
+        F: FnMut(Self::Item, I::Item) -> Option<Ordering>,
     {
         let mut other = other.into_iter();
 
@@ -2601,7 +2692,7 @@ pub trait Iterator {
                 Some(val) => val,
             };
 
-            match x.partial_cmp(&y) {
+            match partial_cmp(x, y) {
                 Some(Ordering::Equal) => (),
                 non_eq => return non_eq,
             }
@@ -2610,11 +2701,44 @@ pub trait Iterator {
 
     /// Determines if the elements of this `Iterator` are equal to those of
     /// another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().eq([1].iter()), true);
+    /// assert_eq!([1].iter().eq([1, 2].iter()), false);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
-    fn eq<I>(mut self, other: I) -> bool where
+    fn eq<I>(self, other: I) -> bool
+    where
         I: IntoIterator,
         Self::Item: PartialEq<I::Item>,
         Self: Sized,
+    {
+        self.eq_by(other, |x, y| x == y)
+    }
+
+    /// Determines if the elements of this `Iterator` are equal to those of
+    /// another with respect to the specified equality function.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(iter_order_by)]
+    ///
+    /// let xs = [1, 2, 3, 4];
+    /// let ys = [1, 4, 9, 16];
+    ///
+    /// assert!(xs.iter().eq_by(&ys, |&x, &y| x * x == y));
+    /// ```
+    #[unstable(feature = "iter_order_by", issue = "0")]
+    fn eq_by<I, F>(mut self, other: I, mut eq: F) -> bool
+    where
+        Self: Sized,
+        I: IntoIterator,
+        F: FnMut(Self::Item, I::Item) -> bool,
     {
         let mut other = other.into_iter();
 
@@ -2629,12 +2753,21 @@ pub trait Iterator {
                 Some(val) => val,
             };
 
-            if x != y { return false }
+            if !eq(x, y) {
+                return false;
+            }
         }
     }
 
     /// Determines if the elements of this `Iterator` are unequal to those of
     /// another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().ne([1].iter()), false);
+    /// assert_eq!([1].iter().ne([1, 2].iter()), true);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn ne<I>(self, other: I) -> bool where
         I: IntoIterator,
@@ -2646,6 +2779,14 @@ pub trait Iterator {
 
     /// Determines if the elements of this `Iterator` are lexicographically
     /// less than those of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().lt([1].iter()), false);
+    /// assert_eq!([1].iter().lt([1, 2].iter()), true);
+    /// assert_eq!([1, 2].iter().lt([1].iter()), false);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn lt<I>(self, other: I) -> bool where
         I: IntoIterator,
@@ -2657,6 +2798,14 @@ pub trait Iterator {
 
     /// Determines if the elements of this `Iterator` are lexicographically
     /// less or equal to those of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().le([1].iter()), true);
+    /// assert_eq!([1].iter().le([1, 2].iter()), true);
+    /// assert_eq!([1, 2].iter().le([1].iter()), false);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn le<I>(self, other: I) -> bool where
         I: IntoIterator,
@@ -2671,6 +2820,14 @@ pub trait Iterator {
 
     /// Determines if the elements of this `Iterator` are lexicographically
     /// greater than those of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().gt([1].iter()), false);
+    /// assert_eq!([1].iter().gt([1, 2].iter()), false);
+    /// assert_eq!([1, 2].iter().gt([1].iter()), true);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn gt<I>(self, other: I) -> bool where
         I: IntoIterator,
@@ -2682,6 +2839,14 @@ pub trait Iterator {
 
     /// Determines if the elements of this `Iterator` are lexicographically
     /// greater than or equal to those of another.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert_eq!([1].iter().ge([1].iter()), true);
+    /// assert_eq!([1].iter().ge([1, 2].iter()), false);
+    /// assert_eq!([1, 2].iter().ge([1].iter()), true);
+    /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn ge<I>(self, other: I) -> bool where
         I: IntoIterator,
@@ -2730,6 +2895,18 @@ pub trait Iterator {
     /// function to determine the ordering of two elements. Apart from that, it's equivalent to
     /// [`is_sorted`]; see its documentation for more information.
     ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_sorted)]
+    ///
+    /// assert!([1, 2, 2, 9].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// assert!(![1, 3, 2, 4].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// assert!([0].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// assert!(std::iter::empty::<i32>().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// ```
+    ///
     /// [`is_sorted`]: trait.Iterator.html#method.is_sorted
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     fn is_sorted_by<F>(mut self, mut compare: F) -> bool
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index c168d5c8a2eac..a2cc585fc51fd 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -87,7 +87,7 @@
 #![feature(link_llvm_intrinsics)]
 #![feature(never_type)]
 #![feature(nll)]
-#![feature(bind_by_move_pattern_guards)]
+#![cfg_attr(boostrap_stdarch_ignore_this, feature(bind_by_move_pattern_guards))]
 #![feature(exhaustive_patterns)]
 #![feature(no_core)]
 #![feature(on_unimplemented)]
@@ -227,6 +227,7 @@ pub mod task;
 pub mod alloc;
 
 // note: does not need to be public
+mod bool;
 mod tuple;
 mod unit;
 
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index ffaca029a8a78..384bc87499887 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -1236,8 +1236,10 @@ pub(crate) mod builtin {
     pub macro test($item:item) { /* compiler built-in */ }
 
     /// Attribute macro applied to a function to turn it into a benchmark test.
-    #[unstable(feature = "test", issue = "50297",
-               reason = "`bench` is a part of custom test frameworks which are unstable")]
+    #[cfg_attr(not(boostrap_stdarch_ignore_this), unstable(soft, feature = "test", issue = "50297",
+               reason = "`bench` is a part of custom test frameworks which are unstable"))]
+    #[cfg_attr(boostrap_stdarch_ignore_this, unstable(feature = "test", issue = "50297",
+               reason = "`bench` is a part of custom test frameworks which are unstable"))]
     #[allow_internal_unstable(test, rustc_attrs)]
     #[rustc_builtin_macro]
     pub macro bench($item:item) { /* compiler built-in */ }
diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 89af2528c052a..347e7dce6e67d 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -602,10 +602,10 @@ unsafe impl<T: ?Sized> Freeze for *mut T {}
 unsafe impl<T: ?Sized> Freeze for &T {}
 unsafe impl<T: ?Sized> Freeze for &mut T {}
 
-/// Types which can be safely moved after being pinned.
+/// Types that can be safely moved after being pinned.
 ///
 /// Since Rust itself has no notion of immovable types, and considers moves
-/// (e.g. through assignment or [`mem::replace`]) to always be safe,
+/// (e.g., through assignment or [`mem::replace`]) to always be safe,
 /// this trait cannot prevent types from moving by itself.
 ///
 /// Instead it is used to prevent moves through the type system,
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index b46e06f8d8ada..0cf2ebb487ddd 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1401,12 +1401,8 @@ $EndFeature, "
 ```"),
             #[stable(feature = "no_panic_abs", since = "1.13.0")]
             #[inline]
-            pub fn wrapping_abs(self) -> Self {
-                if self.is_negative() {
-                    self.wrapping_neg()
-                } else {
-                    self
-                }
+            pub const fn wrapping_abs(self) -> Self {
+                (self ^ (self >> ($BITS - 1))).wrapping_sub(self >> ($BITS - 1))
             }
         }
 
@@ -1764,12 +1760,8 @@ $EndFeature, "
 ```"),
             #[stable(feature = "no_panic_abs", since = "1.13.0")]
             #[inline]
-            pub fn overflowing_abs(self) -> (Self, bool) {
-                if self.is_negative() {
-                    self.overflowing_neg()
-                } else {
-                    (self, false)
-                }
+            pub const fn overflowing_abs(self) -> (Self, bool) {
+                (self ^ (self >> ($BITS - 1))).overflowing_sub(self >> ($BITS - 1))
             }
         }
 
@@ -1973,15 +1965,11 @@ $EndFeature, "
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
             #[rustc_inherit_overflow_checks]
-            pub fn abs(self) -> Self {
-                if self.is_negative() {
-                    // Note that the #[inline] above means that the overflow
-                    // semantics of this negation depend on the crate we're being
-                    // inlined into.
-                    -self
-                } else {
-                    self
-                }
+            pub const fn abs(self) -> Self {
+                // Note that the #[inline] above means that the overflow
+                // semantics of the subtraction depend on the crate we're being
+                // inlined into.
+                (self ^ (self >> ($BITS - 1))) - (self >> ($BITS - 1))
             }
         }
 
@@ -2104,11 +2092,14 @@ $to_xe_bytes_doc,
 
 ```
 let bytes = ", $swap_op, stringify!($SelfT), ".to_ne_bytes();
-assert_eq!(bytes, if cfg!(target_endian = \"big\") {
+assert_eq!(
+    bytes,
+    if cfg!(target_endian = \"big\") {
         ", $be_bytes, "
     } else {
         ", $le_bytes, "
-    });
+    }
+);
 ```"),
             #[stable(feature = "int_to_from_bytes", since = "1.32.0")]
             #[rustc_const_unstable(feature = "const_int_conversion")]
@@ -2200,10 +2191,10 @@ $from_xe_bytes_doc,
 
 ```
 let value = ", stringify!($SelfT), "::from_ne_bytes(if cfg!(target_endian = \"big\") {
-        ", $be_bytes, "
-    } else {
-        ", $le_bytes, "
-    });
+    ", $be_bytes, "
+} else {
+    ", $le_bytes, "
+});
 assert_eq!(value, ", $swap_op, ");
 ```
 
@@ -3923,11 +3914,14 @@ $to_xe_bytes_doc,
 
 ```
 let bytes = ", $swap_op, stringify!($SelfT), ".to_ne_bytes();
-assert_eq!(bytes, if cfg!(target_endian = \"big\") {
+assert_eq!(
+    bytes,
+    if cfg!(target_endian = \"big\") {
         ", $be_bytes, "
     } else {
         ", $le_bytes, "
-    });
+    }
+);
 ```"),
             #[stable(feature = "int_to_from_bytes", since = "1.32.0")]
             #[rustc_const_unstable(feature = "const_int_conversion")]
@@ -4019,10 +4013,10 @@ $from_xe_bytes_doc,
 
 ```
 let value = ", stringify!($SelfT), "::from_ne_bytes(if cfg!(target_endian = \"big\") {
-        ", $be_bytes, "
-    } else {
-        ", $le_bytes, "
-    });
+    ", $be_bytes, "
+} else {
+    ", $le_bytes, "
+});
 assert_eq!(value, ", $swap_op, ");
 ```
 
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 259ed36c57885..5569d99f8d81d 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -295,7 +295,7 @@ impl<T> Option<T> {
     /// [`Pin`]: ../pin/struct.Pin.html
     #[inline]
     #[stable(feature = "pin", since = "1.33.0")]
-    pub fn as_pin_ref<'a>(self: Pin<&'a Option<T>>) -> Option<Pin<&'a T>> {
+    pub fn as_pin_ref(self: Pin<&Self>) -> Option<Pin<&T>> {
         unsafe {
             Pin::get_ref(self).as_ref().map(|x| Pin::new_unchecked(x))
         }
@@ -306,7 +306,7 @@ impl<T> Option<T> {
     /// [`Pin`]: ../pin/struct.Pin.html
     #[inline]
     #[stable(feature = "pin", since = "1.33.0")]
-    pub fn as_pin_mut<'a>(self: Pin<&'a mut Option<T>>) -> Option<Pin<&'a mut T>> {
+    pub fn as_pin_mut(self: Pin<&mut Self>) -> Option<Pin<&mut T>> {
         unsafe {
             Pin::get_unchecked_mut(self).as_mut().map(|x| Pin::new_unchecked(x))
         }
@@ -1110,6 +1110,18 @@ impl<T: Deref> Option<T> {
     /// to the original one, additionally coercing the contents via [`Deref`].
     ///
     /// [`Deref`]: ../../std/ops/trait.Deref.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(inner_deref)]
+    ///
+    /// let x: Option<String> = Some("hey".to_owned());
+    /// assert_eq!(x.as_deref(), Some("hey"));
+    ///
+    /// let x: Option<String> = None;
+    /// assert_eq!(x.as_deref(), None);
+    /// ```
     pub fn as_deref(&self) -> Option<&T::Target> {
         self.as_ref().map(|t| t.deref())
     }
@@ -1121,6 +1133,18 @@ impl<T: DerefMut> Option<T> {
     ///
     /// Leaves the original `Option` in-place, creating a new one containing a mutable reference to
     /// the inner type's `Deref::Target` type.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(inner_deref)]
+    ///
+    /// let mut x: Option<String> = Some("hey".to_owned());
+    /// assert_eq!(x.as_deref_mut().map(|x| {
+    ///     x.make_ascii_uppercase();
+    ///     x
+    /// }), Some("HEY".to_owned().as_mut_str()));
+    /// ```
     pub fn as_deref_mut(&mut self) -> Option<&mut T::Target> {
         self.as_mut().map(|t| t.deref_mut())
     }
@@ -1199,6 +1223,13 @@ impl<T: Clone> Clone for Option<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Default for Option<T> {
     /// Returns [`None`][Option::None].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let opt: Option<u32> = Option::default();
+    /// assert!(opt.is_none());
+    /// ```
     #[inline]
     fn default() -> Option<T> { None }
 }
diff --git a/src/libcore/pin.rs b/src/libcore/pin.rs
index 1080fd32a8862..1dc6d54b08a5a 100644
--- a/src/libcore/pin.rs
+++ b/src/libcore/pin.rs
@@ -233,7 +233,7 @@
 //! # type Field = i32;
 //! # struct Struct { field: Field }
 //! impl Struct {
-//!     fn pin_get_field<'a>(self: Pin<&'a mut Self>) -> &'a mut Field {
+//!     fn pin_get_field(self: Pin<&mut Self>) -> &mut Field {
 //!         // This is okay because `field` is never considered pinned.
 //!         unsafe { &mut self.get_unchecked_mut().field }
 //!     }
@@ -257,7 +257,7 @@
 //! # type Field = i32;
 //! # struct Struct { field: Field }
 //! impl Struct {
-//!     fn pin_get_field<'a>(self: Pin<&'a mut Self>) -> Pin<&'a mut Field> {
+//!     fn pin_get_field(self: Pin<&mut Self>) -> Pin<&mut Field> {
 //!         // This is okay because `field` is pinned when `self` is.
 //!         unsafe { self.map_unchecked_mut(|s| &mut s.field) }
 //!     }
@@ -549,7 +549,7 @@ impl<P: Deref> Pin<P> {
     /// ruled out by the contract of `Pin::new_unchecked`.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn as_ref(self: &Pin<P>) -> Pin<&P::Target> {
+    pub fn as_ref(&self) -> Pin<&P::Target> {
         unsafe { Pin::new_unchecked(&*self.pointer) }
     }
 
@@ -584,9 +584,30 @@ impl<P: DerefMut> Pin<P> {
     /// the pointee cannot move after `Pin<Pointer<T>>` got created.
     /// "Malicious" implementations of `Pointer::DerefMut` are likewise
     /// ruled out by the contract of `Pin::new_unchecked`.
+    ///
+    /// This method is useful when doing multiple calls to functions that consume the pinned type.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::pin::Pin;
+    ///
+    /// # struct Type {}
+    /// impl Type {
+    ///     fn method(self: Pin<&mut Self>) {
+    ///         // do something
+    ///     }
+    ///
+    ///     fn call_method_twice(mut self: Pin<&mut Self>) {
+    ///         // `method` consumes `self`, so reborrow the `Pin<&mut Self>` via `as_mut`.
+    ///         self.as_mut().method();
+    ///         self.as_mut().method();
+    ///     }
+    /// }
+    /// ```
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn as_mut(self: &mut Pin<P>) -> Pin<&mut P::Target> {
+    pub fn as_mut(&mut self) -> Pin<&mut P::Target> {
         unsafe { Pin::new_unchecked(&mut *self.pointer) }
     }
 
@@ -596,7 +617,7 @@ impl<P: DerefMut> Pin<P> {
     /// run before being overwritten, so no pinning guarantee is violated.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn set(self: &mut Pin<P>, value: P::Target)
+    pub fn set(&mut self, value: P::Target)
     where
         P::Target: Sized,
     {
@@ -621,7 +642,7 @@ impl<'a, T: ?Sized> Pin<&'a T> {
     ///
     /// [`pin` module]: ../../std/pin/index.html#projections-and-structural-pinning
     #[stable(feature = "pin", since = "1.33.0")]
-    pub unsafe fn map_unchecked<U, F>(self: Pin<&'a T>, func: F) -> Pin<&'a U> where
+    pub unsafe fn map_unchecked<U, F>(self, func: F) -> Pin<&'a U> where
         F: FnOnce(&T) -> &U,
     {
         let pointer = &*self.pointer;
@@ -648,7 +669,7 @@ impl<'a, T: ?Sized> Pin<&'a T> {
     /// ["pinning projections"]: ../../std/pin/index.html#projections-and-structural-pinning
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn get_ref(self: Pin<&'a T>) -> &'a T {
+    pub fn get_ref(self) -> &'a T {
         self.pointer
     }
 }
@@ -657,7 +678,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
     /// Converts this `Pin<&mut T>` into a `Pin<&T>` with the same lifetime.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn into_ref(self: Pin<&'a mut T>) -> Pin<&'a T> {
+    pub fn into_ref(self) -> Pin<&'a T> {
         Pin { pointer: self.pointer }
     }
 
@@ -672,7 +693,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
     /// with the same lifetime as the original `Pin`.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn get_mut(self: Pin<&'a mut T>) -> &'a mut T
+    pub fn get_mut(self) -> &'a mut T
         where T: Unpin,
     {
         self.pointer
@@ -690,7 +711,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
     /// instead.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub unsafe fn get_unchecked_mut(self: Pin<&'a mut T>) -> &'a mut T {
+    pub unsafe fn get_unchecked_mut(self) -> &'a mut T {
         self.pointer
     }
 
@@ -710,7 +731,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
     ///
     /// [`pin` module]: ../../std/pin/index.html#projections-and-structural-pinning
     #[stable(feature = "pin", since = "1.33.0")]
-    pub unsafe fn map_unchecked_mut<U, F>(self: Pin<&'a mut T>, func: F) -> Pin<&'a mut U> where
+    pub unsafe fn map_unchecked_mut<U, F>(self, func: F) -> Pin<&'a mut U> where
         F: FnOnce(&mut T) -> &mut U,
     {
         let pointer = Pin::get_unchecked_mut(self);
diff --git a/src/libcore/ptr/mod.rs b/src/libcore/ptr/mod.rs
index f5fbd1a6b1325..13ccc9b252a77 100644
--- a/src/libcore/ptr/mod.rs
+++ b/src/libcore/ptr/mod.rs
@@ -1042,7 +1042,7 @@ impl<T: ?Sized> *const T {
         (self as *const u8) == null()
     }
 
-    /// Cast to a pointer to a different type
+    /// Casts to a pointer of another type.
     #[stable(feature = "ptr_cast", since = "1.38.0")]
     #[inline]
     pub const fn cast<U>(self) -> *const U {
@@ -1726,7 +1726,7 @@ impl<T: ?Sized> *mut T {
         (self as *mut u8) == null_mut()
     }
 
-    /// Cast to a pointer to a different type
+    /// Casts to a pointer of another type.
     #[stable(feature = "ptr_cast", since = "1.38.0")]
     #[inline]
     pub const fn cast<U>(self) -> *mut U {
diff --git a/src/libcore/ptr/non_null.rs b/src/libcore/ptr/non_null.rs
index ad3d1ce396ab7..7dcd57f1f9858 100644
--- a/src/libcore/ptr/non_null.rs
+++ b/src/libcore/ptr/non_null.rs
@@ -125,7 +125,7 @@ impl<T: ?Sized> NonNull<T> {
         &mut *self.as_ptr()
     }
 
-    /// Cast to a pointer of another type
+    /// Casts to a pointer of another type.
     #[stable(feature = "nonnull_cast", since = "1.27.0")]
     #[inline]
     pub const fn cast<U>(self) -> NonNull<U> {
diff --git a/src/libcore/sync/atomic.rs b/src/libcore/sync/atomic.rs
index 8dfb19fa03296..c9ccef972c2b5 100644
--- a/src/libcore/sync/atomic.rs
+++ b/src/libcore/sync/atomic.rs
@@ -124,28 +124,31 @@ use crate::fmt;
 
 use crate::hint::spin_loop;
 
-/// Signals the processor that it is entering a busy-wait spin-loop.
+/// Signals the processor that it is inside a busy-wait spin-loop ("spin lock").
 ///
 /// Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving
 /// power or switching hyper-threads.
 ///
-/// This function is different than [`std::thread::yield_now`] which directly yields to the
-/// system's scheduler, whereas `spin_loop_hint` only signals the processor that it is entering a
-/// busy-wait spin-loop without yielding control to the system's scheduler.
+/// This function is different from [`std::thread::yield_now`] which directly yields to the
+/// system's scheduler, whereas `spin_loop_hint` does not interact with the operating system.
 ///
-/// Using a busy-wait spin-loop with `spin_loop_hint` is ideally used in situations where a
-/// contended lock is held by another thread executed on a different CPU and where the waiting
-/// times are relatively small. Because entering busy-wait spin-loop does not trigger the system's
-/// scheduler, no overhead for switching threads occurs. However, if the thread holding the
-/// contended lock is running on the same CPU, the spin-loop is likely to occupy an entire CPU slice
-/// before switching to the thread that holds the lock. If the contending lock is held by a thread
-/// on the same CPU or if the waiting times for acquiring the lock are longer, it is often better to
-/// use [`std::thread::yield_now`].
+/// Spin locks can be very efficient for short lock durations because they do not involve context
+/// switches or interaction with the operating system. For long lock durations they become wasteful
+/// however because they use CPU cycles for the entire lock duration, and using a
+/// [`std::sync::Mutex`] is likely the better approach. If actively spinning for a long time is
+/// required, e.g. because code polls a non-blocking API, calling [`std::thread::yield_now`]
+/// or [`std::thread::sleep`] may be the best option.
+///
+/// **Note**: Spin locks are based on the underlying assumption that another thread will release
+/// the lock 'soon'. In order for this to work, that other thread must run on a different CPU or
+/// core (at least potentially). Spin locks do not work efficiently on single CPU / core platforms.
 ///
 /// **Note**: On platforms that do not support receiving spin-loop hints this function does not
 /// do anything at all.
 ///
 /// [`std::thread::yield_now`]: ../../../std/thread/fn.yield_now.html
+/// [`std::thread::sleep`]: ../../../std/thread/fn.sleep.html
+/// [`std::sync::Mutex`]: ../../../std/sync/struct.Mutex.html
 #[inline]
 #[stable(feature = "spin_loop_hint", since = "1.24.0")]
 pub fn spin_loop_hint() {
@@ -979,9 +982,8 @@ impl<T> AtomicPtr<T> {
     /// let some_ptr  = AtomicPtr::new(ptr);
     ///
     /// let other_ptr   = &mut 10;
-    /// let another_ptr = &mut 10;
     ///
-    /// let value = some_ptr.compare_and_swap(other_ptr, another_ptr, Ordering::Relaxed);
+    /// let value = some_ptr.compare_and_swap(ptr, other_ptr, Ordering::Relaxed);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1021,9 +1023,8 @@ impl<T> AtomicPtr<T> {
     /// let some_ptr  = AtomicPtr::new(ptr);
     ///
     /// let other_ptr   = &mut 10;
-    /// let another_ptr = &mut 10;
     ///
-    /// let value = some_ptr.compare_exchange(other_ptr, another_ptr,
+    /// let value = some_ptr.compare_exchange(ptr, other_ptr,
     ///                                       Ordering::SeqCst, Ordering::Relaxed);
     /// ```
     #[inline]
diff --git a/src/libcore/tests/bool.rs b/src/libcore/tests/bool.rs
new file mode 100644
index 0000000000000..0f1e6e89451e9
--- /dev/null
+++ b/src/libcore/tests/bool.rs
@@ -0,0 +1,7 @@
+#[test]
+fn test_bool_to_option() {
+    assert_eq!(false.then(0), None);
+    assert_eq!(true.then(0), Some(0));
+    assert_eq!(false.then_with(|| 0), None);
+    assert_eq!(true.then_with(|| 0), Some(0));
+}
diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs
index 8e0658d87c1fb..c9096b713f20e 100644
--- a/src/libcore/tests/iter.rs
+++ b/src/libcore/tests/iter.rs
@@ -57,6 +57,62 @@ fn test_multi_iter() {
     assert!(xs.iter().lt(xs.iter().skip(2)));
 }
 
+#[test]
+fn test_cmp_by() {
+    use core::cmp::Ordering;
+
+    let f = |x: i32, y: i32| (x * x).cmp(&y);
+    let xs = || [1, 2, 3, 4].iter().copied();
+    let ys = || [1, 4, 16].iter().copied();
+
+    assert_eq!(xs().cmp_by(ys(), f), Ordering::Less);
+    assert_eq!(ys().cmp_by(xs(), f), Ordering::Greater);
+    assert_eq!(xs().cmp_by(xs().map(|x| x * x), f), Ordering::Equal);
+    assert_eq!(xs().rev().cmp_by(ys().rev(), f), Ordering::Greater);
+    assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
+    assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
+}
+
+#[test]
+fn test_partial_cmp_by() {
+    use core::cmp::Ordering;
+    use core::f64;
+
+    let f = |x: i32, y: i32| (x * x).partial_cmp(&y);
+    let xs = || [1, 2, 3, 4].iter().copied();
+    let ys = || [1, 4, 16].iter().copied();
+
+    assert_eq!(xs().partial_cmp_by(ys(), f), Some(Ordering::Less));
+    assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
+    assert_eq!(xs().partial_cmp_by(xs().map(|x| x * x), f), Some(Ordering::Equal));
+    assert_eq!(xs().rev().partial_cmp_by(ys().rev(), f), Some(Ordering::Greater));
+    assert_eq!(xs().partial_cmp_by(xs().rev(), f), Some(Ordering::Less));
+    assert_eq!(xs().partial_cmp_by(ys().take(2), f), Some(Ordering::Greater));
+
+    let f = |x: f64, y: f64| (x * x).partial_cmp(&y);
+    let xs = || [1.0, 2.0, 3.0, 4.0].iter().copied();
+    let ys = || [1.0, 4.0, f64::NAN, 16.0].iter().copied();
+
+    assert_eq!(xs().partial_cmp_by(ys(), f), None);
+    assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
+}
+
+#[test]
+fn test_eq_by() {
+    let f = |x: i32, y: i32| x * x == y;
+    let xs = || [1, 2, 3, 4].iter().copied();
+    let ys = || [1, 4, 9, 16].iter().copied();
+
+    assert!(xs().eq_by(ys(), f));
+    assert!(!ys().eq_by(xs(), f));
+    assert!(!xs().eq_by(xs(), f));
+    assert!(!ys().eq_by(ys(), f));
+
+    assert!(!xs().take(3).eq_by(ys(), f));
+    assert!(!xs().eq_by(ys().take(3), f));
+    assert!(xs().take(3).eq_by(ys().take(3), f));
+}
+
 #[test]
 fn test_counter_from_iter() {
     let it = (0..).step_by(5).take(10);
@@ -329,6 +385,23 @@ fn test_iterator_step_by_nth_overflow() {
     assert_eq!(it.0, (usize::MAX as Bigger) * 1);
 }
 
+#[test]
+fn test_iterator_step_by_nth_try_fold() {
+    let mut it = (0..).step_by(10);
+    assert_eq!(it.try_fold(0, i8::checked_add), None);
+    assert_eq!(it.next(), Some(60));
+    assert_eq!(it.try_fold(0, i8::checked_add), None);
+    assert_eq!(it.next(), Some(90));
+
+    let mut it = (100..).step_by(10);
+    assert_eq!(it.try_fold(50, i8::checked_add), None);
+    assert_eq!(it.next(), Some(110));
+
+    let mut it = (100..=100).step_by(10);
+    assert_eq!(it.next(), Some(100));
+    assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
+}
+
 #[test]
 fn test_iterator_step_by_nth_back() {
     let mut it = (0..16).step_by(5);
@@ -354,6 +427,24 @@ fn test_iterator_step_by_nth_back() {
     assert_eq!(it().nth_back(42), None);
 }
 
+#[test]
+fn test_iterator_step_by_nth_try_rfold() {
+    let mut it = (0..100).step_by(10);
+    assert_eq!(it.try_rfold(0, i8::checked_add), None);
+    assert_eq!(it.next_back(), Some(70));
+    assert_eq!(it.next(), Some(0));
+    assert_eq!(it.try_rfold(0, i8::checked_add), None);
+    assert_eq!(it.next_back(), Some(30));
+
+    let mut it = (0..100).step_by(10);
+    assert_eq!(it.try_rfold(50, i8::checked_add), None);
+    assert_eq!(it.next_back(), Some(80));
+
+    let mut it = (100..=100).step_by(10);
+    assert_eq!(it.next_back(), Some(100));
+    assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
+}
+
 #[test]
 #[should_panic]
 fn test_iterator_step_by_zero() {
diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index a3b108b2e9cea..050195cd2ef51 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -1,3 +1,4 @@
+#![feature(bool_to_option)]
 #![feature(bound_cloned)]
 #![feature(box_syntax)]
 #![feature(cell_update)]
@@ -32,6 +33,7 @@
 #![feature(const_fn)]
 #![feature(iter_partition_in_place)]
 #![feature(iter_is_partitioned)]
+#![feature(iter_order_by)]
 
 extern crate test;
 
@@ -40,6 +42,7 @@ mod any;
 mod array;
 mod ascii;
 mod atomic;
+mod bool;
 mod cell;
 mod char;
 mod clone;
diff --git a/src/libcore/unicode/printable.py b/src/libcore/unicode/printable.py
index 748917f1d3420..4e8b4ecad0200 100644
--- a/src/libcore/unicode/printable.py
+++ b/src/libcore/unicode/printable.py
@@ -60,7 +60,7 @@ def get_codepoints(f):
         yield Codepoint(codepoint, class_)
         prev_codepoint = codepoint
 
-    if class_first != None:
+    if class_first is not None:
         raise ValueError("Missing Last after First")
 
     for c in range(prev_codepoint + 1, NUM_CODEPOINTS):
diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
index a479fabafc014..0834faf132424 100644
--- a/src/librustc/Cargo.toml
+++ b/src/librustc/Cargo.toml
@@ -15,7 +15,6 @@ bitflags = "1.0"
 fmt_macros = { path = "../libfmt_macros" }
 graphviz = { path = "../libgraphviz" }
 jobserver = "0.1"
-lazy_static = "1.0.0"
 num_cpus = "1.0"
 scoped-tls = "1.0"
 log = { version = "0.4", features = ["release_max_level_info", "std"] }
@@ -31,8 +30,8 @@ rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 backtrace = "0.3.3"
-parking_lot = "0.7"
-byteorder = { version = "1.1", features = ["i128"]}
+parking_lot = "0.9"
+byteorder = { version = "1.3" }
 chalk-engine = { version = "0.9.0", default-features=false }
 rustc_fs_util = { path = "../librustc_fs_util" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
diff --git a/src/librustc/arena.rs b/src/librustc/arena.rs
index b3a561ef74be7..d4fc1b12830a1 100644
--- a/src/librustc/arena.rs
+++ b/src/librustc/arena.rs
@@ -187,7 +187,7 @@ impl<T: Copy> ArenaAllocatable for T {}
 
 unsafe trait ArenaField<'tcx>: Sized {
     /// Returns a specific arena to allocate from.
-    /// If None is returned, the DropArena will be used.
+    /// If `None` is returned, the `DropArena` will be used.
     fn arena<'a>(arena: &'a Arena<'tcx>) -> Option<&'a TypedArena<Self>>;
 }
 
diff --git a/src/librustc/error_codes.rs b/src/librustc/error_codes.rs
index 937a9ea6c1bd4..eee33846139e6 100644
--- a/src/librustc/error_codes.rs
+++ b/src/librustc/error_codes.rs
@@ -1,7 +1,8 @@
 // Error messages for EXXXX errors.
-// Each message should start and end with a new line, and be wrapped to 80 characters.
-// In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
-register_long_diagnostics! {
+// Each message should start and end with a new line, and be wrapped to 80
+// characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use
+// `:set tw=0` to disable.
+syntax::register_diagnostics! {
 E0038: r##"
 Trait objects like `Box<Trait>` can only be constructed when certain
 requirements are satisfied by the trait in question.
@@ -2183,11 +2184,7 @@ Examples of erroneous code:
 static X: u32 = 42;
 ```
 "##,
-
-}
-
-
-register_diagnostics! {
+;
 //  E0006, // merged with E0005
 //  E0101, // replaced with E0282
 //  E0102, // replaced with E0282
@@ -2206,7 +2203,8 @@ register_diagnostics! {
 //  E0305, // expected constant
     E0311, // thing may not live long enough
     E0312, // lifetime of reference outlives lifetime of borrowed content
-    E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
+    E0313, // lifetime of borrowed pointer outlives lifetime of captured
+           // variable
     E0314, // closure outlives stack frame
     E0315, // cannot invoke closure outside of its lifetime
     E0316, // nested quantification of lifetimes
@@ -2223,12 +2221,13 @@ register_diagnostics! {
     E0483, // lifetime of operand does not outlive the operation
     E0484, // reference is not valid at the time of borrow
     E0485, // automatically reference is not valid at the time of borrow
-    E0486, // type of expression contains references that are not valid during...
+    E0486, // type of expression contains references that are not valid during..
     E0487, // unsafe use of destructor: destructor might be called while...
     E0488, // lifetime of variable does not enclose its declaration
     E0489, // type/lifetime parameter not in scope here
     E0490, // a value of type `..` is borrowed for too long
-    E0495, // cannot infer an appropriate lifetime due to conflicting requirements
+    E0495, // cannot infer an appropriate lifetime due to conflicting
+           // requirements
     E0566, // conflicting representation hints
     E0623, // lifetime mismatch where both parameters are anonymous regions
     E0628, // generators cannot have explicit parameters
@@ -2239,7 +2238,8 @@ register_diagnostics! {
     E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
     E0697, // closures cannot be static
     E0707, // multiple elided lifetimes used in arguments of `async fn`
-    E0708, // `async` non-`move` closures with parameters are not currently supported
+    E0708, // `async` non-`move` closures with parameters are not currently
+           // supported
     E0709, // multiple different lifetimes used in arguments of `async fn`
     E0710, // an unknown tool name found in scoped lint
     E0711, // a feature has been declared with conflicting stability attributes
diff --git a/src/librustc/hir/check_attr.rs b/src/librustc/hir/check_attr.rs
index eae956c978a8e..1df09429e519f 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc/hir/check_attr.rs
@@ -4,13 +4,12 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-
-use crate::ty::TyCtxt;
-use crate::ty::query::Providers;
-
 use crate::hir;
 use crate::hir::def_id::DefId;
 use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
+use crate::ty::TyCtxt;
+use crate::ty::query::Providers;
+
 use std::fmt::{self, Display};
 use syntax::symbol::sym;
 use syntax_pos::Span;
diff --git a/src/librustc/hir/def.rs b/src/librustc/hir/def.rs
index f83fbcdc263b0..f7d31ca06ee56 100644
--- a/src/librustc/hir/def.rs
+++ b/src/librustc/hir/def.rs
@@ -1,15 +1,17 @@
+use self::Namespace::*;
+
 use crate::hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use crate::hir;
+use crate::ty;
 use crate::util::nodemap::DefIdMap;
+
 use syntax::ast;
 use syntax::ext::base::MacroKind;
 use syntax::ast::NodeId;
 use syntax_pos::Span;
 use rustc_macros::HashStable;
-use crate::hir;
-use crate::ty;
-use std::fmt::Debug;
 
-use self::Namespace::*;
+use std::fmt::Debug;
 
 /// Encodes if a `DefKind::Ctor` is the constructor of an enum variant or a struct.
 #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, HashStable)]
@@ -115,7 +117,7 @@ impl DefKind {
         }
     }
 
-    /// An English article for the def.
+    /// Gets an English article for the definition.
     pub fn article(&self) -> &'static str {
         match *self {
             DefKind::AssocTy
@@ -134,18 +136,22 @@ pub enum Res<Id = hir::HirId> {
     Def(DefKind, DefId),
 
     // Type namespace
+
     PrimTy(hir::PrimTy),
     SelfTy(Option<DefId> /* trait */, Option<DefId> /* impl */),
     ToolMod, // e.g., `rustfmt` in `#[rustfmt::skip]`
 
     // Value namespace
+
     SelfCtor(DefId /* impl */),  // `DefId` refers to the impl
     Local(Id),
 
     // Macro namespace
+
     NonMacroAttr(NonMacroAttrKind), // e.g., `#[inline]` or `#[rustfmt::skip]`
 
     // All namespaces
+
     Err,
 }
 
@@ -330,7 +336,7 @@ impl NonMacroAttrKind {
 }
 
 impl<Id> Res<Id> {
-    /// Return the `DefId` of this `Def` if it has an id, else panic.
+    /// Return the `DefId` of this `Def` if it has an ID, else panic.
     pub fn def_id(&self) -> DefId
     where
         Id: Debug,
@@ -340,7 +346,7 @@ impl<Id> Res<Id> {
         })
     }
 
-    /// Return `Some(..)` with the `DefId` of this `Res` if it has a id, else `None`.
+    /// Return `Some(..)` with the `DefId` of this `Res` if it has a ID, else `None`.
     pub fn opt_def_id(&self) -> Option<DefId> {
         match *self {
             Res::Def(_, id) => Some(id),
@@ -379,7 +385,7 @@ impl<Id> Res<Id> {
         }
     }
 
-    /// An English article for the res.
+    /// Gets an English article for the `Res`.
     pub fn article(&self) -> &'static str {
         match *self {
             Res::Def(kind, _) => kind.article(),
diff --git a/src/librustc/hir/def_id.rs b/src/librustc/hir/def_id.rs
index c91ad7858d0bb..d0bdc14913183 100644
--- a/src/librustc/hir/def_id.rs
+++ b/src/librustc/hir/def_id.rs
@@ -11,7 +11,7 @@ newtype_index! {
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum CrateNum {
-    /// A special CrateNum that we use for the tcx.rcache when decoding from
+    /// A special `CrateNum` that we use for the `tcx.rcache` when decoding from
     /// the incr. comp. cache.
     ReservedForIncrCompCache,
     Index(CrateId),
@@ -26,11 +26,10 @@ impl ::std::fmt::Debug for CrateNum {
     }
 }
 
-/// Item definitions in the currently-compiled crate would have the CrateNum
-/// LOCAL_CRATE in their DefId.
+/// Item definitions in the currently-compiled crate would have the `CrateNum`
+/// `LOCAL_CRATE` in their `DefId`.
 pub const LOCAL_CRATE: CrateNum = CrateNum::Index(CrateId::from_u32_const(0));
 
-
 impl Idx for CrateNum {
     #[inline]
     fn new(value: usize) -> Self {
diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index bbde3510e29f9..1f125de967216 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/src/librustc/hir/intravisit.rs
@@ -31,11 +31,13 @@
 //! This order consistency is required in a few places in rustc, for
 //! example generator inference, and possibly also HIR borrowck.
 
-use syntax::ast::{Ident, Name, Attribute};
-use syntax_pos::Span;
+use super::itemlikevisit::DeepVisitor;
+
 use crate::hir::*;
 use crate::hir::map::Map;
-use super::itemlikevisit::DeepVisitor;
+
+use syntax::ast::{Ident, Name, Attribute};
+use syntax_pos::Span;
 
 #[derive(Copy, Clone)]
 pub enum FnKind<'a> {
@@ -139,7 +141,7 @@ impl<'this, 'tcx> NestedVisitorMap<'this, 'tcx> {
 /// explicitly, you need to override each method. (And you also need
 /// to monitor future changes to `Visitor` in case a new method with a
 /// new default implementation gets introduced.)
-pub trait Visitor<'v> : Sized {
+pub trait Visitor<'v>: Sized {
     ///////////////////////////////////////////////////////////////////////////
     // Nested items.
 
@@ -162,8 +164,8 @@ pub trait Visitor<'v> : Sized {
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v>;
 
     /// Invoked when a nested item is encountered. By default does
-    /// nothing unless you override `nested_visit_map` to return
-    /// `Some(_)`, in which case it will walk the item. **You probably
+    /// nothing unless you override `nested_visit_map` to return other than
+    /// `None`, in which case it will walk the item. **You probably
     /// don't want to override this method** -- instead, override
     /// `nested_visit_map` or use the "shallow" or "deep" visit
     /// patterns described on `itemlikevisit::ItemLikeVisitor`. The only
@@ -201,8 +203,8 @@ pub trait Visitor<'v> : Sized {
 
     /// Invoked to visit the body of a function, method or closure. Like
     /// visit_nested_item, does nothing by default unless you override
-    /// `nested_visit_map` to return `Some(_)`, in which case it will walk the
-    /// body.
+    /// `nested_visit_map` to return other htan `None`, in which case it will walk
+    /// the body.
     fn visit_nested_body(&mut self, id: BodyId) {
         let opt_body = self.nested_visit_map().intra().map(|map| map.body(id));
         if let Some(body) = opt_body {
@@ -603,7 +605,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             visitor.visit_lifetime(lifetime);
             visitor.visit_ty(&mutable_type.ty)
         }
-        TyKind::Never => {},
+        TyKind::Never => {}
         TyKind::Tup(ref tuple_element_types) => {
             walk_list!(visitor, visit_ty, tuple_element_types);
         }
diff --git a/src/librustc/hir/itemlikevisit.rs b/src/librustc/hir/itemlikevisit.rs
index 35b181245837f..39dd46c2d2903 100644
--- a/src/librustc/hir/itemlikevisit.rs
+++ b/src/librustc/hir/itemlikevisit.rs
@@ -1,7 +1,7 @@
 use super::{Item, ImplItem, TraitItem};
 use super::intravisit::Visitor;
 
-/// The "item-like visitor" visitor defines only the top-level methods
+/// The "item-like visitor" defines only the top-level methods
 /// that can be invoked by `Crate::visit_all_item_likes()`. Whether
 /// this trait is the right one to implement will depend on the
 /// overall pattern you need. Here are the three available patterns,
@@ -18,11 +18,11 @@ use super::intravisit::Visitor;
 ///    an item, but don't care about how item-like things are nested
 ///    within one another.
 ///    - Example: Examine each expression to look for its type and do some check or other.
-///    - How: Implement `intravisit::Visitor` and use
-///      `tcx.hir().krate().visit_all_item_likes(visitor.as_deep_visitor())`. Within
-///      your `intravisit::Visitor` impl, implement methods like
-///      `visit_expr()`; don't forget to invoke
-///      `intravisit::walk_visit_expr()` to keep walking the subparts.
+///    - How: Implement `intravisit::Visitor` and override the `nested_visit_map()` method
+///      to return `NestedVisitorMap::OnlyBodies` and use
+///      `tcx.hir().krate().visit_all_item_likes(&mut visitor.as_deep_visitor())`. Within
+///      your `intravisit::Visitor` impl, implement methods like `visit_expr()` (don't forget
+///      to invoke `intravisit::walk_expr()` to keep walking the subparts).
 ///    - Pro: Visitor methods for any kind of HIR node, not just item-like things.
 ///    - Pro: Integrates well into dependency tracking.
 ///    - Con: Don't get information about nesting between items
@@ -30,10 +30,9 @@ use super::intravisit::Visitor;
 ///    item-like things.
 ///    - Example: Lifetime resolution, which wants to bring lifetimes declared on the
 ///      impl into scope while visiting the impl-items, and then back out again.
-///    - How: Implement `intravisit::Visitor` and override the
-///      `nested_visit_map()` methods to return
-///      `NestedVisitorMap::All`. Walk your crate with
-///      `intravisit::walk_crate()` invoked on `tcx.hir().krate()`.
+///    - How: Implement `intravisit::Visitor` and override the `nested_visit_map()` method
+///      to return `NestedVisitorMap::All`. Walk your crate with `intravisit::walk_crate()`
+///      invoked on `tcx.hir().krate()`.
 ///    - Pro: Visitor methods for any kind of HIR node, not just item-like things.
 ///    - Pro: Preserves nesting information
 ///    - Con: Does not integrate well into dependency tracking.
@@ -79,7 +78,7 @@ impl<'v, 'hir, V> ItemLikeVisitor<'hir> for DeepVisitor<'v, V>
     }
 }
 
-/// A parallel variant of ItemLikeVisitor
+/// A parallel variant of `ItemLikeVisitor`.
 pub trait ParItemLikeVisitor<'hir> {
     fn visit_item(&self, item: &'hir Item);
     fn visit_trait_item(&self, trait_item: &'hir TraitItem);
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index 5e2aebfd3187b..48f7fc4446505 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -79,7 +79,7 @@ const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
 pub struct LoweringContext<'a> {
     crate_root: Option<Symbol>,
 
-    /// Used to assign ids to HIR nodes that do not directly correspond to an AST node.
+    /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes.
     sess: &'a Session,
 
     cstore: &'a dyn CrateStore,
@@ -126,7 +126,7 @@ pub struct LoweringContext<'a> {
     /// lifetime definitions in the corresponding impl or function generics.
     lifetimes_to_define: Vec<(Span, ParamName)>,
 
-    /// Whether or not in-band lifetimes are being collected. This is used to
+    /// `true` if in-band lifetimes are being collected. This is used to
     /// indicate whether or not we're in a place where new lifetimes will result
     /// in in-band lifetime definitions, such a function or an impl header,
     /// including implicit lifetimes from `impl_header_lifetime_elision`.
@@ -154,13 +154,13 @@ pub struct LoweringContext<'a> {
 }
 
 pub trait Resolver {
-    /// Obtain resolution for a `NodeId` with a single resolution.
+    /// Obtains resolution for a `NodeId` with a single resolution.
     fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
 
-    /// Obtain per-namespace resolutions for `use` statement with the given `NoedId`.
+    /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
     fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
 
-    /// Obtain resolution for a label with the given `NodeId`.
+    /// Obtains resolution for a label with the given `NodeId`.
     fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
 
     /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
@@ -425,19 +425,44 @@ impl<'a> LoweringContext<'a> {
 
         impl<'tcx, 'interner> Visitor<'tcx> for MiscCollector<'tcx, 'interner> {
             fn visit_pat(&mut self, p: &'tcx Pat) {
-                match p.node {
+                if let PatKind::Paren(..) | PatKind::Rest = p.node {
                     // Doesn't generate a HIR node
-                    PatKind::Paren(..) | PatKind::Rest => {},
-                    _ => {
-                        if let Some(owner) = self.hir_id_owner {
-                            self.lctx.lower_node_id_with_owner(p.id, owner);
-                        }
-                    }
-                };
+                } else if let Some(owner) = self.hir_id_owner {
+                    self.lctx.lower_node_id_with_owner(p.id, owner);
+                }
 
                 visit::walk_pat(self, p)
             }
 
+            // HACK(or_patterns; Centril | dlrobertson): Avoid creating
+            // HIR  nodes for `PatKind::Or` for the top level of a `ast::Arm`.
+            // This is a temporary hack that should go away once we push down
+            // `arm.pats: HirVec<P<Pat>>` -> `arm.pat: P<Pat>` to HIR. // Centril
+            fn visit_arm(&mut self, arm: &'tcx Arm) {
+                match &arm.pat.node {
+                    PatKind::Or(pats) => pats.iter().for_each(|p| self.visit_pat(p)),
+                    _ => self.visit_pat(&arm.pat),
+                }
+                walk_list!(self, visit_expr, &arm.guard);
+                self.visit_expr(&arm.body);
+                walk_list!(self, visit_attribute, &arm.attrs);
+            }
+
+            // HACK(or_patterns; Centril | dlrobertson): Same as above. // Centril
+            fn visit_expr(&mut self, e: &'tcx Expr) {
+                if let ExprKind::Let(pat, scrutinee) = &e.node {
+                    walk_list!(self, visit_attribute, e.attrs.iter());
+                    match &pat.node {
+                        PatKind::Or(pats) => pats.iter().for_each(|p| self.visit_pat(p)),
+                        _ => self.visit_pat(&pat),
+                    }
+                    self.visit_expr(scrutinee);
+                    self.visit_expr_post(e);
+                    return;
+                }
+                visit::walk_expr(self, e)
+            }
+
             fn visit_item(&mut self, item: &'tcx Item) {
                 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
 
@@ -674,7 +699,7 @@ impl<'a> LoweringContext<'a> {
     fn lower_res(&mut self, res: Res<NodeId>) -> Res {
         res.map_id(|id| {
             self.lower_node_id_generic(id, |_| {
-                panic!("expected node_id to be lowered already for res {:#?}", res)
+                panic!("expected `NodeId` to be lowered already for res {:#?}", res);
             })
         })
     }
@@ -1291,7 +1316,7 @@ impl<'a> LoweringContext<'a> {
                             ImplTraitContext::Universal(in_band_ty_params),
                         );
                         // Set the name to `impl Bound1 + Bound2`.
-                        let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
+                        let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
                         in_band_ty_params.push(hir::GenericParam {
                             hir_id: self.lower_node_id(def_node_id),
                             name: ParamName::Plain(ident),
@@ -1339,7 +1364,7 @@ impl<'a> LoweringContext<'a> {
                     }
                 }
             }
-            TyKind::Mac(_) => bug!("`TyMac` should have been expanded by now."),
+            TyKind::Mac(_) => bug!("`TyMac` should have been expanded by now"),
             TyKind::CVarArgs => {
                 // Create the implicit lifetime of the "spoofed" `VaListImpl`.
                 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
@@ -2657,12 +2682,8 @@ impl<'a> LoweringContext<'a> {
         bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
     }
 
-    fn lower_block_with_stmts(
-        &mut self,
-        b: &Block,
-        targeted_by_break: bool,
-        mut stmts: Vec<hir::Stmt>,
-    ) -> P<hir::Block> {
+    fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
+        let mut stmts = vec![];
         let mut expr = None;
 
         for (index, stmt) in b.stmts.iter().enumerate() {
@@ -2687,8 +2708,11 @@ impl<'a> LoweringContext<'a> {
         })
     }
 
-    fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
-        self.lower_block_with_stmts(b, targeted_by_break, vec![])
+    /// Lowers a block directly to an expression, presuming that it
+    /// has no attributes and is not targeted by a `break`.
+    fn lower_block_expr(&mut self, b: &Block) -> hir::Expr {
+        let block = self.lower_block(b, false);
+        self.expr_block(block, ThinVec::new())
     }
 
     fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
@@ -2974,7 +2998,7 @@ impl<'a> LoweringContext<'a> {
             }
             StmtKind::Expr(ref e) => hir::StmtKind::Expr(P(self.lower_expr(e))),
             StmtKind::Semi(ref e) => hir::StmtKind::Semi(P(self.lower_expr(e))),
-            StmtKind::Mac(..) => panic!("Shouldn't exist here"),
+            StmtKind::Mac(..) => panic!("shouldn't exist here"),
         };
         smallvec![hir::Stmt {
             hir_id: self.lower_node_id(s.id),
@@ -3162,7 +3186,7 @@ impl<'a> LoweringContext<'a> {
 
         hir::Path {
             span,
-            res: res.map_id(|_| panic!("unexpected node_id")),
+            res: res.map_id(|_| panic!("unexpected `NodeId`")),
             segments: segments.into(),
         }
     }
diff --git a/src/librustc/hir/lowering/expr.rs b/src/librustc/hir/lowering/expr.rs
index bd217831faabf..990728fa0e680 100644
--- a/src/librustc/hir/lowering/expr.rs
+++ b/src/librustc/hir/lowering/expr.rs
@@ -68,7 +68,7 @@ impl LoweringContext<'_> {
                 let ohs = P(self.lower_expr(ohs));
                 hir::ExprKind::AddrOf(m, ohs)
             }
-            ExprKind::Let(ref pats, ref scrutinee) => self.lower_expr_let(e.span, pats, scrutinee),
+            ExprKind::Let(ref pat, ref scrutinee) => self.lower_expr_let(e.span, pat, scrutinee),
             ExprKind::If(ref cond, ref then, ref else_opt) => {
                 self.lower_expr_if(e.span, cond, then, else_opt.as_deref())
             }
@@ -90,10 +90,7 @@ impl LoweringContext<'_> {
             ),
             ExprKind::Async(capture_clause, closure_node_id, ref block) => {
                 self.make_async_expr(capture_clause, closure_node_id, None, block.span, |this| {
-                    this.with_new_scopes(|this| {
-                        let block = this.lower_block(block, false);
-                        this.expr_block(block, ThinVec::new())
-                    })
+                    this.with_new_scopes(|this| this.lower_block_expr(block))
                 })
             }
             ExprKind::Await(ref expr) => self.lower_expr_await(e.span, expr),
@@ -227,16 +224,11 @@ impl LoweringContext<'_> {
         }
     }
 
-    /// Emit an error and lower `ast::ExprKind::Let(pats, scrutinee)` into:
+    /// Emit an error and lower `ast::ExprKind::Let(pat, scrutinee)` into:
     /// ```rust
     /// match scrutinee { pats => true, _ => false }
     /// ```
-    fn lower_expr_let(
-        &mut self,
-        span: Span,
-        pats: &[AstP<Pat>],
-        scrutinee: &Expr
-    ) -> hir::ExprKind {
+    fn lower_expr_let(&mut self, span: Span, pat: &Pat, scrutinee: &Expr) -> hir::ExprKind {
         // If we got here, the `let` expression is not allowed.
         self.sess
             .struct_span_err(span, "`let` expressions are not supported here")
@@ -246,23 +238,23 @@ impl LoweringContext<'_> {
 
         // For better recovery, we emit:
         // ```
-        // match scrutinee { pats => true, _ => false }
+        // match scrutinee { pat => true, _ => false }
         // ```
         // While this doesn't fully match the user's intent, it has key advantages:
         // 1. We can avoid using `abort_if_errors`.
-        // 2. We can typeck both `pats` and `scrutinee`.
-        // 3. `pats` is allowed to be refutable.
+        // 2. We can typeck both `pat` and `scrutinee`.
+        // 3. `pat` is allowed to be refutable.
         // 4. The return type of the block is `bool` which seems like what the user wanted.
         let scrutinee = self.lower_expr(scrutinee);
         let then_arm = {
-            let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
+            let pat = self.lower_pat_top_hack(pat);
             let expr = self.expr_bool(span, true);
-            self.arm(pats, P(expr))
+            self.arm(pat, P(expr))
         };
         let else_arm = {
-            let pats = hir_vec![self.pat_wild(span)];
+            let pat = self.pat_wild(span);
             let expr = self.expr_bool(span, false);
-            self.arm(pats, P(expr))
+            self.arm(hir_vec![pat], P(expr))
         };
         hir::ExprKind::Match(
             P(scrutinee),
@@ -289,15 +281,13 @@ impl LoweringContext<'_> {
         let else_arm = self.arm(hir_vec![else_pat], P(else_expr));
 
         // Handle then + scrutinee:
-        let then_blk = self.lower_block(then, false);
-        let then_expr = self.expr_block(then_blk, ThinVec::new());
-        let (then_pats, scrutinee, desugar) = match cond.node {
+        let then_expr = self.lower_block_expr(then);
+        let (then_pat, scrutinee, desugar) = match cond.node {
             // `<pat> => <then>`:
-            ExprKind::Let(ref pats, ref scrutinee) => {
+            ExprKind::Let(ref pat, ref scrutinee) => {
                 let scrutinee = self.lower_expr(scrutinee);
-                let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
-                let desugar = hir::MatchSource::IfLetDesugar { contains_else_clause };
-                (pats, scrutinee, desugar)
+                let pat = self.lower_pat_top_hack(pat);
+                (pat, scrutinee, hir::MatchSource::IfLetDesugar { contains_else_clause })
             }
             // `true => <then>`:
             _ => {
@@ -312,13 +302,11 @@ impl LoweringContext<'_> {
                 // to preserve drop semantics since `if cond { ... }` does not
                 // let temporaries live outside of `cond`.
                 let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
-
-                let desugar = hir::MatchSource::IfDesugar { contains_else_clause };
-                let pats = hir_vec![self.pat_bool(span, true)];
-                (pats, cond, desugar)
+                let pat = self.pat_bool(span, true);
+                (hir_vec![pat], cond, hir::MatchSource::IfDesugar { contains_else_clause })
             }
         };
-        let then_arm = self.arm(then_pats, P(then_expr));
+        let then_arm = self.arm(then_pat, P(then_expr));
 
         hir::ExprKind::Match(P(scrutinee), vec![then_arm, else_arm].into(), desugar)
     }
@@ -343,10 +331,9 @@ impl LoweringContext<'_> {
         };
 
         // Handle then + scrutinee:
-        let then_blk = self.lower_block(body, false);
-        let then_expr = self.expr_block(then_blk, ThinVec::new());
-        let (then_pats, scrutinee, desugar, source) = match cond.node {
-            ExprKind::Let(ref pats, ref scrutinee) => {
+        let then_expr = self.lower_block_expr(body);
+        let (then_pat, scrutinee, desugar, source) = match cond.node {
+            ExprKind::Let(ref pat, ref scrutinee) => {
                 // to:
                 //
                 //   [opt_ident]: loop {
@@ -356,16 +343,15 @@ impl LoweringContext<'_> {
                 //     }
                 //   }
                 let scrutinee = self.with_loop_condition_scope(|t| t.lower_expr(scrutinee));
-                let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
-                let desugar = hir::MatchSource::WhileLetDesugar;
-                (pats, scrutinee, desugar, hir::LoopSource::WhileLet)
+                let pat = self.lower_pat_top_hack(pat);
+                (pat, scrutinee, hir::MatchSource::WhileLetDesugar, hir::LoopSource::WhileLet)
             }
             _ => {
                 // We desugar: `'label: while $cond $body` into:
                 //
                 // ```
                 // 'label: loop {
-                //     match DropTemps($cond) {
+                //     match drop-temps { $cond } {
                 //         true => $body,
                 //         _ => break,
                 //     }
@@ -383,14 +369,12 @@ impl LoweringContext<'_> {
                 // to preserve drop semantics since `while cond { ... }` does not
                 // let temporaries live outside of `cond`.
                 let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
-
-                let desugar = hir::MatchSource::WhileDesugar;
                 // `true => <then>`:
-                let pats = hir_vec![self.pat_bool(span, true)];
-                (pats, cond, desugar, hir::LoopSource::While)
+                let pat = self.pat_bool(span, true);
+                (hir_vec![pat], cond, hir::MatchSource::WhileDesugar, hir::LoopSource::While)
             }
         };
-        let then_arm = self.arm(then_pats, P(then_expr));
+        let then_arm = self.arm(then_pat, P(then_expr));
 
         // `match <scrutinee> { ... }`
         let match_expr = self.expr_match(
@@ -440,7 +424,7 @@ impl LoweringContext<'_> {
         hir::Arm {
             hir_id: self.next_id(),
             attrs: self.lower_attrs(&arm.attrs),
-            pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
+            pats: self.lower_pat_top_hack(&arm.pat),
             guard: match arm.guard {
                 Some(ref x) => Some(hir::Guard::If(P(self.lower_expr(x)))),
                 _ => None,
@@ -450,6 +434,16 @@ impl LoweringContext<'_> {
         }
     }
 
+    /// HACK(or_patterns; Centril | dlrobertson): For now we don't push down top level or-patterns
+    /// `p | q` into `hir::PatKind::Or(...)` as post-lowering bits of the compiler are not ready
+    /// to deal with it. This should by fixed by pushing it down to HIR and then HAIR.
+    fn lower_pat_top_hack(&mut self, pat: &Pat) -> HirVec<P<hir::Pat>> {
+        match pat.node {
+            PatKind::Or(ref ps) => ps.iter().map(|x| self.lower_pat(x)).collect(),
+            _ => hir_vec![self.lower_pat(pat)],
+        }
+    }
+
     pub(super) fn make_async_expr(
         &mut self,
         capture_clause: CaptureBy,
@@ -508,14 +502,13 @@ impl LoweringContext<'_> {
 
     /// Desugar `<expr>.await` into:
     /// ```rust
-    /// {
-    ///     let mut pinned = <expr>;
-    ///     loop {
+    /// match <expr> {
+    ///     mut pinned => loop {
     ///         match ::std::future::poll_with_tls_context(unsafe {
-    ///             ::std::pin::Pin::new_unchecked(&mut pinned)
+    ///             <::std::pin::Pin>::new_unchecked(&mut pinned)
     ///         }) {
     ///             ::std::task::Poll::Ready(result) => break result,
-    ///             ::std::task::Poll::Pending => {},
+    ///             ::std::task::Poll::Pending => {}
     ///         }
     ///         yield ();
     ///     }
@@ -550,21 +543,12 @@ impl LoweringContext<'_> {
             self.allow_gen_future.clone(),
         );
 
-        // let mut pinned = <expr>;
-        let expr = P(self.lower_expr(expr));
         let pinned_ident = Ident::with_dummy_span(sym::pinned);
         let (pinned_pat, pinned_pat_hid) = self.pat_ident_binding_mode(
             span,
             pinned_ident,
             hir::BindingAnnotation::Mutable,
         );
-        let pinned_let = self.stmt_let_pat(
-            ThinVec::new(),
-            span,
-            Some(expr),
-            pinned_pat,
-            hir::LocalSource::AwaitDesugar,
-        );
 
         // ::std::future::poll_with_tls_context(unsafe {
         //     ::std::pin::Pin::new_unchecked(&mut pinned)
@@ -622,7 +606,7 @@ impl LoweringContext<'_> {
             self.arm(hir_vec![pending_pat], empty_block)
         };
 
-        let match_stmt = {
+        let inner_match_stmt = {
             let match_expr = self.expr_match(
                 span,
                 poll_expr,
@@ -644,10 +628,11 @@ impl LoweringContext<'_> {
 
         let loop_block = P(self.block_all(
             span,
-            hir_vec![match_stmt, yield_stmt],
+            hir_vec![inner_match_stmt, yield_stmt],
             None,
         ));
 
+        // loop { .. }
         let loop_expr = P(hir::Expr {
             hir_id: loop_hir_id,
             node: hir::ExprKind::Loop(
@@ -659,10 +644,14 @@ impl LoweringContext<'_> {
             attrs: ThinVec::new(),
         });
 
-        hir::ExprKind::Block(
-            P(self.block_all(span, hir_vec![pinned_let], Some(loop_expr))),
-            None,
-        )
+        // mut pinned => loop { ... }
+        let pinned_arm = self.arm(hir_vec![pinned_pat], loop_expr);
+
+        // match <expr> {
+        //     mut pinned => loop { .. }
+        // }
+        let expr = P(self.lower_expr(expr));
+        hir::ExprKind::Match(expr, hir_vec![pinned_arm], hir::MatchSource::AwaitDesugar)
     }
 
     fn lower_expr_closure(
@@ -1255,7 +1244,6 @@ impl LoweringContext<'_> {
                 ThinVec::from(attrs.clone()),
             ));
             let ok_pat = self.pat_ok(span, val_pat);
-
             self.arm(hir_vec![ok_pat], val_expr)
         };
 
@@ -1317,7 +1305,7 @@ impl LoweringContext<'_> {
     /// `{ let _t = $expr; _t }` but should provide better compile-time performance.
     ///
     /// The drop order can be important in e.g. `if expr { .. }`.
-    fn expr_drop_temps(
+    pub(super) fn expr_drop_temps(
         &mut self,
         span: Span,
         expr: P<hir::Expr>,
@@ -1486,7 +1474,10 @@ impl LoweringContext<'_> {
         }
     }
 
-    fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
+    /// HACK(or_patterns; Centril | dlrobertson): For now we don't push down top level or-patterns
+    /// `p | q` into `hir::PatKind::Or(...)` as post-lowering bits of the compiler are not ready
+    /// to deal with it. This should by fixed by pushing it down to HIR and then HAIR.
+    fn arm(&mut self, pats: HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
         hir::Arm {
             hir_id: self.next_id(),
             attrs: hir_vec![],
diff --git a/src/librustc/hir/lowering/item.rs b/src/librustc/hir/lowering/item.rs
index 4e432f4981d23..61be40a6b907f 100644
--- a/src/librustc/hir/lowering/item.rs
+++ b/src/librustc/hir/lowering/item.rs
@@ -718,7 +718,7 @@ impl LoweringContext<'_> {
                         AnonymousLifetimeMode::PassThrough,
                         |this, _| {
                             (
-                                // Disallow impl Trait in foreign items
+                                // Disallow `impl Trait` in foreign items.
                                 this.lower_fn_decl(fdec, None, false, None),
                                 this.lower_fn_params_to_names(fdec),
                             )
@@ -732,7 +732,7 @@ impl LoweringContext<'_> {
                         self.lower_ty(t, ImplTraitContext::disallowed()), self.lower_mutability(m))
                 }
                 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
-                ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
+                ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
             },
             vis: self.lower_visibility(&i.vis, None),
             span: i.span,
@@ -1071,10 +1071,7 @@ impl LoweringContext<'_> {
     }
 
     fn lower_fn_body_block(&mut self, decl: &FnDecl, body: &Block) -> hir::BodyId {
-        self.lower_fn_body(decl, |this| {
-            let body = this.lower_block(body, false);
-            this.expr_block(body, ThinVec::new())
-        })
+        self.lower_fn_body(decl, |this| this.lower_block_expr(body))
     }
 
     pub(super) fn lower_const_body(&mut self, expr: &Expr) -> hir::BodyId {
@@ -1102,8 +1099,7 @@ impl LoweringContext<'_> {
             // from:
             //
             //     async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
-            //       async move {
-            //       }
+            //         <body>
             //     }
             //
             // into:
@@ -1116,11 +1112,19 @@ impl LoweringContext<'_> {
             //         let <pattern> = __arg1;
             //         let __arg0 = __arg0;
             //         let <pattern> = __arg0;
+            //         drop-temps { <body> } // see comments later in fn for details
             //       }
             //     }
             //
             // If `<pattern>` is a simple ident, then it is lowered to a single
             // `let <pattern> = <pattern>;` statement as an optimization.
+            //
+            // Note that the body is embedded in `drop-temps`; an
+            // equivalent desugaring would be `return { <body>
+            // };`. The key point is that we wish to drop all the
+            // let-bound variables and temporaries created in the body
+            // (and its tail expression!) before we drop the
+            // parameters (c.f. rust-lang/rust#64512).
             for (index, parameter) in decl.inputs.iter().enumerate() {
                 let parameter = this.lower_param(parameter);
                 let span = parameter.pat.span;
@@ -1219,8 +1223,36 @@ impl LoweringContext<'_> {
             let async_expr = this.make_async_expr(
                 CaptureBy::Value, closure_id, None, body.span,
                 |this| {
-                    let body = this.lower_block_with_stmts(body, false, statements);
-                    this.expr_block(body, ThinVec::new())
+                    // Create a block from the user's function body:
+                    let user_body = this.lower_block_expr(body);
+
+                    // Transform into `drop-temps { <user-body> }`, an expression:
+                    let desugared_span = this.mark_span_with_reason(
+                        DesugaringKind::Async,
+                        user_body.span,
+                        None,
+                    );
+                    let user_body = this.expr_drop_temps(
+                        desugared_span,
+                        P(user_body),
+                        ThinVec::new(),
+                    );
+
+                    // As noted above, create the final block like
+                    //
+                    // ```
+                    // {
+                    //   let $param_pattern = $raw_param;
+                    //   ...
+                    //   drop-temps { <user-body> }
+                    // }
+                    // ```
+                    let body = this.block_all(
+                        desugared_span,
+                        statements.into(),
+                        Some(P(user_body)),
+                    );
+                    this.expr_block(P(body), ThinVec::new())
                 });
             (HirVec::from(parameters), this.expr(body.span, async_expr, ThinVec::new()))
         })
diff --git a/src/librustc/hir/map/collector.rs b/src/librustc/hir/map/collector.rs
index b8bd1d73fc28b..4179cf2ff807f 100644
--- a/src/librustc/hir/map/collector.rs
+++ b/src/librustc/hir/map/collector.rs
@@ -340,7 +340,7 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
     /// their outer items.
 
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
-        panic!("visit_nested_xxx must be manually implemented in this visitor")
+        panic!("`visit_nested_xxx` must be manually implemented in this visitor");
     }
 
     fn visit_nested_item(&mut self, item: ItemId) {
diff --git a/src/librustc/hir/map/def_collector.rs b/src/librustc/hir/map/def_collector.rs
index 17bcb1d085968..d1cc7a8ce988f 100644
--- a/src/librustc/hir/map/def_collector.rs
+++ b/src/librustc/hir/map/def_collector.rs
@@ -31,7 +31,7 @@ impl<'a> DefCollector<'a> {
         self.definitions.create_def_with_parent(parent_def, node_id, data, self.expansion, span)
     }
 
-    pub fn with_parent<F: FnOnce(&mut Self)>(&mut self, parent_def: DefIndex, f: F) {
+    fn with_parent<F: FnOnce(&mut Self)>(&mut self, parent_def: DefIndex, f: F) {
         let orig_parent_def = std::mem::replace(&mut self.parent_def, parent_def);
         f(self);
         self.parent_def = orig_parent_def;
@@ -74,6 +74,22 @@ impl<'a> DefCollector<'a> {
         })
     }
 
+    fn collect_field(&mut self, field: &'a StructField, index: Option<usize>) {
+        if field.is_placeholder {
+            self.visit_macro_invoc(field.id);
+        } else {
+            let name = field.ident.map(|ident| ident.name)
+                .or_else(|| index.map(sym::integer))
+                .unwrap_or_else(|| {
+                    let node_id = NodeId::placeholder_from_expn_id(self.expansion);
+                    sym::integer(self.definitions.placeholder_field_indices[&node_id])
+                })
+                .as_interned_str();
+            let def = self.create_def(field.id, DefPathData::ValueNs(name), field.span);
+            self.with_parent(def, |this| visit::walk_struct_field(this, field));
+        }
+    }
+
     pub fn visit_macro_invoc(&mut self, id: NodeId) {
         self.definitions.set_invocation_parent(id.placeholder_to_expn_id(), self.parent_def);
     }
@@ -155,6 +171,9 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
     }
 
     fn visit_variant(&mut self, v: &'a Variant) {
+        if v.is_placeholder {
+            return self.visit_macro_invoc(v.id);
+        }
         let def = self.create_def(v.id,
                                   DefPathData::TypeNs(v.ident.as_interned_str()),
                                   v.span);
@@ -167,17 +186,22 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
     }
 
     fn visit_variant_data(&mut self, data: &'a VariantData) {
+        // The assumption here is that non-`cfg` macro expansion cannot change field indices.
+        // It currently holds because only inert attributes are accepted on fields,
+        // and every such attribute expands into a single field after it's resolved.
         for (index, field) in data.fields().iter().enumerate() {
-            let name = field.ident.map(|ident| ident.name)
-                .unwrap_or_else(|| sym::integer(index));
-            let def = self.create_def(field.id,
-                                      DefPathData::ValueNs(name.as_interned_str()),
-                                      field.span);
-            self.with_parent(def, |this| this.visit_struct_field(field));
+            self.collect_field(field, Some(index));
+            if field.is_placeholder && field.ident.is_none() {
+                self.definitions.placeholder_field_indices.insert(field.id, index);
+            }
         }
     }
 
     fn visit_generic_param(&mut self, param: &'a GenericParam) {
+        if param.is_placeholder {
+            self.visit_macro_invoc(param.id);
+            return;
+        }
         let name = param.ident.as_interned_str();
         let def_path_data = match param.kind {
             GenericParamKind::Lifetime { .. } => DefPathData::LifetimeNs(name),
@@ -294,4 +318,42 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             }
         }
     }
+
+    fn visit_arm(&mut self, arm: &'a Arm) {
+        if arm.is_placeholder {
+            self.visit_macro_invoc(arm.id)
+        } else {
+            visit::walk_arm(self, arm)
+        }
+    }
+
+    fn visit_field(&mut self, f: &'a Field) {
+        if f.is_placeholder {
+            self.visit_macro_invoc(f.id)
+        } else {
+            visit::walk_field(self, f)
+        }
+    }
+
+    fn visit_field_pattern(&mut self, fp: &'a FieldPat) {
+        if fp.is_placeholder {
+            self.visit_macro_invoc(fp.id)
+        } else {
+            visit::walk_field_pattern(self, fp)
+        }
+    }
+
+    fn visit_param(&mut self, p: &'a Param) {
+        if p.is_placeholder {
+            self.visit_macro_invoc(p.id)
+        } else {
+            visit::walk_param(self, p)
+        }
+    }
+
+    // This method is called only when we are visiting an individual field
+    // after expanding an attribute on it.
+    fn visit_struct_field(&mut self, field: &'a StructField) {
+        self.collect_field(field, None);
+    }
 }
diff --git a/src/librustc/hir/map/definitions.rs b/src/librustc/hir/map/definitions.rs
index 6dc3c7038f569..187bc59332460 100644
--- a/src/librustc/hir/map/definitions.rs
+++ b/src/librustc/hir/map/definitions.rs
@@ -7,10 +7,12 @@
 use crate::hir;
 use crate::hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE, CRATE_DEF_INDEX};
 use crate::ich::Fingerprint;
+use crate::session::CrateDisambiguator;
+use crate::util::nodemap::NodeMap;
+
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::{IndexVec};
 use rustc_data_structures::stable_hasher::StableHasher;
-use crate::session::CrateDisambiguator;
 use std::borrow::Borrow;
 use std::fmt::Write;
 use std::hash::Hash;
@@ -18,12 +20,11 @@ use syntax::ast;
 use syntax::ext::hygiene::ExpnId;
 use syntax::symbol::{Symbol, sym, InternedString};
 use syntax_pos::{Span, DUMMY_SP};
-use crate::util::nodemap::NodeMap;
 
-/// The DefPathTable maps DefIndexes to DefKeys and vice versa.
-/// Internally the DefPathTable holds a tree of DefKeys, where each DefKey
-/// stores the DefIndex of its parent.
-/// There is one DefPathTable for each crate.
+/// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
+/// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
+/// stores the `DefIndex` of its parent.
+/// There is one `DefPathTable` for each crate.
 #[derive(Clone, Default, RustcDecodable, RustcEncodable)]
 pub struct DefPathTable {
     index_to_key: Vec<DefKey>,
@@ -103,6 +104,8 @@ pub struct Definitions {
     /// When collecting definitions from an AST fragment produced by a macro invocation `ExpnId`
     /// we know what parent node that fragment should be attached to thanks to this table.
     invocation_parents: FxHashMap<ExpnId, DefIndex>,
+    /// Indices of unnamed struct or variant fields with unresolved attributes.
+    pub(super) placeholder_field_indices: NodeMap<usize>,
 }
 
 /// A unique identifier that we can use to lookup a definition
@@ -121,7 +124,7 @@ impl DefKey {
     fn compute_stable_hash(&self, parent_hash: DefPathHash) -> DefPathHash {
         let mut hasher = StableHasher::new();
 
-        // We hash a 0u8 here to disambiguate between regular DefPath hashes,
+        // We hash a `0u8` here to disambiguate between regular `DefPath` hashes,
         // and the special "root_parent" below.
         0u8.hash(&mut hasher);
         parent_hash.hash(&mut hasher);
@@ -145,8 +148,7 @@ impl DefKey {
                                crate_disambiguator: CrateDisambiguator)
                                -> DefPathHash {
         let mut hasher = StableHasher::new();
-        // Disambiguate this from a regular DefPath hash,
-        // see compute_stable_hash() above.
+        // Disambiguate this from a regular `DefPath` hash; see `compute_stable_hash()` above.
         1u8.hash(&mut hasher);
         crate_name.hash(&mut hasher);
         crate_disambiguator.hash(&mut hasher);
@@ -155,10 +157,10 @@ impl DefKey {
 }
 
 /// A pair of `DefPathData` and an integer disambiguator. The integer is
-/// normally 0, but in the event that there are multiple defs with the
+/// normally `0`, but in the event that there are multiple defs with the
 /// same `parent` and `data`, we use this field to disambiguate
 /// between them. This introduces some artificial ordering dependency
-/// but means that if you have (e.g.) two impls for the same type in
+/// but means that if you have, e.g., two impls for the same type in
 /// the same module, they do get distinct `DefId`s.
 #[derive(Clone, PartialEq, Debug, Hash, RustcEncodable, RustcDecodable)]
 pub struct DisambiguatedDefPathData {
@@ -277,29 +279,34 @@ impl DefPath {
 pub enum DefPathData {
     // Root: these should only be used for the root nodes, because
     // they are treated specially by the `def_path` function.
-    /// The crate root (marker)
+
+    /// The crate root (marker).
     CrateRoot,
-    // Catch-all for random DefId things like `DUMMY_NODE_ID`
+    // Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
     Misc,
+
     // Different kinds of items and item-like things:
-    /// An impl
+
+    /// An impl.
     Impl,
-    /// Something in the type NS
+    /// Something in the type namespace.
     TypeNs(InternedString),
-    /// Something in the value NS
+    /// Something in the value namespace.
     ValueNs(InternedString),
-    /// Something in the macro NS
+    /// Something in the macro namespace.
     MacroNs(InternedString),
-    /// Something in the lifetime NS
+    /// Something in the lifetime namespace.
     LifetimeNs(InternedString),
-    /// A closure expression
+    /// A closure expression.
     ClosureExpr,
-    // Subportions of items
-    /// Implicit ctor for a unit or tuple-like struct or enum variant.
+
+    // Subportions of items:
+
+    /// Implicit constructor for a unit or tuple-like struct or enum variant.
     Ctor,
-    /// A constant expression (see {ast,hir}::AnonConst).
+    /// A constant expression (see `{ast,hir}::AnonConst`).
     AnonConst,
-    /// An `impl Trait` type node
+    /// An `impl Trait` type node.
     ImplTrait,
     /// Identifies a piece of crate metadata that is global to a whole crate
     /// (as opposed to just one item). `GlobalMetaData` components are only
@@ -435,7 +442,7 @@ impl Definitions {
         self.node_to_def_index.insert(ast::CRATE_NODE_ID, root_index);
         self.set_invocation_parent(ExpnId::root(), root_index);
 
-        // Allocate some other DefIndices that always must exist.
+        // Allocate some other `DefIndex`es that always must exist.
         GlobalMetaDataKind::allocate_def_indices(self);
 
         root_index
@@ -458,7 +465,7 @@ impl Definitions {
                 data,
                 self.table.def_key(self.node_to_def_index[&node_id]));
 
-        // The root node must be created with create_root_def()
+        // The root node must be created with `create_root_def()`.
         assert!(data != DefPathData::CrateRoot);
 
         // Find the next free disambiguator for this key.
@@ -486,9 +493,9 @@ impl Definitions {
         assert_eq!(index.index(), self.def_index_to_node.len());
         self.def_index_to_node.push(node_id);
 
-        // Some things for which we allocate DefIndices don't correspond to
-        // anything in the AST, so they don't have a NodeId. For these cases
-        // we don't need a mapping from NodeId to DefIndex.
+        // Some things for which we allocate `DefIndex`es don't correspond to
+        // anything in the AST, so they don't have a `NodeId`. For these cases
+        // we don't need a mapping from `NodeId` to `DefIndex`.
         if node_id != ast::DUMMY_NODE_ID {
             debug!("create_def_with_parent: def_index_to_node[{:?} <-> {:?}", index, node_id);
             self.node_to_def_index.insert(node_id, index);
@@ -498,7 +505,7 @@ impl Definitions {
             self.expansions_that_defined.insert(index, expn_id);
         }
 
-        // The span is added if it isn't dummy
+        // The span is added if it isn't dummy.
         if !span.is_dummy() {
             self.def_index_to_span.insert(index, span);
         }
@@ -506,12 +513,12 @@ impl Definitions {
         index
     }
 
-    /// Initialize the `ast::NodeId` to `HirId` mapping once it has been generated during
+    /// Initializes the `ast::NodeId` to `HirId` mapping once it has been generated during
     /// AST to HIR lowering.
     pub fn init_node_id_to_hir_id_mapping(&mut self,
                                           mapping: IndexVec<ast::NodeId, hir::HirId>) {
         assert!(self.node_to_hir_id.is_empty(),
-                "Trying initialize NodeId -> HirId mapping twice");
+                "trying to initialize `NodeId` -> `HirId` mapping twice");
         self.node_to_hir_id = mapping;
     }
 
@@ -533,7 +540,7 @@ impl Definitions {
 
     pub fn set_invocation_parent(&mut self, invoc_id: ExpnId, parent: DefIndex) {
         let old_parent = self.invocation_parents.insert(invoc_id, parent);
-        assert!(old_parent.is_none(), "parent def-index is reset for an invocation");
+        assert!(old_parent.is_none(), "parent `DefIndex` is reset for an invocation");
     }
 }
 
@@ -585,9 +592,9 @@ impl DefPathData {
     }
 }
 
-// We define the GlobalMetaDataKind enum with this macro because we want to
+// We define the `GlobalMetaDataKind` enum with this macro because we want to
 // make sure that we exhaustively iterate over all variants when registering
-// the corresponding DefIndices in the DefTable.
+// the corresponding `DefIndex`es in the `DefTable`.
 macro_rules! define_global_metadata_kind {
     (pub enum GlobalMetaDataKind {
         $($variant:ident),*
@@ -609,7 +616,7 @@ macro_rules! define_global_metadata_kind {
                         DUMMY_SP
                     );
 
-                    // Make sure calling def_index does not crash.
+                    // Make sure calling `def_index` does not crash.
                     instance.def_index(&definitions.table);
                 })*
             }
@@ -623,7 +630,7 @@ macro_rules! define_global_metadata_kind {
                     }
                 };
 
-                // These DefKeys are all right after the root,
+                // These `DefKey`s are all right after the root,
                 // so a linear search is fine.
                 let index = def_path_table.index_to_key
                                           .iter()
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index eb8be6e6e3cbc..5cec8a593f12a 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -5,10 +5,15 @@ pub use self::definitions::{
 };
 
 use crate::dep_graph::{DepGraph, DepNode, DepKind, DepNodeIndex};
-
+use crate::hir::*;
+use crate::hir::DefKind;
 use crate::hir::def_id::{CRATE_DEF_INDEX, DefId, LocalDefId};
-
+use crate::hir::itemlikevisit::ItemLikeVisitor;
+use crate::hir::print::Nested;
 use crate::middle::cstore::CrateStoreDyn;
+use crate::ty::query::Providers;
+use crate::util::nodemap::FxHashMap;
+use crate::util::common::time;
 
 use rustc_target::spec::abi::Abi;
 use rustc_data_structures::svh::Svh;
@@ -18,15 +23,7 @@ use syntax::source_map::Spanned;
 use syntax::ext::base::MacroKind;
 use syntax_pos::{Span, DUMMY_SP};
 
-use crate::hir::*;
-use crate::hir::DefKind;
-use crate::hir::itemlikevisit::ItemLikeVisitor;
-use crate::hir::print::Nested;
-use crate::util::nodemap::FxHashMap;
-use crate::util::common::time;
-
 use std::result::Result::Err;
-use crate::ty::query::Providers;
 
 pub mod blocks;
 mod collector;
@@ -627,7 +624,7 @@ impl<'hir> Map<'hir> {
             .unwrap_or(hir_id)
     }
 
-    /// Check if the node is an argument. An argument is a local variable whose
+    /// Checks if the node is an argument. An argument is a local variable whose
     /// immediate parent is an item or a closure.
     pub fn is_argument(&self, id: HirId) -> bool {
         match self.find(id) {
@@ -733,7 +730,7 @@ impl<'hir> Map<'hir> {
     /// ```
     /// fn foo(x: usize) -> bool {
     ///     if x == 1 {
-    ///         true  // `get_return_block` gets passed the `id` corresponding
+    ///         true  // If `get_return_block` gets passed the `id` corresponding
     ///     } else {  // to this, it will return `foo`'s `HirId`.
     ///         false
     ///     }
@@ -743,7 +740,7 @@ impl<'hir> Map<'hir> {
     /// ```
     /// fn foo(x: usize) -> bool {
     ///     loop {
-    ///         true  // `get_return_block` gets passed the `id` corresponding
+    ///         true  // If `get_return_block` gets passed the `id` corresponding
     ///     }         // to this, it will return `None`.
     ///     false
     /// }
@@ -994,9 +991,9 @@ impl<'hir> Map<'hir> {
         self.map.iter().enumerate().filter_map(|(i, local_map)| {
             local_map.as_ref().map(|m| (i, m))
         }).flat_map(move |(array_index, local_map)| {
-            // Iterate over each valid entry in the local map
+            // Iterate over each valid entry in the local map.
             local_map.iter_enumerated().filter_map(move |(i, entry)| entry.map(move |_| {
-                // Reconstruct the HirId based on the 3 indices we used to find it
+                // Reconstruct the `HirId` based on the 3 indices we used to find it.
                 HirId {
                     owner: DefIndex::from(array_index),
                     local_id: i,
@@ -1207,7 +1204,7 @@ pub fn map_crate<'hir>(sess: &crate::session::Session,
         definitions,
     };
 
-    time(sess, "validate hir map", || {
+    time(sess, "validate HIR map", || {
         hir_id_validator::check_crate(&map);
     });
 
@@ -1247,9 +1244,9 @@ impl<'a> print::State<'a> {
             Node::Pat(a)          => self.print_pat(&a),
             Node::Arm(a)          => self.print_arm(&a),
             Node::Block(a)        => {
-                // containing cbox, will be closed by print-block at }
+                // Containing cbox, will be closed by print-block at `}`.
                 self.cbox(print::INDENT_UNIT);
-                // head-ibox, will be closed by print-block after {
+                // Head-ibox, will be closed by print-block after `{`.
                 self.ibox(0);
                 self.print_block(&a)
             }
@@ -1257,8 +1254,8 @@ impl<'a> print::State<'a> {
             Node::Visibility(a)   => self.print_visibility(&a),
             Node::GenericParam(_) => bug!("cannot print Node::GenericParam"),
             Node::Field(_)        => bug!("cannot print StructField"),
-            // these cases do not carry enough information in the
-            // hir_map to reconstruct their full structure for pretty
+            // These cases do not carry enough information in the
+            // `hir_map` to reconstruct their full structure for pretty
             // printing.
             Node::Ctor(..)        => bug!("cannot print isolated Ctor"),
             Node::Local(a)        => self.print_local_decl(&a),
@@ -1273,8 +1270,8 @@ fn hir_id_to_string(map: &Map<'_>, id: HirId, include_id: bool) -> String {
     let id_str = if include_id { &id_str[..] } else { "" };
 
     let path_str = || {
-        // This functionality is used for debugging, try to use TyCtxt to get
-        // the user-friendly path, otherwise fall back to stringifying DefPath.
+        // This functionality is used for debugging, try to use `TyCtxt` to get
+        // the user-friendly path, otherwise fall back to stringifying `DefPath`.
         crate::ty::tls::with_opt(|tcx| {
             if let Some(tcx) = tcx {
                 let def_id = map.local_def_id(id);
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index d2c45a5af8598..2c8590aa4e3fa 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -13,26 +13,24 @@ pub use self::UnsafeSource::*;
 use crate::hir::def::{Res, DefKind};
 use crate::hir::def_id::{DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX};
 use crate::hir::ptr::P;
-use crate::util::nodemap::{NodeMap, FxHashSet};
 use crate::mir::mono::Linkage;
+use crate::ty::AdtKind;
+use crate::ty::query::Providers;
+use crate::util::nodemap::{NodeMap, FxHashSet};
 
 use errors::FatalError;
 use syntax_pos::{Span, DUMMY_SP, symbol::InternedString, MultiSpan};
 use syntax::source_map::Spanned;
-use rustc_target::spec::abi::Abi;
 use syntax::ast::{self, CrateSugar, Ident, Name, NodeId, AsmDialect};
 use syntax::ast::{Attribute, Label, LitKind, StrStyle, FloatTy, IntTy, UintTy};
 use syntax::attr::{InlineAttr, OptimizeAttr};
 use syntax::symbol::{Symbol, kw};
 use syntax::tokenstream::TokenStream;
 use syntax::util::parser::ExprPrecedence;
-use crate::ty::AdtKind;
-use crate::ty::query::Providers;
-
+use rustc_target::spec::abi::Abi;
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_macros::HashStable;
-
 use rustc_serialize::{self, Encoder, Encodable, Decoder, Decodable};
 use std::collections::{BTreeSet, BTreeMap};
 use std::fmt;
@@ -99,7 +97,8 @@ impl rustc_serialize::UseSpecializedEncodable for HirId {
         } = *self;
 
         owner.encode(s)?;
-        local_id.encode(s)
+        local_id.encode(s)?;
+        Ok(())
     }
 }
 
@@ -121,7 +120,7 @@ impl fmt::Display for HirId {
     }
 }
 
-// Hack to ensure that we don't try to access the private parts of `ItemLocalId` in this module
+// Hack to ensure that we don't try to access the private parts of `ItemLocalId` in this module.
 mod item_local_id_inner {
     use rustc_data_structures::indexed_vec::Idx;
     use rustc_macros::HashStable;
@@ -191,7 +190,7 @@ pub enum ParamName {
     Fresh(usize),
 
     /// Indicates an illegal name was given and an error has been
-    /// repored (so we should squelch other derived errors). Occurs
+    /// reported (so we should squelch other derived errors). Occurs
     /// when, e.g., `'_` is used in the wrong place.
     Error,
 }
@@ -746,7 +745,7 @@ pub struct Crate {
     // Attributes from non-exported macros, kept only for collecting the library feature list.
     pub non_exported_macro_attrs: HirVec<Attribute>,
 
-    // N.B., we use a BTreeMap here so that `visit_all_items` iterates
+    // N.B., we use a `BTreeMap` here so that `visit_all_items` iterates
     // over the ids in increasing order. In principle it should not
     // matter what order we visit things in, but in *practice* it
     // does, because it can affect the order in which errors are
@@ -1403,13 +1402,13 @@ pub struct AnonConst {
     pub body: BodyId,
 }
 
-/// An expression
+/// An expression.
 #[derive(RustcEncodable, RustcDecodable)]
 pub struct Expr {
-    pub span: Span,
+    pub hir_id: HirId,
     pub node: ExprKind,
     pub attrs: ThinVec<Attribute>,
-    pub hir_id: HirId,
+    pub span: Span,
 }
 
 // `Expr` is used a lot. Make sure it doesn't unintentionally get bigger.
@@ -2422,37 +2421,37 @@ pub enum ItemKind {
     ///
     /// or just
     ///
-    /// `use foo::bar::baz;` (with `as baz` implicitly on the right)
+    /// `use foo::bar::baz;` (with `as baz` implicitly on the right).
     Use(P<Path>, UseKind),
 
-    /// A `static` item
+    /// A `static` item.
     Static(P<Ty>, Mutability, BodyId),
-    /// A `const` item
+    /// A `const` item.
     Const(P<Ty>, BodyId),
-    /// A function declaration
+    /// A function declaration.
     Fn(P<FnDecl>, FnHeader, Generics, BodyId),
-    /// A module
+    /// A module.
     Mod(Mod),
-    /// An external module
+    /// An external module.
     ForeignMod(ForeignMod),
-    /// Module-level inline assembly (from global_asm!)
+    /// Module-level inline assembly (from `global_asm!`).
     GlobalAsm(P<GlobalAsm>),
-    /// A type alias, e.g., `type Foo = Bar<u8>`
+    /// A type alias, e.g., `type Foo = Bar<u8>`.
     TyAlias(P<Ty>, Generics),
-    /// An opaque `impl Trait` type alias, e.g., `type Foo = impl Bar;`
+    /// An opaque `impl Trait` type alias, e.g., `type Foo = impl Bar;`.
     OpaqueTy(OpaqueTy),
-    /// An enum definition, e.g., `enum Foo<A, B> {C<A>, D<B>}`
+    /// An enum definition, e.g., `enum Foo<A, B> {C<A>, D<B>}`.
     Enum(EnumDef, Generics),
-    /// A struct definition, e.g., `struct Foo<A> {x: A}`
+    /// A struct definition, e.g., `struct Foo<A> {x: A}`.
     Struct(VariantData, Generics),
-    /// A union definition, e.g., `union Foo<A, B> {x: A, y: B}`
+    /// A union definition, e.g., `union Foo<A, B> {x: A, y: B}`.
     Union(VariantData, Generics),
-    /// A trait definition
+    /// A trait definition.
     Trait(IsAuto, Unsafety, Generics, GenericBounds, HirVec<TraitItemRef>),
-    /// A trait alias
+    /// A trait alias.
     TraitAlias(Generics, GenericBounds),
 
-    /// An implementation, eg `impl<A> Trait for Foo { .. }`
+    /// An implementation, e.g., `impl<A> Trait for Foo { .. }`.
     Impl(Unsafety,
          ImplPolarity,
          Defaultness,
diff --git a/src/librustc/hir/print.rs b/src/librustc/hir/print.rs
index 21cc72efee4a3..cfbfb5eceb550 100644
--- a/src/librustc/hir/print.rs
+++ b/src/librustc/hir/print.rs
@@ -1293,11 +1293,11 @@ impl<'a> State<'a> {
                 self.print_closure_params(&decl, body);
                 self.s.space();
 
-                // this is a bare expression
+                // This is a bare expression.
                 self.ann.nested(self, Nested::Body(body));
                 self.end(); // need to close a box
 
-                // a box will be closed by print_expr, but we didn't want an overall
+                // A box will be closed by `print_expr`, but we didn't want an overall
                 // wrapper so we closed the corresponding opening. so create an
                 // empty box to satisfy the close.
                 self.ibox(0);
@@ -1307,9 +1307,9 @@ impl<'a> State<'a> {
                     self.print_ident(label.ident);
                     self.word_space(":");
                 }
-                // containing cbox, will be closed by print-block at }
+                // containing cbox, will be closed by print-block at `}`
                 self.cbox(INDENT_UNIT);
-                // head-box, will be closed by print-block after {
+                // head-box, will be closed by print-block after `{`
                 self.ibox(0);
                 self.print_block(&blk);
             }
@@ -1759,7 +1759,7 @@ impl<'a> State<'a> {
                         self.word_space(",");
                     }
                     if let PatKind::Wild = p.node {
-                        // Print nothing
+                        // Print nothing.
                     } else {
                         self.print_pat(&p);
                     }
@@ -1891,7 +1891,7 @@ impl<'a> State<'a> {
             i += 1;
 
             if let hir::TyKind::Infer = ty.node {
-                // Print nothing
+                // Print nothing.
             } else {
                 s.s.word(":");
                 s.s.space();
@@ -2221,7 +2221,6 @@ impl<'a> State<'a> {
     }
 }
 
-// Dup'ed from parse::classify, but adapted for the HIR.
 /// Does this expression require a semicolon to be treated
 /// as a statement? The negation of this: 'can this expression
 /// be used as a statement without a semicolon' -- is used
@@ -2229,6 +2228,8 @@ impl<'a> State<'a> {
 ///     if true {...} else {...}
 ///      |x| 5
 /// isn't parsed as (if true {...} else {...} | x) | 5
+//
+// Duplicated from `parse::classify`, but adapted for the HIR.
 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
     match e.node {
         hir::ExprKind::Match(..) |
@@ -2238,7 +2239,7 @@ fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
     }
 }
 
-/// this statement requires a semicolon after it.
+/// This statement requires a semicolon after it.
 /// note that in one case (stmt_semi), we've already
 /// seen the semicolon, and thus don't need another.
 fn stmt_ends_with_semi(stmt: &hir::StmtKind) -> bool {
@@ -2277,7 +2278,7 @@ fn bin_op_to_assoc_op(op: hir::BinOpKind) -> AssocOp {
     }
 }
 
-/// Expressions that syntactically contain an "exterior" struct literal i.e., not surrounded by any
+/// Expressions that syntactically contain an "exterior" struct literal, i.e., not surrounded by any
 /// parens or other delimiters, e.g., `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
 fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
@@ -2287,7 +2288,7 @@ fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
         hir::ExprKind::Assign(ref lhs, ref rhs) |
         hir::ExprKind::AssignOp(_, ref lhs, ref rhs) |
         hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
-            // X { y: 1 } + X { y: 2 }
+            // `X { y: 1 } + X { y: 2 }`
             contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
         }
         hir::ExprKind::Unary(_, ref x) |
@@ -2295,12 +2296,12 @@ fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
         hir::ExprKind::Type(ref x, _) |
         hir::ExprKind::Field(ref x, _) |
         hir::ExprKind::Index(ref x, _) => {
-            // &X { y: 1 }, X { y: 1 }.y
+            // `&X { y: 1 }, X { y: 1 }.y`
             contains_exterior_struct_lit(&x)
         }
 
         hir::ExprKind::MethodCall(.., ref exprs) => {
-            // X { y: 1 }.bar(...)
+            // `X { y: 1 }.bar(...)`
             contains_exterior_struct_lit(&exprs[0])
         }
 
diff --git a/src/librustc/ich/hcx.rs b/src/librustc/ich/hcx.rs
index e77faea1e4c58..182a9ade8c36e 100644
--- a/src/librustc/ich/hcx.rs
+++ b/src/librustc/ich/hcx.rs
@@ -12,7 +12,6 @@ use std::hash as std_hash;
 use std::cell::RefCell;
 
 use syntax::ast;
-
 use syntax::source_map::SourceMap;
 use syntax::ext::hygiene::SyntaxContext;
 use syntax::symbol::Symbol;
@@ -20,9 +19,9 @@ use syntax::tokenstream::DelimSpan;
 use syntax_pos::{Span, DUMMY_SP};
 use syntax_pos::hygiene;
 
-use rustc_data_structures::stable_hasher::{HashStable,
-                                           StableHasher, StableHasherResult,
-                                           ToStableHashKey};
+use rustc_data_structures::stable_hasher::{
+    HashStable, StableHasher, StableHasherResult, ToStableHashKey,
+};
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use smallvec::SmallVec;
 
@@ -32,9 +31,9 @@ fn compute_ignored_attr_names() -> FxHashSet<Symbol> {
 }
 
 /// This is the context state available during incr. comp. hashing. It contains
-/// enough information to transform DefIds and HirIds into stable DefPaths (i.e.
-/// a reference to the TyCtxt) and it holds a few caches for speeding up various
-/// things (e.g., each DefId/DefPath is only hashed once).
+/// enough information to transform `DefId`s and `HirId`s into stable `DefPath`s (i.e.,
+/// a reference to the `TyCtxt`) and it holds a few caches for speeding up various
+/// things (e.g., each `DefId`/`DefPath` is only hashed once).
 #[derive(Clone)]
 pub struct StableHashingContext<'a> {
     sess: &'a Session,
@@ -46,7 +45,7 @@ pub struct StableHashingContext<'a> {
     node_id_hashing_mode: NodeIdHashingMode,
 
     // Very often, we are hashing something that does not need the
-    // CachingSourceMapView, so we initialize it lazily.
+    // `CachingSourceMapView`, so we initialize it lazily.
     raw_source_map: &'a SourceMap,
     caching_source_map: Option<CachingSourceMapView<'a>>,
 }
@@ -57,24 +56,24 @@ pub enum NodeIdHashingMode {
     HashDefPath,
 }
 
-/// The BodyResolver allows to map a BodyId to the corresponding hir::Body.
-/// We could also just store a plain reference to the hir::Crate but we want
+/// The `BodyResolver` allows mapping a `BodyId` to the corresponding `hir::Body`.
+/// We could also just store a plain reference to the `hir::Crate` but we want
 /// to avoid that the crate is used to get untracked access to all of the HIR.
 #[derive(Clone, Copy)]
 struct BodyResolver<'tcx>(&'tcx hir::Crate);
 
 impl<'tcx> BodyResolver<'tcx> {
-    // Return a reference to the hir::Body with the given BodyId.
-    // DOES NOT DO ANY TRACKING, use carefully.
+    /// Returns a reference to the `hir::Body` with the given `BodyId`.
+    /// **Does not do any tracking**; use carefully.
     fn body(self, id: hir::BodyId) -> &'tcx hir::Body {
         self.0.body(id)
     }
 }
 
 impl<'a> StableHashingContext<'a> {
-    // The `krate` here is only used for mapping BodyIds to Bodies.
-    // Don't use it for anything else or you'll run the risk of
-    // leaking data out of the tracking system.
+    /// The `krate` here is only used for mapping `BodyId`s to `Body`s.
+    /// Don't use it for anything else or you'll run the risk of
+    /// leaking data out of the tracking system.
     #[inline]
     pub fn new(sess: &'a Session,
                krate: &'a hir::Crate,
@@ -217,9 +216,7 @@ impl<'a> StableHashingContextProvider<'a> for StableHashingContext<'a> {
     }
 }
 
-impl<'a> crate::dep_graph::DepGraphSafe for StableHashingContext<'a> {
-}
-
+impl<'a> crate::dep_graph::DepGraphSafe for StableHashingContext<'a> {}
 
 impl<'a> HashStable<StableHashingContext<'a>> for hir::BodyId {
     fn hash_stable<W: StableHasherResult>(&self,
@@ -292,16 +289,15 @@ impl<'a> ToStableHashKey<StableHashingContext<'a>> for ast::NodeId {
 }
 
 impl<'a> HashStable<StableHashingContext<'a>> for Span {
-
-    // Hash a span in a stable way. We can't directly hash the span's BytePos
-    // fields (that would be similar to hashing pointers, since those are just
-    // offsets into the SourceMap). Instead, we hash the (file name, line, column)
-    // triple, which stays the same even if the containing SourceFile has moved
-    // within the SourceMap.
-    // Also note that we are hashing byte offsets for the column, not unicode
-    // codepoint offsets. For the purpose of the hash that's sufficient.
-    // Also, hashing filenames is expensive so we avoid doing it twice when the
-    // span starts and ends in the same file, which is almost always the case.
+    /// Hashes a span in a stable way. We can't directly hash the span's `BytePos`
+    /// fields (that would be similar to hashing pointers, since those are just
+    /// offsets into the `SourceMap`). Instead, we hash the (file name, line, column)
+    /// triple, which stays the same even if the containing `SourceFile` has moved
+    /// within the `SourceMap`.
+    /// Also note that we are hashing byte offsets for the column, not unicode
+    /// codepoint offsets. For the purpose of the hash that's sufficient.
+    /// Also, hashing filenames is expensive so we avoid doing it twice when the
+    /// span starts and ends in the same file, which is almost always the case.
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
@@ -340,7 +336,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for Span {
         }
 
         std_hash::Hash::hash(&TAG_VALID_SPAN, hasher);
-        // We truncate the stable_id hash and line and col numbers. The chances
+        // We truncate the stable ID hash and line and column numbers. The chances
         // of causing a collision this way should be minimal.
         std_hash::Hash::hash(&(file_lo.name_hash as u64), hasher);
 
diff --git a/src/librustc/ich/impls_hir.rs b/src/librustc/ich/impls_hir.rs
index fb981d961129f..6e6492d0426f2 100644
--- a/src/librustc/ich/impls_hir.rs
+++ b/src/librustc/ich/impls_hir.rs
@@ -5,8 +5,10 @@ use crate::hir;
 use crate::hir::map::DefPathHash;
 use crate::hir::def_id::{DefId, LocalDefId, CrateNum, CRATE_DEF_INDEX};
 use crate::ich::{StableHashingContext, NodeIdHashingMode, Fingerprint};
-use rustc_data_structures::stable_hasher::{HashStable, ToStableHashKey,
-                                           StableHasher, StableHasherResult};
+
+use rustc_data_structures::stable_hasher::{
+    HashStable, ToStableHashKey, StableHasher, StableHasherResult,
+};
 use smallvec::SmallVec;
 use std::mem;
 use syntax::ast;
@@ -82,9 +84,9 @@ for hir::ItemLocalId {
     }
 }
 
-// The following implementations of HashStable for ItemId, TraitItemId, and
-// ImplItemId deserve special attention. Normally we do not hash NodeIds within
-// the HIR, since they just signify a HIR nodes own path. But ItemId et al
+// The following implementations of HashStable for `ItemId`, `TraitItemId`, and
+// `ImplItemId` deserve special attention. Normally we do not hash `NodeId`s within
+// the HIR, since they just signify a HIR nodes own path. But `ItemId` et al
 // are used when another item in the HIR is *referenced* and we certainly
 // want to pick up on a reference changing its target, so we hash the NodeIds
 // in "DefPath Mode".
@@ -131,7 +133,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::ImplItemId {
     }
 }
 
-
 impl_stable_hash_for!(struct ast::Label {
     ident
 });
@@ -241,7 +242,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::ImplItem {
     }
 }
 
-impl_stable_hash_for!(enum ::syntax::ast::CrateSugar {
+impl_stable_hash_for!(enum ast::CrateSugar {
     JustCrate,
     PubCrate,
 });
@@ -365,8 +366,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::def_id::DefIndex {
     }
 }
 
-impl<'a> ToStableHashKey<StableHashingContext<'a>>
-for hir::def_id::DefIndex {
+impl<'a> ToStableHashKey<StableHashingContext<'a>> for hir::def_id::DefIndex {
     type KeyType = DefPathHash;
 
     #[inline]
diff --git a/src/librustc/ich/impls_syntax.rs b/src/librustc/ich/impls_syntax.rs
index ddfca3a4cfb72..a33181e5925cd 100644
--- a/src/librustc/ich/impls_syntax.rs
+++ b/src/librustc/ich/impls_syntax.rs
@@ -115,9 +115,10 @@ for ::syntax::attr::StabilityLevel {
                                           hasher: &mut StableHasher<W>) {
         mem::discriminant(self).hash_stable(hcx, hasher);
         match *self {
-            ::syntax::attr::StabilityLevel::Unstable { ref reason, ref issue } => {
+            ::syntax::attr::StabilityLevel::Unstable { ref reason, ref issue, ref is_soft } => {
                 reason.hash_stable(hcx, hasher);
                 issue.hash_stable(hcx, hasher);
+                is_soft.hash_stable(hcx, hasher);
             }
             ::syntax::attr::StabilityLevel::Stable { ref since } => {
                 since.hash_stable(hcx, hasher);
@@ -390,9 +391,17 @@ impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnData {
 impl_stable_hash_for!(enum ::syntax_pos::hygiene::ExpnKind {
     Root,
     Macro(kind, descr),
+    AstPass(kind),
     Desugaring(kind)
 });
 
+impl_stable_hash_for!(enum ::syntax_pos::hygiene::AstPass {
+    StdImports,
+    TestHarness,
+    ProcMacroHarness,
+    PluginMacroDefs,
+});
+
 impl_stable_hash_for!(enum ::syntax_pos::hygiene::DesugaringKind {
     CondTemporary,
     Async,
diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index be7669fcad875..f230c53728748 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -204,7 +204,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ty::TyVid {
     fn hash_stable<W: StableHasherResult>(&self,
                                           _hcx: &mut StableHashingContext<'a>,
                                           _hasher: &mut StableHasher<W>) {
-        // TyVid values are confined to an inference context and hence
+        // `TyVid` values are confined to an inference context and hence
         // should not be hashed.
         bug!("ty::TyKind::hash_stable() - can't hash a TyVid {:?}.", *self)
     }
@@ -214,7 +214,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ty::IntVid {
     fn hash_stable<W: StableHasherResult>(&self,
                                           _hcx: &mut StableHashingContext<'a>,
                                           _hasher: &mut StableHasher<W>) {
-        // IntVid values are confined to an inference context and hence
+        // `IntVid` values are confined to an inference context and hence
         // should not be hashed.
         bug!("ty::TyKind::hash_stable() - can't hash an IntVid {:?}.", *self)
     }
@@ -224,7 +224,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ty::FloatVid {
     fn hash_stable<W: StableHasherResult>(&self,
                                           _hcx: &mut StableHashingContext<'a>,
                                           _hasher: &mut StableHasher<W>) {
-        // FloatVid values are confined to an inference context and hence
+        // `FloatVid` values are confined to an inference context and hence
         // should not be hashed.
         bug!("ty::TyKind::hash_stable() - can't hash a FloatVid {:?}.", *self)
     }
diff --git a/src/librustc/infer/equate.rs b/src/librustc/infer/equate.rs
index 5dfa0d29daf1b..96d40bc81add2 100644
--- a/src/librustc/infer/equate.rs
+++ b/src/librustc/infer/equate.rs
@@ -97,7 +97,7 @@ impl TypeRelation<'tcx> for Equate<'combine, 'infcx, 'tcx> {
                self.tag(),
                a,
                b);
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         self.fields.infcx.borrow_region_constraints()
                          .make_eqregion(origin, a, b);
         Ok(a)
diff --git a/src/librustc/infer/error_reporting/mod.rs b/src/librustc/infer/error_reporting/mod.rs
index 5883be6e26883..ab24b3f2f059f 100644
--- a/src/librustc/infer/error_reporting/mod.rs
+++ b/src/librustc/infer/error_reporting/mod.rs
@@ -55,7 +55,8 @@ use crate::hir::def_id::DefId;
 use crate::hir::Node;
 use crate::infer::opaque_types;
 use crate::middle::region;
-use crate::traits::{ObligationCause, ObligationCauseCode};
+use crate::traits::{IfExpressionCause, MatchExpressionArmCause, ObligationCause};
+use crate::traits::{ObligationCauseCode};
 use crate::ty::error::TypeError;
 use crate::ty::{self, subst::{Subst, SubstsRef}, Region, Ty, TyCtxt, TypeFoldable};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
@@ -624,13 +625,13 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     }
                 }
             }
-            ObligationCauseCode::MatchExpressionArm {
+            ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
                 source,
                 ref prior_arms,
                 last_ty,
                 discrim_hir_id,
                 ..
-            } => match source {
+            }) => match source {
                 hir::MatchSource::IfLetDesugar { .. } => {
                     let msg = "`if let` arms have incompatible types";
                     err.span_label(cause.span, msg);
@@ -681,7 +682,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     }
                 }
             },
-            ObligationCauseCode::IfExpression { then, outer, semicolon } => {
+            ObligationCauseCode::IfExpression(box IfExpressionCause { then, outer, semicolon }) => {
                 err.span_label(then, "expected because of this");
                 outer.map(|sp| err.span_label(sp, "if and else have incompatible types"));
                 if let Some(sp) = semicolon {
@@ -1622,13 +1623,15 @@ impl<'tcx> ObligationCause<'tcx> {
         use crate::traits::ObligationCauseCode::*;
         match self.code {
             CompareImplMethodObligation { .. } => Error0308("method not compatible with trait"),
-            MatchExpressionArm { source, .. } => Error0308(match source {
-                hir::MatchSource::IfLetDesugar { .. } => "`if let` arms have incompatible types",
-                hir::MatchSource::TryDesugar => {
-                    "try expression alternatives have incompatible types"
-                }
-                _ => "match arms have incompatible types",
-            }),
+            MatchExpressionArm(box MatchExpressionArmCause { source, .. }) =>
+                Error0308(match source {
+                    hir::MatchSource::IfLetDesugar { .. } =>
+                        "`if let` arms have incompatible types",
+                    hir::MatchSource::TryDesugar => {
+                        "try expression alternatives have incompatible types"
+                    }
+                    _ => "match arms have incompatible types",
+                }),
             IfExpression { .. } => Error0308("if and else have incompatible types"),
             IfExpressionWithNoElse => Error0317("if may be missing an else clause"),
             MainFunctionType => Error0580("main function has wrong type"),
@@ -1656,7 +1659,7 @@ impl<'tcx> ObligationCause<'tcx> {
         match self.code {
             CompareImplMethodObligation { .. } => "method type is compatible with trait",
             ExprAssignable => "expression is assignable",
-            MatchExpressionArm { source, .. } => match source {
+            MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => match source {
                 hir::MatchSource::IfLetDesugar { .. } => "`if let` arms have compatible types",
                 _ => "match arms have compatible types",
             },
diff --git a/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs b/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
index b4fb018920647..bfa8353ca343f 100644
--- a/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -30,7 +30,7 @@ impl NiceRegionError<'me, 'tcx> {
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -50,7 +50,7 @@ impl NiceRegionError<'me, 'tcx> {
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -70,7 +70,7 @@ impl NiceRegionError<'me, 'tcx> {
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -92,7 +92,7 @@ impl NiceRegionError<'me, 'tcx> {
                 _,
                 _,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -108,7 +108,7 @@ impl NiceRegionError<'me, 'tcx> {
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -125,7 +125,7 @@ impl NiceRegionError<'me, 'tcx> {
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -142,7 +142,7 @@ impl NiceRegionError<'me, 'tcx> {
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -192,23 +192,28 @@ impl NiceRegionError<'me, 'tcx> {
             vid, sub_placeholder, sup_placeholder, trait_def_id, expected_substs, actual_substs
         );
 
-        let mut err = self.tcx().sess.struct_span_err(
-            cause.span(self.tcx()),
-            &format!(
-                "implementation of `{}` is not general enough",
-                self.tcx().def_path_str(trait_def_id),
-            ),
+        let span = cause.span(self.tcx());
+        let msg = format!(
+            "implementation of `{}` is not general enough",
+            self.tcx().def_path_str(trait_def_id),
+        );
+        let mut err = self.tcx().sess.struct_span_err(span, &msg);
+        err.span_label(
+            self.tcx().def_span(trait_def_id),
+            format!("trait `{}` defined here", self.tcx().def_path_str(trait_def_id)),
         );
 
-        match cause.code {
-            ObligationCauseCode::ItemObligation(def_id) => {
-                err.note(&format!(
-                    "Due to a where-clause on `{}`,",
-                    self.tcx().def_path_str(def_id),
-                ));
-            }
-            _ => (),
-        }
+        let leading_ellipsis = if let ObligationCauseCode::ItemObligation(def_id) = cause.code {
+            err.span_label(span, "doesn't satisfy where-clause");
+            err.span_label(
+                self.tcx().def_span(def_id),
+                &format!("due to a where-clause on `{}`...", self.tcx().def_path_str(def_id)),
+            );
+            true
+        } else {
+            err.span_label(span, &msg);
+            false
+        };
 
         let expected_trait_ref = self.infcx.resolve_vars_if_possible(&ty::TraitRef {
             def_id: trait_def_id,
@@ -295,6 +300,7 @@ impl NiceRegionError<'me, 'tcx> {
             expected_has_vid,
             actual_has_vid,
             any_self_ty_has_vid,
+            leading_ellipsis,
         );
 
         err
@@ -318,6 +324,7 @@ impl NiceRegionError<'me, 'tcx> {
         expected_has_vid: Option<usize>,
         actual_has_vid: Option<usize>,
         any_self_ty_has_vid: bool,
+        leading_ellipsis: bool,
     ) {
         // HACK(eddyb) maybe move this in a more central location.
         #[derive(Copy, Clone)]
@@ -392,13 +399,15 @@ impl NiceRegionError<'me, 'tcx> {
 
             let mut note = if passive_voice {
                 format!(
-                    "`{}` would have to be implemented for the type `{}`",
+                    "{}`{}` would have to be implemented for the type `{}`",
+                    if leading_ellipsis { "..." } else { "" },
                     expected_trait_ref,
                     expected_trait_ref.map(|tr| tr.self_ty()),
                 )
             } else {
                 format!(
-                    "`{}` must implement `{}`",
+                    "{}`{}` must implement `{}`",
+                    if leading_ellipsis { "..." } else { "" },
                     expected_trait_ref.map(|tr| tr.self_ty()),
                     expected_trait_ref,
                 )
@@ -407,20 +416,20 @@ impl NiceRegionError<'me, 'tcx> {
             match (has_sub, has_sup) {
                 (Some(n1), Some(n2)) => {
                     let _ = write!(note,
-                        ", for any two lifetimes `'{}` and `'{}`",
+                        ", for any two lifetimes `'{}` and `'{}`...",
                         std::cmp::min(n1, n2),
                         std::cmp::max(n1, n2),
                     );
                 }
                 (Some(n), _) | (_, Some(n)) => {
                     let _ = write!(note,
-                        ", for any lifetime `'{}`",
+                        ", for any lifetime `'{}`...",
                         n,
                     );
                 }
                 (None, None) => if let Some(n) = expected_has_vid {
                     let _ = write!(note,
-                        ", for some specific lifetime `'{}`",
+                        ", for some specific lifetime `'{}`...",
                         n,
                     );
                 },
@@ -439,13 +448,13 @@ impl NiceRegionError<'me, 'tcx> {
 
             let mut note = if passive_voice {
                 format!(
-                    "but `{}` is actually implemented for the type `{}`",
+                    "...but `{}` is actually implemented for the type `{}`",
                     actual_trait_ref,
                     actual_trait_ref.map(|tr| tr.self_ty()),
                 )
             } else {
                 format!(
-                    "but `{}` actually implements `{}`",
+                    "...but `{}` actually implements `{}`",
                     actual_trait_ref.map(|tr| tr.self_ty()),
                     actual_trait_ref,
                 )
diff --git a/src/librustc/infer/error_reporting/note.rs b/src/librustc/infer/error_reporting/note.rs
index caed4288892ef..115ffea97bf1a 100644
--- a/src/librustc/infer/error_reporting/note.rs
+++ b/src/librustc/infer/error_reporting/note.rs
@@ -138,7 +138,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                                           sup: Region<'tcx>)
                                           -> DiagnosticBuilder<'tcx> {
         match origin {
-            infer::Subtype(trace) => {
+            infer::Subtype(box trace) => {
                 let terr = TypeError::RegionsDoesNotOutlive(sup, sub);
                 let mut err = self.report_and_explain_type_error(trace, &terr);
                 self.tcx.note_and_explain_region(region_scope_tree, &mut err, "", sup, "...");
@@ -450,7 +450,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     ) -> DiagnosticBuilder<'tcx> {
         // I can't think how to do better than this right now. -nikomatsakis
         match placeholder_origin {
-            infer::Subtype(trace) => {
+            infer::Subtype(box trace) => {
                 let terr = TypeError::RegionsPlaceholderMismatch;
                 self.report_and_explain_type_error(trace, &terr)
             }
diff --git a/src/librustc/infer/glb.rs b/src/librustc/infer/glb.rs
index 2cef521176269..10e45321a6d6a 100644
--- a/src/librustc/infer/glb.rs
+++ b/src/librustc/infer/glb.rs
@@ -57,7 +57,7 @@ impl TypeRelation<'tcx> for Glb<'combine, 'infcx, 'tcx> {
                a,
                b);
 
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         Ok(self.fields.infcx.borrow_region_constraints().glb_regions(self.tcx(), origin, a, b))
     }
 
diff --git a/src/librustc/infer/lub.rs b/src/librustc/infer/lub.rs
index e20372f151371..8b64cda7bd26d 100644
--- a/src/librustc/infer/lub.rs
+++ b/src/librustc/infer/lub.rs
@@ -57,7 +57,7 @@ impl TypeRelation<'tcx> for Lub<'combine, 'infcx, 'tcx> {
                a,
                b);
 
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         Ok(self.fields.infcx.borrow_region_constraints().lub_regions(self.tcx(), origin, a, b))
     }
 
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index cc28567e2fc9e..c5712cc9941a9 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -254,7 +254,7 @@ pub struct TypeTrace<'tcx> {
 #[derive(Clone, Debug)]
 pub enum SubregionOrigin<'tcx> {
     /// Arose from a subtyping relation
-    Subtype(TypeTrace<'tcx>),
+    Subtype(Box<TypeTrace<'tcx>>),
 
     /// Stack-allocated closures cannot outlive innermost loop
     /// or function so as to ensure we only require finite stack
@@ -340,6 +340,10 @@ pub enum SubregionOrigin<'tcx> {
     },
 }
 
+// `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(SubregionOrigin<'_>, 32);
+
 /// Places that type/region parameters can appear.
 #[derive(Clone, Copy, Debug)]
 pub enum ParameterOrigin {
@@ -1321,13 +1325,13 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         T: TypeFoldable<'tcx>,
     {
         if !value.needs_infer() {
-            return value.clone(); // avoid duplicated subst-folding
+            return value.clone(); // Avoid duplicated subst-folding.
         }
         let mut r = resolve::OpportunisticVarResolver::new(self);
         value.fold_with(&mut r)
     }
 
-    /// Returns first unresolved variable contained in `T`. In the
+    /// Returns the first unresolved variable contained in `T`. In the
     /// process of visiting `T`, this will resolve (where possible)
     /// type variables in `T`, but it never constructs the final,
     /// resolved type, so it's more efficient than
@@ -1462,7 +1466,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
         let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem, None);
 
-        // this can get called from typeck (by euv), and moves_by_default
+        // This can get called from typeck (by euv), and `moves_by_default`
         // rightly refuses to work with inference variables, but
         // moves_by_default has a cache, which we want to use in other
         // cases.
@@ -1482,7 +1486,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         closure_kind_ty.to_opt_closure_kind()
     }
 
-    /// Obtain the signature of a closure. For closures, unlike
+    /// Obtains the signature of a closure. For closures, unlike
     /// `tcx.fn_sig(def_id)`, this method will work during the
     /// type-checking of the enclosing function and return the closure
     /// signature in its partially inferred state.
@@ -1558,11 +1562,7 @@ impl<'a, 'tcx> ShallowResolver<'a, 'tcx> {
         ShallowResolver { infcx }
     }
 
-    // We have this force-inlined variant of `shallow_resolve` for the one
-    // callsite that is extremely hot. All other callsites use the normal
-    // variant.
-    #[inline(always)]
-    pub fn inlined_shallow_resolve(&mut self, typ: Ty<'tcx>) -> Ty<'tcx> {
+    pub fn shallow_resolve(&mut self, typ: Ty<'tcx>) -> Ty<'tcx> {
         match typ.sty {
             ty::Infer(ty::TyVar(v)) => {
                 // Not entirely obvious: if `typ` is a type variable,
@@ -1597,6 +1597,42 @@ impl<'a, 'tcx> ShallowResolver<'a, 'tcx> {
             _ => typ,
         }
     }
+
+    // `resolver.shallow_resolve_changed(ty)` is equivalent to
+    // `resolver.shallow_resolve(ty) != ty`, but more efficient. It's always
+    // inlined, despite being large, because it has a single call site that is
+    // extremely hot.
+    #[inline(always)]
+    pub fn shallow_resolve_changed(&mut self, typ: Ty<'tcx>) -> bool {
+        match typ.sty {
+            ty::Infer(ty::TyVar(v)) => {
+                use self::type_variable::TypeVariableValue;
+
+                // See the comment in `shallow_resolve()`.
+                match self.infcx.type_variables.borrow_mut().probe(v) {
+                    TypeVariableValue::Known { value: t } => self.fold_ty(t) != typ,
+                    TypeVariableValue::Unknown { .. } => false,
+                }
+            }
+
+            ty::Infer(ty::IntVar(v)) => {
+                match self.infcx.int_unification_table.borrow_mut().probe_value(v) {
+                    Some(v) => v.to_type(self.infcx.tcx) != typ,
+                    None => false,
+                }
+            }
+
+            ty::Infer(ty::FloatVar(v)) => {
+                match self.infcx.float_unification_table.borrow_mut().probe_value(v) {
+                    Some(v) => v.to_type(self.infcx.tcx) != typ,
+                    None => false,
+                }
+            }
+
+            _ => false,
+        }
+    }
+
 }
 
 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
@@ -1605,7 +1641,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
     }
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.inlined_shallow_resolve(ty)
+        self.shallow_resolve(ty)
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
diff --git a/src/librustc/infer/sub.rs b/src/librustc/infer/sub.rs
index cd1d206b5fca1..76db55ecfa8ef 100644
--- a/src/librustc/infer/sub.rs
+++ b/src/librustc/infer/sub.rs
@@ -130,7 +130,7 @@ impl TypeRelation<'tcx> for Sub<'combine, 'infcx, 'tcx> {
         // FIXME -- we have more fine-grained information available
         // from the "cause" field, we could perhaps give more tailored
         // error messages.
-        let origin = SubregionOrigin::Subtype(self.fields.trace.clone());
+        let origin = SubregionOrigin::Subtype(box self.fields.trace.clone());
         self.fields.infcx.borrow_region_constraints()
                          .make_subregion(origin, a, b);
 
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 368f5bb64fe6c..7a01ae6b6d9cc 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -45,7 +45,6 @@
 #![feature(non_exhaustive)]
 #![feature(optin_builtin_traits)]
 #![feature(range_is_empty)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
 #![feature(specialization)]
 #![feature(unboxed_closures)]
@@ -68,7 +67,6 @@
 
 #[macro_use] extern crate bitflags;
 extern crate getopts;
-#[macro_use] extern crate lazy_static;
 #[macro_use] extern crate scoped_tls;
 #[cfg(windows)]
 extern crate libc;
@@ -88,8 +86,6 @@ mod tests;
 #[macro_use]
 mod macros;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 pub mod error_codes;
 
 #[macro_use]
@@ -97,7 +93,6 @@ pub mod query;
 
 #[macro_use]
 pub mod arena;
-pub mod cfg;
 pub mod dep_graph;
 pub mod hir;
 pub mod ich;
@@ -143,6 +138,3 @@ pub mod util {
 
 // Allows macros to refer to this crate as `::rustc`
 extern crate self as rustc;
-
-// Build the diagnostics array at the end so that the metadata includes error use sites.
-__build_diagnostic_array! { librustc, DIAGNOSTICS }
diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index 6d9a6bb77dd55..dd290572d7bb7 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -395,6 +395,12 @@ declare_lint! {
     "reservation of a two-phased borrow conflicts with other shared borrows"
 }
 
+declare_lint! {
+    pub SOFT_UNSTABLE,
+    Deny,
+    "a feature gate that doesn't break dependent crates"
+}
+
 declare_lint_pass! {
     /// Does nothing as a lint pass, but registers some `Lint`s
     /// that are used by other parts of the compiler.
@@ -460,6 +466,7 @@ declare_lint_pass! {
         NESTED_IMPL_TRAIT,
         MUTABLE_BORROW_RESERVATION_CONFLICT,
         INDIRECT_STRUCTURAL_MATCH,
+        SOFT_UNSTABLE,
     ]
 }
 
diff --git a/src/librustc/lint/context.rs b/src/librustc/lint/context.rs
index 77df93080cd16..c658120b95df3 100644
--- a/src/librustc/lint/context.rs
+++ b/src/librustc/lint/context.rs
@@ -16,32 +16,32 @@
 
 use self::TargetLint::*;
 
-use std::slice;
-use rustc_data_structures::sync::{ReadGuard, Lock, ParallelIterator, join, par_iter};
+use crate::hir;
+use crate::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
+use crate::hir::intravisit as hir_visit;
+use crate::hir::intravisit::Visitor;
+use crate::hir::map::{definitions::DisambiguatedDefPathData, DefPathData};
 use crate::lint::{EarlyLintPass, LateLintPass, EarlyLintPassObject, LateLintPassObject};
 use crate::lint::{LintArray, Level, Lint, LintId, LintPass, LintBuffer};
 use crate::lint::builtin::BuiltinLintDiagnostics;
 use crate::lint::levels::{LintLevelSets, LintLevelsBuilder};
 use crate::middle::privacy::AccessLevels;
-use rustc_serialize::{Decoder, Decodable, Encoder, Encodable};
 use crate::session::{config, early_error, Session};
 use crate::ty::{self, print::Printer, subst::Kind, TyCtxt, Ty};
 use crate::ty::layout::{LayoutError, LayoutOf, TyLayout};
 use crate::util::nodemap::FxHashMap;
 use crate::util::common::time;
 
+use errors::DiagnosticBuilder;
+use std::slice;
 use std::default::Default as StdDefault;
+use rustc_data_structures::sync::{ReadGuard, Lock, ParallelIterator, join, par_iter};
+use rustc_serialize::{Decoder, Decodable, Encoder, Encodable};
 use syntax::ast;
 use syntax::edition;
-use syntax_pos::{MultiSpan, Span, symbol::Symbol};
-use errors::DiagnosticBuilder;
-use crate::hir;
-use crate::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
-use crate::hir::intravisit as hir_visit;
-use crate::hir::intravisit::Visitor;
-use crate::hir::map::{definitions::DisambiguatedDefPathData, DefPathData};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::visit as ast_visit;
+use syntax_pos::{MultiSpan, Span, symbol::Symbol};
 
 /// Information about the registered lints.
 ///
diff --git a/src/librustc/lint/mod.rs b/src/librustc/lint/mod.rs
index a3518b2b478ad..5b490b701267d 100644
--- a/src/librustc/lint/mod.rs
+++ b/src/librustc/lint/mod.rs
@@ -646,6 +646,30 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
         (Level::Forbid, None) => sess.struct_err(msg),
     };
 
+    // Check for future incompatibility lints and issue a stronger warning.
+    let lints = sess.lint_store.borrow();
+    let lint_id = LintId::of(lint);
+    let future_incompatible = lints.future_incompatible(lint_id);
+
+    // If this code originates in a foreign macro, aka something that this crate
+    // did not itself author, then it's likely that there's nothing this crate
+    // can do about it. We probably want to skip the lint entirely.
+    if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
+        // Any suggestions made here are likely to be incorrect, so anything we
+        // emit shouldn't be automatically fixed by rustfix.
+        err.allow_suggestions(false);
+
+        // If this is a future incompatible lint it'll become a hard error, so
+        // we have to emit *something*. Also allow lints to whitelist themselves
+        // on a case-by-case basis for emission in a foreign macro.
+        if future_incompatible.is_none() && !lint.report_in_external_macro {
+            err.cancel();
+            // Don't continue further, since we don't want to have
+            // `diag_span_note_once` called for a diagnostic that isn't emitted.
+            return err;
+        }
+    }
+
     let name = lint.name_lower();
     match src {
         LintSource::Default => {
@@ -695,10 +719,6 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
 
     err.code(DiagnosticId::Lint(name));
 
-    // Check for future incompatibility lints and issue a stronger warning.
-    let lints = sess.lint_store.borrow();
-    let lint_id = LintId::of(lint);
-    let future_incompatible = lints.future_incompatible(lint_id);
     if let Some(future_incompatible) = future_incompatible {
         const STANDARD_MESSAGE: &str =
             "this was previously accepted by the compiler but is being phased out; \
@@ -723,22 +743,6 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
         err.note(&citation);
     }
 
-    // If this code originates in a foreign macro, aka something that this crate
-    // did not itself author, then it's likely that there's nothing this crate
-    // can do about it. We probably want to skip the lint entirely.
-    if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
-        // Any suggestions made here are likely to be incorrect, so anything we
-        // emit shouldn't be automatically fixed by rustfix.
-        err.allow_suggestions(false);
-
-        // If this is a future incompatible lint it'll become a hard error, so
-        // we have to emit *something*. Also allow lints to whitelist themselves
-        // on a case-by-case basis for emission in a foreign macro.
-        if future_incompatible.is_none() && !lint.report_in_external_macro {
-            err.cancel()
-        }
-    }
-
     return err
 }
 
@@ -868,15 +872,15 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     let expn_data = span.ctxt().outer_expn_data();
     match expn_data.kind {
         ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop) => false,
-        ExpnKind::Desugaring(_) => true, // well, it's "external"
+        ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
         ExpnKind::Macro(MacroKind::Bang, _) => {
             if expn_data.def_site.is_dummy() {
-                // dummy span for the def_site means it's an external macro
+                // Dummy span for the `def_site` means it's an external macro.
                 return true;
             }
             match sess.source_map().span_to_snippet(expn_data.def_site) {
                 Ok(code) => !code.starts_with("macro_rules"),
-                // no snippet = external macro or compiler-builtin expansion
+                // No snippet means external macro or compiler-builtin expansion.
                 Err(_) => true,
             }
         }
@@ -884,7 +888,7 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     }
 }
 
-/// Returns whether `span` originates in a derive macro's expansion
+/// Returns `true` if `span` originates in a derive-macro's expansion.
 pub fn in_derive_expansion(span: Span) -> bool {
     if let ExpnKind::Macro(MacroKind::Derive, _) = span.ctxt().outer_expn_data().kind {
         return true;
diff --git a/src/librustc/middle/entry.rs b/src/librustc/middle/entry.rs
index 53c099c0b4339..ba27d332e43f7 100644
--- a/src/librustc/middle/entry.rs
+++ b/src/librustc/middle/entry.rs
@@ -16,17 +16,17 @@ struct EntryContext<'a, 'tcx> {
 
     map: &'a hir_map::Map<'tcx>,
 
-    // The top-level function called 'main'
+    /// The top-level function called `main`.
     main_fn: Option<(HirId, Span)>,
 
-    // The function that has attribute named 'main'
+    /// The function that has attribute named `main`.
     attr_main_fn: Option<(HirId, Span)>,
 
-    // The function that has the attribute 'start' on it
+    /// The function that has the attribute 'start' on it.
     start_fn: Option<(HirId, Span)>,
 
-    // The functions that one might think are 'main' but aren't, e.g.
-    // main functions not defined at the top level. For diagnostics.
+    /// The functions that one might think are `main` but aren't, e.g.
+    /// main functions not defined at the top level. For diagnostics.
     non_main_fns: Vec<(HirId, Span)> ,
 }
 
@@ -39,11 +39,11 @@ impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
     }
 
     fn visit_trait_item(&mut self, _trait_item: &'tcx TraitItem) {
-        // entry fn is never a trait item
+        // Entry fn is never a trait item.
     }
 
     fn visit_impl_item(&mut self, _impl_item: &'tcx ImplItem) {
-        // entry fn is never an impl item
+        // Entry fn is never a trait item.
     }
 }
 
@@ -54,7 +54,7 @@ fn entry_fn(tcx: TyCtxt<'_>, cnum: CrateNum) -> Option<(DefId, EntryFnType)> {
         *ty == config::CrateType::Executable
     });
     if !any_exe {
-        // No need to find a main function
+        // No need to find a main function.
         return None;
     }
 
@@ -88,7 +88,7 @@ fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
                 EntryPointType::MainAttr
             } else if item.ident.name == sym::main {
                 if at_root {
-                    // This is a top-level function so can be 'main'.
+                    // This is a top-level function so can be `main`.
                     EntryPointType::MainNamed
                 } else {
                     EntryPointType::OtherMain
@@ -109,7 +109,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
                 ctxt.main_fn = Some((item.hir_id, item.span));
             } else {
                 span_err!(ctxt.session, item.span, E0136,
-                          "multiple 'main' functions");
+                          "multiple `main` functions");
             }
         },
         EntryPointType::OtherMain => {
@@ -130,7 +130,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
             if ctxt.start_fn.is_none() {
                 ctxt.start_fn = Some((item.hir_id, item.span));
             } else {
-                struct_span_err!(ctxt.session, item.span, E0138, "multiple 'start' functions")
+                struct_span_err!(ctxt.session, item.span, E0138, "multiple `start` functions")
                     .span_label(ctxt.start_fn.unwrap().1, "previous `start` function here")
                     .span_label(item.span, "multiple `start` functions")
                     .emit();
@@ -148,34 +148,48 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) -> Option<(De
     } else if let Some((hir_id, _)) = visitor.main_fn {
         Some((tcx.hir().local_def_id(hir_id), EntryFnType::Main))
     } else {
-        // No main function
-        let mut err = struct_err!(tcx.sess, E0601,
-            "`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
-        if !visitor.non_main_fns.is_empty() {
-            // There were some functions named 'main' though. Try to give the user a hint.
-            err.note("the main function must be defined at the crate level \
-                      but you have one or more functions named 'main' that are not \
-                      defined at the crate level. Either move the definition or \
-                      attach the `#[main]` attribute to override this behavior.");
-            for &(_, span) in &visitor.non_main_fns {
-                err.span_note(span, "here is a function named 'main'");
-            }
-            err.emit();
-        } else {
-            if let Some(ref filename) = tcx.sess.local_crate_source_file {
-                err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
-            }
-            if tcx.sess.teach(&err.get_code().unwrap()) {
-                err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
-                          to get started: https://doc.rust-lang.org/book/");
-            }
-            err.emit();
-        }
-
+        no_main_err(tcx, visitor);
         None
     }
 }
 
+fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
+    // There is no main function.
+    let mut err = struct_err!(tcx.sess, E0601,
+        "`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
+    let filename = &tcx.sess.local_crate_source_file;
+    let note = if !visitor.non_main_fns.is_empty() {
+        for &(_, span) in &visitor.non_main_fns {
+            err.span_note(span, "here is a function named `main`");
+        }
+        err.note("you have one or more functions named `main` not defined at the crate level");
+        err.help("either move the `main` function definitions or attach the `#[main]` attribute \
+                  to one of them");
+        // There were some functions named `main` though. Try to give the user a hint.
+        format!("the main function must be defined at the crate level{}",
+                 filename.as_ref().map(|f| format!(" (in `{}`)", f.display())).unwrap_or_default())
+    } else if let Some(filename) = filename {
+        format!("consider adding a `main` function to `{}`", filename.display())
+    } else {
+        String::from("consider adding a `main` function at the crate level")
+    };
+    let sp = tcx.hir().krate().span;
+    // The file may be empty, which leads to the diagnostic machinery not emitting this
+    // note. This is a relatively simple way to detect that case and emit a span-less
+    // note instead.
+    if let Ok(_) = tcx.sess.source_map().lookup_line(sp.lo()) {
+        err.set_span(sp);
+        err.span_label(sp, &note);
+    } else {
+        err.note(&note);
+    }
+    if tcx.sess.teach(&err.get_code().unwrap()) {
+        err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
+                  to get started: https://doc.rust-lang.org/book/");
+    }
+    err.emit();
+}
+
 pub fn find_entry_point(tcx: TyCtxt<'_>) -> Option<(DefId, EntryFnType)> {
     tcx.entry_fn(LOCAL_CRATE)
 }
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index 222c2a405d65b..de6dadabcbf56 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -596,7 +596,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
             }
 
             hir::StmtKind::Item(_) => {
-                // we don't visit nested items in this visitor,
+                // We don't visit nested items in this visitor,
                 // only the fn body we were given.
             }
 
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 6b04600eb75f8..c5d9a722ae18e 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -3,10 +3,8 @@
 //! Language items are items that represent concepts intrinsic to the language
 //! itself. Examples are:
 //!
-//! * Traits that specify "kinds"; e.g., "Sync", "Send".
-//!
-//! * Traits that represent operators; e.g., "Add", "Sub", "Index".
-//!
+//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
+//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
 //! * Functions called by the compiler itself.
 
 pub use self::LangItem::*;
@@ -151,11 +149,11 @@ impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> {
     }
 
     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
-        // at present, lang items are always items, not trait items
+        // At present, lang items are always items, not trait items.
     }
 
     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
-        // at present, lang items are always items, not impl items
+        // At present, lang items are always items, not impl items.
     }
 }
 
@@ -204,7 +202,7 @@ impl LanguageItemCollector<'tcx> {
     }
 }
 
-/// Extract the first `lang = "$name"` out of a list of attributes.
+/// Extracts the first `lang = "$name"` out of a list of attributes.
 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
 /// are also extracted out when found.
 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
@@ -216,7 +214,7 @@ pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
     }))
 }
 
-/// Traverse and collect all the lang items in all crates.
+/// Traverses and collects all the lang items in all crates.
 pub fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems {
     // Initialize the collector.
     let mut collector = LanguageItemCollector::new(tcx);
@@ -246,6 +244,7 @@ pub fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems {
 
 language_item_table! {
 //  Variant name,                Name,                 Method name,             Target;
+    BoolImplItem,                "bool",               bool_impl,               Target::Impl;
     CharImplItem,                "char",               char_impl,               Target::Impl;
     StrImplItem,                 "str",                str_impl,                Target::Impl;
     SliceImplItem,               "slice",              slice_impl,              Target::Impl;
@@ -367,7 +366,7 @@ language_item_table! {
 
     MaybeUninitLangItem,         "maybe_uninit",       maybe_uninit,            Target::Union;
 
-    // Align offset for stride != 1, must not panic.
+    // Align offset for stride != 1; must not panic.
     AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
 
     TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
@@ -378,7 +377,7 @@ language_item_table! {
 
 impl<'tcx> TyCtxt<'tcx> {
     /// Returns the `DefId` for a given `LangItem`.
-    /// If not found, fatally abort compilation.
+    /// If not found, fatally aborts compilation.
     pub fn require_lang_item(&self, lang_item: LangItem, span: Option<Span>) -> DefId {
         self.lang_items().require(lang_item).unwrap_or_else(|msg| {
             if let Some(span) = span {
diff --git a/src/librustc/middle/region.rs b/src/librustc/middle/region.rs
index 28aa86ef9afb2..87470140e3148 100644
--- a/src/librustc/middle/region.rs
+++ b/src/librustc/middle/region.rs
@@ -6,29 +6,27 @@
 //!
 //! [rustc guide]: https://rust-lang.github.io/rustc-guide/mir/borrowck.html
 
+use crate::hir;
+use crate::hir::Node;
+use crate::hir::def_id::DefId;
+use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
+use crate::hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
 use crate::ich::{StableHashingContext, NodeIdHashingMode};
 use crate::util::nodemap::{FxHashMap, FxHashSet};
-use crate::ty;
+use crate::ty::{self, DefIdTree, TyCtxt};
+use crate::ty::query::Providers;
 
-use std::mem;
-use std::fmt;
+use rustc_data_structures::indexed_vec::Idx;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableHasherResult};
 use rustc_macros::HashStable;
 use syntax::source_map;
 use syntax_pos::{Span, DUMMY_SP};
-use crate::ty::{DefIdTree, TyCtxt};
-use crate::ty::query::Providers;
 
-use crate::hir;
-use crate::hir::Node;
-use crate::hir::def_id::DefId;
-use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
-use crate::hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
-use rustc_data_structures::indexed_vec::Idx;
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
-                                           StableHasherResult};
+use std::fmt;
+use std::mem;
 
-/// Scope represents a statically-describable scope that can be
-/// used to bound the lifetime/region for values.
+/// Represents a statically-describable scope that can be used to
+/// bound the lifetime/region for values.
 ///
 /// `Node(node_id)`: Any AST node that has any scope at all has the
 /// `Node(node_id)` scope. Other variants represent special cases not
@@ -225,7 +223,7 @@ pub struct ScopeTree {
     /// have lifetime parameters free in this body.
     root_parent: Option<hir::HirId>,
 
-    /// `parent_map` maps from a scope ID to the enclosing scope id;
+    /// Maps from a scope ID to the enclosing scope id;
     /// this is usually corresponding to the lexical nesting, though
     /// in the case of closures the parent scope is the innermost
     /// conditional expression or repeating block. (Note that the
@@ -233,17 +231,17 @@ pub struct ScopeTree {
     /// the closure itself.)
     parent_map: FxHashMap<Scope, (Scope, ScopeDepth)>,
 
-    /// `var_map` maps from a variable or binding ID to the block in
-    /// which that variable is declared.
+    /// Maps from a variable or binding ID to the block in which that
+    /// variable is declared.
     var_map: FxHashMap<hir::ItemLocalId, Scope>,
 
-    /// maps from a `NodeId` to the associated destruction scope (if any)
+    /// Maps from a `NodeId` to the associated destruction scope (if any).
     destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
 
-    /// `rvalue_scopes` includes entries for those expressions whose cleanup scope is
-    /// larger than the default. The map goes from the expression id
-    /// to the cleanup scope id. For rvalues not present in this
-    /// table, the appropriate cleanup scope is the innermost
+    /// `rvalue_scopes` includes entries for those expressions whose
+    /// cleanup scope is larger than the default. The map goes from the
+    /// expression ID to the cleanup scope id. For rvalues not present in
+    /// this table, the appropriate cleanup scope is the innermost
     /// enclosing statement, conditional expression, or repeating
     /// block (see `terminating_scopes`).
     /// In constants, None is used to indicate that certain expressions
@@ -318,7 +316,7 @@ pub struct ScopeTree {
     ///     4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
     ///     QED.
     ///
-    /// I don't think this property relies on `3.` in an essential way - it
+    /// This property ought to not on (3) in an essential way -- it
     /// is probably still correct even if we have "unrestricted" terminating
     /// scopes. However, why use the complicated proof when a simple one
     /// works?
@@ -341,20 +339,20 @@ pub struct ScopeTree {
 
 #[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub struct YieldData {
-    /// `Span` of the yield.
+    /// The `Span` of the yield.
     pub span: Span,
-    /// The number of expressions and patterns appearing before the `yield` in the body + 1.
+    /// The number of expressions and patterns appearing before the `yield` in the body plus one.
     pub expr_and_pat_count: usize,
     pub source: hir::YieldSource,
 }
 
 #[derive(Debug, Copy, Clone)]
 pub struct Context {
-    /// the root of the current region tree. This is typically the id
+    /// The root of the current region tree. This is typically the id
     /// of the innermost fn body. Each fn forms its own disjoint tree
     /// in the region hierarchy. These fn bodies are themselves
     /// arranged into a tree. See the "Modeling closures" section of
-    /// the README in infer::region_constraints for more
+    /// the README in `infer::region_constraints` for more
     /// details.
     root_id: Option<hir::ItemLocalId>,
 
@@ -369,15 +367,15 @@ pub struct Context {
 struct RegionResolutionVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
 
-    // The number of expressions and patterns visited in the current body
+    // The number of expressions and patterns visited in the current body.
     expr_and_pat_count: usize,
     // When this is `true`, we record the `Scopes` we encounter
     // when processing a Yield expression. This allows us to fix
     // up their indices.
     pessimistic_yield: bool,
-    // Stores scopes when pessimistic_yield is true.
+    // Stores scopes when `pessimistic_yield` is `true`.
     fixup_scopes: Vec<Scope>,
-    // Generated scope tree:
+    // The generated scope tree.
     scope_tree: ScopeTree,
 
     cx: Context,
@@ -411,7 +409,7 @@ struct ExprLocatorVisitor {
     expr_and_pat_count: usize,
 }
 
-// This visitor has to have the same visit_expr calls as RegionResolutionVisitor
+// This visitor has to have the same `visit_expr` calls as `RegionResolutionVisitor`
 // since `expr_count` is compared against the results there.
 impl<'tcx> Visitor<'tcx> for ExprLocatorVisitor {
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
@@ -456,7 +454,7 @@ impl<'tcx> ScopeTree {
             assert!(prev.is_none());
         }
 
-        // record the destruction scopes for later so we can query them
+        // Record the destruction scopes for later so we can query them.
         if let ScopeData::Destruction = child.data {
             self.destruction_scopes.insert(child.item_local_id(), child);
         }
@@ -478,7 +476,7 @@ impl<'tcx> ScopeTree {
         self.destruction_scopes.get(&n).cloned()
     }
 
-    /// Records that `sub_closure` is defined within `sup_closure`. These ids
+    /// Records that `sub_closure` is defined within `sup_closure`. These IDs
     /// should be the ID of the block that is the fn body, which is
     /// also the root of the region hierarchy for that fn.
     fn record_closure_parent(&mut self,
@@ -505,14 +503,14 @@ impl<'tcx> ScopeTree {
         self.rvalue_scopes.insert(var, lifetime);
     }
 
+    /// Returns the narrowest scope that encloses `id`, if any.
     pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
-        //! Returns the narrowest scope that encloses `id`, if any.
         self.parent_map.get(&id).cloned().map(|(p, _)| p)
     }
 
+    /// Returns the narrowest scope that encloses `id`, if any.
     #[allow(dead_code)] // used in cfg
     pub fn encl_scope(&self, id: Scope) -> Scope {
-        //! Returns the narrowest scope that encloses `id`, if any.
         self.opt_encl_scope(id).unwrap()
     }
 
@@ -522,16 +520,15 @@ impl<'tcx> ScopeTree {
             bug!("no enclosing scope for id {:?}", var_id))
     }
 
+    /// Returns the scope when the temp created by `expr_id` will be cleaned up.
     pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
-        //! Returns the scope when temp created by expr_id will be cleaned up
-
-        // check for a designated rvalue scope
+        // Check for a designated rvalue scope.
         if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
             debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
             return s;
         }
 
-        // else, locate the innermost terminating scope
+        // Otherwise, locate the innermost terminating scope
         // if there's one. Static items, for instance, won't
         // have an enclosing scope, hence no scope will be
         // returned.
@@ -552,9 +549,8 @@ impl<'tcx> ScopeTree {
         return None;
     }
 
+    /// Returns the lifetime of the variable `id`.
     pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
-        //! Returns the lifetime of the variable `id`.
-
         let scope = ty::ReScope(self.var_scope(id));
         debug!("var_region({:?}) = {:?}", id, scope);
         scope
@@ -589,7 +585,7 @@ impl<'tcx> ScopeTree {
         return true;
     }
 
-    /// Returns the ID of the innermost containing body
+    /// Returns the ID of the innermost containing body.
     pub fn containing_body(&self, mut scope: Scope) -> Option<hir::ItemLocalId> {
         loop {
             if let ScopeData::CallSite = scope.data {
@@ -1140,7 +1136,7 @@ fn resolve_local<'tcx>(
     // Rule A. `let (ref x, ref y) = (foo().x, 44)`. The rvalue `(22, 44)`
     // would have an extended lifetime, but not `foo()`.
     //
-    // Rule B. `let x = &foo().x`. The rvalue ``foo()` would have extended
+    // Rule B. `let x = &foo().x`. The rvalue `foo()` would have extended
     // lifetime.
     //
     // In some cases, multiple rules may apply (though not to the same
diff --git a/src/librustc/middle/stability.rs b/src/librustc/middle/stability.rs
index d02259bf3010b..c06a0feb6a993 100644
--- a/src/librustc/middle/stability.rs
+++ b/src/librustc/middle/stability.rs
@@ -438,6 +438,7 @@ impl<'tcx> Index<'tcx> {
                     level: attr::StabilityLevel::Unstable {
                         reason: Some(Symbol::intern(reason)),
                         issue: 27812,
+                        is_soft: false,
                     },
                     feature: sym::rustc_private,
                     rustc_depr: None,
@@ -480,7 +481,7 @@ pub fn provide(providers: &mut Providers<'_>) {
 }
 
 pub fn report_unstable(
-    sess: &Session, feature: Symbol, reason: Option<Symbol>, issue: u32, span: Span
+    sess: &Session, feature: Symbol, reason: Option<Symbol>, issue: u32, is_soft: bool, span: Span
 ) {
     let msg = match reason {
         Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
@@ -505,7 +506,13 @@ pub fn report_unstable(
     let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
     let fresh = sess.one_time_diagnostics.borrow_mut().insert(error_id);
     if fresh {
-        emit_feature_err(&sess.parse_sess, feature, span, GateIssue::Library(Some(issue)), &msg);
+        if is_soft {
+            sess.buffer_lint(lint::builtin::SOFT_UNSTABLE, CRATE_NODE_ID, span, &msg);
+        } else {
+            emit_feature_err(
+                &sess.parse_sess, feature, span, GateIssue::Library(Some(issue)), &msg
+            );
+        }
     }
 }
 
@@ -621,6 +628,7 @@ pub enum EvalResult {
         feature: Symbol,
         reason: Option<Symbol>,
         issue: u32,
+        is_soft: bool,
     },
     /// The item does not have the `#[stable]` or `#[unstable]` marker assigned.
     Unmarked,
@@ -720,7 +728,9 @@ impl<'tcx> TyCtxt<'tcx> {
         }
 
         match stability {
-            Some(&Stability { level: attr::Unstable { reason, issue }, feature, .. }) => {
+            Some(&Stability {
+                level: attr::Unstable { reason, issue, is_soft }, feature, ..
+            }) => {
                 if span.allows_unstable(feature) {
                     debug!("stability: skipping span={:?} since it is internal", span);
                     return EvalResult::Allow;
@@ -744,7 +754,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     }
                 }
 
-                EvalResult::Deny { feature, reason, issue }
+                EvalResult::Deny { feature, reason, issue, is_soft }
             }
             Some(_) => {
                 // Stable APIs are always ok to call and deprecated APIs are
@@ -767,8 +777,8 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
         match self.eval_stability(def_id, id, span) {
             EvalResult::Allow => {}
-            EvalResult::Deny { feature, reason, issue } =>
-                report_unstable(self.sess, feature, reason, issue, span),
+            EvalResult::Deny { feature, reason, issue, is_soft } =>
+                report_unstable(self.sess, feature, reason, issue, is_soft, span),
             EvalResult::Unmarked => {
                 // The API could be uncallable for other reasons, for example when a private module
                 // was referenced.
diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
index 4fb88dadd1f44..fa5fa2257dbc8 100644
--- a/src/librustc/middle/weak_lang_items.rs
+++ b/src/librustc/middle/weak_lang_items.rs
@@ -116,8 +116,8 @@ fn verify<'tcx>(tcx: TyCtxt<'tcx>,
 }
 
 impl<'a, 'tcx> Context<'a, 'tcx> {
-    fn register(&mut self, name: &str, span: Span) {
-        $(if name == stringify!($name) {
+    fn register(&mut self, name: Symbol, span: Span) {
+        $(if name == sym::$name {
             if self.items.$name().is_none() {
                 self.items.missing.push(lang_items::$item);
             }
@@ -136,7 +136,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
 
     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
         if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
-            self.register(&lang_item.as_str(), i.span);
+            self.register(lang_item, i.span);
         }
         intravisit::walk_foreign_item(self, i)
     }
diff --git a/src/librustc/mir/cache.rs b/src/librustc/mir/cache.rs
index 3d33e249536c7..1f604877841a7 100644
--- a/src/librustc/mir/cache.rs
+++ b/src/librustc/mir/cache.rs
@@ -27,7 +27,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for Cache {
     fn hash_stable<W: StableHasherResult>(&self,
                                           _: &mut StableHashingContext<'a>,
                                           _: &mut StableHasher<W>) {
-        // do nothing
+        // Do nothing.
     }
 }
 
diff --git a/src/librustc/mir/interpret/allocation.rs b/src/librustc/mir/interpret/allocation.rs
index df1d9a987011d..15e6cb6bcabae 100644
--- a/src/librustc/mir/interpret/allocation.rs
+++ b/src/librustc/mir/interpret/allocation.rs
@@ -4,16 +4,17 @@ use super::{
     Pointer, InterpResult, AllocId, ScalarMaybeUndef, write_target_uint, read_target_uint, Scalar,
 };
 
+use crate::mir;
 use crate::ty::layout::{Size, Align};
+
+use rustc_data_structures::sorted_map::SortedMap;
+use rustc_target::abi::HasDataLayout;
 use syntax::ast::Mutability;
 use std::iter;
-use crate::mir;
 use std::ops::{Range, Deref, DerefMut};
-use rustc_data_structures::sorted_map::SortedMap;
-use rustc_target::abi::HasDataLayout;
 use std::borrow::Cow;
 
-// NOTE: When adding new fields, make sure to adjust the Snapshot impl in
+// NOTE: When adding new fields, make sure to adjust the `Snapshot` impl in
 // `src/librustc_mir/interpret/snapshot.rs`.
 #[derive(
     Clone,
@@ -27,7 +28,7 @@ use std::borrow::Cow;
     RustcDecodable,
     HashStable,
 )]
-pub struct Allocation<Tag=(),Extra=()> {
+pub struct Allocation<Tag = (),Extra = ()> {
     /// The actual bytes of the allocation.
     /// Note that the bytes of a pointer represent the offset of the pointer.
     bytes: Vec<u8>,
@@ -42,7 +43,7 @@ pub struct Allocation<Tag=(),Extra=()> {
     pub size: Size,
     /// The alignment of the allocation to detect unaligned reads.
     pub align: Align,
-    /// Whether the allocation is mutable.
+    /// `true` if the allocation is mutable.
     /// Also used by codegen to determine if a static should be put into mutable memory,
     /// which happens for `static mut` and `static` with interior mutability.
     pub mutability: Mutability,
@@ -50,7 +51,6 @@ pub struct Allocation<Tag=(),Extra=()> {
     pub extra: Extra,
 }
 
-
 pub trait AllocationExtra<Tag>: ::std::fmt::Debug + Clone {
     // There is no constructor in here because the constructor's type depends
     // on `MemoryKind`, and making things sufficiently generic leads to painful
@@ -92,7 +92,7 @@ pub trait AllocationExtra<Tag>: ::std::fmt::Debug + Clone {
     }
 }
 
-// For Tag=() and no extra state, we have is a trivial implementation.
+// For `Tag = ()` and no extra state, we have a trivial implementation.
 impl AllocationExtra<()> for () { }
 
 // The constructors are all without extra; the extra gets added by a machine hook later.
@@ -130,6 +130,34 @@ impl<Tag> Allocation<Tag> {
     }
 }
 
+impl Allocation<(), ()> {
+    /// Add Tag and Extra fields
+    pub fn with_tags_and_extra<T, E>(
+        self,
+        mut tagger: impl FnMut(AllocId) -> T,
+        extra: E,
+    ) -> Allocation<T, E> {
+        Allocation {
+            bytes: self.bytes,
+            size: self.size,
+            relocations: Relocations::from_presorted(
+                self.relocations.iter()
+                    // The allocations in the relocations (pointers stored *inside* this allocation)
+                    // all get the base pointer tag.
+                    .map(|&(offset, ((), alloc))| {
+                        let tag = tagger(alloc);
+                        (offset, (tag, alloc))
+                    })
+                    .collect()
+            ),
+            undef_mask: self.undef_mask,
+            align: self.align,
+            mutability: self.mutability,
+            extra,
+        }
+    }
+}
+
 /// Raw accessors. Provide access to otherwise private bytes.
 impl<Tag, Extra> Allocation<Tag, Extra> {
     pub fn len(&self) -> usize {
@@ -157,7 +185,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
 
 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx Allocation {}
 
-/// Byte accessors
+/// Byte accessors.
 impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
     /// Just a small local helper function to avoid a bit of code repetition.
     /// Returns the range of this allocation that was meant.
@@ -167,7 +195,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         offset: Size,
         size: Size
     ) -> Range<usize> {
-        let end = offset + size; // this does overflow checking
+        let end = offset + size; // This does overflow checking.
         assert_eq!(
             end.bytes() as usize as u64, end.bytes(),
             "cannot handle this access on this host architecture"
@@ -204,7 +232,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
             self.check_defined(ptr, size)?;
             self.check_relocations(cx, ptr, size)?;
         } else {
-            // We still don't want relocations on the *edges*
+            // We still don't want relocations on the *edges*.
             self.check_relocation_edges(cx, ptr, size)?;
         }
 
@@ -213,7 +241,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         Ok(&self.bytes[range])
     }
 
-    /// Check that these bytes are initialized and not pointer bytes, and then return them
+    /// Checks that these bytes are initialized and not pointer bytes, and then return them
     /// as a slice.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
@@ -265,7 +293,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
     }
 }
 
-/// Reading and writing
+/// Reading and writing.
 impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
     /// Reads bytes until a `0` is encountered. Will error if the end of the allocation is reached
     /// before a `0` is found.
@@ -301,9 +329,9 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         allow_ptr_and_undef: bool,
     ) -> InterpResult<'tcx>
     {
-        // Check bounds and relocations on the edges
+        // Check bounds and relocations on the edges.
         self.get_bytes_with_undef_and_ptr(cx, ptr, size)?;
-        // Check undef and ptr
+        // Check undef and ptr.
         if !allow_ptr_and_undef {
             self.check_defined(ptr, size)?;
             self.check_relocations(cx, ptr, size)?;
@@ -344,12 +372,12 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         Ok(())
     }
 
-    /// Read a *non-ZST* scalar
+    /// Reads a *non-ZST* scalar.
     ///
-    /// zsts can't be read out of two reasons:
-    /// * byteorder cannot work with zero element buffers
-    /// * in order to obtain a `Pointer` we need to check for ZSTness anyway due to integer pointers
-    ///   being valid for ZSTs
+    /// ZSTs can't be read for two reasons:
+    /// * byte-order cannot work with zero-element buffers;
+    /// * in order to obtain a `Pointer`, we need to check for ZSTness anyway due to integer
+    ///   pointers being valid for ZSTs.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     pub fn read_scalar(
@@ -359,20 +387,20 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         size: Size
     ) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>>
     {
-        // get_bytes_unchecked tests relocation edges
+        // `get_bytes_unchecked` tests relocation edges.
         let bytes = self.get_bytes_with_undef_and_ptr(cx, ptr, size)?;
         // Undef check happens *after* we established that the alignment is correct.
-        // We must not return Ok() for unaligned pointers!
+        // We must not return `Ok()` for unaligned pointers!
         if self.check_defined(ptr, size).is_err() {
-            // this inflates undefined bytes to the entire scalar, even if only a few
-            // bytes are undefined
+            // This inflates undefined bytes to the entire scalar, even if only a few
+            // bytes are undefined.
             return Ok(ScalarMaybeUndef::Undef);
         }
-        // Now we do the actual reading
+        // Now we do the actual reading.
         let bits = read_target_uint(cx.data_layout().endian, bytes).unwrap();
-        // See if we got a pointer
+        // See if we got a pointer.
         if size != cx.data_layout().pointer_size {
-            // *Now* better make sure that the inside also is free of relocations.
+            // *Now*, we better make sure that the inside is free of relocations too.
             self.check_relocations(cx, ptr, size)?;
         } else {
             match self.relocations.get(&ptr.offset) {
@@ -387,7 +415,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         Ok(ScalarMaybeUndef::Scalar(Scalar::from_uint(bits, size)))
     }
 
-    /// Read a pointer-sized scalar.
+    /// Reads a pointer-sized scalar.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     pub fn read_ptr_sized(
@@ -399,12 +427,12 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         self.read_scalar(cx, ptr, cx.data_layout().pointer_size)
     }
 
-    /// Write a *non-ZST* scalar
+    /// Writes a *non-ZST* scalar.
     ///
-    /// zsts can't be read out of two reasons:
-    /// * byteorder cannot work with zero element buffers
-    /// * in oder to obtain a `Pointer` we need to check for ZSTness anyway due to integer pointers
-    ///   being valid for ZSTs
+    /// ZSTs can't be read for two reasons:
+    /// * byte-order cannot work with zero-element buffers;
+    /// * in order to obtain a `Pointer`, we need to check for ZSTness anyway due to integer
+    ///   pointers being valid for ZSTs.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     pub fn write_scalar(
@@ -432,7 +460,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         let dst = self.get_bytes_mut(cx, ptr, type_size)?;
         write_target_uint(endian, dst, bytes).unwrap();
 
-        // See if we have to also write a relocation
+        // See if we have to also write a relocation.
         match val {
             Scalar::Ptr(val) => {
                 self.relocations.insert(
@@ -446,7 +474,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         Ok(())
     }
 
-    /// Write a pointer-sized scalar.
+    /// Writes a pointer-sized scalar.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     pub fn write_ptr_sized(
@@ -461,9 +489,9 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
     }
 }
 
-/// Relocations
+/// Relocations.
 impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
-    /// Returns all relocations overlapping with the given ptr-offset pair.
+    /// Returns all relocations overlapping with the given pointer-offset pair.
     pub fn get_relocations(
         &self,
         cx: &impl HasDataLayout,
@@ -473,7 +501,7 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
         // We have to go back `pointer_size - 1` bytes, as that one would still overlap with
         // the beginning of this range.
         let start = ptr.offset.bytes().saturating_sub(cx.data_layout().pointer_size.bytes() - 1);
-        let end = ptr.offset + size; // this does overflow checking
+        let end = ptr.offset + size; // This does overflow checking.
         self.relocations.range(Size::from_bytes(start)..end)
     }
 
@@ -533,7 +561,7 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
         Ok(())
     }
 
-    /// Error if there are relocations overlapping with the edges of the
+    /// Errors if there are relocations overlapping with the edges of the
     /// given memory range.
     #[inline]
     fn check_relocation_edges(
@@ -549,7 +577,7 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
 }
 
 
-/// Undefined bytes
+/// Undefined bytes.
 impl<'tcx, Tag, Extra> Allocation<Tag, Extra> {
     /// Checks that a range of bytes is defined. If not, returns the `ReadUndefBytes`
     /// error which will report the first byte which is undefined.
@@ -590,7 +618,7 @@ pub struct AllocationDefinedness {
 
 /// Transferring the definedness mask to other allocations.
 impl<Tag, Extra> Allocation<Tag, Extra> {
-    /// Creates a run-length encoding of the undef_mask.
+    /// Creates a run-length encoding of the undef mask.
     pub fn compress_undef_range(
         &self,
         src: Pointer<Tag>,
@@ -603,10 +631,10 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         // Therefor we precompute a compressed version of the undef mask of the source value and
         // then write it back `repeat` times without computing any more information from the source.
 
-        // a precomputed cache for ranges of defined/undefined bits
+        // A precomputed cache for ranges of defined/undefined bits
         // 0000010010001110 will become
-        // [5, 1, 2, 1, 3, 3, 1]
-        // where each element toggles the state
+        // `[5, 1, 2, 1, 3, 3, 1]`,
+        // where each element toggles the state.
 
         let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
         let initial = self.undef_mask.get(src.offset);
@@ -614,7 +642,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         let mut cur = initial;
 
         for i in 1..size.bytes() {
-            // FIXME: optimize to bitshift the current undef block's bits and read the top bit
+            // FIXME: optimize to bitshift the current undef block's bits and read the top bit.
             if self.undef_mask.get(src.offset + Size::from_bytes(i)) == cur {
                 cur_len += 1;
             } else {
@@ -629,7 +657,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         AllocationDefinedness { ranges, initial, }
     }
 
-    /// Apply multiple instances of the run-length encoding to the undef_mask.
+    /// Applies multiple instances of the run-length encoding to the undef mask.
     pub fn mark_compressed_undef_range(
         &mut self,
         defined: &AllocationDefinedness,
@@ -637,7 +665,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         size: Size,
         repeat: u64,
     ) {
-        // an optimization where we can just overwrite an entire range of definedness bits if
+        // An optimization where we can just overwrite an entire range of definedness bits if
         // they are going to be uniformly `1` or `0`.
         if defined.ranges.len() <= 1 {
             self.undef_mask.set_range_inbounds(
@@ -666,9 +694,9 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
     }
 }
 
-/// Relocations
+/// Relocations.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
-pub struct Relocations<Tag=(), Id=AllocId>(SortedMap<Size, (Tag, Id)>);
+pub struct Relocations<Tag = (), Id = AllocId>(SortedMap<Size, (Tag, Id)>);
 
 impl<Tag, Id> Relocations<Tag, Id> {
     pub fn new() -> Self {
@@ -738,7 +766,7 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
         }
     }
 
-    /// Apply a relocation copy.
+    /// Applies a relocation copy.
     /// The affected range, as defined in the parameters to `prepare_relocation_copy` is expected
     /// to be clear of relocations.
     pub fn mark_relocation_range(
@@ -810,8 +838,8 @@ impl UndefMask {
         let (blocka, bita) = bit_index(start);
         let (blockb, bitb) = bit_index(end);
         if blocka == blockb {
-            // first set all bits but the first `bita`
-            // then unset the last `64 - bitb` bits
+            // First set all bits except the first `bita`,
+            // then unset the last `64 - bitb` bits.
             let range = if bitb == 0 {
                 u64::max_value() << bita
             } else {
@@ -826,24 +854,24 @@ impl UndefMask {
         }
         // across block boundaries
         if new_state {
-            // set bita..64 to 1
+            // Set `bita..64` to `1`.
             self.blocks[blocka] |= u64::max_value() << bita;
-            // set 0..bitb to 1
+            // Set `0..bitb` to `1`.
             if bitb != 0 {
                 self.blocks[blockb] |= u64::max_value() >> (64 - bitb);
             }
-            // fill in all the other blocks (much faster than one bit at a time)
+            // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1) .. blockb {
                 self.blocks[block] = u64::max_value();
             }
         } else {
-            // set bita..64 to 0
+            // Set `bita..64` to `0`.
             self.blocks[blocka] &= !(u64::max_value() << bita);
-            // set 0..bitb to 0
+            // Set `0..bitb` to `0`.
             if bitb != 0 {
                 self.blocks[blockb] &= !(u64::max_value() >> (64 - bitb));
             }
-            // fill in all the other blocks (much faster than one bit at a time)
+            // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1) .. blockb {
                 self.blocks[block] = 0;
             }
@@ -880,7 +908,7 @@ impl UndefMask {
             let additional_blocks = amount.bytes() / Self::BLOCK_SIZE + 1;
             assert_eq!(additional_blocks as usize as u64, additional_blocks);
             self.blocks.extend(
-                // FIXME(oli-obk): optimize this by repeating `new_state as Block`
+                // FIXME(oli-obk): optimize this by repeating `new_state as Block`.
                 iter::repeat(0).take(additional_blocks as usize),
             );
         }
diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
index ef0e205184871..ac99ccd45eafe 100644
--- a/src/librustc/mir/interpret/error.rs
+++ b/src/librustc/mir/interpret/error.rs
@@ -1,23 +1,21 @@
-use std::{fmt, env};
+use super::{RawConst, Pointer, CheckInAllocMsg, ScalarMaybeUndef};
 
 use crate::hir;
 use crate::hir::map::definitions::DefPathData;
 use crate::mir;
 use crate::ty::{self, Ty, layout};
 use crate::ty::layout::{Size, Align, LayoutError};
-use rustc_target::spec::abi::Abi;
-use rustc_macros::HashStable;
-
-use super::{RawConst, Pointer, CheckInAllocMsg, ScalarMaybeUndef};
+use crate::ty::query::TyCtxtAt;
 
 use backtrace::Backtrace;
-
-use crate::ty::query::TyCtxtAt;
 use errors::DiagnosticBuilder;
-
+use rustc_macros::HashStable;
+use rustc_target::spec::abi::Abi;
 use syntax_pos::{Pos, Span};
 use syntax::symbol::Symbol;
 
+use std::{fmt, env};
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, RustcEncodable, RustcDecodable)]
 pub enum ErrorHandled {
     /// Already reported a lint or an error for this evaluation.
@@ -215,6 +213,15 @@ fn print_backtrace(backtrace: &mut Backtrace) {
     eprintln!("\n\nAn error occurred in miri:\n{:?}", backtrace);
 }
 
+impl From<ErrorHandled> for InterpErrorInfo<'tcx> {
+    fn from(err: ErrorHandled) -> Self {
+        match err {
+            ErrorHandled::Reported => err_inval!(ReferencedConstant),
+            ErrorHandled::TooGeneric => err_inval!(TooGeneric),
+        }.into()
+    }
+}
+
 impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
     fn from(kind: InterpError<'tcx>) -> Self {
         let backtrace = match env::var("RUSTC_CTFE_BACKTRACE") {
@@ -315,6 +322,9 @@ impl<O: fmt::Debug> fmt::Debug for PanicInfo<O> {
     }
 }
 
+/// Error information for when the program we executed turned out not to actually be a valid
+/// program. This cannot happen in stand-alone Miri, but it can happen during CTFE/ConstProp
+/// where we work on generic code or execution does not have all information available.
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum InvalidProgramInfo<'tcx> {
     /// Resolution can fail if we are in a too generic context.
@@ -344,6 +354,7 @@ impl fmt::Debug for InvalidProgramInfo<'tcx> {
     }
 }
 
+/// Error information for when the program caused Undefined Behavior.
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum UndefinedBehaviorInfo {
     /// Free-form case. Only for errors that are never caught!
@@ -366,12 +377,19 @@ impl fmt::Debug for UndefinedBehaviorInfo {
     }
 }
 
+/// Error information for when the program did something that might (or might not) be correct
+/// to do according to the Rust spec, but due to limitations in the interpreter, the
+/// operation could not be carried out. These limitations can differ between CTFE and the
+/// Miri engine, e.g., CTFE does not support casting pointers to "real" integers.
+///
+/// Currently, we also use this as fall-back error kind for errors that have not been
+/// categorized yet.
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum UnsupportedOpInfo<'tcx> {
     /// Free-form case. Only for errors that are never caught!
     Unsupported(String),
 
-    // -- Everything below is not classified yet --
+    // -- Everything below is not categorized yet --
     FunctionAbiMismatch(Abi, Abi),
     FunctionArgMismatch(Ty<'tcx>, Ty<'tcx>),
     FunctionRetMismatch(Ty<'tcx>, Ty<'tcx>),
@@ -430,13 +448,13 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
         match self {
             PointerOutOfBounds { ptr, msg, allocation_size } => {
                 write!(f, "{} failed: pointer must be in-bounds at offset {}, \
-                          but is outside bounds of allocation {} which has size {}",
+                           but is outside bounds of allocation {} which has size {}",
                     msg, ptr.offset.bytes(), ptr.alloc_id, allocation_size.bytes())
             },
             ValidationFailure(ref err) => {
                 write!(f, "type validation failed: {}", err)
             }
-            NoMirFor(ref func) => write!(f, "no mir for `{}`", func),
+            NoMirFor(ref func) => write!(f, "no MIR for `{}`", func),
             FunctionAbiMismatch(caller_abi, callee_abi) =>
                 write!(f, "tried to call a function with ABI {:?} using caller ABI {:?}",
                     callee_abi, caller_abi),
@@ -451,9 +469,9 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
             FunctionArgCountMismatch =>
                 write!(f, "tried to call a function with incorrect number of arguments"),
             ReallocatedWrongMemoryKind(ref old, ref new) =>
-                write!(f, "tried to reallocate memory from {} to {}", old, new),
+                write!(f, "tried to reallocate memory from `{}` to `{}`", old, new),
             DeallocatedWrongMemoryKind(ref old, ref new) =>
-                write!(f, "tried to deallocate {} memory but gave {} as the kind", old, new),
+                write!(f, "tried to deallocate `{}` memory but gave `{}` as the kind", old, new),
             InvalidChar(c) =>
                 write!(f, "tried to interpret an invalid 32-bit value as a char: {}", c),
             AlignmentCheckFailed { required, has } =>
@@ -462,7 +480,7 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
             TypeNotPrimitive(ty) =>
                 write!(f, "expected primitive type, got {}", ty),
             PathNotFound(ref path) =>
-                write!(f, "Cannot find path {:?}", path),
+                write!(f, "cannot find path {:?}", path),
             IncorrectAllocationInformation(size, size2, align, align2) =>
                 write!(f, "incorrect alloc info: expected size {} and align {}, \
                            got size {} and align {}",
@@ -525,7 +543,7 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
             InvalidBoolOp(_) =>
                 write!(f, "invalid boolean operation"),
             UnterminatedCString(_) =>
-                write!(f, "attempted to get length of a null terminated string, but no null \
+                write!(f, "attempted to get length of a null-terminated string, but no null \
                     found before end of allocation"),
             ReadUndefBytes(_) =>
                 write!(f, "attempted to read undefined bytes"),
@@ -538,6 +556,8 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
     }
 }
 
+/// Error information for when the program exhausted the resources granted to it
+/// by the interpreter.
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum ResourceExhaustionInfo {
     /// The stack grew too big.
@@ -582,7 +602,7 @@ pub type InterpResult<'tcx, T = ()> = Result<T, InterpErrorInfo<'tcx>>;
 
 impl fmt::Display for InterpError<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        // Forward `Display` to `Debug`
+        // Forward `Display` to `Debug`.
         write!(f, "{:?}", self)
     }
 }
diff --git a/src/librustc/mir/interpret/mod.rs b/src/librustc/mir/interpret/mod.rs
index 1ec95c29a4a6f..23433c2e8834d 100644
--- a/src/librustc/mir/interpret/mod.rs
+++ b/src/librustc/mir/interpret/mod.rs
@@ -1,4 +1,4 @@
-//! An interpreter for MIR used in CTFE and by miri
+//! An interpreter for MIR used in CTFE and by miri.
 
 #[macro_export]
 macro_rules! err_unsup {
@@ -107,21 +107,21 @@ pub use self::allocation::{Allocation, AllocationExtra, Relocations, UndefMask};
 
 pub use self::pointer::{Pointer, PointerArithmetic, CheckInAllocMsg};
 
-use std::fmt;
 use crate::mir;
 use crate::hir::def_id::DefId;
 use crate::ty::{self, TyCtxt, Instance, subst::UnpackedKind};
+use crate::ty::codec::TyDecoder;
 use crate::ty::layout::{self, Size};
 use std::io;
+use std::fmt;
+use std::num::NonZeroU32;
+use std::sync::atomic::{AtomicU32, Ordering};
 use rustc_serialize::{Encoder, Decodable, Encodable};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::sync::{Lock as Mutex, HashMapExt};
+use rustc_data_structures::sync::{Lock, HashMapExt};
 use rustc_data_structures::tiny_list::TinyList;
 use rustc_macros::HashStable;
 use byteorder::{WriteBytesExt, ReadBytesExt, LittleEndian, BigEndian};
-use crate::ty::codec::TyDecoder;
-use std::sync::atomic::{AtomicU32, Ordering};
-use std::num::NonZeroU32;
 
 /// Uniquely identifies a specific constant or static.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, RustcEncodable, RustcDecodable, HashStable)]
@@ -152,8 +152,8 @@ pub fn specialized_encode_alloc_id<'tcx, E: Encoder>(
     tcx: TyCtxt<'tcx>,
     alloc_id: AllocId,
 ) -> Result<(), E::Error> {
-    let alloc: GlobalAlloc<'tcx> =
-        tcx.alloc_map.lock().get(alloc_id).expect("no value for AllocId");
+    let alloc: GlobalAlloc<'tcx> = tcx.alloc_map.lock().get(alloc_id)
+        .expect("no value for given alloc ID");
     match alloc {
         GlobalAlloc::Memory(alloc) => {
             trace!("encoding {:?} with {:#?}", alloc_id, alloc);
@@ -166,8 +166,8 @@ pub fn specialized_encode_alloc_id<'tcx, E: Encoder>(
             fn_instance.encode(encoder)?;
         }
         GlobalAlloc::Static(did) => {
-            // referring to statics doesn't need to know about their allocations,
-            // just about its DefId
+            // References to statics doesn't need to know about their allocations,
+            // just about its `DefId`.
             AllocDiscriminant::Static.encode(encoder)?;
             did.encode(encoder)?;
         }
@@ -187,19 +187,18 @@ enum State {
 }
 
 pub struct AllocDecodingState {
-    // For each AllocId we keep track of which decoding state it's currently in.
-    decoding_state: Vec<Mutex<State>>,
+    // For each `AllocId`, we keep track of which decoding state it's currently in.
+    decoding_state: Vec<Lock<State>>,
     // The offsets of each allocation in the data stream.
     data_offsets: Vec<u32>,
 }
 
 impl AllocDecodingState {
-
     pub fn new_decoding_session(&self) -> AllocDecodingSession<'_> {
         static DECODER_SESSION_ID: AtomicU32 = AtomicU32::new(0);
         let counter = DECODER_SESSION_ID.fetch_add(1, Ordering::SeqCst);
 
-        // Make sure this is never zero
+        // Make sure this is never zero.
         let session_id = DecodingSessionId::new((counter & 0x7FFFFFFF) + 1).unwrap();
 
         AllocDecodingSession {
@@ -208,10 +207,10 @@ impl AllocDecodingState {
         }
     }
 
-    pub fn new(data_offsets: Vec<u32>) -> AllocDecodingState {
-        let decoding_state = vec![Mutex::new(State::Empty); data_offsets.len()];
+    pub fn new(data_offsets: Vec<u32>) -> Self {
+        let decoding_state = vec![Lock::new(State::Empty); data_offsets.len()];
 
-        AllocDecodingState {
+        Self {
             decoding_state,
             data_offsets,
         }
@@ -225,23 +224,23 @@ pub struct AllocDecodingSession<'s> {
 }
 
 impl<'s> AllocDecodingSession<'s> {
-    // Decodes an AllocId in a thread-safe way.
+    /// Decodes an `AllocId` in a thread-safe way.
     pub fn decode_alloc_id<D>(&self, decoder: &mut D) -> Result<AllocId, D::Error>
     where
         D: TyDecoder<'tcx>,
     {
-        // Read the index of the allocation
+        // Read the index of the allocation.
         let idx = decoder.read_u32()? as usize;
         let pos = self.state.data_offsets[idx] as usize;
 
-        // Decode the AllocDiscriminant now so that we know if we have to reserve an
-        // AllocId.
+        // Decode the `AllocDiscriminant` now so that we know if we have to reserve an
+        // `AllocId`.
         let (alloc_kind, pos) = decoder.with_position(pos, |decoder| {
             let alloc_kind = AllocDiscriminant::decode(decoder)?;
             Ok((alloc_kind, decoder.position()))
         })?;
 
-        // Check the decoding state, see if it's already decoded or if we should
+        // Check the decoding state to see if it's already decoded or if we should
         // decode it here.
         let alloc_id = {
             let mut entry = self.state.decoding_state[idx].lock();
@@ -251,11 +250,11 @@ impl<'s> AllocDecodingSession<'s> {
                     return Ok(alloc_id);
                 }
                 ref mut entry @ State::Empty => {
-                    // We are allowed to decode
+                    // We are allowed to decode.
                     match alloc_kind {
                         AllocDiscriminant::Alloc => {
                             // If this is an allocation, we need to reserve an
-                            // AllocId so we can decode cyclic graphs.
+                            // `AllocId` so we can decode cyclic graphs.
                             let alloc_id = decoder.tcx().alloc_map.lock().reserve();
                             *entry = State::InProgress(
                                 TinyList::new_single(self.session_id),
@@ -263,8 +262,8 @@ impl<'s> AllocDecodingSession<'s> {
                             Some(alloc_id)
                         },
                         AllocDiscriminant::Fn | AllocDiscriminant::Static => {
-                            // Fns and statics cannot be cyclic and their AllocId
-                            // is determined later by interning
+                            // Fns and statics cannot be cyclic, and their `AllocId`
+                            // is determined later by interning.
                             *entry = State::InProgressNonAlloc(
                                 TinyList::new_single(self.session_id));
                             None
@@ -273,9 +272,9 @@ impl<'s> AllocDecodingSession<'s> {
                 }
                 State::InProgressNonAlloc(ref mut sessions) => {
                     if sessions.contains(&self.session_id) {
-                        bug!("This should be unreachable")
+                        bug!("this should be unreachable");
                     } else {
-                        // Start decoding concurrently
+                        // Start decoding concurrently.
                         sessions.insert(self.session_id);
                         None
                     }
@@ -285,7 +284,7 @@ impl<'s> AllocDecodingSession<'s> {
                         // Don't recurse.
                         return Ok(alloc_id)
                     } else {
-                        // Start decoding concurrently
+                        // Start decoding concurrently.
                         sessions.insert(self.session_id);
                         Some(alloc_id)
                     }
@@ -293,20 +292,20 @@ impl<'s> AllocDecodingSession<'s> {
             }
         };
 
-        // Now decode the actual data
+        // Now decode the actual data.
         let alloc_id = decoder.with_position(pos, |decoder| {
             match alloc_kind {
                 AllocDiscriminant::Alloc => {
-                    let allocation = <&'tcx Allocation as Decodable>::decode(decoder)?;
-                    // We already have a reserved AllocId.
+                    let alloc = <&'tcx Allocation as Decodable>::decode(decoder)?;
+                    // We already have a reserved `AllocId`.
                     let alloc_id = alloc_id.unwrap();
-                    trace!("decoded alloc {:?} {:#?}", alloc_id, allocation);
-                    decoder.tcx().alloc_map.lock().set_alloc_id_same_memory(alloc_id, allocation);
+                    trace!("decoded alloc {:?}: {:#?}", alloc_id, alloc);
+                    decoder.tcx().alloc_map.lock().set_alloc_id_same_memory(alloc_id, alloc);
                     Ok(alloc_id)
                 },
                 AllocDiscriminant::Fn => {
                     assert!(alloc_id.is_none());
-                    trace!("creating fn alloc id");
+                    trace!("creating fn alloc ID");
                     let instance = ty::Instance::decode(decoder)?;
                     trace!("decoded fn alloc instance: {:?}", instance);
                     let alloc_id = decoder.tcx().alloc_map.lock().create_fn_alloc(instance);
@@ -314,8 +313,9 @@ impl<'s> AllocDecodingSession<'s> {
                 },
                 AllocDiscriminant::Static => {
                     assert!(alloc_id.is_none());
-                    trace!("creating extern static alloc id at");
+                    trace!("creating extern static alloc ID");
                     let did = DefId::decode(decoder)?;
+                    trace!("decoded static def-ID: {:?}", did);
                     let alloc_id = decoder.tcx().alloc_map.lock().create_static_alloc(did);
                     Ok(alloc_id)
                 }
@@ -340,7 +340,7 @@ impl fmt::Display for AllocId {
 /// a static, or a "real" allocation with some data in it.
 #[derive(Debug, Clone, Eq, PartialEq, Hash, RustcDecodable, RustcEncodable, HashStable)]
 pub enum GlobalAlloc<'tcx> {
-    /// The alloc ID is used as a function pointer
+    /// The alloc ID is used as a function pointer.
     Function(Instance<'tcx>),
     /// The alloc ID points to a "lazy" static variable that did not get computed (yet).
     /// This is also used to break the cycle in recursive statics.
@@ -350,16 +350,17 @@ pub enum GlobalAlloc<'tcx> {
 }
 
 pub struct AllocMap<'tcx> {
-    /// Lets you know what an `AllocId` refers to.
+    /// Maps `AllocId`s to their corresponding allocations.
     alloc_map: FxHashMap<AllocId, GlobalAlloc<'tcx>>,
 
     /// Used to ensure that statics and functions only get one associated `AllocId`.
     /// Should never contain a `GlobalAlloc::Memory`!
-    /// FIXME: Should we just have two separate dedup maps for statics and functions each?
+    //
+    // FIXME: Should we just have two separate dedup maps for statics and functions each?
     dedup: FxHashMap<GlobalAlloc<'tcx>, AllocId>,
 
     /// The `AllocId` to assign to the next requested ID.
-    /// Always incremented, never gets smaller.
+    /// Always incremented; never gets smaller.
     next_id: AllocId,
 }
 
@@ -389,7 +390,7 @@ impl<'tcx> AllocMap<'tcx> {
         next
     }
 
-    /// Reserve a new ID *if* this allocation has not been dedup-reserved before.
+    /// Reserves a new ID *if* this allocation has not been dedup-reserved before.
     /// Should only be used for function pointers and statics, we don't want
     /// to dedup IDs for "real" memory!
     fn reserve_and_set_dedup(&mut self, alloc: GlobalAlloc<'tcx>) -> AllocId {
@@ -430,17 +431,17 @@ impl<'tcx> AllocMap<'tcx> {
             }
         });
         if is_generic {
-            // Get a fresh ID
+            // Get a fresh ID.
             let id = self.reserve();
             self.alloc_map.insert(id, GlobalAlloc::Function(instance));
             id
         } else {
-            // Deduplicate
+            // Deduplicate.
             self.reserve_and_set_dedup(GlobalAlloc::Function(instance))
         }
     }
 
-    /// Intern the `Allocation` and return a new `AllocId`, even if there's already an identical
+    /// Interns the `Allocation` and return a new `AllocId`, even if there's already an identical
     /// `Allocation` with a different `AllocId`.
     /// Statics with identical content will still point to the same `Allocation`, i.e.,
     /// their data will be deduplicated through `Allocation` interning -- but they
@@ -465,19 +466,19 @@ impl<'tcx> AllocMap<'tcx> {
     pub fn unwrap_memory(&self, id: AllocId) -> &'tcx Allocation {
         match self.get(id) {
             Some(GlobalAlloc::Memory(mem)) => mem,
-            _ => bug!("expected allocation id {} to point to memory", id),
+            _ => bug!("expected allocation ID {} to point to memory", id),
         }
     }
 
-    /// Freeze an `AllocId` created with `reserve` by pointing it at an `Allocation`. Trying to
+    /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. Trying to
     /// call this function twice, even with the same `Allocation` will ICE the compiler.
     pub fn set_alloc_id_memory(&mut self, id: AllocId, mem: &'tcx Allocation) {
         if let Some(old) = self.alloc_map.insert(id, GlobalAlloc::Memory(mem)) {
-            bug!("tried to set allocation id {}, but it was already existing as {:#?}", id, old);
+            bug!("tried to set allocation ID {}, but it was already existing as {:#?}", id, old);
         }
     }
 
-    /// Freeze an `AllocId` created with `reserve` by pointing it at an `Allocation`. May be called
+    /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. May be called
     /// twice for the same `(AllocId, Allocation)` pair.
     fn set_alloc_id_same_memory(&mut self, id: AllocId, mem: &'tcx Allocation) {
         self.alloc_map.insert_same(id, GlobalAlloc::Memory(mem));
@@ -513,7 +514,7 @@ pub fn read_target_uint(endianness: layout::Endian, mut source: &[u8]) -> Result
 // Methods to facilitate working with signed integers stored in a u128
 ////////////////////////////////////////////////////////////////////////////////
 
-/// Truncate `value` to `size` bits and then sign-extend it to 128 bits
+/// Truncates `value` to `size` bits and then sign-extend it to 128 bits
 /// (i.e., if it is negative, fill with 1's on the left).
 #[inline]
 pub fn sign_extend(value: u128, size: Size) -> u128 {
@@ -522,14 +523,14 @@ pub fn sign_extend(value: u128, size: Size) -> u128 {
         // Truncated until nothing is left.
         return 0;
     }
-    // sign extend
+    // Sign-extend it.
     let shift = 128 - size;
-    // shift the unsigned value to the left
-    // and back to the right as signed (essentially fills with FF on the left)
+    // Shift the unsigned value to the left, then shift back to the right as signed
+    // (essentially fills with FF on the left).
     (((value << shift) as i128) >> shift) as u128
 }
 
-/// Truncate `value` to `size` bits.
+/// Truncates `value` to `size` bits.
 #[inline]
 pub fn truncate(value: u128, size: Size) -> u128 {
     let size = size.bits();
@@ -538,6 +539,6 @@ pub fn truncate(value: u128, size: Size) -> u128 {
         return 0;
     }
     let shift = 128 - size;
-    // truncate (shift left to drop out leftover values, shift right to fill with zeroes)
+    // Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
     (value << shift) >> shift
 }
diff --git a/src/librustc/mir/interpret/pointer.rs b/src/librustc/mir/interpret/pointer.rs
index b55e6bc54bc5f..1bb4d9ea4d6d9 100644
--- a/src/librustc/mir/interpret/pointer.rs
+++ b/src/librustc/mir/interpret/pointer.rs
@@ -86,18 +86,17 @@ pub trait PointerArithmetic: layout::HasDataLayout {
 
 impl<T: layout::HasDataLayout> PointerArithmetic for T {}
 
-
-/// Pointer is generic over the type that represents a reference to Allocations,
+/// `Pointer` is generic over the type that represents a reference to `Allocation`s,
 /// thus making it possible for the most convenient representation to be used in
 /// each context.
 ///
-/// Defaults to the index based and loosely coupled AllocId.
+/// Defaults to the index based and loosely coupled `AllocId`.
 ///
 /// Pointer is also generic over the `Tag` associated with each pointer,
 /// which is used to do provenance tracking during execution.
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd,
          RustcEncodable, RustcDecodable, Hash, HashStable)]
-pub struct Pointer<Tag=(),Id=AllocId> {
+pub struct Pointer<Tag = (), Id = AllocId> {
     pub alloc_id: Id,
     pub offset: Size,
     pub tag: Tag,
@@ -117,7 +116,7 @@ impl<Id: fmt::Debug> fmt::Debug for Pointer<(), Id> {
     }
 }
 
-/// Produces a `Pointer` which points to the beginning of the Allocation
+/// Produces a `Pointer` which points to the beginning of the `Allocation`.
 impl From<AllocId> for Pointer {
     #[inline(always)]
     fn from(alloc_id: AllocId) -> Self {
diff --git a/src/librustc/mir/interpret/value.rs b/src/librustc/mir/interpret/value.rs
index 3da5a65c37932..b8bc741419738 100644
--- a/src/librustc/mir/interpret/value.rs
+++ b/src/librustc/mir/interpret/value.rs
@@ -17,8 +17,8 @@ pub struct RawConst<'tcx> {
     pub ty: Ty<'tcx>,
 }
 
-/// Represents a constant value in Rust. `Scalar` and `ScalarPair` are optimizations that
-/// match the `LocalState` optimizations for easy conversions between `Value` and `ConstValue`.
+/// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for
+/// array length computations, enum discriminants and the pattern matching logic.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord,
          RustcEncodable, RustcDecodable, Hash, HashStable)]
 pub enum ConstValue<'tcx> {
@@ -91,7 +91,7 @@ impl<'tcx> ConstValue<'tcx> {
 /// of a simple value or a pointer into another `Allocation`
 #[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd,
          RustcEncodable, RustcDecodable, Hash, HashStable)]
-pub enum Scalar<Tag=(), Id=AllocId> {
+pub enum Scalar<Tag = (), Id = AllocId> {
     /// The raw bytes of a simple value.
     Raw {
         /// The first `size` bytes of `data` are the value.
@@ -359,7 +359,7 @@ impl<'tcx, Tag> Scalar<Tag> {
 
     #[inline(always)]
     pub fn assert_bits(self, target_size: Size) -> u128 {
-        self.to_bits(target_size).expect("Expected Raw bits but got a Pointer")
+        self.to_bits(target_size).expect("expected Raw bits but got a Pointer")
     }
 
     /// Do not call this method!  Use either `assert_ptr` or `force_ptr`.
@@ -374,7 +374,7 @@ impl<'tcx, Tag> Scalar<Tag> {
 
     #[inline(always)]
     pub fn assert_ptr(self) -> Pointer<Tag> {
-        self.to_ptr().expect("Expected a Pointer but got Raw bits")
+        self.to_ptr().expect("expected a Pointer but got Raw bits")
     }
 
     /// Do not call this method!  Dispatch based on the type instead.
@@ -482,8 +482,8 @@ impl<Tag> From<Pointer<Tag>> for Scalar<Tag> {
     }
 }
 
-#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
-pub enum ScalarMaybeUndef<Tag=(), Id=AllocId> {
+#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash, RustcEncodable, RustcDecodable)]
+pub enum ScalarMaybeUndef<Tag = (), Id = AllocId> {
     Scalar(Scalar<Tag, Id>),
     Undef,
 }
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 8956cbb2baefc..0ebc70750a6bb 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -18,6 +18,7 @@ use crate::ty::{
     self, AdtDef, CanonicalUserTypeAnnotations, ClosureSubsts, GeneratorSubsts, Region, Ty, TyCtxt,
     UserTypeAnnotationIndex,
 };
+
 use polonius_engine::Atom;
 use rustc_data_structures::bit_set::BitMatrix;
 use rustc_data_structures::fx::FxHashSet;
@@ -31,7 +32,6 @@ use rustc_serialize::{Encodable, Decodable};
 use smallvec::SmallVec;
 use std::borrow::Cow;
 use std::fmt::{self, Debug, Display, Formatter, Write};
-use std::iter::FusedIterator;
 use std::ops::{Index, IndexMut};
 use std::slice;
 use std::vec::IntoIter;
@@ -70,7 +70,7 @@ impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
 
 /// The various "big phases" that MIR goes through.
 ///
-/// Warning: ordering of variants is significant
+/// Warning: ordering of variants is significant.
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub enum MirPhase {
     Build = 0,
@@ -80,16 +80,16 @@ pub enum MirPhase {
 }
 
 impl MirPhase {
-    /// Gets the index of the current MirPhase within the set of all MirPhases.
+    /// Gets the index of the current MirPhase within the set of all `MirPhase`s.
     pub fn phase_index(&self) -> usize {
         *self as usize
     }
 }
 
-/// Lowered representation of a single function.
+/// The lowered representation of a single function.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Body<'tcx> {
-    /// List of basic blocks. References to basic block use a newtyped index type `BasicBlock`
+    /// A list of basic blocks. References to basic block use a newtyped index type `BasicBlock`
     /// that indexes into this vector.
     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 
@@ -100,7 +100,7 @@ pub struct Body<'tcx> {
     /// us to see the difference and forego optimization on the inlined promoted items.
     pub phase: MirPhase,
 
-    /// List of source scopes; these are referenced by statements
+    /// A list of source scopes; these are referenced by statements
     /// and used for debuginfo. Indexed by a `SourceScope`.
     pub source_scopes: IndexVec<SourceScope, SourceScopeData>,
 
@@ -108,10 +108,10 @@ pub struct Body<'tcx> {
     /// needn't) be tracked across crates.
     pub source_scope_local_data: ClearCrossCrate<IndexVec<SourceScope, SourceScopeLocalData>>,
 
-    /// Yields type of the function, if it is a generator.
+    /// The yield type of the function, if it is a generator.
     pub yield_ty: Option<Ty<'tcx>>,
 
-    /// Generator drop glue
+    /// Generator drop glue.
     pub generator_drop: Option<Box<Body<'tcx>>>,
 
     /// The layout of a generator. Produced by the state transformation.
@@ -124,10 +124,10 @@ pub struct Body<'tcx> {
     /// variables and temporaries.
     pub local_decls: LocalDecls<'tcx>,
 
-    /// User type annotations
+    /// User type annotations.
     pub user_type_annotations: CanonicalUserTypeAnnotations<'tcx>,
 
-    /// Number of arguments this function takes.
+    /// The number of arguments this function takes.
     ///
     /// Starting at local 1, `arg_count` locals will be provided by the caller
     /// and can be assumed to be initialized.
@@ -143,10 +143,11 @@ pub struct Body<'tcx> {
 
     /// Names and capture modes of all the closure upvars, assuming
     /// the first argument is either the closure or a reference to it.
+    //
     // NOTE(eddyb) This is *strictly* a temporary hack for codegen
     // debuginfo generation, and will be removed at some point.
-    // Do **NOT** use it for anything else, upvar information should not be
-    // in the MIR, please rely on local crate HIR or other side-channels.
+    // Do **NOT** use it for anything else; upvar information should not be
+    // in the MIR, so please rely on local crate HIR or other side-channels.
     pub __upvar_debuginfo_codegen_only_do_not_use: Vec<UpvarDebuginfo>,
 
     /// Mark this MIR of a const context other than const functions as having converted a `&&` or
@@ -157,10 +158,10 @@ pub struct Body<'tcx> {
     /// List of places where control flow was destroyed. Used for error reporting.
     pub control_flow_destroyed: Vec<(Span, String)>,
 
-    /// A span representing this MIR, for error reporting
+    /// A span representing this MIR, for error reporting.
     pub span: Span,
 
-    /// A cache for various calculations
+    /// A cache for various calculations.
     cache: cache::Cache,
 }
 
@@ -177,7 +178,7 @@ impl<'tcx> Body<'tcx> {
         span: Span,
         control_flow_destroyed: Vec<(Span, String)>,
     ) -> Self {
-        // We need `arg_count` locals, and one for the return place
+        // We need `arg_count` locals, and one for the return place.
         assert!(
             local_decls.len() >= arg_count + 1,
             "expected at least {} locals, got {}",
@@ -384,12 +385,12 @@ impl<'tcx> Body<'tcx> {
         true
     }
 
-    /// Returns the return type, it always return first element from `local_decls` array
+    /// Returns the return type; it always return first element from `local_decls` array.
     pub fn return_ty(&self) -> Ty<'tcx> {
         self.local_decls[RETURN_PLACE].ty
     }
 
-    /// Gets the location of the terminator for the given block
+    /// Gets the location of the terminator for the given block.
     pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
         Location { block: bb, statement_index: self[bb].statements.len() }
     }
@@ -463,7 +464,7 @@ impl<T: Decodable> rustc_serialize::UseSpecializedDecodable for ClearCrossCrate<
 /// Most passes can work with it as a whole, within a single function.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, HashStable)]
 pub struct SourceInfo {
-    /// Source span for the AST pertaining to this MIR entity.
+    /// The source span for the AST pertaining to this MIR entity.
     pub span: Span,
 
     /// The source scope, keeping track of which bindings can be
@@ -591,13 +592,13 @@ impl Atom for Local {
 /// Classifies locals into categories. See `Body::local_kind`.
 #[derive(PartialEq, Eq, Debug, HashStable)]
 pub enum LocalKind {
-    /// User-declared variable binding
+    /// User-declared variable binding.
     Var,
-    /// Compiler-introduced temporary
+    /// Compiler-introduced temporary.
     Temp,
-    /// Function argument
+    /// Function argument.
     Arg,
-    /// Location of function's return value
+    /// Location of function's return value.
     ReturnPointer,
 }
 
@@ -619,7 +620,7 @@ pub struct VarBindingForm<'tcx> {
     /// (b) it gives a way to separate this case from the remaining cases
     ///     for diagnostics.
     pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
-    /// Span of the pattern in which this variable was bound.
+    /// The span of the pattern in which this variable was bound.
     pub pat_span: Span,
 }
 
@@ -721,12 +722,12 @@ impl_stable_hash_for!(struct BlockTailInfo { tail_result_is_ignored });
 /// argument, or the return place.
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct LocalDecl<'tcx> {
-    /// `let mut x` vs `let x`.
+    /// Whether this is a mutable minding (i.e., `let x` or `let mut x`).
     ///
     /// Temporaries and the return place are always mutable.
     pub mutability: Mutability,
 
-    /// Some(binding_mode) if this corresponds to a user-declared local variable.
+    /// `Some(binding_mode)` if this corresponds to a user-declared local variable.
     ///
     /// This is solely used for local diagnostics when generating
     /// warnings/errors when compiling the current crate, and
@@ -760,7 +761,7 @@ pub struct LocalDecl<'tcx> {
     /// intervening statement context).
     pub is_block_tail: Option<BlockTailInfo>,
 
-    /// Type of this local.
+    /// The type of this local.
     pub ty: Ty<'tcx>,
 
     /// If the user manually ascribed a type to this variable,
@@ -769,7 +770,7 @@ pub struct LocalDecl<'tcx> {
     /// region inference.
     pub user_ty: UserTypeProjections,
 
-    /// Name of the local, used in debuginfo and pretty-printing.
+    /// The name of the local, used in debuginfo and pretty-printing.
     ///
     /// Note that function arguments can also have this set to `Some(_)`
     /// to generate better debuginfo.
@@ -837,8 +838,8 @@ pub struct LocalDecl<'tcx> {
     /// ROOT SCOPE
     ///  │{ argument x: &str }
     ///  │
-    ///  │ │{ #[allow(unused_mut)] } // this is actually split into 2 scopes
-    ///  │ │                        // in practice because I'm lazy.
+    ///  │ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
+    ///  │ │                         // in practice because I'm lazy.
     ///  │ │
     ///  │ │← x.source_info.scope
     ///  │ │← `x.parse().unwrap()`
@@ -852,7 +853,7 @@ pub struct LocalDecl<'tcx> {
     ///  │
     ///  │ │{ let x: u32 }
     ///  │ │← x.visibility_scope
-    ///  │ │← `drop(x)` // this accesses `x: u32`
+    ///  │ │← `drop(x)` // This accesses `x: u32`.
     /// ```
     pub source_info: SourceInfo,
 
@@ -1038,16 +1039,16 @@ pub struct Terminator<'tcx> {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum TerminatorKind<'tcx> {
-    /// block should have one successor in the graph; we jump there
+    /// Block should have one successor in the graph; we jump there.
     Goto { target: BasicBlock },
 
-    /// operand evaluates to an integer; jump depending on its value
-    /// to one of the targets, and otherwise fallback to `otherwise`
+    /// Operand evaluates to an integer; jump depending on its value
+    /// to one of the targets, and otherwise fallback to `otherwise`.
     SwitchInt {
-        /// discriminant value being tested
+        /// The discriminant value being tested.
         discr: Operand<'tcx>,
 
-        /// type of value being tested
+        /// The type of value being tested.
         switch_ty: Ty<'tcx>,
 
         /// Possible values. The locations to branch to in each case
@@ -1057,6 +1058,7 @@ pub enum TerminatorKind<'tcx> {
         /// Possible branch sites. The last element of this vector is used
         /// for the otherwise branch, so targets.len() == values.len() + 1
         /// should hold.
+        //
         // This invariant is quite non-obvious and also could be improved.
         // One way to make this invariant is to have something like this instead:
         //
@@ -1069,7 +1071,7 @@ pub enum TerminatorKind<'tcx> {
     },
 
     /// Indicates that the landing pad is finished and unwinding should
-    /// continue. Emitted by build::scope::diverge_cleanup.
+    /// continue. Emitted by `build::scope::diverge_cleanup`.
     Resume,
 
     /// Indicates that the landing pad is finished and that the process
@@ -1083,10 +1085,10 @@ pub enum TerminatorKind<'tcx> {
     /// Indicates a terminator that can never be reached.
     Unreachable,
 
-    /// Drop the Place
+    /// Drop the `Place`.
     Drop { location: Place<'tcx>, target: BasicBlock, unwind: Option<BasicBlock> },
 
-    /// Drop the Place and assign the new value over it. This ensures
+    /// Drop the `Place` and assign the new value over it. This ensures
     /// that the assignment to `P` occurs *even if* the destructor for
     /// place unwinds. Its semantics are best explained by the
     /// elaboration:
@@ -1119,9 +1121,9 @@ pub enum TerminatorKind<'tcx> {
         unwind: Option<BasicBlock>,
     },
 
-    /// Block ends with a call of a converging function
+    /// Block ends with a call of a converging function.
     Call {
-        /// The function that’s being called
+        /// The function that’s being called.
         func: Operand<'tcx>,
         /// Arguments the function is called with.
         /// These are owned by the callee, which is free to modify them.
@@ -1132,7 +1134,7 @@ pub enum TerminatorKind<'tcx> {
         destination: Option<(Place<'tcx>, BasicBlock)>,
         /// Cleanups to be done if the call unwinds.
         cleanup: Option<BasicBlock>,
-        /// Whether this is from a call in HIR, rather than from an overloaded
+        /// `true` if this is from a call in HIR rather than from an overloaded
         /// operator. True for overloaded function call.
         from_hir_call: bool,
     },
@@ -1147,40 +1149,40 @@ pub enum TerminatorKind<'tcx> {
         cleanup: Option<BasicBlock>,
     },
 
-    /// A suspend point
+    /// A suspend point.
     Yield {
-        /// The value to return
+        /// The value to return.
         value: Operand<'tcx>,
-        /// Where to resume to
+        /// Where to resume to.
         resume: BasicBlock,
-        /// Cleanup to be done if the generator is dropped at this suspend point
+        /// Cleanup to be done if the generator is dropped at this suspend point.
         drop: Option<BasicBlock>,
     },
 
-    /// Indicates the end of the dropping of a generator
+    /// Indicates the end of the dropping of a generator.
     GeneratorDrop,
 
     /// A block where control flow only ever takes one real path, but borrowck
     /// needs to be more conservative.
     FalseEdges {
-        /// The target normal control flow will take
+        /// The target normal control flow will take.
         real_target: BasicBlock,
         /// A block control flow could conceptually jump to, but won't in
-        /// practice
+        /// practice.
         imaginary_target: BasicBlock,
     },
     /// A terminator for blocks that only take one path in reality, but where we
     /// reserve the right to unwind in borrowck, even if it won't happen in practice.
     /// This can arise in infinite loops with no function calls for example.
     FalseUnwind {
-        /// The target normal control flow will take
+        /// The target normal control flow will take.
         real_target: BasicBlock,
         /// The imaginary cleanup block link. This particular path will never be taken
         /// in practice, but in order to avoid fragility we want to always
         /// consider it in borrowck. We don't want to accept programs which
-        /// pass borrowck only when panic=abort or some assertions are disabled
-        /// due to release vs. debug mode builds. This needs to be an Option because
-        /// of the remove_noop_landing_pads and no_landing_pads passes
+        /// pass borrowck only when `panic=abort` or some assertions are disabled
+        /// due to release vs. debug mode builds. This needs to be an `Option` because
+        /// of the `remove_noop_landing_pads` and `no_landing_pads` passes.
         unwind: Option<BasicBlock>,
     },
 }
@@ -1445,7 +1447,7 @@ impl<'tcx> Debug for TerminatorKind<'tcx> {
 }
 
 impl<'tcx> TerminatorKind<'tcx> {
-    /// Write the "head" part of the terminator; that is, its name and the data it uses to pick the
+    /// Writes the "head" part of the terminator; that is, its name and the data it uses to pick the
     /// successor basic block, if any. The only information not included is the list of possible
     /// successors, which may be rendered differently between the text and the graphviz format.
     pub fn fmt_head<W: Write>(&self, fmt: &mut W) -> fmt::Result {
@@ -1545,7 +1547,7 @@ pub struct Statement<'tcx> {
 
 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert_size!(Statement<'_>, 56);
+static_assert_size!(Statement<'_>, 32);
 
 impl Statement<'_> {
     /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
@@ -1566,7 +1568,7 @@ impl Statement<'_> {
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub enum StatementKind<'tcx> {
     /// Write the RHS Rvalue to the LHS Place.
-    Assign(Place<'tcx>, Box<Rvalue<'tcx>>),
+    Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
 
     /// This represents all the reading that a pattern match may do
     /// (e.g., inspecting constants and discriminant values), and the
@@ -1575,10 +1577,10 @@ pub enum StatementKind<'tcx> {
     ///
     /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
     /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
-    FakeRead(FakeReadCause, Place<'tcx>),
+    FakeRead(FakeReadCause, Box<Place<'tcx>>),
 
     /// Write the discriminant for a variant to the enum Place.
-    SetDiscriminant { place: Place<'tcx>, variant_index: VariantIdx },
+    SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
 
     /// Start a live range for the storage of the local.
     StorageLive(Local),
@@ -1595,7 +1597,7 @@ pub enum StatementKind<'tcx> {
     /// by miri and only generated when "-Z mir-emit-retag" is passed.
     /// See <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/>
     /// for more details.
-    Retag(RetagKind, Place<'tcx>),
+    Retag(RetagKind, Box<Place<'tcx>>),
 
     /// Encodes a user's type ascription. These need to be preserved
     /// intact so that NLL can respect them. For example:
@@ -1609,26 +1611,26 @@ pub enum StatementKind<'tcx> {
     /// - `Contravariant` -- requires that `T_y :> T`
     /// - `Invariant` -- requires that `T_y == T`
     /// - `Bivariant` -- no effect
-    AscribeUserType(Place<'tcx>, ty::Variance, Box<UserTypeProjection>),
+    AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
 
     /// No-op. Useful for deleting instructions without affecting statement indices.
     Nop,
 }
 
-/// `RetagKind` describes what kind of retag is to be performed.
+/// Describes what kind of retag is to be performed.
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug, PartialEq, Eq, HashStable)]
 pub enum RetagKind {
-    /// The initial retag when entering a function
+    /// The initial retag when entering a function.
     FnEntry,
-    /// Retag preparing for a two-phase borrow
+    /// Retag preparing for a two-phase borrow.
     TwoPhase,
-    /// Retagging raw pointers
+    /// Retagging raw pointers.
     Raw,
-    /// A "normal" retag
+    /// A "normal" retag.
     Default,
 }
 
-/// The `FakeReadCause` describes the type of pattern why a `FakeRead` statement exists.
+/// The `FakeReadCause` describes the type of pattern why a FakeRead statement exists.
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug, HashStable)]
 pub enum FakeReadCause {
     /// Inject a fake read of the borrowed input at the end of each guards
@@ -1673,7 +1675,7 @@ impl Debug for Statement<'_> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         use self::StatementKind::*;
         match self.kind {
-            Assign(ref place, ref rv) => write!(fmt, "{:?} = {:?}", place, rv),
+            Assign(box(ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
             FakeRead(ref cause, ref place) => write!(fmt, "FakeRead({:?}, {:?})", cause, place),
             Retag(ref kind, ref place) => write!(
                 fmt,
@@ -1694,7 +1696,7 @@ impl Debug for Statement<'_> {
             InlineAsm(ref asm) => {
                 write!(fmt, "asm!({:?} : {:?} : {:?})", asm.asm, asm.outputs, asm.inputs)
             }
-            AscribeUserType(ref place, ref variance, ref c_ty) => {
+            AscribeUserType(box(ref place, ref c_ty), ref variance) => {
                 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
             }
             Nop => write!(fmt, "nop"),
@@ -1714,7 +1716,7 @@ pub struct Place<'tcx> {
     pub base: PlaceBase<'tcx>,
 
     /// projection out of a place (access a field, deref a pointer, etc)
-    pub projection: Option<Box<Projection<'tcx>>>,
+    pub projection: Box<[PlaceElem<'tcx>]>,
 }
 
 #[derive(
@@ -1757,15 +1759,6 @@ impl_stable_hash_for!(struct Static<'tcx> {
     def_id
 });
 
-/// The `Projection` data structure defines things of the form `base.x`, `*b` or `b[index]`.
-#[derive(
-    Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, HashStable,
-)]
-pub struct Projection<'tcx> {
-    pub base: Option<Box<Projection<'tcx>>>,
-    pub elem: PlaceElem<'tcx>,
-}
-
 #[derive(
     Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, HashStable,
 )]
@@ -1847,14 +1840,22 @@ newtype_index! {
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct PlaceRef<'a, 'tcx> {
     pub base: &'a PlaceBase<'tcx>,
-    pub projection: &'a Option<Box<Projection<'tcx>>>,
+    pub projection: &'a [PlaceElem<'tcx>],
 }
 
 impl<'tcx> Place<'tcx> {
-    pub const RETURN_PLACE: Place<'tcx> = Place {
-        base: PlaceBase::Local(RETURN_PLACE),
-        projection: None,
-    };
+    // FIXME change this back to a const when projection is a shared slice.
+    //
+    // pub const RETURN_PLACE: Place<'tcx> = Place {
+    //     base: PlaceBase::Local(RETURN_PLACE),
+    //     projection: &[],
+    // };
+    pub fn return_place() -> Place<'tcx> {
+        Place {
+            base: PlaceBase::Local(RETURN_PLACE),
+            projection: Box::new([]),
+        }
+    }
 
     pub fn field(self, f: Field, ty: Ty<'tcx>) -> Place<'tcx> {
         self.elem(ProjectionElem::Field(f, ty))
@@ -1880,9 +1881,13 @@ impl<'tcx> Place<'tcx> {
     }
 
     pub fn elem(self, elem: PlaceElem<'tcx>) -> Place<'tcx> {
+        // FIXME(spastorino): revisit this again once projection is not a Box<[T]> anymore
+        let mut projection = self.projection.into_vec();
+        projection.push(elem);
+
         Place {
             base: self.base,
-            projection: Some(Box::new(Projection { base: self.projection, elem })),
+            projection: projection.into_boxed_slice(),
         }
     }
 
@@ -1891,7 +1896,7 @@ impl<'tcx> Place<'tcx> {
     /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
     /// same region of memory as its base.
     pub fn is_indirect(&self) -> bool {
-        self.iterate(|_, mut projections| projections.any(|proj| proj.elem.is_indirect()))
+        self.projection.iter().any(|elem| elem.is_indirect())
     }
 
     /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
@@ -1902,61 +1907,16 @@ impl<'tcx> Place<'tcx> {
         match self {
             Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             } |
             Place {
                 base: PlaceBase::Local(local),
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: box [ProjectionElem::Deref],
             } => Some(*local),
             _ => None,
         }
     }
 
-    /// Recursively "iterates" over place components, generating a `PlaceBase` and
-    /// `Projections` list and invoking `op` with a `ProjectionsIter`.
-    pub fn iterate<R>(
-        &self,
-        op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
-    ) -> R {
-        Place::iterate_over(&self.base, &self.projection, op)
-    }
-
-    pub fn iterate_over<R>(
-        place_base: &PlaceBase<'tcx>,
-        place_projection: &Option<Box<Projection<'tcx>>>,
-        op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
-    ) -> R {
-        fn iterate_over2<'tcx, R>(
-            place_base: &PlaceBase<'tcx>,
-            place_projection: &Option<Box<Projection<'tcx>>>,
-            next: &Projections<'_, 'tcx>,
-            op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
-        ) -> R {
-            match place_projection {
-                None => {
-                    op(place_base, next.iter())
-                }
-
-                Some(interior) => {
-                    iterate_over2(
-                        place_base,
-                        &interior.base,
-                        &Projections::List {
-                            projection: interior,
-                            next,
-                        },
-                        op,
-                    )
-                }
-            }
-        }
-
-        iterate_over2(place_base, place_projection, &Projections::Empty, op)
-    }
-
     pub fn as_ref(&self) -> PlaceRef<'_, 'tcx> {
         PlaceRef {
             base: &self.base,
@@ -1969,7 +1929,7 @@ impl From<Local> for Place<'_> {
     fn from(local: Local) -> Self {
         Place {
             base: local.into(),
-            projection: None,
+            projection: Box::new([]),
         }
     }
 }
@@ -1981,13 +1941,6 @@ impl From<Local> for PlaceBase<'_> {
 }
 
 impl<'a, 'tcx> PlaceRef<'a, 'tcx> {
-    pub fn iterate<R>(
-        &self,
-        op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
-    ) -> R {
-        Place::iterate_over(self.base, self.projection, op)
-    }
-
     /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
     /// a single deref of a local.
     //
@@ -1996,143 +1949,71 @@ impl<'a, 'tcx> PlaceRef<'a, 'tcx> {
         match self {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } |
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [ProjectionElem::Deref],
             } => Some(*local),
             _ => None,
         }
     }
 }
 
-/// A linked list of projections running up the stack; begins with the
-/// innermost projection and extends to the outermost (e.g., `a.b.c`
-/// would have the place `b` with a "next" pointer to `b.c`).
-/// Created by `Place::iterate`.
-///
-/// N.B., this particular impl strategy is not the most obvious. It was
-/// chosen because it makes a measurable difference to NLL
-/// performance, as this code (`borrow_conflicts_with_place`) is somewhat hot.
-pub enum Projections<'p, 'tcx> {
-    Empty,
-
-    List { projection: &'p Projection<'tcx>, next: &'p Projections<'p, 'tcx> },
-}
-
-impl<'p, 'tcx> Projections<'p, 'tcx> {
-    fn iter(&self) -> ProjectionsIter<'_, 'tcx> {
-        ProjectionsIter { value: self }
-    }
-}
-
-impl<'p, 'tcx> IntoIterator for &'p Projections<'p, 'tcx> {
-    type Item = &'p Projection<'tcx>;
-    type IntoIter = ProjectionsIter<'p, 'tcx>;
-
-    /// Converts a list of `Projection` components into an iterator;
-    /// this iterator yields up a never-ending stream of `Option<&Place>`.
-    /// These begin with the "innermost" projection and then with each
-    /// projection therefrom. So given a place like `a.b.c` it would
-    /// yield up:
-    ///
-    /// ```notrust
-    /// Some(`a`), Some(`a.b`), Some(`a.b.c`), None, None, ...
-    /// ```
-    fn into_iter(self) -> Self::IntoIter {
-        self.iter()
-    }
-}
-
-/// Iterator over components; see `Projections::iter` for more
-/// information.
-///
-/// N.B., this is not a *true* Rust iterator -- the code above just
-/// manually invokes `next`. This is because we (sometimes) want to
-/// keep executing even after `None` has been returned.
-pub struct ProjectionsIter<'p, 'tcx> {
-    pub value: &'p Projections<'p, 'tcx>,
-}
-
-impl<'p, 'tcx> Iterator for ProjectionsIter<'p, 'tcx> {
-    type Item = &'p Projection<'tcx>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if let &Projections::List { projection, next } = self.value {
-            self.value = next;
-            Some(projection)
-        } else {
-            None
-        }
-    }
-}
-
-impl<'p, 'tcx> FusedIterator for ProjectionsIter<'p, 'tcx> {}
-
 impl Debug for Place<'_> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
-        self.iterate(|_place_base, place_projections| {
-            // FIXME: remove this collect once we have migrated to slices
-            let projs_vec: Vec<_> = place_projections.collect();
-            for projection in projs_vec.iter().rev() {
-                match projection.elem {
-                    ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
-                        write!(fmt, "(").unwrap();
-                    }
-                    ProjectionElem::Deref => {
-                        write!(fmt, "(*").unwrap();
-                    }
-                    ProjectionElem::Index(_)
-                    | ProjectionElem::ConstantIndex { .. }
-                    | ProjectionElem::Subslice { .. } => {}
+        for elem in self.projection.iter().rev() {
+            match elem {
+                ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
+                    write!(fmt, "(").unwrap();
+                }
+                ProjectionElem::Deref => {
+                    write!(fmt, "(*").unwrap();
                 }
+                ProjectionElem::Index(_)
+                | ProjectionElem::ConstantIndex { .. }
+                | ProjectionElem::Subslice { .. } => {}
             }
-        });
+        }
 
-        self.iterate(|place_base, place_projections| {
-            write!(fmt, "{:?}", place_base)?;
+        write!(fmt, "{:?}", self.base)?;
 
-            for projection in place_projections {
-                match projection.elem {
-                    ProjectionElem::Downcast(Some(name), _index) => {
-                        write!(fmt, " as {})", name)?;
-                    }
-                    ProjectionElem::Downcast(None, index) => {
-                        write!(fmt, " as variant#{:?})", index)?;
-                    }
-                    ProjectionElem::Deref => {
-                        write!(fmt, ")")?;
-                    }
-                    ProjectionElem::Field(field, ty) => {
-                        write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
-                    }
-                    ProjectionElem::Index(ref index) => {
-                        write!(fmt, "[{:?}]", index)?;
-                    }
-                    ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
-                        write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
-                    }
-                    ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
-                        write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
-                    }
-                    ProjectionElem::Subslice { from, to } if to == 0 => {
-                        write!(fmt, "[{:?}:]", from)?;
-                    }
-                    ProjectionElem::Subslice { from, to } if from == 0 => {
-                        write!(fmt, "[:-{:?}]", to)?;
-                    }
-                    ProjectionElem::Subslice { from, to } => {
-                        write!(fmt, "[{:?}:-{:?}]", from, to)?;
-                    }
+        for elem in self.projection.iter() {
+            match elem {
+                ProjectionElem::Downcast(Some(name), _index) => {
+                    write!(fmt, " as {})", name)?;
+                }
+                ProjectionElem::Downcast(None, index) => {
+                    write!(fmt, " as variant#{:?})", index)?;
+                }
+                ProjectionElem::Deref => {
+                    write!(fmt, ")")?;
+                }
+                ProjectionElem::Field(field, ty) => {
+                    write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
+                }
+                ProjectionElem::Index(ref index) => {
+                    write!(fmt, "[{:?}]", index)?;
+                }
+                ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
+                    write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
+                }
+                ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
+                    write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
+                }
+                ProjectionElem::Subslice { from, to } if *to == 0 => {
+                    write!(fmt, "[{:?}:]", from)?;
+                }
+                ProjectionElem::Subslice { from, to } if *from == 0 => {
+                    write!(fmt, "[:-{:?}]", to)?;
+                }
+                ProjectionElem::Subslice { from, to } => {
+                    write!(fmt, "[{:?}:-{:?}]", from, to)?;
                 }
             }
+        }
 
-            Ok(())
-        })
+        Ok(())
     }
 }
 
@@ -2171,7 +2052,7 @@ pub struct SourceScopeData {
 
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct SourceScopeLocalData {
-    /// A HirId with lint levels equivalent to this scope's lint levels.
+    /// An `HirId` with lint levels equivalent to this scope's lint levels.
     pub lint_root: hir::HirId,
     /// The unsafe block that contains this node.
     pub safety: Safety,
@@ -2760,11 +2641,12 @@ impl<'a, 'b> graph::GraphSuccessors<'b> for Body<'a> {
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, HashStable)]
 pub struct Location {
-    /// the location is within this block
+    /// The block that the location is within.
     pub block: BasicBlock,
 
-    /// the location is the start of the statement; or, if `statement_index`
-    /// == num-statements, then the start of the terminator.
+    /// The location is the position of the start of the statement; or, if
+    /// `statement_index` equals the number of statements, then the start of the
+    /// terminator.
     pub statement_index: usize,
 }
 
@@ -2827,7 +2709,7 @@ impl Location {
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, HashStable)]
 pub enum UnsafetyViolationKind {
     General,
-    /// Permitted in const fn and regular fns.
+    /// Permitted both in `const fn`s and regular `fn`s.
     GeneralAndConstFn,
     ExternStatic(hir::HirId),
     BorrowPacked(hir::HirId),
@@ -2843,9 +2725,9 @@ pub struct UnsafetyViolation {
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, HashStable)]
 pub struct UnsafetyCheckResult {
-    /// Violations that are propagated *upwards* from this function
+    /// Violations that are propagated *upwards* from this function.
     pub violations: Lrc<[UnsafetyViolation]>,
-    /// unsafe blocks in this function, along with whether they are used. This is
+    /// `unsafe` blocks in this function, along with whether they are used. This is
     /// used for the "unused_unsafe" lint.
     pub unsafe_blocks: Lrc<[(hir::HirId, bool)]>,
 }
@@ -2857,7 +2739,7 @@ newtype_index! {
     }
 }
 
-/// The layout of generator state
+/// The layout of generator state.
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct GeneratorLayout<'tcx> {
     /// The type of every local stored inside the generator.
@@ -2872,11 +2754,14 @@ pub struct GeneratorLayout<'tcx> {
     /// layout.
     pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
 
-    /// Names and scopes of all the stored generator locals.
-    /// NOTE(tmandry) This is *strictly* a temporary hack for codegen
+    /// The names and scopes of all the stored generator locals.
+    ///
+    /// N.B., this is *strictly* a temporary hack for codegen
     /// debuginfo generation, and will be removed at some point.
     /// Do **NOT** use it for anything else, local information should not be
     /// in the MIR, please rely on local crate HIR or other side-channels.
+    //
+    // FIXME(tmandry): see above.
     pub __local_debuginfo_codegen_only_do_not_use: IndexVec<GeneratorSavedLocal, LocalDecl<'tcx>>,
 }
 
@@ -2934,7 +2819,7 @@ pub struct BorrowCheckResult<'tcx> {
 /// instances assigned one of these same indices. Those regions will
 /// be substituted away by the creator. We use `ReClosureBound` in
 /// that case because the regions must be allocated in the global
-/// TyCtxt, and hence we cannot use `ReVar` (which is what we use
+/// `TyCtxt`, and hence we cannot use `ReVar` (which is what we use
 /// internally within the rest of the NLL code).
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct ClosureRegionRequirements<'tcx> {
@@ -2950,8 +2835,8 @@ pub struct ClosureRegionRequirements<'tcx> {
     pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
 }
 
-/// Indicates an outlives constraint between a type or between two
-/// free-regions declared on the closure.
+/// Indicates an outlives-constraint between a type or between two
+/// free regions declared on the closure.
 #[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct ClosureOutlivesRequirement<'tcx> {
     // This region or type ...
@@ -2967,11 +2852,11 @@ pub struct ClosureOutlivesRequirement<'tcx> {
     pub category: ConstraintCategory,
 }
 
-/// Outlives constraints can be categorized to determine whether and why they
+/// Outlives-constraints can be categorized to determine whether and why they
 /// are interesting (for error reporting). Order of variants indicates sort
 /// order of the category, thereby influencing diagnostic output.
 ///
-/// See also [rustc_mir::borrow_check::nll::constraints]
+/// See also [rustc_mir::borrow_check::nll::constraints].
 #[derive(
     Copy,
     Clone,
@@ -3019,7 +2904,7 @@ pub enum ConstraintCategory {
     Internal,
 }
 
-/// The subject of a ClosureOutlivesRequirement -- that is, the thing
+/// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
 /// that must outlive some region.
 #[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub enum ClosureOutlivesSubject<'tcx> {
@@ -3037,7 +2922,7 @@ pub enum ClosureOutlivesSubject<'tcx> {
 }
 
 /*
- * TypeFoldable implementations for MIR types
+ * `TypeFoldable` implementations for MIR types
 */
 
 CloneTypeFoldableAndLiftImpls! {
@@ -3113,14 +2998,14 @@ BraceStructTypeFoldableImpl! {
 
 EnumTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for StatementKind<'tcx> {
-        (StatementKind::Assign)(a, b),
+        (StatementKind::Assign)(a),
         (StatementKind::FakeRead)(cause, place),
         (StatementKind::SetDiscriminant) { place, variant_index },
         (StatementKind::StorageLive)(a),
         (StatementKind::StorageDead)(a),
         (StatementKind::InlineAsm)(a),
         (StatementKind::Retag)(kind, place),
-        (StatementKind::AscribeUserType)(a, v, b),
+        (StatementKind::AscribeUserType)(a, v),
         (StatementKind::Nop),
     }
 }
@@ -3402,30 +3287,26 @@ impl<'tcx> TypeFoldable<'tcx> for Operand<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for Projection<'tcx> {
+impl<'tcx> TypeFoldable<'tcx> for PlaceElem<'tcx> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
         use crate::mir::ProjectionElem::*;
 
-        let base = self.base.fold_with(folder);
-        let elem = match self.elem {
+        match self {
             Deref => Deref,
-            Field(f, ref ty) => Field(f, ty.fold_with(folder)),
-            Index(ref v) => Index(v.fold_with(folder)),
-            ref elem => elem.clone(),
-        };
-
-        Projection { base, elem }
+            Field(f, ty) => Field(*f, ty.fold_with(folder)),
+            Index(v) => Index(v.fold_with(folder)),
+            elem => elem.clone(),
+        }
     }
 
     fn super_visit_with<Vs: TypeVisitor<'tcx>>(&self, visitor: &mut Vs) -> bool {
         use crate::mir::ProjectionElem::*;
 
-        self.base.visit_with(visitor)
-            || match self.elem {
-                Field(_, ref ty) => ty.visit_with(visitor),
-                Index(ref v) => v.visit_with(visitor),
-                _ => false,
-            }
+        match self {
+            Field(_, ty) => ty.visit_with(visitor),
+            Index(v) => v.visit_with(visitor),
+            _ => false,
+        }
     }
 }
 
diff --git a/src/librustc/mir/tcx.rs b/src/librustc/mir/tcx.rs
index e9f7636ba85ae..d776809839743 100644
--- a/src/librustc/mir/tcx.rs
+++ b/src/librustc/mir/tcx.rs
@@ -121,21 +121,16 @@ BraceStructTypeFoldableImpl! {
 impl<'tcx> Place<'tcx> {
     pub fn ty_from<D>(
         base: &PlaceBase<'tcx>,
-        projection: &Option<Box<Projection<'tcx>>>,
+        projection: &[PlaceElem<'tcx>],
         local_decls: &D,
         tcx: TyCtxt<'tcx>
     ) -> PlaceTy<'tcx>
         where D: HasLocalDecls<'tcx>
     {
-        Place::iterate_over(base, projection, |place_base, place_projections| {
-            let mut place_ty = place_base.ty(local_decls);
-
-            for proj in place_projections {
-                place_ty = place_ty.projection_ty(tcx, &proj.elem);
-            }
-
-            place_ty
-        })
+        projection.iter().fold(
+            base.ty(local_decls),
+            |place_ty, elem| place_ty.projection_ty(tcx, elem)
+        )
     }
 
     pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
diff --git a/src/librustc/mir/visit.rs b/src/librustc/mir/visit.rs
index 821367e9ea12c..1e3b9eb29c79d 100644
--- a/src/librustc/mir/visit.rs
+++ b/src/librustc/mir/visit.rs
@@ -152,18 +152,18 @@ macro_rules! make_mir_visitor {
             }
 
             fn visit_place_base(&mut self,
-                                place_base: & $($mutability)? PlaceBase<'tcx>,
+                                base: & $($mutability)? PlaceBase<'tcx>,
                                 context: PlaceContext,
                                 location: Location) {
-                self.super_place_base(place_base, context, location);
+                self.super_place_base(base, context, location);
             }
 
             fn visit_projection(&mut self,
-                                place_base: & $($mutability)? PlaceBase<'tcx>,
-                                place: & $($mutability)? Projection<'tcx>,
+                                base: & $($mutability)? PlaceBase<'tcx>,
+                                projection: & $($mutability)? [PlaceElem<'tcx>],
                                 context: PlaceContext,
                                 location: Location) {
-                self.super_projection(place_base, place, context, location);
+                self.super_projection(base, projection, context, location);
             }
 
             fn visit_constant(&mut self,
@@ -344,7 +344,9 @@ macro_rules! make_mir_visitor {
 
                 self.visit_source_info(source_info);
                 match kind {
-                    StatementKind::Assign(place, rvalue) => {
+                    StatementKind::Assign(
+                        box(ref $($mutability)? place, ref $($mutability)? rvalue)
+                    ) => {
                         self.visit_assign(place, rvalue, location);
                     }
                     StatementKind::FakeRead(_, place) => {
@@ -391,7 +393,10 @@ macro_rules! make_mir_visitor {
                     StatementKind::Retag(kind, place) => {
                         self.visit_retag(kind, place, location);
                     }
-                    StatementKind::AscribeUserType(place, variance, user_ty) => {
+                    StatementKind::AscribeUserType(
+                        box(ref $($mutability)? place, ref $($mutability)? user_ty),
+                        variance
+                    ) => {
                         self.visit_ascribe_user_ty(place, variance, user_ty, location);
                     }
                     StatementKind::Nop => {}
@@ -685,7 +690,7 @@ macro_rules! make_mir_visitor {
                             location: Location) {
                 let mut context = context;
 
-                if place.projection.is_some() {
+                if !place.projection.is_empty() {
                     context = if context.is_mutating_use() {
                         PlaceContext::MutatingUse(MutatingUseContext::Projection)
                     } else {
@@ -695,9 +700,10 @@ macro_rules! make_mir_visitor {
 
                 self.visit_place_base(& $($mutability)? place.base, context, location);
 
-                if let Some(box proj) = & $($mutability)? place.projection {
-                    self.visit_projection(& $($mutability)? place.base, proj, context, location);
-                }
+                self.visit_projection(& $($mutability)? place.base,
+                                      & $($mutability)? place.projection,
+                                      context,
+                                      location);
             }
 
             fn super_place_base(&mut self,
@@ -715,31 +721,31 @@ macro_rules! make_mir_visitor {
             }
 
             fn super_projection(&mut self,
-                                place_base: & $($mutability)? PlaceBase<'tcx>,
-                                proj: & $($mutability)? Projection<'tcx>,
+                                base: & $($mutability)? PlaceBase<'tcx>,
+                                projection: & $($mutability)? [PlaceElem<'tcx>],
                                 context: PlaceContext,
                                 location: Location) {
-                if let Some(box proj_base) = & $($mutability)? proj.base {
-                    self.visit_projection(place_base, proj_base, context, location);
-                }
+                if let [proj_base @ .., elem] = projection {
+                    self.visit_projection(base, proj_base, context, location);
 
-                match & $($mutability)? proj.elem {
-                    ProjectionElem::Field(_field, ty) => {
-                        self.visit_ty(ty, TyContext::Location(location));
-                    }
-                    ProjectionElem::Index(local) => {
-                        self.visit_local(
-                            local,
-                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
-                            location
-                        );
-                    }
-                    ProjectionElem::Deref |
-                    ProjectionElem::Subslice { from: _, to: _ } |
-                    ProjectionElem::ConstantIndex { offset: _,
-                                                    min_length: _,
-                                                    from_end: _ } |
-                    ProjectionElem::Downcast(_, _) => {
+                    match elem {
+                        ProjectionElem::Field(_field, ty) => {
+                            self.visit_ty(ty, TyContext::Location(location));
+                        }
+                        ProjectionElem::Index(local) => {
+                            self.visit_local(
+                                local,
+                                PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
+                                location
+                            );
+                        }
+                        ProjectionElem::Deref |
+                        ProjectionElem::Subslice { from: _, to: _ } |
+                        ProjectionElem::ConstantIndex { offset: _,
+                                                        min_length: _,
+                                                        from_end: _ } |
+                        ProjectionElem::Downcast(_, _) => {
+                        }
                     }
                 }
             }
diff --git a/src/librustc/query/mod.rs b/src/librustc/query/mod.rs
index ef838114f6c36..c7260945295a6 100644
--- a/src/librustc/query/mod.rs
+++ b/src/librustc/query/mod.rs
@@ -17,7 +17,6 @@ use crate::traits::query::{
 use std::borrow::Cow;
 use syntax_pos::symbol::InternedString;
 
-
 // Each of these queries corresponds to a function pointer field in the
 // `Providers` struct for requesting a value of that type, and a method
 // on `tcx: TyCtxt` (and `tcx.at(span)`) for doing that request in a way
@@ -463,15 +462,6 @@ rustc_queries! {
             no_force
             desc { "extract field of const" }
         }
-
-        /// Produces an absolute path representation of the given type. See also the documentation
-        /// on `std::any::type_name`.
-        query type_name(key: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
-            eval_always
-            no_force
-            desc { "get absolute path of type" }
-        }
-
     }
 
     TypeChecking {
@@ -854,7 +844,7 @@ rustc_queries! {
             desc { "calculating the lang items map" }
         }
 
-        /// Returns all diagnostic items defined in all crates
+        /// Returns all diagnostic items defined in all crates.
         query all_diagnostic_items(_: CrateNum) -> &'tcx FxHashMap<Symbol, DefId> {
             eval_always
             desc { "calculating the diagnostic items map" }
@@ -865,7 +855,7 @@ rustc_queries! {
             desc { "calculating the lang items defined in a crate" }
         }
 
-        /// Returns the diagnostic items defined in a crate
+        /// Returns the diagnostic items defined in a crate.
         query diagnostic_items(_: CrateNum) -> &'tcx FxHashMap<Symbol, DefId> {
             desc { "calculating the diagnostic items map in a crate" }
         }
diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 740d9db7edcf7..723855c7c29cf 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1,36 +1,38 @@
 //! Contains infrastructure for configuring the compiler, including parsing
-//! command line options.
-
-use std::str::FromStr;
+//! command-line options.
 
+use crate::lint;
+use crate::middle::cstore;
 use crate::session::{early_error, early_warn, Session};
 use crate::session::search_paths::SearchPath;
 
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::sync::Lrc;
+
 use rustc_target::spec::{LinkerFlavor, MergeFunctions, PanicStrategy, RelroLevel};
 use rustc_target::spec::{Target, TargetTriple};
-use crate::lint;
-use crate::middle::cstore;
 
 use syntax;
 use syntax::ast::{self, IntTy, UintTy, MetaItemKind};
 use syntax::source_map::{FileName, FilePathMapping};
 use syntax::edition::{Edition, EDITION_NAME_LIST, DEFAULT_EDITION};
+use syntax::parse::{ParseSess, new_parser_from_source_str};
 use syntax::parse::token;
-use syntax::parse;
 use syntax::symbol::{sym, Symbol};
 use syntax::feature_gate::UnstableFeatures;
-use errors::emitter::HumanReadableErrorType;
+use syntax::source_map::SourceMap;
 
+use errors::emitter::HumanReadableErrorType;
 use errors::{ColorConfig, FatalError, Handler};
 
 use getopts;
-use std::collections::{BTreeMap, BTreeSet};
-use std::collections::btree_map::Iter as BTreeMapIter;
-use std::collections::btree_map::Keys as BTreeMapKeysIter;
-use std::collections::btree_map::Values as BTreeMapValuesIter;
 
-use rustc_data_structures::fx::FxHashSet;
-use std::{fmt, str};
+use std::collections::{BTreeMap, BTreeSet};
+use std::collections::btree_map::{
+    Iter as BTreeMapIter, Keys as BTreeMapKeysIter, Values as BTreeMapValuesIter,
+};
+use std::fmt;
+use std::str::{self, FromStr};
 use std::hash::Hasher;
 use std::collections::hash_map::DefaultHasher;
 use std::iter::FromIterator;
@@ -241,14 +243,14 @@ pub enum ErrorOutputType {
 }
 
 impl Default for ErrorOutputType {
-    fn default() -> ErrorOutputType {
-        ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(ColorConfig::Auto))
+    fn default() -> Self {
+        Self::HumanReadable(HumanReadableErrorType::Default(ColorConfig::Auto))
     }
 }
 
-// Use tree-based collections to cheaply get a deterministic Hash implementation.
-// DO NOT switch BTreeMap out for an unsorted container type! That would break
-// dependency tracking for command-line arguments.
+/// Use tree-based collections to cheaply get a deterministic `Hash` implementation.
+/// *Do not* switch `BTreeMap` out for an unsorted container type! That would break
+/// dependency tracking for command-line arguments.
 #[derive(Clone, Hash)]
 pub struct OutputTypes(BTreeMap<OutputType, Option<PathBuf>>);
 
@@ -281,7 +283,7 @@ impl OutputTypes {
         self.0.len()
     }
 
-    // True if any of the output types require codegen or linking.
+    // Returns `true` if any of the output types require codegen or linking.
     pub fn should_codegen(&self) -> bool {
         self.0.keys().any(|k| match *k {
             OutputType::Bitcode
@@ -295,9 +297,9 @@ impl OutputTypes {
     }
 }
 
-// Use tree-based collections to cheaply get a deterministic Hash implementation.
-// DO NOT switch BTreeMap or BTreeSet out for an unsorted container type! That
-// would break dependency tracking for command-line arguments.
+/// Use tree-based collections to cheaply get a deterministic `Hash` implementation.
+/// *Do not* switch `BTreeMap` or `BTreeSet` out for an unsorted container type! That
+/// would break dependency tracking for command-line arguments.
 #[derive(Clone, Hash)]
 pub struct Externs(BTreeMap<String, ExternEntry>);
 
@@ -327,7 +329,7 @@ macro_rules! hash_option {
     ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, [TRACKED]) => ({
         if $sub_hashes.insert(stringify!($opt_name),
                               $opt_expr as &dyn dep_tracking::DepTrackingHash).is_some() {
-            bug!("Duplicate key in CLI DepTrackingHash: {}", stringify!($opt_name))
+            bug!("duplicate key in CLI DepTrackingHash: {}", stringify!($opt_name))
         }
     });
 }
@@ -362,7 +364,7 @@ macro_rules! top_level_options {
     );
 }
 
-// The top-level command-line options struct
+// The top-level command-line options struct.
 //
 // For each option, one has to specify how it behaves with regard to the
 // dependency tracking system of incremental compilation. This is done via the
@@ -376,16 +378,16 @@ macro_rules! top_level_options {
 // Incremental compilation is not influenced by this option.
 //
 // If you add a new option to this struct or one of the sub-structs like
-// CodegenOptions, think about how it influences incremental compilation. If in
+// `CodegenOptions`, think about how it influences incremental compilation. If in
 // doubt, specify [TRACKED], which is always "correct" but might lead to
 // unnecessary re-compilation.
 top_level_options!(
     pub struct Options {
         // The crate config requested for the session, which may be combined
-        // with additional crate configurations during the compile process
+        // with additional crate configurations during the compile process.
         crate_types: Vec<CrateType> [TRACKED],
         optimize: OptLevel [TRACKED],
-        // Include the debug_assertions flag into dependency tracking, since it
+        // Include the `debug_assertions` flag in dependency tracking, since it
         // can influence whether overflow checks are done or not.
         debug_assertions: bool [TRACKED],
         debuginfo: DebugInfo [TRACKED],
@@ -402,8 +404,8 @@ top_level_options!(
         test: bool [TRACKED],
         error_format: ErrorOutputType [UNTRACKED],
 
-        // if Some, enable incremental compilation, using the given
-        // directory to store intermediate results
+        // If `Some`, enable incremental compilation, using the given
+        // directory to store intermediate results.
         incremental: Option<PathBuf> [UNTRACKED],
 
         debugging_opts: DebuggingOptions [TRACKED],
@@ -418,7 +420,7 @@ top_level_options!(
         // written `extern crate name as std`. Defaults to `std`. Used by
         // out-of-tree drivers.
         alt_std_name: Option<String> [TRACKED],
-        // Indicates how the compiler should treat unstable features
+        // Indicates how the compiler should treat unstable features.
         unstable_features: UnstableFeatures [TRACKED],
 
         // Indicates whether this run of the compiler is actually rustdoc. This
@@ -434,12 +436,12 @@ top_level_options!(
         cli_forced_codegen_units: Option<usize> [UNTRACKED],
         cli_forced_thinlto_off: bool [UNTRACKED],
 
-        // Remap source path prefixes in all output (messages, object files, debug, etc)
+        // Remap source path prefixes in all output (messages, object files, debug, etc.).
         remap_path_prefix: Vec<(PathBuf, PathBuf)> [UNTRACKED],
 
         edition: Edition [TRACKED],
 
-        // Whether or not we're emitting JSON blobs about each artifact produced
+        // `true` if we're emitting JSON blobs about each artifact produced
         // by the compiler.
         json_artifact_notifications: bool [TRACKED],
     }
@@ -468,7 +470,7 @@ pub enum BorrowckMode {
 }
 
 impl BorrowckMode {
-    /// Should we run the MIR-based borrow check, but also fall back
+    /// Returns whether we should run the MIR-based borrow check, but also fall back
     /// on the AST borrow check if the MIR-based one errors.
     pub fn migrate(self) -> bool {
         match self {
@@ -477,7 +479,7 @@ impl BorrowckMode {
         }
     }
 
-    /// Should we emit the AST-based borrow checker errors?
+    /// Returns whether we should emit the AST-based borrow checker errors.
     pub fn use_ast(self) -> bool {
         match self {
             BorrowckMode::Mir => false,
@@ -487,12 +489,13 @@ impl BorrowckMode {
 }
 
 pub enum Input {
-    /// Loads source from file
+    /// Load source code from a file.
     File(PathBuf),
+    /// Load source code from a string.
     Str {
-        /// String that is shown in place of a filename
+        /// A string that is shown in place of a filename.
         name: FileName,
-        /// Anonymous source string
+        /// An anonymous string containing the source code.
         input: String,
     },
 }
@@ -651,7 +654,7 @@ impl Options {
         FilePathMapping::new(self.remap_path_prefix.clone())
     }
 
-    /// Returns `true` if there will be an output file generated
+    /// Returns `true` if there will be an output file generated.
     pub fn will_create_output_file(&self) -> bool {
         !self.debugging_opts.parse_only && // The file is just being parsed
             !self.debugging_opts.ls // The file is just being queried
@@ -709,16 +712,14 @@ impl Passes {
     }
 }
 
-/// Declare a macro that will define all CodegenOptions/DebuggingOptions fields and parsers all
-/// at once. The goal of this macro is to define an interface that can be
-/// programmatically used by the option parser in order to initialize the struct
-/// without hardcoding field names all over the place.
+/// Defines all `CodegenOptions`/`DebuggingOptions` fields and parsers all at once. The goal of this
+/// macro is to define an interface that can be programmatically used by the option parser
+/// to initialize the struct without hardcoding field names all over the place.
 ///
-/// The goal is to invoke this macro once with the correct fields, and then this
-/// macro generates all necessary code. The main gotcha of this macro is the
-/// cgsetters module which is a bunch of generated code to parse an option into
-/// its respective field in the struct. There are a few hand-written parsers for
-/// parsing specific types of values in this module.
+/// The goal is to invoke this macro once with the correct fields, and then this macro generates all
+/// necessary code. The main gotcha of this macro is the `cgsetters` module which is a bunch of
+/// generated code to parse an option into its respective field in the struct. There are a few
+/// hand-written parsers for parsing specific types of values in this module.
 macro_rules! options {
     ($struct_name:ident, $setter_name:ident, $defaultfn:ident,
      $buildfn:ident, $prefix:expr, $outputname:expr,
@@ -1539,7 +1540,7 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
     ret
 }
 
-/// Converts the crate cfg! configuration from String to Symbol.
+/// Converts the crate `cfg!` configuration from `String` to `Symbol`.
 /// `rustc_interface::interface::Config` accepts this in the compiler configuration,
 /// but the symbol interner is not yet set up then, so we must convert it later.
 pub fn to_crate_config(cfg: FxHashSet<(String, Option<String>)>) -> ast::CrateConfig {
@@ -1550,9 +1551,9 @@ pub fn to_crate_config(cfg: FxHashSet<(String, Option<String>)>) -> ast::CrateCo
 
 pub fn build_configuration(sess: &Session, mut user_cfg: ast::CrateConfig) -> ast::CrateConfig {
     // Combine the configuration requested by the session (command line) with
-    // some default and generated configuration items
+    // some default and generated configuration items.
     let default_cfg = default_configuration(sess);
-    // If the user wants a test runner, then add the test cfg
+    // If the user wants a test runner, then add the test cfg.
     if sess.opts.test {
         user_cfg.insert((sym::test, None));
     }
@@ -1851,13 +1852,22 @@ pub fn rustc_optgroups() -> Vec<RustcOptGroup> {
     opts
 }
 
-// Convert strings provided as --cfg [cfgspec] into a crate_cfg
+struct NullEmitter;
+
+impl errors::emitter::Emitter for NullEmitter {
+    fn emit_diagnostic(&mut self, _: &errors::DiagnosticBuilder<'_>) {}
+}
+
+// Converts strings provided as `--cfg [cfgspec]` into a `crate_cfg`.
 pub fn parse_cfgspecs(cfgspecs: Vec<String>) -> FxHashSet<(String, Option<String>)> {
     syntax::with_default_globals(move || {
         let cfg = cfgspecs.into_iter().map(|s| {
-            let sess = parse::ParseSess::new(FilePathMapping::empty());
+
+            let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let handler = Handler::with_emitter(false, None, Box::new(NullEmitter));
+            let sess = ParseSess::with_span_handler(handler, cm);
             let filename = FileName::cfg_spec_source_code(&s);
-            let mut parser = parse::new_parser_from_source_str(&sess, filename, s.to_string());
+            let mut parser = new_parser_from_source_str(&sess, filename, s.to_string());
 
             macro_rules! error {($reason: expr) => {
                 early_error(ErrorOutputType::default(),
@@ -1917,7 +1927,7 @@ pub fn get_cmd_lint_options(matches: &getopts::Matches,
     (lint_opts, describe_lints, lint_cap)
 }
 
-/// Parse the `--color` flag
+/// Parses the `--color` flag.
 pub fn parse_color(matches: &getopts::Matches) -> ColorConfig {
     match matches.opt_str("color").as_ref().map(|s| &s[..]) {
         Some("auto") => ColorConfig::Auto,
@@ -1929,7 +1939,7 @@ pub fn parse_color(matches: &getopts::Matches) -> ColorConfig {
         Some(arg) => early_error(
             ErrorOutputType::default(),
             &format!(
-                "argument for --color must be auto, \
+                "argument for `--color` must be auto, \
                  always or never (instead was `{}`)",
                 arg
             ),
@@ -1974,16 +1984,16 @@ pub fn parse_json(matches: &getopts::Matches) -> (HumanReadableErrorType, bool)
     (json_rendered(json_color), json_artifact_notifications)
 }
 
-/// Parse the `--error-format` flag
+/// Parses the `--error-format` flag.
 pub fn parse_error_format(
     matches: &getopts::Matches,
     color: ColorConfig,
     json_rendered: HumanReadableErrorType,
 ) -> ErrorOutputType {
-    // We need the opts_present check because the driver will send us Matches
+    // We need the `opts_present` check because the driver will send us Matches
     // with only stable options if no unstable options are used. Since error-format
-    // is unstable, it will not be present. We have to use opts_present not
-    // opt_present because the latter will panic.
+    // is unstable, it will not be present. We have to use `opts_present` not
+    // `opt_present` because the latter will panic.
     let error_format = if matches.opts_present(&["error-format".to_owned()]) {
         match matches.opt_str("error-format").as_ref().map(|s| &s[..]) {
             None |
@@ -1998,7 +2008,7 @@ pub fn parse_error_format(
             Some(arg) => early_error(
                 ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(color)),
                 &format!(
-                    "argument for --error-format must be `human`, `json` or \
+                    "argument for `--error-format` must be `human`, `json` or \
                      `short` (instead was `{}`)",
                     arg
                 ),
@@ -2037,7 +2047,7 @@ pub fn build_session_options_and_crate_config(
             early_error(
                 ErrorOutputType::default(),
                 &format!(
-                    "argument for --edition must be one of: \
+                    "argument for `--edition` must be one of: \
                      {}. (instead was `{}`)",
                     EDITION_NAME_LIST,
                     arg
@@ -2051,7 +2061,7 @@ pub fn build_session_options_and_crate_config(
         early_error(
                 ErrorOutputType::default(),
                 &format!(
-                    "Edition {} is unstable and only \
+                    "edition {} is unstable and only \
                      available for nightly builds of rustc.",
                     edition,
                 )
@@ -2075,14 +2085,14 @@ pub fn build_session_options_and_crate_config(
         if let ErrorOutputType::Json { pretty: true, json_rendered } = error_format {
             early_error(
                 ErrorOutputType::Json { pretty: false, json_rendered },
-                "--error-format=pretty-json is unstable",
+                "`--error-format=pretty-json` is unstable",
             );
         }
         if let ErrorOutputType::HumanReadable(HumanReadableErrorType::AnnotateSnippet(_)) =
             error_format {
             early_error(
                 ErrorOutputType::Json { pretty: false, json_rendered },
-                "--error-format=human-annotate-rs is unstable",
+                "`--error-format=human-annotate-rs` is unstable",
             );
         }
     }
@@ -2116,7 +2126,7 @@ pub fn build_session_options_and_crate_config(
     let mut codegen_units = cg.codegen_units;
     let mut disable_thinlto = false;
 
-    // Issue #30063: if user requests llvm-related output to one
+    // Issue #30063: if user requests LLVM-related output to one
     // particular path, disable codegen-units.
     let incompatible: Vec<_> = output_types
         .iter()
@@ -2132,8 +2142,8 @@ pub fn build_session_options_and_crate_config(
                         early_warn(
                             error_format,
                             &format!(
-                                "--emit={} with -o incompatible with \
-                                 -C codegen-units=N for N > 1",
+                                "`--emit={}` with `-o` incompatible with \
+                                 `-C codegen-units=N` for N > 1",
                                 ot
                             ),
                         );
@@ -2153,21 +2163,21 @@ pub fn build_session_options_and_crate_config(
     if debugging_opts.threads == Some(0) {
         early_error(
             error_format,
-            "Value for threads must be a positive nonzero integer",
+            "value for threads must be a positive non-zero integer",
         );
     }
 
     if debugging_opts.threads.unwrap_or(1) > 1 && debugging_opts.fuel.is_some() {
         early_error(
             error_format,
-            "Optimization fuel is incompatible with multiple threads",
+            "optimization fuel is incompatible with multiple threads",
         );
     }
 
     if codegen_units == Some(0) {
         early_error(
             error_format,
-            "Value for codegen units must be a positive nonzero integer",
+            "value for codegen units must be a positive non-zero integer",
         );
     }
 
@@ -2414,10 +2424,10 @@ pub fn build_session_options_and_crate_config(
         )
     }
 
-    // We start out with a Vec<(Option<String>, bool)>>,
-    // and later convert it into a BTreeSet<(Option<String>, bool)>
+    // We start out with a `Vec<(Option<String>, bool)>>`,
+    // and later convert it into a `BTreeSet<(Option<String>, bool)>`
     // This allows to modify entries in-place to set their correct
-    // 'public' value
+    // 'public' value.
     let mut externs: BTreeMap<String, ExternEntry> = BTreeMap::new();
     for (arg, private) in matches.opt_strs("extern").into_iter().map(|v| (v, false))
         .chain(matches.opt_strs("extern-private").into_iter().map(|v| (v, true))) {
@@ -2616,15 +2626,15 @@ impl fmt::Display for CrateType {
 /// The values of all command-line arguments that are relevant for dependency
 /// tracking are hashed into a single value that determines whether the
 /// incremental compilation cache can be re-used or not. This hashing is done
-/// via the DepTrackingHash trait defined below, since the standard Hash
-/// implementation might not be suitable (e.g., arguments are stored in a Vec,
+/// via the `DepTrackingHash` trait defined below, since the standard `Hash`
+/// implementation might not be suitable (e.g., arguments are stored in a `Vec`,
 /// the hash of which is order dependent, but we might not want the order of
 /// arguments to make a difference for the hash).
 ///
-/// However, since the value provided by Hash::hash often *is* suitable,
+/// However, since the value provided by `Hash::hash` often *is* suitable,
 /// especially for primitive types, there is the
-/// impl_dep_tracking_hash_via_hash!() macro that allows to simply reuse the
-/// Hash implementation for DepTrackingHash. It's important though that
+/// `impl_dep_tracking_hash_via_hash!()` macro that allows to simply reuse the
+/// `Hash` implementation for `DepTrackingHash`. It's important though that
 /// we have an opt-in scheme here, so one is hopefully forced to think about
 /// how the hash should be calculated when adding a new command-line argument.
 mod dep_tracking {
@@ -2637,9 +2647,9 @@ mod dep_tracking {
     use super::{CrateType, DebugInfo, ErrorOutputType, OptLevel, OutputTypes,
                 Passes, Sanitizer, LtoCli, LinkerPluginLto, SwitchWithOptPath,
                 SymbolManglingVersion};
-    use syntax::feature_gate::UnstableFeatures;
     use rustc_target::spec::{MergeFunctions, PanicStrategy, RelroLevel, TargetTriple};
     use syntax::edition::Edition;
+    use syntax::feature_gate::UnstableFeatures;
 
     pub trait DepTrackingHash {
         fn hash(&self, hasher: &mut DefaultHasher, error_format: ErrorOutputType);
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index f01883d9634cd..8656ebb2e6d72 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -79,12 +79,12 @@ pub struct Session {
     /// if the value stored here has been affected by path remapping.
     pub working_dir: (PathBuf, bool),
 
-    // FIXME: lint_store and buffered_lints are not thread-safe,
-    // but are only used in a single thread
+    // FIXME: `lint_store` and `buffered_lints` are not thread-safe,
+    // but are only used in a single thread.
     pub lint_store: RwLock<lint::LintStore>,
     pub buffered_lints: Lock<Option<lint::LintBuffer>>,
 
-    /// Set of (DiagnosticId, Option<Span>, message) tuples tracking
+    /// Set of `(DiagnosticId, Option<Span>, message)` tuples tracking
     /// (sub)diagnostics that have been set once, but should not be set again,
     /// in order to avoid redundantly verbose output (Issue #24690, #44953).
     pub one_time_diagnostics: Lock<FxHashSet<(DiagnosticMessageId, Option<Span>, String)>>,
@@ -92,11 +92,11 @@ pub struct Session {
     pub plugin_attributes: Lock<Vec<(Symbol, AttributeType)>>,
     pub crate_types: Once<Vec<config::CrateType>>,
     pub dependency_formats: Once<dependency_format::Dependencies>,
-    /// The crate_disambiguator is constructed out of all the `-C metadata`
+    /// The `crate_disambiguator` is constructed out of all the `-C metadata`
     /// arguments passed to the compiler. Its value together with the crate-name
     /// forms a unique global identifier for the crate. It is used to allow
     /// multiple crates with the same name to coexist. See the
-    /// rustc_codegen_llvm::back::symbol_names module for more information.
+    /// `rustc_codegen_llvm::back::symbol_names` module for more information.
     pub crate_disambiguator: Once<CrateDisambiguator>,
 
     features: Once<feature_gate::Features>,
@@ -111,7 +111,7 @@ pub struct Session {
     /// The maximum number of stackframes allowed in const eval.
     pub const_eval_stack_frame_limit: usize,
 
-    /// The metadata::creader module may inject an allocator/panic_runtime
+    /// The `metadata::creader` module may inject an allocator/`panic_runtime`
     /// dependency if it didn't already find one, and this tracks what was
     /// injected.
     pub allocator_kind: Once<Option<AllocatorKind>>,
@@ -130,7 +130,7 @@ pub struct Session {
     /// Used by `-Z profile-queries` in `util::common`.
     pub profile_channel: Lock<Option<mpsc::Sender<ProfileQueriesMsg>>>,
 
-    /// Used by -Z self-profile
+    /// Used by `-Z self-profile`.
     pub self_profiling: Option<Arc<SelfProfiler>>,
 
     /// Some measurements that are being gathered during compilation.
@@ -187,16 +187,16 @@ pub struct PerfStats {
     pub normalize_projection_ty: AtomicUsize,
 }
 
-/// Enum to support dispatch of one-time diagnostics (in Session.diag_once)
+/// Enum to support dispatch of one-time diagnostics (in `Session.diag_once`).
 enum DiagnosticBuilderMethod {
     Note,
     SpanNote,
     SpanSuggestion(String), // suggestion
-                            // add more variants as needed to support one-time diagnostics
+                            // Add more variants as needed to support one-time diagnostics.
 }
 
-/// Diagnostic message ID—used by `Session.one_time_diagnostics` to avoid
-/// emitting the same message more than once
+/// Diagnostic message ID, used by `Session.one_time_diagnostics` to avoid
+/// emitting the same message more than once.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum DiagnosticMessageId {
     ErrorId(u16), // EXXXX error code as integer
@@ -408,7 +408,7 @@ impl Session {
             Some(next) => {
                 self.next_node_id.set(ast::NodeId::from_usize(next));
             }
-            None => bug!("Input too large, ran out of node ids!"),
+            None => bug!("input too large; ran out of node-IDs!"),
         }
 
         id
@@ -440,11 +440,11 @@ impl Session {
                     diag_builder.note(message);
                 }
                 DiagnosticBuilderMethod::SpanNote => {
-                    let span = span_maybe.expect("span_note needs a span");
+                    let span = span_maybe.expect("`span_note` needs a span");
                     diag_builder.span_note(span, message);
                 }
                 DiagnosticBuilderMethod::SpanSuggestion(suggestion) => {
-                    let span = span_maybe.expect("span_suggestion_* needs a span");
+                    let span = span_maybe.expect("`span_suggestion_*` needs a span");
                     diag_builder.span_suggestion(
                         span,
                         message,
@@ -688,7 +688,7 @@ impl Session {
 
     pub fn must_not_eliminate_frame_pointers(&self) -> bool {
         // "mcount" function relies on stack pointer.
-        // See https://sourceware.org/binutils/docs/gprof/Implementation.html
+        // See <https://sourceware.org/binutils/docs/gprof/Implementation.html>.
         if self.instrument_mcount() {
             true
         } else if let Some(x) = self.opts.cg.force_frame_pointers {
@@ -699,7 +699,7 @@ impl Session {
     }
 
     /// Returns the symbol name for the registrar function,
-    /// given the crate Svh and the function DefIndex.
+    /// given the crate `Svh` and the function `DefIndex`.
     pub fn generate_plugin_registrar_symbol(&self, disambiguator: CrateDisambiguator) -> String {
         format!(
             "__rustc_plugin_registrar_{}__",
@@ -719,7 +719,7 @@ impl Session {
             &self.sysroot,
             self.opts.target_triple.triple(),
             &self.opts.search_paths,
-            // target_tlib_path==None means it's the same as host_tlib_path.
+            // `target_tlib_path == None` means it's the same as `host_tlib_path`.
             self.target_tlib_path.as_ref().unwrap_or(&self.host_tlib_path),
             kind,
         )
@@ -779,12 +779,12 @@ impl Session {
         if let IncrCompSession::Active { .. } = *incr_comp_session {
         } else {
             bug!(
-                "Trying to finalize IncrCompSession `{:?}`",
+                "trying to finalize `IncrCompSession` `{:?}`",
                 *incr_comp_session
-            )
+            );
         }
 
-        // Note: This will also drop the lock file, thus unlocking the directory
+        // Note: this will also drop the lock file, thus unlocking the directory.
         *incr_comp_session = IncrCompSession::Finalized {
             session_directory: new_directory_path,
         };
@@ -800,13 +800,15 @@ impl Session {
             } => session_directory.clone(),
             IncrCompSession::InvalidBecauseOfErrors { .. } => return,
             _ => bug!(
-                "Trying to invalidate IncrCompSession `{:?}`",
+                "trying to invalidate `IncrCompSession` `{:?}`",
                 *incr_comp_session
             ),
         };
 
-        // Note: This will also drop the lock file, thus unlocking the directory
-        *incr_comp_session = IncrCompSession::InvalidBecauseOfErrors { session_directory };
+        // Note: this will also drop the lock file, thus unlocking the directory.
+        *incr_comp_session = IncrCompSession::InvalidBecauseOfErrors {
+            session_directory,
+        };
     }
 
     pub fn incr_comp_session_dir(&self) -> cell::Ref<'_, PathBuf> {
@@ -815,8 +817,8 @@ impl Session {
             incr_comp_session,
             |incr_comp_session| match *incr_comp_session {
                 IncrCompSession::NotInitialized => bug!(
-                    "Trying to get session directory from IncrCompSession `{:?}`",
-                    *incr_comp_session
+                    "trying to get session directory from `IncrCompSession`: {:?}",
+                    *incr_comp_session,
                 ),
                 IncrCompSession::Active {
                     ref session_directory,
@@ -1185,7 +1187,10 @@ fn build_session_(
     );
     let target_cfg = config::build_target_config(&sopts, &span_diagnostic);
 
-    let p_s = parse::ParseSess::with_span_handler(span_diagnostic, source_map);
+    let parse_sess = parse::ParseSess::with_span_handler(
+        span_diagnostic,
+        source_map,
+    );
     let sysroot = match &sopts.maybe_sysroot {
         Some(sysroot) => sysroot.clone(),
         None => filesearch::get_or_default_sysroot(),
@@ -1214,7 +1219,7 @@ fn build_session_(
     let print_fuel = AtomicU64::new(0);
 
     let working_dir = env::current_dir().unwrap_or_else(|e|
-        p_s.span_diagnostic
+        parse_sess.span_diagnostic
             .fatal(&format!("Current directory is invalid: {}", e))
             .raise()
     );
@@ -1232,7 +1237,7 @@ fn build_session_(
         opts: sopts,
         host_tlib_path,
         target_tlib_path,
-        parse_sess: p_s,
+        parse_sess,
         sysroot,
         local_crate_source_file,
         working_dir,
diff --git a/src/librustc/traits/chalk_fulfill.rs b/src/librustc/traits/chalk_fulfill.rs
index 0c7c94b684a9f..a7e1f2a6a73a7 100644
--- a/src/librustc/traits/chalk_fulfill.rs
+++ b/src/librustc/traits/chalk_fulfill.rs
@@ -81,6 +81,7 @@ impl TraitEngine<'tcx> for FulfillmentContext<'tcx> {
                 .map(|obligation| FulfillmentError {
                     obligation: obligation.goal.clone(),
                     code: FulfillmentErrorCode::CodeAmbiguity,
+                    points_at_arg_span: false,
                 })
                 .collect();
             Err(errors)
@@ -129,6 +130,7 @@ impl TraitEngine<'tcx> for FulfillmentContext<'tcx> {
                                     code: FulfillmentErrorCode::CodeSelectionError(
                                         SelectionError::Unimplemented
                                     ),
+                                    points_at_arg_span: false,
                                 }),
                             }
                         } else {
@@ -142,6 +144,7 @@ impl TraitEngine<'tcx> for FulfillmentContext<'tcx> {
                         code: FulfillmentErrorCode::CodeSelectionError(
                             SelectionError::Unimplemented
                         ),
+                        points_at_arg_span: false,
                     })
                 }
             }
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index 03cc00d87e3cd..1d87484ef09be 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -119,11 +119,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
     // returns if `cond` not occurring implies that `error` does not occur - i.e., that
     // `error` occurring implies that `cond` occurs.
-    fn error_implies(&self,
-                     cond: &ty::Predicate<'tcx>,
-                     error: &ty::Predicate<'tcx>)
-                     -> bool
-    {
+    fn error_implies(
+        &self,
+        cond: &ty::Predicate<'tcx>,
+        error: &ty::Predicate<'tcx>,
+    ) -> bool {
         if cond == error {
             return true
         }
@@ -155,13 +155,21 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         false
     }
 
-    fn report_fulfillment_error(&self, error: &FulfillmentError<'tcx>,
-                                body_id: Option<hir::BodyId>,
-                                fallback_has_occurred: bool) {
+    fn report_fulfillment_error(
+        &self,
+        error: &FulfillmentError<'tcx>,
+        body_id: Option<hir::BodyId>,
+        fallback_has_occurred: bool,
+    ) {
         debug!("report_fulfillment_errors({:?})", error);
         match error.code {
-            FulfillmentErrorCode::CodeSelectionError(ref e) => {
-                self.report_selection_error(&error.obligation, e, fallback_has_occurred);
+            FulfillmentErrorCode::CodeSelectionError(ref selection_error) => {
+                self.report_selection_error(
+                    &error.obligation,
+                    selection_error,
+                    fallback_has_occurred,
+                    error.points_at_arg_span,
+                );
             }
             FulfillmentErrorCode::CodeProjectionError(ref e) => {
                 self.report_projection_error(&error.obligation, e);
@@ -170,19 +178,21 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 self.maybe_report_ambiguity(&error.obligation, body_id);
             }
             FulfillmentErrorCode::CodeSubtypeError(ref expected_found, ref err) => {
-                self.report_mismatched_types(&error.obligation.cause,
-                                             expected_found.expected,
-                                             expected_found.found,
-                                             err.clone())
-                    .emit();
+                self.report_mismatched_types(
+                    &error.obligation.cause,
+                    expected_found.expected,
+                    expected_found.found,
+                    err.clone(),
+                ).emit();
             }
         }
     }
 
-    fn report_projection_error(&self,
-                               obligation: &PredicateObligation<'tcx>,
-                               error: &MismatchedProjectionTypes<'tcx>)
-    {
+    fn report_projection_error(
+        &self,
+        obligation: &PredicateObligation<'tcx>,
+        error: &MismatchedProjectionTypes<'tcx>,
+    ) {
         let predicate =
             self.resolve_vars_if_possible(&obligation.predicate);
 
@@ -603,6 +613,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         obligation: &PredicateObligation<'tcx>,
         error: &SelectionError<'tcx>,
         fallback_has_occurred: bool,
+        points_at_arg: bool,
     ) {
         let span = obligation.cause.span;
 
@@ -690,7 +701,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                         }
 
                         self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err);
-                        self.suggest_fn_call(&obligation, &mut err, &trait_ref);
+                        self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg);
                         self.suggest_remove_reference(&obligation, &mut err, &trait_ref);
                         self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref);
 
@@ -963,6 +974,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         obligation: &PredicateObligation<'tcx>,
         err: &mut DiagnosticBuilder<'tcx>,
         trait_ref: &ty::Binder<ty::TraitRef<'tcx>>,
+        points_at_arg: bool,
     ) {
         let self_ty = trait_ref.self_ty();
         match self_ty.sty {
@@ -991,15 +1003,31 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             ..
                         })) = self.tcx.hir().get_if_local(def_id) {
                             let body = self.tcx.hir().body(*body_id);
-                            err.help(&format!(
-                                "use parentheses to call the function: `{}({})`",
+                            let msg = "use parentheses to call the function";
+                            let snippet = format!(
+                                "{}({})",
                                 ident,
                                 body.params.iter()
                                     .map(|arg| match &arg.pat.node {
                                         hir::PatKind::Binding(_, _, ident, None)
                                         if ident.name != kw::SelfLower => ident.to_string(),
                                         _ => "_".to_string(),
-                                    }).collect::<Vec<_>>().join(", ")));
+                                    }).collect::<Vec<_>>().join(", "),
+                            );
+                            // When the obligation error has been ensured to have been caused by
+                            // an argument, the `obligation.cause.span` points at the expression
+                            // of the argument, so we can provide a suggestion. This is signaled
+                            // by `points_at_arg`. Otherwise, we give a more general note.
+                            if points_at_arg {
+                                err.span_suggestion(
+                                    obligation.cause.span,
+                                    msg,
+                                    snippet,
+                                    Applicability::HasPlaceholders,
+                                );
+                            } else {
+                                err.help(&format!("{}: `{}`", msg, snippet));
+                            }
                         }
                     }
                     _ => {}
diff --git a/src/librustc/traits/fulfill.rs b/src/librustc/traits/fulfill.rs
index c1de4939c1d91..805727b6ce0d7 100644
--- a/src/librustc/traits/fulfill.rs
+++ b/src/librustc/traits/fulfill.rs
@@ -68,6 +68,10 @@ pub struct PendingPredicateObligation<'tcx> {
     pub stalled_on: Vec<Ty<'tcx>>,
 }
 
+// `PendingPredicateObligation` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(PendingPredicateObligation<'_>, 136);
+
 impl<'a, 'tcx> FulfillmentContext<'tcx> {
     /// Creates a new fulfillment context.
     pub fn new() -> FulfillmentContext<'tcx> {
@@ -252,15 +256,20 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
         &mut self,
         pending_obligation: &mut Self::Obligation,
     ) -> ProcessResult<Self::Obligation, Self::Error> {
-        // if we were stalled on some unresolved variables, first check
+        // If we were stalled on some unresolved variables, first check
         // whether any of them have been resolved; if not, don't bother
         // doing more work yet
         if !pending_obligation.stalled_on.is_empty() {
-            if pending_obligation.stalled_on.iter().all(|&ty| {
-                // Use the force-inlined variant of shallow_resolve() because this code is hot.
-                let resolved = ShallowResolver::new(self.selcx.infcx()).inlined_shallow_resolve(ty);
-                resolved == ty // nothing changed here
-            }) {
+            let mut changed = false;
+            // This `for` loop was once a call to `all()`, but this lower-level
+            // form was a perf win. See #64545 for details.
+            for &ty in &pending_obligation.stalled_on {
+                if ShallowResolver::new(self.selcx.infcx()).shallow_resolve_changed(ty) {
+                    changed = true;
+                    break;
+                }
+            }
+            if !changed {
                 debug!("process_predicate: pending obligation {:?} still stalled on {:?}",
                        self.selcx.infcx()
                            .resolve_vars_if_possible(&pending_obligation.obligation),
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 1ca92d79fa5f6..c53f4e49971bf 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -123,6 +123,10 @@ pub struct Obligation<'tcx, T> {
 pub type PredicateObligation<'tcx> = Obligation<'tcx, ty::Predicate<'tcx>>;
 pub type TraitObligation<'tcx> = Obligation<'tcx, ty::PolyTraitPredicate<'tcx>>;
 
+// `PredicateObligation` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(PredicateObligation<'_>, 112);
+
 /// The reason why we incurred this obligation; used for error reporting.
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct ObligationCause<'tcx> {
@@ -147,7 +151,8 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::StartFunctionType => {
                 tcx.sess.source_map().def_span(self.span)
             }
-            ObligationCauseCode::MatchExpressionArm { arm_span, .. } => arm_span,
+            ObligationCauseCode::MatchExpressionArm(
+                box MatchExpressionArmCause { arm_span, .. }) => arm_span,
             _ => self.span,
         }
     }
@@ -223,23 +228,13 @@ pub enum ObligationCauseCode<'tcx> {
     ExprAssignable,
 
     /// Computing common supertype in the arms of a match expression
-    MatchExpressionArm {
-        arm_span: Span,
-        source: hir::MatchSource,
-        prior_arms: Vec<Span>,
-        last_ty: Ty<'tcx>,
-        discrim_hir_id: hir::HirId,
-    },
+    MatchExpressionArm(Box<MatchExpressionArmCause<'tcx>>),
 
     /// Computing common supertype in the pattern guard for the arms of a match expression
     MatchExpressionArmPattern { span: Span, ty: Ty<'tcx> },
 
     /// Computing common supertype in an if expression
-    IfExpression {
-        then: Span,
-        outer: Option<Span>,
-        semicolon: Option<Span>,
-    },
+    IfExpression(Box<IfExpressionCause>),
 
     /// Computing common supertype of an if expression with no else counter-part
     IfExpressionWithNoElse,
@@ -269,6 +264,26 @@ pub enum ObligationCauseCode<'tcx> {
     TrivialBound,
 }
 
+// `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(ObligationCauseCode<'_>, 32);
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct MatchExpressionArmCause<'tcx> {
+    pub arm_span: Span,
+    pub source: hir::MatchSource,
+    pub prior_arms: Vec<Span>,
+    pub last_ty: Ty<'tcx>,
+    pub discrim_hir_id: hir::HirId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct IfExpressionCause {
+    pub then: Span,
+    pub outer: Option<Span>,
+    pub semicolon: Option<Span>,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct DerivedObligationCause<'tcx> {
     /// The trait reference of the parent obligation that led to the
@@ -469,7 +484,11 @@ EnumTypeFoldableImpl! {
 
 pub struct FulfillmentError<'tcx> {
     pub obligation: PredicateObligation<'tcx>,
-    pub code: FulfillmentErrorCode<'tcx>
+    pub code: FulfillmentErrorCode<'tcx>,
+    /// Diagnostics only: we opportunistically change the `code.span` when we encounter an
+    /// obligation error caused by a call argument. When this is the case, we also signal that in
+    /// this field to ensure accuracy of suggestions.
+    pub points_at_arg_span: bool,
 }
 
 #[derive(Clone)]
@@ -1168,7 +1187,7 @@ impl<'tcx> FulfillmentError<'tcx> {
            code: FulfillmentErrorCode<'tcx>)
            -> FulfillmentError<'tcx>
     {
-        FulfillmentError { obligation: obligation, code: code }
+        FulfillmentError { obligation: obligation, code: code, points_at_arg_span: false }
     }
 }
 
diff --git a/src/librustc/traits/object_safety.rs b/src/librustc/traits/object_safety.rs
index f7f459cd27f68..a7990c4af69fd 100644
--- a/src/librustc/traits/object_safety.rs
+++ b/src/librustc/traits/object_safety.rs
@@ -130,13 +130,13 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// We say a method is *vtable safe* if it can be invoked on a trait
-    /// object.  Note that object-safe traits can have some
-    /// non-vtable-safe methods, so long as they require `Self:Sized` or
-    /// otherwise ensure that they cannot be used when `Self=Trait`.
+    /// object. Note that object-safe traits can have some
+    /// non-vtable-safe methods, so long as they require `Self: Sized` or
+    /// otherwise ensure that they cannot be used when `Self = Trait`.
     pub fn is_vtable_safe_method(self, trait_def_id: DefId, method: &ty::AssocItem) -> bool {
         debug_assert!(self.generics_of(trait_def_id).has_self);
         debug!("is_vtable_safe_method({:?}, {:?})", trait_def_id, method);
-        // Any method that has a `Self : Sized` requisite can't be called.
+        // Any method that has a `Self: Sized` bound cannot be called.
         if self.generics_require_sized_self(method.def_id) {
             return false;
         }
@@ -350,15 +350,15 @@ impl<'tcx> TyCtxt<'tcx> {
             &sig.map_bound(|sig| sig.inputs()[0]),
         );
 
-        // until `unsized_locals` is fully implemented, `self: Self` can't be dispatched on.
+        // Until `unsized_locals` is fully implemented, `self: Self` can't be dispatched on.
         // However, this is already considered object-safe. We allow it as a special case here.
         // FIXME(mikeyhew) get rid of this `if` statement once `receiver_is_dispatchable` allows
-        // `Receiver: Unsize<Receiver[Self => dyn Trait]>`
+        // `Receiver: Unsize<Receiver[Self => dyn Trait]>`.
         if receiver_ty != self.types.self_param {
             if !self.receiver_is_dispatchable(method, receiver_ty) {
                 return Some(MethodViolationCode::UndispatchableReceiver);
             } else {
-                // sanity check to make sure the receiver actually has the layout of a pointer
+                // Do sanity check to make sure the receiver actually has the layout of a pointer.
 
                 use crate::ty::layout::Abi;
 
@@ -368,12 +368,12 @@ impl<'tcx> TyCtxt<'tcx> {
                     match self.layout_of(param_env.and(ty)) {
                         Ok(layout) => &layout.abi,
                         Err(err) => bug!(
-                            "Error: {}\n while computing layout for type {:?}", err, ty
+                            "error: {}\n while computing layout for type {:?}", err, ty
                         )
                     }
                 };
 
-                // e.g., Rc<()>
+                // e.g., `Rc<()>`
                 let unit_receiver_ty = self.receiver_for_self_ty(
                     receiver_ty, self.mk_unit(), method.def_id
                 );
@@ -384,7 +384,7 @@ impl<'tcx> TyCtxt<'tcx> {
                         self.sess.delay_span_bug(
                             self.def_span(method.def_id),
                             &format!(
-                                "Receiver when Self = () should have a Scalar ABI, found {:?}",
+                                "receiver when `Self = ()` should have a Scalar ABI; found {:?}",
                                 abi
                             ),
                         );
@@ -395,7 +395,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     trait_def_id, self.mk_region(ty::ReStatic)
                 );
 
-                // e.g., Rc<dyn Trait>
+                // e.g., `Rc<dyn Trait>`
                 let trait_object_receiver = self.receiver_for_self_ty(
                     receiver_ty, trait_object_ty, method.def_id
                 );
@@ -406,7 +406,8 @@ impl<'tcx> TyCtxt<'tcx> {
                         self.sess.delay_span_bug(
                             self.def_span(method.def_id),
                             &format!(
-                                "Receiver when Self = {} should have a ScalarPair ABI, found {:?}",
+                                "receiver when `Self = {}` should have a ScalarPair ABI; \
+                                 found {:?}",
                                 trait_object_ty, abi
                             ),
                         );
@@ -418,8 +419,8 @@ impl<'tcx> TyCtxt<'tcx> {
         None
     }
 
-    /// Performs a type substitution to produce the version of receiver_ty when `Self = self_ty`
-    /// e.g., for receiver_ty = `Rc<Self>` and self_ty = `Foo`, returns `Rc<Foo>`.
+    /// Performs a type substitution to produce the version of `receiver_ty` when `Self = self_ty`.
+    /// For example, for `receiver_ty = Rc<Self>` and `self_ty = Foo`, returns `Rc<Foo>`.
     fn receiver_for_self_ty(
         self,
         receiver_ty: Ty<'tcx>,
diff --git a/src/librustc/traits/query/evaluate_obligation.rs b/src/librustc/traits/query/evaluate_obligation.rs
index 2ee63647aaded..b9557ceaa6d9f 100644
--- a/src/librustc/traits/query/evaluate_obligation.rs
+++ b/src/librustc/traits/query/evaluate_obligation.rs
@@ -1,7 +1,8 @@
 use crate::infer::InferCtxt;
 use crate::infer::canonical::OriginalQueryValues;
-use crate::traits::{EvaluationResult, PredicateObligation, SelectionContext,
-             TraitQueryMode, OverflowError};
+use crate::traits::{
+    EvaluationResult, PredicateObligation, SelectionContext, TraitQueryMode, OverflowError,
+};
 
 impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
     /// Evaluates whether the predicate can be satisfied (by any means)
diff --git a/src/librustc/traits/query/method_autoderef.rs b/src/librustc/traits/query/method_autoderef.rs
index 6b9bdfd63f4d0..039dea1ffcd16 100644
--- a/src/librustc/traits/query/method_autoderef.rs
+++ b/src/librustc/traits/query/method_autoderef.rs
@@ -6,11 +6,11 @@ use crate::ty::Ty;
 pub struct CandidateStep<'tcx> {
     pub self_ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
     pub autoderefs: usize,
-    // true if the type results from a dereference of a raw pointer.
-    // when assembling candidates, we include these steps, but not when
-    // picking methods. This so that if we have `foo: *const Foo` and `Foo` has methods
-    // `fn by_raw_ptr(self: *const Self)` and `fn by_ref(&self)`, then
-    // `foo.by_raw_ptr()` will work and `foo.by_ref()` won't.
+    /// `true` if the type results from a dereference of a raw pointer.
+    /// when assembling candidates, we include these steps, but not when
+    /// picking methods. This so that if we have `foo: *const Foo` and `Foo` has methods
+    /// `fn by_raw_ptr(self: *const Self)` and `fn by_ref(&self)`, then
+    /// `foo.by_raw_ptr()` will work and `foo.by_ref()` won't.
     pub from_unsafe_deref: bool,
     pub unsize: bool,
 }
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 217c887d5254e..a54bc05f16961 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -134,7 +134,7 @@ impl IntercrateAmbiguityCause {
                     String::new()
                 };
                 format!(
-                    "upstream crates may add new impl of trait `{}`{} \
+                    "upstream crates may add a new impl of trait `{}`{} \
                      in future versions",
                     trait_desc, self_desc
                 )
diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs
index 05b698eb4c4ea..6930c9368282b 100644
--- a/src/librustc/traits/structural_impls.rs
+++ b/src/librustc/traits/structural_impls.rs
@@ -508,31 +508,33 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
                 trait_item_def_id,
             }),
             super::ExprAssignable => Some(super::ExprAssignable),
-            super::MatchExpressionArm {
+            super::MatchExpressionArm(box super::MatchExpressionArmCause {
                 arm_span,
                 source,
                 ref prior_arms,
                 last_ty,
                 discrim_hir_id,
-            } => {
+            }) => {
                 tcx.lift(&last_ty).map(|last_ty| {
-                    super::MatchExpressionArm {
+                    super::MatchExpressionArm(box super::MatchExpressionArmCause {
                         arm_span,
                         source,
                         prior_arms: prior_arms.clone(),
                         last_ty,
                         discrim_hir_id,
-                    }
+                    })
                 })
             }
             super::MatchExpressionArmPattern { span, ty } => {
                 tcx.lift(&ty).map(|ty| super::MatchExpressionArmPattern { span, ty })
             }
-            super::IfExpression { then, outer, semicolon } => Some(super::IfExpression {
-                then,
-                outer,
-                semicolon,
-            }),
+            super::IfExpression(box super::IfExpressionCause { then, outer, semicolon }) => {
+                Some(super::IfExpression(box super::IfExpressionCause {
+                    then,
+                    outer,
+                    semicolon,
+                }))
+            }
             super::IfExpressionWithNoElse => Some(super::IfExpressionWithNoElse),
             super::MainFunctionType => Some(super::MainFunctionType),
             super::StartFunctionType => Some(super::StartFunctionType),
diff --git a/src/librustc/traits/util.rs b/src/librustc/traits/util.rs
index 07d6f633143a2..3d36790c94b8c 100644
--- a/src/librustc/traits/util.rs
+++ b/src/librustc/traits/util.rs
@@ -512,7 +512,7 @@ pub fn impl_trait_ref_and_oblig<'a, 'tcx>(
     (impl_trait_ref, impl_obligations)
 }
 
-/// See `super::obligations_for_generics`
+/// See [`super::obligations_for_generics`].
 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
                                      recursion_depth: usize,
                                      param_env: ty::ParamEnv<'tcx>,
@@ -562,7 +562,7 @@ impl<'tcx> TyCtxt<'tcx> {
         predicate_for_trait_ref(cause, param_env, trait_ref, recursion_depth)
     }
 
-    /// Cast a trait reference into a reference to one of its super
+    /// Casts a trait reference into a reference to one of its super
     /// traits; returns `None` if `target_trait_def_id` is not a
     /// supertrait.
     pub fn upcast_choices(self,
@@ -571,7 +571,7 @@ impl<'tcx> TyCtxt<'tcx> {
                           -> Vec<ty::PolyTraitRef<'tcx>>
     {
         if source_trait_ref.def_id() == target_trait_def_id {
-            return vec![source_trait_ref]; // shorcut the most common case
+            return vec![source_trait_ref]; // Shortcut the most common case.
         }
 
         supertraits(self, source_trait_ref)
diff --git a/src/librustc/ty/codec.rs b/src/librustc/ty/codec.rs
index 1ddc6780aca89..1aa21501129c8 100644
--- a/src/librustc/ty/codec.rs
+++ b/src/librustc/ty/codec.rs
@@ -284,9 +284,11 @@ where
 #[macro_export]
 macro_rules! __impl_decoder_methods {
     ($($name:ident -> $ty:ty;)*) => {
-        $(fn $name(&mut self) -> Result<$ty, Self::Error> {
-            self.opaque.$name()
-        })*
+        $(
+            fn $name(&mut self) -> Result<$ty, Self::Error> {
+                self.opaque.$name()
+            }
+        )*
     }
 }
 
@@ -327,14 +329,17 @@ macro_rules! impl_arena_allocatable_decoders {
 macro_rules! implement_ty_decoder {
     ($DecoderName:ident <$($typaram:tt),*>) => {
         mod __ty_decoder_impl {
-            use super::$DecoderName;
+            use std::borrow::Cow;
+
+            use rustc_serialize::{Decoder, SpecializedDecoder};
+
             use $crate::infer::canonical::CanonicalVarInfos;
             use $crate::ty;
             use $crate::ty::codec::*;
             use $crate::ty::subst::SubstsRef;
             use $crate::hir::def_id::{CrateNum};
-            use rustc_serialize::{Decoder, SpecializedDecoder};
-            use std::borrow::Cow;
+
+            use super::$DecoderName;
 
             impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
                 type Error = String;
@@ -368,8 +373,8 @@ macro_rules! implement_ty_decoder {
                 }
             }
 
-            // FIXME(#36588) These impls are horribly unsound as they allow
-            // the caller to pick any lifetime for 'tcx, including 'static,
+            // FIXME(#36588): These impls are horribly unsound as they allow
+            // the caller to pick any lifetime for `'tcx`, including `'static`,
             // by using the unspecialized proxies to them.
 
             arena_types!(impl_arena_allocatable_decoders, [$DecoderName [$($typaram),*]], 'tcx);
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 17c9e520bcea2..0155803e30580 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -7,7 +7,7 @@ use crate::session::Session;
 use crate::session::config::{BorrowckMode, OutputFilenames};
 use crate::session::config::CrateType;
 use crate::middle;
-use crate::hir::{TraitCandidate, HirId, ItemKind, ItemLocalId, Node};
+use crate::hir::{self, TraitCandidate, HirId, ItemKind, ItemLocalId, Node};
 use crate::hir::def::{Res, DefKind, Export};
 use crate::hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE};
 use crate::hir::map as hir_map;
@@ -45,15 +45,16 @@ use crate::ty::CanonicalPolyFnSig;
 use crate::util::common::ErrorReported;
 use crate::util::nodemap::{DefIdMap, DefIdSet, ItemLocalMap, ItemLocalSet};
 use crate::util::nodemap::{FxHashMap, FxHashSet};
+
 use errors::DiagnosticBuilder;
-use smallvec::SmallVec;
-use rustc_data_structures::stable_hasher::{HashStable, hash_stable_hashmap,
-                                           StableHasher, StableHasherResult,
-                                           StableVec};
 use arena::SyncDroplessArena;
+use smallvec::SmallVec;
+use rustc_data_structures::stable_hasher::{
+    HashStable, StableHasher, StableHasherResult, StableVec, hash_stable_hashmap,
+};
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
-use rustc_data_structures::sync::{Lrc, Lock, WorkerLocal};
 use rustc_data_structures::sharded::ShardedHashMap;
+use rustc_data_structures::sync::{Lrc, Lock, WorkerLocal};
 use std::any::Any;
 use std::borrow::Borrow;
 use std::cmp::Ordering;
@@ -74,8 +75,6 @@ use syntax::feature_gate;
 use syntax::symbol::{Symbol, InternedString, kw, sym};
 use syntax_pos::Span;
 
-use crate::hir;
-
 pub struct AllArenas {
     pub interner: SyncDroplessArena,
 }
@@ -91,10 +90,10 @@ impl AllArenas {
 type InternedSet<'tcx, T> = ShardedHashMap<Interned<'tcx, T>, ()>;
 
 pub struct CtxtInterners<'tcx> {
-    /// The arena that types, regions, etc are allocated from
+    /// The arena that types, regions, etc. are allocated from.
     arena: &'tcx SyncDroplessArena,
 
-    /// Specifically use a speedy hash algorithm for these hash sets,
+    /// Specifically use a speedy hash algorithm for these hash sets, since
     /// they're accessed quite often.
     type_: InternedSet<'tcx, TyS<'tcx>>,
     type_list: InternedSet<'tcx, List<Ty<'tcx>>>,
@@ -129,7 +128,7 @@ impl<'tcx> CtxtInterners<'tcx> {
         }
     }
 
-    /// Intern a type
+    /// Interns a type.
     #[allow(rustc::usage_of_ty_tykind)]
     #[inline(never)]
     fn intern_ty(&self,
@@ -144,7 +143,6 @@ impl<'tcx> CtxtInterners<'tcx> {
                 outer_exclusive_binder: flags.outer_exclusive_binder,
             };
 
-
             Interned(self.arena.alloc(ty_struct))
         }).0
     }
@@ -207,26 +205,24 @@ pub struct LocalTableInContext<'a, V> {
 fn validate_hir_id_for_typeck_tables(local_id_root: Option<DefId>,
                                      hir_id: hir::HirId,
                                      mut_access: bool) {
-    if cfg!(debug_assertions) {
-        if let Some(local_id_root) = local_id_root {
-            if hir_id.owner != local_id_root.index {
-                ty::tls::with(|tcx| {
-                    bug!("node {} with HirId::owner {:?} cannot be placed in \
-                          TypeckTables with local_id_root {:?}",
-                         tcx.hir().node_to_string(hir_id),
-                         DefId::local(hir_id.owner),
-                         local_id_root)
-                });
-            }
-        } else {
-            // We use "Null Object" TypeckTables in some of the analysis passes.
-            // These are just expected to be empty and their `local_id_root` is
-            // `None`. Therefore we cannot verify whether a given `HirId` would
-            // be a valid key for the given table. Instead we make sure that
-            // nobody tries to write to such a Null Object table.
-            if mut_access {
-                bug!("access to invalid TypeckTables")
-            }
+    if let Some(local_id_root) = local_id_root {
+        if hir_id.owner != local_id_root.index {
+            ty::tls::with(|tcx| {
+                bug!("node {} with HirId::owner {:?} cannot be placed in \
+                        TypeckTables with local_id_root {:?}",
+                        tcx.hir().node_to_string(hir_id),
+                        DefId::local(hir_id.owner),
+                        local_id_root)
+            });
+        }
+    } else {
+        // We use "Null Object" TypeckTables in some of the analysis passes.
+        // These are just expected to be empty and their `local_id_root` is
+        // `None`. Therefore we cannot verify whether a given `HirId` would
+        // be a valid key for the given table. Instead we make sure that
+        // nobody tries to write to such a Null Object table.
+        if mut_access {
+            bug!("access to invalid TypeckTables")
         }
     }
 }
@@ -1025,7 +1021,7 @@ pub struct GlobalCtxt<'tcx> {
 
     hir_map: hir_map::Map<'tcx>,
 
-    /// A map from DefPathHash -> DefId. Includes DefIds from the local crate
+    /// A map from `DefPathHash` -> `DefId`. Includes `DefId`s from the local crate
     /// as well as all upstream crates. Only populated in incremental mode.
     pub def_path_hash_to_def_id: Option<FxHashMap<DefPathHash, DefId>>,
 
@@ -1124,9 +1120,9 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    /// Allocates a byte or string literal for `mir::interpret`, read-only
+    /// Allocates a read-only byte or string literal for `mir::interpret`.
     pub fn allocate_bytes(self, bytes: &[u8]) -> interpret::AllocId {
-        // create an allocation that just contains these bytes
+        // Create an allocation that just contains these bytes.
         let alloc = interpret::Allocation::from_byte_aligned_bytes(bytes);
         let alloc = self.intern_const_alloc(alloc);
         self.alloc_map.lock().create_memory_alloc(alloc)
@@ -1346,7 +1342,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Converts a `DefId` into its fully expanded `DefPath` (every
-    /// `DefId` is really just an interned def-path).
+    /// `DefId` is really just an interned `DefPath`).
     ///
     /// Note that if `id` is not local to this crate, the result will
     ///  be a non-local `DefPath`.
@@ -1402,6 +1398,10 @@ impl<'tcx> TyCtxt<'tcx> {
         self.cstore.metadata_encoding_version().to_vec()
     }
 
+    pub fn encode_metadata(self)-> EncodedMetadata {
+        self.cstore.encode_metadata(self)
+    }
+
     // Note that this is *untracked* and should only be used within the query
     // system if the result is otherwise tracked through queries
     pub fn crate_data_as_rc_any(self, cnum: CrateNum) -> Lrc<dyn Any> {
@@ -1446,25 +1446,25 @@ impl<'tcx> TyCtxt<'tcx> {
         self.queries.on_disk_cache.serialize(self.global_tcx(), encoder)
     }
 
-    /// If true, we should use the AST-based borrowck (we may *also* use
+    /// If `true`, we should use the AST-based borrowck (we may *also* use
     /// the MIR-based borrowck).
     pub fn use_ast_borrowck(self) -> bool {
         self.borrowck_mode().use_ast()
     }
 
-    /// If true, we should use the MIR-based borrow check, but also
-    /// fall back on the AST borrow check if the MIR-based one errors.
+    /// If `true`, we should use the MIR-based borrowck, but also
+    /// fall back on the AST borrowck if the MIR-based one errors.
     pub fn migrate_borrowck(self) -> bool {
         self.borrowck_mode().migrate()
     }
 
-    /// If true, make MIR codegen for `match` emit a temp that holds a
+    /// If `true`, make MIR codegen for `match` emit a temp that holds a
     /// borrow of the input to the match expression.
     pub fn generate_borrow_of_any_match_input(&self) -> bool {
         self.emit_read_for_match()
     }
 
-    /// If true, make MIR codegen for `match` emit FakeRead
+    /// If `true`, make MIR codegen for `match` emit FakeRead
     /// statements (which simulate the maximal effect of executing the
     /// patterns in a match arm).
     pub fn emit_read_for_match(&self) -> bool {
@@ -1517,7 +1517,7 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    // This method returns the DefId and the BoundRegion corresponding to the given region.
+    // Returns the `DefId` and the `BoundRegion` corresponding to the given region.
     pub fn is_suitable_region(&self, region: Region<'tcx>) -> Option<FreeRegionInfo> {
         let (suitable_region_binding_scope, bound_region) = match *region {
             ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
@@ -1550,18 +1550,18 @@ impl<'tcx> TyCtxt<'tcx> {
         &self,
         scope_def_id: DefId,
     ) -> Option<Ty<'tcx>> {
-        // HACK: `type_of_def_id()` will fail on these (#55796), so return None
+        // HACK: `type_of_def_id()` will fail on these (#55796), so return `None`.
         let hir_id = self.hir().as_local_hir_id(scope_def_id).unwrap();
         match self.hir().get(hir_id) {
             Node::Item(item) => {
                 match item.node {
-                    ItemKind::Fn(..) => { /* type_of_def_id() will work */ }
+                    ItemKind::Fn(..) => { /* `type_of_def_id()` will work */ }
                     _ => {
                         return None;
                     }
                 }
             }
-            _ => { /* type_of_def_id() will work or panic */ }
+            _ => { /* `type_of_def_id()` will work or panic */ }
         }
 
         let ret_ty = self.type_of(scope_def_id);
@@ -1579,7 +1579,7 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    // Here we check if the bound region is in Impl Item.
+    // Checks if the bound region is in Impl Item.
     pub fn is_bound_region_in_impl_item(
         &self,
         suitable_region_binding_scope: DefId,
@@ -1599,23 +1599,15 @@ impl<'tcx> TyCtxt<'tcx> {
         false
     }
 
-    /// Determine whether identifiers in the assembly have strict naming rules.
+    /// Determines whether identifiers in the assembly have strict naming rules.
     /// Currently, only NVPTX* targets need it.
     pub fn has_strict_asm_symbol_naming(&self) -> bool {
-        self.gcx.sess.target.target.arch.contains("nvptx")
-    }
-}
-
-impl<'tcx> TyCtxt<'tcx> {
-    pub fn encode_metadata(self)
-        -> EncodedMetadata
-    {
-        self.cstore.encode_metadata(self)
+        self.sess.target.target.arch.contains("nvptx")
     }
 }
 
 impl<'tcx> GlobalCtxt<'tcx> {
-    /// Call the closure with a local `TyCtxt` using the given arena.
+    /// Calls the closure with a local `TyCtxt` using the given arena.
     /// `interners` is a slot passed so we can create a CtxtInterners
     /// with the same lifetime as `arena`.
     pub fn enter_local<F, R>(&'tcx self, f: F) -> R
@@ -1651,7 +1643,7 @@ impl<'tcx> GlobalCtxt<'tcx> {
 /// It would be more efficient if `TypedArena` provided a way to
 /// determine whether the address is in the allocated range.
 ///
-/// None is returned if the value or one of the components is not part
+/// `None` is returned if the value or one of the components is not part
 /// of the provided context.
 /// For `Ty`, `None` can be returned if either the type interner doesn't
 /// contain the `TyKind` key or if the address of the interned
@@ -1662,7 +1654,6 @@ pub trait Lift<'tcx>: fmt::Debug {
     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted>;
 }
 
-
 macro_rules! nop_lift {
     ($ty:ty => $lifted:ty) => {
         impl<'a, 'tcx> Lift<'tcx> for $ty {
@@ -1709,7 +1700,7 @@ nop_list_lift!{Predicate<'a> => Predicate<'tcx>}
 nop_list_lift!{CanonicalVarInfo => CanonicalVarInfo}
 nop_list_lift!{ProjectionKind => ProjectionKind}
 
-// this is the impl for `&'a InternalSubsts<'a>`
+// This is the impl for `&'a InternalSubsts<'a>`.
 nop_list_lift!{Kind<'a> => Kind<'tcx>}
 
 pub mod tls {
@@ -1732,43 +1723,43 @@ pub mod tls {
     use rustc_rayon_core as rayon_core;
 
     /// This is the implicit state of rustc. It contains the current
-    /// TyCtxt and query. It is updated when creating a local interner or
-    /// executing a new query. Whenever there's a TyCtxt value available
-    /// you should also have access to an ImplicitCtxt through the functions
+    /// `TyCtxt` and query. It is updated when creating a local interner or
+    /// executing a new query. Whenever there's a `TyCtxt` value available
+    /// you should also have access to an `ImplicitCtxt` through the functions
     /// in this module.
     #[derive(Clone)]
     pub struct ImplicitCtxt<'a, 'tcx> {
-        /// The current TyCtxt. Initially created by `enter_global` and updated
-        /// by `enter_local` with a new local interner
+        /// The current `TyCtxt`. Initially created by `enter_global` and updated
+        /// by `enter_local` with a new local interner.
         pub tcx: TyCtxt<'tcx>,
 
-        /// The current query job, if any. This is updated by JobOwner::start in
-        /// ty::query::plumbing when executing a query
+        /// The current query job, if any. This is updated by `JobOwner::start` in
+        /// `ty::query::plumbing` when executing a query.
         pub query: Option<Lrc<query::QueryJob<'tcx>>>,
 
         /// Where to store diagnostics for the current query job, if any.
-        /// This is updated by JobOwner::start in ty::query::plumbing when executing a query
+        /// This is updated by `JobOwner::start` in `ty::query::plumbing` when executing a query.
         pub diagnostics: Option<&'a Lock<ThinVec<Diagnostic>>>,
 
         /// Used to prevent layout from recursing too deeply.
         pub layout_depth: usize,
 
         /// The current dep graph task. This is used to add dependencies to queries
-        /// when executing them
+        /// when executing them.
         pub task_deps: Option<&'a Lock<TaskDeps>>,
     }
 
-    /// Sets Rayon's thread local variable which is preserved for Rayon jobs
+    /// Sets Rayon's thread-local variable, which is preserved for Rayon jobs
     /// to `value` during the call to `f`. It is restored to its previous value after.
-    /// This is used to set the pointer to the new ImplicitCtxt.
+    /// This is used to set the pointer to the new `ImplicitCtxt`.
     #[cfg(parallel_compiler)]
     #[inline]
     fn set_tlv<F: FnOnce() -> R, R>(value: usize, f: F) -> R {
         rayon_core::tlv::with(value, f)
     }
 
-    /// Gets Rayon's thread local variable which is preserved for Rayon jobs.
-    /// This is used to get the pointer to the current ImplicitCtxt.
+    /// Gets Rayon's thread-local variable, which is preserved for Rayon jobs.
+    /// This is used to get the pointer to the current `ImplicitCtxt`.
     #[cfg(parallel_compiler)]
     #[inline]
     fn get_tlv() -> usize {
@@ -1777,13 +1768,13 @@ pub mod tls {
 
     #[cfg(not(parallel_compiler))]
     thread_local! {
-        /// A thread local variable which stores a pointer to the current ImplicitCtxt.
+        /// A thread local variable that stores a pointer to the current `ImplicitCtxt`.
         static TLV: Cell<usize> = Cell::new(0);
     }
 
     /// Sets TLV to `value` during the call to `f`.
     /// It is restored to its previous value after.
-    /// This is used to set the pointer to the new ImplicitCtxt.
+    /// This is used to set the pointer to the new `ImplicitCtxt`.
     #[cfg(not(parallel_compiler))]
     #[inline]
     fn set_tlv<F: FnOnce() -> R, R>(value: usize, f: F) -> R {
@@ -1793,14 +1784,14 @@ pub mod tls {
         f()
     }
 
-    /// This is used to get the pointer to the current ImplicitCtxt.
+    /// Gets the pointer to the current `ImplicitCtxt`.
     #[cfg(not(parallel_compiler))]
     fn get_tlv() -> usize {
         TLV.with(|tlv| tlv.get())
     }
 
     /// This is a callback from libsyntax as it cannot access the implicit state
-    /// in librustc otherwise
+    /// in librustc otherwise.
     fn span_debug(span: syntax_pos::Span, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         with_opt(|tcx| {
             if let Some(tcx) = tcx {
@@ -1825,7 +1816,7 @@ pub mod tls {
         })
     }
 
-    /// Sets up the callbacks from libsyntax on the current thread
+    /// Sets up the callbacks from libsyntax on the current thread.
     pub fn with_thread_locals<F, R>(f: F) -> R
         where F: FnOnce() -> R
     {
@@ -1850,7 +1841,7 @@ pub mod tls {
         })
     }
 
-    /// Sets `context` as the new current ImplicitCtxt for the duration of the function `f`
+    /// Sets `context` as the new current `ImplicitCtxt` for the duration of the function `f`.
     #[inline]
     pub fn enter_context<'a, 'tcx, F, R>(context: &ImplicitCtxt<'a, 'tcx>, f: F) -> R
     where
@@ -1861,19 +1852,19 @@ pub mod tls {
         })
     }
 
-    /// Enters GlobalCtxt by setting up libsyntax callbacks and
-    /// creating a initial TyCtxt and ImplicitCtxt.
-    /// This happens once per rustc session and TyCtxts only exists
+    /// Enters `GlobalCtxt` by setting up libsyntax callbacks and
+    /// creating a initial `TyCtxt` and `ImplicitCtxt`.
+    /// This happens once per rustc session and `TyCtxt`s only exists
     /// inside the `f` function.
     pub fn enter_global<'tcx, F, R>(gcx: &'tcx GlobalCtxt<'tcx>, f: F) -> R
     where
         F: FnOnce(TyCtxt<'tcx>) -> R,
     {
-        // Update GCX_PTR to indicate there's a GlobalCtxt available
+        // Update `GCX_PTR` to indicate there's a `GlobalCtxt` available.
         GCX_PTR.with(|lock| {
             *lock.lock() = gcx as *const _ as usize;
         });
-        // Set GCX_PTR back to 0 when we exit
+        // Set `GCX_PTR` back to 0 when we exit.
         let _on_drop = OnDrop(move || {
             GCX_PTR.with(|lock| *lock.lock() = 0);
         });
@@ -1894,12 +1885,12 @@ pub mod tls {
     }
 
     scoped_thread_local! {
-        /// Stores a pointer to the GlobalCtxt if one is available.
-        /// This is used to access the GlobalCtxt in the deadlock handler given to Rayon.
+        /// Stores a pointer to the `GlobalCtxt` if one is available.
+        /// This is used to access the `GlobalCtxt` in the deadlock handler given to Rayon.
         pub static GCX_PTR: Lock<usize>
     }
 
-    /// Creates a TyCtxt and ImplicitCtxt based on the GCX_PTR thread local.
+    /// Creates a `TyCtxt` and `ImplicitCtxt` based on the `GCX_PTR` thread local.
     /// This is used in the deadlock handler.
     pub unsafe fn with_global<F, R>(f: F) -> R
     where
@@ -1921,7 +1912,7 @@ pub mod tls {
         enter_context(&icx, |_| f(tcx))
     }
 
-    /// Allows access to the current ImplicitCtxt in a closure if one is available
+    /// Allows access to the current `ImplicitCtxt` in a closure if one is available.
     #[inline]
     pub fn with_context_opt<F, R>(f: F) -> R
     where
@@ -1931,16 +1922,16 @@ pub mod tls {
         if context == 0 {
             f(None)
         } else {
-            // We could get a ImplicitCtxt pointer from another thread.
-            // Ensure that ImplicitCtxt is Sync
+            // We could get a `ImplicitCtxt` pointer from another thread.
+            // Ensure that `ImplicitCtxt` is `Sync`.
             sync::assert_sync::<ImplicitCtxt<'_, '_>>();
 
             unsafe { f(Some(&*(context as *const ImplicitCtxt<'_, '_>))) }
         }
     }
 
-    /// Allows access to the current ImplicitCtxt.
-    /// Panics if there is no ImplicitCtxt available
+    /// Allows access to the current `ImplicitCtxt`.
+    /// Panics if there is no `ImplicitCtxt` available.
     #[inline]
     pub fn with_context<F, R>(f: F) -> R
     where
@@ -1949,11 +1940,11 @@ pub mod tls {
         with_context_opt(|opt_context| f(opt_context.expect("no ImplicitCtxt stored in tls")))
     }
 
-    /// Allows access to the current ImplicitCtxt whose tcx field has the same global
-    /// interner as the tcx argument passed in. This means the closure is given an ImplicitCtxt
-    /// with the same 'tcx lifetime as the TyCtxt passed in.
-    /// This will panic if you pass it a TyCtxt which has a different global interner from
-    /// the current ImplicitCtxt's tcx field.
+    /// Allows access to the current `ImplicitCtxt` whose tcx field has the same global
+    /// interner as the tcx argument passed in. This means the closure is given an `ImplicitCtxt`
+    /// with the same `'tcx` lifetime as the `TyCtxt` passed in.
+    /// This will panic if you pass it a `TyCtxt` which has a different global interner from
+    /// the current `ImplicitCtxt`'s `tcx` field.
     #[inline]
     pub fn with_related_context<'tcx, F, R>(tcx: TyCtxt<'tcx>, f: F) -> R
     where
@@ -1968,8 +1959,8 @@ pub mod tls {
         })
     }
 
-    /// Allows access to the TyCtxt in the current ImplicitCtxt.
-    /// Panics if there is no ImplicitCtxt available
+    /// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
+    /// Panics if there is no `ImplicitCtxt` available.
     #[inline]
     pub fn with<F, R>(f: F) -> R
     where
@@ -1978,8 +1969,8 @@ pub mod tls {
         with_context(|context| f(context.tcx))
     }
 
-    /// Allows access to the TyCtxt in the current ImplicitCtxt.
-    /// The closure is passed None if there is no ImplicitCtxt available
+    /// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
+    /// The closure is passed None if there is no `ImplicitCtxt` available.
     #[inline]
     pub fn with_opt<F, R>(f: F) -> R
     where
@@ -1991,7 +1982,7 @@ pub mod tls {
 
 macro_rules! sty_debug_print {
     ($ctxt: expr, $($variant: ident),*) => {{
-        // curious inner module to allow variant names to be used as
+        // Curious inner module to allow variant names to be used as
         // variable names.
         #[allow(non_snake_case)]
         mod inner {
@@ -2265,9 +2256,9 @@ slice_interners!(
     projs: _intern_projs(ProjectionKind)
 );
 
-// This isn't a perfect fit: CanonicalVarInfo slices are always
+// This isn't a perfect fit: `CanonicalVarInfo` slices are always
 // allocated in the global arena, so this `intern_method!` macro is
-// overly general.  But we just return false for the code that checks
+// overly general. However, we just return `false` for the code that checks
 // whether they belong in the thread-local arena, so no harm done, and
 // seems better than open-coding the rest.
 intern_method! {
@@ -2366,7 +2357,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_adt(self, def: &'tcx AdtDef, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        // take a copy of substs so that we own the vectors inside
+        // Take a copy of substs so that we own the vectors inside.
         self.mk_ty(Adt(def, substs))
     }
 
@@ -2403,9 +2394,9 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline]
-    pub fn mk_lang_item(self, ty: Ty<'tcx>, item: lang_items::LangItem)  -> Ty<'tcx> {
-        let def_id = self.require_lang_item(item, None);
-        self.mk_generic_adt(def_id, ty)
+    pub fn mk_lang_item(self, ty: Ty<'tcx>, item: lang_items::LangItem)  -> Option<Ty<'tcx>> {
+        let def_id = self.lang_items().require(item).ok()?;
+        Some(self.mk_generic_adt(def_id, ty))
     }
 
     #[inline]
diff --git a/src/librustc/ty/error.rs b/src/librustc/ty/error.rs
index fe8f94ab1d314..62910ec320494 100644
--- a/src/librustc/ty/error.rs
+++ b/src/librustc/ty/error.rs
@@ -4,6 +4,7 @@ use std::borrow::Cow;
 use std::fmt;
 use rustc_target::spec::abi;
 use syntax::ast;
+use syntax::errors::pluralise;
 use errors::{Applicability, DiagnosticBuilder};
 use syntax_pos::Span;
 
@@ -82,12 +83,6 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             }
         };
 
-        macro_rules! pluralise {
-            ($x:expr) => {
-                if $x != 1 { "s" } else { "" }
-            };
-        }
-
         match *self {
             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
             Mismatch => write!(f, "types differ"),
@@ -200,7 +195,9 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::Array(_, n) => {
                 let n = tcx.lift_to_global(&n).unwrap();
                 match n.try_eval_usize(tcx, ty::ParamEnv::empty()) {
-                    Some(n) => format!("array of {} elements", n).into(),
+                    Some(n) => {
+                        format!("array of {} element{}", n, if n != 1 { "s" } else { "" }).into()
+                    }
                     None => "array".into(),
                 }
             }
diff --git a/src/librustc/ty/fold.rs b/src/librustc/ty/fold.rs
index 4b30412b41954..1e08ae45951d1 100644
--- a/src/librustc/ty/fold.rs
+++ b/src/librustc/ty/fold.rs
@@ -39,8 +39,8 @@ use std::collections::BTreeMap;
 use std::fmt;
 use crate::util::nodemap::FxHashSet;
 
-/// The TypeFoldable trait is implemented for every type that can be folded.
-/// Basically, every type that has a corresponding method in TypeFolder.
+/// This trait is implemented for every type that can be folded.
+/// Basically, every type that has a corresponding method in `TypeFolder`.
 ///
 /// To implement this conveniently, use the
 /// `BraceStructTypeFoldableImpl` etc macros found in `macros.rs`.
diff --git a/src/librustc/ty/inhabitedness/def_id_forest.rs b/src/librustc/ty/inhabitedness/def_id_forest.rs
index 4453624fa4502..63cc60d80aada 100644
--- a/src/librustc/ty/inhabitedness/def_id_forest.rs
+++ b/src/librustc/ty/inhabitedness/def_id_forest.rs
@@ -4,20 +4,20 @@ use rustc::hir::CRATE_HIR_ID;
 use crate::ty::context::TyCtxt;
 use crate::ty::{DefId, DefIdTree};
 
-/// Represents a forest of DefIds closed under the ancestor relation. That is,
-/// if a DefId representing a module is contained in the forest then all
-/// DefIds defined in that module or submodules are also implicitly contained
+/// Represents a forest of `DefId`s closed under the ancestor relation. That is,
+/// if a `DefId` representing a module is contained in the forest then all
+/// `DefId`s defined in that module or submodules are also implicitly contained
 /// in the forest.
 ///
 /// This is used to represent a set of modules in which a type is visibly
 /// uninhabited.
 #[derive(Clone)]
 pub struct DefIdForest {
-    /// The minimal set of DefIds required to represent the whole set.
-    /// If A and B are DefIds in the DefIdForest, and A is a descendant
-    /// of B, then only B will be in root_ids.
-    /// We use a SmallVec here because (for its use for caching inhabitedness)
-    /// its rare that this will contain even two ids.
+    /// The minimal set of `DefId`s required to represent the whole set.
+    /// If A and B are DefIds in the `DefIdForest`, and A is a descendant
+    /// of B, then only B will be in `root_ids`.
+    /// We use a `SmallVec` here because (for its use for caching inhabitedness)
+    /// its rare that this will contain even two IDs.
     root_ids: SmallVec<[DefId; 1]>,
 }
 
@@ -37,7 +37,7 @@ impl<'tcx> DefIdForest {
         DefIdForest::from_id(crate_id)
     }
 
-    /// Creates a forest containing a DefId and all its descendants.
+    /// Creates a forest containing a `DefId` and all its descendants.
     pub fn from_id(id: DefId) -> DefIdForest {
         let mut root_ids = SmallVec::new();
         root_ids.push(id);
diff --git a/src/librustc/ty/inhabitedness/mod.rs b/src/librustc/ty/inhabitedness/mod.rs
index 2b3291656653f..1a0e351733877 100644
--- a/src/librustc/ty/inhabitedness/mod.rs
+++ b/src/librustc/ty/inhabitedness/mod.rs
@@ -1,3 +1,5 @@
+pub use self::def_id_forest::DefIdForest;
+
 use crate::ty::context::TyCtxt;
 use crate::ty::{AdtDef, VariantDef, FieldDef, Ty, TyS};
 use crate::ty::{DefId, SubstsRef};
@@ -5,12 +7,10 @@ use crate::ty::{AdtKind, Visibility};
 use crate::ty::TyKind::*;
 use crate::ty;
 
-pub use self::def_id_forest::DefIdForest;
-
 mod def_id_forest;
 
-// The methods in this module calculate DefIdForests of modules in which a
-// AdtDef/VariantDef/FieldDef is visibly uninhabited.
+// The methods in this module calculate `DefIdForest`s of modules in which a
+// `AdtDef`/`VariantDef`/`FieldDef` is visibly uninhabited.
 //
 // # Example
 // ```rust
@@ -36,24 +36,25 @@ mod def_id_forest;
 //     y: c::AlsoSecretlyUninhabited,
 // }
 // ```
-// In this code, the type Foo will only be visibly uninhabited inside the
-// modules b, c and d. Calling uninhabited_from on Foo or its AdtDef will
-// return the forest of modules {b, c->d} (represented in a DefIdForest by the
-// set {b, c})
+// In this code, the type `Foo` will only be visibly uninhabited inside the
+// modules `b`, `c` and `d`. Calling `uninhabited_from` on `Foo` or its `AdtDef` will
+// return the forest of modules {`b`, `c`->`d`} (represented in a `DefIdForest` by the
+// set {`b`, `c`}).
 //
-// We need this information for pattern-matching on Foo or types that contain
-// Foo.
+// We need this information for pattern-matching on `Foo` or types that contain
+// `Foo`.
 //
 // # Example
 // ```rust
 // let foo_result: Result<T, Foo> = ... ;
 // let Ok(t) = foo_result;
 // ```
-// This code should only compile in modules where the uninhabitedness of Foo is
+// This code should only compile in modules where the uninhabitedness of `Foo` is
 // visible.
 
 impl<'tcx> TyCtxt<'tcx> {
     /// Checks whether a type is visibly uninhabited from a particular module.
+    ///
     /// # Example
     /// ```rust
     /// enum Void {}
@@ -91,7 +92,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// visible.
     pub fn is_ty_uninhabited_from(self, module: DefId, ty: Ty<'tcx>) -> bool {
         // To check whether this type is uninhabited at all (not just from the
-        // given node) you could check whether the forest is empty.
+        // given node), you could check whether the forest is empty.
         // ```
         // forest.is_empty()
         // ```
@@ -108,7 +109,7 @@ impl<'tcx> TyCtxt<'tcx> {
 }
 
 impl<'tcx> AdtDef {
-    /// Calculate the forest of DefIds from which this adt is visibly uninhabited.
+    /// Calculates the forest of `DefId`s from which this ADT is visibly uninhabited.
     fn uninhabited_from(&self, tcx: TyCtxt<'tcx>, substs: SubstsRef<'tcx>) -> DefIdForest {
         // Non-exhaustive ADTs from other crates are always considered inhabited.
         if self.is_variant_list_non_exhaustive() && !self.did.is_local() {
@@ -122,7 +123,7 @@ impl<'tcx> AdtDef {
 }
 
 impl<'tcx> VariantDef {
-    /// Calculate the forest of DefIds from which this variant is visibly uninhabited.
+    /// Calculates the forest of `DefId`s from which this variant is visibly uninhabited.
     pub fn uninhabited_from(
         &self,
         tcx: TyCtxt<'tcx>,
@@ -148,7 +149,7 @@ impl<'tcx> VariantDef {
 }
 
 impl<'tcx> FieldDef {
-    /// Calculate the forest of DefIds from which this field is visibly uninhabited.
+    /// Calculates the forest of `DefId`s from which this field is visibly uninhabited.
     fn uninhabited_from(
         &self,
         tcx: TyCtxt<'tcx>,
@@ -159,7 +160,7 @@ impl<'tcx> FieldDef {
             self.ty(tcx, substs).uninhabited_from(tcx)
         };
         // FIXME(canndrew): Currently enum fields are (incorrectly) stored with
-        // Visibility::Invisible so we need to override self.vis if we're
+        // `Visibility::Invisible` so we need to override `self.vis` if we're
         // dealing with an enum.
         if is_enum {
             data_uninhabitedness()
@@ -178,7 +179,7 @@ impl<'tcx> FieldDef {
 }
 
 impl<'tcx> TyS<'tcx> {
-    /// Calculate the forest of DefIds from which this type is visibly uninhabited.
+    /// Calculates the forest of `DefId`s from which this type is visibly uninhabited.
     fn uninhabited_from(&self, tcx: TyCtxt<'tcx>) -> DefIdForest {
         match self.sty {
             Adt(def, substs) => def.uninhabited_from(tcx, substs),
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 5ec4754c4535b..e52feea1624c1 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -127,6 +127,7 @@ impl IntegerExt for Integer {
 
 pub trait PrimitiveExt {
     fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
+    fn to_int_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
 }
 
 impl PrimitiveExt for Primitive {
@@ -138,6 +139,16 @@ impl PrimitiveExt for Primitive {
             Pointer => tcx.mk_mut_ptr(tcx.mk_unit()),
         }
     }
+
+    /// Return an *integer* type matching this primitive.
+    /// Useful in particular when dealing with enum discriminants.
+    fn to_int_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        match *self {
+            Int(i, signed) => i.to_ty(tcx, signed),
+            Pointer => tcx.types.usize,
+            Float(..) => bug!("floats do not have an int type"),
+        }
+    }
 }
 
 /// The first half of a fat pointer.
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 2da50f37409ae..5ca819e12f232 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -590,7 +590,7 @@ impl<'tcx> rustc_serialize::UseSpecializedDecodable for Ty<'tcx> {}
 pub type CanonicalTy<'tcx> = Canonical<'tcx, Ty<'tcx>>;
 
 extern {
-    /// A dummy type used to force List to by unsized without requiring fat pointers
+    /// A dummy type used to force `List` to by unsized without requiring fat pointers.
     type OpaqueListContents;
 }
 
@@ -1938,9 +1938,15 @@ pub struct FieldDef {
     pub vis: Visibility,
 }
 
-/// The definition of an abstract data type -- a struct or enum.
+/// The definition of a user-defined type, e.g., a `struct`, `enum`, or `union`.
 ///
 /// These are all interned (by `intern_adt_def`) into the `adt_defs` table.
+///
+/// The initialism *"Adt"* stands for an [*algebraic data type (ADT)*][adt].
+/// This is slightly wrong because `union`s are not ADTs.
+/// Moreover, Rust only allows recursive data types through indirection.
+///
+/// [adt]: https://en.wikipedia.org/wiki/Algebraic_data_type
 pub struct AdtDef {
     /// `DefId` of the struct, enum or union item.
     pub did: DefId,
@@ -2894,6 +2900,13 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn impls_are_allowed_to_overlap(self, def_id1: DefId, def_id2: DefId)
                                         -> Option<ImplOverlapKind>
     {
+        // If either trait impl references an error, they're allowed to overlap,
+        // as one of them essentially doesn't exist.
+        if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error()) ||
+            self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error()) {
+            return Some(ImplOverlapKind::Permitted);
+        }
+
         let is_legit = if self.features().overlapping_marker_traits {
             let trait1_is_empty = self.impl_trait_ref(def_id1)
                 .map_or(false, |trait_ref| {
diff --git a/src/librustc/ty/print/mod.rs b/src/librustc/ty/print/mod.rs
index 092e7c6f3fffb..50789bf6213b6 100644
--- a/src/librustc/ty/print/mod.rs
+++ b/src/librustc/ty/print/mod.rs
@@ -27,7 +27,8 @@ pub trait Print<'tcx, P> {
 /// which the associated types allow passing through the methods.
 ///
 /// For pretty-printing/formatting in particular, see `PrettyPrinter`.
-// FIXME(eddyb) find a better name, this is more general than "printing".
+//
+// FIXME(eddyb) find a better name; this is more general than "printing".
 pub trait Printer<'tcx>: Sized {
     type Error;
 
@@ -46,6 +47,7 @@ pub trait Printer<'tcx>: Sized {
     ) -> Result<Self::Path, Self::Error> {
         self.default_print_def_path(def_id, substs)
     }
+
     fn print_impl_path(
         self,
         impl_def_id: DefId,
@@ -80,6 +82,7 @@ pub trait Printer<'tcx>: Sized {
         self,
         cnum: CrateNum,
     ) -> Result<Self::Path, Self::Error>;
+
     fn path_qualified(
         self,
         self_ty: Ty<'tcx>,
@@ -93,11 +96,13 @@ pub trait Printer<'tcx>: Sized {
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<Self::Path, Self::Error>;
+
     fn path_append(
         self,
         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
         disambiguated_data: &DisambiguatedDefPathData,
     ) -> Result<Self::Path, Self::Error>;
+
     fn path_generic_args(
         self,
         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
diff --git a/src/librustc/ty/print/pretty.rs b/src/librustc/ty/print/pretty.rs
index a72ecdb5745bb..d99580116e4ae 100644
--- a/src/librustc/ty/print/pretty.rs
+++ b/src/librustc/ty/print/pretty.rs
@@ -8,10 +8,11 @@ use crate::ty::{self, DefIdTree, ParamConst, Ty, TyCtxt, TypeFoldable};
 use crate::ty::subst::{Kind, Subst, UnpackedKind};
 use crate::ty::layout::{Integer, IntegerExt, Size};
 use crate::mir::interpret::{ConstValue, sign_extend, Scalar, truncate};
-use syntax::ast;
+
 use rustc_apfloat::ieee::{Double, Single};
 use rustc_apfloat::Float;
 use rustc_target::spec::abi::Abi;
+use syntax::ast;
 use syntax::attr::{SignedInt, UnsignedInt};
 use syntax::symbol::{kw, InternedString};
 
@@ -194,7 +195,7 @@ pub trait PrettyPrinter<'tcx>:
         value.skip_binder().print(self)
     }
 
-    /// Print comma-separated elements.
+    /// Prints comma-separated elements.
     fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
     where
         T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
@@ -209,14 +210,14 @@ pub trait PrettyPrinter<'tcx>:
         Ok(self)
     }
 
-    /// Print `<...>` around what `f` prints.
+    /// Prints `<...>` around what `f` prints.
     fn generic_delimiters(
         self,
         f: impl FnOnce(Self) -> Result<Self, Self::Error>,
     ) -> Result<Self, Self::Error>;
 
-    /// Return `true` if the region should be printed in
-    /// optional positions, e.g. `&'a T` or `dyn Tr + 'b`.
+    /// Returns `true` if the region should be printed in
+    /// optional positions, e.g., `&'a T` or `dyn Tr + 'b`.
     /// This is typically the case for all non-`'_` regions.
     fn region_should_not_be_omitted(
         &self,
@@ -226,7 +227,7 @@ pub trait PrettyPrinter<'tcx>:
     // Defaults (should not be overriden):
 
     /// If possible, this returns a global path resolving to `def_id` that is visible
-    /// from at least one local module and returns true. If the crate defining `def_id` is
+    /// from at least one local module, and returns `true`. If the crate defining `def_id` is
     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
     fn try_print_visible_def_path(
         self,
@@ -267,11 +268,11 @@ pub trait PrettyPrinter<'tcx>:
             // In local mode, when we encounter a crate other than
             // LOCAL_CRATE, execution proceeds in one of two ways:
             //
-            // 1. for a direct dependency, where user added an
+            // 1. For a direct dependency, where user added an
             //    `extern crate` manually, we put the `extern
             //    crate` as the parent. So you wind up with
             //    something relative to the current crate.
-            // 2. for an extern inferred from a path or an indirect crate,
+            // 2. For an extern inferred from a path or an indirect crate,
             //    where there is no explicit `extern crate`, we just prepend
             //    the crate name.
             match self.tcx().extern_crate(def_id) {
@@ -304,13 +305,13 @@ pub trait PrettyPrinter<'tcx>:
         let mut cur_def_key = self.tcx().def_key(def_id);
         debug!("try_print_visible_def_path: cur_def_key={:?}", cur_def_key);
 
-        // For a constructor we want the name of its parent rather than <unnamed>.
+        // For a constructor, we want the name of its parent rather than <unnamed>.
         match cur_def_key.disambiguated_data.data {
             DefPathData::Ctor => {
                 let parent = DefId {
                     krate: def_id.krate,
                     index: cur_def_key.parent
-                        .expect("DefPathData::Ctor/VariantData missing a parent"),
+                        .expect("`DefPathData::Ctor` / `VariantData` missing a parent"),
                 };
 
                 cur_def_key = self.tcx().def_key(parent);
@@ -630,7 +631,7 @@ pub trait PrettyPrinter<'tcx>:
                         sep = ", ";
                     }
                 } else {
-                    // cross-crate closure types should only be
+                    // Cross-crate closure types should only be
                     // visible in codegen bug reports, I imagine.
                     p!(write("@{:?}", did));
                     let mut sep = " ";
@@ -673,7 +674,7 @@ pub trait PrettyPrinter<'tcx>:
                         sep = ", ";
                     }
                 } else {
-                    // cross-crate closure types should only be
+                    // Cross-crate closure types should only be
                     // visible in codegen bug reports, I imagine.
                     p!(write("@{:?}", did));
                     let mut sep = " ";
@@ -1173,6 +1174,7 @@ impl<F: fmt::Write> Printer<'tcx> for FmtPrinter<'_, 'tcx, F> {
         }
         Ok(self)
     }
+
     fn path_qualified(
         mut self,
         self_ty: Ty<'tcx>,
@@ -1201,6 +1203,7 @@ impl<F: fmt::Write> Printer<'tcx> for FmtPrinter<'_, 'tcx, F> {
         self.empty_path = false;
         Ok(self)
     }
+
     fn path_append(
         mut self,
         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
@@ -1238,6 +1241,7 @@ impl<F: fmt::Write> Printer<'tcx> for FmtPrinter<'_, 'tcx, F> {
 
         Ok(self)
     }
+
     fn path_generic_args(
         mut self,
         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
diff --git a/src/librustc/ty/query/on_disk_cache.rs b/src/librustc/ty/query/on_disk_cache.rs
index 674f8944f261a..c20e758688959 100644
--- a/src/librustc/ty/query/on_disk_cache.rs
+++ b/src/librustc/ty/query/on_disk_cache.rs
@@ -5,9 +5,6 @@ use crate::hir::map::definitions::DefPathHash;
 use crate::ich::{CachingSourceMapView, Fingerprint};
 use crate::mir::{self, interpret};
 use crate::mir::interpret::{AllocDecodingSession, AllocDecodingState};
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder, opaque,
-                      SpecializedDecoder, SpecializedEncoder,
-                      UseSpecializedDecodable, UseSpecializedEncodable};
 use crate::session::{CrateDisambiguator, Session};
 use crate::ty::{self, Ty};
 use crate::ty::codec::{self as ty_codec, TyDecoder, TyEncoder};
@@ -19,6 +16,10 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_data_structures::sync::{Lrc, Lock, HashMapExt, Once};
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
+use rustc_serialize::{
+    Decodable, Decoder, Encodable, Encoder, SpecializedDecoder, SpecializedEncoder,
+    UseSpecializedDecodable, UseSpecializedEncodable, opaque,
+};
 use std::mem;
 use syntax::ast::{Ident, NodeId};
 use syntax::source_map::{SourceMap, StableSourceFileId};
@@ -37,17 +38,16 @@ const TAG_EXPN_DATA_INLINE: u8 = 2;
 const TAG_VALID_SPAN: u8 = 0;
 const TAG_INVALID_SPAN: u8 = 1;
 
-/// `OnDiskCache` provides an interface to incr. comp. data cached from the
+/// Provides an interface to incremental compilation data cached from the
 /// previous compilation session. This data will eventually include the results
 /// of a few selected queries (like `typeck_tables_of` and `mir_optimized`) and
 /// any diagnostics that have been emitted during a query.
 pub struct OnDiskCache<'sess> {
-
     // The complete cache data in serialized form.
     serialized_data: Vec<u8>,
 
-    // This field collects all Diagnostics emitted during the current
-    // compilation session.
+    // Collects all `Diagnostic`s emitted during the current compilation
+    // session.
     current_diagnostics: Lock<FxHashMap<DepNodeIndex, Vec<Diagnostic>>>,
 
     prev_cnums: Vec<(u32, String, CrateDisambiguator)>,
@@ -56,7 +56,7 @@ pub struct OnDiskCache<'sess> {
     source_map: &'sess SourceMap,
     file_index_to_stable_id: FxHashMap<SourceFileIndex, StableSourceFileId>,
 
-    // These two fields caches that are populated lazily during decoding.
+    // Caches that are populated lazily during decoding.
     file_index_to_file: Lock<FxHashMap<SourceFileIndex, Lrc<SourceFile>>>,
     synthetic_syntax_contexts: Lock<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
 
@@ -78,7 +78,7 @@ struct Footer {
     prev_cnums: Vec<(u32, String, CrateDisambiguator)>,
     query_result_index: EncodedQueryResultIndex,
     diagnostics_index: EncodedQueryResultIndex,
-    // the location of all allocations
+    // The location of all allocations.
     interpret_alloc_index: Vec<u32>,
 }
 
@@ -104,28 +104,28 @@ impl AbsoluteBytePos {
 }
 
 impl<'sess> OnDiskCache<'sess> {
-    /// Creates a new OnDiskCache instance from the serialized data in `data`.
-    pub fn new(sess: &'sess Session, data: Vec<u8>, start_pos: usize) -> OnDiskCache<'sess> {
+    /// Creates a new `OnDiskCache` instance from the serialized data in `data`.
+    pub fn new(sess: &'sess Session, data: Vec<u8>, start_pos: usize) -> Self {
         debug_assert!(sess.opts.incremental.is_some());
 
-        // Wrapping in a scope so we can borrow `data`
+        // Wrap in a scope so we can borrow `data`.
         let footer: Footer = {
             let mut decoder = opaque::Decoder::new(&data[..], start_pos);
 
-            // Decode the *position* of the footer which can be found in the
+            // Decode the *position* of the footer, which can be found in the
             // last 8 bytes of the file.
             decoder.set_position(data.len() - IntEncodedWithFixedSize::ENCODED_SIZE);
-            let query_result_index_pos = IntEncodedWithFixedSize::decode(&mut decoder)
-                .expect("Error while trying to decode query result index position.")
+            let footer_pos = IntEncodedWithFixedSize::decode(&mut decoder)
+                .expect("error while trying to decode footer position")
                 .0 as usize;
 
-            // Decoder the file footer which contains all the lookup tables, etc.
-            decoder.set_position(query_result_index_pos);
+            // Decode the file footer, which contains all the lookup tables, etc.
+            decoder.set_position(footer_pos);
             decode_tagged(&mut decoder, TAG_FILE_FOOTER)
-                .expect("Error while trying to decode query result index position.")
+                .expect("error while trying to decode footer position")
         };
 
-        OnDiskCache {
+        Self {
             serialized_data: data,
             file_index_to_stable_id: footer.file_index_to_stable_id,
             file_index_to_file: Default::default(),
@@ -140,8 +140,8 @@ impl<'sess> OnDiskCache<'sess> {
         }
     }
 
-    pub fn new_empty(source_map: &'sess SourceMap) -> OnDiskCache<'sess> {
-        OnDiskCache {
+    pub fn new_empty(source_map: &'sess SourceMap) -> Self {
+        Self {
             serialized_data: Vec::new(),
             file_index_to_stable_id: Default::default(),
             file_index_to_file: Default::default(),
@@ -158,11 +158,11 @@ impl<'sess> OnDiskCache<'sess> {
 
     pub fn serialize<'tcx, E>(&self, tcx: TyCtxt<'tcx>, encoder: &mut E) -> Result<(), E::Error>
     where
-        E: ty_codec::TyEncoder,
+        E: TyEncoder,
     {
-        // Serializing the DepGraph should not modify it:
+        // Serializing the `DepGraph` should not modify it.
         tcx.dep_graph.with_ignore(|| {
-            // Allocate SourceFileIndices
+            // Allocate `SourceFileIndex`es.
             let (file_to_file_index, file_index_to_stable_id) = {
                 let files = tcx.sess.source_map().files();
                 let mut file_to_file_index = FxHashMap::with_capacity_and_hasher(
@@ -197,7 +197,7 @@ impl<'sess> OnDiskCache<'sess> {
             // be in memory, so this should be a cheap operation.
             tcx.dep_graph.exec_cache_promotions(tcx);
 
-            // Encode query results
+            // Encode query results.
             let mut query_result_index = EncodedQueryResultIndex::new();
 
             time(tcx.sess, "encode query results", || {
@@ -221,29 +221,28 @@ impl<'sess> OnDiskCache<'sess> {
                 Ok(())
             })?;
 
-            // Encode diagnostics
+            // Encode diagnostics.
             let diagnostics_index: EncodedDiagnosticsIndex = self.current_diagnostics.borrow()
                 .iter()
-                .map(|(dep_node_index, diagnostics)|
-            {
-                let pos = AbsoluteBytePos::new(encoder.position());
-                // Let's make sure we get the expected type here:
-                let diagnostics: &EncodedDiagnostics = diagnostics;
-                let dep_node_index = SerializedDepNodeIndex::new(dep_node_index.index());
-                encoder.encode_tagged(dep_node_index, diagnostics)?;
-
-                Ok((dep_node_index, pos))
-            })
-            .collect::<Result<_, _>>()?;
+                .map(|(dep_node_index, diagnostics)| {
+                    let pos = AbsoluteBytePos::new(encoder.position());
+                    // Let's make sure we get the expected type here.
+                    let diagnostics: &EncodedDiagnostics = diagnostics;
+                    let dep_node_index = SerializedDepNodeIndex::new(dep_node_index.index());
+                    encoder.encode_tagged(dep_node_index, diagnostics)?;
+
+                    Ok((dep_node_index, pos))
+                })
+                .collect::<Result<_, _>>()?;
 
             let interpret_alloc_index = {
                 let mut interpret_alloc_index = Vec::new();
                 let mut n = 0;
                 loop {
                     let new_n = encoder.interpret_allocs_inverse.len();
-                    // if we have found new ids, serialize those, too
+                    // If we have found new IDs, serialize those too.
                     if n == new_n {
-                        // otherwise, abort
+                        // Otherwise, abort.
                         break;
                     }
                     interpret_alloc_index.reserve(new_n - n);
@@ -263,13 +262,15 @@ impl<'sess> OnDiskCache<'sess> {
             };
 
             let sorted_cnums = sorted_cnums_including_local_crate(tcx);
-            let prev_cnums: Vec<_> = sorted_cnums.iter().map(|&cnum| {
-                let crate_name = tcx.original_crate_name(cnum).as_str().to_string();
-                let crate_disambiguator = tcx.crate_disambiguator(cnum);
-                (cnum.as_u32(), crate_name, crate_disambiguator)
-            }).collect();
-
-            // Encode the file footer
+            let prev_cnums: Vec<_> = sorted_cnums.iter()
+                .map(|&cnum| {
+                    let crate_name = tcx.original_crate_name(cnum).as_str().to_string();
+                    let crate_disambiguator = tcx.crate_disambiguator(cnum);
+                    (cnum.as_u32(), crate_name, crate_disambiguator)
+                })
+                .collect();
+
+            // Encode the file footer.
             let footer_pos = encoder.position() as u64;
             encoder.encode_tagged(TAG_FILE_FOOTER, &Footer {
                 file_index_to_stable_id,
@@ -371,7 +372,7 @@ impl<'sess> OnDiskCache<'sess> {
     {
         let pos = index.get(&dep_node_index).cloned()?;
 
-        // Initialize the cnum_map using the value from the thread which finishes the closure first
+        // Initialize `cnum_map` using the value from the thread that finishes the closure first.
         self.cnum_map.init_nonlocking_same(|| {
             Self::compute_cnum_map(tcx, &self.prev_cnums[..])
         });
@@ -381,25 +382,21 @@ impl<'sess> OnDiskCache<'sess> {
             opaque: opaque::Decoder::new(&self.serialized_data[..], pos.to_usize()),
             source_map: self.source_map,
             cnum_map: self.cnum_map.get(),
+            synthetic_syntax_contexts: &self.synthetic_syntax_contexts,
             file_index_to_file: &self.file_index_to_file,
             file_index_to_stable_id: &self.file_index_to_stable_id,
-            synthetic_syntax_contexts: &self.synthetic_syntax_contexts,
             alloc_decoding_session: self.alloc_decoding_state.new_decoding_session(),
         };
 
         match decode_tagged(&mut decoder, dep_node_index) {
-            Ok(value) => {
-                Some(value)
-            }
-            Err(e) => {
-                bug!("Could not decode cached {}: {}", debug_tag, e)
-            }
+            Ok(v) => Some(v),
+            Err(e) => bug!("could not decode cached {}: {}", debug_tag, e),
         }
     }
 
-    // This function builds mapping from previous-session-CrateNum to
-    // current-session-CrateNum. There might be CrateNums from the previous
-    // Session that don't occur in the current one. For these, the mapping
+    // This function builds mapping from previous-session-`CrateNum` to
+    // current-session-`CrateNum`. There might be `CrateNum`s from the previous
+    // `Session` that don't occur in the current one. For these, the mapping
     // maps to None.
     fn compute_cnum_map(
         tcx: TyCtxt<'_>,
@@ -432,9 +429,9 @@ impl<'sess> OnDiskCache<'sess> {
 
 //- DECODING -------------------------------------------------------------------
 
-/// A decoder that can read the incr. comp. cache. It is similar to the one
-/// we use for crate metadata decoding in that it can rebase spans and
-/// eventually will also handle things that contain `Ty` instances.
+/// A decoder that can read fro the incr. comp. cache. It is similar to the one
+/// we use for crate metadata decoding in that it can rebase spans and eventually
+/// will also handle things that contain `Ty` instances.
 struct CacheDecoder<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     opaque: opaque::Decoder<'a>,
@@ -458,7 +455,7 @@ impl<'a, 'tcx> CacheDecoder<'a, 'tcx> {
         file_index_to_file.borrow_mut().entry(index).or_insert_with(|| {
             let stable_id = file_index_to_stable_id[&index];
             source_map.source_file_by_stable_id(stable_id)
-                .expect("Failed to lookup SourceFile in new context.")
+                .expect("failed to lookup `SourceFile` in new context")
         }).clone()
     }
 }
@@ -479,7 +476,7 @@ impl<'a, 'tcx> DecoderWithPosition for CacheDecoder<'a, 'tcx> {
     }
 }
 
-// Decode something that was encoded with encode_tagged() and verify that the
+// Decodes something that was encoded with `encode_tagged()` and verify that the
 // tag matches and the correct amount of bytes was read.
 fn decode_tagged<D, T, V>(decoder: &mut D, expected_tag: T) -> Result<V, D::Error>
 where
@@ -500,7 +497,7 @@ where
     Ok(value)
 }
 
-impl<'a, 'tcx> ty_codec::TyDecoder<'tcx> for CacheDecoder<'a, 'tcx> {
+impl<'a, 'tcx> TyDecoder<'tcx> for CacheDecoder<'a, 'tcx> {
     #[inline]
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
@@ -534,7 +531,7 @@ impl<'a, 'tcx> ty_codec::TyDecoder<'tcx> for CacheDecoder<'a, 'tcx> {
         }
 
         let ty = or_insert_with(self)?;
-        // This may overwrite the entry, but it should overwrite with the same value
+        // This may overwrite the entry, but it should overwrite with the same value.
         tcx.rcache.borrow_mut().insert_same(cache_key, ty);
         Ok(ty)
     }
@@ -553,7 +550,7 @@ impl<'a, 'tcx> ty_codec::TyDecoder<'tcx> for CacheDecoder<'a, 'tcx> {
 
     fn map_encoded_cnum_to_current(&self, cnum: CrateNum) -> CrateNum {
         self.cnum_map[cnum].unwrap_or_else(|| {
-            bug!("Could not find new CrateNum for {:?}", cnum)
+            bug!("could not find new `CrateNum` for {:?}", cnum)
         })
     }
 }
@@ -635,25 +632,25 @@ impl<'a, 'tcx> SpecializedDecoder<Ident> for CacheDecoder<'a, 'tcx> {
 }
 
 // This impl makes sure that we get a runtime error when we try decode a
-// DefIndex that is not contained in a DefId. Such a case would be problematic
-// because we would not know how to transform the DefIndex to the current
+// `DefIndex` that is not contained in a `DefId`. Such a case would be problematic
+// because we would not know how to transform the `DefIndex` to the current
 // context.
 impl<'a, 'tcx> SpecializedDecoder<DefIndex> for CacheDecoder<'a, 'tcx> {
     fn specialized_decode(&mut self) -> Result<DefIndex, Self::Error> {
-        bug!("Trying to decode DefIndex outside the context of a DefId")
+        bug!("trying to decode `DefIndex` outside the context of a `DefId`")
     }
 }
 
-// Both the CrateNum and the DefIndex of a DefId can change in between two
-// compilation sessions. We use the DefPathHash, which is stable across
-// sessions, to map the old DefId to the new one.
+// Both the `CrateNum` and the `DefIndex` of a `DefId` can change in between two
+// compilation sessions. We use the `DefPathHash`, which is stable across
+// sessions, to map the old `DefId` to the new one.
 impl<'a, 'tcx> SpecializedDecoder<DefId> for CacheDecoder<'a, 'tcx> {
     #[inline]
     fn specialized_decode(&mut self) -> Result<DefId, Self::Error> {
-        // Load the DefPathHash which is was we encoded the DefId as.
+        // Load the `DefPathHash` which is was we encoded the `DefId` as.
         let def_path_hash = DefPathHash::decode(self)?;
 
-        // Using the DefPathHash, we can lookup the new DefId
+        // Using the `DefPathHash`, we can lookup the new `DefId`.
         Ok(self.tcx().def_path_hash_to_def_id.as_ref().unwrap()[&def_path_hash])
     }
 }
@@ -667,10 +664,10 @@ impl<'a, 'tcx> SpecializedDecoder<LocalDefId> for CacheDecoder<'a, 'tcx> {
 
 impl<'a, 'tcx> SpecializedDecoder<hir::HirId> for CacheDecoder<'a, 'tcx> {
     fn specialized_decode(&mut self) -> Result<hir::HirId, Self::Error> {
-        // Load the DefPathHash which is was we encoded the DefIndex as.
+        // Load the `DefPathHash` which is what we encoded the `DefIndex` as.
         let def_path_hash = DefPathHash::decode(self)?;
 
-        // Use the DefPathHash to map to the current DefId.
+        // Use the `DefPathHash` to map to the current `DefId`.
         let def_id = self.tcx()
                          .def_path_hash_to_def_id
                          .as_ref()
@@ -678,10 +675,10 @@ impl<'a, 'tcx> SpecializedDecoder<hir::HirId> for CacheDecoder<'a, 'tcx> {
 
         debug_assert!(def_id.is_local());
 
-        // The ItemLocalId needs no remapping.
+        // The `ItemLocalId` needs no remapping.
         let local_id = hir::ItemLocalId::decode(self)?;
 
-        // Reconstruct the HirId and look up the corresponding NodeId in the
+        // Reconstruct the `HirId` and look up the corresponding `NodeId` in the
         // context of the current session.
         Ok(hir::HirId {
             owner: def_id.index,
@@ -690,8 +687,8 @@ impl<'a, 'tcx> SpecializedDecoder<hir::HirId> for CacheDecoder<'a, 'tcx> {
     }
 }
 
-// NodeIds are not stable across compilation sessions, so we store them in their
-// HirId representation. This allows use to map them to the current NodeId.
+// `NodeId`s are not stable across compilation sessions, so we store them in their
+// `HirId` representation. This allows use to map them to the current `NodeId`.
 impl<'a, 'tcx> SpecializedDecoder<NodeId> for CacheDecoder<'a, 'tcx> {
     #[inline]
     fn specialized_decode(&mut self) -> Result<NodeId, Self::Error> {
@@ -728,6 +725,7 @@ impl<'a, 'tcx, T: Decodable> SpecializedDecoder<mir::ClearCrossCrate<T>>
 
 //- ENCODING -------------------------------------------------------------------
 
+/// An encoder that can write the incr. comp. cache.
 struct CacheEncoder<'a, 'tcx, E: ty_codec::TyEncoder> {
     tcx: TyCtxt<'tcx>,
     encoder: &'a mut E,
@@ -742,7 +740,7 @@ struct CacheEncoder<'a, 'tcx, E: ty_codec::TyEncoder> {
 
 impl<'a, 'tcx, E> CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     fn source_file_index(&mut self, source_file: Lrc<SourceFile>) -> SourceFileIndex {
         self.file_to_file_index[&(&*source_file as *const SourceFile)]
@@ -753,11 +751,11 @@ where
     /// encode the specified tag, then the given value, then the number of
     /// bytes taken up by tag and value. On decoding, we can then verify that
     /// we get the expected tag and read the expected number of bytes.
-    fn encode_tagged<T: Encodable, V: Encodable>(&mut self,
-                                                 tag: T,
-                                                 value: &V)
-                                                 -> Result<(), E::Error>
-    {
+    fn encode_tagged<T: Encodable, V: Encodable>(
+        &mut self,
+        tag: T,
+        value: &V
+    ) -> Result<(), E::Error> {
         let start_pos = self.position();
 
         tag.encode(self)?;
@@ -770,7 +768,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<interpret::AllocId> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
         use std::collections::hash_map::Entry;
@@ -790,10 +788,9 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<Span> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
-
         if *span == DUMMY_SP {
             return TAG_INVALID_SPAN.encode(self);
         }
@@ -849,14 +846,14 @@ where
         // We don't currently encode enough information to ensure hygiene works
         // with incremental, so panic rather than risk incremental bugs.
 
-        // FIXME: Handle hygiene in incremental
-        bug!("Trying to encode Ident for incremental")
+        // FIXME: handle hygiene in incremental.
+        bug!("trying to encode `Ident` for incremental");
     }
 }
 
 impl<'a, 'tcx, E> ty_codec::TyEncoder for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn position(&self) -> usize {
@@ -866,7 +863,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<CrateNum> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, cnum: &CrateNum) -> Result<(), Self::Error> {
@@ -876,7 +873,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<Ty<'tcx>> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
@@ -887,7 +884,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<ty::GenericPredicates<'tcx>> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self,
@@ -900,7 +897,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<hir::HirId> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, id: &hir::HirId) -> Result<(), Self::Error> {
@@ -918,7 +915,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<DefId> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, id: &DefId) -> Result<(), Self::Error> {
@@ -929,7 +926,7 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<LocalDefId> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, id: &LocalDefId) -> Result<(), Self::Error> {
@@ -939,18 +936,18 @@ where
 
 impl<'a, 'tcx, E> SpecializedEncoder<DefIndex> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     fn specialized_encode(&mut self, _: &DefIndex) -> Result<(), Self::Error> {
-        bug!("Encoding DefIndex without context.")
+        bug!("encoding `DefIndex` without context");
     }
 }
 
-// NodeIds are not stable across compilation sessions, so we store them in their
-// HirId representation. This allows use to map them to the current NodeId.
+// `NodeId`s are not stable across compilation sessions, so we store them in their
+// `HirId` representation. This allows use to map them to the current `NodeId`.
 impl<'a, 'tcx, E> SpecializedEncoder<NodeId> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self, node_id: &NodeId) -> Result<(), Self::Error> {
@@ -967,7 +964,7 @@ impl<'a, 'tcx> SpecializedEncoder<Fingerprint> for CacheEncoder<'a, 'tcx, opaque
 
 impl<'a, 'tcx, E, T> SpecializedEncoder<mir::ClearCrossCrate<T>> for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
     T: Encodable,
 {
     #[inline]
@@ -996,7 +993,7 @@ macro_rules! encoder_methods {
 
 impl<'a, 'tcx, E> Encoder for CacheEncoder<'a, 'tcx, E>
 where
-    E: 'a + ty_codec::TyEncoder,
+    E: 'a + TyEncoder,
 {
     type Error = E::Error;
 
@@ -1040,7 +1037,7 @@ impl UseSpecializedDecodable for IntEncodedWithFixedSize {}
 impl SpecializedEncoder<IntEncodedWithFixedSize> for opaque::Encoder {
     fn specialized_encode(&mut self, x: &IntEncodedWithFixedSize) -> Result<(), Self::Error> {
         let start_pos = self.position();
-        for i in 0 .. IntEncodedWithFixedSize::ENCODED_SIZE {
+        for i in 0..IntEncodedWithFixedSize::ENCODED_SIZE {
             ((x.0 >> i * 8) as u8).encode(self)?;
         }
         let end_pos = self.position();
@@ -1085,10 +1082,10 @@ where
             if Q::cache_on_disk(tcx, key.clone(), Some(&entry.value)) {
                 let dep_node = SerializedDepNodeIndex::new(entry.index.index());
 
-                // Record position of the cache entry
+                // Record position of the cache entry.
                 query_result_index.push((dep_node, AbsoluteBytePos::new(encoder.position())));
 
-                // Encode the type check tables with the SerializedDepNodeIndex
+                // Encode the type check tables with the `SerializedDepNodeIndex`
                 // as tag.
                 encoder.encode_tagged(dep_node, &entry.value)?;
             }
diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
index 4dce55f589233..d199a26475be7 100644
--- a/src/librustc/ty/query/plumbing.rs
+++ b/src/librustc/ty/query/plumbing.rs
@@ -61,7 +61,7 @@ impl<'tcx, M: QueryConfig<'tcx>> Default for QueryCache<'tcx, M> {
     }
 }
 
-// If enabled, send a message to the profile-queries thread
+// If enabled, sends a message to the profile-queries thread.
 macro_rules! profq_msg {
     ($tcx:expr, $msg:expr) => {
         if cfg!(debug_assertions) {
@@ -72,7 +72,7 @@ macro_rules! profq_msg {
     }
 }
 
-// If enabled, format a key using its debug string, which can be
+// If enabled, formats a key using its debug string, which can be
 // expensive to compute (in terms of time).
 macro_rules! profq_query_msg {
     ($query:expr, $tcx:expr, $key:expr) => {{
@@ -98,7 +98,7 @@ pub(super) struct JobOwner<'a, 'tcx, Q: QueryDescription<'tcx>> {
 
 impl<'a, 'tcx, Q: QueryDescription<'tcx>> JobOwner<'a, 'tcx, Q> {
     /// Either gets a `JobOwner` corresponding the query, allowing us to
-    /// start executing the query, or it returns with the result of the query.
+    /// start executing the query, or returns with the result of the query.
     /// If the query is executing elsewhere, this will wait for it.
     /// If the query panicked, this will silently panic.
     ///
@@ -215,30 +215,30 @@ impl<'a, 'tcx, Q: QueryDescription<'tcx>> Drop for JobOwner<'a, 'tcx, Q> {
     #[inline(never)]
     #[cold]
     fn drop(&mut self) {
-        // Poison the query so jobs waiting on it panic
+        // Poison the query so jobs waiting on it panic.
         let shard = self.cache.get_shard_by_value(&self.key);
         shard.lock().active.insert(self.key.clone(), QueryResult::Poisoned);
         // Also signal the completion of the job, so waiters
-        // will continue execution
+        // will continue execution.
         self.job.signal_complete();
     }
 }
 
 #[derive(Clone)]
 pub struct CycleError<'tcx> {
-    /// The query and related span which uses the cycle
+    /// The query and related span that uses the cycle.
     pub(super) usage: Option<(Span, Query<'tcx>)>,
     pub(super) cycle: Vec<QueryInfo<'tcx>>,
 }
 
-/// The result of `try_get_lock`
+/// The result of `try_get_lock`.
 pub(super) enum TryGetJob<'a, 'tcx, D: QueryDescription<'tcx>> {
     /// The query is not yet started. Contains a guard to the cache eventually used to start it.
     NotYetStarted(JobOwner<'a, 'tcx, D>),
 
     /// The query was already completed.
-    /// Returns the result of the query and its dep node index
-    /// if it succeeded or a cycle error if it failed
+    /// Returns the result of the query and its dep-node index
+    /// if it succeeded or a cycle error if it failed.
     JobCompleted((D::Value, DepNodeIndex)),
 
     /// Trying to execute the query resulted in a cycle.
@@ -246,7 +246,7 @@ pub(super) enum TryGetJob<'a, 'tcx, D: QueryDescription<'tcx>> {
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    /// Executes a job by changing the ImplicitCtxt to point to the
+    /// Executes a job by changing the `ImplicitCtxt` to point to the
     /// new query job while it executes. It returns the diagnostics
     /// captured during execution and the actual result.
     #[inline(always)]
@@ -259,11 +259,11 @@ impl<'tcx> TyCtxt<'tcx> {
     where
         F: FnOnce(TyCtxt<'tcx>) -> R,
     {
-        // The TyCtxt stored in TLS has the same global interner lifetime
+        // The `TyCtxt` stored in TLS has the same global interner lifetime
         // as `self`, so we use `with_related_context` to relate the 'tcx lifetimes
-        // when accessing the ImplicitCtxt
+        // when accessing the `ImplicitCtxt`.
         tls::with_related_context(self, move |current_icx| {
-            // Update the ImplicitCtxt to point to our new query job
+            // Update the `ImplicitCtxt` to point to our new query job.
             let new_icx = tls::ImplicitCtxt {
                 tcx: self.global_tcx(),
                 query: Some(job),
@@ -272,7 +272,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 task_deps: current_icx.task_deps,
             };
 
-            // Use the ImplicitCtxt while we execute the query
+            // Use the `ImplicitCtxt` while we execute the query.
             tls::enter_context(&new_icx, |_| {
                 compute(self.global_tcx())
             })
@@ -372,7 +372,7 @@ impl<'tcx> TyCtxt<'tcx> {
         };
 
         // Fast path for when incr. comp. is off. `to_dep_node` is
-        // expensive for some DepKinds.
+        // expensive for some `DepKind`s.
         if !self.dep_graph.is_fully_enabled() {
             let null_dep_node = DepNode::new_no_params(crate::dep_graph::DepKind::Null);
             return self.force_query_with_job::<Q>(key, job, null_dep_node).0;
@@ -410,7 +410,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if !Q::EVAL_ALWAYS {
             // The diagnostics for this query will be
             // promoted to the current session during
-            // try_mark_green(), so we can ignore them here.
+            // `try_mark_green()`, so we can ignore them here.
             let loaded = self.start_query(job.job.clone(), None, |tcx| {
                 let marked = tcx.dep_graph.try_mark_green_and_read(tcx, &dep_node);
                 marked.map(|(prev_dep_node_index, dep_node_index)| {
@@ -441,11 +441,11 @@ impl<'tcx> TyCtxt<'tcx> {
         dep_node: &DepNode,
     ) -> Q::Value {
         // Note this function can be called concurrently from the same query
-        // We must ensure that this is handled correctly
+        // We must ensure that this is handled correctly.
 
         debug_assert!(self.dep_graph.is_green(dep_node));
 
-        // First we try to load the result from the on-disk cache
+        // First we try to load the result from the on-disk cache.
         let result = if Q::cache_on_disk(self.global_tcx(), key.clone(), None) &&
                         self.sess.opts.debugging_opts.incremental_queries {
             self.sess.profiler(|p| p.incremental_load_result_start(Q::NAME));
@@ -453,10 +453,10 @@ impl<'tcx> TyCtxt<'tcx> {
             self.sess.profiler(|p| p.incremental_load_result_end(Q::NAME));
 
             // We always expect to find a cached result for things that
-            // can be forced from DepNode.
+            // can be forced from `DepNode`.
             debug_assert!(!dep_node.kind.can_reconstruct_query_key() ||
                           result.is_some(),
-                          "Missing on-disk cache entry for {:?}",
+                          "missing on-disk cache entry for {:?}",
                           dep_node);
             result
         } else {
@@ -475,8 +475,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
             self.sess.profiler(|p| p.start_query(Q::NAME));
 
-            // The dep-graph for this computation is already in
-            // place
+            // The dep-graph for this computation is already in-place.
             let result = self.dep_graph.with_ignore(|| {
                 Q::compute(self, key)
             });
@@ -485,7 +484,7 @@ impl<'tcx> TyCtxt<'tcx> {
             result
         };
 
-        // If -Zincremental-verify-ich is specified, re-hash results from
+        // If `-Zincremental-verify-ich` is specified, re-hash results from
         // the cache and make sure that they have the expected fingerprint.
         if unlikely!(self.sess.opts.debugging_opts.incremental_verify_ich) {
             self.incremental_verify_ich::<Q>(&result, dep_node, dep_node_index);
@@ -508,10 +507,12 @@ impl<'tcx> TyCtxt<'tcx> {
     ) {
         use crate::ich::Fingerprint;
 
-        assert!(Some(self.dep_graph.fingerprint_of(dep_node_index)) ==
+        assert!(
+            Some(self.dep_graph.fingerprint_of(dep_node_index)) ==
                 self.dep_graph.prev_fingerprint_of(dep_node),
-                "Fingerprint for green query instance not loaded \
-                    from cache: {:?}", dep_node);
+            "fingerprint for green query instance not loaded from cache: {:?}",
+            dep_node,
+        );
 
         debug!("BEGIN verify_ich({:?})", dep_node);
         let mut hcx = self.create_stable_hashing_context();
@@ -521,8 +522,11 @@ impl<'tcx> TyCtxt<'tcx> {
 
         let old_hash = self.dep_graph.fingerprint_of(dep_node_index);
 
-        assert!(new_hash == old_hash, "Found unstable fingerprints \
-            for {:?}", dep_node);
+        assert!(
+            new_hash == old_hash,
+            "found unstable fingerprints for {:?}",
+            dep_node,
+        );
     }
 
     #[inline(always)]
@@ -534,11 +538,11 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> (Q::Value, DepNodeIndex) {
         // If the following assertion triggers, it can have two reasons:
         // 1. Something is wrong with DepNode creation, either here or
-        //    in DepGraph::try_mark_green()
-        // 2. Two distinct query keys get mapped to the same DepNode
-        //    (see for example #48923)
+        //    in `DepGraph::try_mark_green()`.
+        // 2. Two distinct query keys get mapped to the same `DepNode`
+        //    (see for example #48923).
         assert!(!self.dep_graph.dep_node_exists(&dep_node),
-                "Forcing query with already existing DepNode.\n\
+                "forcing query with already existing `DepNode`\n\
                  - query-key: {:?}\n\
                  - dep-node: {:?}",
                 key, dep_node);
@@ -584,7 +588,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Ensure that either this query has all green inputs or been executed.
-    /// Executing query::ensure(D) is considered a read of the dep-node D.
+    /// Executing `query::ensure(D)` is considered a read of the dep-node `D`.
     ///
     /// This function is particularly useful when executing passes for their
     /// side-effects -- e.g., in order to report errors for erroneous programs.
@@ -899,13 +903,13 @@ macro_rules! define_queries_inner {
                 }
             }
 
-            // FIXME(eddyb) Get more valid Span's on queries.
+            // FIXME(eddyb) Get more valid `Span`s on queries.
             pub fn default_span(&self, tcx: TyCtxt<$tcx>, span: Span) -> Span {
                 if !span.is_dummy() {
                     return span;
                 }
-                // The def_span query is used to calculate default_span,
-                // so exit to avoid infinite recursion
+                // The `def_span` query is used to calculate `default_span`,
+                // so exit to avoid infinite recursion.
                 if let Query::def_span(..) = *self {
                     return span
                 }
@@ -1116,7 +1120,7 @@ macro_rules! define_provider_struct {
         impl<$tcx> Default for Providers<$tcx> {
             fn default() -> Self {
                 $(fn $name<$tcx>(_: TyCtxt<$tcx>, key: $K) -> $R {
-                    bug!("tcx.{}({:?}) unsupported by its crate",
+                    bug!("`tcx.{}({:?})` unsupported by its crate",
                          stringify!($name), key);
                 })*
                 Providers { $($name),* }
@@ -1128,26 +1132,26 @@ macro_rules! define_provider_struct {
 
 /// The red/green evaluation system will try to mark a specific DepNode in the
 /// dependency graph as green by recursively trying to mark the dependencies of
-/// that DepNode as green. While doing so, it will sometimes encounter a DepNode
+/// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode`
 /// where we don't know if it is red or green and we therefore actually have
 /// to recompute its value in order to find out. Since the only piece of
-/// information that we have at that point is the DepNode we are trying to
+/// information that we have at that point is the `DepNode` we are trying to
 /// re-evaluate, we need some way to re-run a query from just that. This is what
 /// `force_from_dep_node()` implements.
 ///
-/// In the general case, a DepNode consists of a DepKind and an opaque
+/// In the general case, a `DepNode` consists of a `DepKind` and an opaque
 /// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint
 /// is usually constructed by computing a stable hash of the query-key that the
-/// DepNode corresponds to. Consequently, it is not in general possible to go
+/// `DepNode` corresponds to. Consequently, it is not in general possible to go
 /// back from hash to query-key (since hash functions are not reversible). For
 /// this reason `force_from_dep_node()` is expected to fail from time to time
-/// because we just cannot find out, from the DepNode alone, what the
+/// because we just cannot find out, from the `DepNode` alone, what the
 /// corresponding query-key is and therefore cannot re-run the query.
 ///
 /// The system deals with this case letting `try_mark_green` fail which forces
 /// the root query to be re-evaluated.
 ///
-/// Now, if force_from_dep_node() would always fail, it would be pretty useless.
+/// Now, if `force_from_dep_node()` would always fail, it would be pretty useless.
 /// Fortunately, we can use some contextual information that will allow us to
 /// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we
 /// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a
@@ -1171,9 +1175,9 @@ macro_rules! define_provider_struct {
 pub fn force_from_dep_node(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool {
     use crate::dep_graph::RecoverKey;
 
-    // We must avoid ever having to call force_from_dep_node() for a
-    // DepNode::codegen_unit:
-    // Since we cannot reconstruct the query key of a DepNode::codegen_unit, we
+    // We must avoid ever having to call `force_from_dep_node()` for a
+    // `DepNode::codegen_unit`:
+    // Since we cannot reconstruct the query key of a `DepNode::codegen_unit`, we
     // would always end up having to evaluate the first caller of the
     // `codegen_unit` query that *is* reconstructible. This might very well be
     // the `compile_codegen_unit` query, thus re-codegenning the whole CGU just
@@ -1196,7 +1200,7 @@ pub fn force_from_dep_node(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool {
             if let Some(def_id) = dep_node.extract_def_id(tcx) {
                 def_id
             } else {
-                // return from the whole function
+                // Return from the whole function.
                 return false
             }
         }
@@ -1224,20 +1228,20 @@ pub fn force_from_dep_node(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool {
 
     rustc_dep_node_force!([dep_node, tcx]
         // These are inputs that are expected to be pre-allocated and that
-        // should therefore always be red or green already
+        // should therefore always be red or green already.
         DepKind::AllLocalTraitImpls |
         DepKind::Krate |
         DepKind::CrateMetadata |
         DepKind::HirBody |
         DepKind::Hir |
 
-        // This are anonymous nodes
+        // These are anonymous nodes.
         DepKind::TraitSelect |
 
         // We don't have enough information to reconstruct the query key of
-        // these
+        // these.
         DepKind::CompileCodegenUnit => {
-            bug!("force_from_dep_node() - Encountered {:?}", dep_node)
+            bug!("force_from_dep_node: encountered {:?}", dep_node)
         }
 
         DepKind::Analysis => { force!(analysis, krate!()); }
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index d2edf6fb1ee80..e73a51e6f78e5 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -644,7 +644,7 @@ impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
 
 impl<'tcx> List<ExistentialPredicate<'tcx>> {
-    /// Returns the "principal def id" of this set of existential predicates.
+    /// Returns the "principal `DefId`" of this set of existential predicates.
     ///
     /// A Rust trait object type consists (in addition to a lifetime bound)
     /// of a set of trait bounds, which are separated into any number
@@ -1052,7 +1052,7 @@ impl<'tcx> PolyGenSig<'tcx> {
     }
 }
 
-/// Signature of a function type, which I have arbitrarily
+/// Signature of a function type, which we have arbitrarily
 /// decided to use to refer to the input/output types.
 ///
 /// - `inputs`: is the list of arguments and their modes.
@@ -1076,7 +1076,8 @@ impl<'tcx> FnSig<'tcx> {
         self.inputs_and_output[self.inputs_and_output.len() - 1]
     }
 
-    // Create a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible method
+    // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
+    // method.
     fn fake() -> FnSig<'tcx> {
         FnSig {
             inputs_and_output: List::empty(),
@@ -1118,7 +1119,6 @@ impl<'tcx> PolyFnSig<'tcx> {
 
 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
 
-
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord,
          Hash, RustcEncodable, RustcDecodable, HashStable)]
 pub struct ParamTy {
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index a08c82a0ae82f..78d94df4fa03b 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -996,6 +996,24 @@ impl<'tcx> ty::TyS<'tcx> {
         debug!("is_type_representable: {:?} is {:?}", self, r);
         r
     }
+
+    /// Peel off all reference types in this type until there are none left.
+    ///
+    /// This method is idempotent, i.e. `ty.peel_refs().peel_refs() == ty.peel_refs()`.
+    ///
+    /// # Examples
+    ///
+    /// - `u8` -> `u8`
+    /// - `&'a mut u8` -> `u8`
+    /// - `&'a &'b u8` -> `u8`
+    /// - `&'a *const &'b u8 -> *const &'b u8`
+    pub fn peel_refs(&'tcx self) -> Ty<'tcx> {
+        let mut ty = self;
+        while let Ref(_, inner_ty, _) = ty.sty {
+            ty = inner_ty;
+        }
+        ty
+    }
 }
 
 fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
diff --git a/src/librustc/util/common.rs b/src/librustc/util/common.rs
index 7118d05204c3b..2475b93d95f32 100644
--- a/src/librustc/util/common.rs
+++ b/src/librustc/util/common.rs
@@ -5,17 +5,13 @@ use rustc_data_structures::{fx::FxHashMap, sync::Lock};
 use std::cell::{RefCell, Cell};
 use std::fmt::Debug;
 use std::hash::Hash;
-use std::panic;
-use std::env;
 use std::time::{Duration, Instant};
 
 use std::sync::mpsc::{Sender};
 use syntax_pos::{SpanData};
 use syntax::symbol::{Symbol, sym};
 use rustc_macros::HashStable;
-use crate::ty::TyCtxt;
 use crate::dep_graph::{DepNode};
-use lazy_static;
 use crate::session::Session;
 
 #[cfg(test)]
@@ -31,39 +27,6 @@ pub struct ErrorReported;
 
 thread_local!(static TIME_DEPTH: Cell<usize> = Cell::new(0));
 
-lazy_static! {
-    static ref DEFAULT_HOOK: Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static> = {
-        let hook = panic::take_hook();
-        panic::set_hook(Box::new(panic_hook));
-        hook
-    };
-}
-
-fn panic_hook(info: &panic::PanicInfo<'_>) {
-    (*DEFAULT_HOOK)(info);
-
-    let backtrace = env::var_os("RUST_BACKTRACE").map(|x| &x != "0").unwrap_or(false);
-
-    if backtrace {
-        TyCtxt::try_print_query_stack();
-    }
-
-    #[cfg(windows)]
-    unsafe {
-        if env::var("RUSTC_BREAK_ON_ICE").is_ok() {
-            extern "system" {
-                fn DebugBreak();
-            }
-            // Trigger a debugger if we crashed during bootstrap.
-            DebugBreak();
-        }
-    }
-}
-
-pub fn install_panic_hook() {
-    lazy_static::initialize(&DEFAULT_HOOK);
-}
-
 /// Parameters to the `Dump` variant of type `ProfileQueriesMsg`.
 #[derive(Clone,Debug)]
 pub struct ProfQDumpParams {
diff --git a/src/librustc_asan/build.rs b/src/librustc_asan/build.rs
index a2b4b090efb4f..645707ccc0338 100644
--- a/src/librustc_asan/build.rs
+++ b/src/librustc_asan/build.rs
@@ -4,6 +4,10 @@ use build_helper::sanitizer_lib_boilerplate;
 use cmake::Config;
 
 fn main() {
+    println!("cargo:rerun-if-env-changed=RUSTC_BUILD_SANITIZERS");
+    if env::var("RUSTC_BUILD_SANITIZERS") != Ok("1".to_string()) {
+        return;
+    }
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
         build_helper::restore_library_path();
 
diff --git a/src/librustc_ast_borrowck/borrowck/mod.rs b/src/librustc_ast_borrowck/borrowck/mod.rs
index 3bbd7ae5c352f..23d5480c60562 100644
--- a/src/librustc_ast_borrowck/borrowck/mod.rs
+++ b/src/librustc_ast_borrowck/borrowck/mod.rs
@@ -9,7 +9,6 @@ use InteriorKind::*;
 
 use rustc::hir::HirId;
 use rustc::hir::Node;
-use rustc::cfg;
 use rustc::middle::borrowck::{BorrowCheckResult, SignalledError};
 use rustc::hir::def_id::{DefId, LocalDefId};
 use rustc::middle::mem_categorization as mc;
@@ -28,6 +27,7 @@ use log::debug;
 
 use rustc::hir;
 
+use crate::cfg;
 use crate::dataflow::{DataFlowContext, BitwiseOperator, DataFlowOperator, KillFrom};
 
 pub mod check_loans;
diff --git a/src/librustc_ast_borrowck/borrowck/move_data.rs b/src/librustc_ast_borrowck/borrowck/move_data.rs
index 887a0e2f20e16..67d818161b1b5 100644
--- a/src/librustc_ast_borrowck/borrowck/move_data.rs
+++ b/src/librustc_ast_borrowck/borrowck/move_data.rs
@@ -4,7 +4,7 @@
 use crate::dataflow::{DataFlowContext, BitwiseOperator, DataFlowOperator, KillFrom};
 
 use crate::borrowck::*;
-use rustc::cfg;
+use crate::cfg;
 use rustc::ty::{self, TyCtxt};
 use rustc::util::nodemap::FxHashMap;
 
diff --git a/src/librustc/cfg/construct.rs b/src/librustc_ast_borrowck/cfg/construct.rs
similarity index 84%
rename from src/librustc/cfg/construct.rs
rename to src/librustc_ast_borrowck/cfg/construct.rs
index 0dad2dda837b5..0dc999083a91a 100644
--- a/src/librustc/cfg/construct.rs
+++ b/src/librustc_ast_borrowck/cfg/construct.rs
@@ -1,11 +1,12 @@
 use crate::cfg::*;
-use crate::middle::region;
-use rustc_data_structures::graph::implementation as graph;
-use crate::ty::{self, TyCtxt};
 
-use crate::hir::{self, PatKind};
-use crate::hir::def_id::DefId;
-use crate::hir::ptr::P;
+use rustc::hir::{self, PatKind};
+use rustc::hir::def_id::DefId;
+use rustc::hir::ptr::P;
+use rustc::middle::region;
+use rustc::ty::{self, TyCtxt};
+
+use rustc_data_structures::graph::implementation as graph;
 
 struct CFGBuilder<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
@@ -19,18 +20,18 @@ struct CFGBuilder<'a, 'tcx> {
 
 #[derive(Copy, Clone)]
 struct BlockScope {
-    block_expr_id: hir::ItemLocalId, // id of breakable block expr node
+    block_expr_id: hir::ItemLocalId, // ID of breakable block expr node
     break_index: CFGIndex, // where to go on `break`
 }
 
 #[derive(Copy, Clone)]
 struct LoopScope {
-    loop_id: hir::ItemLocalId,     // id of loop/while node
+    loop_id: hir::ItemLocalId, // ID of `loop`/`while` node
     continue_index: CFGIndex, // where to go on a `loop`
-    break_index: CFGIndex,    // where to go on a `break`
+    break_index: CFGIndex, // where to go on a `break`
 }
 
-pub fn construct(tcx: TyCtxt<'_>, body: &hir::Body) -> CFG {
+pub(super) fn construct(tcx: TyCtxt<'_>, body: &hir::Body) -> CFG {
     let mut graph = graph::Graph::new();
     let entry = graph.add_node(CFGNodeData::Entry);
 
@@ -103,9 +104,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 let init_exit = self.opt_expr(&local.init, pred);
                 self.pat(&local.pat, init_exit)
             }
-            hir::StmtKind::Item(_) => {
-                pred
-            }
+            hir::StmtKind::Item(_) => pred,
             hir::StmtKind::Expr(ref expr) |
             hir::StmtKind::Semi(ref expr) => {
                 self.expr(&expr, pred)
@@ -154,12 +153,12 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         }
     }
 
-    fn pats_all<'b, I: Iterator<Item=&'b P<hir::Pat>>>(
+    /// Handles case where all of the patterns must match.
+    fn pats_all<'b, I: Iterator<Item = &'b P<hir::Pat>>>(
         &mut self,
         pats: I,
-        pred: CFGIndex
+        pred: CFGIndex,
     ) -> CFGIndex {
-        //! Handles case where all of the patterns must match.
         pats.fold(pred, |pred, pat| self.pat(&pat, pred))
     }
 
@@ -185,15 +184,15 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 // Note that `break` and `loop` statements
                 // may cause additional edges.
 
-                let loopback = self.add_dummy_node(&[pred]);              // 1
-                let expr_exit = self.add_ast_node(expr.hir_id.local_id, &[]);          // 2
+                let loopback = self.add_dummy_node(&[pred]); // 1
+                let expr_exit = self.add_ast_node(expr.hir_id.local_id, &[]); // 2
                 self.loop_scopes.push(LoopScope {
                     loop_id: expr.hir_id.local_id,
                     continue_index: loopback,
                     break_index: expr_exit,
                 });
-                let body_exit = self.block(&body, loopback);           // 3
-                self.add_contained_edge(body_exit, loopback);            // 4
+                let body_exit = self.block(&body, loopback); // 3
+                self.add_contained_edge(body_exit, loopback); // 4
                 self.loop_scopes.pop();
                 expr_exit
             }
@@ -217,9 +216,9 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 //    v 3  v 4
                 //   [..exit..]
                 //
-                let l_exit = self.expr(&l, pred);                      // 1
-                let r_exit = self.expr(&r, l_exit);                    // 2
-                self.add_ast_node(expr.hir_id.local_id, &[l_exit, r_exit])            // 3,4
+                let l_exit = self.expr(&l, pred); // 1
+                let r_exit = self.expr(&r, l_exit); // 2
+                self.add_ast_node(expr.hir_id.local_id, &[l_exit, r_exit]) // 3,4
             }
 
             hir::ExprKind::Ret(ref v) => {
@@ -313,11 +312,13 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         }
     }
 
-    fn call<'b, I: Iterator<Item=&'b hir::Expr>>(&mut self,
-            call_expr: &hir::Expr,
-            pred: CFGIndex,
-            func_or_rcvr: &hir::Expr,
-            args: I) -> CFGIndex {
+    fn call<'b, I: Iterator<Item = &'b hir::Expr>>(
+        &mut self,
+        call_expr: &hir::Expr,
+        pred: CFGIndex,
+        func_or_rcvr: &hir::Expr,
+        args: I,
+    ) -> CFGIndex {
         let func_or_rcvr_exit = self.expr(func_or_rcvr, pred);
         let ret = self.straightline(call_expr, func_or_rcvr_exit, args);
         let m = self.tcx.hir().get_module_parent(call_expr.hir_id);
@@ -328,33 +329,38 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         }
     }
 
-    fn exprs<'b, I: Iterator<Item=&'b hir::Expr>>(&mut self,
-                                             exprs: I,
-                                             pred: CFGIndex) -> CFGIndex {
-        //! Constructs graph for `exprs` evaluated in order
+    /// Constructs graph for `exprs` evaluated in order.
+    fn exprs<'b, I: Iterator<Item = &'b hir::Expr>>(
+        &mut self,
+        exprs: I,
+        pred: CFGIndex,
+    ) -> CFGIndex {
         exprs.fold(pred, |p, e| self.expr(e, p))
     }
 
-    fn opt_expr(&mut self,
-                opt_expr: &Option<P<hir::Expr>>,
-                pred: CFGIndex) -> CFGIndex {
-        //! Constructs graph for `opt_expr` evaluated, if Some
+    /// Constructs graph for `opt_expr` evaluated, if `Some`.
+    fn opt_expr(
+        &mut self,
+        opt_expr: &Option<P<hir::Expr>>,
+        pred: CFGIndex,
+    ) -> CFGIndex {
         opt_expr.iter().fold(pred, |p, e| self.expr(&e, p))
     }
 
-    fn straightline<'b, I: Iterator<Item=&'b hir::Expr>>(&mut self,
-                    expr: &hir::Expr,
-                    pred: CFGIndex,
-                    subexprs: I) -> CFGIndex {
-        //! Handles case of an expression that evaluates `subexprs` in order
-
+    /// Handles case of an expression that evaluates `subexprs` in order.
+    fn straightline<'b, I: Iterator<Item = &'b hir::Expr>>(
+        &mut self,
+        expr: &hir::Expr,
+        pred: CFGIndex,
+        subexprs: I,
+    ) -> CFGIndex {
         let subexprs_exit = self.exprs(subexprs, pred);
         self.add_ast_node(expr.hir_id.local_id, &[subexprs_exit])
     }
 
     fn match_(&mut self, id: hir::ItemLocalId, discr: &hir::Expr,
               arms: &[hir::Arm], pred: CFGIndex) -> CFGIndex {
-        // The CFG for match expression is quite complex, so no ASCII
+        // The CFG for match expressions is quite complex, so no ASCII
         // art for it (yet).
         //
         // The CFG generated below matches roughly what MIR contains.
@@ -369,13 +375,13 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         //
         // What is going on is explained in further comments.
 
-        // Visit the discriminant expression
+        // Visit the discriminant expression.
         let discr_exit = self.expr(discr, pred);
 
         // Add a node for the exit of the match expression as a whole.
         let expr_exit = self.add_ast_node(id, &[]);
 
-        // Keep track of the previous guard expressions
+        // Keep track of the previous guard expressions.
         let mut prev_guard = None;
         let match_scope = region::Scope { id, data: region::ScopeData::Node };
 
@@ -388,12 +394,12 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 // Visit the pattern, coming from the discriminant exit
                 let mut pat_exit = self.pat(&pat, discr_exit);
 
-                // If there is a guard expression, handle it here
+                // If there is a guard expression, handle it here.
                 if let Some(ref guard) = arm.guard {
                     // Add a dummy node for the previous guard
-                    // expression to target
+                    // expression to target.
                     let guard_start = self.add_dummy_node(&[pat_exit]);
-                    // Visit the guard expression
+                    // Visit the guard expression.
                     let guard_exit = match guard {
                         hir::Guard::If(ref e) => (&**e, self.expr(e, guard_start)),
                     };
@@ -407,24 +413,23 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                         self.add_exiting_edge(prev_guard, prev_index, match_scope, guard_start);
                     }
 
-                    // Push the guard onto the list of previous guards
+                    // Push the guard onto the list of previous guards.
                     prev_guard = Some(guard_exit);
 
-                    // Update the exit node for the pattern
+                    // Update the exit node for the pattern.
                     pat_exit = guard_exit.1;
                 }
 
-                // Add an edge from the exit of this pattern to the
-                // exit of the arm
+                // Add an edge from the exit of this pattern to the exit of the arm.
                 self.add_contained_edge(pat_exit, bindings_exit);
             }
 
-            // Visit the body of this arm
+            // Visit the body of this arm.
             let body_exit = self.expr(&arm.body, bindings_exit);
 
             let arm_exit = self.add_ast_node(arm.hir_id.local_id, &[body_exit]);
 
-            // Link the body to the exit of the expression
+            // Link the body to the exit of the expression.
             self.add_contained_edge(arm_exit, expr_exit);
         }
 
@@ -451,18 +456,22 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         node
     }
 
-    fn add_contained_edge(&mut self,
-                          source: CFGIndex,
-                          target: CFGIndex) {
+    fn add_contained_edge(
+        &mut self,
+        source: CFGIndex,
+        target: CFGIndex,
+    ) {
         let data = CFGEdgeData {exiting_scopes: vec![] };
         self.graph.add_edge(source, target, data);
     }
 
-    fn add_exiting_edge(&mut self,
-                        from_expr: &hir::Expr,
-                        from_index: CFGIndex,
-                        target_scope: region::Scope,
-                        to_index: CFGIndex) {
+    fn add_exiting_edge(
+        &mut self,
+        from_expr: &hir::Expr,
+        from_index: CFGIndex,
+        target_scope: region::Scope,
+        to_index: CFGIndex,
+    ) {
         let mut data = CFGEdgeData { exiting_scopes: vec![] };
         let mut scope = region::Scope {
             id: from_expr.hir_id.local_id,
@@ -476,9 +485,11 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         self.graph.add_edge(from_index, to_index, data);
     }
 
-    fn add_returning_edge(&mut self,
-                          _from_expr: &hir::Expr,
-                          from_index: CFGIndex) {
+    fn add_returning_edge(
+        &mut self,
+        _from_expr: &hir::Expr,
+        from_index: CFGIndex,
+    ) {
         let data = CFGEdgeData {
             exiting_scopes: self.loop_scopes.iter()
                                             .rev()
@@ -488,11 +499,12 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         self.graph.add_edge(from_index, self.fn_exit, data);
     }
 
-    fn find_scope_edge(&self,
-                  expr: &hir::Expr,
-                  destination: hir::Destination,
-                  scope_cf_kind: ScopeCfKind) -> (region::Scope, CFGIndex) {
-
+    fn find_scope_edge(
+        &self,
+        expr: &hir::Expr,
+        destination: hir::Destination,
+        scope_cf_kind: ScopeCfKind,
+    ) -> (region::Scope, CFGIndex) {
         match destination.target_id {
             Ok(loop_id) => {
                 for b in &self.breakable_block_scopes {
@@ -519,7 +531,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                         });
                     }
                 }
-                span_bug!(expr.span, "no scope for id {}", loop_id);
+                span_bug!(expr.span, "no scope for ID {}", loop_id);
             }
             Err(err) => span_bug!(expr.span, "scope error: {}",  err),
         }
diff --git a/src/librustc/cfg/graphviz.rs b/src/librustc_ast_borrowck/cfg/graphviz.rs
similarity index 88%
rename from src/librustc/cfg/graphviz.rs
rename to src/librustc_ast_borrowck/cfg/graphviz.rs
index 918120057d4d3..99c6b49cad5d9 100644
--- a/src/librustc/cfg/graphviz.rs
+++ b/src/librustc_ast_borrowck/cfg/graphviz.rs
@@ -1,21 +1,18 @@
-/// This module provides linkage between rustc::middle::graph and
+/// This module provides linkage between `rustc::middle::graph` and
 /// libgraphviz traits.
 
-// For clarity, rename the graphviz crate locally to dot.
-use graphviz as dot;
-
 use crate::cfg;
-use crate::hir;
-use crate::ty::TyCtxt;
+use rustc::hir;
+use rustc::ty::TyCtxt;
 
-pub type Node<'a> = (cfg::CFGIndex, &'a cfg::CFGNode);
-pub type Edge<'a> = &'a cfg::CFGEdge;
+pub(crate) type Node<'a> = (cfg::CFGIndex, &'a cfg::CFGNode);
+pub(crate) type Edge<'a> = &'a cfg::CFGEdge;
 
 pub struct LabelledCFG<'a, 'tcx> {
     pub tcx: TyCtxt<'tcx>,
     pub cfg: &'a cfg::CFG,
     pub name: String,
-    /// `labelled_edges` controls whether we emit labels on the edges
+    /// `labelled_edges` controls whether we emit labels on the edges.
     pub labelled_edges: bool,
 }
 
@@ -28,12 +25,12 @@ impl<'a, 'tcx> LabelledCFG<'a, 'tcx> {
         };
         let s = self.tcx.hir().node_to_string(hir_id);
 
-        // Replacing newlines with \\l causes each line to be left-aligned,
+        // Replacing newlines with `\\l` causes each line to be left-aligned,
         // improving presentation of (long) pretty-printed expressions.
         if s.contains("\n") {
             let mut s = s.replace("\n", "\\l");
             // Apparently left-alignment applies to the line that precedes
-            // \l, not the line that follows; so, add \l at end of string
+            // `\l`, not the line that follows; so, add `\l` at end of string
             // if not already present, ensuring last line gets left-aligned
             // as well.
             let mut last_two: Vec<_> =
@@ -112,8 +109,7 @@ impl<'a> dot::GraphWalk<'a> for &'a cfg::CFG {
     }
 }
 
-impl<'a, 'hir> dot::GraphWalk<'a> for LabelledCFG<'a, 'hir>
-{
+impl<'a, 'hir> dot::GraphWalk<'a> for LabelledCFG<'a, 'hir> {
     type Node = Node<'a>;
     type Edge = Edge<'a>;
     fn nodes(&'a self) -> dot::Nodes<'a, Node<'a>> { self.cfg.nodes() }
diff --git a/src/librustc/cfg/mod.rs b/src/librustc_ast_borrowck/cfg/mod.rs
similarity index 51%
rename from src/librustc/cfg/mod.rs
rename to src/librustc_ast_borrowck/cfg/mod.rs
index 88fc7fbfad51f..981199c91d513 100644
--- a/src/librustc/cfg/mod.rs
+++ b/src/librustc_ast_borrowck/cfg/mod.rs
@@ -2,18 +2,18 @@
 //! Uses `Graph` as the underlying representation.
 
 use rustc_data_structures::graph::implementation as graph;
-use crate::ty::TyCtxt;
-use crate::hir;
-use crate::hir::def_id::DefId;
+use rustc::ty::TyCtxt;
+use rustc::hir;
+use rustc::hir::def_id::DefId;
 
 mod construct;
 pub mod graphviz;
 
 pub struct CFG {
-    pub owner_def_id: DefId,
-    pub graph: CFGGraph,
-    pub entry: CFGIndex,
-    pub exit: CFGIndex,
+    owner_def_id: DefId,
+    pub(crate) graph: CFGGraph,
+    pub(crate) entry: CFGIndex,
+    exit: CFGIndex,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq)]
@@ -26,7 +26,7 @@ pub enum CFGNodeData {
 }
 
 impl CFGNodeData {
-    pub fn id(&self) -> hir::ItemLocalId {
+    pub(crate) fn id(&self) -> hir::ItemLocalId {
         if let CFGNodeData::AST(id) = *self {
             id
         } else {
@@ -37,24 +37,19 @@ impl CFGNodeData {
 
 #[derive(Debug)]
 pub struct CFGEdgeData {
-    pub exiting_scopes: Vec<hir::ItemLocalId>
+    pub(crate) exiting_scopes: Vec<hir::ItemLocalId>
 }
 
-pub type CFGIndex = graph::NodeIndex;
+pub(crate) type CFGIndex = graph::NodeIndex;
 
-pub type CFGGraph = graph::Graph<CFGNodeData, CFGEdgeData>;
+pub(crate) type CFGGraph = graph::Graph<CFGNodeData, CFGEdgeData>;
 
-pub type CFGNode = graph::Node<CFGNodeData>;
+pub(crate) type CFGNode = graph::Node<CFGNodeData>;
 
-pub type CFGEdge = graph::Edge<CFGEdgeData>;
+pub(crate) type CFGEdge = graph::Edge<CFGEdgeData>;
 
 impl CFG {
     pub fn new(tcx: TyCtxt<'_>, body: &hir::Body) -> CFG {
         construct::construct(tcx, body)
     }
-
-    pub fn node_is_reachable(&self, id: hir::ItemLocalId) -> bool {
-        self.graph.depth_traverse(self.entry, graph::OUTGOING)
-                  .any(|idx| self.graph.node_data(idx).id() == id)
-    }
 }
diff --git a/src/librustc_ast_borrowck/dataflow.rs b/src/librustc_ast_borrowck/dataflow.rs
index 3a4c8c924764e..a8562901d99c5 100644
--- a/src/librustc_ast_borrowck/dataflow.rs
+++ b/src/librustc_ast_borrowck/dataflow.rs
@@ -3,9 +3,7 @@
 //! and thus uses bitvectors. Your job is simply to specify the so-called
 //! GEN and KILL bits for each expression.
 
-use rustc::cfg;
-use rustc::cfg::CFGIndex;
-use rustc::ty::TyCtxt;
+use crate::cfg::{self, CFGIndex};
 use std::mem;
 use std::usize;
 use log::debug;
@@ -16,6 +14,7 @@ use rustc::util::nodemap::FxHashMap;
 use rustc::hir;
 use rustc::hir::intravisit;
 use rustc::hir::print as pprust;
+use rustc::ty::TyCtxt;
 
 #[derive(Copy, Clone, Debug)]
 pub enum EntryOrExit {
diff --git a/src/librustc_ast_borrowck/graphviz.rs b/src/librustc_ast_borrowck/graphviz.rs
index 7a8a23ca76afc..c077dc828aba2 100644
--- a/src/librustc_ast_borrowck/graphviz.rs
+++ b/src/librustc_ast_borrowck/graphviz.rs
@@ -4,13 +4,12 @@
 
 pub use Variant::*;
 
-pub use rustc::cfg::graphviz::{Node, Edge};
-use rustc::cfg::graphviz as cfg_dot;
-
+pub(crate) use crate::cfg::graphviz::{Node, Edge};
+use crate::cfg::graphviz as cfg_dot;
+use crate::cfg::CFGIndex;
 use crate::borrowck::{self, BorrowckCtxt, LoanPath};
 use crate::dataflow::{DataFlowOperator, DataFlowContext, EntryOrExit};
 use log::debug;
-use rustc::cfg::CFGIndex;
 use std::rc::Rc;
 
 #[derive(Debug, Copy, Clone)]
diff --git a/src/librustc_ast_borrowck/lib.rs b/src/librustc_ast_borrowck/lib.rs
index dc818278a4b74..aea97fea1a9fd 100644
--- a/src/librustc_ast_borrowck/lib.rs
+++ b/src/librustc_ast_borrowck/lib.rs
@@ -18,5 +18,6 @@ mod borrowck;
 pub mod graphviz;
 
 mod dataflow;
+pub mod cfg;
 
 pub use borrowck::provide;
diff --git a/src/librustc_codegen_llvm/Cargo.toml b/src/librustc_codegen_llvm/Cargo.toml
index 5e1b0eafdec36..98efa6a5804bd 100644
--- a/src/librustc_codegen_llvm/Cargo.toml
+++ b/src/librustc_codegen_llvm/Cargo.toml
@@ -11,11 +11,7 @@ crate-type = ["dylib"]
 test = false
 
 [dependencies]
-cc = "1.0.1" # Used to locate MSVC
-num_cpus = "1.0"
-tempfile = "3.0"
 rustc_llvm = { path = "../librustc_llvm" }
-memmap = "0.6"
 
 [features]
 # This is used to convince Cargo to separately cache builds of `rustc_codegen_llvm`
diff --git a/src/librustc_codegen_llvm/abi.rs b/src/librustc_codegen_llvm/abi.rs
index ff87afe0c444b..2ca517dc3b1a7 100644
--- a/src/librustc_codegen_llvm/abi.rs
+++ b/src/librustc_codegen_llvm/abi.rs
@@ -229,7 +229,7 @@ impl ArgTypeExt<'ll, 'tcx> for ArgType<'tcx, Ty<'tcx>> {
                 // We instead thus allocate some scratch space...
                 let scratch_size = cast.size(bx);
                 let scratch_align = cast.align(bx);
-                let llscratch = bx.alloca(cast.llvm_type(bx), "abi_cast", scratch_align);
+                let llscratch = bx.alloca(cast.llvm_type(bx), scratch_align);
                 bx.lifetime_start(llscratch, scratch_size);
 
                 // ...where we first store the value...
diff --git a/src/librustc_codegen_llvm/back/archive.rs b/src/librustc_codegen_llvm/back/archive.rs
index e3b7cb235c678..68d3f90cd3991 100644
--- a/src/librustc_codegen_llvm/back/archive.rs
+++ b/src/librustc_codegen_llvm/back/archive.rs
@@ -12,6 +12,7 @@ use crate::llvm::{self, ArchiveKind};
 use rustc_codegen_ssa::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION};
 use rustc_codegen_ssa::back::archive::{ArchiveBuilder, find_library};
 use rustc::session::Session;
+use syntax::symbol::Symbol;
 
 struct ArchiveConfig<'a> {
     pub sess: &'a Session,
@@ -109,7 +110,7 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
 
     /// Adds all of the contents of a native library to this archive. This will
     /// search in the relevant locations for a library named `name`.
-    fn add_native_library(&mut self, name: &str) {
+    fn add_native_library(&mut self, name: Symbol) {
         let location = find_library(name, &self.config.lib_search_paths,
                                     self.config.sess);
         self.add_archive(&location, |_| false).unwrap_or_else(|e| {
diff --git a/src/librustc_codegen_llvm/builder.rs b/src/librustc_codegen_llvm/builder.rs
index e13a5ecc2ebfd..423a01ad1f937 100644
--- a/src/librustc_codegen_llvm/builder.rs
+++ b/src/librustc_codegen_llvm/builder.rs
@@ -387,23 +387,17 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         )
     }
 
-    fn alloca(&mut self, ty: &'ll Type, name: &str, align: Align) -> &'ll Value {
+    fn alloca(&mut self, ty: &'ll Type, align: Align) -> &'ll Value {
         let mut bx = Builder::with_cx(self.cx);
         bx.position_at_start(unsafe {
             llvm::LLVMGetFirstBasicBlock(self.llfn())
         });
-        bx.dynamic_alloca(ty, name, align)
+        bx.dynamic_alloca(ty, align)
     }
 
-    fn dynamic_alloca(&mut self, ty: &'ll Type, name: &str, align: Align) -> &'ll Value {
+    fn dynamic_alloca(&mut self, ty: &'ll Type, align: Align) -> &'ll Value {
         unsafe {
-            let alloca = if name.is_empty() {
-                llvm::LLVMBuildAlloca(self.llbuilder, ty, UNNAMED)
-            } else {
-                let name = SmallCStr::new(name);
-                llvm::LLVMBuildAlloca(self.llbuilder, ty,
-                                      name.as_ptr())
-            };
+            let alloca = llvm::LLVMBuildAlloca(self.llbuilder, ty, UNNAMED);
             llvm::LLVMSetAlignment(alloca, align.bytes() as c_uint);
             alloca
         }
@@ -412,16 +406,9 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn array_alloca(&mut self,
                         ty: &'ll Type,
                         len: &'ll Value,
-                        name: &str,
                         align: Align) -> &'ll Value {
         unsafe {
-            let alloca = if name.is_empty() {
-                llvm::LLVMBuildArrayAlloca(self.llbuilder, ty, len, UNNAMED)
-            } else {
-                let name = SmallCStr::new(name);
-                llvm::LLVMBuildArrayAlloca(self.llbuilder, ty, len,
-                                           name.as_ptr())
-            };
+            let alloca = llvm::LLVMBuildArrayAlloca(self.llbuilder, ty, len, UNNAMED);
             llvm::LLVMSetAlignment(alloca, align.bytes() as c_uint);
             alloca
         }
diff --git a/src/librustc_codegen_llvm/debuginfo/mod.rs b/src/librustc_codegen_llvm/debuginfo/mod.rs
index cad2bcdc05fc9..6dedf10f0ab83 100644
--- a/src/librustc_codegen_llvm/debuginfo/mod.rs
+++ b/src/librustc_codegen_llvm/debuginfo/mod.rs
@@ -32,7 +32,7 @@ use rustc_codegen_ssa::debuginfo::{FunctionDebugContext, MirDebugScope, Variable
 
 use libc::c_uint;
 use std::cell::RefCell;
-use std::ffi::CString;
+use std::ffi::{CStr, CString};
 
 use syntax_pos::{self, Span, Pos};
 use syntax::ast;
@@ -224,8 +224,37 @@ impl DebugInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
         gdb::insert_reference_to_gdb_debug_scripts_section_global(self)
     }
 
-    fn set_value_name(&mut self, value: &'ll Value, name: &str) {
-        let cname = SmallCStr::new(name);
+    fn set_var_name(&mut self, value: &'ll Value, name: impl ToString) {
+        // Avoid wasting time if LLVM value names aren't even enabled.
+        if self.sess().fewer_names() {
+            return;
+        }
+
+        // Only function parameters and instructions are local to a function,
+        // don't change the name of anything else (e.g. globals).
+        let param_or_inst = unsafe {
+            llvm::LLVMIsAArgument(value).is_some() ||
+            llvm::LLVMIsAInstruction(value).is_some()
+        };
+        if !param_or_inst {
+            return;
+        }
+
+        let old_name = unsafe {
+            CStr::from_ptr(llvm::LLVMGetValueName(value))
+        };
+        match old_name.to_str() {
+            Ok("") => {}
+            Ok(_) => {
+                // Avoid replacing the name if it already exists.
+                // While we could combine the names somehow, it'd
+                // get noisy quick, and the usefulness is dubious.
+                return;
+            }
+            Err(_) => return,
+        }
+
+        let cname = CString::new(name.to_string()).unwrap();
         unsafe {
             llvm::LLVMSetValueName(value, cname.as_ptr());
         }
diff --git a/src/librustc_codegen_llvm/error_codes.rs b/src/librustc_codegen_llvm/error_codes.rs
index c6b5dc03a6f0a..042e51ed2ba7a 100644
--- a/src/librustc_codegen_llvm/error_codes.rs
+++ b/src/librustc_codegen_llvm/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+register_diagnostics! {
 
 E0511: r##"
 Invalid monomorphization of an intrinsic function was used. Erroneous code
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index fc0b9ffd11d83..3f3c5ac1460a3 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -15,6 +15,7 @@ use rustc_codegen_ssa::glue;
 use rustc_codegen_ssa::base::{to_immediate, wants_msvc_seh, compare_simd_types};
 use rustc::ty::{self, Ty};
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, Primitive};
+use rustc::mir::interpret::GlobalId;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc::hir;
 use syntax::ast::{self, FloatTy};
@@ -81,13 +82,14 @@ fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: &str) -> Option<&'ll Valu
 impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
     fn codegen_intrinsic_call(
         &mut self,
-        callee_ty: Ty<'tcx>,
+        instance: ty::Instance<'tcx>,
         fn_ty: &FnType<'tcx, Ty<'tcx>>,
         args: &[OperandRef<'tcx, &'ll Value>],
         llresult: &'ll Value,
         span: Span,
     ) {
         let tcx = self.tcx;
+        let callee_ty = instance.ty(tcx);
 
         let (def_id, substs) = match callee_ty.sty {
             ty::FnDef(def_id, substs) => (def_id, substs),
@@ -133,10 +135,6 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 let llfn = self.get_intrinsic(&("llvm.debugtrap"));
                 self.call(llfn, &[], None)
             }
-            "size_of" => {
-                let tp_ty = substs.type_at(0);
-                self.const_usize(self.size_of(tp_ty).bytes())
-            }
             "va_start" => {
                 self.va_start(args[0].immediate())
             }
@@ -188,10 +186,6 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     self.const_usize(self.size_of(tp_ty).bytes())
                 }
             }
-            "min_align_of" => {
-                let tp_ty = substs.type_at(0);
-                self.const_usize(self.align_of(tp_ty).bytes())
-            }
             "min_align_of_val" => {
                 let tp_ty = substs.type_at(0);
                 if let OperandValue::Pair(_, meta) = args[0].val {
@@ -201,18 +195,19 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     self.const_usize(self.align_of(tp_ty).bytes())
                 }
             }
-            "pref_align_of" => {
-                let tp_ty = substs.type_at(0);
-                self.const_usize(self.layout_of(tp_ty).align.pref.bytes())
-            }
+            "size_of" |
+            "pref_align_of" |
+            "min_align_of" |
+            "needs_drop" |
+            "type_id" |
             "type_name" => {
-                let tp_ty = substs.type_at(0);
-                let ty_name = self.tcx.type_name(tp_ty);
+                let gid = GlobalId {
+                    instance,
+                    promoted: None,
+                };
+                let ty_name = self.tcx.const_eval(ty::ParamEnv::reveal_all().and(gid)).unwrap();
                 OperandRef::from_const(self, ty_name).immediate_or_packed_pair(self)
             }
-            "type_id" => {
-                self.const_u64(self.tcx.type_id_hash(substs.type_at(0)))
-            }
             "init" => {
                 let ty = substs.type_at(0);
                 if !self.layout_of(ty).is_zst() {
@@ -235,11 +230,6 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
             "uninit" | "forget" => {
                 return;
             }
-            "needs_drop" => {
-                let tp_ty = substs.type_at(0);
-
-                self.const_bool(self.type_needs_drop(tp_ty))
-            }
             "offset" => {
                 let ptr = args[0].immediate();
                 let offset = args[1].immediate();
@@ -871,7 +861,7 @@ fn codegen_msvc_try(
         // More information can be found in libstd's seh.rs implementation.
         let i64p = bx.type_ptr_to(bx.type_i64());
         let ptr_align = bx.tcx().data_layout.pointer_align.abi;
-        let slot = bx.alloca(i64p, "slot", ptr_align);
+        let slot = bx.alloca(i64p, ptr_align);
         bx.invoke(func, &[data], normal.llbb(), catchswitch.llbb(), None);
 
         normal.ret(bx.const_i32(0));
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 2fd78885bd01e..34e39af3c39fc 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -14,7 +14,6 @@
 #![feature(in_band_lifetimes)]
 #![feature(libc)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(optin_builtin_traits)]
 #![feature(concat_idents)]
 #![feature(link_args)]
@@ -227,21 +226,21 @@ impl CodegenBackend for LlvmCodegenBackend {
                 for &(name, _) in back::write::RELOC_MODEL_ARGS.iter() {
                     println!("    {}", name);
                 }
-                println!("");
+                println!();
             }
             PrintRequest::CodeModels => {
                 println!("Available code models:");
                 for &(name, _) in back::write::CODE_GEN_MODEL_ARGS.iter(){
                     println!("    {}", name);
                 }
-                println!("");
+                println!();
             }
             PrintRequest::TlsModels => {
                 println!("Available TLS models:");
                 for &(name, _) in back::write::TLS_MODEL_ARGS.iter(){
                     println!("    {}", name);
                 }
-                println!("");
+                println!();
             }
             req => llvm_util::print(req, sess),
         }
@@ -256,7 +255,7 @@ impl CodegenBackend for LlvmCodegenBackend {
     }
 
     fn diagnostics(&self) -> &[(&'static str, &'static str)] {
-        &DIAGNOSTICS
+        &error_codes::DIAGNOSTICS
     }
 
     fn target_features(&self, sess: &Session) -> Vec<Symbol> {
@@ -425,5 +424,3 @@ impl Drop for ModuleLlvm {
         }
     }
 }
-
-__build_diagnostic_array! { librustc_codegen_llvm, DIAGNOSTICS }
diff --git a/src/librustc_codegen_llvm/llvm/ffi.rs b/src/librustc_codegen_llvm/llvm/ffi.rs
index 9f9410560e373..b07214fdc03f3 100644
--- a/src/librustc_codegen_llvm/llvm/ffi.rs
+++ b/src/librustc_codegen_llvm/llvm/ffi.rs
@@ -806,6 +806,7 @@ extern "C" {
     pub fn LLVMRustRemoveFunctionAttributes(Fn: &Value, index: c_uint, attr: Attribute);
 
     // Operations on parameters
+    pub fn LLVMIsAArgument(Val: &Value) -> Option<&Value>;
     pub fn LLVMCountParams(Fn: &Value) -> c_uint;
     pub fn LLVMGetParam(Fn: &Value, Index: c_uint) -> &Value;
 
@@ -818,6 +819,7 @@ extern "C" {
     pub fn LLVMDeleteBasicBlock(BB: &BasicBlock);
 
     // Operations on instructions
+    pub fn LLVMIsAInstruction(Val: &Value) -> Option<&Value>;
     pub fn LLVMGetFirstBasicBlock(Fn: &Value) -> &BasicBlock;
 
     // Operations on call sites
diff --git a/src/librustc_codegen_ssa/Cargo.toml b/src/librustc_codegen_ssa/Cargo.toml
index 89a6ec27fe595..bc028d6624279 100644
--- a/src/librustc_codegen_ssa/Cargo.toml
+++ b/src/librustc_codegen_ssa/Cargo.toml
@@ -17,8 +17,8 @@ memmap = "0.6"
 log = "0.4.5"
 libc = "0.2.44"
 jobserver = "0.1.11"
-parking_lot = "0.7"
-tempfile = "3.0.5"
+parking_lot = "0.9"
+tempfile = "3.1"
 
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
diff --git a/src/librustc_codegen_ssa/back/archive.rs b/src/librustc_codegen_ssa/back/archive.rs
index 23d580ef08b2d..8d2120a345a8d 100644
--- a/src/librustc_codegen_ssa/back/archive.rs
+++ b/src/librustc_codegen_ssa/back/archive.rs
@@ -1,9 +1,10 @@
 use rustc::session::Session;
+use syntax::symbol::Symbol;
 
 use std::io;
 use std::path::{Path, PathBuf};
 
-pub fn find_library(name: &str, search_paths: &[PathBuf], sess: &Session)
+pub fn find_library(name: Symbol, search_paths: &[PathBuf], sess: &Session)
                     -> PathBuf {
     // On Windows, static libraries sometimes show up as libfoo.a and other
     // times show up as foo.lib
@@ -40,7 +41,7 @@ pub trait ArchiveBuilder<'a> {
         lto: bool,
         skip_objects: bool,
     ) -> io::Result<()>;
-    fn add_native_library(&mut self, name: &str);
+    fn add_native_library(&mut self, name: Symbol);
     fn update_symbols(&mut self);
 
     fn build(self);
diff --git a/src/librustc_codegen_ssa/back/command.rs b/src/librustc_codegen_ssa/back/command.rs
index 340cc772e5f07..2d84d67e3c85b 100644
--- a/src/librustc_codegen_ssa/back/command.rs
+++ b/src/librustc_codegen_ssa/back/command.rs
@@ -8,12 +8,14 @@ use std::mem;
 use std::process::{self, Output};
 
 use rustc_target::spec::LldFlavor;
+use syntax::symbol::Symbol;
 
 #[derive(Clone)]
 pub struct Command {
     program: Program,
     args: Vec<OsString>,
     env: Vec<(OsString, OsString)>,
+    env_remove: Vec<OsString>,
 }
 
 #[derive(Clone)]
@@ -41,6 +43,7 @@ impl Command {
             program,
             args: Vec::new(),
             env: Vec::new(),
+            env_remove: Vec::new(),
         }
     }
 
@@ -49,6 +52,11 @@ impl Command {
         self
     }
 
+    pub fn sym_arg(&mut self, arg: Symbol) -> &mut Command {
+        self.arg(&arg.as_str());
+        self
+    }
+
     pub fn args<I>(&mut self, args: I) -> &mut Command
     where
         I: IntoIterator<Item: AsRef<OsStr>>,
@@ -75,6 +83,17 @@ impl Command {
         self.env.push((key.to_owned(), value.to_owned()));
     }
 
+    pub fn env_remove<K>(&mut self, key: K) -> &mut Command
+        where K: AsRef<OsStr>,
+    {
+        self._env_remove(key.as_ref());
+        self
+    }
+
+    fn _env_remove(&mut self, key: &OsStr) {
+        self.env_remove.push(key.to_owned());
+    }
+
     pub fn output(&mut self) -> io::Result<Output> {
         self.command().output()
     }
@@ -100,6 +119,9 @@ impl Command {
         };
         ret.args(&self.args);
         ret.envs(self.env.clone());
+        for k in &self.env_remove {
+            ret.env_remove(k);
+        }
         return ret
     }
 
diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs
index 8603d61fb5453..9b044d9b45377 100644
--- a/src/librustc_codegen_ssa/back/link.rs
+++ b/src/librustc_codegen_ssa/back/link.rs
@@ -13,6 +13,7 @@ use rustc::hir::def_id::CrateNum;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_fs_util::fix_windows_verbatim_for_gcc;
 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
+use syntax::symbol::Symbol;
 
 use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo, CodegenResults};
 use super::archive::ArchiveBuilder;
@@ -316,7 +317,7 @@ fn link_rlib<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
             NativeLibraryKind::NativeUnknown => continue,
         }
         if let Some(name) = lib.name {
-            ab.add_native_library(&name.as_str());
+            ab.add_native_library(name);
         }
     }
 
@@ -532,6 +533,9 @@ fn link_natively<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
     for &(ref k, ref v) in &sess.target.target.options.link_env {
         cmd.env(k, v);
     }
+    for k in &sess.target.target.options.link_env_remove {
+        cmd.env_remove(k);
+    }
 
     if sess.opts.debugging_opts.print_link_args {
         println!("{:?}", &cmd);
@@ -1273,15 +1277,14 @@ pub fn add_local_native_libraries(cmd: &mut dyn Linker,
     let search_path = archive_search_paths(sess);
     for lib in relevant_libs {
         let name = match lib.name {
-            Some(ref l) => l,
+            Some(l) => l,
             None => continue,
         };
         match lib.kind {
-            NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
-            NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
-            NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
-            NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
-                                                                        &search_path)
+            NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
+            NativeLibraryKind::NativeFramework => cmd.link_framework(name),
+            NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(name),
+            NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(name, &search_path)
         }
     }
 }
@@ -1594,7 +1597,7 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
             cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
         }
         let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
-        cmd.link_rust_dylib(&unlib(&sess.target, filestem),
+        cmd.link_rust_dylib(Symbol::intern(&unlib(&sess.target, filestem)),
                             parent.unwrap_or(Path::new("")));
     }
 }
@@ -1637,22 +1640,22 @@ pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
     for &(cnum, _) in crates {
         for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
             let name = match lib.name {
-                Some(ref l) => l,
+                Some(l) => l,
                 None => continue,
             };
             if !relevant_lib(sess, &lib) {
                 continue
             }
             match lib.kind {
-                NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
-                NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
+                NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
+                NativeLibraryKind::NativeFramework => cmd.link_framework(name),
                 NativeLibraryKind::NativeStaticNobundle => {
                     // Link "static-nobundle" native libs only if the crate they originate from
                     // is being linked statically to the current crate.  If it's linked dynamically
                     // or is an rlib already included via some other dylib crate, the symbols from
                     // native libs will have already been included in that dylib.
                     if data[cnum.as_usize() - 1] == Linkage::Static {
-                        cmd.link_staticlib(&name.as_str())
+                        cmd.link_staticlib(name)
                     }
                 },
                 // ignore statically included native libraries here as we've
diff --git a/src/librustc_codegen_ssa/back/linker.rs b/src/librustc_codegen_ssa/back/linker.rs
index de481d2262478..c42cd024926dc 100644
--- a/src/librustc_codegen_ssa/back/linker.rs
+++ b/src/librustc_codegen_ssa/back/linker.rs
@@ -17,6 +17,7 @@ use rustc::session::config::{self, CrateType, OptLevel, DebugInfo,
 use rustc::ty::TyCtxt;
 use rustc_target::spec::{LinkerFlavor, LldFlavor};
 use rustc_serialize::{json, Encoder};
+use syntax::symbol::Symbol;
 
 /// For all the linkers we support, and information they might
 /// need out of the shared crate context before we get rid of it.
@@ -99,13 +100,13 @@ impl LinkerInfo {
 /// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
 /// MSVC linker (e.g., `link.exe`) is being used.
 pub trait Linker {
-    fn link_dylib(&mut self, lib: &str);
-    fn link_rust_dylib(&mut self, lib: &str, path: &Path);
-    fn link_framework(&mut self, framework: &str);
-    fn link_staticlib(&mut self, lib: &str);
+    fn link_dylib(&mut self, lib: Symbol);
+    fn link_rust_dylib(&mut self, lib: Symbol, path: &Path);
+    fn link_framework(&mut self, framework: Symbol);
+    fn link_staticlib(&mut self, lib: Symbol);
     fn link_rlib(&mut self, lib: &Path);
     fn link_whole_rlib(&mut self, lib: &Path);
-    fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]);
+    fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]);
     fn include_path(&mut self, path: &Path);
     fn framework_path(&mut self, path: &Path);
     fn output_filename(&mut self, path: &Path);
@@ -215,9 +216,13 @@ impl<'a> GccLinker<'a> {
 }
 
 impl<'a> Linker for GccLinker<'a> {
-    fn link_dylib(&mut self, lib: &str) { self.hint_dynamic(); self.cmd.arg(format!("-l{}", lib)); }
-    fn link_staticlib(&mut self, lib: &str) {
-        self.hint_static(); self.cmd.arg(format!("-l{}", lib));
+    fn link_dylib(&mut self, lib: Symbol) {
+        self.hint_dynamic();
+        self.cmd.arg(format!("-l{}", lib));
+    }
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.hint_static();
+        self.cmd.arg(format!("-l{}", lib));
     }
     fn link_rlib(&mut self, lib: &Path) { self.hint_static(); self.cmd.arg(lib); }
     fn include_path(&mut self, path: &Path) { self.cmd.arg("-L").arg(path); }
@@ -232,14 +237,14 @@ impl<'a> Linker for GccLinker<'a> {
     fn build_static_executable(&mut self) { self.cmd.arg("-static"); }
     fn args(&mut self, args: &[String]) { self.cmd.args(args); }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
         self.hint_dynamic();
         self.cmd.arg(format!("-l{}", lib));
     }
 
-    fn link_framework(&mut self, framework: &str) {
+    fn link_framework(&mut self, framework: Symbol) {
         self.hint_dynamic();
-        self.cmd.arg("-framework").arg(framework);
+        self.cmd.arg("-framework").sym_arg(framework);
     }
 
     // Here we explicitly ask that the entire archive is included into the
@@ -248,7 +253,7 @@ impl<'a> Linker for GccLinker<'a> {
     // don't otherwise explicitly reference them. This can occur for
     // libraries which are just providing bindings, libraries with generic
     // functions, etc.
-    fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]) {
         self.hint_static();
         let target = &self.sess.target.target;
         if !target.options.is_like_osx {
@@ -539,11 +544,11 @@ impl<'a> Linker for MsvcLinker<'a> {
         }
     }
 
-    fn link_dylib(&mut self, lib: &str) {
+    fn link_dylib(&mut self, lib: Symbol) {
         self.cmd.arg(&format!("{}.lib", lib));
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, path: &Path) {
         // When producing a dll, the MSVC linker may not actually emit a
         // `foo.lib` file if the dll doesn't actually export any symbols, so we
         // check to see if the file is there and just omit linking to it if it's
@@ -554,7 +559,7 @@ impl<'a> Linker for MsvcLinker<'a> {
         }
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
+    fn link_staticlib(&mut self, lib: Symbol) {
         self.cmd.arg(&format!("{}.lib", lib));
     }
 
@@ -605,11 +610,11 @@ impl<'a> Linker for MsvcLinker<'a> {
     fn framework_path(&mut self, _path: &Path) {
         bug!("frameworks are not supported on windows")
     }
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         bug!("frameworks are not supported on windows")
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
         // not supported?
         self.link_staticlib(lib);
     }
@@ -740,8 +745,8 @@ impl<'a> Linker for EmLinker<'a> {
         self.cmd.arg("-L").arg(path);
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn output_filename(&mut self, path: &Path) {
@@ -752,12 +757,12 @@ impl<'a> Linker for EmLinker<'a> {
         self.cmd.arg(path);
     }
 
-    fn link_dylib(&mut self, lib: &str) {
+    fn link_dylib(&mut self, lib: Symbol) {
         // Emscripten always links statically
         self.link_staticlib(lib);
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
         // not supported?
         self.link_staticlib(lib);
     }
@@ -767,7 +772,7 @@ impl<'a> Linker for EmLinker<'a> {
         self.link_rlib(lib);
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
         self.link_dylib(lib);
     }
 
@@ -803,7 +808,7 @@ impl<'a> Linker for EmLinker<'a> {
         bug!("frameworks are not supported on Emscripten")
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         bug!("frameworks are not supported on Emscripten")
     }
 
@@ -948,12 +953,12 @@ impl<'a> WasmLd<'a> {
 }
 
 impl<'a> Linker for WasmLd<'a> {
-    fn link_dylib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_dylib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn link_rlib(&mut self, lib: &Path) {
@@ -995,16 +1000,16 @@ impl<'a> Linker for WasmLd<'a> {
         self.cmd.args(args);
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         panic!("frameworks not supported")
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn link_whole_rlib(&mut self, lib: &Path) {
@@ -1162,19 +1167,19 @@ impl<'a> Linker for PtxLinker<'a> {
         ::std::mem::replace(&mut self.cmd, Command::new(""))
     }
 
-    fn link_dylib(&mut self, _lib: &str) {
+    fn link_dylib(&mut self, _lib: Symbol) {
         panic!("external dylibs not supported")
     }
 
-    fn link_rust_dylib(&mut self, _lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, _lib: Symbol, _path: &Path) {
         panic!("external dylibs not supported")
     }
 
-    fn link_staticlib(&mut self, _lib: &str) {
+    fn link_staticlib(&mut self, _lib: Symbol) {
         panic!("staticlibs not supported")
     }
 
-    fn link_whole_staticlib(&mut self, _lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, _lib: Symbol, _search_path: &[PathBuf]) {
         panic!("staticlibs not supported")
     }
 
@@ -1182,7 +1187,7 @@ impl<'a> Linker for PtxLinker<'a> {
         panic!("frameworks not supported")
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         panic!("frameworks not supported")
     }
 
diff --git a/src/librustc_codegen_ssa/error_codes.rs b/src/librustc_codegen_ssa/error_codes.rs
index 8d46dcb7c09c3..8ff41c275a8f4 100644
--- a/src/librustc_codegen_ssa/error_codes.rs
+++ b/src/librustc_codegen_ssa/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0668: r##"
 Malformed inline assembly rejected by LLVM.
diff --git a/src/librustc_codegen_ssa/lib.rs b/src/librustc_codegen_ssa/lib.rs
index 68640abb0433e..1708d7235b45b 100644
--- a/src/librustc_codegen_ssa/lib.rs
+++ b/src/librustc_codegen_ssa/lib.rs
@@ -4,7 +4,7 @@
 #![feature(box_syntax)]
 #![feature(core_intrinsics)]
 #![feature(libc)]
-#![feature(rustc_diagnostic_macros)]
+#![feature(slice_patterns)]
 #![feature(stmt_expr_attributes)]
 #![feature(try_blocks)]
 #![feature(in_band_lifetimes)]
@@ -35,8 +35,6 @@ use rustc_data_structures::svh::Svh;
 use rustc::middle::cstore::{LibSource, CrateSource, NativeLibrary};
 use syntax_pos::symbol::Symbol;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 mod error_codes;
 
 pub mod common;
@@ -158,5 +156,3 @@ pub struct CodegenResults {
     pub linker_info: back::linker::LinkerInfo,
     pub crate_info: CrateInfo,
 }
-
-__build_diagnostic_array! { librustc_codegen_ssa, DIAGNOSTICS }
diff --git a/src/librustc_codegen_ssa/mir/analyze.rs b/src/librustc_codegen_ssa/mir/analyze.rs
index e63f1b91dd7d5..d192f2ffb6fba 100644
--- a/src/librustc_codegen_ssa/mir/analyze.rs
+++ b/src/librustc_codegen_ssa/mir/analyze.rs
@@ -105,7 +105,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
     ) {
         let cx = self.fx.cx;
 
-        if let Some(proj) = place_ref.projection {
+        if let [proj_base @ .., elem] = place_ref.projection {
             // Allow uses of projections that are ZSTs or from scalar fields.
             let is_consume = match context {
                 PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
@@ -114,12 +114,12 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
             };
             if is_consume {
                 let base_ty =
-                    mir::Place::ty_from(place_ref.base, &proj.base, self.fx.mir, cx.tcx());
+                    mir::Place::ty_from(place_ref.base, proj_base, self.fx.mir, cx.tcx());
                 let base_ty = self.fx.monomorphize(&base_ty);
 
                 // ZSTs don't require any actual memory access.
                 let elem_ty = base_ty
-                    .projection_ty(cx.tcx(), &proj.elem)
+                    .projection_ty(cx.tcx(), elem)
                     .ty;
                 let elem_ty = self.fx.monomorphize(&elem_ty);
                 let span = if let mir::PlaceBase::Local(index) = place_ref.base {
@@ -131,7 +131,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
                     return;
                 }
 
-                if let mir::ProjectionElem::Field(..) = proj.elem {
+                if let mir::ProjectionElem::Field(..) = elem {
                     let layout = cx.spanned_layout_of(base_ty.ty, span);
                     if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
                         // Recurse with the same context, instead of `Projection`,
@@ -140,7 +140,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
                         self.process_place(
                             &mir::PlaceRef {
                                 base: place_ref.base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             },
                             context,
                             location,
@@ -151,11 +151,11 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
             }
 
             // A deref projection only reads the pointer, never needs the place.
-            if let mir::ProjectionElem::Deref = proj.elem {
+            if let mir::ProjectionElem::Deref = elem {
                 self.process_place(
                     &mir::PlaceRef {
                         base: place_ref.base,
-                        projection: &proj.base,
+                        projection: proj_base,
                     },
                     PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
                     location
@@ -168,7 +168,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
         // visit_place API
         let mut context = context;
 
-        if place_ref.projection.is_some() {
+        if !place_ref.projection.is_empty() {
             context = if context.is_mutating_use() {
                 PlaceContext::MutatingUse(MutatingUseContext::Projection)
             } else {
@@ -177,10 +177,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
         }
 
         self.visit_place_base(place_ref.base, context, location);
-
-        if let Some(box proj) = place_ref.projection {
-            self.visit_projection(place_ref.base, proj, context, location);
-        }
+        self.visit_projection(place_ref.base, place_ref.projection, context, location);
     }
 
 }
@@ -196,7 +193,7 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
 
         if let mir::Place {
             base: mir::PlaceBase::Local(index),
-            projection: None,
+            projection: box [],
         } = *place {
             self.assign(index, location);
             let decl_span = self.fx.mir.local_decls[index].source_info.span;
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index c41e46398467a..1bb0ea5dae44b 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -253,7 +253,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
             PassMode::Direct(_) | PassMode::Pair(..) => {
                 let op =
-                    self.codegen_consume(&mut bx, &mir::Place::RETURN_PLACE.as_ref());
+                    self.codegen_consume(&mut bx, &mir::Place::return_place().as_ref());
                 if let Ref(llval, _, align) = op.val {
                     bx.load(llval, align)
                 } else {
@@ -276,7 +276,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let llslot = match op.val {
                     Immediate(_) | Pair(..) => {
                         let scratch =
-                            PlaceRef::alloca(&mut bx, self.fn_ty.ret.layout, "ret");
+                            PlaceRef::alloca(&mut bx, self.fn_ty.ret.layout);
                         op.val.store(&mut bx, scratch);
                         scratch.llval
                     }
@@ -612,7 +612,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                     ty,
                                     def_id: _,
                                 }),
-                                projection: None,
+                                projection: box [],
                             }
                         ) |
                         mir::Operand::Move(
@@ -622,7 +622,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                     ty,
                                     def_id: _,
                                 }),
-                                projection: None,
+                                projection: box [],
                             }
                         ) => {
                             let param_env = ty::ParamEnv::reveal_all();
@@ -667,8 +667,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }).collect();
 
 
-            let callee_ty = instance.as_ref().unwrap().ty(bx.tcx());
-            bx.codegen_intrinsic_call(callee_ty, &fn_ty, &args, dest,
+            bx.codegen_intrinsic_call(*instance.as_ref().unwrap(), &fn_ty, &args, dest,
                                       terminator.source_info.span);
 
             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
@@ -767,7 +766,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             match (arg, op.val) {
                 (&mir::Operand::Copy(_), Ref(_, None, _)) |
                 (&mir::Operand::Constant(_), Ref(_, None, _)) => {
-                    let tmp = PlaceRef::alloca(&mut bx, op.layout, "const");
+                    let tmp = PlaceRef::alloca(&mut bx, op.layout);
                     op.val.store(&mut bx, tmp);
                     op.val = Ref(tmp.llval, None, tmp.align);
                 }
@@ -925,7 +924,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             Immediate(_) | Pair(..) => {
                 match arg.mode {
                     PassMode::Indirect(..) | PassMode::Cast(_) => {
-                        let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
+                        let scratch = PlaceRef::alloca(bx, arg.layout);
                         op.val.store(bx, scratch);
                         (scratch.llval, scratch.align, true)
                     }
@@ -940,7 +939,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
                     // have scary latent bugs around.
 
-                    let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
+                    let scratch = PlaceRef::alloca(bx, arg.layout);
                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
                                     op.layout, MemFlags::empty());
                     (scratch.llval, scratch.align, true)
@@ -1017,7 +1016,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 cx.tcx().mk_mut_ptr(cx.tcx().types.u8),
                 cx.tcx().types.i32
             ]));
-            let slot = PlaceRef::alloca(bx, layout, "personalityslot");
+            let slot = PlaceRef::alloca(bx, layout);
             self.personality_slot = Some(slot);
             slot
         }
@@ -1105,7 +1104,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
         let dest = if let mir::Place {
             base: mir::PlaceBase::Local(index),
-            projection: None,
+            projection: box [],
         } = *dest {
             match self.locals[index] {
                 LocalRef::Place(dest) => dest,
@@ -1116,7 +1115,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     return if fn_ret.is_indirect() {
                         // Odd, but possible, case, we have an operand temporary,
                         // but the calling convention has an indirect return.
-                        let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
+                        let tmp = PlaceRef::alloca(bx, fn_ret.layout);
                         tmp.storage_live(bx);
                         llargs.push(tmp.llval);
                         ReturnDest::IndirectOperand(tmp, index)
@@ -1124,7 +1123,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         // Currently, intrinsics always need a location to store
                         // the result, so we create a temporary `alloca` for the
                         // result.
-                        let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
+                        let tmp = PlaceRef::alloca(bx, fn_ret.layout);
                         tmp.storage_live(bx);
                         ReturnDest::IndirectOperand(tmp, index)
                     } else {
@@ -1166,7 +1165,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) {
         if let mir::Place {
             base: mir::PlaceBase::Local(index),
-            projection: None,
+            projection: box [],
         } = *dst {
             match self.locals[index] {
                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
@@ -1174,7 +1173,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 LocalRef::Operand(None) => {
                     let dst_layout = bx.layout_of(self.monomorphized_place_ty(&dst.as_ref()));
                     assert!(!dst_layout.ty.has_erasable_regions());
-                    let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
+                    let place = PlaceRef::alloca(bx, dst_layout);
                     place.storage_live(bx);
                     self.codegen_transmute_into(bx, src, place);
                     let op = bx.load_operand(place);
@@ -1227,7 +1226,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             DirectOperand(index) => {
                 // If there is a cast, we have to store and reload.
                 let op = if let PassMode::Cast(_) = ret_ty.mode {
-                    let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
+                    let tmp = PlaceRef::alloca(bx, ret_ty.layout);
                     tmp.storage_live(bx);
                     bx.store_arg_ty(&ret_ty, llval, tmp);
                     let op = bx.load_operand(tmp);
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
index 8acb3ba06267e..aa3971a1da81a 100644
--- a/src/librustc_codegen_ssa/mir/mod.rs
+++ b/src/librustc_codegen_ssa/mir/mod.rs
@@ -268,11 +268,13 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 debug!("alloc: {:?} ({}) -> place", local, name);
                 if layout.is_unsized() {
                     let indirect_place =
-                        PlaceRef::alloca_unsized_indirect(&mut bx, layout, &name.as_str());
+                        PlaceRef::alloca_unsized_indirect(&mut bx, layout);
+                    bx.set_var_name(indirect_place.llval, name);
                     // FIXME: add an appropriate debuginfo
                     LocalRef::UnsizedPlace(indirect_place)
                 } else {
-                    let place = PlaceRef::alloca(&mut bx, layout, &name.as_str());
+                    let place = PlaceRef::alloca(&mut bx, layout);
+                    bx.set_var_name(place.llval, name);
                     if dbg {
                         let (scope, span) = fx.debug_loc(mir::SourceInfo {
                             span: decl.source_info.span,
@@ -293,14 +295,13 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 } else if memory_locals.contains(local) {
                     debug!("alloc: {:?} -> place", local);
                     if layout.is_unsized() {
-                        let indirect_place = PlaceRef::alloca_unsized_indirect(
-                            &mut bx,
-                            layout,
-                            &format!("{:?}", local),
-                        );
+                        let indirect_place = PlaceRef::alloca_unsized_indirect(&mut bx, layout);
+                        bx.set_var_name(indirect_place.llval, format_args!("{:?}", local));
                         LocalRef::UnsizedPlace(indirect_place)
                     } else {
-                        LocalRef::Place(PlaceRef::alloca(&mut bx, layout, &format!("{:?}", local)))
+                        let place = PlaceRef::alloca(&mut bx, layout);
+                        bx.set_var_name(place.llval, format_args!("{:?}", local));
+                        LocalRef::Place(place)
                     }
                 } else {
                     // If this is an immediate local, we do not create an
@@ -452,10 +453,11 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     mir.args_iter().enumerate().map(|(arg_index, local)| {
         let arg_decl = &mir.local_decls[local];
 
+        // FIXME(eddyb) don't allocate a `String` unless it gets used.
         let name = if let Some(name) = arg_decl.name {
             name.as_str().to_string()
         } else {
-            format!("arg{}", arg_index)
+            format!("{:?}", local)
         };
 
         if Some(local) == mir.spread_arg {
@@ -470,7 +472,8 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 _ => bug!("spread argument isn't a tuple?!")
             };
 
-            let place = PlaceRef::alloca(bx, bx.layout_of(arg_ty), &name);
+            let place = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
+            bx.set_var_name(place.llval, name);
             for i in 0..tupled_arg_tys.len() {
                 let arg = &fx.fn_ty.args[idx];
                 idx += 1;
@@ -518,19 +521,19 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 PassMode::Ignore(IgnoreMode::CVarArgs) => {}
                 PassMode::Direct(_) => {
                     let llarg = bx.get_param(llarg_idx);
-                    bx.set_value_name(llarg, &name);
+                    bx.set_var_name(llarg, &name);
                     llarg_idx += 1;
                     return local(
                         OperandRef::from_immediate_or_packed_pair(bx, llarg, arg.layout));
                 }
                 PassMode::Pair(..) => {
-                    let a = bx.get_param(llarg_idx);
-                    bx.set_value_name(a, &(name.clone() + ".0"));
-                    llarg_idx += 1;
+                    let (a, b) = (bx.get_param(llarg_idx), bx.get_param(llarg_idx + 1));
+                    llarg_idx += 2;
 
-                    let b = bx.get_param(llarg_idx);
-                    bx.set_value_name(b, &(name + ".1"));
-                    llarg_idx += 1;
+                    // FIXME(eddyb) these are scalar components,
+                    // maybe extract the high-level fields?
+                    bx.set_var_name(a, format_args!("{}.0", name));
+                    bx.set_var_name(b, format_args!("{}.1", name));
 
                     return local(OperandRef {
                         val: OperandValue::Pair(a, b),
@@ -546,7 +549,7 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
             // already put it in a temporary alloca and gave it up.
             // FIXME: lifetimes
             let llarg = bx.get_param(llarg_idx);
-            bx.set_value_name(llarg, &name);
+            bx.set_var_name(llarg, &name);
             llarg_idx += 1;
             PlaceRef::new_sized(llarg, arg.layout)
         } else if arg.is_unsized_indirect() {
@@ -558,11 +561,13 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
             llarg_idx += 1;
             let indirect_operand = OperandValue::Pair(llarg, llextra);
 
-            let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout, &name);
+            let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
+            bx.set_var_name(tmp.llval, name);
             indirect_operand.store(bx, tmp);
             tmp
         } else {
-            let tmp = PlaceRef::alloca(bx, arg.layout, &name);
+            let tmp = PlaceRef::alloca(bx, arg.layout);
+            bx.set_var_name(tmp.llval, name);
             if fx.fn_ty.c_variadic && last_arg_idx.map(|idx| arg_index == idx).unwrap_or(false) {
                 let va_list_did = match tcx.lang_items().va_list() {
                     Some(did) => did,
diff --git a/src/librustc_codegen_ssa/mir/operand.rs b/src/librustc_codegen_ssa/mir/operand.rs
index a8ab3ea10ed16..daa25b2ea0591 100644
--- a/src/librustc_codegen_ssa/mir/operand.rs
+++ b/src/librustc_codegen_ssa/mir/operand.rs
@@ -367,7 +367,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
 
         // Allocate an appropriate region on the stack, and copy the value into it
         let (llsize, _) = glue::size_and_align_of_dst(bx, unsized_ty, Some(llextra));
-        let lldst = bx.array_alloca(bx.cx().type_i8(), llsize, "unsized_tmp", max_align);
+        let lldst = bx.array_alloca(bx.cx().type_i8(), llsize, max_align);
         bx.memcpy(lldst, max_align, llptr, min_align, llsize, flags);
 
         // Store the allocated region and the extra to the indirect place.
@@ -384,47 +384,45 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> Option<OperandRef<'tcx, Bx::Value>> {
         debug!("maybe_codegen_consume_direct(place_ref={:?})", place_ref);
 
-        place_ref.iterate(|place_base, place_projection| {
-            if let mir::PlaceBase::Local(index) = place_base {
-                match self.locals[*index] {
-                    LocalRef::Operand(Some(mut o)) => {
-                        // Moves out of scalar and scalar pair fields are trivial.
-                        for proj in place_projection {
-                            match proj.elem {
-                                mir::ProjectionElem::Field(ref f, _) => {
-                                    o = o.extract_field(bx, f.index());
-                                }
-                                mir::ProjectionElem::Index(_) |
-                                mir::ProjectionElem::ConstantIndex { .. } => {
-                                    // ZSTs don't require any actual memory access.
-                                    // FIXME(eddyb) deduplicate this with the identical
-                                    // checks in `codegen_consume` and `extract_field`.
-                                    let elem = o.layout.field(bx.cx(), 0);
-                                    if elem.is_zst() {
-                                        o = OperandRef::new_zst(bx, elem);
-                                    } else {
-                                        return None;
-                                    }
+        if let mir::PlaceBase::Local(index) = place_ref.base {
+            match self.locals[*index] {
+                LocalRef::Operand(Some(mut o)) => {
+                    // Moves out of scalar and scalar pair fields are trivial.
+                    for elem in place_ref.projection.iter() {
+                        match elem {
+                            mir::ProjectionElem::Field(ref f, _) => {
+                                o = o.extract_field(bx, f.index());
+                            }
+                            mir::ProjectionElem::Index(_) |
+                            mir::ProjectionElem::ConstantIndex { .. } => {
+                                // ZSTs don't require any actual memory access.
+                                // FIXME(eddyb) deduplicate this with the identical
+                                // checks in `codegen_consume` and `extract_field`.
+                                let elem = o.layout.field(bx.cx(), 0);
+                                if elem.is_zst() {
+                                    o = OperandRef::new_zst(bx, elem);
+                                } else {
+                                    return None;
                                 }
-                                _ => return None,
                             }
+                            _ => return None,
                         }
-
-                        Some(o)
-                    }
-                    LocalRef::Operand(None) => {
-                        bug!("use of {:?} before def", place_ref);
-                    }
-                    LocalRef::Place(..) | LocalRef::UnsizedPlace(..) => {
-                        // watch out for locals that do not have an
-                        // alloca; they are handled somewhat differently
-                        None
                     }
+
+                    Some(o)
+                }
+                LocalRef::Operand(None) => {
+                    bug!("use of {:?} before def", place_ref);
+                }
+                LocalRef::Place(..) | LocalRef::UnsizedPlace(..) => {
+                    // watch out for locals that do not have an
+                    // alloca; they are handled somewhat differently
+                    None
                 }
-            } else {
-                None
             }
-        })
+        } else {
+            None
+        }
     }
 
     pub fn codegen_consume(
diff --git a/src/librustc_codegen_ssa/mir/place.rs b/src/librustc_codegen_ssa/mir/place.rs
index b8e10d3430292..a4b4cb53bb1fb 100644
--- a/src/librustc_codegen_ssa/mir/place.rs
+++ b/src/librustc_codegen_ssa/mir/place.rs
@@ -71,11 +71,9 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
     pub fn alloca<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
         bx: &mut Bx,
         layout: TyLayout<'tcx>,
-        name: &str
     ) -> Self {
-        debug!("alloca({:?}: {:?})", name, layout);
         assert!(!layout.is_unsized(), "tried to statically allocate unsized place");
-        let tmp = bx.alloca(bx.cx().backend_type(layout), name, layout.align.abi);
+        let tmp = bx.alloca(bx.cx().backend_type(layout), layout.align.abi);
         Self::new_sized(tmp, layout)
     }
 
@@ -83,13 +81,11 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
     pub fn alloca_unsized_indirect<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
         bx: &mut Bx,
         layout: TyLayout<'tcx>,
-        name: &str,
     ) -> Self {
-        debug!("alloca_unsized_indirect({:?}: {:?})", name, layout);
         assert!(layout.is_unsized(), "tried to allocate indirect place for sized values");
         let ptr_ty = bx.cx().tcx().mk_mut_ptr(layout.ty);
         let ptr_layout = bx.cx().layout_of(ptr_ty);
-        Self::alloca(bx, ptr_layout, name)
+        Self::alloca(bx, ptr_layout)
     }
 
     pub fn len<Cx: ConstMethods<'tcx, Value = V>>(
@@ -449,7 +445,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let result = match &place_ref {
             mir::PlaceRef {
                 base: mir::PlaceBase::Local(index),
-                projection: None,
+                projection: [],
             } => {
                 match self.locals[*index] {
                     LocalRef::Place(place) => {
@@ -469,7 +465,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     kind: mir::StaticKind::Promoted(promoted, substs),
                     def_id,
                 }),
-                projection: None,
+                projection: [],
             } => {
                 let param_env = ty::ParamEnv::reveal_all();
                 let instance = Instance::new(*def_id, self.monomorphize(substs));
@@ -504,7 +500,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     kind: mir::StaticKind::Static,
                     def_id,
                 }),
-                projection: None,
+                projection: [],
             } => {
                 // NB: The layout of a static may be unsized as is the case when working
                 // with a static that is an extern_type.
@@ -514,10 +510,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             },
             mir::PlaceRef {
                 base,
-                projection: Some(box mir::Projection {
-                    base: proj_base,
-                    elem: mir::ProjectionElem::Deref,
-                }),
+                projection: [proj_base @ .., mir::ProjectionElem::Deref],
             } => {
                 // Load the pointer from its location.
                 self.codegen_consume(bx, &mir::PlaceRef {
@@ -527,22 +520,22 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
             mir::PlaceRef {
                 base,
-                projection: Some(projection),
+                projection: [proj_base @ .., elem],
             } => {
                 // FIXME turn this recursion into iteration
                 let cg_base = self.codegen_place(bx, &mir::PlaceRef {
                     base,
-                    projection: &projection.base,
+                    projection: proj_base,
                 });
 
-                match projection.elem {
+                match elem {
                     mir::ProjectionElem::Deref => bug!(),
                     mir::ProjectionElem::Field(ref field, _) => {
                         cg_base.project_field(bx, field.index())
                     }
                     mir::ProjectionElem::Index(index) => {
                         let index = &mir::Operand::Copy(
-                            mir::Place::from(index)
+                            mir::Place::from(*index)
                         );
                         let index = self.codegen_operand(bx, index);
                         let llindex = index.immediate();
@@ -551,27 +544,27 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     mir::ProjectionElem::ConstantIndex { offset,
                                                          from_end: false,
                                                          min_length: _ } => {
-                        let lloffset = bx.cx().const_usize(offset as u64);
+                        let lloffset = bx.cx().const_usize(*offset as u64);
                         cg_base.project_index(bx, lloffset)
                     }
                     mir::ProjectionElem::ConstantIndex { offset,
                                                          from_end: true,
                                                          min_length: _ } => {
-                        let lloffset = bx.cx().const_usize(offset as u64);
+                        let lloffset = bx.cx().const_usize(*offset as u64);
                         let lllen = cg_base.len(bx.cx());
                         let llindex = bx.sub(lllen, lloffset);
                         cg_base.project_index(bx, llindex)
                     }
                     mir::ProjectionElem::Subslice { from, to } => {
                         let mut subslice = cg_base.project_index(bx,
-                            bx.cx().const_usize(from as u64));
+                            bx.cx().const_usize(*from as u64));
                         let projected_ty = PlaceTy::from_ty(cg_base.layout.ty)
-                            .projection_ty(tcx, &projection.elem).ty;
+                            .projection_ty(tcx, elem).ty;
                         subslice.layout = bx.cx().layout_of(self.monomorphize(&projected_ty));
 
                         if subslice.layout.is_unsized() {
                             subslice.llextra = Some(bx.sub(cg_base.llextra.unwrap(),
-                                bx.cx().const_usize((from as u64) + (to as u64))));
+                                bx.cx().const_usize((*from as u64) + (*to as u64))));
                         }
 
                         // Cast the place pointer type to the new
@@ -582,7 +575,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         subslice
                     }
                     mir::ProjectionElem::Downcast(_, v) => {
-                        cg_base.project_downcast(bx, v)
+                        cg_base.project_downcast(bx, *v)
                     }
                 }
             }
diff --git a/src/librustc_codegen_ssa/mir/rvalue.rs b/src/librustc_codegen_ssa/mir/rvalue.rs
index e0ad2527229ba..f21836a953c22 100644
--- a/src/librustc_codegen_ssa/mir/rvalue.rs
+++ b/src/librustc_codegen_ssa/mir/rvalue.rs
@@ -64,7 +64,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         // index into the struct, and this case isn't
                         // important enough for it.
                         debug!("codegen_rvalue: creating ugly alloca");
-                        let scratch = PlaceRef::alloca(&mut bx, operand.layout, "__unsize_temp");
+                        let scratch = PlaceRef::alloca(&mut bx, operand.layout);
                         scratch.storage_live(&mut bx);
                         operand.val.store(&mut bx, scratch);
                         base::coerce_unsized_into(&mut bx, scratch, dest);
@@ -522,7 +522,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // because codegen_place() panics if Local is operand.
         if let mir::Place {
             base: mir::PlaceBase::Local(index),
-            projection: None,
+            projection: box [],
         } = *place {
             if let LocalRef::Operand(Some(op)) = self.locals[index] {
                 if let ty::Array(_, n) = op.layout.ty.sty {
diff --git a/src/librustc_codegen_ssa/mir/statement.rs b/src/librustc_codegen_ssa/mir/statement.rs
index 3617f3afaae41..dab7dfc041751 100644
--- a/src/librustc_codegen_ssa/mir/statement.rs
+++ b/src/librustc_codegen_ssa/mir/statement.rs
@@ -16,12 +16,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         self.set_debug_loc(&mut bx, statement.source_info);
         match statement.kind {
-            mir::StatementKind::Assign(ref place, ref rvalue) => {
+            mir::StatementKind::Assign(box(ref place, ref rvalue)) => {
                 if let mir::Place {
                     base: mir::PlaceBase::Local(index),
-                    projection: None,
-                } = *place {
-                    match self.locals[index] {
+                    projection: box [],
+                } = place {
+                    match self.locals[*index] {
                         LocalRef::Place(cg_dest) => {
                             self.codegen_rvalue(bx, cg_dest, rvalue)
                         }
@@ -29,8 +29,22 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             self.codegen_rvalue_unsized(bx, cg_indirect_dest, rvalue)
                         }
                         LocalRef::Operand(None) => {
-                            let (bx, operand) = self.codegen_rvalue_operand(bx, rvalue);
-                            self.locals[index] = LocalRef::Operand(Some(operand));
+                            let (mut bx, operand) = self.codegen_rvalue_operand(bx, rvalue);
+                            if let Some(name) = self.mir.local_decls[*index].name {
+                                match operand.val {
+                                    OperandValue::Ref(x, ..) |
+                                    OperandValue::Immediate(x) => {
+                                        bx.set_var_name(x, name);
+                                    }
+                                    OperandValue::Pair(a, b) => {
+                                        // FIXME(eddyb) these are scalar components,
+                                        // maybe extract the high-level fields?
+                                        bx.set_var_name(a, format_args!("{}.0", name));
+                                        bx.set_var_name(b, format_args!("{}.1", name));
+                                    }
+                                }
+                            }
+                            self.locals[*index] = LocalRef::Operand(Some(operand));
                             bx
                         }
                         LocalRef::Operand(Some(op)) => {
@@ -50,7 +64,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     self.codegen_rvalue(bx, cg_dest, rvalue)
                 }
             }
-            mir::StatementKind::SetDiscriminant{ref place, variant_index} => {
+            mir::StatementKind::SetDiscriminant{box ref place, variant_index} => {
                 self.codegen_place(&mut bx, &place.as_ref())
                     .codegen_set_discr(&mut bx, variant_index);
                 bx
diff --git a/src/librustc_codegen_ssa/traits/builder.rs b/src/librustc_codegen_ssa/traits/builder.rs
index 3a144f0b0e0aa..1886701fb3a88 100644
--- a/src/librustc_codegen_ssa/traits/builder.rs
+++ b/src/librustc_codegen_ssa/traits/builder.rs
@@ -109,13 +109,12 @@ pub trait BuilderMethods<'a, 'tcx>:
         rhs: Self::Value,
     ) -> (Self::Value, Self::Value);
 
-    fn alloca(&mut self, ty: Self::Type, name: &str, align: Align) -> Self::Value;
-    fn dynamic_alloca(&mut self, ty: Self::Type, name: &str, align: Align) -> Self::Value;
+    fn alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
+    fn dynamic_alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
     fn array_alloca(
         &mut self,
         ty: Self::Type,
         len: Self::Value,
-        name: &str,
         align: Align,
     ) -> Self::Value;
 
diff --git a/src/librustc_codegen_ssa/traits/debuginfo.rs b/src/librustc_codegen_ssa/traits/debuginfo.rs
index be2fa7279aa7c..9c16b864ef21d 100644
--- a/src/librustc_codegen_ssa/traits/debuginfo.rs
+++ b/src/librustc_codegen_ssa/traits/debuginfo.rs
@@ -57,5 +57,5 @@ pub trait DebugInfoBuilderMethods<'tcx>: BackendTypes {
         span: Span,
     );
     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self);
-    fn set_value_name(&mut self, value: Self::Value, name: &str);
+    fn set_var_name(&mut self, value: Self::Value, name: impl ToString);
 }
diff --git a/src/librustc_codegen_ssa/traits/intrinsic.rs b/src/librustc_codegen_ssa/traits/intrinsic.rs
index ede30a0bed756..7c79cd6021031 100644
--- a/src/librustc_codegen_ssa/traits/intrinsic.rs
+++ b/src/librustc_codegen_ssa/traits/intrinsic.rs
@@ -1,6 +1,6 @@
 use super::BackendTypes;
 use crate::mir::operand::OperandRef;
-use rustc::ty::Ty;
+use rustc::ty::{self, Ty};
 use rustc_target::abi::call::FnType;
 use syntax_pos::Span;
 
@@ -10,7 +10,7 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
     /// add them to librustc_codegen_llvm/context.rs
     fn codegen_intrinsic_call(
         &mut self,
-        callee_ty: Ty<'tcx>,
+        instance: ty::Instance<'tcx>,
         fn_ty: &FnType<'tcx, Ty<'tcx>>,
         args: &[OperandRef<'tcx, Self::Value>],
         llresult: Self::Value,
diff --git a/src/librustc_codegen_utils/lib.rs b/src/librustc_codegen_utils/lib.rs
index 4ea375b59b2c0..1201446afb531 100644
--- a/src/librustc_codegen_utils/lib.rs
+++ b/src/librustc_codegen_utils/lib.rs
@@ -10,7 +10,6 @@
 #![feature(core_intrinsics)]
 #![feature(never_type)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(in_band_lifetimes)]
 
 #![recursion_limit="256"]
diff --git a/src/librustc_data_structures/Cargo.toml b/src/librustc_data_structures/Cargo.toml
index 288676ce3ff67..be9f79c83bb5a 100644
--- a/src/librustc_data_structures/Cargo.toml
+++ b/src/librustc_data_structures/Cargo.toml
@@ -26,5 +26,5 @@ rustc-hash = "1.0.1"
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
 
 [dependencies.parking_lot]
-version = "0.7"
+version = "0.9"
 features = ["nightly"]
diff --git a/src/librustc_data_structures/indexed_vec.rs b/src/librustc_data_structures/indexed_vec.rs
index 6f40d059be27f..6e80b48a68560 100644
--- a/src/librustc_data_structures/indexed_vec.rs
+++ b/src/librustc_data_structures/indexed_vec.rs
@@ -149,7 +149,7 @@ macro_rules! newtype_index {
 
             #[inline]
             $v const unsafe fn from_u32_unchecked(value: u32) -> Self {
-                unsafe { $type { private: value } }
+                $type { private: value }
             }
 
             /// Extracts the value of this index as an integer.
diff --git a/src/librustc_data_structures/obligation_forest/graphviz.rs b/src/librustc_data_structures/obligation_forest/graphviz.rs
index a0363e165e049..ddf89d99621ca 100644
--- a/src/librustc_data_structures/obligation_forest/graphviz.rs
+++ b/src/librustc_data_structures/obligation_forest/graphviz.rs
@@ -74,9 +74,7 @@ impl<'a, O: ForestObligation + 'a> dot::GraphWalk<'a> for &'a ObligationForest<O
             .flat_map(|i| {
                 let node = &self.nodes[i];
 
-                node.parent.iter().map(|p| p.get())
-                    .chain(node.dependents.iter().map(|p| p.get()))
-                    .map(move |p| (p, i))
+                node.dependents.iter().map(move |&d| (d, i))
             })
             .collect()
     }
diff --git a/src/librustc_data_structures/obligation_forest/mod.rs b/src/librustc_data_structures/obligation_forest/mod.rs
index 04d2b23ab1a1c..98ae1a5832447 100644
--- a/src/librustc_data_structures/obligation_forest/mod.rs
+++ b/src/librustc_data_structures/obligation_forest/mod.rs
@@ -9,7 +9,7 @@
 //! `ObligationForest` supports two main public operations (there are a
 //! few others not discussed here):
 //!
-//! 1. Add a new root obligations (`push_tree`).
+//! 1. Add a new root obligations (`register_obligation`).
 //! 2. Process the pending obligations (`process_obligations`).
 //!
 //! When a new obligation `N` is added, it becomes the root of an
@@ -20,13 +20,13 @@
 //! with every pending obligation (so that will include `N`, the first
 //! time). The callback also receives a (mutable) reference to the
 //! per-tree state `T`. The callback should process the obligation `O`
-//! that it is given and return one of three results:
+//! that it is given and return a `ProcessResult`:
 //!
-//! - `Ok(None)` -> ambiguous result. Obligation was neither a success
+//! - `Unchanged` -> ambiguous result. Obligation was neither a success
 //!   nor a failure. It is assumed that further attempts to process the
 //!   obligation will yield the same result unless something in the
 //!   surrounding environment changes.
-//! - `Ok(Some(C))` - the obligation was *shallowly successful*. The
+//! - `Changed(C)` - the obligation was *shallowly successful*. The
 //!   vector `C` is a list of subobligations. The meaning of this is that
 //!   `O` was successful on the assumption that all the obligations in `C`
 //!   are also successful. Therefore, `O` is only considered a "true"
@@ -34,7 +34,7 @@
 //!   state and the obligations in `C` become the new pending
 //!   obligations. They will be processed the next time you call
 //!   `process_obligations`.
-//! - `Err(E)` -> obligation failed with error `E`. We will collect this
+//! - `Error(E)` -> obligation failed with error `E`. We will collect this
 //!   error and return it from `process_obligations`, along with the
 //!   "backtrace" of obligations (that is, the list of obligations up to
 //!   and including the root of the failed obligation). No further
@@ -47,50 +47,39 @@
 //! - `completed`: a list of obligations where processing was fully
 //!   completed without error (meaning that all transitive subobligations
 //!   have also been completed). So, for example, if the callback from
-//!   `process_obligations` returns `Ok(Some(C))` for some obligation `O`,
+//!   `process_obligations` returns `Changed(C)` for some obligation `O`,
 //!   then `O` will be considered completed right away if `C` is the
 //!   empty vector. Otherwise it will only be considered completed once
 //!   all the obligations in `C` have been found completed.
 //! - `errors`: a list of errors that occurred and associated backtraces
 //!   at the time of error, which can be used to give context to the user.
 //! - `stalled`: if true, then none of the existing obligations were
-//!   *shallowly successful* (that is, no callback returned `Ok(Some(_))`).
+//!   *shallowly successful* (that is, no callback returned `Changed(_)`).
 //!   This implies that all obligations were either errors or returned an
 //!   ambiguous result, which means that any further calls to
 //!   `process_obligations` would simply yield back further ambiguous
 //!   results. This is used by the `FulfillmentContext` to decide when it
 //!   has reached a steady state.
 //!
-//! #### Snapshots
-//!
-//! The `ObligationForest` supports a limited form of snapshots; see
-//! `start_snapshot`, `commit_snapshot`, and `rollback_snapshot`. In
-//! particular, you can use a snapshot to roll back new root
-//! obligations. However, it is an error to attempt to
-//! `process_obligations` during a snapshot.
-//!
 //! ### Implementation details
 //!
 //! For the most part, comments specific to the implementation are in the
 //! code. This file only contains a very high-level overview. Basically,
 //! the forest is stored in a vector. Each element of the vector is a node
-//! in some tree. Each node in the vector has the index of an (optional)
-//! parent and (for convenience) its root (which may be itself). It also
-//! has a current state, described by `NodeState`. After each
-//! processing step, we compress the vector to remove completed and error
-//! nodes, which aren't needed anymore.
+//! in some tree. Each node in the vector has the index of its dependents,
+//! including the first dependent which is known as the parent. It also
+//! has a current state, described by `NodeState`. After each processing
+//! step, we compress the vector to remove completed and error nodes, which
+//! aren't needed anymore.
 
 use crate::fx::{FxHashMap, FxHashSet};
 
-use std::cell::Cell;
+use std::cell::{Cell, RefCell};
 use std::collections::hash_map::Entry;
 use std::fmt::Debug;
 use std::hash;
 use std::marker::PhantomData;
 
-mod node_index;
-use self::node_index::NodeIndex;
-
 mod graphviz;
 
 #[cfg(test)]
@@ -148,18 +137,23 @@ pub struct ObligationForest<O: ForestObligation> {
     /// At the end of processing, those nodes will be removed by a
     /// call to `compress`.
     ///
-    /// At all times we maintain the invariant that every node appears
-    /// at a higher index than its parent. This is needed by the
-    /// backtrace iterator (which uses `split_at`).
+    /// `usize` indices are used here and throughout this module, rather than
+    /// `newtype_index!` indices, because this code is hot enough that the
+    /// `u32`-to-`usize` conversions that would be required are significant,
+    /// and space considerations are not important.
     nodes: Vec<Node<O>>,
 
     /// A cache of predicates that have been successfully completed.
     done_cache: FxHashSet<O::Predicate>,
 
-    /// An cache of the nodes in `nodes`, indexed by predicate.
-    waiting_cache: FxHashMap<O::Predicate, NodeIndex>,
+    /// A cache of the nodes in `nodes`, indexed by predicate. Unfortunately,
+    /// its contents are not guaranteed to match those of `nodes`. See the
+    /// comments in `process_obligation` for details.
+    waiting_cache: FxHashMap<O::Predicate, usize>,
 
-    scratch: Option<Vec<usize>>,
+    /// A scratch vector reused in various operations, to avoid allocating new
+    /// vectors.
+    scratch: RefCell<Vec<usize>>,
 
     obligation_tree_id_generator: ObligationTreeIdGenerator,
 
@@ -178,19 +172,42 @@ struct Node<O> {
     obligation: O,
     state: Cell<NodeState>,
 
-    /// The parent of a node - the original obligation of
-    /// which it is a subobligation. Except for error reporting,
-    /// it is just like any member of `dependents`.
-    parent: Option<NodeIndex>,
+    /// Obligations that depend on this obligation for their completion. They
+    /// must all be in a non-pending state.
+    dependents: Vec<usize>,
 
-    /// Obligations that depend on this obligation for their
-    /// completion. They must all be in a non-pending state.
-    dependents: Vec<NodeIndex>,
+    /// If true, dependents[0] points to a "parent" node, which requires
+    /// special treatment upon error but is otherwise treated the same.
+    /// (It would be more idiomatic to store the parent node in a separate
+    /// `Option<usize>` field, but that slows down the common case of
+    /// iterating over the parent and other descendants together.)
+    has_parent: bool,
 
     /// Identifier of the obligation tree to which this node belongs.
     obligation_tree_id: ObligationTreeId,
 }
 
+impl<O> Node<O> {
+    fn new(
+        parent: Option<usize>,
+        obligation: O,
+        obligation_tree_id: ObligationTreeId
+    ) -> Node<O> {
+        Node {
+            obligation,
+            state: Cell::new(NodeState::Pending),
+            dependents:
+                if let Some(parent_index) = parent {
+                    vec![parent_index]
+                } else {
+                    vec![]
+                },
+            has_parent: parent.is_some(),
+            obligation_tree_id,
+        }
+    }
+}
+
 /// The state of one node in some tree within the forest. This
 /// represents the current state of processing for the obligation (of
 /// type `O`) associated with this node.
@@ -262,7 +279,7 @@ impl<O: ForestObligation> ObligationForest<O> {
             nodes: vec![],
             done_cache: Default::default(),
             waiting_cache: Default::default(),
-            scratch: Some(vec![]),
+            scratch: RefCell::new(vec![]),
             obligation_tree_id_generator: (0..).map(ObligationTreeId),
             error_cache: Default::default(),
         }
@@ -275,17 +292,13 @@ impl<O: ForestObligation> ObligationForest<O> {
     }
 
     /// Registers an obligation.
-    ///
-    /// This CAN be done in a snapshot
     pub fn register_obligation(&mut self, obligation: O) {
         // Ignore errors here - there is no guarantee of success.
         let _ = self.register_obligation_at(obligation, None);
     }
 
-    // returns Err(()) if we already know this obligation failed.
-    fn register_obligation_at(&mut self, obligation: O, parent: Option<NodeIndex>)
-                              -> Result<(), ()>
-    {
+    // Returns Err(()) if we already know this obligation failed.
+    fn register_obligation_at(&mut self, obligation: O, parent: Option<usize>) -> Result<(), ()> {
         if self.done_cache.contains(obligation.as_predicate()) {
             return Ok(());
         }
@@ -294,15 +307,14 @@ impl<O: ForestObligation> ObligationForest<O> {
             Entry::Occupied(o) => {
                 debug!("register_obligation_at({:?}, {:?}) - duplicate of {:?}!",
                        obligation, parent, o.get());
-                let node = &mut self.nodes[o.get().get()];
-                if let Some(parent) = parent {
-                    // If the node is already in `waiting_cache`, it's already
-                    // been marked with a parent. (It's possible that parent
-                    // has been cleared by `apply_rewrites`, though.) So just
-                    // dump `parent` into `node.dependents`... unless it's
-                    // already in `node.dependents` or `node.parent`.
-                    if !node.dependents.contains(&parent) && Some(parent) != node.parent {
-                        node.dependents.push(parent);
+                let node = &mut self.nodes[*o.get()];
+                if let Some(parent_index) = parent {
+                    // If the node is already in `waiting_cache`, it has
+                    // already had its chance to be marked with a parent. So if
+                    // it's not already present, just dump `parent` into the
+                    // dependents as a non-parent.
+                    if !node.dependents.contains(&parent_index) {
+                        node.dependents.push(parent_index);
                     }
                 }
                 if let NodeState::Error = node.state.get() {
@@ -316,11 +328,8 @@ impl<O: ForestObligation> ObligationForest<O> {
                        obligation, parent, self.nodes.len());
 
                 let obligation_tree_id = match parent {
-                    Some(p) => {
-                        let parent_node = &self.nodes[p.get()];
-                        parent_node.obligation_tree_id
-                    }
-                    None => self.obligation_tree_id_generator.next().unwrap()
+                    Some(parent_index) => self.nodes[parent_index].obligation_tree_id,
+                    None => self.obligation_tree_id_generator.next().unwrap(),
                 };
 
                 let already_failed =
@@ -333,7 +342,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                 if already_failed {
                     Err(())
                 } else {
-                    v.insert(NodeIndex::new(self.nodes.len()));
+                    v.insert(self.nodes.len());
                     self.nodes.push(Node::new(parent, obligation, obligation_tree_id));
                     Ok(())
                 }
@@ -342,12 +351,10 @@ impl<O: ForestObligation> ObligationForest<O> {
     }
 
     /// Converts all remaining obligations to the given error.
-    ///
-    /// This cannot be done during a snapshot.
     pub fn to_errors<E: Clone>(&mut self, error: E) -> Vec<Error<O, E>> {
         let mut errors = vec![];
-        for index in 0..self.nodes.len() {
-            if let NodeState::Pending = self.nodes[index].state.get() {
+        for (index, node) in self.nodes.iter().enumerate() {
+            if let NodeState::Pending = node.state.get() {
                 let backtrace = self.error_at(index);
                 errors.push(Error {
                     error: error.clone(),
@@ -373,7 +380,6 @@ impl<O: ForestObligation> ObligationForest<O> {
 
     fn insert_into_error_cache(&mut self, node_index: usize) {
         let node = &self.nodes[node_index];
-
         self.error_cache
             .entry(node.obligation_tree_id)
             .or_default()
@@ -394,11 +400,17 @@ impl<O: ForestObligation> ObligationForest<O> {
         let mut stalled = true;
 
         for index in 0..self.nodes.len() {
-            debug!("process_obligations: node {} == {:?}", index, self.nodes[index]);
+            let node = &mut self.nodes[index];
+
+            debug!("process_obligations: node {} == {:?}", index, node);
 
-            let result = match self.nodes[index] {
-                Node { ref state, ref mut obligation, .. } if state.get() == NodeState::Pending =>
-                    processor.process_obligation(obligation),
+            // `processor.process_obligation` can modify the predicate within
+            // `node.obligation`, and that predicate is the key used for
+            // `self.waiting_cache`. This means that `self.waiting_cache` can
+            // get out of sync with `nodes`. It's not very common, but it does
+            // happen, and code in `compress` has to allow for it.
+            let result = match node.state.get() {
+                NodeState::Pending => processor.process_obligation(&mut node.obligation),
                 _ => continue
             };
 
@@ -411,15 +423,15 @@ impl<O: ForestObligation> ObligationForest<O> {
                 ProcessResult::Changed(children) => {
                     // We are not (yet) stalled.
                     stalled = false;
-                    self.nodes[index].state.set(NodeState::Success);
+                    node.state.set(NodeState::Success);
 
                     for child in children {
                         let st = self.register_obligation_at(
                             child,
-                            Some(NodeIndex::new(index))
+                            Some(index)
                         );
                         if let Err(()) = st {
-                            // error already reported - propagate it
+                            // Error already reported - propagate it
                             // to our node.
                             self.error_at(index);
                         }
@@ -448,8 +460,6 @@ impl<O: ForestObligation> ObligationForest<O> {
 
         self.mark_as_waiting();
         self.process_cycles(processor);
-
-        // Now we have to compress the result
         let completed = self.compress(do_completed);
 
         debug!("process_obligations: complete");
@@ -465,21 +475,20 @@ impl<O: ForestObligation> ObligationForest<O> {
     /// report all cycles between them. This should be called
     /// after `mark_as_waiting` marks all nodes with pending
     /// subobligations as NodeState::Waiting.
-    fn process_cycles<P>(&mut self, processor: &mut P)
+    fn process_cycles<P>(&self, processor: &mut P)
         where P: ObligationProcessor<Obligation=O>
     {
-        let mut stack = self.scratch.take().unwrap();
+        let mut stack = self.scratch.replace(vec![]);
         debug_assert!(stack.is_empty());
 
         debug!("process_cycles()");
 
-        for index in 0..self.nodes.len() {
+        for (index, node) in self.nodes.iter().enumerate() {
             // For rustc-benchmarks/inflate-0.1.0 this state test is extremely
             // hot and the state is almost always `Pending` or `Waiting`. It's
             // a win to handle the no-op cases immediately to avoid the cost of
             // the function call.
-            let state = self.nodes[index].state.get();
-            match state {
+            match node.state.get() {
                 NodeState::Waiting | NodeState::Pending | NodeState::Done | NodeState::Error => {},
                 _ => self.find_cycles_from_node(&mut stack, processor, index),
             }
@@ -488,84 +497,88 @@ impl<O: ForestObligation> ObligationForest<O> {
         debug!("process_cycles: complete");
 
         debug_assert!(stack.is_empty());
-        self.scratch = Some(stack);
+        self.scratch.replace(stack);
     }
 
-    fn find_cycles_from_node<P>(&self, stack: &mut Vec<usize>,
-                                processor: &mut P, index: usize)
+    fn find_cycles_from_node<P>(&self, stack: &mut Vec<usize>, processor: &mut P, index: usize)
         where P: ObligationProcessor<Obligation=O>
     {
         let node = &self.nodes[index];
-        let state = node.state.get();
-        match state {
+        match node.state.get() {
             NodeState::OnDfsStack => {
-                let index =
-                    stack.iter().rposition(|n| *n == index).unwrap();
+                let index = stack.iter().rposition(|&n| n == index).unwrap();
                 processor.process_backedge(stack[index..].iter().map(GetObligation(&self.nodes)),
                                            PhantomData);
             }
             NodeState::Success => {
                 node.state.set(NodeState::OnDfsStack);
                 stack.push(index);
-                for dependent in node.parent.iter().chain(node.dependents.iter()) {
-                    self.find_cycles_from_node(stack, processor, dependent.get());
+                for &index in node.dependents.iter() {
+                    self.find_cycles_from_node(stack, processor, index);
                 }
                 stack.pop();
                 node.state.set(NodeState::Done);
             },
             NodeState::Waiting | NodeState::Pending => {
-                // this node is still reachable from some pending node. We
+                // This node is still reachable from some pending node. We
                 // will get to it when they are all processed.
             }
             NodeState::Done | NodeState::Error => {
-                // already processed that node
+                // Already processed that node.
             }
         };
     }
 
     /// Returns a vector of obligations for `p` and all of its
     /// ancestors, putting them into the error state in the process.
-    fn error_at(&mut self, p: usize) -> Vec<O> {
-        let mut error_stack = self.scratch.take().unwrap();
+    fn error_at(&self, mut index: usize) -> Vec<O> {
+        let mut error_stack = self.scratch.replace(vec![]);
         let mut trace = vec![];
 
-        let mut n = p;
         loop {
-            self.nodes[n].state.set(NodeState::Error);
-            trace.push(self.nodes[n].obligation.clone());
-            error_stack.extend(self.nodes[n].dependents.iter().map(|x| x.get()));
-
-            // loop to the parent
-            match self.nodes[n].parent {
-                Some(q) => n = q.get(),
-                None => break
+            let node = &self.nodes[index];
+            node.state.set(NodeState::Error);
+            trace.push(node.obligation.clone());
+            if node.has_parent {
+                // The first dependent is the parent, which is treated
+                // specially.
+                error_stack.extend(node.dependents.iter().skip(1));
+                index = node.dependents[0];
+            } else {
+                // No parent; treat all dependents non-specially.
+                error_stack.extend(node.dependents.iter());
+                break;
             }
         }
 
-        while let Some(i) = error_stack.pop() {
-            match self.nodes[i].state.get() {
+        while let Some(index) = error_stack.pop() {
+            let node = &self.nodes[index];
+            match node.state.get() {
                 NodeState::Error => continue,
-                _ => self.nodes[i].state.set(NodeState::Error),
+                _ => node.state.set(NodeState::Error),
             }
 
-            let node = &self.nodes[i];
-
-            error_stack.extend(
-                node.parent.iter().chain(node.dependents.iter()).map(|x| x.get())
-            );
+            error_stack.extend(node.dependents.iter());
         }
 
-        self.scratch = Some(error_stack);
+        self.scratch.replace(error_stack);
         trace
     }
 
-    #[inline]
-    fn mark_neighbors_as_waiting_from(&self, node: &Node<O>) {
-        for dependent in node.parent.iter().chain(node.dependents.iter()) {
-            self.mark_as_waiting_from(&self.nodes[dependent.get()]);
+    // This always-inlined function is for the hot call site.
+    #[inline(always)]
+    fn inlined_mark_neighbors_as_waiting_from(&self, node: &Node<O>) {
+        for &index in node.dependents.iter() {
+            self.mark_as_waiting_from(&self.nodes[index]);
         }
     }
 
+    // This never-inlined function is for the cold call site.
+    #[inline(never)]
+    fn uninlined_mark_neighbors_as_waiting_from(&self, node: &Node<O>) {
+        self.inlined_mark_neighbors_as_waiting_from(node)
+    }
+
     /// Marks all nodes that depend on a pending node as `NodeState::Waiting`.
     fn mark_as_waiting(&self) {
         for node in &self.nodes {
@@ -576,7 +589,8 @@ impl<O: ForestObligation> ObligationForest<O> {
 
         for node in &self.nodes {
             if node.state.get() == NodeState::Pending {
-                self.mark_neighbors_as_waiting_from(node);
+                // This call site is hot.
+                self.inlined_mark_neighbors_as_waiting_from(node);
             }
         }
     }
@@ -588,7 +602,8 @@ impl<O: ForestObligation> ObligationForest<O> {
             NodeState::Pending | NodeState::Done => {},
         }
 
-        self.mark_neighbors_as_waiting_from(node);
+        // This call site is cold.
+        self.uninlined_mark_neighbors_as_waiting_from(node);
     }
 
     /// Compresses the vector, removing all popped nodes. This adjusts
@@ -600,44 +615,48 @@ impl<O: ForestObligation> ObligationForest<O> {
     #[inline(never)]
     fn compress(&mut self, do_completed: DoCompleted) -> Option<Vec<O>> {
         let nodes_len = self.nodes.len();
-        let mut node_rewrites: Vec<_> = self.scratch.take().unwrap();
+        let mut node_rewrites: Vec<_> = self.scratch.replace(vec![]);
         node_rewrites.extend(0..nodes_len);
         let mut dead_nodes = 0;
 
         // Now move all popped nodes to the end. Try to keep the order.
         //
         // LOOP INVARIANT:
-        //     self.nodes[0..i - dead_nodes] are the first remaining nodes
-        //     self.nodes[i - dead_nodes..i] are all dead
-        //     self.nodes[i..] are unchanged
-        for i in 0..self.nodes.len() {
-            match self.nodes[i].state.get() {
+        //     self.nodes[0..index - dead_nodes] are the first remaining nodes
+        //     self.nodes[index - dead_nodes..index] are all dead
+        //     self.nodes[index..] are unchanged
+        for index in 0..self.nodes.len() {
+            let node = &self.nodes[index];
+            match node.state.get() {
                 NodeState::Pending | NodeState::Waiting => {
                     if dead_nodes > 0 {
-                        self.nodes.swap(i, i - dead_nodes);
-                        node_rewrites[i] -= dead_nodes;
+                        self.nodes.swap(index, index - dead_nodes);
+                        node_rewrites[index] -= dead_nodes;
                     }
                 }
                 NodeState::Done => {
-                    // Avoid cloning the key (predicate) in case it exists in the waiting cache
+                    // This lookup can fail because the contents of
+                    // `self.waiting_cache` is not guaranteed to match those of
+                    // `self.nodes`. See the comment in `process_obligation`
+                    // for more details.
                     if let Some((predicate, _)) = self.waiting_cache
-                        .remove_entry(self.nodes[i].obligation.as_predicate())
+                        .remove_entry(node.obligation.as_predicate())
                     {
                         self.done_cache.insert(predicate);
                     } else {
-                        self.done_cache.insert(self.nodes[i].obligation.as_predicate().clone());
+                        self.done_cache.insert(node.obligation.as_predicate().clone());
                     }
-                    node_rewrites[i] = nodes_len;
+                    node_rewrites[index] = nodes_len;
                     dead_nodes += 1;
                 }
                 NodeState::Error => {
                     // We *intentionally* remove the node from the cache at this point. Otherwise
                     // tests must come up with a different type on every type error they
                     // check against.
-                    self.waiting_cache.remove(self.nodes[i].obligation.as_predicate());
-                    node_rewrites[i] = nodes_len;
+                    self.waiting_cache.remove(node.obligation.as_predicate());
+                    node_rewrites[index] = nodes_len;
                     dead_nodes += 1;
-                    self.insert_into_error_cache(i);
+                    self.insert_into_error_cache(index);
                 }
                 NodeState::OnDfsStack | NodeState::Success => unreachable!()
             }
@@ -646,12 +665,11 @@ impl<O: ForestObligation> ObligationForest<O> {
         // No compression needed.
         if dead_nodes == 0 {
             node_rewrites.truncate(0);
-            self.scratch = Some(node_rewrites);
+            self.scratch.replace(node_rewrites);
             return if do_completed == DoCompleted::Yes { Some(vec![]) } else { None };
         }
 
-        // Pop off all the nodes we killed and extract the success
-        // stories.
+        // Pop off all the nodes we killed and extract the success stories.
         let successful = if do_completed == DoCompleted::Yes {
             Some((0..dead_nodes)
                 .map(|_| self.nodes.pop().unwrap())
@@ -670,7 +688,7 @@ impl<O: ForestObligation> ObligationForest<O> {
         self.apply_rewrites(&node_rewrites);
 
         node_rewrites.truncate(0);
-        self.scratch = Some(node_rewrites);
+        self.scratch.replace(node_rewrites);
 
         successful
     }
@@ -679,59 +697,37 @@ impl<O: ForestObligation> ObligationForest<O> {
         let nodes_len = node_rewrites.len();
 
         for node in &mut self.nodes {
-            if let Some(index) = node.parent {
-                let new_index = node_rewrites[index.get()];
-                if new_index >= nodes_len {
-                    // parent dead due to error
-                    node.parent = None;
-                } else {
-                    node.parent = Some(NodeIndex::new(new_index));
-                }
-            }
-
-            let mut i = 0;
-            while i < node.dependents.len() {
-                let new_index = node_rewrites[node.dependents[i].get()];
+            let mut index = 0;
+            while index < node.dependents.len() {
+                let new_index = node_rewrites[node.dependents[index]];
                 if new_index >= nodes_len {
-                    node.dependents.swap_remove(i);
+                    node.dependents.swap_remove(index);
+                    if index == 0 && node.has_parent {
+                        // We just removed the parent.
+                        node.has_parent = false;
+                    }
                 } else {
-                    node.dependents[i] = NodeIndex::new(new_index);
-                    i += 1;
+                    node.dependents[index] = new_index;
+                    index += 1;
                 }
             }
         }
 
-        let mut kill_list = vec![];
-        for (predicate, index) in &mut self.waiting_cache {
-            let new_index = node_rewrites[index.get()];
+        // This updating of `self.waiting_cache` is necessary because the
+        // removal of nodes within `compress` can fail. See above.
+        self.waiting_cache.retain(|_predicate, index| {
+            let new_index = node_rewrites[*index];
             if new_index >= nodes_len {
-                kill_list.push(predicate.clone());
+                false
             } else {
-                *index = NodeIndex::new(new_index);
+                *index = new_index;
+                true
             }
-        }
-
-        for predicate in kill_list { self.waiting_cache.remove(&predicate); }
-    }
-}
-
-impl<O> Node<O> {
-    fn new(
-        parent: Option<NodeIndex>,
-        obligation: O,
-        obligation_tree_id: ObligationTreeId
-    ) -> Node<O> {
-        Node {
-            obligation,
-            state: Cell::new(NodeState::Pending),
-            parent,
-            dependents: vec![],
-            obligation_tree_id,
-        }
+        });
     }
 }
 
-// I need a Clone closure
+// I need a Clone closure.
 #[derive(Clone)]
 struct GetObligation<'a, O>(&'a [Node<O>]);
 
diff --git a/src/librustc_data_structures/obligation_forest/node_index.rs b/src/librustc_data_structures/obligation_forest/node_index.rs
deleted file mode 100644
index 69ea473e05461..0000000000000
--- a/src/librustc_data_structures/obligation_forest/node_index.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-use std::num::NonZeroU32;
-use std::u32;
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub struct NodeIndex {
-    index: NonZeroU32,
-}
-
-impl NodeIndex {
-    #[inline]
-    pub fn new(value: usize) -> NodeIndex {
-        assert!(value < (u32::MAX as usize));
-        NodeIndex { index: NonZeroU32::new((value as u32) + 1).unwrap() }
-    }
-
-    #[inline]
-    pub fn get(self) -> usize {
-        (self.index.get() - 1) as usize
-    }
-}
diff --git a/src/librustc_driver/Cargo.toml b/src/librustc_driver/Cargo.toml
index b030517e28ec2..25f67b30468cc 100644
--- a/src/librustc_driver/Cargo.toml
+++ b/src/librustc_driver/Cargo.toml
@@ -11,8 +11,9 @@ crate-type = ["dylib"]
 
 [dependencies]
 graphviz = { path = "../libgraphviz" }
+lazy_static = "1.0"
 log = "0.4"
-env_logger = { version = "0.5", default-features = false }
+env_logger = { version = "0.6", default-features = false }
 rustc = { path = "../librustc" }
 rustc_target = { path = "../librustc_target" }
 rustc_ast_borrowck = { path = "../librustc_ast_borrowck" }
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 9a6a12e261c10..8c5d8536c32fa 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -9,7 +9,6 @@
 #![feature(box_syntax)]
 #![cfg_attr(unix, feature(libc))]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(set_stdio)]
 #![feature(no_debug)]
 #![feature(integer_atomics)]
@@ -21,6 +20,8 @@ pub extern crate getopts;
 extern crate libc;
 #[macro_use]
 extern crate log;
+#[macro_use]
+extern crate lazy_static;
 
 pub extern crate rustc_plugin_impl as plugin;
 
@@ -36,8 +37,8 @@ use rustc::session::{early_error, early_warn};
 use rustc::lint::Lint;
 use rustc::lint;
 use rustc::hir::def_id::LOCAL_CRATE;
-use rustc::util::common::{ErrorReported, install_panic_hook, print_time_passes_entry};
-use rustc::util::common::{set_time_depth, time};
+use rustc::ty::TyCtxt;
+use rustc::util::common::{set_time_depth, time, print_time_passes_entry, ErrorReported};
 use rustc_metadata::locator;
 use rustc_metadata::cstore::CStore;
 use rustc_codegen_utils::codegen_backend::CodegenBackend;
@@ -133,8 +134,11 @@ pub struct TimePassesCallbacks {
 
 impl Callbacks for TimePassesCallbacks {
     fn config(&mut self, config: &mut interface::Config) {
+        // If a --prints=... option has been given, we don't print the "total"
+        // time because it will mess up the --prints output. See #64339.
         self.time_passes =
-            config.opts.debugging_opts.time_passes || config.opts.debugging_opts.time;
+            config.opts.prints.is_empty() &&
+            (config.opts.debugging_opts.time_passes || config.opts.debugging_opts.time);
     }
 }
 
@@ -162,8 +166,6 @@ pub fn run_compiler(
         None => return Ok(()),
     };
 
-    install_panic_hook();
-
     let (sopts, cfg) = config::build_session_options_and_crate_config(&matches);
 
     let mut dummy_config = |sopts, cfg, diagnostic_output| {
@@ -1152,61 +1154,105 @@ fn extra_compiler_flags() -> Option<(Vec<String>, bool)> {
     }
 }
 
-/// Runs a procedure which will detect panics in the compiler and print nicer
-/// error messages rather than just failing the test.
+/// Runs a closure and catches unwinds triggered by fatal errors.
 ///
-/// The diagnostic emitter yielded to the procedure should be used for reporting
-/// errors of the compiler.
-pub fn report_ices_to_stderr_if_any<F: FnOnce() -> R, R>(f: F) -> Result<R, ErrorReported> {
+/// The compiler currently unwinds with a special sentinel value to abort
+/// compilation on fatal errors. This function catches that sentinel and turns
+/// the panic into a `Result` instead.
+pub fn catch_fatal_errors<F: FnOnce() -> R, R>(f: F) -> Result<R, ErrorReported> {
     catch_unwind(panic::AssertUnwindSafe(f)).map_err(|value| {
         if value.is::<errors::FatalErrorMarker>() {
             ErrorReported
         } else {
-            // Thread panicked without emitting a fatal diagnostic
-            eprintln!("");
-
-            let emitter = Box::new(errors::emitter::EmitterWriter::stderr(
-                errors::ColorConfig::Auto,
-                None,
-                false,
-                false,
-                None,
-            ));
-            let handler = errors::Handler::with_emitter(true, None, emitter);
-
-            // a .span_bug or .bug call has already printed what
-            // it wants to print.
-            if !value.is::<errors::ExplicitBug>() {
-                handler.emit(&MultiSpan::new(),
-                             "unexpected panic",
-                             errors::Level::Bug);
-            }
+            panic::resume_unwind(value);
+        }
+    })
+}
 
-            let mut xs: Vec<Cow<'static, str>> = vec![
-                "the compiler unexpectedly panicked. this is a bug.".into(),
-                format!("we would appreciate a bug report: {}", BUG_REPORT_URL).into(),
-                format!("rustc {} running on {}",
-                        option_env!("CFG_VERSION").unwrap_or("unknown_version"),
-                        config::host_triple()).into(),
-            ];
+lazy_static! {
+    static ref DEFAULT_HOOK: Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static> = {
+        let hook = panic::take_hook();
+        panic::set_hook(Box::new(|info| report_ice(info, BUG_REPORT_URL)));
+        hook
+    };
+}
 
-            if let Some((flags, excluded_cargo_defaults)) = extra_compiler_flags() {
-                xs.push(format!("compiler flags: {}", flags.join(" ")).into());
+/// Prints the ICE message, including backtrace and query stack.
+///
+/// The message will point the user at `bug_report_url` to report the ICE.
+///
+/// When `install_ice_hook` is called, this function will be called as the panic
+/// hook.
+pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
+    // Invoke the default handler, which prints the actual panic message and optionally a backtrace
+    (*DEFAULT_HOOK)(info);
+
+    // Separate the output with an empty line
+    eprintln!();
+
+    let emitter = Box::new(errors::emitter::EmitterWriter::stderr(
+        errors::ColorConfig::Auto,
+        None,
+        false,
+        false,
+        None,
+    ));
+    let handler = errors::Handler::with_emitter(true, None, emitter);
+
+    // a .span_bug or .bug call has already printed what
+    // it wants to print.
+    if !info.payload().is::<errors::ExplicitBug>() {
+        handler.emit(&MultiSpan::new(),
+                     "unexpected panic",
+                     errors::Level::Bug);
+    }
 
-                if excluded_cargo_defaults {
-                    xs.push("some of the compiler flags provided by cargo are hidden".into());
-                }
-            }
+    let mut xs: Vec<Cow<'static, str>> = vec![
+        "the compiler unexpectedly panicked. this is a bug.".into(),
+        format!("we would appreciate a bug report: {}", bug_report_url).into(),
+        format!("rustc {} running on {}",
+                option_env!("CFG_VERSION").unwrap_or("unknown_version"),
+                config::host_triple()).into(),
+    ];
 
-            for note in &xs {
-                handler.emit(&MultiSpan::new(),
-                             note,
-                             errors::Level::Note);
-            }
+    if let Some((flags, excluded_cargo_defaults)) = extra_compiler_flags() {
+        xs.push(format!("compiler flags: {}", flags.join(" ")).into());
 
-            panic::resume_unwind(Box::new(errors::FatalErrorMarker));
+        if excluded_cargo_defaults {
+            xs.push("some of the compiler flags provided by cargo are hidden".into());
         }
-    })
+    }
+
+    for note in &xs {
+        handler.emit(&MultiSpan::new(),
+                     note,
+                     errors::Level::Note);
+    }
+
+    // If backtraces are enabled, also print the query stack
+    let backtrace = env::var_os("RUST_BACKTRACE").map(|x| &x != "0").unwrap_or(false);
+
+    if backtrace {
+        TyCtxt::try_print_query_stack();
+    }
+
+    #[cfg(windows)]
+    unsafe {
+        if env::var("RUSTC_BREAK_ON_ICE").is_ok() {
+            extern "system" {
+                fn DebugBreak();
+            }
+            // Trigger a debugger if we crashed during bootstrap
+            DebugBreak();
+        }
+    }
+}
+
+/// Installs a panic hook that will print the ICE message on unexpected panics.
+///
+/// A custom rustc driver can skip calling this to set up a custom ICE hook.
+pub fn install_ice_hook() {
+    lazy_static::initialize(&DEFAULT_HOOK);
 }
 
 /// This allows tools to enable rust logging without having to magically match rustc's
@@ -1219,7 +1265,8 @@ pub fn main() {
     let start = Instant::now();
     init_rustc_env_logger();
     let mut callbacks = TimePassesCallbacks::default();
-    let result = report_ices_to_stderr_if_any(|| {
+    install_ice_hook();
+    let result = catch_fatal_errors(|| {
         let args = env::args_os().enumerate()
             .map(|(i, arg)| arg.into_string().unwrap_or_else(|arg| {
                     early_error(ErrorOutputType::default(),
diff --git a/src/librustc_driver/pretty.rs b/src/librustc_driver/pretty.rs
index cb17401f6247b..fa9504e22019e 100644
--- a/src/librustc_driver/pretty.rs
+++ b/src/librustc_driver/pretty.rs
@@ -1,7 +1,5 @@
 //! The various pretty-printing routines.
 
-use rustc::cfg;
-use rustc::cfg::graphviz::LabelledCFG;
 use rustc::hir;
 use rustc::hir::map as hir_map;
 use rustc::hir::map::blocks;
@@ -14,6 +12,7 @@ use rustc::util::common::ErrorReported;
 use rustc_interface::util::ReplaceBodyWithLoop;
 use rustc_ast_borrowck as borrowck;
 use rustc_ast_borrowck::graphviz as borrowck_dot;
+use rustc_ast_borrowck::cfg::{self, graphviz::LabelledCFG};
 use rustc_mir::util::{write_mir_pretty, write_mir_graphviz};
 
 use syntax::ast;
@@ -327,6 +326,7 @@ impl<'hir> pprust::PpAnn for IdentifiedAnnotation<'hir> {
     }
     fn post(&self, s: &mut pprust::State<'_>, node: pprust::AnnNode<'_>) {
         match node {
+            pprust::AnnNode::Crate(_) |
             pprust::AnnNode::Ident(_) |
             pprust::AnnNode::Name(_) => {},
 
@@ -432,14 +432,18 @@ impl<'a> pprust::PpAnn for HygieneAnnotation<'a> {
         match node {
             pprust::AnnNode::Ident(&ast::Ident { name, span }) => {
                 s.s.space();
-                // FIXME #16420: this doesn't display the connections
-                // between syntax contexts
                 s.synth_comment(format!("{}{:?}", name.as_u32(), span.ctxt()))
             }
             pprust::AnnNode::Name(&name) => {
                 s.s.space();
                 s.synth_comment(name.as_u32().to_string())
             }
+            pprust::AnnNode::Crate(_) => {
+                s.s.hardbreak();
+                let verbose = self.sess.verbose();
+                s.synth_comment(syntax_pos::hygiene::debug_hygiene_data(verbose));
+                s.s.hardbreak_if_not_bol();
+            }
             _ => {}
         }
     }
diff --git a/src/librustc_errors/annotate_snippet_emitter_writer.rs b/src/librustc_errors/annotate_snippet_emitter_writer.rs
index 3bed5d81dc514..c626dd0434d52 100644
--- a/src/librustc_errors/annotate_snippet_emitter_writer.rs
+++ b/src/librustc_errors/annotate_snippet_emitter_writer.rs
@@ -30,10 +30,14 @@ pub struct AnnotateSnippetEmitterWriter {
 impl Emitter for AnnotateSnippetEmitterWriter {
     /// The entry point for the diagnostics generation
     fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
-        let children = db.children.clone();
-        let (primary_span, suggestions) = self.primary_span_formatted(&db);
+        let mut children = db.children.clone();
+        let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
 
-        // FIXME(#59346): Add `fix_multispans_in_std_macros` function from emitter.rs
+        self.fix_multispans_in_std_macros(&self.source_map,
+                                          &mut primary_span,
+                                          &mut children,
+                                          &db.level,
+                                          db.handler().flags.external_macro_backtrace);
 
         self.emit_messages_default(&db.level,
                                    db.message(),
@@ -105,7 +109,7 @@ impl<'a>  DiagnosticConverter<'a> {
         annotated_files: Vec<FileWithAnnotatedLines>,
         primary_lo: Loc
     ) -> Vec<Slice> {
-        // FIXME(#59346): Provide a test case where `annotated_files` is > 1
+        // FIXME(#64205): Provide a test case where `annotated_files` is > 1
         annotated_files.iter().flat_map(|annotated_file| {
             annotated_file.lines.iter().map(|line| {
                 let line_source = Self::source_string(annotated_file.file.clone(), &line);
diff --git a/src/librustc_errors/diagnostic_builder.rs b/src/librustc_errors/diagnostic_builder.rs
index 41d0638f7c6bd..7b8902f125aee 100644
--- a/src/librustc_errors/diagnostic_builder.rs
+++ b/src/librustc_errors/diagnostic_builder.rs
@@ -18,8 +18,17 @@ use log::debug;
 /// extending `HandlerFlags`, accessed via `self.handler.flags`.
 #[must_use]
 #[derive(Clone)]
-pub struct DiagnosticBuilder<'a> {
-    pub handler: &'a Handler,
+pub struct DiagnosticBuilder<'a>(Box<DiagnosticBuilderInner<'a>>);
+
+/// This is a large type, and often used as a return value, especially within
+/// the frequently-used `PResult` type. In theory, return value optimization
+/// (RVO) should avoid unnecessary copying. In practice, it does not (at the
+/// time of writing). The split between `DiagnosticBuilder` and
+/// `DiagnosticBuilderInner` exists to avoid many `memcpy` calls.
+#[must_use]
+#[derive(Clone)]
+struct DiagnosticBuilderInner<'a> {
+    handler: &'a Handler,
     diagnostic: Diagnostic,
     allow_suggestions: bool,
 }
@@ -52,7 +61,7 @@ macro_rules! forward {
     ) => {
         $(#[$attrs])*
         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
-            self.diagnostic.$n($($name),*);
+            self.0.diagnostic.$n($($name),*);
             self
         }
     };
@@ -69,7 +78,7 @@ macro_rules! forward {
     ) => {
         $(#[$attrs])*
         pub fn $n<S: Into<MultiSpan>>(&mut self, $($name: $ty),*) -> &mut Self {
-            self.diagnostic.$n($($name),*);
+            self.0.diagnostic.$n($($name),*);
             self
         }
     };
@@ -79,24 +88,28 @@ impl<'a> Deref for DiagnosticBuilder<'a> {
     type Target = Diagnostic;
 
     fn deref(&self) -> &Diagnostic {
-        &self.diagnostic
+        &self.0.diagnostic
     }
 }
 
 impl<'a> DerefMut for DiagnosticBuilder<'a> {
     fn deref_mut(&mut self) -> &mut Diagnostic {
-        &mut self.diagnostic
+        &mut self.0.diagnostic
     }
 }
 
 impl<'a> DiagnosticBuilder<'a> {
+    pub fn handler(&self) -> &'a Handler{
+        self.0.handler
+    }
+
     /// Emit the diagnostic.
     pub fn emit(&mut self) {
         if self.cancelled() {
             return;
         }
 
-        self.handler.emit_db(&self);
+        self.0.handler.emit_db(&self);
         self.cancel();
     }
 
@@ -115,8 +128,8 @@ impl<'a> DiagnosticBuilder<'a> {
     /// Buffers the diagnostic for later emission, unless handler
     /// has disabled such buffering.
     pub fn buffer(mut self, buffered_diagnostics: &mut Vec<Diagnostic>) {
-        if self.handler.flags.dont_buffer_diagnostics ||
-            self.handler.flags.treat_err_as_bug.is_some()
+        if self.0.handler.flags.dont_buffer_diagnostics ||
+            self.0.handler.flags.treat_err_as_bug.is_some()
         {
             self.emit();
             return;
@@ -126,7 +139,7 @@ impl<'a> DiagnosticBuilder<'a> {
         // implements `Drop`.
         let diagnostic;
         unsafe {
-            diagnostic = std::ptr::read(&self.diagnostic);
+            diagnostic = std::ptr::read(&self.0.diagnostic);
             std::mem::forget(self);
         };
         // Logging here is useful to help track down where in logs an error was
@@ -144,7 +157,7 @@ impl<'a> DiagnosticBuilder<'a> {
         span: Option<S>,
     ) -> &mut Self {
         let span = span.map(|s| s.into()).unwrap_or_else(|| MultiSpan::new());
-        self.diagnostic.sub(level, message, span, None);
+        self.0.diagnostic.sub(level, message, span, None);
         self
     }
 
@@ -160,7 +173,7 @@ impl<'a> DiagnosticBuilder<'a> {
     /// locally in whichever way makes the most sense.
     pub fn delay_as_bug(&mut self) {
         self.level = Level::Bug;
-        self.handler.delay_as_bug(self.diagnostic.clone());
+        self.0.handler.delay_as_bug(self.0.diagnostic.clone());
         self.cancel();
     }
 
@@ -171,7 +184,7 @@ impl<'a> DiagnosticBuilder<'a> {
     /// then the snippet will just include that `Span`, which is
     /// called the primary span.
     pub fn span_label<T: Into<String>>(&mut self, span: Span, label: T) -> &mut Self {
-        self.diagnostic.span_label(span, label);
+        self.0.diagnostic.span_label(span, label);
         self
     }
 
@@ -208,10 +221,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: Vec<(Span, String)>,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.multipart_suggestion(
+        self.0.diagnostic.multipart_suggestion(
             msg,
             suggestion,
             applicability,
@@ -225,10 +238,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: Vec<(Span, String)>,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.tool_only_multipart_suggestion(
+        self.0.diagnostic.tool_only_multipart_suggestion(
             msg,
             suggestion,
             applicability,
@@ -236,7 +249,6 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
-
     pub fn span_suggestion(
         &mut self,
         sp: Span,
@@ -244,10 +256,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: String,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.span_suggestion(
+        self.0.diagnostic.span_suggestion(
             sp,
             msg,
             suggestion,
@@ -263,10 +275,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestions: impl Iterator<Item = String>,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.span_suggestions(
+        self.0.diagnostic.span_suggestions(
             sp,
             msg,
             suggestions,
@@ -282,10 +294,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: String,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.span_suggestion_short(
+        self.0.diagnostic.span_suggestion_short(
             sp,
             msg,
             suggestion,
@@ -301,10 +313,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: String,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.span_suggestion_hidden(
+        self.0.diagnostic.span_suggestion_hidden(
             sp,
             msg,
             suggestion,
@@ -320,10 +332,10 @@ impl<'a> DiagnosticBuilder<'a> {
         suggestion: String,
         applicability: Applicability,
     ) -> &mut Self {
-        if !self.allow_suggestions {
+        if !self.0.allow_suggestions {
             return self
         }
-        self.diagnostic.tool_only_span_suggestion(
+        self.0.diagnostic.tool_only_span_suggestion(
             sp,
             msg,
             suggestion,
@@ -336,7 +348,7 @@ impl<'a> DiagnosticBuilder<'a> {
     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 
     pub fn allow_suggestions(&mut self, allow: bool) -> &mut Self {
-        self.allow_suggestions = allow;
+        self.0.allow_suggestions = allow;
         self
     }
 
@@ -359,19 +371,18 @@ impl<'a> DiagnosticBuilder<'a> {
 
     /// Creates a new `DiagnosticBuilder` with an already constructed
     /// diagnostic.
-    pub fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic)
-                         -> DiagnosticBuilder<'a> {
-        DiagnosticBuilder {
+    pub fn new_diagnostic(handler: &'a Handler, diagnostic: Diagnostic) -> DiagnosticBuilder<'a> {
+        DiagnosticBuilder(Box::new(DiagnosticBuilderInner {
             handler,
             diagnostic,
             allow_suggestions: true,
-        }
+        }))
     }
 }
 
 impl<'a> Debug for DiagnosticBuilder<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.diagnostic.fmt(f)
+        self.0.diagnostic.fmt(f)
     }
 }
 
@@ -381,7 +392,7 @@ impl<'a> Drop for DiagnosticBuilder<'a> {
     fn drop(&mut self) {
         if !panicking() && !self.cancelled() {
             let mut db = DiagnosticBuilder::new(
-                self.handler,
+                self.0.handler,
                 Level::Bug,
                 "the following error was constructed but not emitted",
             );
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index a298f9958f2d1..d238de2a17e29 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -247,6 +247,133 @@ pub trait Emitter {
             (primary_span, &db.suggestions)
         }
     }
+
+    // This does a small "fix" for multispans by looking to see if it can find any that
+    // point directly at <*macros>. Since these are often difficult to read, this
+    // will change the span to point at the use site.
+    fn fix_multispans_in_std_macros(&self,
+                                    source_map: &Option<Lrc<SourceMapperDyn>>,
+                                    span: &mut MultiSpan,
+                                    children: &mut Vec<SubDiagnostic>,
+                                    level: &Level,
+                                    backtrace: bool) {
+        let mut spans_updated = self.fix_multispan_in_std_macros(source_map, span, backtrace);
+        for child in children.iter_mut() {
+            spans_updated |= self.fix_multispan_in_std_macros(
+                                 source_map,
+                                 &mut child.span,
+                                 backtrace
+                             );
+        }
+        let msg = if level == &Error {
+            "this error originates in a macro outside of the current crate \
+             (in Nightly builds, run with -Z external-macro-backtrace \
+              for more info)".to_string()
+        } else {
+            "this warning originates in a macro outside of the current crate \
+             (in Nightly builds, run with -Z external-macro-backtrace \
+              for more info)".to_string()
+        };
+
+        if spans_updated {
+            children.push(SubDiagnostic {
+                level: Level::Note,
+                message: vec![
+                    (msg,
+                     Style::NoStyle),
+                ],
+                span: MultiSpan::new(),
+                render_span: None,
+            });
+        }
+    }
+
+    // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
+    // <*macros>. Since these locations are often difficult to read, we move these Spans from
+    // <*macros> to their corresponding use site.
+    fn fix_multispan_in_std_macros(&self,
+                                   source_map: &Option<Lrc<SourceMapperDyn>>,
+                                   span: &mut MultiSpan,
+                                   always_backtrace: bool) -> bool {
+        let mut spans_updated = false;
+
+        if let Some(ref sm) = source_map {
+            let mut before_after: Vec<(Span, Span)> = vec![];
+            let mut new_labels: Vec<(Span, String)> = vec![];
+
+            // First, find all the spans in <*macros> and point instead at their use site
+            for sp in span.primary_spans() {
+                if sp.is_dummy() {
+                    continue;
+                }
+                let call_sp = sm.call_span_if_macro(*sp);
+                if call_sp != *sp && !always_backtrace {
+                    before_after.push((*sp, call_sp));
+                }
+                let backtrace_len = sp.macro_backtrace().len();
+                for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
+                    // Only show macro locations that are local
+                    // and display them like a span_note
+                    if trace.def_site_span.is_dummy() {
+                        continue;
+                    }
+                    if always_backtrace {
+                        new_labels.push((trace.def_site_span,
+                                            format!("in this expansion of `{}`{}",
+                                                    trace.macro_decl_name,
+                                                    if backtrace_len > 2 {
+                                                        // if backtrace_len == 1 it'll be pointed
+                                                        // at by "in this macro invocation"
+                                                        format!(" (#{})", i + 1)
+                                                    } else {
+                                                        String::new()
+                                                    })));
+                    }
+                    // Check to make sure we're not in any <*macros>
+                    if !sm.span_to_filename(trace.def_site_span).is_macros() &&
+                        !trace.macro_decl_name.starts_with("desugaring of ") &&
+                        !trace.macro_decl_name.starts_with("#[") ||
+                        always_backtrace {
+                        new_labels.push((trace.call_site,
+                                            format!("in this macro invocation{}",
+                                                    if backtrace_len > 2 && always_backtrace {
+                                                        // only specify order when the macro
+                                                        // backtrace is multiple levels deep
+                                                        format!(" (#{})", i + 1)
+                                                    } else {
+                                                        String::new()
+                                                    })));
+                        if !always_backtrace {
+                            break;
+                        }
+                    }
+                }
+            }
+            for (label_span, label_text) in new_labels {
+                span.push_span_label(label_span, label_text);
+            }
+            for sp_label in span.span_labels() {
+                if sp_label.span.is_dummy() {
+                    continue;
+                }
+                if sm.span_to_filename(sp_label.span.clone()).is_macros() &&
+                    !always_backtrace
+                {
+                    let v = sp_label.span.macro_backtrace();
+                    if let Some(use_site) = v.last() {
+                        before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
+                    }
+                }
+            }
+            // After we have them, make sure we replace these 'bad' def sites with their use sites
+            for (before, after) in before_after {
+                span.replace(before, after);
+                spans_updated = true;
+            }
+        }
+
+        spans_updated
+    }
 }
 
 impl Emitter for EmitterWriter {
@@ -254,10 +381,11 @@ impl Emitter for EmitterWriter {
         let mut children = db.children.clone();
         let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
 
-        self.fix_multispans_in_std_macros(&mut primary_span,
+        self.fix_multispans_in_std_macros(&self.sm,
+                                          &mut primary_span,
                                           &mut children,
                                           &db.level,
-                                          db.handler.flags.external_macro_backtrace);
+                                          db.handler().flags.external_macro_backtrace);
 
         self.emit_messages_default(&db.level,
                                    &db.styled_message(),
@@ -919,127 +1047,6 @@ impl EmitterWriter {
         max
     }
 
-    // This "fixes" MultiSpans that contain Spans that are pointing to locations inside of
-    // <*macros>. Since these locations are often difficult to read, we move these Spans from
-    // <*macros> to their corresponding use site.
-    fn fix_multispan_in_std_macros(&mut self,
-                                   span: &mut MultiSpan,
-                                   always_backtrace: bool) -> bool {
-        let mut spans_updated = false;
-
-        if let Some(ref sm) = self.sm {
-            let mut before_after: Vec<(Span, Span)> = vec![];
-            let mut new_labels: Vec<(Span, String)> = vec![];
-
-            // First, find all the spans in <*macros> and point instead at their use site
-            for sp in span.primary_spans() {
-                if sp.is_dummy() {
-                    continue;
-                }
-                let call_sp = sm.call_span_if_macro(*sp);
-                if call_sp != *sp && !always_backtrace {
-                    before_after.push((*sp, call_sp));
-                }
-                let backtrace_len = sp.macro_backtrace().len();
-                for (i, trace) in sp.macro_backtrace().iter().rev().enumerate() {
-                    // Only show macro locations that are local
-                    // and display them like a span_note
-                    if trace.def_site_span.is_dummy() {
-                        continue;
-                    }
-                    if always_backtrace {
-                        new_labels.push((trace.def_site_span,
-                                            format!("in this expansion of `{}`{}",
-                                                    trace.macro_decl_name,
-                                                    if backtrace_len > 2 {
-                                                        // if backtrace_len == 1 it'll be pointed
-                                                        // at by "in this macro invocation"
-                                                        format!(" (#{})", i + 1)
-                                                    } else {
-                                                        String::new()
-                                                    })));
-                    }
-                    // Check to make sure we're not in any <*macros>
-                    if !sm.span_to_filename(trace.def_site_span).is_macros() &&
-                        !trace.macro_decl_name.starts_with("desugaring of ") &&
-                        !trace.macro_decl_name.starts_with("#[") ||
-                        always_backtrace {
-                        new_labels.push((trace.call_site,
-                                            format!("in this macro invocation{}",
-                                                    if backtrace_len > 2 && always_backtrace {
-                                                        // only specify order when the macro
-                                                        // backtrace is multiple levels deep
-                                                        format!(" (#{})", i + 1)
-                                                    } else {
-                                                        String::new()
-                                                    })));
-                        if !always_backtrace {
-                            break;
-                        }
-                    }
-                }
-            }
-            for (label_span, label_text) in new_labels {
-                span.push_span_label(label_span, label_text);
-            }
-            for sp_label in span.span_labels() {
-                if sp_label.span.is_dummy() {
-                    continue;
-                }
-                if sm.span_to_filename(sp_label.span.clone()).is_macros() &&
-                    !always_backtrace
-                {
-                    let v = sp_label.span.macro_backtrace();
-                    if let Some(use_site) = v.last() {
-                        before_after.push((sp_label.span.clone(), use_site.call_site.clone()));
-                    }
-                }
-            }
-            // After we have them, make sure we replace these 'bad' def sites with their use sites
-            for (before, after) in before_after {
-                span.replace(before, after);
-                spans_updated = true;
-            }
-        }
-
-        spans_updated
-    }
-
-    // This does a small "fix" for multispans by looking to see if it can find any that
-    // point directly at <*macros>. Since these are often difficult to read, this
-    // will change the span to point at the use site.
-    fn fix_multispans_in_std_macros(&mut self,
-                                    span: &mut MultiSpan,
-                                    children: &mut Vec<SubDiagnostic>,
-                                    level: &Level,
-                                    backtrace: bool) {
-        let mut spans_updated = self.fix_multispan_in_std_macros(span, backtrace);
-        for child in children.iter_mut() {
-            spans_updated |= self.fix_multispan_in_std_macros(&mut child.span, backtrace);
-        }
-        let msg = if level == &Error {
-            "this error originates in a macro outside of the current crate \
-             (in Nightly builds, run with -Z external-macro-backtrace \
-              for more info)".to_string()
-        } else {
-            "this warning originates in a macro outside of the current crate \
-             (in Nightly builds, run with -Z external-macro-backtrace \
-              for more info)".to_string()
-        };
-
-        if spans_updated {
-            children.push(SubDiagnostic {
-                level: Level::Note,
-                message: vec![
-                    (msg,
-                     Style::NoStyle),
-                ],
-                span: MultiSpan::new(),
-                render_span: None,
-            });
-        }
-    }
-
     /// Adds a left margin to every line but the first, given a padding length and the label being
     /// displayed, keeping the provided highlighting.
     fn msg_to_buffer(&self,
@@ -1137,15 +1144,18 @@ impl EmitterWriter {
                 buffer.prepend(0, " ", Style::NoStyle);
             }
             draw_note_separator(&mut buffer, 0, max_line_num_len + 1);
-            let level_str = level.to_string();
-            if !level_str.is_empty() {
-                buffer.append(0, &level_str, Style::MainHeaderMsg);
-                buffer.append(0, ": ", Style::NoStyle);
+            if *level != Level::FailureNote {
+                let level_str = level.to_string();
+                if !level_str.is_empty() {
+                    buffer.append(0, &level_str, Style::MainHeaderMsg);
+                    buffer.append(0, ": ", Style::NoStyle);
+                }
             }
             self.msg_to_buffer(&mut buffer, msg, max_line_num_len, "note", None);
         } else {
             let level_str = level.to_string();
-            if !level_str.is_empty() {
+            // The failure note level itself does not provide any useful diagnostic information
+            if *level != Level::FailureNote && !level_str.is_empty() {
                 buffer.append(0, &level_str, Style::Level(level.clone()));
             }
             // only render error codes, not lint codes
@@ -1154,7 +1164,7 @@ impl EmitterWriter {
                 buffer.append(0, &code, Style::Level(level.clone()));
                 buffer.append(0, "]", Style::Level(level.clone()));
             }
-            if !level_str.is_empty() {
+            if *level != Level::FailureNote && !level_str.is_empty() {
                 buffer.append(0, ": ", header_style);
             }
             for &(ref text, _) in msg.iter() {
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 6585633e00af8..8b543be6e6497 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -833,7 +833,7 @@ impl Level {
             Warning => "warning",
             Note => "note",
             Help => "help",
-            FailureNote => "",
+            FailureNote => "failure-note",
             Cancelled => panic!("Shouldn't call on cancelled error"),
         }
     }
@@ -845,3 +845,10 @@ impl Level {
         }
     }
 }
+
+#[macro_export]
+macro_rules! pluralise {
+    ($x:expr) => {
+        if $x != 1 { "s" } else { "" }
+    };
+}
diff --git a/src/librustc_incremental/Cargo.toml b/src/librustc_incremental/Cargo.toml
index a931ad3b66e21..659c4c89fe33c 100644
--- a/src/librustc_incremental/Cargo.toml
+++ b/src/librustc_incremental/Cargo.toml
@@ -12,7 +12,7 @@ doctest = false
 [dependencies]
 graphviz = { path = "../libgraphviz" }
 log = "0.4"
-rand = "0.6"
+rand = "0.7"
 rustc = { path = "../librustc" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
diff --git a/src/librustc_incremental/assert_module_sources.rs b/src/librustc_incremental/assert_module_sources.rs
index 046fdc72270db..e08eeaf85758e 100644
--- a/src/librustc_incremental/assert_module_sources.rs
+++ b/src/librustc_incremental/assert_module_sources.rs
@@ -27,7 +27,7 @@ use rustc::mir::mono::CodegenUnitNameBuilder;
 use rustc::ty::TyCtxt;
 use std::collections::BTreeSet;
 use syntax::ast;
-use syntax::symbol::{Symbol, sym};
+use syntax::symbol::{InternedString, Symbol, sym};
 use rustc::ich::{ATTR_PARTITION_REUSED, ATTR_PARTITION_CODEGENED,
                  ATTR_EXPECTED_CGU_REUSE};
 
@@ -45,8 +45,8 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
             .collect_and_partition_mono_items(LOCAL_CRATE)
             .1
             .iter()
-            .map(|cgu| format!("{}", cgu.name()))
-            .collect::<BTreeSet<String>>();
+            .map(|cgu| *cgu.name())
+            .collect::<BTreeSet<InternedString>>();
 
         let ams = AssertModuleSource {
             tcx,
@@ -61,7 +61,7 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
 
 struct AssertModuleSource<'tcx> {
     tcx: TyCtxt<'tcx>,
-    available_cgus: BTreeSet<String>,
+    available_cgus: BTreeSet<InternedString>,
 }
 
 impl AssertModuleSource<'tcx> {
@@ -127,7 +127,7 @@ impl AssertModuleSource<'tcx> {
 
         debug!("mapping '{}' to cgu name '{}'", self.field(attr, MODULE), cgu_name);
 
-        if !self.available_cgus.contains(&cgu_name.as_str()[..]) {
+        if !self.available_cgus.contains(&cgu_name) {
             self.tcx.sess.span_err(attr.span,
                 &format!("no module named `{}` (mangled: {}). \
                           Available modules: {}",
@@ -135,7 +135,7 @@ impl AssertModuleSource<'tcx> {
                     cgu_name,
                     self.available_cgus
                         .iter()
-                        .cloned()
+                        .map(|cgu| cgu.as_str().to_string())
                         .collect::<Vec<_>>()
                         .join(", ")));
         }
diff --git a/src/librustc_interface/Cargo.toml b/src/librustc_interface/Cargo.toml
index 16b377d5bccea..f6293107a940e 100644
--- a/src/librustc_interface/Cargo.toml
+++ b/src/librustc_interface/Cargo.toml
@@ -34,3 +34,4 @@ rustc_plugin = { path = "../librustc_plugin", package = "rustc_plugin_impl" }
 rustc_privacy = { path = "../librustc_privacy" }
 rustc_resolve = { path = "../librustc_resolve" }
 tempfile = "3.0.5"
+once_cell = "1"
diff --git a/src/librustc_interface/build.rs b/src/librustc_interface/build.rs
new file mode 100644
index 0000000000000..79a343e0fee0b
--- /dev/null
+++ b/src/librustc_interface/build.rs
@@ -0,0 +1,4 @@
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=RUSTC_INSTALL_BINDIR");
+}
diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 24b44964e4fd2..e8e8da6733471 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -34,14 +34,13 @@ use rustc_privacy;
 use rustc_resolve::{Resolver, ResolverArenas};
 use rustc_traits;
 use rustc_typeck as typeck;
-use syntax::{self, ast, diagnostics, visit};
+use syntax::{self, ast, visit};
 use syntax::early_buffered_lints::BufferedEarlyLint;
 use syntax::ext::base::{NamedSyntaxExtension, ExtCtxt};
 use syntax::mut_visit::MutVisitor;
 use syntax::parse::{self, PResult};
 use syntax::util::node_count::NodeCounter;
 use syntax::symbol::Symbol;
-use syntax::feature_gate::AttributeType;
 use syntax_pos::FileName;
 use syntax_ext;
 
@@ -219,7 +218,6 @@ impl BoxedResolver {
 
 pub struct PluginInfo {
     syntax_exts: Vec<NamedSyntaxExtension>,
-    attributes: Vec<(Symbol, AttributeType)>,
 }
 
 pub fn register_plugins<'a>(
@@ -230,10 +228,12 @@ pub fn register_plugins<'a>(
     crate_name: &str,
 ) -> Result<(ast::Crate, PluginInfo)> {
     krate = time(sess, "attributes injection", || {
-        syntax::attr::inject(krate, &sess.parse_sess, &sess.opts.debugging_opts.crate_attr)
+        syntax_ext::cmdline_attrs::inject(
+            krate, &sess.parse_sess, &sess.opts.debugging_opts.crate_attr
+        )
     });
 
-    let (mut krate, features) = syntax::config::features(
+    let (krate, features) = syntax::config::features(
         krate,
         &sess.parse_sess,
         sess.edition(),
@@ -268,16 +268,6 @@ pub fn register_plugins<'a>(
         middle::recursion_limit::update_limits(sess, &krate);
     });
 
-    krate = time(sess, "crate injection", || {
-        let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| &**s);
-        let (krate, name) =
-            syntax_ext::standard_library_imports::inject(krate, alt_std_name, sess.edition());
-        if let Some(name) = name {
-            sess.parse_sess.injected_crate_name.set(name);
-        }
-        krate
-    });
-
     let registrars = time(sess, "plugin loading", || {
         plugin::load::load_plugins(
             sess,
@@ -291,21 +281,6 @@ pub fn register_plugins<'a>(
     let mut registry = Registry::new(sess, krate.span);
 
     time(sess, "plugin registration", || {
-        if sess.features_untracked().rustc_diagnostic_macros {
-            registry.register_macro(
-                "__diagnostic_used",
-                diagnostics::plugin::expand_diagnostic_used,
-            );
-            registry.register_macro(
-                "__register_diagnostic",
-                diagnostics::plugin::expand_register_diagnostic,
-            );
-            registry.register_macro(
-                "__build_diagnostic_array",
-                diagnostics::plugin::expand_build_diagnostic_array,
-            );
-        }
-
         for registrar in registrars {
             registry.args_hidden = Some(registrar.args);
             (registrar.fun)(&mut registry);
@@ -335,12 +310,9 @@ pub fn register_plugins<'a>(
     }
 
     *sess.plugin_llvm_passes.borrow_mut() = llvm_passes;
-    *sess.plugin_attributes.borrow_mut() = attributes.clone();
+    *sess.plugin_attributes.borrow_mut() = attributes;
 
-    Ok((krate, PluginInfo {
-        syntax_exts,
-        attributes,
-    }))
+    Ok((krate, PluginInfo { syntax_exts }))
 }
 
 fn configure_and_expand_inner<'a>(
@@ -352,7 +324,6 @@ fn configure_and_expand_inner<'a>(
     crate_loader: &'a mut CrateLoader<'a>,
     plugin_info: PluginInfo,
 ) -> Result<(ast::Crate, Resolver<'a>)> {
-    let attributes = plugin_info.attributes;
     time(sess, "pre ast expansion lint checks", || {
         lint::check_ast_crate(
             sess,
@@ -370,6 +341,21 @@ fn configure_and_expand_inner<'a>(
         &resolver_arenas,
     );
     syntax_ext::register_builtin_macros(&mut resolver, sess.edition());
+
+    krate = time(sess, "crate injection", || {
+        let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| Symbol::intern(s));
+        let (krate, name) = syntax_ext::standard_library_imports::inject(
+            krate,
+            &mut resolver,
+            &sess.parse_sess,
+            alt_std_name,
+        );
+        if let Some(name) = name {
+            sess.parse_sess.injected_crate_name.set(name);
+        }
+        krate
+    });
+
     syntax_ext::plugin_macro_defs::inject(
         &mut krate, &mut resolver, plugin_info.syntax_exts, sess.edition()
     );
@@ -530,7 +516,6 @@ fn configure_and_expand_inner<'a>(
             &krate,
             &sess.parse_sess,
             &sess.features_untracked(),
-            &attributes,
             sess.opts.unstable_features,
         );
     });
diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
index f007a0cf2abee..b81f814de0f4a 100644
--- a/src/librustc_interface/util.rs
+++ b/src/librustc_interface/util.rs
@@ -43,17 +43,17 @@ use std::{thread, panic};
 
 pub fn diagnostics_registry() -> Registry {
     let mut all_errors = Vec::new();
-    all_errors.extend_from_slice(&rustc::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_typeck::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_resolve::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_privacy::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_typeck::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_resolve::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_privacy::error_codes::DIAGNOSTICS);
     // FIXME: need to figure out a way to get these back in here
     // all_errors.extend_from_slice(get_codegen_backend(sess).diagnostics());
-    all_errors.extend_from_slice(&rustc_metadata::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_passes::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_plugin::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_mir::DIAGNOSTICS);
-    all_errors.extend_from_slice(&syntax::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_metadata::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_passes::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_plugin::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_mir::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&syntax::error_codes::DIAGNOSTICS);
 
     Registry::new(&all_errors)
 }
@@ -289,20 +289,39 @@ pub fn get_codegen_backend(sess: &Session) -> Box<dyn CodegenBackend> {
     backend
 }
 
-pub fn get_codegen_sysroot(backend_name: &str) -> fn() -> Box<dyn CodegenBackend> {
-    // For now we only allow this function to be called once as it'll dlopen a
-    // few things, which seems to work best if we only do that once. In
-    // general this assertion never trips due to the once guard in `get_codegen_backend`,
-    // but there's a few manual calls to this function in this file we protect
-    // against.
-    static LOADED: AtomicBool = AtomicBool::new(false);
-    assert!(!LOADED.fetch_or(true, Ordering::SeqCst),
-            "cannot load the default codegen backend twice");
+// This is used for rustdoc, but it uses similar machinery to codegen backend
+// loading, so we leave the code here. It is potentially useful for other tools
+// that want to invoke the rustc binary while linking to rustc as well.
+pub fn rustc_path<'a>() -> Option<&'a Path> {
+    static RUSTC_PATH: once_cell::sync::OnceCell<Option<PathBuf>> =
+        once_cell::sync::OnceCell::new();
 
+    const BIN_PATH: &str = env!("RUSTC_INSTALL_BINDIR");
+
+    RUSTC_PATH.get_or_init(|| get_rustc_path_inner(BIN_PATH)).as_ref().map(|v| &**v)
+}
+
+fn get_rustc_path_inner(bin_path: &str) -> Option<PathBuf> {
+    sysroot_candidates().iter()
+        .filter_map(|sysroot| {
+            let candidate = sysroot.join(bin_path).join(if cfg!(target_os = "windows") {
+                "rustc.exe"
+            } else {
+                "rustc"
+            });
+            if candidate.exists() {
+                Some(candidate)
+            } else {
+                None
+            }
+        })
+        .next()
+}
+
+fn sysroot_candidates() -> Vec<PathBuf> {
     let target = session::config::host_triple();
     let mut sysroot_candidates = vec![filesearch::get_or_default_sysroot()];
-    let path = current_dll_path()
-        .and_then(|s| s.canonicalize().ok());
+    let path = current_dll_path().and_then(|s| s.canonicalize().ok());
     if let Some(dll) = path {
         // use `parent` twice to chop off the file name and then also the
         // directory containing the dll which should be either `lib` or `bin`.
@@ -327,69 +346,7 @@ pub fn get_codegen_sysroot(backend_name: &str) -> fn() -> Box<dyn CodegenBackend
         }
     }
 
-    let sysroot = sysroot_candidates.iter()
-        .map(|sysroot| {
-            let libdir = filesearch::relative_target_lib_path(&sysroot, &target);
-            sysroot.join(libdir).with_file_name(
-                option_env!("CFG_CODEGEN_BACKENDS_DIR").unwrap_or("codegen-backends"))
-        })
-        .filter(|f| {
-            info!("codegen backend candidate: {}", f.display());
-            f.exists()
-        })
-        .next();
-    let sysroot = sysroot.unwrap_or_else(|| {
-        let candidates = sysroot_candidates.iter()
-            .map(|p| p.display().to_string())
-            .collect::<Vec<_>>()
-            .join("\n* ");
-        let err = format!("failed to find a `codegen-backends` folder \
-                           in the sysroot candidates:\n* {}", candidates);
-        early_error(ErrorOutputType::default(), &err);
-    });
-    info!("probing {} for a codegen backend", sysroot.display());
-
-    let d = sysroot.read_dir().unwrap_or_else(|e| {
-        let err = format!("failed to load default codegen backend, couldn't \
-                           read `{}`: {}", sysroot.display(), e);
-        early_error(ErrorOutputType::default(), &err);
-    });
-
-    let mut file: Option<PathBuf> = None;
-
-    let expected_name = format!("rustc_codegen_llvm-{}", backend_name);
-    for entry in d.filter_map(|e| e.ok()) {
-        let path = entry.path();
-        let filename = match path.file_name().and_then(|s| s.to_str()) {
-            Some(s) => s,
-            None => continue,
-        };
-        if !(filename.starts_with(DLL_PREFIX) && filename.ends_with(DLL_SUFFIX)) {
-            continue
-        }
-        let name = &filename[DLL_PREFIX.len() .. filename.len() - DLL_SUFFIX.len()];
-        if name != expected_name {
-            continue
-        }
-        if let Some(ref prev) = file {
-            let err = format!("duplicate codegen backends found\n\
-                               first:  {}\n\
-                               second: {}\n\
-            ", prev.display(), path.display());
-            early_error(ErrorOutputType::default(), &err);
-        }
-        file = Some(path.clone());
-    }
-
-    match file {
-        Some(ref s) => return load_backend_from_dylib(s),
-        None => {
-            let err = format!("failed to load default codegen backend for `{}`, \
-                               no appropriate codegen dylib found in `{}`",
-                              backend_name, sysroot.display());
-            early_error(ErrorOutputType::default(), &err);
-        }
-    }
+    return sysroot_candidates;
 
     #[cfg(unix)]
     fn current_dll_path() -> Option<PathBuf> {
@@ -459,6 +416,85 @@ pub fn get_codegen_sysroot(backend_name: &str) -> fn() -> Box<dyn CodegenBackend
     }
 }
 
+pub fn get_codegen_sysroot(backend_name: &str) -> fn() -> Box<dyn CodegenBackend> {
+    // For now we only allow this function to be called once as it'll dlopen a
+    // few things, which seems to work best if we only do that once. In
+    // general this assertion never trips due to the once guard in `get_codegen_backend`,
+    // but there's a few manual calls to this function in this file we protect
+    // against.
+    static LOADED: AtomicBool = AtomicBool::new(false);
+    assert!(!LOADED.fetch_or(true, Ordering::SeqCst),
+            "cannot load the default codegen backend twice");
+
+    let target = session::config::host_triple();
+    let sysroot_candidates = sysroot_candidates();
+
+    let sysroot = sysroot_candidates.iter()
+        .map(|sysroot| {
+            let libdir = filesearch::relative_target_lib_path(&sysroot, &target);
+            sysroot.join(libdir).with_file_name(
+                option_env!("CFG_CODEGEN_BACKENDS_DIR").unwrap_or("codegen-backends"))
+        })
+        .filter(|f| {
+            info!("codegen backend candidate: {}", f.display());
+            f.exists()
+        })
+        .next();
+    let sysroot = sysroot.unwrap_or_else(|| {
+        let candidates = sysroot_candidates.iter()
+            .map(|p| p.display().to_string())
+            .collect::<Vec<_>>()
+            .join("\n* ");
+        let err = format!("failed to find a `codegen-backends` folder \
+                           in the sysroot candidates:\n* {}", candidates);
+        early_error(ErrorOutputType::default(), &err);
+    });
+    info!("probing {} for a codegen backend", sysroot.display());
+
+    let d = sysroot.read_dir().unwrap_or_else(|e| {
+        let err = format!("failed to load default codegen backend, couldn't \
+                           read `{}`: {}", sysroot.display(), e);
+        early_error(ErrorOutputType::default(), &err);
+    });
+
+    let mut file: Option<PathBuf> = None;
+
+    let expected_name = format!("rustc_codegen_llvm-{}", backend_name);
+    for entry in d.filter_map(|e| e.ok()) {
+        let path = entry.path();
+        let filename = match path.file_name().and_then(|s| s.to_str()) {
+            Some(s) => s,
+            None => continue,
+        };
+        if !(filename.starts_with(DLL_PREFIX) && filename.ends_with(DLL_SUFFIX)) {
+            continue
+        }
+        let name = &filename[DLL_PREFIX.len() .. filename.len() - DLL_SUFFIX.len()];
+        if name != expected_name {
+            continue
+        }
+        if let Some(ref prev) = file {
+            let err = format!("duplicate codegen backends found\n\
+                               first:  {}\n\
+                               second: {}\n\
+            ", prev.display(), path.display());
+            early_error(ErrorOutputType::default(), &err);
+        }
+        file = Some(path.clone());
+    }
+
+    match file {
+        Some(ref s) => return load_backend_from_dylib(s),
+        None => {
+            let err = format!("failed to load default codegen backend for `{}`, \
+                               no appropriate codegen dylib found in `{}`",
+                              backend_name, sysroot.display());
+            early_error(ErrorOutputType::default(), &err);
+        }
+    }
+
+}
+
 pub(crate) fn compute_crate_disambiguator(session: &Session) -> CrateDisambiguator {
     use std::hash::Hasher;
 
diff --git a/src/librustc_lexer/Cargo.toml b/src/librustc_lexer/Cargo.toml
index 675d3065c5b28..950771f0a6927 100644
--- a/src/librustc_lexer/Cargo.toml
+++ b/src/librustc_lexer/Cargo.toml
@@ -2,8 +2,14 @@
 authors = ["The Rust Project Developers"]
 name = "rustc_lexer"
 version = "0.1.0"
+license = "MIT OR Apache-2.0"
 edition = "2018"
 
+repository = "https://github.com/rust-lang/rust/"
+description = """
+Rust lexer used by rustc. No stability guarantees are provided.
+"""
+
 # Note: do not remove this blank `[lib]` section.
 # This will be used when publishing this crate as `rustc-ap-rustc_lexer`.
 [lib]
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 26e7b789f8f90..cf19a9eb147a8 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -669,6 +669,22 @@ impl DeprecatedAttr {
     }
 }
 
+fn lint_deprecated_attr(
+    cx: &EarlyContext<'_>,
+    attr: &ast::Attribute,
+    msg: &str,
+    suggestion: Option<&str>,
+) {
+    cx.struct_span_lint(DEPRECATED, attr.span, &msg)
+        .span_suggestion_short(
+            attr.span,
+            suggestion.unwrap_or("remove this attribute"),
+            String::new(),
+            Applicability::MachineApplicable
+        )
+        .emit();
+}
+
 impl EarlyLintPass for DeprecatedAttr {
     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
         for &&(n, _, _, ref g) in &self.depr_attrs {
@@ -679,18 +695,15 @@ impl EarlyLintPass for DeprecatedAttr {
                                              _) = g {
                     let msg = format!("use of deprecated attribute `{}`: {}. See {}",
                                       name, reason, link);
-                    let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
-                    err.span_suggestion_short(
-                        attr.span,
-                        suggestion.unwrap_or("remove this attribute"),
-                        String::new(),
-                        Applicability::MachineApplicable
-                    );
-                    err.emit();
+                    lint_deprecated_attr(cx, attr, &msg, suggestion);
                 }
                 return;
             }
         }
+        if attr.check_name(sym::no_start) || attr.check_name(sym::crate_id) {
+            let msg = format!("use of deprecated attribute `{}`: no longer used.", attr.path);
+            lint_deprecated_attr(cx, attr, &msg, None);
+        }
     }
 }
 
@@ -772,7 +785,7 @@ impl EarlyLintPass for UnusedDocComment {
     }
 
     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
-        let arm_span = arm.pats[0].span.with_hi(arm.body.span.hi());
+        let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
         self.warn_if_doc(cx, arm_span, "match arms", false, &arm.attrs);
     }
 
diff --git a/src/librustc_lint/error_codes.rs b/src/librustc_lint/error_codes.rs
index d7c39b780bfdf..ea2e1d9ecc53f 100644
--- a/src/librustc_lint/error_codes.rs
+++ b/src/librustc_lint/error_codes.rs
@@ -1,5 +1,4 @@
-use syntax::register_diagnostics;
-
-register_diagnostics! {
+syntax::register_diagnostics! {
+;
     E0721, // `await` keyword
 }
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index 27833161ef23d..0e054013cd779 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -15,7 +15,6 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 
 #![recursion_limit="256"]
 
@@ -436,7 +435,12 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
             id: LintId::of(INDIRECT_STRUCTURAL_MATCH),
             reference: "issue #62411 <https://github.com/rust-lang/rust/issues/62411>",
             edition: None,
-        }
+        },
+        FutureIncompatibleInfo {
+            id: LintId::of(SOFT_UNSTABLE),
+            reference: "issue #64266 <https://github.com/rust-lang/rust/issues/64266>",
+            edition: None,
+        },
         ]);
 
     // Register renamed and removed lints.
diff --git a/src/librustc_lint/types.rs b/src/librustc_lint/types.rs
index 217e10ab24f55..3b8c06ba154c6 100644
--- a/src/librustc_lint/types.rs
+++ b/src/librustc_lint/types.rs
@@ -624,7 +624,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                     AdtKind::Struct => {
                         if !def.repr.c() && !def.repr.transparent() {
                             return FfiUnsafe {
-                                ty: ty,
+                                ty,
                                 reason: "this struct has unspecified layout",
                                 help: Some("consider adding a `#[repr(C)]` or \
                                             `#[repr(transparent)]` attribute to this struct"),
@@ -633,7 +633,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
                         if def.non_enum_variant().fields.is_empty() {
                             return FfiUnsafe {
-                                ty: ty,
+                                ty,
                                 reason: "this struct has no fields",
                                 help: Some("consider adding a member to this struct"),
                             };
@@ -669,7 +669,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                     AdtKind::Union => {
                         if !def.repr.c() && !def.repr.transparent() {
                             return FfiUnsafe {
-                                ty: ty,
+                                ty,
                                 reason: "this union has unspecified layout",
                                 help: Some("consider adding a `#[repr(C)]` or \
                                             `#[repr(transparent)]` attribute to this union"),
@@ -678,7 +678,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
                         if def.non_enum_variant().fields.is_empty() {
                             return FfiUnsafe {
-                                ty: ty,
+                                ty,
                                 reason: "this union has no fields",
                                 help: Some("consider adding a field to this union"),
                             };
@@ -721,7 +721,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             // Special-case types like `Option<extern fn()>`.
                             if !is_repr_nullable_ptr(cx, ty, def, substs) {
                                 return FfiUnsafe {
-                                    ty: ty,
+                                    ty,
                                     reason: "enum has no representation hint",
                                     help: Some("consider adding a `#[repr(C)]`, \
                                                 `#[repr(transparent)]`, or integer `#[repr(...)]` \
@@ -750,7 +750,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                                     }
                                     FfiPhantom(..) => {
                                         return FfiUnsafe {
-                                            ty: ty,
+                                            ty,
                                             reason: "this enum contains a PhantomData field",
                                             help: None,
                                         };
@@ -764,13 +764,13 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             }
 
             ty::Char => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "the `char` type has no C equivalent",
                 help: Some("consider using `u32` or `libc::wchar_t` instead"),
             },
 
             ty::Int(ast::IntTy::I128) | ty::Uint(ast::UintTy::U128) => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "128-bit integers don't currently have a known stable ABI",
                 help: None,
             },
@@ -779,25 +779,25 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
 
             ty::Slice(_) => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "slices have no C equivalent",
                 help: Some("consider using a raw pointer instead"),
             },
 
             ty::Dynamic(..) => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "trait objects have no C equivalent",
                 help: None,
             },
 
             ty::Str => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "string slices have no C equivalent",
                 help: Some("consider using `*const u8` and a length instead"),
             },
 
             ty::Tuple(..) => FfiUnsafe {
-                ty: ty,
+                ty,
                 reason: "tuples have unspecified layout",
                 help: Some("consider using a struct instead"),
             },
@@ -811,7 +811,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 match sig.abi() {
                     Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic | Abi::RustCall => {
                         return FfiUnsafe {
-                            ty: ty,
+                            ty,
                             reason: "this function pointer has Rust-specific calling convention",
                             help: Some("consider using an `extern fn(...) -> ...` \
                                         function pointer instead"),
@@ -855,11 +855,76 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             ty::UnnormalizedProjection(..) |
             ty::Projection(..) |
             ty::Opaque(..) |
-            ty::FnDef(..) => bug!("Unexpected type in foreign function"),
+            ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
+        }
+    }
+
+    fn emit_ffi_unsafe_type_lint(
+        &mut self,
+        ty: Ty<'tcx>,
+        sp: Span,
+        note: &str,
+        help: Option<&str>,
+    ) {
+        let mut diag = self.cx.struct_span_lint(
+            IMPROPER_CTYPES,
+            sp,
+            &format!("`extern` block uses type `{}`, which is not FFI-safe", ty),
+        );
+        diag.span_label(sp, "not FFI-safe");
+        if let Some(help) = help {
+            diag.help(help);
+        }
+        diag.note(note);
+        if let ty::Adt(def, _) = ty.sty {
+            if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did) {
+                diag.span_note(sp, "type defined here");
+            }
+        }
+        diag.emit();
+    }
+
+    fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
+        use crate::rustc::ty::TypeFoldable;
+
+        struct ProhibitOpaqueTypes<'tcx> {
+            ty: Option<Ty<'tcx>>,
+        };
+
+        impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'tcx> {
+            fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
+                if let ty::Opaque(..) = ty.sty {
+                    self.ty = Some(ty);
+                    true
+                } else {
+                    ty.super_visit_with(self)
+                }
+            }
+        }
+
+        let mut visitor = ProhibitOpaqueTypes { ty: None };
+        ty.visit_with(&mut visitor);
+        if let Some(ty) = visitor.ty {
+            self.emit_ffi_unsafe_type_lint(
+                ty,
+                sp,
+                "opaque types have no C equivalent",
+                None,
+            );
+            true
+        } else {
+            false
         }
     }
 
     fn check_type_for_ffi_and_report_errors(&mut self, sp: Span, ty: Ty<'tcx>) {
+        // We have to check for opaque types before `normalize_erasing_regions`,
+        // which will replace opaque types with their underlying concrete type.
+        if self.check_for_opaque_ty(sp, ty) {
+            // We've already emitted an error due to an opaque type.
+            return;
+        }
+
         // it is only OK to use this function because extern fns cannot have
         // any generic types right now:
         let ty = self.cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
@@ -867,24 +932,10 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
             FfiResult::FfiSafe => {}
             FfiResult::FfiPhantom(ty) => {
-                self.cx.span_lint(IMPROPER_CTYPES,
-                                  sp,
-                                  &format!("`extern` block uses type `{}` which is not FFI-safe: \
-                                            composed only of PhantomData", ty));
+                self.emit_ffi_unsafe_type_lint(ty, sp, "composed only of `PhantomData`", None);
             }
-            FfiResult::FfiUnsafe { ty: unsafe_ty, reason, help } => {
-                let msg = format!("`extern` block uses type `{}` which is not FFI-safe: {}",
-                                  unsafe_ty, reason);
-                let mut diag = self.cx.struct_span_lint(IMPROPER_CTYPES, sp, &msg);
-                if let Some(s) = help {
-                    diag.help(s);
-                }
-                if let ty::Adt(def, _) = unsafe_ty.sty {
-                    if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did) {
-                        diag.span_note(sp, "type defined here");
-                    }
-                }
-                diag.emit();
+            FfiResult::FfiUnsafe { ty, reason, help } => {
+                self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
             }
         }
     }
diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs
index 39c0698aeec9f..c3975098351af 100644
--- a/src/librustc_lint/unused.rs
+++ b/src/librustc_lint/unused.rs
@@ -370,7 +370,8 @@ impl UnusedParens {
                                      right_pos: Option<BytePos>) {
         match value.node {
             ast::ExprKind::Paren(ref inner) => {
-                if !Self::is_expr_parens_necessary(inner, followed_by_block) {
+                if !Self::is_expr_parens_necessary(inner, followed_by_block) &&
+                    value.attrs.is_empty() {
                     let expr_text = if let Ok(snippet) = cx.sess().source_map()
                         .span_to_snippet(value.span) {
                             snippet
@@ -493,10 +494,8 @@ impl EarlyLintPass for UnusedParens {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         use syntax::ast::ExprKind::*;
         let (value, msg, followed_by_block, left_pos, right_pos) = match e.node {
-            Let(ref pats, ..) => {
-                for p in pats {
-                    self.check_unused_parens_pat(cx, p, false, false);
-                }
+            Let(ref pat, ..) => {
+                self.check_unused_parens_pat(cx, pat, false, false);
                 return;
             }
 
@@ -594,9 +593,7 @@ impl EarlyLintPass for UnusedParens {
     }
 
     fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
-        for p in &arm.pats {
-            self.check_unused_parens_pat(cx, p, false, false);
-        }
+        self.check_unused_parens_pat(cx, &arm.pat, false, false);
     }
 }
 
@@ -622,24 +619,19 @@ impl UnusedImportBraces {
             }
 
             // Trigger the lint if the nested item is a non-self single item
-            let node_ident;
-            match items[0].0.kind {
+            let node_name = match items[0].0.kind {
                 ast::UseTreeKind::Simple(rename, ..) => {
                     let orig_ident = items[0].0.prefix.segments.last().unwrap().ident;
                     if orig_ident.name == kw::SelfLower {
                         return;
                     }
-                    node_ident = rename.unwrap_or(orig_ident);
-                }
-                ast::UseTreeKind::Glob => {
-                    node_ident = ast::Ident::from_str("*");
+                    rename.unwrap_or(orig_ident).name
                 }
-                ast::UseTreeKind::Nested(_) => {
-                    return;
-                }
-            }
+                ast::UseTreeKind::Glob => Symbol::intern("*"),
+                ast::UseTreeKind::Nested(_) => return,
+            };
 
-            let msg = format!("braces around {} is unnecessary", node_ident.name);
+            let msg = format!("braces around {} is unnecessary", node_name);
             cx.span_lint(UNUSED_IMPORT_BRACES, item.span, &msg);
         }
     }
diff --git a/src/librustc_lsan/build.rs b/src/librustc_lsan/build.rs
index b8c7b7c2d5537..73720d8c2d64e 100644
--- a/src/librustc_lsan/build.rs
+++ b/src/librustc_lsan/build.rs
@@ -4,6 +4,10 @@ use build_helper::sanitizer_lib_boilerplate;
 use cmake::Config;
 
 fn main() {
+    println!("cargo:rerun-if-env-changed=RUSTC_BUILD_SANITIZERS");
+    if env::var("RUSTC_BUILD_SANITIZERS") != Ok("1".to_string()) {
+        return;
+    }
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
         build_helper::restore_library_path();
 
diff --git a/src/librustc_metadata/cstore_impl.rs b/src/librustc_metadata/cstore_impl.rs
index d6450f00c8b6a..a1e3bbcbf8ea9 100644
--- a/src/librustc_metadata/cstore_impl.rs
+++ b/src/librustc_metadata/cstore_impl.rs
@@ -444,7 +444,8 @@ impl cstore::CStore {
             .insert(local_span, (name.to_string(), data.get_span(id.index, sess)));
 
         LoadedMacro::MacroDef(ast::Item {
-            ident: ast::Ident::from_str(&name.as_str()),
+            // FIXME: cross-crate hygiene
+            ident: ast::Ident::with_dummy_span(name.as_symbol()),
             id: ast::DUMMY_NODE_ID,
             span: local_span,
             attrs: attrs.iter().cloned().collect(),
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 75d7261704722..34c84b1d79d4b 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -489,7 +489,11 @@ impl<'a, 'tcx> CrateMetadata {
 
     fn raw_proc_macro(&self, id: DefIndex) -> &ProcMacro {
         // DefIndex's in root.proc_macro_data have a one-to-one correspondence
-        // with items in 'raw_proc_macros'
+        // with items in 'raw_proc_macros'.
+        // NOTE: If you update the order of macros in 'proc_macro_data' for any reason,
+        // you must also update src/libsyntax_ext/proc_macro_harness.rs
+        // Failing to do so will result in incorrect data being associated
+        // with proc macros when deserialized.
         let pos = self.root.proc_macro_data.unwrap().decode(self).position(|i| i == id).unwrap();
         &self.raw_proc_macros.unwrap()[pos]
     }
diff --git a/src/librustc_metadata/error_codes.rs b/src/librustc_metadata/error_codes.rs
index 0708a6243bf29..cd8e95e6c3a11 100644
--- a/src/librustc_metadata/error_codes.rs
+++ b/src/librustc_metadata/error_codes.rs
@@ -1,6 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 E0454: r##"
 A link name was given with an empty name. Erroneous code example:
 
@@ -84,10 +82,7 @@ You need to link your code to the relevant crate in order to be able to use it
 (through Cargo or the `-L` option of rustc example). Plugins are crates as
 well, and you link to them the same way.
 "##,
-
-}
-
-register_diagnostics! {
+;
     E0456, // plugin `..` is not available for triple `..`
     E0457, // plugin `..` only found in rlib format, but must be available...
     E0514, // metadata version mismatch
@@ -97,5 +92,6 @@ register_diagnostics! {
     E0464, // multiple matching crates for `..`
     E0465, // multiple .. candidates for `..` found
     E0519, // local crate and dependency have same (crate-name, disambiguator)
-    E0523, // two dependencies have same (crate-name, disambiguator) but different SVH
+    // two dependencies have same (crate-name, disambiguator) but different SVH
+    E0523,
 }
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index c96d02d9b37de..e6104e629e9fb 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -8,7 +8,6 @@
 #![feature(nll)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(slice_patterns)]
 #![feature(specialization)]
@@ -23,7 +22,7 @@ extern crate rustc;
 #[macro_use]
 extern crate rustc_data_structures;
 
-mod error_codes;
+pub mod error_codes;
 
 mod index;
 mod encoder;
@@ -68,5 +67,3 @@ pub fn validate_crate_name(
         sess.unwrap().abort_if_errors();
     }
 }
-
-__build_diagnostic_array! { librustc_metadata, DIAGNOSTICS }
diff --git a/src/librustc_metadata/native_libs.rs b/src/librustc_metadata/native_libs.rs
index 66971bb6f8b1c..ada1a8c615d44 100644
--- a/src/librustc_metadata/native_libs.rs
+++ b/src/librustc_metadata/native_libs.rs
@@ -8,7 +8,7 @@ use rustc_target::spec::abi::Abi;
 use syntax::attr;
 use syntax::source_map::Span;
 use syntax::feature_gate::{self, GateIssue};
-use syntax::symbol::{Symbol, sym};
+use syntax::symbol::{kw, sym, Symbol};
 use syntax::{span_err, struct_span_err};
 
 pub fn collect(tcx: TyCtxt<'_>) -> Vec<NativeLibrary> {
@@ -132,7 +132,7 @@ impl ItemLikeVisitor<'tcx> for Collector<'tcx> {
 
 impl Collector<'tcx> {
     fn register_native_lib(&mut self, span: Option<Span>, lib: NativeLibrary) {
-        if lib.name.as_ref().map(|s| s.as_str().is_empty()).unwrap_or(false) {
+        if lib.name.as_ref().map(|&s| s == kw::Invalid).unwrap_or(false) {
             match span {
                 Some(span) => {
                     struct_span_err!(self.tcx.sess, span, E0454,
@@ -159,7 +159,7 @@ impl Collector<'tcx> {
                                            sym::link_cfg,
                                            span.unwrap(),
                                            GateIssue::Language,
-                                           "is feature gated");
+                                           "is unstable");
         }
         if lib.kind == cstore::NativeStaticNobundle &&
            !self.tcx.features().static_nobundle {
@@ -167,7 +167,7 @@ impl Collector<'tcx> {
                                            sym::static_nobundle,
                                            span.unwrap_or_else(|| syntax_pos::DUMMY_SP),
                                            GateIssue::Language,
-                                           "kind=\"static-nobundle\" is feature gated");
+                                           "kind=\"static-nobundle\" is unstable");
         }
         self.libs.push(lib);
     }
diff --git a/src/librustc_mir/Cargo.toml b/src/librustc_mir/Cargo.toml
index e02736078b571..0691390bead4b 100644
--- a/src/librustc_mir/Cargo.toml
+++ b/src/librustc_mir/Cargo.toml
@@ -24,6 +24,6 @@ rustc_lexer = { path = "../librustc_lexer" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
-byteorder = { version = "1.1", features = ["i128"] }
+byteorder = { version = "1.3" }
 rustc_apfloat = { path = "../librustc_apfloat" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
diff --git a/src/librustc_mir/borrow_check/borrow_set.rs b/src/librustc_mir/borrow_check/borrow_set.rs
index c9e6e7f70a2b4..db19cbc3175f8 100644
--- a/src/librustc_mir/borrow_check/borrow_set.rs
+++ b/src/librustc_mir/borrow_check/borrow_set.rs
@@ -317,7 +317,7 @@ impl<'a, 'tcx> GatherBorrows<'a, 'tcx> {
         // so extract `temp`.
         let temp = if let &mir::Place {
             base: mir::PlaceBase::Local(temp),
-            projection: None,
+            projection: box [],
         } = assigned_place {
             temp
         } else {
diff --git a/src/librustc_mir/borrow_check/conflict_errors.rs b/src/librustc_mir/borrow_check/conflict_errors.rs
index 247783c420e25..81359c6a46e99 100644
--- a/src/librustc_mir/borrow_check/conflict_errors.rs
+++ b/src/librustc_mir/borrow_check/conflict_errors.rs
@@ -2,8 +2,8 @@ use rustc::hir;
 use rustc::hir::def_id::DefId;
 use rustc::mir::{
     self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory, Local,
-    LocalDecl, LocalKind, Location, Operand, Place, PlaceBase, Projection, PlaceRef,
-    ProjectionElem, Rvalue, Statement, StatementKind, TerminatorKind, VarBindingForm,
+    LocalDecl, LocalKind, Location, Operand, Place, PlaceBase, PlaceRef, ProjectionElem, Rvalue,
+    Statement, StatementKind, TerminatorKind, VarBindingForm,
 };
 use rustc::ty::{self, Ty};
 use rustc_data_structures::fx::FxHashSet;
@@ -98,7 +98,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 &self.describe_place_with_options(moved_place, IncludingDowncast(true))
                     .unwrap_or_else(|| "_".to_owned()),
             );
-            err.span_label(span, format!("use of possibly uninitialized {}", item_msg));
+            err.span_label(span, format!("use of possibly-uninitialized {}", item_msg));
 
             use_spans.var_span_label(
                 &mut err,
@@ -244,7 +244,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 }
                 let span = if let Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } = place {
                     let decl = &self.body.local_decls[*local];
                     Some(decl.source_info.span)
@@ -614,17 +614,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     projection,
                 } = first_borrowed_place;
 
-                let mut current = projection;
+                let mut cursor = &**projection;
+                while let [proj_base @ .., elem] = cursor {
+                    cursor = proj_base;
 
-                while let Some(box Projection { base: base_proj, elem }) = current {
                     match elem {
-                        ProjectionElem::Field(field, _) if union_ty(base, base_proj).is_some() => {
+                        ProjectionElem::Field(field, _) if union_ty(base, proj_base).is_some() => {
                             return Some((PlaceRef {
                                 base: base,
-                                projection: base_proj,
+                                projection: proj_base,
                             }, field));
                         },
-                        _ => current = base_proj,
+                        _ => {},
                     }
                 }
                 None
@@ -637,9 +638,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     projection,
                 } = second_borrowed_place;
 
-                let mut current = projection;
+                let mut cursor = &**projection;
+                while let [proj_base @ .., elem] = cursor {
+                    cursor = proj_base;
 
-                while let Some(box Projection { base: proj_base, elem }) = current {
                     if let ProjectionElem::Field(field, _) = elem {
                         if let Some(union_ty) = union_ty(base, proj_base) {
                             if field != target_field
@@ -660,8 +662,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             }
                         }
                     }
-
-                    current = proj_base;
                 }
                 None
             })
@@ -707,7 +707,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let borrow_spans = self.retrieve_borrow_spans(borrow);
         let borrow_span = borrow_spans.var_or_use();
 
-        assert!(root_place.projection.is_none());
+        assert!(root_place.projection.is_empty());
         let proper_span = match root_place.base {
             PlaceBase::Local(local) => self.body.local_decls[*local].source_info.span,
             _ => drop_span,
@@ -716,7 +716,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         if self.access_place_error_reported
             .contains(&(Place {
                 base: root_place.base.clone(),
-                projection: root_place.projection.clone(),
+                projection: root_place.projection.to_vec().into_boxed_slice(),
             }, borrow_span))
         {
             debug!(
@@ -729,7 +729,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         self.access_place_error_reported
             .insert((Place {
                 base: root_place.base.clone(),
-                projection: root_place.projection.clone(),
+                projection: root_place.projection.to_vec().into_boxed_slice(),
             }, borrow_span));
 
         if let StorageDeadOrDrop::Destructor(dropped_ty) =
@@ -1107,7 +1107,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             let local_kind = match borrow.borrowed_place {
                 Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } => {
                     match self.body.local_kind(local) {
                         LocalKind::ReturnPointer
@@ -1136,7 +1136,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 .unwrap();
             let local = if let PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } = root_place {
                 local
             } else {
@@ -1446,7 +1446,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     ) {
         let (from_arg, local_decl) = if let Place {
             base: PlaceBase::Local(local),
-            projection: None,
+            projection: box [],
         } = *err_place {
             if let LocalKind::Arg = self.body.local_kind(local) {
                 (true, Some(&self.body.local_decls[local]))
@@ -1519,20 +1519,21 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn classify_drop_access_kind(&self, place: PlaceRef<'cx, 'tcx>) -> StorageDeadOrDrop<'tcx> {
         let tcx = self.infcx.tcx;
         match place.projection {
-            None => {
+            [] => {
                 StorageDeadOrDrop::LocalStorageDead
             }
-            Some(box Projection { ref base, ref elem }) => {
+            [proj_base @ .., elem] => {
+                // FIXME(spastorino) make this iterate
                 let base_access = self.classify_drop_access_kind(PlaceRef {
                     base: place.base,
-                    projection: base,
+                    projection: proj_base,
                 });
                 match elem {
                     ProjectionElem::Deref => match base_access {
                         StorageDeadOrDrop::LocalStorageDead
                         | StorageDeadOrDrop::BoxedStorageDead => {
                             assert!(
-                                Place::ty_from(&place.base, base, self.body, tcx).ty.is_box(),
+                                Place::ty_from(&place.base, proj_base, self.body, tcx).ty.is_box(),
                                 "Drop of value behind a reference or raw pointer"
                             );
                             StorageDeadOrDrop::BoxedStorageDead
@@ -1540,7 +1541,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         StorageDeadOrDrop::Destructor(_) => base_access,
                     },
                     ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => {
-                        let base_ty = Place::ty_from(&place.base, base, self.body, tcx).ty;
+                        let base_ty = Place::ty_from(&place.base, proj_base, self.body, tcx).ty;
                         match base_ty.sty {
                             ty::Adt(def, _) if def.has_dtor(tcx) => {
                                 // Report the outermost adt with a destructor
@@ -1598,7 +1599,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             "annotate_argument_and_return_for_borrow: location={:?}",
             location
         );
-        if let Some(&Statement { kind: StatementKind::Assign(ref reservation, _), ..})
+        if let Some(&Statement { kind: StatementKind::Assign(box(ref reservation, _)), ..})
              = &self.body[location.block].statements.get(location.statement_index)
         {
             debug!(
@@ -1609,7 +1610,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             let mut target = *match reservation {
                 Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } if self.body.local_kind(*local) == LocalKind::Temp => local,
                 _ => return None,
             };
@@ -1623,11 +1624,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     target, stmt
                 );
                 if let StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(assigned_to),
-                        projection: None,
-                    },
-                    box rvalue
+                    box(
+                        Place {
+                            base: PlaceBase::Local(assigned_to),
+                            projection: box [],
+                        },
+                        rvalue
+                    )
                 ) = &stmt.kind {
                     debug!(
                         "annotate_argument_and_return_for_borrow: assigned_to={:?} \
@@ -1753,7 +1756,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if let TerminatorKind::Call {
                 destination: Some((Place {
                     base: PlaceBase::Local(assigned_to),
-                    projection: None,
+                    projection: box [],
                 }, _)),
                 args,
                 ..
diff --git a/src/librustc_mir/borrow_check/error_reporting.rs b/src/librustc_mir/borrow_check/error_reporting.rs
index 9f25e98052ec4..5bccd2835c980 100644
--- a/src/librustc_mir/borrow_check/error_reporting.rs
+++ b/src/librustc_mir/borrow_check/error_reporting.rs
@@ -41,7 +41,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let mut target = place.local_or_deref_local();
         for stmt in &self.body[location.block].statements[location.statement_index..] {
             debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
-            if let StatementKind::Assign(into, box Rvalue::Use(from)) = &stmt.kind {
+            if let StatementKind::Assign(box(into, Rvalue::Use(from))) = &stmt.kind {
                 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
                 match from {
                     Operand::Copy(ref place) |
@@ -152,7 +152,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match place {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } => {
                 self.append_local_to_string(*local, buf)?;
             }
@@ -162,7 +162,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         kind: StaticKind::Promoted(..),
                         ..
                     }),
-                projection: None,
+                projection: [],
             } => {
                 buf.push_str("promoted");
             }
@@ -173,15 +173,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         def_id,
                         ..
                     }),
-                projection: None,
+                projection: [],
             } => {
                 buf.push_str(&self.infcx.tcx.item_name(*def_id).to_string());
             }
             PlaceRef {
                 base,
-                projection: Some(ref proj),
+                projection: [proj_base @ .., elem],
             } => {
-                match proj.elem {
+                match elem {
                     ProjectionElem::Deref => {
                         let upvar_field_projection =
                             self.is_upvar_field_projection(place);
@@ -199,20 +199,20 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 self.append_place_to_string(
                                     PlaceRef {
                                         base,
-                                        projection: &proj.base,
+                                        projection: proj_base,
                                     },
                                     buf,
                                     autoderef,
                                     &including_downcast,
                                 )?;
                             } else {
-                                match (&proj.base, base) {
-                                    (None, PlaceBase::Local(local)) => {
+                                match (proj_base, base) {
+                                    ([], PlaceBase::Local(local)) => {
                                         if self.body.local_decls[*local].is_ref_for_guard() {
                                             self.append_place_to_string(
                                                 PlaceRef {
                                                     base,
-                                                    projection: &proj.base,
+                                                    projection: proj_base,
                                                 },
                                                 buf,
                                                 autoderef,
@@ -224,7 +224,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                             self.append_place_to_string(
                                                 PlaceRef {
                                                     base,
-                                                    projection: &proj.base,
+                                                    projection: proj_base,
                                                 },
                                                 buf,
                                                 autoderef,
@@ -238,7 +238,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                         self.append_place_to_string(
                                             PlaceRef {
                                                 base,
-                                                projection: &proj.base,
+                                                projection: proj_base,
                                             },
                                             buf,
                                             autoderef,
@@ -253,7 +253,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         self.append_place_to_string(
                             PlaceRef {
                                 base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             },
                             buf,
                             autoderef,
@@ -275,12 +275,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         } else {
                             let field_name = self.describe_field(PlaceRef {
                                 base,
-                                projection: &proj.base,
-                            }, field);
+                                projection: proj_base,
+                            }, *field);
                             self.append_place_to_string(
                                 PlaceRef {
                                     base,
-                                    projection: &proj.base,
+                                    projection: proj_base,
                                 },
                                 buf,
                                 autoderef,
@@ -295,14 +295,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         self.append_place_to_string(
                             PlaceRef {
                                 base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             },
                             buf,
                             autoderef,
                             &including_downcast,
                         )?;
                         buf.push_str("[");
-                        if self.append_local_to_string(index, buf).is_err() {
+                        if self.append_local_to_string(*index, buf).is_err() {
                             buf.push_str("_");
                         }
                         buf.push_str("]");
@@ -315,7 +315,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         self.append_place_to_string(
                             PlaceRef {
                                 base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             },
                             buf,
                             autoderef,
@@ -349,28 +349,30 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match place {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } => {
                 let local = &self.body.local_decls[*local];
                 self.describe_field_from_ty(&local.ty, field, None)
             }
             PlaceRef {
                 base: PlaceBase::Static(static_),
-                projection: None,
+                projection: [],
             } =>
                 self.describe_field_from_ty(&static_.ty, field, None),
             PlaceRef {
                 base,
-                projection: Some(proj),
-            } => match proj.elem {
-                ProjectionElem::Deref => self.describe_field(PlaceRef {
-                    base,
-                    projection: &proj.base,
-                }, field),
+                projection: [proj_base @ .., elem],
+            } => match elem {
+                ProjectionElem::Deref => {
+                    self.describe_field(PlaceRef {
+                        base,
+                        projection: proj_base,
+                    }, field)
+                }
                 ProjectionElem::Downcast(_, variant_index) => {
                     let base_ty =
                         Place::ty_from(place.base, place.projection, self.body, self.infcx.tcx).ty;
-                    self.describe_field_from_ty(&base_ty, field, Some(variant_index))
+                    self.describe_field_from_ty(&base_ty, field, Some(*variant_index))
                 }
                 ProjectionElem::Field(_, field_type) => {
                     self.describe_field_from_ty(&field_type, field, None)
@@ -380,7 +382,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 | ProjectionElem::Subslice { .. } => {
                     self.describe_field(PlaceRef {
                         base,
-                        projection: &proj.base,
+                        projection: proj_base,
                     }, field)
                 }
             },
@@ -445,7 +447,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 def_id,
                 ..
             }),
-            projection: None,
+            projection: [],
         } = place_ref {
             let attrs = self.infcx.tcx.get_attrs(*def_id);
             let is_thread_local = attrs.iter().any(|attr| attr.check_name(sym::thread_local));
@@ -790,8 +792,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
         if let  StatementKind::Assign(
-            _,
-            box Rvalue::Aggregate(ref kind, ref places)
+            box(_, Rvalue::Aggregate(ref kind, ref places))
         ) = stmt.kind {
             let (def_id, is_generator) = match kind {
                 box AggregateKind::Closure(def_id, _) => (def_id, false),
@@ -828,10 +829,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             .get(location.statement_index)
         {
             Some(&Statement {
-                kind: StatementKind::Assign(Place {
+                kind: StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
-                }, _),
+                    projection: box [],
+                }, _)),
                 ..
             }) => local,
             _ => return OtherUse(use_span),
@@ -844,7 +845,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
             if let StatementKind::Assign(
-                _, box Rvalue::Aggregate(ref kind, ref places)
+                box(_, Rvalue::Aggregate(ref kind, ref places))
             ) = stmt.kind {
                 let (def_id, is_generator) = match kind {
                     box AggregateKind::Closure(def_id, _) => (def_id, false),
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index 8ded539e7205a..1d3576244c4af 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -10,10 +10,10 @@ use rustc::lint::builtin::{MUTABLE_BORROW_RESERVATION_CONFLICT};
 use rustc::middle::borrowck::SignalledError;
 use rustc::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
 use rustc::mir::{
-    ClearCrossCrate, Local, Location, Body, Mutability, Operand, Place, PlaceBase, PlaceRef,
-    Static, StaticKind
+    ClearCrossCrate, Local, Location, Body, Mutability, Operand, Place, PlaceBase, PlaceElem,
+    PlaceRef, Static, StaticKind
 };
-use rustc::mir::{Field, Projection, ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
+use rustc::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
 use rustc::mir::{Terminator, TerminatorKind};
 use rustc::ty::query::Providers;
 use rustc::ty::{self, TyCtxt};
@@ -164,8 +164,8 @@ fn do_mir_borrowck<'a, 'tcx>(
         };
 
     let mdpe = MoveDataParamEnv {
-        move_data: move_data,
-        param_env: param_env,
+        move_data,
+        param_env,
     };
 
     let dead_unwinds = BitSet::new_empty(body.basic_blocks().len());
@@ -259,7 +259,10 @@ fn do_mir_borrowck<'a, 'tcx>(
         move_error_reported: BTreeMap::new(),
         uninitialized_error_reported: Default::default(),
         errors_buffer,
-        disable_error_downgrading: false,
+        // Only downgrade errors on Rust 2015 and refuse to do so on Rust 2018.
+        // FIXME(Centril): In Rust 1.40.0, refuse doing so on 2015 as well and
+        // proceed to throwing out the migration infrastructure.
+        disable_error_downgrading: body.span.rust_2018(),
         nonlexical_regioncx: regioncx,
         used_mut: Default::default(),
         used_mut_upvars: SmallVec::new(),
@@ -543,7 +546,7 @@ impl<'cx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tcx
         self.check_activations(location, span, flow_state);
 
         match stmt.kind {
-            StatementKind::Assign(ref lhs, ref rhs) => {
+            StatementKind::Assign(box(ref lhs, ref rhs)) => {
                 self.consume_rvalue(
                     location,
                     (rhs, span),
@@ -558,7 +561,7 @@ impl<'cx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tcx
                     flow_state,
                 );
             }
-            StatementKind::FakeRead(_, ref place) => {
+            StatementKind::FakeRead(_, box ref place) => {
                 // Read for match doesn't access any memory and is used to
                 // assert that a place is safe and live. So we don't have to
                 // do any checks here.
@@ -902,7 +905,7 @@ enum InitializationRequiringAction {
 
 struct RootPlace<'d, 'tcx> {
     place_base: &'d PlaceBase<'tcx>,
-    place_projection: &'d Option<Box<Projection<'tcx>>>,
+    place_projection: &'d [PlaceElem<'tcx>],
     is_local_mutation_allowed: LocalMutationIsAllowed,
 }
 
@@ -1188,7 +1191,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         // before (at this point in the flow).
         if let Place {
             base: PlaceBase::Local(local),
-            projection: None,
+            projection: box [],
         } = place_span.0 {
             if let Mutability::Not = self.body.local_decls[*local].mutability {
                 // check for reassignments to immutable local variables
@@ -1328,7 +1331,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn propagate_closure_used_mut_upvar(&mut self, operand: &Operand<'tcx>) {
         let propagate_closure_used_mut_place = |this: &mut Self, place: &Place<'tcx>| {
-            if place.projection.is_some() {
+            if !place.projection.is_empty() {
                 if let Some(field) = this.is_upvar_field_projection(place.as_ref()) {
                     this.used_mut_upvars.push(field);
                 }
@@ -1343,11 +1346,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match *operand {
             Operand::Move(Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             }) |
             Operand::Copy(Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             }) if self.body.local_decls[local].is_user_variable.is_none() => {
                 if self.body.local_decls[local].ty.is_mutable_ptr() {
                     // The variable will be marked as mutable by the borrow.
@@ -1384,7 +1387,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 let stmt = &bbd.statements[loc.statement_index];
                 debug!("temporary assigned in: stmt={:?}", stmt);
 
-                if let StatementKind::Assign(_, box Rvalue::Ref(_, _, ref source)) = stmt.kind {
+                if let StatementKind::Assign(box(_, Rvalue::Ref(_, _, ref source))) = stmt.kind {
                     propagate_closure_used_mut_place(self, source);
                 } else {
                     bug!("closures should only capture user variables \
@@ -1465,7 +1468,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         //
         // FIXME: allow thread-locals to borrow other thread locals?
 
-        assert!(root_place.projection.is_none());
+        assert!(root_place.projection.is_empty());
         let (might_be_alive, will_be_dropped) = match root_place.base {
             PlaceBase::Static(box Static {
                 kind: StaticKind::Promoted(..),
@@ -1753,13 +1756,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         flow_state: &Flows<'cx, 'tcx>,
     ) {
         debug!("check_if_assigned_path_is_moved place: {:?}", place);
-        // recur down place; dispatch to external checks when necessary
-        let mut place_projection = &place.projection;
 
         // None case => assigning to `x` does not require `x` be initialized.
-        while let Some(proj) = place_projection {
-            let Projection { ref base, ref elem } = **proj;
-            match *elem {
+        let mut cursor = &*place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
+
+            match elem {
                 ProjectionElem::Index(_/*operand*/) |
                 ProjectionElem::ConstantIndex { .. } |
                 // assigning to P[i] requires P to be valid.
@@ -1775,7 +1778,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         location, InitializationRequiringAction::Use,
                         (PlaceRef {
                             base: &place.base,
-                            projection: base,
+                            projection: proj_base,
                         }, span), flow_state);
                     // (base initialized; no need to
                     // recur further)
@@ -1792,14 +1795,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     // assigning to `P.f` requires `P` itself
                     // be already initialized
                     let tcx = self.infcx.tcx;
-                    let base_ty = Place::ty_from(&place.base, base, self.body, tcx).ty;
+                    let base_ty = Place::ty_from(&place.base, proj_base, self.body, tcx).ty;
                     match base_ty.sty {
                         ty::Adt(def, _) if def.has_dtor(tcx) => {
                             self.check_if_path_or_subpath_is_moved(
                                 location, InitializationRequiringAction::Assignment,
                                 (PlaceRef {
                                     base: &place.base,
-                                    projection: base,
+                                    projection: proj_base,
                                 }, span), flow_state);
 
                             // (base initialized; no need to
@@ -1812,7 +1815,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         ty::Adt(..) | ty::Tuple(..) => {
                             check_parent_of_field(self, location, PlaceRef {
                                 base: &place.base,
-                                projection: base,
+                                projection: proj_base,
                             }, span, flow_state);
 
                             if let PlaceBase::Local(local) = place.base {
@@ -1832,8 +1835,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     }
                 }
             }
-
-            place_projection = base;
         }
 
         fn check_parent_of_field<'cx, 'tcx>(
@@ -2081,7 +2082,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match root_place {
             RootPlace {
                 place_base: PlaceBase::Local(local),
-                place_projection: None,
+                place_projection: [],
                 is_local_mutation_allowed,
             } => {
                 // If the local may have been initialized, and it is now currently being
@@ -2100,7 +2101,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             } => {}
             RootPlace {
                 place_base,
-                place_projection: place_projection @ Some(_),
+                place_projection: place_projection @ [.., _],
                 is_local_mutation_allowed: _,
             } => {
                 if let Some(field) = self.is_upvar_field_projection(PlaceRef {
@@ -2112,7 +2113,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
             RootPlace {
                 place_base: PlaceBase::Static(..),
-                place_projection: None,
+                place_projection: [],
                 is_local_mutation_allowed: _,
             } => {}
         }
@@ -2128,7 +2129,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match place {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } => {
                 let local = &self.body.local_decls[*local];
                 match local.mutability {
@@ -2159,7 +2160,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     kind: StaticKind::Promoted(..),
                     ..
                 }),
-                projection: None,
+                projection: [],
             } =>
                 Ok(RootPlace {
                     place_base: place.base,
@@ -2172,7 +2173,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     def_id,
                     ..
                 }),
-                projection: None,
+                projection: [],
             } => {
                 if !self.infcx.tcx.is_mutable_static(*def_id) {
                     Err(place)
@@ -2186,12 +2187,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
             PlaceRef {
                 base: _,
-                projection: Some(proj),
+                projection: [proj_base @ .., elem],
             } => {
-                match proj.elem {
+                match elem {
                     ProjectionElem::Deref => {
                         let base_ty =
-                            Place::ty_from(place.base, &proj.base, self.body, self.infcx.tcx).ty;
+                            Place::ty_from(place.base, proj_base, self.body, self.infcx.tcx).ty;
 
                         // Check the kind of deref to decide
                         match base_ty.sty {
@@ -2213,7 +2214,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
                                         self.is_mutable(PlaceRef {
                                             base: place.base,
-                                            projection: &proj.base,
+                                            projection: proj_base,
                                         }, mode)
                                     }
                                 }
@@ -2237,7 +2238,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             _ if base_ty.is_box() => {
                                 self.is_mutable(PlaceRef {
                                     base: place.base,
-                                    projection: &proj.base,
+                                    projection: proj_base,
                                 }, is_local_mutation_allowed)
                             }
                             // Deref should only be for reference, pointers or boxes
@@ -2294,7 +2295,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                     // ```
                                     let _ = self.is_mutable(PlaceRef {
                                         base: place.base,
-                                        projection: &proj.base,
+                                        projection: proj_base,
                                     }, is_local_mutation_allowed)?;
                                     Ok(RootPlace {
                                         place_base: place.base,
@@ -2306,7 +2307,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         } else {
                             self.is_mutable(PlaceRef {
                                 base: place.base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             }, is_local_mutation_allowed)
                         }
                     }
@@ -2323,21 +2324,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let mut place_projection = place_ref.projection;
         let mut by_ref = false;
 
-        if let Some(box Projection {
-            base,
-            elem: ProjectionElem::Deref,
-        }) = place_projection {
-            place_projection = &base;
+        if let [proj_base @ .., ProjectionElem::Deref] = place_projection {
+            place_projection = proj_base;
             by_ref = true;
         }
 
         match place_projection {
-            Some(box Projection {
-                base,
-                elem: ProjectionElem::Field(field, _ty),
-            }) => {
+            [base @ .., ProjectionElem::Field(field, _ty)] => {
                 let tcx = self.infcx.tcx;
-                let base_ty = Place::ty_from(place_ref.base, &base, self.body, tcx).ty;
+                let base_ty = Place::ty_from(place_ref.base, base, self.body, tcx).ty;
 
                 if (base_ty.is_closure() || base_ty.is_generator()) &&
                     (!by_ref || self.upvars[field.index()].by_ref) {
diff --git a/src/librustc_mir/borrow_check/move_errors.rs b/src/librustc_mir/borrow_check/move_errors.rs
index 0d13db2f5a413..aa732b0092a22 100644
--- a/src/librustc_mir/borrow_check/move_errors.rs
+++ b/src/librustc_mir/borrow_check/move_errors.rs
@@ -89,11 +89,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 // If that ever stops being the case, then the ever initialized
                 // flow could be used.
                 if let Some(StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(local),
-                        projection: None,
-                    },
-                    box Rvalue::Use(Operand::Move(move_from)),
+                    box(
+                        Place {
+                            base: PlaceBase::Local(local),
+                            projection: box [],
+                        },
+                        Rvalue::Use(Operand::Move(move_from))
+                    )
                 )) = self.body.basic_blocks()[location.block]
                     .statements
                     .get(location.statement_index)
@@ -274,16 +276,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         place: &Place<'tcx>,
         span: Span
     ) -> DiagnosticBuilder<'a> {
-        let description = if place.projection.is_none() {
+        let description = if place.projection.is_empty() {
             format!("static item `{}`", self.describe_place(place.as_ref()).unwrap())
         } else {
-            let mut base_static = &place.projection;
-            while let Some(box Projection { base: Some(ref proj), .. }) = base_static {
-                base_static = &proj.base;
-            }
             let base_static = PlaceRef {
                 base: &place.base,
-                projection: base_static,
+                projection: &place.projection[..1],
             };
 
             format!(
@@ -309,17 +307,19 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         let upvar_field = self.prefixes(move_place.as_ref(), PrefixSet::All)
             .find_map(|p| self.is_upvar_field_projection(p));
 
-        let deref_base = match deref_target_place.projection {
-            Some(box Projection { ref base, elem: ProjectionElem::Deref }) => PlaceRef {
-                base: &deref_target_place.base,
-                projection: base,
-            },
+        let deref_base = match &deref_target_place.projection {
+            box [proj_base @ .., ProjectionElem::Deref] => {
+                PlaceRef {
+                    base: &deref_target_place.base,
+                    projection: proj_base,
+                }
+            }
             _ => bug!("deref_target_place is not a deref projection"),
         };
 
         if let PlaceRef {
             base: PlaceBase::Local(local),
-            projection: None,
+            projection: [],
         } = deref_base {
             let decl = &self.body.local_decls[*local];
             if decl.is_ref_for_guard() {
diff --git a/src/librustc_mir/borrow_check/mutability_errors.rs b/src/librustc_mir/borrow_check/mutability_errors.rs
index 8f2ce80aafa22..14b76d97b3e57 100644
--- a/src/librustc_mir/borrow_check/mutability_errors.rs
+++ b/src/librustc_mir/borrow_check/mutability_errors.rs
@@ -2,7 +2,7 @@ use rustc::hir;
 use rustc::hir::Node;
 use rustc::mir::{self, BindingForm, ClearCrossCrate, Local, Location, Body};
 use rustc::mir::{
-    Mutability, Place, PlaceRef, PlaceBase, Projection, ProjectionElem, Static, StaticKind
+    Mutability, Place, PlaceRef, PlaceBase, ProjectionElem, Static, StaticKind
 };
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc_data_structures::indexed_vec::Idx;
@@ -47,12 +47,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         match the_place_err {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } => {
                 item_msg = format!("`{}`", access_place_desc.unwrap());
                 if let Place {
                     base: PlaceBase::Local(_),
-                    projection: None,
+                    projection: box [],
                 } = access_place {
                     reason = ", as it is not declared as mutable".to_string();
                 } else {
@@ -65,14 +65,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base: _,
-                projection:
-                    Some(box Projection {
-                        base,
-                        elem: ProjectionElem::Field(upvar_index, _),
-                    }),
+                projection: [proj_base @ .., ProjectionElem::Field(upvar_index, _)],
             } => {
                 debug_assert!(is_closure_or_generator(
-                    Place::ty_from(&the_place_err.base, &base, self.body, self.infcx.tcx).ty
+                    Place::ty_from(&the_place_err.base, proj_base, self.body, self.infcx.tcx).ty
                 ));
 
                 item_msg = format!("`{}`", access_place_desc.unwrap());
@@ -86,14 +82,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base: _,
-                projection:
-                    Some(box Projection {
-                        base,
-                        elem: ProjectionElem::Deref,
-                    }),
+                projection: [proj_base @ .., ProjectionElem::Deref],
             } => {
                 if the_place_err.base == &PlaceBase::Local(Local::new(1)) &&
-                    base.is_none() &&
+                    proj_base.is_empty() &&
                     !self.upvars.is_empty() {
                     item_msg = format!("`{}`", access_place_desc.unwrap());
                     debug_assert!(self.body.local_decls[Local::new(1)].ty.is_region_ptr());
@@ -114,7 +106,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                             ", as `Fn` closures cannot mutate their captured variables".to_string()
                         }
                 } else if {
-                    if let (PlaceBase::Local(local), None) = (&the_place_err.base, base) {
+                    if let (PlaceBase::Local(local), []) = (&the_place_err.base, proj_base) {
                         self.body.local_decls[*local].is_ref_for_guard()
                     } else {
                         false
@@ -125,7 +117,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 } else {
                     let source = self.borrowed_content_source(PlaceRef {
                         base: the_place_err.base,
-                        projection: base,
+                        projection: proj_base,
                     });
                     let pointer_type = source.describe_for_immutable_place();
                     opt_source = Some(source);
@@ -151,7 +143,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         kind: StaticKind::Promoted(..),
                         ..
                     }),
-                projection: None,
+                projection: [],
             } => unreachable!(),
 
             PlaceRef {
@@ -161,11 +153,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         def_id,
                         ..
                     }),
-                projection: None,
+                projection: [],
             } => {
                 if let Place {
                     base: PlaceBase::Static(_),
-                    projection: None,
+                    projection: box [],
                 } = access_place {
                     item_msg = format!("immutable static item `{}`", access_place_desc.unwrap());
                     reason = String::new();
@@ -178,33 +170,19 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base: _,
-                projection:
-                    Some(box Projection {
-                        base: _,
-                        elem: ProjectionElem::Index(_),
-                    }),
+                projection: [.., ProjectionElem::Index(_)],
             }
             | PlaceRef {
                 base: _,
-                projection:
-                    Some(box Projection {
-                        base: _,
-                        elem: ProjectionElem::ConstantIndex { .. },
-                    }),
+                projection: [.., ProjectionElem::ConstantIndex { .. }],
             }
             | PlaceRef {
                 base: _,
-                projection: Some(box Projection {
-                    base: _,
-                    elem: ProjectionElem::Subslice { .. },
-                }),
+                projection: [.., ProjectionElem::Subslice { .. }],
             }
             | PlaceRef {
                 base: _,
-                projection: Some(box Projection {
-                    base: _,
-                    elem: ProjectionElem::Downcast(..),
-                }),
+                projection: [.., ProjectionElem::Downcast(..)],
             } => bug!("Unexpected immutable place."),
         }
 
@@ -262,22 +240,17 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // after the field access).
             PlaceRef {
                 base,
-                projection: Some(box Projection {
-                    base: Some(box Projection {
-                        base: Some(box Projection {
-                            base: base_proj,
-                            elem: ProjectionElem::Deref,
-                        }),
-                        elem: ProjectionElem::Field(field, _),
-                    }),
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [proj_base @ ..,
+                             ProjectionElem::Deref,
+                             ProjectionElem::Field(field, _),
+                             ProjectionElem::Deref,
+                ],
             } => {
                 err.span_label(span, format!("cannot {ACT}", ACT = act));
 
                 if let Some((span, message)) = annotate_struct_field(
                     self.infcx.tcx,
-                    Place::ty_from(&base, &base_proj, self.body, self.infcx.tcx).ty,
+                    Place::ty_from(base, proj_base, self.body, self.infcx.tcx).ty,
                     field,
                 ) {
                     err.span_suggestion(
@@ -292,7 +265,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // Suggest removing a `&mut` from the use of a mutable reference.
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } if {
                 self.body.local_decls.get(*local).map(|local_decl| {
                     if let ClearCrossCrate::Set(
@@ -328,7 +301,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // variable) mutations...
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } if self.body.local_decls[*local].can_be_made_mutable() => {
                 // ... but it doesn't make sense to suggest it on
                 // variables that are `ref x`, `ref mut x`, `&self`,
@@ -349,13 +322,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // Also suggest adding mut for upvars
             PlaceRef {
                 base,
-                projection: Some(box Projection {
-                    base: proj_base,
-                    elem: ProjectionElem::Field(upvar_index, _),
-                }),
+                projection: [proj_base @ .., ProjectionElem::Field(upvar_index, _)],
             } => {
                 debug_assert!(is_closure_or_generator(
-                    Place::ty_from(&base, &proj_base, self.body, self.infcx.tcx).ty
+                    Place::ty_from(base, proj_base, self.body, self.infcx.tcx).ty
                 ));
 
                 err.span_label(span, format!("cannot {ACT}", ACT = act));
@@ -385,7 +355,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // a local variable, then just suggest the user remove it.
             PlaceRef {
                 base: PlaceBase::Local(_),
-                projection: None,
+                projection: [],
             } if {
                     if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) {
                         snippet.starts_with("&mut ")
@@ -400,10 +370,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [ProjectionElem::Deref],
             } if {
                 if let Some(ClearCrossCrate::Set(BindingForm::RefForGuard)) =
                     self.body.local_decls[*local].is_user_variable
@@ -427,10 +394,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // arbitrary base for the projection?
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [ProjectionElem::Deref],
             } if self.body.local_decls[*local].is_user_variable.is_some() =>
             {
                 let local_decl = &self.body.local_decls[*local];
@@ -510,10 +474,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base,
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [ProjectionElem::Deref],
             // FIXME document what is this 1 magic number about
             } if *base == PlaceBase::Local(Local::new(1)) &&
                   !self.upvars.is_empty() =>
@@ -527,10 +488,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
             PlaceRef {
                 base: _,
-                projection: Some(box Projection {
-                    base: _,
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: [.., ProjectionElem::Deref],
             } => {
                 err.span_label(span, format!("cannot {ACT}", ACT = act));
 
diff --git a/src/librustc_mir/borrow_check/nll/constraint_generation.rs b/src/librustc_mir/borrow_check/nll/constraint_generation.rs
index 5c230913a0da3..1e5f613aedc23 100644
--- a/src/librustc_mir/borrow_check/nll/constraint_generation.rs
+++ b/src/librustc_mir/borrow_check/nll/constraint_generation.rs
@@ -8,9 +8,8 @@ use rustc::infer::InferCtxt;
 use rustc::mir::visit::TyContext;
 use rustc::mir::visit::Visitor;
 use rustc::mir::{
-    BasicBlock, BasicBlockData, Body, Local, Location, Place, PlaceBase, Projection,
-    ProjectionElem, Rvalue, SourceInfo, Statement, StatementKind, Terminator, TerminatorKind,
-    UserTypeProjection,
+    BasicBlock, BasicBlockData, Body, Local, Location, Place, PlaceBase, ProjectionElem, Rvalue,
+    SourceInfo, Statement, StatementKind, Terminator, TerminatorKind, UserTypeProjection,
 };
 use rustc::ty::fold::TypeFoldable;
 use rustc::ty::{self, ClosureSubsts, GeneratorSubsts, RegionVid, Ty};
@@ -229,14 +228,11 @@ impl<'cx, 'cg, 'tcx> ConstraintGeneration<'cx, 'cg, 'tcx> {
             match place {
                 Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } |
                 Place {
                     base: PlaceBase::Local(local),
-                    projection: Some(box Projection {
-                        base: None,
-                        elem: ProjectionElem::Deref,
-                    }),
+                    projection: box [ProjectionElem::Deref],
                 } => {
                     debug!(
                         "Recording `killed` facts for borrows of local={:?} at location={:?}",
@@ -261,7 +257,7 @@ impl<'cx, 'cg, 'tcx> ConstraintGeneration<'cx, 'cg, 'tcx> {
 
                 Place {
                     base: PlaceBase::Local(local),
-                    projection: Some(_),
+                    projection: box [.., _],
                 } => {
                     // Kill conflicting borrows of the innermost local.
                     debug!(
diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
index aba3ef1cbbfc9..eae2f832ba791 100644
--- a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
@@ -274,7 +274,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if let Some((WriteKind::StorageDeadOrDrop, place)) = kind_place {
                         if let Place {
                             base: PlaceBase::Local(borrowed_local),
-                            projection: None,
+                            projection: box [],
                         } = place {
                              if body.local_decls[*borrowed_local].name.is_some()
                                 && local != *borrowed_local
@@ -495,11 +495,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             Operand::Constant(c) => c.span,
                             Operand::Copy(Place {
                                 base: PlaceBase::Local(l),
-                                projection: None,
+                                projection: box [],
                             }) |
                             Operand::Move(Place {
                                 base: PlaceBase::Local(l),
-                                projection: None,
+                                projection: box [],
                             }) => {
                                 let local_decl = &self.body.local_decls[*l];
                                 if local_decl.name.is_none() {
@@ -541,10 +541,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         // it which simplifies the termination logic.
         let mut queue = vec![location];
         let mut target = if let Some(&Statement {
-            kind: StatementKind::Assign(Place {
+            kind: StatementKind::Assign(box(Place {
                 base: PlaceBase::Local(local),
-                projection: None,
-            }, _),
+                projection: box [],
+            }, _)),
             ..
         }) = stmt
         {
@@ -567,7 +567,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 debug!("was_captured_by_trait_object: stmt={:?}", stmt);
 
                 // The only kind of statement that we care about is assignments...
-                if let StatementKind::Assign(place, box rvalue) = &stmt.kind {
+                if let StatementKind::Assign(box(place, rvalue)) = &stmt.kind {
                     let into = match place.local_or_deref_local() {
                         Some(into) => into,
                         None => {
@@ -583,11 +583,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         Rvalue::Use(operand) => match operand {
                             Operand::Copy(Place {
                                 base: PlaceBase::Local(from),
-                                projection: None,
+                                projection: box [],
                             })
                             | Operand::Move(Place {
                                 base: PlaceBase::Local(from),
-                                projection: None,
+                                projection: box [],
                             })
                                 if *from == target =>
                             {
@@ -602,11 +602,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         ) => match operand {
                             Operand::Copy(Place {
                                 base: PlaceBase::Local(from),
-                                projection: None,
+                                projection: box [],
                             })
                             | Operand::Move(Place {
                                 base: PlaceBase::Local(from),
-                                projection: None,
+                                projection: box [],
                             })
                                 if *from == target =>
                             {
@@ -639,7 +639,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 if let TerminatorKind::Call {
                     destination: Some((Place {
                         base: PlaceBase::Local(dest),
-                        projection: None,
+                        projection: box [],
                     }, block)),
                     args,
                     ..
@@ -653,7 +653,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     let found_target = args.iter().any(|arg| {
                         if let Operand::Move(Place {
                             base: PlaceBase::Local(potential),
-                            projection: None,
+                            projection: box [],
                         }) = arg {
                             *potential == target
                         } else {
diff --git a/src/librustc_mir/borrow_check/nll/invalidation.rs b/src/librustc_mir/borrow_check/nll/invalidation.rs
index 71106af767064..1d429e3a6dee6 100644
--- a/src/librustc_mir/borrow_check/nll/invalidation.rs
+++ b/src/librustc_mir/borrow_check/nll/invalidation.rs
@@ -66,7 +66,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
         self.check_activations(location);
 
         match statement.kind {
-            StatementKind::Assign(ref lhs, ref rhs) => {
+            StatementKind::Assign(box(ref lhs, ref rhs)) => {
                 self.consume_rvalue(
                     location,
                     rhs,
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs
index efa18587b7ddb..26a89b4e7a8d1 100644
--- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs
@@ -13,7 +13,7 @@ use rustc::infer::NLLRegionVariableOrigin;
 use rustc::mir::{ConstraintCategory, Location, Body};
 use rustc::ty::{self, RegionVid};
 use rustc_data_structures::indexed_vec::IndexVec;
-use rustc_errors::{Diagnostic, DiagnosticBuilder};
+use rustc_errors::DiagnosticBuilder;
 use std::collections::VecDeque;
 use syntax::errors::Applicability;
 use syntax::symbol::kw;
@@ -22,7 +22,7 @@ use syntax_pos::Span;
 mod region_name;
 mod var_name;
 
-crate use self::region_name::{RegionName, RegionNameSource};
+crate use self::region_name::{RegionName, RegionNameSource, RegionErrorNamingCtx};
 
 impl ConstraintDescription for ConstraintCategory {
     fn description(&self) -> &'static str {
@@ -54,6 +54,39 @@ enum Trace {
     NotVisited,
 }
 
+/// Various pieces of state used when reporting borrow checker errors.
+pub struct ErrorReportingCtx<'a, 'b, 'tcx> {
+    /// The region inference context used for borrow chekcing this MIR body.
+    #[allow(dead_code)] // FIXME(mark-i-m): used by outlives suggestions
+    region_infcx: &'b RegionInferenceContext<'tcx>,
+
+    /// The inference context used for type checking.
+    infcx: &'b InferCtxt<'a, 'tcx>,
+
+    /// The MIR def we are reporting errors on.
+    mir_def_id: DefId,
+
+    /// The MIR body we are reporting errors on (for convenience).
+    body: &'b Body<'tcx>,
+
+    /// Any upvars for the MIR body we have kept track of during borrow checking.
+    upvars: &'b [Upvar],
+}
+
+/// Information about the various region constraints involved in a borrow checker error.
+#[derive(Clone, Debug)]
+pub struct ErrorConstraintInfo {
+    // fr: outlived_fr
+    fr: RegionVid,
+    fr_is_local: bool,
+    outlived_fr: RegionVid,
+    outlived_fr_is_local: bool,
+
+    // Category and span for best blame constraint
+    category: ConstraintCategory,
+    span: Span,
+}
+
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Tries to find the best constraint to blame for the fact that
     /// `R: from_region`, where `R` is some region that meets
@@ -257,16 +290,16 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// ```
     ///
     /// Here we would be invoked with `fr = 'a` and `outlived_fr = `'b`.
-    pub(super) fn report_error(
-        &self,
+    pub(super) fn report_error<'a>(
+        &'a self,
         body: &Body<'tcx>,
         upvars: &[Upvar],
-        infcx: &InferCtxt<'_, 'tcx>,
+        infcx: &'a InferCtxt<'a, 'tcx>,
         mir_def_id: DefId,
         fr: RegionVid,
         outlived_fr: RegionVid,
-        errors_buffer: &mut Vec<Diagnostic>,
-    ) {
+        renctx: &mut RegionErrorNamingCtx,
+    ) -> DiagnosticBuilder<'a> {
         debug!("report_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr);
 
         let (category, _, span) = self.best_blame_constraint(body, fr, |r| {
@@ -279,8 +312,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             let tables = infcx.tcx.typeck_tables_of(mir_def_id);
             let nice = NiceRegionError::new_from_span(infcx, span, o, f, Some(tables));
             if let Some(diag) = nice.try_report_from_nll() {
-                diag.buffer(errors_buffer);
-                return;
+                return diag;
             }
         }
 
@@ -293,45 +325,28 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             "report_error: fr_is_local={:?} outlived_fr_is_local={:?} category={:?}",
             fr_is_local, outlived_fr_is_local, category
         );
+
+        let errctx = ErrorReportingCtx {
+            region_infcx: self,
+            infcx,
+            mir_def_id,
+            body,
+            upvars,
+        };
+
+        let errci = ErrorConstraintInfo {
+            fr, outlived_fr, fr_is_local, outlived_fr_is_local, category, span
+        };
+
         match (category, fr_is_local, outlived_fr_is_local) {
             (ConstraintCategory::Return, true, false) if self.is_closure_fn_mut(infcx, fr) => {
-                self.report_fnmut_error(
-                    body,
-                    upvars,
-                    infcx,
-                    mir_def_id,
-                    fr,
-                    outlived_fr,
-                    span,
-                    errors_buffer,
-                )
+                self.report_fnmut_error(&errctx, &errci, renctx)
             }
             (ConstraintCategory::Assignment, true, false)
-            | (ConstraintCategory::CallArgument, true, false) => self.report_escaping_data_error(
-                body,
-                upvars,
-                infcx,
-                mir_def_id,
-                fr,
-                outlived_fr,
-                category,
-                span,
-                errors_buffer,
-            ),
-            _ => self.report_general_error(
-                body,
-                upvars,
-                infcx,
-                mir_def_id,
-                fr,
-                fr_is_local,
-                outlived_fr,
-                outlived_fr_is_local,
-                category,
-                span,
-                errors_buffer,
-            ),
-        };
+            | (ConstraintCategory::CallArgument, true, false) =>
+                self.report_escaping_data_error(&errctx, &errci, renctx),
+            _ => self.report_general_error(&errctx, &errci, renctx),
+        }
     }
 
     /// We have a constraint `fr1: fr2` that is not satisfied, where
@@ -379,19 +394,19 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// ```
     fn report_fnmut_error(
         &self,
-        body: &Body<'tcx>,
-        upvars: &[Upvar],
-        infcx: &InferCtxt<'_, 'tcx>,
-        mir_def_id: DefId,
-        _fr: RegionVid,
-        outlived_fr: RegionVid,
-        span: Span,
-        errors_buffer: &mut Vec<Diagnostic>,
-    ) {
-        let mut diag = infcx
+        errctx: &ErrorReportingCtx<'_, '_, 'tcx>,
+        errci: &ErrorConstraintInfo,
+        renctx: &mut RegionErrorNamingCtx,
+    ) -> DiagnosticBuilder<'_> {
+        let ErrorConstraintInfo {
+            outlived_fr, span, ..
+        } = errci;
+
+        let mut diag = errctx
+            .infcx
             .tcx
             .sess
-            .struct_span_err(span, "captured variable cannot escape `FnMut` closure body");
+            .struct_span_err(*span, "captured variable cannot escape `FnMut` closure body");
 
         // We should check if the return type of this closure is in fact a closure - in that
         // case, we can special case the error further.
@@ -403,11 +418,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             "returns a reference to a captured variable which escapes the closure body"
         };
 
-        diag.span_label(span, message);
+        diag.span_label(*span, message);
 
-        match self.give_region_a_name(infcx, body, upvars, mir_def_id, outlived_fr, &mut 1)
-            .unwrap().source
-        {
+        match self.give_region_a_name(errctx, renctx, *outlived_fr).unwrap().source {
             RegionNameSource::NamedEarlyBoundRegion(fr_span)
             | RegionNameSource::NamedFreeRegion(fr_span)
             | RegionNameSource::SynthesizedFreeEnvRegion(fr_span, _)
@@ -427,7 +440,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         );
         diag.note("...therefore, they cannot allow references to captured variables to escape");
 
-        diag.buffer(errors_buffer);
+        diag
     }
 
     /// Reports a error specifically for when data is escaping a closure.
@@ -444,20 +457,22 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// ```
     fn report_escaping_data_error(
         &self,
-        body: &Body<'tcx>,
-        upvars: &[Upvar],
-        infcx: &InferCtxt<'_, 'tcx>,
-        mir_def_id: DefId,
-        fr: RegionVid,
-        outlived_fr: RegionVid,
-        category: ConstraintCategory,
-        span: Span,
-        errors_buffer: &mut Vec<Diagnostic>,
-    ) {
+        errctx: &ErrorReportingCtx<'_, '_, 'tcx>,
+        errci: &ErrorConstraintInfo,
+        renctx: &mut RegionErrorNamingCtx,
+    ) -> DiagnosticBuilder<'_> {
+        let ErrorReportingCtx {
+            infcx, body, upvars, ..
+        } = errctx;
+
+        let ErrorConstraintInfo {
+            span, category, ..
+        } = errci;
+
         let fr_name_and_span =
-            self.get_var_name_and_span_for_region(infcx.tcx, body, upvars, fr);
+            self.get_var_name_and_span_for_region(infcx.tcx, body, upvars, errci.fr);
         let outlived_fr_name_and_span =
-            self.get_var_name_and_span_for_region(infcx.tcx, body, upvars, outlived_fr);
+            self.get_var_name_and_span_for_region(infcx.tcx, body, upvars, errci.outlived_fr);
 
         let escapes_from = match self.universal_regions.defining_ty {
             DefiningTy::Closure(..) => "closure",
@@ -469,27 +484,23 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // Revert to the normal error in these cases.
         // Assignments aren't "escapes" in function items.
         if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none())
-            || (category == ConstraintCategory::Assignment && escapes_from == "function")
+            || (*category == ConstraintCategory::Assignment && escapes_from == "function")
             || escapes_from == "const"
         {
             return self.report_general_error(
-                body,
-                upvars,
-                infcx,
-                mir_def_id,
-                fr,
-                true,
-                outlived_fr,
-                false,
-                category,
-                span,
-                errors_buffer,
+                errctx,
+                &ErrorConstraintInfo {
+                    fr_is_local: true,
+                    outlived_fr_is_local: false,
+                    .. *errci
+                },
+                renctx,
             );
         }
 
         let mut diag = borrowck_errors::borrowed_data_escapes_closure(
             infcx.tcx,
-            span,
+            *span,
             escapes_from,
         );
 
@@ -513,12 +524,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             );
 
             diag.span_label(
-                span,
+                *span,
                 format!("`{}` escapes the {} body here", fr_name, escapes_from),
             );
         }
 
-        diag.buffer(errors_buffer);
+        diag
     }
 
     /// Reports a region inference error for the general case with named/synthesized lifetimes to
@@ -538,41 +549,37 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// ```
     fn report_general_error(
         &self,
-        body: &Body<'tcx>,
-        upvars: &[Upvar],
-        infcx: &InferCtxt<'_, 'tcx>,
-        mir_def_id: DefId,
-        fr: RegionVid,
-        fr_is_local: bool,
-        outlived_fr: RegionVid,
-        outlived_fr_is_local: bool,
-        category: ConstraintCategory,
-        span: Span,
-        errors_buffer: &mut Vec<Diagnostic>,
-    ) {
+        errctx: &ErrorReportingCtx<'_, '_, 'tcx>,
+        errci: &ErrorConstraintInfo,
+        renctx: &mut RegionErrorNamingCtx,
+    ) -> DiagnosticBuilder<'_> {
+        let ErrorReportingCtx {
+            infcx, mir_def_id, ..
+        } = errctx;
+        let ErrorConstraintInfo {
+            fr, fr_is_local, outlived_fr, outlived_fr_is_local, span, category, ..
+        } = errci;
+
         let mut diag = infcx.tcx.sess.struct_span_err(
-            span,
+            *span,
             "lifetime may not live long enough"
         );
 
-        let counter = &mut 1;
-        let fr_name = self.give_region_a_name(
-            infcx, body, upvars, mir_def_id, fr, counter).unwrap();
-        fr_name.highlight_region_name(&mut diag);
-        let outlived_fr_name =
-            self.give_region_a_name(infcx, body, upvars, mir_def_id, outlived_fr, counter).unwrap();
-        outlived_fr_name.highlight_region_name(&mut diag);
-
-        let mir_def_name = if infcx.tcx.is_closure(mir_def_id) {
+        let mir_def_name = if infcx.tcx.is_closure(*mir_def_id) {
             "closure"
         } else {
             "function"
         };
 
+        let fr_name = self.give_region_a_name(errctx, renctx, *fr).unwrap();
+        fr_name.highlight_region_name(&mut diag);
+        let outlived_fr_name = self.give_region_a_name(errctx, renctx, *outlived_fr).unwrap();
+        outlived_fr_name.highlight_region_name(&mut diag);
+
         match (category, outlived_fr_is_local, fr_is_local) {
             (ConstraintCategory::Return, true, _) => {
                 diag.span_label(
-                    span,
+                    *span,
                     format!(
                         "{} was supposed to return data with lifetime `{}` but it is returning \
                          data with lifetime `{}`",
@@ -582,7 +589,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
             _ => {
                 diag.span_label(
-                    span,
+                    *span,
                     format!(
                         "{}requires that `{}` must outlive `{}`",
                         category.description(),
@@ -593,9 +600,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
         }
 
-        self.add_static_impl_trait_suggestion(infcx, &mut diag, fr, fr_name, outlived_fr);
+        self.add_static_impl_trait_suggestion(infcx, &mut diag, *fr, fr_name, *outlived_fr);
 
-        diag.buffer(errors_buffer);
+        diag
     }
 
     /// Adds a suggestion to errors where a `impl Trait` is returned.
@@ -704,8 +711,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             borrow_region,
             |r| self.provides_universal_region(r, borrow_region, outlived_region)
         );
-        let outlived_fr_name =
-            self.give_region_a_name(infcx, body, upvars, mir_def_id, outlived_region, &mut 1);
+
+        let mut renctx = RegionErrorNamingCtx::new();
+        let errctx = ErrorReportingCtx {
+            infcx, body, upvars, mir_def_id,
+            region_infcx: self,
+        };
+        let outlived_fr_name = self.give_region_a_name(&errctx, &mut renctx, outlived_region);
+
         (category, from_closure, span, outlived_fr_name)
     }
 
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
index 75a31628a54b6..6fa94269107f5 100644
--- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
+++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
@@ -1,5 +1,9 @@
 use std::fmt::{self, Display};
-use crate::borrow_check::nll::region_infer::RegionInferenceContext;
+
+use crate::borrow_check::nll::region_infer::{
+    RegionInferenceContext,
+    error_reporting::ErrorReportingCtx,
+};
 use crate::borrow_check::nll::universal_regions::DefiningTy;
 use crate::borrow_check::nll::ToRegionVid;
 use crate::borrow_check::Upvar;
@@ -13,29 +17,75 @@ use rustc::ty::{self, RegionKind, RegionVid, Ty, TyCtxt};
 use rustc::ty::print::RegionHighlightMode;
 use rustc_errors::DiagnosticBuilder;
 use syntax::symbol::kw;
-use syntax_pos::Span;
-use syntax_pos::symbol::InternedString;
+use rustc_data_structures::fx::FxHashMap;
+use syntax_pos::{Span, symbol::InternedString};
 
-#[derive(Debug)]
+/// A name for a particular region used in emitting diagnostics. This name could be a generated
+/// name like `'1`, a name used by the user like `'a`, or a name like `'static`.
+#[derive(Debug, Clone)]
 crate struct RegionName {
+    /// The name of the region (interned).
     crate name: InternedString,
+    /// Where the region comes from.
     crate source: RegionNameSource,
 }
 
-#[derive(Debug)]
+/// Denotes the source of a region that is named by a `RegionName`. For example, a free region that
+/// was named by the user would get `NamedFreeRegion` and `'static` lifetime would get `Static`.
+/// This helps to print the right kinds of diagnostics.
+#[derive(Debug, Clone)]
 crate enum RegionNameSource {
+    /// A bound (not free) region that was substituted at the def site (not an HRTB).
     NamedEarlyBoundRegion(Span),
+    /// A free region that the user has a name (`'a`) for.
     NamedFreeRegion(Span),
+    /// The `'static` region.
     Static,
+    /// The free region corresponding to the environment of a closure.
     SynthesizedFreeEnvRegion(Span, String),
+    /// The region name corresponds to a region where the type annotation is completely missing
+    /// from the code, e.g. in a closure arguments `|x| { ... }`, where `x` is a reference.
     CannotMatchHirTy(Span, String),
+    /// The region name corresponds a reference that was found by traversing the type in the HIR.
     MatchedHirTy(Span),
+    /// A region name from the generics list of a struct/enum/union.
     MatchedAdtAndSegment(Span),
+    /// The region corresponding to a closure upvar.
     AnonRegionFromUpvar(Span, String),
+    /// The region corresponding to the return type of a closure.
     AnonRegionFromOutput(Span, String, String),
     AnonRegionFromYieldTy(Span, String),
 }
 
+/// Records region names that have been assigned before so that we can use the same ones in later
+/// diagnostics.
+#[derive(Debug, Clone)]
+crate struct RegionErrorNamingCtx {
+    /// Record the region names generated for each region in the given
+    /// MIR def so that we can reuse them later in help/error messages.
+    renctx: FxHashMap<RegionVid, RegionName>,
+
+    /// The counter for generating new region names.
+    counter: usize,
+}
+
+impl RegionErrorNamingCtx {
+    crate fn new() -> Self {
+        Self {
+            counter: 1,
+            renctx: FxHashMap::default(),
+        }
+    }
+
+    crate fn get(&self, region: &RegionVid) -> Option<&RegionName> {
+        self.renctx.get(region)
+    }
+
+    crate fn insert(&mut self, region: RegionVid, name: RegionName) {
+        self.renctx.insert(region, name);
+    }
+}
+
 impl RegionName {
     #[allow(dead_code)]
     crate fn was_named(&self) -> bool {
@@ -63,43 +113,40 @@ impl RegionName {
         self.name
     }
 
-    crate fn highlight_region_name(
-        &self,
-        diag: &mut DiagnosticBuilder<'_>
-    ) {
+    crate fn highlight_region_name(&self, diag: &mut DiagnosticBuilder<'_>) {
         match &self.source {
-            RegionNameSource::NamedFreeRegion(span) |
-            RegionNameSource::NamedEarlyBoundRegion(span) => {
-                diag.span_label(
-                    *span,
-                    format!("lifetime `{}` defined here", self),
-                );
-            },
+            RegionNameSource::NamedFreeRegion(span)
+            | RegionNameSource::NamedEarlyBoundRegion(span) => {
+                diag.span_label(*span, format!("lifetime `{}` defined here", self));
+            }
             RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
                 diag.span_label(
                     *span,
                     format!("lifetime `{}` represents this closure's body", self),
                 );
                 diag.note(&note);
-            },
+            }
             RegionNameSource::CannotMatchHirTy(span, type_name) => {
                 diag.span_label(*span, format!("has type `{}`", type_name));
-            },
+            }
             RegionNameSource::MatchedHirTy(span) => {
                 diag.span_label(
                     *span,
                     format!("let's call the lifetime of this reference `{}`", self),
                 );
-            },
+            }
             RegionNameSource::MatchedAdtAndSegment(span) => {
                 diag.span_label(*span, format!("let's call this `{}`", self));
-            },
+            }
             RegionNameSource::AnonRegionFromUpvar(span, upvar_name) => {
                 diag.span_label(
                     *span,
-                    format!("lifetime `{}` appears in the type of `{}`", self, upvar_name),
+                    format!(
+                        "lifetime `{}` appears in the type of `{}`",
+                        self, upvar_name
+                    ),
                 );
-            },
+            }
             RegionNameSource::AnonRegionFromOutput(span, mir_description, type_name) => {
                 diag.span_label(
                     *span,
@@ -151,39 +198,49 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// and then return the name `'1` for us to use.
     crate fn give_region_a_name(
         &self,
-        infcx: &InferCtxt<'_, 'tcx>,
-        body: &Body<'tcx>,
-        upvars: &[Upvar],
-        mir_def_id: DefId,
+        errctx: &ErrorReportingCtx<'_, '_, 'tcx>,
+        renctx: &mut RegionErrorNamingCtx,
         fr: RegionVid,
-        counter: &mut usize,
     ) -> Option<RegionName> {
-        debug!("give_region_a_name(fr={:?}, counter={})", fr, counter);
+        let ErrorReportingCtx {
+            infcx, body, mir_def_id, upvars, ..
+        } = errctx;
+
+        debug!("give_region_a_name(fr={:?}, counter={:?})", fr, renctx.counter);
 
         assert!(self.universal_regions.is_universal_region(fr));
 
-        let value = self.give_name_from_error_region(infcx.tcx, mir_def_id, fr, counter)
+        if let Some(value) = renctx.get(&fr) {
+            return Some(value.clone());
+        }
+
+        let value = self
+            .give_name_from_error_region(infcx.tcx, *mir_def_id, fr, renctx)
             .or_else(|| {
                 self.give_name_if_anonymous_region_appears_in_arguments(
-                    infcx, body, mir_def_id, fr, counter,
+                    infcx, body, *mir_def_id, fr, renctx,
                 )
             })
             .or_else(|| {
                 self.give_name_if_anonymous_region_appears_in_upvars(
-                    infcx.tcx, upvars, fr, counter,
+                    infcx.tcx, upvars, fr, renctx
                 )
             })
             .or_else(|| {
                 self.give_name_if_anonymous_region_appears_in_output(
-                    infcx, body, mir_def_id, fr, counter,
+                    infcx, body, *mir_def_id, fr, renctx,
                 )
             })
             .or_else(|| {
                 self.give_name_if_anonymous_region_appears_in_yield_ty(
-                    infcx, body, mir_def_id, fr, counter,
+                    infcx, body, *mir_def_id, fr, renctx,
                 )
             });
 
+        if let Some(ref value) = value {
+            renctx.insert(fr, value.clone());
+        }
+
         debug!("give_region_a_name: gave name {:?}", value);
         value
     }
@@ -197,7 +254,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         tcx: TyCtxt<'tcx>,
         mir_def_id: DefId,
         fr: RegionVid,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let error_region = self.to_error_region(fr)?;
 
@@ -208,7 +265,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     let span = self.get_named_span(tcx, error_region, ebr.name);
                     Some(RegionName {
                         name: ebr.name,
-                        source: RegionNameSource::NamedEarlyBoundRegion(span)
+                        source: RegionNameSource::NamedEarlyBoundRegion(span),
                     })
                 } else {
                     None
@@ -227,12 +284,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                         name,
                         source: RegionNameSource::NamedFreeRegion(span),
                     })
-                },
+                }
 
                 ty::BoundRegion::BrEnv => {
-                    let mir_hir_id = tcx.hir()
-                                        .as_local_hir_id(mir_def_id)
-                                        .expect("non-local mir");
+                    let mir_hir_id = tcx.hir().as_local_hir_id(mir_def_id).expect("non-local mir");
                     let def_ty = self.universal_regions.defining_ty;
 
                     if let DefiningTy::Closure(def_id, substs) = def_ty {
@@ -243,7 +298,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                         } else {
                             bug!("Closure is not defined by a closure expr");
                         };
-                        let region_name = self.synthesize_region_name(counter);
+                        let region_name = self.synthesize_region_name(renctx);
 
                         let closure_kind_ty = substs.closure_kind_ty(def_id, tcx);
                         let note = match closure_kind_ty.to_opt_closure_kind() {
@@ -265,7 +320,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                             name: region_name,
                             source: RegionNameSource::SynthesizedFreeEnvRegion(
                                 args_span,
-                                note.to_string()
+                                note.to_string(),
                             ),
                         })
                     } else {
@@ -335,7 +390,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         body: &Body<'tcx>,
         mir_def_id: DefId,
         fr: RegionVid,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs();
         let argument_index = self.get_argument_index_for_region(infcx.tcx, fr)?;
@@ -349,12 +404,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             fr,
             arg_ty,
             argument_index,
-            counter,
+            renctx,
         ) {
             return Some(region_name);
         }
 
-        self.give_name_if_we_cannot_match_hir_ty(infcx, body, fr, arg_ty, counter)
+        self.give_name_if_we_cannot_match_hir_ty(infcx, body, fr, arg_ty, renctx)
     }
 
     fn give_name_if_we_can_match_hir_ty_from_argument(
@@ -365,7 +420,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         needle_fr: RegionVid,
         argument_ty: Ty<'tcx>,
         argument_index: usize,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let mir_hir_id = infcx.tcx.hir().as_local_hir_id(mir_def_id)?;
         let fn_decl = infcx.tcx.hir().fn_decl_by_hir_id(mir_hir_id)?;
@@ -379,7 +434,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 body,
                 needle_fr,
                 argument_ty,
-                counter,
+                renctx,
             ),
 
             _ => self.give_name_if_we_can_match_hir_ty(
@@ -387,7 +442,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 needle_fr,
                 argument_ty,
                 argument_hir_ty,
-                counter,
+                renctx,
             ),
         }
     }
@@ -409,10 +464,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         body: &Body<'tcx>,
         needle_fr: RegionVid,
         argument_ty: Ty<'tcx>,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
+        let counter = renctx.counter;
         let mut highlight = RegionHighlightMode::default();
-        highlight.highlighting_region_vid(needle_fr, *counter);
+        highlight.highlighting_region_vid(needle_fr, counter);
         let type_name = infcx.extract_type_name(&argument_ty, Some(highlight)).0;
 
         debug!(
@@ -428,7 +484,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 // This counter value will already have been used, so this function will increment
                 // it so the next value will be used next and return the region name that would
                 // have been used.
-                name: self.synthesize_region_name(counter),
+                name: self.synthesize_region_name(renctx),
                 source: RegionNameSource::CannotMatchHirTy(span, type_name),
             })
         } else {
@@ -455,7 +511,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// type. Once we find that, we can use the span of the `hir::Ty`
     /// to add the highlight.
     ///
-    /// This is a somewhat imperfect process, so long the way we also
+    /// This is a somewhat imperfect process, so along the way we also
     /// keep track of the **closest** type we've found. If we fail to
     /// find the exact `&` or `'_` to highlight, then we may fall back
     /// to highlighting that closest type instead.
@@ -465,7 +521,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         needle_fr: RegionVid,
         argument_ty: Ty<'tcx>,
         argument_hir_ty: &hir::Ty,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let search_stack: &mut Vec<(Ty<'tcx>, &hir::Ty)> =
             &mut vec![(argument_ty, argument_hir_ty)];
@@ -483,7 +539,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     hir::TyKind::Rptr(_lifetime, referent_hir_ty),
                 ) => {
                     if region.to_region_vid() == needle_fr {
-                        let region_name = self.synthesize_region_name(counter);
+                        let region_name = self.synthesize_region_name(renctx);
 
                         // Just grab the first character, the `&`.
                         let source_map = tcx.sess.source_map();
@@ -515,7 +571,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                                 substs,
                                 needle_fr,
                                 last_segment,
-                                counter,
+                                renctx,
                                 search_stack,
                             ) {
                                 return Some(name);
@@ -559,18 +615,19 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         substs: SubstsRef<'tcx>,
         needle_fr: RegionVid,
         last_segment: &'hir hir::PathSegment,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
         search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty)>,
     ) -> Option<RegionName> {
         // Did the user give explicit arguments? (e.g., `Foo<..>`)
         let args = last_segment.args.as_ref()?;
-        let lifetime = self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?;
+        let lifetime =
+            self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?;
         match lifetime.name {
             hir::LifetimeName::Param(_)
             | hir::LifetimeName::Error
             | hir::LifetimeName::Static
             | hir::LifetimeName::Underscore => {
-                let region_name = self.synthesize_region_name(counter);
+                let region_name = self.synthesize_region_name(renctx);
                 let ampersand_span = lifetime.span;
                 Some(RegionName {
                     name: region_name,
@@ -657,12 +714,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         tcx: TyCtxt<'tcx>,
         upvars: &[Upvar],
         fr: RegionVid,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let upvar_index = self.get_upvar_index_for_region(tcx, fr)?;
         let (upvar_name, upvar_span) =
             self.get_upvar_name_and_span_for_region(tcx, upvars, upvar_index);
-        let region_name = self.synthesize_region_name(counter);
+        let region_name = self.synthesize_region_name(renctx);
 
         Some(RegionName {
             name: region_name,
@@ -680,7 +737,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         body: &Body<'tcx>,
         mir_def_id: DefId,
         fr: RegionVid,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         let tcx = infcx.tcx;
 
@@ -694,7 +751,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
 
         let mut highlight = RegionHighlightMode::default();
-        highlight.highlighting_region_vid(fr, *counter);
+        highlight.highlighting_region_vid(fr, renctx.counter);
         let type_name = infcx.extract_type_name(&return_ty, Some(highlight)).0;
 
         let mir_hir_id = tcx.hir().as_local_hir_id(mir_def_id).expect("non-local mir");
@@ -725,11 +782,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // This counter value will already have been used, so this function will increment it
             // so the next value will be used next and return the region name that would have been
             // used.
-            name: self.synthesize_region_name(counter),
+            name: self.synthesize_region_name(renctx),
             source: RegionNameSource::AnonRegionFromOutput(
                 return_span,
                 mir_description.to_string(),
-                type_name
+                type_name,
             ),
         })
     }
@@ -740,7 +797,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         body: &Body<'tcx>,
         mir_def_id: DefId,
         fr: RegionVid,
-        counter: &mut usize,
+        renctx: &mut RegionErrorNamingCtx,
     ) -> Option<RegionName> {
         // Note: generators from `async fn` yield `()`, so we don't have to
         // worry about them here.
@@ -757,7 +814,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
 
         let mut highlight = RegionHighlightMode::default();
-        highlight.highlighting_region_vid(fr, *counter);
+        highlight.highlighting_region_vid(fr, renctx.counter);
         let type_name = infcx.extract_type_name(&yield_ty, Some(highlight)).0;
 
         let mir_hir_id = tcx.hir().as_local_hir_id(mir_def_id).expect("non-local mir");
@@ -780,16 +837,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         );
 
         Some(RegionName {
-            name: self.synthesize_region_name(counter),
+            name: self.synthesize_region_name(renctx),
             source: RegionNameSource::AnonRegionFromYieldTy(yield_span, type_name),
         })
     }
 
-    /// Creates a synthetic region named `'1`, incrementing the
-    /// counter.
-    fn synthesize_region_name(&self, counter: &mut usize) -> InternedString {
-        let c = *counter;
-        *counter += 1;
+    /// Creates a synthetic region named `'1`, incrementing the counter.
+    fn synthesize_region_name(&self, renctx: &mut RegionErrorNamingCtx) -> InternedString {
+        let c = renctx.counter;
+        renctx.counter += 1;
 
         InternedString::intern(&format!("'{:?}", c))
     }
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/mod.rs b/src/librustc_mir/borrow_check/nll/region_infer/mod.rs
index 40388722bcac9..78e7943598d68 100644
--- a/src/librustc_mir/borrow_check/nll/region_infer/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/region_infer/mod.rs
@@ -1,15 +1,20 @@
-use super::universal_regions::UniversalRegions;
-use crate::borrow_check::nll::constraints::graph::NormalConstraintGraph;
-use crate::borrow_check::nll::constraints::{
-    ConstraintSccIndex, OutlivesConstraint, OutlivesConstraintSet,
-};
-use crate::borrow_check::nll::member_constraints::{MemberConstraintSet, NllMemberConstraintIndex};
-use crate::borrow_check::nll::region_infer::values::{
-    PlaceholderIndices, RegionElement, ToElementIndex,
+use std::rc::Rc;
+
+use crate::borrow_check::nll::{
+    constraints::{
+        graph::NormalConstraintGraph,
+        ConstraintSccIndex,
+        OutlivesConstraint,
+        OutlivesConstraintSet,
+    },
+    member_constraints::{MemberConstraintSet, NllMemberConstraintIndex},
+    region_infer::values::{
+        PlaceholderIndices, RegionElement, ToElementIndex
+    },
+    type_check::{free_region_relations::UniversalRegionRelations, Locations},
 };
-use crate::borrow_check::nll::type_check::free_region_relations::UniversalRegionRelations;
-use crate::borrow_check::nll::type_check::Locations;
 use crate::borrow_check::Upvar;
+
 use rustc::hir::def_id::DefId;
 use rustc::infer::canonical::QueryOutlivesConstraint;
 use rustc::infer::opaque_types;
@@ -31,16 +36,16 @@ use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_errors::{Diagnostic, DiagnosticBuilder};
 use syntax_pos::Span;
 
-use std::rc::Rc;
+crate use self::error_reporting::{RegionName, RegionNameSource, RegionErrorNamingCtx};
+use self::values::{LivenessValues, RegionValueElements, RegionValues};
+use super::universal_regions::UniversalRegions;
+use super::ToRegionVid;
 
 mod dump_mir;
 mod error_reporting;
-crate use self::error_reporting::{RegionName, RegionNameSource};
 mod graphviz;
-pub mod values;
-use self::values::{LivenessValues, RegionValueElements, RegionValues};
 
-use super::ToRegionVid;
+pub mod values;
 
 pub struct RegionInferenceContext<'tcx> {
     /// Contains the definition for every region variable. Region
@@ -487,6 +492,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             errors_buffer,
         );
 
+        // If we produce any errors, we keep track of the names of all regions, so that we can use
+        // the same error names in any suggestions we produce. Note that we need names to be unique
+        // across different errors for the same MIR def so that we can make suggestions that fix
+        // multiple problems.
+        let mut region_naming = RegionErrorNamingCtx::new();
+
         self.check_universal_regions(
             infcx,
             body,
@@ -494,6 +505,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             mir_def_id,
             outlives_requirements.as_mut(),
             errors_buffer,
+            &mut region_naming,
         );
 
         self.check_member_constraints(infcx, mir_def_id, errors_buffer);
@@ -1312,6 +1324,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         mir_def_id: DefId,
         mut propagated_outlives_requirements: Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut Vec<Diagnostic>,
+        region_naming: &mut RegionErrorNamingCtx,
     ) {
         for (fr, fr_definition) in self.definitions.iter_enumerated() {
             match fr_definition.origin {
@@ -1327,6 +1340,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                         fr,
                         &mut propagated_outlives_requirements,
                         errors_buffer,
+                        region_naming,
                     );
                 }
 
@@ -1358,6 +1372,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         longer_fr: RegionVid,
         propagated_outlives_requirements: &mut Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut Vec<Diagnostic>,
+        region_naming: &mut RegionErrorNamingCtx,
     ) {
         debug!("check_universal_region(fr={:?})", longer_fr);
 
@@ -1385,6 +1400,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 mir_def_id,
                 propagated_outlives_requirements,
                 errors_buffer,
+                region_naming,
             );
             return;
         }
@@ -1401,8 +1417,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 mir_def_id,
                 propagated_outlives_requirements,
                 errors_buffer,
+                region_naming,
             ) {
                 // continuing to iterate just reports more errors than necessary
+                //
+                // FIXME It would also allow us to report more Outlives Suggestions, though, so
+                // it's not clear that that's a bad thing. Somebody should try commenting out this
+                // line and see it is actually a regression.
                 return;
             }
         }
@@ -1418,6 +1439,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         mir_def_id: DefId,
         propagated_outlives_requirements: &mut Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut Vec<Diagnostic>,
+        region_naming: &mut RegionErrorNamingCtx,
     ) -> Option<ErrorReported> {
         // If it is known that `fr: o`, carry on.
         if self.universal_region_relations.outlives(longer_fr, shorter_fr) {
@@ -1466,7 +1488,18 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         //
         // Note: in this case, we use the unapproximated regions to report the
         // error. This gives better error messages in some cases.
-        self.report_error(body, upvars, infcx, mir_def_id, longer_fr, shorter_fr, errors_buffer);
+        let db = self.report_error(
+            body,
+            upvars,
+            infcx,
+            mir_def_id,
+            longer_fr,
+            shorter_fr,
+            region_naming,
+        );
+
+        db.buffer(errors_buffer);
+
         Some(ErrorReported)
     }
 
diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index da1f64b05151b..6a764b19c4ddf 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -421,107 +421,104 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
     ) -> PlaceTy<'tcx> {
         debug!("sanitize_place: {:?}", place);
 
-        place.iterate(|place_base, place_projection| {
-            let mut place_ty = match place_base {
-                PlaceBase::Local(index) =>
-                    PlaceTy::from_ty(self.body.local_decls[*index].ty),
-                PlaceBase::Static(box Static { kind, ty: sty, def_id }) => {
-                    let sty = self.sanitize_type(place, sty);
-                    let check_err =
-                        |verifier: &mut TypeVerifier<'a, 'b, 'tcx>,
-                         place: &Place<'tcx>,
-                         ty,
-                         sty| {
-                            if let Err(terr) = verifier.cx.eq_types(
-                                sty,
-                                ty,
-                                location.to_locations(),
-                                ConstraintCategory::Boring,
-                            ) {
-                                span_mirbug!(
-                                verifier,
-                                place,
-                                "bad promoted type ({:?}: {:?}): {:?}",
-                                ty,
-                                sty,
-                                terr
-                            );
-                            };
+        let mut place_ty = match &place.base {
+            PlaceBase::Local(index) =>
+                PlaceTy::from_ty(self.body.local_decls[*index].ty),
+            PlaceBase::Static(box Static { kind, ty: sty, def_id }) => {
+                let sty = self.sanitize_type(place, sty);
+                let check_err =
+                    |verifier: &mut TypeVerifier<'a, 'b, 'tcx>,
+                     place: &Place<'tcx>,
+                     ty,
+                     sty| {
+                        if let Err(terr) = verifier.cx.eq_types(
+                            sty,
+                            ty,
+                            location.to_locations(),
+                            ConstraintCategory::Boring,
+                        ) {
+                            span_mirbug!(
+                            verifier,
+                            place,
+                            "bad promoted type ({:?}: {:?}): {:?}",
+                            ty,
+                            sty,
+                            terr
+                        );
                         };
-                    match kind {
-                        StaticKind::Promoted(promoted, _) => {
-                            if !self.errors_reported {
-                                let promoted_body = &self.promoted[*promoted];
-                                self.sanitize_promoted(promoted_body, location);
-
-                                let promoted_ty = promoted_body.return_ty();
-                                check_err(self, place, promoted_ty, sty);
-                            }
+                    };
+                match kind {
+                    StaticKind::Promoted(promoted, _) => {
+                        if !self.errors_reported {
+                            let promoted_body = &self.promoted[*promoted];
+                            self.sanitize_promoted(promoted_body, location);
+
+                            let promoted_ty = promoted_body.return_ty();
+                            check_err(self, place, promoted_ty, sty);
                         }
-                        StaticKind::Static => {
-                            let ty = self.tcx().type_of(*def_id);
-                            let ty = self.cx.normalize(ty, location);
+                    }
+                    StaticKind::Static => {
+                        let ty = self.tcx().type_of(*def_id);
+                        let ty = self.cx.normalize(ty, location);
 
-                            check_err(self, place, ty, sty);
-                        }
+                        check_err(self, place, ty, sty);
                     }
-                    PlaceTy::from_ty(sty)
                 }
-            };
+                PlaceTy::from_ty(sty)
+            }
+        };
 
-            // FIXME use place_projection.is_empty() when is available
-            if place.projection.is_none() {
-                if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
-                    let is_promoted = match place {
-                        Place {
-                            base: PlaceBase::Static(box Static {
-                                kind: StaticKind::Promoted(..),
-                                ..
-                            }),
-                            projection: None,
-                        } => true,
-                        _ => false,
-                    };
+        if place.projection.is_empty() {
+            if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
+                let is_promoted = match place {
+                    Place {
+                        base: PlaceBase::Static(box Static {
+                            kind: StaticKind::Promoted(..),
+                            ..
+                        }),
+                        projection: box [],
+                    } => true,
+                    _ => false,
+                };
 
-                    if !is_promoted {
-                        let tcx = self.tcx();
-                        let trait_ref = ty::TraitRef {
-                            def_id: tcx.lang_items().copy_trait().unwrap(),
-                            substs: tcx.mk_substs_trait(place_ty.ty, &[]),
-                        };
+                if !is_promoted {
+                    let tcx = self.tcx();
+                    let trait_ref = ty::TraitRef {
+                        def_id: tcx.lang_items().copy_trait().unwrap(),
+                        substs: tcx.mk_substs_trait(place_ty.ty, &[]),
+                    };
 
-                        // In order to have a Copy operand, the type T of the
-                        // value must be Copy. Note that we prove that T: Copy,
-                        // rather than using the `is_copy_modulo_regions`
-                        // test. This is important because
-                        // `is_copy_modulo_regions` ignores the resulting region
-                        // obligations and assumes they pass. This can result in
-                        // bounds from Copy impls being unsoundly ignored (e.g.,
-                        // #29149). Note that we decide to use Copy before knowing
-                        // whether the bounds fully apply: in effect, the rule is
-                        // that if a value of some type could implement Copy, then
-                        // it must.
-                        self.cx.prove_trait_ref(
-                            trait_ref,
-                            location.to_locations(),
-                            ConstraintCategory::CopyBound,
-                        );
-                    }
+                    // To have a `Copy` operand, the type `T` of the
+                    // value must be `Copy`. Note that we prove that `T: Copy`,
+                    // rather than using the `is_copy_modulo_regions`
+                    // test. This is important because
+                    // `is_copy_modulo_regions` ignores the resulting region
+                    // obligations and assumes they pass. This can result in
+                    // bounds from `Copy` impls being unsoundly ignored (e.g.,
+                    // #29149). Note that we decide to use `Copy` before knowing
+                    // whether the bounds fully apply: in effect, the rule is
+                    // that if a value of some type could implement `Copy`, then
+                    // it must.
+                    self.cx.prove_trait_ref(
+                        trait_ref,
+                        location.to_locations(),
+                        ConstraintCategory::CopyBound,
+                    );
                 }
             }
+        }
 
-            for proj in place_projection {
-                if place_ty.variant_index.is_none() {
-                    if place_ty.ty.references_error() {
-                        assert!(self.errors_reported);
-                        return PlaceTy::from_ty(self.tcx().types.err);
-                    }
+        for elem in place.projection.iter() {
+            if place_ty.variant_index.is_none() {
+                if place_ty.ty.references_error() {
+                    assert!(self.errors_reported);
+                    return PlaceTy::from_ty(self.tcx().types.err);
                 }
-                place_ty = self.sanitize_projection(place_ty, &proj.elem, place, location)
             }
+            place_ty = self.sanitize_projection(place_ty, elem, place, location)
+        }
 
-            place_ty
-        })
+        place_ty
     }
 
     fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Location) {
@@ -1346,7 +1343,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         debug!("check_stmt: {:?}", stmt);
         let tcx = self.tcx();
         match stmt.kind {
-            StatementKind::Assign(ref place, ref rv) => {
+            StatementKind::Assign(box(ref place, ref rv)) => {
                 // Assignments to temporaries are not "interesting";
                 // they are not caused by the user, but rather artifacts
                 // of lowering. Assignments to other sorts of places *are* interesting
@@ -1354,7 +1351,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 let category = match *place {
                     Place {
                         base: PlaceBase::Local(RETURN_PLACE),
-                        projection: None,
+                        projection: box [],
                     } => if let BorrowCheckContext {
                         universal_regions:
                             UniversalRegions {
@@ -1373,7 +1370,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     },
                     Place {
                         base: PlaceBase::Local(l),
-                        projection: None,
+                        projection: box [],
                     } if !body.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -1453,7 +1450,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     );
                 };
             }
-            StatementKind::AscribeUserType(ref place, variance, box ref projection) => {
+            StatementKind::AscribeUserType(box(ref place, ref projection), variance) => {
                 let place_ty = place.ty(body, tcx).ty;
                 if let Err(terr) = self.relate_type_and_user_type(
                     place_ty,
@@ -1660,7 +1657,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 let category = match *dest {
                     Place {
                         base: PlaceBase::Local(RETURN_PLACE),
-                        projection: None,
+                        projection: box [],
                     } => {
                         if let BorrowCheckContext {
                             universal_regions:
@@ -1682,7 +1679,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
                     Place {
                         base: PlaceBase::Local(l),
-                        projection: None,
+                        projection: box [],
                     } if !body.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -2002,6 +1999,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             ),
                             &traits::SelectionError::Unimplemented,
                             false,
+                            false,
                         );
                     }
                 }
@@ -2416,19 +2414,21 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         // *p`, where the `p` has type `&'b mut Foo`, for example, we
         // need to ensure that `'b: 'a`.
 
-        let mut borrowed_projection = &borrowed_place.projection;
-
         debug!(
             "add_reborrow_constraint({:?}, {:?}, {:?})",
             location, borrow_region, borrowed_place
         );
-        while let Some(box proj) = borrowed_projection {
-            debug!("add_reborrow_constraint - iteration {:?}", borrowed_projection);
 
-            match proj.elem {
+        let mut cursor = &*borrowed_place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
+
+            debug!("add_reborrow_constraint - iteration {:?}", elem);
+
+            match elem {
                 ProjectionElem::Deref => {
                     let tcx = self.infcx.tcx;
-                    let base_ty = Place::ty_from(&borrowed_place.base, &proj.base, body, tcx).ty;
+                    let base_ty = Place::ty_from(&borrowed_place.base, proj_base, body, tcx).ty;
 
                     debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
                     match base_ty.sty {
@@ -2490,10 +2490,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     // other field access
                 }
             }
-
-            // The "propagate" case. We need to check that our base is valid
-            // for the borrow's lifetime.
-            borrowed_projection = &proj.base;
         }
     }
 
diff --git a/src/librustc_mir/borrow_check/place_ext.rs b/src/librustc_mir/borrow_check/place_ext.rs
index 5caba637ccc4a..411fa5b596765 100644
--- a/src/librustc_mir/borrow_check/place_ext.rs
+++ b/src/librustc_mir/borrow_check/place_ext.rs
@@ -25,55 +25,54 @@ impl<'tcx> PlaceExt<'tcx> for Place<'tcx> {
         body: &Body<'tcx>,
         locals_state_at_exit: &LocalsStateAtExit,
     ) -> bool {
-        self.iterate(|place_base, place_projection| {
-            let ignore = match place_base {
-                // If a local variable is immutable, then we only need to track borrows to guard
-                // against two kinds of errors:
-                // * The variable being dropped while still borrowed (e.g., because the fn returns
-                //   a reference to a local variable)
-                // * The variable being moved while still borrowed
-                //
-                // In particular, the variable cannot be mutated -- the "access checks" will fail --
-                // so we don't have to worry about mutation while borrowed.
-                PlaceBase::Local(index) => {
-                    match locals_state_at_exit {
-                        LocalsStateAtExit::AllAreInvalidated => false,
-                        LocalsStateAtExit::SomeAreInvalidated { has_storage_dead_or_moved } => {
-                            let ignore = !has_storage_dead_or_moved.contains(*index) &&
-                                body.local_decls[*index].mutability == Mutability::Not;
-                            debug!("ignore_borrow: local {:?} => {:?}", index, ignore);
-                            ignore
-                        }
+        let ignore = match self.base {
+            // If a local variable is immutable, then we only need to track borrows to guard
+            // against two kinds of errors:
+            // * The variable being dropped while still borrowed (e.g., because the fn returns
+            //   a reference to a local variable)
+            // * The variable being moved while still borrowed
+            //
+            // In particular, the variable cannot be mutated -- the "access checks" will fail --
+            // so we don't have to worry about mutation while borrowed.
+            PlaceBase::Local(index) => {
+                match locals_state_at_exit {
+                    LocalsStateAtExit::AllAreInvalidated => false,
+                    LocalsStateAtExit::SomeAreInvalidated { has_storage_dead_or_moved } => {
+                        let ignore = !has_storage_dead_or_moved.contains(index) &&
+                            body.local_decls[index].mutability == Mutability::Not;
+                        debug!("ignore_borrow: local {:?} => {:?}", index, ignore);
+                        ignore
                     }
                 }
-                PlaceBase::Static(box Static{ kind: StaticKind::Promoted(_, _), .. }) =>
-                    false,
-                PlaceBase::Static(box Static{ kind: StaticKind::Static, def_id, .. }) => {
-                    tcx.is_mutable_static(*def_id)
-                }
-            };
+            }
+            PlaceBase::Static(box Static{ kind: StaticKind::Promoted(_, _), .. }) =>
+                false,
+            PlaceBase::Static(box Static{ kind: StaticKind::Static, def_id, .. }) => {
+                tcx.is_mutable_static(def_id)
+            }
+        };
 
-            for proj in place_projection {
-                if proj.elem == ProjectionElem::Deref {
-                    let ty = Place::ty_from(place_base, &proj.base, body, tcx).ty;
-                    match ty.sty {
-                        // For both derefs of raw pointers and `&T`
-                        // references, the original path is `Copy` and
-                        // therefore not significant.  In particular,
-                        // there is nothing the user can do to the
-                        // original path that would invalidate the
-                        // newly created reference -- and if there
-                        // were, then the user could have copied the
-                        // original path into a new variable and
-                        // borrowed *that* one, leaving the original
-                        // path unborrowed.
-                        ty::RawPtr(..) | ty::Ref(_, _, hir::MutImmutable) => return true,
-                        _ => {}
-                    }
+        for (i, elem) in self.projection.iter().enumerate() {
+            let proj_base = &self.projection[..i];
+
+            if *elem == ProjectionElem::Deref {
+                let ty = Place::ty_from(&self.base, proj_base, body, tcx).ty;
+                if let ty::RawPtr(..) | ty::Ref(_, _, hir::MutImmutable) = ty.sty {
+                    // For both derefs of raw pointers and `&T`
+                    // references, the original path is `Copy` and
+                    // therefore not significant.  In particular,
+                    // there is nothing the user can do to the
+                    // original path that would invalidate the
+                    // newly created reference -- and if there
+                    // were, then the user could have copied the
+                    // original path into a new variable and
+                    // borrowed *that* one, leaving the original
+                    // path unborrowed.
+                    return true;
                 }
             }
+        }
 
-            ignore
-        })
+        ignore
     }
 }
diff --git a/src/librustc_mir/borrow_check/places_conflict.rs b/src/librustc_mir/borrow_check/places_conflict.rs
index 4f469174b392d..dafa0b6631fe2 100644
--- a/src/librustc_mir/borrow_check/places_conflict.rs
+++ b/src/librustc_mir/borrow_check/places_conflict.rs
@@ -3,8 +3,7 @@ use crate::borrow_check::Overlap;
 use crate::borrow_check::{Deep, Shallow, AccessDepth};
 use rustc::hir;
 use rustc::mir::{
-    Body, BorrowKind, Place, PlaceBase, PlaceRef, Projection, ProjectionElem, ProjectionsIter,
-    StaticKind,
+    Body, BorrowKind, Place, PlaceBase, PlaceElem, PlaceRef, ProjectionElem, StaticKind,
 };
 use rustc::ty::{self, TyCtxt};
 use std::cmp::max;
@@ -67,39 +66,35 @@ pub(super) fn borrow_conflicts_with_place<'tcx>(
     // it's so common that it's a speed win to check for it first.
     if let Place {
         base: PlaceBase::Local(l1),
-        projection: None,
+        projection: box [],
     } = borrow_place {
         if let PlaceRef {
             base: PlaceBase::Local(l2),
-            projection: None,
+            projection: [],
         } = access_place {
             return l1 == l2;
         }
     }
 
-    borrow_place.iterate(|borrow_base, borrow_projections| {
-        access_place.iterate(|access_base, access_projections| {
-            place_components_conflict(
-                tcx,
-                param_env,
-                body,
-                (borrow_base, borrow_projections),
-                borrow_kind,
-                (access_base, access_projections),
-                access,
-                bias,
-            )
-        })
-    })
+    place_components_conflict(
+        tcx,
+        param_env,
+        body,
+        borrow_place,
+        borrow_kind,
+        access_place,
+        access,
+        bias,
+    )
 }
 
 fn place_components_conflict<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body: &Body<'tcx>,
-    borrow_projections: (&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>),
+    borrow_place: &Place<'tcx>,
     borrow_kind: BorrowKind,
-    access_projections: (&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>),
+    access_place: PlaceRef<'_, 'tcx>,
     access: AccessDepth,
     bias: PlaceConflictBias,
 ) -> bool {
@@ -145,8 +140,8 @@ fn place_components_conflict<'tcx>(
     //    and either equal or disjoint.
     //  - If we did run out of access, the borrow can access a part of it.
 
-    let borrow_base = borrow_projections.0;
-    let access_base = access_projections.0;
+    let borrow_base = &borrow_place.base;
+    let access_base = access_place.base;
 
     match place_base_conflict(tcx, param_env, borrow_base, access_base) {
         Overlap::Arbitrary => {
@@ -163,147 +158,157 @@ fn place_components_conflict<'tcx>(
         }
     }
 
-    let mut borrow_projections = borrow_projections.1;
-    let mut access_projections = access_projections.1;
-
-    loop {
-        // loop invariant: borrow_c is always either equal to access_c or disjoint from it.
-        if let Some(borrow_c) = borrow_projections.next() {
-            debug!("borrow_conflicts_with_place: borrow_c = {:?}", borrow_c);
+    // loop invariant: borrow_c is always either equal to access_c or disjoint from it.
+    for (i, (borrow_c, access_c)) in
+        borrow_place.projection.iter().zip(access_place.projection.iter()).enumerate()
+    {
+        debug!("borrow_conflicts_with_place: borrow_c = {:?}", borrow_c);
+        let borrow_proj_base = &borrow_place.projection[..i];
 
-            if let Some(access_c) = access_projections.next() {
-                debug!("borrow_conflicts_with_place: access_c = {:?}", access_c);
+        debug!("borrow_conflicts_with_place: access_c = {:?}", access_c);
 
-                // Borrow and access path both have more components.
-                //
-                // Examples:
-                //
-                // - borrow of `a.(...)`, access to `a.(...)`
-                // - borrow of `a.(...)`, access to `b.(...)`
-                //
-                // Here we only see the components we have checked so
-                // far (in our examples, just the first component). We
-                // check whether the components being borrowed vs
-                // accessed are disjoint (as in the second example,
-                // but not the first).
-                match place_projection_conflict(tcx, body, borrow_base, borrow_c, access_c, bias) {
-                    Overlap::Arbitrary => {
-                        // We have encountered different fields of potentially
-                        // the same union - the borrow now partially overlaps.
-                        //
-                        // There is no *easy* way of comparing the fields
-                        // further on, because they might have different types
-                        // (e.g., borrows of `u.a.0` and `u.b.y` where `.0` and
-                        // `.y` come from different structs).
-                        //
-                        // We could try to do some things here - e.g., count
-                        // dereferences - but that's probably not a good
-                        // idea, at least for now, so just give up and
-                        // report a conflict. This is unsafe code anyway so
-                        // the user could always use raw pointers.
-                        debug!("borrow_conflicts_with_place: arbitrary -> conflict");
-                        return true;
-                    }
-                    Overlap::EqualOrDisjoint => {
-                        // This is the recursive case - proceed to the next element.
-                    }
-                    Overlap::Disjoint => {
-                        // We have proven the borrow disjoint - further
-                        // projections will remain disjoint.
-                        debug!("borrow_conflicts_with_place: disjoint");
-                        return false;
-                    }
-                }
-            } else {
-                // Borrow path is longer than the access path. Examples:
+        // Borrow and access path both have more components.
+        //
+        // Examples:
+        //
+        // - borrow of `a.(...)`, access to `a.(...)`
+        // - borrow of `a.(...)`, access to `b.(...)`
+        //
+        // Here we only see the components we have checked so
+        // far (in our examples, just the first component). We
+        // check whether the components being borrowed vs
+        // accessed are disjoint (as in the second example,
+        // but not the first).
+        match place_projection_conflict(
+            tcx,
+            body,
+            borrow_base,
+            borrow_proj_base,
+            borrow_c,
+            access_c,
+            bias,
+        ) {
+            Overlap::Arbitrary => {
+                // We have encountered different fields of potentially
+                // the same union - the borrow now partially overlaps.
                 //
-                // - borrow of `a.b.c`, access to `a.b`
+                // There is no *easy* way of comparing the fields
+                // further on, because they might have different types
+                // (e.g., borrows of `u.a.0` and `u.b.y` where `.0` and
+                // `.y` come from different structs).
                 //
-                // Here, we know that the borrow can access a part of
-                // our place. This is a conflict if that is a part our
-                // access cares about.
+                // We could try to do some things here - e.g., count
+                // dereferences - but that's probably not a good
+                // idea, at least for now, so just give up and
+                // report a conflict. This is unsafe code anyway so
+                // the user could always use raw pointers.
+                debug!("borrow_conflicts_with_place: arbitrary -> conflict");
+                return true;
+            }
+            Overlap::EqualOrDisjoint => {
+                // This is the recursive case - proceed to the next element.
+            }
+            Overlap::Disjoint => {
+                // We have proven the borrow disjoint - further
+                // projections will remain disjoint.
+                debug!("borrow_conflicts_with_place: disjoint");
+                return false;
+            }
+        }
+    }
+
+    if borrow_place.projection.len() > access_place.projection.len() {
+        for (i, elem) in borrow_place.projection[access_place.projection.len()..].iter().enumerate()
+        {
+            // Borrow path is longer than the access path. Examples:
+            //
+            // - borrow of `a.b.c`, access to `a.b`
+            //
+            // Here, we know that the borrow can access a part of
+            // our place. This is a conflict if that is a part our
+            // access cares about.
 
-                let base = &borrow_c.base;
-                let elem = &borrow_c.elem;
-                let base_ty = Place::ty_from(borrow_base, base, body, tcx).ty;
+            let proj_base = &borrow_place.projection[..access_place.projection.len() + i];
+            let base_ty = Place::ty_from(borrow_base, proj_base, body, tcx).ty;
 
-                match (elem, &base_ty.sty, access) {
-                    (_, _, Shallow(Some(ArtificialField::ArrayLength)))
-                    | (_, _, Shallow(Some(ArtificialField::ShallowBorrow))) => {
-                        // The array length is like  additional fields on the
-                        // type; it does not overlap any existing data there.
-                        // Furthermore, if cannot actually be a prefix of any
-                        // borrowed place (at least in MIR as it is currently.)
-                        //
-                        // e.g., a (mutable) borrow of `a[5]` while we read the
-                        // array length of `a`.
-                        debug!("borrow_conflicts_with_place: implicit field");
-                        return false;
-                    }
+            match (elem, &base_ty.sty, access) {
+                (_, _, Shallow(Some(ArtificialField::ArrayLength)))
+                | (_, _, Shallow(Some(ArtificialField::ShallowBorrow))) => {
+                    // The array length is like  additional fields on the
+                    // type; it does not overlap any existing data there.
+                    // Furthermore, if cannot actually be a prefix of any
+                    // borrowed place (at least in MIR as it is currently.)
+                    //
+                    // e.g., a (mutable) borrow of `a[5]` while we read the
+                    // array length of `a`.
+                    debug!("borrow_conflicts_with_place: implicit field");
+                    return false;
+                }
 
-                    (ProjectionElem::Deref, _, Shallow(None)) => {
-                        // e.g., a borrow of `*x.y` while we shallowly access `x.y` or some
-                        // prefix thereof - the shallow access can't touch anything behind
-                        // the pointer.
-                        debug!("borrow_conflicts_with_place: shallow access behind ptr");
-                        return false;
-                    }
-                    (ProjectionElem::Deref, ty::Ref(_, _, hir::MutImmutable), _) => {
-                        // Shouldn't be tracked
-                        bug!("Tracking borrow behind shared reference.");
-                    }
-                    (ProjectionElem::Deref, ty::Ref(_, _, hir::MutMutable), AccessDepth::Drop) => {
-                        // Values behind a mutable reference are not access either by dropping a
-                        // value, or by StorageDead
-                        debug!("borrow_conflicts_with_place: drop access behind ptr");
-                        return false;
-                    }
+                (ProjectionElem::Deref, _, Shallow(None)) => {
+                    // e.g., a borrow of `*x.y` while we shallowly access `x.y` or some
+                    // prefix thereof - the shallow access can't touch anything behind
+                    // the pointer.
+                    debug!("borrow_conflicts_with_place: shallow access behind ptr");
+                    return false;
+                }
+                (ProjectionElem::Deref, ty::Ref(_, _, hir::MutImmutable), _) => {
+                    // Shouldn't be tracked
+                    bug!("Tracking borrow behind shared reference.");
+                }
+                (ProjectionElem::Deref, ty::Ref(_, _, hir::MutMutable), AccessDepth::Drop) => {
+                    // Values behind a mutable reference are not access either by dropping a
+                    // value, or by StorageDead
+                    debug!("borrow_conflicts_with_place: drop access behind ptr");
+                    return false;
+                }
 
-                    (ProjectionElem::Field { .. }, ty::Adt(def, _), AccessDepth::Drop) => {
-                        // Drop can read/write arbitrary projections, so places
-                        // conflict regardless of further projections.
-                        if def.has_dtor(tcx) {
-                            return true;
-                        }
+                (ProjectionElem::Field { .. }, ty::Adt(def, _), AccessDepth::Drop) => {
+                    // Drop can read/write arbitrary projections, so places
+                    // conflict regardless of further projections.
+                    if def.has_dtor(tcx) {
+                        return true;
                     }
+                }
 
-                    (ProjectionElem::Deref, _, Deep)
-                    | (ProjectionElem::Deref, _, AccessDepth::Drop)
-                    | (ProjectionElem::Field { .. }, _, _)
-                    | (ProjectionElem::Index { .. }, _, _)
-                    | (ProjectionElem::ConstantIndex { .. }, _, _)
-                    | (ProjectionElem::Subslice { .. }, _, _)
-                    | (ProjectionElem::Downcast { .. }, _, _) => {
-                        // Recursive case. This can still be disjoint on a
-                        // further iteration if this a shallow access and
-                        // there's a deref later on, e.g., a borrow
-                        // of `*x.y` while accessing `x`.
-                    }
+                (ProjectionElem::Deref, _, Deep)
+                | (ProjectionElem::Deref, _, AccessDepth::Drop)
+                | (ProjectionElem::Field { .. }, _, _)
+                | (ProjectionElem::Index { .. }, _, _)
+                | (ProjectionElem::ConstantIndex { .. }, _, _)
+                | (ProjectionElem::Subslice { .. }, _, _)
+                | (ProjectionElem::Downcast { .. }, _, _) => {
+                    // Recursive case. This can still be disjoint on a
+                    // further iteration if this a shallow access and
+                    // there's a deref later on, e.g., a borrow
+                    // of `*x.y` while accessing `x`.
                 }
             }
-        } else {
-            // Borrow path ran out but access path may not
-            // have. Examples:
-            //
-            // - borrow of `a.b`, access to `a.b.c`
-            // - borrow of `a.b`, access to `a.b`
-            //
-            // In the first example, where we didn't run out of
-            // access, the borrow can access all of our place, so we
-            // have a conflict.
-            //
-            // If the second example, where we did, then we still know
-            // that the borrow can access a *part* of our place that
-            // our access cares about, so we still have a conflict.
-            if borrow_kind == BorrowKind::Shallow && access_projections.next().is_some() {
-                debug!("borrow_conflicts_with_place: shallow borrow");
-                return false;
-            } else {
-                debug!("borrow_conflicts_with_place: full borrow, CONFLICT");
-                return true;
-            }
         }
     }
+
+    // Borrow path ran out but access path may not
+    // have. Examples:
+    //
+    // - borrow of `a.b`, access to `a.b.c`
+    // - borrow of `a.b`, access to `a.b`
+    //
+    // In the first example, where we didn't run out of
+    // access, the borrow can access all of our place, so we
+    // have a conflict.
+    //
+    // If the second example, where we did, then we still know
+    // that the borrow can access a *part* of our place that
+    // our access cares about, so we still have a conflict.
+    if borrow_kind == BorrowKind::Shallow
+        && borrow_place.projection.len() < access_place.projection.len()
+    {
+        debug!("borrow_conflicts_with_place: shallow borrow");
+        false
+    } else {
+        debug!("borrow_conflicts_with_place: full borrow, CONFLICT");
+        true
+    }
 }
 
 // Given that the bases of `elem1` and `elem2` are always either equal
@@ -381,11 +386,12 @@ fn place_projection_conflict<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
     pi1_base: &PlaceBase<'tcx>,
-    pi1: &Projection<'tcx>,
-    pi2: &Projection<'tcx>,
+    pi1_proj_base: &[PlaceElem<'tcx>],
+    pi1_elem: &PlaceElem<'tcx>,
+    pi2_elem: &PlaceElem<'tcx>,
     bias: PlaceConflictBias,
 ) -> Overlap {
-    match (&pi1.elem, &pi2.elem) {
+    match (pi1_elem, pi2_elem) {
         (ProjectionElem::Deref, ProjectionElem::Deref) => {
             // derefs (e.g., `*x` vs. `*x`) - recur.
             debug!("place_element_conflict: DISJOINT-OR-EQ-DEREF");
@@ -397,7 +403,7 @@ fn place_projection_conflict<'tcx>(
                 debug!("place_element_conflict: DISJOINT-OR-EQ-FIELD");
                 Overlap::EqualOrDisjoint
             } else {
-                let ty = Place::ty_from(pi1_base, &pi1.base, body, tcx).ty;
+                let ty = Place::ty_from(pi1_base, pi1_proj_base, body, tcx).ty;
                 match ty.sty {
                     ty::Adt(def, _) if def.is_union() => {
                         // Different fields of a union, we are basically stuck.
@@ -493,7 +499,7 @@ fn place_projection_conflict<'tcx>(
             // element (like -1 in Python) and `min_length` the first.
             // Therefore, `min_length - offset_from_end` gives the minimal possible
             // offset from the beginning
-            if *offset_from_begin >= min_length - offset_from_end {
+            if *offset_from_begin >= *min_length - *offset_from_end {
                 debug!("place_element_conflict: DISJOINT-OR-EQ-ARRAY-CONSTANT-INDEX-FE");
                 Overlap::EqualOrDisjoint
             } else {
@@ -538,8 +544,8 @@ fn place_projection_conflict<'tcx>(
         | (ProjectionElem::Subslice { .. }, _)
         | (ProjectionElem::Downcast(..), _) => bug!(
             "mismatched projections in place_element_conflict: {:?} and {:?}",
-            pi1,
-            pi2
+            pi1_elem,
+            pi2_elem
         ),
     }
 }
diff --git a/src/librustc_mir/borrow_check/prefixes.rs b/src/librustc_mir/borrow_check/prefixes.rs
index 4c6be23de28be..0a268ec134023 100644
--- a/src/librustc_mir/borrow_check/prefixes.rs
+++ b/src/librustc_mir/borrow_check/prefixes.rs
@@ -19,17 +19,9 @@ pub trait IsPrefixOf<'cx, 'tcx> {
 
 impl<'cx, 'tcx> IsPrefixOf<'cx, 'tcx> for PlaceRef<'cx, 'tcx> {
     fn is_prefix_of(&self, other: PlaceRef<'cx, 'tcx>) -> bool {
-        let mut cursor = other.projection;
-        loop {
-            if self.projection == cursor {
-                return self.base == other.base;
-            }
-
-            match cursor {
-                None => return false,
-                Some(proj) => cursor = &proj.base,
-            }
-        }
+        self.base == other.base
+            && self.projection.len() <= other.projection.len()
+            && self.projection == &other.projection[..self.projection.len()]
     }
 }
 
@@ -81,112 +73,113 @@ impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
         // downcasts here, but may return a base of a downcast).
 
         'cursor: loop {
-            let proj = match &cursor {
+            match &cursor {
                 PlaceRef {
                     base: PlaceBase::Local(_),
-                    projection: None,
+                    projection: [],
                 }
                 | // search yielded this leaf
                 PlaceRef {
                     base: PlaceBase::Static(_),
-                    projection: None,
+                    projection: [],
                 } => {
                     self.next = None;
                     return Some(cursor);
                 }
                 PlaceRef {
                     base: _,
-                    projection: Some(proj),
-                } => proj,
-            };
-
-            match proj.elem {
-                ProjectionElem::Field(_ /*field*/, _ /*ty*/) => {
-                    // FIXME: add union handling
-                    self.next = Some(PlaceRef {
-                        base: cursor.base,
-                        projection: &proj.base,
-                    });
-                    return Some(cursor);
-                }
-                ProjectionElem::Downcast(..) |
-                ProjectionElem::Subslice { .. } |
-                ProjectionElem::ConstantIndex { .. } |
-                ProjectionElem::Index(_) => {
-                    cursor = PlaceRef {
-                        base: cursor.base,
-                        projection: &proj.base,
-                    };
-                    continue 'cursor;
-                }
-                ProjectionElem::Deref => {
-                    // (handled below)
-                }
-            }
-
-            assert_eq!(proj.elem, ProjectionElem::Deref);
-
-            match self.kind {
-                PrefixSet::Shallow => {
-                    // shallow prefixes are found by stripping away
-                    // fields, but stop at *any* dereference.
-                    // So we can just stop the traversal now.
-                    self.next = None;
-                    return Some(cursor);
-                }
-                PrefixSet::All => {
-                    // all prefixes: just blindly enqueue the base
-                    // of the projection.
-                    self.next = Some(PlaceRef {
-                        base: cursor.base,
-                        projection: &proj.base,
-                    });
-                    return Some(cursor);
-                }
-                PrefixSet::Supporting => {
-                    // fall through!
-                }
-            }
-
-            assert_eq!(self.kind, PrefixSet::Supporting);
-            // supporting prefixes: strip away fields and
-            // derefs, except we stop at the deref of a shared
-            // reference.
-
-            let ty = Place::ty_from(cursor.base, &proj.base, self.body, self.tcx).ty;
-            match ty.sty {
-                ty::RawPtr(_) |
-                ty::Ref(
-                    _, /*rgn*/
-                    _, /*ty*/
-                    hir::MutImmutable
-                    ) => {
-                    // don't continue traversing over derefs of raw pointers or shared borrows.
-                    self.next = None;
-                    return Some(cursor);
-                }
-
-                ty::Ref(
-                    _, /*rgn*/
-                    _, /*ty*/
-                    hir::MutMutable,
-                    ) => {
-                    self.next = Some(PlaceRef {
-                        base: cursor.base,
-                        projection: &proj.base,
-                    });
-                    return Some(cursor);
-                }
-
-                ty::Adt(..) if ty.is_box() => {
-                    self.next = Some(PlaceRef {
-                        base: cursor.base,
-                        projection: &proj.base,
-                    });
-                    return Some(cursor);
+                    projection: [proj_base @ .., elem],
+                } => {
+                    match elem {
+                        ProjectionElem::Field(_ /*field*/, _ /*ty*/) => {
+                            // FIXME: add union handling
+                            self.next = Some(PlaceRef {
+                                base: cursor.base,
+                                projection: proj_base,
+                            });
+                            return Some(cursor);
+                        }
+                        ProjectionElem::Downcast(..) |
+                        ProjectionElem::Subslice { .. } |
+                        ProjectionElem::ConstantIndex { .. } |
+                        ProjectionElem::Index(_) => {
+                            cursor = PlaceRef {
+                                base: cursor.base,
+                                projection: proj_base,
+                            };
+                            continue 'cursor;
+                        }
+                        ProjectionElem::Deref => {
+                            // (handled below)
+                        }
+                    }
+
+                    assert_eq!(*elem, ProjectionElem::Deref);
+
+                    match self.kind {
+                        PrefixSet::Shallow => {
+                            // Shallow prefixes are found by stripping away
+                            // fields, but stop at *any* dereference.
+                            // So we can just stop the traversal now.
+                            self.next = None;
+                            return Some(cursor);
+                        }
+                        PrefixSet::All => {
+                            // All prefixes: just blindly enqueue the base
+                            // of the projection.
+                            self.next = Some(PlaceRef {
+                                base: cursor.base,
+                                projection: proj_base,
+                            });
+                            return Some(cursor);
+                        }
+                        PrefixSet::Supporting => {
+                            // Fall through!
+                        }
+                    }
+
+                    assert_eq!(self.kind, PrefixSet::Supporting);
+                    // Supporting prefixes: strip away fields and
+                    // derefs, except we stop at the deref of a shared
+                    // reference.
+
+                    let ty = Place::ty_from(cursor.base, proj_base, self.body, self.tcx).ty;
+                    match ty.sty {
+                        ty::RawPtr(_) |
+                        ty::Ref(
+                            _, /*rgn*/
+                            _, /*ty*/
+                            hir::MutImmutable
+                            ) => {
+                            // don't continue traversing over derefs of raw pointers or shared
+                            // borrows.
+                            self.next = None;
+                            return Some(cursor);
+                        }
+
+                        ty::Ref(
+                            _, /*rgn*/
+                            _, /*ty*/
+                            hir::MutMutable,
+                            ) => {
+                            self.next = Some(PlaceRef {
+                                base: cursor.base,
+                                projection: proj_base,
+                            });
+                            return Some(cursor);
+                        }
+
+                        ty::Adt(..) if ty.is_box() => {
+                            self.next = Some(PlaceRef {
+                                base: cursor.base,
+                                projection: proj_base,
+                            });
+                            return Some(cursor);
+                        }
+
+                        _ => panic!("unknown type fed to Projection Deref."),
+                    }
                 }
-
-                _ => panic!("unknown type fed to Projection Deref."),
             }
         }
     }
diff --git a/src/librustc_mir/borrow_check/used_muts.rs b/src/librustc_mir/borrow_check/used_muts.rs
index 2587d14a73a8f..695080dfe23d9 100644
--- a/src/librustc_mir/borrow_check/used_muts.rs
+++ b/src/librustc_mir/borrow_check/used_muts.rs
@@ -89,7 +89,7 @@ impl<'visit, 'cx, 'tcx> Visitor<'tcx> for GatherUsedMutsVisitor<'visit, 'cx, 'tc
         _location: Location,
     ) {
         match &statement.kind {
-            StatementKind::Assign(into, _) => {
+            StatementKind::Assign(box(into, _)) => {
                 if let PlaceBase::Local(local) = into.base {
                     debug!(
                         "visit_statement: statement={:?} local={:?} \
@@ -120,7 +120,7 @@ impl<'visit, 'cx, 'tcx> Visitor<'tcx> for GatherUsedMutsVisitor<'visit, 'cx, 'tc
                 );
                 if let Place {
                     base: PlaceBase::Local(user_local),
-                    projection: None,
+                    projection: box [],
                 } = path.place {
                     self.mbcx.used_mut.insert(user_local);
                 }
diff --git a/src/librustc_mir/build/cfg.rs b/src/librustc_mir/build/cfg.rs
index 778d1e71cedfc..3ed6b4ff34678 100644
--- a/src/librustc_mir/build/cfg.rs
+++ b/src/librustc_mir/build/cfg.rs
@@ -37,7 +37,7 @@ impl<'tcx> CFG<'tcx> {
                        rvalue: Rvalue<'tcx>) {
         self.push(block, Statement {
             source_info,
-            kind: StatementKind::Assign(place.clone(), box rvalue)
+            kind: StatementKind::Assign(box(place.clone(), rvalue))
         });
     }
 
diff --git a/src/librustc_mir/build/expr/as_place.rs b/src/librustc_mir/build/expr/as_place.rs
index 98cf4bba1c75f..09b33c6654a9d 100644
--- a/src/librustc_mir/build/expr/as_place.rs
+++ b/src/librustc_mir/build/expr/as_place.rs
@@ -129,7 +129,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     kind: StaticKind::Static,
                     def_id: id,
                 })),
-                projection: None,
+                projection: box [],
             }),
 
             ExprKind::PlaceTypeAscription { source, user_ty } => {
@@ -147,9 +147,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         Statement {
                             source_info,
                             kind: StatementKind::AscribeUserType(
-                                place.clone(),
+                                box(
+                                    place.clone(),
+                                    UserTypeProjection { base: annotation_index, projs: vec![], }
+                                ),
                                 Variance::Invariant,
-                                box UserTypeProjection { base: annotation_index, projs: vec![], },
                             ),
                         },
                     );
@@ -174,9 +176,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         Statement {
                             source_info,
                             kind: StatementKind::AscribeUserType(
-                                Place::from(temp.clone()),
+                                box(
+                                    Place::from(temp.clone()),
+                                    UserTypeProjection { base: annotation_index, projs: vec![], },
+                                ),
                                 Variance::Invariant,
-                                box UserTypeProjection { base: annotation_index, projs: vec![], },
                             ),
                         },
                     );
diff --git a/src/librustc_mir/build/expr/as_rvalue.rs b/src/librustc_mir/build/expr/as_rvalue.rs
index 1a186fa932ddb..7dfe98cbebfc2 100644
--- a/src/librustc_mir/build/expr/as_rvalue.rs
+++ b/src/librustc_mir/build/expr/as_rvalue.rs
@@ -500,14 +500,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let mutability = match arg_place {
             Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             } => this.local_decls[local].mutability,
             Place {
                 base: PlaceBase::Local(local),
-                projection: Some(box Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                })
+                projection: box [ProjectionElem::Deref],
             } => {
                 debug_assert!(
                     this.local_decls[local].is_ref_for_guard(),
@@ -517,24 +514,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
             Place {
                 ref base,
-                projection: Some(box Projection {
-                    base: ref base_proj,
-                    elem: ProjectionElem::Field(upvar_index, _),
-                }),
+                projection: box [ref proj_base @ .., ProjectionElem::Field(upvar_index, _)],
             }
             | Place {
                 ref base,
-                projection: Some(box Projection {
-                    base: Some(box Projection {
-                        base: ref base_proj,
-                        elem: ProjectionElem::Field(upvar_index, _),
-                    }),
-                    elem: ProjectionElem::Deref,
-                }),
+                projection: box [
+                    ref proj_base @ ..,
+                    ProjectionElem::Field(upvar_index, _),
+                    ProjectionElem::Deref
+                ],
             } => {
                 let place = PlaceRef {
                     base,
-                    projection: base_proj,
+                    projection: proj_base,
                 };
 
                 // Not projected from the implicit `self` in a closure.
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index 889861b856748..45f4a16853606 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -301,7 +301,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // Create a "fake" temporary variable so that we check that the
                 // value is Sized. Usually, this is caught in type checking, but
                 // in the case of box expr there is no such check.
-                if destination.projection.is_some() {
+                if !destination.projection.is_empty() {
                     this.local_decls
                         .push(LocalDecl::new_temp(expr.ty, expr.span));
                 }
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index 94323b15b696f..2b0237c7c08b9 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -135,7 +135,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             source_info,
             kind: StatementKind::FakeRead(
                 FakeReadCause::ForMatchedPlace,
-                scrutinee_place.clone(),
+                box(scrutinee_place.clone()),
             ),
         });
 
@@ -320,7 +320,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     block,
                     Statement {
                         source_info,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, place),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, box(place)),
                     },
                 );
 
@@ -362,12 +362,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     block,
                     Statement {
                         source_info: pattern_source_info,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, place.clone()),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForLet, box(place.clone())),
                     },
                 );
 
                 let ty_source_info = self.source_info(user_ty_span);
-                let user_ty = box pat_ascription_ty.user_ty(
+                let user_ty = pat_ascription_ty.user_ty(
                     &mut self.canonical_user_type_annotations,
                     place.ty(&self.local_decls, self.hir.tcx()).ty,
                     ty_source_info.span,
@@ -377,7 +377,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     Statement {
                         source_info: ty_source_info,
                         kind: StatementKind::AscribeUserType(
-                            place,
+                            box(
+                                place,
+                                user_ty,
+                            ),
                             // We always use invariant as the variance here. This is because the
                             // variance field from the ascription refers to the variance to use
                             // when applying the type to the value being matched, but this
@@ -393,7 +396,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             // contrast, is intended to be used to relate `T` to the type of
                             // `<expr>`.
                             ty::Variance::Invariant,
-                            user_ty,
                         ),
                     },
                 );
@@ -942,16 +944,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             for Binding { source, .. }
                 in matched_candidates.iter().flat_map(|candidate| &candidate.bindings)
             {
-                let mut cursor = &source.projection;
-                while let Some(box Projection { base, elem }) = cursor {
-                    cursor = base;
-                    if let ProjectionElem::Deref = elem {
-                        fake_borrows.insert(Place {
-                            base: source.base.clone(),
-                            projection: cursor.clone(),
-                        });
-                        break;
-                    }
+                if let Some(i) =
+                    source.projection.iter().rposition(|elem| *elem == ProjectionElem::Deref)
+                {
+                    let proj_base = &source.projection[..i];
+
+                    fake_borrows.insert(Place {
+                        base: source.base.clone(),
+                        projection: proj_base.to_vec().into_boxed_slice(),
+                    });
                 }
             }
         }
@@ -1295,18 +1296,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // Insert a Shallow borrow of the prefixes of any fake borrows.
         for place in fake_borrows
         {
-            let mut prefix_cursor = &place.projection;
-            while let Some(box Projection { base, elem }) = prefix_cursor {
+            let mut cursor = &*place.projection;
+            while let [proj_base @ .., elem] = cursor {
+                cursor = proj_base;
+
                 if let ProjectionElem::Deref = elem {
                     // Insert a shallow borrow after a deref. For other
                     // projections the borrow of prefix_cursor will
                     // conflict with any mutation of base.
                     all_fake_borrows.push(PlaceRef {
                         base: &place.base,
-                        projection: base,
+                        projection: proj_base,
                     });
                 }
-                prefix_cursor = base;
             }
 
             all_fake_borrows.push(place.as_ref());
@@ -1345,13 +1347,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// any, and then branches to the arm. Returns the block for the case where
     /// the guard fails.
     ///
-    /// Note: we check earlier that if there is a guard, there cannot be move
-    /// bindings (unless feature(bind_by_move_pattern_guards) is used). This
-    /// isn't really important for the self-consistency of this fn, but the
-    /// reason for it should be clear: after we've done the assignments, if
-    /// there were move bindings, further tests would be a use-after-move.
-    /// bind_by_move_pattern_guards avoids this by only moving the binding once
-    /// the guard has evaluated to true (see below).
+    /// Note: we do not check earlier that if there is a guard,
+    /// there cannot be move bindings. We avoid a use-after-move by only
+    /// moving the binding once the guard has evaluated to true (see below).
     fn bind_and_guard_matched_candidate<'pat>(
         &mut self,
         candidate: Candidate<'pat, 'tcx>,
@@ -1493,7 +1491,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     BorrowKind::Shallow,
                     Place {
                         base: place.base.clone(),
-                        projection: place.projection.clone(),
+                        projection: place.projection.to_vec().into_boxed_slice(),
                     },
                 );
                 self.cfg.push_assign(
@@ -1524,7 +1522,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     source_info: guard_end,
                     kind: StatementKind::FakeRead(
                         FakeReadCause::ForMatchGuard,
-                        Place::from(temp),
+                        box(Place::from(temp)),
                     ),
                 });
             }
@@ -1574,7 +1572,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     post_guard_block,
                     Statement {
                         source_info: guard_end,
-                        kind: StatementKind::FakeRead(FakeReadCause::ForGuardBinding, place),
+                        kind: StatementKind::FakeRead(FakeReadCause::ForGuardBinding, box(place)),
                     },
                 );
             }
@@ -1607,7 +1605,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 ascription.user_ty,
             );
 
-            let user_ty = box ascription.user_ty.clone().user_ty(
+            let user_ty = ascription.user_ty.clone().user_ty(
                 &mut self.canonical_user_type_annotations,
                 ascription.source.ty(&self.local_decls, self.hir.tcx()).ty,
                 source_info.span
@@ -1617,9 +1615,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 Statement {
                     source_info,
                     kind: StatementKind::AscribeUserType(
-                        ascription.source.clone(),
+                        box(
+                            ascription.source.clone(),
+                            user_ty,
+                        ),
                         ascription.variance,
-                        user_ty,
                     ),
                 },
             );
diff --git a/src/librustc_mir/build/mod.rs b/src/librustc_mir/build/mod.rs
index 7ab0bf7d66a64..647d7515fe98d 100644
--- a/src/librustc_mir/build/mod.rs
+++ b/src/librustc_mir/build/mod.rs
@@ -609,7 +609,7 @@ where
         unpack!(block = builder.in_breakable_scope(
             None,
             START_BLOCK,
-            Place::RETURN_PLACE,
+            Place::return_place(),
             |builder| {
                 builder.in_scope(arg_scope_s, LintLevel::Inherited, |builder| {
                     builder.args_and_body(block, &arguments, arg_scope, &body.value)
@@ -670,7 +670,7 @@ fn construct_const<'a, 'tcx>(
     let mut block = START_BLOCK;
     let ast_expr = &tcx.hir().body(body_id).value;
     let expr = builder.hir.mirror(ast_expr);
-    unpack!(block = builder.into_expr(&Place::RETURN_PLACE, block, expr));
+    unpack!(block = builder.into_expr(&Place::return_place(), block, expr));
 
     let source_info = builder.source_info(span);
     builder.cfg.terminate(block, source_info, TerminatorKind::Return);
@@ -871,7 +871,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
 
         let body = self.hir.mirror(ast_body);
-        self.into(&Place::RETURN_PLACE, block, body)
+        self.into(&Place::return_place(), block, body)
     }
 
     fn set_correct_source_scope_for_arg(
diff --git a/src/librustc_mir/build/scope.rs b/src/librustc_mir/build/scope.rs
index a04c041ca9dc7..ee6d42de388d9 100644
--- a/src/librustc_mir/build/scope.rs
+++ b/src/librustc_mir/build/scope.rs
@@ -314,7 +314,7 @@ impl<'tcx> Scopes<'tcx> {
         match target {
             BreakableTarget::Return => {
                 let scope = &self.breakable_scopes[0];
-                if scope.break_destination != Place::RETURN_PLACE {
+                if scope.break_destination != Place::return_place() {
                     span_bug!(span, "`return` in item with no return scope");
                 }
                 (scope.break_block, scope.region_scope, Some(scope.break_destination.clone()))
@@ -853,11 +853,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             _ if self.local_scope().is_none() => (),
             Operand::Copy(Place {
                 base: PlaceBase::Local(cond_temp),
-                projection: None,
+                projection: box [],
             })
             | Operand::Move(Place {
                 base: PlaceBase::Local(cond_temp),
-                projection: None,
+                projection: box [],
             }) => {
                 // Manually drop the condition on both branches.
                 let top_scope = self.scopes.scopes.last_mut().unwrap();
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index 5aa487d901663..435159827e6c3 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -15,6 +15,7 @@ use rustc::ty::{self, Ty, TyCtxt, subst::Subst};
 use rustc::ty::layout::{self, LayoutOf, VariantIdx};
 use rustc::traits::Reveal;
 use rustc_data_structures::fx::FxHashMap;
+use crate::interpret::eval_nullary_intrinsic;
 
 use syntax::source_map::{Span, DUMMY_SP};
 
@@ -134,9 +135,8 @@ fn eval_body_using_ecx<'mir, 'tcx>(
     ecx: &mut CompileTimeEvalContext<'mir, 'tcx>,
     cid: GlobalId<'tcx>,
     body: &'mir mir::Body<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
 ) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
-    debug!("eval_body_using_ecx: {:?}, {:?}", cid, param_env);
+    debug!("eval_body_using_ecx: {:?}, {:?}", cid, ecx.param_env);
     let tcx = ecx.tcx.tcx;
     let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?;
     assert!(!layout.is_unsized());
@@ -162,7 +162,6 @@ fn eval_body_using_ecx<'mir, 'tcx>(
         ecx,
         cid.instance.def_id(),
         ret,
-        param_env,
     )?;
 
     debug!("eval_body_using_ecx done: {:?}", *ret);
@@ -383,7 +382,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             return Ok(());
         }
         // An intrinsic that we do not support
-        let intrinsic_name = &ecx.tcx.item_name(instance.def_id()).as_str()[..];
+        let intrinsic_name = ecx.tcx.item_name(instance.def_id());
         Err(
             ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", intrinsic_name)).into()
         )
@@ -533,8 +532,8 @@ pub fn error_to_const_error<'mir, 'tcx>(
 
 pub fn note_on_undefined_behavior_error() -> &'static str {
     "The rules on what exactly is undefined behavior aren't clear, \
-    so this check might be overzealous. Please open an issue on the rust compiler \
-    repository if you believe it should not be considered undefined behavior"
+     so this check might be overzealous. Please open an issue on the rustc \
+     repository if you believe it should not be considered undefined behavior."
 }
 
 fn validate_and_turn_into_const<'tcx>(
@@ -589,7 +588,7 @@ pub fn const_eval_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
 ) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> {
-    // see comment in const_eval_provider for what we're doing here
+    // see comment in const_eval_raw_provider for what we're doing here
     if key.param_env.reveal == Reveal::All {
         let mut key = key.clone();
         key.param_env.reveal = Reveal::UserFacing;
@@ -604,6 +603,23 @@ pub fn const_eval_provider<'tcx>(
             other => return other,
         }
     }
+
+    // We call `const_eval` for zero arg intrinsics, too, in order to cache their value.
+    // Catch such calls and evaluate them instead of trying to load a constant's MIR.
+    if let ty::InstanceDef::Intrinsic(def_id) = key.value.instance.def {
+        let ty = key.value.instance.ty(tcx);
+        let substs = match ty.sty {
+            ty::FnDef(_, substs) => substs,
+            _ => bug!("intrinsic with type {:?}", ty),
+        };
+        return eval_nullary_intrinsic(tcx, key.param_env, def_id, substs)
+            .map_err(|error| {
+                let span = tcx.def_span(def_id);
+                let error = ConstEvalErr { error: error.kind, stacktrace: vec![], span };
+                error.report_as_error(tcx.at(span), "could not evaluate nullary intrinsic")
+            })
+    }
+
     tcx.const_eval_raw(key).and_then(|val| {
         validate_and_turn_into_const(tcx, val, key)
     })
@@ -658,7 +674,7 @@ pub fn const_eval_raw_provider<'tcx>(
 
     let res = ecx.load_mir(cid.instance.def, cid.promoted);
     res.and_then(
-        |body| eval_body_using_ecx(&mut ecx, cid, body, key.param_env)
+        |body| eval_body_using_ecx(&mut ecx, cid, body)
     ).and_then(|place| {
         Ok(RawConst {
             alloc_id: place.ptr.assert_ptr().alloc_id,
diff --git a/src/librustc_mir/dataflow/drop_flag_effects.rs b/src/librustc_mir/dataflow/drop_flag_effects.rs
index c071b3101fce3..444cc008ae785 100644
--- a/src/librustc_mir/dataflow/drop_flag_effects.rs
+++ b/src/librustc_mir/dataflow/drop_flag_effects.rs
@@ -10,19 +10,17 @@ pub fn move_path_children_matching<'tcx, F>(move_data: &MoveData<'tcx>,
                                         path: MovePathIndex,
                                         mut cond: F)
                                         -> Option<MovePathIndex>
-    where F: FnMut(&mir::Projection<'tcx>) -> bool
+    where F: FnMut(&mir::PlaceElem<'tcx>) -> bool
 {
     let mut next_child = move_data.move_paths[path].first_child;
     while let Some(child_index) = next_child {
-        match move_data.move_paths[child_index].place.projection {
-            Some(ref proj) => {
-                if cond(proj) {
-                    return Some(child_index)
-                }
+        let move_path_children = &move_data.move_paths[child_index];
+        if let Some(elem) = move_path_children.place.projection.last() {
+            if cond(elem) {
+                return Some(child_index)
             }
-            _ => {}
         }
-        next_child = move_data.move_paths[child_index].next_sibling;
+        next_child = move_path_children.next_sibling;
     }
 
     None
diff --git a/src/librustc_mir/dataflow/generic.rs b/src/librustc_mir/dataflow/generic.rs
new file mode 100644
index 0000000000000..886044c069282
--- /dev/null
+++ b/src/librustc_mir/dataflow/generic.rs
@@ -0,0 +1,512 @@
+//! Dataflow analysis with arbitrary transfer functions.
+//!
+//! This module is a work in progress. You should instead use `BitDenotation` in
+//! `librustc_mir/dataflow/mod.rs` and encode your transfer function as a [gen/kill set][gk]. In
+//! doing so, your analysis will run faster and you will be able to generate graphviz diagrams for
+//! debugging with no extra effort. The interface in this module is intended only for dataflow
+//! problems that cannot be expressed using gen/kill sets.
+//!
+//! FIXME(ecstaticmorse): In the long term, the plan is to preserve the existing `BitDenotation`
+//! interface, but make `Engine` and `ResultsCursor` the canonical way to perform and inspect a
+//! dataflow analysis. This requires porting the graphviz debugging logic to this module, deciding
+//! on a way to handle the `before` methods in `BitDenotation` and creating an adapter so that
+//! gen-kill problems can still be evaluated efficiently. See the discussion in [#64566][] for more
+//! information.
+//!
+//! [gk]: https://en.wikipedia.org/wiki/Data-flow_analysis#Bit_vector_problems
+//! [#64566]: https://github.com/rust-lang/rust/pull/64566
+
+use std::cmp::Ordering;
+use std::ops;
+
+use rustc::mir::{self, traversal, BasicBlock, Location};
+use rustc_data_structures::bit_set::BitSet;
+use rustc_data_structures::indexed_vec::{Idx, IndexVec};
+use rustc_data_structures::work_queue::WorkQueue;
+
+use crate::dataflow::BottomValue;
+
+/// A specific kind of dataflow analysis.
+///
+/// To run a dataflow analysis, one must set the initial state of the `START_BLOCK` via
+/// `initialize_start_block` and define a transfer function for each statement or terminator via
+/// the various `effect` methods. The entry set for all other basic blocks is initialized to
+/// `Self::BOTTOM_VALUE`. The dataflow `Engine` then iteratively updates the various entry sets for
+/// each block with the cumulative effects of the transfer functions of all preceding blocks.
+///
+/// You should use an `Engine` to actually run an analysis, and a `ResultsCursor` to inspect the
+/// results of that analysis like so:
+///
+/// ```ignore(cross-crate-imports)
+/// fn do_my_analysis(body: &mir::Body<'tcx>, dead_unwinds: &BitSet<BasicBlock>) {
+///     // `MyAnalysis` implements `Analysis`.
+///     let analysis = MyAnalysis::new();
+///
+///     let results = Engine::new(body, dead_unwinds, analysis).iterate_to_fixpoint();
+///     let mut cursor = ResultsCursor::new(body, results);
+///
+///     for (_, statement_index) in body.block_data[START_BLOCK].statements.iter_enumerated() {
+///         cursor.seek_after(Location { block: START_BLOCK, statement_index });
+///         let state = cursor.get();
+///         println!("{:?}", state);
+///     }
+/// }
+/// ```
+pub trait Analysis<'tcx>: BottomValue {
+    /// The index type used to access the dataflow state.
+    type Idx: Idx;
+
+    /// A name, used for debugging, that describes this dataflow analysis.
+    ///
+    /// The name should be suitable as part of a filename, so avoid whitespace, slashes or periods
+    /// and try to keep it short.
+    const NAME: &'static str;
+
+    /// The size of each bitvector allocated for each block.
+    fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize;
+
+    /// Mutates the entry set of the `START_BLOCK` to contain the initial state for dataflow
+    /// analysis.
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut BitSet<Self::Idx>);
+
+    /// Updates the current dataflow state with the effect of evaluating a statement.
+    fn apply_statement_effect(
+        &self,
+        state: &mut BitSet<Self::Idx>,
+        statement: &mir::Statement<'tcx>,
+        location: Location,
+    );
+
+    /// Updates the current dataflow state with the effect of evaluating a statement.
+    ///
+    /// Note that the effect of a successful return from a `Call` terminator should **not** be
+    /// acounted for in this function. That should go in `apply_call_return_effect`. For example,
+    /// in the `InitializedPlaces` analyses, the return place is not marked as initialized here.
+    fn apply_terminator_effect(
+        &self,
+        state: &mut BitSet<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        location: Location,
+    );
+
+    /// Updates the current dataflow state with the effect of a successful return from a `Call`
+    /// terminator.
+    ///
+    /// This is separated from `apply_terminator_effect` to properly track state across
+    /// unwind edges for `Call`s.
+    fn apply_call_return_effect(
+        &self,
+        state: &mut BitSet<Self::Idx>,
+        block: BasicBlock,
+        func: &mir::Operand<'tcx>,
+        args: &[mir::Operand<'tcx>],
+        return_place: &mir::Place<'tcx>,
+    );
+
+    /// Applies the cumulative effect of an entire basic block to the dataflow state (except for
+    /// `call_return_effect`, which is handled in the `Engine`).
+    ///
+    /// The default implementation calls `statement_effect` for every statement in the block before
+    /// finally calling `terminator_effect`. However, some dataflow analyses are able to coalesce
+    /// transfer functions for an entire block and apply them at once. Such analyses should
+    /// override `block_effect`.
+    fn apply_whole_block_effect(
+        &self,
+        state: &mut BitSet<Self::Idx>,
+        block: BasicBlock,
+        block_data: &mir::BasicBlockData<'tcx>,
+    ) {
+        for (statement_index, stmt) in block_data.statements.iter().enumerate() {
+            let location = Location { block, statement_index };
+            self.apply_statement_effect(state, stmt, location);
+        }
+
+        let location = Location { block, statement_index: block_data.statements.len() };
+        self.apply_terminator_effect(state, block_data.terminator(), location);
+    }
+
+    /// Applies the cumulative effect of a sequence of statements (and possibly a terminator)
+    /// within a single basic block.
+    ///
+    /// When called with `0..block_data.statements.len() + 1` as the statement range, this function
+    /// is equivalent to `apply_whole_block_effect`.
+    fn apply_partial_block_effect(
+        &self,
+        state: &mut BitSet<Self::Idx>,
+        block: BasicBlock,
+        block_data: &mir::BasicBlockData<'tcx>,
+        mut range: ops::Range<usize>,
+    ) {
+        if range.is_empty() {
+            return;
+        }
+
+        // The final location might be a terminator, so iterate through all statements until the
+        // final one, then check to see whether the final one is a statement or terminator.
+        //
+        // This can't cause the range to wrap-around since we check that the range contains at
+        // least one element above.
+        range.end -= 1;
+        let final_location = Location { block, statement_index: range.end };
+
+        for statement_index in range {
+            let location = Location { block, statement_index };
+            let stmt = &block_data.statements[statement_index];
+            self.apply_statement_effect(state, stmt, location);
+        }
+
+        if final_location.statement_index == block_data.statements.len() {
+            let terminator = block_data.terminator();
+            self.apply_terminator_effect(state, terminator, final_location);
+        } else {
+            let stmt = &block_data.statements[final_location.statement_index];
+            self.apply_statement_effect(state, stmt, final_location);
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+enum CursorPosition {
+    AtBlockStart(BasicBlock),
+    After(Location),
+}
+
+impl CursorPosition {
+    fn block(&self) -> BasicBlock {
+        match *self {
+            Self::AtBlockStart(block) => block,
+            Self::After(Location { block, .. }) => block,
+        }
+    }
+}
+
+/// Inspect the results of dataflow analysis.
+///
+/// This cursor has linear performance when visiting statements in a block in order. Visiting
+/// statements within a block in reverse order is `O(n^2)`, where `n` is the number of statements
+/// in that block.
+pub struct ResultsCursor<'mir, 'tcx, A>
+where
+    A: Analysis<'tcx>,
+{
+    body: &'mir mir::Body<'tcx>,
+    results: Results<'tcx, A>,
+    state: BitSet<A::Idx>,
+
+    pos: CursorPosition,
+
+    /// Whether the effects of `apply_call_return_effect` are currently stored in `state`.
+    ///
+    /// This flag ensures that multiple calls to `seek_after_assume_call_returns` with the same
+    /// target only result in one invocation of `apply_call_return_effect`.
+    is_call_return_effect_applied: bool,
+}
+
+impl<'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A>
+where
+    A: Analysis<'tcx>,
+{
+    /// Returns a new cursor for `results` that points to the start of the `START_BLOCK`.
+    pub fn new(body: &'mir mir::Body<'tcx>, results: Results<'tcx, A>) -> Self {
+        ResultsCursor {
+            body,
+            pos: CursorPosition::AtBlockStart(mir::START_BLOCK),
+            is_call_return_effect_applied: false,
+            state: results.entry_sets[mir::START_BLOCK].clone(),
+            results,
+        }
+    }
+
+    /// Resets the cursor to the start of the given `block`.
+    pub fn seek_to_block_start(&mut self, block: BasicBlock) {
+        self.state.overwrite(&self.results.entry_sets[block]);
+        self.pos = CursorPosition::AtBlockStart(block);
+        self.is_call_return_effect_applied = false;
+    }
+
+    /// Updates the cursor to hold the dataflow state immediately before `target`.
+    pub fn seek_before(&mut self, target: Location) {
+        assert!(target <= self.body.terminator_loc(target.block));
+
+        if target.statement_index == 0 {
+            self.seek_to_block_start(target.block);
+        } else {
+            self._seek_after(Location {
+                block: target.block,
+                statement_index: target.statement_index - 1,
+            });
+        }
+    }
+
+    /// Updates the cursor to hold the dataflow state at `target`.
+    ///
+    /// If `target` is a `Call` terminator, `apply_call_return_effect` will not be called. See
+    /// `seek_after_assume_call_returns` if you wish to observe the dataflow state upon a
+    /// successful return.
+    pub fn seek_after(&mut self, target: Location) {
+        assert!(target <= self.body.terminator_loc(target.block));
+
+        // This check ensures the correctness of a call to `seek_after_assume_call_returns`
+        // followed by one to `seek_after` with the same target.
+        if self.is_call_return_effect_applied {
+            self.seek_to_block_start(target.block);
+        }
+
+        self._seek_after(target);
+    }
+
+    /// Equivalent to `seek_after`, but also calls `apply_call_return_effect` if `target` is a
+    /// `Call` terminator whose callee is convergent.
+    pub fn seek_after_assume_call_returns(&mut self, target: Location) {
+        assert!(target <= self.body.terminator_loc(target.block));
+
+        self._seek_after(target);
+
+        if target != self.body.terminator_loc(target.block) {
+            return;
+        }
+
+        let term = self.body.basic_blocks()[target.block].terminator();
+        if let mir::TerminatorKind::Call {
+            destination: Some((return_place, _)),
+            func,
+            args,
+            ..
+        } = &term.kind {
+            if !self.is_call_return_effect_applied {
+                self.is_call_return_effect_applied = true;
+                self.results.analysis.apply_call_return_effect(
+                    &mut self.state,
+                    target.block,
+                    func,
+                    args,
+                    return_place,
+                );
+            }
+        }
+    }
+
+    fn _seek_after(&mut self, target: Location) {
+        let Location { block: target_block, statement_index: target_index } = target;
+
+        if self.pos.block() != target_block {
+            self.seek_to_block_start(target_block);
+        }
+
+        // If we're in the same block but after the target statement, we need to reset to the start
+        // of the block.
+        if let CursorPosition::After(Location { statement_index: curr_index, .. }) = self.pos {
+            match curr_index.cmp(&target_index) {
+                Ordering::Equal => return,
+                Ordering::Less => {},
+                Ordering::Greater => self.seek_to_block_start(target_block),
+            }
+        }
+
+        // The cursor is now in the same block as the target location pointing at an earlier
+        // statement.
+        debug_assert_eq!(self.pos.block(), target_block);
+        if let CursorPosition::After(Location { statement_index, .. }) = self.pos {
+            debug_assert!(statement_index < target_index);
+        }
+
+        let first_unapplied_statement = match self.pos {
+            CursorPosition::AtBlockStart(_) => 0,
+            CursorPosition::After(Location { statement_index, .. }) => statement_index + 1,
+        };
+
+        let block_data = &self.body.basic_blocks()[target_block];
+        self.results.analysis.apply_partial_block_effect(
+            &mut self.state,
+            target_block,
+            block_data,
+            first_unapplied_statement..target_index + 1,
+        );
+
+        self.pos = CursorPosition::After(target);
+        self.is_call_return_effect_applied = false;
+    }
+
+    /// Gets the dataflow state at the current location.
+    pub fn get(&self) -> &BitSet<A::Idx> {
+        &self.state
+    }
+}
+
+/// A completed dataflow analysis.
+pub struct Results<'tcx, A>
+where
+    A: Analysis<'tcx>,
+{
+    analysis: A,
+    entry_sets: IndexVec<BasicBlock, BitSet<A::Idx>>,
+}
+
+/// All information required to iterate a dataflow analysis to fixpoint.
+pub struct Engine<'a, 'tcx, A>
+where
+    A: Analysis<'tcx>,
+{
+    analysis: A,
+    bits_per_block: usize,
+    body: &'a mir::Body<'tcx>,
+    dead_unwinds: &'a BitSet<BasicBlock>,
+    entry_sets: IndexVec<BasicBlock, BitSet<A::Idx>>,
+}
+
+impl<A> Engine<'a, 'tcx, A>
+where
+    A: Analysis<'tcx>,
+{
+    pub fn new(
+        body: &'a mir::Body<'tcx>,
+        dead_unwinds: &'a BitSet<BasicBlock>,
+        analysis: A,
+    ) -> Self {
+        let bits_per_block = analysis.bits_per_block(body);
+
+        let bottom_value_set = if A::BOTTOM_VALUE == true {
+            BitSet::new_filled(bits_per_block)
+        } else {
+            BitSet::new_empty(bits_per_block)
+        };
+
+        let mut entry_sets = IndexVec::from_elem(bottom_value_set, body.basic_blocks());
+        analysis.initialize_start_block(body, &mut entry_sets[mir::START_BLOCK]);
+
+        Engine {
+            analysis,
+            bits_per_block,
+            body,
+            dead_unwinds,
+            entry_sets,
+        }
+    }
+
+    pub fn iterate_to_fixpoint(mut self) -> Results<'tcx, A> {
+        let mut temp_state = BitSet::new_empty(self.bits_per_block);
+
+        let mut dirty_queue: WorkQueue<BasicBlock> =
+            WorkQueue::with_none(self.body.basic_blocks().len());
+
+        for (bb, _) in traversal::reverse_postorder(self.body) {
+            dirty_queue.insert(bb);
+        }
+
+        // Add blocks that are not reachable from START_BLOCK to the work queue. These blocks will
+        // be processed after the ones added above.
+        for bb in self.body.basic_blocks().indices() {
+            dirty_queue.insert(bb);
+        }
+
+        while let Some(bb) = dirty_queue.pop() {
+            let bb_data = &self.body[bb];
+            let on_entry = &self.entry_sets[bb];
+
+            temp_state.overwrite(on_entry);
+            self.analysis.apply_whole_block_effect(&mut temp_state, bb, bb_data);
+
+            self.propagate_bits_into_graph_successors_of(
+                &mut temp_state,
+                (bb, bb_data),
+                &mut dirty_queue,
+            );
+        }
+
+        Results {
+            analysis: self.analysis,
+            entry_sets: self.entry_sets,
+        }
+    }
+
+    fn propagate_bits_into_graph_successors_of(
+        &mut self,
+        in_out: &mut BitSet<A::Idx>,
+        (bb, bb_data): (BasicBlock, &'a mir::BasicBlockData<'tcx>),
+        dirty_list: &mut WorkQueue<BasicBlock>,
+    ) {
+        match bb_data.terminator().kind {
+            mir::TerminatorKind::Return
+            | mir::TerminatorKind::Resume
+            | mir::TerminatorKind::Abort
+            | mir::TerminatorKind::GeneratorDrop
+            | mir::TerminatorKind::Unreachable => {}
+
+            mir::TerminatorKind::Goto { target }
+            | mir::TerminatorKind::Assert { target, cleanup: None, .. }
+            | mir::TerminatorKind::Yield { resume: target, drop: None, .. }
+            | mir::TerminatorKind::Drop { target, location: _, unwind: None }
+            | mir::TerminatorKind::DropAndReplace { target, value: _, location: _, unwind: None } =>
+            {
+                self.propagate_bits_into_entry_set_for(in_out, target, dirty_list);
+            }
+
+            mir::TerminatorKind::Yield { resume: target, drop: Some(drop), .. } => {
+                self.propagate_bits_into_entry_set_for(in_out, target, dirty_list);
+                self.propagate_bits_into_entry_set_for(in_out, drop, dirty_list);
+            }
+
+            mir::TerminatorKind::Assert { target, cleanup: Some(unwind), .. }
+            | mir::TerminatorKind::Drop { target, location: _, unwind: Some(unwind) }
+            | mir::TerminatorKind::DropAndReplace {
+                target,
+                value: _,
+                location: _,
+                unwind: Some(unwind),
+            } => {
+                self.propagate_bits_into_entry_set_for(in_out, target, dirty_list);
+                if !self.dead_unwinds.contains(bb) {
+                    self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list);
+                }
+            }
+
+            mir::TerminatorKind::SwitchInt { ref targets, .. } => {
+                for target in targets {
+                    self.propagate_bits_into_entry_set_for(in_out, *target, dirty_list);
+                }
+            }
+
+            mir::TerminatorKind::Call { cleanup, ref destination, ref func, ref args, .. } => {
+                if let Some(unwind) = cleanup {
+                    if !self.dead_unwinds.contains(bb) {
+                        self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list);
+                    }
+                }
+
+                if let Some((ref dest_place, dest_bb)) = *destination {
+                    // N.B.: This must be done *last*, after all other
+                    // propagation, as documented in comment above.
+                    self.analysis.apply_call_return_effect(in_out, bb, func, args, dest_place);
+                    self.propagate_bits_into_entry_set_for(in_out, dest_bb, dirty_list);
+                }
+            }
+
+            mir::TerminatorKind::FalseEdges { real_target, imaginary_target } => {
+                self.propagate_bits_into_entry_set_for(in_out, real_target, dirty_list);
+                self.propagate_bits_into_entry_set_for(in_out, imaginary_target, dirty_list);
+            }
+
+            mir::TerminatorKind::FalseUnwind { real_target, unwind } => {
+                self.propagate_bits_into_entry_set_for(in_out, real_target, dirty_list);
+                if let Some(unwind) = unwind {
+                    if !self.dead_unwinds.contains(bb) {
+                        self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list);
+                    }
+                }
+            }
+        }
+    }
+
+    fn propagate_bits_into_entry_set_for(
+        &mut self,
+        in_out: &BitSet<A::Idx>,
+        bb: BasicBlock,
+        dirty_queue: &mut WorkQueue<BasicBlock>,
+    ) {
+        let entry_set = &mut self.entry_sets[bb];
+        let set_changed = self.analysis.join(entry_set, &in_out);
+        if set_changed {
+            dirty_queue.insert(bb);
+        }
+    }
+}
diff --git a/src/librustc_mir/dataflow/impls/borrows.rs b/src/librustc_mir/dataflow/impls/borrows.rs
index 2ea6c4ae10fdc..a86fcb30f4d36 100644
--- a/src/librustc_mir/dataflow/impls/borrows.rs
+++ b/src/librustc_mir/dataflow/impls/borrows.rs
@@ -208,7 +208,7 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
             // If the borrowed place is a local with no projections, all other borrows of this
             // local must conflict. This is purely an optimization so we don't have to call
             // `places_conflict` for every borrow.
-            if place.projection.is_none() {
+            if place.projection.is_empty() {
                 trans.kill_all(other_borrows_of_local);
                 return;
             }
@@ -268,8 +268,8 @@ impl<'a, 'tcx> BitDenotation<'tcx> for Borrows<'a, 'tcx> {
 
         debug!("Borrows::statement_effect: stmt={:?}", stmt);
         match stmt.kind {
-            mir::StatementKind::Assign(ref lhs, ref rhs) => {
-                if let mir::Rvalue::Ref(_, _, ref place) = **rhs {
+            mir::StatementKind::Assign(box(ref lhs, ref rhs)) => {
+                if let mir::Rvalue::Ref(_, _, ref place) = *rhs {
                     if place.ignore_borrow(
                         self.tcx,
                         self.body,
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 0e01701ea9e44..0f66b13fdc51a 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -119,8 +119,8 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         match stmt.kind {
             StatementKind::StorageLive(l) => sets.gen(l),
             StatementKind::StorageDead(l) => sets.kill(l),
-            StatementKind::Assign(ref place, _)
-            | StatementKind::SetDiscriminant { ref place, .. } => {
+            StatementKind::Assign(box(ref place, _))
+            | StatementKind::SetDiscriminant { box ref place, .. } => {
                 if let PlaceBase::Local(local) = place.base {
                     sets.gen(local);
                 }
diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs
index 7fe2a890a5371..5ab4e25b683cb 100644
--- a/src/librustc_mir/dataflow/mod.rs
+++ b/src/librustc_mir/dataflow/mod.rs
@@ -30,6 +30,7 @@ use self::move_paths::MoveData;
 
 mod at_location;
 pub mod drop_flag_effects;
+pub mod generic;
 mod graphviz;
 mod impls;
 pub mod move_paths;
@@ -56,7 +57,7 @@ where
 /// string (as well as that of rendering up-front); in exchange, you
 /// don't have to hand over ownership of your value or deal with
 /// borrowing it.
-pub(crate) struct DebugFormatted(String);
+pub struct DebugFormatted(String);
 
 impl DebugFormatted {
     pub fn new(input: &dyn fmt::Debug) -> DebugFormatted {
@@ -70,7 +71,7 @@ impl fmt::Debug for DebugFormatted {
     }
 }
 
-pub(crate) trait Dataflow<'tcx, BD: BitDenotation<'tcx>> {
+pub trait Dataflow<'tcx, BD: BitDenotation<'tcx>> {
     /// Sets up and runs the dataflow problem, using `p` to render results if
     /// implementation so chooses.
     fn dataflow<P>(&mut self, p: P) where P: Fn(&BD, BD::Idx) -> DebugFormatted {
@@ -121,7 +122,7 @@ pub struct MoveDataParamEnv<'tcx> {
     pub(crate) param_env: ty::ParamEnv<'tcx>,
 }
 
-pub(crate) fn do_dataflow<'a, 'tcx, BD, P>(
+pub fn do_dataflow<'a, 'tcx, BD, P>(
     tcx: TyCtxt<'tcx>,
     body: &'a Body<'tcx>,
     def_id: DefId,
@@ -453,34 +454,10 @@ where
     {
         self.flow_state.each_gen_bit(f)
     }
-}
-
-pub fn state_for_location<'tcx, T: BitDenotation<'tcx>>(loc: Location,
-                                                        analysis: &T,
-                                                        result: &DataflowResults<'tcx, T>,
-                                                        body: &Body<'tcx>)
-    -> BitSet<T::Idx> {
-    let mut trans = GenKill::from_elem(HybridBitSet::new_empty(analysis.bits_per_block()));
 
-    for stmt in 0..loc.statement_index {
-        let mut stmt_loc = loc;
-        stmt_loc.statement_index = stmt;
-        analysis.before_statement_effect(&mut trans, stmt_loc);
-        analysis.statement_effect(&mut trans, stmt_loc);
+    pub fn get(&self) -> &BitSet<BD::Idx> {
+        self.flow_state.as_dense()
     }
-
-    // Apply the pre-statement effect of the statement we're evaluating.
-    if loc.statement_index == body[loc.block].statements.len() {
-        analysis.before_terminator_effect(&mut trans, loc);
-    } else {
-        analysis.before_statement_effect(&mut trans, loc);
-    }
-
-    // Apply the transfer function for all preceding statements to the fixpoint
-    // at the start of the block.
-    let mut state = result.sets().entry_set_for(loc.block.index()).to_owned();
-    trans.apply(&mut state);
-    state
 }
 
 pub struct DataflowAnalysis<'a, 'tcx, O>
@@ -565,7 +542,7 @@ pub struct GenKill<T> {
     pub(crate) kill_set: T,
 }
 
-type GenKillSet<T> = GenKill<HybridBitSet<T>>;
+pub type GenKillSet<T> = GenKill<HybridBitSet<T>>;
 
 impl<T> GenKill<T> {
     /// Creates a new tuple where `gen_set == kill_set == elem`.
@@ -580,28 +557,28 @@ impl<T> GenKill<T> {
 }
 
 impl<E:Idx> GenKillSet<E> {
-    pub(crate) fn clear(&mut self) {
+    pub fn clear(&mut self) {
         self.gen_set.clear();
         self.kill_set.clear();
     }
 
-    fn gen(&mut self, e: E) {
+    pub fn gen(&mut self, e: E) {
         self.gen_set.insert(e);
         self.kill_set.remove(e);
     }
 
-    fn gen_all(&mut self, i: impl IntoIterator<Item: Borrow<E>>) {
+    pub fn gen_all(&mut self, i: impl IntoIterator<Item: Borrow<E>>) {
         for j in i {
             self.gen(*j.borrow());
         }
     }
 
-    fn kill(&mut self, e: E) {
+    pub fn kill(&mut self, e: E) {
         self.gen_set.remove(e);
         self.kill_set.insert(e);
     }
 
-    fn kill_all(&mut self, i: impl IntoIterator<Item: Borrow<E>>) {
+    pub fn kill_all(&mut self, i: impl IntoIterator<Item: Borrow<E>>) {
         for j in i {
             self.kill(*j.borrow());
         }
diff --git a/src/librustc_mir/dataflow/move_paths/builder.rs b/src/librustc_mir/dataflow/move_paths/builder.rs
index 81451c2500c47..698c50166270a 100644
--- a/src/librustc_mir/dataflow/move_paths/builder.rs
+++ b/src/librustc_mir/dataflow/move_paths/builder.rs
@@ -94,72 +94,74 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     /// Maybe we should have separate "borrowck" and "moveck" modes.
     fn move_path_for(&mut self, place: &Place<'tcx>) -> Result<MovePathIndex, MoveError<'tcx>> {
         debug!("lookup({:?})", place);
-        place.iterate(|place_base, place_projection| {
-            let mut base = match place_base {
-                PlaceBase::Local(local) => self.builder.data.rev_lookup.locals[*local],
-                PlaceBase::Static(..) => {
-                    return Err(MoveError::cannot_move_out_of(self.loc, Static));
-                }
-            };
+        let mut base = match place.base {
+            PlaceBase::Local(local) => self.builder.data.rev_lookup.locals[local],
+            PlaceBase::Static(..) => {
+                return Err(MoveError::cannot_move_out_of(self.loc, Static));
+            }
+        };
 
-            for proj in place_projection {
-                let body = self.builder.body;
-                let tcx = self.builder.tcx;
-                let place_ty = Place::ty_from(place_base, &proj.base, body, tcx).ty;
-                match place_ty.sty {
-                    ty::Ref(..) | ty::RawPtr(..) => {
-                        return Err(MoveError::cannot_move_out_of(
-                            self.loc,
-                            BorrowedContent {
-                                target_place: Place {
-                                    base: place_base.clone(),
-                                    projection: Some(Box::new(proj.clone())),
-                                },
+        for (i, elem) in place.projection.iter().enumerate() {
+            let proj_base = &place.projection[..i];
+            let body = self.builder.body;
+            let tcx = self.builder.tcx;
+            let place_ty = Place::ty_from(&place.base, proj_base, body, tcx).ty;
+            match place_ty.sty {
+                ty::Ref(..) | ty::RawPtr(..) => {
+                    let proj = &place.projection[..i+1];
+                    return Err(MoveError::cannot_move_out_of(
+                        self.loc,
+                        BorrowedContent {
+                            target_place: Place {
+                                base: place.base.clone(),
+                                projection: proj.to_vec().into_boxed_slice(),
                             },
-                        ));
-                    }
-                    ty::Adt(adt, _) if adt.has_dtor(tcx) && !adt.is_box() => {
+                        },
+                    ));
+                }
+                ty::Adt(adt, _) if adt.has_dtor(tcx) && !adt.is_box() => {
+                    return Err(MoveError::cannot_move_out_of(
+                        self.loc,
+                        InteriorOfTypeWithDestructor { container_ty: place_ty },
+                    ));
+                }
+                // move out of union - always move the entire union
+                ty::Adt(adt, _) if adt.is_union() => {
+                    return Err(MoveError::UnionMove { path: base });
+                }
+                ty::Slice(_) => {
+                    return Err(MoveError::cannot_move_out_of(
+                        self.loc,
+                        InteriorOfSliceOrArray {
+                            ty: place_ty,
+                            is_index: match elem {
+                                ProjectionElem::Index(..) => true,
+                                _ => false,
+                            },
+                        },
+                    ));
+                }
+                ty::Array(..) => match elem {
+                    ProjectionElem::Index(..) => {
                         return Err(MoveError::cannot_move_out_of(
                             self.loc,
-                            InteriorOfTypeWithDestructor { container_ty: place_ty },
+                            InteriorOfSliceOrArray { ty: place_ty, is_index: true },
                         ));
                     }
-                    // move out of union - always move the entire union
-                    ty::Adt(adt, _) if adt.is_union() => {
-                        return Err(MoveError::UnionMove { path: base });
-                    }
-                    ty::Slice(_) => {
-                        return Err(MoveError::cannot_move_out_of(
-                            self.loc,
-                            InteriorOfSliceOrArray {
-                                ty: place_ty,
-                                is_index: match proj.elem {
-                                    ProjectionElem::Index(..) => true,
-                                    _ => false,
-                                },
-                            },
-                        ));
+                    _ => {
+                        // FIXME: still badly broken
                     }
-                    ty::Array(..) => match proj.elem {
-                        ProjectionElem::Index(..) => {
-                            return Err(MoveError::cannot_move_out_of(
-                                self.loc,
-                                InteriorOfSliceOrArray { ty: place_ty, is_index: true },
-                            ));
-                        }
-                        _ => {
-                            // FIXME: still badly broken
-                        }
-                    },
-                    _ => {}
-                };
+                },
+                _ => {}
+            };
 
-                base = match self
-                    .builder
-                    .data
-                    .rev_lookup
-                    .projections
-                    .entry((base, proj.elem.lift()))
+            let proj = &place.projection[..i+1];
+            base = match self
+                .builder
+                .data
+                .rev_lookup
+                .projections
+                .entry((base, elem.lift()))
                 {
                     Entry::Occupied(ent) => *ent.get(),
                     Entry::Vacant(ent) => {
@@ -169,18 +171,17 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                             &mut self.builder.data.init_path_map,
                             Some(base),
                             Place {
-                                base: place_base.clone(),
-                                projection: Some(Box::new(proj.clone())),
+                                base: place.base.clone(),
+                                projection: proj.to_vec().into_boxed_slice(),
                             },
                         );
                         ent.insert(path);
                         path
                     }
                 };
-            }
+        }
 
-            Ok(base)
-        })
+        Ok(base)
     }
 
     fn create_move_path(&mut self, place: &Place<'tcx>) {
@@ -267,7 +268,7 @@ struct Gatherer<'b, 'a, 'tcx> {
 impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     fn gather_statement(&mut self, stmt: &Statement<'tcx>) {
         match stmt.kind {
-            StatementKind::Assign(ref place, ref rval) => {
+            StatementKind::Assign(box(ref place, ref rval)) => {
                 self.create_move_path(place);
                 if let RvalueInitializationState::Shallow = rval.initialization_state() {
                     // Box starts out uninitialized - need to create a separate
@@ -355,7 +356,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             | TerminatorKind::Unreachable => {}
 
             TerminatorKind::Return => {
-                self.gather_move(&Place::RETURN_PLACE);
+                self.gather_move(&Place::return_place());
             }
 
             TerminatorKind::Assert { ref cond, .. } => {
@@ -435,9 +436,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
 
         // Check if we are assigning into a field of a union, if so, lookup the place
         // of the union so it is marked as initialized again.
-        if let Some(box Projection { base: proj_base, elem: ProjectionElem::Field(_, _) }) =
-            place.projection
-        {
+        if let [proj_base @ .., ProjectionElem::Field(_, _)] = place.projection {
             if let ty::Adt(def, _) =
                 Place::ty_from(place.base, proj_base, self.builder.body, self.builder.tcx).ty.sty
             {
diff --git a/src/librustc_mir/dataflow/move_paths/mod.rs b/src/librustc_mir/dataflow/move_paths/mod.rs
index 5028e9650918c..156c19c6363e5 100644
--- a/src/librustc_mir/dataflow/move_paths/mod.rs
+++ b/src/librustc_mir/dataflow/move_paths/mod.rs
@@ -245,23 +245,21 @@ impl MovePathLookup {
     // alternative will *not* create a MovePath on the fly for an
     // unknown place, but will rather return the nearest available
     // parent.
-    pub fn find(&self, place_ref: PlaceRef<'_, '_>) -> LookupResult {
-        place_ref.iterate(|place_base, place_projection| {
-            let mut result = match place_base {
-                PlaceBase::Local(local) => self.locals[*local],
-                PlaceBase::Static(..) => return LookupResult::Parent(None),
-            };
-
-            for proj in place_projection {
-                if let Some(&subpath) = self.projections.get(&(result, proj.elem.lift())) {
-                    result = subpath;
-                } else {
-                    return LookupResult::Parent(Some(result));
-                }
+    pub fn find(&self, place: PlaceRef<'_, '_>) -> LookupResult {
+        let mut result = match place.base {
+            PlaceBase::Local(local) => self.locals[*local],
+            PlaceBase::Static(..) => return LookupResult::Parent(None),
+        };
+
+        for elem in place.projection.iter() {
+            if let Some(&subpath) = self.projections.get(&(result, elem.lift())) {
+                result = subpath;
+            } else {
+                return LookupResult::Parent(Some(result));
             }
+        }
 
-            LookupResult::Exact(result)
-        })
+        LookupResult::Exact(result)
     }
 
     pub fn find_local(&self, local: Local) -> MovePathIndex {
@@ -329,7 +327,7 @@ impl<'tcx> MoveData<'tcx> {
     pub fn base_local(&self, mut mpi: MovePathIndex) -> Option<Local> {
         loop {
             let path = &self.move_paths[mpi];
-            if let Place { base: PlaceBase::Local(l), projection: None } = path.place {
+            if let Place { base: PlaceBase::Local(l), projection: box [] } = path.place {
                 return Some(l);
             }
             if let Some(parent) = path.parent {
diff --git a/src/librustc_mir/error_codes.rs b/src/librustc_mir/error_codes.rs
index 86c263a447bb6..ba299e9463b8d 100644
--- a/src/librustc_mir/error_codes.rs
+++ b/src/librustc_mir/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 
 E0001: r##"
@@ -157,81 +157,6 @@ match x {
 See also the error E0303.
 "##,
 
-E0008: r##"
-Names bound in match arms retain their type in pattern guards. As such, if a
-name is bound by move in a pattern, it should also be moved to wherever it is
-referenced in the pattern guard code. Doing so however would prevent the name
-from being available in the body of the match arm. Consider the following:
-
-```compile_fail,E0008
-match Some("hi".to_string()) {
-    Some(s) if s.len() == 0 => {}, // use s.
-    _ => {},
-}
-```
-
-The variable `s` has type `String`, and its use in the guard is as a variable of
-type `String`. The guard code effectively executes in a separate scope to the
-body of the arm, so the value would be moved into this anonymous scope and
-therefore becomes unavailable in the body of the arm.
-
-The problem above can be solved by using the `ref` keyword.
-
-```
-match Some("hi".to_string()) {
-    Some(ref s) if s.len() == 0 => {},
-    _ => {},
-}
-```
-
-Though this example seems innocuous and easy to solve, the problem becomes clear
-when it encounters functions which consume the value:
-
-```compile_fail,E0008
-struct A{}
-
-impl A {
-    fn consume(self) -> usize {
-        0
-    }
-}
-
-fn main() {
-    let a = Some(A{});
-    match a {
-        Some(y) if y.consume() > 0 => {}
-        _ => {}
-    }
-}
-```
-
-In this situation, even the `ref` keyword cannot solve it, since borrowed
-content cannot be moved. This problem cannot be solved generally. If the value
-can be cloned, here is a not-so-specific solution:
-
-```
-#[derive(Clone)]
-struct A{}
-
-impl A {
-    fn consume(self) -> usize {
-        0
-    }
-}
-
-fn main() {
-    let a = Some(A{});
-    match a{
-        Some(ref y) if y.clone().consume() > 0 => {}
-        _ => {}
-    }
-}
-```
-
-If the value will be consumed in the pattern guard, using its clone will not
-move its ownership, so the code works.
-"##,
-
 E0009: r##"
 In a pattern, all values that don't implement the `Copy` trait have to be bound
 the same way. The goal here is to avoid binding simultaneously by-move and
@@ -475,13 +400,15 @@ for item in xs {
 "##,
 
 E0301: r##"
+#### Note: this error code is no longer emitted by the compiler.
+
 Mutable borrows are not allowed in pattern guards, because matching cannot have
 side effects. Side effects could alter the matched object or the environment
 on which the match depends in such a way, that the match would not be
 exhaustive. For instance, the following would not match any arm if mutable
 borrows were allowed:
 
-```compile_fail,E0301
+```compile_fail,E0596
 match Some(()) {
     None => { },
     option if option.take().is_none() => {
@@ -493,13 +420,15 @@ match Some(()) {
 "##,
 
 E0302: r##"
+#### Note: this error code is no longer emitted by the compiler.
+
 Assignments are not allowed in pattern guards, because matching cannot have
 side effects. Side effects could alter the matched object or the environment
 on which the match depends in such a way, that the match would not be
 exhaustive. For instance, the following would not match any arm if assignments
 were allowed:
 
-```compile_fail,E0302
+```compile_fail,E0594
 match Some(()) {
     None => { },
     option if { option = None; false } => { },
@@ -748,7 +677,7 @@ It is not allowed to use or capture an uninitialized variable. For example:
 ```compile_fail,E0381
 fn main() {
     let x: i32;
-    let y = x; // error, use of possibly uninitialized variable
+    let y = x; // error, use of possibly-uninitialized variable
 }
 ```
 
@@ -1717,7 +1646,14 @@ fn print_fancy_ref(fancy_ref: &FancyNum){
 "##,
 
 E0507: r##"
-You tried to move out of a value which was borrowed. Erroneous code example:
+You tried to move out of a value which was borrowed.
+
+This can also happen when using a type implementing `Fn` or `FnMut`, as neither
+allows moving out of them (they usually represent closures which can be called
+more than once). Much of the text following applies equally well to non-`FnOnce`
+closure bodies.
+
+Erroneous code example:
 
 ```compile_fail,E0507
 use std::cell::RefCell;
@@ -1989,7 +1925,6 @@ When matching on a variable it cannot be mutated in the match guards, as this
 could cause the match to be non-exhaustive:
 
 ```compile_fail,E0510
-#![feature(bind_by_move_pattern_guards)]
 let mut x = Some(0);
 match x {
     None => (),
@@ -2448,9 +2383,10 @@ information.
 
 There are some known bugs that trigger this message.
 "##,
-}
 
-register_diagnostics! {
+;
+
+//  E0008, // cannot bind by-move into a pattern guard
 //  E0298, // cannot compare constants
 //  E0299, // mismatched types between arms
 //  E0471, // constant evaluation error (in pattern)
diff --git a/src/librustc_mir/hair/pattern/_match.rs b/src/librustc_mir/hair/pattern/_match.rs
index 222750e602df9..a6d955f336910 100644
--- a/src/librustc_mir/hair/pattern/_match.rs
+++ b/src/librustc_mir/hair/pattern/_match.rs
@@ -517,9 +517,9 @@ struct PatternContext<'tcx> {
 pub struct Witness<'tcx>(Vec<Pattern<'tcx>>);
 
 impl<'tcx> Witness<'tcx> {
-    pub fn single_pattern(&self) -> &Pattern<'tcx> {
+    pub fn single_pattern(self) -> Pattern<'tcx> {
         assert_eq!(self.0.len(), 1);
-        &self.0[0]
+        self.0.into_iter().next().unwrap()
     }
 
     fn push_wild_constructor<'a>(
diff --git a/src/librustc_mir/hair/pattern/check_match.rs b/src/librustc_mir/hair/pattern/check_match.rs
index 5352888006c30..161c58a175579 100644
--- a/src/librustc_mir/hair/pattern/check_match.rs
+++ b/src/librustc_mir/hair/pattern/check_match.rs
@@ -5,11 +5,6 @@ use super::_match::WitnessPreference::*;
 use super::{Pattern, PatternContext, PatternError, PatternKind};
 
 use rustc::middle::borrowck::SignalledError;
-use rustc::middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor};
-use rustc::middle::expr_use_visitor::{LoanCause, MutateMode};
-use rustc::middle::expr_use_visitor as euv;
-use rustc::middle::mem_categorization::cmt_;
-use rustc::middle::region;
 use rustc::session::Session;
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::subst::{InternalSubsts, SubstsRef};
@@ -36,9 +31,7 @@ crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) -> SignalledError {
 
     let mut visitor = MatchVisitor {
         tcx,
-        body_owner: def_id,
         tables: tcx.body_tables(body_id),
-        region_scope_tree: &tcx.region_scope_tree(def_id),
         param_env: tcx.param_env(def_id),
         identity_substs: InternalSubsts::identity_for_item(tcx, def_id),
         signalled_error: SignalledError::NoErrorsSeen,
@@ -53,15 +46,13 @@ fn create_e0004(sess: &Session, sp: Span, error_message: String) -> DiagnosticBu
 
 struct MatchVisitor<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    body_owner: DefId,
     tables: &'a ty::TypeckTables<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     identity_substs: SubstsRef<'tcx>,
-    region_scope_tree: &'a region::ScopeTree,
     signalled_error: SignalledError,
 }
 
-impl<'a, 'tcx> Visitor<'tcx> for MatchVisitor<'a, 'tcx> {
+impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, 'tcx> {
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
         NestedVisitorMap::None
     }
@@ -98,8 +89,7 @@ impl<'a, 'tcx> Visitor<'tcx> for MatchVisitor<'a, 'tcx> {
     }
 }
 
-
-impl<'a, 'tcx> PatternContext<'a, 'tcx> {
+impl PatternContext<'_, '_> {
     fn report_inlining_errors(&self, pat_span: Span) {
         for error in &self.errors {
             match *error {
@@ -131,7 +121,7 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
+impl<'tcx> MatchVisitor<'_, 'tcx> {
     fn check_patterns(&mut self, has_guard: bool, pats: &[P<Pat>]) {
         check_legality_of_move_bindings(self, has_guard, pats);
         for pat in pats {
@@ -151,11 +141,8 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
 
             // Second, if there is a guard on each arm, make sure it isn't
             // assigning or borrowing anything mutably.
-            if let Some(ref guard) = arm.guard {
+            if arm.guard.is_some() {
                 self.signalled_error = SignalledError::SawSomeError;
-                if !self.tcx.features().bind_by_move_pattern_guards {
-                    check_for_mutation_in_guard(self, &guard);
-                }
             }
 
             // Third, perform some lints.
@@ -277,37 +264,26 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
                 expand_pattern(cx, pattern)
             ]].into_iter().collect();
 
-            let wild_pattern = Pattern {
-                ty: pattern_ty,
-                span: DUMMY_SP,
-                kind: box PatternKind::Wild,
-            };
-            let witness = match is_useful(cx, &pats, &[&wild_pattern], ConstructWitness) {
-                UsefulWithWitness(witness) => witness,
-                NotUseful => return,
-                Useful => bug!()
+            let witnesses = match check_not_useful(cx, pattern_ty, &pats) {
+                Ok(_) => return,
+                Err(err) => err,
             };
 
-            let pattern_string = witness[0].single_pattern().to_string();
+            let joined_patterns = joined_uncovered_patterns(&witnesses);
             let mut err = struct_span_err!(
                 self.tcx.sess, pat.span, E0005,
-                "refutable pattern in {}: `{}` not covered",
-                origin, pattern_string
+                "refutable pattern in {}: {} not covered",
+                origin, joined_patterns
             );
-            let label_msg = match pat.node {
-                PatKind::Path(hir::QPath::Resolved(None, ref path))
-                        if path.segments.len() == 1 && path.segments[0].args.is_none() => {
+            err.span_label(pat.span, match &pat.node {
+                PatKind::Path(hir::QPath::Resolved(None, path))
+                    if path.segments.len() == 1 && path.segments[0].args.is_none() => {
                     format!("interpreted as {} {} pattern, not new variable",
                             path.res.article(), path.res.descr())
                 }
-                _ => format!("pattern `{}` not covered", pattern_string),
-            };
-            err.span_label(pat.span, label_msg);
-            if let ty::Adt(def, _) = pattern_ty.sty {
-                if let Some(sp) = self.tcx.hir().span_if_local(def.did){
-                    err.span_label(sp, format!("`{}` defined here", pattern_ty));
-                }
-            }
+                _ => pattern_not_convered_label(&witnesses, &joined_patterns),
+            });
+            adt_defined_here(cx, &mut err, pattern_ty, &witnesses);
             err.emit();
         });
     }
@@ -362,9 +338,9 @@ fn pat_is_catchall(pat: &Pat) -> bool {
 }
 
 // Check for unreachable patterns
-fn check_arms<'a, 'tcx>(
-    cx: &mut MatchCheckCtxt<'a, 'tcx>,
-    arms: &[(Vec<(&'a Pattern<'tcx>, &hir::Pat)>, Option<&hir::Expr>)],
+fn check_arms<'tcx>(
+    cx: &mut MatchCheckCtxt<'_, 'tcx>,
+    arms: &[(Vec<(&Pattern<'tcx>, &hir::Pat)>, Option<&hir::Expr>)],
     source: hir::MatchSource,
 ) {
     let mut seen = Matrix::empty();
@@ -445,104 +421,124 @@ fn check_arms<'a, 'tcx>(
     }
 }
 
-fn check_exhaustive<'p, 'a, 'tcx>(
-    cx: &mut MatchCheckCtxt<'a, 'tcx>,
+fn check_not_useful(
+    cx: &mut MatchCheckCtxt<'_, 'tcx>,
+    ty: Ty<'tcx>,
+    matrix: &Matrix<'_, 'tcx>,
+) -> Result<(), Vec<Pattern<'tcx>>> {
+    let wild_pattern = Pattern { ty, span: DUMMY_SP, kind: box PatternKind::Wild };
+    match is_useful(cx, matrix, &[&wild_pattern], ConstructWitness) {
+        NotUseful => Ok(()), // This is good, wildcard pattern isn't reachable.
+        UsefulWithWitness(pats) => Err(if pats.is_empty() {
+            vec![wild_pattern]
+        } else {
+            pats.into_iter().map(|w| w.single_pattern()).collect()
+        }),
+        Useful => bug!(),
+    }
+}
+
+fn check_exhaustive<'tcx>(
+    cx: &mut MatchCheckCtxt<'_, 'tcx>,
     scrut_ty: Ty<'tcx>,
     sp: Span,
-    matrix: &Matrix<'p, 'tcx>,
+    matrix: &Matrix<'_, 'tcx>,
 ) {
-    let wild_pattern = Pattern {
-        ty: scrut_ty,
-        span: DUMMY_SP,
-        kind: box PatternKind::Wild,
+    let witnesses = match check_not_useful(cx, scrut_ty, matrix) {
+        Ok(_) => return,
+        Err(err) => err,
     };
-    match is_useful(cx, matrix, &[&wild_pattern], ConstructWitness) {
-        UsefulWithWitness(pats) => {
-            let witnesses = if pats.is_empty() {
-                vec![&wild_pattern]
-            } else {
-                pats.iter().map(|w| w.single_pattern()).collect()
-            };
 
-            const LIMIT: usize = 3;
-            let joined_patterns = match witnesses.len() {
-                0 => bug!(),
-                1 => format!("`{}`", witnesses[0]),
-                2..=LIMIT => {
-                    let (tail, head) = witnesses.split_last().unwrap();
-                    let head: Vec<_> = head.iter().map(|w| w.to_string()).collect();
-                    format!("`{}` and `{}`", head.join("`, `"), tail)
-                }
-                _ => {
-                    let (head, tail) = witnesses.split_at(LIMIT);
-                    let head: Vec<_> = head.iter().map(|w| w.to_string()).collect();
-                    format!("`{}` and {} more", head.join("`, `"), tail.len())
-                }
-            };
+    let joined_patterns = joined_uncovered_patterns(&witnesses);
+    let mut err = create_e0004(
+        cx.tcx.sess, sp,
+        format!("non-exhaustive patterns: {} not covered", joined_patterns),
+    );
+    err.span_label(sp, pattern_not_convered_label(&witnesses, &joined_patterns));
+    adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
+    err.help(
+        "ensure that all possible cases are being handled, \
+        possibly by adding wildcards or more match arms"
+    )
+    .emit();
+}
 
-            let label_text = match witnesses.len() {
-                1 => format!("pattern {} not covered", joined_patterns),
-                _ => format!("patterns {} not covered", joined_patterns),
-            };
-            let mut err = create_e0004(cx.tcx.sess, sp, format!(
-                "non-exhaustive patterns: {} not covered",
-                joined_patterns,
-            ));
-            err.span_label(sp, label_text);
-            // point at the definition of non-covered enum variants
-            if let ty::Adt(def, _) = scrut_ty.sty {
-                if let Some(sp) = cx.tcx.hir().span_if_local(def.did){
-                    err.span_label(sp, format!("`{}` defined here", scrut_ty));
-                }
-            }
-            let patterns = witnesses.iter().map(|p| (**p).clone()).collect::<Vec<Pattern<'_>>>();
-            if patterns.len() < 4 {
-                for sp in maybe_point_at_variant(cx, scrut_ty, patterns.as_slice()) {
-                    err.span_label(sp, "not covered");
-                }
-            }
-            err.help("ensure that all possible cases are being handled, \
-                      possibly by adding wildcards or more match arms");
-            err.emit();
+fn joined_uncovered_patterns(witnesses: &[Pattern<'_>]) -> String {
+    const LIMIT: usize = 3;
+    match witnesses {
+        [] => bug!(),
+        [witness] => format!("`{}`", witness),
+        [head @ .., tail] if head.len() < LIMIT => {
+            let head: Vec<_> = head.iter().map(<_>::to_string).collect();
+            format!("`{}` and `{}`", head.join("`, `"), tail)
         }
-        NotUseful => {
-            // This is good, wildcard pattern isn't reachable
+        _ => {
+            let (head, tail) = witnesses.split_at(LIMIT);
+            let head: Vec<_> = head.iter().map(<_>::to_string).collect();
+            format!("`{}` and {} more", head.join("`, `"), tail.len())
         }
-        _ => bug!()
     }
 }
 
-fn maybe_point_at_variant(
-    cx: &mut MatchCheckCtxt<'a, 'tcx>,
-    ty: Ty<'tcx>,
-    patterns: &[Pattern<'_>],
-) -> Vec<Span> {
+fn pattern_not_convered_label(witnesses: &[Pattern<'_>], joined_patterns: &str) -> String {
+    format!("pattern{} {} not covered", rustc_errors::pluralise!(witnesses.len()), joined_patterns)
+}
+
+/// Point at the definition of non-covered `enum` variants.
+fn adt_defined_here(
+    cx: &MatchCheckCtxt<'_, '_>,
+    err: &mut DiagnosticBuilder<'_>,
+    ty: Ty<'_>,
+    witnesses: &[Pattern<'_>],
+) {
+    let ty = ty.peel_refs();
+    if let ty::Adt(def, _) = ty.sty {
+        if let Some(sp) = cx.tcx.hir().span_if_local(def.did) {
+            err.span_label(sp, format!("`{}` defined here", ty));
+        }
+
+        if witnesses.len() < 4 {
+            for sp in maybe_point_at_variant(ty, &witnesses) {
+                err.span_label(sp, "not covered");
+            }
+        }
+    }
+}
+
+fn maybe_point_at_variant(ty: Ty<'_>, patterns: &[Pattern<'_>]) -> Vec<Span> {
     let mut covered = vec![];
     if let ty::Adt(def, _) = ty.sty {
         // Don't point at variants that have already been covered due to other patterns to avoid
-        // visual clutter
+        // visual clutter.
         for pattern in patterns {
-            let pk: &PatternKind<'_> = &pattern.kind;
-            if let PatternKind::Variant { adt_def, variant_index, subpatterns, .. } = pk {
-                if adt_def.did == def.did {
+            use PatternKind::{AscribeUserType, Deref, Variant, Or, Leaf};
+            match &*pattern.kind {
+                AscribeUserType { subpattern, .. } | Deref { subpattern } => {
+                    covered.extend(maybe_point_at_variant(ty, slice::from_ref(&subpattern)));
+                }
+                Variant { adt_def, variant_index, subpatterns, .. } if adt_def.did == def.did => {
                     let sp = def.variants[*variant_index].ident.span;
                     if covered.contains(&sp) {
                         continue;
                     }
                     covered.push(sp);
-                    let subpatterns = subpatterns.iter()
+
+                    let pats = subpatterns.iter()
                         .map(|field_pattern| field_pattern.pattern.clone())
-                        .collect::<Vec<_>>();
-                    covered.extend(
-                        maybe_point_at_variant(cx, ty, subpatterns.as_slice()),
-                    );
+                        .collect::<Box<[_]>>();
+                    covered.extend(maybe_point_at_variant(ty, &pats));
                 }
-            }
-            if let PatternKind::Leaf { subpatterns } = pk {
-                let subpatterns = subpatterns.iter()
-                    .map(|field_pattern| field_pattern.pattern.clone())
-                    .collect::<Vec<_>>();
-                covered.extend(maybe_point_at_variant(cx, ty, subpatterns.as_slice()));
+                Leaf { subpatterns } => {
+                    let pats = subpatterns.iter()
+                        .map(|field_pattern| field_pattern.pattern.clone())
+                        .collect::<Box<[_]>>();
+                    covered.extend(maybe_point_at_variant(ty, &pats));
+                }
+                Or { pats } => {
+                    let pats = pats.iter().cloned().collect::<Box<[_]>>();
+                    covered.extend(maybe_point_at_variant(ty, &pats));
+                }
+                _ => {}
             }
         }
     }
@@ -582,19 +578,10 @@ fn check_legality_of_move_bindings(
                              "cannot bind by-move with sub-bindings")
                 .span_label(p.span, "binds an already bound by-move value by moving it")
                 .emit();
-        } else if has_guard {
-            if !cx.tcx.features().bind_by_move_pattern_guards {
-                let mut err = struct_span_err!(cx.tcx.sess, p.span, E0008,
-                                            "cannot bind by-move into a pattern guard");
-                err.span_label(p.span, "moves value into pattern guard");
-                if cx.tcx.sess.opts.unstable_features.is_nightly_build() {
-                    err.help("add `#![feature(bind_by_move_pattern_guards)]` to the \
-                            crate attributes to enable");
-                }
-                err.emit();
+        } else if !has_guard {
+            if let Some(_by_ref_span) = by_ref_span {
+                span_vec.push(p.span);
             }
-        } else if let Some(_by_ref_span) = by_ref_span {
-            span_vec.push(p.span);
         }
     };
 
@@ -636,67 +623,6 @@ fn check_legality_of_move_bindings(
     }
 }
 
-/// Ensures that a pattern guard doesn't borrow by mutable reference or assign.
-//
-// FIXME: this should be done by borrowck.
-fn check_for_mutation_in_guard(cx: &MatchVisitor<'_, '_>, guard: &hir::Guard) {
-    let mut checker = MutationChecker {
-        cx,
-    };
-    match guard {
-        hir::Guard::If(expr) =>
-            ExprUseVisitor::new(&mut checker,
-                                cx.tcx,
-                                cx.body_owner,
-                                cx.param_env,
-                                cx.region_scope_tree,
-                                cx.tables,
-                                None).walk_expr(expr),
-    };
-}
-
-struct MutationChecker<'a, 'tcx> {
-    cx: &'a MatchVisitor<'a, 'tcx>,
-}
-
-impl<'a, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'tcx> {
-    fn matched_pat(&mut self, _: &Pat, _: &cmt_<'_>, _: euv::MatchMode) {}
-    fn consume(&mut self, _: hir::HirId, _: Span, _: &cmt_<'_>, _: ConsumeMode) {}
-    fn consume_pat(&mut self, _: &Pat, _: &cmt_<'_>, _: ConsumeMode) {}
-    fn borrow(&mut self,
-              _: hir::HirId,
-              span: Span,
-              _: &cmt_<'_>,
-              _: ty::Region<'tcx>,
-              kind:ty:: BorrowKind,
-              _: LoanCause) {
-        match kind {
-            ty::MutBorrow => {
-                let mut err = struct_span_err!(self.cx.tcx.sess, span, E0301,
-                          "cannot mutably borrow in a pattern guard");
-                err.span_label(span, "borrowed mutably in pattern guard");
-                if self.cx.tcx.sess.opts.unstable_features.is_nightly_build() {
-                    err.help("add `#![feature(bind_by_move_pattern_guards)]` to the \
-                              crate attributes to enable");
-                }
-                err.emit();
-            }
-            ty::ImmBorrow | ty::UniqueImmBorrow => {}
-        }
-    }
-    fn decl_without_init(&mut self, _: hir::HirId, _: Span) {}
-    fn mutate(&mut self, _: hir::HirId, span: Span, _: &cmt_<'_>, mode: MutateMode) {
-        match mode {
-            MutateMode::JustWrite | MutateMode::WriteAndRead => {
-                struct_span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard")
-                    .span_label(span, "assignment in pattern guard")
-                    .emit();
-            }
-            MutateMode::Init => {}
-        }
-    }
-}
-
 /// Forbids bindings in `@` patterns. This is necessary for memory safety,
 /// because of the way rvalues are handled in the borrow check. (See issue
 /// #14587.)
@@ -709,7 +635,7 @@ struct AtBindingPatternVisitor<'a, 'b, 'tcx> {
     bindings_allowed: bool
 }
 
-impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> {
+impl<'v> Visitor<'v> for AtBindingPatternVisitor<'_, '_, '_> {
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
         NestedVisitorMap::None
     }
diff --git a/src/librustc_mir/hair/pattern/mod.rs b/src/librustc_mir/hair/pattern/mod.rs
index 6caccfddfa422..4aaa5e8ee259a 100644
--- a/src/librustc_mir/hair/pattern/mod.rs
+++ b/src/librustc_mir/hair/pattern/mod.rs
@@ -1229,7 +1229,13 @@ fn search_for_adt_without_structural_match<'tcx>(tcx: TyCtxt<'tcx>,
                 ty::RawPtr(..) => {
                     // `#[structural_match]` ignores substructure of
                     // `*const _`/`*mut _`, so skip super_visit_with
-
+                    //
+                    // (But still tell caller to continue search.)
+                    return false;
+                }
+                ty::FnDef(..) | ty::FnPtr(..) => {
+                    // types of formals and return in `fn(_) -> _` are also irrelevant
+                    //
                     // (But still tell caller to continue search.)
                     return false;
                 }
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index 054b65f0e1a9e..78996ed6939d8 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -14,7 +14,6 @@ use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc::ty::query::TyCtxtAt;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc::mir::interpret::{
-    ErrorHandled,
     GlobalId, Scalar, Pointer, FrameInfo, AllocId,
     InterpResult, truncate, sign_extend,
 };
@@ -672,14 +671,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Our result will later be validated anyway, and there seems no good reason
         // to have to fail early here.  This is also more consistent with
         // `Memory::get_static_alloc` which has to use `const_eval_raw` to avoid cycles.
-        let val = self.tcx.const_eval_raw(param_env.and(gid)).map_err(|err| {
-            match err {
-                ErrorHandled::Reported =>
-                    err_inval!(ReferencedConstant),
-                ErrorHandled::TooGeneric =>
-                    err_inval!(TooGeneric),
-            }
-        })?;
+        let val = self.tcx.const_eval_raw(param_env.and(gid))?;
         self.raw_const_to_mplace(val)
     }
 
diff --git a/src/librustc_mir/interpret/intern.rs b/src/librustc_mir/interpret/intern.rs
index 4cbbc0ffe17cc..95647ce642c5b 100644
--- a/src/librustc_mir/interpret/intern.rs
+++ b/src/librustc_mir/interpret/intern.rs
@@ -3,7 +3,7 @@
 //! After a const evaluation has computed a value, before we destroy the const evaluator's session
 //! memory, we need to extract all memory allocations to the global memory pool so they stay around.
 
-use rustc::ty::{Ty, TyCtxt, ParamEnv, self};
+use rustc::ty::{Ty, self};
 use rustc::mir::interpret::{InterpResult, ErrorHandled};
 use rustc::hir;
 use rustc::hir::def_id::DefId;
@@ -11,32 +11,29 @@ use super::validity::RefTracking;
 use rustc_data_structures::fx::FxHashSet;
 
 use syntax::ast::Mutability;
-use syntax_pos::Span;
 
 use super::{
-    ValueVisitor, MemoryKind, Pointer, AllocId, MPlaceTy, Scalar,
+    ValueVisitor, MemoryKind, AllocId, MPlaceTy, Scalar,
 };
 use crate::const_eval::{CompileTimeInterpreter, CompileTimeEvalContext};
 
 struct InternVisitor<'rt, 'mir, 'tcx> {
-    /// previously encountered safe references
-    ref_tracking: &'rt mut RefTracking<(MPlaceTy<'tcx>, Mutability, InternMode)>,
+    /// The ectx from which we intern.
     ecx: &'rt mut CompileTimeEvalContext<'mir, 'tcx>,
-    param_env: ParamEnv<'tcx>,
+    /// Previously encountered safe references.
+    ref_tracking: &'rt mut RefTracking<(MPlaceTy<'tcx>, Mutability, InternMode)>,
+    /// A list of all encountered allocations. After type-based interning, we traverse this list to
+    /// also intern allocations that are only referenced by a raw pointer or inside a union.
+    leftover_allocations: &'rt mut FxHashSet<AllocId>,
     /// The root node of the value that we're looking at. This field is never mutated and only used
     /// for sanity assertions that will ICE when `const_qualif` screws up.
     mode: InternMode,
     /// This field stores the mutability of the value *currently* being checked.
-    /// It is set to mutable when an `UnsafeCell` is encountered
-    /// When recursing across a reference, we don't recurse but store the
-    /// value to be checked in `ref_tracking` together with the mutability at which we are checking
-    /// the value.
-    /// When encountering an immutable reference, we treat everything as immutable that is behind
-    /// it.
+    /// When encountering a mutable reference, we determine the pointee mutability
+    /// taking into account the mutability of the context: `& &mut i32` is entirely immutable,
+    /// despite the nested mutable reference!
+    /// The field gets updated when an `UnsafeCell` is encountered.
     mutability: Mutability,
-    /// A list of all encountered relocations. After type-based interning, we traverse this list to
-    /// also intern allocations that are only referenced by a raw pointer or inside a union.
-    leftover_relocations: &'rt mut FxHashSet<AllocId>,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Hash, Eq)]
@@ -45,9 +42,10 @@ enum InternMode {
     /// `static`. In a `static mut` we start out as mutable and thus can also contain further `&mut`
     /// that will actually be treated as mutable.
     Static,
-    /// UnsafeCell is OK in the value of a constant, but not behind references in a constant
+    /// UnsafeCell is OK in the value of a constant: `const FOO = Cell::new(0)` creates
+    /// a new cell every time it is used.
     ConstBase,
-    /// `UnsafeCell` ICEs
+    /// `UnsafeCell` ICEs.
     Const,
 }
 
@@ -55,48 +53,100 @@ enum InternMode {
 /// into the memory of other constants or statics
 struct IsStaticOrFn;
 
+/// Intern an allocation without looking at its children.
+/// `mode` is the mode of the environment where we found this pointer.
+/// `mutablity` is the mutability of the place to be interned; even if that says
+/// `immutable` things might become mutable if `ty` is not frozen.
+/// `ty` can be `None` if there is no potential interior mutability
+/// to account for (e.g. for vtables).
+fn intern_shallow<'rt, 'mir, 'tcx>(
+    ecx: &'rt mut CompileTimeEvalContext<'mir, 'tcx>,
+    leftover_allocations: &'rt mut FxHashSet<AllocId>,
+    mode: InternMode,
+    alloc_id: AllocId,
+    mutability: Mutability,
+    ty: Option<Ty<'tcx>>,
+) -> InterpResult<'tcx, Option<IsStaticOrFn>> {
+    trace!(
+        "InternVisitor::intern {:?} with {:?}",
+        alloc_id, mutability,
+    );
+    // remove allocation
+    let tcx = ecx.tcx;
+    let memory = ecx.memory_mut();
+    let (kind, mut alloc) = match memory.alloc_map.remove(&alloc_id) {
+        Some(entry) => entry,
+        None => {
+            // Pointer not found in local memory map. It is either a pointer to the global
+            // map, or dangling.
+            // If the pointer is dangling (neither in local nor global memory), we leave it
+            // to validation to error. The `delay_span_bug` ensures that we don't forget such
+            // a check in validation.
+            if tcx.alloc_map.lock().get(alloc_id).is_none() {
+                tcx.sess.delay_span_bug(ecx.tcx.span, "tried to intern dangling pointer");
+            }
+            // treat dangling pointers like other statics
+            // just to stop trying to recurse into them
+            return Ok(Some(IsStaticOrFn));
+        },
+    };
+    // This match is just a canary for future changes to `MemoryKind`, which most likely need
+    // changes in this function.
+    match kind {
+        MemoryKind::Stack | MemoryKind::Vtable => {},
+    }
+    // Set allocation mutability as appropriate. This is used by LLVM to put things into
+    // read-only memory, and also by Miri when evluating other constants/statics that
+    // access this one.
+    if mode == InternMode::Static {
+        // When `ty` is `None`, we assume no interior mutability.
+        let frozen = ty.map_or(true, |ty| ty.is_freeze(
+            ecx.tcx.tcx,
+            ecx.param_env,
+            ecx.tcx.span,
+        ));
+        // For statics, allocation mutability is the combination of the place mutability and
+        // the type mutability.
+        // The entire allocation needs to be mutable if it contains an `UnsafeCell` anywhere.
+        if mutability == Mutability::Immutable && frozen {
+            alloc.mutability = Mutability::Immutable;
+        } else {
+            // Just making sure we are not "upgrading" an immutable allocation to mutable.
+            assert_eq!(alloc.mutability, Mutability::Mutable);
+        }
+    } else {
+        // We *could* be non-frozen at `ConstBase`, for constants like `Cell::new(0)`.
+        // But we still intern that as immutable as the memory cannot be changed once the
+        // initial value was computed.
+        // Constants are never mutable.
+        assert_eq!(
+            mutability, Mutability::Immutable,
+            "Something went very wrong: mutability requested for a constant"
+        );
+        alloc.mutability = Mutability::Immutable;
+    };
+    // link the alloc id to the actual allocation
+    let alloc = tcx.intern_const_alloc(alloc);
+    leftover_allocations.extend(alloc.relocations().iter().map(|&(_, ((), reloc))| reloc));
+    tcx.alloc_map.lock().set_alloc_id_memory(alloc_id, alloc);
+    Ok(None)
+}
+
 impl<'rt, 'mir, 'tcx> InternVisitor<'rt, 'mir, 'tcx> {
-    /// Intern an allocation without looking at its children
     fn intern_shallow(
         &mut self,
-        ptr: Pointer,
+        alloc_id: AllocId,
         mutability: Mutability,
+        ty: Option<Ty<'tcx>>,
     ) -> InterpResult<'tcx, Option<IsStaticOrFn>> {
-        trace!(
-            "InternVisitor::intern {:?} with {:?}",
-            ptr, mutability,
-        );
-        // remove allocation
-        let tcx = self.ecx.tcx;
-        let memory = self.ecx.memory_mut();
-        let (kind, mut alloc) = match memory.alloc_map.remove(&ptr.alloc_id) {
-            Some(entry) => entry,
-            None => {
-                // if the pointer is dangling (neither in local nor global memory), we leave it
-                // to validation to error. The `delay_span_bug` ensures that we don't forget such
-                // a check in validation.
-                if tcx.alloc_map.lock().get(ptr.alloc_id).is_none() {
-                    tcx.sess.delay_span_bug(self.ecx.tcx.span, "tried to intern dangling pointer");
-                }
-                // treat dangling pointers like other statics
-                // just to stop trying to recurse into them
-                return Ok(Some(IsStaticOrFn));
-            },
-        };
-        // This match is just a canary for future changes to `MemoryKind`, which most likely need
-        // changes in this function.
-        match kind {
-            MemoryKind::Stack | MemoryKind::Vtable => {},
-        }
-        // Ensure llvm knows to only put this into immutable memory if the value is immutable either
-        // by being behind a reference or by being part of a static or const without interior
-        // mutability
-        alloc.mutability = mutability;
-        // link the alloc id to the actual allocation
-        let alloc = tcx.intern_const_alloc(alloc);
-        self.leftover_relocations.extend(alloc.relocations().iter().map(|&(_, ((), reloc))| reloc));
-        tcx.alloc_map.lock().set_alloc_id_memory(ptr.alloc_id, alloc);
-        Ok(None)
+        intern_shallow(
+            self.ecx,
+            self.leftover_allocations,
+            self.mode,
+            alloc_id,
+            mutability,
+            ty,
+        )
     }
 }
 
@@ -119,14 +169,16 @@ for
     ) -> InterpResult<'tcx> {
         if let Some(def) = mplace.layout.ty.ty_adt_def() {
             if Some(def.did) == self.ecx.tcx.lang_items().unsafe_cell_type() {
-                // We are crossing over an `UnsafeCell`, we can mutate again
+                // We are crossing over an `UnsafeCell`, we can mutate again. This means that
+                // References we encounter inside here are interned as pointing to mutable
+                // allocations.
                 let old = std::mem::replace(&mut self.mutability, Mutability::Mutable);
                 assert_ne!(
                     self.mode, InternMode::Const,
                     "UnsafeCells are not allowed behind references in constants. This should have \
                     been prevented statically by const qualification. If this were allowed one \
-                    would be able to change a constant at one use site and other use sites may \
-                    arbitrarily decide to change, too.",
+                    would be able to change a constant at one use site and other use sites could \
+                    observe that mutation.",
                 );
                 let walked = self.walk_aggregate(mplace, fields);
                 self.mutability = old;
@@ -145,12 +197,13 @@ for
             // Handle trait object vtables
             if let Ok(meta) = value.to_meta() {
                 if let ty::Dynamic(..) =
-                    self.ecx.tcx.struct_tail_erasing_lifetimes(referenced_ty, self.param_env).sty
+                    self.ecx.tcx.struct_tail_erasing_lifetimes(
+                        referenced_ty, self.ecx.param_env).sty
                 {
                     if let Ok(vtable) = meta.unwrap().to_ptr() {
                         // explitly choose `Immutable` here, since vtables are immutable, even
                         // if the reference of the fat pointer is mutable
-                        self.intern_shallow(vtable, Mutability::Immutable)?;
+                        self.intern_shallow(vtable.alloc_id, Mutability::Immutable, None)?;
                     }
                 }
             }
@@ -177,7 +230,7 @@ for
                     (InternMode::Const, hir::Mutability::MutMutable) => {
                         match referenced_ty.sty {
                             ty::Array(_, n)
-                                if n.eval_usize(self.ecx.tcx.tcx, self.param_env) == 0 => {}
+                                if n.eval_usize(self.ecx.tcx.tcx, self.ecx.param_env) == 0 => {}
                             ty::Slice(_)
                                 if value.to_meta().unwrap().unwrap().to_usize(self.ecx)? == 0 => {}
                             _ => bug!("const qualif failed to prevent mutable references"),
@@ -195,21 +248,13 @@ for
                     (Mutability::Mutable, hir::Mutability::MutMutable) => Mutability::Mutable,
                     _ => Mutability::Immutable,
                 };
-                // Compute the mutability of the allocation
-                let intern_mutability = intern_mutability(
-                    self.ecx.tcx.tcx,
-                    self.param_env,
-                    mplace.layout.ty,
-                    self.ecx.tcx.span,
-                    mutability,
-                );
                 // Recursing behind references changes the intern mode for constants in order to
                 // cause assertions to trigger if we encounter any `UnsafeCell`s.
                 let mode = match self.mode {
                     InternMode::ConstBase => InternMode::Const,
                     other => other,
                 };
-                match self.intern_shallow(ptr, intern_mutability)? {
+                match self.intern_shallow(ptr.alloc_id, mutability, Some(mplace.layout.ty))? {
                     // No need to recurse, these are interned already and statics may have
                     // cycles, so we don't want to recurse there
                     Some(IsStaticOrFn) => {},
@@ -224,69 +269,45 @@ for
     }
 }
 
-/// Figure out the mutability of the allocation.
-/// Mutable if it has interior mutability *anywhere* in the type.
-fn intern_mutability<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    param_env: ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
-    span: Span,
-    mutability: Mutability,
-) -> Mutability {
-    let has_interior_mutability = !ty.is_freeze(tcx, param_env, span);
-    if has_interior_mutability {
-        Mutability::Mutable
-    } else {
-        mutability
-    }
-}
-
 pub fn intern_const_alloc_recursive(
     ecx: &mut CompileTimeEvalContext<'mir, 'tcx>,
     def_id: DefId,
     ret: MPlaceTy<'tcx>,
-    // FIXME(oli-obk): can we scrap the param env? I think we can, the final value of a const eval
-    // must always be monomorphic, right?
-    param_env: ty::ParamEnv<'tcx>,
 ) -> InterpResult<'tcx> {
     let tcx = ecx.tcx;
     // this `mutability` is the mutability of the place, ignoring the type
-    let (mutability, base_intern_mode) = match tcx.static_mutability(def_id) {
+    let (base_mutability, base_intern_mode) = match tcx.static_mutability(def_id) {
         Some(hir::Mutability::MutImmutable) => (Mutability::Immutable, InternMode::Static),
-        None => (Mutability::Immutable, InternMode::ConstBase),
         // `static mut` doesn't care about interior mutability, it's mutable anyway
         Some(hir::Mutability::MutMutable) => (Mutability::Mutable, InternMode::Static),
+        // consts, promoteds. FIXME: what about array lengths, array initializers?
+        None => (Mutability::Immutable, InternMode::ConstBase),
     };
 
-    // type based interning
-    let mut ref_tracking = RefTracking::new((ret, mutability, base_intern_mode));
-    let leftover_relocations = &mut FxHashSet::default();
-
-    // This mutability is the combination of the place mutability and the type mutability. If either
-    // is mutable, `alloc_mutability` is mutable. This exists because the entire allocation needs
-    // to be mutable if it contains an `UnsafeCell` anywhere. The other `mutability` exists so that
-    // the visitor does not treat everything outside the `UnsafeCell` as mutable.
-    let alloc_mutability = intern_mutability(
-        tcx.tcx, param_env, ret.layout.ty, tcx.span, mutability,
-    );
+    // Type based interning.
+    // `ref_tracking` tracks typed references we have seen and still need to crawl for
+    // more typed information inside them.
+    // `leftover_allocations` collects *all* allocations we see, because some might not
+    // be available in a typed way. They get interned at the end.
+    let mut ref_tracking = RefTracking::new((ret, base_mutability, base_intern_mode));
+    let leftover_allocations = &mut FxHashSet::default();
 
     // start with the outermost allocation
-    InternVisitor {
-        ref_tracking: &mut ref_tracking,
+    intern_shallow(
         ecx,
-        mode: base_intern_mode,
-        leftover_relocations,
-        param_env,
-        mutability,
-    }.intern_shallow(ret.ptr.to_ptr()?, alloc_mutability)?;
+        leftover_allocations,
+        base_intern_mode,
+        ret.ptr.to_ptr()?.alloc_id,
+        base_mutability,
+        Some(ret.layout.ty)
+    )?;
 
     while let Some(((mplace, mutability, mode), _)) = ref_tracking.todo.pop() {
         let interned = InternVisitor {
             ref_tracking: &mut ref_tracking,
             ecx,
             mode,
-            leftover_relocations,
-            param_env,
+            leftover_allocations,
             mutability,
         }.visit_value(mplace);
         if let Err(error) = interned {
@@ -309,15 +330,23 @@ pub fn intern_const_alloc_recursive(
     // Intern the rest of the allocations as mutable. These might be inside unions, padding, raw
     // pointers, ... So we can't intern them according to their type rules
 
-    let mut todo: Vec<_> = leftover_relocations.iter().cloned().collect();
+    let mut todo: Vec<_> = leftover_allocations.iter().cloned().collect();
     while let Some(alloc_id) = todo.pop() {
-        if let Some((_, alloc)) = ecx.memory_mut().alloc_map.remove(&alloc_id) {
-            // We can't call the `intern` method here, as its logic is tailored to safe references.
-            // So we hand-roll the interning logic here again
+        if let Some((_, mut alloc)) = ecx.memory_mut().alloc_map.remove(&alloc_id) {
+            // We can't call the `intern_shallow` method here, as its logic is tailored to safe
+            // references and a `leftover_allocations` set (where we only have a todo-list here).
+            // So we hand-roll the interning logic here again.
+            if base_intern_mode != InternMode::Static {
+                // If it's not a static, it *must* be immutable.
+                // We cannot have mutable memory inside a constant.
+                // FIXME: ideally we would assert that they already are immutable, to double-
+                // check our static checks.
+                alloc.mutability = Mutability::Immutable;
+            }
             let alloc = tcx.intern_const_alloc(alloc);
             tcx.alloc_map.lock().set_alloc_id_memory(alloc_id, alloc);
             for &(_, ((), reloc)) in alloc.relocations().iter() {
-                if leftover_relocations.insert(reloc) {
+                if leftover_allocations.insert(reloc) {
                     todo.push(reloc);
                 }
             }
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 0f2305e03ff33..ec09e69ec8537 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -5,17 +5,18 @@
 use syntax::symbol::Symbol;
 use rustc::ty;
 use rustc::ty::layout::{LayoutOf, Primitive, Size};
+use rustc::ty::subst::SubstsRef;
+use rustc::hir::def_id::DefId;
+use rustc::ty::TyCtxt;
 use rustc::mir::BinOp;
-use rustc::mir::interpret::{InterpResult, Scalar};
+use rustc::mir::interpret::{InterpResult, Scalar, GlobalId, ConstValue};
 
 use super::{
-    Machine, PlaceTy, OpTy, InterpCx, Immediate,
+    Machine, PlaceTy, OpTy, InterpCx,
 };
 
 mod type_name;
 
-pub use type_name::*;
-
 fn numeric_intrinsic<'tcx, Tag>(
     name: &str,
     bits: u128,
@@ -37,6 +38,50 @@ fn numeric_intrinsic<'tcx, Tag>(
     Ok(Scalar::from_uint(bits_out, size))
 }
 
+/// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated
+/// inside an `InterpCx` and instead have their value computed directly from rustc internal info.
+crate fn eval_nullary_intrinsic<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    def_id: DefId,
+    substs: SubstsRef<'tcx>,
+) -> InterpResult<'tcx, &'tcx ty::Const<'tcx>> {
+    let tp_ty = substs.type_at(0);
+    let name = &*tcx.item_name(def_id).as_str();
+    Ok(match name {
+        "type_name" => {
+            let alloc = type_name::alloc_type_name(tcx, tp_ty);
+            tcx.mk_const(ty::Const {
+                val: ConstValue::Slice {
+                    data: alloc,
+                    start: 0,
+                    end: alloc.len(),
+                },
+                ty: tcx.mk_static_str(),
+            })
+        },
+        "needs_drop" => ty::Const::from_bool(tcx, tp_ty.needs_drop(tcx, param_env)),
+        "size_of" |
+        "min_align_of" |
+        "pref_align_of" => {
+            let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?;
+            let n = match name {
+                "pref_align_of" => layout.align.pref.bytes(),
+                "min_align_of" => layout.align.abi.bytes(),
+                "size_of" => layout.size.bytes(),
+                _ => bug!(),
+            };
+            ty::Const::from_usize(tcx, n)
+        },
+        "type_id" => ty::Const::from_bits(
+            tcx,
+            tcx.type_id_hash(tp_ty).into(),
+            param_env.and(tcx.types.u64),
+        ),
+        other => bug!("`{}` is not a zero arg intrinsic", other),
+    })
+}
+
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// Returns `true` if emulation happened.
     pub fn emulate_intrinsic(
@@ -49,41 +94,19 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         let intrinsic_name = &self.tcx.item_name(instance.def_id()).as_str()[..];
         match intrinsic_name {
-            "min_align_of" => {
-                let elem_ty = substs.type_at(0);
-                let elem_align = self.layout_of(elem_ty)?.align.abi.bytes();
-                let align_val = Scalar::from_uint(elem_align, dest.layout.size);
-                self.write_scalar(align_val, dest)?;
-            }
-
-            "needs_drop" => {
-                let ty = substs.type_at(0);
-                let ty_needs_drop = ty.needs_drop(self.tcx.tcx, self.param_env);
-                let val = Scalar::from_bool(ty_needs_drop);
-                self.write_scalar(val, dest)?;
-            }
-
-            "size_of" => {
-                let ty = substs.type_at(0);
-                let size = self.layout_of(ty)?.size.bytes() as u128;
-                let size_val = Scalar::from_uint(size, dest.layout.size);
-                self.write_scalar(size_val, dest)?;
-            }
-
-            "type_id" => {
-                let ty = substs.type_at(0);
-                let type_id = self.tcx.type_id_hash(ty) as u128;
-                let id_val = Scalar::from_uint(type_id, dest.layout.size);
-                self.write_scalar(id_val, dest)?;
-            }
-
+            "min_align_of" |
+            "pref_align_of" |
+            "needs_drop" |
+            "size_of" |
+            "type_id" |
             "type_name" => {
-                let alloc = alloc_type_name(self.tcx.tcx, substs.type_at(0));
-                let name_id = self.tcx.alloc_map.lock().create_memory_alloc(alloc);
-                let id_ptr = self.memory.tag_static_base_pointer(name_id.into());
-                let alloc_len = alloc.size.bytes();
-                let name_val = Immediate::new_slice(Scalar::Ptr(id_ptr), alloc_len, self);
-                self.write_immediate(name_val, dest)?;
+                let gid = GlobalId {
+                    instance,
+                    promoted: None,
+                };
+                let val = self.tcx.const_eval(self.param_env.and(gid))?;
+                let val = self.eval_const_to_op(val, None)?;
+                self.copy_op(val, dest)?;
             }
 
             | "ctpop"
diff --git a/src/librustc_mir/interpret/intrinsics/type_name.rs b/src/librustc_mir/interpret/intrinsics/type_name.rs
index 032d16a49db4b..1e765a4ed982c 100644
--- a/src/librustc_mir/interpret/intrinsics/type_name.rs
+++ b/src/librustc_mir/interpret/intrinsics/type_name.rs
@@ -7,7 +7,7 @@ use rustc::ty::{
 use rustc::hir::map::{DefPathData, DisambiguatedDefPathData};
 use rustc::hir::def_id::CrateNum;
 use std::fmt::Write;
-use rustc::mir::interpret::{Allocation, ConstValue};
+use rustc::mir::interpret::Allocation;
 
 struct AbsolutePathPrinter<'tcx> {
     tcx: TyCtxt<'tcx>,
@@ -213,22 +213,11 @@ impl Write for AbsolutePathPrinter<'_> {
     }
 }
 
-/// Produces an absolute path representation of the given type. See also the documentation on
-/// `std::any::type_name`
-pub fn type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
-    let alloc = alloc_type_name(tcx, ty);
-    tcx.mk_const(ty::Const {
-        val: ConstValue::Slice {
-            data: alloc,
-            start: 0,
-            end: alloc.len(),
-        },
-        ty: tcx.mk_static_str(),
-    })
-}
-
 /// Directly returns an `Allocation` containing an absolute path representation of the given type.
-pub(super) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Allocation {
+crate fn alloc_type_name<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    ty: Ty<'tcx>
+) -> &'tcx Allocation {
     let path = AbsolutePathPrinter { tcx, path: String::new() }.print_type(ty).unwrap().path;
     let alloc = Allocation::from_byte_aligned_bytes(path.into_bytes());
     tcx.intern_const_alloc(alloc)
diff --git a/src/librustc_mir/interpret/mod.rs b/src/librustc_mir/interpret/mod.rs
index 45d24347e4efd..0c61be283dfd0 100644
--- a/src/librustc_mir/interpret/mod.rs
+++ b/src/librustc_mir/interpret/mod.rs
@@ -34,6 +34,6 @@ pub use self::visitor::{ValueVisitor, MutValueVisitor};
 
 pub use self::validity::RefTracking;
 
-pub(super) use self::intrinsics::type_name;
-
 pub use self::intern::intern_const_alloc_recursive;
+
+crate use self::intrinsics::eval_nullary_intrinsic;
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index b5aab992e3adb..dd214c4a031f7 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -1,11 +1,11 @@
 //! Functions concerning immediate values and operands, and reading from operands.
 //! All high-level functions to read from memory work on operands as sources.
 
-use std::convert::TryInto;
+use std::convert::{TryInto, TryFrom};
 
 use rustc::{mir, ty};
 use rustc::ty::layout::{
-    self, Size, LayoutOf, TyLayout, HasDataLayout, IntegerExt, VariantIdx,
+    self, Size, LayoutOf, TyLayout, HasDataLayout, IntegerExt, PrimitiveExt, VariantIdx,
 };
 
 use rustc::mir::interpret::{
@@ -472,39 +472,38 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     // avoid allocations.
     pub(super) fn eval_place_to_op(
         &self,
-        mir_place: &mir::Place<'tcx>,
+        place: &mir::Place<'tcx>,
         layout: Option<TyLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
         use rustc::mir::PlaceBase;
 
-        mir_place.iterate(|place_base, place_projection| {
-            let mut op = match place_base {
-                PlaceBase::Local(mir::RETURN_PLACE) =>
-                    throw_unsup!(ReadFromReturnPointer),
-                PlaceBase::Local(local) => {
-                    // Do not use the layout passed in as argument if the base we are looking at
-                    // here is not the entire place.
-                    // FIXME use place_projection.is_empty() when is available
-                    let layout = if mir_place.projection.is_none() {
-                        layout
-                    } else {
-                        None
-                    };
-
-                    self.access_local(self.frame(), *local, layout)?
-                }
-                PlaceBase::Static(place_static) => {
-                    self.eval_static_to_mplace(place_static)?.into()
-                }
-            };
+        let base_op = match &place.base {
+            PlaceBase::Local(mir::RETURN_PLACE) =>
+                throw_unsup!(ReadFromReturnPointer),
+            PlaceBase::Local(local) => {
+                // Do not use the layout passed in as argument if the base we are looking at
+                // here is not the entire place.
+                // FIXME use place_projection.is_empty() when is available
+                let layout = if place.projection.is_empty() {
+                    layout
+                } else {
+                    None
+                };
 
-            for proj in place_projection {
-                op = self.operand_projection(op, &proj.elem)?
+                self.access_local(self.frame(), *local, layout)?
+            }
+            PlaceBase::Static(place_static) => {
+                self.eval_static_to_mplace(&place_static)?.into()
             }
+        };
 
-            trace!("eval_place_to_op: got {:?}", *op);
-            Ok(op)
-        })
+        let op = place.projection.iter().try_fold(
+            base_op,
+            |op, elem| self.operand_projection(op, elem)
+        )?;
+
+        trace!("eval_place_to_op: got {:?}", *op);
+        Ok(op)
     }
 
     /// Evaluate the operand, returning a place where you can then find the data.
@@ -610,15 +609,20 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> InterpResult<'tcx, (u128, VariantIdx)> {
         trace!("read_discriminant_value {:#?}", rval.layout);
 
-        let (discr_kind, discr_index) = match rval.layout.variants {
+        let (discr_layout, discr_kind, discr_index) = match rval.layout.variants {
             layout::Variants::Single { index } => {
                 let discr_val = rval.layout.ty.discriminant_for_variant(*self.tcx, index).map_or(
                     index.as_u32() as u128,
                     |discr| discr.val);
                 return Ok((discr_val, index));
             }
-            layout::Variants::Multiple { ref discr_kind, discr_index, .. } =>
-                (discr_kind, discr_index),
+            layout::Variants::Multiple {
+                discr: ref discr_layout,
+                ref discr_kind,
+                discr_index,
+                ..
+            } =>
+                (discr_layout, discr_kind, discr_index),
         };
 
         // read raw discriminant value
@@ -635,7 +639,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     .map_err(|_| err_unsup!(InvalidDiscriminant(raw_discr.erase_tag())))?;
                 let real_discr = if discr_val.layout.ty.is_signed() {
                     // going from layout tag type to typeck discriminant type
-                    // requires first sign extending with the layout discriminant
+                    // requires first sign extending with the discriminant layout
                     let sexted = sign_extend(bits_discr, discr_val.layout.size) as i128;
                     // and then zeroing with the typeck discriminant type
                     let discr_ty = rval.layout.ty
@@ -667,8 +671,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 ref niche_variants,
                 niche_start,
             } => {
-                let variants_start = niche_variants.start().as_u32() as u128;
-                let variants_end = niche_variants.end().as_u32() as u128;
+                let variants_start = niche_variants.start().as_u32();
+                let variants_end = niche_variants.end().as_u32();
                 let raw_discr = raw_discr.not_undef().map_err(|_| {
                     err_unsup!(InvalidDiscriminant(ScalarMaybeUndef::Undef))
                 })?;
@@ -683,18 +687,34 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         (dataful_variant.as_u32() as u128, dataful_variant)
                     },
                     Ok(raw_discr) => {
-                        let adjusted_discr = raw_discr.wrapping_sub(niche_start)
-                            .wrapping_add(variants_start);
-                        if variants_start <= adjusted_discr && adjusted_discr <= variants_end {
-                            let index = adjusted_discr as usize;
-                            assert_eq!(index as u128, adjusted_discr);
-                            assert!(index < rval.layout.ty
+                        // We need to use machine arithmetic to get the relative variant idx:
+                        // variant_index_relative = discr_val - niche_start_val
+                        let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
+                        let discr_val = ImmTy::from_uint(raw_discr, discr_layout);
+                        let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
+                        let variant_index_relative_val = self.binary_op(
+                            mir::BinOp::Sub,
+                            discr_val,
+                            niche_start_val,
+                        )?;
+                        let variant_index_relative = variant_index_relative_val
+                            .to_scalar()?
+                            .assert_bits(discr_val.layout.size);
+                        // Check if this is in the range that indicates an actual discriminant.
+                        if variant_index_relative <= u128::from(variants_end - variants_start) {
+                            let variant_index_relative = u32::try_from(variant_index_relative)
+                                .expect("we checked that this fits into a u32");
+                            // Then computing the absolute variant idx should not overflow any more.
+                            let variant_index = variants_start
+                                .checked_add(variant_index_relative)
+                                .expect("oveflow computing absolute variant idx");
+                            assert!((variant_index as usize) < rval.layout.ty
                                 .ty_adt_def()
                                 .expect("tagged layout for non adt")
                                 .variants.len());
-                            (adjusted_discr, VariantIdx::from_usize(index))
+                            (u128::from(variant_index), VariantIdx::from_u32(variant_index))
                         } else {
-                            (dataful_variant.as_u32() as u128, dataful_variant)
+                            (u128::from(dataful_variant.as_u32()), dataful_variant)
                         }
                     },
                 }
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index f358bb00f4d12..c3660fb7a2e28 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -8,7 +8,9 @@ use std::hash::Hash;
 use rustc::mir;
 use rustc::mir::interpret::truncate;
 use rustc::ty::{self, Ty};
-use rustc::ty::layout::{self, Size, Align, LayoutOf, TyLayout, HasDataLayout, VariantIdx};
+use rustc::ty::layout::{
+    self, Size, Align, LayoutOf, TyLayout, HasDataLayout, VariantIdx, PrimitiveExt
+};
 use rustc::ty::TypeFoldable;
 
 use super::{
@@ -629,45 +631,43 @@ where
     /// place; for reading, a more efficient alternative is `eval_place_for_read`.
     pub fn eval_place(
         &mut self,
-        mir_place: &mir::Place<'tcx>,
+        place: &mir::Place<'tcx>,
     ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
         use rustc::mir::PlaceBase;
 
-        mir_place.iterate(|place_base, place_projection| {
-            let mut place = match place_base {
-                PlaceBase::Local(mir::RETURN_PLACE) => match self.frame().return_place {
-                    Some(return_place) => {
-                        // We use our layout to verify our assumption; caller will validate
-                        // their layout on return.
-                        PlaceTy {
-                            place: *return_place,
-                            layout: self.layout_of(
-                                self.subst_from_frame_and_normalize_erasing_regions(
-                                    self.frame().body.return_ty()
-                                )
-                            )?,
-                        }
+        let mut place_ty = match &place.base {
+            PlaceBase::Local(mir::RETURN_PLACE) => match self.frame().return_place {
+                Some(return_place) => {
+                    // We use our layout to verify our assumption; caller will validate
+                    // their layout on return.
+                    PlaceTy {
+                        place: *return_place,
+                        layout: self.layout_of(
+                            self.subst_from_frame_and_normalize_erasing_regions(
+                                self.frame().body.return_ty()
+                            )
+                        )?,
                     }
-                    None => throw_unsup!(InvalidNullPointerUsage),
-                },
-                PlaceBase::Local(local) => PlaceTy {
-                    // This works even for dead/uninitialized locals; we check further when writing
-                    place: Place::Local {
-                        frame: self.cur_frame(),
-                        local: *local,
-                    },
-                    layout: self.layout_of_local(self.frame(), *local, None)?,
+                }
+                None => throw_unsup!(InvalidNullPointerUsage),
+            },
+            PlaceBase::Local(local) => PlaceTy {
+                // This works even for dead/uninitialized locals; we check further when writing
+                place: Place::Local {
+                    frame: self.cur_frame(),
+                    local: *local,
                 },
-                PlaceBase::Static(place_static) => self.eval_static_to_mplace(place_static)?.into(),
-            };
+                layout: self.layout_of_local(self.frame(), *local, None)?,
+            },
+            PlaceBase::Static(place_static) => self.eval_static_to_mplace(&place_static)?.into(),
+        };
 
-            for proj in place_projection {
-                place = self.place_projection(place, &proj.elem)?
-            }
+        for elem in place.projection.iter() {
+            place_ty = self.place_projection(place_ty, elem)?
+        }
 
-            self.dump_place(place.place);
-            Ok(place)
-        })
+        self.dump_place(place_ty.place);
+        Ok(place_ty)
     }
 
     /// Write a scalar to a place
@@ -1029,7 +1029,7 @@ where
             }
             layout::Variants::Multiple {
                 discr_kind: layout::DiscriminantKind::Tag,
-                ref discr,
+                discr: ref discr_layout,
                 discr_index,
                 ..
             } => {
@@ -1040,7 +1040,7 @@ where
                 // raw discriminants for enums are isize or bigger during
                 // their computation, but the in-memory tag is the smallest possible
                 // representation
-                let size = discr.value.size(self);
+                let size = discr_layout.value.size(self);
                 let discr_val = truncate(discr_val, size);
 
                 let discr_dest = self.place_field(dest, discr_index as u64)?;
@@ -1052,6 +1052,7 @@ where
                     ref niche_variants,
                     niche_start,
                 },
+                discr: ref discr_layout,
                 discr_index,
                 ..
             } => {
@@ -1059,15 +1060,24 @@ where
                     variant_index.as_usize() < dest.layout.ty.ty_adt_def().unwrap().variants.len(),
                 );
                 if variant_index != dataful_variant {
-                    let niche_dest =
-                        self.place_field(dest, discr_index as u64)?;
-                    let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
-                    let niche_value = (niche_value as u128)
-                        .wrapping_add(niche_start);
-                    self.write_scalar(
-                        Scalar::from_uint(niche_value, niche_dest.layout.size),
-                        niche_dest
+                    let variants_start = niche_variants.start().as_u32();
+                    let variant_index_relative = variant_index.as_u32()
+                        .checked_sub(variants_start)
+                        .expect("overflow computing relative variant idx");
+                    // We need to use machine arithmetic when taking into account `niche_start`:
+                    // discr_val = variant_index_relative + niche_start_val
+                    let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
+                    let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
+                    let variant_index_relative_val =
+                        ImmTy::from_uint(variant_index_relative, discr_layout);
+                    let discr_val = self.binary_op(
+                        mir::BinOp::Add,
+                        variant_index_relative_val,
+                        niche_start_val,
                     )?;
+                    // Write result.
+                    let niche_dest = self.place_field(dest, discr_index as u64)?;
+                    self.write_immediate(*discr_val, niche_dest)?;
                 }
             }
         }
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index ca4da451a1f2d..affca10bf5265 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -82,7 +82,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         self.memory.tcx.span = stmt.source_info.span;
 
         match stmt.kind {
-            Assign(ref place, ref rvalue) => self.eval_rvalue_into_place(rvalue, place)?,
+            Assign(box(ref place, ref rvalue)) => self.eval_rvalue_into_place(rvalue, place)?,
 
             SetDiscriminant {
                 ref place,
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index 5de297923ce7b..8310ef02f9669 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -391,7 +391,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     // Don't forget to check the return type!
                     if let Some(caller_ret) = dest {
                         let callee_ret = self.eval_place(
-                            &mir::Place::RETURN_PLACE
+                            &mir::Place::return_place()
                         )?;
                         if !Self::check_argument_compat(
                             rust_abi,
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index cccf7b9545bdb..9a03719ab61f5 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -14,7 +14,6 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(const_fn)]
 #![feature(decl_macro)]
 #![feature(exhaustive_patterns)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(never_type)]
 #![feature(specialization)]
 #![feature(try_trait)]
@@ -24,6 +23,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(try_blocks)]
 #![feature(mem_take)]
 #![feature(associated_type_bounds)]
+#![feature(range_is_empty)]
 
 #![recursion_limit="256"]
 
@@ -32,11 +32,11 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #[macro_use] extern crate rustc_data_structures;
 #[macro_use] extern crate syntax;
 
-mod error_codes;
+pub mod error_codes;
 
 mod borrow_check;
 mod build;
-mod dataflow;
+pub mod dataflow;
 mod hair;
 mod lints;
 mod shim;
@@ -60,7 +60,4 @@ pub fn provide(providers: &mut Providers<'_>) {
         let (param_env, (value, field)) = param_env_and_value.into_parts();
         const_eval::const_field(tcx, param_env, None, field, value)
     };
-    providers.type_name = interpret::type_name;
 }
-
-__build_diagnostic_array! { librustc_mir, DIAGNOSTICS }
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index aa83255bf62f4..6daca5e261431 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -217,7 +217,7 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
             // Function arguments should be retagged, and we make this one raw.
             body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
                 source_info,
-                kind: StatementKind::Retag(RetagKind::Raw, dropee_ptr.clone()),
+                kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
             });
         }
         let patch = {
@@ -308,7 +308,7 @@ fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -
     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
     let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env, builder.span);
 
-    let dest = Place::RETURN_PLACE;
+    let dest = Place::return_place();
     let src = Place::from(Local::new(1+0)).deref();
 
     match self_ty.sty {
@@ -415,8 +415,10 @@ impl CloneShimBuilder<'tcx> {
         let rcvr = Place::from(Local::new(1+0)).deref();
         let ret_statement = self.make_statement(
             StatementKind::Assign(
-                Place::RETURN_PLACE,
-                box Rvalue::Use(Operand::Copy(rcvr))
+                box(
+                    Place::return_place(),
+                    Rvalue::Use(Operand::Copy(rcvr))
+                )
             )
         );
         self.block(vec![ret_statement], TerminatorKind::Return, false);
@@ -458,8 +460,10 @@ impl CloneShimBuilder<'tcx> {
         // `let ref_loc: &ty = &src;`
         let statement = self.make_statement(
             StatementKind::Assign(
-                ref_loc.clone(),
-                box Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
+                box(
+                    ref_loc.clone(),
+                    Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
+                )
             )
         );
 
@@ -486,8 +490,10 @@ impl CloneShimBuilder<'tcx> {
         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
         let compute_cond = self.make_statement(
             StatementKind::Assign(
-                cond.clone(),
-                box Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
+                box(
+                    cond.clone(),
+                    Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
+                )
             )
         );
 
@@ -521,14 +527,18 @@ impl CloneShimBuilder<'tcx> {
         let inits = vec![
             self.make_statement(
                 StatementKind::Assign(
-                    Place::from(beg),
-                    box Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                    box(
+                        Place::from(beg),
+                        Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                    )
                 )
             ),
             self.make_statement(
                 StatementKind::Assign(
-                    end.clone(),
-                    box Rvalue::Use(Operand::Constant(self.make_usize(len)))
+                    box(
+                        end.clone(),
+                        Rvalue::Use(Operand::Constant(self.make_usize(len)))
+                    )
                 )
             )
         ];
@@ -559,11 +569,13 @@ impl CloneShimBuilder<'tcx> {
         let statements = vec![
             self.make_statement(
                 StatementKind::Assign(
-                    Place::from(beg),
-                    box Rvalue::BinaryOp(
-                        BinOp::Add,
-                        Operand::Copy(Place::from(beg)),
-                        Operand::Constant(self.make_usize(1))
+                    box(
+                        Place::from(beg),
+                        Rvalue::BinaryOp(
+                            BinOp::Add,
+                            Operand::Copy(Place::from(beg)),
+                            Operand::Constant(self.make_usize(1))
+                        )
                     )
                 )
             )
@@ -582,8 +594,10 @@ impl CloneShimBuilder<'tcx> {
         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
         let init = self.make_statement(
             StatementKind::Assign(
-                Place::from(beg),
-                box Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                box(
+                    Place::from(beg),
+                    Rvalue::Use(Operand::Constant(self.make_usize(0)))
+                )
             )
         );
         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
@@ -609,11 +623,13 @@ impl CloneShimBuilder<'tcx> {
         // `goto #6;`
         let statement = self.make_statement(
             StatementKind::Assign(
-                Place::from(beg),
-                box Rvalue::BinaryOp(
-                    BinOp::Add,
-                    Operand::Copy(Place::from(beg)),
-                    Operand::Constant(self.make_usize(1))
+                box(
+                    Place::from(beg),
+                    Rvalue::BinaryOp(
+                        BinOp::Add,
+                        Operand::Copy(Place::from(beg)),
+                        Operand::Constant(self.make_usize(1))
+                    )
                 )
             )
         );
@@ -727,8 +743,10 @@ fn build_call_shim<'tcx>(
             statements.push(Statement {
                 source_info,
                 kind: StatementKind::Assign(
-                    Place::from(ref_rcvr),
-                    box Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
+                    box(
+                        Place::from(ref_rcvr),
+                        Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
+                    )
                 )
             });
             Operand::Move(Place::from(ref_rcvr))
@@ -773,7 +791,7 @@ fn build_call_shim<'tcx>(
     block(&mut blocks, statements, TerminatorKind::Call {
         func: callee,
         args,
-        destination: Some((Place::RETURN_PLACE,
+        destination: Some((Place::return_place(),
                            BasicBlock::new(1))),
         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
             Some(BasicBlock::new(3))
@@ -868,7 +886,7 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> &Body<'_> {
     debug!("build_ctor: variant_index={:?}", variant_index);
 
     let statements = expand_aggregate(
-        Place::RETURN_PLACE,
+        Place::return_place(),
         adt_def
             .variants[variant_index]
             .fields
diff --git a/src/librustc_mir/transform/add_retag.rs b/src/librustc_mir/transform/add_retag.rs
index 0fd75cd57b2ac..833c8b1646bb6 100644
--- a/src/librustc_mir/transform/add_retag.rs
+++ b/src/librustc_mir/transform/add_retag.rs
@@ -17,12 +17,11 @@ pub struct AddRetag;
 fn is_stable(
     place: PlaceRef<'_, '_>,
 ) -> bool {
-    if let Some(proj) = &place.projection {
-        match proj.elem {
+    place.projection.iter().all(|elem| {
+        match elem {
             // Which place this evaluates to can change with any memory write,
             // so cannot assume this to be stable.
-            ProjectionElem::Deref =>
-                false,
+            ProjectionElem::Deref => false,
             // Array indices are intersting, but MIR building generates a *fresh*
             // temporary for every array access, so the index cannot be changed as
             // a side-effect.
@@ -31,15 +30,9 @@ fn is_stable(
             ProjectionElem::Field { .. } |
             ProjectionElem::ConstantIndex { .. } |
             ProjectionElem::Subslice { .. } |
-            ProjectionElem::Downcast { .. } =>
-                is_stable(PlaceRef {
-                    base: place.base,
-                    projection: &proj.base,
-                }),
+            ProjectionElem::Downcast { .. } => true,
         }
-    } else {
-        true
-    }
+    })
 }
 
 /// Determine whether this type may be a reference (or box), and thus needs retagging.
@@ -96,7 +89,7 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
             basic_blocks[START_BLOCK].statements.splice(0..0,
                 places.into_iter().map(|place| Statement {
                     source_info,
-                    kind: StatementKind::Retag(RetagKind::FnEntry, place),
+                    kind: StatementKind::Retag(RetagKind::FnEntry, box(place)),
                 })
             );
         }
@@ -132,7 +125,7 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
         for (source_info, dest_place, dest_block) in returns {
             basic_blocks[dest_block].statements.insert(0, Statement {
                 source_info,
-                kind: StatementKind::Retag(RetagKind::Default, dest_place),
+                kind: StatementKind::Retag(RetagKind::Default, box(dest_place)),
             });
         }
 
@@ -144,11 +137,11 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
             for i in (0..block_data.statements.len()).rev() {
                 let (retag_kind, place) = match block_data.statements[i].kind {
                     // If we are casting *from* a reference, we may have to retag-as-raw.
-                    StatementKind::Assign(ref place, box Rvalue::Cast(
+                    StatementKind::Assign(box(ref place, Rvalue::Cast(
                         CastKind::Misc,
                         ref src,
                         dest_ty,
-                    )) => {
+                    ))) => {
                         let src_ty = src.ty(&*local_decls, tcx);
                         if src_ty.is_region_ptr() {
                             // The only `Misc` casts on references are those creating raw pointers.
@@ -162,7 +155,7 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
                     // Assignments of reference or ptr type are the ones where we may have
                     // to update tags.  This includes `x = &[mut] ...` and hence
                     // we also retag after taking a reference!
-                    StatementKind::Assign(ref place, box ref rvalue) if needs_retag(place) => {
+                    StatementKind::Assign(box(ref place, ref rvalue)) if needs_retag(place) => {
                         let kind = match rvalue {
                             Rvalue::Ref(_, borrow_kind, _)
                                 if borrow_kind.allows_two_phase_borrow()
@@ -180,7 +173,7 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
                 let source_info = block_data.statements[i].source_info;
                 block_data.statements.insert(i+1, Statement {
                     source_info,
-                    kind: StatementKind::Retag(retag_kind, place),
+                    kind: StatementKind::Retag(retag_kind, box(place)),
                 });
             }
         }
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 539922c54d12d..39aa5c717acc1 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -200,127 +200,127 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                     place: &Place<'tcx>,
                     context: PlaceContext,
                     _location: Location) {
-        place.iterate(|place_base, place_projections| {
-            match place_base {
-                PlaceBase::Local(..) => {
-                    // Locals are safe.
-                }
-                PlaceBase::Static(box Static { kind: StaticKind::Promoted(_, _), .. }) => {
-                    bug!("unsafety checking should happen before promotion")
-                }
-                PlaceBase::Static(box Static { kind: StaticKind::Static, def_id, .. }) => {
-                    if self.tcx.is_mutable_static(*def_id) {
-                        self.require_unsafe("use of mutable static",
-                            "mutable statics can be mutated by multiple threads: aliasing \
-                             violations or data races will cause undefined behavior",
-                             UnsafetyViolationKind::General);
-                    } else if self.tcx.is_foreign_item(*def_id) {
-                        let source_info = self.source_info;
-                        let lint_root =
-                            self.source_scope_local_data[source_info.scope].lint_root;
-                        self.register_violations(&[UnsafetyViolation {
-                            source_info,
-                            description: InternedString::intern("use of extern static"),
-                            details: InternedString::intern(
-                                "extern statics are not controlled by the Rust type system: \
-                                invalid data, aliasing violations or data races will cause \
-                                undefined behavior"),
-                            kind: UnsafetyViolationKind::ExternStatic(lint_root)
-                        }], &[]);
-                    }
+        match place.base {
+            PlaceBase::Local(..) => {
+                // Locals are safe.
+            }
+            PlaceBase::Static(box Static { kind: StaticKind::Promoted(_, _), .. }) => {
+                bug!("unsafety checking should happen before promotion")
+            }
+            PlaceBase::Static(box Static { kind: StaticKind::Static, def_id, .. }) => {
+                if self.tcx.is_mutable_static(def_id) {
+                    self.require_unsafe("use of mutable static",
+                        "mutable statics can be mutated by multiple threads: aliasing \
+                         violations or data races will cause undefined behavior",
+                         UnsafetyViolationKind::General);
+                } else if self.tcx.is_foreign_item(def_id) {
+                    let source_info = self.source_info;
+                    let lint_root =
+                        self.source_scope_local_data[source_info.scope].lint_root;
+                    self.register_violations(&[UnsafetyViolation {
+                        source_info,
+                        description: InternedString::intern("use of extern static"),
+                        details: InternedString::intern(
+                            "extern statics are not controlled by the Rust type system: \
+                            invalid data, aliasing violations or data races will cause \
+                            undefined behavior"),
+                        kind: UnsafetyViolationKind::ExternStatic(lint_root)
+                    }], &[]);
                 }
             }
+        }
 
-            for proj in place_projections {
-                if context.is_borrow() {
-                    if util::is_disaligned(self.tcx, self.body, self.param_env, place) {
-                        let source_info = self.source_info;
-                        let lint_root =
-                            self.source_scope_local_data[source_info.scope].lint_root;
-                        self.register_violations(&[UnsafetyViolation {
-                            source_info,
-                            description: InternedString::intern("borrow of packed field"),
-                            details: InternedString::intern(
-                                "fields of packed structs might be misaligned: dereferencing a \
-                                misaligned pointer or even just creating a misaligned reference \
-                                is undefined behavior"),
-                            kind: UnsafetyViolationKind::BorrowPacked(lint_root)
-                        }], &[]);
-                    }
+        for (i, elem) in place.projection.iter().enumerate() {
+            let proj_base = &place.projection[..i];
+
+            if context.is_borrow() {
+                if util::is_disaligned(self.tcx, self.body, self.param_env, place) {
+                    let source_info = self.source_info;
+                    let lint_root =
+                        self.source_scope_local_data[source_info.scope].lint_root;
+                    self.register_violations(&[UnsafetyViolation {
+                        source_info,
+                        description: InternedString::intern("borrow of packed field"),
+                        details: InternedString::intern(
+                            "fields of packed structs might be misaligned: dereferencing a \
+                            misaligned pointer or even just creating a misaligned reference \
+                            is undefined behavior"),
+                        kind: UnsafetyViolationKind::BorrowPacked(lint_root)
+                    }], &[]);
                 }
-                let is_borrow_of_interior_mut = context.is_borrow() &&
-                    !Place::ty_from(&place.base, &proj.base, self.body, self.tcx)
-                    .ty
-                    .is_freeze(self.tcx, self.param_env, self.source_info.span);
-                // prevent
-                // * `&mut x.field`
-                // * `x.field = y;`
-                // * `&x.field` if `field`'s type has interior mutability
-                // because either of these would allow modifying the layout constrained field and
-                // insert values that violate the layout constraints.
-                if context.is_mutating_use() || is_borrow_of_interior_mut {
-                    self.check_mut_borrowing_layout_constrained_field(
-                        place, context.is_mutating_use(),
-                    );
+            }
+            let is_borrow_of_interior_mut = context.is_borrow() &&
+                !Place::ty_from(&place.base, proj_base, self.body, self.tcx)
+                .ty
+                .is_freeze(self.tcx, self.param_env, self.source_info.span);
+            // prevent
+            // * `&mut x.field`
+            // * `x.field = y;`
+            // * `&x.field` if `field`'s type has interior mutability
+            // because either of these would allow modifying the layout constrained field and
+            // insert values that violate the layout constraints.
+            if context.is_mutating_use() || is_borrow_of_interior_mut {
+                self.check_mut_borrowing_layout_constrained_field(
+                    place, context.is_mutating_use(),
+                );
+            }
+            let old_source_info = self.source_info;
+            if let (PlaceBase::Local(local), []) = (&place.base, proj_base) {
+                if self.body.local_decls[*local].internal {
+                    // Internal locals are used in the `move_val_init` desugaring.
+                    // We want to check unsafety against the source info of the
+                    // desugaring, rather than the source info of the RHS.
+                    self.source_info = self.body.local_decls[*local].source_info;
                 }
-                let old_source_info = self.source_info;
-                if let (PlaceBase::Local(local), None) = (&place.base, &proj.base) {
-                    if self.body.local_decls[*local].internal {
-                        // Internal locals are used in the `move_val_init` desugaring.
-                        // We want to check unsafety against the source info of the
-                        // desugaring, rather than the source info of the RHS.
-                        self.source_info = self.body.local_decls[*local].source_info;
-                    }
+            }
+            let base_ty = Place::ty_from(&place.base, proj_base, self.body, self.tcx).ty;
+            match base_ty.sty {
+                ty::RawPtr(..) => {
+                    self.require_unsafe("dereference of raw pointer",
+                        "raw pointers may be NULL, dangling or unaligned; they can violate \
+                         aliasing rules and cause data races: all of these are undefined \
+                         behavior", UnsafetyViolationKind::General)
                 }
-                let base_ty = Place::ty_from(&place.base, &proj.base, self.body, self.tcx).ty;
-                match base_ty.sty {
-                    ty::RawPtr(..) => {
-                        self.require_unsafe("dereference of raw pointer",
-                            "raw pointers may be NULL, dangling or unaligned; they can violate \
-                             aliasing rules and cause data races: all of these are undefined \
-                             behavior", UnsafetyViolationKind::General)
-                    }
-                    ty::Adt(adt, _) => {
-                        if adt.is_union() {
-                            if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
-                                context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
-                                context == PlaceContext::MutatingUse(
-                                    MutatingUseContext::AsmOutput
-                                )
-                            {
-                                let elem_ty = match proj.elem {
-                                    ProjectionElem::Field(_, ty) => ty,
-                                    _ => span_bug!(
-                                        self.source_info.span,
-                                        "non-field projection {:?} from union?",
-                                        place)
-                                };
-                                if !elem_ty.is_copy_modulo_regions(
-                                    self.tcx,
-                                    self.param_env,
+                ty::Adt(adt, _) => {
+                    if adt.is_union() {
+                        if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
+                            context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
+                            context == PlaceContext::MutatingUse(
+                                MutatingUseContext::AsmOutput
+                            )
+                        {
+                            let elem_ty = match elem {
+                                ProjectionElem::Field(_, ty) => ty,
+                                _ => span_bug!(
                                     self.source_info.span,
-                                ) {
-                                    self.require_unsafe(
-                                        "assignment to non-`Copy` union field",
-                                        "the previous content of the field will be dropped, which \
-                                         causes undefined behavior if the field was not properly \
-                                         initialized", UnsafetyViolationKind::General)
-                                } else {
-                                    // write to non-move union, safe
-                                }
+                                    "non-field projection {:?} from union?",
+                                    place)
+                            };
+                            if !elem_ty.is_copy_modulo_regions(
+                                self.tcx,
+                                self.param_env,
+                                self.source_info.span,
+                            ) {
+                                self.require_unsafe(
+                                    "assignment to non-`Copy` union field",
+                                    "the previous content of the field will be dropped, which \
+                                     causes undefined behavior if the field was not properly \
+                                     initialized", UnsafetyViolationKind::General)
                             } else {
-                                self.require_unsafe("access to union field",
-                                    "the field may not be properly initialized: using \
-                                     uninitialized data will cause undefined behavior",
-                                     UnsafetyViolationKind::General)
+                                // write to non-move union, safe
                             }
+                        } else {
+                            self.require_unsafe("access to union field",
+                                "the field may not be properly initialized: using \
+                                 uninitialized data will cause undefined behavior",
+                                 UnsafetyViolationKind::General)
                         }
                     }
-                    _ => {}
                 }
-                self.source_info = old_source_info;
+                _ => {}
             }
-        });
+            self.source_info = old_source_info;
+        }
     }
 }
 
@@ -407,12 +407,14 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
         place: &Place<'tcx>,
         is_mut_use: bool,
     ) {
-        let mut projection = &place.projection;
-        while let Some(proj) = projection {
-            match proj.elem {
+        let mut cursor = &*place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
+
+            match elem {
                 ProjectionElem::Field(..) => {
                     let ty =
-                        Place::ty_from(&place.base, &proj.base, &self.body.local_decls, self.tcx)
+                        Place::ty_from(&place.base, proj_base, &self.body.local_decls, self.tcx)
                             .ty;
                     match ty.sty {
                         ty::Adt(def, _) => match self.tcx.layout_scalar_valid_range(def.did) {
@@ -447,7 +449,6 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
                 }
                 _ => {}
             }
-            projection = &proj.base;
         }
     }
 }
diff --git a/src/librustc_mir/transform/cleanup_post_borrowck.rs b/src/librustc_mir/transform/cleanup_post_borrowck.rs
index ede1cb62f9451..ea173279aa073 100644
--- a/src/librustc_mir/transform/cleanup_post_borrowck.rs
+++ b/src/librustc_mir/transform/cleanup_post_borrowck.rs
@@ -39,7 +39,7 @@ impl<'tcx> MutVisitor<'tcx> for DeleteNonCodegenStatements {
                        location: Location) {
         match statement.kind {
             StatementKind::AscribeUserType(..)
-            | StatementKind::Assign(_, box Rvalue::Ref(_, BorrowKind::Shallow, _))
+            | StatementKind::Assign(box(_, Rvalue::Ref(_, BorrowKind::Shallow, _)))
             | StatementKind::FakeRead(..) => statement.make_nop(),
             _ => (),
         }
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index e4b186736e2a1..614d5d2a4a2fb 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -282,53 +282,53 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
     fn eval_place(&mut self, place: &Place<'tcx>, source_info: SourceInfo) -> Option<Const<'tcx>> {
         trace!("eval_place(place={:?})", place);
-        place.iterate(|place_base, place_projection| {
-            let mut eval = match place_base {
-                PlaceBase::Local(loc) => self.get_const(*loc).clone()?,
-                PlaceBase::Static(box Static {kind: StaticKind::Promoted(promoted, _), ..}) => {
-                    let generics = self.tcx.generics_of(self.source.def_id());
-                    if generics.requires_monomorphization(self.tcx) {
-                        // FIXME: can't handle code with generics
-                        return None;
-                    }
-                    let substs = InternalSubsts::identity_for_item(self.tcx, self.source.def_id());
-                    let instance = Instance::new(self.source.def_id(), substs);
-                    let cid = GlobalId {
-                        instance,
-                        promoted: Some(*promoted),
-                    };
-                    let res = self.use_ecx(source_info, |this| {
-                        this.ecx.const_eval_raw(cid)
+        let mut eval = match place.base {
+            PlaceBase::Local(loc) => self.get_const(loc).clone()?,
+            PlaceBase::Static(box Static {kind: StaticKind::Promoted(promoted, _), ..}) => {
+                let generics = self.tcx.generics_of(self.source.def_id());
+                if generics.requires_monomorphization(self.tcx) {
+                    // FIXME: can't handle code with generics
+                    return None;
+                }
+                let substs = InternalSubsts::identity_for_item(self.tcx, self.source.def_id());
+                let instance = Instance::new(self.source.def_id(), substs);
+                let cid = GlobalId {
+                    instance,
+                    promoted: Some(promoted),
+                };
+                let res = self.use_ecx(source_info, |this| {
+                    this.ecx.const_eval_raw(cid)
+                })?;
+                trace!("evaluated promoted {:?} to {:?}", promoted, res);
+                res.into()
+            }
+            _ => return None,
+        };
+
+        for (i, elem) in place.projection.iter().enumerate() {
+            let proj_base = &place.projection[..i];
+
+            match elem {
+                ProjectionElem::Field(field, _) => {
+                    trace!("field proj on {:?}", proj_base);
+                    eval = self.use_ecx(source_info, |this| {
+                        this.ecx.operand_field(eval, field.index() as u64)
                     })?;
-                    trace!("evaluated promoted {:?} to {:?}", promoted, res);
-                    res.into()
+                },
+                ProjectionElem::Deref => {
+                    trace!("processing deref");
+                    eval = self.use_ecx(source_info, |this| {
+                        this.ecx.deref_operand(eval)
+                    })?.into();
                 }
+                // We could get more projections by using e.g., `operand_projection`,
+                // but we do not even have the stack frame set up properly so
+                // an `Index` projection would throw us off-track.
                 _ => return None,
-            };
-
-            for proj in place_projection {
-                match proj.elem {
-                    ProjectionElem::Field(field, _) => {
-                        trace!("field proj on {:?}", proj.base);
-                        eval = self.use_ecx(source_info, |this| {
-                            this.ecx.operand_field(eval, field.index() as u64)
-                        })?;
-                    },
-                    ProjectionElem::Deref => {
-                        trace!("processing deref");
-                        eval = self.use_ecx(source_info, |this| {
-                            this.ecx.deref_operand(eval)
-                        })?.into();
-                    }
-                    // We could get more projections by using e.g., `operand_projection`,
-                    // but we do not even have the stack frame set up properly so
-                    // an `Index` projection would throw us off-track.
-                    _ => return None,
-                }
             }
+        }
 
-            Some(eval)
-        })
+        Some(eval)
     }
 
     fn eval_operand(&mut self, op: &Operand<'tcx>, source_info: SourceInfo) -> Option<Const<'tcx>> {
@@ -665,7 +665,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
         location: Location,
     ) {
         trace!("visit_statement: {:?}", statement);
-        if let StatementKind::Assign(ref place, ref mut rval) = statement.kind {
+        if let StatementKind::Assign(box(ref place, ref mut rval)) = statement.kind {
             let place_ty: Ty<'tcx> = place
                 .ty(&self.local_decls, self.tcx)
                 .ty;
@@ -673,7 +673,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                 if let Some(value) = self.const_prop(rval, place_layout, statement.source_info) {
                     if let Place {
                         base: PlaceBase::Local(local),
-                        projection: None,
+                        projection: box [],
                     } = *place {
                         trace!("checking whether {:?} can be stored to {:?}", value, local);
                         if self.can_const_prop[local] {
diff --git a/src/librustc_mir/transform/copy_prop.rs b/src/librustc_mir/transform/copy_prop.rs
index f3a523a813413..28f97f41b50cf 100644
--- a/src/librustc_mir/transform/copy_prop.rs
+++ b/src/librustc_mir/transform/copy_prop.rs
@@ -94,11 +94,13 @@ impl<'tcx> MirPass<'tcx> for CopyPropagation {
                     // That use of the source must be an assignment.
                     match statement.kind {
                         StatementKind::Assign(
-                            Place {
-                                base: PlaceBase::Local(local),
-                                projection: None,
-                            },
-                            box Rvalue::Use(ref operand)
+                            box(
+                                Place {
+                                    base: PlaceBase::Local(local),
+                                    projection: box [],
+                                },
+                                Rvalue::Use(ref operand)
+                            )
                         ) if local == dest_local => {
                             let maybe_action = match *operand {
                                 Operand::Copy(ref src_place) |
@@ -148,24 +150,28 @@ fn eliminate_self_assignments(
             if let Some(stmt) = body[location.block].statements.get(location.statement_index) {
                 match stmt.kind {
                     StatementKind::Assign(
-                        Place {
-                            base: PlaceBase::Local(local),
-                            projection: None,
-                        },
-                        box Rvalue::Use(Operand::Copy(Place {
-                            base: PlaceBase::Local(src_local),
-                            projection: None,
-                        })),
+                        box(
+                            Place {
+                                base: PlaceBase::Local(local),
+                                projection: box [],
+                            },
+                            Rvalue::Use(Operand::Copy(Place {
+                                base: PlaceBase::Local(src_local),
+                                projection: box [],
+                            })),
+                        )
                     ) |
                     StatementKind::Assign(
-                        Place {
-                            base: PlaceBase::Local(local),
-                            projection: None,
-                        },
-                        box Rvalue::Use(Operand::Move(Place {
-                            base: PlaceBase::Local(src_local),
-                            projection: None,
-                        })),
+                        box(
+                            Place {
+                                base: PlaceBase::Local(local),
+                                projection: box [],
+                            },
+                            Rvalue::Use(Operand::Move(Place {
+                                base: PlaceBase::Local(src_local),
+                                projection: box [],
+                            })),
+                        )
                     ) if local == dest_local && dest_local == src_local => {}
                     _ => {
                         continue;
@@ -194,7 +200,7 @@ impl<'tcx> Action<'tcx> {
         // The source must be a local.
         let src_local = if let Place {
             base: PlaceBase::Local(local),
-            projection: None,
+            projection: box [],
         } = *src_place {
             local
         } else {
@@ -351,11 +357,11 @@ impl<'tcx> MutVisitor<'tcx> for ConstantPropagationVisitor<'tcx> {
         match *operand {
             Operand::Copy(Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             }) |
             Operand::Move(Place {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: box [],
             }) if local == self.dest_local => {}
             _ => return,
         }
diff --git a/src/librustc_mir/transform/deaggregator.rs b/src/librustc_mir/transform/deaggregator.rs
index 1fc7ce09aa647..c1224be6324e2 100644
--- a/src/librustc_mir/transform/deaggregator.rs
+++ b/src/librustc_mir/transform/deaggregator.rs
@@ -12,8 +12,8 @@ impl<'tcx> MirPass<'tcx> for Deaggregator {
         for bb in basic_blocks {
             bb.expand_statements(|stmt| {
                 // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
-                if let StatementKind::Assign(_, ref rhs) = stmt.kind {
-                    if let Rvalue::Aggregate(ref kind, _) = **rhs {
+                if let StatementKind::Assign(box(_, ref rhs)) = stmt.kind {
+                    if let Rvalue::Aggregate(ref kind, _) = *rhs {
                         // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
                         if let AggregateKind::Array(_) = **kind {
                             return None;
@@ -28,7 +28,7 @@ impl<'tcx> MirPass<'tcx> for Deaggregator {
                 let stmt = stmt.replace_nop();
                 let source_info = stmt.source_info;
                 let (lhs, kind, operands) = match stmt.kind {
-                    StatementKind::Assign(lhs, box rvalue) => {
+                    StatementKind::Assign(box(lhs, rvalue)) => {
                         match rvalue {
                             Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
                             _ => bug!()
diff --git a/src/librustc_mir/transform/elaborate_drops.rs b/src/librustc_mir/transform/elaborate_drops.rs
index 7a5c00c859629..a9c66b3c8c6d1 100644
--- a/src/librustc_mir/transform/elaborate_drops.rs
+++ b/src/librustc_mir/transform/elaborate_drops.rs
@@ -236,47 +236,34 @@ impl<'a, 'b, 'tcx> DropElaborator<'a, 'tcx> for Elaborator<'a, 'b, 'tcx> {
     }
 
     fn field_subpath(&self, path: Self::Path, field: Field) -> Option<Self::Path> {
-        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |p| {
-            match p {
-                &Projection {
-                    elem: ProjectionElem::Field(idx, _), ..
-                } => idx == field,
-                _ => false
-            }
+        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |e| match e {
+            ProjectionElem::Field(idx, _) => *idx == field,
+            _ => false,
         })
     }
 
     fn array_subpath(&self, path: Self::Path, index: u32, size: u32) -> Option<Self::Path> {
-        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |p| {
-            match p {
-                &Projection {
-                    elem: ProjectionElem::ConstantIndex{offset, min_length: _, from_end: false}, ..
-                } => offset == index,
-                &Projection {
-                    elem: ProjectionElem::ConstantIndex{offset, min_length: _, from_end: true}, ..
-                } => size - offset == index,
-                _ => false
+        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |e| match e {
+            ProjectionElem::ConstantIndex { offset, min_length: _, from_end: false } => {
+                *offset == index
+            }
+            ProjectionElem::ConstantIndex { offset, min_length: _, from_end: true } => {
+                size - offset == index
             }
+            _ => false,
         })
     }
 
     fn deref_subpath(&self, path: Self::Path) -> Option<Self::Path> {
-        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |p| {
-            match p {
-                &Projection { elem: ProjectionElem::Deref, .. } => true,
-                _ => false
-            }
+        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |e| {
+            *e == ProjectionElem::Deref
         })
     }
 
     fn downcast_subpath(&self, path: Self::Path, variant: VariantIdx) -> Option<Self::Path> {
-        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |p| {
-            match p {
-                &Projection {
-                    elem: ProjectionElem::Downcast(_, idx), ..
-                } => idx == variant,
-                _ => false
-            }
+        dataflow::move_path_children_matching(self.ctxt.move_data(), path, |e| match e {
+            ProjectionElem::Downcast(_, idx) => *idx == variant,
+            _ => false
         })
     }
 
@@ -465,7 +452,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
         assert!(!data.is_cleanup, "DropAndReplace in unwind path not supported");
 
         let assign = Statement {
-            kind: StatementKind::Assign(location.clone(), box Rvalue::Use(value.clone())),
+            kind: StatementKind::Assign(box(location.clone(), Rvalue::Use(value.clone()))),
             source_info: terminator.source_info
         };
 
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
index d87331195dd24..caf588af851dd 100644
--- a/src/librustc_mir/transform/generator.rs
+++ b/src/librustc_mir/transform/generator.rs
@@ -67,7 +67,7 @@ use crate::transform::{MirPass, MirSource};
 use crate::transform::simplify;
 use crate::transform::no_landing_pads::no_landing_pads;
 use crate::dataflow::{DataflowResults, DataflowResultsConsumer, FlowAtLocation};
-use crate::dataflow::{do_dataflow, DebugFormatted, state_for_location};
+use crate::dataflow::{do_dataflow, DebugFormatted, DataflowResultsCursor};
 use crate::dataflow::{MaybeStorageLive, HaveBeenBorrowedLocals, RequiresStorage};
 use crate::util::dump_mir;
 use crate::util::liveness;
@@ -107,10 +107,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefArgVisitor {
         if place.base == PlaceBase::Local(self_arg()) {
             replace_base(place, Place {
                 base: PlaceBase::Local(self_arg()),
-                projection: Some(Box::new(Projection {
-                    base: None,
-                    elem: ProjectionElem::Deref,
-                })),
+                projection: Box::new([ProjectionElem::Deref]),
             });
         } else {
             self.super_place(place, context, location);
@@ -137,10 +134,7 @@ impl<'tcx> MutVisitor<'tcx> for PinArgVisitor<'tcx> {
         if place.base == PlaceBase::Local(self_arg()) {
             replace_base(place, Place {
                 base: PlaceBase::Local(self_arg()),
-                projection: Some(Box::new(Projection {
-                    base: None,
-                    elem: ProjectionElem::Field(Field::new(0), self.ref_gen_ty),
-                })),
+                projection: Box::new([ProjectionElem::Field(Field::new(0), self.ref_gen_ty)]),
             });
         } else {
             self.super_place(place, context, location);
@@ -149,13 +143,12 @@ impl<'tcx> MutVisitor<'tcx> for PinArgVisitor<'tcx> {
 }
 
 fn replace_base(place: &mut Place<'tcx>, new_base: Place<'tcx>) {
-    let mut projection = &mut place.projection;
-    while let Some(box proj) = projection {
-        projection = &mut proj.base;
-    }
-
     place.base = new_base.base;
-    *projection = new_base.projection;
+
+    let mut new_projection = new_base.projection.to_vec();
+    new_projection.append(&mut place.projection.to_vec());
+
+    place.projection = new_projection.into_boxed_slice();
 }
 
 fn self_arg() -> Local {
@@ -210,13 +203,12 @@ impl TransformVisitor<'tcx> {
     fn make_field(&self, variant_index: VariantIdx, idx: usize, ty: Ty<'tcx>) -> Place<'tcx> {
         let self_place = Place::from(self_arg());
         let base = self_place.downcast_unnamed(variant_index);
-        let field = Projection {
-            base: base.projection,
-            elem: ProjectionElem::Field(Field::new(idx), ty),
-        };
+        let mut projection = base.projection.to_vec();
+        projection.push(ProjectionElem::Field(Field::new(idx), ty));
+
         Place {
             base: base.base,
-            projection: Some(Box::new(field)),
+            projection: projection.into_boxed_slice(),
         }
     }
 
@@ -225,7 +217,10 @@ impl TransformVisitor<'tcx> {
         let self_place = Place::from(self_arg());
         Statement {
             source_info,
-            kind: StatementKind::SetDiscriminant { place: self_place, variant_index: state_disc },
+            kind: StatementKind::SetDiscriminant {
+                place: box self_place,
+                variant_index: state_disc,
+            },
         }
     }
 
@@ -238,7 +233,7 @@ impl TransformVisitor<'tcx> {
         let self_place = Place::from(self_arg());
         let assign = Statement {
             source_info: source_info(body),
-            kind: StatementKind::Assign(temp.clone(), box Rvalue::Discriminant(self_place)),
+            kind: StatementKind::Assign(box(temp.clone(), Rvalue::Discriminant(self_place))),
         };
         (assign, temp)
     }
@@ -296,8 +291,12 @@ impl MutVisitor<'tcx> for TransformVisitor<'tcx> {
             // We must assign the value first in case it gets declared dead below
             data.statements.push(Statement {
                 source_info,
-                kind: StatementKind::Assign(Place::RETURN_PLACE,
-                                            box self.make_state(state_idx, v)),
+                kind: StatementKind::Assign(
+                    box(
+                        Place::return_place(),
+                        self.make_state(state_idx, v)
+                    )
+                ),
             });
             let state = if let Some(resume) = resume { // Yield
                 let state = 3 + self.suspension_points.len();
@@ -437,9 +436,10 @@ fn locals_live_across_suspend_points(
     // Calculate when MIR locals have live storage. This gives us an upper bound of their
     // lifetimes.
     let storage_live_analysis = MaybeStorageLive::new(body);
-    let storage_live =
+    let storage_live_results =
         do_dataflow(tcx, body, def_id, &[], &dead_unwinds, storage_live_analysis,
                     |bd, p| DebugFormatted::new(&bd.body().local_decls[p]));
+    let mut storage_live_cursor = DataflowResultsCursor::new(&storage_live_results, body);
 
     // Find the MIR locals which do not use StorageLive/StorageDead statements.
     // The storage of these locals are always live.
@@ -449,17 +449,18 @@ fn locals_live_across_suspend_points(
     // Calculate the MIR locals which have been previously
     // borrowed (even if they are still active).
     let borrowed_locals_analysis = HaveBeenBorrowedLocals::new(body);
-    let borrowed_locals_result =
+    let borrowed_locals_results =
         do_dataflow(tcx, body, def_id, &[], &dead_unwinds, borrowed_locals_analysis,
                     |bd, p| DebugFormatted::new(&bd.body().local_decls[p]));
+    let mut borrowed_locals_cursor = DataflowResultsCursor::new(&borrowed_locals_results, body);
 
     // Calculate the MIR locals that we actually need to keep storage around
     // for.
-    let requires_storage_analysis = RequiresStorage::new(body, &borrowed_locals_result);
-    let requires_storage =
+    let requires_storage_analysis = RequiresStorage::new(body, &borrowed_locals_results);
+    let requires_storage_results =
         do_dataflow(tcx, body, def_id, &[], &dead_unwinds, requires_storage_analysis,
                     |bd, p| DebugFormatted::new(&bd.body().local_decls[p]));
-    let requires_storage_analysis = RequiresStorage::new(body, &borrowed_locals_result);
+    let mut requires_storage_cursor = DataflowResultsCursor::new(&requires_storage_results, body);
 
     // Calculate the liveness of MIR locals ignoring borrows.
     let mut live_locals = liveness::LiveVarSet::new_empty(body.local_decls.len());
@@ -485,10 +486,6 @@ fn locals_live_across_suspend_points(
             };
 
             if !movable {
-                let borrowed_locals = state_for_location(loc,
-                                                         &borrowed_locals_analysis,
-                                                         &borrowed_locals_result,
-                                                         body);
                 // The `liveness` variable contains the liveness of MIR locals ignoring borrows.
                 // This is correct for movable generators since borrows cannot live across
                 // suspension points. However for immovable generators we need to account for
@@ -499,22 +496,19 @@ fn locals_live_across_suspend_points(
                 // If a borrow is converted to a raw reference, we must also assume that it lives
                 // forever. Note that the final liveness is still bounded by the storage liveness
                 // of the local, which happens using the `intersect` operation below.
-                liveness.outs[block].union(&borrowed_locals);
+                borrowed_locals_cursor.seek(loc);
+                liveness.outs[block].union(borrowed_locals_cursor.get());
             }
 
-            let storage_liveness = state_for_location(loc,
-                                                      &storage_live_analysis,
-                                                      &storage_live,
-                                                      body);
+            storage_live_cursor.seek(loc);
+            let storage_liveness = storage_live_cursor.get();
 
             // Store the storage liveness for later use so we can restore the state
             // after a suspension point
             storage_liveness_map.insert(block, storage_liveness.clone());
 
-            let mut storage_required = state_for_location(loc,
-                                                          &requires_storage_analysis,
-                                                          &requires_storage,
-                                                          body);
+            requires_storage_cursor.seek(loc);
+            let mut storage_required = requires_storage_cursor.get().clone();
 
             // Mark locals without storage statements as always requiring storage
             storage_required.union(&ignored.0);
@@ -550,8 +544,7 @@ fn locals_live_across_suspend_points(
         body,
         &live_locals,
         &ignored,
-        requires_storage,
-        requires_storage_analysis);
+        requires_storage_results);
 
     LivenessInfo {
         live_locals,
@@ -589,7 +582,6 @@ fn compute_storage_conflicts(
     stored_locals: &liveness::LiveVarSet,
     ignored: &StorageIgnored,
     requires_storage: DataflowResults<'tcx, RequiresStorage<'mir, 'tcx>>,
-    _requires_storage_analysis: RequiresStorage<'mir, 'tcx>,
 ) -> BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal> {
     assert_eq!(body.local_decls.len(), ignored.0.domain_size());
     assert_eq!(body.local_decls.len(), stored_locals.domain_size());
@@ -848,7 +840,7 @@ fn elaborate_generator_drops<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, body: &mut
                 kind: TerminatorKind::Drop {
                     location: Place {
                         base: PlaceBase::Local(local),
-                        projection: None,
+                        projection: box [],
                     },
                     target,
                     unwind
@@ -937,7 +929,7 @@ fn create_generator_drop_shim<'tcx>(
         // Alias tracking must know we changed the type
         body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
             source_info,
-            kind: StatementKind::Retag(RetagKind::Raw, Place::from(self_arg())),
+            kind: StatementKind::Retag(RetagKind::Raw, box Place::from(self_arg())),
         })
     }
 
diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
index f31303c642faa..5ad026dc143c9 100644
--- a/src/librustc_mir/transform/inline.rs
+++ b/src/librustc_mir/transform/inline.rs
@@ -425,22 +425,20 @@ impl Inliner<'tcx> {
                 // writes to `i`. To prevent this we need to create a temporary
                 // borrow of the place and pass the destination as `*temp` instead.
                 fn dest_needs_borrow(place: &Place<'_>) -> bool {
-                    place.iterate(|place_base, place_projection| {
-                        for proj in place_projection {
-                            match proj.elem {
-                                ProjectionElem::Deref |
-                                ProjectionElem::Index(_) => return true,
-                                _ => {}
-                            }
+                    for elem in place.projection.iter() {
+                        match elem {
+                            ProjectionElem::Deref |
+                            ProjectionElem::Index(_) => return true,
+                            _ => {}
                         }
+                    }
 
-                        match place_base {
-                            // Static variables need a borrow because the callee
-                            // might modify the same static.
-                            PlaceBase::Static(_) => true,
-                            _ => false
-                        }
-                    })
+                    match place.base {
+                        // Static variables need a borrow because the callee
+                        // might modify the same static.
+                        PlaceBase::Static(_) => true,
+                        _ => false
+                    }
                 }
 
                 let dest = if dest_needs_borrow(&destination.0) {
@@ -459,7 +457,7 @@ impl Inliner<'tcx> {
 
                     let stmt = Statement {
                         source_info: callsite.location,
-                        kind: StatementKind::Assign(tmp.clone(), box dest)
+                        kind: StatementKind::Assign(box(tmp.clone(), dest))
                     };
                     caller_body[callsite.bb]
                         .statements.push(stmt);
@@ -591,7 +589,7 @@ impl Inliner<'tcx> {
 
         if let Operand::Move(Place {
             base: PlaceBase::Local(local),
-            projection: None,
+            projection: box [],
         }) = arg {
             if caller_body.local_kind(local) == LocalKind::Temp {
                 // Reuse the operand if it's a temporary already
@@ -610,7 +608,7 @@ impl Inliner<'tcx> {
 
         let stmt = Statement {
             source_info: callsite.location,
-            kind: StatementKind::Assign(Place::from(arg_tmp), box arg),
+            kind: StatementKind::Assign(box(Place::from(arg_tmp), arg)),
         };
         caller_body[callsite.bb].statements.push(stmt);
         arg_tmp
@@ -660,7 +658,7 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
             match self.destination {
                 Place {
                     base: PlaceBase::Local(l),
-                    projection: None,
+                    projection: box [],
                 } => {
                     *local = l;
                     return;
@@ -684,7 +682,7 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
         match place {
             Place {
                 base: PlaceBase::Local(RETURN_PLACE),
-                projection: None,
+                projection: box [],
             } => {
                 // Return pointer; update the place itself
                 *place = self.destination.clone();
diff --git a/src/librustc_mir/transform/instcombine.rs b/src/librustc_mir/transform/instcombine.rs
index abe41606e8079..0e04e63af4522 100644
--- a/src/librustc_mir/transform/instcombine.rs
+++ b/src/librustc_mir/transform/instcombine.rs
@@ -43,12 +43,21 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
             let new_place = match *rvalue {
                 Rvalue::Ref(_, _, Place {
                     ref mut base,
-                    projection: Some(ref mut projection),
-                }) => Place {
-                    // Replace with dummy
-                    base: mem::replace(base, PlaceBase::Local(Local::new(0))),
-                    projection: projection.base.take(),
-                },
+                    projection: ref mut projection @ box [.., _],
+                }) => {
+                    if let box [proj_l @ .., proj_r] = projection {
+                        let place = Place {
+                            // Replace with dummy
+                            base: mem::replace(base, PlaceBase::Local(Local::new(0))),
+                            projection: proj_l.to_vec().into_boxed_slice(),
+                        };
+                        *projection = vec![proj_r.clone()].into_boxed_slice();
+
+                        place
+                    } else {
+                        unreachable!();
+                    }
+                }
                 _ => bug!("Detected `&*` but didn't find `&*`!"),
             };
             *rvalue = Rvalue::Use(Operand::Copy(new_place))
@@ -83,13 +92,11 @@ impl OptimizationFinder<'b, 'tcx> {
 impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {
     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
         if let Rvalue::Ref(_, _, Place {
-            ref base,
-            projection: Some(ref projection),
-        }) = *rvalue {
-            if let ProjectionElem::Deref = projection.elem {
-                if Place::ty_from(&base, &projection.base, self.body, self.tcx).ty.is_region_ptr() {
-                    self.optimizations.and_stars.insert(location);
-                }
+            base,
+            projection: box [proj_base @ .., ProjectionElem::Deref],
+        }) = rvalue {
+            if Place::ty_from(base, proj_base, self.body, self.tcx).ty.is_region_ptr() {
+                self.optimizations.and_stars.insert(location);
             }
         }
 
diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs
index cdccdfea39943..7d1b96b8be170 100644
--- a/src/librustc_mir/transform/promote_consts.rs
+++ b/src/librustc_mir/transform/promote_consts.rs
@@ -187,7 +187,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                 span,
                 scope: OUTERMOST_SOURCE_SCOPE
             },
-            kind: StatementKind::Assign(Place::from(dest), box rvalue)
+            kind: StatementKind::Assign(box(Place::from(dest), rvalue))
         });
     }
 
@@ -222,10 +222,10 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
         // First, take the Rvalue or Call out of the source MIR,
         // or duplicate it, depending on keep_original.
         if loc.statement_index < no_stmts {
-            let (rvalue, source_info) = {
+            let (mut rvalue, source_info) = {
                 let statement = &mut self.source[loc.block].statements[loc.statement_index];
                 let rhs = match statement.kind {
-                    StatementKind::Assign(_, ref mut rhs) => rhs,
+                    StatementKind::Assign(box(_, ref mut rhs)) => rhs,
                     _ => {
                         span_bug!(statement.source_info.span, "{:?} is not an assignment",
                                   statement);
@@ -235,12 +235,11 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                 (if self.keep_original {
                     rhs.clone()
                 } else {
-                    let unit = box Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);
+                    let unit = Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);
                     mem::replace(rhs, unit)
                 }, statement.source_info)
             };
 
-            let mut rvalue = *rvalue;
             self.visit_rvalue(&mut rvalue, loc);
             self.assign(new_temp, rvalue, source_info.span);
         } else {
@@ -318,7 +317,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                         ty,
                         def_id,
                     }),
-                    projection: None,
+                    projection: box [],
                 }
             };
             let (blocks, local_decls) = self.source.basic_blocks_and_local_decls_mut();
@@ -326,7 +325,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                 Candidate::Ref(loc) => {
                     let ref mut statement = blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
-                        StatementKind::Assign(_, box Rvalue::Ref(_, _, ref mut place)) => {
+                        StatementKind::Assign(box(_, Rvalue::Ref(_, _, ref mut place))) => {
                             // Use the underlying local for this (necessarily interior) borrow.
                             let ty = place.base.ty(local_decls).ty;
                             let span = statement.source_info.span;
@@ -334,9 +333,9 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                             Operand::Move(Place {
                                 base: mem::replace(
                                     &mut place.base,
-                                    promoted_place(ty, span).base
+                                    promoted_place(ty, span).base,
                                 ),
-                                projection: None,
+                                projection: box [],
                             })
                         }
                         _ => bug!()
@@ -345,7 +344,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                 Candidate::Repeat(loc) => {
                     let ref mut statement = blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
-                        StatementKind::Assign(_, box Rvalue::Repeat(ref mut operand, _)) => {
+                        StatementKind::Assign(box(_, Rvalue::Repeat(ref mut operand, _))) => {
                             let ty = operand.ty(local_decls, self.tcx);
                             let span = statement.source_info.span;
                             mem::replace(
@@ -420,10 +419,10 @@ pub fn promote_candidates<'tcx>(
             Candidate::Repeat(Location { block, statement_index }) |
             Candidate::Ref(Location { block, statement_index }) => {
                 match body[block].statements[statement_index].kind {
-                    StatementKind::Assign(Place {
+                    StatementKind::Assign(box(Place {
                         base: PlaceBase::Local(local),
-                        projection: None,
-                    }, _) => {
+                        projection: box [],
+                    }, _)) => {
                         if temps[local] == TempState::PromotedOut {
                             // Already promoted.
                             continue;
@@ -473,10 +472,10 @@ pub fn promote_candidates<'tcx>(
     for block in body.basic_blocks_mut() {
         block.statements.retain(|statement| {
             match statement.kind {
-                StatementKind::Assign(Place {
+                StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(index),
-                    projection: None,
-                }, _) |
+                    projection: box [],
+                }, _)) |
                 StatementKind::StorageLive(index) |
                 StatementKind::StorageDead(index) => {
                     !promoted(index)
@@ -488,7 +487,7 @@ pub fn promote_candidates<'tcx>(
         match terminator.kind {
             TerminatorKind::Drop { location: Place {
                 base: PlaceBase::Local(index),
-                projection: None,
+                projection: box [],
             }, target, .. } => {
                 if promoted(index) {
                     terminator.kind = TerminatorKind::Goto {
diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs
index a77421ce15008..7cc1e634cf812 100644
--- a/src/librustc_mir/transform/qualify_consts.rs
+++ b/src/librustc_mir/transform/qualify_consts.rs
@@ -25,11 +25,13 @@ use syntax::feature_gate::{emit_feature_err, GateIssue};
 use syntax::symbol::sym;
 use syntax_pos::{Span, DUMMY_SP};
 
+use std::borrow::Cow;
 use std::cell::Cell;
 use std::fmt;
 use std::ops::{Deref, Index, IndexMut};
 use std::usize;
 
+use rustc::hir::HirId;
 use crate::transform::{MirPass, MirSource};
 use super::promote_consts::{self, Candidate, TempState};
 
@@ -185,26 +187,28 @@ trait Qualif {
         cx: &ConstCx<'_, 'tcx>,
         place: PlaceRef<'_, 'tcx>,
     ) -> bool {
-        let proj = place.projection.as_ref().unwrap();
-
-        let base_qualif = Self::in_place(cx, PlaceRef {
-            base: place.base,
-            projection: &proj.base,
-        });
-        let qualif = base_qualif && Self::mask_for_ty(
-            cx,
-            Place::ty_from(place.base, &proj.base, cx.body, cx.tcx)
-                .projection_ty(cx.tcx, &proj.elem)
-                .ty,
-        );
-        match proj.elem {
-            ProjectionElem::Deref |
-            ProjectionElem::Subslice { .. } |
-            ProjectionElem::Field(..) |
-            ProjectionElem::ConstantIndex { .. } |
-            ProjectionElem::Downcast(..) => qualif,
-
-            ProjectionElem::Index(local) => qualif || Self::in_local(cx, local),
+        if let [proj_base @ .., elem] = place.projection {
+            let base_qualif = Self::in_place(cx, PlaceRef {
+                base: place.base,
+                projection: proj_base,
+            });
+            let qualif = base_qualif && Self::mask_for_ty(
+                cx,
+                Place::ty_from(place.base, proj_base, cx.body, cx.tcx)
+                    .projection_ty(cx.tcx, elem)
+                    .ty,
+            );
+            match elem {
+                ProjectionElem::Deref |
+                ProjectionElem::Subslice { .. } |
+                ProjectionElem::Field(..) |
+                ProjectionElem::ConstantIndex { .. } |
+                ProjectionElem::Downcast(..) => qualif,
+
+                ProjectionElem::Index(local) => qualif || Self::in_local(cx, *local),
+            }
+        } else {
+            bug!("This should be called if projection is not empty");
         }
     }
 
@@ -219,24 +223,24 @@ trait Qualif {
         match place {
             PlaceRef {
                 base: PlaceBase::Local(local),
-                projection: None,
+                projection: [],
             } => Self::in_local(cx, *local),
             PlaceRef {
                 base: PlaceBase::Static(box Static {
                     kind: StaticKind::Promoted(..),
                     ..
                 }),
-                projection: None,
+                projection: [],
             } => bug!("qualifying already promoted MIR"),
             PlaceRef {
                 base: PlaceBase::Static(static_),
-                projection: None,
+                projection: [],
             } => {
                 Self::in_static(cx, static_)
             },
             PlaceRef {
                 base: _,
-                projection: Some(_),
+                projection: [.., _],
             } => Self::in_projection(cx, place),
         }
     }
@@ -287,13 +291,13 @@ trait Qualif {
 
             Rvalue::Ref(_, _, ref place) => {
                 // Special-case reborrows to be more like a copy of the reference.
-                if let Some(ref proj) = place.projection {
-                    if let ProjectionElem::Deref = proj.elem {
-                        let base_ty = Place::ty_from(&place.base, &proj.base, cx.body, cx.tcx).ty;
+                if let box [proj_base @ .., elem] = &place.projection {
+                    if ProjectionElem::Deref == *elem {
+                        let base_ty = Place::ty_from(&place.base, proj_base, cx.body, cx.tcx).ty;
                         if let ty::Ref(..) = base_ty.sty {
                             return Self::in_place(cx, PlaceRef {
                                 base: &place.base,
-                                projection: &proj.base,
+                                projection: proj_base,
                             });
                         }
                     }
@@ -451,30 +455,32 @@ impl Qualif for IsNotPromotable {
         cx: &ConstCx<'_, 'tcx>,
         place: PlaceRef<'_, 'tcx>,
     ) -> bool {
-        let proj = place.projection.as_ref().unwrap();
-
-        match proj.elem {
-            ProjectionElem::Deref |
-            ProjectionElem::Downcast(..) => return true,
-
-            ProjectionElem::ConstantIndex {..} |
-            ProjectionElem::Subslice {..} |
-            ProjectionElem::Index(_) => {}
-
-            ProjectionElem::Field(..) => {
-                if cx.mode == Mode::NonConstFn {
-                    let base_ty = Place::ty_from(place.base, &proj.base, cx.body, cx.tcx).ty;
-                    if let Some(def) = base_ty.ty_adt_def() {
-                        // No promotion of union field accesses.
-                        if def.is_union() {
-                            return true;
+        if let [proj_base @ .., elem] = place.projection {
+            match elem {
+                ProjectionElem::Deref |
+                ProjectionElem::Downcast(..) => return true,
+
+                ProjectionElem::ConstantIndex {..} |
+                ProjectionElem::Subslice {..} |
+                ProjectionElem::Index(_) => {}
+
+                ProjectionElem::Field(..) => {
+                    if cx.mode == Mode::NonConstFn {
+                        let base_ty = Place::ty_from(place.base, proj_base, cx.body, cx.tcx).ty;
+                        if let Some(def) = base_ty.ty_adt_def() {
+                            // No promotion of union field accesses.
+                            if def.is_union() {
+                                return true;
+                            }
                         }
                     }
                 }
             }
-        }
 
-        Self::in_projection_structurally(cx, place)
+            Self::in_projection_structurally(cx, place)
+        } else {
+            bug!("This should be called if projection is not empty");
+        }
     }
 
     fn in_rvalue(cx: &ConstCx<'_, 'tcx>, rvalue: &Rvalue<'tcx>) -> bool {
@@ -804,23 +810,18 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
                     // We might have a candidate for promotion.
                     let candidate = Candidate::Ref(location);
                     // Start by traversing to the "base", with non-deref projections removed.
-                    let mut place_projection = &place.projection;
-                    while let Some(proj) = place_projection {
-                        if proj.elem == ProjectionElem::Deref {
-                            break;
-                        }
-                        place_projection = &proj.base;
-                    }
+                    let deref_proj =
+                        place.projection.iter().rev().find(|&elem| *elem == ProjectionElem::Deref);
 
                     debug!(
                         "qualify_consts: promotion candidate: place={:?} {:?}",
-                        place.base, place_projection
+                        place.base, deref_proj
                     );
                     // We can only promote interior borrows of promotable temps (non-temps
                     // don't get promoted anyway).
                     // (If we bailed out of the loop due to a `Deref` above, we will definitely
                     // not enter the conditional here.)
-                    if let (PlaceBase::Local(local), None) = (&place.base, place_projection) {
+                    if let (PlaceBase::Local(local), None) = (&place.base, deref_proj) {
                         if self.body.local_kind(*local) == LocalKind::Temp {
                             debug!("qualify_consts: promotion candidate: local={:?}", local);
                             // The borrowed place doesn't have `HasMutInterior`
@@ -856,27 +857,27 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
             _ => {},
         }
 
-        let mut dest_projection = &dest.projection;
+        let mut dest_projection = &dest.projection[..];
         let index = loop {
             match (&dest.base, dest_projection) {
                 // We treat all locals equal in constants
-                (&PlaceBase::Local(index), None) => break index,
+                (&PlaceBase::Local(index), []) => break index,
                 // projections are transparent for assignments
                 // we qualify the entire destination at once, even if just a field would have
                 // stricter qualification
-                (base, Some(proj)) => {
+                (base, [proj_base @ .., _]) => {
                     // Catch more errors in the destination. `visit_place` also checks various
                     // projection rules like union field access and raw pointer deref
                     let context = PlaceContext::MutatingUse(MutatingUseContext::Store);
                     self.visit_place_base(base, context, location);
-                    self.visit_projection(base, proj, context, location);
-                    dest_projection = &proj.base;
+                    self.visit_projection(base, dest_projection, context, location);
+                    dest_projection = proj_base;
                 },
                 (&PlaceBase::Static(box Static {
                     kind: StaticKind::Promoted(..),
                     ..
-                }), None) => bug!("promoteds don't exist yet during promotion"),
-                (&PlaceBase::Static(box Static{ kind: _, .. }), None) => {
+                }), []) => bug!("promoteds don't exist yet during promotion"),
+                (&PlaceBase::Static(box Static{ kind: _, .. }), []) => {
                     // Catch more errors in the destination. `visit_place` also checks that we
                     // do not try to access statics from constants or try to mutate statics
                     let context = PlaceContext::MutatingUse(MutatingUseContext::Store);
@@ -981,23 +982,25 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
         for candidate in &self.promotion_candidates {
             match *candidate {
                 Candidate::Repeat(Location { block: bb, statement_index: stmt_idx }) => {
-                    if let StatementKind::Assign(_, box Rvalue::Repeat(
+                    if let StatementKind::Assign(box(_, Rvalue::Repeat(
                         Operand::Move(Place {
                             base: PlaceBase::Local(index),
-                            projection: None,
+                            projection: box [],
                         }),
                         _
-                    )) = self.body[bb].statements[stmt_idx].kind {
+                    ))) = self.body[bb].statements[stmt_idx].kind {
                         promoted_temps.insert(index);
                     }
                 }
                 Candidate::Ref(Location { block: bb, statement_index: stmt_idx }) => {
                     if let StatementKind::Assign(
-                        _,
-                        box Rvalue::Ref(_, _, Place {
-                            base: PlaceBase::Local(index),
-                            projection: None,
-                        })
+                        box(
+                            _,
+                            Rvalue::Ref(_, _, Place {
+                                base: PlaceBase::Local(index),
+                                projection: box [],
+                            })
+                        )
                     ) = self.body[bb].statements[stmt_idx].kind {
                         promoted_temps.insert(index);
                     }
@@ -1082,7 +1085,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
     fn visit_projection(
         &mut self,
         place_base: &PlaceBase<'tcx>,
-        proj: &Projection<'tcx>,
+        proj: &[PlaceElem<'tcx>],
         context: PlaceContext,
         location: Location,
     ) {
@@ -1091,62 +1094,65 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
             proj, context, location,
         );
         self.super_projection(place_base, proj, context, location);
-        match proj.elem {
-            ProjectionElem::Deref => {
-                if context.is_mutating_use() {
-                    // `not_const` errors out in const contexts
-                    self.not_const()
-                }
-                let base_ty = Place::ty_from(place_base, &proj.base, self.body, self.tcx).ty;
-                match self.mode {
-                    Mode::NonConstFn => {},
-                    _ => {
-                        if let ty::RawPtr(_) = base_ty.sty {
-                            if !self.tcx.features().const_raw_ptr_deref {
-                                emit_feature_err(
-                                    &self.tcx.sess.parse_sess, sym::const_raw_ptr_deref,
-                                    self.span, GateIssue::Language,
-                                    &format!(
-                                        "dereferencing raw pointers in {}s is unstable",
-                                        self.mode,
-                                    ),
-                                );
-                            }
-                        }
-                    }
-                }
-            }
 
-            ProjectionElem::ConstantIndex {..} |
-            ProjectionElem::Subslice {..} |
-            ProjectionElem::Field(..) |
-            ProjectionElem::Index(_) => {
-                let base_ty = Place::ty_from(place_base, &proj.base, self.body, self.tcx).ty;
-                if let Some(def) = base_ty.ty_adt_def() {
-                    if def.is_union() {
-                        match self.mode {
-                            Mode::ConstFn => {
-                                if !self.tcx.features().const_fn_union {
+        if let [proj_base @ .., elem] = proj {
+            match elem {
+                ProjectionElem::Deref => {
+                    if context.is_mutating_use() {
+                        // `not_const` errors out in const contexts
+                        self.not_const()
+                    }
+                    let base_ty = Place::ty_from(place_base, proj_base, self.body, self.tcx).ty;
+                    match self.mode {
+                        Mode::NonConstFn => {},
+                        _ => {
+                            if let ty::RawPtr(_) = base_ty.sty {
+                                if !self.tcx.features().const_raw_ptr_deref {
                                     emit_feature_err(
-                                        &self.tcx.sess.parse_sess, sym::const_fn_union,
+                                        &self.tcx.sess.parse_sess, sym::const_raw_ptr_deref,
                                         self.span, GateIssue::Language,
-                                        "unions in const fn are unstable",
+                                        &format!(
+                                            "dereferencing raw pointers in {}s is unstable",
+                                            self.mode,
+                                        ),
                                     );
                                 }
-                            },
+                            }
+                        }
+                    }
+                }
 
-                            | Mode::NonConstFn
-                            | Mode::Static
-                            | Mode::StaticMut
-                            | Mode::Const
-                            => {},
+                ProjectionElem::ConstantIndex {..} |
+                ProjectionElem::Subslice {..} |
+                ProjectionElem::Field(..) |
+                ProjectionElem::Index(_) => {
+                    let base_ty = Place::ty_from(place_base, proj_base, self.body, self.tcx).ty;
+                    if let Some(def) = base_ty.ty_adt_def() {
+                        if def.is_union() {
+                            match self.mode {
+                                Mode::ConstFn => {
+                                    if !self.tcx.features().const_fn_union {
+                                        emit_feature_err(
+                                            &self.tcx.sess.parse_sess, sym::const_fn_union,
+                                            self.span, GateIssue::Language,
+                                            "unions in const fn are unstable",
+                                        );
+                                    }
+                                },
+
+                                | Mode::NonConstFn
+                                | Mode::Static
+                                | Mode::StaticMut
+                                | Mode::Const
+                                => {},
+                            }
                         }
                     }
                 }
-            }
 
-            ProjectionElem::Downcast(..) => {
-                self.not_const()
+                ProjectionElem::Downcast(..) => {
+                    self.not_const()
+                }
             }
         }
     }
@@ -1160,7 +1166,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
                 // Mark the consumed locals to indicate later drops are noops.
                 if let Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } = *place {
                     self.cx.per_local[NeedsDrop].remove(local);
                 }
@@ -1177,11 +1183,11 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
         if let Rvalue::Ref(_, kind, ref place) = *rvalue {
             // Special-case reborrows.
             let mut reborrow_place = None;
-            if let Some(ref proj) = place.projection {
-                if let ProjectionElem::Deref = proj.elem {
-                    let base_ty = Place::ty_from(&place.base, &proj.base, self.body, self.tcx).ty;
+            if let box [proj_base @ .., elem] = &place.projection {
+                if *elem == ProjectionElem::Deref {
+                    let base_ty = Place::ty_from(&place.base, proj_base, self.body, self.tcx).ty;
                     if let ty::Ref(..) = base_ty.sty {
-                        reborrow_place = Some(&proj.base);
+                        reborrow_place = Some(proj_base);
                     }
                 }
             }
@@ -1202,9 +1208,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
                     ),
                 };
                 self.visit_place_base(&place.base, ctx, location);
-                if let Some(proj) = proj {
-                    self.visit_projection(&place.base, proj, ctx, location);
-                }
+                self.visit_projection(&place.base, proj, ctx, location);
             } else {
                 self.super_rvalue(rvalue, location);
             }
@@ -1475,7 +1479,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
                 // conservatively, that drop elaboration will do.
                 let needs_drop = if let Place {
                     base: PlaceBase::Local(local),
-                    projection: None,
+                    projection: box [],
                 } = *place {
                     if NeedsDrop::in_local(self, local) {
                         Some(self.body.local_decls[local].source_info.span)
@@ -1596,51 +1600,24 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> {
         }
 
         let def_id = src.def_id();
-        let id = tcx.hir().as_local_hir_id(def_id).unwrap();
-        let mut const_promoted_temps = None;
-        let mode = match tcx.hir().body_owner_kind(id) {
-            hir::BodyOwnerKind::Closure => Mode::NonConstFn,
-            hir::BodyOwnerKind::Fn => {
-                if tcx.is_const_fn(def_id) {
-                    Mode::ConstFn
-                } else {
-                    Mode::NonConstFn
-                }
-            }
-            hir::BodyOwnerKind::Const => {
-                const_promoted_temps = Some(tcx.mir_const_qualif(def_id).1);
-                Mode::Const
-            }
-            hir::BodyOwnerKind::Static(hir::MutImmutable) => Mode::Static,
-            hir::BodyOwnerKind::Static(hir::MutMutable) => Mode::StaticMut,
-        };
+        let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
+
+        let mode = determine_mode(tcx, hir_id, def_id);
 
         debug!("run_pass: mode={:?}", mode);
-        if mode == Mode::NonConstFn || mode == Mode::ConstFn {
+        if let Mode::NonConstFn | Mode::ConstFn = mode {
             // This is ugly because Checker holds onto mir,
             // which can't be mutated until its scope ends.
             let (temps, candidates) = {
                 let mut checker = Checker::new(tcx, def_id, body, mode);
-                if mode == Mode::ConstFn {
+                if let Mode::ConstFn = mode {
                     if tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
                         checker.check_const();
                     } else if tcx.is_min_const_fn(def_id) {
-                        // enforce `min_const_fn` for stable const fns
+                        // Enforce `min_const_fn` for stable `const fn`s.
                         use super::qualify_min_const_fn::is_min_const_fn;
                         if let Err((span, err)) = is_min_const_fn(tcx, def_id, body) {
-                            let mut diag = struct_span_err!(
-                                tcx.sess,
-                                span,
-                                E0723,
-                                "{}",
-                                err,
-                            );
-                            diag.note("for more information, see issue \
-                                       https://github.com/rust-lang/rust/issues/57563");
-                            diag.help(
-                                "add `#![feature(const_fn)]` to the crate attributes to enable",
-                            );
-                            diag.emit();
+                            error_min_const_fn_violation(tcx, span, err);
                         } else {
                             // this should not produce any errors, but better safe than sorry
                             // FIXME(#53819)
@@ -1664,107 +1641,119 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> {
                 promote_consts::promote_candidates(def_id, body, tcx, temps, candidates)
             );
         } else {
-            if !body.control_flow_destroyed.is_empty() {
-                let mut locals = body.vars_iter();
-                if let Some(local) = locals.next() {
-                    let span = body.local_decls[local].source_info.span;
-                    let mut error = tcx.sess.struct_span_err(
-                        span,
-                        &format!(
-                            "new features like let bindings are not permitted in {}s \
-                            which also use short circuiting operators",
-                            mode,
-                        ),
-                    );
-                    for (span, kind) in body.control_flow_destroyed.iter() {
-                        error.span_note(
-                            *span,
-                            &format!("use of {} here does not actually short circuit due to \
-                            the const evaluator presently not being able to do control flow. \
-                            See https://github.com/rust-lang/rust/issues/49146 for more \
-                            information.", kind),
-                        );
-                    }
-                    for local in locals {
-                        let span = body.local_decls[local].source_info.span;
-                        error.span_note(
-                            span,
-                            "more locals defined here",
-                        );
-                    }
-                    error.emit();
-                }
-            }
-            let promoted_temps = if mode == Mode::Const {
-                // Already computed by `mir_const_qualif`.
-                const_promoted_temps.unwrap()
-            } else {
-                Checker::new(tcx, def_id, body, mode).check_const().1
+            check_short_circuiting_in_const_local(tcx, body, mode);
+
+            let promoted_temps = match mode {
+                Mode::Const => tcx.mir_const_qualif(def_id).1,
+                _ => Checker::new(tcx, def_id, body, mode).check_const().1,
             };
+            remove_drop_and_storage_dead_on_promoted_locals(body, promoted_temps);
+        }
 
-            // In `const` and `static` everything without `StorageDead`
-            // is `'static`, we don't have to create promoted MIR fragments,
-            // just remove `Drop` and `StorageDead` on "promoted" locals.
-            debug!("run_pass: promoted_temps={:?}", promoted_temps);
-            for block in body.basic_blocks_mut() {
-                block.statements.retain(|statement| {
-                    match statement.kind {
-                        StatementKind::StorageDead(index) => {
-                            !promoted_temps.contains(index)
-                        }
-                        _ => true
-                    }
-                });
-                let terminator = block.terminator_mut();
-                match terminator.kind {
-                    TerminatorKind::Drop {
-                        location: Place {
-                            base: PlaceBase::Local(index),
-                            projection: None,
-                        },
-                        target,
-                        ..
-                    } => {
-                        if promoted_temps.contains(index) {
-                            terminator.kind = TerminatorKind::Goto {
-                                target,
-                            };
-                        }
-                    }
-                    _ => {}
-                }
-            }
+        if mode == Mode::Static && !tcx.has_attr(def_id, sym::thread_local) {
+            // `static`s (not `static mut`s) which are not `#[thread_local]` must be `Sync`.
+            check_static_is_sync(tcx, body, hir_id);
+        }
+    }
+}
+
+fn determine_mode(tcx: TyCtxt<'_>, hir_id: HirId, def_id: DefId) -> Mode {
+    match tcx.hir().body_owner_kind(hir_id) {
+        hir::BodyOwnerKind::Closure => Mode::NonConstFn,
+        hir::BodyOwnerKind::Fn if tcx.is_const_fn(def_id) => Mode::ConstFn,
+        hir::BodyOwnerKind::Fn => Mode::NonConstFn,
+        hir::BodyOwnerKind::Const => Mode::Const,
+        hir::BodyOwnerKind::Static(hir::MutImmutable) => Mode::Static,
+        hir::BodyOwnerKind::Static(hir::MutMutable) => Mode::StaticMut,
+    }
+}
+
+fn error_min_const_fn_violation(tcx: TyCtxt<'_>, span: Span, msg: Cow<'_, str>) {
+    struct_span_err!(tcx.sess, span, E0723, "{}", msg)
+        .note("for more information, see issue https://github.com/rust-lang/rust/issues/57563")
+        .help("add `#![feature(const_fn)]` to the crate attributes to enable")
+        .emit();
+}
+
+fn check_short_circuiting_in_const_local(tcx: TyCtxt<'_>, body: &mut Body<'tcx>, mode: Mode) {
+    if body.control_flow_destroyed.is_empty() {
+        return;
+    }
+
+    let mut locals = body.vars_iter();
+    if let Some(local) = locals.next() {
+        let span = body.local_decls[local].source_info.span;
+        let mut error = tcx.sess.struct_span_err(
+            span,
+            &format!(
+                "new features like let bindings are not permitted in {}s \
+                which also use short circuiting operators",
+                mode,
+            ),
+        );
+        for (span, kind) in body.control_flow_destroyed.iter() {
+            error.span_note(
+                *span,
+                &format!("use of {} here does not actually short circuit due to \
+                the const evaluator presently not being able to do control flow. \
+                See https://github.com/rust-lang/rust/issues/49146 for more \
+                information.", kind),
+            );
+        }
+        for local in locals {
+            let span = body.local_decls[local].source_info.span;
+            error.span_note(span, "more locals defined here");
         }
+        error.emit();
+    }
+}
 
-        // Statics must be Sync.
-        if mode == Mode::Static {
-            // `#[thread_local]` statics don't have to be `Sync`.
-            for attr in &tcx.get_attrs(def_id)[..] {
-                if attr.check_name(sym::thread_local) {
-                    return;
-                }
+/// In `const` and `static` everything without `StorageDead`
+/// is `'static`, we don't have to create promoted MIR fragments,
+/// just remove `Drop` and `StorageDead` on "promoted" locals.
+fn remove_drop_and_storage_dead_on_promoted_locals(
+    body: &mut Body<'tcx>,
+    promoted_temps: &BitSet<Local>,
+) {
+    debug!("run_pass: promoted_temps={:?}", promoted_temps);
+
+    for block in body.basic_blocks_mut() {
+        block.statements.retain(|statement| {
+            match statement.kind {
+                StatementKind::StorageDead(index) => !promoted_temps.contains(index),
+                _ => true
             }
-            let ty = body.return_ty();
-            tcx.infer_ctxt().enter(|infcx| {
-                let param_env = ty::ParamEnv::empty();
-                let cause = traits::ObligationCause::new(body.span, id, traits::SharedStatic);
-                let mut fulfillment_cx = traits::FulfillmentContext::new();
-                fulfillment_cx.register_bound(&infcx,
-                                              param_env,
-                                              ty,
-                                              tcx.require_lang_item(
-                                                  lang_items::SyncTraitLangItem,
-                                                  Some(body.span)
-                                              ),
-                                              cause);
-                if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) {
-                    infcx.report_fulfillment_errors(&err, None, false);
-                }
-            });
+        });
+        let terminator = block.terminator_mut();
+        match terminator.kind {
+            TerminatorKind::Drop {
+                location: Place {
+                    base: PlaceBase::Local(index),
+                    projection: box [],
+                },
+                target,
+                ..
+            } if promoted_temps.contains(index) => {
+                terminator.kind = TerminatorKind::Goto { target };
+            }
+            _ => {}
         }
     }
 }
 
+fn check_static_is_sync(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, hir_id: HirId) {
+    let ty = body.return_ty();
+    tcx.infer_ctxt().enter(|infcx| {
+        let cause = traits::ObligationCause::new(body.span, hir_id, traits::SharedStatic);
+        let mut fulfillment_cx = traits::FulfillmentContext::new();
+        let sync_def_id = tcx.require_lang_item(lang_items::SyncTraitLangItem, Some(body.span));
+        fulfillment_cx.register_bound(&infcx, ty::ParamEnv::empty(), ty, sync_def_id, cause);
+        if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) {
+            infcx.report_fulfillment_errors(&err, None, false);
+        }
+    });
+}
+
 fn args_required_const(tcx: TyCtxt<'_>, def_id: DefId) -> Option<FxHashSet<usize>> {
     let attrs = tcx.get_attrs(def_id);
     let attr = attrs.iter().find(|a| a.check_name(sym::rustc_args_required_const))?;
diff --git a/src/librustc_mir/transform/qualify_min_const_fn.rs b/src/librustc_mir/transform/qualify_min_const_fn.rs
index 56093527aee24..80e020a9eb7e6 100644
--- a/src/librustc_mir/transform/qualify_min_const_fn.rs
+++ b/src/librustc_mir/transform/qualify_min_const_fn.rs
@@ -206,7 +206,7 @@ fn check_statement(
 ) -> McfResult {
     let span = statement.source_info.span;
     match &statement.kind {
-        StatementKind::Assign(place, rval) => {
+        StatementKind::Assign(box(place, rval)) => {
             check_place(place, span)?;
             check_rvalue(tcx, body, rval, span)
         }
@@ -249,28 +249,26 @@ fn check_place(
     place: &Place<'tcx>,
     span: Span,
 ) -> McfResult {
-    place.iterate(|place_base, place_projection| {
-        for proj in place_projection {
-            match proj.elem {
-                ProjectionElem::Downcast(..) => {
-                    return Err((span, "`match` or `if let` in `const fn` is unstable".into()));
-                }
-                ProjectionElem::ConstantIndex { .. }
-                | ProjectionElem::Subslice { .. }
-                | ProjectionElem::Deref
-                | ProjectionElem::Field(..)
-                | ProjectionElem::Index(_) => {}
+    for elem in place.projection.iter() {
+        match elem {
+            ProjectionElem::Downcast(..) => {
+                return Err((span, "`match` or `if let` in `const fn` is unstable".into()));
             }
+            ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::Subslice { .. }
+            | ProjectionElem::Deref
+            | ProjectionElem::Field(..)
+            | ProjectionElem::Index(_) => {}
         }
+    }
 
-        match place_base {
-            PlaceBase::Static(box Static { kind: StaticKind::Static, .. }) => {
-                Err((span, "cannot access `static` items in const fn".into()))
-            }
-            PlaceBase::Local(_)
-            | PlaceBase::Static(box Static { kind: StaticKind::Promoted(_, _), .. }) => Ok(()),
+    match place.base {
+        PlaceBase::Static(box Static { kind: StaticKind::Static, .. }) => {
+            Err((span, "cannot access `static` items in const fn".into()))
         }
-    })
+        PlaceBase::Local(_)
+        | PlaceBase::Static(box Static { kind: StaticKind::Promoted(_, _), .. }) => Ok(()),
+    }
 }
 
 fn check_terminator(
diff --git a/src/librustc_mir/transform/remove_noop_landing_pads.rs b/src/librustc_mir/transform/remove_noop_landing_pads.rs
index 73089a2106f6b..70b11944e2fbc 100644
--- a/src/librustc_mir/transform/remove_noop_landing_pads.rs
+++ b/src/librustc_mir/transform/remove_noop_landing_pads.rs
@@ -41,10 +41,10 @@ impl RemoveNoopLandingPads {
                     // These are all nops in a landing pad
                 }
 
-                StatementKind::Assign(Place {
+                StatementKind::Assign(box(Place {
                     base: PlaceBase::Local(_),
-                    projection: None,
-                }, box Rvalue::Use(_)) => {
+                    projection: box [],
+                }, Rvalue::Use(_))) => {
                     // Writing to a local (e.g., a drop flag) does not
                     // turn a landing pad to a non-nop
                 }
diff --git a/src/librustc_mir/transform/rustc_peek.rs b/src/librustc_mir/transform/rustc_peek.rs
index 1d3bf247387a7..68fa082d29407 100644
--- a/src/librustc_mir/transform/rustc_peek.rs
+++ b/src/librustc_mir/transform/rustc_peek.rs
@@ -120,11 +120,11 @@ fn each_block<'tcx, O>(
     let peek_arg_place = match args[0] {
         mir::Operand::Copy(ref place @ mir::Place {
             base: mir::PlaceBase::Local(_),
-            projection: None,
+            projection: box [],
         }) |
         mir::Operand::Move(ref place @ mir::Place {
             base: mir::PlaceBase::Local(_),
-            projection: None,
+            projection: box [],
         }) => Some(place),
         _ => None,
     };
@@ -150,7 +150,7 @@ fn each_block<'tcx, O>(
     for (j, stmt) in statements.iter().enumerate() {
         debug!("rustc_peek: ({:?},{}) {:?}", bb, j, stmt);
         let (place, rvalue) = match stmt.kind {
-            mir::StatementKind::Assign(ref place, ref rvalue) => {
+            mir::StatementKind::Assign(box(ref place, ref rvalue)) => {
                 (place, rvalue)
             }
             mir::StatementKind::FakeRead(..) |
@@ -166,7 +166,7 @@ fn each_block<'tcx, O>(
         };
 
         if place == peek_arg_place {
-            if let mir::Rvalue::Ref(_, mir::BorrowKind::Shared, ref peeking_at_place) = **rvalue {
+            if let mir::Rvalue::Ref(_, mir::BorrowKind::Shared, ref peeking_at_place) = *rvalue {
                 // Okay, our search is over.
                 match move_data.rev_lookup.find(peeking_at_place.as_ref()) {
                     LookupResult::Exact(peek_mpi) => {
diff --git a/src/librustc_mir/transform/uniform_array_move_out.rs b/src/librustc_mir/transform/uniform_array_move_out.rs
index 8199a252e78b0..34ad5cb5dc787 100644
--- a/src/librustc_mir/transform/uniform_array_move_out.rs
+++ b/src/librustc_mir/transform/uniform_array_move_out.rs
@@ -61,14 +61,14 @@ impl<'a, 'tcx> Visitor<'tcx> for UniformArrayMoveOutVisitor<'a, 'tcx> {
                     rvalue: &Rvalue<'tcx>,
                     location: Location) {
         if let Rvalue::Use(Operand::Move(ref src_place)) = rvalue {
-            if let Some(ref proj) = src_place.projection {
+            if let box [proj_base @ .., elem] = &src_place.projection {
                 if let ProjectionElem::ConstantIndex{offset: _,
                                                      min_length: _,
-                                                     from_end: false} = proj.elem {
+                                                     from_end: false} = elem {
                     // no need to transformation
                 } else {
                     let place_ty =
-                        Place::ty_from(&src_place.base, &proj.base, self.body, self.tcx).ty;
+                        Place::ty_from(&src_place.base, proj_base, self.body, self.tcx).ty;
                     if let ty::Array(item_ty, const_size) = place_ty.sty {
                         if let Some(size) = const_size.try_eval_usize(self.tcx, self.param_env) {
                             assert!(size <= u32::max_value() as u64,
@@ -78,7 +78,7 @@ impl<'a, 'tcx> Visitor<'tcx> for UniformArrayMoveOutVisitor<'a, 'tcx> {
                                 location,
                                 dst_place,
                                 &src_place.base,
-                                proj,
+                                &src_place.projection,
                                 item_ty,
                                 size as u32,
                             );
@@ -97,73 +97,76 @@ impl<'a, 'tcx> UniformArrayMoveOutVisitor<'a, 'tcx> {
                location: Location,
                dst_place: &Place<'tcx>,
                base: &PlaceBase<'tcx>,
-               proj: &Projection<'tcx>,
+               proj: &[PlaceElem<'tcx>],
                item_ty: &'tcx ty::TyS<'tcx>,
                size: u32) {
-        match proj.elem {
-            // uniforms statements like_10 = move _2[:-1];
-            ProjectionElem::Subslice{from, to} => {
-                self.patch.make_nop(location);
-                let temps : Vec<_> = (from..(size-to)).map(|i| {
-                    let temp = self.patch.new_temp(item_ty, self.body.source_info(location).span);
-                    self.patch.add_statement(location, StatementKind::StorageLive(temp));
+        if let [proj_base @ .., elem] = proj {
+            match elem {
+                // uniforms statements like_10 = move _2[:-1];
+                ProjectionElem::Subslice{from, to} => {
+                    self.patch.make_nop(location);
+                    let temps : Vec<_> = (*from..(size-*to)).map(|i| {
+                        let temp =
+                            self.patch.new_temp(item_ty, self.body.source_info(location).span);
+                        self.patch.add_statement(location, StatementKind::StorageLive(temp));
+
+                        let mut projection = proj_base.to_vec();
+                        projection.push(ProjectionElem::ConstantIndex {
+                            offset: i,
+                            min_length: size,
+                            from_end: false,
+                        });
+                        self.patch.add_assign(location,
+                                              Place::from(temp),
+                                              Rvalue::Use(
+                                                  Operand::Move(
+                                                      Place {
+                                                          base: base.clone(),
+                                                          projection: projection.into_boxed_slice(),
+                                                      }
+                                                  )
+                                              )
+                        );
+                        temp
+                    }).collect();
+                    self.patch.add_assign(
+                        location,
+                        dst_place.clone(),
+                        Rvalue::Aggregate(
+                            box AggregateKind::Array(item_ty),
+                            temps.iter().map(
+                                |x| Operand::Move(Place::from(*x))
+                            ).collect()
+                        )
+                    );
+                    for temp in temps {
+                        self.patch.add_statement(location, StatementKind::StorageDead(temp));
+                    }
+                }
+                // uniforms statements like _11 = move _2[-1 of 1];
+                ProjectionElem::ConstantIndex{offset, min_length: _, from_end: true} => {
+                    self.patch.make_nop(location);
+
+                    let mut projection = proj_base.to_vec();
+                    projection.push(ProjectionElem::ConstantIndex {
+                        offset: size - offset,
+                        min_length: size,
+                        from_end: false,
+                    });
                     self.patch.add_assign(location,
-                                          Place::from(temp),
+                                          dst_place.clone(),
                                           Rvalue::Use(
                                               Operand::Move(
                                                   Place {
                                                       base: base.clone(),
-                                                      projection: Some(box Projection {
-                                                          base: proj.base.clone(),
-                                                          elem: ProjectionElem::ConstantIndex {
-                                                              offset: i,
-                                                              min_length: size,
-                                                              from_end: false,
-                                                          }
-                                                      }),
+                                                      projection: projection.into_boxed_slice(),
                                                   }
                                               )
                                           )
                     );
-                    temp
-                }).collect();
-                self.patch.add_assign(
-                    location,
-                    dst_place.clone(),
-                    Rvalue::Aggregate(
-                        box AggregateKind::Array(item_ty),
-                        temps.iter().map(
-                            |x| Operand::Move(Place::from(*x))
-                        ).collect()
-                    )
-                );
-                for temp in temps {
-                    self.patch.add_statement(location, StatementKind::StorageDead(temp));
                 }
+                _ => {}
             }
-            // uniforms statements like _11 = move _2[-1 of 1];
-            ProjectionElem::ConstantIndex{offset, min_length: _, from_end: true} => {
-                self.patch.make_nop(location);
-                self.patch.add_assign(location,
-                                      dst_place.clone(),
-                                      Rvalue::Use(
-                                          Operand::Move(
-                                              Place {
-                                                  base: base.clone(),
-                                                  projection: Some(box Projection {
-                                                      base: proj.base.clone(),
-                                                      elem: ProjectionElem::ConstantIndex {
-                                                          offset: size - offset,
-                                                          min_length: size,
-                                                          from_end: false,
-                                                      },
-                                                  }),
-                                              }
-                                          )
-                                      )
-                );
-            }
-            _ => {}
         }
     }
 }
@@ -197,12 +200,12 @@ impl<'tcx> MirPass<'tcx> for RestoreSubsliceArrayMoveOut {
 
             for candidate in &visitor.candidates {
                 let statement = &body[candidate.block].statements[candidate.statement_index];
-                if let StatementKind::Assign(ref dst_place, ref rval) = statement.kind {
-                    if let Rvalue::Aggregate(box AggregateKind::Array(_), ref items) = **rval {
+                if let StatementKind::Assign(box(ref dst_place, ref rval)) = statement.kind {
+                    if let Rvalue::Aggregate(box AggregateKind::Array(_), ref items) = *rval {
                         let items : Vec<_> = items.iter().map(|item| {
                             if let Operand::Move(Place {
                                 base: PlaceBase::Local(local),
-                                projection: None,
+                                projection: box [],
                             }) = item {
                                 let local_use = &visitor.locals_use[*local];
                                 let opt_index_and_place =
@@ -269,16 +272,17 @@ impl RestoreSubsliceArrayMoveOut {
             }
             patch.make_nop(candidate);
             let size = opt_size.unwrap() as u32;
-            patch.add_assign(candidate,
-                             dst_place.clone(),
-                             Rvalue::Use(
-                                 Operand::Move(
-                                     Place {
-                                         base: src_place.base.clone(),
-                                         projection: Some(box Projection {
-                                             base: src_place.projection.clone(),
-                                             elem: ProjectionElem::Subslice{
-                                                 from: min, to: size - max - 1}})})));
+
+            let mut projection = src_place.projection.to_vec();
+            projection.push(ProjectionElem::Subslice { from: min, to: size - max - 1 });
+            patch.add_assign(
+                candidate,
+                dst_place.clone(),
+                Rvalue::Use(Operand::Move(Place {
+                    base: src_place.base.clone(),
+                    projection: projection.into_boxed_slice(),
+                })),
+            );
         }
     }
 
@@ -289,23 +293,34 @@ impl RestoreSubsliceArrayMoveOut {
             if block.statements.len() > location.statement_index {
                 let statement = &block.statements[location.statement_index];
                 if let StatementKind::Assign(
-                    Place {
-                        base: PlaceBase::Local(_),
-                        projection: None,
-                    },
-                    box Rvalue::Use(Operand::Move(Place {
-                        base,
-                        projection: Some(box Projection {
-                            base: proj_base,
-                            elem: ProjectionElem::ConstantIndex {
+                    box(
+                        Place {
+                            base: PlaceBase::Local(_),
+                            projection: box [],
+                        },
+                        Rvalue::Use(Operand::Move(Place {
+                            base: _,
+                            projection: box [.., ProjectionElem::ConstantIndex {
                                 offset, min_length: _, from_end: false
-                            }
-                        }),
-                    }))) = &statement.kind {
-                    return Some((*offset, PlaceRef {
-                        base,
-                        projection: proj_base,
-                    }))
+                            }],
+                        })),
+                    )
+                ) = &statement.kind {
+                    // FIXME remove once we can use slices patterns
+                    if let StatementKind::Assign(
+                        box(
+                            _,
+                            Rvalue::Use(Operand::Move(Place {
+                                base,
+                                projection: box [proj_base @ .., _],
+                            })),
+                        )
+                    ) = &statement.kind {
+                        return Some((*offset, PlaceRef {
+                            base,
+                            projection: proj_base,
+                        }))
+                    }
                 }
             }
         }
diff --git a/src/librustc_mir/util/aggregate.rs b/src/librustc_mir/util/aggregate.rs
index 98e70671ab715..b3565d40b8e21 100644
--- a/src/librustc_mir/util/aggregate.rs
+++ b/src/librustc_mir/util/aggregate.rs
@@ -24,7 +24,7 @@ pub fn expand_aggregate<'tcx>(
             if adt_def.is_enum() {
                 set_discriminant = Some(Statement {
                     kind: StatementKind::SetDiscriminant {
-                        place: lhs.clone(),
+                        place: box(lhs.clone()),
                         variant_index,
                     },
                     source_info,
@@ -39,7 +39,7 @@ pub fn expand_aggregate<'tcx>(
             let variant_index = VariantIdx::new(0);
             set_discriminant = Some(Statement {
                 kind: StatementKind::SetDiscriminant {
-                    place: lhs.clone(),
+                    place: box(lhs.clone()),
                     variant_index,
                 },
                 source_info,
@@ -70,7 +70,7 @@ pub fn expand_aggregate<'tcx>(
         };
         Statement {
             source_info,
-            kind: StatementKind::Assign(lhs_field, box Rvalue::Use(op)),
+            kind: StatementKind::Assign(box(lhs_field, Rvalue::Use(op))),
         }
     }).chain(set_discriminant)
 }
diff --git a/src/librustc_mir/util/alignment.rs b/src/librustc_mir/util/alignment.rs
index b8ef77da02e60..a75c1af04f047 100644
--- a/src/librustc_mir/util/alignment.rs
+++ b/src/librustc_mir/util/alignment.rs
@@ -38,14 +38,15 @@ fn is_within_packed<'tcx, L>(tcx: TyCtxt<'tcx>, local_decls: &L, place: &Place<'
 where
     L: HasLocalDecls<'tcx>,
 {
-    let mut place_projection = &place.projection;
+    let mut cursor = &*place.projection;
+    while let [proj_base @ .., elem] = cursor {
+        cursor = proj_base;
 
-    while let Some(proj) = place_projection {
-        match proj.elem {
+        match elem {
             // encountered a Deref, which is ABI-aligned
             ProjectionElem::Deref => break,
             ProjectionElem::Field(..) => {
-                let ty = Place::ty_from(&place.base, &proj.base, local_decls, tcx).ty;
+                let ty = Place::ty_from(&place.base, proj_base, local_decls, tcx).ty;
                 match ty.sty {
                     ty::Adt(def, _) if def.repr.packed() => {
                         return true
@@ -55,7 +56,6 @@ where
             }
             _ => {}
         }
-        place_projection = &proj.base;
     }
 
     false
diff --git a/src/librustc_mir/util/borrowck_errors.rs b/src/librustc_mir/util/borrowck_errors.rs
index 3359d1b3bbfe1..cf9ef55c17b34 100644
--- a/src/librustc_mir/util/borrowck_errors.rs
+++ b/src/librustc_mir/util/borrowck_errors.rs
@@ -50,7 +50,7 @@ impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
             self,
             span,
             E0381,
-            "{} of possibly uninitialized variable: `{}`",
+            "{} of possibly-uninitialized variable: `{}`",
             verb,
             desc,
         )
diff --git a/src/librustc_mir/util/elaborate_drops.rs b/src/librustc_mir/util/elaborate_drops.rs
index f3e03e7f81daa..52ad97bbde1d7 100644
--- a/src/librustc_mir/util/elaborate_drops.rs
+++ b/src/librustc_mir/util/elaborate_drops.rs
@@ -586,10 +586,7 @@ where
                 BorrowKind::Mut { allow_two_phase_borrow: false },
                 Place {
                     base: PlaceBase::Local(cur),
-                    projection: Some(Box::new(Projection {
-                        base: None,
-                        elem: ProjectionElem::Deref,
-                    })),
+                    projection: Box::new([ProjectionElem::Deref]),
                 }
              ),
              Rvalue::BinaryOp(BinOp::Offset, move_(&Place::from(cur)), one))
@@ -981,7 +978,7 @@ where
     fn assign(&self, lhs: &Place<'tcx>, rhs: Rvalue<'tcx>) -> Statement<'tcx> {
         Statement {
             source_info: self.source_info,
-            kind: StatementKind::Assign(lhs.clone(), box rhs)
+            kind: StatementKind::Assign(box(lhs.clone(), rhs))
         }
     }
 }
diff --git a/src/librustc_mir/util/patch.rs b/src/librustc_mir/util/patch.rs
index eb457dacf8467..2ea9924af7f28 100644
--- a/src/librustc_mir/util/patch.rs
+++ b/src/librustc_mir/util/patch.rs
@@ -120,7 +120,7 @@ impl<'tcx> MirPatch<'tcx> {
     }
 
     pub fn add_assign(&mut self, loc: Location, place: Place<'tcx>, rv: Rvalue<'tcx>) {
-        self.add_statement(loc, StatementKind::Assign(place, box rv));
+        self.add_statement(loc, StatementKind::Assign(box(place, rv)));
     }
 
     pub fn make_nop(&mut self, loc: Location) {
diff --git a/src/librustc_mir/util/pretty.rs b/src/librustc_mir/util/pretty.rs
index ac2701971dfd5..c35c9e4da9f48 100644
--- a/src/librustc_mir/util/pretty.rs
+++ b/src/librustc_mir/util/pretty.rs
@@ -227,12 +227,12 @@ pub(crate) fn create_dump_file(
     pass_name: &str,
     disambiguator: &dyn Display,
     source: MirSource<'tcx>,
-) -> io::Result<fs::File> {
+) -> io::Result<io::BufWriter<fs::File>> {
     let file_path = dump_path(tcx, extension, pass_num, pass_name, disambiguator, source);
     if let Some(parent) = file_path.parent() {
         fs::create_dir_all(parent)?;
     }
-    fs::File::create(&file_path)
+    Ok(io::BufWriter::new(fs::File::create(&file_path)?))
 }
 
 /// Write out a human-readable textual representation for the given MIR.
diff --git a/src/librustc_msan/build.rs b/src/librustc_msan/build.rs
index 1c66b0a9cd3cf..a81786ee36d04 100644
--- a/src/librustc_msan/build.rs
+++ b/src/librustc_msan/build.rs
@@ -4,6 +4,10 @@ use build_helper::sanitizer_lib_boilerplate;
 use cmake::Config;
 
 fn main() {
+    println!("cargo:rerun-if-env-changed=RUSTC_BUILD_SANITIZERS");
+    if env::var("RUSTC_BUILD_SANITIZERS") != Ok("1".to_string()) {
+        return;
+    }
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
         build_helper::restore_library_path();
 
diff --git a/src/librustc_passes/error_codes.rs b/src/librustc_passes/error_codes.rs
index a30cd8a627fe3..af07c790e2a87 100644
--- a/src/librustc_passes/error_codes.rs
+++ b/src/librustc_passes/error_codes.rs
@@ -1,6 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 /*
 E0014: r##"
 Constants can only be initialized by a constant value or, in a future
@@ -320,10 +318,8 @@ async fn foo() {}
 ```
 
 Switch to the Rust 2018 edition to use `async fn`.
-"##
-}
-
-register_diagnostics! {
+"##,
+;
     E0226, // only a single explicit lifetime bound is permitted
     E0472, // asm! is unsupported on this target
     E0561, // patterns aren't allowed in function pointer types
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index 5614b570b927a..a5a8315a1e73f 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -8,8 +8,7 @@
 
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
-#![feature(bind_by_move_pattern_guards)]
-#![feature(rustc_diagnostic_macros)]
+#![cfg_attr(bootstrap, feature(bind_by_move_pattern_guards))]
 
 #![recursion_limit="256"]
 
@@ -18,7 +17,7 @@ extern crate rustc;
 
 use rustc::ty::query::Providers;
 
-mod error_codes;
+pub mod error_codes;
 
 pub mod ast_validation;
 pub mod rvalue_promotion;
@@ -26,8 +25,6 @@ pub mod hir_stats;
 pub mod layout_test;
 pub mod loops;
 
-__build_diagnostic_array! { librustc_passes, DIAGNOSTICS }
-
 pub fn provide(providers: &mut Providers<'_>) {
     rvalue_promotion::provide(providers);
     loops::provide(providers);
diff --git a/src/librustc_plugin/error_codes.rs b/src/librustc_plugin/error_codes.rs
index b5f6a8d905d31..7b3f01c0ee111 100644
--- a/src/librustc_plugin/error_codes.rs
+++ b/src/librustc_plugin/error_codes.rs
@@ -1,9 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
-
-}
-
-register_diagnostics! {
-    E0498  // malformed plugin attribute
+syntax::register_diagnostics! {
+;
+    E0498,  // malformed plugin attribute
 }
diff --git a/src/librustc_plugin/lib.rs b/src/librustc_plugin/lib.rs
index 952bc9fff6a71..4e1a47c503e59 100644
--- a/src/librustc_plugin/lib.rs
+++ b/src/librustc_plugin/lib.rs
@@ -54,15 +54,12 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 
 #![recursion_limit="256"]
 
 pub use registry::Registry;
 
-mod error_codes;
+pub mod error_codes;
 pub mod registry;
 pub mod load;
 pub mod build;
-
-__build_diagnostic_array! { librustc_plugin, DIAGNOSTICS }
diff --git a/src/librustc_privacy/error_codes.rs b/src/librustc_privacy/error_codes.rs
index 70a799d426a07..67066466f1d22 100644
--- a/src/librustc_privacy/error_codes.rs
+++ b/src/librustc_privacy/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0445: r##"
 A private trait was used on a public type parameter bound. Erroneous code
@@ -154,8 +154,5 @@ let f = Bar::Foo::new(); // ok!
 ```
 "##,
 
-}
-
-register_diagnostics! {
 //  E0450, moved into resolve
 }
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 146058963b69d..1e61f78c357df 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -2,7 +2,6 @@
 
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 
 #![recursion_limit="256"]
 
@@ -31,7 +30,7 @@ use syntax_pos::Span;
 use std::{cmp, fmt, mem};
 use std::marker::PhantomData;
 
-mod error_codes;
+pub mod error_codes;
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Generic infrastructure used to implement specific visitors below.
@@ -2035,5 +2034,3 @@ fn check_private_in_public(tcx: TyCtxt<'_>, krate: CrateNum) {
     };
     krate.visit_all_item_likes(&mut DeepVisitor::new(&mut visitor));
 }
-
-__build_diagnostic_array! { librustc_privacy, DIAGNOSTICS }
diff --git a/src/librustc_resolve/build_reduced_graph.rs b/src/librustc_resolve/build_reduced_graph.rs
index 165a4c707bb6d..11dcf5b4b0019 100644
--- a/src/librustc_resolve/build_reduced_graph.rs
+++ b/src/librustc_resolve/build_reduced_graph.rs
@@ -31,7 +31,7 @@ use syntax::ast::{Name, Ident};
 use syntax::attr;
 
 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
-use syntax::ast::{MetaItemKind, StmtKind, TraitItem, TraitItemKind, Variant};
+use syntax::ast::{MetaItemKind, StmtKind, TraitItem, TraitItemKind};
 use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::expand::AstFragment;
 use syntax::ext::hygiene::ExpnId;
@@ -126,7 +126,8 @@ impl<'a> Resolver<'a> {
     crate fn macro_def_scope(&mut self, expn_id: ExpnId) -> Module<'a> {
         let def_id = match self.macro_defs.get(&expn_id) {
             Some(def_id) => *def_id,
-            None => return self.graph_root,
+            None => return self.ast_transform_scopes.get(&expn_id)
+                .unwrap_or(&self.graph_root),
         };
         if let Some(id) = self.definitions.as_local_node_id(def_id) {
             self.local_macro_def_scopes[&id]
@@ -579,7 +580,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     }
 
     /// Constructs the reduced graph for one item.
-    fn build_reduced_graph_for_item(&mut self, item: &Item) {
+    fn build_reduced_graph_for_item(&mut self, item: &'b Item) {
         let parent_scope = &self.parent_scope;
         let parent = parent_scope.module;
         let expansion = parent_scope.expansion;
@@ -715,22 +716,17 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 self.r.define(parent, ident, TypeNS, (res, vis, sp, expansion));
             }
 
-            ItemKind::Enum(ref enum_definition, _) => {
-                let module_kind = ModuleKind::Def(
-                    DefKind::Enum,
-                    self.r.definitions.local_def_id(item.id),
-                    ident.name,
-                );
+            ItemKind::Enum(_, _) => {
+                let def_id = self.r.definitions.local_def_id(item.id);
+                self.r.variant_vis.insert(def_id, vis);
+                let module_kind = ModuleKind::Def(DefKind::Enum, def_id, ident.name);
                 let module = self.r.new_module(parent,
                                              module_kind,
                                              parent.normal_ancestor_id,
                                              expansion,
                                              item.span);
                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
-
-                for variant in &(*enum_definition).variants {
-                    self.build_reduced_graph_for_variant(variant, module, vis);
-                }
+                self.parent_scope.module = module;
             }
 
             ItemKind::TraitAlias(..) => {
@@ -815,40 +811,6 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         }
     }
 
-    // Constructs the reduced graph for one variant. Variants exist in the
-    // type and value namespaces.
-    fn build_reduced_graph_for_variant(&mut self,
-                                       variant: &Variant,
-                                       parent: Module<'a>,
-                                       vis: ty::Visibility) {
-        let expn_id = self.parent_scope.expansion;
-        let ident = variant.ident;
-
-        // Define a name in the type namespace.
-        let def_id = self.r.definitions.local_def_id(variant.id);
-        let res = Res::Def(DefKind::Variant, def_id);
-        self.r.define(parent, ident, TypeNS, (res, vis, variant.span, expn_id));
-
-        // If the variant is marked as non_exhaustive then lower the visibility to within the
-        // crate.
-        let mut ctor_vis = vis;
-        let has_non_exhaustive = attr::contains_name(&variant.attrs, sym::non_exhaustive);
-        if has_non_exhaustive && vis == ty::Visibility::Public {
-            ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
-        }
-
-        // Define a constructor name in the value namespace.
-        // Braced variants, unlike structs, generate unusable names in
-        // value namespace, they are reserved for possible future use.
-        // It's ok to use the variant's id as a ctor id since an
-        // error will be reported on any use of such resolution anyway.
-        let ctor_node_id = variant.data.ctor_id().unwrap_or(variant.id);
-        let ctor_def_id = self.r.definitions.local_def_id(ctor_node_id);
-        let ctor_kind = CtorKind::from_ast(&variant.data);
-        let ctor_res = Res::Def(DefKind::Ctor(CtorOf::Variant, ctor_kind), ctor_def_id);
-        self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, variant.span, expn_id));
-    }
-
     /// Constructs the reduced graph for one foreign item.
     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem) {
         let (res, ns) = match item.node {
@@ -1188,7 +1150,6 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
             ItemKind::Mod(..) => self.contains_macro_use(&item.attrs),
             _ => false,
         };
-
         let orig_current_module = self.parent_scope.module;
         let orig_current_legacy_scope = self.parent_scope.legacy;
         self.build_reduced_graph_for_item(item);
@@ -1252,9 +1213,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
         let expansion = self.parent_scope.expansion;
         self.r.define(parent, item.ident, ns, (res, vis, item.span, expansion));
 
-        self.parent_scope.module = parent.parent.unwrap(); // nearest normal ancestor
         visit::walk_trait_item(self, item);
-        self.parent_scope.module = parent;
     }
 
     fn visit_token(&mut self, t: Token) {
@@ -1273,4 +1232,92 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
         }
         visit::walk_attribute(self, attr);
     }
+
+    fn visit_arm(&mut self, arm: &'b ast::Arm) {
+        if arm.is_placeholder {
+            self.visit_invoc(arm.id);
+        } else {
+            visit::walk_arm(self, arm);
+        }
+    }
+
+    fn visit_field(&mut self, f: &'b ast::Field) {
+        if f.is_placeholder {
+            self.visit_invoc(f.id);
+        } else {
+            visit::walk_field(self, f);
+        }
+    }
+
+    fn visit_field_pattern(&mut self, fp: &'b ast::FieldPat) {
+        if fp.is_placeholder {
+            self.visit_invoc(fp.id);
+        } else {
+            visit::walk_field_pattern(self, fp);
+        }
+    }
+
+    fn visit_generic_param(&mut self, param: &'b ast::GenericParam) {
+        if param.is_placeholder {
+            self.visit_invoc(param.id);
+        } else {
+            visit::walk_generic_param(self, param);
+        }
+    }
+
+    fn visit_param(&mut self, p: &'b ast::Param) {
+        if p.is_placeholder {
+            self.visit_invoc(p.id);
+        } else {
+            visit::walk_param(self, p);
+        }
+    }
+
+    fn visit_struct_field(&mut self, sf: &'b ast::StructField) {
+        if sf.is_placeholder {
+            self.visit_invoc(sf.id);
+        } else {
+            visit::walk_struct_field(self, sf);
+        }
+    }
+
+    // Constructs the reduced graph for one variant. Variants exist in the
+    // type and value namespaces.
+    fn visit_variant(&mut self, variant: &'b ast::Variant) {
+        if variant.is_placeholder {
+            self.visit_invoc(variant.id);
+            return;
+        }
+
+        let parent = self.parent_scope.module;
+        let vis = self.r.variant_vis[&parent.def_id().expect("enum without def-id")];
+        let expn_id = self.parent_scope.expansion;
+        let ident = variant.ident;
+
+        // Define a name in the type namespace.
+        let def_id = self.r.definitions.local_def_id(variant.id);
+        let res = Res::Def(DefKind::Variant, def_id);
+        self.r.define(parent, ident, TypeNS, (res, vis, variant.span, expn_id));
+
+        // If the variant is marked as non_exhaustive then lower the visibility to within the
+        // crate.
+        let mut ctor_vis = vis;
+        let has_non_exhaustive = attr::contains_name(&variant.attrs, sym::non_exhaustive);
+        if has_non_exhaustive && vis == ty::Visibility::Public {
+            ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
+        }
+
+        // Define a constructor name in the value namespace.
+        // Braced variants, unlike structs, generate unusable names in
+        // value namespace, they are reserved for possible future use.
+        // It's ok to use the variant's id as a ctor id since an
+        // error will be reported on any use of such resolution anyway.
+        let ctor_node_id = variant.data.ctor_id().unwrap_or(variant.id);
+        let ctor_def_id = self.r.definitions.local_def_id(ctor_node_id);
+        let ctor_kind = CtorKind::from_ast(&variant.data);
+        let ctor_res = Res::Def(DefKind::Ctor(CtorOf::Variant, ctor_kind), ctor_def_id);
+        self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, variant.span, expn_id));
+
+        visit::walk_variant(self, variant);
+    }
 }
diff --git a/src/librustc_resolve/diagnostics.rs b/src/librustc_resolve/diagnostics.rs
index b79e0c2bd3b26..c479912b4ef81 100644
--- a/src/librustc_resolve/diagnostics.rs
+++ b/src/librustc_resolve/diagnostics.rs
@@ -604,6 +604,14 @@ impl<'a> Resolver<'a> {
         if lookup_ident.span.rust_2018() {
             let extern_prelude_names = self.extern_prelude.clone();
             for (ident, _) in extern_prelude_names.into_iter() {
+                if ident.span.from_expansion() {
+                    // Idents are adjusted to the root context before being
+                    // resolved in the extern prelude, so reporting this to the
+                    // user is no help. This skips the injected
+                    // `extern crate std` in the 2018 edition, which would
+                    // otherwise cause duplicate suggestions.
+                    continue;
+                }
                 if let Some(crate_id) = self.crate_loader.maybe_process_path_extern(ident.name,
                                                                                     ident.span) {
                     let crate_root = self.get_module(DefId {
diff --git a/src/librustc_resolve/error_codes.rs b/src/librustc_resolve/error_codes.rs
index 1faaf97e981c1..adbff67cc8dac 100644
--- a/src/librustc_resolve/error_codes.rs
+++ b/src/librustc_resolve/error_codes.rs
@@ -1,9 +1,7 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
 // Error messages for EXXXX errors.  Each message should start and end with a
 // new line, and be wrapped to 80 characters.  In vim you can `:set tw=80` and
 // use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0128: r##"
 Type parameter defaults can only use parameters that occur before them.
@@ -1662,10 +1660,7 @@ fn const_id<T, const N: T>() -> T { // error: const parameter
 }
 ```
 "##,
-
-}
-
-register_diagnostics! {
+;
 //  E0153, unused error code
 //  E0157, unused error code
 //  E0257,
diff --git a/src/librustc_resolve/late.rs b/src/librustc_resolve/late.rs
index e15d02a9f7ec7..aae283b745236 100644
--- a/src/librustc_resolve/late.rs
+++ b/src/librustc_resolve/late.rs
@@ -9,7 +9,7 @@ use GenericParameters::*;
 use RibKind::*;
 
 use crate::{path_names_to_string, BindingError, CrateLint, LexicalScopeBinding};
-use crate::{Module, ModuleOrUniformRoot, NameBinding, NameBindingKind, ParentScope, PathResult};
+use crate::{Module, ModuleOrUniformRoot, NameBindingKind, ParentScope, PathResult};
 use crate::{ResolutionError, Resolver, Segment, UseError};
 
 use log::debug;
@@ -18,7 +18,7 @@ use rustc::hir::def::{self, PartialRes, DefKind, CtorKind, PerNS};
 use rustc::hir::def::Namespace::{self, *};
 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc::hir::TraitCandidate;
-use rustc::util::nodemap::FxHashMap;
+use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use smallvec::{smallvec, SmallVec};
 use syntax::{unwrap_or, walk_list};
 use syntax::ast::*;
@@ -35,8 +35,10 @@ mod diagnostics;
 
 type Res = def::Res<NodeId>;
 
+type IdentMap<T> = FxHashMap<Ident, T>;
+
 /// Map from the name in a pattern to its binding mode.
-type BindingMap = FxHashMap<Ident, BindingInfo>;
+type BindingMap = IdentMap<BindingInfo>;
 
 #[derive(Copy, Clone, Debug)]
 struct BindingInfo {
@@ -73,6 +75,16 @@ impl PatternSource {
     }
 }
 
+/// Denotes whether the context for the set of already bound bindings is a `Product`
+/// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
+/// See those functions for more information.
+enum PatBoundCtx {
+    /// A product pattern context, e.g., `Variant(a, b)`.
+    Product,
+    /// An or-pattern context, e.g., `p_0 | ... | p_n`.
+    Or,
+}
+
 /// The rib kind restricts certain accesses,
 /// e.g. to a `Res::Local` of an outer item.
 #[derive(Copy, Clone, Debug)]
@@ -143,7 +155,7 @@ impl RibKind<'_> {
 /// resolving, the name is looked up from inside out.
 #[derive(Debug)]
 crate struct Rib<'a, R = Res> {
-    pub bindings: FxHashMap<Ident, R>,
+    pub bindings: IdentMap<R>,
     pub kind: RibKind<'a>,
 }
 
@@ -286,18 +298,18 @@ impl<'a> PathSource<'a> {
     }
 
     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
-        __diagnostic_used!(E0404);
-        __diagnostic_used!(E0405);
-        __diagnostic_used!(E0412);
-        __diagnostic_used!(E0422);
-        __diagnostic_used!(E0423);
-        __diagnostic_used!(E0425);
-        __diagnostic_used!(E0531);
-        __diagnostic_used!(E0532);
-        __diagnostic_used!(E0573);
-        __diagnostic_used!(E0574);
-        __diagnostic_used!(E0575);
-        __diagnostic_used!(E0576);
+        syntax::diagnostic_used!(E0404);
+        syntax::diagnostic_used!(E0405);
+        syntax::diagnostic_used!(E0412);
+        syntax::diagnostic_used!(E0422);
+        syntax::diagnostic_used!(E0423);
+        syntax::diagnostic_used!(E0425);
+        syntax::diagnostic_used!(E0531);
+        syntax::diagnostic_used!(E0532);
+        syntax::diagnostic_used!(E0573);
+        syntax::diagnostic_used!(E0574);
+        syntax::diagnostic_used!(E0575);
+        syntax::diagnostic_used!(E0576);
         match (self, has_unexpected_resolution) {
             (PathSource::Trait(_), true) => "E0404",
             (PathSource::Trait(_), false) => "E0405",
@@ -406,50 +418,32 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
             visit::walk_foreign_item(this, foreign_item);
         });
     }
-    fn visit_fn(&mut self,
-                function_kind: FnKind<'tcx>,
-                declaration: &'tcx FnDecl,
-                _: Span,
-                _: NodeId)
-    {
+    fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, _: Span, _: NodeId) {
         debug!("(resolving function) entering function");
-        let rib_kind = match function_kind {
+        let rib_kind = match fn_kind {
             FnKind::ItemFn(..) => FnItemRibKind,
             FnKind::Method(..) | FnKind::Closure(_) => NormalRibKind,
         };
 
         // Create a value rib for the function.
-        self.ribs[ValueNS].push(Rib::new(rib_kind));
-
-        // Create a label rib for the function.
-        self.label_ribs.push(Rib::new(rib_kind));
-
-        // Add each argument to the rib.
-        let mut bindings_list = FxHashMap::default();
-        for argument in &declaration.inputs {
-            self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
-
-            self.visit_ty(&argument.ty);
-
-            debug!("(resolving function) recorded argument");
-        }
-        visit::walk_fn_ret_ty(self, &declaration.output);
-
-        // Resolve the function body, potentially inside the body of an async closure
-        match function_kind {
-            FnKind::ItemFn(.., body) |
-            FnKind::Method(.., body) => {
-                self.visit_block(body);
-            }
-            FnKind::Closure(body) => {
-                self.visit_expr(body);
-            }
-        };
-
-        debug!("(resolving function) leaving function");
-
-        self.label_ribs.pop();
-        self.ribs[ValueNS].pop();
+        self.with_rib(ValueNS, rib_kind, |this| {
+            // Create a label rib for the function.
+            this.with_label_rib(rib_kind, |this| {
+                // Add each argument to the rib.
+                this.resolve_params(&declaration.inputs);
+
+                visit::walk_fn_ret_ty(this, &declaration.output);
+
+                // Resolve the function body, potentially inside the body of an async closure
+                match fn_kind {
+                    FnKind::ItemFn(.., body) |
+                    FnKind::Method(.., body) => this.visit_block(body),
+                    FnKind::Closure(body) => this.visit_expr(body),
+                };
+
+                debug!("(resolving function) leaving function");
+            })
+        });
     }
 
     fn visit_generics(&mut self, generics: &'tcx Generics) {
@@ -528,13 +522,14 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         // although it may be useful to track other components as well for diagnostics.
         let graph_root = resolver.graph_root;
         let parent_scope = ParentScope::module(graph_root);
+        let start_rib_kind = ModuleRibKind(graph_root);
         LateResolutionVisitor {
             r: resolver,
             parent_scope,
             ribs: PerNS {
-                value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
-                type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
-                macro_ns: vec![Rib::new(ModuleRibKind(graph_root))],
+                value_ns: vec![Rib::new(start_rib_kind)],
+                type_ns: vec![Rib::new(start_rib_kind)],
+                macro_ns: vec![Rib::new(start_rib_kind)],
             },
             label_ribs: Vec::new(),
             current_trait_ref: None,
@@ -588,23 +583,32 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     // generate a fake "implementation scope" containing all the
     // implementations thus found, for compatibility with old resolve pass.
 
-    fn with_scope<F, T>(&mut self, id: NodeId, f: F) -> T
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>) -> T
-    {
+    /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
+    fn with_rib<T>(
+        &mut self,
+        ns: Namespace,
+        kind: RibKind<'a>,
+        work: impl FnOnce(&mut Self) -> T,
+    ) -> T {
+        self.ribs[ns].push(Rib::new(kind));
+        let ret = work(self);
+        self.ribs[ns].pop();
+        ret
+    }
+
+    fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
         let id = self.r.definitions.local_def_id(id);
         let module = self.r.module_map.get(&id).cloned(); // clones a reference
         if let Some(module) = module {
             // Move down in the graph.
             let orig_module = replace(&mut self.parent_scope.module, module);
-            self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
-            self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
-
-            let ret = f(self);
-
-            self.parent_scope.module = orig_module;
-            self.ribs[ValueNS].pop();
-            self.ribs[TypeNS].pop();
-            ret
+            self.with_rib(ValueNS, ModuleRibKind(module), |this| {
+                this.with_rib(TypeNS, ModuleRibKind(module), |this| {
+                    let ret = f(this);
+                    this.parent_scope.module = orig_module;
+                    ret
+                })
+            })
         } else {
             f(self)
         }
@@ -808,7 +812,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     }
 
     fn with_generic_param_rib<'c, F>(&'c mut self, generic_params: GenericParameters<'a, 'c>, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
+        where F: FnOnce(&mut Self)
     {
         debug!("with_generic_param_rib");
         match generic_params {
@@ -894,38 +898,24 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         }
     }
 
-    fn with_label_rib<F>(&mut self, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
-        self.label_ribs.push(Rib::new(NormalRibKind));
+    fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) {
+        self.label_ribs.push(Rib::new(kind));
         f(self);
         self.label_ribs.pop();
     }
 
-    fn with_item_rib<F>(&mut self, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
-        self.ribs[ValueNS].push(Rib::new(ItemRibKind));
-        self.ribs[TypeNS].push(Rib::new(ItemRibKind));
-        f(self);
-        self.ribs[TypeNS].pop();
-        self.ribs[ValueNS].pop();
+    fn with_item_rib(&mut self, f: impl FnOnce(&mut Self)) {
+        self.with_rib(ValueNS, ItemRibKind, |this| this.with_rib(TypeNS, ItemRibKind, f))
     }
 
-    fn with_constant_rib<F>(&mut self, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
+    fn with_constant_rib(&mut self, f: impl FnOnce(&mut Self)) {
         debug!("with_constant_rib");
-        self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
-        self.label_ribs.push(Rib::new(ConstantItemRibKind));
-        f(self);
-        self.label_ribs.pop();
-        self.ribs[ValueNS].pop();
+        self.with_rib(ValueNS, ConstantItemRibKind, |this| {
+            this.with_label_rib(ConstantItemRibKind, f);
+        });
     }
 
-    fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>) -> T
-    {
+    fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
         // Handle nested impls (inside fn bodies)
         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
         let result = f(self);
@@ -933,9 +923,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         result
     }
 
-    fn with_current_self_item<T, F>(&mut self, self_item: &Item, f: F) -> T
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>) -> T
-    {
+    fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
         let previous_value = replace(&mut self.current_self_item, Some(self_item.id));
         let result = f(self);
         self.current_self_item = previous_value;
@@ -943,9 +931,11 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     }
 
     /// When evaluating a `trait` use its associated types' idents for suggestionsa in E0412.
-    fn with_trait_items<T, F>(&mut self, trait_items: &Vec<TraitItem>, f: F) -> T
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>) -> T
-    {
+    fn with_trait_items<T>(
+        &mut self,
+        trait_items: &Vec<TraitItem>,
+        f: impl FnOnce(&mut Self) -> T,
+    ) -> T {
         let trait_assoc_types = replace(
             &mut self.current_trait_assoc_types,
             trait_items.iter().filter_map(|item| match &item.node {
@@ -959,9 +949,11 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
     }
 
     /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
-    fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>, Option<DefId>) -> T
-    {
+    fn with_optional_trait_ref<T>(
+        &mut self,
+        opt_trait_ref: Option<&TraitRef>,
+        f: impl FnOnce(&mut Self, Option<DefId>) -> T
+    ) -> T {
         let mut new_val = None;
         let mut new_id = None;
         if let Some(trait_ref) = opt_trait_ref {
@@ -996,27 +988,18 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         result
     }
 
-    fn with_self_rib<F>(&mut self, self_res: Res, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
+    fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
         let mut self_type_rib = Rib::new(NormalRibKind);
 
         // Plain insert (no renaming, since types are not currently hygienic)
         self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
-        self.ribs[TypeNS].push(self_type_rib);
+        self.ribs[ns].push(self_type_rib);
         f(self);
-        self.ribs[TypeNS].pop();
+        self.ribs[ns].pop();
     }
 
-    fn with_self_struct_ctor_rib<F>(&mut self, impl_id: DefId, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
-        let self_res = Res::SelfCtor(impl_id);
-        let mut self_type_rib = Rib::new(NormalRibKind);
-        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
-        self.ribs[ValueNS].push(self_type_rib);
-        f(self);
-        self.ribs[ValueNS].pop();
+    fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
+        self.with_self_rib_ns(TypeNS, self_res, f)
     }
 
     fn resolve_implementation(&mut self,
@@ -1044,8 +1027,8 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
                         this.visit_generics(generics);
                         // Resolve the items within the impl.
                         this.with_current_self_type(self_type, |this| {
-                            this.with_self_struct_ctor_rib(item_def_id, |this| {
-                                debug!("resolve_implementation with_self_struct_ctor_rib");
+                            this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
+                                debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
                                 for impl_item in impl_items {
                                     // We also need a new scope for the impl item type parameters.
                                     let generic_params = HasGenericParams(&impl_item.generics,
@@ -1135,6 +1118,15 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         }
     }
 
+    fn resolve_params(&mut self, params: &[Param]) {
+        let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
+        for Param { pat, ty, .. } in params {
+            self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
+            self.visit_ty(ty);
+            debug!("(resolving function / closure) recorded parameter");
+        }
+    }
+
     fn resolve_local(&mut self, local: &Local) {
         // Resolve the type.
         walk_list!(self, visit_ty, &local.ty);
@@ -1143,72 +1135,93 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         walk_list!(self, visit_expr, &local.init);
 
         // Resolve the pattern.
-        self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap::default());
+        self.resolve_pattern_top(&local.pat, PatternSource::Let);
     }
 
-    // build a map from pattern identifiers to binding-info's.
-    // this is done hygienically. This could arise for a macro
-    // that expands into an or-pattern where one 'x' was from the
-    // user and one 'x' came from the macro.
+    /// build a map from pattern identifiers to binding-info's.
+    /// this is done hygienically. This could arise for a macro
+    /// that expands into an or-pattern where one 'x' was from the
+    /// user and one 'x' came from the macro.
     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
         let mut binding_map = FxHashMap::default();
 
         pat.walk(&mut |pat| {
-            if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
-                if sub_pat.is_some() || match self.r.partial_res_map.get(&pat.id)
-                                                                  .map(|res| res.base_res()) {
-                    Some(Res::Local(..)) => true,
-                    _ => false,
-                } {
-                    let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
-                    binding_map.insert(ident, binding_info);
+            match pat.node {
+                PatKind::Ident(binding_mode, ident, ref sub_pat)
+                    if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
+                {
+                    binding_map.insert(ident, BindingInfo { span: ident.span, binding_mode });
+                }
+                PatKind::Or(ref ps) => {
+                    // Check the consistency of this or-pattern and
+                    // then add all bindings to the larger map.
+                    for bm in self.check_consistent_bindings(ps) {
+                        binding_map.extend(bm);
+                    }
+                    return false;
                 }
+                _ => {}
             }
+
             true
         });
 
         binding_map
     }
 
-    // Checks that all of the arms in an or-pattern have exactly the
-    // same set of bindings, with the same binding modes for each.
-    fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) {
+    fn is_base_res_local(&self, nid: NodeId) -> bool {
+        match self.r.partial_res_map.get(&nid).map(|res| res.base_res()) {
+            Some(Res::Local(..)) => true,
+            _ => false,
+        }
+    }
+
+    /// Checks that all of the arms in an or-pattern have exactly the
+    /// same set of bindings, with the same binding modes for each.
+    fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
         let mut missing_vars = FxHashMap::default();
         let mut inconsistent_vars = FxHashMap::default();
 
-        for pat_outer in pats.iter() {
-            let map_outer = self.binding_mode_map(&pat_outer);
-
-            for pat_inner in pats.iter().filter(|pat| pat.id != pat_outer.id) {
-                let map_inner = self.binding_mode_map(&pat_inner);
-
-                for (&key_inner, &binding_inner) in map_inner.iter() {
-                    match map_outer.get(&key_inner) {
-                        None => {  // missing binding
-                            let binding_error = missing_vars
-                                .entry(key_inner.name)
-                                .or_insert(BindingError {
-                                    name: key_inner.name,
-                                    origin: BTreeSet::new(),
-                                    target: BTreeSet::new(),
-                                    could_be_path:
-                                        key_inner.name.as_str().starts_with(char::is_uppercase)
-                                });
-                            binding_error.origin.insert(binding_inner.span);
-                            binding_error.target.insert(pat_outer.span);
-                        }
-                        Some(binding_outer) => {  // check consistent binding
-                            if binding_outer.binding_mode != binding_inner.binding_mode {
-                                inconsistent_vars
-                                    .entry(key_inner.name)
-                                    .or_insert((binding_inner.span, binding_outer.span));
-                            }
+        // 1) Compute the binding maps of all arms.
+        let maps = pats.iter()
+            .map(|pat| self.binding_mode_map(pat))
+            .collect::<Vec<_>>();
+
+        // 2) Record any missing bindings or binding mode inconsistencies.
+        for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) {
+            // Check against all arms except for the same pattern which is always self-consistent.
+            let inners = pats.iter().enumerate()
+                .filter(|(_, pat)| pat.id != pat_outer.id)
+                .flat_map(|(idx, _)| maps[idx].iter())
+                .map(|(key, binding)| (key.name, map_outer.get(&key), binding));
+
+            for (name, info, &binding_inner) in inners {
+                match info {
+                    None => { // The inner binding is missing in the outer.
+                        let binding_error = missing_vars
+                            .entry(name)
+                            .or_insert_with(|| BindingError {
+                                name,
+                                origin: BTreeSet::new(),
+                                target: BTreeSet::new(),
+                                could_be_path: name.as_str().starts_with(char::is_uppercase),
+                            });
+                        binding_error.origin.insert(binding_inner.span);
+                        binding_error.target.insert(pat_outer.span);
+                    }
+                    Some(binding_outer) => {
+                        if binding_outer.binding_mode != binding_inner.binding_mode {
+                            // The binding modes in the outer and inner bindings differ.
+                            inconsistent_vars
+                                .entry(name)
+                                .or_insert((binding_inner.span, binding_outer.span));
                         }
                     }
                 }
             }
         }
 
+        // 3) Report all missing variables we found.
         let mut missing_vars = missing_vars.iter_mut().collect::<Vec<_>>();
         missing_vars.sort();
         for (name, mut v) in missing_vars {
@@ -1220,212 +1233,245 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
                 ResolutionError::VariableNotBoundInPattern(v));
         }
 
+        // 4) Report all inconsistencies in binding modes we found.
         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
         inconsistent_vars.sort();
         for (name, v) in inconsistent_vars {
             self.r.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
         }
-    }
 
-    fn resolve_arm(&mut self, arm: &Arm) {
-        self.ribs[ValueNS].push(Rib::new(NormalRibKind));
-
-        self.resolve_pats(&arm.pats, PatternSource::Match);
-
-        if let Some(ref expr) = arm.guard {
-            self.visit_expr(expr)
-        }
-        self.visit_expr(&arm.body);
-
-        self.ribs[ValueNS].pop();
+        // 5) Finally bubble up all the binding maps.
+        maps
     }
 
-    /// Arising from `source`, resolve a sequence of patterns (top level or-patterns).
-    fn resolve_pats(&mut self, pats: &[P<Pat>], source: PatternSource) {
-        let mut bindings_list = FxHashMap::default();
-        for pat in pats {
-            self.resolve_pattern(pat, source, &mut bindings_list);
-        }
-        // This has to happen *after* we determine which pat_idents are variants
-        if pats.len() > 1 {
-            self.check_consistent_bindings(pats);
-        }
+    /// Check the consistency of the outermost or-patterns.
+    fn check_consistent_bindings_top(&mut self, pat: &Pat) {
+        pat.walk(&mut |pat| match pat.node {
+            PatKind::Or(ref ps) => {
+                self.check_consistent_bindings(ps);
+                false
+            },
+            _ => true,
+        })
     }
 
-    fn resolve_block(&mut self, block: &Block) {
-        debug!("(resolving block) entering block");
-        // Move down in the graph, if there's an anonymous module rooted here.
-        let orig_module = self.parent_scope.module;
-        let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
-
-        let mut num_macro_definition_ribs = 0;
-        if let Some(anonymous_module) = anonymous_module {
-            debug!("(resolving block) found anonymous module, moving down");
-            self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
-            self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
-            self.parent_scope.module = anonymous_module;
-        } else {
-            self.ribs[ValueNS].push(Rib::new(NormalRibKind));
-        }
-
-        // Descend into the block.
-        for stmt in &block.stmts {
-            if let StmtKind::Item(ref item) = stmt.node {
-                if let ItemKind::MacroDef(..) = item.node {
-                    num_macro_definition_ribs += 1;
-                    let res = self.r.definitions.local_def_id(item.id);
-                    self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
-                    self.label_ribs.push(Rib::new(MacroDefinition(res)));
-                }
-            }
-
-            self.visit_stmt(stmt);
-        }
-
-        // Move back up.
-        self.parent_scope.module = orig_module;
-        for _ in 0 .. num_macro_definition_ribs {
-            self.ribs[ValueNS].pop();
-            self.label_ribs.pop();
-        }
-        self.ribs[ValueNS].pop();
-        if anonymous_module.is_some() {
-            self.ribs[TypeNS].pop();
-        }
-        debug!("(resolving block) leaving block");
+    fn resolve_arm(&mut self, arm: &Arm) {
+        self.with_rib(ValueNS, NormalRibKind, |this| {
+            this.resolve_pattern_top(&arm.pat, PatternSource::Match);
+            walk_list!(this, visit_expr, &arm.guard);
+            this.visit_expr(&arm.body);
+        });
     }
 
-    fn fresh_binding(&mut self,
-                     ident: Ident,
-                     pat_id: NodeId,
-                     outer_pat_id: NodeId,
-                     pat_src: PatternSource,
-                     bindings: &mut FxHashMap<Ident, NodeId>)
-                     -> Res {
-        // Add the binding to the local ribs, if it
-        // doesn't already exist in the bindings map. (We
-        // must not add it if it's in the bindings map
-        // because that breaks the assumptions later
-        // passes make about or-patterns.)
-        let ident = ident.modern_and_legacy();
-        let mut res = Res::Local(pat_id);
-        match bindings.get(&ident).cloned() {
-            Some(id) if id == outer_pat_id => {
-                // `Variant(a, a)`, error
-                self.r.report_error(
-                    ident.span,
-                    ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
-                        &ident.as_str())
-                );
-            }
-            Some(..) if pat_src == PatternSource::FnParam => {
-                // `fn f(a: u8, a: u8)`, error
-                self.r.report_error(
-                    ident.span,
-                    ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
-                        &ident.as_str())
-                );
-            }
-            Some(..) if pat_src == PatternSource::Match ||
-                        pat_src == PatternSource::Let => {
-                // `Variant1(a) | Variant2(a)`, ok
-                // Reuse definition from the first `a`.
-                res = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident];
-            }
-            Some(..) => {
-                span_bug!(ident.span, "two bindings with the same name from \
-                                       unexpected pattern source {:?}", pat_src);
-            }
-            None => {
-                // A completely fresh binding, add to the lists if it's valid.
-                if ident.name != kw::Invalid {
-                    bindings.insert(ident, outer_pat_id);
-                    self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident, res);
-                }
-            }
-        }
+    /// Arising from `source`, resolve a top level pattern.
+    fn resolve_pattern_top(&mut self, pat: &Pat, pat_src: PatternSource) {
+        let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
+        self.resolve_pattern(pat, pat_src, &mut bindings);
+    }
 
-        res
+    fn resolve_pattern(
+        &mut self,
+        pat: &Pat,
+        pat_src: PatternSource,
+        bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
+    ) {
+        self.resolve_pattern_inner(pat, pat_src, bindings);
+        // This has to happen *after* we determine which pat_idents are variants:
+        self.check_consistent_bindings_top(pat);
+        visit::walk_pat(self, pat);
     }
 
-    fn resolve_pattern(&mut self,
-                       pat: &Pat,
-                       pat_src: PatternSource,
-                       // Maps idents to the node ID for the
-                       // outermost pattern that binds them.
-                       bindings: &mut FxHashMap<Ident, NodeId>) {
+    /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
+    ///
+    /// ### `bindings`
+    ///
+    /// A stack of sets of bindings accumulated.
+    ///
+    /// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
+    /// be interpreted as re-binding an already bound binding. This results in an error.
+    /// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
+    /// in reusing this binding rather than creating a fresh one.
+    ///
+    /// When called at the top level, the stack must have a single element
+    /// with `PatBound::Product`. Otherwise, pushing to the stack happens as
+    /// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
+    /// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
+    /// When each `p_i` has been dealt with, the top set is merged with its parent.
+    /// When a whole or-pattern has been dealt with, the thing happens.
+    ///
+    /// See the implementation and `fresh_binding` for more details.
+    fn resolve_pattern_inner(
+        &mut self,
+        pat: &Pat,
+        pat_src: PatternSource,
+        bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
+    ) {
         // Visit all direct subpatterns of this pattern.
-        let outer_pat_id = pat.id;
         pat.walk(&mut |pat| {
             debug!("resolve_pattern pat={:?} node={:?}", pat, pat.node);
             match pat.node {
-                PatKind::Ident(bmode, ident, ref opt_pat) => {
-                    // First try to resolve the identifier as some existing
-                    // entity, then fall back to a fresh binding.
-                    let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS,
-                                                                      None, pat.span)
-                                      .and_then(LexicalScopeBinding::item);
-                    let res = binding.map(NameBinding::res).and_then(|res| {
-                        let is_syntactic_ambiguity = opt_pat.is_none() &&
-                            bmode == BindingMode::ByValue(Mutability::Immutable);
-                        match res {
-                            Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
-                            Res::Def(DefKind::Const, _) if is_syntactic_ambiguity => {
-                                // Disambiguate in favor of a unit struct/variant
-                                // or constant pattern.
-                                self.r.record_use(ident, ValueNS, binding.unwrap(), false);
-                                Some(res)
-                            }
-                            Res::Def(DefKind::Ctor(..), _)
-                            | Res::Def(DefKind::Const, _)
-                            | Res::Def(DefKind::Static, _) => {
-                                // This is unambiguously a fresh binding, either syntactically
-                                // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
-                                // to something unusable as a pattern (e.g., constructor function),
-                                // but we still conservatively report an error, see
-                                // issues/33118#issuecomment-233962221 for one reason why.
-                                self.r.report_error(
-                                    ident.span,
-                                    ResolutionError::BindingShadowsSomethingUnacceptable(
-                                        pat_src.descr(), ident.name, binding.unwrap())
-                                );
-                                None
-                            }
-                            Res::Def(DefKind::Fn, _) | Res::Err => {
-                                // These entities are explicitly allowed
-                                // to be shadowed by fresh bindings.
-                                None
-                            }
-                            res => {
-                                span_bug!(ident.span, "unexpected resolution for an \
-                                                       identifier in pattern: {:?}", res);
-                            }
-                        }
-                    }).unwrap_or_else(|| {
-                        self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
-                    });
-
+                PatKind::Ident(bmode, ident, ref sub) => {
+                    // First try to resolve the identifier as some existing entity,
+                    // then fall back to a fresh binding.
+                    let has_sub = sub.is_some();
+                    let res = self.try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
+                        .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
                     self.r.record_partial_res(pat.id, PartialRes::new(res));
                 }
-
                 PatKind::TupleStruct(ref path, ..) => {
                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
                 }
-
                 PatKind::Path(ref qself, ref path) => {
                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
                 }
-
                 PatKind::Struct(ref path, ..) => {
                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
                 }
-
+                PatKind::Or(ref ps) => {
+                    // Add a new set of bindings to the stack. `Or` here records that when a
+                    // binding already exists in this set, it should not result in an error because
+                    // `V1(a) | V2(a)` must be allowed and are checked for consistency later.
+                    bindings.push((PatBoundCtx::Or, Default::default()));
+                    for p in ps {
+                        // Now we need to switch back to a product context so that each
+                        // part of the or-pattern internally rejects already bound names.
+                        // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
+                        bindings.push((PatBoundCtx::Product, Default::default()));
+                        self.resolve_pattern_inner(p, pat_src, bindings);
+                        // Move up the non-overlapping bindings to the or-pattern.
+                        // Existing bindings just get "merged".
+                        let collected = bindings.pop().unwrap().1;
+                        bindings.last_mut().unwrap().1.extend(collected);
+                    }
+                    // This or-pattern itself can itself be part of a product,
+                    // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
+                    // Both cases bind `a` again in a product pattern and must be rejected.
+                    let collected = bindings.pop().unwrap().1;
+                    bindings.last_mut().unwrap().1.extend(collected);
+
+                    // Prevent visiting `ps` as we've already done so above.
+                    return false;
+                }
                 _ => {}
             }
             true
         });
+    }
 
-        visit::walk_pat(self, pat);
+    fn fresh_binding(
+        &mut self,
+        ident: Ident,
+        pat_id: NodeId,
+        pat_src: PatternSource,
+        bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
+    ) -> Res {
+        // Add the binding to the local ribs, if it doesn't already exist in the bindings map.
+        // (We must not add it if it's in the bindings map because that breaks the assumptions
+        // later passes make about or-patterns.)
+        let ident = ident.modern_and_legacy();
+
+        // Walk outwards the stack of products / or-patterns and
+        // find out if the identifier has been bound in any of these.
+        let mut already_bound_and = false;
+        let mut already_bound_or = false;
+        for (is_sum, set) in bindings.iter_mut().rev() {
+            match (is_sum, set.get(&ident).cloned()) {
+                // Already bound in a product pattern, e.g. `(a, a)` which is not allowed.
+                (PatBoundCtx::Product, Some(..)) => already_bound_and = true,
+                // Already bound in an or-pattern, e.g. `V1(a) | V2(a)`.
+                // This is *required* for consistency which is checked later.
+                (PatBoundCtx::Or, Some(..)) => already_bound_or = true,
+                // Not already bound here.
+                _ => {}
+            }
+        }
+
+        if already_bound_and {
+            // Overlap in a product pattern somewhere; report an error.
+            use ResolutionError::*;
+            let error = match pat_src {
+                // `fn f(a: u8, a: u8)`:
+                PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
+                // `Variant(a, a)`:
+                _ => IdentifierBoundMoreThanOnceInSamePattern,
+            };
+            self.r.report_error(ident.span, error(&ident.as_str()));
+        }
+
+        // Record as bound if it's valid:
+        let ident_valid = ident.name != kw::Invalid;
+        if ident_valid {
+            bindings.last_mut().unwrap().1.insert(ident);
+        }
+
+        if already_bound_or {
+            // `Variant1(a) | Variant2(a)`, ok
+            // Reuse definition from the first `a`.
+            self.innermost_rib_bindings(ValueNS)[&ident]
+        } else {
+            let res = Res::Local(pat_id);
+            if ident_valid {
+                // A completely fresh binding add to the set if it's valid.
+                self.innermost_rib_bindings(ValueNS).insert(ident, res);
+            }
+            res
+        }
+    }
+
+    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
+        &mut self.ribs[ns].last_mut().unwrap().bindings
+    }
+
+    fn try_resolve_as_non_binding(
+        &mut self,
+        pat_src: PatternSource,
+        pat: &Pat,
+        bm: BindingMode,
+        ident: Ident,
+        has_sub: bool,
+    ) -> Option<Res> {
+        let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?.item()?;
+        let res = binding.res();
+
+        // An immutable (no `mut`) by-value (no `ref`) binding pattern without
+        // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
+        // also be interpreted as a path to e.g. a constant, variant, etc.
+        let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Immutable);
+
+        match res {
+            Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
+            Res::Def(DefKind::Const, _) if is_syntactic_ambiguity => {
+                // Disambiguate in favor of a unit struct/variant or constant pattern.
+                self.r.record_use(ident, ValueNS, binding, false);
+                Some(res)
+            }
+            Res::Def(DefKind::Ctor(..), _)
+            | Res::Def(DefKind::Const, _)
+            | Res::Def(DefKind::Static, _) => {
+                // This is unambiguously a fresh binding, either syntactically
+                // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
+                // to something unusable as a pattern (e.g., constructor function),
+                // but we still conservatively report an error, see
+                // issues/33118#issuecomment-233962221 for one reason why.
+                self.r.report_error(
+                    ident.span,
+                    ResolutionError::BindingShadowsSomethingUnacceptable(
+                        pat_src.descr(),
+                        ident.name,
+                        binding,
+                    ),
+                );
+                None
+            }
+            Res::Def(DefKind::Fn, _) | Res::Err => {
+                // These entities are explicitly allowed to be shadowed by fresh bindings.
+                None
+            }
+            res => {
+                span_bug!(ident.span, "unexpected resolution for an \
+                                        identifier in pattern: {:?}", res);
+            }
+        }
     }
 
     // High-level and context dependent path resolution routine.
@@ -1723,12 +1769,10 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         Some(result)
     }
 
-    fn with_resolved_label<F>(&mut self, label: Option<Label>, id: NodeId, f: F)
-        where F: FnOnce(&mut LateResolutionVisitor<'_, '_>)
-    {
+    fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
         if let Some(label) = label {
             self.unused_labels.insert(id, label.ident.span);
-            self.with_label_rib(|this| {
+            self.with_label_rib(NormalRibKind, |this| {
                 let ident = label.ident.modern_and_legacy();
                 this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
                 f(this);
@@ -1742,6 +1786,49 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
         self.with_resolved_label(label, id, |this| this.visit_block(block));
     }
 
+    fn resolve_block(&mut self, block: &Block) {
+        debug!("(resolving block) entering block");
+        // Move down in the graph, if there's an anonymous module rooted here.
+        let orig_module = self.parent_scope.module;
+        let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
+
+        let mut num_macro_definition_ribs = 0;
+        if let Some(anonymous_module) = anonymous_module {
+            debug!("(resolving block) found anonymous module, moving down");
+            self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
+            self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
+            self.parent_scope.module = anonymous_module;
+        } else {
+            self.ribs[ValueNS].push(Rib::new(NormalRibKind));
+        }
+
+        // Descend into the block.
+        for stmt in &block.stmts {
+            if let StmtKind::Item(ref item) = stmt.node {
+                if let ItemKind::MacroDef(..) = item.node {
+                    num_macro_definition_ribs += 1;
+                    let res = self.r.definitions.local_def_id(item.id);
+                    self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
+                    self.label_ribs.push(Rib::new(MacroDefinition(res)));
+                }
+            }
+
+            self.visit_stmt(stmt);
+        }
+
+        // Move back up.
+        self.parent_scope.module = orig_module;
+        for _ in 0 .. num_macro_definition_ribs {
+            self.ribs[ValueNS].pop();
+            self.label_ribs.pop();
+        }
+        self.ribs[ValueNS].pop();
+        if anonymous_module.is_some() {
+            self.ribs[TypeNS].pop();
+        }
+        debug!("(resolving block) leaving block");
+    }
+
     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
         // First, record candidate traits for this expression if it could
         // result in the invocation of a method call.
@@ -1796,39 +1883,36 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
                 visit::walk_expr(self, expr);
             }
 
-            ExprKind::Let(ref pats, ref scrutinee) => {
+            ExprKind::Let(ref pat, ref scrutinee) => {
                 self.visit_expr(scrutinee);
-                self.resolve_pats(pats, PatternSource::Let);
+                self.resolve_pattern_top(pat, PatternSource::Let);
             }
 
             ExprKind::If(ref cond, ref then, ref opt_else) => {
-                self.ribs[ValueNS].push(Rib::new(NormalRibKind));
-                self.visit_expr(cond);
-                self.visit_block(then);
-                self.ribs[ValueNS].pop();
-
+                self.with_rib(ValueNS, NormalRibKind, |this| {
+                    this.visit_expr(cond);
+                    this.visit_block(then);
+                });
                 opt_else.as_ref().map(|expr| self.visit_expr(expr));
             }
 
             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
 
-            ExprKind::While(ref subexpression, ref block, label) => {
+            ExprKind::While(ref cond, ref block, label) => {
                 self.with_resolved_label(label, expr.id, |this| {
-                    this.ribs[ValueNS].push(Rib::new(NormalRibKind));
-                    this.visit_expr(subexpression);
-                    this.visit_block(block);
-                    this.ribs[ValueNS].pop();
+                    this.with_rib(ValueNS, NormalRibKind, |this| {
+                        this.visit_expr(cond);
+                        this.visit_block(block);
+                    })
                 });
             }
 
-            ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
-                self.visit_expr(subexpression);
-                self.ribs[ValueNS].push(Rib::new(NormalRibKind));
-                self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap::default());
-
-                self.resolve_labeled_block(label, expr.id, block);
-
-                self.ribs[ValueNS].pop();
+            ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
+                self.visit_expr(iter_expr);
+                self.with_rib(ValueNS, NormalRibKind, |this| {
+                    this.resolve_pattern_top(pat, PatternSource::For);
+                    this.resolve_labeled_block(label, expr.id, block);
+                });
             }
 
             ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
@@ -1860,30 +1944,22 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
             // `async |x| ...` gets desugared to `|x| future_from_generator(|| ...)`, so we need to
             // resolve the arguments within the proper scopes so that usages of them inside the
             // closure are detected as upvars rather than normal closure arg usages.
-            ExprKind::Closure(
-                _, IsAsync::Async { .. }, _,
-                ref fn_decl, ref body, _span,
-            ) => {
-                let rib_kind = NormalRibKind;
-                self.ribs[ValueNS].push(Rib::new(rib_kind));
-                // Resolve arguments:
-                let mut bindings_list = FxHashMap::default();
-                for argument in &fn_decl.inputs {
-                    self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
-                    self.visit_ty(&argument.ty);
-                }
-                // No need to resolve return type-- the outer closure return type is
-                // FunctionRetTy::Default
-
-                // Now resolve the inner closure
-                {
-                    // No need to resolve arguments: the inner closure has none.
-                    // Resolve the return type:
-                    visit::walk_fn_ret_ty(self, &fn_decl.output);
-                    // Resolve the body
-                    self.visit_expr(body);
-                }
-                self.ribs[ValueNS].pop();
+            ExprKind::Closure(_, IsAsync::Async { .. }, _, ref fn_decl, ref body, _span) => {
+                self.with_rib(ValueNS, NormalRibKind, |this| {
+                    // Resolve arguments:
+                    this.resolve_params(&fn_decl.inputs);
+                    // No need to resolve return type --
+                    // the outer closure return type is `FunctionRetTy::Default`.
+
+                    // Now resolve the inner closure
+                    {
+                        // No need to resolve arguments: the inner closure has none.
+                        // Resolve the return type:
+                        visit::walk_fn_ret_ty(this, &fn_decl.output);
+                        // Resolve the body
+                        this.visit_expr(body);
+                    }
+                });
             }
             _ => {
                 visit::walk_expr(self, expr);
diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs
index a822fa049ca1c..0c86d8494fde8 100644
--- a/src/librustc_resolve/late/diagnostics.rs
+++ b/src/librustc_resolve/late/diagnostics.rs
@@ -113,7 +113,7 @@ impl<'a> LateResolutionVisitor<'a, '_> {
 
         // Emit special messages for unresolved `Self` and `self`.
         if is_self_type(path, ns) {
-            __diagnostic_used!(E0411);
+            syntax::diagnostic_used!(E0411);
             err.code(DiagnosticId::Error("E0411".into()));
             err.span_label(span, format!("`Self` is only available in impls, traits, \
                                           and type definitions"));
@@ -122,7 +122,7 @@ impl<'a> LateResolutionVisitor<'a, '_> {
         if is_self_value(path, ns) {
             debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
 
-            __diagnostic_used!(E0424);
+            syntax::diagnostic_used!(E0424);
             err.code(DiagnosticId::Error("E0424".into()));
             err.span_label(span, match source {
                 PathSource::Pat => {
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 875ae449d94e0..74f68e5147126 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -9,11 +9,11 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
+#![feature(inner_deref)]
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]
 #![feature(mem_take)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 
 #![recursion_limit="256"]
 
@@ -40,7 +40,7 @@ use rustc_metadata::cstore::CStore;
 use syntax::ext::hygiene::{ExpnId, Transparency, SyntaxContext};
 use syntax::ast::{self, Name, NodeId, Ident, FloatTy, IntTy, UintTy};
 use syntax::ext::base::{SyntaxExtension, MacroKind, SpecialDerives};
-use syntax::symbol::{Symbol, kw, sym};
+use syntax::symbol::{kw, sym};
 
 use syntax::visit::{self, Visitor};
 use syntax::attr;
@@ -67,9 +67,7 @@ use macros::{LegacyBinding, LegacyScope};
 
 type Res = def::Res<NodeId>;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
-mod error_codes;
+pub mod error_codes;
 mod diagnostics;
 mod late;
 mod macros;
@@ -243,7 +241,7 @@ impl Segment {
 
     fn names_to_string(segments: &[Segment]) -> String {
         names_to_string(&segments.iter()
-                            .map(|seg| seg.ident)
+                            .map(|seg| seg.ident.name)
                             .collect::<Vec<_>>())
     }
 }
@@ -537,7 +535,11 @@ impl<'a> ModuleData<'a> {
     }
 
     fn nearest_item_scope(&'a self) -> Module<'a> {
-        if self.is_trait() { self.parent.unwrap() } else { self }
+        match self.kind {
+            ModuleKind::Def(DefKind::Enum, ..) | ModuleKind::Def(DefKind::Trait, ..) =>
+                self.parent.expect("enum or trait module without a parent"),
+            _ => self,
+        }
     }
 
     fn is_ancestor_of(&self, mut other: &Self) -> bool {
@@ -879,6 +881,10 @@ pub struct Resolver<'a> {
     /// There will be an anonymous module created around `g` with the ID of the
     /// entry block for `f`.
     block_map: NodeMap<Module<'a>>,
+    /// A fake module that contains no definition and no prelude. Used so that
+    /// some AST passes can generate identifiers that only resolve to local or
+    /// language items.
+    empty_module: Module<'a>,
     module_map: FxHashMap<DefId, Module<'a>>,
     extern_module_map: FxHashMap<(DefId, bool /* MacrosOnly? */), Module<'a>>,
     binding_parent_modules: FxHashMap<PtrKey<'a, NameBinding<'a>>, Module<'a>>,
@@ -913,6 +919,7 @@ pub struct Resolver<'a> {
     non_macro_attrs: [Lrc<SyntaxExtension>; 2],
     macro_defs: FxHashMap<ExpnId, DefId>,
     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
+    ast_transform_scopes: FxHashMap<ExpnId, Module<'a>>,
     unused_macros: NodeMap<Span>,
     proc_macro_stubs: NodeSet,
     /// Traces collected during macro resolution and validated when it's complete.
@@ -944,7 +951,11 @@ pub struct Resolver<'a> {
     struct_constructors: DefIdMap<(Res, ty::Visibility)>,
 
     /// Features enabled for this crate.
-    active_features: FxHashSet<Symbol>,
+    active_features: FxHashSet<Name>,
+
+    /// Stores enum visibilities to properly build a reduced graph
+    /// when visiting the correspondent variants.
+    variant_vis: DefIdMap<ty::Visibility>,
 }
 
 /// Nothing really interesting here; it just provides memory for the rest of the crate.
@@ -1007,8 +1018,8 @@ impl<'a> hir::lowering::Resolver for Resolver<'a> {
     fn resolve_str_path(
         &mut self,
         span: Span,
-        crate_root: Option<Symbol>,
-        components: &[Symbol],
+        crate_root: Option<Name>,
+        components: &[Name],
         ns: Namespace,
     ) -> (ast::Path, Res) {
         let root = if crate_root.is_some() {
@@ -1080,6 +1091,21 @@ impl<'a> Resolver<'a> {
             no_implicit_prelude: attr::contains_name(&krate.attrs, sym::no_implicit_prelude),
             ..ModuleData::new(None, root_module_kind, root_def_id, ExpnId::root(), krate.span)
         });
+        let empty_module_kind = ModuleKind::Def(
+            DefKind::Mod,
+            root_def_id,
+            kw::Invalid,
+        );
+        let empty_module = arenas.alloc_module(ModuleData {
+            no_implicit_prelude: true,
+            ..ModuleData::new(
+                Some(graph_root),
+                empty_module_kind,
+                root_def_id,
+                ExpnId::root(),
+                DUMMY_SP,
+            )
+        });
         let mut module_map = FxHashMap::default();
         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
 
@@ -1139,10 +1165,12 @@ impl<'a> Resolver<'a> {
             label_res_map: Default::default(),
             export_map: FxHashMap::default(),
             trait_map: Default::default(),
+            empty_module,
             module_map,
             block_map: Default::default(),
             extern_module_map: FxHashMap::default(),
             binding_parent_modules: FxHashMap::default(),
+            ast_transform_scopes: FxHashMap::default(),
 
             glob_map: Default::default(),
 
@@ -1190,6 +1218,7 @@ impl<'a> Resolver<'a> {
                 features.declared_lib_features.iter().map(|(feat, ..)| *feat)
                     .chain(features.declared_lang_features.iter().map(|(feat, ..)| *feat))
                     .collect(),
+            variant_vis: Default::default()
         }
     }
 
@@ -1617,7 +1646,7 @@ impl<'a> Resolver<'a> {
         }
 
         if let ModuleKind::Block(..) = module.kind {
-            return Some(module.parent.unwrap());
+            return Some(module.parent.unwrap().nearest_item_scope());
         }
 
         None
@@ -2526,7 +2555,7 @@ impl<'a> Resolver<'a> {
     fn add_suggestion_for_rename_of_use(
         &self,
         err: &mut DiagnosticBuilder<'_>,
-        name: Symbol,
+        name: Name,
         directive: &ImportDirective<'_>,
         binding_span: Span,
     ) {
@@ -2741,22 +2770,22 @@ impl<'a> Resolver<'a> {
     }
 }
 
-fn names_to_string(idents: &[Ident]) -> String {
+fn names_to_string(names: &[Name]) -> String {
     let mut result = String::new();
-    for (i, ident) in idents.iter()
-                            .filter(|ident| ident.name != kw::PathRoot)
+    for (i, name) in names.iter()
+                            .filter(|name| **name != kw::PathRoot)
                             .enumerate() {
         if i > 0 {
             result.push_str("::");
         }
-        result.push_str(&ident.as_str());
+        result.push_str(&name.as_str());
     }
     result
 }
 
 fn path_names_to_string(path: &Path) -> String {
     names_to_string(&path.segments.iter()
-                        .map(|seg| seg.ident)
+                        .map(|seg| seg.ident.name)
                         .collect::<Vec<_>>())
 }
 
@@ -2764,15 +2793,14 @@ fn path_names_to_string(path: &Path) -> String {
 fn module_to_string(module: Module<'_>) -> Option<String> {
     let mut names = Vec::new();
 
-    fn collect_mod(names: &mut Vec<Ident>, module: Module<'_>) {
+    fn collect_mod(names: &mut Vec<Name>, module: Module<'_>) {
         if let ModuleKind::Def(.., name) = module.kind {
             if let Some(parent) = module.parent {
-                names.push(Ident::with_dummy_span(name));
+                names.push(name);
                 collect_mod(names, parent);
             }
         } else {
-            // danger, shouldn't be ident?
-            names.push(Ident::from_str("<opaque>"));
+            names.push(Name::intern("<opaque>"));
             collect_mod(names, module.parent.unwrap());
         }
     }
@@ -2781,9 +2809,8 @@ fn module_to_string(module: Module<'_>) -> Option<String> {
     if names.is_empty() {
         return None;
     }
-    Some(names_to_string(&names.into_iter()
-                        .rev()
-                        .collect::<Vec<_>>()))
+    names.reverse();
+    Some(names_to_string(&names))
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -2817,5 +2844,3 @@ impl CrateLint {
         }
     }
 }
-
-__build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index 7224bd74230b3..3900a3dbb3872 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -8,6 +8,7 @@ use crate::{ModuleOrUniformRoot, KNOWN_TOOLS};
 use crate::Namespace::*;
 use crate::resolve_imports::ImportResolver;
 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
+use rustc::hir::def_id;
 use rustc::middle::stability;
 use rustc::{ty, lint, span_bug};
 use syntax::ast::{self, NodeId, Ident};
@@ -15,7 +16,7 @@ use syntax::attr::StabilityLevel;
 use syntax::edition::Edition;
 use syntax::ext::base::{self, InvocationRes, Indeterminate, SpecialDerives};
 use syntax::ext::base::{MacroKind, SyntaxExtension};
-use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
+use syntax::ext::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
 use syntax::ext::hygiene::{self, ExpnId, ExpnData, ExpnKind};
 use syntax::ext::tt::macro_rules;
 use syntax::feature_gate::{emit_feature_err, is_builtin_attr_name};
@@ -25,6 +26,7 @@ use syntax_pos::{Span, DUMMY_SP};
 
 use std::{mem, ptr};
 use rustc_data_structures::sync::Lrc;
+use syntax_pos::hygiene::AstPass;
 
 type Res = def::Res<NodeId>;
 
@@ -95,16 +97,6 @@ impl<'a> base::Resolver for Resolver<'a> {
         self.session.next_node_id()
     }
 
-    fn get_module_scope(&mut self, id: NodeId) -> ExpnId {
-        let expn_id = ExpnId::fresh(Some(ExpnData::default(
-            ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, self.session.edition()
-        )));
-        let module = self.module_map[&self.definitions.local_def_id(id)];
-        self.invocation_parent_scopes.insert(expn_id, ParentScope::module(module));
-        self.definitions.set_invocation_parent(expn_id, module.def_id().unwrap().index);
-        expn_id
-    }
-
     fn resolve_dollar_crates(&mut self) {
         hygiene::update_dollar_crate_names(|ctxt| {
             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
@@ -136,6 +128,37 @@ impl<'a> base::Resolver for Resolver<'a> {
         }
     }
 
+    // Create a new Expansion with a definition site of the provided module, or
+    // a fake empty `#[no_implicit_prelude]` module if no module is provided.
+    fn expansion_for_ast_pass(
+        &mut self,
+        call_site: Span,
+        pass: AstPass,
+        features: &[Symbol],
+        parent_module_id: Option<NodeId>,
+    ) -> ExpnId {
+        let expn_id = ExpnId::fresh(Some(ExpnData::allow_unstable(
+            ExpnKind::AstPass(pass),
+            call_site,
+            self.session.edition(),
+            features.into(),
+        )));
+
+        let parent_scope = if let Some(module_id) = parent_module_id {
+            let parent_def_id = self.definitions.local_def_id(module_id);
+            self.definitions.add_parent_module_of_macro_def(expn_id, parent_def_id);
+            self.module_map[&parent_def_id]
+        } else {
+            self.definitions.add_parent_module_of_macro_def(
+                expn_id,
+                def_id::DefId::local(def_id::CRATE_DEF_INDEX),
+            );
+            self.empty_module
+        };
+        self.ast_transform_scopes.insert(expn_id, parent_scope);
+        expn_id
+    }
+
     fn resolve_imports(&mut self) {
         ImportResolver { r: self }.resolve_imports()
     }
@@ -202,6 +225,27 @@ impl<'a> base::Resolver for Resolver<'a> {
             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
         }
 
+        match invoc.fragment_kind {
+            AstFragmentKind::Arms
+                | AstFragmentKind::Fields
+                | AstFragmentKind::FieldPats
+                | AstFragmentKind::GenericParams
+                | AstFragmentKind::Params
+                | AstFragmentKind::StructFields
+                | AstFragmentKind::Variants =>
+            {
+                if let Res::Def(..) = res {
+                    self.session.span_err(
+                        span,
+                        &format!("expected an inert attribute, found {} {}",
+                                 res.article(), res.descr()),
+                    );
+                    return Ok(InvocationRes::Single(self.dummy_ext(kind)));
+                }
+            },
+            _ => {}
+        }
+
         Ok(InvocationRes::Single(ext))
     }
 
@@ -279,7 +323,7 @@ impl<'a> Resolver<'a> {
         self.check_stability_and_deprecation(&ext, path);
 
         Ok(if ext.macro_kind() != kind {
-            let expected = if kind == MacroKind::Attr { "attribute" } else  { kind.descr() };
+            let expected = kind.descr_expected();
             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path);
             self.session.struct_span_err(path.span, &msg)
                         .span_label(path.span, format!("not {} {}", kind.article(), expected))
@@ -730,9 +774,8 @@ impl<'a> Resolver<'a> {
                 }
                 Err(..) => {
                     assert!(initial_binding.is_none());
-                    let bang = if kind == MacroKind::Bang { "!" } else { "" };
-                    let msg =
-                        format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
+                    let expected = kind.descr_expected();
+                    let msg = format!("cannot find {} `{}` in this scope", expected, ident);
                     let mut err = self.session.struct_span_err(ident.span, &msg);
                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
                     err.emit();
@@ -751,10 +794,10 @@ impl<'a> Resolver<'a> {
     fn check_stability_and_deprecation(&self, ext: &SyntaxExtension, path: &ast::Path) {
         let span = path.span;
         if let Some(stability) = &ext.stability {
-            if let StabilityLevel::Unstable { reason, issue } = stability.level {
+            if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
                 let feature = stability.feature;
                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
-                    stability::report_unstable(self.session, feature, reason, issue, span);
+                    stability::report_unstable(self.session, feature, reason, issue, is_soft, span);
                 }
             }
             if let Some(depr) = &stability.rustc_depr {
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index fd222a132a3f8..e77e8290f1faa 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/src/librustc_resolve/resolve_imports.rs
@@ -71,7 +71,7 @@ pub enum ImportDirectiveSubclass<'a> {
 }
 
 /// One import directive.
-#[derive(Debug,Clone)]
+#[derive(Debug, Clone)]
 crate struct ImportDirective<'a> {
     /// The ID of the `extern crate`, `UseTree` etc that imported this `ImportDirective`.
     ///
@@ -447,12 +447,13 @@ impl<'a> Resolver<'a> {
     }
 
     // Define the name or return the existing binding if there is a collision.
-    pub fn try_define(&mut self,
-                      module: Module<'a>,
-                      ident: Ident,
-                      ns: Namespace,
-                      binding: &'a NameBinding<'a>)
-                      -> Result<(), &'a NameBinding<'a>> {
+    pub fn try_define(
+        &mut self,
+        module: Module<'a>,
+        ident: Ident,
+        ns: Namespace,
+        binding: &'a NameBinding<'a>,
+    ) -> Result<(), &'a NameBinding<'a>> {
         let res = binding.res();
         self.check_reserved_macro_name(ident, res);
         self.set_binding_parent_module(binding, module);
@@ -480,8 +481,11 @@ impl<'a> Resolver<'a> {
                         };
                         if glob_binding.res() != nonglob_binding.res() &&
                            ns == MacroNS && nonglob_binding.expansion != ExpnId::root() {
-                            resolution.binding = Some(this.ambiguity(AmbiguityKind::GlobVsExpanded,
-                                                                    nonglob_binding, glob_binding));
+                            resolution.binding = Some(this.ambiguity(
+                                AmbiguityKind::GlobVsExpanded,
+                                nonglob_binding,
+                                glob_binding,
+                            ));
                         } else {
                             resolution.binding = Some(nonglob_binding);
                         }
@@ -513,9 +517,11 @@ impl<'a> Resolver<'a> {
         })
     }
 
-    fn ambiguity(&self, kind: AmbiguityKind,
-                 primary_binding: &'a NameBinding<'a>, secondary_binding: &'a NameBinding<'a>)
-                 -> &'a NameBinding<'a> {
+    fn ambiguity(
+        &self, kind: AmbiguityKind,
+        primary_binding: &'a NameBinding<'a>,
+        secondary_binding: &'a NameBinding<'a>,
+    ) -> &'a NameBinding<'a> {
         self.arenas.alloc_name_binding(NameBinding {
             ambiguity: Some((secondary_binding, kind)),
             ..primary_binding.clone()
@@ -524,8 +530,12 @@ impl<'a> Resolver<'a> {
 
     // Use `f` to mutate the resolution of the name in the module.
     // If the resolution becomes a success, define it in the module's glob importers.
-    fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Namespace, f: F)
-                               -> T
+    fn update_resolution<T, F>(
+        &mut self, module: Module<'a>,
+        ident: Ident,
+        ns: Namespace,
+        f: F,
+    ) -> T
         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
     {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
@@ -627,14 +637,18 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             self.finalize_resolutions_in(module);
         }
 
-        let mut has_errors = false;
         let mut seen_spans = FxHashSet::default();
         let mut errors = vec![];
         let mut prev_root_id: NodeId = NodeId::from_u32(0);
-        for i in 0 .. self.r.determined_imports.len() {
-            let import = self.r.determined_imports[i];
+        let determined_imports = mem::take(&mut self.r.determined_imports);
+        let indeterminate_imports = mem::take(&mut self.r.indeterminate_imports);
+
+        for (is_indeterminate, import) in determined_imports
+            .into_iter()
+            .map(|i| (false, i))
+            .chain(indeterminate_imports.into_iter().map(|i| (true, i)))
+        {
             if let Some(err) = self.finalize_import(import) {
-                has_errors = true;
 
                 if let SingleImport { source, ref source_bindings, .. } = import.subclass {
                     if source.name == kw::SelfLower {
@@ -666,21 +680,27 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     errors.push((path, err));
                     prev_root_id = import.root_id;
                 }
+            } else if is_indeterminate {
+                // Consider erroneous imports used to avoid duplicate diagnostics.
+                self.r.used_imports.insert((import.id, TypeNS));
+                let path = import_path_to_string(
+                    &import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),
+                    &import.subclass,
+                    import.span,
+                );
+                let err = UnresolvedImportError {
+                    span: import.span,
+                    label: None,
+                    note: Vec::new(),
+                    suggestion: None,
+                };
+                errors.push((path, err));
             }
         }
 
         if !errors.is_empty() {
             self.throw_unresolved_import_error(errors.clone(), None);
         }
-
-        // Report unresolved imports only if no hard error was already reported
-        // to avoid generating multiple errors on the same import.
-        if !has_errors {
-            for import in &self.r.indeterminate_imports {
-                self.throw_unresolved_import_error(errors, Some(MultiSpan::from(import.span)));
-                break;
-            }
-        }
     }
 
     fn throw_unresolved_import_error(
@@ -835,10 +855,20 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     ) -> Option<UnresolvedImportError> {
         let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
         let prev_ambiguity_errors_len = self.r.ambiguity_errors.len();
-        let path_res = self.r.resolve_path(&directive.module_path, None, &directive.parent_scope,
-                                         true, directive.span, directive.crate_lint());
+        let path_res = self.r.resolve_path(
+            &directive.module_path,
+            None,
+            &directive.parent_scope,
+            true,
+            directive.span,
+            directive.crate_lint(),
+        );
         let no_ambiguity = self.r.ambiguity_errors.len() == prev_ambiguity_errors_len;
         directive.vis.set(orig_vis);
+        if let PathResult::Failed { .. } | PathResult::NonModule(..) = path_res {
+            // Consider erroneous imports used to avoid duplicate diagnostics.
+            self.r.used_imports.insert((directive.id, TypeNS));
+        }
         let module = match path_res {
             PathResult::Module(module) => {
                 // Consistency checks, analogous to `finalize_macro_resolutions`.
@@ -895,7 +925,6 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                             }
                         }
                     };
-
                     return Some(err);
                 }
                 return None;
@@ -1307,12 +1336,11 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                 None => continue,
             };
 
-            // Filter away ambiguous and gensymed imports. Gensymed imports
-            // (e.g. implicitly injected `std`) cannot be properly encoded in metadata,
-            // so they can cause name conflict errors downstream.
-            let is_good_import = binding.is_import() && !binding.is_ambiguity() &&
-                                 // Note that as_str() de-gensyms the Symbol
-                                 !(ident.is_gensymed() && ident.name.as_str() != "_");
+            // Filter away ambiguous imports and anything that has def-site
+            // hygiene.
+            // FIXME: Implement actual cross-crate hygiene.
+            let is_good_import = binding.is_import() && !binding.is_ambiguity()
+                && !ident.span.modern().from_expansion();
             if is_good_import || binding.is_macro_def() {
                 let res = binding.res();
                 if res != Res::Err {
@@ -1405,15 +1433,17 @@ fn import_path_to_string(names: &[Ident],
     let global = !names.is_empty() && names[0].name == kw::PathRoot;
     if let Some(pos) = pos {
         let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] };
-        names_to_string(names)
+        names_to_string(&names.iter().map(|ident| ident.name).collect::<Vec<_>>())
     } else {
         let names = if global { &names[1..] } else { names };
         if names.is_empty() {
             import_directive_subclass_to_string(subclass)
         } else {
-            format!("{}::{}",
-                    names_to_string(names),
-                    import_directive_subclass_to_string(subclass))
+            format!(
+                "{}::{}",
+                names_to_string(&names.iter().map(|ident| ident.name).collect::<Vec<_>>()),
+                import_directive_subclass_to_string(subclass),
+            )
         }
     }
 }
diff --git a/src/librustc_save_analysis/dump_visitor.rs b/src/librustc_save_analysis/dump_visitor.rs
index d1fd51a97f683..55f6b91e71431 100644
--- a/src/librustc_save_analysis/dump_visitor.rs
+++ b/src/librustc_save_analysis/dump_visitor.rs
@@ -130,6 +130,10 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
         self.save_ctxt.span_from_span(span)
     }
 
+    fn lookup_def_id(&self, ref_id: NodeId) -> Option<DefId> {
+        self.save_ctxt.lookup_def_id(ref_id)
+    }
+
     pub fn dump_crate_info(&mut self, name: &str, krate: &ast::Crate) {
         let source_file = self.tcx.sess.local_crate_source_file.as_ref();
         let crate_root = source_file.map(|source_file| {
@@ -223,13 +227,6 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
         }
     }
 
-    fn lookup_def_id(&self, ref_id: NodeId) -> Option<DefId> {
-        match self.save_ctxt.get_path_res(ref_id) {
-            Res::PrimTy(..) | Res::SelfTy(..) | Res::Err => None,
-            def => Some(def.def_id()),
-        }
-    }
-
     fn process_formals(&mut self, formals: &'l [ast::Param], qualname: &str) {
         for arg in formals {
             self.visit_pat(&arg.pat);
@@ -283,36 +280,32 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
     ) {
         debug!("process_method: {}:{}", id, ident);
 
-        if let Some(mut method_data) = self.save_ctxt.get_method_data(id, ident, span) {
-            let sig_str = crate::make_signature(&sig.decl, &generics);
-            if body.is_some() {
-                self.nest_tables(
-                    id,
-                    |v| v.process_formals(&sig.decl.inputs, &method_data.qualname),
-                );
-            }
+        let hir_id = self.tcx.hir().node_to_hir_id(id);
+        self.nest_tables(id, |v| {
+            if let Some(mut method_data) = v.save_ctxt.get_method_data(id, ident, span) {
+                v.process_formals(&sig.decl.inputs, &method_data.qualname);
+                v.process_generic_params(&generics, &method_data.qualname, id);
 
-            self.process_generic_params(&generics, &method_data.qualname, id);
+                method_data.value = crate::make_signature(&sig.decl, &generics);
+                method_data.sig = sig::method_signature(id, ident, generics, sig, &v.save_ctxt);
 
-            method_data.value = sig_str;
-            method_data.sig = sig::method_signature(id, ident, generics, sig, &self.save_ctxt);
-            let hir_id = self.tcx.hir().node_to_hir_id(id);
-            self.dumper.dump_def(&access_from_vis!(self.save_ctxt, vis, hir_id), method_data);
-        }
+                v.dumper.dump_def(&access_from_vis!(v.save_ctxt, vis, hir_id), method_data);
+            }
 
-        // walk arg and return types
-        for arg in &sig.decl.inputs {
-            self.visit_ty(&arg.ty);
-        }
+            // walk arg and return types
+            for arg in &sig.decl.inputs {
+                v.visit_ty(&arg.ty);
+            }
 
-        if let ast::FunctionRetTy::Ty(ref ret_ty) = sig.decl.output {
-            self.visit_ty(ret_ty);
-        }
+            if let ast::FunctionRetTy::Ty(ref ret_ty) = sig.decl.output {
+                v.visit_ty(ret_ty);
+            }
 
-        // walk the fn body
-        if let Some(body) = body {
-            self.nest_tables(id, |v| v.visit_block(body));
-        }
+            // walk the fn body
+            if let Some(body) = body {
+                v.visit_block(body);
+            }
+        });
     }
 
     fn process_struct_field_def(&mut self, field: &ast::StructField, parent_id: NodeId) {
@@ -377,26 +370,31 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
         ty_params: &'l ast::Generics,
         body: &'l ast::Block,
     ) {
-        if let Some(fn_data) = self.save_ctxt.get_item_data(item) {
-            down_cast_data!(fn_data, DefData, item.span);
-            self.nest_tables(
-                item.id,
-                |v| v.process_formals(&decl.inputs, &fn_data.qualname),
-            );
-            self.process_generic_params(ty_params, &fn_data.qualname, item.id);
-            let hir_id = self.tcx.hir().node_to_hir_id(item.id);
-            self.dumper.dump_def(&access_from!(self.save_ctxt, item, hir_id), fn_data);
-        }
+        let hir_id = self.tcx.hir().node_to_hir_id(item.id);
+        self.nest_tables(item.id, |v| {
+            if let Some(fn_data) = v.save_ctxt.get_item_data(item) {
+                down_cast_data!(fn_data, DefData, item.span);
+                v.process_formals(&decl.inputs, &fn_data.qualname);
+                v.process_generic_params(ty_params, &fn_data.qualname, item.id);
 
-        for arg in &decl.inputs {
-            self.visit_ty(&arg.ty);
-        }
+                v.dumper.dump_def(&access_from!(v.save_ctxt, item, hir_id), fn_data);
+            }
 
-        if let ast::FunctionRetTy::Ty(ref ret_ty) = decl.output {
-            self.visit_ty(&ret_ty);
-        }
+            for arg in &decl.inputs {
+                v.visit_ty(&arg.ty)
+            }
+
+            if let ast::FunctionRetTy::Ty(ref ret_ty) = decl.output {
+                if let ast::TyKind::ImplTrait(..) = ret_ty.node {
+                    // FIXME: Opaque type desugaring prevents us from easily
+                    // processing trait bounds. See `visit_ty` for more details.
+                } else {
+                    v.visit_ty(&ret_ty);
+                }
+            }
 
-        self.nest_tables(item.id, |v| v.visit_block(&body));
+            v.visit_block(&body);
+        });
     }
 
     fn process_static_or_const_item(
@@ -897,32 +895,23 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
         }
     }
 
-    fn process_var_decl_multi(&mut self, pats: &'l [P<ast::Pat>]) {
+    fn process_var_decl(&mut self, pat: &'l ast::Pat) {
+        // The pattern could declare multiple new vars,
+        // we must walk the pattern and collect them all.
         let mut collector = PathCollector::new();
-        for pattern in pats {
-            // collect paths from the arm's patterns
-            collector.visit_pat(&pattern);
-            self.visit_pat(&pattern);
-        }
+        collector.visit_pat(&pat);
+        self.visit_pat(&pat);
 
-        // process collected paths
-        for (id, ident, immut) in collector.collected_idents {
+        // Process collected paths.
+        for (id, ident, _) in collector.collected_idents {
             match self.save_ctxt.get_path_res(id) {
                 Res::Local(hir_id) => {
-                    let mut value = if immut == ast::Mutability::Immutable {
-                        self.span.snippet(ident.span)
-                    } else {
-                        "<mutable>".to_owned()
-                    };
                     let id = self.tcx.hir().hir_to_node_id(hir_id);
-                    let typ = self.save_ctxt
-                        .tables
-                        .node_type_opt(hir_id)
+                    let typ = self.save_ctxt.tables.node_type_opt(hir_id)
                         .map(|t| t.to_string())
                         .unwrap_or_default();
-                    value.push_str(": ");
-                    value.push_str(&typ);
 
+                    // Rust uses the id of the pattern for var lookups, so we'll use it too.
                     if !self.span.filter_generated(ident.span) {
                         let qualname = format!("{}${}", ident.to_string(), id);
                         let id = id_from_node_id(id, &self.save_ctxt);
@@ -972,61 +961,6 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
         }
     }
 
-    fn process_var_decl(&mut self, p: &'l ast::Pat, value: String) {
-        // The local could declare multiple new vars, we must walk the
-        // pattern and collect them all.
-        let mut collector = PathCollector::new();
-        collector.visit_pat(&p);
-        self.visit_pat(&p);
-
-        for (id, ident, immut) in collector.collected_idents {
-            let mut value = match immut {
-                ast::Mutability::Immutable => value.to_string(),
-                _ => String::new(),
-            };
-            let hir_id = self.tcx.hir().node_to_hir_id(id);
-            let typ = match self.save_ctxt.tables.node_type_opt(hir_id) {
-                Some(typ) => {
-                    let typ = typ.to_string();
-                    if !value.is_empty() {
-                        value.push_str(": ");
-                    }
-                    value.push_str(&typ);
-                    typ
-                }
-                None => String::new(),
-            };
-
-            // Rust uses the id of the pattern for var lookups, so we'll use it too.
-            if !self.span.filter_generated(ident.span) {
-                let qualname = format!("{}${}", ident.to_string(), id);
-                let id = id_from_node_id(id, &self.save_ctxt);
-                let span = self.span_from_span(ident.span);
-
-                self.dumper.dump_def(
-                    &Access {
-                        public: false,
-                        reachable: false,
-                    },
-                    Def {
-                        kind: DefKind::Local,
-                        id,
-                        span,
-                        name: ident.to_string(),
-                        qualname,
-                        value: typ,
-                        parent: None,
-                        children: vec![],
-                        decl_id: None,
-                        docs: String::new(),
-                        sig: None,
-                        attributes: vec![],
-                    },
-                );
-            }
-        }
-    }
-
     /// Extracts macro use and definition information from the AST node defined
     /// by the given NodeId, using the expansion information from the node's
     /// span.
@@ -1177,11 +1111,7 @@ impl<'l, 'tcx> DumpVisitor<'l, 'tcx> {
                 // FIXME: uses of the assoc type should ideally point to this
                 // 'def' and the name here should be a ref to the def in the
                 // trait.
-                for bound in bounds.iter() {
-                    if let ast::GenericBound::Trait(trait_ref, _) = bound {
-                        self.process_path(trait_ref.trait_ref.ref_id, &trait_ref.trait_ref.path)
-                    }
-                }
+                self.process_bounds(&bounds);
             }
             ast::ImplItemKind::Macro(_) => {}
         }
@@ -1428,10 +1358,10 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
                 self.visit_ty(&ty);
                 self.process_generic_params(ty_params, &qualname, item.id);
             }
-            OpaqueTy(ref _bounds, ref ty_params) => {
+            OpaqueTy(ref bounds, ref ty_params) => {
                 let qualname = format!("::{}",
                     self.tcx.def_path_str(self.tcx.hir().local_def_id_from_node_id(item.id)));
-                // FIXME do something with _bounds
+
                 let value = String::new();
                 if !self.span.filter_generated(item.ident.span) {
                     let span = self.span_from_span(item.ident.span);
@@ -1457,6 +1387,7 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
                     );
                 }
 
+                self.process_bounds(bounds);
                 self.process_generic_params(ty_params, &qualname, item.id);
             }
             Mac(_) => (),
@@ -1513,6 +1444,18 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
                 self.visit_ty(element);
                 self.nest_tables(length.id, |v| v.visit_expr(&length.value));
             }
+            ast::TyKind::ImplTrait(id, ref bounds) => {
+                // FIXME: As of writing, the opaque type lowering introduces
+                // another DefPath scope/segment (used to declare the resulting
+                // opaque type item).
+                // However, the synthetic scope does *not* have associated
+                // typeck tables, which means we can't nest it and we fire an
+                // assertion when resolving the qualified type paths in trait
+                // bounds...
+                // This will panic if called on return type `impl Trait`, which
+                // we guard against in `process_fn`.
+                self.nest_tables(id, |v| v.process_bounds(bounds));
+            }
             _ => visit::walk_ty(self, t),
         }
     }
@@ -1565,14 +1508,13 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
                 });
             }
             ast::ExprKind::ForLoop(ref pattern, ref subexpression, ref block, _) => {
-                let value = self.span.snippet(subexpression.span);
-                self.process_var_decl(pattern, value);
+                self.process_var_decl(pattern);
                 debug!("for loop, walk sub-expr: {:?}", subexpression.node);
                 self.visit_expr(subexpression);
                 visit::walk_block(self, block);
             }
-            ast::ExprKind::Let(ref pats, ref scrutinee) => {
-                self.process_var_decl_multi(pats);
+            ast::ExprKind::Let(ref pat, ref scrutinee) => {
+                self.process_var_decl(pat);
                 self.visit_expr(scrutinee);
             }
             ast::ExprKind::Repeat(ref element, ref count) => {
@@ -1599,7 +1541,7 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
     }
 
     fn visit_arm(&mut self, arm: &'l ast::Arm) {
-        self.process_var_decl_multi(&arm.pats);
+        self.process_var_decl(&arm.pat);
         if let Some(expr) = &arm.guard {
             self.visit_expr(expr);
         }
@@ -1617,11 +1559,7 @@ impl<'l, 'tcx> Visitor<'l> for DumpVisitor<'l, 'tcx> {
 
     fn visit_local(&mut self, l: &'l ast::Local) {
         self.process_macro_use(l.span);
-        let value = l.init
-            .as_ref()
-            .map(|i| self.span.snippet(i.span))
-            .unwrap_or_default();
-        self.process_var_decl(&l.pat, value);
+        self.process_var_decl(&l.pat);
 
         // Just walk the initialiser and type (don't want to walk the pattern again).
         walk_list!(self, visit_ty, &l.ty);
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index 92ccd4f49f6b9..055ccf6c2c4f8 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -1,5 +1,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(nll)]
+#![feature(inner_deref)]
 
 #![recursion_limit="256"]
 
@@ -311,7 +312,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
                     let impl_id = self.next_impl_id();
                     let span = self.span_from_span(sub_span);
 
-                    let type_data = self.lookup_ref_id(typ.id);
+                    let type_data = self.lookup_def_id(typ.id);
                     type_data.map(|type_data| {
                         Data::RelationData(Relation {
                             kind: RelationKind::Impl {
@@ -321,7 +322,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
                             from: id_from_def_id(type_data),
                             to: trait_ref
                                 .as_ref()
-                                .and_then(|t| self.lookup_ref_id(t.ref_id))
+                                .and_then(|t| self.lookup_def_id(t.ref_id))
                                 .map(id_from_def_id)
                                 .unwrap_or_else(|| null_id()),
                         },
@@ -494,7 +495,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
     }
 
     pub fn get_trait_ref_data(&self, trait_ref: &ast::TraitRef) -> Option<Ref> {
-        self.lookup_ref_id(trait_ref.ref_id).and_then(|def_id| {
+        self.lookup_def_id(trait_ref.ref_id).and_then(|def_id| {
             let span = trait_ref.path.span;
             if generated_code(span) {
                 return None;
@@ -869,7 +870,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
         })
     }
 
-    fn lookup_ref_id(&self, ref_id: NodeId) -> Option<DefId> {
+    fn lookup_def_id(&self, ref_id: NodeId) -> Option<DefId> {
         match self.get_path_res(ref_id) {
             Res::PrimTy(_) | Res::SelfTy(..) | Res::Err => None,
             def => Some(def.def_id()),
diff --git a/src/librustc_target/spec/apple_base.rs b/src/librustc_target/spec/apple_base.rs
index 53364e72bfe3a..f7551aa768dfc 100644
--- a/src/librustc_target/spec/apple_base.rs
+++ b/src/librustc_target/spec/apple_base.rs
@@ -51,3 +51,19 @@ pub fn macos_llvm_target(arch: &str) -> String {
     let (major, minor) = macos_deployment_target();
     format!("{}-apple-macosx{}.{}.0", arch, major, minor)
 }
+
+pub fn macos_link_env_remove() -> Vec<String> {
+    let mut env_remove = Vec::with_capacity(2);
+    // Remove the `SDKROOT` environment variable if it's clearly set for the wrong platform, which
+    // may occur when we're linking a custom build script while targeting iOS for example.
+    if let Some(sdkroot) = env::var("SDKROOT").ok() {
+        if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("iPhoneSimulator.platform") {
+            env_remove.push("SDKROOT".to_string())
+        }
+    }
+    // Additionally, `IPHONEOS_DEPLOYMENT_TARGET` must not be set when using the Xcode linker at
+    // "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld",
+    // although this is apparently ignored when using the linker at "/usr/bin/ld".
+    env_remove.push("IPHONEOS_DEPLOYMENT_TARGET".to_string());
+    env_remove
+}
diff --git a/src/librustc_target/spec/apple_ios_base.rs b/src/librustc_target/spec/apple_ios_base.rs
index 6d3900c0b203f..fdbb1bd5db34b 100644
--- a/src/librustc_target/spec/apple_ios_base.rs
+++ b/src/librustc_target/spec/apple_ios_base.rs
@@ -38,9 +38,18 @@ pub fn get_sdk_root(sdk_name: &str) -> Result<String, String> {
     // SDKROOT; for rustc, the user or build system can set it, or we
     // can fall back to checking for xcrun on PATH.)
     if let Some(sdkroot) = env::var("SDKROOT").ok() {
-        let sdkroot_path = Path::new(&sdkroot);
-        if sdkroot_path.is_absolute() && sdkroot_path != Path::new("/") && sdkroot_path.exists() {
-            return Ok(sdkroot);
+        let p = Path::new(&sdkroot);
+        match sdk_name {
+            // Ignore `SDKROOT` if it's clearly set for the wrong platform.
+            "iphoneos" if sdkroot.contains("iPhoneSimulator.platform")
+                       || sdkroot.contains("MacOSX.platform") => (),
+            "iphonesimulator" if sdkroot.contains("iPhoneOS.platform")
+                              || sdkroot.contains("MacOSX.platform") => (),
+            "macosx10.15" if sdkroot.contains("iPhoneOS.platform")
+                          || sdkroot.contains("iPhoneSimulator.platform") => (),
+            // Ignore `SDKROOT` if it's not a valid path.
+            _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => (),
+            _ => return Ok(sdkroot),
         }
     }
     let res = Command::new("xcrun")
@@ -100,6 +109,13 @@ fn target_cpu(arch: Arch) -> String {
     }.to_string()
 }
 
+fn link_env_remove(arch: Arch) -> Vec<String> {
+    match arch {
+        Armv7 | Armv7s | Arm64 | I386 | X86_64 => vec!["MACOSX_DEPLOYMENT_TARGET".to_string()],
+        X86_64_macabi => vec!["IPHONEOS_DEPLOYMENT_TARGET".to_string()],
+    }
+}
+
 pub fn opts(arch: Arch) -> Result<TargetOptions, String> {
     let pre_link_args = build_pre_link_args(arch)?;
     Ok(TargetOptions {
@@ -107,6 +123,7 @@ pub fn opts(arch: Arch) -> Result<TargetOptions, String> {
         dynamic_linking: false,
         executables: true,
         pre_link_args,
+        link_env_remove: link_env_remove(arch),
         has_elf_tls: false,
         eliminate_frame_pointer: false,
         .. super::apple_base::opts()
diff --git a/src/librustc_target/spec/i686_apple_darwin.rs b/src/librustc_target/spec/i686_apple_darwin.rs
index 7d804ea53fb31..27d05823bf21e 100644
--- a/src/librustc_target/spec/i686_apple_darwin.rs
+++ b/src/librustc_target/spec/i686_apple_darwin.rs
@@ -5,6 +5,7 @@ pub fn target() -> TargetResult {
     base.cpu = "yonah".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m32".to_string()]);
+    base.link_env_remove.extend(super::apple_base::macos_link_env_remove());
     base.stack_probes = true;
     base.eliminate_frame_pointer = false;
 
diff --git a/src/librustc_target/spec/i686_unknown_uefi.rs b/src/librustc_target/spec/i686_unknown_uefi.rs
new file mode 100644
index 0000000000000..c60f7b422d18f
--- /dev/null
+++ b/src/librustc_target/spec/i686_unknown_uefi.rs
@@ -0,0 +1,98 @@
+// This defines the ia32 target for UEFI systems as described in the UEFI specification. See the
+// uefi-base module for generic UEFI options. On ia32 systems
+// UEFI systems always run in protected-mode, have the interrupt-controller pre-configured and
+// force a single-CPU execution.
+// The cdecl ABI is used. It differs from the stdcall or fastcall ABI.
+// "i686-unknown-windows" is used to get the minimal subset of windows-specific features.
+
+use crate::spec::{LinkerFlavor, LldFlavor, Target, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::uefi_base::opts();
+    base.cpu = "pentium4".to_string();
+    base.max_atomic_width = Some(64);
+
+    // We disable MMX and SSE for now, even though UEFI allows using them. Problem is, you have to
+    // enable these CPU features explicitly before their first use, otherwise their instructions
+    // will trigger an exception. Rust does not inject any code that enables AVX/MMX/SSE
+    // instruction sets, so this must be done by the firmware. However, existing firmware is known
+    // to leave these uninitialized, thus triggering exceptions if we make use of them. Which is
+    // why we avoid them and instead use soft-floats. This is also what GRUB and friends did so
+    // far.
+    // If you initialize FP units yourself, you can override these flags with custom linker
+    // arguments, thus giving you access to full MMX/SSE acceleration.
+    base.features = "-mmx,-sse,+soft-float".to_string();
+
+    // UEFI mirrors the calling-conventions used on windows. In case of i686 this means small
+    // structs will be returned as int. This shouldn't matter much, since the restrictions placed
+    // by the UEFI specifications forbid any ABI to return structures.
+    base.abi_return_struct_as_int = true;
+
+    // Use -GNU here, because of the reason below:
+    // Backgound and Problem:
+    //   If we use i686-unknown-windows, the LLVM IA32 MSVC generates compiler intrinsic
+    //   _alldiv, _aulldiv, _allrem, _aullrem, _allmul, which will cause undefined symbol.
+    //   A real issue is __aulldiv() is refered by __udivdi3() - udivmod_inner!(), from
+    //   https://github.com/rust-lang-nursery/compiler-builtins.
+    //   As result, rust-lld generates link error finally.
+    // Root-cause:
+    //   In rust\src\llvm-project\llvm\lib\Target\X86\X86ISelLowering.cpp,
+    //   we have below code to use MSVC intrinsics. It assumes MSVC target
+    //   will link MSVC library. But that is NOT true in UEFI environment.
+    //   UEFI does not link any MSVC or GCC standard library.
+    //      if (Subtarget.isTargetKnownWindowsMSVC() ||
+    //          Subtarget.isTargetWindowsItanium()) {
+    //        // Setup Windows compiler runtime calls.
+    //        setLibcallName(RTLIB::SDIV_I64, "_alldiv");
+    //        setLibcallName(RTLIB::UDIV_I64, "_aulldiv");
+    //        setLibcallName(RTLIB::SREM_I64, "_allrem");
+    //        setLibcallName(RTLIB::UREM_I64, "_aullrem");
+    //        setLibcallName(RTLIB::MUL_I64, "_allmul");
+    //        setLibcallCallingConv(RTLIB::SDIV_I64, CallingConv::X86_StdCall);
+    //        setLibcallCallingConv(RTLIB::UDIV_I64, CallingConv::X86_StdCall);
+    //        setLibcallCallingConv(RTLIB::SREM_I64, CallingConv::X86_StdCall);
+    //        setLibcallCallingConv(RTLIB::UREM_I64, CallingConv::X86_StdCall);
+    //        setLibcallCallingConv(RTLIB::MUL_I64, CallingConv::X86_StdCall);
+    //      }
+    //   The compiler intrisics should be implemented by compiler-builtins.
+    //   Unfortunately, compiler-builtins has not provided those intrinsics yet. Such as:
+    //      i386/divdi3.S
+    //      i386/lshrdi3.S
+    //      i386/moddi3.S
+    //      i386/muldi3.S
+    //      i386/udivdi3.S
+    //      i386/umoddi3.S
+    // Possible solution:
+    //   1. Eliminate Intrinsics generation.
+    //      1.1 Choose differnt target to bypass isTargetKnownWindowsMSVC().
+    //      1.2 Remove the "Setup Windows compiler runtime calls" in LLVM
+    //   2. Implement Intrinsics.
+    //   We evaluated all options.
+    //   #2 is hard because we need implement the intrinsics (_aulldiv) generated
+    //   from the other intrinscis (__udivdi3) implementation with the same
+    //   functionality (udivmod_inner). If we let _aulldiv() call udivmod_inner!(),
+    //   then we are in loop. We may have to find another way to implement udivmod_inner!().
+    //   #1.2 may break the existing usage.
+    //   #1.1 seems the simplest solution today.
+    //   The IA32 -gnu calling convention is same as the one defined in UEFI specification.
+    //   It uses cdecl, EAX/ECX/EDX as volatile register, and EAX/EDX as return value.
+    //   We also checked the LLVM X86TargetLowering, the differences between -gnu and -msvc
+    //   is fmodf(f32), longjmp() and TLS. None of them impacts the UEFI code.
+    // As a result, we choose -gnu for i686 version before those intrisics are implemented in
+    // compiler-builtins. After compiler-builtins implements all required intrinsics, we may
+    // remove -gnu and use the default one.
+    Ok(Target {
+        llvm_target: "i686-unknown-windows-gnu".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "32".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32".to_string(),
+        target_os: "uefi".to_string(),
+        target_env: "".to_string(),
+        target_vendor: "unknown".to_string(),
+        arch: "x86".to_string(),
+        linker_flavor: LinkerFlavor::Lld(LldFlavor::Link),
+
+        options: base,
+    })
+}
diff --git a/src/librustc_target/spec/mod.rs b/src/librustc_target/spec/mod.rs
index 503d8a08b6f4f..626fa374a1bd4 100644
--- a/src/librustc_target/spec/mod.rs
+++ b/src/librustc_target/spec/mod.rs
@@ -493,6 +493,7 @@ supported_targets! {
     ("x86_64-fortanix-unknown-sgx", x86_64_fortanix_unknown_sgx),
 
     ("x86_64-unknown-uefi", x86_64_unknown_uefi),
+    ("i686-unknown-uefi", i686_unknown_uefi),
 
     ("nvptx64-nvidia-cuda", nvptx64_nvidia_cuda),
 
@@ -580,8 +581,10 @@ pub struct TargetOptions {
     /// user-defined libraries.
     pub post_link_args: LinkArgs,
 
-    /// Environment variables to be set before invoking the linker.
+    /// Environment variables to be set for the linker invocation.
     pub link_env: Vec<(String, String)>,
+    /// Environment variables to be removed for the linker invocation.
+    pub link_env_remove: Vec<String>,
 
     /// Extra arguments to pass to the external assembler (when used)
     pub asm_args: Vec<String>,
@@ -843,6 +846,7 @@ impl Default for TargetOptions {
             post_link_objects_crt: Vec::new(),
             late_link_args: LinkArgs::new(),
             link_env: Vec::new(),
+            link_env_remove: Vec::new(),
             archive_format: "gnu".to_string(),
             custom_unwind_resume: false,
             allow_asm: true,
@@ -1118,6 +1122,7 @@ impl Target {
         key!(post_link_objects_crt, list);
         key!(post_link_args, link_args);
         key!(link_env, env);
+        key!(link_env_remove, list);
         key!(asm_args, list);
         key!(cpu);
         key!(features);
@@ -1334,6 +1339,7 @@ impl ToJson for Target {
         target_option_val!(post_link_objects_crt);
         target_option_val!(link_args - post_link_args);
         target_option_val!(env - link_env);
+        target_option_val!(link_env_remove);
         target_option_val!(asm_args);
         target_option_val!(cpu);
         target_option_val!(features);
diff --git a/src/librustc_target/spec/wasm32_wasi.rs b/src/librustc_target/spec/wasm32_wasi.rs
index bb33493a77333..86978c05b15d0 100644
--- a/src/librustc_target/spec/wasm32_wasi.rs
+++ b/src/librustc_target/spec/wasm32_wasi.rs
@@ -97,6 +97,10 @@ pub fn target() -> Result<Target, String> {
     options.crt_static_default = true;
     options.crt_static_respected = true;
 
+    // Allow `+crt-static` to create a "cdylib" output which is just a wasm file
+    // without a main function.
+    options.crt_static_allows_dylibs = true;
+
     Ok(Target {
         llvm_target: "wasm32-wasi".to_string(),
         target_endian: "little".to_string(),
diff --git a/src/librustc_target/spec/x86_64_apple_darwin.rs b/src/librustc_target/spec/x86_64_apple_darwin.rs
index 182103440f035..d059e44c5c82a 100644
--- a/src/librustc_target/spec/x86_64_apple_darwin.rs
+++ b/src/librustc_target/spec/x86_64_apple_darwin.rs
@@ -6,6 +6,7 @@ pub fn target() -> TargetResult {
     base.max_atomic_width = Some(128); // core2 support cmpxchg16b
     base.eliminate_frame_pointer = false;
     base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m64".to_string()]);
+    base.link_env_remove.extend(super::apple_base::macos_link_env_remove());
     base.stack_probes = true;
 
     // Clang automatically chooses a more specific target based on
diff --git a/src/librustc_tsan/build.rs b/src/librustc_tsan/build.rs
index ed9c37087c7e5..f9333e1502327 100644
--- a/src/librustc_tsan/build.rs
+++ b/src/librustc_tsan/build.rs
@@ -4,6 +4,10 @@ use build_helper::sanitizer_lib_boilerplate;
 use cmake::Config;
 
 fn main() {
+    println!("cargo:rerun-if-env-changed=RUSTC_BUILD_SANITIZERS");
+    if env::var("RUSTC_BUILD_SANITIZERS") != Ok("1".to_string()) {
+        return;
+    }
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
         build_helper::restore_library_path();
 
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 9e52eae88ef45..09e6b76900396 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -23,6 +23,7 @@ use rustc_target::spec::abi;
 use crate::require_c_abi_if_c_variadic;
 use smallvec::SmallVec;
 use syntax::ast;
+use syntax::errors::pluralise;
 use syntax::feature_gate::{GateIssue, emit_feature_err};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::symbol::sym;
@@ -377,7 +378,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     quantifier,
                     bound,
                     kind,
-                    if bound != 1 { "s" } else { "" },
+                    pluralise!(bound),
                 ))
             };
 
@@ -1461,7 +1462,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         span: Span,
         type_str: &str,
         trait_str: &str,
-        name: &str,
+        name: ast::Name,
     ) {
         let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
         if let (Some(_), Ok(snippet)) = (
@@ -1688,7 +1689,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         span,
                         &qself_ty.to_string(),
                         "Trait",
-                        &assoc_ident.as_str(),
+                        assoc_ident.name,
                     );
                 }
                 return Err(ErrorReported);
@@ -1761,7 +1762,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 span,
                 "Type",
                 &path_str,
-                &item_segment.ident.as_str(),
+                item_segment.ident.name,
             );
             return tcx.types.err;
         };
diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index 7427ae9ce8de3..50fd72f061319 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -2,7 +2,8 @@ use crate::check::{FnCtxt, Expectation, Diverges, Needs};
 use crate::check::coercion::CoerceMany;
 use rustc::hir::{self, ExprKind};
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc::traits::{ObligationCause, ObligationCauseCode};
+use rustc::traits::{IfExpressionCause, MatchExpressionArmCause, ObligationCause};
+use rustc::traits::{ObligationCauseCode};
 use rustc::ty::Ty;
 use syntax_pos::Span;
 
@@ -42,7 +43,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // If there are no arms, that is a diverging match; a special case.
         if arms.is_empty() {
-            self.diverges.set(self.diverges.get() | Diverges::Always);
+            self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
             return tcx.types.never;
         }
 
@@ -68,7 +69,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // warnings).
             match all_pats_diverge {
                 Diverges::Maybe => Diverges::Maybe,
-                Diverges::Always | Diverges::WarnedAlways => Diverges::WarnedAlways,
+                Diverges::Always { .. } | Diverges::WarnedAlways => Diverges::WarnedAlways,
             }
         }).collect();
 
@@ -146,13 +147,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // The reason for the first arm to fail is not that the match arms diverge,
                     // but rather that there's a prior obligation that doesn't hold.
                     0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
-                    _ => (expr.span, ObligationCauseCode::MatchExpressionArm {
-                        arm_span,
-                        source: match_src,
-                        prior_arms: other_arms.clone(),
-                        last_ty: prior_arm_ty.unwrap(),
-                        discrim_hir_id: discrim.hir_id,
-                    }),
+                    _ => (expr.span,
+                          ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
+                            arm_span,
+                            source: match_src,
+                            prior_arms: other_arms.clone(),
+                            last_ty: prior_arm_ty.unwrap(),
+                            discrim_hir_id: discrim.hir_id,
+                          })
+                         ),
                 };
                 let cause = self.cause(span, code);
                 coercion.coerce(self, &cause, &arm.body, arm_ty);
@@ -164,6 +167,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             prior_arm_ty = Some(arm_ty);
         }
 
+        // If all of the arms in the `match` diverge,
+        // and we're dealing with an actual `match` block
+        // (as opposed to a `match` desugared from something else'),
+        // we can emit a better note. Rather than pointing
+        // at a diverging expression in an arbitrary arm,
+        // we can point at the entire `match` expression
+        if let (Diverges::Always { .. }, hir::MatchSource::Normal) = (all_arms_diverge, match_src) {
+            all_arms_diverge = Diverges::Always {
+                span: expr.span,
+                custom_note: Some(
+                    "any code following this `match` expression is unreachable, as all arms diverge"
+                )
+            };
+        }
+
         // We won't diverge unless the discriminant or all arms diverge.
         self.diverges.set(discrim_diverges | all_arms_diverge);
 
@@ -173,7 +191,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// When the previously checked expression (the scrutinee) diverges,
     /// warn the user about the match arms being unreachable.
     fn warn_arms_when_scrutinee_diverges(&self, arms: &'tcx [hir::Arm], source: hir::MatchSource) {
-        if self.diverges.get().always() {
+        if self.diverges.get().is_always() {
             use hir::MatchSource::*;
             let msg = match source {
                 IfDesugar { .. } | IfLetDesugar { .. } => "block in `if` expression",
@@ -345,11 +363,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // Finally construct the cause:
-        self.cause(error_sp, ObligationCauseCode::IfExpression {
+        self.cause(error_sp, ObligationCauseCode::IfExpression(box IfExpressionCause {
             then: then_sp,
             outer: outer_sp,
             semicolon: remove_semicolon,
-        })
+        }))
     }
 
     fn demand_discriminant_type(
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index e9370429f3f55..d626bff150020 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -529,11 +529,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ); // recreated from (*) above
 
                 // Check that E' = S'.
-                let cause = &self.misc(hir_ty.span);
+                let cause = self.misc(hir_ty.span);
                 let InferOk {
                     value: (),
                     obligations,
-                } = self.at(cause, self.param_env)
+                } = self.at(&cause, self.param_env)
                     .eq(*expected_ty, supplied_ty)?;
                 all_obligations.extend(obligations);
 
@@ -549,7 +549,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
                 all_obligations.push(
                     Obligation::new(
-                        cause.clone(),
+                        cause,
                         self.param_env,
                         ty::Predicate::TypeOutlives(
                             ty::Binder::dummy(
diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs
index f2e1a6e29d6fc..ee4f0a868c10a 100644
--- a/src/librustc_typeck/check/coercion.rs
+++ b/src/librustc_typeck/check/coercion.rs
@@ -617,7 +617,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
                 // Object safety violations or miscellaneous.
                 Err(err) => {
-                    self.report_selection_error(&obligation, &err, false);
+                    self.report_selection_error(&obligation, &err, false, false);
                     // Treat this like an obligation and follow through
                     // with the unsizing - the lack of a coercion should
                     // be silent, as it causes a type mismatch later.
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
index 8e187b7e05b51..51adf501b4db8 100644
--- a/src/librustc_typeck/check/compare_method.rs
+++ b/src/librustc_typeck/check/compare_method.rs
@@ -10,6 +10,7 @@ use rustc::util::common::ErrorReported;
 use errors::{Applicability, DiagnosticId};
 
 use syntax_pos::Span;
+use syntax::errors::pluralise;
 
 use super::{Inherited, FnCtxt, potentially_plural_count};
 
@@ -308,7 +309,7 @@ fn compare_predicate_entailment<'tcx>(
 
             let cause = ObligationCause {
                 span: impl_err_span,
-                ..cause.clone()
+                ..cause
             };
 
             let mut diag = struct_span_err!(tcx.sess,
@@ -648,9 +649,9 @@ fn compare_number_of_generics<'tcx>(
                      declaration has {} {kind} parameter{}",
                     trait_.ident,
                     impl_count,
-                    if impl_count != 1 { "s" } else { "" },
+                    pluralise!(impl_count),
                     trait_count,
-                    if trait_count != 1 { "s" } else { "" },
+                    pluralise!(trait_count),
                     kind = kind,
                 ),
                 DiagnosticId::Error("E0049".into()),
@@ -665,7 +666,7 @@ fn compare_number_of_generics<'tcx>(
                         "expected {} {} parameter{}",
                         trait_count,
                         kind,
-                        if trait_count != 1 { "s" } else { "" },
+                        pluralise!(trait_count),
                     ));
                 }
                 for span in spans {
@@ -680,7 +681,7 @@ fn compare_number_of_generics<'tcx>(
                     "found {} {} parameter{}{}",
                     impl_count,
                     kind,
-                    if impl_count != 1 { "s" } else { "" },
+                    pluralise!(impl_count),
                     suffix.unwrap_or_else(|| String::new()),
                 ));
             }
diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
index 9644815f805d9..049f2eb16bb00 100644
--- a/src/librustc_typeck/check/expr.rs
+++ b/src/librustc_typeck/check/expr.rs
@@ -161,12 +161,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Warn for non-block expressions with diverging children.
         match expr.node {
             ExprKind::Block(..) | ExprKind::Loop(..) | ExprKind::Match(..) => {},
+            ExprKind::Call(ref callee, _) =>
+                self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
+            ExprKind::MethodCall(_, ref span, _) =>
+                self.warn_if_unreachable(expr.hir_id, *span, "call"),
             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
         }
 
         // Any expression that produces a value of type `!` must have diverged
         if ty.is_never() {
-            self.diverges.set(self.diverges.get() | Diverges::Always);
+            self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
         }
 
         // Record the type, which applies it effects.
@@ -809,18 +813,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         error: MethodError<'tcx>
     ) {
         let rcvr = &args[0];
-        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
-            if let Ok(pick) = self.lookup_probe(
-                span,
-                segment.ident,
-                new_rcvr_t,
-                rcvr,
-                probe::ProbeScope::AllTraits,
-            ) {
-                err.span_label(
-                    pick.item.ident.span,
-                    &format!("the method is available for `{}` here", new_rcvr_t),
-                );
+        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, rcvr_t, lang_item| {
+            if let Some(new_rcvr_t) = self.tcx.mk_lang_item(rcvr_t, lang_item) {
+                if let Ok(pick) = self.lookup_probe(
+                    span,
+                    segment.ident,
+                    new_rcvr_t,
+                    rcvr,
+                    probe::ProbeScope::AllTraits,
+                ) {
+                    err.span_label(
+                        pick.item.ident.span,
+                        &format!("the method is available for `{}` here", new_rcvr_t),
+                    );
+                }
             }
         };
 
@@ -836,17 +842,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // Try alternative arbitrary self types that could fulfill this call.
                 // FIXME: probe for all types that *could* be arbitrary self-types, not
                 // just this whitelist.
-                let box_rcvr_t = self.tcx.mk_box(rcvr_t);
-                try_alt_rcvr(&mut err, box_rcvr_t);
-                let pin_rcvr_t = self.tcx.mk_lang_item(
-                    rcvr_t,
-                    lang_items::PinTypeLangItem,
-                );
-                try_alt_rcvr(&mut err, pin_rcvr_t);
-                let arc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Arc);
-                try_alt_rcvr(&mut err, arc_rcvr_t);
-                let rc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Rc);
-                try_alt_rcvr(&mut err, rc_rcvr_t);
+                try_alt_rcvr(&mut err, rcvr_t, lang_items::OwnedBoxLangItem);
+                try_alt_rcvr(&mut err, rcvr_t, lang_items::PinTypeLangItem);
+                try_alt_rcvr(&mut err, rcvr_t, lang_items::Arc);
+                try_alt_rcvr(&mut err, rcvr_t, lang_items::Rc);
             }
             err.emit();
         }
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 1c01c8408be6c..c8838311e8dbf 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -578,6 +578,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             ty::Param(p) => {
                 self.assemble_inherent_candidates_from_param(p);
             }
+            ty::Bool => {
+                let lang_def_id = lang_items.bool_impl();
+                self.assemble_inherent_impl_for_primitive(lang_def_id);
+            }
             ty::Char => {
                 let lang_def_id = lang_items.char_impl();
                 self.assemble_inherent_impl_for_primitive(lang_def_id);
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index 72e6f59715960..3e45b1e98d4ec 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -425,6 +425,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             "private field"
                         };
                         err.span_label(item_name.span, format!("{}, not a method", field_kind));
+                    } else if lev_candidate.is_none() && static_sources.is_empty() {
+                        err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
+                        self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
                     }
                 } else {
                     err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index d8d01624f1d56..0eeeee01c82f1 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -400,7 +400,7 @@ pub struct UnsafetyState {
 
 impl UnsafetyState {
     pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
-        UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
+        UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
     }
 
     pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
@@ -450,7 +450,20 @@ pub enum Diverges {
 
     /// Definitely known to diverge and therefore
     /// not reach the next sibling or its parent.
-    Always,
+    Always {
+        /// The `Span` points to the expression
+        /// that caused us to diverge
+        /// (e.g. `return`, `break`, etc).
+        span: Span,
+        /// In some cases (e.g. a `match` expression
+        /// where all arms diverge), we may be
+        /// able to provide a more informative
+        /// message to the user.
+        /// If this is `None`, a default messsage
+        /// will be generated, which is suitable
+        /// for most cases.
+        custom_note: Option<&'static str>
+    },
 
     /// Same as `Always` but with a reachability
     /// warning already emitted.
@@ -486,8 +499,22 @@ impl ops::BitOrAssign for Diverges {
 }
 
 impl Diverges {
-    fn always(self) -> bool {
-        self >= Diverges::Always
+    /// Creates a `Diverges::Always` with the provided `span` and the default note message.
+    fn always(span: Span) -> Diverges {
+        Diverges::Always {
+            span,
+            custom_note: None
+        }
+    }
+
+    fn is_always(self) -> bool {
+        // Enum comparison ignores the
+        // contents of fields, so we just
+        // fill them in with garbage here.
+        self >= Diverges::Always {
+            span: DUMMY_SP,
+            custom_note: None
+        }
     }
 }
 
@@ -885,12 +912,12 @@ fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
         };
 
         // All type checking constraints were added, try to fallback unsolved variables.
-        fcx.select_obligations_where_possible(false);
+        fcx.select_obligations_where_possible(false, |_| {});
         let mut fallback_has_occurred = false;
         for ty in &fcx.unsolved_variables() {
             fallback_has_occurred |= fcx.fallback_if_possible(ty);
         }
-        fcx.select_obligations_where_possible(fallback_has_occurred);
+        fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
 
         // Even though coercion casts provide type hints, we check casts after fallback for
         // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
@@ -1088,6 +1115,8 @@ fn check_fn<'a, 'tcx>(
 
     let span = body.value.span;
 
+    fn_maybe_err(fcx.tcx, span, fn_sig.abi);
+
     if body.generator_kind.is_some() && can_be_generator.is_some() {
         let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
             kind: TypeVariableOriginKind::TypeInference,
@@ -1439,6 +1468,14 @@ fn check_opaque_for_cycles<'tcx>(
     }
 }
 
+// Forbid defining intrinsics in Rust code,
+// as they must always be defined by the compiler.
+fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
+    if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
+        tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
+    }
+}
+
 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
     debug!(
         "check_item_type(it.hir_id={}, it.name={})",
@@ -1475,9 +1512,17 @@ pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
                 check_on_unimplemented(tcx, trait_def_id, it);
             }
         }
-        hir::ItemKind::Trait(..) => {
+        hir::ItemKind::Trait(_, _, _, _, ref items) => {
             let def_id = tcx.hir().local_def_id(it.hir_id);
             check_on_unimplemented(tcx, def_id, it);
+
+            for item in items.iter() {
+                let item = tcx.hir().trait_item(item.id);
+                if let hir::TraitItemKind::Method(sig, _) = &item.node {
+                    let abi = sig.header.abi;
+                    fn_maybe_err(tcx, item.ident.span, abi);
+                }
+            }
         }
         hir::ItemKind::Struct(..) => {
             check_struct(tcx, it.hir_id, it.span);
@@ -1511,21 +1556,34 @@ pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
             } else {
                 for item in &m.items {
                     let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
-                    if generics.params.len() - generics.own_counts().lifetimes != 0 {
-                        let mut err = struct_span_err!(
+                    let own_counts = generics.own_counts();
+                    if generics.params.len() - own_counts.lifetimes != 0 {
+                        let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
+                            (_, 0) => ("type", "types", Some("u32")),
+                            // We don't specify an example value, because we can't generate
+                            // a valid value for any type.
+                            (0, _) => ("const", "consts", None),
+                            _ => ("type or const", "types or consts", None),
+                        };
+                        struct_span_err!(
                             tcx.sess,
                             item.span,
                             E0044,
-                            "foreign items may not have type parameters"
-                        );
-                        err.span_label(item.span, "can't have type parameters");
-                        // FIXME: once we start storing spans for type arguments, turn this into a
-                        // suggestion.
-                        err.help(
-                            "use specialization instead of type parameters by replacing them \
-                             with concrete types like `u32`",
-                        );
-                        err.emit();
+                            "foreign items may not have {} parameters",
+                            kinds,
+                        ).span_label(
+                            item.span,
+                            &format!("can't have {} parameters", kinds),
+                        ).help(
+                            // FIXME: once we start storing spans for type arguments, turn this
+                            // into a suggestion.
+                            &format!(
+                                "replace the {} parameters with concrete {}{}",
+                                kinds,
+                                kinds_pl,
+                                egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
+                            ),
+                        ).emit();
                     }
 
                     if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
@@ -2276,17 +2334,25 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Produces warning on the given node, if the current point in the
     /// function is unreachable, and there hasn't been another warning.
     fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
-        if self.diverges.get() == Diverges::Always &&
+        // FIXME: Combine these two 'if' expressions into one once
+        // let chains are implemented
+        if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
             // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
             // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
             // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
-            !span.is_desugaring(DesugaringKind::CondTemporary) {
-            self.diverges.set(Diverges::WarnedAlways);
+            if !span.is_desugaring(DesugaringKind::CondTemporary) {
+                self.diverges.set(Diverges::WarnedAlways);
 
-            debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
+                debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
 
-            let msg = format!("unreachable {}", kind);
-            self.tcx().lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg);
+                let msg = format!("unreachable {}", kind);
+                self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
+                    .span_note(
+                        orig_span,
+                        custom_note.unwrap_or("any code following this expression is unreachable")
+                    )
+                    .emit();
+            }
         }
     }
 
@@ -2325,7 +2391,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // possible. This can help substantially when there are
         // indirect dependencies that don't seem worth tracking
         // precisely.
-        self.select_obligations_where_possible(false);
+        self.select_obligations_where_possible(false, |_| {});
         ty = self.resolve_vars_if_possible(&ty);
 
         debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
@@ -2776,7 +2842,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn resolve_generator_interiors(&self, def_id: DefId) {
         let mut generators = self.deferred_generator_interiors.borrow_mut();
         for (body_id, interior, kind) in generators.drain(..) {
-            self.select_obligations_where_possible(false);
+            self.select_obligations_where_possible(false, |_| {});
             generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
         }
     }
@@ -2813,8 +2879,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// Select as many obligations as we can at present.
-    fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
-        if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
+    fn select_obligations_where_possible(
+        &self,
+        fallback_has_occurred: bool,
+        mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
+    ) {
+        if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
+            mutate_fullfillment_errors(&mut errors);
             self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
         }
     }
@@ -3222,6 +3293,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             formal_tys.clone()
         };
 
+        let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
+
         // Check the arguments.
         // We do this in a pretty awful way: first we type-check any arguments
         // that are not closures, then we type-check the closures. This is so
@@ -3234,7 +3307,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // an "opportunistic" vtable resolution of any trait bounds on
             // the call. This helps coercions.
             if check_closures {
-                self.select_obligations_where_possible(false);
+                self.select_obligations_where_possible(false, |errors| {
+                    self.point_at_arg_instead_of_call_if_possible(
+                        errors,
+                        &final_arg_types[..],
+                        sp,
+                        &args,
+                    );
+                })
             }
 
             // For C-variadic functions, we don't have a declared type for all of
@@ -3280,6 +3360,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // We're processing function arguments so we definitely want to use
                 // two-phase borrows.
                 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
+                final_arg_types.push((i, coerce_ty));
 
                 // 3. Relate the expected type and the formal one,
                 //    if the expected type was used for the coercion.
@@ -3326,6 +3407,44 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         vec![self.tcx.types.err; len]
     }
 
+    /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
+    /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
+    /// reference a type argument. If they do, and there's only *one* argument that does, we point
+    /// at the corresponding argument's expression span instead of the `fn` call path span.
+    fn point_at_arg_instead_of_call_if_possible(
+        &self,
+        errors: &mut Vec<traits::FulfillmentError<'_>>,
+        final_arg_types: &[(usize, Ty<'tcx>)],
+        call_sp: Span,
+        args: &'tcx [hir::Expr],
+    ) {
+        if !call_sp.desugaring_kind().is_some() {
+            // We *do not* do this for desugared call spans to keep good diagnostics when involving
+            // the `?` operator.
+            for error in errors {
+                if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
+                    // Collect the argument position for all arguments that could have caused this
+                    // `FullfillmentError`.
+                    let mut referenced_in = final_arg_types.iter()
+                        .flat_map(|(i, ty)| {
+                            let ty = self.resolve_vars_if_possible(ty);
+                            // We walk the argument type because the argument's type could have
+                            // been `Option<T>`, but the `FullfillmentError` references `T`.
+                            ty.walk()
+                                .filter(|&ty| ty == predicate.skip_binder().self_ty())
+                                .map(move |_| *i)
+                        });
+                    if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
+                        // We make sure that only *one* argument matches the obligation failure
+                        // and thet the obligation's span to its expression's.
+                        error.obligation.cause.span = args[ref_in].span;
+                        error.points_at_arg_span = true;
+                    }
+                }
+            }
+        }
+    }
+
     // AST fragment checking
     fn check_lit(&self,
                  lit: &hir::Lit,
@@ -3483,8 +3602,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // Check bounds on type arguments used in the path.
             let bounds = self.instantiate_bounds(path_span, did, substs);
-            let cause = traits::ObligationCause::new(path_span, self.body_id,
-                                                     traits::ItemObligation(did));
+            let cause = traits::ObligationCause::new(
+                path_span,
+                self.body_id,
+                traits::ItemObligation(did),
+            );
             self.add_obligations_for_parameters(cause, &bounds);
 
             Some((variant, ty))
@@ -3794,7 +3916,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 //
                 // #41425 -- label the implicit `()` as being the
                 // "found type" here, rather than the "expected type".
-                if !self.diverges.get().always() {
+                if !self.diverges.get().is_always() {
                     // #50009 -- Do not point at the entire fn block span, point at the return type
                     // span, as it is the cause of the requirement, and
                     // `consider_hint_about_removing_semicolon` will point at the last expression
@@ -4608,7 +4730,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let bounds = self.instantiate_bounds(span, def_id, &substs);
         self.add_obligations_for_parameters(
             traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
-            &bounds);
+            &bounds,
+        );
 
         // Substitute the values for the type parameters into the type of
         // the referenced item.
diff --git a/src/librustc_typeck/check/op.rs b/src/librustc_typeck/check/op.rs
index 93855a3b68a7f..956d04ff6229b 100644
--- a/src/librustc_typeck/check/op.rs
+++ b/src/librustc_typeck/check/op.rs
@@ -268,7 +268,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 op.node.as_str(), lhs_ty),
                             );
                             let mut suggested_deref = false;
-                            if let Ref(_, mut rty, _) = lhs_ty.sty {
+                            if let Ref(_, rty, _) = lhs_ty.sty {
                                 if {
                                     self.infcx.type_is_copy_modulo_regions(self.param_env,
                                                                            rty,
@@ -279,13 +279,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                             .is_ok()
                                 } {
                                     if let Ok(lstring) = source_map.span_to_snippet(lhs_expr.span) {
-                                        while let Ref(_, rty_inner, _) = rty.sty {
-                                            rty = rty_inner;
-                                        }
                                         let msg = &format!(
                                             "`{}=` can be used on '{}', you can dereference `{}`",
                                             op.node.as_str(),
-                                            rty,
+                                            rty.peel_refs(),
                                             lstring,
                                         );
                                         err.span_suggestion(
@@ -361,7 +358,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             }
 
                             let mut suggested_deref = false;
-                            if let Ref(_, mut rty, _) = lhs_ty.sty {
+                            if let Ref(_, rty, _) = lhs_ty.sty {
                                 if {
                                     self.infcx.type_is_copy_modulo_regions(self.param_env,
                                                                            rty,
@@ -372,17 +369,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                             .is_ok()
                                 } {
                                     if let Ok(lstring) = source_map.span_to_snippet(lhs_expr.span) {
-                                        while let Ref(_, rty_inner, _) = rty.sty {
-                                            rty = rty_inner;
-                                        }
-                                        let msg = &format!(
-                                                "`{}` can be used on '{}', you can \
-                                                dereference `{2}`: `*{2}`",
-                                                op.node.as_str(),
-                                                rty,
-                                                lstring
-                                        );
-                                        err.help(msg);
+                                        err.help(&format!(
+                                            "`{}` can be used on '{}', you can \
+                                            dereference `{2}`: `*{2}`",
+                                            op.node.as_str(),
+                                            rty.peel_refs(),
+                                            lstring
+                                        ));
                                         suggested_deref = true;
                                     }
                                 }
@@ -731,7 +724,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match method {
             Some(ok) => {
                 let method = self.register_infer_ok_obligations(ok);
-                self.select_obligations_where_possible(false);
+                self.select_obligations_where_possible(false, |_| {});
 
                 Ok(method)
             }
diff --git a/src/librustc_typeck/check/pat.rs b/src/librustc_typeck/check/pat.rs
index 4cf0df308fb4c..8502b89de1469 100644
--- a/src/librustc_typeck/check/pat.rs
+++ b/src/librustc_typeck/check/pat.rs
@@ -675,21 +675,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span);
             }
         } else {
-            let subpats_ending = if subpats.len() == 1 { "" } else { "s" };
-            let fields_ending = if variant.fields.len() == 1 { "" } else { "s" };
-            struct_span_err!(tcx.sess, pat.span, E0023,
-                             "this pattern has {} field{}, but the corresponding {} has {} field{}",
-                             subpats.len(), subpats_ending, res.descr(),
-                             variant.fields.len(),  fields_ending)
-                .span_label(pat.span, format!("expected {} field{}, found {}",
-                                              variant.fields.len(), fields_ending, subpats.len()))
-                .emit();
+            // Pattern has wrong number of fields.
+            self.e0023(pat.span, res, &subpats, &variant.fields);
             on_error();
             return tcx.types.err;
         }
         pat_ty
     }
 
+    fn e0023(&self, pat_span: Span, res: Res, subpats: &'tcx [P<Pat>], fields: &[ty::FieldDef]) {
+        let subpats_ending = if subpats.len() == 1 { "" } else { "s" };
+        let fields_ending = if fields.len() == 1 { "" } else { "s" };
+        let res_span = self.tcx.def_span(res.def_id());
+        struct_span_err!(
+            self.tcx.sess,
+            pat_span,
+            E0023,
+            "this pattern has {} field{}, but the corresponding {} has {} field{}",
+            subpats.len(),
+            subpats_ending,
+            res.descr(),
+            fields.len(),
+            fields_ending,
+        )
+            .span_label(pat_span, format!(
+                "expected {} field{}, found {}",
+                fields.len(),
+                fields_ending,
+                subpats.len(),
+            ))
+            .span_label(res_span, format!("{} defined here", res.descr()))
+            .emit();
+    }
+
     fn check_pat_tuple(
         &self,
         span: Span,
@@ -1080,22 +1098,35 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     fn error_scrutinee_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
         struct_span_err!(
-            self.tcx.sess, span, E0527,
-            "pattern requires {} elements but array has {}",
-            min_len, size
+            self.tcx.sess,
+            span,
+            E0527,
+            "pattern requires {} element{} but array has {}",
+            min_len,
+            if min_len != 1 { "s" } else { "" },
+            size,
         )
-        .span_label(span, format!("expected {} elements", size))
+        .span_label(span, format!("expected {} element{}", size, if size != 1 { "s" } else { "" }))
         .emit();
     }
 
     fn error_scrutinee_with_rest_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
         struct_span_err!(
-            self.tcx.sess, span, E0528,
-            "pattern requires at least {} elements but array has {}",
-            min_len, size
-        )
-        .span_label(span, format!("pattern cannot match array of {} elements", size))
-        .emit();
+            self.tcx.sess,
+            span,
+            E0528,
+            "pattern requires at least {} element{} but array has {}",
+            min_len,
+            if min_len != 1 { "s" } else { "" },
+            size,
+        ).span_label(
+            span,
+            format!(
+                "pattern cannot match array of {} element{}",
+                size,
+                if size != 1 { "s" } else { "" },
+            ),
+        ).emit();
     }
 
     fn error_scrutinee_unfixed_length(&self, span: Span) {
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index ac8ee43dd0801..b0e886a2aa2eb 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -506,7 +506,7 @@ fn check_where_clauses<'tcx, 'fcx>(
     });
 
     // Now we build the substituted predicates.
-    let default_obligations = predicates.predicates.iter().flat_map(|&(pred, _)| {
+    let default_obligations = predicates.predicates.iter().flat_map(|&(pred, sp)| {
         #[derive(Default)]
         struct CountParams { params: FxHashSet<u32> }
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams {
@@ -539,9 +539,9 @@ fn check_where_clauses<'tcx, 'fcx>(
             // Avoid duplication of predicates that contain no parameters, for example.
             None
         } else {
-            Some(substituted_pred)
+            Some((substituted_pred, sp))
         }
-    }).map(|pred| {
+    }).map(|(pred, sp)| {
         // Convert each of those into an obligation. So if you have
         // something like `struct Foo<T: Copy = String>`, we would
         // take that predicate `T: Copy`, substitute to `String: Copy`
@@ -551,8 +551,8 @@ fn check_where_clauses<'tcx, 'fcx>(
         // Note the subtle difference from how we handle `predicates`
         // below: there, we are not trying to prove those predicates
         // to be *true* but merely *well-formed*.
-        let pred = fcx.normalize_associated_types_in(span, &pred);
-        let cause = traits::ObligationCause::new(span, fcx.body_id, traits::ItemObligation(def_id));
+        let pred = fcx.normalize_associated_types_in(sp, &pred);
+        let cause = traits::ObligationCause::new(sp, fcx.body_id, traits::ItemObligation(def_id));
         traits::Obligation::new(cause, fcx.param_env, pred)
     });
 
diff --git a/src/librustc_typeck/coherence/inherent_impls.rs b/src/librustc_typeck/coherence/inherent_impls.rs
index fb79a85ea25bf..e7c2126cfd727 100644
--- a/src/librustc_typeck/coherence/inherent_impls.rs
+++ b/src/librustc_typeck/coherence/inherent_impls.rs
@@ -67,6 +67,14 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
             ty::Dynamic(ref data, ..) if data.principal_def_id().is_some() => {
                 self.check_def_id(item, data.principal_def_id().unwrap());
             }
+            ty::Bool => {
+                self.check_primitive_impl(def_id,
+                                          lang_items.bool_impl(),
+                                          None,
+                                          "bool",
+                                          "bool",
+                                          item.span);
+            }
             ty::Char => {
                 self.check_primitive_impl(def_id,
                                           lang_items.char_impl(),
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 312a598af02bf..d2e9203779cc8 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -519,15 +519,15 @@ fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
     tcx.predicates_of(def_id);
 }
 
-fn convert_enum_variant_types<'tcx>(
-    tcx: TyCtxt<'tcx>,
+fn convert_enum_variant_types(
+    tcx: TyCtxt<'_>,
     def_id: DefId,
     variants: &[hir::Variant]
 ) {
     let def = tcx.adt_def(def_id);
     let repr_type = def.repr.discr_type();
     let initial = repr_type.initial_discriminant(tcx);
-    let mut prev_discr = None::<Discr<'tcx>>;
+    let mut prev_discr = None::<Discr<'_>>;
 
     // fill the discriminant values and field types
     for variant in variants {
diff --git a/src/librustc_typeck/constrained_generic_params.rs b/src/librustc_typeck/constrained_generic_params.rs
index 79a04b9423a8e..dd44f86717fe5 100644
--- a/src/librustc_typeck/constrained_generic_params.rs
+++ b/src/librustc_typeck/constrained_generic_params.rs
@@ -20,10 +20,10 @@ impl From<ty::ParamConst> for Parameter {
 }
 
 /// Returns the set of parameters constrained by the impl header.
-pub fn parameters_for_impl<'tcx>(impl_self_ty: Ty<'tcx>,
-                                 impl_trait_ref: Option<ty::TraitRef<'tcx>>)
-                                 -> FxHashSet<Parameter>
-{
+pub fn parameters_for_impl<'tcx>(
+    impl_self_ty: Ty<'tcx>,
+    impl_trait_ref: Option<ty::TraitRef<'tcx>>,
+) -> FxHashSet<Parameter> {
     let vec = match impl_trait_ref {
         Some(tr) => parameters_for(&tr, false),
         None => parameters_for(&impl_self_ty, false),
@@ -36,12 +36,10 @@ pub fn parameters_for_impl<'tcx>(impl_self_ty: Ty<'tcx>,
 /// uniquely determined by `t` (see RFC 447). If it is true, return the list
 /// of parameters whose values are needed in order to constrain `ty` - these
 /// differ, with the latter being a superset, in the presence of projections.
-pub fn parameters_for<'tcx, T>(t: &T,
-                               include_nonconstraining: bool)
-                               -> Vec<Parameter>
-    where T: TypeFoldable<'tcx>
-{
-
+pub fn parameters_for<'tcx>(
+    t: &impl TypeFoldable<'tcx>,
+    include_nonconstraining: bool,
+) -> Vec<Parameter> {
     let mut collector = ParameterCollector {
         parameters: vec![],
         include_nonconstraining,
diff --git a/src/librustc_typeck/error_codes.rs b/src/librustc_typeck/error_codes.rs
index 093446d28533e..e11dcfafb8f8b 100644
--- a/src/librustc_typeck/error_codes.rs
+++ b/src/librustc_typeck/error_codes.rs
@@ -1,6 +1,6 @@
 // ignore-tidy-filelength
 
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0023: r##"
 A pattern used to match against an enum variant must provide a sub-pattern for
@@ -4870,10 +4870,7 @@ fn foo_recursive(n: usize) -> Pin<Box<dyn Future<Output = ()>>> {
 The `Box<...>` ensures that the result is of known size,
 and the pin is required to keep it in the same place in memory.
 "##,
-
-}  // (end of detailed error messages)
-
-register_diagnostics! {
+;
 //  E0035, merged into E0087/E0089
 //  E0036, merged into E0087/E0089
 //  E0068,
@@ -4930,7 +4927,8 @@ register_diagnostics! {
 //  E0245, // not a trait
 //  E0246, // invalid recursive type
 //  E0247,
-//  E0248, // value used as a type, now reported earlier during resolution as E0412
+//  E0248, // value used as a type, now reported earlier during resolution
+           // as E0412
 //  E0249,
 //  E0319, // trait impls for defaulted traits allowed just for structs/enums
 //  E0372, // coherence not object safe
@@ -4938,7 +4936,7 @@ register_diagnostics! {
            // between structures with the same definition
 //  E0558, // replaced with a generic attribute input check
     E0533, // `{}` does not name a unit variant, unit struct or a constant
-//  E0563, // cannot determine a type for this `impl Trait`: {} // removed in 6383de15
+//  E0563, // cannot determine a type for this `impl Trait` removed in 6383de15
     E0564, // only named lifetimes are allowed in `impl Trait`,
            // but `{}` was found in the type `{}`
     E0587, // type has conflicting packed and align representation hints
@@ -4947,8 +4945,8 @@ register_diagnostics! {
 //  E0612, // merged into E0609
 //  E0613, // Removed (merged with E0609)
     E0627, // yield statement outside of generator literal
-    E0632, // cannot provide explicit type parameters when `impl Trait` is used in
-           // argument position.
+    E0632, // cannot provide explicit type parameters when `impl Trait` is used
+           // in argument position.
     E0634, // type has conflicting packed representaton hints
     E0640, // infer outlives requirements
     E0641, // cannot cast to/from a pointer with an unknown kind
diff --git a/src/librustc_typeck/impl_wf_check.rs b/src/librustc_typeck/impl_wf_check.rs
index fcfd9adef54df..bc0f17c3bf0fb 100644
--- a/src/librustc_typeck/impl_wf_check.rs
+++ b/src/librustc_typeck/impl_wf_check.rs
@@ -12,7 +12,7 @@ use crate::constrained_generic_params as cgp;
 use rustc::hir;
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
 use rustc::hir::def_id::DefId;
-use rustc::ty::{self, TyCtxt};
+use rustc::ty::{self, TyCtxt, TypeFoldable};
 use rustc::ty::query::Providers;
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use std::collections::hash_map::Entry::{Occupied, Vacant};
@@ -99,6 +99,15 @@ fn enforce_impl_params_are_constrained(
 ) {
     // Every lifetime used in an associated type must be constrained.
     let impl_self_ty = tcx.type_of(impl_def_id);
+    if impl_self_ty.references_error() {
+        // Don't complain about unconstrained type params when self ty isn't known due to errors.
+        // (#36836)
+        tcx.sess.delay_span_bug(
+            tcx.def_span(impl_def_id),
+            "potentially unconstrained type parameters weren't evaluated",
+        );
+        return;
+    }
     let impl_generics = tcx.generics_of(impl_def_id);
     let impl_predicates = tcx.predicates_of(impl_def_id);
     let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 9d9a9d9b559e4..959483e4439ff 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -65,7 +65,6 @@ This API is completely unstable and subject to change.
 #![feature(exhaustive_patterns)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
 #![feature(never_type)]
 #![feature(inner_deref)]
@@ -78,9 +77,7 @@ This API is completely unstable and subject to change.
 
 #[macro_use] extern crate rustc;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
-mod error_codes;
+pub mod error_codes;
 
 mod astconv;
 mod check;
@@ -389,5 +386,3 @@ pub fn hir_trait_to_predicates<'tcx>(
 
     bounds
 }
-
-__build_diagnostic_array! { librustc_typeck, DIAGNOSTICS }
diff --git a/src/librustc_typeck/structured_errors.rs b/src/librustc_typeck/structured_errors.rs
index 3e3eab8cf4cfb..273a36edc56ff 100644
--- a/src/librustc_typeck/structured_errors.rs
+++ b/src/librustc_typeck/structured_errors.rs
@@ -48,7 +48,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for VariadicError<'tcx> {
     fn session(&self) -> &Session { self.sess }
 
     fn code(&self) -> DiagnosticId {
-        __diagnostic_used!(E0617);
+        syntax::diagnostic_used!(E0617);
         DiagnosticId::Error("E0617".to_owned())
     }
 
@@ -104,7 +104,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCastError<'tcx> {
     fn session(&self) -> &Session { self.sess }
 
     fn code(&self) -> DiagnosticId {
-        __diagnostic_used!(E0607);
+        syntax::diagnostic_used!(E0607);
         DiagnosticId::Error("E0607".to_owned())
     }
 
diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
index b9b3e621bb740..c3092cea9833c 100644
--- a/src/librustdoc/clean/cfg.rs
+++ b/src/librustdoc/clean/cfg.rs
@@ -81,10 +81,10 @@ impl Cfg {
             },
             MetaItemKind::List(ref items) => {
                 let mut sub_cfgs = items.iter().map(Cfg::parse_nested);
-                match &*name.as_str() {
-                    "all" => sub_cfgs.fold(Ok(Cfg::True), |x, y| Ok(x? & y?)),
-                    "any" => sub_cfgs.fold(Ok(Cfg::False), |x, y| Ok(x? | y?)),
-                    "not" => if sub_cfgs.len() == 1 {
+                match name {
+                    sym::all => sub_cfgs.fold(Ok(Cfg::True), |x, y| Ok(x? & y?)),
+                    sym::any => sub_cfgs.fold(Ok(Cfg::False), |x, y| Ok(x? | y?)),
+                    sym::not => if sub_cfgs.len() == 1 {
                         Ok(!sub_cfgs.next().unwrap()?)
                     } else {
                         Err(InvalidCfgError {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 4971155113263..ae70fdc530be6 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1039,7 +1039,7 @@ impl GenericBound {
     fn maybe_sized(cx: &DocContext<'_>) -> GenericBound {
         let did = cx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
         let empty = cx.tcx.intern_substs(&[]);
-        let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+        let path = external_path(cx, cx.tcx.item_name(did),
             Some(did), false, vec![], empty);
         inline::record_extern_fqn(cx, did, TypeKind::Trait);
         GenericBound::TraitBound(PolyTrait {
@@ -1138,13 +1138,13 @@ fn external_generic_args(
 
 // trait_did should be set to a trait's DefId if called on a TraitRef, in order to sugar
 // from Fn<(A, B,), C> to Fn(A, B) -> C
-fn external_path(cx: &DocContext<'_>, name: &str, trait_did: Option<DefId>, has_self: bool,
+fn external_path(cx: &DocContext<'_>, name: Symbol, trait_did: Option<DefId>, has_self: bool,
                  bindings: Vec<TypeBinding>, substs: SubstsRef<'_>) -> Path {
     Path {
         global: false,
         res: Res::Err,
         segments: vec![PathSegment {
-            name: name.to_string(),
+            name: name.as_str().to_string(),
             args: external_generic_args(cx, trait_did, has_self, bindings, substs)
         }],
     }
@@ -1154,7 +1154,7 @@ impl<'a, 'tcx> Clean<GenericBound> for (&'a ty::TraitRef<'tcx>, Vec<TypeBinding>
     fn clean(&self, cx: &DocContext<'_>) -> GenericBound {
         let (trait_ref, ref bounds) = *self;
         inline::record_extern_fqn(cx, trait_ref.def_id, TypeKind::Trait);
-        let path = external_path(cx, &cx.tcx.item_name(trait_ref.def_id).as_str(),
+        let path = external_path(cx, cx.tcx.item_name(trait_ref.def_id),
                                  Some(trait_ref.def_id), true, bounds.clone(), trait_ref.substs);
 
         debug!("ty::TraitRef\n  subst: {:?}\n", trait_ref.substs);
@@ -3089,8 +3089,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     AdtKind::Enum => TypeKind::Enum,
                 };
                 inline::record_extern_fqn(cx, did, kind);
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
-                                         None, false, vec![], substs);
+                let path = external_path(cx, cx.tcx.item_name(did), None, false, vec![], substs);
                 ResolvedPath {
                     path,
                     param_names: None,
@@ -3100,7 +3099,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
             }
             ty::Foreign(did) => {
                 inline::record_extern_fqn(cx, did, TypeKind::Foreign);
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+                let path = external_path(cx, cx.tcx.item_name(did),
                                          None, false, vec![], InternalSubsts::empty());
                 ResolvedPath {
                     path: path,
@@ -3129,7 +3128,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                 reg.clean(cx).map(|b| param_names.push(GenericBound::Outlives(b)));
                 for did in dids {
                     let empty = cx.tcx.intern_substs(&[]);
-                    let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+                    let path = external_path(cx, cx.tcx.item_name(did),
                         Some(did), false, vec![], empty);
                     inline::record_extern_fqn(cx, did, TypeKind::Trait);
                     let bound = GenericBound::TraitBound(PolyTrait {
@@ -3154,7 +3153,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     });
                 }
 
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(), Some(did),
+                let path = external_path(cx, cx.tcx.item_name(did), Some(did),
                     false, bindings, substs);
                 ResolvedPath {
                     path,
@@ -3977,7 +3976,7 @@ fn build_deref_target_impls(cx: &DocContext<'_>,
             F32 => tcx.lang_items().f32_impl(),
             F64 => tcx.lang_items().f64_impl(),
             Char => tcx.lang_items().char_impl(),
-            Bool => None,
+            Bool => tcx.lang_items().bool_impl(),
             Str => tcx.lang_items().str_impl(),
             Slice => tcx.lang_items().slice_impl(),
             Array => tcx.lang_items().slice_impl(),
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index d261408fc148a..19ea781430041 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -9,7 +9,7 @@ use rustc::session;
 use rustc::session::config::{CrateType, parse_crate_types_from_list};
 use rustc::session::config::{CodegenOptions, DebuggingOptions, ErrorOutputType, Externs};
 use rustc::session::config::{nightly_options, build_codegen_options, build_debugging_options,
-                             get_cmd_lint_options, ExternEntry};
+                             get_cmd_lint_options, host_triple, ExternEntry};
 use rustc::session::search_paths::SearchPath;
 use rustc_driver;
 use rustc_target::spec::TargetTriple;
@@ -54,7 +54,7 @@ pub struct Options {
     /// Debugging (`-Z`) options to pass to the compiler.
     pub debugging_options: DebuggingOptions,
     /// The target used to compile the crate against.
-    pub target: Option<TargetTriple>,
+    pub target: TargetTriple,
     /// Edition used when reading the crate. Defaults to "2015". Also used by default when
     /// compiling doctests from the crate.
     pub edition: Edition,
@@ -77,6 +77,18 @@ pub struct Options {
     /// Optional path to persist the doctest executables to, defaults to a
     /// temporary directory if not set.
     pub persist_doctests: Option<PathBuf>,
+    /// Runtool to run doctests with
+    pub runtool: Option<String>,
+    /// Arguments to pass to the runtool
+    pub runtool_args: Vec<String>,
+    /// Whether to allow ignoring doctests on a per-target basis
+    /// For example, using ignore-foo to ignore running the doctest on any target that
+    /// contains "foo" as a substring
+    pub enable_per_target_ignores: bool,
+
+    /// The path to a rustc-like binary to build tests with. If not set, we
+    /// default to loading from $sysroot/bin/rustc.
+    pub test_builder: Option<PathBuf>,
 
     // Options that affect the documentation process
 
@@ -140,6 +152,9 @@ impl fmt::Debug for Options {
             .field("show_coverage", &self.show_coverage)
             .field("crate_version", &self.crate_version)
             .field("render_options", &self.render_options)
+            .field("runtool", &self.runtool)
+            .field("runtool_args", &self.runtool_args)
+            .field("enable-per-target-ignores", &self.enable_per_target_ignores)
             .finish()
     }
 }
@@ -414,7 +429,9 @@ impl Options {
             }
         }
 
-        let target = matches.opt_str("target").map(|target| {
+        let target = matches.opt_str("target").map_or(
+            TargetTriple::from_triple(host_triple()),
+            |target| {
             if target.ends_with(".json") {
                 TargetTriple::TargetPath(PathBuf::from(target))
             } else {
@@ -463,9 +480,13 @@ impl Options {
         let generate_search_filter = !matches.opt_present("disable-per-crate-search");
         let persist_doctests = matches.opt_str("persist-doctests").map(PathBuf::from);
         let generate_redirect_pages = matches.opt_present("generate-redirect-pages");
+        let test_builder = matches.opt_str("test-builder").map(PathBuf::from);
         let codegen_options_strs = matches.opt_strs("C");
         let lib_strs = matches.opt_strs("L");
         let extern_strs = matches.opt_strs("extern");
+        let runtool = matches.opt_str("runtool");
+        let runtool_args = matches.opt_strs("runtool-arg");
+        let enable_per_target_ignores = matches.opt_present("enable-per-target-ignores");
 
         let (lint_opts, describe_lints, lint_cap) = get_cmd_lint_options(matches, error_format);
 
@@ -496,6 +517,10 @@ impl Options {
             show_coverage,
             crate_version,
             persist_doctests,
+            runtool,
+            runtool_args,
+            enable_per_target_ignores,
+            test_builder,
             render_options: RenderOptions {
                 output,
                 external_html,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 9cfcad4271966..57b016a08c2fe 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -13,7 +13,6 @@ use rustc_interface::interface;
 use rustc_driver::abort_on_err;
 use rustc_resolve as resolve;
 use rustc_metadata::cstore::CStore;
-use rustc_target::spec::TargetTriple;
 
 use syntax::source_map;
 use syntax::attr;
@@ -294,7 +293,6 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         }
     }).collect();
 
-    let host_triple = TargetTriple::from_triple(config::host_triple());
     let crate_types = if proc_macro_crate {
         vec![config::CrateType::ProcMacro]
     } else {
@@ -313,7 +311,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         lint_cap: Some(lint_cap.unwrap_or_else(|| lint::Forbid)),
         cg: codegen_options,
         externs,
-        target_triple: target.unwrap_or(host_triple),
+        target_triple: target,
         // Ensure that rustdoc works even if rustc is feature-staged
         unstable_features: UnstableFeatures::Allow,
         actually_rustdoc: true,
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 313734e3fdd6b..dcd32192ff384 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -18,6 +18,100 @@ use crate::clean::{self, PrimitiveType};
 use crate::html::item_type::ItemType;
 use crate::html::render::{self, cache, CURRENT_DEPTH};
 
+pub trait Print {
+    fn print(self, buffer: &mut Buffer);
+}
+
+impl<F> Print for F
+    where F: FnOnce(&mut Buffer),
+{
+    fn print(self, buffer: &mut Buffer) {
+        (self)(buffer)
+    }
+}
+
+impl Print for String {
+    fn print(self, buffer: &mut Buffer) {
+        buffer.write_str(&self);
+    }
+}
+
+impl Print for &'_ str {
+    fn print(self, buffer: &mut Buffer) {
+        buffer.write_str(self);
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Buffer {
+    for_html: bool,
+    buffer: String,
+}
+
+impl Buffer {
+    crate fn empty_from(v: &Buffer) -> Buffer {
+        Buffer {
+            for_html: v.for_html,
+            buffer: String::new(),
+        }
+    }
+
+    crate fn html() -> Buffer {
+        Buffer {
+            for_html: true,
+            buffer: String::new(),
+        }
+    }
+
+    crate fn is_empty(&self) -> bool {
+        self.buffer.is_empty()
+    }
+
+    crate fn into_inner(self) -> String {
+        self.buffer
+    }
+
+    crate fn insert_str(&mut self, idx: usize, s: &str) {
+        self.buffer.insert_str(idx, s);
+    }
+
+    crate fn push_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    crate fn write_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    crate fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
+        use fmt::Write;
+        self.buffer.write_fmt(v).unwrap();
+    }
+
+    crate fn to_display<T: Print>(mut self, t: T) -> String {
+        t.print(&mut self);
+        self.into_inner()
+    }
+
+    crate fn with_formatter<T: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result>(&mut self, t: T) {
+        self.from_display(display_fn(move |f| (t)(f)));
+    }
+
+    crate fn from_display<T: std::fmt::Display>(&mut self, t: T) {
+        if self.for_html {
+            write!(self, "{}", t);
+        } else {
+            write!(self, "{:#}", t);
+        }
+    }
+}
+
 /// Helper to render an optional visibility with a space after it (if the
 /// visibility is preset)
 #[derive(Copy, Clone)]
@@ -200,11 +294,11 @@ impl<'a> fmt::Display for WhereClause<'a> {
                 }
                 &clean::WherePredicate::RegionPredicate { ref lifetime, ref bounds } => {
                     clause.push_str(&format!("{}: {}",
-                                             lifetime,
-                                             bounds.iter()
-                                                   .map(|b| b.to_string())
-                                                   .collect::<Vec<_>>()
-                                                   .join(" + ")));
+                                                lifetime,
+                                                bounds.iter()
+                                                    .map(|b| b.to_string())
+                                                    .collect::<Vec<_>>()
+                                                    .join(" + ")));
                 }
                 &clean::WherePredicate::EqPredicate { ref lhs, ref rhs } => {
                     if f.alternate() {
@@ -778,9 +872,9 @@ impl fmt::Display for clean::Impl {
 
 // The difference from above is that trait is not hyperlinked.
 pub fn fmt_impl_for_trait_page(i: &clean::Impl,
-                               f: &mut fmt::Formatter<'_>,
-                               use_absolute: bool) -> fmt::Result {
-    fmt_impl(i, f, false, use_absolute)
+                               f: &mut Buffer,
+                               use_absolute: bool) {
+    f.with_formatter(|f| fmt_impl(i, f, false, use_absolute))
 }
 
 impl fmt::Display for clean::Arguments {
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index ae0bd1aafa8f1..56074f4ab1192 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -1,9 +1,8 @@
-use std::fmt;
-use std::io;
 use std::path::PathBuf;
 
 use crate::externalfiles::ExternalHtml;
 use crate::html::render::SlashChecker;
+use crate::html::format::{Buffer, Print};
 
 #[derive(Clone)]
 pub struct Layout {
@@ -11,6 +10,12 @@ pub struct Layout {
     pub favicon: String,
     pub external_html: ExternalHtml,
     pub krate: String,
+    /// The given user css file which allow to customize the generated
+    /// documentation theme.
+    pub css_file_extension: Option<PathBuf>,
+    /// If false, the `select` element to have search filtering by crates on rendered docs
+    /// won't be generated.
+    pub generate_search_filter: bool,
 }
 
 pub struct Page<'a> {
@@ -25,19 +30,15 @@ pub struct Page<'a> {
     pub static_extra_scripts: &'a [&'a str],
 }
 
-pub fn render<T: fmt::Display, S: fmt::Display>(
-    dst: &mut dyn io::Write,
+pub fn render<T: Print, S: Print>(
     layout: &Layout,
     page: &Page<'_>,
-    sidebar: &S,
-    t: &T,
-    css_file_extension: bool,
+    sidebar: S,
+    t: T,
     themes: &[PathBuf],
-    generate_search_filter: bool,
-) -> io::Result<()> {
+) -> String {
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
-    write!(dst,
-"<!DOCTYPE html>\
+    format!("<!DOCTYPE html>\
 <html lang=\"en\">\
 <head>\
     <meta charset=\"utf-8\">\
@@ -164,7 +165,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     <script defer src=\"{root_path}search-index{suffix}.js\"></script>\
 </body>\
 </html>",
-    css_extension = if css_file_extension {
+    css_extension = if layout.css_file_extension.is_some() {
         format!("<link rel=\"stylesheet\" \
                        type=\"text/css\" \
                        href=\"{static_root_path}theme{suffix}.css\">",
@@ -173,7 +174,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     } else {
         String::new()
     },
-    content   = *t,
+    content   = Buffer::html().to_display(t),
     static_root_path = static_root_path,
     root_path = page.root_path,
     css_class = page.css_class,
@@ -207,7 +208,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     in_header = layout.external_html.in_header,
     before_content = layout.external_html.before_content,
     after_content = layout.external_html.after_content,
-    sidebar   = *sidebar,
+    sidebar   = Buffer::html().to_display(sidebar),
     krate     = layout.krate,
     themes = themes.iter()
                    .filter_map(|t| t.file_stem())
@@ -228,7 +229,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
                 root_path=page.root_path,
                 extra_script=e)
     }).collect::<String>(),
-    filter_crates=if generate_search_filter {
+    filter_crates=if layout.generate_search_filter {
         "<select id=\"crate-search\">\
             <option value=\"All crates\">All crates</option>\
         </select>"
@@ -238,9 +239,9 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     )
 }
 
-pub fn redirect(dst: &mut dyn io::Write, url: &str) -> io::Result<()> {
+pub fn redirect(url: &str) -> String {
     // <script> triggers a redirect before refresh, so this is fine.
-    write!(dst,
+    format!(
 r##"<!DOCTYPE html>
 <html lang="en">
 <head>
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index 74413a7f905d4..1a4fa38ff8db0 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -199,7 +199,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
         let ignore;
         let edition;
         if let Some(Event::Start(Tag::CodeBlock(lang))) = event {
-            let parse_result = LangString::parse(&lang, self.check_error_codes);
+            let parse_result = LangString::parse(&lang, self.check_error_codes, false);
             if !parse_result.rust {
                 return Some(Event::Start(Tag::CodeBlock(lang)));
             }
@@ -272,7 +272,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
             ))
         });
 
-        let tooltip = if ignore {
+        let tooltip = if ignore != Ignore::None {
             Some(("This example is not tested".to_owned(), "ignore"))
         } else if compile_fail {
             Some(("This example deliberately fails to compile".to_owned(), "compile_fail"))
@@ -286,7 +286,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
             s.push_str(&highlight::render_with_highlighting(
                 &text,
                 Some(&format!("rust-example-rendered{}",
-                                if ignore { " ignore" }
+                                if ignore != Ignore::None { " ignore" }
                                 else if compile_fail { " compile_fail" }
                                 else if explicit_edition { " edition " }
                                 else { "" })),
@@ -297,7 +297,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
             s.push_str(&highlight::render_with_highlighting(
                 &text,
                 Some(&format!("rust-example-rendered{}",
-                                if ignore { " ignore" }
+                                if ignore != Ignore::None { " ignore" }
                                 else if compile_fail { " compile_fail" }
                                 else if explicit_edition { " edition " }
                                 else { "" })),
@@ -551,7 +551,8 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for Footnotes<'a, I> {
     }
 }
 
-pub fn find_testable_code<T: test::Tester>(doc: &str, tests: &mut T, error_codes: ErrorCodes) {
+pub fn find_testable_code<T: test::Tester>(doc: &str, tests: &mut T, error_codes: ErrorCodes,
+                                           enable_per_target_ignores: bool) {
     let mut parser = Parser::new(doc);
     let mut prev_offset = 0;
     let mut nb_lines = 0;
@@ -564,7 +565,7 @@ pub fn find_testable_code<T: test::Tester>(doc: &str, tests: &mut T, error_codes
                 let block_info = if s.is_empty() {
                     LangString::all_false()
                 } else {
-                    LangString::parse(&*s, error_codes)
+                    LangString::parse(&*s, error_codes, enable_per_target_ignores)
                 };
                 if !block_info.rust {
                     continue;
@@ -607,7 +608,7 @@ pub struct LangString {
     original: String,
     pub should_panic: bool,
     pub no_run: bool,
-    pub ignore: bool,
+    pub ignore: Ignore,
     pub rust: bool,
     pub test_harness: bool,
     pub compile_fail: bool,
@@ -616,13 +617,20 @@ pub struct LangString {
     pub edition: Option<Edition>
 }
 
+#[derive(Eq, PartialEq, Clone, Debug)]
+pub enum Ignore {
+    All,
+    None,
+    Some(Vec<String>),
+}
+
 impl LangString {
     fn all_false() -> LangString {
         LangString {
             original: String::new(),
             should_panic: false,
             no_run: false,
-            ignore: false,
+            ignore: Ignore::None,
             rust: true,  // NB This used to be `notrust = false`
             test_harness: false,
             compile_fail: false,
@@ -632,11 +640,16 @@ impl LangString {
         }
     }
 
-    fn parse(string: &str, allow_error_code_check: ErrorCodes) -> LangString {
+    fn parse(
+        string: &str,
+        allow_error_code_check: ErrorCodes,
+        enable_per_target_ignores: bool
+    ) -> LangString {
         let allow_error_code_check = allow_error_code_check.as_bool();
         let mut seen_rust_tags = false;
         let mut seen_other_tags = false;
         let mut data = LangString::all_false();
+        let mut ignores = vec![];
 
         data.original = string.to_owned();
         let tokens = string.split(|c: char|
@@ -651,7 +664,11 @@ impl LangString {
                     seen_rust_tags = seen_other_tags == false;
                 }
                 "no_run" => { data.no_run = true; seen_rust_tags = !seen_other_tags; }
-                "ignore" => { data.ignore = true; seen_rust_tags = !seen_other_tags; }
+                "ignore" => { data.ignore = Ignore::All; seen_rust_tags = !seen_other_tags; }
+                x if x.starts_with("ignore-") => if enable_per_target_ignores {
+                    ignores.push(x.trim_start_matches("ignore-").to_owned());
+                    seen_rust_tags = !seen_other_tags;
+                }
                 "allow_fail" => { data.allow_fail = true; seen_rust_tags = !seen_other_tags; }
                 "rust" => { data.rust = true; seen_rust_tags = true; }
                 "test_harness" => {
@@ -679,6 +696,10 @@ impl LangString {
                 _ => { seen_other_tags = true }
             }
         }
+        // ignore-foo overrides ignore
+        if !ignores.is_empty() {
+            data.ignore = Ignore::Some(ignores);
+        }
 
         data.rust &= !seen_other_tags || seen_rust_tags;
 
@@ -919,7 +940,7 @@ crate fn rust_code_blocks(md: &str) -> Vec<RustCodeBlock> {
                 let lang_string = if syntax.is_empty() {
                     LangString::all_false()
                 } else {
-                    LangString::parse(&*syntax, ErrorCodes::Yes)
+                    LangString::parse(&*syntax, ErrorCodes::Yes, false)
                 };
 
                 if lang_string.rust {
@@ -931,7 +952,10 @@ crate fn rust_code_blocks(md: &str) -> Vec<RustCodeBlock> {
                             is_fenced = true;
                             previous_offset + fence_idx
                         }
-                        None => offset,
+                        None => {
+                            is_fenced = false;
+                            offset
+                        }
                     };
                 }
             }
diff --git a/src/librustdoc/html/markdown/tests.rs b/src/librustdoc/html/markdown/tests.rs
index a95c29038d46f..5d6811a29a3eb 100644
--- a/src/librustdoc/html/markdown/tests.rs
+++ b/src/librustdoc/html/markdown/tests.rs
@@ -1,4 +1,4 @@
-use super::{ErrorCodes, LangString, Markdown, MarkdownHtml, IdMap};
+use super::{ErrorCodes, LangString, Markdown, MarkdownHtml, IdMap, Ignore};
 use super::plain_summary_line;
 use std::cell::RefCell;
 use syntax::edition::{Edition, DEFAULT_EDITION};
@@ -26,10 +26,10 @@ fn test_unique_id() {
 #[test]
 fn test_lang_string_parse() {
     fn t(s: &str,
-        should_panic: bool, no_run: bool, ignore: bool, rust: bool, test_harness: bool,
+        should_panic: bool, no_run: bool, ignore: Ignore, rust: bool, test_harness: bool,
         compile_fail: bool, allow_fail: bool, error_codes: Vec<String>,
-         edition: Option<Edition>) {
-        assert_eq!(LangString::parse(s, ErrorCodes::Yes), LangString {
+        edition: Option<Edition>) {
+        assert_eq!(LangString::parse(s, ErrorCodes::Yes, true), LangString {
             should_panic,
             no_run,
             ignore,
@@ -42,6 +42,7 @@ fn test_lang_string_parse() {
             edition,
         })
     }
+    let ignore_foo = Ignore::Some(vec!("foo".to_string()));
 
     fn v() -> Vec<String> {
         Vec::new()
@@ -50,23 +51,24 @@ fn test_lang_string_parse() {
     // ignore-tidy-linelength
     // marker                | should_panic | no_run | ignore | rust | test_harness
     //                       | compile_fail | allow_fail | error_codes | edition
-    t("",                      false,         false,   false,   true,  false, false, false, v(), None);
-    t("rust",                  false,         false,   false,   true,  false, false, false, v(), None);
-    t("sh",                    false,         false,   false,   false, false, false, false, v(), None);
-    t("ignore",                false,         false,   true,    true,  false, false, false, v(), None);
-    t("should_panic",          true,          false,   false,   true,  false, false, false, v(), None);
-    t("no_run",                false,         true,    false,   true,  false, false, false, v(), None);
-    t("test_harness",          false,         false,   false,   true,  true,  false, false, v(), None);
-    t("compile_fail",          false,         true,    false,   true,  false, true,  false, v(), None);
-    t("allow_fail",            false,         false,   false,   true,  false, false, true,  v(), None);
-    t("{.no_run .example}",    false,         true,    false,   true,  false, false, false, v(), None);
-    t("{.sh .should_panic}",   true,          false,   false,   false, false, false, false, v(), None);
-    t("{.example .rust}",      false,         false,   false,   true,  false, false, false, v(), None);
-    t("{.test_harness .rust}", false,         false,   false,   true,  true,  false, false, v(), None);
-    t("text, no_run",          false,         true,    false,   false, false, false, false, v(), None);
-    t("text,no_run",           false,         true,    false,   false, false, false, false, v(), None);
-    t("edition2015",           false,         false,   false,   true,  false, false, false, v(), Some(Edition::Edition2015));
-    t("edition2018",           false,         false,   false,   true,  false, false, false, v(), Some(Edition::Edition2018));
+    t("",                      false,         false,   Ignore::None,   true,  false, false, false, v(), None);
+    t("rust",                  false,         false,   Ignore::None,   true,  false, false, false, v(), None);
+    t("sh",                    false,         false,   Ignore::None,   false, false, false, false, v(), None);
+    t("ignore",                false,         false,   Ignore::All,    true,  false, false, false, v(), None);
+    t("ignore-foo",            false,         false,   ignore_foo,     true,  false, false, false, v(), None);
+    t("should_panic",          true,          false,   Ignore::None,   true,  false, false, false, v(), None);
+    t("no_run",                false,         true,    Ignore::None,   true,  false, false, false, v(), None);
+    t("test_harness",          false,         false,   Ignore::None,   true,  true,  false, false, v(), None);
+    t("compile_fail",          false,         true,    Ignore::None,   true,  false, true,  false, v(), None);
+    t("allow_fail",            false,         false,   Ignore::None,   true,  false, false, true,  v(), None);
+    t("{.no_run .example}",    false,         true,    Ignore::None,   true,  false, false, false, v(), None);
+    t("{.sh .should_panic}",   true,          false,   Ignore::None,   false, false, false, false, v(), None);
+    t("{.example .rust}",      false,         false,   Ignore::None,   true,  false, false, false, v(), None);
+    t("{.test_harness .rust}", false,         false,   Ignore::None,   true,  true,  false, false, v(), None);
+    t("text, no_run",          false,         true,    Ignore::None,   false, false, false, false, v(), None);
+    t("text,no_run",           false,         true,    Ignore::None,   false, false, false, false, v(), None);
+    t("edition2015",           false,         false,   Ignore::None,   true,  false, false, false, v(), Some(Edition::Edition2015));
+    t("edition2018",           false,         false,   Ignore::None,   true,  false, false, false, v(), Some(Edition::Edition2018));
 }
 
 #[test]
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index d5c47a15948fb..9846073cad4bc 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{AsyncSpace, ConstnessSpace};
+use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -192,9 +192,6 @@ crate struct SharedContext {
     /// The base-URL of the issue tracker for when an item has been tagged with
     /// an issue number.
     pub issue_tracker_base_url: Option<String>,
-    /// The given user css file which allow to customize the generated
-    /// documentation theme.
-    pub css_file_extension: Option<PathBuf>,
     /// The directories that have already been created in this doc run. Used to reduce the number
     /// of spurious `create_dir_all` calls.
     pub created_dirs: RefCell<FxHashSet<PathBuf>>,
@@ -209,9 +206,6 @@ crate struct SharedContext {
     /// Optional path string to be used to load static files on output pages. If not set, uses
     /// combinations of `../` to reach the documentation root.
     pub static_root_path: Option<String>,
-    /// If false, the `select` element to have search filtering by crates on rendered docs
-    /// won't be generated.
-    pub generate_search_filter: bool,
     /// Option disabled by default to generate files used by RLS and some other tools.
     pub generate_redirect_pages: bool,
     /// The fs handle we are working with.
@@ -387,14 +381,6 @@ pub struct RenderInfo {
 // Helper structs for rendering items/sidebars and carrying along contextual
 // information
 
-#[derive(Copy, Clone)]
-struct Item<'a> {
-    cx: &'a Context,
-    item: &'a clean::Item,
-}
-
-struct Sidebar<'a> { cx: &'a Context, item: &'a clean::Item, }
-
 /// Struct representing one entry in the JS search index. These are all emitted
 /// by hand to a large JS file at the end of cache-creation.
 #[derive(Debug)]
@@ -545,14 +531,14 @@ pub fn run(mut krate: clean::Crate,
             favicon: String::new(),
             external_html,
             krate: krate.name.clone(),
+            css_file_extension: extension_css,
+            generate_search_filter,
         },
-        css_file_extension: extension_css,
         created_dirs: Default::default(),
         sort_modules_alphabetically,
         themes,
         resource_suffix,
         static_root_path,
-        generate_search_filter,
         generate_redirect_pages,
         fs: DocFS::new(&errors),
     };
@@ -932,7 +918,7 @@ themePicker.onblur = handleThemeButtonsBlur;
             options.enable_minification)?;
     }
 
-    if let Some(ref css) = cx.shared.css_file_extension {
+    if let Some(ref css) = cx.shared.layout.css_file_extension {
         let out = cx.dst.join(&format!("theme{}.css", cx.shared.resource_suffix));
         let buffer = try_err!(fs::read_to_string(css), css);
         if !options.enable_minification {
@@ -1031,12 +1017,12 @@ themePicker.onblur = handleThemeButtonsBlur;
         }
         all_aliases.push(format!("ALIASES[\"{}\"] = {{{}}};", krate.name, output));
         all_aliases.sort();
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "var ALIASES = {{}};"), &dst);
+        let mut v = Buffer::html();
+        writeln!(&mut v, "var ALIASES = {{}};");
         for aliases in &all_aliases {
-            try_err!(writeln!(&mut v, "{}", aliases), &dst);
+            writeln!(&mut v, "{}", aliases);
         }
-        cx.shared.fs.write(&dst, &v)?;
+        cx.shared.fs.write(&dst, v.into_inner().into_bytes())?;
     }
 
     use std::ffi::OsString;
@@ -1120,12 +1106,9 @@ themePicker.onblur = handleThemeButtonsBlur;
                                  &krate.name,
                                  hierarchy.to_json_string()));
         all_sources.sort();
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v,
-                          "var N = null;var sourcesIndex = {{}};\n{}\ncreateSourceSidebar();",
-                          all_sources.join("\n")),
-                 &dst);
-        cx.shared.fs.write(&dst, &v)?;
+        let v = format!("var N = null;var sourcesIndex = {{}};\n{}\ncreateSourceSidebar();\n",
+                          all_sources.join("\n"));
+        cx.shared.fs.write(&dst, v.as_bytes())?;
     }
 
     // Update the search index
@@ -1140,14 +1123,11 @@ themePicker.onblur = handleThemeButtonsBlur;
     // with rustdoc running in parallel.
     all_indexes.sort();
     {
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "var N=null,E=\"\",T=\"t\",U=\"u\",searchIndex={{}};"), &dst);
-        try_err!(write_minify_replacer(
-            &mut v,
+        let mut v = String::from("var N=null,E=\"\",T=\"t\",U=\"u\",searchIndex={};\n");
+        v.push_str(&minify_replacer(
             &format!("{}\n{}", variables.join(""), all_indexes.join("\n")),
-            options.enable_minification),
-            &dst);
-        try_err!(write!(&mut v, "initSearch(searchIndex);addSearchOptions(searchIndex);"), &dst);
+            options.enable_minification));
+        v.push_str("initSearch(searchIndex);addSearchOptions(searchIndex);");
         cx.shared.fs.write(&dst, &v)?;
     }
     if options.enable_index_page {
@@ -1185,13 +1165,10 @@ themePicker.onblur = handleThemeButtonsBlur;
                                                 SlashChecker(s), s)
                                     })
                                     .collect::<String>());
-            let mut v = Vec::new();
-            try_err!(layout::render(&mut v, &cx.shared.layout,
-                                    &page, &(""), &content,
-                                    cx.shared.css_file_extension.is_some(),
-                                    &cx.shared.themes,
-                                    cx.shared.generate_search_filter), &dst);
-            cx.shared.fs.write(&dst, &v)?;
+            let v = layout::render(&cx.shared.layout,
+                           &page, "", content,
+                           &cx.shared.themes);
+            cx.shared.fs.write(&dst, v.as_bytes())?;
         }
     }
 
@@ -1256,19 +1233,18 @@ themePicker.onblur = handleThemeButtonsBlur;
         // identically even with rustdoc running in parallel.
         all_implementors.sort();
 
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "(function() {{var implementors = {{}};"), &mydst);
+        let mut v = String::from("(function() {var implementors = {};\n");
         for implementor in &all_implementors {
-            try_err!(writeln!(&mut v, "{}", *implementor), &mydst);
+            writeln!(v, "{}", *implementor).unwrap();
         }
-        try_err!(writeln!(&mut v, "{}", r"
+        v.push_str(r"
             if (window.register_implementors) {
                 window.register_implementors(implementors);
             } else {
                 window.pending_implementors = implementors;
             }
-        "), &mydst);
-        try_err!(writeln!(&mut v, r"}})()"), &mydst);
+        ");
+        v.push_str("})()");
         cx.shared.fs.write(&mydst, &v)?;
     }
     Ok(())
@@ -1288,68 +1264,65 @@ fn write_minify(fs:&DocFS, dst: PathBuf, contents: &str, enable_minification: bo
     }
 }
 
-fn write_minify_replacer<W: Write>(
-    dst: &mut W,
+fn minify_replacer(
     contents: &str,
     enable_minification: bool,
-) -> io::Result<()> {
+) -> String {
     use minifier::js::{simple_minify, Keyword, ReservedChar, Token, Tokens};
 
     if enable_minification {
-        writeln!(dst, "{}",
-                 {
-                    let tokens: Tokens<'_> = simple_minify(contents)
-                        .into_iter()
-                        .filter(|(f, next)| {
-                            // We keep backlines.
-                            minifier::js::clean_token_except(f, next, &|c: &Token<'_>| {
-                                c.get_char() != Some(ReservedChar::Backline)
-                            })
-                        })
-                        .map(|(f, _)| {
-                            minifier::js::replace_token_with(f, &|t: &Token<'_>| {
-                                match *t {
-                                    Token::Keyword(Keyword::Null) => Some(Token::Other("N")),
-                                    Token::String(s) => {
-                                        let s = &s[1..s.len() -1]; // The quotes are included
-                                        if s.is_empty() {
-                                            Some(Token::Other("E"))
-                                        } else if s == "t" {
-                                            Some(Token::Other("T"))
-                                        } else if s == "u" {
-                                            Some(Token::Other("U"))
-                                        } else {
-                                            None
-                                        }
-                                    }
-                                    _ => None,
-                                }
-                            })
-                        })
-                        .collect::<Vec<_>>()
-                        .into();
-                    tokens.apply(|f| {
-                        // We add a backline after the newly created variables.
-                        minifier::js::aggregate_strings_into_array_with_separation_filter(
-                            f,
-                            "R",
-                            Token::Char(ReservedChar::Backline),
-                            // This closure prevents crates' names from being aggregated.
-                            //
-                            // The point here is to check if the string is preceded by '[' and
-                            // "searchIndex". If so, it means this is a crate name and that it
-                            // shouldn't be aggregated.
-                            |tokens, pos| {
-                                pos < 2 ||
-                                !tokens[pos - 1].eq_char(ReservedChar::OpenBracket) ||
-                                tokens[pos - 2].get_other() != Some("searchIndex")
+        let tokens: Tokens<'_> = simple_minify(contents)
+            .into_iter()
+            .filter(|(f, next)| {
+                // We keep backlines.
+                minifier::js::clean_token_except(f, next, &|c: &Token<'_>| {
+                    c.get_char() != Some(ReservedChar::Backline)
+                })
+            })
+            .map(|(f, _)| {
+                minifier::js::replace_token_with(f, &|t: &Token<'_>| {
+                    match *t {
+                        Token::Keyword(Keyword::Null) => Some(Token::Other("N")),
+                        Token::String(s) => {
+                            let s = &s[1..s.len() -1]; // The quotes are included
+                            if s.is_empty() {
+                                Some(Token::Other("E"))
+                            } else if s == "t" {
+                                Some(Token::Other("T"))
+                            } else if s == "u" {
+                                Some(Token::Other("U"))
+                            } else {
+                                None
                             }
-                        )
-                    })
-                    .to_string()
+                        }
+                        _ => None,
+                    }
                 })
+            })
+            .collect::<Vec<_>>()
+            .into();
+        let o = tokens.apply(|f| {
+            // We add a backline after the newly created variables.
+            minifier::js::aggregate_strings_into_array_with_separation_filter(
+                f,
+                "R",
+                Token::Char(ReservedChar::Backline),
+                // This closure prevents crates' names from being aggregated.
+                //
+                // The point here is to check if the string is preceded by '[' and
+                // "searchIndex". If so, it means this is a crate name and that it
+                // shouldn't be aggregated.
+                |tokens, pos| {
+                    pos < 2 ||
+                    !tokens[pos - 1].eq_char(ReservedChar::OpenBracket) ||
+                    tokens[pos - 2].get_other() != Some("searchIndex")
+                }
+            )
+        })
+        .to_string();
+        format!("{}\n", o)
     } else {
-        writeln!(dst, "{}", contents)
+        format!("{}\n", contents)
     }
 }
 
@@ -1778,8 +1751,7 @@ impl AllTypes {
     }
 }
 
-fn print_entries(f: &mut fmt::Formatter<'_>, e: &FxHashSet<ItemEntry>, title: &str,
-                 class: &str) -> fmt::Result {
+fn print_entries(f: &mut Buffer, e: &FxHashSet<ItemEntry>, title: &str, class: &str) {
     if !e.is_empty() {
         let mut e: Vec<&ItemEntry> = e.iter().collect();
         e.sort();
@@ -1787,90 +1759,71 @@ fn print_entries(f: &mut fmt::Formatter<'_>, e: &FxHashSet<ItemEntry>, title: &s
                title,
                Escape(title),
                class,
-               e.iter().map(|s| format!("<li>{}</li>", s)).collect::<String>())?;
+               e.iter().map(|s| format!("<li>{}</li>", s)).collect::<String>());
     }
-    Ok(())
 }
 
-impl fmt::Display for AllTypes {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl AllTypes {
+    fn print(self, f: &mut Buffer) {
         write!(f,
-"<h1 class='fqn'>\
-     <span class='out-of-band'>\
-         <span id='render-detail'>\
-             <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
-                 [<span class='inner'>&#x2212;</span>]\
-             </a>\
-         </span>
-     </span>
-     <span class='in-band'>List of all items</span>\
-</h1>")?;
-        print_entries(f, &self.structs, "Structs", "structs")?;
-        print_entries(f, &self.enums, "Enums", "enums")?;
-        print_entries(f, &self.unions, "Unions", "unions")?;
-        print_entries(f, &self.primitives, "Primitives", "primitives")?;
-        print_entries(f, &self.traits, "Traits", "traits")?;
-        print_entries(f, &self.macros, "Macros", "macros")?;
-        print_entries(f, &self.attributes, "Attribute Macros", "attributes")?;
-        print_entries(f, &self.derives, "Derive Macros", "derives")?;
-        print_entries(f, &self.functions, "Functions", "functions")?;
-        print_entries(f, &self.typedefs, "Typedefs", "typedefs")?;
-        print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases")?;
-        print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types")?;
-        print_entries(f, &self.statics, "Statics", "statics")?;
+    "<h1 class='fqn'>\
+        <span class='out-of-band'>\
+            <span id='render-detail'>\
+                <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
+                    [<span class='inner'>&#x2212;</span>]\
+                </a>\
+            </span>
+        </span>
+        <span class='in-band'>List of all items</span>\
+    </h1>");
+        print_entries(f, &self.structs, "Structs", "structs");
+        print_entries(f, &self.enums, "Enums", "enums");
+        print_entries(f, &self.unions, "Unions", "unions");
+        print_entries(f, &self.primitives, "Primitives", "primitives");
+        print_entries(f, &self.traits, "Traits", "traits");
+        print_entries(f, &self.macros, "Macros", "macros");
+        print_entries(f, &self.attributes, "Attribute Macros", "attributes");
+        print_entries(f, &self.derives, "Derive Macros", "derives");
+        print_entries(f, &self.functions, "Functions", "functions");
+        print_entries(f, &self.typedefs, "Typedefs", "typedefs");
+        print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases");
+        print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types");
+        print_entries(f, &self.statics, "Statics", "statics");
         print_entries(f, &self.constants, "Constants", "constants")
     }
 }
 
-#[derive(Debug)]
-struct Settings<'a> {
+fn settings(root_path: &str, suffix: &str) -> String {
     // (id, explanation, default value)
-    settings: Vec<(&'static str, &'static str, bool)>,
-    root_path: &'a str,
-    suffix: &'a str,
-}
-
-impl<'a> Settings<'a> {
-    pub fn new(root_path: &'a str, suffix: &'a str) -> Settings<'a> {
-        Settings {
-            settings: vec![
-                ("item-declarations", "Auto-hide item declarations.", true),
-                ("item-attributes", "Auto-hide item attributes.", true),
-                ("trait-implementations", "Auto-hide trait implementations documentation",
-                 true),
-                ("method-docs", "Auto-hide item methods' documentation", false),
-                ("go-to-only-result", "Directly go to item in search if there is only one result",
-                 false),
-                ("line-numbers", "Show line numbers on code examples", false),
-            ],
-            root_path,
-            suffix,
-        }
-    }
-}
-
-impl<'a> fmt::Display for Settings<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f,
+    let settings = [
+        ("item-declarations", "Auto-hide item declarations.", true),
+        ("item-attributes", "Auto-hide item attributes.", true),
+        ("trait-implementations", "Auto-hide trait implementations documentation",
+            true),
+        ("method-docs", "Auto-hide item methods' documentation", false),
+        ("go-to-only-result", "Directly go to item in search if there is only one result",
+            false),
+        ("line-numbers", "Show line numbers on code examples", false),
+    ];
+    format!(
 "<h1 class='fqn'>\
-     <span class='in-band'>Rustdoc settings</span>\
+    <span class='in-band'>Rustdoc settings</span>\
 </h1>\
 <div class='settings'>{}</div>\
 <script src='{}settings{}.js'></script>",
-               self.settings.iter()
-                            .map(|(id, text, enabled)| {
-                                format!("<div class='setting-line'>\
-                                             <label class='toggle'>\
-                                                <input type='checkbox' id='{}' {}>\
-                                                <span class='slider'></span>\
-                                             </label>\
-                                             <div>{}</div>\
-                                         </div>", id, if *enabled { " checked" } else { "" }, text)
-                            })
-                            .collect::<String>(),
-               self.root_path,
-               self.suffix)
-    }
+            settings.iter()
+                        .map(|(id, text, enabled)| {
+                            format!("<div class='setting-line'>\
+                                            <label class='toggle'>\
+                                            <input type='checkbox' id='{}' {}>\
+                                            <span class='slider'></span>\
+                                            </label>\
+                                            <div>{}</div>\
+                                        </div>", id, if *enabled { " checked" } else { "" }, text)
+                        })
+                        .collect::<String>(),
+            root_path,
+            suffix)
 }
 
 impl Context {
@@ -1939,18 +1892,12 @@ impl Context {
         } else {
             String::new()
         };
-        let mut v = Vec::new();
-        try_err!(layout::render(&mut v, &self.shared.layout,
-                                &page, &sidebar, &all,
-                                self.shared.css_file_extension.is_some(),
-                                &self.shared.themes,
-                                self.shared.generate_search_filter),
-                 &final_file);
-        self.shared.fs.write(&final_file, &v)?;
+        let v = layout::render(&self.shared.layout,
+                       &page, sidebar, |buf: &mut Buffer| all.print(buf),
+                       &self.shared.themes);
+        self.shared.fs.write(&final_file, v.as_bytes())?;
 
         // Generating settings page.
-        let settings = Settings::new(self.shared.static_root_path.as_deref().unwrap_or("./"),
-                                     &self.shared.resource_suffix);
         page.title = "Rustdoc settings";
         page.description = "Settings of Rustdoc";
         page.root_path = "./";
@@ -1958,24 +1905,21 @@ impl Context {
         let mut themes = self.shared.themes.clone();
         let sidebar = "<p class='location'>Settings</p><div class='sidebar-elems'></div>";
         themes.push(PathBuf::from("settings.css"));
-        let layout = self.shared.layout.clone();
-        let mut v = Vec::new();
-        try_err!(layout::render(&mut v, &layout,
-                                &page, &sidebar, &settings,
-                                self.shared.css_file_extension.is_some(),
-                                &themes,
-                                self.shared.generate_search_filter),
-                 &settings_file);
-        self.shared.fs.write(&settings_file, &v)?;
+        let v = layout::render(
+            &self.shared.layout,
+            &page, sidebar, settings(
+                self.shared.static_root_path.as_deref().unwrap_or("./"),
+                &self.shared.resource_suffix
+            ),
+            &themes);
+        self.shared.fs.write(&settings_file, v.as_bytes())?;
 
         Ok(())
     }
 
     fn render_item(&self,
-                   writer: &mut dyn io::Write,
                    it: &clean::Item,
-                   pushname: bool)
-                   -> io::Result<()> {
+                   pushname: bool) -> String {
         // A little unfortunate that this is done like this, but it sure
         // does make formatting *a lot* nicer.
         CURRENT_DEPTH.with(|slot| {
@@ -2022,12 +1966,10 @@ impl Context {
         }
 
         if !self.render_redirect_pages {
-            layout::render(writer, &self.shared.layout, &page,
-                           &Sidebar{ cx: self, item: it },
-                           &Item{ cx: self, item: it },
-                           self.shared.css_file_extension.is_some(),
-                           &self.shared.themes,
-                           self.shared.generate_search_filter)?;
+            layout::render(&self.shared.layout, &page,
+                           |buf: &mut _| print_sidebar(self, it, buf),
+                           |buf: &mut _| print_item(self, it, buf),
+                           &self.shared.themes)
         } else {
             let mut url = self.root_path();
             if let Some(&(ref names, ty)) = cache().paths.get(&it.def_id) {
@@ -2036,10 +1978,11 @@ impl Context {
                     url.push_str("/");
                 }
                 url.push_str(&item_path(ty, names.last().unwrap()));
-                layout::redirect(writer, &url)?;
+                layout::redirect(&url)
+            } else {
+                String::new()
             }
         }
-        Ok(())
     }
 
     /// Non-parallelized version of rendering an item. This will take the input
@@ -2075,13 +2018,12 @@ impl Context {
 
             info!("Recursing into {}", self.dst.display());
 
-            let mut buf = Vec::new();
-            self.render_item(&mut buf, &item, false).unwrap();
+            let buf = self.render_item(&item, false);
             // buf will be empty if the module is stripped and there is no redirect for it
             if !buf.is_empty() {
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join("index.html");
-                scx.fs.write(&joint_dst, buf)?;
+                scx.fs.write(&joint_dst, buf.as_bytes())?;
             }
 
             let m = match item.inner {
@@ -2094,9 +2036,7 @@ impl Context {
             if !self.render_redirect_pages {
                 let items = self.build_sidebar_items(&m);
                 let js_dst = self.dst.join("sidebar-items.js");
-                let mut v = Vec::new();
-                try_err!(write!(&mut v, "initSidebarItems({});",
-                                as_json(&items)), &js_dst);
+                let v = format!("initSidebarItems({});", as_json(&items));
                 scx.fs.write(&js_dst, &v)?;
             }
 
@@ -2110,8 +2050,7 @@ impl Context {
             self.dst = prev;
             self.current.pop().unwrap();
         } else if item.name.is_some() {
-            let mut buf = Vec::new();
-            self.render_item(&mut buf, &item, true).unwrap();
+            let buf = self.render_item(&item, true);
             // buf will be empty if the item is stripped and there is no redirect for it
             if !buf.is_empty() {
                 let name = item.name.as_ref().unwrap();
@@ -2119,7 +2058,7 @@ impl Context {
                 let file_name = &item_path(item_type, name);
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join(file_name);
-                self.shared.fs.write(&joint_dst, buf)?;
+                self.shared.fs.write(&joint_dst, buf.as_bytes())?;
 
                 if !self.render_redirect_pages {
                     all.append(full_path(self, &item), &item_type);
@@ -2129,18 +2068,16 @@ impl Context {
                     // URL for the page.
                     let redir_name = format!("{}.{}.html", name, item_type.name_space());
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Vec::new();
-                    try_err!(layout::redirect(&mut v, file_name), &redir_dst);
-                    self.shared.fs.write(&redir_dst, &v)?;
+                    let v = layout::redirect(file_name);
+                    self.shared.fs.write(&redir_dst, v.as_bytes())?;
                 }
                 // If the item is a macro, redirect from the old macro URL (with !)
                 // to the new one (without).
                 if item_type == ItemType::Macro {
                     let redir_name = format!("{}.{}!.html", item_type, name);
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Vec::new();
-                    try_err!(layout::redirect(&mut v, file_name), &redir_dst);
-                    self.shared.fs.write(&redir_dst, &v)?;
+                    let v = layout::redirect(file_name);
+                    self.shared.fs.write(&redir_dst, v.as_bytes())?;
                 }
             }
         }
@@ -2172,7 +2109,7 @@ impl Context {
     }
 }
 
-impl<'a> Item<'a> {
+impl Context {
     /// Generates a url appropriate for an `href` attribute back to the source of
     /// this item.
     ///
@@ -2182,26 +2119,26 @@ impl<'a> Item<'a> {
     /// If `None` is returned, then a source link couldn't be generated. This
     /// may happen, for example, with externally inlined items where the source
     /// of their crate documentation isn't known.
-    fn src_href(&self) -> Option<String> {
-        let mut root = self.cx.root_path();
+    fn src_href(&self, item: &clean::Item) -> Option<String> {
+        let mut root = self.root_path();
 
         let cache = cache();
         let mut path = String::new();
 
         // We can safely ignore macros from other libraries
-        let file = match self.item.source.filename {
+        let file = match item.source.filename {
             FileName::Real(ref path) => path,
             _ => return None,
         };
 
-        let (krate, path) = if self.item.def_id.is_local() {
-            if let Some(path) = self.cx.shared.local_sources.get(file) {
-                (&self.cx.shared.layout.krate, path)
+        let (krate, path) = if item.def_id.is_local() {
+            if let Some(path) = self.shared.local_sources.get(file) {
+                (&self.shared.layout.krate, path)
             } else {
                 return None;
             }
         } else {
-            let (krate, src_root) = match *cache.extern_locations.get(&self.item.def_id.krate)? {
+            let (krate, src_root) = match *cache.extern_locations.get(&item.def_id.krate)? {
                 (ref name, ref src, Local) => (name, src),
                 (ref name, ref src, Remote(ref s)) => {
                     root = s.to_string();
@@ -2221,10 +2158,10 @@ impl<'a> Item<'a> {
             (krate, &path)
         };
 
-        let lines = if self.item.source.loline == self.item.source.hiline {
-            self.item.source.loline.to_string()
+        let lines = if item.source.loline == item.source.hiline {
+            item.source.loline.to_string()
         } else {
-            format!("{}-{}", self.item.source.loline, self.item.source.hiline)
+            format!("{}-{}", item.source.loline, item.source.hiline)
         };
         Some(format!("{root}src/{krate}/{path}#{lines}",
                      root = Escape(&root),
@@ -2234,114 +2171,113 @@ impl<'a> Item<'a> {
     }
 }
 
-fn wrap_into_docblock<F>(w: &mut fmt::Formatter<'_>,
-                         f: F) -> fmt::Result
-where F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(w, "<div class=\"docblock type-decl hidden-by-usual-hider\">")?;
-    f(w)?;
+fn wrap_into_docblock<F>(w: &mut Buffer, f: F)
+    where F: FnOnce(&mut Buffer)
+{
+    write!(w, "<div class=\"docblock type-decl hidden-by-usual-hider\">");
+    f(w);
     write!(w, "</div>")
 }
 
-impl<'a> fmt::Display for Item<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        debug_assert!(!self.item.is_stripped());
-        // Write the breadcrumb trail header for the top
-        write!(fmt, "<h1 class='fqn'><span class='out-of-band'>")?;
-        if let Some(version) = self.item.stable_since() {
-            write!(fmt, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
-                   version)?;
-        }
-        write!(fmt,
-               "<span id='render-detail'>\
-                   <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" \
-                      title=\"collapse all docs\">\
-                       [<span class='inner'>&#x2212;</span>]\
-                   </a>\
-               </span>")?;
-
-        // Write `src` tag
-        //
-        // When this item is part of a `pub use` in a downstream crate, the
-        // [src] link in the downstream documentation will actually come back to
-        // this page, and this link will be auto-clicked. The `id` attribute is
-        // used to find the link to auto-click.
-        if self.cx.shared.include_sources && !self.item.is_primitive() {
-            if let Some(l) = self.src_href() {
-                write!(fmt, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                       l, "goto source code")?;
-            }
-        }
-
-        write!(fmt, "</span>")?; // out-of-band
-        write!(fmt, "<span class='in-band'>")?;
-        match self.item.inner {
-            clean::ModuleItem(ref m) => if m.is_crate {
-                    write!(fmt, "Crate ")?;
-                } else {
-                    write!(fmt, "Module ")?;
-                },
-            clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => write!(fmt, "Function ")?,
-            clean::TraitItem(..) => write!(fmt, "Trait ")?,
-            clean::StructItem(..) => write!(fmt, "Struct ")?,
-            clean::UnionItem(..) => write!(fmt, "Union ")?,
-            clean::EnumItem(..) => write!(fmt, "Enum ")?,
-            clean::TypedefItem(..) => write!(fmt, "Type Definition ")?,
-            clean::MacroItem(..) => write!(fmt, "Macro ")?,
-            clean::ProcMacroItem(ref mac) => match mac.kind {
-                MacroKind::Bang => write!(fmt, "Macro ")?,
-                MacroKind::Attr => write!(fmt, "Attribute Macro ")?,
-                MacroKind::Derive => write!(fmt, "Derive Macro ")?,
-            }
-            clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
-            clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
-            clean::ConstantItem(..) => write!(fmt, "Constant ")?,
-            clean::ForeignTypeItem => write!(fmt, "Foreign Type ")?,
-            clean::KeywordItem(..) => write!(fmt, "Keyword ")?,
-            clean::OpaqueTyItem(..) => write!(fmt, "Opaque Type ")?,
-            clean::TraitAliasItem(..) => write!(fmt, "Trait Alias ")?,
-            _ => {
-                // We don't generate pages for any other type.
-                unreachable!();
-            }
+fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
+    debug_assert!(!item.is_stripped());
+    // Write the breadcrumb trail header for the top
+    write!(buf, "<h1 class='fqn'><span class='out-of-band'>");
+    if let Some(version) = item.stable_since() {
+        write!(buf, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
+                version);
+    }
+    write!(buf,
+            "<span id='render-detail'>\
+                <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" \
+                    title=\"collapse all docs\">\
+                    [<span class='inner'>&#x2212;</span>]\
+                </a>\
+            </span>");
+
+    // Write `src` tag
+    //
+    // When this item is part of a `pub use` in a downstream crate, the
+    // [src] link in the downstream documentation will actually come back to
+    // this page, and this link will be auto-clicked. The `id` attribute is
+    // used to find the link to auto-click.
+    if cx.shared.include_sources && !item.is_primitive() {
+        if let Some(l) = cx.src_href(item) {
+            write!(buf, "<a class='srclink' href='{}' title='{}'>[src]</a>",
+                    l, "goto source code");
+        }
+    }
+
+    write!(buf, "</span>"); // out-of-band
+    write!(buf, "<span class='in-band'>");
+    let name = match item.inner {
+        clean::ModuleItem(ref m) => if m.is_crate {
+                "Crate "
+            } else {
+                "Module "
+            },
+        clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => "Function ",
+        clean::TraitItem(..) => "Trait ",
+        clean::StructItem(..) => "Struct ",
+        clean::UnionItem(..) => "Union ",
+        clean::EnumItem(..) => "Enum ",
+        clean::TypedefItem(..) => "Type Definition ",
+        clean::MacroItem(..) => "Macro ",
+        clean::ProcMacroItem(ref mac) => match mac.kind {
+            MacroKind::Bang => "Macro ",
+            MacroKind::Attr => "Attribute Macro ",
+            MacroKind::Derive => "Derive Macro ",
+        }
+        clean::PrimitiveItem(..) => "Primitive Type ",
+        clean::StaticItem(..) | clean::ForeignStaticItem(..) => "Static ",
+        clean::ConstantItem(..) => "Constant ",
+        clean::ForeignTypeItem => "Foreign Type ",
+        clean::KeywordItem(..) => "Keyword ",
+        clean::OpaqueTyItem(..) => "Opaque Type ",
+        clean::TraitAliasItem(..) => "Trait Alias ",
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
         }
-        if !self.item.is_primitive() && !self.item.is_keyword() {
-            let cur = &self.cx.current;
-            let amt = if self.item.is_mod() { cur.len() - 1 } else { cur.len() };
-            for (i, component) in cur.iter().enumerate().take(amt) {
-                write!(fmt, "<a href='{}index.html'>{}</a>::<wbr>",
-                       "../".repeat(cur.len() - i - 1),
-                       component)?;
-            }
+    };
+    buf.write_str(name);
+    if !item.is_primitive() && !item.is_keyword() {
+        let cur = &cx.current;
+        let amt = if item.is_mod() { cur.len() - 1 } else { cur.len() };
+        for (i, component) in cur.iter().enumerate().take(amt) {
+            write!(buf, "<a href='{}index.html'>{}</a>::<wbr>",
+                    "../".repeat(cur.len() - i - 1),
+                    component);
         }
-        write!(fmt, "<a class=\"{}\" href=''>{}</a>",
-               self.item.type_(), self.item.name.as_ref().unwrap())?;
-
-        write!(fmt, "</span></h1>")?; // in-band
-
-        match self.item.inner {
-            clean::ModuleItem(ref m) =>
-                item_module(fmt, self.cx, self.item, &m.items),
-            clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
-                item_function(fmt, self.cx, self.item, f),
-            clean::TraitItem(ref t) => item_trait(fmt, self.cx, self.item, t),
-            clean::StructItem(ref s) => item_struct(fmt, self.cx, self.item, s),
-            clean::UnionItem(ref s) => item_union(fmt, self.cx, self.item, s),
-            clean::EnumItem(ref e) => item_enum(fmt, self.cx, self.item, e),
-            clean::TypedefItem(ref t, _) => item_typedef(fmt, self.cx, self.item, t),
-            clean::MacroItem(ref m) => item_macro(fmt, self.cx, self.item, m),
-            clean::ProcMacroItem(ref m) => item_proc_macro(fmt, self.cx, self.item, m),
-            clean::PrimitiveItem(ref p) => item_primitive(fmt, self.cx, self.item, p),
-            clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
-                item_static(fmt, self.cx, self.item, i),
-            clean::ConstantItem(ref c) => item_constant(fmt, self.cx, self.item, c),
-            clean::ForeignTypeItem => item_foreign_type(fmt, self.cx, self.item),
-            clean::KeywordItem(ref k) => item_keyword(fmt, self.cx, self.item, k),
-            clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, self.cx, self.item, e),
-            clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, self.cx, self.item, ta),
-            _ => {
-                // We don't generate pages for any other type.
-                unreachable!();
-            }
+    }
+    write!(buf, "<a class=\"{}\" href=''>{}</a>",
+            item.type_(), item.name.as_ref().unwrap());
+
+    write!(buf, "</span></h1>"); // in-band
+
+    match item.inner {
+        clean::ModuleItem(ref m) =>
+            item_module(buf, cx, item, &m.items),
+        clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
+            item_function(buf, cx, item, f),
+        clean::TraitItem(ref t) => item_trait(buf, cx, item, t),
+        clean::StructItem(ref s) => item_struct(buf, cx, item, s),
+        clean::UnionItem(ref s) => item_union(buf, cx, item, s),
+        clean::EnumItem(ref e) => item_enum(buf, cx, item, e),
+        clean::TypedefItem(ref t, _) => item_typedef(buf, cx, item, t),
+        clean::MacroItem(ref m) => item_macro(buf, cx, item, m),
+        clean::ProcMacroItem(ref m) => item_proc_macro(buf, cx, item, m),
+        clean::PrimitiveItem(ref p) => item_primitive(buf, cx, item, p),
+        clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
+            item_static(buf, cx, item, i),
+        clean::ConstantItem(ref c) => item_constant(buf, cx, item, c),
+        clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
+        clean::KeywordItem(ref k) => item_keyword(buf, cx, item, k),
+        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(buf, cx, item, e),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
         }
     }
 }
@@ -2395,24 +2331,23 @@ fn shorten(s: String) -> String {
     }
 }
 
-fn document(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item) -> fmt::Result {
+fn document(w: &mut Buffer, cx: &Context, item: &clean::Item) {
     if let Some(ref name) = item.name {
         info!("Documenting {}", name);
     }
-    document_stability(w, cx, item, false)?;
-    document_full(w, item, cx, "", false)?;
-    Ok(())
+    document_stability(w, cx, item, false);
+    document_full(w, item, cx, "", false);
 }
 
 /// Render md_text as markdown.
 fn render_markdown(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     md_text: &str,
     links: Vec<(String, String)>,
     prefix: &str,
     is_hidden: bool,
-) -> fmt::Result {
+) {
     let mut ids = cx.id_map.borrow_mut();
     write!(w, "<div class='docblock{}'>{}{}</div>",
            if is_hidden { " hidden" } else { "" },
@@ -2422,13 +2357,13 @@ fn render_markdown(
 }
 
 fn document_short(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     item: &clean::Item,
     link: AssocItemLink<'_>,
     prefix: &str,
     is_hidden: bool,
-) -> fmt::Result {
+) {
     if let Some(s) = item.doc_value() {
         let markdown = if s.contains('\n') {
             format!("{} [Read more]({})",
@@ -2436,46 +2371,41 @@ fn document_short(
         } else {
             plain_summary_line(Some(s))
         };
-        render_markdown(w, cx, &markdown, item.links(), prefix, is_hidden)?;
+        render_markdown(w, cx, &markdown, item.links(), prefix, is_hidden);
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock{}'>{}</div>",
                if is_hidden { " hidden" } else { "" },
-               prefix)?;
+               prefix);
     }
-    Ok(())
 }
 
-fn document_full(w: &mut fmt::Formatter<'_>, item: &clean::Item,
-                 cx: &Context, prefix: &str, is_hidden: bool) -> fmt::Result {
+fn document_full(w: &mut Buffer, item: &clean::Item, cx: &Context, prefix: &str, is_hidden: bool) {
     if let Some(s) = cx.shared.maybe_collapsed_doc_value(item) {
         debug!("Doc block: =====\n{}\n=====", s);
-        render_markdown(w, cx, &*s, item.links(), prefix, is_hidden)?;
+        render_markdown(w, cx, &*s, item.links(), prefix, is_hidden);
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock{}'>{}</div>",
                if is_hidden { " hidden" } else { "" },
-               prefix)?;
+               prefix);
     }
-    Ok(())
 }
 
-fn document_stability(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item,
-                      is_hidden: bool) -> fmt::Result {
+fn document_stability(w: &mut Buffer, cx: &Context, item: &clean::Item, is_hidden: bool) {
     let stabilities = short_stability(item, cx);
     if !stabilities.is_empty() {
-        write!(w, "<div class='stability{}'>", if is_hidden { " hidden" } else { "" })?;
+        write!(w, "<div class='stability{}'>", if is_hidden { " hidden" } else { "" });
         for stability in stabilities {
-            write!(w, "{}", stability)?;
+            write!(w, "{}", stability);
         }
-        write!(w, "</div>")?;
+        write!(w, "</div>");
     }
-    Ok(())
 }
 
 fn document_non_exhaustive_header(item: &clean::Item) -> &str {
     if item.is_non_exhaustive() { " (Non-exhaustive)" } else { "" }
 }
 
-fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fmt::Result {
+fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
     if item.is_non_exhaustive() {
         write!(w, "<div class='docblock non-exhaustive non-exhaustive-{}'>", {
             if item.is_struct() {
@@ -2487,31 +2417,29 @@ fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fm
             } else {
                 "type"
             }
-        })?;
+        });
 
         if item.is_struct() {
             write!(w, "Non-exhaustive structs could have additional fields added in future. \
                        Therefore, non-exhaustive structs cannot be constructed in external crates \
                        using the traditional <code>Struct {{ .. }}</code> syntax; cannot be \
                        matched against without a wildcard <code>..</code>; and \
-                       struct update syntax will not work.")?;
+                       struct update syntax will not work.");
         } else if item.is_enum() {
             write!(w, "Non-exhaustive enums could have additional variants added in future. \
                        Therefore, when matching against variants of non-exhaustive enums, an \
-                       extra wildcard arm must be added to account for any future variants.")?;
+                       extra wildcard arm must be added to account for any future variants.");
         } else if item.is_variant() {
             write!(w, "Non-exhaustive enum variants could have additional fields added in future. \
                        Therefore, non-exhaustive enum variants cannot be constructed in external \
-                       crates and cannot be matched against.")?;
+                       crates and cannot be matched against.");
         } else {
             write!(w, "This type will require a wildcard arm in any match statements or \
-                       constructors.")?;
+                       constructors.");
         }
 
-        write!(w, "</div>")?;
+        write!(w, "</div>");
     }
-
-    Ok(())
 }
 
 fn name_key(name: &str) -> (&str, u64, usize) {
@@ -2535,9 +2463,8 @@ fn name_key(name: &str) -> (&str, u64, usize) {
     }
 }
 
-fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
-               item: &clean::Item, items: &[clean::Item]) -> fmt::Result {
-    document(w, cx, item)?;
+fn item_module(w: &mut Buffer, cx: &Context, item: &clean::Item, items: &[clean::Item]) {
+    document(w, cx, item);
 
     let mut indices = (0..items.len()).filter(|i| !items[*i].is_stripped()).collect::<Vec<usize>>();
 
@@ -2628,13 +2555,13 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
             curty = myty;
         } else if myty != curty {
             if curty.is_some() {
-                write!(w, "</table>")?;
+                write!(w, "</table>");
             }
             curty = myty;
             let (short, name) = item_ty_to_strs(&myty.unwrap());
             write!(w, "<h2 id='{id}' class='section-header'>\
                        <a href=\"#{id}\">{name}</a></h2>\n<table>",
-                   id = cx.derive_id(short.to_owned()), name = name)?;
+                   id = cx.derive_id(short.to_owned()), name = name);
         }
 
         match myitem.inner {
@@ -2646,20 +2573,20 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
                         write!(w, "<tr><td><code>{}extern crate {} as {};",
                                VisSpace(&myitem.visibility),
                                anchor(myitem.def_id, src),
-                               name)?
+                               name)
                     }
                     None => {
                         write!(w, "<tr><td><code>{}extern crate {};",
                                VisSpace(&myitem.visibility),
-                               anchor(myitem.def_id, name))?
+                               anchor(myitem.def_id, name))
                     }
                 }
-                write!(w, "</code></td></tr>")?;
+                write!(w, "</code></td></tr>");
             }
 
             clean::ImportItem(ref import) => {
                 write!(w, "<tr><td><code>{}{}</code></td></tr>",
-                       VisSpace(&myitem.visibility), *import)?;
+                       VisSpace(&myitem.visibility), *import);
             }
 
             _ => {
@@ -2704,15 +2631,14 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
                                 })
                                 .collect::<Vec<_>>()
                                 .join(" "),
-                      )?;
+                      );
             }
         }
     }
 
     if curty.is_some() {
-        write!(w, "</table>")?;
+        write!(w, "</table>");
     }
-    Ok(())
 }
 
 /// Render the stability and deprecation tags that are displayed in the item's summary at the
@@ -2861,33 +2787,30 @@ fn short_stability(item: &clean::Item, cx: &Context) -> Vec<String> {
     stability
 }
 
-fn item_constant(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                 c: &clean::Constant) -> fmt::Result {
-    write!(w, "<pre class='rust const'>")?;
-    render_attributes(w, it, false)?;
+fn item_constant(w: &mut Buffer, cx: &Context, it: &clean::Item, c: &clean::Constant) {
+    write!(w, "<pre class='rust const'>");
+    render_attributes(w, it, false);
     write!(w, "{vis}const \
                {name}: {typ}</pre>",
            vis = VisSpace(&it.visibility),
            name = it.name.as_ref().unwrap(),
-           typ = c.type_)?;
+           typ = c.type_);
     document(w, cx, it)
 }
 
-fn item_static(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Static) -> fmt::Result {
-    write!(w, "<pre class='rust static'>")?;
-    render_attributes(w, it, false)?;
+fn item_static(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Static) {
+    write!(w, "<pre class='rust static'>");
+    render_attributes(w, it, false);
     write!(w, "{vis}static {mutability}\
                {name}: {typ}</pre>",
            vis = VisSpace(&it.visibility),
            mutability = MutableSpace(s.mutability),
            name = it.name.as_ref().unwrap(),
-           typ = s.type_)?;
+           typ = s.type_);
     document(w, cx, it)
 }
 
-fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                 f: &clean::Function) -> fmt::Result {
+fn item_function(w: &mut Buffer, cx: &Context, it: &clean::Item, f: &clean::Function) {
     let header_len = format!(
         "{}{}{}{}{:#}fn {}{:#}",
         VisSpace(&it.visibility),
@@ -2898,8 +2821,8 @@ fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
         it.name.as_ref().unwrap(),
         f.generics
     ).len();
-    write!(w, "{}<pre class='rust fn'>", render_spotlight_traits(it)?)?;
-    render_attributes(w, it, false)?;
+    write!(w, "{}<pre class='rust fn'>", render_spotlight_traits(it));
+    render_attributes(w, it, false);
     write!(w,
            "{vis}{constness}{unsafety}{asyncness}{abi}fn \
            {name}{generics}{decl}{where_clause}</pre>",
@@ -2916,12 +2839,12 @@ fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
               header_len,
               indent: 0,
               asyncness: f.header.asyncness,
-           })?;
+           });
     document(w, cx, it)
 }
 
-fn render_implementor(cx: &Context, implementor: &Impl, w: &mut fmt::Formatter<'_>,
-                      implementor_dups: &FxHashMap<&str, (DefId, bool)>) -> fmt::Result {
+fn render_implementor(cx: &Context, implementor: &Impl, w: &mut Buffer,
+                      implementor_dups: &FxHashMap<&str, (DefId, bool)>) {
     // If there's already another implementor that has the same abbridged name, use the
     // full path, for example in `std::iter::ExactSizeIterator`
     let use_absolute = match implementor.inner_impl().for_ {
@@ -2933,20 +2856,18 @@ fn render_implementor(cx: &Context, implementor: &Impl, w: &mut fmt::Formatter<'
         _ => false,
     };
     render_impl(w, cx, implementor, AssocItemLink::Anchor(None), RenderMode::Normal,
-                implementor.impl_item.stable_since(), false, Some(use_absolute), false, false)?;
-    Ok(())
+                implementor.impl_item.stable_since(), false, Some(use_absolute), false, false);
 }
 
-fn render_impls(cx: &Context, w: &mut fmt::Formatter<'_>,
+fn render_impls(cx: &Context, w: &mut Buffer,
                 traits: &[&&Impl],
-                containing_item: &clean::Item) -> fmt::Result {
+                containing_item: &clean::Item) {
     for i in traits {
         let did = i.trait_did().unwrap();
         let assoc_link = AssocItemLink::GotoSource(did, &i.inner_impl().provided_trait_methods);
         render_impl(w, cx, i, assoc_link,
-                    RenderMode::Normal, containing_item.stable_since(), true, None, false, true)?;
+                    RenderMode::Normal, containing_item.stable_since(), true, None, false, true);
     }
-    Ok(())
 }
 
 fn bounds(t_bounds: &[clean::GenericBound], trait_alias: bool) -> String {
@@ -2974,11 +2895,11 @@ fn compare_impl<'a, 'b>(lhs: &'a &&Impl, rhs: &'b &&Impl) -> Ordering {
 }
 
 fn item_trait(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     it: &clean::Item,
     t: &clean::Trait,
-) -> fmt::Result {
+) {
     let bounds = bounds(&t.bounds, false);
     let types = t.items.iter().filter(|m| m.is_associated_type()).collect::<Vec<_>>();
     let consts = t.items.iter().filter(|m| m.is_associated_const()).collect::<Vec<_>>();
@@ -2987,146 +2908,144 @@ fn item_trait(
 
     // Output the trait definition
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust trait'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust trait'>");
+        render_attributes(w, it, true);
         write!(w, "{}{}{}trait {}{}{}",
                VisSpace(&it.visibility),
                UnsafetySpace(t.unsafety),
                if t.is_auto { "auto " } else { "" },
                it.name.as_ref().unwrap(),
                t.generics,
-               bounds)?;
+               bounds);
 
         if !t.generics.where_predicates.is_empty() {
-            write!(w, "{}", WhereClause { gens: &t.generics, indent: 0, end_newline: true })?;
+            write!(w, "{}", WhereClause { gens: &t.generics, indent: 0, end_newline: true });
         } else {
-            write!(w, " ")?;
+            write!(w, " ");
         }
 
         if t.items.is_empty() {
-            write!(w, "{{ }}")?;
+            write!(w, "{{ }}");
         } else {
             // FIXME: we should be using a derived_id for the Anchors here
-            write!(w, "{{\n")?;
+            write!(w, "{{\n");
             for t in &types {
-                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
             }
             if !types.is_empty() && !consts.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for t in &consts {
-                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
             }
             if !consts.is_empty() && !required.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for (pos, m) in required.iter().enumerate() {
-                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
 
                 if pos < required.len() - 1 {
-                   write!(w, "<div class='item-spacer'></div>")?;
+                   write!(w, "<div class='item-spacer'></div>");
                 }
             }
             if !required.is_empty() && !provided.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for (pos, m) in provided.iter().enumerate() {
-                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait)?;
+                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait);
                 match m.inner {
                     clean::MethodItem(ref inner) if !inner.generics.where_predicates.is_empty() => {
-                        write!(w, ",\n    {{ ... }}\n")?;
+                        write!(w, ",\n    {{ ... }}\n");
                     },
                     _ => {
-                        write!(w, " {{ ... }}\n")?;
+                        write!(w, " {{ ... }}\n");
                     },
                 }
                 if pos < provided.len() - 1 {
-                   write!(w, "<div class='item-spacer'></div>")?;
+                   write!(w, "<div class='item-spacer'></div>");
                 }
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         write!(w, "</pre>")
-    })?;
+    });
 
     // Trait documentation
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     fn write_small_section_header(
-        w: &mut fmt::Formatter<'_>,
+        w: &mut Buffer,
         id: &str,
         title: &str,
         extra_content: &str,
-    ) -> fmt::Result {
+    ) {
         write!(w, "
             <h2 id='{0}' class='small-section-header'>\
               {1}<a href='#{0}' class='anchor'></a>\
             </h2>{2}", id, title, extra_content)
     }
 
-    fn write_loading_content(w: &mut fmt::Formatter<'_>, extra_content: &str) -> fmt::Result {
+    fn write_loading_content(w: &mut Buffer, extra_content: &str) {
         write!(w, "{}<span class='loading-content'>Loading content...</span>", extra_content)
     }
 
-    fn trait_item(w: &mut fmt::Formatter<'_>, cx: &Context, m: &clean::Item, t: &clean::Item)
-                  -> fmt::Result {
+    fn trait_item(w: &mut Buffer, cx: &Context, m: &clean::Item, t: &clean::Item) {
         let name = m.name.as_ref().unwrap();
         let item_type = m.type_();
         let id = cx.derive_id(format!("{}.{}", item_type, name));
         let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
         write!(w, "<h3 id='{id}' class='method'>{extra}<code id='{ns_id}'>",
-               extra = render_spotlight_traits(m)?,
+               extra = render_spotlight_traits(m),
                id = id,
-               ns_id = ns_id)?;
-        render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl)?;
-        write!(w, "</code>")?;
-        render_stability_since(w, m, t)?;
-        write!(w, "</h3>")?;
-        document(w, cx, m)?;
-        Ok(())
+               ns_id = ns_id);
+        render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl);
+        write!(w, "</code>");
+        render_stability_since(w, m, t);
+        write!(w, "</h3>");
+        document(w, cx, m);
     }
 
     if !types.is_empty() {
         write_small_section_header(w, "associated-types", "Associated Types",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for t in &types {
-            trait_item(w, cx, *t, it)?;
+            trait_item(w, cx, *t, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     if !consts.is_empty() {
         write_small_section_header(w, "associated-const", "Associated Constants",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for t in &consts {
-            trait_item(w, cx, *t, it)?;
+            trait_item(w, cx, *t, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     // Output the documentation for each function individually
     if !required.is_empty() {
         write_small_section_header(w, "required-methods", "Required methods",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for m in &required {
-            trait_item(w, cx, *m, it)?;
+            trait_item(w, cx, *m, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
     if !provided.is_empty() {
         write_small_section_header(w, "provided-methods", "Provided methods",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for m in &provided {
-            trait_item(w, cx, *m, it)?;
+            trait_item(w, cx, *m, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     // If there are methods directly on this trait object, render them here.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)?;
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All);
 
     let cache = cache();
 
@@ -3165,7 +3084,7 @@ fn item_trait(
         concrete.sort_by(compare_impl);
 
         if !foreign.is_empty() {
-            write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "")?;
+            write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "");
 
             for implementor in foreign {
                 let assoc_link = AssocItemLink::GotoSource(
@@ -3174,44 +3093,44 @@ fn item_trait(
                 );
                 render_impl(w, cx, &implementor, assoc_link,
                             RenderMode::Normal, implementor.impl_item.stable_since(), false,
-                            None, true, false)?;
+                            None, true, false);
             }
-            write_loading_content(w, "")?;
+            write_loading_content(w, "");
         }
 
         write_small_section_header(w, "implementors", "Implementors",
-                                   "<div class='item-list' id='implementors-list'>")?;
+                                   "<div class='item-list' id='implementors-list'>");
         for implementor in concrete {
-            render_implementor(cx, implementor, w, &implementor_dups)?;
+            render_implementor(cx, implementor, w, &implementor_dups);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
 
         if t.auto {
             write_small_section_header(w, "synthetic-implementors", "Auto implementors",
-                                       "<div class='item-list' id='synthetic-implementors-list'>")?;
+                                       "<div class='item-list' id='synthetic-implementors-list'>");
             for implementor in synthetic {
                 synthetic_types.extend(
                     collect_paths_for_type(implementor.inner_impl().for_.clone())
                 );
-                render_implementor(cx, implementor, w, &implementor_dups)?;
+                render_implementor(cx, implementor, w, &implementor_dups);
             }
-            write_loading_content(w, "</div>")?;
+            write_loading_content(w, "</div>");
         }
     } else {
         // even without any implementations to write in, we still want the heading and list, so the
         // implementors javascript file pulled in below has somewhere to write the impls into
         write_small_section_header(w, "implementors", "Implementors",
-                                   "<div class='item-list' id='implementors-list'>")?;
-        write_loading_content(w, "</div>")?;
+                                   "<div class='item-list' id='implementors-list'>");
+        write_loading_content(w, "</div>");
 
         if t.auto {
             write_small_section_header(w, "synthetic-implementors", "Auto implementors",
-                                       "<div class='item-list' id='synthetic-implementors-list'>")?;
-            write_loading_content(w, "</div>")?;
+                                       "<div class='item-list' id='synthetic-implementors-list'>");
+            write_loading_content(w, "</div>");
         }
     }
     write!(w, r#"<script type="text/javascript">window.inlined_types=new Set({});</script>"#,
-           as_json(&synthetic_types))?;
+           as_json(&synthetic_types));
 
     write!(w, r#"<script type="text/javascript" async
                          src="{root_path}/implementors/{path}/{ty}.{name}.js">
@@ -3224,8 +3143,7 @@ fn item_trait(
                path[..path.len() - 1].join("/")
            },
            ty = it.type_().css_class(),
-           name = *it.name.as_ref().unwrap())?;
-    Ok(())
+           name = *it.name.as_ref().unwrap());
 }
 
 fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
@@ -3247,70 +3165,60 @@ fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
     }
 }
 
-fn assoc_const(w: &mut fmt::Formatter<'_>,
+fn assoc_const(w: &mut Buffer,
                it: &clean::Item,
                ty: &clean::Type,
                _default: Option<&String>,
                link: AssocItemLink<'_>,
-               extra: &str) -> fmt::Result {
+               extra: &str) {
     write!(w, "{}{}const <a href='{}' class=\"constant\"><b>{}</b></a>: {}",
            extra,
            VisSpace(&it.visibility),
            naive_assoc_href(it, link),
            it.name.as_ref().unwrap(),
-           ty)?;
-    Ok(())
+           ty);
 }
 
-fn assoc_type<W: fmt::Write>(w: &mut W, it: &clean::Item,
-                             bounds: &[clean::GenericBound],
-                             default: Option<&clean::Type>,
-                             link: AssocItemLink<'_>,
-                             extra: &str) -> fmt::Result {
+fn assoc_type(w: &mut Buffer, it: &clean::Item,
+              bounds: &[clean::GenericBound],
+              default: Option<&clean::Type>,
+              link: AssocItemLink<'_>,
+              extra: &str) {
     write!(w, "{}type <a href='{}' class=\"type\">{}</a>",
            extra,
            naive_assoc_href(it, link),
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if !bounds.is_empty() {
-        write!(w, ": {}", GenericBounds(bounds))?
+        write!(w, ": {}", GenericBounds(bounds))
     }
     if let Some(default) = default {
-        write!(w, " = {}", default)?;
+        write!(w, " = {}", default)
     }
-    Ok(())
 }
 
-fn render_stability_since_raw<'a, T: fmt::Write>(
-    w: &mut T,
-    ver: Option<&'a str>,
-    containing_ver: Option<&'a str>,
-) -> fmt::Result {
+fn render_stability_since_raw(w: &mut Buffer, ver: Option<&str>, containing_ver: Option<&str>) {
     if let Some(v) = ver {
         if containing_ver != ver && v.len() > 0 {
-            write!(w, "<span class='since' title='Stable since Rust version {0}'>{0}</span>", v)?
+            write!(w, "<span class='since' title='Stable since Rust version {0}'>{0}</span>", v)
         }
     }
-    Ok(())
 }
 
-fn render_stability_since(w: &mut fmt::Formatter<'_>,
-                          item: &clean::Item,
-                          containing_item: &clean::Item) -> fmt::Result {
+fn render_stability_since(w: &mut Buffer, item: &clean::Item, containing_item: &clean::Item) {
     render_stability_since_raw(w, item.stable_since(), containing_item.stable_since())
 }
 
-fn render_assoc_item(w: &mut fmt::Formatter<'_>,
+fn render_assoc_item(w: &mut Buffer,
                      item: &clean::Item,
                      link: AssocItemLink<'_>,
-                     parent: ItemType) -> fmt::Result {
-    fn method(w: &mut fmt::Formatter<'_>,
+                     parent: ItemType) {
+    fn method(w: &mut Buffer,
               meth: &clean::Item,
               header: hir::FnHeader,
               g: &clean::Generics,
               d: &clean::FnDecl,
               link: AssocItemLink<'_>,
-              parent: ItemType)
-              -> fmt::Result {
+              parent: ItemType) {
         let name = meth.name.as_ref().unwrap();
         let anchor = format!("#{}.{}", meth.type_(), name);
         let href = match link {
@@ -3345,7 +3253,7 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
         } else {
             (0, true)
         };
-        render_attributes(w, meth, false)?;
+        render_attributes(w, meth, false);
         write!(w, "{}{}{}{}{}{}{}fn <a href='{href}' class='fnname'>{name}</a>\
                    {generics}{decl}{where_clause}",
                if parent == ItemType::Trait { "    " } else { "" },
@@ -3371,7 +3279,7 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
                })
     }
     match item.inner {
-        clean::StrippedItem(..) => Ok(()),
+        clean::StrippedItem(..) => {},
         clean::TyMethodItem(ref m) => {
             method(w, item, m.header, &m.generics, &m.decl, link, parent)
         }
@@ -3390,22 +3298,21 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
     }
 }
 
-fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Struct) -> fmt::Result {
+fn item_struct(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Struct) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust struct'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust struct'>");
+        render_attributes(w, it, true);
         render_struct(w,
                       it,
                       Some(&s.generics),
                       s.struct_type,
                       &s.fields,
                       "",
-                      true)?;
+                      true);
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     let mut fields = s.fields.iter().filter_map(|f| {
         match f.inner {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
@@ -3416,8 +3323,8 @@ fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
         if fields.peek().is_some() {
             write!(w, "<h2 id='fields' class='fields small-section-header'>
                        Fields{}<a href='#fields' class='anchor'></a></h2>",
-                       document_non_exhaustive_header(it))?;
-            document_non_exhaustive(w, it)?;
+                       document_non_exhaustive_header(it));
+            document_non_exhaustive(w, it);
             for (field, ty) in fields {
                 let id = cx.derive_id(format!("{}.{}",
                                            ItemType::StructField,
@@ -3433,29 +3340,28 @@ fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                        id = id,
                        ns_id = ns_id,
                        name = field.name.as_ref().unwrap(),
-                       ty = ty)?;
-                document(w, cx, field)?;
+                       ty = ty);
+                document(w, cx, field);
             }
         }
     }
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Union) -> fmt::Result {
+fn item_union(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Union) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust union'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust union'>");
+        render_attributes(w, it, true);
         render_union(w,
                      it,
                      Some(&s.generics),
                      &s.fields,
                      "",
-                     true)?;
+                     true);
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     let mut fields = s.fields.iter().filter_map(|f| {
         match f.inner {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
@@ -3464,7 +3370,7 @@ fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     }).peekable();
     if fields.peek().is_some() {
         write!(w, "<h2 id='fields' class='fields small-section-header'>
-                   Fields<a href='#fields' class='anchor'></a></h2>")?;
+                   Fields<a href='#fields' class='anchor'></a></h2>");
         for (field, ty) in fields {
             let name = field.name.as_ref().expect("union field name");
             let id = format!("{}.{}", ItemType::StructField, name);
@@ -3475,47 +3381,46 @@ fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                    id = id,
                    name = name,
                    shortty = ItemType::StructField,
-                   ty = ty)?;
+                   ty = ty);
             if let Some(stability_class) = field.stability_class() {
                 write!(w, "<span class='stab {stab}'></span>",
-                    stab = stability_class)?;
+                    stab = stability_class);
             }
-            document(w, cx, field)?;
+            document(w, cx, field);
         }
     }
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-             e: &clean::Enum) -> fmt::Result {
+fn item_enum(w: &mut Buffer, cx: &Context, it: &clean::Item, e: &clean::Enum) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust enum'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust enum'>");
+        render_attributes(w, it, true);
         write!(w, "{}enum {}{}{}",
                VisSpace(&it.visibility),
                it.name.as_ref().unwrap(),
                e.generics,
-               WhereClause { gens: &e.generics, indent: 0, end_newline: true })?;
+               WhereClause { gens: &e.generics, indent: 0, end_newline: true });
         if e.variants.is_empty() && !e.variants_stripped {
-            write!(w, " {{}}")?;
+            write!(w, " {{}}");
         } else {
-            write!(w, " {{\n")?;
+            write!(w, " {{\n");
             for v in &e.variants {
-                write!(w, "    ")?;
+                write!(w, "    ");
                 let name = v.name.as_ref().unwrap();
                 match v.inner {
                     clean::VariantItem(ref var) => {
                         match var.kind {
-                            clean::VariantKind::CLike => write!(w, "{}", name)?,
+                            clean::VariantKind::CLike => write!(w, "{}", name),
                             clean::VariantKind::Tuple(ref tys) => {
-                                write!(w, "{}(", name)?;
+                                write!(w, "{}(", name);
                                 for (i, ty) in tys.iter().enumerate() {
                                     if i > 0 {
-                                        write!(w, ",&nbsp;")?
+                                        write!(w, ",&nbsp;")
                                     }
-                                    write!(w, "{}", *ty)?;
+                                    write!(w, "{}", *ty);
                                 }
-                                write!(w, ")")?;
+                                write!(w, ")");
                             }
                             clean::VariantKind::Struct(ref s) => {
                                 render_struct(w,
@@ -3524,29 +3429,29 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                                               s.struct_type,
                                               &s.fields,
                                               "    ",
-                                              false)?;
+                                              false);
                             }
                         }
                     }
                     _ => unreachable!()
                 }
-                write!(w, ",\n")?;
+                write!(w, ",\n");
             }
 
             if e.variants_stripped {
-                write!(w, "    // some variants omitted\n")?;
+                write!(w, "    // some variants omitted\n");
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     if !e.variants.is_empty() {
         write!(w, "<h2 id='variants' class='variants small-section-header'>
                    Variants{}<a href='#variants' class='anchor'></a></h2>\n",
-                   document_non_exhaustive_header(it))?;
-        document_non_exhaustive(w, it)?;
+                   document_non_exhaustive_header(it));
+        document_non_exhaustive(w, it);
         for variant in &e.variants {
             let id = cx.derive_id(format!("{}.{}",
                                        ItemType::Variant,
@@ -3554,27 +3459,27 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
             let ns_id = cx.derive_id(format!("{}.{}",
                                           variant.name.as_ref().unwrap(),
                                           ItemType::Variant.name_space()));
-            write!(w, "<span id=\"{id}\" class=\"variant small-section-header\">\
+            write!(w, "<div id=\"{id}\" class=\"variant small-section-header\">\
                        <a href=\"#{id}\" class=\"anchor field\"></a>\
                        <code id='{ns_id}'>{name}",
                    id = id,
                    ns_id = ns_id,
-                   name = variant.name.as_ref().unwrap())?;
+                   name = variant.name.as_ref().unwrap());
             if let clean::VariantItem(ref var) = variant.inner {
                 if let clean::VariantKind::Tuple(ref tys) = var.kind {
-                    write!(w, "(")?;
+                    write!(w, "(");
                     for (i, ty) in tys.iter().enumerate() {
                         if i > 0 {
-                            write!(w, ",&nbsp;")?;
+                            write!(w, ",&nbsp;");
                         }
-                        write!(w, "{}", *ty)?;
+                        write!(w, "{}", *ty);
                     }
-                    write!(w, ")")?;
+                    write!(w, ")");
                 }
             }
-            write!(w, "</code></span>")?;
-            document(w, cx, variant)?;
-            document_non_exhaustive(w, variant)?;
+            write!(w, "</code></div>");
+            document(w, cx, variant);
+            document_non_exhaustive(w, variant);
 
             use crate::clean::{Variant, VariantKind};
             if let clean::VariantItem(Variant {
@@ -3583,10 +3488,10 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                 let variant_id = cx.derive_id(format!("{}.{}.fields",
                                                    ItemType::Variant,
                                                    variant.name.as_ref().unwrap()));
-                write!(w, "<span class='autohide sub-variant' id='{id}'>",
-                       id = variant_id)?;
+                write!(w, "<div class='autohide sub-variant' id='{id}'>",
+                       id = variant_id);
                 write!(w, "<h3>Fields of <b>{name}</b></h3><div>",
-                       name = variant.name.as_ref().unwrap())?;
+                       name = variant.name.as_ref().unwrap());
                 for field in &s.fields {
                     use crate::clean::StructFieldItem;
                     if let StructFieldItem(ref ty) = field.inner {
@@ -3605,17 +3510,16 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                                id = id,
                                ns_id = ns_id,
                                f = field.name.as_ref().unwrap(),
-                               t = *ty)?;
-                        document(w, cx, field)?;
+                               t = *ty);
+                        document(w, cx, field);
                     }
                 }
-                write!(w, "</div></span>")?;
+                write!(w, "</div></div>");
             }
-            render_stability_since(w, variant, it)?;
+            render_stability_since(w, variant, it);
         }
     }
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)?;
-    Ok(())
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
 fn render_attribute(attr: &ast::MetaItem) -> Option<String> {
@@ -3658,7 +3562,7 @@ const ATTRIBUTE_WHITELIST: &'static [Symbol] = &[
 //     #[bar] <---- not "top" attribute
 //     bar: usize,
 // }
-fn render_attributes(w: &mut dyn fmt::Write, it: &clean::Item, top: bool) -> fmt::Result {
+fn render_attributes(w: &mut Buffer, it: &clean::Item, top: bool) {
     let mut attrs = String::new();
 
     for attr in &it.attrs.other_attrs {
@@ -3671,117 +3575,114 @@ fn render_attributes(w: &mut dyn fmt::Write, it: &clean::Item, top: bool) -> fmt
     }
     if attrs.len() > 0 {
         write!(w, "<span class=\"docblock attributes{}\">{}</span>",
-               if top { " top-attr" } else { "" }, &attrs)?;
+               if top { " top-attr" } else { "" }, &attrs);
     }
-    Ok(())
 }
 
-fn render_struct(w: &mut fmt::Formatter<'_>, it: &clean::Item,
+fn render_struct(w: &mut Buffer, it: &clean::Item,
                  g: Option<&clean::Generics>,
                  ty: doctree::StructType,
                  fields: &[clean::Item],
                  tab: &str,
-                 structhead: bool) -> fmt::Result {
+                 structhead: bool) {
     write!(w, "{}{}{}",
            VisSpace(&it.visibility),
            if structhead {"struct "} else {""},
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if let Some(g) = g {
-        write!(w, "{}", g)?
+        write!(w, "{}", g)
     }
     match ty {
         doctree::Plain => {
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })
             }
             let mut has_visible_fields = false;
-            write!(w, " {{")?;
+            write!(w, " {{");
             for field in fields {
                 if let clean::StructFieldItem(ref ty) = field.inner {
                     write!(w, "\n{}    {}{}: {},",
                            tab,
                            VisSpace(&field.visibility),
                            field.name.as_ref().unwrap(),
-                           *ty)?;
+                           *ty);
                     has_visible_fields = true;
                 }
             }
 
             if has_visible_fields {
                 if it.has_stripped_fields().unwrap() {
-                    write!(w, "\n{}    // some fields omitted", tab)?;
+                    write!(w, "\n{}    // some fields omitted", tab);
                 }
-                write!(w, "\n{}", tab)?;
+                write!(w, "\n{}", tab);
             } else if it.has_stripped_fields().unwrap() {
                 // If there are no visible fields we can just display
                 // `{ /* fields omitted */ }` to save space.
-                write!(w, " /* fields omitted */ ")?;
+                write!(w, " /* fields omitted */ ");
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         doctree::Tuple => {
-            write!(w, "(")?;
+            write!(w, "(");
             for (i, field) in fields.iter().enumerate() {
                 if i > 0 {
-                    write!(w, ", ")?;
+                    write!(w, ", ");
                 }
                 match field.inner {
                     clean::StrippedItem(box clean::StructFieldItem(..)) => {
-                        write!(w, "_")?
+                        write!(w, "_")
                     }
                     clean::StructFieldItem(ref ty) => {
-                        write!(w, "{}{}", VisSpace(&field.visibility), *ty)?
+                        write!(w, "{}{}", VisSpace(&field.visibility), *ty)
                     }
                     _ => unreachable!()
                 }
             }
-            write!(w, ")")?;
+            write!(w, ")");
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })
             }
-            write!(w, ";")?;
+            write!(w, ";");
         }
         doctree::Unit => {
             // Needed for PhantomData.
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })
             }
-            write!(w, ";")?;
+            write!(w, ";");
         }
     }
-    Ok(())
 }
 
-fn render_union(w: &mut fmt::Formatter<'_>, it: &clean::Item,
+fn render_union(w: &mut Buffer, it: &clean::Item,
                 g: Option<&clean::Generics>,
                 fields: &[clean::Item],
                 tab: &str,
-                structhead: bool) -> fmt::Result {
+                structhead: bool) {
     write!(w, "{}{}{}",
            VisSpace(&it.visibility),
            if structhead {"union "} else {""},
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if let Some(g) = g {
-        write!(w, "{}", g)?;
-        write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })?;
+        write!(w, "{}", g);
+        write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true });
     }
 
-    write!(w, " {{\n{}", tab)?;
+    write!(w, " {{\n{}", tab);
     for field in fields {
         if let clean::StructFieldItem(ref ty) = field.inner {
             write!(w, "    {}{}: {},\n{}",
                    VisSpace(&field.visibility),
                    field.name.as_ref().unwrap(),
                    *ty,
-                   tab)?;
+                   tab);
         }
     }
 
     if it.has_stripped_fields().unwrap() {
-        write!(w, "    // some fields omitted\n{}", tab)?;
+        write!(w, "    // some fields omitted\n{}", tab);
     }
-    write!(w, "}}")?;
-    Ok(())
+    write!(w, "}}");
 }
 
 #[derive(Copy, Clone)]
@@ -3810,15 +3711,15 @@ enum RenderMode {
     ForDeref { mut_: bool },
 }
 
-fn render_assoc_items(w: &mut fmt::Formatter<'_>,
+fn render_assoc_items(w: &mut Buffer,
                       cx: &Context,
                       containing_item: &clean::Item,
                       it: DefId,
-                      what: AssocItemRender<'_>) -> fmt::Result {
+                      what: AssocItemRender<'_>) {
     let c = cache();
     let v = match c.impls.get(&it) {
         Some(v) => v,
-        None => return Ok(()),
+        None => return,
     };
     let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| {
         i.inner_impl().trait_.is_none()
@@ -3830,7 +3731,7 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                     <h2 id='methods' class='small-section-header'>\
                       Methods<a href='#methods' class='anchor'></a>\
                     </h2>\
-                ")?;
+                ");
                 RenderMode::Normal
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
@@ -3839,17 +3740,17 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                       Methods from {}&lt;Target = {}&gt;\
                       <a href='#deref-methods' class='anchor'></a>\
                     </h2>\
-                ", trait_, type_)?;
+                ", trait_, type_);
                 RenderMode::ForDeref { mut_: deref_mut_ }
             }
         };
         for i in &non_trait {
             render_impl(w, cx, i, AssocItemLink::Anchor(None), render_mode,
-                        containing_item.stable_since(), true, None, false, true)?;
+                        containing_item.stable_since(), true, None, false, true);
         }
     }
     if let AssocItemRender::DerefFor { .. } = what {
-        return Ok(());
+        return;
     }
     if !traits.is_empty() {
         let deref_impl = traits.iter().find(|t| {
@@ -3859,31 +3760,25 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
             let has_deref_mut = traits.iter().find(|t| {
                 t.inner_impl().trait_.def_id() == c.deref_mut_trait_did
             }).is_some();
-            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut)?;
+            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut);
         }
 
         let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) = traits
             .iter()
             .partition(|t| t.inner_impl().synthetic);
-        let (blanket_impl, concrete) = concrete
+        let (blanket_impl, concrete): (Vec<&&Impl>, _) = concrete
             .into_iter()
             .partition(|t| t.inner_impl().blanket_impl.is_some());
 
-        struct RendererStruct<'a, 'b, 'c>(&'a Context, Vec<&'b &'b Impl>, &'c clean::Item);
-
-        impl<'a, 'b, 'c> fmt::Display for RendererStruct<'a, 'b, 'c> {
-            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-                render_impls(self.0, fmt, &self.1, self.2)
-            }
-        }
-
-        let impls = RendererStruct(cx, concrete, containing_item).to_string();
+        let mut impls = Buffer::empty_from(&w);
+        render_impls(cx, &mut impls, &concrete, containing_item);
+        let impls = impls.into_inner();
         if !impls.is_empty() {
             write!(w, "\
                 <h2 id='implementations' class='small-section-header'>\
                   Trait Implementations<a href='#implementations' class='anchor'></a>\
                 </h2>\
-                <div id='implementations-list'>{}</div>", impls)?;
+                <div id='implementations-list'>{}</div>", impls);
         }
 
         if !synthetic.is_empty() {
@@ -3893,9 +3788,9 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                   <a href='#synthetic-implementations' class='anchor'></a>\
                 </h2>\
                 <div id='synthetic-implementations-list'>\
-            ")?;
-            render_impls(cx, w, &synthetic, containing_item)?;
-            write!(w, "</div>")?;
+            ");
+            render_impls(cx, w, &synthetic, containing_item);
+            write!(w, "</div>");
         }
 
         if !blanket_impl.is_empty() {
@@ -3905,16 +3800,15 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                   <a href='#blanket-implementations' class='anchor'></a>\
                 </h2>\
                 <div id='blanket-implementations-list'>\
-            ")?;
-            render_impls(cx, w, &blanket_impl, containing_item)?;
-            write!(w, "</div>")?;
+            ");
+            render_impls(cx, w, &blanket_impl, containing_item);
+            write!(w, "</div>");
         }
     }
-    Ok(())
 }
 
-fn render_deref_methods(w: &mut fmt::Formatter<'_>, cx: &Context, impl_: &Impl,
-                        container_item: &clean::Item, deref_mut: bool) -> fmt::Result {
+fn render_deref_methods(w: &mut Buffer, cx: &Context, impl_: &Impl,
+                        container_item: &clean::Item, deref_mut: bool) {
     let deref_type = impl_.inner_impl().trait_.as_ref().unwrap();
     let target = impl_.inner_impl().items.iter().filter_map(|item| {
         match item.inner {
@@ -3929,10 +3823,9 @@ fn render_deref_methods(w: &mut fmt::Formatter<'_>, cx: &Context, impl_: &Impl,
     } else {
         if let Some(prim) = target.primitive_type() {
             if let Some(&did) = cache().primitive_locations.get(&prim) {
-                render_assoc_items(w, cx, container_item, did, what)?;
+                render_assoc_items(w, cx, container_item, did, what);
             }
         }
-        Ok(())
     }
 }
 
@@ -3962,7 +3855,7 @@ fn should_render_item(item: &clean::Item, deref_mut_: bool) -> bool {
     }
 }
 
-fn render_spotlight_traits(item: &clean::Item) -> Result<String, fmt::Error> {
+fn render_spotlight_traits(item: &clean::Item) -> String {
     let mut out = String::new();
 
     match item.inner {
@@ -3970,16 +3863,16 @@ fn render_spotlight_traits(item: &clean::Item) -> Result<String, fmt::Error> {
         clean::TyMethodItem(clean::TyMethod { ref decl, .. }) |
         clean::MethodItem(clean::Method { ref decl, .. }) |
         clean::ForeignFunctionItem(clean::Function { ref decl, .. }) => {
-            out = spotlight_decl(decl)?;
+            out = spotlight_decl(decl);
         }
         _ => {}
     }
 
-    Ok(out)
+    out
 }
 
-fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
-    let mut out = String::new();
+fn spotlight_decl(decl: &clean::FnDecl) -> String {
+    let mut out = Buffer::html();
     let mut trait_ = String::new();
 
     if let Some(did) = decl.output.def_id() {
@@ -4005,7 +3898,7 @@ fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
                             assoc_type(&mut out, it, &[],
                                        Some(&tydef.type_),
                                        AssocItemLink::GotoSource(t_did, &FxHashSet::default()),
-                                       "")?;
+                                       "");
                             out.push_str(";</span>");
                         }
                     }
@@ -4022,13 +3915,13 @@ fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
         out.push_str("</code></div></div>");
     }
 
-    Ok(out)
+    out.into_inner()
 }
 
-fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocItemLink<'_>,
+fn render_impl(w: &mut Buffer, cx: &Context, i: &Impl, link: AssocItemLink<'_>,
                render_mode: RenderMode, outer_version: Option<&str>, show_def_docs: bool,
                use_absolute: Option<bool>, is_on_foreign_type: bool,
-               show_default_items: bool) -> fmt::Result {
+               show_default_items: bool) {
     if render_mode == RenderMode::Normal {
         let id = cx.derive_id(match i.inner_impl().trait_ {
             Some(ref t) => if is_on_foreign_type {
@@ -4039,45 +3932,45 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
             None => "impl".to_string(),
         });
         if let Some(use_absolute) = use_absolute {
-            write!(w, "<h3 id='{}' class='impl'><code class='in-band'>", id)?;
-            fmt_impl_for_trait_page(&i.inner_impl(), w, use_absolute)?;
+            write!(w, "<h3 id='{}' class='impl'><code class='in-band'>", id);
+            fmt_impl_for_trait_page(&i.inner_impl(), w, use_absolute);
             if show_def_docs {
                 for it in &i.inner_impl().items {
                     if let clean::TypedefItem(ref tydef, _) = it.inner {
-                        write!(w, "<span class=\"where fmt-newline\">  ")?;
+                        write!(w, "<span class=\"where fmt-newline\">  ");
                         assoc_type(w, it, &vec![], Some(&tydef.type_),
                                    AssocItemLink::Anchor(None),
-                                   "")?;
-                        write!(w, ";</span>")?;
+                                   "");
+                        write!(w, ";</span>");
                     }
                 }
             }
-            write!(w, "</code>")?;
+            write!(w, "</code>");
         } else {
             write!(w, "<h3 id='{}' class='impl'><code class='in-band'>{}</code>",
                 id, i.inner_impl()
-            )?;
+            );
         }
-        write!(w, "<a href='#{}' class='anchor'></a>", id)?;
+        write!(w, "<a href='#{}' class='anchor'></a>", id);
         let since = i.impl_item.stability.as_ref().map(|s| &s.since[..]);
-        render_stability_since_raw(w, since, outer_version)?;
-        if let Some(l) = (Item { item: &i.impl_item, cx: cx }).src_href() {
+        render_stability_since_raw(w, since, outer_version);
+        if let Some(l) = cx.src_href(&i.impl_item) {
             write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                   l, "goto source code")?;
+                   l, "goto source code");
         }
-        write!(w, "</h3>")?;
+        write!(w, "</h3>");
         if let Some(ref dox) = cx.shared.maybe_collapsed_doc_value(&i.impl_item) {
             let mut ids = cx.id_map.borrow_mut();
             write!(w, "<div class='docblock'>{}</div>",
                    Markdown(&*dox, &i.impl_item.links(), &mut ids,
-                            cx.codes, cx.edition, &cx.playground).to_string())?;
+                            cx.codes, cx.edition, &cx.playground).to_string());
         }
     }
 
-    fn doc_impl_item(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item,
+    fn doc_impl_item(w: &mut Buffer, cx: &Context, item: &clean::Item,
                      link: AssocItemLink<'_>, render_mode: RenderMode,
                      is_default_item: bool, outer_version: Option<&str>,
-                     trait_: Option<&clean::Trait>, show_def_docs: bool) -> fmt::Result {
+                     trait_: Option<&clean::Trait>, show_def_docs: bool) {
         let item_type = item.type_();
         let name = item.name.as_ref().unwrap();
 
@@ -4101,50 +3994,50 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                 if render_method_item {
                     let id = cx.derive_id(format!("{}.{}", item_type, name));
                     let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                    write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                    write!(w, "{}", spotlight_decl(decl)?)?;
-                    write!(w, "<code id='{}'>", ns_id)?;
-                    render_assoc_item(w, item, link.anchor(&id), ItemType::Impl)?;
-                    write!(w, "</code>")?;
-                    render_stability_since_raw(w, item.stable_since(), outer_version)?;
-                    if let Some(l) = (Item { cx, item }).src_href() {
+                    write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                    write!(w, "{}", spotlight_decl(decl));
+                    write!(w, "<code id='{}'>", ns_id);
+                    render_assoc_item(w, item, link.anchor(&id), ItemType::Impl);
+                    write!(w, "</code>");
+                    render_stability_since_raw(w, item.stable_since(), outer_version);
+                    if let Some(l) = cx.src_href(item) {
                         write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                               l, "goto source code")?;
+                               l, "goto source code");
                     }
-                    write!(w, "</h4>")?;
+                    write!(w, "</h4>");
                 }
             }
             clean::TypedefItem(ref tydef, _) => {
                 let id = cx.derive_id(format!("{}.{}", ItemType::AssocType, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_type(w, item, &Vec::new(), Some(&tydef.type_), link.anchor(&id), "")?;
-                write!(w, "</code></h4>")?;
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_type(w, item, &Vec::new(), Some(&tydef.type_), link.anchor(&id), "");
+                write!(w, "</code></h4>");
             }
             clean::AssocConstItem(ref ty, ref default) => {
                 let id = cx.derive_id(format!("{}.{}", item_type, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "")?;
-                write!(w, "</code>")?;
-                render_stability_since_raw(w, item.stable_since(), outer_version)?;
-                if let Some(l) = (Item { cx, item }).src_href() {
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "");
+                write!(w, "</code>");
+                render_stability_since_raw(w, item.stable_since(), outer_version);
+                if let Some(l) = cx.src_href(item) {
                     write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                            l, "goto source code")?;
+                            l, "goto source code");
                 }
-                write!(w, "</h4>")?;
+                write!(w, "</h4>");
             }
             clean::AssocTypeItem(ref bounds, ref default) => {
                 let id = cx.derive_id(format!("{}.{}", item_type, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_type(w, item, bounds, default.as_ref(), link.anchor(&id), "")?;
-                write!(w, "</code></h4>")?;
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_type(w, item, bounds, default.as_ref(), link.anchor(&id), "");
+                write!(w, "</code></h4>");
             }
-            clean::StrippedItem(..) => return Ok(()),
+            clean::StrippedItem(..) => return,
             _ => panic!("can't make docs for trait item with name {:?}", item.name)
         }
 
@@ -4156,47 +4049,46 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                     if let Some(it) = t.items.iter().find(|i| i.name == item.name) {
                         // We need the stability of the item from the trait
                         // because impls can't have a stability.
-                        document_stability(w, cx, it, is_hidden)?;
+                        document_stability(w, cx, it, is_hidden);
                         if item.doc_value().is_some() {
-                            document_full(w, item, cx, "", is_hidden)?;
+                            document_full(w, item, cx, "", is_hidden);
                         } else if show_def_docs {
                             // In case the item isn't documented,
                             // provide short documentation from the trait.
-                            document_short(w, cx, it, link, "", is_hidden)?;
+                            document_short(w, cx, it, link, "", is_hidden);
                         }
                     }
                 } else {
-                    document_stability(w, cx, item, is_hidden)?;
+                    document_stability(w, cx, item, is_hidden);
                     if show_def_docs {
-                        document_full(w, item, cx, "", is_hidden)?;
+                        document_full(w, item, cx, "", is_hidden);
                     }
                 }
             } else {
-                document_stability(w, cx, item, is_hidden)?;
+                document_stability(w, cx, item, is_hidden);
                 if show_def_docs {
-                    document_short(w, cx, item, link, "", is_hidden)?;
+                    document_short(w, cx, item, link, "", is_hidden);
                 }
             }
         }
-        Ok(())
     }
 
     let traits = &cache().traits;
     let trait_ = i.trait_did().map(|did| &traits[&did]);
 
-    write!(w, "<div class='impl-items'>")?;
+    write!(w, "<div class='impl-items'>");
     for trait_item in &i.inner_impl().items {
         doc_impl_item(w, cx, trait_item, link, render_mode,
-                      false, outer_version, trait_, show_def_docs)?;
+                      false, outer_version, trait_, show_def_docs);
     }
 
-    fn render_default_items(w: &mut fmt::Formatter<'_>,
+    fn render_default_items(w: &mut Buffer,
                             cx: &Context,
                             t: &clean::Trait,
                             i: &clean::Impl,
                             render_mode: RenderMode,
                             outer_version: Option<&str>,
-                            show_def_docs: bool) -> fmt::Result {
+                            show_def_docs: bool) {
         for trait_item in &t.items {
             let n = trait_item.name.clone();
             if i.items.iter().find(|m| m.name == n).is_some() {
@@ -4206,9 +4098,8 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
             let assoc_link = AssocItemLink::GotoSource(did, &i.provided_trait_methods);
 
             doc_impl_item(w, cx, trait_item, assoc_link, render_mode, true,
-                          outer_version, None, show_def_docs)?;
+                          outer_version, None, show_def_docs);
         }
-        Ok(())
     }
 
     // If we've implemented a trait, then also emit documentation for all
@@ -4218,29 +4109,27 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
     if show_default_items {
         if let Some(t) = trait_ {
             render_default_items(w, cx, t, &i.inner_impl(),
-                                render_mode, outer_version, show_def_docs)?;
+                                render_mode, outer_version, show_def_docs);
         }
     }
-    write!(w, "</div>")?;
-
-    Ok(())
+    write!(w, "</div>");
 }
 
 fn item_opaque_ty(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     it: &clean::Item,
     t: &clean::OpaqueTy,
-) -> fmt::Result {
-    write!(w, "<pre class='rust opaque'>")?;
-    render_attributes(w, it, false)?;
+) {
+    write!(w, "<pre class='rust opaque'>");
+    render_attributes(w, it, false);
     write!(w, "type {}{}{where_clause} = impl {bounds};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            where_clause = WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           bounds = bounds(&t.bounds, false))?;
+           bounds = bounds(&t.bounds, false));
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4249,17 +4138,17 @@ fn item_opaque_ty(
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_trait_alias(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                    t: &clean::TraitAlias) -> fmt::Result {
-    write!(w, "<pre class='rust trait-alias'>")?;
-    render_attributes(w, it, false)?;
+fn item_trait_alias(w: &mut Buffer, cx: &Context, it: &clean::Item,
+                    t: &clean::TraitAlias) {
+    write!(w, "<pre class='rust trait-alias'>");
+    render_attributes(w, it, false);
     write!(w, "trait {}{}{} = {};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           bounds(&t.bounds, true))?;
+           bounds(&t.bounds, true));
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4268,17 +4157,16 @@ fn item_trait_alias(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_typedef(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                t: &clean::Typedef) -> fmt::Result {
-    write!(w, "<pre class='rust typedef'>")?;
-    render_attributes(w, it, false)?;
+fn item_typedef(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Typedef) {
+    write!(w, "<pre class='rust typedef'>");
+    render_attributes(w, it, false);
     write!(w, "type {}{}{where_clause} = {type_};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            where_clause = WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           type_ = t.type_)?;
+           type_ = t.type_);
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4287,117 +4175,111 @@ fn item_typedef(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item) -> fmt::Result {
-    writeln!(w, "<pre class='rust foreigntype'>extern {{")?;
-    render_attributes(w, it, false)?;
+fn item_foreign_type(w: &mut Buffer, cx: &Context, it: &clean::Item) {
+    writeln!(w, "<pre class='rust foreigntype'>extern {{");
+    render_attributes(w, it, false);
     write!(
         w,
         "    {}type {};\n}}</pre>",
         VisSpace(&it.visibility),
         it.name.as_ref().unwrap(),
-    )?;
+    );
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-impl<'a> fmt::Display for Sidebar<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let cx = self.cx;
-        let it = self.item;
-        let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
-
-        if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
-            || it.is_enum() || it.is_mod() || it.is_typedef() {
-            write!(fmt, "<p class='location'>{}{}</p>",
-                match it.inner {
-                    clean::StructItem(..) => "Struct ",
-                    clean::TraitItem(..) => "Trait ",
-                    clean::PrimitiveItem(..) => "Primitive Type ",
-                    clean::UnionItem(..) => "Union ",
-                    clean::EnumItem(..) => "Enum ",
-                    clean::TypedefItem(..) => "Type Definition ",
-                    clean::ForeignTypeItem => "Foreign Type ",
-                    clean::ModuleItem(..) => if it.is_crate() {
-                        "Crate "
-                    } else {
-                        "Module "
-                    },
-                    _ => "",
+fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
+    let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
+
+    if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
+        || it.is_enum() || it.is_mod() || it.is_typedef() {
+        write!(buffer, "<p class='location'>{}{}</p>",
+            match it.inner {
+                clean::StructItem(..) => "Struct ",
+                clean::TraitItem(..) => "Trait ",
+                clean::PrimitiveItem(..) => "Primitive Type ",
+                clean::UnionItem(..) => "Union ",
+                clean::EnumItem(..) => "Enum ",
+                clean::TypedefItem(..) => "Type Definition ",
+                clean::ForeignTypeItem => "Foreign Type ",
+                clean::ModuleItem(..) => if it.is_crate() {
+                    "Crate "
+                } else {
+                    "Module "
                 },
-                it.name.as_ref().unwrap())?;
-        }
-
-        if it.is_crate() {
-            if let Some(ref version) = cache().crate_version {
-                write!(fmt,
-                       "<div class='block version'>\
-                        <p>Version {}</p>\
-                        </div>",
-                       version)?;
-            }
-        }
-
-        write!(fmt, "<div class=\"sidebar-elems\">")?;
-        if it.is_crate() {
-            write!(fmt, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
-                   it.name.as_ref().expect("crates always have a name"))?;
-        }
-        match it.inner {
-            clean::StructItem(ref s) => sidebar_struct(fmt, it, s)?,
-            clean::TraitItem(ref t) => sidebar_trait(fmt, it, t)?,
-            clean::PrimitiveItem(ref p) => sidebar_primitive(fmt, it, p)?,
-            clean::UnionItem(ref u) => sidebar_union(fmt, it, u)?,
-            clean::EnumItem(ref e) => sidebar_enum(fmt, it, e)?,
-            clean::TypedefItem(ref t, _) => sidebar_typedef(fmt, it, t)?,
-            clean::ModuleItem(ref m) => sidebar_module(fmt, it, &m.items)?,
-            clean::ForeignTypeItem => sidebar_foreign_type(fmt, it)?,
-            _ => (),
-        }
-
-        // The sidebar is designed to display sibling functions, modules and
-        // other miscellaneous information. since there are lots of sibling
-        // items (and that causes quadratic growth in large modules),
-        // we refactor common parts into a shared JavaScript file per module.
-        // still, we don't move everything into JS because we want to preserve
-        // as much HTML as possible in order to allow non-JS-enabled browsers
-        // to navigate the documentation (though slightly inefficiently).
-
-        write!(fmt, "<p class='location'>")?;
-        for (i, name) in cx.current.iter().take(parentlen).enumerate() {
-            if i > 0 {
-                write!(fmt, "::<wbr>")?;
-            }
-            write!(fmt, "<a href='{}index.html'>{}</a>",
-                   &cx.root_path()[..(cx.current.len() - i - 1) * 3],
-                   *name)?;
-        }
-        write!(fmt, "</p>")?;
-
-        // Sidebar refers to the enclosing module, not this module.
-        let relpath = if it.is_mod() { "../" } else { "" };
-        write!(fmt,
-               "<script>window.sidebarCurrent = {{\
-                   name: '{name}', \
-                   ty: '{ty}', \
-                   relpath: '{path}'\
-                }};</script>",
-               name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
-               ty = it.type_().css_class(),
-               path = relpath)?;
-        if parentlen == 0 {
-            // There is no sidebar-items.js beyond the crate root path
-            // FIXME maybe dynamic crate loading can be merged here
-        } else {
-            write!(fmt, "<script defer src=\"{path}sidebar-items.js\"></script>",
-                   path = relpath)?;
-        }
-        // Closes sidebar-elems div.
-        write!(fmt, "</div>")?;
-
-        Ok(())
+                _ => "",
+            },
+            it.name.as_ref().unwrap());
+    }
+
+    if it.is_crate() {
+        if let Some(ref version) = cache().crate_version {
+            write!(buffer,
+                    "<div class='block version'>\
+                    <p>Version {}</p>\
+                    </div>",
+                    version);
+        }
+    }
+
+    write!(buffer, "<div class=\"sidebar-elems\">");
+    if it.is_crate() {
+        write!(buffer, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
+                it.name.as_ref().expect("crates always have a name"));
+    }
+    match it.inner {
+        clean::StructItem(ref s) => sidebar_struct(buffer, it, s),
+        clean::TraitItem(ref t) => sidebar_trait(buffer, it, t),
+        clean::PrimitiveItem(ref p) => sidebar_primitive(buffer, it, p),
+        clean::UnionItem(ref u) => sidebar_union(buffer, it, u),
+        clean::EnumItem(ref e) => sidebar_enum(buffer, it, e),
+        clean::TypedefItem(ref t, _) => sidebar_typedef(buffer, it, t),
+        clean::ModuleItem(ref m) => sidebar_module(buffer, it, &m.items),
+        clean::ForeignTypeItem => sidebar_foreign_type(buffer, it),
+        _ => (),
+    }
+
+    // The sidebar is designed to display sibling functions, modules and
+    // other miscellaneous information. since there are lots of sibling
+    // items (and that causes quadratic growth in large modules),
+    // we refactor common parts into a shared JavaScript file per module.
+    // still, we don't move everything into JS because we want to preserve
+    // as much HTML as possible in order to allow non-JS-enabled browsers
+    // to navigate the documentation (though slightly inefficiently).
+
+    write!(buffer, "<p class='location'>");
+    for (i, name) in cx.current.iter().take(parentlen).enumerate() {
+        if i > 0 {
+            write!(buffer, "::<wbr>");
+        }
+        write!(buffer, "<a href='{}index.html'>{}</a>",
+                &cx.root_path()[..(cx.current.len() - i - 1) * 3],
+                *name);
+    }
+    write!(buffer, "</p>");
+
+    // Sidebar refers to the enclosing module, not this module.
+    let relpath = if it.is_mod() { "../" } else { "" };
+    write!(buffer,
+            "<script>window.sidebarCurrent = {{\
+                name: '{name}', \
+                ty: '{ty}', \
+                relpath: '{path}'\
+            }};</script>",
+            name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
+            ty = it.type_().css_class(),
+            path = relpath);
+    if parentlen == 0 {
+        // There is no sidebar-items.js beyond the crate root path
+        // FIXME maybe dynamic crate loading can be merged here
+    } else {
+        write!(buffer, "<script defer src=\"{path}sidebar-items.js\"></script>",
+                path = relpath);
     }
+    // Closes sidebar-elems div.
+    write!(buffer, "</div>");
 }
 
 fn get_next_url(used_links: &mut FxHashSet<String>, url: String) -> String {
@@ -4570,8 +4452,7 @@ fn sidebar_assoc_items(it: &clean::Item) -> String {
     out
 }
 
-fn sidebar_struct(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                  s: &clean::Struct) -> fmt::Result {
+fn sidebar_struct(buf: &mut Buffer, it: &clean::Item, s: &clean::Struct) {
     let mut sidebar = String::new();
     let fields = get_struct_fields_name(&s.fields);
 
@@ -4585,9 +4466,8 @@ fn sidebar_struct(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn get_id_for_impl_on_foreign_type(for_: &clean::Type, trait_: &clean::Type) -> String {
@@ -4611,8 +4491,7 @@ fn is_negative_impl(i: &clean::Impl) -> bool {
     i.polarity == Some(clean::ImplPolarity::Negative)
 }
 
-fn sidebar_trait(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                 t: &clean::Trait) -> fmt::Result {
+fn sidebar_trait(buf: &mut Buffer, it: &clean::Item, t: &clean::Trait) {
     let mut sidebar = String::new();
 
     let types = t.items
@@ -4720,27 +4599,23 @@ fn sidebar_trait(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
 
     sidebar.push_str(&sidebar_assoc_items(it));
 
-    write!(fmt, "<div class=\"block items\">{}</div>", sidebar)
+    write!(buf, "<div class=\"block items\">{}</div>", sidebar)
 }
 
-fn sidebar_primitive(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                     _p: &clean::PrimitiveType) -> fmt::Result {
+fn sidebar_primitive(buf: &mut Buffer, it: &clean::Item, _p: &clean::PrimitiveType) {
     let sidebar = sidebar_assoc_items(it);
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_typedef(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                   _t: &clean::Typedef) -> fmt::Result {
+fn sidebar_typedef(buf: &mut Buffer, it: &clean::Item, _t: &clean::Typedef) {
     let sidebar = sidebar_assoc_items(it);
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn get_struct_fields_name(fields: &[clean::Item]) -> String {
@@ -4758,8 +4633,7 @@ fn get_struct_fields_name(fields: &[clean::Item]) -> String {
           .collect()
 }
 
-fn sidebar_union(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                 u: &clean::Union) -> fmt::Result {
+fn sidebar_union(buf: &mut Buffer, it: &clean::Item, u: &clean::Union) {
     let mut sidebar = String::new();
     let fields = get_struct_fields_name(&u.fields);
 
@@ -4771,13 +4645,11 @@ fn sidebar_union(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_enum(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                e: &clean::Enum) -> fmt::Result {
+fn sidebar_enum(buf: &mut Buffer, it: &clean::Item, e: &clean::Enum) {
     let mut sidebar = String::new();
 
     let variants = e.variants.iter()
@@ -4795,9 +4667,8 @@ fn sidebar_enum(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn item_ty_to_strs(ty: &ItemType) -> (&'static str, &'static str) {
@@ -4831,8 +4702,7 @@ fn item_ty_to_strs(ty: &ItemType) -> (&'static str, &'static str) {
     }
 }
 
-fn sidebar_module(fmt: &mut fmt::Formatter<'_>, _it: &clean::Item,
-                  items: &[clean::Item]) -> fmt::Result {
+fn sidebar_module(buf: &mut Buffer, _it: &clean::Item, items: &[clean::Item]) {
     let mut sidebar = String::new();
 
     if items.iter().any(|it| it.type_() == ItemType::ExternCrate ||
@@ -4859,72 +4729,67 @@ fn sidebar_module(fmt: &mut fmt::Formatter<'_>, _it: &clean::Item,
     }
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\"><ul>{}</ul></div>", sidebar)?;
+        write!(buf, "<div class=\"block items\"><ul>{}</ul></div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_foreign_type(fmt: &mut fmt::Formatter<'_>, it: &clean::Item) -> fmt::Result {
+fn sidebar_foreign_type(buf: &mut Buffer, it: &clean::Item) {
     let sidebar = sidebar_assoc_items(it);
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
-fn item_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-              t: &clean::Macro) -> fmt::Result {
+fn item_macro(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Macro) {
     wrap_into_docblock(w, |w| {
         w.write_str(&highlight::render_with_highlighting(&t.source,
                                                          Some("macro"),
                                                          None,
                                                          None))
-    })?;
+    });
     document(w, cx, it)
 }
 
-fn item_proc_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item, m: &clean::ProcMacro)
-    -> fmt::Result
-{
+fn item_proc_macro(w: &mut Buffer, cx: &Context, it: &clean::Item, m: &clean::ProcMacro) {
     let name = it.name.as_ref().expect("proc-macros always have names");
     match m.kind {
         MacroKind::Bang => {
-            write!(w, "<pre class='rust macro'>")?;
-            write!(w, "{}!() {{ /* proc-macro */ }}", name)?;
-            write!(w, "</pre>")?;
+            write!(w, "<pre class='rust macro'>");
+            write!(w, "{}!() {{ /* proc-macro */ }}", name);
+            write!(w, "</pre>");
         }
         MacroKind::Attr => {
-            write!(w, "<pre class='rust attr'>")?;
-            write!(w, "#[{}]", name)?;
-            write!(w, "</pre>")?;
+            write!(w, "<pre class='rust attr'>");
+            write!(w, "#[{}]", name);
+            write!(w, "</pre>");
         }
         MacroKind::Derive => {
-            write!(w, "<pre class='rust derive'>")?;
-            write!(w, "#[derive({})]", name)?;
+            write!(w, "<pre class='rust derive'>");
+            write!(w, "#[derive({})]", name);
             if !m.helpers.is_empty() {
-                writeln!(w, "\n{{")?;
-                writeln!(w, "    // Attributes available to this derive:")?;
+                writeln!(w, "\n{{");
+                writeln!(w, "    // Attributes available to this derive:");
                 for attr in &m.helpers {
-                    writeln!(w, "    #[{}]", attr)?;
+                    writeln!(w, "    #[{}]", attr);
                 }
-                write!(w, "}}")?;
+                write!(w, "}}");
             }
-            write!(w, "</pre>")?;
+            write!(w, "</pre>");
         }
     }
     document(w, cx, it)
 }
 
-fn item_primitive(w: &mut fmt::Formatter<'_>, cx: &Context,
+fn item_primitive(w: &mut Buffer, cx: &Context,
                   it: &clean::Item,
-                  _p: &clean::PrimitiveType) -> fmt::Result {
-    document(w, cx, it)?;
+                  _p: &clean::PrimitiveType) {
+    document(w, cx, it);
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_keyword(w: &mut fmt::Formatter<'_>, cx: &Context,
+fn item_keyword(w: &mut Buffer, cx: &Context,
                 it: &clean::Item,
-                _p: &str) -> fmt::Result {
+                _p: &str) {
     document(w, cx, it)
 }
 
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index c1f1f59d9149a..d840683a7af87 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -4,10 +4,10 @@ use crate::fold::DocFolder;
 use crate::html::layout;
 use crate::html::render::{Error, SharedContext, BASIC_KEYWORDS};
 use crate::html::highlight;
+use crate::html::format::Buffer;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::{Component, Path, PathBuf};
-use std::fmt;
 use syntax::source_map::FileName;
 
 crate fn render(dst: &Path, scx: &mut SharedContext,
@@ -105,7 +105,6 @@ impl<'a> SourceCollector<'a> {
         cur.push(&fname);
         href.push_str(&fname.to_string_lossy());
 
-        let mut v = Vec::new();
         let title = format!("{} -- source", cur.file_name().expect("failed to get file name")
                                                .to_string_lossy());
         let desc = format!("Source to the Rust file `{}`.", filename);
@@ -120,15 +119,10 @@ impl<'a> SourceCollector<'a> {
             extra_scripts: &[&format!("source-files{}", self.scx.resource_suffix)],
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
-        let result = layout::render(&mut v, &self.scx.layout,
-                       &page, &(""), &Source(contents),
-                       self.scx.css_file_extension.is_some(),
-                       &self.scx.themes,
-                       self.scx.generate_search_filter);
-        if let Err(e) = result {
-            return Err(Error::new(e, &cur));
-        }
-        self.scx.fs.write(&cur, &v)?;
+        let v = layout::render(&self.scx.layout,
+                       &page, "", |buf: &mut _| print_src(buf, &contents),
+                       &self.scx.themes);
+        self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);
         Ok(())
     }
@@ -163,25 +157,19 @@ where
 
 /// Wrapper struct to render the source code of a file. This will do things like
 /// adding line numbers to the left-hand side.
-struct Source<'a>(&'a str);
-
-impl<'a> fmt::Display for Source<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let Source(s) = *self;
-        let lines = s.lines().count();
-        let mut cols = 0;
-        let mut tmp = lines;
-        while tmp > 0 {
-            cols += 1;
-            tmp /= 10;
-        }
-        write!(fmt, "<pre class=\"line-numbers\">")?;
-        for i in 1..=lines {
-            write!(fmt, "<span id=\"{0}\">{0:1$}</span>\n", i, cols)?;
-        }
-        write!(fmt, "</pre>")?;
-        write!(fmt, "{}",
-               highlight::render_with_highlighting(s, None, None, None))?;
-        Ok(())
+fn print_src(buf: &mut Buffer, s: &str) {
+    let lines = s.lines().count();
+    let mut cols = 0;
+    let mut tmp = lines;
+    while tmp > 0 {
+        cols += 1;
+        tmp /= 10;
+    }
+    write!(buf, "<pre class=\"line-numbers\">");
+    for i in 1..=lines {
+        write!(buf, "<span id=\"{0}\">{0:1$}</span>\n", i, cols);
     }
+    write!(buf, "</pre>");
+    write!(buf, "{}",
+            highlight::render_with_highlighting(s, None, None, None));
 }
diff --git a/src/librustdoc/html/static/main.js b/src/librustdoc/html/static/main.js
index 309e5575ee403..17a940cc4c9f8 100644
--- a/src/librustdoc/html/static/main.js
+++ b/src/librustdoc/html/static/main.js
@@ -39,6 +39,14 @@ if (!DOMTokenList.prototype.remove) {
     };
 }
 
+function getSearchInput() {
+    return document.getElementsByClassName("search-input")[0];
+}
+
+function getSearchElement() {
+    return document.getElementById("search");
+}
+
 (function() {
     "use strict";
 
@@ -71,7 +79,7 @@ if (!DOMTokenList.prototype.remove) {
                      "derive",
                      "traitalias"];
 
-    var search_input = document.getElementsByClassName("search-input")[0];
+    var search_input = getSearchInput();
 
     // On the search screen, so you remain on the last tab you opened.
     //
@@ -158,7 +166,7 @@ if (!DOMTokenList.prototype.remove) {
         // If we're in mobile mode, we should add the sidebar in any case.
         hideSidebar();
         var elem;
-        var search = document.getElementById("search");
+        var search = getSearchElement();
         var i, from, to, match = window.location.hash.match(/^#?(\d+)(?:-(\d+))?$/);
         if (match) {
             from = parseInt(match[1], 10);
@@ -250,7 +258,12 @@ if (!DOMTokenList.prototype.remove) {
         return String.fromCharCode(c);
     }
 
+    function getHelpElement() {
+        return document.getElementById("help");
+    }
+
     function displayHelp(display, ev, help) {
+        var help = help ? help : getHelpElement();
         if (display === true) {
             if (hasClass(help, "hidden")) {
                 ev.preventDefault();
@@ -264,9 +277,10 @@ if (!DOMTokenList.prototype.remove) {
         }
     }
 
-    function handleEscape(ev, help) {
+    function handleEscape(ev) {
+        var help = getHelpElement();
+        var search = getSearchElement();
         hideModal();
-        var search = document.getElementById("search");
         if (hasClass(help, "hidden") === false) {
             displayHelp(false, ev, help);
         } else if (hasClass(search, "hidden") === false) {
@@ -284,22 +298,21 @@ if (!DOMTokenList.prototype.remove) {
             return;
         }
 
-        var help = document.getElementById("help");
         if (document.activeElement.tagName === "INPUT") {
             switch (getVirtualKey(ev)) {
             case "Escape":
-                handleEscape(ev, help);
+                handleEscape(ev);
                 break;
             }
         } else {
             switch (getVirtualKey(ev)) {
             case "Escape":
-                handleEscape(ev, help);
+                handleEscape(ev);
                 break;
 
             case "s":
             case "S":
-                displayHelp(false, ev, help);
+                displayHelp(false, ev);
                 hideModal();
                 ev.preventDefault();
                 focusSearchBar();
@@ -314,7 +327,7 @@ if (!DOMTokenList.prototype.remove) {
             case "?":
                 if (ev.shiftKey) {
                     hideModal();
-                    displayHelp(true, ev, help);
+                    displayHelp(true, ev);
                 }
                 break;
             }
@@ -547,6 +560,11 @@ if (!DOMTokenList.prototype.remove) {
                 results.sort(function(aaa, bbb) {
                     var a, b;
 
+                    // sort by exact match with regard to the last word (mismatch goes later)
+                    a = (aaa.word !== val);
+                    b = (bbb.word !== val);
+                    if (a !== b) { return a - b; }
+
                     // Sort by non levenshtein results and then levenshtein results by the distance
                     // (less changes required to match means higher rankings)
                     a = (aaa.lev);
@@ -558,11 +576,6 @@ if (!DOMTokenList.prototype.remove) {
                     b = (bbb.item.crate !== window.currentCrate);
                     if (a !== b) { return a - b; }
 
-                    // sort by exact match (mismatch goes later)
-                    a = (aaa.word !== valLower);
-                    b = (bbb.word !== valLower);
-                    if (a !== b) { return a - b; }
-
                     // sort by item name length (longer goes later)
                     a = aaa.word.length;
                     b = bbb.word.length;
@@ -1028,7 +1041,7 @@ if (!DOMTokenList.prototype.remove) {
                         if (lev > MAX_LEV_DISTANCE) {
                             continue;
                         } else if (lev > 0) {
-                            lev_add = 1;
+                            lev_add = lev / 10;
                         }
                     }
 
@@ -1099,10 +1112,6 @@ if (!DOMTokenList.prototype.remove) {
                     if (index !== -1 || lev <= MAX_LEV_DISTANCE) {
                         if (index !== -1 && paths.length < 2) {
                             lev = 0;
-                        } else if (searchWords[j] === val) {
-                            // Small trick to fix when you're looking for a one letter type
-                            // and there are other short named types.
-                            lev = -1;
                         }
                         if (results[fullId] === undefined) {
                             results[fullId] = {
@@ -1285,9 +1294,7 @@ if (!DOMTokenList.prototype.remove) {
                 } else if (e.which === 16) { // shift
                     // Does nothing, it's just to avoid losing "focus" on the highlighted element.
                 } else if (e.which === 27) { // escape
-                    removeClass(actives[currentTab][0], "highlighted");
-                    search_input.value = "";
-                    defocusSearchBar();
+                    handleEscape(e);
                 } else if (actives[currentTab].length > 0) {
                     removeClass(actives[currentTab][0], "highlighted");
                 }
@@ -1438,7 +1445,7 @@ if (!DOMTokenList.prototype.remove) {
                 ret_others[0] + ret_in_args[0] + ret_returned[0] + "</div>";
 
             addClass(main, "hidden");
-            var search = document.getElementById("search");
+            var search = getSearchElement();
             removeClass(search, "hidden");
             search.innerHTML = output;
             var tds = search.getElementsByTagName("td");
@@ -1648,7 +1655,7 @@ if (!DOMTokenList.prototype.remove) {
                     if (hasClass(main, "content")) {
                         removeClass(main, "hidden");
                     }
-                    var search_c = document.getElementById("search");
+                    var search_c = getSearchElement();
                     if (hasClass(search_c, "content")) {
                         addClass(search_c, "hidden");
                     }
@@ -1695,7 +1702,7 @@ if (!DOMTokenList.prototype.remove) {
                         if (hasClass(main, "content")) {
                             removeClass(main, "hidden");
                         }
-                        var search_c = document.getElementById("search");
+                        var search_c = getSearchElement();
                         if (hasClass(search_c, "content")) {
                             addClass(search_c, "hidden");
                         }
@@ -2464,7 +2471,7 @@ if (!DOMTokenList.prototype.remove) {
     var params = getQueryStringParams();
     if (params && params.search) {
         addClass(main, "hidden");
-        var search = document.getElementById("search");
+        var search = getSearchElement();
         removeClass(search, "hidden");
         search.innerHTML = "<h3 style=\"text-align: center;\">Loading search results...</h3>";
     }
@@ -2549,10 +2556,10 @@ if (!DOMTokenList.prototype.remove) {
 
 // Sets the focus on the search bar at the top of the page
 function focusSearchBar() {
-    document.getElementsByClassName("search-input")[0].focus();
+    getSearchInput().focus();
 }
 
 // Removes the focus from the search bar
 function defocusSearchBar() {
-    document.getElementsByClassName("search-input")[0].blur();
+    getSearchInput().blur();
 }
diff --git a/src/librustdoc/html/static/storage.js b/src/librustdoc/html/static/storage.js
index 40a6a156972f6..eae998ca3ecbf 100644
--- a/src/librustdoc/html/static/storage.js
+++ b/src/librustdoc/html/static/storage.js
@@ -119,7 +119,7 @@ function switchTheme(styleElem, mainStyleElem, newTheme, saveTheme) {
 
 function getSystemValue() {
     var property = getComputedStyle(document.documentElement).getPropertyValue('content');
-    return property.replace(/\"\'/g, "");
+    return property.replace(/[\"\']/g, "");
 }
 
 switchTheme(currentTheme, mainTheme,
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 301946733dc55..0b9e717221f2d 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -1,7 +1,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/")]
 
-#![feature(bind_by_move_pattern_guards)]
+#![cfg_attr(bootstrap, feature(bind_by_move_pattern_guards))]
 #![feature(rustc_private)]
 #![feature(arbitrary_self_types)]
 #![feature(box_patterns)]
@@ -90,7 +90,7 @@ pub fn main() {
         32_000_000 // 32MB on other platforms
     };
     rustc_driver::set_sigpipe_handler();
-    env_logger::init();
+    env_logger::init_from_env("RUSTDOC_LOG");
     let res = std::thread::Builder::new().stack_size(thread_stack_size).spawn(move || {
         get_args().map(|args| main_args(&args)).unwrap_or(1)
     }).unwrap().join().unwrap_or(rustc_driver::EXIT_FAILURE);
@@ -356,6 +356,28 @@ fn opts() -> Vec<RustcOptGroup> {
                       "show-coverage",
                       "calculate percentage of public items with documentation")
         }),
+        unstable("enable-per-target-ignores", |o| {
+            o.optflag("",
+                      "enable-per-target-ignores",
+                      "parse ignore-foo for ignoring doctests on a per-target basis")
+        }),
+        unstable("runtool", |o| {
+            o.optopt("",
+                     "runtool",
+                     "",
+                     "The tool to run tests with when building for a different target than host")
+        }),
+        unstable("runtool-arg", |o| {
+            o.optmulti("",
+                       "runtool-arg",
+                       "",
+                       "One (of possibly many) arguments to pass to the runtool")
+        }),
+        unstable("test-builder", |o| {
+            o.optflag("",
+                      "test-builder",
+                      "specified the rustc-like binary to use as the test builder")
+        }),
     ]
 }
 
@@ -451,7 +473,7 @@ where R: 'static + Send,
     // First, parse the crate and extract all relevant information.
     info!("starting to run rustc");
 
-    let result = rustc_driver::report_ices_to_stderr_if_any(move || {
+    let result = rustc_driver::catch_fatal_errors(move || {
         let crate_name = options.crate_name.clone();
         let crate_version = options.crate_version.clone();
         let (mut krate, renderinfo, renderopts) = core::run_core(options);
diff --git a/src/librustdoc/markdown.rs b/src/librustdoc/markdown.rs
index a30fc05f36acd..8431271e62d56 100644
--- a/src/librustdoc/markdown.rs
+++ b/src/librustdoc/markdown.rs
@@ -43,7 +43,7 @@ pub fn render(
     edition: Edition
 ) -> i32 {
     let mut output = options.output;
-    output.push(input.file_stem().unwrap());
+    output.push(input.file_name().unwrap());
     output.set_extension("html");
 
     let mut css = String::new();
@@ -143,11 +143,12 @@ pub fn test(mut options: Options, diag: &errors::Handler) -> i32 {
     opts.no_crate_inject = true;
     opts.display_warnings = options.display_warnings;
     let mut collector = Collector::new(options.input.display().to_string(), options.clone(),
-                                       true, opts, None, Some(options.input));
+                                       true, opts, None, Some(options.input),
+                                       options.enable_per_target_ignores);
     collector.set_position(DUMMY_SP);
     let codes = ErrorCodes::from(UnstableFeatures::from_environment().is_nightly_build());
 
-    find_testable_code(&input_str, &mut collector, codes);
+    find_testable_code(&input_str, &mut collector, codes, options.enable_per_target_ignores);
 
     options.test_args.insert(0, "rustdoctest".to_string());
     testing::test_main(&options.test_args, collector.tests,
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 2951b2ccb2af9..d6073cdc1e11d 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -679,6 +679,7 @@ fn primitive_impl(cx: &DocContext<'_>, path_str: &str) -> Option<DefId> {
         "f32" => tcx.lang_items().f32_impl(),
         "f64" => tcx.lang_items().f64_impl(),
         "str" => tcx.lang_items().str_impl(),
+        "bool" => tcx.lang_items().bool_impl(),
         "char" => tcx.lang_items().char_impl(),
         _ => None,
     }
diff --git a/src/librustdoc/passes/collect_trait_impls.rs b/src/librustdoc/passes/collect_trait_impls.rs
index 86e4e9fd95637..28c64d0b9638e 100644
--- a/src/librustdoc/passes/collect_trait_impls.rs
+++ b/src/librustdoc/passes/collect_trait_impls.rs
@@ -53,6 +53,7 @@ pub fn collect_trait_impls(krate: Crate, cx: &DocContext<'_>) -> Crate {
         lang_items.f64_impl(),
         lang_items.f32_runtime_impl(),
         lang_items.f64_runtime_impl(),
+        lang_items.bool_impl(),
         lang_items.char_impl(),
         lang_items.str_impl(),
         lang_items.slice_impl(),
diff --git a/src/librustdoc/passes/mod.rs b/src/librustdoc/passes/mod.rs
index 49a34c7e46281..14f8b16dc3067 100644
--- a/src/librustdoc/passes/mod.rs
+++ b/src/librustdoc/passes/mod.rs
@@ -336,7 +336,7 @@ pub fn look_for_tests<'tcx>(
         found_tests: 0,
     };
 
-    find_testable_code(&dox, &mut tests, ErrorCodes::No);
+    find_testable_code(&dox, &mut tests, ErrorCodes::No, false);
 
     if check_missing_code == true && tests.found_tests == 0 {
         let sp = span_of_attrs(&item.attrs).unwrap_or(item.source.span());
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 000d2843adce3..482c69c1ab5b5 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -1,5 +1,6 @@
 use rustc_data_structures::sync::Lrc;
 use rustc_interface::interface;
+use rustc_target::spec::TargetTriple;
 use rustc::hir;
 use rustc::hir::intravisit;
 use rustc::session::{self, config, DiagnosticOutput};
@@ -22,7 +23,7 @@ use testing;
 
 use crate::clean::Attributes;
 use crate::config::Options;
-use crate::html::markdown::{self, ErrorCodes, LangString};
+use crate::html::markdown::{self, ErrorCodes, LangString, Ignore};
 
 #[derive(Clone, Default)]
 pub struct TestOptions {
@@ -57,6 +58,7 @@ pub fn run(options: Options) -> i32 {
             ..config::basic_debugging_options()
         },
         edition: options.edition,
+        target_triple: options.target.clone(),
         ..config::Options::default()
     };
 
@@ -82,6 +84,7 @@ pub fn run(options: Options) -> i32 {
 
         let mut opts = scrape_test_config(lower_to_hir.peek().0.borrow().krate());
         opts.display_warnings |= options.display_warnings;
+        let enable_per_target_ignores = options.enable_per_target_ignores;
         let mut collector = Collector::new(
             compiler.crate_name()?.peek().to_string(),
             options,
@@ -89,6 +92,7 @@ pub fn run(options: Options) -> i32 {
             opts,
             Some(compiler.source_map().clone()),
             None,
+            enable_per_target_ignores,
         );
 
         let mut global_ctxt = compiler.global_ctxt()?.take();
@@ -181,6 +185,9 @@ fn run_test(
     should_panic: bool,
     no_run: bool,
     as_test_harness: bool,
+    runtool: Option<String>,
+    runtool_args: Vec<String>,
+    target: TargetTriple,
     compile_fail: bool,
     mut error_codes: Vec<String>,
     opts: &TestOptions,
@@ -241,7 +248,10 @@ fn run_test(
     };
     let output_file = outdir.path().join("rust_out");
 
-    let mut compiler = Command::new(std::env::current_exe().unwrap().with_file_name("rustc"));
+    let rustc_binary = options.test_builder.as_ref().map(|v| &**v).unwrap_or_else(|| {
+        rustc_interface::util::rustc_path().expect("found rustc")
+    });
+    let mut compiler = Command::new(&rustc_binary);
     compiler.arg("--crate-type").arg("bin");
     for cfg in &options.cfgs {
         compiler.arg("--cfg").arg(&cfg);
@@ -270,6 +280,7 @@ fn run_test(
     if no_run {
         compiler.arg("--emit=metadata");
     }
+    compiler.arg("--target").arg(target.to_string());
 
     compiler.arg("-");
     compiler.stdin(Stdio::piped());
@@ -315,7 +326,15 @@ fn run_test(
     }
 
     // Run the code!
-    let mut cmd = Command::new(output_file);
+    let mut cmd;
+
+    if let Some(tool) = runtool {
+        cmd = Command::new(tool);
+        cmd.arg(output_file);
+        cmd.args(runtool_args);
+    } else {
+        cmd = Command::new(output_file);
+    }
 
     match cmd.output() {
         Err(e) => return Err(TestFailure::ExecutionError(e)),
@@ -407,7 +426,7 @@ pub fn make_test(s: &str,
                 Ok(Some(item)) => {
                     if !found_main {
                         if let ast::ItemKind::Fn(..) = item.node {
-                            if item.ident.as_str() == "main" {
+                            if item.ident.name == sym::main {
                                 found_main = true;
                             }
                         }
@@ -603,6 +622,7 @@ pub struct Collector {
 
     options: Options,
     use_headers: bool,
+    enable_per_target_ignores: bool,
     cratename: String,
     opts: TestOptions,
     position: Span,
@@ -612,12 +632,14 @@ pub struct Collector {
 
 impl Collector {
     pub fn new(cratename: String, options: Options, use_headers: bool, opts: TestOptions,
-               source_map: Option<Lrc<SourceMap>>, filename: Option<PathBuf>,) -> Collector {
+               source_map: Option<Lrc<SourceMap>>, filename: Option<PathBuf>,
+               enable_per_target_ignores: bool) -> Collector {
         Collector {
             tests: Vec::new(),
             names: Vec::new(),
             options,
             use_headers,
+            enable_per_target_ignores,
             cratename,
             opts,
             position: DUMMY_SP,
@@ -661,12 +683,22 @@ impl Tester for Collector {
         let opts = self.opts.clone();
         let edition = config.edition.unwrap_or(self.options.edition.clone());
         let options = self.options.clone();
+        let runtool = self.options.runtool.clone();
+        let runtool_args = self.options.runtool_args.clone();
+        let target = self.options.target.clone();
+        let target_str = target.to_string();
 
         debug!("creating test {}: {}", name, test);
         self.tests.push(testing::TestDescAndFn {
             desc: testing::TestDesc {
-                name: testing::DynTestName(name),
-                ignore: config.ignore,
+                name: testing::DynTestName(name.clone()),
+                ignore: match config.ignore {
+                    Ignore::All => true,
+                    Ignore::None => false,
+                    Ignore::Some(ref ignores) => {
+                        ignores.iter().any(|s| target_str.contains(s))
+                    },
+                },
                 // compiler failures are test failures
                 should_panic: testing::ShouldPanic::No,
                 allow_fail: config.allow_fail,
@@ -681,6 +713,9 @@ impl Tester for Collector {
                     config.should_panic,
                     config.no_run,
                     config.test_harness,
+                    runtool,
+                    runtool_args,
+                    target,
                     config.compile_fail,
                     config.error_codes,
                     &opts,
@@ -827,7 +862,10 @@ impl<'a, 'hir> HirCollector<'a, 'hir> {
         // anything else, this will combine them for us.
         if let Some(doc) = attrs.collapsed_doc_value() {
             self.collector.set_position(attrs.span.unwrap_or(DUMMY_SP));
-            markdown::find_testable_code(&doc, self.collector, self.codes);
+            markdown::find_testable_code(&doc,
+                                         self.collector,
+                                         self.codes,
+                                         self.collector.enable_per_target_ignores);
         }
 
         nested(self);
diff --git a/src/libstd/Cargo.toml b/src/libstd/Cargo.toml
index 157faa0af9bca..af1d2402f88e7 100644
--- a/src/libstd/Cargo.toml
+++ b/src/libstd/Cargo.toml
@@ -25,20 +25,14 @@ profiler_builtins = { path = "../libprofiler_builtins", optional = true }
 unwind = { path = "../libunwind" }
 hashbrown = { version = "0.5.0", features = ['rustc-dep-of-std'] }
 
-[dependencies.backtrace]
-version = "0.3.35"
-default-features = false # don't use coresymbolication on OSX
-features = [
-  "rustc-dep-of-std", # enable build support for integrating into libstd
-  "dbghelp",          # backtrace/symbolize on MSVC
-  "libbacktrace",     # symbolize on most platforms
-  "libunwind",        # backtrace on most platforms
-  "dladdr",           # symbolize on platforms w/o libbacktrace
-]
-optional = true
+[dependencies.backtrace_rs]
+package = "backtrace"
+version = "0.3.37"
+default-features = false # without the libstd `backtrace` feature, stub out everything
+features = [ "rustc-dep-of-std" ] # enable build support for integrating into libstd
 
 [dev-dependencies]
-rand = "0.6.1"
+rand = "0.7"
 
 [target.x86_64-apple-darwin.dependencies]
 rustc_asan = { path = "../librustc_asan" }
@@ -56,12 +50,22 @@ dlmalloc = { version = "0.1", features = ['rustc-dep-of-std'] }
 [target.x86_64-fortanix-unknown-sgx.dependencies]
 fortanix-sgx-abi = { version = "0.3.2", features = ['rustc-dep-of-std'] }
 
+[target.wasm32-wasi.dependencies]
+wasi = { version = "0.7.0", features = ['rustc-dep-of-std', 'alloc'] }
+
 [build-dependencies]
 cc = "1.0"
 
 [features]
 default = ["std_detect_file_io", "std_detect_dlsym_getauxval"]
 
+backtrace = [
+  "backtrace_rs/dbghelp",          # backtrace/symbolize on MSVC
+  "backtrace_rs/libbacktrace",     # symbolize on most platforms
+  "backtrace_rs/libunwind",        # backtrace on most platforms
+  "backtrace_rs/dladdr",           # symbolize on platforms w/o libbacktrace
+]
+
 panic-unwind = ["panic_unwind"]
 profiler = ["profiler_builtins"]
 compiler-builtins-c = ["alloc/compiler-builtins-c"]
diff --git a/src/libstd/backtrace.rs b/src/libstd/backtrace.rs
new file mode 100644
index 0000000000000..61c42a56071e6
--- /dev/null
+++ b/src/libstd/backtrace.rs
@@ -0,0 +1,353 @@
+//! Support for capturing a stack backtrace of an OS thread
+//!
+//! This module contains the support necessary to capture a stack backtrace of a
+//! running OS thread from the OS thread itself. The `Backtrace` type supports
+//! capturing a stack trace via the `Backtrace::capture` and
+//! `Backtrace::force_capture` functions.
+//!
+//! A backtrace is typically quite handy to attach to errors (e.g. types
+//! implementing `std::error::Error`) to get a causal chain of where an error
+//! was generated.
+//!
+//! > **Note**: this module is unstable and is designed in [RFC 2504], and you
+//! > can learn more about its status in the [tracking issue].
+//!
+//! [RFC 2504]: https://github.com/rust-lang/rfcs/blob/master/text/2504-fix-error.md
+//! [tracking issue]: https://github.com/rust-lang/rust/issues/53487
+//!
+//! ## Accuracy
+//!
+//! Backtraces are attempted to be as accurate as possible, but no guarantees
+//! are provided about the exact accuracy of a backtrace. Instruction pointers,
+//! symbol names, filenames, line numbers, etc, may all be incorrect when
+//! reported. Accuracy is attempted on a best-effort basis, however, and bugs
+//! are always welcome to indicate areas of improvement!
+//!
+//! For most platforms a backtrace with a filename/line number requires that
+//! programs be compiled with debug information. Without debug information
+//! filenames/line numbers will not be reported.
+//!
+//! ## Platform support
+//!
+//! Not all platforms that libstd compiles for support capturing backtraces.
+//! Some platforms simply do nothing when capturing a backtrace. To check
+//! whether the platform supports capturing backtraces you can consult the
+//! `BacktraceStatus` enum as a result of `Backtrace::status`.
+//!
+//! Like above with accuracy platform support is done on a best effort basis.
+//! Sometimes libraries may not be available at runtime or something may go
+//! wrong which would cause a backtrace to not be captured. Please feel free to
+//! report issues with platforms where a backtrace cannot be captured though!
+//!
+//! ## Environment Variables
+//!
+//! The `Backtrace::capture` function may not actually capture a backtrace by
+//! default. Its behavior is governed by two environment variables:
+//!
+//! * `RUST_LIB_BACKTRACE` - if this is set to `0` then `Backtrace::capture`
+//!   will never capture a backtrace. Any other value this is set to will enable
+//!   `Backtrace::capture`.
+//!
+//! * `RUST_BACKTRACE` - if `RUST_LIB_BACKTRACE` is not set, then this variable
+//!   is consulted with the same rules of `RUST_LIB_BACKTRACE`.
+//!
+//! * If neither of the above env vars are set, then `Backtrace::capture` will
+//!   be disabled.
+//!
+//! Capturing a backtrace can be a quite expensive runtime operation, so the
+//! environment variables allow either forcibly disabling this runtime
+//! performance hit or allow selectively enabling it in some programs.
+//!
+//! Note that the `Backtrace::force_capture` function can be used to ignore
+//! these environment variables. Also note that the state of environment
+//! variables is cached once the first backtrace is created, so altering
+//! `RUST_LIB_BACKTRACE` or `RUST_BACKTRACE` at runtime may not actually change
+//! how backtraces are captured.
+
+#![unstable(feature = "backtrace", issue = "53487")]
+
+// NB: A note on resolution of a backtrace:
+//
+// Backtraces primarily happen in two steps, one is where we actually capture
+// the stack backtrace, giving us a list of instruction pointers corresponding
+// to stack frames. Next we take these instruction pointers and, one-by-one,
+// turn them into a human readable name (like `main`).
+//
+// The first phase can be somewhat expensive (walking the stack), especially
+// on MSVC where debug information is consulted to return inline frames each as
+// their own frame. The second phase, however, is almost always extremely
+// expensive (on the order of milliseconds sometimes) when it's consulting debug
+// information.
+//
+// We attempt to amortize this cost as much as possible by delaying resolution
+// of an address to a human readable name for as long as possible. When
+// `Backtrace::create` is called to capture a backtrace it doesn't actually
+// perform any symbol resolution, but rather we lazily resolve symbols only just
+// before they're needed for printing. This way we can make capturing a
+// backtrace and throwing it away much cheaper, but actually printing a
+// backtrace is still basically the same cost.
+//
+// This strategy comes at the cost of some synchronization required inside of a
+// `Backtrace`, but that's a relatively small price to pay relative to capturing
+// a backtrace or actually symbolizing it.
+
+use crate::env;
+use crate::fmt;
+use crate::sync::atomic::{AtomicUsize, Ordering::SeqCst};
+use crate::sync::Mutex;
+use crate::sys_common::backtrace::{output_filename, lock};
+use crate::vec::Vec;
+use backtrace_rs as backtrace;
+use backtrace::BytesOrWideString;
+
+/// A captured OS thread stack backtrace.
+///
+/// This type represents a stack backtrace for an OS thread captured at a
+/// previous point in time. In some instances the `Backtrace` type may
+/// internally be empty due to configuration. For more information see
+/// `Backtrace::capture`.
+pub struct Backtrace {
+    inner: Inner,
+}
+
+/// The current status of a backtrace, indicating whether it was captured or
+/// whether it is empty for some other reason.
+#[non_exhaustive]
+#[derive(Debug)]
+pub enum BacktraceStatus {
+    /// Capturing a backtrace is not supported, likely because it's not
+    /// implemented for the current platform.
+    Unsupported,
+    /// Capturing a backtrace has been disabled through either the
+    /// `RUST_LIB_BACKTRACE` or `RUST_BACKTRACE` environment variables.
+    Disabled,
+    /// A backtrace has been captured and the `Backtrace` should print
+    /// reasonable information when rendered.
+    Captured,
+}
+
+enum Inner {
+    Unsupported,
+    Disabled,
+    Captured(Mutex<Capture>),
+}
+
+struct Capture {
+    actual_start: usize,
+    resolved: bool,
+    frames: Vec<BacktraceFrame>,
+}
+
+fn _assert_send_sync() {
+    fn _assert<T: Send + Sync>() {}
+    _assert::<Backtrace>();
+}
+
+struct BacktraceFrame {
+    frame: backtrace::Frame,
+    symbols: Vec<BacktraceSymbol>,
+}
+
+struct BacktraceSymbol {
+    name: Option<Vec<u8>>,
+    filename: Option<BytesOrWide>,
+    lineno: Option<u32>,
+}
+
+enum BytesOrWide {
+    Bytes(Vec<u8>),
+    Wide(Vec<u16>),
+}
+
+impl Backtrace {
+    /// Returns whether backtrace captures are enabled through environment
+    /// variables.
+    fn enabled() -> bool {
+        // Cache the result of reading the environment variables to make
+        // backtrace captures speedy, because otherwise reading environment
+        // variables every time can be somewhat slow.
+        static ENABLED: AtomicUsize = AtomicUsize::new(0);
+        match ENABLED.load(SeqCst) {
+            0 => {}
+            1 => return false,
+            _ => return true,
+        }
+        let enabled = match env::var("RUST_LIB_BACKTRACE") {
+            Ok(s) => s != "0",
+            Err(_) => match env::var("RUST_BACKTRACE") {
+                Ok(s) => s != "0",
+                Err(_) => false,
+            },
+        };
+        ENABLED.store(enabled as usize + 1, SeqCst);
+        return enabled;
+    }
+
+    /// Capture a stack backtrace of the current thread.
+    ///
+    /// This function will capture a stack backtrace of the current OS thread of
+    /// execution, returning a `Backtrace` type which can be later used to print
+    /// the entire stack trace or render it to a string.
+    ///
+    /// This function will be a noop if the `RUST_BACKTRACE` or
+    /// `RUST_LIB_BACKTRACE` backtrace variables are both not set. If either
+    /// environment variable is set and enabled then this function will actually
+    /// capture a backtrace. Capturing a backtrace can be both memory intensive
+    /// and slow, so these environment variables allow liberally using
+    /// `Backtrace::capture` and only incurring a slowdown when the environment
+    /// variables are set.
+    ///
+    /// To forcibly capture a backtrace regardless of environment variables, use
+    /// the `Backtrace::force_capture` function.
+    #[inline(never)] // want to make sure there's a frame here to remove
+    pub fn capture() -> Backtrace {
+        if !Backtrace::enabled() {
+            return Backtrace { inner: Inner::Disabled };
+        }
+        Backtrace::create(Backtrace::capture as usize)
+    }
+
+    /// Forcibly captures a full backtrace, regardless of environment variable
+    /// configuration.
+    ///
+    /// This function behaves the same as `capture` except that it ignores the
+    /// values of the `RUST_BACKTRACE` and `RUST_LIB_BACKTRACE` environment
+    /// variables, always capturing a backtrace.
+    ///
+    /// Note that capturing a backtrace can be an expensive operation on some
+    /// platforms, so this should be used with caution in performance-sensitive
+    /// parts of code.
+    #[inline(never)] // want to make sure there's a frame here to remove
+    pub fn force_capture() -> Backtrace {
+        Backtrace::create(Backtrace::force_capture as usize)
+    }
+
+    // Capture a backtrace which start just before the function addressed by
+    // `ip`
+    fn create(ip: usize) -> Backtrace {
+        let _lock = lock();
+        let mut frames = Vec::new();
+        let mut actual_start = None;
+        unsafe {
+            backtrace::trace_unsynchronized(|frame| {
+                frames.push(BacktraceFrame { frame: frame.clone(), symbols: Vec::new() });
+                if frame.symbol_address() as usize == ip && actual_start.is_none() {
+                    actual_start = Some(frames.len());
+                }
+                true
+            });
+        }
+
+        // If no frames came out assume that this is an unsupported platform
+        // since `backtrace` doesn't provide a way of learning this right now,
+        // and this should be a good enough approximation.
+        let inner = if frames.len() == 0 {
+            Inner::Unsupported
+        } else {
+            Inner::Captured(Mutex::new(Capture {
+                actual_start: actual_start.unwrap_or(0),
+                frames,
+                resolved: false,
+            }))
+        };
+
+        Backtrace { inner }
+    }
+
+    /// Returns the status of this backtrace, indicating whether this backtrace
+    /// request was unsupported, disabled, or a stack trace was actually
+    /// captured.
+    pub fn status(&self) -> BacktraceStatus {
+        match self.inner {
+            Inner::Unsupported => BacktraceStatus::Unsupported,
+            Inner::Disabled => BacktraceStatus::Disabled,
+            Inner::Captured(_) => BacktraceStatus::Captured,
+        }
+    }
+}
+
+impl fmt::Display for Backtrace {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(self, fmt)
+    }
+}
+
+impl fmt::Debug for Backtrace {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut capture = match &self.inner {
+            Inner::Unsupported => return fmt.write_str("unsupported backtrace"),
+            Inner::Disabled => return fmt.write_str("disabled backtrace"),
+            Inner::Captured(c) => c.lock().unwrap(),
+        };
+        capture.resolve();
+
+        let full = fmt.alternate();
+        let (frames, style) = if full {
+            (&capture.frames[..], backtrace::PrintFmt::Full)
+        } else {
+            (&capture.frames[capture.actual_start..], backtrace::PrintFmt::Short)
+        };
+
+        // When printing paths we try to strip the cwd if it exists, otherwise
+        // we just print the path as-is. Note that we also only do this for the
+        // short format, because if it's full we presumably want to print
+        // everything.
+        let cwd = crate::env::current_dir();
+        let mut print_path = move |fmt: &mut fmt::Formatter<'_>, path: BytesOrWideString<'_>| {
+            output_filename(fmt, path, style, cwd.as_ref().ok())
+        };
+
+        let mut f = backtrace::BacktraceFmt::new(fmt, style, &mut print_path);
+        f.add_context()?;
+        for frame in frames {
+            let mut f = f.frame();
+            if frame.symbols.is_empty() {
+                f.print_raw(frame.frame.ip(), None, None, None)?;
+            } else {
+                for symbol in frame.symbols.iter() {
+                    f.print_raw(
+                        frame.frame.ip(),
+                        symbol.name.as_ref().map(|b| backtrace::SymbolName::new(b)),
+                        symbol.filename.as_ref().map(|b| match b {
+                            BytesOrWide::Bytes(w) => BytesOrWideString::Bytes(w),
+                            BytesOrWide::Wide(w) => BytesOrWideString::Wide(w),
+                        }),
+                        symbol.lineno,
+                    )?;
+                }
+            }
+        }
+        f.finish()?;
+        Ok(())
+    }
+}
+
+impl Capture {
+    fn resolve(&mut self) {
+        // If we're already resolved, nothing to do!
+        if self.resolved {
+            return;
+        }
+        self.resolved = true;
+
+        // Use the global backtrace lock to synchronize this as it's a
+        // requirement of the `backtrace` crate, and then actually resolve
+        // everything.
+        let _lock = lock();
+        for frame in self.frames.iter_mut() {
+            let symbols = &mut frame.symbols;
+            unsafe {
+                backtrace::resolve_frame_unsynchronized(&frame.frame, |symbol| {
+                    symbols.push(BacktraceSymbol {
+                        name: symbol.name().map(|m| m.as_bytes().to_vec()),
+                        filename: symbol.filename_raw().map(|b| match b {
+                            BytesOrWideString::Bytes(b) => BytesOrWide::Bytes(b.to_owned()),
+                            BytesOrWideString::Wide(b) => BytesOrWide::Wide(b.to_owned()),
+                        }),
+                        lineno: symbol.lineno(),
+                    });
+                });
+            }
+        }
+    }
+}
diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index eca93399e5807..b89893692698c 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -290,7 +290,7 @@ impl Error for VarError {
 ///
 /// Note that while concurrent access to environment variables is safe in Rust,
 /// some platforms only expose inherently unsafe non-threadsafe APIs for
-/// inspecting the environment. As a result extra care needs to be taken when
+/// inspecting the environment. As a result, extra care needs to be taken when
 /// auditing calls to unsafe external FFI functions to ensure that any external
 /// environment accesses are properly synchronized with accesses in Rust.
 ///
diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 117a430eec6b9..4a1bb75d588c9 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -17,6 +17,7 @@ use core::array;
 
 use crate::alloc::{AllocErr, LayoutErr, CannotReallocInPlace};
 use crate::any::TypeId;
+use crate::backtrace::Backtrace;
 use crate::borrow::Cow;
 use crate::cell;
 use crate::char;
@@ -196,14 +197,28 @@ pub trait Error: Debug + Display {
     #[stable(feature = "error_source", since = "1.30.0")]
     fn source(&self) -> Option<&(dyn Error + 'static)> { None }
 
-    /// Gets the `TypeId` of `self`
+    /// Gets the `TypeId` of `self`.
     #[doc(hidden)]
     #[unstable(feature = "error_type_id",
-               reason = "this is memory unsafe to override in user code",
+               reason = "this is memory-unsafe to override in user code",
                issue = "60784")]
     fn type_id(&self, _: private::Internal) -> TypeId where Self: 'static {
         TypeId::of::<Self>()
     }
+
+    /// Returns a stack backtrace, if available, of where this error ocurred.
+    ///
+    /// This function allows inspecting the location, in code, of where an error
+    /// happened. The returned `Backtrace` contains information about the stack
+    /// trace of the OS thread of execution of where the error originated from.
+    ///
+    /// Note that not all errors contain a `Backtrace`. Also note that a
+    /// `Backtrace` may actually be empty. For more information consult the
+    /// `Backtrace` type itself.
+    #[unstable(feature = "backtrace", issue = "53487")]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        None
+    }
 }
 
 mod private {
@@ -601,19 +616,19 @@ impl Error for char::ParseCharError {
     }
 }
 
-// copied from any.rs
+// Copied from `any.rs`.
 impl dyn Error + 'static {
     /// Returns `true` if the boxed type is the same as `T`
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn is<T: Error + 'static>(&self) -> bool {
-        // Get TypeId of the type this function is instantiated with
+        // Get `TypeId` of the type this function is instantiated with.
         let t = TypeId::of::<T>();
 
-        // Get TypeId of the type in the trait object
+        // Get `TypeId` of the type in the trait object.
         let boxed = self.type_id(private::Internal);
 
-        // Compare both TypeIds on equality
+        // Compare both `TypeId`s on equality.
         t == boxed
     }
 
@@ -647,21 +662,21 @@ impl dyn Error + 'static {
 }
 
 impl dyn Error + 'static + Send {
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn is<T: Error + 'static>(&self) -> bool {
         <dyn Error + 'static>::is::<T>(self)
     }
 
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
         <dyn Error + 'static>::downcast_ref::<T>(self)
     }
 
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
@@ -670,21 +685,21 @@ impl dyn Error + 'static + Send {
 }
 
 impl dyn Error + 'static + Send + Sync {
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn is<T: Error + 'static>(&self) -> bool {
         <dyn Error + 'static>::is::<T>(self)
     }
 
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
         <dyn Error + 'static>::downcast_ref::<T>(self)
     }
 
-    /// Forwards to the method defined on the type `Any`.
+    /// Forwards to the method defined on the type `dyn Error`.
     #[stable(feature = "error_downcast", since = "1.3.0")]
     #[inline]
     pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
@@ -695,7 +710,7 @@ impl dyn Error + 'static + Send + Sync {
 impl dyn Error {
     #[inline]
     #[stable(feature = "error_downcast", since = "1.3.0")]
-    /// Attempt to downcast the box to a concrete type.
+    /// Attempts to downcast the box to a concrete type.
     pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> {
         if self.is::<T>() {
             unsafe {
@@ -863,12 +878,12 @@ impl<'a> Iterator for ErrorIter<'a> {
 impl dyn Error + Send {
     #[inline]
     #[stable(feature = "error_downcast", since = "1.3.0")]
-    /// Attempt to downcast the box to a concrete type.
+    /// Attempts to downcast the box to a concrete type.
     pub fn downcast<T: Error + 'static>(self: Box<Self>)
                                         -> Result<Box<T>, Box<dyn Error + Send>> {
         let err: Box<dyn Error> = self;
         <dyn Error>::downcast(err).map_err(|s| unsafe {
-            // reapply the Send marker
+            // Reapply the `Send` marker.
             transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s)
         })
     }
@@ -877,12 +892,12 @@ impl dyn Error + Send {
 impl dyn Error + Send + Sync {
     #[inline]
     #[stable(feature = "error_downcast", since = "1.3.0")]
-    /// Attempt to downcast the box to a concrete type.
+    /// Attempts to downcast the box to a concrete type.
     pub fn downcast<T: Error + 'static>(self: Box<Self>)
                                         -> Result<Box<T>, Box<Self>> {
         let err: Box<dyn Error> = self;
         <dyn Error>::downcast(err).map_err(|s| unsafe {
-            // reapply the Send+Sync marker
+            // Reapply the `Send + Sync` marker.
             transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s)
         })
     }
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 65f4e0cafe09e..d7f4cc5d1fdaa 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -615,7 +615,7 @@ impl CString {
 }
 
 // Turns this `CString` into an empty string to prevent
-// memory unsafe code from working by accident. Inline
+// memory-unsafe code from working by accident. Inline
 // to prevent LLVM from optimizing it away in debug builds.
 #[stable(feature = "cstring_drop", since = "1.13.0")]
 impl Drop for CString {
@@ -935,8 +935,10 @@ impl CStr {
     /// Wraps a raw C string with a safe C string wrapper.
     ///
     /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
-    /// allows inspection and interoperation of non-owned C strings. This method
-    /// is unsafe for a number of reasons:
+    /// allows inspection and interoperation of non-owned C strings. The total
+    /// size of the raw C string must be smaller than `isize::MAX` **bytes**
+    /// in memory due to calling the `slice::from_raw_parts` function.
+    /// This method is unsafe for a number of reasons:
     ///
     /// * There is no guarantee to the validity of `ptr`.
     /// * The returned lifetime is not guaranteed to be the actual lifetime of
diff --git a/src/libstd/fs.rs b/src/libstd/fs.rs
index 5f76875bd66c4..b5265fe369e83 100644
--- a/src/libstd/fs.rs
+++ b/src/libstd/fs.rs
@@ -1956,7 +1956,8 @@ pub fn remove_dir_all<P: AsRef<Path>>(path: P) -> io::Result<()> {
 /// # Platform-specific behavior
 ///
 /// This function currently corresponds to the `opendir` function on Unix
-/// and the `FindFirstFile` function on Windows.
+/// and the `FindFirstFile` function on Windows. Advancing the iterator
+/// currently corresponds to `readdir` on Unix and `FindNextFile` on Windows.
 /// Note that, this [may change in the future][changes].
 ///
 /// [changes]: ../io/index.html#platform-specific-behavior
@@ -2144,7 +2145,7 @@ mod tests {
     use crate::sys_common::io::test::{TempDir, tmpdir};
     use crate::thread;
 
-    use rand::{rngs::StdRng, FromEntropy, RngCore};
+    use rand::{rngs::StdRng, RngCore, SeedableRng};
 
     #[cfg(windows)]
     use crate::os::windows::fs::{symlink_dir, symlink_file};
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 0386dbd490d03..be364a10593da 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -2326,10 +2326,10 @@ impl<R: Read> Iterator for Bytes<R> {
 /// An iterator over the contents of an instance of `BufRead` split on a
 /// particular byte.
 ///
-/// This struct is generally created by calling [`split`][split] on a
-/// `BufRead`. Please see the documentation of `split()` for more details.
+/// This struct is generally created by calling [`split`] on a `BufRead`.
+/// Please see the documentation of [`split`] for more details.
 ///
-/// [split]: trait.BufRead.html#method.split
+/// [`split`]: trait.BufRead.html#method.split
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct Split<B> {
@@ -2358,10 +2358,10 @@ impl<B: BufRead> Iterator for Split<B> {
 
 /// An iterator over the lines of an instance of `BufRead`.
 ///
-/// This struct is generally created by calling [`lines`][lines] on a
-/// `BufRead`. Please see the documentation of `lines()` for more details.
+/// This struct is generally created by calling [`lines`] on a `BufRead`.
+/// Please see the documentation of [`lines`] for more details.
 ///
-/// [lines]: trait.BufRead.html#method.lines
+/// [`lines`]: trait.BufRead.html#method.lines
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct Lines<B> {
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index 990c0eb8955e4..c798ee0e2209a 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -201,9 +201,9 @@ pub struct StdinLock<'a> {
 ///
 /// Each handle returned is a reference to a shared global buffer whose access
 /// is synchronized via a mutex. If you need more explicit control over
-/// locking, see the [`lock() method`][lock].
+/// locking, see the [`Stdin::lock`] method.
 ///
-/// [lock]: struct.Stdin.html#method.lock
+/// [`Stdin::lock`]: struct.Stdin.html#method.lock
 ///
 /// ### Note: Windows Portability Consideration
 /// When operating in a console, the Windows implementation of this stream does not support
@@ -425,9 +425,9 @@ pub struct StdoutLock<'a> {
 ///
 /// Each handle returned is a reference to a shared global buffer whose access
 /// is synchronized via a mutex. If you need more explicit control over
-/// locking, see the [Stdout::lock] method.
+/// locking, see the [`Stdout::lock`] method.
 ///
-/// [Stdout::lock]: struct.Stdout.html#method.lock
+/// [`Stdout::lock`]: struct.Stdout.html#method.lock
 ///
 /// ### Note: Windows Portability Consideration
 /// When operating in a console, the Windows implementation of this stream does not support
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 71050b0dcd1f5..21aeb9c26f83c 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -238,7 +238,7 @@
 #![feature(array_error_internals)]
 #![feature(asm)]
 #![feature(associated_type_bounds)]
-#![feature(bind_by_move_pattern_guards)]
+#![cfg_attr(bootstrap, feature(bind_by_move_pattern_guards))]
 #![feature(box_syntax)]
 #![feature(c_variadic)]
 #![feature(cfg_target_has_atomic)]
@@ -452,6 +452,7 @@ pub mod f64;
 #[macro_use]
 pub mod thread;
 pub mod ascii;
+pub mod backtrace;
 pub mod collections;
 pub mod env;
 pub mod error;
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 952fd9ebfdf07..28fb40244043e 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -17,8 +17,7 @@ use crate::ptr;
 use crate::raw;
 use crate::sys::stdio::panic_output;
 use crate::sys_common::rwlock::RWLock;
-use crate::sys_common::thread_info;
-use crate::sys_common::util;
+use crate::sys_common::{thread_info, util, backtrace};
 use crate::thread;
 
 #[cfg(not(test))]
@@ -157,20 +156,18 @@ pub fn take_hook() -> Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send> {
 }
 
 fn default_hook(info: &PanicInfo<'_>) {
-    #[cfg(feature = "backtrace")]
-    use crate::sys_common::backtrace;
-
     // If this is a double panic, make sure that we print a backtrace
     // for this panic. Otherwise only print it if logging is enabled.
-    #[cfg(feature = "backtrace")]
-    let log_backtrace = {
+    let log_backtrace = if cfg!(feature = "backtrace") {
         let panics = update_panic_count(0);
 
         if panics >= 2 {
-            Some(backtrace::PrintFormat::Full)
+            Some(backtrace_rs::PrintFmt::Full)
         } else {
             backtrace::log_enabled()
         }
+    } else {
+        None
     };
 
     // The current implementation always returns `Some`.
@@ -190,8 +187,7 @@ fn default_hook(info: &PanicInfo<'_>) {
         let _ = writeln!(err, "thread '{}' panicked at '{}', {}",
                          name, msg, location);
 
-        #[cfg(feature = "backtrace")]
-        {
+        if cfg!(feature = "backtrace") {
             use crate::sync::atomic::{AtomicBool, Ordering};
 
             static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
diff --git a/src/libstd/process.rs b/src/libstd/process.rs
index 000f80f99e7a9..c6dc02fea2d84 100644
--- a/src/libstd/process.rs
+++ b/src/libstd/process.rs
@@ -422,7 +422,7 @@ impl fmt::Debug for ChildStderr {
 /// // Execute `ls` in the current directory of the program.
 /// list_dir.status().expect("process failed to execute");
 ///
-/// println!("");
+/// println!();
 ///
 /// // Change `ls` to execute in the root directory.
 /// list_dir.current_dir("/");
@@ -935,7 +935,7 @@ impl Stdio {
     ///     .expect("Failed to spawn child process");
     ///
     /// {
-    ///     let mut stdin = child.stdin.as_mut().expect("Failed to open stdin");
+    ///     let stdin = child.stdin.as_mut().expect("Failed to open stdin");
     ///     stdin.write_all("Hello, world!".as_bytes()).expect("Failed to write to stdin");
     /// }
     ///
@@ -1595,7 +1595,7 @@ pub fn id() -> u32 {
 
 /// A trait for implementing arbitrary return types in the `main` function.
 ///
-/// The c-main function only supports to return integers as return type.
+/// The C-main function only supports to return integers as return type.
 /// So, every type implementing the `Termination` trait has to be converted
 /// to an integer.
 ///
diff --git a/src/libstd/sys/cloudabi/shims/process.rs b/src/libstd/sys/cloudabi/shims/process.rs
index e719b362cbf55..03a59d6d7c832 100644
--- a/src/libstd/sys/cloudabi/shims/process.rs
+++ b/src/libstd/sys/cloudabi/shims/process.rs
@@ -4,14 +4,16 @@ use crate::io;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::{unsupported, Void};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
+
+pub use crate::ffi::OsString as EnvKey;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Command
 ////////////////////////////////////////////////////////////////////////////////
 
 pub struct Command {
-    env: CommandEnv<DefaultEnvKey>,
+    env: CommandEnv,
 }
 
 // passed back to std::process with the pipes connected to the child, if any
@@ -37,7 +39,7 @@ impl Command {
 
     pub fn arg(&mut self, _arg: &OsStr) {}
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
diff --git a/src/libstd/sys/sgx/process.rs b/src/libstd/sys/sgx/process.rs
index a02e009d95356..edf933d10e074 100644
--- a/src/libstd/sys/sgx/process.rs
+++ b/src/libstd/sys/sgx/process.rs
@@ -4,14 +4,16 @@ use crate::io;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::{unsupported, Void};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
+
+pub use crate::ffi::OsString as EnvKey;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Command
 ////////////////////////////////////////////////////////////////////////////////
 
 pub struct Command {
-    env: CommandEnv<DefaultEnvKey>
+    env: CommandEnv,
 }
 
 // passed back to std::process with the pipes connected to the child, if any
@@ -38,7 +40,7 @@ impl Command {
     pub fn arg(&mut self, _arg: &OsStr) {
     }
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
diff --git a/src/libstd/sys/unix/process/mod.rs b/src/libstd/sys/unix/process/mod.rs
index bba4b21c46232..056a20345f404 100644
--- a/src/libstd/sys/unix/process/mod.rs
+++ b/src/libstd/sys/unix/process/mod.rs
@@ -1,5 +1,6 @@
 pub use self::process_common::{Command, ExitStatus, ExitCode, Stdio, StdioPipes};
 pub use self::process_inner::Process;
+pub use crate::ffi::OsString as EnvKey;
 
 mod process_common;
 #[cfg(not(target_os = "fuchsia"))]
diff --git a/src/libstd/sys/unix/process/process_common.rs b/src/libstd/sys/unix/process/process_common.rs
index 21fca23a8fe9e..713d308555956 100644
--- a/src/libstd/sys/unix/process/process_common.rs
+++ b/src/libstd/sys/unix/process/process_common.rs
@@ -1,19 +1,27 @@
 use crate::os::unix::prelude::*;
 
-use crate::ffi::{OsString, OsStr, CString, CStr};
+use crate::ffi::{OsString, OsStr, CString};
 use crate::fmt;
 use crate::io;
 use crate::ptr;
 use crate::sys::fd::FileDesc;
-use crate::sys::fs::{File, OpenOptions};
+use crate::sys::fs::File;
 use crate::sys::pipe::{self, AnonPipe};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
 use crate::collections::BTreeMap;
 
+#[cfg(not(target_os = "fuchsia"))]
+use {
+    crate::ffi::CStr,
+    crate::sys::fs::OpenOptions,
+};
+
 use libc::{c_int, gid_t, uid_t, c_char, EXIT_SUCCESS, EXIT_FAILURE};
 
 cfg_if::cfg_if! {
-    if #[cfg(target_os = "redox")] {
+    if #[cfg(target_os = "fuchsia")] {
+        // fuchsia doesn't have /dev/null
+    } else if #[cfg(target_os = "redox")] {
         const DEV_NULL: &'static str = "null:\0";
     } else {
         const DEV_NULL: &'static str = "/dev/null\0";
@@ -69,7 +77,7 @@ pub struct Command {
     program: CString,
     args: Vec<CString>,
     argv: Argv,
-    env: CommandEnv<DefaultEnvKey>,
+    env: CommandEnv,
 
     cwd: Option<CString>,
     uid: Option<uid_t>,
@@ -107,6 +115,11 @@ pub enum ChildStdio {
     Inherit,
     Explicit(c_int),
     Owned(FileDesc),
+
+    // On Fuchsia, null stdio is the default, so we simply don't specify
+    // any actions at the time of spawning.
+    #[cfg(target_os = "fuchsia")]
+    Null,
 }
 
 pub enum Stdio {
@@ -201,7 +214,7 @@ impl Command {
         self.stderr = Some(stderr);
     }
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
@@ -271,7 +284,7 @@ impl CStringArray {
     }
 }
 
-fn construct_envp(env: BTreeMap<DefaultEnvKey, OsString>, saw_nul: &mut bool) -> CStringArray {
+fn construct_envp(env: BTreeMap<OsString, OsString>, saw_nul: &mut bool) -> CStringArray {
     let mut result = CStringArray::with_capacity(env.len());
     for (k, v) in env {
         let mut k: OsString = k.into();
@@ -325,6 +338,7 @@ impl Stdio {
                 Ok((ChildStdio::Owned(theirs.into_fd()), Some(ours)))
             }
 
+            #[cfg(not(target_os = "fuchsia"))]
             Stdio::Null => {
                 let mut opts = OpenOptions::new();
                 opts.read(readable);
@@ -335,6 +349,11 @@ impl Stdio {
                 let fd = File::open_c(&path, &opts)?;
                 Ok((ChildStdio::Owned(fd.into_fd()), None))
             }
+
+            #[cfg(target_os = "fuchsia")]
+            Stdio::Null => {
+                Ok((ChildStdio::Null, None))
+            }
         }
     }
 }
@@ -357,6 +376,9 @@ impl ChildStdio {
             ChildStdio::Inherit => None,
             ChildStdio::Explicit(fd) => Some(fd),
             ChildStdio::Owned(ref fd) => Some(fd.raw()),
+
+            #[cfg(target_os = "fuchsia")]
+            ChildStdio::Null => None,
         }
     }
 }
diff --git a/src/libstd/sys/unix/process/process_fuchsia.rs b/src/libstd/sys/unix/process/process_fuchsia.rs
index 7c6be9b0a6047..fff9fc6b3bbc8 100644
--- a/src/libstd/sys/unix/process/process_fuchsia.rs
+++ b/src/libstd/sys/unix/process/process_fuchsia.rs
@@ -48,30 +48,51 @@ impl Command {
         use crate::sys::process::zircon::*;
 
         let envp = match maybe_envp {
-            Some(envp) => envp.as_ptr(),
+            // None means to clone the current environment, which is done in the
+            // flags below.
             None => ptr::null(),
+            Some(envp) => envp.as_ptr(),
         };
 
-        let transfer_or_clone = |opt_fd, target_fd| if let Some(local_fd) = opt_fd {
-            fdio_spawn_action_t {
-                action: FDIO_SPAWN_ACTION_TRANSFER_FD,
-                local_fd,
-                target_fd,
-                ..Default::default()
-            }
-        } else {
-            fdio_spawn_action_t {
-                action: FDIO_SPAWN_ACTION_CLONE_FD,
-                local_fd: target_fd,
-                target_fd,
-                ..Default::default()
+        let make_action = |local_io: &ChildStdio, target_fd| -> io::Result<fdio_spawn_action_t> {
+            if let Some(local_fd) = local_io.fd() {
+                Ok(fdio_spawn_action_t {
+                    action: FDIO_SPAWN_ACTION_TRANSFER_FD,
+                    local_fd,
+                    target_fd,
+                    ..Default::default()
+                })
+            } else {
+                if let ChildStdio::Null = local_io {
+                    // acts as no-op
+                    return Ok(Default::default());
+                }
+
+                let mut handle = ZX_HANDLE_INVALID;
+                let status = fdio_fd_clone(target_fd, &mut handle);
+                if status == ERR_INVALID_ARGS || status == ERR_NOT_SUPPORTED {
+                    // This descriptor is closed; skip it rather than generating an
+                    // error.
+                    return Ok(Default::default());
+                }
+                zx_cvt(status)?;
+
+                let mut cloned_fd = 0;
+                zx_cvt(fdio_fd_create(handle, &mut cloned_fd))?;
+
+                Ok(fdio_spawn_action_t {
+                    action: FDIO_SPAWN_ACTION_TRANSFER_FD,
+                    local_fd: cloned_fd as i32,
+                    target_fd,
+                    ..Default::default()
+                })
             }
         };
 
         // Clone stdin, stdout, and stderr
-        let action1 = transfer_or_clone(stdio.stdin.fd(), 0);
-        let action2 = transfer_or_clone(stdio.stdout.fd(), 1);
-        let action3 = transfer_or_clone(stdio.stderr.fd(), 2);
+        let action1 = make_action(&stdio.stdin, 0)?;
+        let action2 = make_action(&stdio.stdout, 1)?;
+        let action3 = make_action(&stdio.stderr, 2)?;
         let actions = [action1, action2, action3];
 
         // We don't want FileDesc::drop to be called on any stdio. fdio_spawn_etc
@@ -84,9 +105,11 @@ impl Command {
 
         let mut process_handle: zx_handle_t = 0;
         zx_cvt(fdio_spawn_etc(
-            0,
-            FDIO_SPAWN_CLONE_JOB | FDIO_SPAWN_CLONE_LDSVC | FDIO_SPAWN_CLONE_NAMESPACE,
-            self.get_argv()[0], self.get_argv().as_ptr(), envp, 3, actions.as_ptr(),
+            ZX_HANDLE_INVALID,
+            FDIO_SPAWN_CLONE_JOB | FDIO_SPAWN_CLONE_LDSVC | FDIO_SPAWN_CLONE_NAMESPACE
+            | FDIO_SPAWN_CLONE_ENVIRON,  // this is ignored when envp is non-null
+            self.get_argv()[0], self.get_argv().as_ptr(), envp,
+            actions.len() as size_t, actions.as_ptr(),
             &mut process_handle,
             ptr::null_mut(),
         ))?;
diff --git a/src/libstd/sys/unix/process/zircon.rs b/src/libstd/sys/unix/process/zircon.rs
index ec715d5490f6f..1ba48de3c0785 100644
--- a/src/libstd/sys/unix/process/zircon.rs
+++ b/src/libstd/sys/unix/process/zircon.rs
@@ -2,8 +2,9 @@
 
 use crate::convert::TryInto;
 use crate::io;
+use crate::i64;
+use crate::mem::MaybeUninit;
 use crate::os::raw::c_char;
-use crate::u64;
 
 use libc::{c_int, c_void, size_t};
 
@@ -14,8 +15,8 @@ pub type zx_status_t = i32;
 
 pub const ZX_HANDLE_INVALID: zx_handle_t = 0;
 
-pub type zx_time_t = u64;
-pub const ZX_TIME_INFINITE : zx_time_t = u64::MAX;
+pub type zx_time_t = i64;
+pub const ZX_TIME_INFINITE : zx_time_t = i64::MAX;
 
 pub type zx_signals_t = u32;
 
@@ -120,8 +121,11 @@ pub struct fdio_spawn_action_t {
 extern {
     pub fn fdio_spawn_etc(job: zx_handle_t, flags: u32, path: *const c_char,
                           argv: *const *const c_char, envp: *const *const c_char,
-                          action_count: u64, actions: *const fdio_spawn_action_t,
+                          action_count: size_t, actions: *const fdio_spawn_action_t,
                           process: *mut zx_handle_t, err_msg: *mut c_char) -> zx_status_t;
+
+    pub fn fdio_fd_clone(fd: c_int, out_handle: *mut zx_handle_t) -> zx_status_t;
+    pub fn fdio_fd_create(handle: zx_handle_t, fd: *mut c_int) -> zx_status_t;
 }
 
 // fdio_spawn_etc flags
diff --git a/src/libstd/sys/unix/time.rs b/src/libstd/sys/unix/time.rs
index 02f377d55c919..fd6796ad22c12 100644
--- a/src/libstd/sys/unix/time.rs
+++ b/src/libstd/sys/unix/time.rs
@@ -311,6 +311,7 @@ mod inner {
         pub fn actually_monotonic() -> bool {
             (cfg!(target_os = "linux") && cfg!(target_arch = "x86_64")) ||
             (cfg!(target_os = "linux") && cfg!(target_arch = "x86")) ||
+            cfg!(target_os = "fuchsia") ||
             false // last clause, used so `||` is always trailing above
         }
 
diff --git a/src/libstd/sys/vxworks/fast_thread_local.rs b/src/libstd/sys/vxworks/fast_thread_local.rs
index 2e021980778e5..8b55939b8e54a 100644
--- a/src/libstd/sys/vxworks/fast_thread_local.rs
+++ b/src/libstd/sys/vxworks/fast_thread_local.rs
@@ -1,5 +1,3 @@
-// Copyright (c) 2019 Wind River Systems, Inc.
-
 #![cfg(target_thread_local)]
 #![unstable(feature = "thread_local_internals", issue = "0")]
 
diff --git a/src/libstd/sys/vxworks/process/mod.rs b/src/libstd/sys/vxworks/process/mod.rs
index 4dc706006f4ce..1fc88fbde742f 100644
--- a/src/libstd/sys/vxworks/process/mod.rs
+++ b/src/libstd/sys/vxworks/process/mod.rs
@@ -1,5 +1,6 @@
 pub use self::process_common::{Command, ExitStatus, ExitCode, Stdio, StdioPipes};
 pub use self::process_inner::Process;
+pub use crate::ffi::OsString as EnvKey;
 
 mod process_common;
 #[path = "process_vxworks.rs"]
diff --git a/src/libstd/sys/vxworks/process/process_common.rs b/src/libstd/sys/vxworks/process/process_common.rs
index ba797354a7380..13648abd1e447 100644
--- a/src/libstd/sys/vxworks/process/process_common.rs
+++ b/src/libstd/sys/vxworks/process/process_common.rs
@@ -7,7 +7,7 @@ use crate::ptr;
 use crate::sys::fd::FileDesc;
 use crate::sys::fs::{File, OpenOptions};
 use crate::sys::pipe::{self, AnonPipe};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
 use crate::collections::BTreeMap;
 
 use libc::{c_int, gid_t, uid_t, c_char, EXIT_SUCCESS, EXIT_FAILURE};
@@ -37,7 +37,7 @@ pub struct Command {
     program: CString,
     args: Vec<CString>,
     argv: Argv,
-    env: CommandEnv<DefaultEnvKey>,
+    env: CommandEnv,
 
     cwd: Option<CString>,
     uid: Option<uid_t>,
@@ -170,7 +170,7 @@ impl Command {
         self.stderr = Some(stderr);
     }
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
@@ -240,7 +240,7 @@ impl CStringArray {
     }
 }
 
-fn construct_envp(env: BTreeMap<DefaultEnvKey, OsString>, saw_nul: &mut bool) -> CStringArray {
+fn construct_envp(env: BTreeMap<OsString, OsString>, saw_nul: &mut bool) -> CStringArray {
     let mut result = CStringArray::with_capacity(env.len());
     for (k, v) in env {
         let mut k: OsString = k.into();
diff --git a/src/libstd/sys/vxworks/process/process_vxworks.rs b/src/libstd/sys/vxworks/process/process_vxworks.rs
index b07966fa20626..8780df17a1c7e 100644
--- a/src/libstd/sys/vxworks/process/process_vxworks.rs
+++ b/src/libstd/sys/vxworks/process/process_vxworks.rs
@@ -5,6 +5,7 @@ use crate::sys;
 use crate::sys::cvt;
 use crate::sys::process::rtp;
 use crate::sys::process::process_common::*;
+use crate::sys_common::thread;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Command
@@ -57,8 +58,7 @@ impl Command {
                 self.get_argv().as_ptr() as *const _, // argv
                 *sys::os::environ() as *const *const c_char,
                 100 as c_int,                         // initial priority
-                0x16000,                                    // initial stack size. 0 defaults
-                                                      // to 0x4000 in 32 bit and 0x8000 in 64 bit
+                thread::min_stack(),                  // initial stack size.
                 0,                                    // options
                 0                                     // task options
             );
diff --git a/src/libstd/sys/vxworks/thread.rs b/src/libstd/sys/vxworks/thread.rs
index ef896f6a6e8cf..e4396b05c0065 100644
--- a/src/libstd/sys/vxworks/thread.rs
+++ b/src/libstd/sys/vxworks/thread.rs
@@ -8,7 +8,7 @@ use crate::time::Duration;
 
 use crate::sys_common::thread::*;
 
-pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
+pub const DEFAULT_MIN_STACK_SIZE: usize = 0x40000; // 256K
 
 pub struct Thread {
     id: libc::pthread_t,
diff --git a/src/libstd/sys/wasi/args.rs b/src/libstd/sys/wasi/args.rs
index 8b4b354d9fc20..3280c4990dc66 100644
--- a/src/libstd/sys/wasi/args.rs
+++ b/src/libstd/sys/wasi/args.rs
@@ -1,11 +1,10 @@
-use crate::ffi::CStr;
-use crate::io;
-use crate::sys::cvt_wasi;
 use crate::ffi::OsString;
 use crate::marker::PhantomData;
 use crate::os::wasi::ffi::OsStringExt;
 use crate::vec;
 
+use ::wasi::wasi_unstable as wasi;
+
 pub unsafe fn init(_argc: isize, _argv: *const *const u8) {
 }
 
@@ -19,31 +18,17 @@ pub struct Args {
 
 /// Returns the command line arguments
 pub fn args() -> Args {
-    maybe_args().unwrap_or_else(|_| {
-        Args {
-            iter: Vec::new().into_iter(),
-            _dont_send_or_sync_me: PhantomData
-        }
-    })
-}
-
-fn maybe_args() -> io::Result<Args> {
-    unsafe {
-        let (mut argc, mut argv_buf_size) = (0, 0);
-        cvt_wasi(libc::__wasi_args_sizes_get(&mut argc, &mut argv_buf_size))?;
-
-        let mut argc = vec![core::ptr::null_mut::<libc::c_char>(); argc];
-        let mut argv_buf = vec![0; argv_buf_size];
-        cvt_wasi(libc::__wasi_args_get(argc.as_mut_ptr(), argv_buf.as_mut_ptr()))?;
-
-        let args = argc.into_iter()
-            .map(|ptr| CStr::from_ptr(ptr).to_bytes().to_vec())
-            .map(|bytes| OsString::from_vec(bytes))
-            .collect::<Vec<_>>();
-        Ok(Args {
-            iter: args.into_iter(),
-            _dont_send_or_sync_me: PhantomData,
-        })
+    let buf = wasi::args_sizes_get().and_then(|args_sizes| {
+        let mut buf = Vec::with_capacity(args_sizes.get_count());
+        wasi::args_get(args_sizes, |arg| {
+            let arg = OsString::from_vec(arg.to_vec());
+            buf.push(arg);
+        })?;
+        Ok(buf)
+    }).unwrap_or(vec![]);
+    Args {
+        iter: buf.into_iter(),
+        _dont_send_or_sync_me: PhantomData
     }
 }
 
diff --git a/src/libstd/sys/wasi/ext/fs.rs b/src/libstd/sys/wasi/ext/fs.rs
index 0ec4122f385da..9fa4abfd171b5 100644
--- a/src/libstd/sys/wasi/ext/fs.rs
+++ b/src/libstd/sys/wasi/ext/fs.rs
@@ -8,6 +8,8 @@ use crate::os::wasi::ffi::OsStrExt;
 use crate::path::{Path, PathBuf};
 use crate::sys_common::{AsInner, AsInnerMut, FromInner};
 
+use ::wasi::wasi_unstable as wasi;
+
 /// WASI-specific extensions to [`File`].
 ///
 /// [`File`]: ../../../../std/fs/struct.File.html
@@ -336,16 +338,16 @@ pub trait FileTypeExt {
 
 impl FileTypeExt for fs::FileType {
     fn is_block_device(&self) -> bool {
-        self.as_inner().bits() == libc::__WASI_FILETYPE_BLOCK_DEVICE
+        self.as_inner().bits() == wasi::FILETYPE_BLOCK_DEVICE
     }
     fn is_character_device(&self) -> bool {
-        self.as_inner().bits() == libc::__WASI_FILETYPE_CHARACTER_DEVICE
+        self.as_inner().bits() == wasi::FILETYPE_CHARACTER_DEVICE
     }
     fn is_socket_dgram(&self) -> bool {
-        self.as_inner().bits() == libc::__WASI_FILETYPE_SOCKET_DGRAM
+        self.as_inner().bits() == wasi::FILETYPE_SOCKET_DGRAM
     }
     fn is_socket_stream(&self) -> bool {
-        self.as_inner().bits() == libc::__WASI_FILETYPE_SOCKET_STREAM
+        self.as_inner().bits() == wasi::FILETYPE_SOCKET_STREAM
     }
 }
 
diff --git a/src/libstd/sys/wasi/ext/io.rs b/src/libstd/sys/wasi/ext/io.rs
index 12afd1d42dc19..f1839df380112 100644
--- a/src/libstd/sys/wasi/ext/io.rs
+++ b/src/libstd/sys/wasi/ext/io.rs
@@ -8,6 +8,8 @@ use crate::sys;
 use crate::net;
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 
+use ::wasi::wasi_unstable as wasi;
+
 /// Raw file descriptors.
 pub type RawFd = u32;
 
@@ -125,18 +127,18 @@ impl IntoRawFd for fs::File {
 
 impl AsRawFd for io::Stdin {
     fn as_raw_fd(&self) -> RawFd {
-        libc::STDIN_FILENO as u32
+        wasi::STDIN_FD
     }
 }
 
 impl AsRawFd for io::Stdout {
     fn as_raw_fd(&self) -> RawFd {
-        libc::STDOUT_FILENO as u32
+        wasi::STDOUT_FD
     }
 }
 
 impl AsRawFd for io::Stderr {
     fn as_raw_fd(&self) -> RawFd {
-        libc::STDERR_FILENO as u32
+        wasi::STDERR_FD
     }
 }
diff --git a/src/libstd/sys/wasi/fd.rs b/src/libstd/sys/wasi/fd.rs
index 25692ec086801..5b7a8678b66ea 100644
--- a/src/libstd/sys/wasi/fd.rs
+++ b/src/libstd/sys/wasi/fd.rs
@@ -3,348 +3,248 @@
 use crate::io::{self, IoSlice, IoSliceMut, SeekFrom};
 use crate::mem;
 use crate::net::Shutdown;
-use crate::sys::cvt_wasi;
-use libc::{self, c_char, c_void};
+use super::err2io;
+use ::wasi::wasi_unstable as wasi;
 
 #[derive(Debug)]
 pub struct WasiFd {
-    fd: libc::__wasi_fd_t,
+    fd: wasi::Fd,
 }
 
-// FIXME: these should probably all be fancier structs, builders, enums, etc
-pub type LookupFlags = u32;
-pub type FdFlags = u16;
-pub type Advice = u8;
-pub type Rights = u64;
-pub type Oflags = u16;
-pub type DirCookie = u64;
-pub type Timestamp = u64;
-pub type FstFlags = u16;
-pub type RiFlags = u16;
-pub type RoFlags = u16;
-pub type SiFlags = u16;
-
-fn iovec(a: &mut [IoSliceMut<'_>]) -> (*const libc::__wasi_iovec_t, usize) {
+fn iovec<'a>(a: &'a mut [IoSliceMut<'_>]) -> &'a [wasi::IoVec] {
     assert_eq!(
         mem::size_of::<IoSliceMut<'_>>(),
-        mem::size_of::<libc::__wasi_iovec_t>()
+        mem::size_of::<wasi::IoVec>()
     );
     assert_eq!(
         mem::align_of::<IoSliceMut<'_>>(),
-        mem::align_of::<libc::__wasi_iovec_t>()
+        mem::align_of::<wasi::IoVec>()
     );
-    (a.as_ptr() as *const libc::__wasi_iovec_t, a.len())
+    /// SAFETY: `IoSliceMut` and `IoVec` have exactly the same memory layout
+    unsafe { mem::transmute(a) }
 }
 
-fn ciovec(a: &[IoSlice<'_>]) -> (*const libc::__wasi_ciovec_t, usize) {
+fn ciovec<'a>(a: &'a [IoSlice<'_>]) -> &'a [wasi::CIoVec] {
     assert_eq!(
         mem::size_of::<IoSlice<'_>>(),
-        mem::size_of::<libc::__wasi_ciovec_t>()
+        mem::size_of::<wasi::CIoVec>()
     );
     assert_eq!(
         mem::align_of::<IoSlice<'_>>(),
-        mem::align_of::<libc::__wasi_ciovec_t>()
+        mem::align_of::<wasi::CIoVec>()
     );
-    (a.as_ptr() as *const libc::__wasi_ciovec_t, a.len())
+    /// SAFETY: `IoSlice` and `CIoVec` have exactly the same memory layout
+    unsafe { mem::transmute(a) }
 }
 
 impl WasiFd {
-    pub unsafe fn from_raw(fd: libc::__wasi_fd_t) -> WasiFd {
+    pub unsafe fn from_raw(fd: wasi::Fd) -> WasiFd {
         WasiFd { fd }
     }
 
-    pub fn into_raw(self) -> libc::__wasi_fd_t {
+    pub fn into_raw(self) -> wasi::Fd {
         let ret = self.fd;
         mem::forget(self);
         ret
     }
 
-    pub fn as_raw(&self) -> libc::__wasi_fd_t {
+    pub fn as_raw(&self) -> wasi::Fd {
         self.fd
     }
 
     pub fn datasync(&self) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_datasync(self.fd) })
+        unsafe { wasi::fd_datasync(self.fd).map_err(err2io) }
     }
 
     pub fn pread(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
-        let mut read = 0;
-        let (ptr, len) = iovec(bufs);
-        cvt_wasi(unsafe { libc::__wasi_fd_pread(self.fd, ptr, len, offset, &mut read) })?;
-        Ok(read)
+        unsafe { wasi::fd_pread(self.fd, iovec(bufs), offset).map_err(err2io) }
     }
 
     pub fn pwrite(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
-        let mut read = 0;
-        let (ptr, len) = ciovec(bufs);
-        cvt_wasi(unsafe { libc::__wasi_fd_pwrite(self.fd, ptr, len, offset, &mut read) })?;
-        Ok(read)
+        unsafe { wasi::fd_pwrite(self.fd, ciovec(bufs), offset).map_err(err2io) }
     }
 
     pub fn read(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-        let mut read = 0;
-        let (ptr, len) = iovec(bufs);
-        cvt_wasi(unsafe { libc::__wasi_fd_read(self.fd, ptr, len, &mut read) })?;
-        Ok(read)
+        unsafe { wasi::fd_read(self.fd, iovec(bufs)).map_err(err2io) }
     }
 
     pub fn write(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
-        let mut read = 0;
-        let (ptr, len) = ciovec(bufs);
-        cvt_wasi(unsafe { libc::__wasi_fd_write(self.fd, ptr, len, &mut read) })?;
-        Ok(read)
+        unsafe { wasi::fd_write(self.fd, ciovec(bufs)).map_err(err2io) }
     }
 
     pub fn seek(&self, pos: SeekFrom) -> io::Result<u64> {
         let (whence, offset) = match pos {
-            SeekFrom::Start(pos) => (libc::__WASI_WHENCE_SET, pos as i64),
-            SeekFrom::End(pos) => (libc::__WASI_WHENCE_END, pos),
-            SeekFrom::Current(pos) => (libc::__WASI_WHENCE_CUR, pos),
+            SeekFrom::Start(pos) => (wasi::WHENCE_SET, pos as i64),
+            SeekFrom::End(pos) => (wasi::WHENCE_END, pos),
+            SeekFrom::Current(pos) => (wasi::WHENCE_CUR, pos),
         };
-        let mut pos = 0;
-        cvt_wasi(unsafe { libc::__wasi_fd_seek(self.fd, offset, whence, &mut pos) })?;
-        Ok(pos)
+        unsafe { wasi::fd_seek(self.fd, offset, whence).map_err(err2io) }
     }
 
     pub fn tell(&self) -> io::Result<u64> {
-        let mut pos = 0;
-        cvt_wasi(unsafe { libc::__wasi_fd_tell(self.fd, &mut pos) })?;
-        Ok(pos)
+        unsafe { wasi::fd_tell(self.fd).map_err(err2io) }
     }
 
     // FIXME: __wasi_fd_fdstat_get
 
-    pub fn set_flags(&self, flags: FdFlags) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_fdstat_set_flags(self.fd, flags) })
+    pub fn set_flags(&self, flags: wasi::FdFlags) -> io::Result<()> {
+        unsafe { wasi::fd_fdstat_set_flags(self.fd, flags).map_err(err2io) }
     }
 
-    pub fn set_rights(&self, base: Rights, inheriting: Rights) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_fdstat_set_rights(self.fd, base, inheriting) })
+    pub fn set_rights(&self, base: wasi::Rights, inheriting: wasi::Rights) -> io::Result<()> {
+        unsafe { wasi::fd_fdstat_set_rights(self.fd, base, inheriting).map_err(err2io) }
     }
 
     pub fn sync(&self) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_sync(self.fd) })
+        unsafe { wasi::fd_sync(self.fd).map_err(err2io) }
     }
 
-    pub fn advise(&self, offset: u64, len: u64, advice: Advice) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_advise(self.fd, offset, len, advice as u8) })
+    pub fn advise(&self, offset: u64, len: u64, advice: wasi::Advice) -> io::Result<()> {
+        unsafe { wasi::fd_advise(self.fd, offset, len, advice).map_err(err2io) }
     }
 
     pub fn allocate(&self, offset: u64, len: u64) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_allocate(self.fd, offset, len) })
+        unsafe { wasi::fd_allocate(self.fd, offset, len).map_err(err2io) }
     }
 
     pub fn create_directory(&self, path: &[u8]) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_create_directory(self.fd, path.as_ptr() as *const c_char, path.len())
-        })
+        unsafe { wasi::path_create_directory(self.fd, path).map_err(err2io) }
     }
 
     pub fn link(
         &self,
-        old_flags: LookupFlags,
+        old_flags: wasi::LookupFlags,
         old_path: &[u8],
         new_fd: &WasiFd,
         new_path: &[u8],
     ) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_link(
-                self.fd,
-                old_flags,
-                old_path.as_ptr() as *const c_char,
-                old_path.len(),
-                new_fd.fd,
-                new_path.as_ptr() as *const c_char,
-                new_path.len(),
-            )
-        })
+        unsafe {
+            wasi::path_link(self.fd, old_flags, old_path, new_fd.fd, new_path)
+                .map_err(err2io)
+        }
     }
 
     pub fn open(
         &self,
-        dirflags: LookupFlags,
+        dirflags: wasi::LookupFlags,
         path: &[u8],
-        oflags: Oflags,
-        fs_rights_base: Rights,
-        fs_rights_inheriting: Rights,
-        fs_flags: FdFlags,
+        oflags: wasi::OFlags,
+        fs_rights_base: wasi::Rights,
+        fs_rights_inheriting: wasi::Rights,
+        fs_flags: wasi::FdFlags,
     ) -> io::Result<WasiFd> {
         unsafe {
-            let mut fd = 0;
-            cvt_wasi(libc::__wasi_path_open(
+            wasi::path_open(
                 self.fd,
                 dirflags,
-                path.as_ptr() as *const c_char,
-                path.len(),
+                path,
                 oflags,
                 fs_rights_base,
                 fs_rights_inheriting,
                 fs_flags,
-                &mut fd,
-            ))?;
-            Ok(WasiFd::from_raw(fd))
+            ).map(|fd| WasiFd::from_raw(fd)).map_err(err2io)
         }
     }
 
-    pub fn readdir(&self, buf: &mut [u8], cookie: DirCookie) -> io::Result<usize> {
-        let mut used = 0;
-        cvt_wasi(unsafe {
-            libc::__wasi_fd_readdir(
-                self.fd,
-                buf.as_mut_ptr() as *mut c_void,
-                buf.len(),
-                cookie,
-                &mut used,
-            )
-        })?;
-        Ok(used)
+    pub fn readdir(&self, buf: &mut [u8], cookie: wasi::DirCookie) -> io::Result<usize> {
+        unsafe { wasi::fd_readdir(self.fd, buf, cookie).map_err(err2io) }
     }
 
     pub fn readlink(&self, path: &[u8], buf: &mut [u8]) -> io::Result<usize> {
-        let mut used = 0;
-        cvt_wasi(unsafe {
-            libc::__wasi_path_readlink(
-                self.fd,
-                path.as_ptr() as *const c_char,
-                path.len(),
-                buf.as_mut_ptr() as *mut c_char,
-                buf.len(),
-                &mut used,
-            )
-        })?;
-        Ok(used)
+        unsafe { wasi::path_readlink(self.fd, path, buf).map_err(err2io) }
     }
 
     pub fn rename(&self, old_path: &[u8], new_fd: &WasiFd, new_path: &[u8]) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_rename(
-                self.fd,
-                old_path.as_ptr() as *const c_char,
-                old_path.len(),
-                new_fd.fd,
-                new_path.as_ptr() as *const c_char,
-                new_path.len(),
-            )
-        })
+        unsafe {
+            wasi::path_rename(self.fd, old_path, new_fd.fd, new_path).map_err(err2io)
+        }
     }
 
-    pub fn filestat_get(&self, buf: *mut libc::__wasi_filestat_t) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_filestat_get(self.fd, buf) })
+    pub fn filestat_get(&self) -> io::Result<wasi::FileStat> {
+        unsafe { wasi::fd_filestat_get(self.fd).map_err(err2io) }
     }
 
     pub fn filestat_set_times(
         &self,
-        atim: Timestamp,
-        mtim: Timestamp,
-        fstflags: FstFlags,
+        atim: wasi::Timestamp,
+        mtim: wasi::Timestamp,
+        fstflags: wasi::FstFlags,
     ) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_filestat_set_times(self.fd, atim, mtim, fstflags) })
+        unsafe {
+            wasi::fd_filestat_set_times(self.fd, atim, mtim, fstflags).map_err(err2io)
+        }
     }
 
     pub fn filestat_set_size(&self, size: u64) -> io::Result<()> {
-        cvt_wasi(unsafe { libc::__wasi_fd_filestat_set_size(self.fd, size) })
+        unsafe { wasi::fd_filestat_set_size(self.fd, size).map_err(err2io) }
     }
 
     pub fn path_filestat_get(
         &self,
-        flags: LookupFlags,
+        flags: wasi::LookupFlags,
         path: &[u8],
-        buf: *mut libc::__wasi_filestat_t,
-    ) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_filestat_get(
-                self.fd,
-                flags,
-                path.as_ptr() as *const c_char,
-                path.len(),
-                buf,
-            )
-        })
+    ) -> io::Result<wasi::FileStat> {
+        unsafe { wasi::path_filestat_get(self.fd, flags, path).map_err(err2io) }
     }
 
     pub fn path_filestat_set_times(
         &self,
-        flags: LookupFlags,
+        flags: wasi::LookupFlags,
         path: &[u8],
-        atim: Timestamp,
-        mtim: Timestamp,
-        fstflags: FstFlags,
+        atim: wasi::Timestamp,
+        mtim: wasi::Timestamp,
+        fstflags: wasi::FstFlags,
     ) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_filestat_set_times(
+        unsafe {
+            wasi::path_filestat_set_times(
                 self.fd,
                 flags,
-                path.as_ptr() as *const c_char,
-                path.len(),
+                path,
                 atim,
                 mtim,
                 fstflags,
-            )
-        })
+            ).map_err(err2io)
+        }
     }
 
     pub fn symlink(&self, old_path: &[u8], new_path: &[u8]) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_symlink(
-                old_path.as_ptr() as *const c_char,
-                old_path.len(),
-                self.fd,
-                new_path.as_ptr() as *const c_char,
-                new_path.len(),
-            )
-        })
+        unsafe { wasi::path_symlink(old_path, self.fd, new_path).map_err(err2io) }
     }
 
     pub fn unlink_file(&self, path: &[u8]) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_unlink_file(self.fd, path.as_ptr() as *const c_char, path.len())
-        })
+        unsafe { wasi::path_unlink_file(self.fd, path).map_err(err2io) }
     }
 
     pub fn remove_directory(&self, path: &[u8]) -> io::Result<()> {
-        cvt_wasi(unsafe {
-            libc::__wasi_path_remove_directory(self.fd, path.as_ptr() as *const c_char, path.len())
-        })
+        unsafe { wasi::path_remove_directory(self.fd, path).map_err(err2io) }
     }
 
     pub fn sock_recv(
         &self,
         ri_data: &mut [IoSliceMut<'_>],
-        ri_flags: RiFlags,
-    ) -> io::Result<(usize, RoFlags)> {
-        let mut ro_datalen = 0;
-        let mut ro_flags = 0;
-        let (ptr, len) = iovec(ri_data);
-        cvt_wasi(unsafe {
-            libc::__wasi_sock_recv(self.fd, ptr, len, ri_flags, &mut ro_datalen, &mut ro_flags)
-        })?;
-        Ok((ro_datalen, ro_flags))
+        ri_flags: wasi::RiFlags,
+    ) -> io::Result<(usize, wasi::RoFlags)> {
+        unsafe { wasi::sock_recv(self.fd, iovec(ri_data), ri_flags).map_err(err2io) }
     }
 
-    pub fn sock_send(&self, si_data: &[IoSlice<'_>], si_flags: SiFlags) -> io::Result<usize> {
-        let mut so_datalen = 0;
-        let (ptr, len) = ciovec(si_data);
-        cvt_wasi(unsafe { libc::__wasi_sock_send(self.fd, ptr, len, si_flags, &mut so_datalen) })?;
-        Ok(so_datalen)
+    pub fn sock_send(&self, si_data: &[IoSlice<'_>], si_flags: wasi::SiFlags) -> io::Result<usize> {
+        unsafe { wasi::sock_send(self.fd, ciovec(si_data), si_flags).map_err(err2io) }
     }
 
     pub fn sock_shutdown(&self, how: Shutdown) -> io::Result<()> {
         let how = match how {
-            Shutdown::Read => libc::__WASI_SHUT_RD,
-            Shutdown::Write => libc::__WASI_SHUT_WR,
-            Shutdown::Both => libc::__WASI_SHUT_WR | libc::__WASI_SHUT_RD,
+            Shutdown::Read => wasi::SHUT_RD,
+            Shutdown::Write => wasi::SHUT_WR,
+            Shutdown::Both => wasi::SHUT_WR | wasi::SHUT_RD,
         };
-        cvt_wasi(unsafe { libc::__wasi_sock_shutdown(self.fd, how) })?;
-        Ok(())
+        unsafe { wasi::sock_shutdown(self.fd, how).map_err(err2io) }
     }
 }
 
 impl Drop for WasiFd {
     fn drop(&mut self) {
-        unsafe {
-            // FIXME: can we handle the return code here even though we can't on
-            // unix?
-            libc::__wasi_fd_close(self.fd);
-        }
+        // FIXME: can we handle the return code here even though we can't on
+        // unix?
+        let _ = unsafe { wasi::fd_close(self.fd) };
     }
 }
diff --git a/src/libstd/sys/wasi/fs.rs b/src/libstd/sys/wasi/fs.rs
index 172c60385b317..4113f6a2e09c0 100644
--- a/src/libstd/sys/wasi/fs.rs
+++ b/src/libstd/sys/wasi/fs.rs
@@ -7,7 +7,7 @@ use crate::os::wasi::ffi::{OsStrExt, OsStringExt};
 use crate::path::{Path, PathBuf};
 use crate::ptr;
 use crate::sync::Arc;
-use crate::sys::fd::{DirCookie, WasiFd};
+use crate::sys::fd::WasiFd;
 use crate::sys::time::SystemTime;
 use crate::sys::unsupported;
 use crate::sys_common::FromInner;
@@ -15,18 +15,20 @@ use crate::sys_common::FromInner;
 pub use crate::sys_common::fs::copy;
 pub use crate::sys_common::fs::remove_dir_all;
 
+use ::wasi::wasi_unstable as wasi;
+
 pub struct File {
     fd: WasiFd,
 }
 
 #[derive(Clone)]
 pub struct FileAttr {
-    meta: libc::__wasi_filestat_t,
+    meta: wasi::FileStat,
 }
 
 pub struct ReadDir {
     inner: Arc<ReadDirInner>,
-    cookie: Option<DirCookie>,
+    cookie: Option<wasi::DirCookie>,
     buf: Vec<u8>,
     offset: usize,
     cap: usize,
@@ -38,7 +40,7 @@ struct ReadDirInner {
 }
 
 pub struct DirEntry {
-    meta: libc::__wasi_dirent_t,
+    meta: wasi::Dirent,
     name: Vec<u8>,
     inner: Arc<ReadDirInner>,
 }
@@ -47,11 +49,11 @@ pub struct DirEntry {
 pub struct OpenOptions {
     read: bool,
     write: bool,
-    dirflags: libc::__wasi_lookupflags_t,
-    fdflags: libc::__wasi_fdflags_t,
-    oflags: libc::__wasi_oflags_t,
-    rights_base: Option<libc::__wasi_rights_t>,
-    rights_inheriting: Option<libc::__wasi_rights_t>,
+    dirflags: wasi::LookupFlags,
+    fdflags: wasi::FdFlags,
+    oflags: wasi::OFlags,
+    rights_base: Option<wasi::Rights>,
+    rights_inheriting: Option<wasi::Rights>,
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -61,19 +63,13 @@ pub struct FilePermissions {
 
 #[derive(PartialEq, Eq, Hash, Debug, Copy, Clone)]
 pub struct FileType {
-    bits: libc::__wasi_filetype_t,
+    bits: wasi::FileType,
 }
 
 #[derive(Debug)]
 pub struct DirBuilder {}
 
 impl FileAttr {
-    fn zero() -> FileAttr {
-        FileAttr {
-            meta: unsafe { mem::zeroed() },
-        }
-    }
-
     pub fn size(&self) -> u64 {
         self.meta.st_size
     }
@@ -101,7 +97,7 @@ impl FileAttr {
         Ok(SystemTime::from_wasi_timestamp(self.meta.st_ctim))
     }
 
-    pub fn as_wasi(&self) -> &libc::__wasi_filestat_t {
+    pub fn as_wasi(&self) -> &wasi::FileStat {
         &self.meta
     }
 }
@@ -118,18 +114,18 @@ impl FilePermissions {
 
 impl FileType {
     pub fn is_dir(&self) -> bool {
-        self.bits == libc::__WASI_FILETYPE_DIRECTORY
+        self.bits == wasi::FILETYPE_DIRECTORY
     }
 
     pub fn is_file(&self) -> bool {
-        self.bits == libc::__WASI_FILETYPE_REGULAR_FILE
+        self.bits == wasi::FILETYPE_REGULAR_FILE
     }
 
     pub fn is_symlink(&self) -> bool {
-        self.bits == libc::__WASI_FILETYPE_SYMBOLIC_LINK
+        self.bits == wasi::FILETYPE_SYMBOLIC_LINK
     }
 
-    pub fn bits(&self) -> libc::__wasi_filetype_t {
+    pub fn bits(&self) -> wasi::FileType {
         self.bits
     }
 }
@@ -173,7 +169,7 @@ impl Iterator for ReadDir {
             // must have been truncated at the end of the buffer, so reset our
             // offset so we can go back and reread into the buffer, picking up
             // where we last left off.
-            let dirent_size = mem::size_of::<libc::__wasi_dirent_t>();
+            let dirent_size = mem::size_of::<wasi::Dirent>();
             if data.len() < dirent_size {
                 assert!(self.cookie.is_some());
                 assert!(self.buf.len() >= dirent_size);
@@ -182,7 +178,7 @@ impl Iterator for ReadDir {
             }
             let (dirent, data) = data.split_at(dirent_size);
             let dirent =
-                unsafe { ptr::read_unaligned(dirent.as_ptr() as *const libc::__wasi_dirent_t) };
+                unsafe { ptr::read_unaligned(dirent.as_ptr() as *const wasi::Dirent) };
 
             // If the file name was truncated, then we need to reinvoke
             // `readdir` so we truncate our buffer to start over and reread this
@@ -241,7 +237,7 @@ impl DirEntry {
         })
     }
 
-    pub fn ino(&self) -> libc::__wasi_inode_t {
+    pub fn ino(&self) -> wasi::Inode {
         self.meta.d_ino
     }
 }
@@ -249,7 +245,7 @@ impl DirEntry {
 impl OpenOptions {
     pub fn new() -> OpenOptions {
         let mut base = OpenOptions::default();
-        base.dirflags = libc::__WASI_LOOKUP_SYMLINK_FOLLOW;
+        base.dirflags = wasi::LOOKUP_SYMLINK_FOLLOW;
         return base;
     }
 
@@ -262,23 +258,23 @@ impl OpenOptions {
     }
 
     pub fn truncate(&mut self, truncate: bool) {
-        self.oflag(libc::__WASI_O_TRUNC, truncate);
+        self.oflag(wasi::O_TRUNC, truncate);
     }
 
     pub fn create(&mut self, create: bool) {
-        self.oflag(libc::__WASI_O_CREAT, create);
+        self.oflag(wasi::O_CREAT, create);
     }
 
     pub fn create_new(&mut self, create_new: bool) {
-        self.oflag(libc::__WASI_O_EXCL, create_new);
-        self.oflag(libc::__WASI_O_CREAT, create_new);
+        self.oflag(wasi::O_EXCL, create_new);
+        self.oflag(wasi::O_CREAT, create_new);
     }
 
     pub fn directory(&mut self, directory: bool) {
-        self.oflag(libc::__WASI_O_DIRECTORY, directory);
+        self.oflag(wasi::O_DIRECTORY, directory);
     }
 
-    fn oflag(&mut self, bit: libc::__wasi_oflags_t, set: bool) {
+    fn oflag(&mut self, bit: wasi::OFlags, set: bool) {
         if set {
             self.oflags |= bit;
         } else {
@@ -287,26 +283,26 @@ impl OpenOptions {
     }
 
     pub fn append(&mut self, set: bool) {
-        self.fdflag(libc::__WASI_FDFLAG_APPEND, set);
+        self.fdflag(wasi::FDFLAG_APPEND, set);
     }
 
     pub fn dsync(&mut self, set: bool) {
-        self.fdflag(libc::__WASI_FDFLAG_DSYNC, set);
+        self.fdflag(wasi::FDFLAG_DSYNC, set);
     }
 
     pub fn nonblock(&mut self, set: bool) {
-        self.fdflag(libc::__WASI_FDFLAG_NONBLOCK, set);
+        self.fdflag(wasi::FDFLAG_NONBLOCK, set);
     }
 
     pub fn rsync(&mut self, set: bool) {
-        self.fdflag(libc::__WASI_FDFLAG_RSYNC, set);
+        self.fdflag(wasi::FDFLAG_RSYNC, set);
     }
 
     pub fn sync(&mut self, set: bool) {
-        self.fdflag(libc::__WASI_FDFLAG_SYNC, set);
+        self.fdflag(wasi::FDFLAG_SYNC, set);
     }
 
-    fn fdflag(&mut self, bit: libc::__wasi_fdflags_t, set: bool) {
+    fn fdflag(&mut self, bit: wasi::FdFlags, set: bool) {
         if set {
             self.fdflags |= bit;
         } else {
@@ -314,15 +310,15 @@ impl OpenOptions {
         }
     }
 
-    pub fn fs_rights_base(&mut self, rights: libc::__wasi_rights_t) {
+    pub fn fs_rights_base(&mut self, rights: wasi::Rights) {
         self.rights_base = Some(rights);
     }
 
-    pub fn fs_rights_inheriting(&mut self, rights: libc::__wasi_rights_t) {
+    pub fn fs_rights_inheriting(&mut self, rights: wasi::Rights) {
         self.rights_inheriting = Some(rights);
     }
 
-    fn rights_base(&self) -> libc::__wasi_rights_t {
+    fn rights_base(&self) -> wasi::Rights {
         if let Some(rights) = self.rights_base {
             return rights;
         }
@@ -334,52 +330,52 @@ impl OpenOptions {
         // based on that.
         let mut base = 0;
         if self.read {
-            base |= libc::__WASI_RIGHT_FD_READ;
-            base |= libc::__WASI_RIGHT_FD_READDIR;
+            base |= wasi::RIGHT_FD_READ;
+            base |= wasi::RIGHT_FD_READDIR;
         }
         if self.write {
-            base |= libc::__WASI_RIGHT_FD_WRITE;
-            base |= libc::__WASI_RIGHT_FD_DATASYNC;
-            base |= libc::__WASI_RIGHT_FD_ALLOCATE;
-            base |= libc::__WASI_RIGHT_FD_FILESTAT_SET_SIZE;
+            base |= wasi::RIGHT_FD_WRITE;
+            base |= wasi::RIGHT_FD_DATASYNC;
+            base |= wasi::RIGHT_FD_ALLOCATE;
+            base |= wasi::RIGHT_FD_FILESTAT_SET_SIZE;
         }
 
         // FIXME: some of these should probably be read-only or write-only...
-        base |= libc::__WASI_RIGHT_FD_ADVISE;
-        base |= libc::__WASI_RIGHT_FD_FDSTAT_SET_FLAGS;
-        base |= libc::__WASI_RIGHT_FD_FILESTAT_SET_TIMES;
-        base |= libc::__WASI_RIGHT_FD_SEEK;
-        base |= libc::__WASI_RIGHT_FD_SYNC;
-        base |= libc::__WASI_RIGHT_FD_TELL;
-        base |= libc::__WASI_RIGHT_PATH_CREATE_DIRECTORY;
-        base |= libc::__WASI_RIGHT_PATH_CREATE_FILE;
-        base |= libc::__WASI_RIGHT_PATH_FILESTAT_GET;
-        base |= libc::__WASI_RIGHT_PATH_LINK_SOURCE;
-        base |= libc::__WASI_RIGHT_PATH_LINK_TARGET;
-        base |= libc::__WASI_RIGHT_PATH_OPEN;
-        base |= libc::__WASI_RIGHT_PATH_READLINK;
-        base |= libc::__WASI_RIGHT_PATH_REMOVE_DIRECTORY;
-        base |= libc::__WASI_RIGHT_PATH_RENAME_SOURCE;
-        base |= libc::__WASI_RIGHT_PATH_RENAME_TARGET;
-        base |= libc::__WASI_RIGHT_PATH_SYMLINK;
-        base |= libc::__WASI_RIGHT_PATH_UNLINK_FILE;
-        base |= libc::__WASI_RIGHT_POLL_FD_READWRITE;
+        base |= wasi::RIGHT_FD_ADVISE;
+        base |= wasi::RIGHT_FD_FDSTAT_SET_FLAGS;
+        base |= wasi::RIGHT_FD_FILESTAT_SET_TIMES;
+        base |= wasi::RIGHT_FD_SEEK;
+        base |= wasi::RIGHT_FD_SYNC;
+        base |= wasi::RIGHT_FD_TELL;
+        base |= wasi::RIGHT_PATH_CREATE_DIRECTORY;
+        base |= wasi::RIGHT_PATH_CREATE_FILE;
+        base |= wasi::RIGHT_PATH_FILESTAT_GET;
+        base |= wasi::RIGHT_PATH_LINK_SOURCE;
+        base |= wasi::RIGHT_PATH_LINK_TARGET;
+        base |= wasi::RIGHT_PATH_OPEN;
+        base |= wasi::RIGHT_PATH_READLINK;
+        base |= wasi::RIGHT_PATH_REMOVE_DIRECTORY;
+        base |= wasi::RIGHT_PATH_RENAME_SOURCE;
+        base |= wasi::RIGHT_PATH_RENAME_TARGET;
+        base |= wasi::RIGHT_PATH_SYMLINK;
+        base |= wasi::RIGHT_PATH_UNLINK_FILE;
+        base |= wasi::RIGHT_POLL_FD_READWRITE;
 
         return base;
     }
 
-    fn rights_inheriting(&self) -> libc::__wasi_rights_t {
+    fn rights_inheriting(&self) -> wasi::Rights {
         self.rights_inheriting.unwrap_or_else(|| self.rights_base())
     }
 
-    pub fn lookup_flags(&mut self, flags: libc::__wasi_lookupflags_t) {
+    pub fn lookup_flags(&mut self, flags: wasi::LookupFlags) {
         self.dirflags = flags;
     }
 }
 
 impl File {
     pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
-        let (dir, file) = open_parent(path, libc::__WASI_RIGHT_PATH_OPEN)?;
+        let (dir, file) = open_parent(path, wasi::RIGHT_PATH_OPEN)?;
         open_at(&dir, &file, opts)
     }
 
@@ -388,14 +384,12 @@ impl File {
     }
 
     pub fn file_attr(&self) -> io::Result<FileAttr> {
-        let mut ret = FileAttr::zero();
-        self.fd.filestat_get(&mut ret.meta)?;
-        Ok(ret)
+        self.fd.filestat_get().map(|meta| FileAttr { meta })
     }
 
     pub fn metadata_at(
         &self,
-        flags: libc::__wasi_lookupflags_t,
+        flags: wasi::LookupFlags,
         path: &Path,
     ) -> io::Result<FileAttr> {
         metadata_at(&self.fd, flags, path)
@@ -477,7 +471,7 @@ impl DirBuilder {
     }
 
     pub fn mkdir(&self, p: &Path) -> io::Result<()> {
-        let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_CREATE_DIRECTORY)?;
+        let (dir, file) = open_parent(p, wasi::RIGHT_PATH_CREATE_DIRECTORY)?;
         dir.create_directory(file.as_os_str().as_bytes())
     }
 }
@@ -508,13 +502,13 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
 }
 
 pub fn unlink(p: &Path) -> io::Result<()> {
-    let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_UNLINK_FILE)?;
+    let (dir, file) = open_parent(p, wasi::RIGHT_PATH_UNLINK_FILE)?;
     dir.unlink_file(file.as_os_str().as_bytes())
 }
 
 pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
-    let (old, old_file) = open_parent(old, libc::__WASI_RIGHT_PATH_RENAME_SOURCE)?;
-    let (new, new_file) = open_parent(new, libc::__WASI_RIGHT_PATH_RENAME_TARGET)?;
+    let (old, old_file) = open_parent(old, wasi::RIGHT_PATH_RENAME_SOURCE)?;
+    let (new, new_file) = open_parent(new, wasi::RIGHT_PATH_RENAME_TARGET)?;
     old.rename(
         old_file.as_os_str().as_bytes(),
         &new,
@@ -529,12 +523,12 @@ pub fn set_perm(_p: &Path, _perm: FilePermissions) -> io::Result<()> {
 }
 
 pub fn rmdir(p: &Path) -> io::Result<()> {
-    let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_REMOVE_DIRECTORY)?;
+    let (dir, file) = open_parent(p, wasi::RIGHT_PATH_REMOVE_DIRECTORY)?;
     dir.remove_directory(file.as_os_str().as_bytes())
 }
 
 pub fn readlink(p: &Path) -> io::Result<PathBuf> {
-    let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_READLINK)?;
+    let (dir, file) = open_parent(p, wasi::RIGHT_PATH_READLINK)?;
     read_link(&dir, &file)
 }
 
@@ -570,15 +564,15 @@ fn read_link(fd: &WasiFd, file: &Path) -> io::Result<PathBuf> {
 }
 
 pub fn symlink(src: &Path, dst: &Path) -> io::Result<()> {
-    let (dst, dst_file) = open_parent(dst, libc::__WASI_RIGHT_PATH_SYMLINK)?;
+    let (dst, dst_file) = open_parent(dst, wasi::RIGHT_PATH_SYMLINK)?;
     dst.symlink(src.as_os_str().as_bytes(), dst_file.as_os_str().as_bytes())
 }
 
 pub fn link(src: &Path, dst: &Path) -> io::Result<()> {
-    let (src, src_file) = open_parent(src, libc::__WASI_RIGHT_PATH_LINK_SOURCE)?;
-    let (dst, dst_file) = open_parent(dst, libc::__WASI_RIGHT_PATH_LINK_TARGET)?;
+    let (src, src_file) = open_parent(src, wasi::RIGHT_PATH_LINK_SOURCE)?;
+    let (dst, dst_file) = open_parent(dst, wasi::RIGHT_PATH_LINK_TARGET)?;
     src.link(
-        libc::__WASI_LOOKUP_SYMLINK_FOLLOW,
+        wasi::LOOKUP_SYMLINK_FOLLOW,
         src_file.as_os_str().as_bytes(),
         &dst,
         dst_file.as_os_str().as_bytes(),
@@ -586,23 +580,22 @@ pub fn link(src: &Path, dst: &Path) -> io::Result<()> {
 }
 
 pub fn stat(p: &Path) -> io::Result<FileAttr> {
-    let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_FILESTAT_GET)?;
-    metadata_at(&dir, libc::__WASI_LOOKUP_SYMLINK_FOLLOW, &file)
+    let (dir, file) = open_parent(p, wasi::RIGHT_PATH_FILESTAT_GET)?;
+    metadata_at(&dir, wasi::LOOKUP_SYMLINK_FOLLOW, &file)
 }
 
 pub fn lstat(p: &Path) -> io::Result<FileAttr> {
-    let (dir, file) = open_parent(p, libc::__WASI_RIGHT_PATH_FILESTAT_GET)?;
+    let (dir, file) = open_parent(p, wasi::RIGHT_PATH_FILESTAT_GET)?;
     metadata_at(&dir, 0, &file)
 }
 
 fn metadata_at(
     fd: &WasiFd,
-    flags: libc::__wasi_lookupflags_t,
+    flags: wasi::LookupFlags,
     path: &Path,
 ) -> io::Result<FileAttr> {
-    let mut ret = FileAttr::zero();
-    fd.path_filestat_get(flags, path.as_os_str().as_bytes(), &mut ret.meta)?;
-    Ok(ret)
+    fd.path_filestat_get(flags, path.as_os_str().as_bytes())
+        .map(|meta| FileAttr { meta })
 }
 
 pub fn canonicalize(_p: &Path) -> io::Result<PathBuf> {
@@ -652,12 +645,12 @@ fn open_at(fd: &WasiFd, path: &Path, opts: &OpenOptions) -> io::Result<File> {
 /// to any preopened file descriptor.
 fn open_parent(
     p: &Path,
-    rights: libc::__wasi_rights_t,
+    rights: wasi::Rights,
 ) -> io::Result<(ManuallyDrop<WasiFd>, PathBuf)> {
     let p = CString::new(p.as_os_str().as_bytes())?;
     unsafe {
         let mut ret = ptr::null();
-        let fd = __wasilibc_find_relpath(p.as_ptr(), rights, 0, &mut ret);
+        let fd = libc::__wasilibc_find_relpath(p.as_ptr(), rights, 0, &mut ret);
         if fd == -1 {
             let msg = format!(
                 "failed to find a preopened file descriptor \
@@ -677,15 +670,4 @@ fn open_parent(
 
         return Ok((ManuallyDrop::new(WasiFd::from_raw(fd as u32)), path));
     }
-
-    // FIXME(rust-lang/libc#1314) use the `libc` crate for this when the API
-    // there is published
-    extern "C" {
-        pub fn __wasilibc_find_relpath(
-            path: *const libc::c_char,
-            rights_base: libc::__wasi_rights_t,
-            rights_inheriting: libc::__wasi_rights_t,
-            relative_path: *mut *const libc::c_char,
-        ) -> libc::c_int;
-    }
 }
diff --git a/src/libstd/sys/wasi/io.rs b/src/libstd/sys/wasi/io.rs
index ffecca5d1b6ff..4be92faed308f 100644
--- a/src/libstd/sys/wasi/io.rs
+++ b/src/libstd/sys/wasi/io.rs
@@ -1,11 +1,12 @@
 use crate::marker::PhantomData;
 use crate::slice;
 
-use libc::{__wasi_ciovec_t, __wasi_iovec_t, c_void};
+use ::wasi::wasi_unstable as wasi;
+use core::ffi::c_void;
 
 #[repr(transparent)]
 pub struct IoSlice<'a> {
-    vec: __wasi_ciovec_t,
+    vec: wasi::CIoVec,
     _p: PhantomData<&'a [u8]>,
 }
 
@@ -13,7 +14,7 @@ impl<'a> IoSlice<'a> {
     #[inline]
     pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
         IoSlice {
-            vec: __wasi_ciovec_t {
+            vec: wasi::CIoVec {
                 buf: buf.as_ptr() as *const c_void,
                 buf_len: buf.len(),
             },
@@ -43,7 +44,7 @@ impl<'a> IoSlice<'a> {
 
 #[repr(transparent)]
 pub struct IoSliceMut<'a> {
-    vec: __wasi_iovec_t,
+    vec: wasi::IoVec,
     _p: PhantomData<&'a mut [u8]>,
 }
 
@@ -51,7 +52,7 @@ impl<'a> IoSliceMut<'a> {
     #[inline]
     pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
         IoSliceMut {
-            vec: __wasi_iovec_t {
+            vec: wasi::IoVec {
                 buf: buf.as_mut_ptr() as *mut c_void,
                 buf_len: buf.len()
             },
diff --git a/src/libstd/sys/wasi/mod.rs b/src/libstd/sys/wasi/mod.rs
index 57da81b41e7ca..517e3be9cb58c 100644
--- a/src/libstd/sys/wasi/mod.rs
+++ b/src/libstd/sys/wasi/mod.rs
@@ -14,10 +14,10 @@
 //! compiling for wasm. That way it's a compile time error for something that's
 //! guaranteed to be a runtime error!
 
-use libc;
-use crate::io::{Error, ErrorKind};
+use crate::io as std_io;
 use crate::mem;
 use crate::os::raw::c_char;
+use ::wasi::wasi_unstable as wasi;
 
 pub mod alloc;
 pub mod args;
@@ -56,31 +56,42 @@ pub mod ext;
 pub fn init() {
 }
 
-pub fn unsupported<T>() -> crate::io::Result<T> {
+pub fn unsupported<T>() -> std_io::Result<T> {
     Err(unsupported_err())
 }
 
-pub fn unsupported_err() -> Error {
-    Error::new(ErrorKind::Other, "operation not supported on wasm yet")
+pub fn unsupported_err() -> std_io::Error {
+    std_io::Error::new(
+        std_io::ErrorKind::Other,
+        "operation not supported on wasm yet",
+    )
 }
 
-pub fn decode_error_kind(errno: i32) -> ErrorKind {
-    match errno as libc::c_int {
-        libc::ECONNREFUSED => ErrorKind::ConnectionRefused,
-        libc::ECONNRESET => ErrorKind::ConnectionReset,
-        libc::EPERM | libc::EACCES => ErrorKind::PermissionDenied,
-        libc::EPIPE => ErrorKind::BrokenPipe,
-        libc::ENOTCONN => ErrorKind::NotConnected,
-        libc::ECONNABORTED => ErrorKind::ConnectionAborted,
-        libc::EADDRNOTAVAIL => ErrorKind::AddrNotAvailable,
-        libc::EADDRINUSE => ErrorKind::AddrInUse,
-        libc::ENOENT => ErrorKind::NotFound,
-        libc::EINTR => ErrorKind::Interrupted,
-        libc::EINVAL => ErrorKind::InvalidInput,
-        libc::ETIMEDOUT => ErrorKind::TimedOut,
-        libc::EEXIST => ErrorKind::AlreadyExists,
-        libc::EAGAIN => ErrorKind::WouldBlock,
-        _ => ErrorKind::Other,
+pub fn decode_error_kind(errno: i32) -> std_io::ErrorKind {
+    use std_io::ErrorKind::*;
+    if errno > u16::max_value() as i32 || errno < 0 {
+        return Other;
+    }
+    let code = match wasi::Error::new(errno as u16) {
+        Some(code) => code,
+        None => return Other,
+    };
+    match code {
+        wasi::ECONNREFUSED => ConnectionRefused,
+        wasi::ECONNRESET => ConnectionReset,
+        wasi::EPERM | wasi::EACCES => PermissionDenied,
+        wasi::EPIPE => BrokenPipe,
+        wasi::ENOTCONN => NotConnected,
+        wasi::ECONNABORTED => ConnectionAborted,
+        wasi::EADDRNOTAVAIL => AddrNotAvailable,
+        wasi::EADDRINUSE => AddrInUse,
+        wasi::ENOENT => NotFound,
+        wasi::EINTR => Interrupted,
+        wasi::EINVAL => InvalidInput,
+        wasi::ETIMEDOUT => TimedOut,
+        wasi::EEXIST => AlreadyExists,
+        wasi::EAGAIN => WouldBlock,
+        _ => Other,
     }
 }
 
@@ -105,40 +116,16 @@ pub unsafe fn abort_internal() -> ! {
 pub fn hashmap_random_keys() -> (u64, u64) {
     let mut ret = (0u64, 0u64);
     unsafe {
-        let base = &mut ret as *mut (u64, u64) as *mut libc::c_void;
+        let base = &mut ret as *mut (u64, u64) as *mut core::ffi::c_void;
         let len = mem::size_of_val(&ret);
-        cvt_wasi(libc::__wasi_random_get(base, len)).unwrap();
-    }
-    return ret
-}
-
-#[doc(hidden)]
-pub trait IsMinusOne {
-    fn is_minus_one(&self) -> bool;
-}
-
-macro_rules! impl_is_minus_one {
-    ($($t:ident)*) => ($(impl IsMinusOne for $t {
-        fn is_minus_one(&self) -> bool {
-            *self == -1
+        let ret = wasi::raw::__wasi_random_get(base, len);
+        if ret != 0 {
+            panic!("__wasi_random_get failure")
         }
-    })*)
-}
-
-impl_is_minus_one! { i8 i16 i32 i64 isize }
-
-pub fn cvt<T: IsMinusOne>(t: T) -> crate::io::Result<T> {
-    if t.is_minus_one() {
-        Err(Error::last_os_error())
-    } else {
-        Ok(t)
     }
+    return ret
 }
 
-pub fn cvt_wasi(r: u16) -> crate::io::Result<()> {
-    if r != libc::__WASI_ESUCCESS {
-        Err(Error::from_raw_os_error(r as i32))
-    } else {
-        Ok(())
-    }
+fn err2io(err: wasi::Error) -> std_io::Error {
+    std_io::Error::from_raw_os_error(err.get() as i32)
 }
diff --git a/src/libstd/sys/wasi/os.rs b/src/libstd/sys/wasi/os.rs
index 822ea02a11b89..feee840782550 100644
--- a/src/libstd/sys/wasi/os.rs
+++ b/src/libstd/sys/wasi/os.rs
@@ -9,7 +9,7 @@ use crate::path::{self, PathBuf};
 use crate::ptr;
 use crate::str;
 use crate::sys::memchr;
-use crate::sys::{cvt, unsupported, Void};
+use crate::sys::{unsupported, Void};
 use crate::vec;
 
 #[cfg(not(target_feature = "atomics"))]
@@ -28,16 +28,11 @@ pub fn errno() -> i32 {
 }
 
 pub fn error_string(errno: i32) -> String {
-    extern {
-        fn strerror_r(errnum: libc::c_int, buf: *mut libc::c_char,
-                      buflen: libc::size_t) -> libc::c_int;
-    }
-
     let mut buf = [0 as libc::c_char; 1024];
 
     let p = buf.as_mut_ptr();
     unsafe {
-        if strerror_r(errno as libc::c_int, p, buf.len()) < 0 {
+        if libc::strerror_r(errno as libc::c_int, p, buf.len()) < 0 {
             panic!("strerror_r failure");
         }
         str::from_utf8(CStr::from_ptr(p).to_bytes()).unwrap().to_owned()
@@ -89,7 +84,6 @@ impl StdError for JoinPathsError {
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
 }
-
 pub struct Env {
     iter: vec::IntoIter<(OsString, OsString)>,
     _dont_send_or_sync_me: PhantomData<*mut ()>,
@@ -182,3 +176,26 @@ pub fn exit(code: i32) -> ! {
 pub fn getpid() -> u32 {
     panic!("unsupported");
 }
+
+#[doc(hidden)]
+pub trait IsMinusOne {
+    fn is_minus_one(&self) -> bool;
+}
+
+macro_rules! impl_is_minus_one {
+    ($($t:ident)*) => ($(impl IsMinusOne for $t {
+        fn is_minus_one(&self) -> bool {
+            *self == -1
+        }
+    })*)
+}
+
+impl_is_minus_one! { i8 i16 i32 i64 isize }
+
+fn cvt<T: IsMinusOne>(t: T) -> io::Result<T> {
+    if t.is_minus_one() {
+        Err(io::Error::last_os_error())
+    } else {
+        Ok(t)
+    }
+}
diff --git a/src/libstd/sys/wasi/process.rs b/src/libstd/sys/wasi/process.rs
index 788b829f4bac9..1c4d028b7618b 100644
--- a/src/libstd/sys/wasi/process.rs
+++ b/src/libstd/sys/wasi/process.rs
@@ -4,14 +4,16 @@ use crate::io;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::{unsupported, Void};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
+
+pub use crate::ffi::OsString as EnvKey;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Command
 ////////////////////////////////////////////////////////////////////////////////
 
 pub struct Command {
-    env: CommandEnv<DefaultEnvKey>
+    env: CommandEnv
 }
 
 // passed back to std::process with the pipes connected to the child, if any
@@ -38,7 +40,7 @@ impl Command {
     pub fn arg(&mut self, _arg: &OsStr) {
     }
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
diff --git a/src/libstd/sys/wasi/stdio.rs b/src/libstd/sys/wasi/stdio.rs
index 2bf8d803c01bb..1d57b9922e599 100644
--- a/src/libstd/sys/wasi/stdio.rs
+++ b/src/libstd/sys/wasi/stdio.rs
@@ -1,8 +1,9 @@
 use crate::io::{self, IoSlice, IoSliceMut};
-use crate::libc;
 use crate::mem::ManuallyDrop;
 use crate::sys::fd::WasiFd;
 
+use ::wasi::wasi_unstable as wasi;
+
 pub struct Stdin;
 pub struct Stdout;
 pub struct Stderr;
@@ -17,7 +18,7 @@ impl Stdin {
     }
 
     pub fn read_vectored(&self, data: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-        ManuallyDrop::new(unsafe { WasiFd::from_raw(libc::STDIN_FILENO as u32) })
+        ManuallyDrop::new(unsafe { WasiFd::from_raw(wasi::STDIN_FD) })
             .read(data)
     }
 }
@@ -32,7 +33,7 @@ impl Stdout {
     }
 
     pub fn write_vectored(&self, data: &[IoSlice<'_>]) -> io::Result<usize> {
-        ManuallyDrop::new(unsafe { WasiFd::from_raw(libc::STDOUT_FILENO as u32) })
+        ManuallyDrop::new(unsafe { WasiFd::from_raw(wasi::STDOUT_FD) })
             .write(data)
     }
 
@@ -51,7 +52,7 @@ impl Stderr {
     }
 
     pub fn write_vectored(&self, data: &[IoSlice<'_>]) -> io::Result<usize> {
-        ManuallyDrop::new(unsafe { WasiFd::from_raw(libc::STDERR_FILENO as u32) })
+        ManuallyDrop::new(unsafe { WasiFd::from_raw(wasi::STDERR_FD) })
             .write(data)
     }
 
@@ -73,7 +74,7 @@ impl io::Write for Stderr {
 pub const STDIN_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
 
 pub fn is_ebadf(err: &io::Error) -> bool {
-    err.raw_os_error() == Some(libc::__WASI_EBADF as i32)
+    err.raw_os_error() == Some(wasi::EBADF.get() as i32)
 }
 
 pub fn panic_output() -> Option<impl io::Write> {
diff --git a/src/libstd/sys/wasi/thread.rs b/src/libstd/sys/wasi/thread.rs
index 5e69e4d948fee..28a504f197974 100644
--- a/src/libstd/sys/wasi/thread.rs
+++ b/src/libstd/sys/wasi/thread.rs
@@ -1,10 +1,10 @@
-use crate::cmp;
 use crate::ffi::CStr;
 use crate::io;
-use crate::sys::cvt;
+use crate::mem;
 use crate::sys::{unsupported, Void};
 use crate::time::Duration;
-use libc;
+
+use ::wasi::wasi_unstable as wasi;
 
 pub struct Thread(Void);
 
@@ -19,8 +19,8 @@ impl Thread {
     }
 
     pub fn yield_now() {
-        let ret = unsafe { libc::__wasi_sched_yield() };
-        debug_assert_eq!(ret, 0);
+        let ret = wasi::sched_yield();
+        debug_assert_eq!(ret, Ok(()));
     }
 
     pub fn set_name(_name: &CStr) {
@@ -28,19 +28,37 @@ impl Thread {
     }
 
     pub fn sleep(dur: Duration) {
-        let mut secs = dur.as_secs();
-        let mut nsecs = dur.subsec_nanos() as i32;
-
-        unsafe {
-            while secs > 0 || nsecs > 0 {
-                let mut ts = libc::timespec {
-                    tv_sec: cmp::min(libc::time_t::max_value() as u64, secs) as libc::time_t,
-                    tv_nsec: nsecs,
-                };
-                secs -= ts.tv_sec as u64;
-                cvt(libc::nanosleep(&ts, &mut ts)).unwrap();
-                nsecs = 0;
-            }
+        let nanos = dur.as_nanos();
+        assert!(nanos <= u64::max_value() as u128);
+
+        const CLOCK_ID: wasi::Userdata = 0x0123_45678;
+
+        let clock = wasi::raw::__wasi_subscription_u_clock_t {
+            identifier: CLOCK_ID,
+            clock_id: wasi::CLOCK_MONOTONIC,
+            timeout: nanos as u64,
+            precision: 0,
+            flags: 0,
+        };
+
+        let in_ = [wasi::Subscription {
+            userdata: 0,
+            type_: wasi::EVENTTYPE_CLOCK,
+            u: wasi::raw::__wasi_subscription_u { clock: clock },
+        }];
+        let (res, event) = unsafe {
+            let mut out: [wasi::Event; 1] = mem::zeroed();
+            let res = wasi::poll_oneoff(&in_, &mut out);
+            (res, out[0])
+        };
+        match (res, event) {
+            (Ok(1), wasi::Event {
+                userdata: CLOCK_ID,
+                error: 0,
+                type_: wasi::EVENTTYPE_CLOCK,
+                ..
+            }) => {}
+            _ => panic!("thread::sleep(): unexpected result of poll_oneoff"),
         }
     }
 
diff --git a/src/libstd/sys/wasi/time.rs b/src/libstd/sys/wasi/time.rs
index 3f14c80928c67..4394a22f9c233 100644
--- a/src/libstd/sys/wasi/time.rs
+++ b/src/libstd/sys/wasi/time.rs
@@ -1,7 +1,5 @@
 use crate::time::Duration;
-use crate::mem;
-use crate::sys::cvt_wasi;
-use libc;
+use ::wasi::wasi_unstable as wasi;
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 pub struct Instant(Duration);
@@ -12,23 +10,19 @@ pub struct SystemTime(Duration);
 pub const UNIX_EPOCH: SystemTime = SystemTime(Duration::from_secs(0));
 
 fn current_time(clock: u32) -> Duration {
-    unsafe {
-        let mut ts = mem::zeroed();
-        cvt_wasi(libc::__wasi_clock_time_get(
-            clock,
-            1, // precision... seems ignored though?
-            &mut ts,
-        )).unwrap();
-        Duration::new(
-            (ts / 1_000_000_000) as u64,
-            (ts % 1_000_000_000) as u32,
-        )
-    }
+    let ts = wasi::clock_time_get(
+        clock,
+        1, // precision... seems ignored though?
+    ).unwrap();
+    Duration::new(
+        (ts / 1_000_000_000) as u64,
+        (ts % 1_000_000_000) as u32,
+    )
 }
 
 impl Instant {
     pub fn now() -> Instant {
-        Instant(current_time(libc::__WASI_CLOCK_MONOTONIC))
+        Instant(current_time(wasi::CLOCK_MONOTONIC))
     }
 
     pub const fn zero() -> Instant {
@@ -54,10 +48,10 @@ impl Instant {
 
 impl SystemTime {
     pub fn now() -> SystemTime {
-        SystemTime(current_time(libc::__WASI_CLOCK_REALTIME))
+        SystemTime(current_time(wasi::CLOCK_REALTIME))
     }
 
-    pub fn from_wasi_timestamp(ts: libc::__wasi_timestamp_t) -> SystemTime {
+    pub fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
         SystemTime(Duration::from_nanos(ts))
     }
 
diff --git a/src/libstd/sys/wasm/process.rs b/src/libstd/sys/wasm/process.rs
index a02e009d95356..edf933d10e074 100644
--- a/src/libstd/sys/wasm/process.rs
+++ b/src/libstd/sys/wasm/process.rs
@@ -4,14 +4,16 @@ use crate::io;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::{unsupported, Void};
-use crate::sys_common::process::{CommandEnv, DefaultEnvKey};
+use crate::sys_common::process::CommandEnv;
+
+pub use crate::ffi::OsString as EnvKey;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Command
 ////////////////////////////////////////////////////////////////////////////////
 
 pub struct Command {
-    env: CommandEnv<DefaultEnvKey>
+    env: CommandEnv,
 }
 
 // passed back to std::process with the pipes connected to the child, if any
@@ -38,7 +40,7 @@ impl Command {
     pub fn arg(&mut self, _arg: &OsStr) {
     }
 
-    pub fn env_mut(&mut self) -> &mut CommandEnv<DefaultEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
 
diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index 05e0ca6706453..8658deb854635 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -19,7 +19,7 @@ use crate::sys::pipe::{self, AnonPipe};
 use crate::sys::stdio;
 use crate::sys::cvt;
 use crate::sys_common::{AsInner, FromInner, IntoInner};
-use crate::sys_common::process::{CommandEnv, EnvKey};
+use crate::sys_common::process::CommandEnv;
 use crate::borrow::Borrow;
 
 use libc::{c_void, EXIT_SUCCESS, EXIT_FAILURE};
@@ -30,30 +30,28 @@ use libc::{c_void, EXIT_SUCCESS, EXIT_FAILURE};
 
 #[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd)]
 #[doc(hidden)]
-pub struct WindowsEnvKey(OsString);
+pub struct EnvKey(OsString);
 
-impl From<OsString> for WindowsEnvKey {
+impl From<OsString> for EnvKey {
     fn from(k: OsString) -> Self {
         let mut buf = k.into_inner().into_inner();
         buf.make_ascii_uppercase();
-        WindowsEnvKey(FromInner::from_inner(FromInner::from_inner(buf)))
+        EnvKey(FromInner::from_inner(FromInner::from_inner(buf)))
     }
 }
 
-impl From<WindowsEnvKey> for OsString {
-    fn from(k: WindowsEnvKey) -> Self { k.0 }
+impl From<EnvKey> for OsString {
+    fn from(k: EnvKey) -> Self { k.0 }
 }
 
-impl Borrow<OsStr> for WindowsEnvKey {
+impl Borrow<OsStr> for EnvKey {
     fn borrow(&self) -> &OsStr { &self.0 }
 }
 
-impl AsRef<OsStr> for WindowsEnvKey {
+impl AsRef<OsStr> for EnvKey {
     fn as_ref(&self) -> &OsStr { &self.0 }
 }
 
-impl EnvKey for WindowsEnvKey {}
-
 
 fn ensure_no_nuls<T: AsRef<OsStr>>(str: T) -> io::Result<T> {
     if str.as_ref().encode_wide().any(|b| b == 0) {
@@ -66,7 +64,7 @@ fn ensure_no_nuls<T: AsRef<OsStr>>(str: T) -> io::Result<T> {
 pub struct Command {
     program: OsString,
     args: Vec<OsString>,
-    env: CommandEnv<WindowsEnvKey>,
+    env: CommandEnv,
     cwd: Option<OsString>,
     flags: u32,
     detach: bool, // not currently exposed in std::process
@@ -110,7 +108,7 @@ impl Command {
     pub fn arg(&mut self, arg: &OsStr) {
         self.args.push(arg.to_os_string())
     }
-    pub fn env_mut(&mut self) -> &mut CommandEnv<WindowsEnvKey> {
+    pub fn env_mut(&mut self) -> &mut CommandEnv {
         &mut self.env
     }
     pub fn cwd(&mut self, dir: &OsStr) {
@@ -498,7 +496,7 @@ fn make_command_line(prog: &OsStr, args: &[OsString]) -> io::Result<Vec<u16>> {
     }
 }
 
-fn make_envp(maybe_env: Option<BTreeMap<WindowsEnvKey, OsString>>)
+fn make_envp(maybe_env: Option<BTreeMap<EnvKey, OsString>>)
              -> io::Result<(*mut c_void, Vec<u16>)> {
     // On Windows we pass an "environment block" which is not a char**, but
     // rather a concatenation of null-terminated k=v\0 sequences, with a final
diff --git a/src/libstd/sys_common/backtrace.rs b/src/libstd/sys_common/backtrace.rs
index bf37ff7ddbd3a..01711d415d86c 100644
--- a/src/libstd/sys_common/backtrace.rs
+++ b/src/libstd/sys_common/backtrace.rs
@@ -2,25 +2,38 @@
 /// supported platforms.
 
 use crate::env;
+use crate::fmt;
 use crate::io;
+use crate::borrow::Cow;
 use crate::io::prelude::*;
-use crate::mem;
-use crate::path::{self, Path};
-use crate::ptr;
-use crate::sync::atomic::{self, Ordering};
+use crate::path::{self, Path, PathBuf};
 use crate::sys::mutex::Mutex;
 
-use backtrace::{BytesOrWideString, Frame, Symbol};
-
-pub const HEX_WIDTH: usize = 2 + 2 * mem::size_of::<usize>();
+use backtrace_rs::{BacktraceFmt, BytesOrWideString, PrintFmt};
 
 /// Max number of frames to print.
 const MAX_NB_FRAMES: usize = 100;
 
-/// Prints the current backtrace.
-pub fn print(w: &mut dyn Write, format: PrintFormat) -> io::Result<()> {
+pub fn lock() -> impl Drop {
+    struct Guard;
     static LOCK: Mutex = Mutex::new();
 
+    impl Drop for Guard {
+        fn drop(&mut self) {
+            unsafe {
+                LOCK.unlock();
+            }
+        }
+    }
+
+    unsafe {
+        LOCK.lock();
+        return Guard;
+    }
+}
+
+/// Prints the current backtrace.
+pub fn print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
     // There are issues currently linking libbacktrace into tests, and in
     // general during libstd's own unit tests we're not testing this path. In
     // test mode immediately return here to optimize away any references to the
@@ -32,33 +45,69 @@ pub fn print(w: &mut dyn Write, format: PrintFormat) -> io::Result<()> {
     // Use a lock to prevent mixed output in multithreading context.
     // Some platforms also requires it, like `SymFromAddr` on Windows.
     unsafe {
-        LOCK.lock();
-        let res = _print(w, format);
-        LOCK.unlock();
-        res
+        let _lock = lock();
+        _print(w, format)
+    }
+}
+
+unsafe fn _print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
+    struct DisplayBacktrace {
+        format: PrintFmt,
     }
+    impl fmt::Display for DisplayBacktrace {
+        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+            unsafe {
+                _print_fmt(fmt, self.format)
+            }
+        }
+    }
+    write!(w, "{}", DisplayBacktrace { format })
 }
 
-fn _print(w: &mut dyn Write, format: PrintFormat) -> io::Result<()> {
-    writeln!(w, "stack backtrace:")?;
+unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::Result {
+    let cwd = env::current_dir().ok();
+    let mut print_path = move |fmt: &mut fmt::Formatter<'_>, bows: BytesOrWideString<'_>| {
+        output_filename(fmt, bows, print_fmt, cwd.as_ref())
+    };
+    let mut bt_fmt = BacktraceFmt::new(fmt, print_fmt, &mut print_path);
+    bt_fmt.add_context()?;
+    let mut idx = 0;
+    let mut res = Ok(());
+    backtrace_rs::trace_unsynchronized(|frame| {
+        if print_fmt == PrintFmt::Short && idx > MAX_NB_FRAMES {
+            return false;
+        }
 
-    let mut printer = Printer::new(format, w);
-    unsafe {
-        backtrace::trace_unsynchronized(|frame| {
-            let mut hit = false;
-            backtrace::resolve_frame_unsynchronized(frame, |symbol| {
-                hit = true;
-                printer.output(frame, Some(symbol));
-            });
-            if !hit {
-                printer.output(frame, None);
+        let mut hit = false;
+        let mut stop = false;
+        backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
+            hit = true;
+            if print_fmt == PrintFmt::Short {
+                if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
+                    if sym.contains("__rust_begin_short_backtrace") {
+                        stop = true;
+                        return;
+                    }
+                }
             }
-            !printer.done
+
+            res = bt_fmt.frame().symbol(frame, symbol);
         });
-    }
-    if printer.skipped {
+        if stop {
+            return false;
+        }
+        if !hit {
+            res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
+        }
+
+        idx += 1;
+        res.is_ok()
+    });
+    res?;
+    bt_fmt.finish()?;
+    if print_fmt == PrintFmt::Short {
         writeln!(
-            w,
+            fmt,
             "note: Some details are omitted, \
              run with `RUST_BACKTRACE=full` for a verbose backtrace."
         )?;
@@ -77,33 +126,32 @@ where
     f()
 }
 
-/// Controls how the backtrace should be formatted.
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub enum PrintFormat {
-    /// Show only relevant data from the backtrace.
-    Short = 2,
-    /// Show all the frames with absolute path for files.
-    Full = 3,
-}
-
 // For now logging is turned off by default, and this function checks to see
 // whether the magical environment variable is present to see if it's turned on.
-pub fn log_enabled() -> Option<PrintFormat> {
+pub fn log_enabled() -> Option<PrintFmt> {
+    use crate::sync::atomic::{self, Ordering};
+
+    // Setting environment variables for Fuchsia components isn't a standard
+    // or easily supported workflow. For now, always display backtraces.
+    if cfg!(target_os = "fuchsia") {
+        return Some(PrintFmt::Full);
+    }
+
     static ENABLED: atomic::AtomicIsize = atomic::AtomicIsize::new(0);
     match ENABLED.load(Ordering::SeqCst) {
         0 => {}
         1 => return None,
-        2 => return Some(PrintFormat::Short),
-        _ => return Some(PrintFormat::Full),
+        2 => return Some(PrintFmt::Short),
+        _ => return Some(PrintFmt::Full),
     }
 
     let val = env::var_os("RUST_BACKTRACE").and_then(|x| {
         if &x == "0" {
             None
         } else if &x == "full" {
-            Some(PrintFormat::Full)
+            Some(PrintFmt::Full)
         } else {
-            Some(PrintFormat::Short)
+            Some(PrintFmt::Short)
         }
     });
     ENABLED.store(
@@ -116,130 +164,43 @@ pub fn log_enabled() -> Option<PrintFormat> {
     val
 }
 
-struct Printer<'a, 'b> {
-    format: PrintFormat,
-    done: bool,
-    skipped: bool,
-    idx: usize,
-    out: &'a mut (dyn Write + 'b),
-}
-
-impl<'a, 'b> Printer<'a, 'b> {
-    fn new(format: PrintFormat, out: &'a mut (dyn Write + 'b)) -> Printer<'a, 'b> {
-        Printer { format, done: false, skipped: false, idx: 0, out }
-    }
-
-    /// Prints the symbol of the backtrace frame.
-    ///
-    /// These output functions should now be used everywhere to ensure consistency.
-    /// You may want to also use `output_fileline`.
-    fn output(&mut self, frame: &Frame, symbol: Option<&Symbol>) {
-        if self.idx > MAX_NB_FRAMES {
-            self.done = true;
-            self.skipped = true;
-            return;
-        }
-        if self._output(frame, symbol).is_err() {
-            self.done = true;
-        }
-        self.idx += 1;
-    }
-
-    fn _output(&mut self, frame: &Frame, symbol: Option<&Symbol>) -> io::Result<()> {
-        if self.format == PrintFormat::Short {
-            if let Some(sym) = symbol.and_then(|s| s.name()).and_then(|s| s.as_str()) {
-                if sym.contains("__rust_begin_short_backtrace") {
-                    self.skipped = true;
-                    self.done = true;
-                    return Ok(());
-                }
-            }
-
-            // Remove the `17: 0x0 - <unknown>` line.
-            if self.format == PrintFormat::Short && frame.ip() == ptr::null_mut() {
-                self.skipped = true;
-                return Ok(());
-            }
-        }
-
-        match self.format {
-            PrintFormat::Full => {
-                write!(self.out, "  {:2}: {:2$?} - ", self.idx, frame.ip(), HEX_WIDTH)?
-            }
-            PrintFormat::Short => write!(self.out, "  {:2}: ", self.idx)?,
-        }
-
-        match symbol.and_then(|s| s.name()) {
-            Some(symbol) => {
-                match self.format {
-                    PrintFormat::Full => write!(self.out, "{}", symbol)?,
-                    // Strip the trailing hash if short mode.
-                    PrintFormat::Short => write!(self.out, "{:#}", symbol)?,
-                }
-            }
-            None => self.out.write_all(b"<unknown>")?,
+/// Prints the filename of the backtrace frame.
+///
+/// See also `output`.
+pub fn output_filename(
+    fmt: &mut fmt::Formatter<'_>,
+    bows: BytesOrWideString<'_>,
+    print_fmt: PrintFmt,
+    cwd: Option<&PathBuf>,
+) -> fmt::Result {
+    let file: Cow<'_, Path> = match bows {
+        #[cfg(unix)]
+        BytesOrWideString::Bytes(bytes) => {
+            use crate::os::unix::prelude::*;
+            Path::new(crate::ffi::OsStr::from_bytes(bytes)).into()
         }
-        self.out.write_all(b"\n")?;
-        if let Some(sym) = symbol {
-            self.output_fileline(sym)?;
+        #[cfg(not(unix))]
+        BytesOrWideString::Bytes(bytes) => {
+            Path::new(crate::str::from_utf8(bytes).unwrap_or("<unknown>")).into()
         }
-        Ok(())
-    }
-
-    /// Prints the filename and line number of the backtrace frame.
-    ///
-    /// See also `output`.
-    fn output_fileline(&mut self, symbol: &Symbol) -> io::Result<()> {
         #[cfg(windows)]
-        let path_buf;
-        let file = match symbol.filename_raw() {
-            #[cfg(unix)]
-            Some(BytesOrWideString::Bytes(bytes)) => {
-                use crate::os::unix::prelude::*;
-                Path::new(crate::ffi::OsStr::from_bytes(bytes))
-            }
-            #[cfg(not(unix))]
-            Some(BytesOrWideString::Bytes(bytes)) => {
-                Path::new(crate::str::from_utf8(bytes).unwrap_or("<unknown>"))
-            }
-            #[cfg(windows)]
-            Some(BytesOrWideString::Wide(wide)) => {
-                use crate::os::windows::prelude::*;
-                path_buf = crate::ffi::OsString::from_wide(wide);
-                Path::new(&path_buf)
-            }
-            #[cfg(not(windows))]
-            Some(BytesOrWideString::Wide(_wide)) => {
-                Path::new("<unknown>")
-            }
-            None => return Ok(()),
-        };
-        let line = match symbol.lineno() {
-            Some(line) => line,
-            None => return Ok(()),
-        };
-        // prior line: "  ##: {:2$} - func"
-        self.out.write_all(b"")?;
-        match self.format {
-            PrintFormat::Full => write!(self.out, "           {:1$}", "", HEX_WIDTH)?,
-            PrintFormat::Short => write!(self.out, "           ")?,
+        BytesOrWideString::Wide(wide) => {
+            use crate::os::windows::prelude::*;
+            Cow::Owned(crate::ffi::OsString::from_wide(wide).into())
         }
-
-        let mut already_printed = false;
-        if self.format == PrintFormat::Short && file.is_absolute() {
-            if let Ok(cwd) = env::current_dir() {
-                if let Ok(stripped) = file.strip_prefix(&cwd) {
-                    if let Some(s) = stripped.to_str() {
-                        write!(self.out, "  at .{}{}:{}", path::MAIN_SEPARATOR, s, line)?;
-                        already_printed = true;
-                    }
+        #[cfg(not(windows))]
+        BytesOrWideString::Wide(_wide) => {
+            Path::new("<unknown>").into()
+        }
+    };
+    if print_fmt == PrintFmt::Short && file.is_absolute() {
+        if let Some(cwd) = cwd {
+            if let Ok(stripped) = file.strip_prefix(&cwd) {
+                if let Some(s) = stripped.to_str() {
+                    return write!(fmt, ".{}{}", path::MAIN_SEPARATOR, s);
                 }
             }
         }
-        if !already_printed {
-            write!(self.out, "  at {}:{}", file.display(), line)?;
-        }
-
-        self.out.write_all(b"\n")
     }
+    fmt::Display::fmt(&file.display(), fmt)
 }
diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
index 9190a3b0d5fc7..cba3eca538625 100644
--- a/src/libstd/sys_common/mod.rs
+++ b/src/libstd/sys_common/mod.rs
@@ -41,7 +41,6 @@ macro_rules! rtunwrap {
 
 pub mod alloc;
 pub mod at_exit_imp;
-#[cfg(feature = "backtrace")]
 pub mod backtrace;
 pub mod condvar;
 pub mod io;
diff --git a/src/libstd/sys_common/process.rs b/src/libstd/sys_common/process.rs
index 4d40dec97245a..bdf66fca35970 100644
--- a/src/libstd/sys_common/process.rs
+++ b/src/libstd/sys_common/process.rs
@@ -1,47 +1,20 @@
 #![allow(dead_code)]
 #![unstable(feature = "process_internals", issue = "0")]
 
-use crate::ffi::{OsStr, OsString};
-use crate::env;
 use crate::collections::BTreeMap;
-use crate::borrow::Borrow;
-
-pub trait EnvKey:
-    From<OsString> + Into<OsString> +
-    Borrow<OsStr> + Borrow<Self> + AsRef<OsStr> +
-    Ord + Clone {}
-
-// Implement a case-sensitive environment variable key
-#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd)]
-pub struct DefaultEnvKey(OsString);
-
-impl From<OsString> for DefaultEnvKey {
-    fn from(k: OsString) -> Self { DefaultEnvKey(k) }
-}
-
-impl From<DefaultEnvKey> for OsString {
-    fn from(k: DefaultEnvKey) -> Self { k.0 }
-}
-
-impl Borrow<OsStr> for DefaultEnvKey {
-    fn borrow(&self) -> &OsStr { &self.0 }
-}
-
-impl AsRef<OsStr> for DefaultEnvKey {
-    fn as_ref(&self) -> &OsStr { &self.0 }
-}
-
-impl EnvKey for DefaultEnvKey {}
+use crate::env;
+use crate::ffi::{OsStr, OsString};
+use crate::sys::process::EnvKey;
 
 // Stores a set of changes to an environment
 #[derive(Clone, Debug)]
-pub struct CommandEnv<K> {
+pub struct CommandEnv {
     clear: bool,
     saw_path: bool,
-    vars: BTreeMap<K, Option<OsString>>
+    vars: BTreeMap<EnvKey, Option<OsString>>
 }
 
-impl<K: EnvKey> Default for CommandEnv<K> {
+impl Default for CommandEnv {
     fn default() -> Self {
         CommandEnv {
             clear: false,
@@ -51,10 +24,10 @@ impl<K: EnvKey> Default for CommandEnv<K> {
     }
 }
 
-impl<K: EnvKey> CommandEnv<K> {
+impl CommandEnv {
     // Capture the current environment with these changes applied
-    pub fn capture(&self) -> BTreeMap<K, OsString> {
-        let mut result = BTreeMap::<K, OsString>::new();
+    pub fn capture(&self) -> BTreeMap<EnvKey, OsString> {
+        let mut result = BTreeMap::<EnvKey, OsString>::new();
         if !self.clear {
             for (k, v) in env::vars_os() {
                 result.insert(k.into(), v);
@@ -90,7 +63,7 @@ impl<K: EnvKey> CommandEnv<K> {
         !self.clear && self.vars.is_empty()
     }
 
-    pub fn capture_if_changed(&self) -> Option<BTreeMap<K, OsString>> {
+    pub fn capture_if_changed(&self) -> Option<BTreeMap<EnvKey, OsString>> {
         if self.is_unchanged() {
             None
         } else {
@@ -103,6 +76,7 @@ impl<K: EnvKey> CommandEnv<K> {
         self.maybe_saw_path(&key);
         self.vars.insert(key.to_owned().into(), Some(value.to_owned()));
     }
+
     pub fn remove(&mut self, key: &OsStr) {
         self.maybe_saw_path(&key);
         if self.clear {
@@ -111,13 +85,16 @@ impl<K: EnvKey> CommandEnv<K> {
             self.vars.insert(key.to_owned().into(), None);
         }
     }
+
     pub fn clear(&mut self) {
         self.clear = true;
         self.vars.clear();
     }
+
     pub fn have_changed_path(&self) -> bool {
         self.saw_path || self.clear
     }
+
     fn maybe_saw_path(&mut self, key: &OsStr) {
         if !self.saw_path && key == "PATH" {
             self.saw_path = true;
diff --git a/src/libstd/tests/env.rs b/src/libstd/tests/env.rs
index 06fb5533afdd8..f8014cb2ad9af 100644
--- a/src/libstd/tests/env.rs
+++ b/src/libstd/tests/env.rs
@@ -5,7 +5,7 @@ use rand::{thread_rng, Rng};
 use rand::distributions::Alphanumeric;
 
 fn make_rand_name() -> OsString {
-    let mut rng = thread_rng();
+    let rng = thread_rng();
     let n = format!("TEST{}", rng.sample_iter(&Alphanumeric).take(10)
                                  .collect::<String>());
     let n = OsString::from(n);
diff --git a/src/libstd/time.rs b/src/libstd/time.rs
index d59085cd44a6f..3bf2b8be1fe8e 100644
--- a/src/libstd/time.rs
+++ b/src/libstd/time.rs
@@ -59,6 +59,30 @@ pub use core::time::Duration;
 ///    println!("{}", now.elapsed().as_secs());
 /// }
 /// ```
+///
+/// # Underlying System calls
+/// Currently, the following system calls are being used to get the current time using `now()`:
+///
+/// |  Platform |               System call                                            |
+/// |:---------:|:--------------------------------------------------------------------:|
+/// | Cloud ABI | [clock_time_get (Monotonic Clock)]                                   |
+/// | SGX       | [`insecure_time` usercall]. More information on [timekeeping in SGX] |
+/// | UNIX      | [clock_time_get (Monotonic Clock)]                                   |
+/// | Darwin    | [mach_absolute_time]                                                 |
+/// | VXWorks   | [clock_gettime (Monotonic Clock)]                                    |
+/// | WASI      | [__wasi_clock_time_get (Monotonic Clock)]                            |
+/// | Windows   | [QueryPerformanceCounter]                                            |
+///
+/// [QueryPerformanceCounter]: https://docs.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter
+/// [`insecure_time` usercall]: https://edp.fortanix.com/docs/api/fortanix_sgx_abi/struct.Usercalls.html#method.insecure_time
+/// [timekeeping in SGX]: https://edp.fortanix.com/docs/concepts/rust-std/#codestdtimecode
+/// [__wasi_clock_time_get (Monotonic Clock)]: https://github.com/CraneStation/wasmtime/blob/master/docs/WASI-api.md#clock_time_get
+/// [clock_gettime (Monotonic Clock)]: https://linux.die.net/man/3/clock_gettime
+/// [mach_absolute_time]: https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/KernelProgramming/services/services.html
+/// [clock_time_get (Monotonic Clock)]: https://github.com/NuxiNL/cloudabi/blob/master/cloudabi.txt
+///
+/// **Disclaimer:** These system calls might change over time.
+///
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[stable(feature = "time2", since = "1.8.0")]
 pub struct Instant(time::Instant);
@@ -114,6 +138,28 @@ pub struct Instant(time::Instant);
 ///    }
 /// }
 /// ```
+///
+/// # Underlying System calls
+/// Currently, the following system calls are being used to get the current time using `now()`:
+///
+/// |  Platform |               System call                                            |
+/// |:---------:|:--------------------------------------------------------------------:|
+/// | Cloud ABI | [clock_time_get (Realtime Clock)]                                    |
+/// | SGX       | [`insecure_time` usercall]. More information on [timekeeping in SGX] |
+/// | UNIX      | [clock_gettime (Realtime Clock)]                                     |
+/// | DARWIN    | [gettimeofday]                                                       |
+/// | VXWorks   | [clock_gettime (Realtime Clock)]                                     |
+/// | WASI      | [__wasi_clock_time_get (Realtime Clock)]                             |
+/// | Windows   | [GetSystemTimeAsFileTime]                                            |
+///
+/// [clock_time_get (Realtime Clock)]: https://github.com/NuxiNL/cloudabi/blob/master/cloudabi.txt
+/// [gettimeofday]: http://man7.org/linux/man-pages/man2/gettimeofday.2.html
+/// [clock_gettime (Realtime Clock)]: https://linux.die.net/man/3/clock_gettime
+/// [__wasi_clock_time_get (Realtime Clock)]: https://github.com/CraneStation/wasmtime/blob/master/docs/WASI-api.md#clock_time_get
+/// [GetSystemTimeAsFileTime]: https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime
+///
+/// **Disclaimer:** These system calls might change over time.
+///
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[stable(feature = "time2", since = "1.8.0")]
 pub struct SystemTime(time::SystemTime);
@@ -216,7 +262,7 @@ impl Instant {
     }
 
     /// Returns the amount of time elapsed from another instant to this one,
-    /// or None if that instant is earlier than this one.
+    /// or None if that instant is later than this one.
     ///
     /// # Examples
     ///
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 6be00bcef45c0..b634dcca7fca2 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -352,7 +352,7 @@ pub struct GenericParam {
     pub ident: Ident,
     pub attrs: ThinVec<Attribute>,
     pub bounds: GenericBounds,
-
+    pub is_placeholder: bool,
     pub kind: GenericParamKind,
 }
 
@@ -413,11 +413,11 @@ impl WherePredicate {
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct WhereBoundPredicate {
     pub span: Span,
-    /// Any generics from a `for` binding
+    /// Any generics from a `for` binding.
     pub bound_generic_params: Vec<GenericParam>,
-    /// The type being bounded
+    /// The type being bounded.
     pub bounded_ty: P<Ty>,
-    /// Trait and lifetime bounds (`Clone+Send+'static`)
+    /// Trait and lifetime bounds (`Clone + Send + 'static`).
     pub bounds: GenericBounds,
 }
 
@@ -495,15 +495,15 @@ pub enum MetaItemKind {
     NameValue(Lit),
 }
 
-/// A Block (`{ .. }`).
+/// A block (`{ .. }`).
 ///
 /// E.g., `{ .. }` as in `fn foo() { .. }`.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Block {
-    /// Statements in a block
+    /// The statements in the block.
     pub stmts: Vec<Stmt>,
     pub id: NodeId,
-    /// Distinguishes between `unsafe { ... }` and `{ ... }`
+    /// Distinguishes between `unsafe { ... }` and `{ ... }`.
     pub rules: BlockCheckMode,
     pub span: Span,
 }
@@ -561,29 +561,31 @@ impl Pat {
         }))
     }
 
-    pub fn walk<F>(&self, it: &mut F) -> bool
-    where
-        F: FnMut(&Pat) -> bool,
-    {
+    /// Walk top-down and call `it` in each place where a pattern occurs
+    /// starting with the root pattern `walk` is called on. If `it` returns
+    /// false then we will descend no further but siblings will be processed.
+    pub fn walk(&self, it: &mut impl FnMut(&Pat) -> bool) {
         if !it(self) {
-            return false;
+            return;
         }
 
         match &self.node {
             PatKind::Ident(_, _, Some(p)) => p.walk(it),
-            PatKind::Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk(it)),
+            PatKind::Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk(it)),
             PatKind::TupleStruct(_, s)
             | PatKind::Tuple(s)
             | PatKind::Slice(s)
-            | PatKind::Or(s) => s.iter().all(|p| p.walk(it)),
-            PatKind::Box(s) | PatKind::Ref(s, _) | PatKind::Paren(s) => s.walk(it),
+            | PatKind::Or(s) => s.iter().for_each(|p| p.walk(it)),
+            PatKind::Box(s)
+            | PatKind::Ref(s, _)
+            | PatKind::Paren(s) => s.walk(it),
             PatKind::Wild
             | PatKind::Rest
             | PatKind::Lit(_)
             | PatKind::Range(..)
             | PatKind::Ident(..)
             | PatKind::Path(..)
-            | PatKind::Mac(_) => true,
+            | PatKind::Mac(_) => {},
         }
     }
 
@@ -611,6 +613,7 @@ pub struct FieldPat {
     pub attrs: ThinVec<Attribute>,
     pub id: NodeId,
     pub span: Span,
+    pub is_placeholder: bool,
 }
 
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)]
@@ -906,11 +909,11 @@ pub enum MacStmtStyle {
 /// Local represents a `let` statement, e.g., `let <pat>:<ty> = <expr>;`.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Local {
+    pub id: NodeId,
     pub pat: P<Pat>,
     pub ty: Option<P<Ty>>,
     /// Initializer expression to set the value, if any.
     pub init: Option<P<Expr>>,
-    pub id: NodeId,
     pub span: Span,
     pub attrs: ThinVec<Attribute>,
 }
@@ -928,11 +931,12 @@ pub struct Local {
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Arm {
     pub attrs: Vec<Attribute>,
-    pub pats: Vec<P<Pat>>,
+    pub pat: P<Pat>,
     pub guard: Option<P<Expr>>,
     pub body: P<Expr>,
     pub span: Span,
     pub id: NodeId,
+    pub is_placeholder: bool,
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
@@ -943,6 +947,7 @@ pub struct Field {
     pub is_shorthand: bool,
     pub attrs: ThinVec<Attribute>,
     pub id: NodeId,
+    pub is_placeholder: bool,
 }
 
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)]
@@ -968,7 +973,7 @@ pub struct AnonConst {
     pub value: P<Expr>,
 }
 
-/// An expression
+/// An expression.
 #[derive(Clone, RustcEncodable, RustcDecodable)]
 pub struct Expr {
     pub id: NodeId,
@@ -982,26 +987,26 @@ pub struct Expr {
 static_assert_size!(Expr, 96);
 
 impl Expr {
-    /// Whether this expression would be valid somewhere that expects a value; for example, an `if`
-    /// condition.
+    /// Returns `true` if this expression would be valid somewhere that expects a value;
+    /// for example, an `if` condition.
     pub fn returns(&self) -> bool {
         if let ExprKind::Block(ref block, _) = self.node {
             match block.stmts.last().map(|last_stmt| &last_stmt.node) {
-                // implicit return
+                // Implicit return
                 Some(&StmtKind::Expr(_)) => true,
                 Some(&StmtKind::Semi(ref expr)) => {
                     if let ExprKind::Ret(_) = expr.node {
-                        // last statement is explicit return
+                        // Last statement is explicit return.
                         true
                     } else {
                         false
                     }
                 }
-                // This is a block that doesn't end in either an implicit or explicit return
+                // This is a block that doesn't end in either an implicit or explicit return.
                 _ => false,
             }
         } else {
-            // This is not a block, it is a value
+            // This is not a block, it is a value.
             true
         }
     }
@@ -1146,12 +1151,9 @@ pub enum ExprKind {
     Cast(P<Expr>, P<Ty>),
     /// A type ascription (e.g., `42: usize`).
     Type(P<Expr>, P<Ty>),
-    /// A `let pats = expr` expression that is only semantically allowed in the condition
+    /// A `let pat = expr` expression that is only semantically allowed in the condition
     /// of `if` / `while` expressions. (e.g., `if let 0 = x { .. }`).
-    ///
-    /// The `Vec<P<Pat>>` is for or-patterns at the top level.
-    /// FIXME(54883): Change this to just `P<Pat>`.
-    Let(Vec<P<Pat>>, P<Expr>),
+    Let(P<Pat>, P<Expr>),
     /// An `if` block, with an optional `else` block.
     ///
     /// `if expr { block } else { expr }`
@@ -1799,6 +1801,7 @@ pub struct Param {
     pub pat: P<Pat>,
     pub id: NodeId,
     pub span: Span,
+    pub is_placeholder: bool,
 }
 
 /// Alternative representation for `Arg`s describing `self` parameter of methods.
@@ -1860,6 +1863,7 @@ impl Param {
             span,
             ty,
             id: DUMMY_NODE_ID,
+            is_placeholder: false
         };
         match eself.node {
             SelfKind::Explicit(ty, mutbl) => param(mutbl, ty),
@@ -2055,6 +2059,8 @@ pub struct Variant {
     pub disr_expr: Option<AnonConst>,
     /// Span
     pub span: Span,
+    /// Is a macro placeholder
+    pub is_placeholder: bool,
 }
 
 /// Part of `use` item to the right of its prefix.
@@ -2217,6 +2223,7 @@ pub struct StructField {
     pub id: NodeId,
     pub ty: P<Ty>,
     pub attrs: Vec<Attribute>,
+    pub is_placeholder: bool,
 }
 
 /// Fields and constructor ids of enum variants and structs.
@@ -2308,37 +2315,37 @@ impl Default for FnHeader {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub enum ItemKind {
-    /// An `extern crate` item, with optional *original* crate name if the crate was renamed.
+    /// An `extern crate` item, with the optional *original* crate name if the crate was renamed.
     ///
     /// E.g., `extern crate foo` or `extern crate foo_bar as foo`.
     ExternCrate(Option<Name>),
-    /// A use declaration (`use` or `pub use`) item.
+    /// A use declaration item (`use`).
     ///
     /// E.g., `use foo;`, `use foo::bar;` or `use foo::bar as FooBar;`.
     Use(P<UseTree>),
-    /// A static item (`static` or `pub static`).
+    /// A static item (`static`).
     ///
     /// E.g., `static FOO: i32 = 42;` or `static FOO: &'static str = "bar";`.
     Static(P<Ty>, Mutability, P<Expr>),
-    /// A constant item (`const` or `pub const`).
+    /// A constant item (`const`).
     ///
     /// E.g., `const FOO: i32 = 42;`.
     Const(P<Ty>, P<Expr>),
-    /// A function declaration (`fn` or `pub fn`).
+    /// A function declaration (`fn`).
     ///
     /// E.g., `fn foo(bar: usize) -> usize { .. }`.
     Fn(P<FnDecl>, FnHeader, Generics, P<Block>),
-    /// A module declaration (`mod` or `pub mod`).
+    /// A module declaration (`mod`).
     ///
     /// E.g., `mod foo;` or `mod foo { .. }`.
     Mod(Mod),
-    /// An external module (`extern` or `pub extern`).
+    /// An external module (`extern`).
     ///
     /// E.g., `extern {}` or `extern "C" {}`.
     ForeignMod(ForeignMod),
     /// Module-level inline assembly (from `global_asm!()`).
     GlobalAsm(P<GlobalAsm>),
-    /// A type alias (`type` or `pub type`).
+    /// A type alias (`type`).
     ///
     /// E.g., `type Foo = Bar<u8>;`.
     TyAlias(P<Ty>, Generics),
@@ -2346,19 +2353,19 @@ pub enum ItemKind {
     ///
     /// E.g., `type Foo = impl Bar + Boo;`.
     OpaqueTy(GenericBounds, Generics),
-    /// An enum definition (`enum` or `pub enum`).
+    /// An enum definition (`enum`).
     ///
     /// E.g., `enum Foo<A, B> { C<A>, D<B> }`.
     Enum(EnumDef, Generics),
-    /// A struct definition (`struct` or `pub struct`).
+    /// A struct definition (`struct`).
     ///
     /// E.g., `struct Foo<A> { x: A }`.
     Struct(VariantData, Generics),
-    /// A union definition (`union` or `pub union`).
+    /// A union definition (`union`).
     ///
     /// E.g., `union Foo<A, B> { x: A, y: B }`.
     Union(VariantData, Generics),
-    /// A Trait declaration (`trait` or `pub trait`).
+    /// A trait declaration (`trait`).
     ///
     /// E.g., `trait Foo { .. }`, `trait Foo<T> { .. }` or `auto trait Foo {}`.
     Trait(IsAuto, Unsafety, Generics, GenericBounds, Vec<TraitItem>),
@@ -2380,7 +2387,7 @@ pub enum ItemKind {
     ),
     /// A macro invocation.
     ///
-    /// E.g., `macro_rules! foo { .. }` or `foo!(..)`.
+    /// E.g., `foo!(..)`.
     Mac(Mac),
 
     /// A macro definition.
diff --git a/src/libsyntax/attr/builtin.rs b/src/libsyntax/attr/builtin.rs
index 5fb513783fbaa..b5037b75f79e7 100644
--- a/src/libsyntax/attr/builtin.rs
+++ b/src/libsyntax/attr/builtin.rs
@@ -154,23 +154,10 @@ pub struct Stability {
 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Copy, Clone, Debug, Eq, Hash)]
 pub enum StabilityLevel {
     // Reason for the current stability level and the relevant rust-lang issue
-    Unstable { reason: Option<Symbol>, issue: u32 },
+    Unstable { reason: Option<Symbol>, issue: u32, is_soft: bool },
     Stable { since: Symbol },
 }
 
-impl Stability {
-    pub fn unstable(feature: Symbol, reason: Option<Symbol>, issue: u32) -> Stability {
-        Stability {
-            level: StabilityLevel::Unstable { reason, issue },
-            feature,
-            rustc_depr: None,
-            const_stability: None,
-            promotable: false,
-            allow_const_fn_ptr: false,
-        }
-    }
-}
-
 impl StabilityLevel {
     pub fn is_unstable(&self) -> bool {
         if let StabilityLevel::Unstable {..} = *self {
@@ -356,19 +343,27 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
                     let mut feature = None;
                     let mut reason = None;
                     let mut issue = None;
+                    let mut is_soft = false;
                     for meta in metas {
                         if let Some(mi) = meta.meta_item() {
                             match mi.name_or_empty() {
                                 sym::feature => if !get(mi, &mut feature) { continue 'outer },
                                 sym::reason => if !get(mi, &mut reason) { continue 'outer },
                                 sym::issue => if !get(mi, &mut issue) { continue 'outer },
+                                sym::soft => {
+                                    if !mi.is_word() {
+                                        let msg = "`soft` should not have any arguments";
+                                        sess.span_diagnostic.span_err(mi.span, msg);
+                                    }
+                                    is_soft = true;
+                                }
                                 _ => {
                                     handle_errors(
                                         sess,
                                         meta.span(),
                                         AttrError::UnknownMetaItem(
                                             mi.path.to_string(),
-                                            &["feature", "reason", "issue"]
+                                            &["feature", "reason", "issue", "soft"]
                                         ),
                                     );
                                     continue 'outer
@@ -400,7 +395,8 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
                                                       "incorrect 'issue'");
                                             continue
                                         }
-                                    }
+                                    },
+                                    is_soft,
                                 },
                                 feature,
                                 rustc_depr: None,
diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index 0e5cfa73a9e3a..1f954064944dc 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -1,4 +1,4 @@
-//! Functions dealing with attributes and meta items
+//! Functions dealing with attributes and meta items.
 
 mod builtin;
 
@@ -16,7 +16,7 @@ use crate::mut_visit::visit_clobber;
 use crate::source_map::{BytePos, Spanned, DUMMY_SP};
 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
 use crate::parse::parser::Parser;
-use crate::parse::{self, ParseSess, PResult};
+use crate::parse::{ParseSess, PResult};
 use crate::parse::token::{self, Token};
 use crate::ptr::P;
 use crate::symbol::{sym, Symbol};
@@ -25,7 +25,7 @@ use crate::tokenstream::{TokenStream, TokenTree, DelimSpan};
 use crate::GLOBALS;
 
 use log::debug;
-use syntax_pos::{FileName, Span};
+use syntax_pos::Span;
 
 use std::iter;
 use std::ops::DerefMut;
@@ -61,7 +61,7 @@ pub fn is_known_lint_tool(m_item: Ident) -> bool {
 }
 
 impl NestedMetaItem {
-    /// Returns the MetaItem if self is a NestedMetaItem::MetaItem.
+    /// Returns the `MetaItem` if `self` is a `NestedMetaItem::MetaItem`.
     pub fn meta_item(&self) -> Option<&MetaItem> {
         match *self {
             NestedMetaItem::MetaItem(ref item) => Some(item),
@@ -69,7 +69,7 @@ impl NestedMetaItem {
         }
     }
 
-    /// Returns the Lit if self is a NestedMetaItem::Literal.
+    /// Returns the `Lit` if `self` is a `NestedMetaItem::Literal`s.
     pub fn literal(&self) -> Option<&Lit> {
         match *self {
             NestedMetaItem::Literal(ref lit) => Some(lit),
@@ -82,7 +82,7 @@ impl NestedMetaItem {
         self.meta_item().map_or(false, |meta_item| meta_item.check_name(name))
     }
 
-    /// For a single-segment meta-item returns its name, otherwise returns `None`.
+    /// For a single-segment meta item, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
         self.meta_item().and_then(|meta_item| meta_item.ident())
     }
@@ -90,13 +90,13 @@ impl NestedMetaItem {
         self.ident().unwrap_or(Ident::invalid()).name
     }
 
-    /// Gets the string value if self is a MetaItem and the MetaItem is a
-    /// MetaItemKind::NameValue variant containing a string, otherwise None.
+    /// Gets the string value if `self` is a `MetaItem` and the `MetaItem` is a
+    /// `MetaItemKind::NameValue` variant containing a string, otherwise `None`.
     pub fn value_str(&self) -> Option<Symbol> {
         self.meta_item().and_then(|meta_item| meta_item.value_str())
     }
 
-    /// Returns a name and single literal value tuple of the MetaItem.
+    /// Returns a name and single literal value tuple of the `MetaItem`.
     pub fn name_value_literal(&self) -> Option<(Name, &Lit)> {
         self.meta_item().and_then(
             |meta_item| meta_item.meta_item_list().and_then(
@@ -112,32 +112,32 @@ impl NestedMetaItem {
                 }))
     }
 
-    /// Gets a list of inner meta items from a list MetaItem type.
+    /// Gets a list of inner meta items from a list `MetaItem` type.
     pub fn meta_item_list(&self) -> Option<&[NestedMetaItem]> {
         self.meta_item().and_then(|meta_item| meta_item.meta_item_list())
     }
 
-    /// Returns `true` if the variant is MetaItem.
+    /// Returns `true` if the variant is `MetaItem`.
     pub fn is_meta_item(&self) -> bool {
         self.meta_item().is_some()
     }
 
-    /// Returns `true` if the variant is Literal.
+    /// Returns `true` if the variant is `Literal`.
     pub fn is_literal(&self) -> bool {
         self.literal().is_some()
     }
 
-    /// Returns `true` if self is a MetaItem and the meta item is a word.
+    /// Returns `true` if `self` is a `MetaItem` and the meta item is a word.
     pub fn is_word(&self) -> bool {
         self.meta_item().map_or(false, |meta_item| meta_item.is_word())
     }
 
-    /// Returns `true` if self is a MetaItem and the meta item is a ValueString.
+    /// Returns `true` if `self` is a `MetaItem` and the meta item is a `ValueString`.
     pub fn is_value_str(&self) -> bool {
         self.value_str().is_some()
     }
 
-    /// Returns `true` if self is a MetaItem and the meta item is a list.
+    /// Returns `true` if `self` is a `MetaItem` and the meta item is a list.
     pub fn is_meta_item_list(&self) -> bool {
         self.meta_item_list().is_some()
     }
@@ -156,7 +156,7 @@ impl Attribute {
         matches
     }
 
-    /// For a single-segment attribute returns its name, otherwise returns `None`.
+    /// For a single-segment attribute, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
         if self.path.segments.len() == 1 {
             Some(self.path.segments[0].ident)
@@ -187,14 +187,14 @@ impl Attribute {
         self.meta_item_list().is_some()
     }
 
-    /// Indicates if the attribute is a Value String.
+    /// Indicates if the attribute is a `ValueString`.
     pub fn is_value_str(&self) -> bool {
         self.value_str().is_some()
     }
 }
 
 impl MetaItem {
-    /// For a single-segment meta-item returns its name, otherwise returns `None`.
+    /// For a single-segment meta item, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
         if self.path.segments.len() == 1 {
             Some(self.path.segments[0].ident)
@@ -206,8 +206,9 @@ impl MetaItem {
         self.ident().unwrap_or(Ident::invalid()).name
     }
 
-    // #[attribute(name = "value")]
-    //             ^^^^^^^^^^^^^^
+    // Example:
+    //     #[attribute(name = "value")]
+    //                 ^^^^^^^^^^^^^^
     pub fn name_value_literal(&self) -> Option<&Lit> {
         match &self.node {
             MetaItemKind::NameValue(v) => Some(v),
@@ -255,7 +256,7 @@ impl MetaItem {
 }
 
 impl Attribute {
-    /// Extracts the MetaItem from inside this Attribute.
+    /// Extracts the `MetaItem` from inside this `Attribute`.
     pub fn meta(&self) -> Option<MetaItem> {
         let mut tokens = self.tokens.trees().peekable();
         Some(MetaItem {
@@ -318,8 +319,8 @@ impl Attribute {
         })
     }
 
-    /// Converts self to a normal #[doc="foo"] comment, if it is a
-    /// comment like `///` or `/** */`. (Returns self unchanged for
+    /// Converts `self` to a normal `#[doc="foo"]` comment, if it is a
+    /// comment like `///` or `/** */`. (Returns `self` unchanged for
     /// non-sugared doc attributes.)
     pub fn with_desugared_doc<T, F>(&self, f: F) -> T where
         F: FnOnce(&Attribute) -> T,
@@ -381,28 +382,25 @@ crate fn mk_attr_id() -> AttrId {
     AttrId(id)
 }
 
-/// Returns an inner attribute with the given value and span.
-pub fn mk_attr_inner(item: MetaItem) -> Attribute {
+pub fn mk_attr(style: AttrStyle, path: Path, tokens: TokenStream, span: Span) -> Attribute {
     Attribute {
         id: mk_attr_id(),
-        style: ast::AttrStyle::Inner,
-        path: item.path,
-        tokens: item.node.tokens(item.span),
+        style,
+        path,
+        tokens,
         is_sugared_doc: false,
-        span: item.span,
+        span,
     }
 }
 
+/// Returns an inner attribute with the given value and span.
+pub fn mk_attr_inner(item: MetaItem) -> Attribute {
+    mk_attr(AttrStyle::Inner, item.path, item.node.tokens(item.span), item.span)
+}
+
 /// Returns an outer attribute with the given value and span.
 pub fn mk_attr_outer(item: MetaItem) -> Attribute {
-    Attribute {
-        id: mk_attr_id(),
-        style: ast::AttrStyle::Outer,
-        path: item.path,
-        tokens: item.node.tokens(item.span),
-        is_sugared_doc: false,
-        span: item.span,
-    }
+    mk_attr(AttrStyle::Outer, item.path, item.node.tokens(item.span), item.span)
 }
 
 pub fn mk_sugared_doc_attr(text: Symbol, span: Span) -> Attribute {
@@ -716,33 +714,3 @@ derive_has_attrs! {
     Item, Expr, Local, ast::ForeignItem, ast::StructField, ast::ImplItem, ast::TraitItem, ast::Arm,
     ast::Field, ast::FieldPat, ast::Variant, ast::Param
 }
-
-pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -> ast::Crate {
-    for raw_attr in attrs {
-        let mut parser = parse::new_parser_from_source_str(
-            parse_sess,
-            FileName::cli_crate_attr_source_code(&raw_attr),
-            raw_attr.clone(),
-        );
-
-        let start_span = parser.token.span;
-        let (path, tokens) = panictry!(parser.parse_meta_item_unrestricted());
-        let end_span = parser.token.span;
-        if parser.token != token::Eof {
-            parse_sess.span_diagnostic
-                .span_err(start_span.to(end_span), "invalid crate attribute");
-            continue;
-        }
-
-        krate.attrs.push(Attribute {
-            id: mk_attr_id(),
-            style: AttrStyle::Inner,
-            path,
-            tokens,
-            is_sugared_doc: false,
-            span: start_span.to(end_span),
-        });
-    }
-
-    krate
-}
diff --git a/src/libsyntax/diagnostics/macros.rs b/src/libsyntax/diagnostics/macros.rs
index b754d0833761e..c95c5bd5d02d4 100644
--- a/src/libsyntax/diagnostics/macros.rs
+++ b/src/libsyntax/diagnostics/macros.rs
@@ -1,13 +1,14 @@
 #[macro_export]
-macro_rules! register_diagnostic {
-    ($code:tt, $description:tt) => (__register_diagnostic! { $code, $description });
-    ($code:tt) => (__register_diagnostic! { $code })
+macro_rules! diagnostic_used {
+    ($code:ident) => (
+        let _ = crate::error_codes::$code;
+    )
 }
 
 #[macro_export]
 macro_rules! span_fatal {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_fatal_with_code(
             $span,
             &format!($($message)*),
@@ -19,7 +20,7 @@ macro_rules! span_fatal {
 #[macro_export]
 macro_rules! span_err {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_err_with_code(
             $span,
             &format!($($message)*),
@@ -31,7 +32,7 @@ macro_rules! span_err {
 #[macro_export]
 macro_rules! span_warn {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_warn_with_code(
             $span,
             &format!($($message)*),
@@ -43,7 +44,7 @@ macro_rules! span_warn {
 #[macro_export]
 macro_rules! struct_err {
     ($session:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_err_with_code(
             &format!($($message)*),
             $crate::errors::DiagnosticId::Error(stringify!($code).to_owned()),
@@ -54,7 +55,7 @@ macro_rules! struct_err {
 #[macro_export]
 macro_rules! span_err_or_warn {
     ($is_warning:expr, $session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         if $is_warning {
             $session.span_warn_with_code(
                 $span,
@@ -74,7 +75,7 @@ macro_rules! span_err_or_warn {
 #[macro_export]
 macro_rules! struct_span_fatal {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_fatal_with_code(
             $span,
             &format!($($message)*),
@@ -86,7 +87,7 @@ macro_rules! struct_span_fatal {
 #[macro_export]
 macro_rules! struct_span_err {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_err_with_code(
             $span,
             &format!($($message)*),
@@ -98,7 +99,7 @@ macro_rules! struct_span_err {
 #[macro_export]
 macro_rules! stringify_error_code {
     ($code:ident) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $crate::errors::DiagnosticId::Error(stringify!($code).to_owned())
     })
 }
@@ -117,7 +118,7 @@ macro_rules! type_error_struct {
 #[macro_export]
 macro_rules! struct_span_warn {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_warn_with_code(
             $span,
             &format!($($message)*),
@@ -129,7 +130,7 @@ macro_rules! struct_span_warn {
 #[macro_export]
 macro_rules! struct_span_err_or_warn {
     ($is_warning:expr, $session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         if $is_warning {
             $session.struct_span_warn_with_code(
                 $span,
@@ -169,20 +170,22 @@ macro_rules! help {
 
 #[macro_export]
 macro_rules! register_diagnostics {
-    ($($code:tt),*) => (
-        $($crate::register_diagnostic! { $code })*
+    ($($ecode:ident: $message:expr,)*) => (
+        $crate::register_diagnostics!{$($ecode:$message,)* ;}
     );
-    ($($code:tt),*,) => (
-        $($crate::register_diagnostic! { $code })*
-    )
-}
 
-#[macro_export]
-macro_rules! register_long_diagnostics {
-    ($($code:tt: $description:tt),*) => (
-        $($crate::register_diagnostic! { $code, $description })*
-    );
-    ($($code:tt: $description:tt),*,) => (
-        $($crate::register_diagnostic! { $code, $description })*
+    ($($ecode:ident: $message:expr,)* ; $($code:ident,)*) => (
+        pub static DIAGNOSTICS: &[(&str, &str)] = &[
+            $( (stringify!($ecode), $message), )*
+        ];
+
+        $(
+            #[deny(unused)]
+            pub(crate) const $ecode: &str = $message;
+        )*
+        $(
+            #[deny(unused)]
+            pub(crate) const $code: () = ();
+        )*
     )
 }
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
deleted file mode 100644
index 5de39c8d14d17..0000000000000
--- a/src/libsyntax/diagnostics/plugin.rs
+++ /dev/null
@@ -1,185 +0,0 @@
-use std::collections::BTreeMap;
-
-use crate::ast::{self, Ident, Name};
-use crate::source_map;
-use crate::ext::base::{ExtCtxt, MacEager, MacResult};
-use crate::parse::token::{self, Token};
-use crate::ptr::P;
-use crate::symbol::kw;
-use crate::tokenstream::{TokenTree, TokenStream};
-
-use smallvec::smallvec;
-use syntax_pos::Span;
-
-pub use errors::*;
-
-// Maximum width of any line in an extended error description (inclusive).
-const MAX_DESCRIPTION_WIDTH: usize = 80;
-
-/// Error information type.
-pub struct ErrorInfo {
-    pub description: Option<Name>,
-    pub use_site: Option<Span>
-}
-
-/// Mapping from error codes to metadata.
-pub type ErrorMap = BTreeMap<Name, ErrorInfo>;
-
-pub fn expand_diagnostic_used<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                   span: Span,
-                                   tts: TokenStream)
-                                   -> Box<dyn MacResult+'cx> {
-    assert_eq!(tts.len(), 1);
-    let code = match tts.into_trees().next() {
-        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
-        _ => unreachable!()
-    };
-
-    ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-        match diagnostics.get_mut(&code) {
-            // Previously used errors.
-            Some(&mut ErrorInfo { description: _, use_site: Some(previous_span) }) => {
-                ecx.struct_span_warn(span, &format!(
-                    "diagnostic code {} already used", code
-                )).span_note(previous_span, "previous invocation")
-                  .emit();
-            }
-            // Newly used errors.
-            Some(ref mut info) => {
-                info.use_site = Some(span);
-            }
-            // Unregistered errors.
-            None => {
-                ecx.span_err(span, &format!(
-                    "used diagnostic code {} not registered", code
-                ));
-            }
-        }
-    });
-    MacEager::expr(ecx.expr_tuple(span, Vec::new()))
-}
-
-pub fn expand_register_diagnostic<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                       span: Span,
-                                       tts: TokenStream)
-                                       -> Box<dyn MacResult+'cx> {
-    assert!(tts.len() == 1 || tts.len() == 3);
-    let mut cursor = tts.into_trees();
-    let code = match cursor.next() {
-        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
-        _ => unreachable!()
-    };
-    let description = match  (cursor.next(), cursor.next()) {
-        (None, None) => None,
-        (
-            Some(TokenTree::Token(Token { kind: token::Comma, .. })),
-            Some(TokenTree::Token(Token { kind: token::Literal(token::Lit { symbol, .. }), ..}))
-        ) => {
-            Some(symbol)
-        },
-        _ => unreachable!()
-    };
-
-    // Check that the description starts and ends with a newline and doesn't
-    // overflow the maximum line width.
-    description.map(|raw_msg| {
-        let msg = raw_msg.as_str();
-        if !msg.starts_with("\n") || !msg.ends_with("\n") {
-            ecx.span_err(span, &format!(
-                "description for error code {} doesn't start and end with a newline",
-                code
-            ));
-        }
-
-        // URLs can be unavoidably longer than the line limit, so we allow them.
-        // Allowed format is: `[name]: https://www.rust-lang.org/`
-        let is_url = |l: &str| l.starts_with("[") && l.contains("]:") && l.contains("http");
-
-        if msg.lines().any(|line| line.len() > MAX_DESCRIPTION_WIDTH && !is_url(line)) {
-            ecx.span_err(span, &format!(
-                "description for error code {} contains a line longer than {} characters.\n\
-                 if you're inserting a long URL use the footnote style to bypass this check.",
-                code, MAX_DESCRIPTION_WIDTH
-            ));
-        }
-    });
-    // Add the error to the map.
-    ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-        let info = ErrorInfo {
-            description,
-            use_site: None
-        };
-        if diagnostics.insert(code, info).is_some() {
-            ecx.span_err(span, &format!(
-                "diagnostic code {} already registered", code
-            ));
-        }
-    });
-
-    MacEager::items(smallvec![])
-}
-
-pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                          span: Span,
-                                          tts: TokenStream)
-                                          -> Box<dyn MacResult+'cx> {
-    assert_eq!(tts.len(), 3);
-    let ident = match tts.into_trees().nth(2) {
-        // DIAGNOSTICS ident.
-        Some(TokenTree::Token(Token { kind: token::Ident(name, _), span }))
-        => Ident::new(name, span),
-        _ => unreachable!()
-    };
-
-    // Construct the output expression.
-    let (count, expr) =
-        ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-            let descriptions: Vec<P<ast::Expr>> =
-                diagnostics.iter().filter_map(|(&code, info)| {
-                    info.description.map(|description| {
-                        ecx.expr_tuple(span, vec![
-                            ecx.expr_str(span, code),
-                            ecx.expr_str(span, description)
-                        ])
-                    })
-                }).collect();
-            (descriptions.len(), ecx.expr_vec(span, descriptions))
-        });
-
-    let static_ = ecx.lifetime(span, Ident::with_dummy_span(kw::StaticLifetime));
-    let ty_str = ecx.ty_rptr(
-        span,
-        ecx.ty_ident(span, ecx.ident_of("str")),
-        Some(static_),
-        ast::Mutability::Immutable,
-    );
-
-    let ty = ecx.ty(
-        span,
-        ast::TyKind::Array(
-            ecx.ty(
-                span,
-                ast::TyKind::Tup(vec![ty_str.clone(), ty_str])
-            ),
-            ast::AnonConst {
-                id: ast::DUMMY_NODE_ID,
-                value: ecx.expr_usize(span, count),
-            },
-        ),
-    );
-
-    MacEager::items(smallvec![
-        P(ast::Item {
-            ident,
-            attrs: Vec::new(),
-            id: ast::DUMMY_NODE_ID,
-            node: ast::ItemKind::Const(
-                ty,
-                expr,
-            ),
-            vis: source_map::respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
-            span,
-            tokens: None,
-        })
-    ])
-}
diff --git a/src/libsyntax/error_codes.rs b/src/libsyntax/error_codes.rs
index 1ba29011f75a4..9925dd8ada0d5 100644
--- a/src/libsyntax/error_codes.rs
+++ b/src/libsyntax/error_codes.rs
@@ -1,7 +1,8 @@
 // Error messages for EXXXX errors.
-// Each message should start and end with a new line, and be wrapped to 80 characters.
-// In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
-register_long_diagnostics! {
+// Each message should start and end with a new line, and be wrapped to 80
+// characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use
+// `:set tw=0` to disable.
+register_diagnostics! {
 
 E0178: r##"
 In types, the `+` type operator has low precedence, so it is often necessary
@@ -420,9 +421,8 @@ Delete the offending feature attribute, or add it to the list of allowed
 features in the `-Z allow_features` flag.
 "##,
 
-}
+;
 
-register_diagnostics! {
     E0539, // incorrect meta item
     E0540, // multiple rustc_deprecated attributes
     E0542, // missing 'since'
@@ -432,7 +432,9 @@ register_diagnostics! {
     E0546, // missing 'feature'
     E0547, // missing 'issue'
 //  E0548, // replaced with a generic attribute input check
-    E0549, // rustc_deprecated attribute must be paired with either stable or unstable attribute
+    // rustc_deprecated attribute must be paired with either stable or unstable
+    // attribute
+    E0549,
     E0550, // multiple deprecated attributes
     E0551, // incorrect meta item
     E0553, // multiple rustc_const_unstable attributes
@@ -440,9 +442,11 @@ register_diagnostics! {
     E0556, // malformed feature, expected just one word
     E0584, // file for module `..` found at both .. and ..
     E0629, // missing 'feature' (rustc_const_unstable)
-    E0630, // rustc_const_unstable attribute must be paired with stable/unstable attribute
+    // rustc_const_unstable attribute must be paired with stable/unstable
+    // attribute
+    E0630,
     E0693, // incorrect `repr(align)` attribute format
-    E0694, // an unknown tool name found in scoped attributes
+//  E0694, // an unknown tool name found in scoped attributes
     E0703, // invalid ABI
     E0717, // rustc_promotable without stability attribute
 }
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 109ba041016c6..384c0555c85bd 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -3,7 +3,7 @@ use crate::attr::{self, HasAttrs, Stability, Deprecation};
 use crate::source_map::SourceMap;
 use crate::edition::Edition;
 use crate::ext::expand::{self, AstFragment, Invocation};
-use crate::ext::hygiene::{ExpnId, Transparency};
+use crate::ext::hygiene::ExpnId;
 use crate::mut_visit::{self, MutVisitor};
 use crate::parse::{self, parser, ParseSess, DirectoryOwnership};
 use crate::parse::token;
@@ -16,7 +16,7 @@ use crate::visit::Visitor;
 use errors::{DiagnosticBuilder, DiagnosticId};
 use smallvec::{smallvec, SmallVec};
 use syntax_pos::{FileName, Span, MultiSpan, DUMMY_SP};
-use syntax_pos::hygiene::{ExpnData, ExpnKind};
+use syntax_pos::hygiene::{AstPass, ExpnData, ExpnKind};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
@@ -35,6 +35,13 @@ pub enum Annotatable {
     ForeignItem(P<ast::ForeignItem>),
     Stmt(P<ast::Stmt>),
     Expr(P<ast::Expr>),
+    Arm(ast::Arm),
+    Field(ast::Field),
+    FieldPat(ast::FieldPat),
+    GenericParam(ast::GenericParam),
+    Param(ast::Param),
+    StructField(ast::StructField),
+    Variant(ast::Variant),
 }
 
 impl HasAttrs for Annotatable {
@@ -46,6 +53,13 @@ impl HasAttrs for Annotatable {
             Annotatable::ForeignItem(ref foreign_item) => &foreign_item.attrs,
             Annotatable::Stmt(ref stmt) => stmt.attrs(),
             Annotatable::Expr(ref expr) => &expr.attrs,
+            Annotatable::Arm(ref arm) => &arm.attrs,
+            Annotatable::Field(ref field) => &field.attrs,
+            Annotatable::FieldPat(ref fp) => &fp.attrs,
+            Annotatable::GenericParam(ref gp) => &gp.attrs,
+            Annotatable::Param(ref p) => &p.attrs,
+            Annotatable::StructField(ref sf) => &sf.attrs,
+            Annotatable::Variant(ref v) => &v.attrs(),
         }
     }
 
@@ -57,6 +71,13 @@ impl HasAttrs for Annotatable {
             Annotatable::ForeignItem(foreign_item) => foreign_item.visit_attrs(f),
             Annotatable::Stmt(stmt) => stmt.visit_attrs(f),
             Annotatable::Expr(expr) => expr.visit_attrs(f),
+            Annotatable::Arm(arm) => arm.visit_attrs(f),
+            Annotatable::Field(field) => field.visit_attrs(f),
+            Annotatable::FieldPat(fp) => fp.visit_attrs(f),
+            Annotatable::GenericParam(gp) => gp.visit_attrs(f),
+            Annotatable::Param(p) => p.visit_attrs(f),
+            Annotatable::StructField(sf) => sf.visit_attrs(f),
+            Annotatable::Variant(v) => v.visit_attrs(f),
         }
     }
 }
@@ -70,6 +91,13 @@ impl Annotatable {
             Annotatable::ForeignItem(ref foreign_item) => foreign_item.span,
             Annotatable::Stmt(ref stmt) => stmt.span,
             Annotatable::Expr(ref expr) => expr.span,
+            Annotatable::Arm(ref arm) => arm.span,
+            Annotatable::Field(ref field) => field.span,
+            Annotatable::FieldPat(ref fp) => fp.pat.span,
+            Annotatable::GenericParam(ref gp) => gp.ident.span,
+            Annotatable::Param(ref p) => p.span,
+            Annotatable::StructField(ref sf) => sf.span,
+            Annotatable::Variant(ref v) => v.span,
         }
     }
 
@@ -81,6 +109,13 @@ impl Annotatable {
             Annotatable::ForeignItem(foreign_item) => visitor.visit_foreign_item(foreign_item),
             Annotatable::Stmt(stmt) => visitor.visit_stmt(stmt),
             Annotatable::Expr(expr) => visitor.visit_expr(expr),
+            Annotatable::Arm(arm) => visitor.visit_arm(arm),
+            Annotatable::Field(field) => visitor.visit_field(field),
+            Annotatable::FieldPat(fp) => visitor.visit_field_pattern(fp),
+            Annotatable::GenericParam(gp) => visitor.visit_generic_param(gp),
+            Annotatable::Param(p) => visitor.visit_param(p),
+            Annotatable::StructField(sf) =>visitor.visit_struct_field(sf),
+            Annotatable::Variant(v) => visitor.visit_variant(v),
         }
     }
 
@@ -136,6 +171,55 @@ impl Annotatable {
         }
     }
 
+    pub fn expect_arm(self) -> ast::Arm {
+        match self {
+            Annotatable::Arm(arm) => arm,
+            _ => panic!("expected match arm")
+        }
+    }
+
+    pub fn expect_field(self) -> ast::Field {
+        match self {
+            Annotatable::Field(field) => field,
+            _ => panic!("expected field")
+        }
+    }
+
+    pub fn expect_field_pattern(self) -> ast::FieldPat {
+        match self {
+            Annotatable::FieldPat(fp) => fp,
+            _ => panic!("expected field pattern")
+        }
+    }
+
+    pub fn expect_generic_param(self) -> ast::GenericParam {
+        match self {
+            Annotatable::GenericParam(gp) => gp,
+            _ => panic!("expected generic parameter")
+        }
+    }
+
+    pub fn expect_param(self) -> ast::Param {
+        match self {
+            Annotatable::Param(param) => param,
+            _ => panic!("expected parameter")
+        }
+    }
+
+    pub fn expect_struct_field(self) -> ast::StructField {
+        match self {
+            Annotatable::StructField(sf) => sf,
+            _ => panic!("expected struct field")
+        }
+    }
+
+    pub fn expect_variant(self) -> ast::Variant {
+        match self {
+            Annotatable::Variant(v) => v,
+            _ => panic!("expected variant")
+        }
+    }
+
     pub fn derive_allowed(&self) -> bool {
         match *self {
             Annotatable::Item(ref item) => match item.node {
@@ -325,6 +409,34 @@ pub trait MacResult {
     fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
         None
     }
+
+    fn make_arms(self: Box<Self>) -> Option<SmallVec<[ast::Arm; 1]>> {
+        None
+    }
+
+    fn make_fields(self: Box<Self>) -> Option<SmallVec<[ast::Field; 1]>> {
+        None
+    }
+
+    fn make_field_patterns(self: Box<Self>) -> Option<SmallVec<[ast::FieldPat; 1]>> {
+        None
+    }
+
+    fn make_generic_params(self: Box<Self>) -> Option<SmallVec<[ast::GenericParam; 1]>> {
+        None
+    }
+
+    fn make_params(self: Box<Self>) -> Option<SmallVec<[ast::Param; 1]>> {
+        None
+    }
+
+    fn make_struct_fields(self: Box<Self>) -> Option<SmallVec<[ast::StructField; 1]>> {
+        None
+    }
+
+    fn make_variants(self: Box<Self>) -> Option<SmallVec<[ast::Variant; 1]>> {
+        None
+    }
 }
 
 macro_rules! make_MacEager {
@@ -498,6 +610,34 @@ impl MacResult for DummyResult {
     fn make_ty(self: Box<DummyResult>) -> Option<P<ast::Ty>> {
         Some(DummyResult::raw_ty(self.span, self.is_error))
     }
+
+    fn make_arms(self: Box<DummyResult>) -> Option<SmallVec<[ast::Arm; 1]>> {
+       Some(SmallVec::new())
+    }
+
+    fn make_fields(self: Box<DummyResult>) -> Option<SmallVec<[ast::Field; 1]>> {
+        Some(SmallVec::new())
+    }
+
+    fn make_field_patterns(self: Box<DummyResult>) -> Option<SmallVec<[ast::FieldPat; 1]>> {
+        Some(SmallVec::new())
+    }
+
+    fn make_generic_params(self: Box<DummyResult>) -> Option<SmallVec<[ast::GenericParam; 1]>> {
+        Some(SmallVec::new())
+    }
+
+    fn make_params(self: Box<DummyResult>) -> Option<SmallVec<[ast::Param; 1]>> {
+        Some(SmallVec::new())
+    }
+
+    fn make_struct_fields(self: Box<DummyResult>) -> Option<SmallVec<[ast::StructField; 1]>> {
+        Some(SmallVec::new())
+    }
+
+    fn make_variants(self: Box<DummyResult>) -> Option<SmallVec<[ast::Variant; 1]>> {
+        Some(SmallVec::new())
+    }
 }
 
 /// A syntax extension kind.
@@ -732,13 +872,19 @@ bitflags::bitflags! {
 pub trait Resolver {
     fn next_node_id(&mut self) -> NodeId;
 
-    fn get_module_scope(&mut self, id: NodeId) -> ExpnId;
-
     fn resolve_dollar_crates(&mut self);
     fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
                                             extra_placeholders: &[NodeId]);
     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension);
 
+    fn expansion_for_ast_pass(
+        &mut self,
+        call_site: Span,
+        pass: AstPass,
+        features: &[Symbol],
+        parent_module_id: Option<NodeId>,
+    ) -> ExpnId;
+
     fn resolve_imports(&mut self);
 
     fn resolve_macro_invocation(
@@ -822,20 +968,13 @@ impl<'a> ExtCtxt<'a> {
     /// Equivalent of `Span::def_site` from the proc macro API,
     /// except that the location is taken from the span passed as an argument.
     pub fn with_def_site_ctxt(&self, span: Span) -> Span {
-        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::Opaque)
+        span.with_def_site_ctxt(self.current_expansion.id)
     }
 
     /// Equivalent of `Span::call_site` from the proc macro API,
     /// except that the location is taken from the span passed as an argument.
     pub fn with_call_site_ctxt(&self, span: Span) -> Span {
-        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::Transparent)
-    }
-
-    /// Span with a context reproducing `macro_rules` hygiene (hygienic locals, unhygienic items).
-    /// FIXME: This should be eventually replaced either with `with_def_site_ctxt` (preferably),
-    /// or with `with_call_site_ctxt` (where necessary).
-    pub fn with_legacy_ctxt(&self, span: Span) -> Span {
-        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::SemiTransparent)
+        span.with_call_site_ctxt(self.current_expansion.id)
     }
 
     /// Returns span for the macro which originally caused the current expansion to happen.
@@ -935,8 +1074,8 @@ impl<'a> ExtCtxt<'a> {
     pub fn set_trace_macros(&mut self, x: bool) {
         self.ecfg.trace_mac = x
     }
-    pub fn ident_of(&self, st: &str) -> ast::Ident {
-        ast::Ident::from_str(st)
+    pub fn ident_of(&self, st: &str, sp: Span) -> ast::Ident {
+        ast::Ident::from_str_and_span(st, sp)
     }
     pub fn std_path(&self, components: &[Symbol]) -> Vec<ast::Ident> {
         let def_site = self.with_def_site_ctxt(DUMMY_SP);
@@ -952,7 +1091,7 @@ impl<'a> ExtCtxt<'a> {
         self.resolver.check_unused_macros();
     }
 
-    /// Resolve a path mentioned inside Rust code.
+    /// Resolves a path mentioned inside Rust code.
     ///
     /// This unifies the logic used for resolving `include_X!`, and `#[doc(include)]` file paths.
     ///
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index e894fd17ff587..f1d0e0b68f735 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -166,7 +166,8 @@ impl<'a> ExtCtxt<'a> {
             bounds,
             kind: ast::GenericParamKind::Type {
                 default,
-            }
+            },
+            is_placeholder: false
         }
     }
 
@@ -207,6 +208,7 @@ impl<'a> ExtCtxt<'a> {
             attrs: attrs.into(),
             bounds,
             kind: ast::GenericParamKind::Lifetime,
+            is_placeholder: false
         }
     }
 
@@ -361,7 +363,7 @@ impl<'a> ExtCtxt<'a> {
         self.expr(sp, ast::ExprKind::Field(expr, ident.with_span_pos(sp)))
     }
     pub fn expr_tup_field_access(&self, sp: Span, expr: P<ast::Expr>, idx: usize) -> P<ast::Expr> {
-        let ident = Ident::from_str(&idx.to_string()).with_span_pos(sp);
+        let ident = Ident::new(sym::integer(idx), sp);
         self.expr(sp, ast::ExprKind::Field(expr, ident))
     }
     pub fn expr_addr_of(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
@@ -404,6 +406,7 @@ impl<'a> ExtCtxt<'a> {
             is_shorthand: false,
             attrs: ThinVec::new(),
             id: ast::DUMMY_NODE_ID,
+            is_placeholder: false,
         }
     }
     pub fn expr_struct(
@@ -522,7 +525,7 @@ impl<'a> ExtCtxt<'a> {
         let err = self.std_path(&[sym::result, sym::Result, sym::Err]);
         let err_path = self.path_global(sp, err);
 
-        let binding_variable = self.ident_of("__try_var");
+        let binding_variable = self.ident_of("__try_var", sp);
         let binding_pat = self.pat_ident(sp, binding_variable);
         let binding_expr = self.expr_ident(sp, binding_variable);
 
@@ -537,9 +540,9 @@ impl<'a> ExtCtxt<'a> {
         let err_expr = self.expr(sp, ast::ExprKind::Ret(Some(err_inner_expr)));
 
         // `Ok(__try_var) => __try_var`
-        let ok_arm = self.arm(sp, vec![ok_pat], binding_expr);
+        let ok_arm = self.arm(sp, ok_pat, binding_expr);
         // `Err(__try_var) => return Err(__try_var)`
-        let err_arm = self.arm(sp, vec![err_pat], err_expr);
+        let err_arm = self.arm(sp, err_pat, err_expr);
 
         // `match head { Ok() => ..., Err() => ... }`
         self.expr_match(sp, head, vec![ok_arm, err_arm])
@@ -606,19 +609,20 @@ impl<'a> ExtCtxt<'a> {
         self.pat_tuple_struct(span, path, vec![pat])
     }
 
-    pub fn arm(&self, span: Span, pats: Vec<P<ast::Pat>>, expr: P<ast::Expr>) -> ast::Arm {
+    pub fn arm(&self, span: Span, pat: P<ast::Pat>, expr: P<ast::Expr>) -> ast::Arm {
         ast::Arm {
             attrs: vec![],
-            pats,
+            pat,
             guard: None,
             body: expr,
             span,
             id: ast::DUMMY_NODE_ID,
+            is_placeholder: false,
         }
     }
 
     pub fn arm_unreachable(&self, span: Span) -> ast::Arm {
-        self.arm(span, vec![self.pat_wild(span)], self.expr_unreachable(span))
+        self.arm(span, self.pat_wild(span), self.expr_unreachable(span))
     }
 
     pub fn expr_match(&self, span: Span, arg: P<ast::Expr>, arms: Vec<ast::Arm>) -> P<Expr> {
@@ -701,6 +705,7 @@ impl<'a> ExtCtxt<'a> {
             pat: arg_pat,
             span,
             ty,
+            is_placeholder: false,
         }
     }
 
@@ -774,6 +779,7 @@ impl<'a> ExtCtxt<'a> {
                 vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
                 attrs: Vec::new(),
                 id: ast::DUMMY_NODE_ID,
+                is_placeholder: false,
             }
         }).collect();
 
@@ -790,6 +796,7 @@ impl<'a> ExtCtxt<'a> {
             id: ast::DUMMY_NODE_ID,
             ident,
             span,
+            is_placeholder: false,
         }
     }
 
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 4fd0c367288bf..b80c530731dfc 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -26,7 +26,7 @@ use syntax_pos::{Span, DUMMY_SP, FileName};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use std::io::ErrorKind;
-use std::{iter, mem};
+use std::{iter, mem, slice};
 use std::ops::DerefMut;
 use std::rc::Rc;
 use std::path::PathBuf;
@@ -141,7 +141,40 @@ ast_fragments! {
         "impl item"; many fn flat_map_impl_item; fn visit_impl_item; fn make_impl_items;
     }
     ForeignItems(SmallVec<[ast::ForeignItem; 1]>) {
-        "foreign item"; many fn flat_map_foreign_item; fn visit_foreign_item; fn make_foreign_items;
+        "foreign item";
+        many fn flat_map_foreign_item;
+        fn visit_foreign_item;
+        fn make_foreign_items;
+    }
+    Arms(SmallVec<[ast::Arm; 1]>) {
+        "match arm"; many fn flat_map_arm; fn visit_arm; fn make_arms;
+    }
+    Fields(SmallVec<[ast::Field; 1]>) {
+        "field expression"; many fn flat_map_field; fn visit_field; fn make_fields;
+    }
+    FieldPats(SmallVec<[ast::FieldPat; 1]>) {
+        "field pattern";
+        many fn flat_map_field_pattern;
+        fn visit_field_pattern;
+        fn make_field_patterns;
+    }
+    GenericParams(SmallVec<[ast::GenericParam; 1]>) {
+        "generic parameter";
+        many fn flat_map_generic_param;
+        fn visit_generic_param;
+        fn make_generic_params;
+    }
+    Params(SmallVec<[ast::Param; 1]>) {
+        "function parameter"; many fn flat_map_param; fn visit_param; fn make_params;
+    }
+    StructFields(SmallVec<[ast::StructField; 1]>) {
+        "field";
+        many fn flat_map_struct_field;
+        fn visit_struct_field;
+        fn make_struct_fields;
+    }
+    Variants(SmallVec<[ast::Variant; 1]>) {
+        "variant"; many fn flat_map_variant; fn visit_variant; fn make_variants;
     }
 }
 
@@ -154,6 +187,21 @@ impl AstFragmentKind {
                                                                      -> AstFragment {
         let mut items = items.into_iter();
         match self {
+            AstFragmentKind::Arms =>
+                AstFragment::Arms(items.map(Annotatable::expect_arm).collect()),
+            AstFragmentKind::Fields =>
+                AstFragment::Fields(items.map(Annotatable::expect_field).collect()),
+            AstFragmentKind::FieldPats =>
+                AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect()),
+            AstFragmentKind::GenericParams =>
+                AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect()),
+            AstFragmentKind::Params =>
+                AstFragment::Params(items.map(Annotatable::expect_param).collect()),
+            AstFragmentKind::StructFields => AstFragment::StructFields(
+                items.map(Annotatable::expect_struct_field).collect()
+            ),
+            AstFragmentKind::Variants =>
+                AstFragment::Variants(items.map(Annotatable::expect_variant).collect()),
             AstFragmentKind::Items =>
                 AstFragment::Items(items.map(Annotatable::expect_item).collect()),
             AstFragmentKind::ImplItems =>
@@ -177,7 +225,7 @@ impl AstFragmentKind {
 
 pub struct Invocation {
     pub kind: InvocationKind,
-    fragment_kind: AstFragmentKind,
+    pub fragment_kind: AstFragmentKind,
     pub expansion_data: ExpansionData,
 }
 
@@ -482,6 +530,27 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             Annotatable::Expr(mut expr) => {
                 Annotatable::Expr({ cfg.visit_expr(&mut expr); expr })
             }
+            Annotatable::Arm(arm) => {
+                Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap())
+            }
+            Annotatable::Field(field) => {
+                Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
+            }
+            Annotatable::FieldPat(fp) => {
+                Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
+            }
+            Annotatable::GenericParam(param) => {
+                Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
+            }
+            Annotatable::Param(param) => {
+                Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
+            }
+            Annotatable::StructField(sf) => {
+                Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
+            }
+            Annotatable::Variant(v) => {
+                Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap())
+            }
         }
     }
 
@@ -547,6 +616,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
                         Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
                         Annotatable::Expr(expr) => token::NtExpr(expr),
+                        Annotatable::Arm(..)
+                        | Annotatable::Field(..)
+                        | Annotatable::FieldPat(..)
+                        | Annotatable::GenericParam(..)
+                        | Annotatable::Param(..)
+                        | Annotatable::StructField(..)
+                        | Annotatable::Variant(..)
+                            => panic!("unexpected annotatable"),
                     })), DUMMY_SP).into();
                     let input = self.extract_proc_macro_attr_input(attr.tokens, span);
                     let tok_result = expander.expand(self.cx, span, input, item_tok);
@@ -625,6 +702,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_hygiene() => return,
             Annotatable::Stmt(_) => ("statements", sym::proc_macro_hygiene),
             Annotatable::Expr(_) => ("expressions", sym::proc_macro_hygiene),
+            Annotatable::Arm(..)
+            | Annotatable::Field(..)
+            | Annotatable::FieldPat(..)
+            | Annotatable::GenericParam(..)
+            | Annotatable::Param(..)
+            | Annotatable::StructField(..)
+            | Annotatable::Variant(..)
+            => panic!("unexpected annotatable"),
         };
         emit_feature_err(
             self.cx.parse_sess,
@@ -681,6 +766,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             AstFragmentKind::TraitItems => return,
             AstFragmentKind::ImplItems => return,
             AstFragmentKind::ForeignItems => return,
+            AstFragmentKind::Arms
+            | AstFragmentKind::Fields
+            | AstFragmentKind::FieldPats
+            | AstFragmentKind::GenericParams
+            | AstFragmentKind::Params
+            | AstFragmentKind::StructFields
+            | AstFragmentKind::Variants
+                => panic!("unexpected AST fragment kind"),
         };
         if self.cx.ecfg.proc_macro_hygiene() {
             return
@@ -771,6 +864,14 @@ impl<'a> Parser<'a> {
             },
             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat(None)?),
+            AstFragmentKind::Arms
+            | AstFragmentKind::Fields
+            | AstFragmentKind::FieldPats
+            | AstFragmentKind::GenericParams
+            | AstFragmentKind::Params
+            | AstFragmentKind::StructFields
+            | AstFragmentKind::Variants
+                => panic!("unexpected AST fragment kind"),
         })
     }
 
@@ -918,7 +1019,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
         let features = self.cx.ecfg.features.unwrap();
         for attr in attrs.iter() {
-            self.check_attribute_inner(attr, features);
+            feature_gate::check_attribute(attr, self.cx.parse_sess, features);
 
             // macros are expanded before any lint passes so this warning has to be hardcoded
             if attr.path == sym::derive {
@@ -928,15 +1029,6 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
             }
         }
     }
-
-    fn check_attribute(&mut self, at: &ast::Attribute) {
-        let features = self.cx.ecfg.features.unwrap();
-        self.check_attribute_inner(at, features);
-    }
-
-    fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
-        feature_gate::check_attribute(at, self.cx.parse_sess, features);
-    }
 }
 
 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
@@ -972,6 +1064,84 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         });
     }
 
+    fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
+        let mut arm = configure!(self, arm);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut arm);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::Arm(arm),
+                                     AstFragmentKind::Arms, after_derive)
+                                     .make_arms();
+        }
+
+        noop_flat_map_arm(arm, self)
+    }
+
+    fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
+        let mut field = configure!(self, field);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut field);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::Field(field),
+                                     AstFragmentKind::Fields, after_derive)
+                                     .make_fields();
+        }
+
+        noop_flat_map_field(field, self)
+    }
+
+    fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
+        let mut fp = configure!(self, fp);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut fp);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::FieldPat(fp),
+                                     AstFragmentKind::FieldPats, after_derive)
+                                     .make_field_patterns();
+        }
+
+        noop_flat_map_field_pattern(fp, self)
+    }
+
+    fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
+        let mut p = configure!(self, p);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut p);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::Param(p),
+                                     AstFragmentKind::Params, after_derive)
+                                     .make_params();
+        }
+
+        noop_flat_map_param(p, self)
+    }
+
+    fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
+        let mut sf = configure!(self, sf);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut sf);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::StructField(sf),
+                                     AstFragmentKind::StructFields, after_derive)
+                                     .make_struct_fields();
+        }
+
+        noop_flat_map_struct_field(sf, self)
+    }
+
+    fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
+        let mut variant = configure!(self, variant);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut variant);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::Variant(variant),
+                                     AstFragmentKind::Variants, after_derive)
+                                     .make_variants();
+        }
+
+        noop_flat_map_variant(variant, self)
+    }
+
     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
         let expr = configure!(self, expr);
         expr.filter_map(|mut expr| {
@@ -1227,12 +1397,20 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         }
     }
 
-   fn flat_map_generic_param(
-       &mut self,
-       param: ast::GenericParam
+    fn flat_map_generic_param(
+        &mut self,
+        param: ast::GenericParam
     ) -> SmallVec<[ast::GenericParam; 1]>
     {
-        let param = configure!(self, param);
+        let mut param = configure!(self, param);
+
+        let (attr, traits, after_derive) = self.classify_item(&mut param);
+        if attr.is_some() || !traits.is_empty() {
+            return self.collect_attr(attr, traits, Annotatable::GenericParam(param),
+                                     AstFragmentKind::GenericParams, after_derive)
+                                     .make_generic_params();
+        }
+
         noop_flat_map_generic_param(param, self)
     }
 
@@ -1258,7 +1436,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
 
                 if let Some(file) = it.value_str() {
                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
-                    self.check_attribute(&at);
+                    self.check_attributes(slice::from_ref(at));
                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
                         // avoid loading the file if they haven't enabled the feature
                         return noop_visit_attribute(at, self);
diff --git a/src/libsyntax/ext/placeholders.rs b/src/libsyntax/ext/placeholders.rs
index d800cfedcfb4b..52a0f95bce7ff 100644
--- a/src/libsyntax/ext/placeholders.rs
+++ b/src/libsyntax/ext/placeholders.rs
@@ -32,6 +32,16 @@ pub fn placeholder(kind: AstFragmentKind, id: ast::NodeId) -> AstFragment {
         attrs: ThinVec::new(),
         node: ast::ExprKind::Mac(mac_placeholder()),
     });
+    let ty = P(ast::Ty {
+        id,
+        node: ast::TyKind::Mac(mac_placeholder()),
+        span,
+    });
+    let pat = P(ast::Pat {
+        id,
+        node: ast::PatKind::Mac(mac_placeholder()),
+        span,
+    });
 
     match kind {
         AstFragmentKind::Expr => AstFragment::Expr(expr_placeholder()),
@@ -67,6 +77,81 @@ pub fn placeholder(kind: AstFragmentKind, id: ast::NodeId) -> AstFragment {
             let mac = P((mac_placeholder(), ast::MacStmtStyle::Braces, ThinVec::new()));
             ast::Stmt { id, span, node: ast::StmtKind::Mac(mac) }
         }]),
+        AstFragmentKind::Arms => AstFragment::Arms(smallvec![
+            ast::Arm {
+                attrs: Default::default(),
+                body: expr_placeholder(),
+                guard: None,
+                id,
+                pat,
+                span,
+                is_placeholder: true,
+            }
+        ]),
+        AstFragmentKind::Fields => AstFragment::Fields(smallvec![
+            ast::Field {
+                attrs: Default::default(),
+                expr: expr_placeholder(),
+                id,
+                ident,
+                is_shorthand: false,
+                span,
+                is_placeholder: true,
+            }
+        ]),
+        AstFragmentKind::FieldPats => AstFragment::FieldPats(smallvec![
+            ast::FieldPat {
+                attrs: Default::default(),
+                id,
+                ident,
+                is_shorthand: false,
+                pat,
+                span,
+                is_placeholder: true,
+            }
+        ]),
+        AstFragmentKind::GenericParams => AstFragment::GenericParams(smallvec![{
+            ast::GenericParam {
+                attrs: Default::default(),
+                bounds: Default::default(),
+                id,
+                ident,
+                is_placeholder: true,
+                kind: ast::GenericParamKind::Lifetime,
+            }
+        }]),
+        AstFragmentKind::Params => AstFragment::Params(smallvec![
+            ast::Param {
+                attrs: Default::default(),
+                id,
+                pat,
+                span,
+                ty,
+                is_placeholder: true,
+            }
+        ]),
+        AstFragmentKind::StructFields => AstFragment::StructFields(smallvec![
+            ast::StructField {
+                attrs: Default::default(),
+                id,
+                ident: None,
+                span,
+                ty,
+                vis,
+                is_placeholder: true,
+            }
+        ]),
+        AstFragmentKind::Variants => AstFragment::Variants(smallvec![
+            ast::Variant {
+                attrs: Default::default(),
+                data: ast::VariantData::Struct(Default::default(), false),
+                disr_expr: None,
+                id,
+                ident,
+                span,
+                is_placeholder: true,
+            }
+        ])
     }
 }
 
@@ -105,6 +190,66 @@ impl<'a, 'b> PlaceholderExpander<'a, 'b> {
 }
 
 impl<'a, 'b> MutVisitor for PlaceholderExpander<'a, 'b> {
+    fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
+        if arm.is_placeholder {
+            self.remove(arm.id).make_arms()
+        } else {
+            noop_flat_map_arm(arm, self)
+        }
+    }
+
+    fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
+        if field.is_placeholder {
+            self.remove(field.id).make_fields()
+        } else {
+            noop_flat_map_field(field, self)
+        }
+    }
+
+    fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
+        if fp.is_placeholder {
+            self.remove(fp.id).make_field_patterns()
+        } else {
+            noop_flat_map_field_pattern(fp, self)
+        }
+    }
+
+    fn flat_map_generic_param(
+        &mut self,
+        param: ast::GenericParam
+    ) -> SmallVec<[ast::GenericParam; 1]>
+    {
+        if param.is_placeholder {
+            self.remove(param.id).make_generic_params()
+        } else {
+            noop_flat_map_generic_param(param, self)
+        }
+    }
+
+    fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
+        if p.is_placeholder {
+            self.remove(p.id).make_params()
+        } else {
+            noop_flat_map_param(p, self)
+        }
+    }
+
+    fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
+        if sf.is_placeholder {
+            self.remove(sf.id).make_struct_fields()
+        } else {
+            noop_flat_map_struct_field(sf, self)
+        }
+    }
+
+    fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
+        if variant.is_placeholder {
+            self.remove(variant.id).make_variants()
+        } else {
+            noop_flat_map_variant(variant, self)
+        }
+    }
+
     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
         match item.node {
             ast::ItemKind::Mac(_) => return self.remove(item.id).make_items(),
diff --git a/src/libsyntax/ext/proc_macro.rs b/src/libsyntax/ext/proc_macro.rs
index 4a44c9a9f1f31..47b17ced8163e 100644
--- a/src/libsyntax/ext/proc_macro.rs
+++ b/src/libsyntax/ext/proc_macro.rs
@@ -88,6 +88,14 @@ impl MultiItemModifier for ProcMacroDerive {
               item: Annotatable)
               -> Vec<Annotatable> {
         let item = match item {
+            Annotatable::Arm(..) |
+            Annotatable::Field(..) |
+            Annotatable::FieldPat(..) |
+            Annotatable::GenericParam(..) |
+            Annotatable::Param(..) |
+            Annotatable::StructField(..) |
+            Annotatable::Variant(..)
+                => panic!("unexpected annotatable"),
             Annotatable::Item(item) => item,
             Annotatable::ImplItem(_) |
             Annotatable::TraitItem(_) |
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 46ffa52f7f572..b27e9c543377a 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -877,9 +877,9 @@ fn check_matcher_core(
         // Now `last` holds the complete set of NT tokens that could
         // end the sequence before SUFFIX. Check that every one works with `suffix`.
         'each_last: for token in &last.tokens {
-            if let TokenTree::MetaVarDecl(_, ref name, ref frag_spec) = *token {
+            if let TokenTree::MetaVarDecl(_, name, frag_spec) = *token {
                 for next_token in &suffix_first.tokens {
-                    match is_in_follow(next_token, &frag_spec.as_str()) {
+                    match is_in_follow(next_token, frag_spec.name) {
                         IsInFollow::Invalid(msg, help) => {
                             sess.span_diagnostic
                                 .struct_span_err(next_token.span(), &msg)
@@ -948,7 +948,7 @@ fn check_matcher_core(
 
 fn token_can_be_followed_by_any(tok: &quoted::TokenTree) -> bool {
     if let quoted::TokenTree::MetaVarDecl(_, _, frag_spec) = *tok {
-        frag_can_be_followed_by_any(&frag_spec.as_str())
+        frag_can_be_followed_by_any(frag_spec.name)
     } else {
         // (Non NT's can always be followed by anthing in matchers.)
         true
@@ -963,15 +963,15 @@ fn token_can_be_followed_by_any(tok: &quoted::TokenTree) -> bool {
 /// specifier which consumes at most one token tree can be followed by
 /// a fragment specifier (indeed, these fragments can be followed by
 /// ANYTHING without fear of future compatibility hazards).
-fn frag_can_be_followed_by_any(frag: &str) -> bool {
+fn frag_can_be_followed_by_any(frag: Symbol) -> bool {
     match frag {
-        "item"     | // always terminated by `}` or `;`
-        "block"    | // exactly one token tree
-        "ident"    | // exactly one token tree
-        "literal"  | // exactly one token tree
-        "meta"     | // exactly one token tree
-        "lifetime" | // exactly one token tree
-        "tt" =>   // exactly one token tree
+        sym::item     | // always terminated by `}` or `;`
+        sym::block    | // exactly one token tree
+        sym::ident    | // exactly one token tree
+        sym::literal  | // exactly one token tree
+        sym::meta     | // exactly one token tree
+        sym::lifetime | // exactly one token tree
+        sym::tt =>   // exactly one token tree
             true,
 
         _ =>
@@ -993,7 +993,7 @@ enum IsInFollow {
 /// break macros that were relying on that binary operator as a
 /// separator.
 // when changing this do not forget to update doc/book/macros.md!
-fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
+fn is_in_follow(tok: &quoted::TokenTree, frag: Symbol) -> IsInFollow {
     use quoted::TokenTree;
 
     if let TokenTree::Token(Token { kind: token::CloseDelim(_), .. }) = *tok {
@@ -1002,17 +1002,17 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
         IsInFollow::Yes
     } else {
         match frag {
-            "item" => {
+            sym::item => {
                 // since items *must* be followed by either a `;` or a `}`, we can
                 // accept anything after them
                 IsInFollow::Yes
             }
-            "block" => {
+            sym::block => {
                 // anything can follow block, the braces provide an easy boundary to
                 // maintain
                 IsInFollow::Yes
             }
-            "stmt" | "expr" => {
+            sym::stmt | sym::expr => {
                 const TOKENS: &[&str] = &["`=>`", "`,`", "`;`"];
                 match tok {
                     TokenTree::Token(token) => match token.kind {
@@ -1022,7 +1022,7 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                     _ => IsInFollow::No(TOKENS),
                 }
             }
-            "pat" => {
+            sym::pat => {
                 const TOKENS: &[&str] = &["`=>`", "`,`", "`=`", "`|`", "`if`", "`in`"];
                 match tok {
                     TokenTree::Token(token) => match token.kind {
@@ -1033,7 +1033,7 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                     _ => IsInFollow::No(TOKENS),
                 }
             }
-            "path" | "ty" => {
+            sym::path | sym::ty => {
                 const TOKENS: &[&str] = &[
                     "`{`", "`[`", "`=>`", "`,`", "`>`", "`=`", "`:`", "`;`", "`|`", "`as`",
                     "`where`",
@@ -1061,20 +1061,20 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                     _ => IsInFollow::No(TOKENS),
                 }
             }
-            "ident" | "lifetime" => {
+            sym::ident | sym::lifetime => {
                 // being a single token, idents and lifetimes are harmless
                 IsInFollow::Yes
             }
-            "literal" => {
+            sym::literal => {
                 // literals may be of a single token, or two tokens (negative numbers)
                 IsInFollow::Yes
             }
-            "meta" | "tt" => {
+            sym::meta | sym::tt => {
                 // being either a single token or a delimited sequence, tt is
                 // harmless
                 IsInFollow::Yes
             }
-            "vis" => {
+            sym::vis => {
                 // Explicitly disallow `priv`, on the off chance it comes back.
                 const TOKENS: &[&str] = &["`,`", "an ident", "a type"];
                 match tok {
@@ -1099,7 +1099,7 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                     _ => IsInFollow::No(TOKENS),
                 }
             }
-            "" => IsInFollow::Yes, // kw::Invalid
+            kw::Invalid => IsInFollow::Yes,
             _ => IsInFollow::Invalid(
                 format!("invalid fragment specifier `{}`", frag),
                 VALID_FRAGMENT_NAMES_MSG,
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 30d5df13dcedb..23735727fe8cf 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -345,8 +345,13 @@ impl LockstepIterSize {
                 LockstepIterSize::Constraint(r_len, _) if l_len == r_len => self,
                 LockstepIterSize::Constraint(r_len, r_id) => {
                     let msg = format!(
-                        "meta-variable `{}` repeats {} times, but `{}` repeats {} times",
-                        l_id, l_len, r_id, r_len
+                        "meta-variable `{}` repeats {} time{}, but `{}` repeats {} time{}",
+                        l_id,
+                        l_len,
+                        if l_len != 1 { "s" } else { "" },
+                        r_id,
+                        r_len,
+                        if r_len != 1 { "s" } else { "" },
                     );
                     LockstepIterSize::Contradiction(msg)
                 }
diff --git a/src/libsyntax/feature_gate/accepted.rs b/src/libsyntax/feature_gate/accepted.rs
index 6c0b271c6c5e9..eff9f90a8619e 100644
--- a/src/libsyntax/feature_gate/accepted.rs
+++ b/src/libsyntax/feature_gate/accepted.rs
@@ -241,6 +241,8 @@ declare_features! (
     (accepted, underscore_const_names, "1.37.0", Some(54912), None),
     /// Allows free and inherent `async fn`s, `async` blocks, and `<expr>.await` expressions.
     (accepted, async_await, "1.39.0", Some(50547), None),
+    /// Allows mixing bind-by-move in patterns and references to those identifiers in guards.
+    (accepted, bind_by_move_pattern_guards, "1.39.0", Some(15287), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features
diff --git a/src/libsyntax/feature_gate/active.rs b/src/libsyntax/feature_gate/active.rs
index c947b09fdcb57..dd78777b56986 100644
--- a/src/libsyntax/feature_gate/active.rs
+++ b/src/libsyntax/feature_gate/active.rs
@@ -1,9 +1,11 @@
 //! List of the active feature gates.
 
+use super::{State, Feature};
+
 use crate::edition::Edition;
 use crate::symbol::{Symbol, sym};
+
 use syntax_pos::Span;
-use super::{State, Feature};
 
 macro_rules! set {
     ($field: ident) => {{
@@ -37,9 +39,9 @@ macro_rules! declare_features {
         /// A set of features to be used by later passes.
         #[derive(Clone)]
         pub struct Features {
-            /// `#![feature]` attrs for language features, for error reporting
+            /// `#![feature]` attrs for language features, for error reporting.
             pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
-            /// `#![feature]` attrs for non-language (library) features
+            /// `#![feature]` attrs for non-language (library) features.
             pub declared_lib_features: Vec<(Symbol, Span)>,
             $(
                 $(#[doc = $doc])*
@@ -66,11 +68,11 @@ macro_rules! declare_features {
 }
 
 impl Feature {
-    /// Set this feature in `Features`. Panics if called on a non-active feature.
+    /// Sets this feature in `Features`. Panics if called on a non-active feature.
     pub fn set(&self, features: &mut Features, span: Span) {
         match self.state {
             State::Active { set } => set(features, span),
-            _ => panic!("Called `set` on feature `{}` which is not `active`", self.name)
+            _ => panic!("called `set` on feature `{}` which is not `active`", self.name)
         }
     }
 }
@@ -120,12 +122,6 @@ declare_features! (
     /// macros disappear).
     (active, allow_internal_unsafe, "1.0.0", None, None),
 
-    /// Allows using the macros:
-    /// + `__diagnostic_used`
-    /// + `__register_diagnostic`
-    /// +`__build_diagnostic_array`
-    (active, rustc_diagnostic_macros, "1.0.0", None, None),
-
     /// Allows using `#[rustc_const_unstable(feature = "foo", ..)]` which
     /// lets a function to be `const` when opted into with `#![feature(foo)]`.
     (active, rustc_const_unstable, "1.0.0", None, None),
@@ -465,9 +461,6 @@ declare_features! (
     /// Allows non-builtin attributes in inner attribute position.
     (active, custom_inner_attributes, "1.30.0", Some(54726), None),
 
-    /// Allows mixing bind-by-move in patterns and references to those identifiers in guards.
-    (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
-
     /// Allows `impl Trait` in bindings (`let`, `const`, `static`).
     (active, impl_trait_in_bindings, "1.30.0", Some(63065), None),
 
@@ -478,7 +471,7 @@ declare_features! (
     (active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
 
     /// Allows relaxing the coherence rules such that
-    /// `impl<T> ForeignTrait<LocalType> for ForeignType<T> is permitted.
+    /// `impl<T> ForeignTrait<LocalType> for ForeignType<T>` is permitted.
     (active, re_rebalance_coherence, "1.32.0", Some(55437), None),
 
     /// Allows using `#[ffi_returns_twice]` on foreign functions.
@@ -520,7 +513,7 @@ declare_features! (
     /// Allows `async || body` closures.
     (active, async_closure, "1.37.0", Some(62290), None),
 
-    /// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests
+    /// Allows the use of `#[cfg(doctest)]`; set when rustdoc is collecting doctests.
     (active, cfg_doctest, "1.37.0", Some(62210), None),
 
     /// Allows `[x; N]` where `x` is a constant (RFC 2203).
@@ -529,7 +522,7 @@ declare_features! (
     /// Allows `impl Trait` to be used inside type aliases (RFC 2515).
     (active, type_alias_impl_trait, "1.38.0", Some(63063), None),
 
-    /// Allows the use of or-patterns, e.g. `0 | 1`.
+    /// Allows the use of or-patterns (e.g., `0 | 1`).
     (active, or_patterns, "1.38.0", Some(54883), None),
 
     // -------------------------------------------------------------------------
diff --git a/src/libsyntax/feature_gate/builtin_attrs.rs b/src/libsyntax/feature_gate/builtin_attrs.rs
index ee7ac3b15d955..b6e13200f32af 100644
--- a/src/libsyntax/feature_gate/builtin_attrs.rs
+++ b/src/libsyntax/feature_gate/builtin_attrs.rs
@@ -79,6 +79,7 @@ pub enum AttributeType {
     CrateLevel,
 }
 
+#[derive(Clone, Copy)]
 pub enum AttributeGate {
     /// Is gated by a given feature gate, reason
     /// and function to check if enabled
@@ -169,7 +170,7 @@ const INTERAL_UNSTABLE: &str = "this is an internal attribute that will never be
 
 pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
 
-/// Attributes that have a special meaning to rustc or rustdoc
+/// Attributes that have a special meaning to rustc or rustdoc.
 pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     // ==========================================================================
     // Stable attributes:
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index f3a9d135125ae..b4491a87f0600 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -1,7 +1,7 @@
 use super::{active::{ACTIVE_FEATURES, Features}, Feature, State as FeatureState};
 use super::accepted::ACCEPTED_FEATURES;
 use super::removed::{REMOVED_FEATURES, STABLE_REMOVED_FEATURES};
-use super::builtin_attrs::{AttributeGate, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
+use super::builtin_attrs::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
 
 use crate::ast::{
     self, AssocTyConstraint, AssocTyConstraintKind, NodeId, GenericParam, GenericParamKind,
@@ -32,16 +32,10 @@ pub enum Stability {
     Deprecated(&'static str, Option<&'static str>),
 }
 
-struct Context<'a> {
-    features: &'a Features,
-    parse_sess: &'a ParseSess,
-    plugin_attributes: &'a [(Symbol, AttributeType)],
-}
-
 macro_rules! gate_feature_fn {
     ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
         let (cx, has_feature, span,
-             name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
+             name, explain, level) = (&*$cx, $has_feature, $span, $name, $explain, $level);
         let has_feature: bool = has_feature(&$cx.features);
         debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
         if !has_feature && !span.allows_unstable($name) {
@@ -62,68 +56,8 @@ macro_rules! gate_feature {
     };
 }
 
-impl<'a> Context<'a> {
-    fn check_attribute(
-        &self,
-        attr: &ast::Attribute,
-        attr_info: Option<&BuiltinAttribute>,
-        is_macro: bool
-    ) {
-        debug!("check_attribute(attr = {:?})", attr);
-        if let Some(&(name, ty, _template, ref gateage)) = attr_info {
-            if let AttributeGate::Gated(_, name, desc, ref has_feature) = *gateage {
-                if !attr.span.allows_unstable(name) {
-                    gate_feature_fn!(
-                        self, has_feature, attr.span, name, desc, GateStrength::Hard
-                    );
-                }
-            } else if name == sym::doc {
-                if let Some(content) = attr.meta_item_list() {
-                    if content.iter().any(|c| c.check_name(sym::include)) {
-                        gate_feature!(self, external_doc, attr.span,
-                            "`#[doc(include = \"...\")]` is experimental"
-                        );
-                    }
-                }
-            }
-            debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
-            return;
-        } else {
-            for segment in &attr.path.segments {
-                if segment.ident.as_str().starts_with("rustc") {
-                    let msg = "attributes starting with `rustc` are \
-                               reserved for use by the `rustc` compiler";
-                    gate_feature!(self, rustc_attrs, segment.ident.span, msg);
-                }
-            }
-        }
-        for &(n, ty) in self.plugin_attributes {
-            if attr.path == n {
-                // Plugins can't gate attributes, so we don't check for it
-                // unlike the code above; we only use this loop to
-                // short-circuit to avoid the checks below.
-                debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
-                return;
-            }
-        }
-        if !is_macro && !attr::is_known(attr) {
-            // Only run the custom attribute lint during regular feature gate
-            // checking. Macro gating runs before the plugin attributes are
-            // registered, so we skip this in that case.
-            let msg = format!("the attribute `{}` is currently unknown to the compiler and \
-                               may have meaning added to it in the future", attr.path);
-            gate_feature!(self, custom_attribute, attr.span, &msg);
-        }
-    }
-}
-
-pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
-    let cx = Context { features, parse_sess, plugin_attributes: &[] };
-    cx.check_attribute(
-        attr,
-        attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name).map(|a| *a)),
-        true
-    );
+crate fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
+    PostExpansionVisitor { parse_sess, features }.visit_attribute(attr)
 }
 
 fn find_lang_feature_issue(feature: Symbol) -> Option<u32> {
@@ -238,21 +172,21 @@ pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &str =
     "unsized tuple coercion is not stable enough for use and is subject to change";
 
 struct PostExpansionVisitor<'a> {
-    context: &'a Context<'a>,
-    builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>,
+    parse_sess: &'a ParseSess,
+    features: &'a Features,
 }
 
 macro_rules! gate_feature_post {
     ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
         let (cx, span) = ($cx, $span);
         if !span.allows_unstable(sym::$feature) {
-            gate_feature!(cx.context, $feature, span, $explain)
+            gate_feature!(cx, $feature, span, $explain)
         }
     }};
     ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
         let (cx, span) = ($cx, $span);
         if !span.allows_unstable(sym::$feature) {
-            gate_feature!(cx.context, $feature, span, $explain, $level)
+            gate_feature!(cx, $feature, span, $explain, $level)
         }
     }}
 }
@@ -316,50 +250,44 @@ impl<'a> PostExpansionVisitor<'a> {
 
 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_attribute(&mut self, attr: &ast::Attribute) {
-        let attr_info = attr.ident().and_then(|ident| {
-            self.builtin_attributes.get(&ident.name).map(|a| *a)
-        });
-
-        // Check for gated attributes.
-        self.context.check_attribute(attr, attr_info, false);
-
-        if attr.check_name(sym::doc) {
-            if let Some(content) = attr.meta_item_list() {
-                if content.len() == 1 && content[0].check_name(sym::cfg) {
-                    gate_feature_post!(&self, doc_cfg, attr.span,
-                        "`#[doc(cfg(...))]` is experimental"
-                    );
-                } else if content.iter().any(|c| c.check_name(sym::masked)) {
-                    gate_feature_post!(&self, doc_masked, attr.span,
-                        "`#[doc(masked)]` is experimental"
-                    );
-                } else if content.iter().any(|c| c.check_name(sym::spotlight)) {
-                    gate_feature_post!(&self, doc_spotlight, attr.span,
-                        "`#[doc(spotlight)]` is experimental"
-                    );
-                } else if content.iter().any(|c| c.check_name(sym::alias)) {
-                    gate_feature_post!(&self, doc_alias, attr.span,
-                        "`#[doc(alias = \"...\")]` is experimental"
-                    );
-                } else if content.iter().any(|c| c.check_name(sym::keyword)) {
-                    gate_feature_post!(&self, doc_keyword, attr.span,
-                        "`#[doc(keyword = \"...\")]` is experimental"
-                    );
-                }
-            }
+        let attr_info =
+            attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
+        // Check feature gates for built-in attributes.
+        if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
+            gate_feature_fn!(self, has_feature, attr.span, name, descr, GateStrength::Hard);
         }
-
+        // Check input tokens for built-in and key-value attributes.
         match attr_info {
             // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
-            Some(&(name, _, template, _)) if name != sym::rustc_dummy =>
-                check_builtin_attribute(self.context.parse_sess, attr, name, template),
+            Some((name, _, template, _)) if name != sym::rustc_dummy =>
+                check_builtin_attribute(self.parse_sess, attr, name, template),
             _ => if let Some(TokenTree::Token(token)) = attr.tokens.trees().next() {
                 if token == token::Eq {
                     // All key-value attributes are restricted to meta-item syntax.
-                    attr.parse_meta(self.context.parse_sess).map_err(|mut err| err.emit()).ok();
+                    attr.parse_meta(self.parse_sess).map_err(|mut err| err.emit()).ok();
                 }
             }
         }
+        // Check unstable flavors of the `#[doc]` attribute.
+        if attr.check_name(sym::doc) {
+            for nested_meta in attr.meta_item_list().unwrap_or_default() {
+                macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
+                    $(if nested_meta.check_name(sym::$name) {
+                        let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
+                        gate_feature!(self, $feature, attr.span, msg);
+                    })*
+                }}
+
+                gate_doc!(
+                    include => external_doc
+                    cfg => doc_cfg
+                    masked => doc_masked
+                    spotlight => doc_spotlight
+                    alias => doc_alias
+                    keyword => doc_keyword
+                );
+            }
+        }
     }
 
     fn visit_name(&mut self, sp: Span, name: ast::Name) {
@@ -367,7 +295,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             gate_feature_post!(
                 &self,
                 non_ascii_idents,
-                self.context.parse_sess.source_map().def_span(sp),
+                self.parse_sess.source_map().def_span(sp),
                 "non-ascii idents are not fully supported"
             );
         }
@@ -423,12 +351,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     }
                 }
 
-                let has_feature = self.context.features.arbitrary_enum_discriminant;
+                let has_feature = self.features.arbitrary_enum_discriminant;
                 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
-                    Parser::maybe_report_invalid_custom_discriminants(
-                        self.context.parse_sess,
-                        &variants,
-                    );
+                    Parser::maybe_report_invalid_custom_discriminants(self.parse_sess, &variants);
                 }
             }
 
@@ -538,7 +463,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ExprKind::Type(..) => {
                 // To avoid noise about type ascription in common syntax errors, only emit if it
                 // is the *only* error.
-                if self.context.parse_sess.span_diagnostic.err_count() == 0 {
+                if self.parse_sess.span_diagnostic.err_count() == 0 {
                     gate_feature_post!(&self, type_ascription, e.span,
                                        "type ascription is experimental");
                 }
@@ -872,22 +797,17 @@ fn active_features_up_to(edition: Edition) -> impl Iterator<Item=&'static Featur
 }
 
 pub fn check_crate(krate: &ast::Crate,
-                   sess: &ParseSess,
+                   parse_sess: &ParseSess,
                    features: &Features,
-                   plugin_attributes: &[(Symbol, AttributeType)],
                    unstable: UnstableFeatures) {
-    maybe_stage_features(&sess.span_diagnostic, krate, unstable);
-    let ctx = Context {
-        features,
-        parse_sess: sess,
-        plugin_attributes,
-    };
+    maybe_stage_features(&parse_sess.span_diagnostic, krate, unstable);
+    let mut visitor = PostExpansionVisitor { parse_sess, features };
 
     macro_rules! gate_all {
         ($gate:ident, $msg:literal) => { gate_all!($gate, $gate, $msg); };
         ($spans:ident, $gate:ident, $msg:literal) => {
-            for span in &*sess.gated_spans.$spans.borrow() {
-                gate_feature!(&ctx, $gate, *span, $msg);
+            for span in &*parse_sess.gated_spans.$spans.borrow() {
+                gate_feature!(&visitor, $gate, *span, $msg);
             }
         }
     }
@@ -898,11 +818,7 @@ pub fn check_crate(krate: &ast::Crate,
     gate_all!(yields, generators, "yield syntax is experimental");
     gate_all!(or_patterns, "or-patterns syntax is experimental");
 
-    let visitor = &mut PostExpansionVisitor {
-        context: &ctx,
-        builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP,
-    };
-    visit::walk_crate(visitor, krate);
+    visit::walk_crate(&mut visitor, krate);
 }
 
 #[derive(Clone, Copy, Hash)]
@@ -920,9 +836,9 @@ pub enum UnstableFeatures {
 
 impl UnstableFeatures {
     pub fn from_environment() -> UnstableFeatures {
-        // Whether this is a feature-staged build, i.e., on the beta or stable channel
+        // `true` if this is a feature-staged build, i.e., on the beta or stable channel.
         let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
-        // Whether we should enable unstable features for bootstrapping
+        // `true` if we should enable unstable features for bootstrapping.
         let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
         match (disable_unstable_features, bootstrap) {
             (_, true) => UnstableFeatures::Cheat,
diff --git a/src/libsyntax/feature_gate/mod.rs b/src/libsyntax/feature_gate/mod.rs
index 1e41667ea411e..ca13ab3620508 100644
--- a/src/libsyntax/feature_gate/mod.rs
+++ b/src/libsyntax/feature_gate/mod.rs
@@ -58,7 +58,8 @@ pub use builtin_attrs::{
     deprecated_attributes, is_builtin_attr,  is_builtin_attr_name,
 };
 pub use check::{
-    check_attribute, check_crate, get_features, feature_err, emit_feature_err,
+    check_crate, get_features, feature_err, emit_feature_err,
     Stability, GateIssue, UnstableFeatures,
     EXPLAIN_STMT_ATTR_SYNTAX, EXPLAIN_UNSIZED_TUPLE_COERCION,
 };
+crate use check::check_attribute;
diff --git a/src/libsyntax/feature_gate/removed.rs b/src/libsyntax/feature_gate/removed.rs
index ad7d69b3e7372..2c29e1ebf1493 100644
--- a/src/libsyntax/feature_gate/removed.rs
+++ b/src/libsyntax/feature_gate/removed.rs
@@ -94,6 +94,11 @@ declare_features! (
     /// Allows defining `existential type`s.
     (removed, existential_type, "1.38.0", Some(63063), None,
      Some("removed in favor of `#![feature(type_alias_impl_trait)]`")),
+    /// Allows using the macros:
+    /// + `__diagnostic_used`
+    /// + `__register_diagnostic`
+    /// +`__build_diagnostic_array`
+    (removed, rustc_diagnostic_macros, "1.38.0", None, None, None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: removed features
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 1741932c1b80e..aaf6f3e537eb6 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -7,7 +7,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/",
        test(attr(deny(warnings))))]
 
-#![feature(bind_by_move_pattern_guards)]
+#![cfg_attr(bootstrap, feature(bind_by_move_pattern_guards))]
 #![feature(box_syntax)]
 #![feature(const_fn)]
 #![feature(const_transmute)]
@@ -18,7 +18,6 @@
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_span)]
-#![feature(rustc_diagnostic_macros)]
 #![feature(try_trait)]
 #![feature(unicode_internals)]
 
@@ -123,11 +122,8 @@ scoped_tls::scoped_thread_local!(pub static GLOBALS: Globals);
 pub mod diagnostics {
     #[macro_use]
     pub mod macros;
-    pub mod plugin;
 }
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 pub mod error_codes;
 
 pub mod util {
@@ -182,5 +178,3 @@ pub mod ext {
 }
 
 pub mod early_buffered_lints;
-
-__build_diagnostic_array! { libsyntax, DIAGNOSTICS }
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index e14ca4b06a09e..5a37222ee5590 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -1,10 +1,10 @@
-//! A MutVisitor represents an AST modification; it accepts an AST piece and
-//! and mutates it in place. So, for instance, macro expansion is a MutVisitor
+//! A `MutVisitor` represents an AST modification; it accepts an AST piece and
+//! and mutates it in place. So, for instance, macro expansion is a `MutVisitor`
 //! that walks over an AST and modifies it.
 //!
-//! Note: using a MutVisitor (other than the MacroExpander MutVisitor) on
+//! Note: using a `MutVisitor` (other than the `MacroExpander` `MutVisitor`) on
 //! an AST before macro expansion is probably a bad idea. For instance,
-//! a MutVisitor renaming item names in a module will miss all of those
+//! a `MutVisitor` renaming item names in a module will miss all of those
 //! that are created by the expansion of a macro.
 
 use crate::ast::*;
@@ -370,6 +370,7 @@ pub fn noop_flat_map_field_pattern<T: MutVisitor>(
         attrs,
         id,
         ident,
+        is_placeholder: _,
         is_shorthand: _,
         pat,
         span,
@@ -402,14 +403,11 @@ pub fn noop_visit_use_tree<T: MutVisitor>(use_tree: &mut UseTree, vis: &mut T) {
     vis.visit_span(span);
 }
 
-pub fn noop_flat_map_arm<T: MutVisitor>(
-    mut arm: Arm,
-    vis: &mut T,
-) -> SmallVec<[Arm; 1]> {
-    let Arm { attrs, pats, guard, body, span, id } = &mut arm;
+pub fn noop_flat_map_arm<T: MutVisitor>(mut arm: Arm, vis: &mut T) -> SmallVec<[Arm; 1]> {
+    let Arm { attrs, pat, guard, body, span, id, is_placeholder: _ } = &mut arm;
     visit_attrs(attrs, vis);
     vis.visit_id(id);
-    visit_vec(pats, |pat| vis.visit_pat(pat));
+    vis.visit_pat(pat);
     visit_opt(guard, |guard| vis.visit_expr(guard));
     vis.visit_expr(body);
     vis.visit_span(span);
@@ -480,7 +478,7 @@ pub fn noop_visit_foreign_mod<T: MutVisitor>(foreign_mod: &mut ForeignMod, vis:
 pub fn noop_flat_map_variant<T: MutVisitor>(mut variant: Variant, vis: &mut T)
     -> SmallVec<[Variant; 1]>
 {
-    let Variant { ident, attrs, id, data, disr_expr, span } = &mut variant;
+    let Variant { ident, attrs, id, data, disr_expr, span, is_placeholder: _ } = &mut variant;
     vis.visit_ident(ident);
     visit_attrs(attrs, vis);
     vis.visit_id(id);
@@ -588,7 +586,7 @@ pub fn noop_visit_meta_item<T: MutVisitor>(mi: &mut MetaItem, vis: &mut T) {
 }
 
 pub fn noop_flat_map_param<T: MutVisitor>(mut param: Param, vis: &mut T) -> SmallVec<[Param; 1]> {
-    let Param { attrs, id, pat, span, ty } = &mut param;
+    let Param { attrs, id, pat, span, ty, is_placeholder: _ } = &mut param;
     vis.visit_id(id);
     visit_thin_attrs(attrs, vis);
     vis.visit_pat(pat);
@@ -617,7 +615,7 @@ pub fn noop_visit_tts<T: MutVisitor>(TokenStream(tts): &mut TokenStream, vis: &m
     })
 }
 
-// Apply ident visitor if it's an ident, apply other visits to interpolated nodes.
+// Applies ident visitor if it's an ident; applies other visits to interpolated nodes.
 // In practice the ident part is not actually used by specific visitors right now,
 // but there's a test below checking that it works.
 pub fn noop_visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
@@ -628,7 +626,7 @@ pub fn noop_visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
             vis.visit_ident(&mut ident);
             *name = ident.name;
             *span = ident.span;
-            return; // avoid visiting the span for the second time
+            return; // Avoid visiting the span for the second time.
         }
         token::Interpolated(nt) => {
             let mut nt = Lrc::make_mut(nt);
@@ -639,28 +637,28 @@ pub fn noop_visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
     vis.visit_span(span);
 }
 
-/// Apply visitor to elements of interpolated nodes.
+/// Applies the visitor to elements of interpolated nodes.
 //
 // N.B., this can occur only when applying a visitor to partially expanded
 // code, where parsed pieces have gotten implanted ito *other* macro
 // invocations. This is relevant for macro hygiene, but possibly not elsewhere.
 //
 // One problem here occurs because the types for flat_map_item, flat_map_stmt,
-// etc. allow the visitor to return *multiple* items; this is a problem for the
+// etc., allow the visitor to return *multiple* items; this is a problem for the
 // nodes here, because they insist on having exactly one piece. One solution
 // would be to mangle the MutVisitor trait to include one-to-many and
 // one-to-one versions of these entry points, but that would probably confuse a
 // lot of people and help very few. Instead, I'm just going to put in dynamic
 // checks. I think the performance impact of this will be pretty much
-// nonexistent. The danger is that someone will apply a MutVisitor to a
+// nonexistent. The danger is that someone will apply a `MutVisitor` to a
 // partially expanded node, and will be confused by the fact that their
-// "flat_map_item" or "flat_map_stmt" isn't getting called on NtItem or NtStmt
+// `flat_map_item` or `flat_map_stmt` isn't getting called on `NtItem` or `NtStmt`
 // nodes. Hopefully they'll wind up reading this comment, and doing something
 // appropriate.
 //
-// BTW, design choice: I considered just changing the type of, e.g., NtItem to
+// BTW, design choice: I considered just changing the type of, e.g., `NtItem` to
 // contain multiple items, but decided against it when I looked at
-// parse_item_or_view_item and tried to figure out what I would do with
+// `parse_item_or_view_item` and tried to figure out what I would do with
 // multiple items there....
 pub fn noop_visit_interpolated<T: MutVisitor>(nt: &mut token::Nonterminal, vis: &mut T) {
     match nt {
@@ -739,7 +737,7 @@ pub fn noop_flat_map_generic_param<T: MutVisitor>(
     vis: &mut T
 ) -> SmallVec<[GenericParam; 1]>
 {
-    let GenericParam { id, ident, attrs, bounds, kind } = &mut param;
+    let GenericParam { id, ident, attrs, bounds, kind, is_placeholder: _ } = &mut param;
     vis.visit_id(id);
     vis.visit_ident(ident);
     visit_thin_attrs(attrs, vis);
@@ -831,7 +829,7 @@ pub fn noop_visit_poly_trait_ref<T: MutVisitor>(p: &mut PolyTraitRef, vis: &mut
 pub fn noop_flat_map_struct_field<T: MutVisitor>(mut sf: StructField, visitor: &mut T)
     -> SmallVec<[StructField; 1]>
 {
-    let StructField { span, ident, vis, id, ty, attrs } = &mut sf;
+    let StructField { span, ident, vis, id, ty, attrs, is_placeholder: _ } = &mut sf;
     visitor.visit_span(span);
     visit_opt(ident, |ident| visitor.visit_ident(ident));
     visitor.visit_vis(vis);
@@ -842,7 +840,7 @@ pub fn noop_flat_map_struct_field<T: MutVisitor>(mut sf: StructField, visitor: &
 }
 
 pub fn noop_flat_map_field<T: MutVisitor>(mut f: Field, vis: &mut T) -> SmallVec<[Field; 1]> {
-    let Field { ident, expr, span, is_shorthand: _, attrs, id } = &mut f;
+    let Field { ident, expr, span, is_shorthand: _, attrs, id, is_placeholder: _ } = &mut f;
     vis.visit_ident(ident);
     vis.visit_expr(expr);
     vis.visit_id(id);
@@ -1017,7 +1015,7 @@ pub fn noop_visit_crate<T: MutVisitor>(krate: &mut Crate, vis: &mut T) {
     });
 }
 
-// Mutate one item into possibly many items.
+// Mutates one item into possibly many items.
 pub fn noop_flat_map_item<T: MutVisitor>(mut item: P<Item>, visitor: &mut T)
                                          -> SmallVec<[P<Item>; 1]> {
     let Item { ident, attrs, id, node, vis, span, tokens: _ } = item.deref_mut();
@@ -1132,8 +1130,8 @@ pub fn noop_visit_expr<T: MutVisitor>(Expr { node, id, span, attrs }: &mut Expr,
             vis.visit_ty(ty);
         }
         ExprKind::AddrOf(_m, ohs) => vis.visit_expr(ohs),
-        ExprKind::Let(pats, scrutinee) => {
-            visit_vec(pats, |pat| vis.visit_pat(pat));
+        ExprKind::Let(pat, scrutinee) => {
+            vis.visit_pat(pat);
             vis.visit_expr(scrutinee);
         }
         ExprKind::If(cond, tr, fl) => {
@@ -1227,7 +1225,7 @@ pub fn noop_visit_expr<T: MutVisitor>(Expr { node, id, span, attrs }: &mut Expr,
         ExprKind::Paren(expr) => {
             vis.visit_expr(expr);
 
-            // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
+            // Nodes that are equal modulo `Paren` sugar no-ops should have the same IDs.
             *id = expr.id;
             vis.visit_span(span);
             visit_thin_attrs(attrs, vis);
diff --git a/src/libsyntax/mut_visit/tests.rs b/src/libsyntax/mut_visit/tests.rs
index 6868736976b25..f779e0d0a6014 100644
--- a/src/libsyntax/mut_visit/tests.rs
+++ b/src/libsyntax/mut_visit/tests.rs
@@ -6,13 +6,13 @@ use crate::print::pprust;
 use crate::mut_visit;
 use crate::with_default_globals;
 
-// this version doesn't care about getting comments or docstrings in.
+// This version doesn't care about getting comments or doc-strings in.
 fn fake_print_crate(s: &mut pprust::State<'_>,
                     krate: &ast::Crate) {
     s.print_mod(&krate.module, &krate.attrs)
 }
 
-// change every identifier to "zz"
+// Change every identifier to "zz".
 struct ToZzIdentMutVisitor;
 
 impl MutVisitor for ToZzIdentMutVisitor {
@@ -24,7 +24,7 @@ impl MutVisitor for ToZzIdentMutVisitor {
     }
 }
 
-// maybe add to expand.rs...
+// Maybe add to `expand.rs`.
 macro_rules! assert_pred {
     ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
         {
@@ -39,7 +39,7 @@ macro_rules! assert_pred {
     )
 }
 
-// make sure idents get transformed everywhere
+// Make sure idents get transformed everywhere.
 #[test] fn ident_transformation () {
     with_default_globals(|| {
         let mut zz_visitor = ToZzIdentMutVisitor;
@@ -54,7 +54,7 @@ macro_rules! assert_pred {
     })
 }
 
-// even inside macro defs....
+// Make sure idents get transformed even inside macro defs.
 #[test] fn ident_transformation_in_defs () {
     with_default_globals(|| {
         let mut zz_visitor = ToZzIdentMutVisitor;
diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index 671178223f503..9aa1ec0b14fe9 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -26,7 +26,7 @@ impl<'a> Parser<'a> {
         Ok(attrs)
     }
 
-    /// Parse attributes that appear before an item
+    /// Parses attributes that appear before an item.
     crate fn parse_outer_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
         let mut attrs: Vec<ast::Attribute> = Vec::new();
         let mut just_parsed_doc_comment = false;
@@ -69,10 +69,10 @@ impl<'a> Parser<'a> {
         Ok(attrs)
     }
 
-    /// Matches `attribute = # ! [ meta_item ]`
+    /// Matches `attribute = # ! [ meta_item ]`.
     ///
-    /// If permit_inner is true, then a leading `!` indicates an inner
-    /// attribute
+    /// If `permit_inner` is `true`, then a leading `!` indicates an inner
+    /// attribute.
     pub fn parse_attribute(&mut self, permit_inner: bool) -> PResult<'a, ast::Attribute> {
         debug!("parse_attribute: permit_inner={:?} self.token={:?}",
                permit_inner,
@@ -167,16 +167,16 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// Parse an inner part of attribute - path and following tokens.
+    /// Parses an inner part of an attribute (the path and following tokens).
     /// The tokens must be either a delimited token stream, or empty token stream,
     /// or the "legacy" key-value form.
-    /// PATH `(` TOKEN_STREAM `)`
-    /// PATH `[` TOKEN_STREAM `]`
-    /// PATH `{` TOKEN_STREAM `}`
-    /// PATH
-    /// PATH `=` TOKEN_TREE
+    ///     PATH `(` TOKEN_STREAM `)`
+    ///     PATH `[` TOKEN_STREAM `]`
+    ///     PATH `{` TOKEN_STREAM `}`
+    ///     PATH
+    ///     PATH `=` TOKEN_TREE
     /// The delimiters or `=` are still put into the resulting token stream.
-    crate fn parse_meta_item_unrestricted(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
+    pub fn parse_meta_item_unrestricted(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
         let meta = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
                 Nonterminal::NtMeta(ref meta) => Some(meta.clone()),
@@ -217,11 +217,11 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// Parse attributes that appear after the opening of an item. These should
+    /// Parses attributes that appear after the opening of an item. These should
     /// be preceded by an exclamation mark, but we accept and warn about one
     /// terminated by a semicolon.
-
-    /// matches inner_attrs*
+    ///
+    /// Matches `inner_attrs*`.
     crate fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
         let mut attrs: Vec<ast::Attribute> = vec![];
         loop {
@@ -237,7 +237,7 @@ impl<'a> Parser<'a> {
                     attrs.push(attr);
                 }
                 token::DocComment(s) => {
-                    // we need to get the position of this token before we bump.
+                    // We need to get the position of this token before we bump.
                     let attr = attr::mk_sugared_doc_attr(s, self.token.span);
                     if attr.style == ast::AttrStyle::Inner {
                         attrs.push(attr);
@@ -268,10 +268,10 @@ impl<'a> Parser<'a> {
         Ok(lit)
     }
 
-    /// Per RFC#1559, matches the following grammar:
+    /// Matches the following grammar (per RFC 1559).
     ///
-    /// meta_item : IDENT ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
-    /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
+    ///     meta_item : IDENT ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
+    ///     meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
     pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
         let nt_meta = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
@@ -303,7 +303,7 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// matches meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;
+    /// Matches `meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;`.
     fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
         match self.parse_unsuffixed_lit() {
             Ok(lit) => {
@@ -324,7 +324,7 @@ impl<'a> Parser<'a> {
         Err(self.diagnostic().struct_span_err(self.token.span, &msg))
     }
 
-    /// matches meta_seq = ( COMMASEP(meta_item_inner) )
+    /// Matches `meta_seq = ( COMMASEP(meta_item_inner) )`.
     fn parse_meta_seq(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
         self.parse_seq_to_end(&token::CloseDelim(token::Paren),
                               SeqSep::trailing_allowed(token::Comma),
diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
index d4e661d1a38b7..b74f2492c351f 100644
--- a/src/libsyntax/parse/diagnostics.rs
+++ b/src/libsyntax/parse/diagnostics.rs
@@ -29,7 +29,14 @@ crate fn dummy_arg(ident: Ident) -> Param {
         span: ident.span,
         id: ast::DUMMY_NODE_ID
     };
-    Param { attrs: ThinVec::default(), id: ast::DUMMY_NODE_ID, pat, span: ident.span, ty: P(ty) }
+    Param {
+        attrs: ThinVec::default(),
+        id: ast::DUMMY_NODE_ID,
+        pat,
+        span: ident.span,
+        ty: P(ty),
+        is_placeholder: false,
+    }
 }
 
 pub enum Error {
@@ -240,7 +247,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, bool /* recovered */> {
         fn tokens_to_string(tokens: &[TokenType]) -> String {
             let mut i = tokens.iter();
-            // This might be a sign we need a connect method on Iterator.
+            // This might be a sign we need a connect method on `Iterator`.
             let b = i.next()
                      .map_or(String::new(), |t| t.to_string());
             i.enumerate().fold(b, |mut b, (i, a)| {
@@ -301,7 +308,7 @@ impl<'a> Parser<'a> {
             );
         }
         let sp = if self.token == token::Eof {
-            // This is EOF, don't want to point at the following char, but rather the last token
+            // This is EOF; don't want to point at the following char, but rather the last token.
             self.prev_span
         } else {
             label_sp
@@ -317,9 +324,9 @@ impl<'a> Parser<'a> {
         }
 
         let is_semi_suggestable = expected.iter().any(|t| match t {
-            TokenType::Token(token::Semi) => true, // we expect a `;` here
+            TokenType::Token(token::Semi) => true, // We expect a `;` here.
             _ => false,
-        }) && ( // a `;` would be expected before the current keyword
+        }) && ( // A `;` would be expected before the current keyword.
             self.token.is_keyword(kw::Break) ||
             self.token.is_keyword(kw::Continue) ||
             self.token.is_keyword(kw::For) ||
@@ -541,16 +548,16 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Produce an error if comparison operators are chained (RFC #558).
-    /// We only need to check lhs, not rhs, because all comparison ops
-    /// have same precedence and are left-associative
-    crate fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) {
+    /// Produces an error if comparison operators are chained (RFC #558).
+    /// We only need to check the LHS, not the RHS, because all comparison ops
+    /// have same precedence and are left-associative.
+    crate fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) -> PResult<'a, ()> {
         debug_assert!(outer_op.is_comparison(),
                       "check_no_chained_comparison: {:?} is not comparison",
                       outer_op);
         match lhs.node {
             ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
-                // respan to include both operators
+                // Respan to include both operators.
                 let op_span = op.span.to(self.token.span);
                 let mut err = self.struct_span_err(
                     op_span,
@@ -563,11 +570,14 @@ impl<'a> Parser<'a> {
                     err.help(
                         "use `::<...>` instead of `<...>` if you meant to specify type arguments");
                     err.help("or use `(...)` if you meant to specify fn arguments");
+                    // These cases cause too many knock-down errors, bail out (#61329).
+                    return Err(err);
                 }
                 err.emit();
             }
             _ => {}
         }
+        Ok(())
     }
 
     crate fn maybe_report_ambiguous_plus(
@@ -688,9 +698,9 @@ impl<'a> Parser<'a> {
         Ok(())
     }
 
-    /// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
-    /// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
-    /// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
+    /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
+    /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
+    /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
     crate fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
         &mut self,
         base: P<T>,
@@ -705,8 +715,8 @@ impl<'a> Parser<'a> {
         Ok(base)
     }
 
-    /// Given an already parsed `Ty` parse the `::AssocItem` tail and
-    /// combine them into a `<Ty>::AssocItem` expression/pattern/type.
+    /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
+    /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
     crate fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
         &mut self,
         ty_span: Span,
@@ -727,7 +737,7 @@ impl<'a> Parser<'a> {
         self.diagnostic()
             .struct_span_err(path.span, "missing angle brackets in associated item path")
             .span_suggestion(
-                // this is a best-effort recovery
+                // This is a best-effort recovery.
                 path.span,
                 "try",
                 format!("<{}>::{}", ty_str, path),
@@ -735,7 +745,7 @@ impl<'a> Parser<'a> {
             )
             .emit();
 
-        let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
+        let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
         Ok(P(T::recovered(
             Some(QSelf {
                 ty,
@@ -758,8 +768,8 @@ impl<'a> Parser<'a> {
             if !items.is_empty() {
                 let previous_item = &items[items.len() - 1];
                 let previous_item_kind_name = match previous_item.node {
-                    // say "braced struct" because tuple-structs and
-                    // braceless-empty-struct declarations do take a semicolon
+                    // Say "braced struct" because tuple-structs and
+                    // braceless-empty-struct declarations do take a semicolon.
                     ItemKind::Struct(..) => Some("braced struct"),
                     ItemKind::Enum(..) => Some("enum"),
                     ItemKind::Trait(..) => Some("trait"),
@@ -780,7 +790,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Create a `DiagnosticBuilder` for an unexpected token `t` and try to recover if it is a
+    /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
     /// closing delimiter.
     pub fn unexpected_try_recover(
         &mut self,
@@ -838,7 +848,7 @@ impl<'a> Parser<'a> {
         extern_sp: Span,
     ) -> PResult<'a, ()> {
         if self.token != token::Semi {
-            // this might be an incorrect fn definition (#62109)
+            // This might be an incorrect fn definition (#62109).
             let parser_snapshot = self.clone();
             match self.parse_inner_attrs_and_block() {
                 Ok((_, body)) => {
@@ -868,7 +878,7 @@ impl<'a> Parser<'a> {
         Ok(())
     }
 
-    /// Consume alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
+    /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
     /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
     crate fn parse_incorrect_await_syntax(
         &mut self,
@@ -921,7 +931,7 @@ impl<'a> Parser<'a> {
         sp
     }
 
-    /// If encountering `future.await()`, consume and emit error.
+    /// If encountering `future.await()`, consumes and emits an error.
     crate fn recover_from_await_method_call(&mut self) {
         if self.token == token::OpenDelim(token::Paren) &&
             self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
@@ -941,7 +951,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Recover a situation like `for ( $pat in $expr )`
+    /// Recovers a situation like `for ( $pat in $expr )`
     /// and suggest writing `for $pat in $expr` instead.
     ///
     /// This should be called before parsing the `$block`.
@@ -1007,7 +1017,7 @@ impl<'a> Parser<'a> {
             Ok(x) => x,
             Err(mut err) => {
                 err.emit();
-                // recover from parse error
+                // Recover from parse error.
                 self.consume_block(delim);
                 self.mk_expr(lo.to(self.prev_span), ExprKind::Err, ThinVec::new())
             }
@@ -1020,7 +1030,7 @@ impl<'a> Parser<'a> {
         mut err: DiagnosticBuilder<'a>,
     ) -> PResult<'a, bool> {
         let mut pos = None;
-        // we want to use the last closing delim that would apply
+        // We want to use the last closing delim that would apply.
         for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
             if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
                 && Some(self.token.span) > unmatched.unclosed_span
@@ -1038,7 +1048,7 @@ impl<'a> Parser<'a> {
                 let unmatched = self.unclosed_delims.remove(pos);
                 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
 
-                 // We want to suggest the inclusion of the closing delimiter where it makes
+                // We want to suggest the inclusion of the closing delimiter where it makes
                 // the most sense, which is immediately after the last token:
                 //
                 //  {foo(bar {}}
@@ -1064,7 +1074,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Recover from `pub` keyword in places where it seems _reasonable_ but isn't valid.
+    /// Recovers from `pub` keyword in places where it seems _reasonable_ but isn't valid.
     crate fn eat_bad_pub(&mut self) {
         if self.token.is_keyword(kw::Pub) {
             match self.parse_visibility(false) {
@@ -1079,21 +1089,21 @@ impl<'a> Parser<'a> {
         }
     }
 
-    // Eat tokens until we can be relatively sure we reached the end of the
-    // statement. This is something of a best-effort heuristic.
-    //
-    // We terminate when we find an unmatched `}` (without consuming it).
+    /// Eats tokens until we can be relatively sure we reached the end of the
+    /// statement. This is something of a best-effort heuristic.
+    ///
+    /// We terminate when we find an unmatched `}` (without consuming it).
     crate fn recover_stmt(&mut self) {
         self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
     }
 
-    // If `break_on_semi` is `Break`, then we will stop consuming tokens after
-    // finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
-    // approximate - it can mean we break too early due to macros, but that
-    // should only lead to sub-optimal recovery, not inaccurate parsing).
-    //
-    // If `break_on_block` is `Break`, then we will stop consuming tokens
-    // after finding (and consuming) a brace-delimited block.
+    /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
+    /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
+    /// approximate -- it can mean we break too early due to macros, but that
+    /// should only lead to sub-optimal recovery, not inaccurate parsing).
+    ///
+    /// If `break_on_block` is `Break`, then we will stop consuming tokens
+    /// after finding (and consuming) a brace-delimited block.
     crate fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
         let mut brace_depth = 0;
         let mut bracket_depth = 0;
diff --git a/src/libsyntax/parse/lexer/tests.rs b/src/libsyntax/parse/lexer/tests.rs
index 652ae95c85349..c1ec41902e2be 100644
--- a/src/libsyntax/parse/lexer/tests.rs
+++ b/src/libsyntax/parse/lexer/tests.rs
@@ -4,9 +4,10 @@ use crate::symbol::Symbol;
 use crate::source_map::{SourceMap, FilePathMapping};
 use crate::parse::token;
 use crate::with_default_globals;
+
+use errors::{Handler, emitter::EmitterWriter};
 use std::io;
 use std::path::PathBuf;
-use errors::{Handler, emitter::EmitterWriter};
 use syntax_pos::{BytePos, Span};
 
 fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
@@ -21,7 +22,7 @@ fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
     ParseSess::with_span_handler(Handler::with_emitter(true, None, Box::new(emitter)), sm)
 }
 
-// open a string reader for the given string
+// Creates a string reader for the given string.
 fn setup<'a>(sm: &SourceMap,
                 sess: &'a ParseSess,
                 teststr: String)
@@ -50,7 +51,7 @@ fn t1() {
         assert_eq!(tok1.kind, tok2.kind);
         assert_eq!(tok1.span, tok2.span);
         assert_eq!(string_reader.next_token(), token::Whitespace);
-        // read another token:
+        // Read another token.
         let tok3 = string_reader.next_token();
         assert_eq!(string_reader.pos.clone(), BytePos(28));
         let tok4 = Token::new(
@@ -65,15 +66,15 @@ fn t1() {
     })
 }
 
-// check that the given reader produces the desired stream
-// of tokens (stop checking after exhausting the expected vec)
+// Checks that the given reader produces the desired stream
+// of tokens (stop checking after exhausting `expected`).
 fn check_tokenization(mut string_reader: StringReader<'_>, expected: Vec<TokenKind>) {
     for expected_tok in &expected {
         assert_eq!(&string_reader.next_token(), expected_tok);
     }
 }
 
-// make the identifier by looking up the string in the interner
+// Makes the identifier by looking up the string in the interner.
 fn mk_ident(id: &str) -> TokenKind {
     token::Ident(Symbol::intern(id), false)
 }
@@ -201,7 +202,7 @@ fn literal_suffixes() {
                     setup(&sm, &sh, format!("{}suffix", $input)).next_token(),
                     mk_lit(token::$tok_type, $tok_contents, Some("suffix")),
                 );
-                // with a whitespace separator:
+                // with a whitespace separator
                 assert_eq!(
                     setup(&sm, &sh, format!("{} suffix", $input)).next_token(),
                     mk_lit(token::$tok_type, $tok_contents, None),
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index b1af4806e2d78..2441a027f9940 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -8,17 +8,18 @@ use crate::parse::parser::Parser;
 use crate::parse::parser::emit_unclosed_delims;
 use crate::parse::token::TokenKind;
 use crate::tokenstream::{TokenStream, TokenTree};
-use crate::diagnostics::plugin::ErrorMap;
 use crate::print::pprust;
 use crate::symbol::Symbol;
 
 use errors::{Applicability, FatalError, Level, Handler, ColorConfig, Diagnostic, DiagnosticBuilder};
+use rustc_data_structures::fx::{FxHashSet, FxHashMap};
+#[cfg(target_arch = "x86_64")]
+use rustc_data_structures::static_assert_size;
 use rustc_data_structures::sync::{Lrc, Lock, Once};
 use syntax_pos::{Span, SourceFile, FileName, MultiSpan};
 use syntax_pos::edition::Edition;
 use syntax_pos::hygiene::ExpnId;
 
-use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use std::borrow::Cow;
 use std::path::{Path, PathBuf};
 use std::str;
@@ -39,6 +40,11 @@ crate mod unescape_error_reporting;
 
 pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
 
+// `PResult` is used a lot. Make sure it doesn't unintentionally get bigger.
+// (See also the comment on `DiagnosticBuilderInner`.)
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(PResult<'_, bool>, 16);
+
 /// Collected spans during parsing for places where a certain feature was
 /// used and should be feature gated accordingly in `check_crate`.
 #[derive(Default)]
@@ -64,8 +70,6 @@ pub struct ParseSess {
     pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
     pub raw_identifier_spans: Lock<Vec<Span>>,
-    /// The registered diagnostics codes.
-    crate registered_diagnostics: Lock<ErrorMap>,
     /// Used to determine and report recursive module inclusions.
     included_mod_stack: Lock<Vec<PathBuf>>,
     source_map: Lrc<SourceMap>,
@@ -81,25 +85,26 @@ pub struct ParseSess {
 impl ParseSess {
     pub fn new(file_path_mapping: FilePathMapping) -> Self {
         let cm = Lrc::new(SourceMap::new(file_path_mapping));
-        let handler = Handler::with_tty_emitter(ColorConfig::Auto,
-                                                true,
-                                                None,
-                                                Some(cm.clone()));
+        let handler = Handler::with_tty_emitter(
+            ColorConfig::Auto,
+            true,
+            None,
+            Some(cm.clone()),
+        );
         ParseSess::with_span_handler(handler, cm)
     }
 
-    pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> ParseSess {
-        ParseSess {
+    pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> Self {
+        Self {
             span_diagnostic: handler,
             unstable_features: UnstableFeatures::from_environment(),
             config: FxHashSet::default(),
+            edition: ExpnId::root().expn_data().edition,
             missing_fragment_specifiers: Lock::new(FxHashSet::default()),
             raw_identifier_spans: Lock::new(Vec::new()),
-            registered_diagnostics: Lock::new(ErrorMap::new()),
             included_mod_stack: Lock::new(vec![]),
             source_map,
             buffered_lints: Lock::new(vec![]),
-            edition: ExpnId::root().expn_data().edition,
             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
             injected_crate_name: Once::new(),
             gated_spans: GatedSpans::default(),
@@ -155,17 +160,17 @@ pub struct Directory<'a> {
 #[derive(Copy, Clone)]
 pub enum DirectoryOwnership {
     Owned {
-        // None if `mod.rs`, `Some("foo")` if we're in `foo.rs`
+        // None if `mod.rs`, `Some("foo")` if we're in `foo.rs`.
         relative: Option<ast::Ident>,
     },
     UnownedViaBlock,
     UnownedViaMod(bool /* legacy warnings? */),
 }
 
-// a bunch of utility functions of the form parse_<thing>_from_<source>
+// A bunch of utility functions of the form `parse_<thing>_from_<source>`
 // where <thing> includes crate, expr, item, stmt, tts, and one that
 // uses a HOF to parse anything, and <source> includes file and
-// source_str.
+// `source_str`.
 
 pub fn parse_crate_from_file<'a>(input: &Path, sess: &'a ParseSess) -> PResult<'a, ast::Crate> {
     let mut parser = new_parser_from_file(sess, input);
@@ -219,14 +224,13 @@ pub fn maybe_new_parser_from_source_str(sess: &ParseSess, name: FileName, source
     Ok(parser)
 }
 
-/// Creates a new parser, handling errors as appropriate
-/// if the file doesn't exist
+/// Creates a new parser, handling errors as appropriate if the file doesn't exist.
 pub fn new_parser_from_file<'a>(sess: &'a ParseSess, path: &Path) -> Parser<'a> {
     source_file_to_parser(sess, file_to_source_file(sess, path, None))
 }
 
-/// Creates a new parser, returning buffered diagnostics if the file doesn't
-/// exist or from lexing the initial token stream.
+/// Creates a new parser, returning buffered diagnostics if the file doesn't exist,
+/// or from lexing the initial token stream.
 pub fn maybe_new_parser_from_file<'a>(sess: &'a ParseSess, path: &Path)
     -> Result<Parser<'a>, Vec<Diagnostic>> {
     let file = try_file_to_source_file(sess, path, None).map_err(|db| vec![db])?;
@@ -234,8 +238,8 @@ pub fn maybe_new_parser_from_file<'a>(sess: &'a ParseSess, path: &Path)
 }
 
 /// Given a session, a crate config, a path, and a span, add
-/// the file at the given path to the source_map, and return a parser.
-/// On an error, use the given span as the source of the problem.
+/// the file at the given path to the `source_map`, and returns a parser.
+/// On an error, uses the given span as the source of the problem.
 pub fn new_sub_parser_from_file<'a>(sess: &'a ParseSess,
                                     path: &Path,
                                     directory_ownership: DirectoryOwnership,
@@ -247,13 +251,13 @@ pub fn new_sub_parser_from_file<'a>(sess: &'a ParseSess,
     p
 }
 
-/// Given a source_file and config, return a parser
+/// Given a `source_file` and config, returns a parser.
 fn source_file_to_parser(sess: &ParseSess, source_file: Lrc<SourceFile>) -> Parser<'_> {
     panictry_buffer!(&sess.span_diagnostic,
                      maybe_source_file_to_parser(sess, source_file))
 }
 
-/// Given a source_file and config, return a parser. Returns any buffered errors from lexing the
+/// Given a `source_file` and config, return a parser. Returns any buffered errors from lexing the
 /// initial token stream.
 fn maybe_source_file_to_parser(
     sess: &ParseSess,
@@ -270,14 +274,14 @@ fn maybe_source_file_to_parser(
     Ok(parser)
 }
 
-// must preserve old name for now, because quote! from the *existing*
-// compiler expands into it
+// Must preserve old name for now, because `quote!` from the *existing*
+// compiler expands into it.
 pub fn new_parser_from_tts(sess: &ParseSess, tts: Vec<TokenTree>) -> Parser<'_> {
     stream_to_parser(sess, tts.into_iter().collect(), crate::MACRO_ARGUMENTS)
 }
 
 
-// base abstractions
+// Base abstractions
 
 /// Given a session and a path and an optional span (for error reporting),
 /// add the path to the session's source_map and return the new source_file or
@@ -296,7 +300,7 @@ fn try_file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>)
 }
 
 /// Given a session and a path and an optional span (for error reporting),
-/// add the path to the session's `source_map` and return the new `source_file`.
+/// adds the path to the session's `source_map` and returns the new `source_file`.
 fn file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>)
                    -> Lrc<SourceFile> {
     match try_file_to_source_file(sess, path, spanopt) {
@@ -308,7 +312,7 @@ fn file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>)
     }
 }
 
-/// Given a source_file, produces a sequence of token trees.
+/// Given a `source_file`, produces a sequence of token trees.
 pub fn source_file_to_stream(
     sess: &ParseSess,
     source_file: Lrc<SourceFile>,
@@ -352,7 +356,7 @@ pub fn maybe_file_to_stream(
     }
 }
 
-/// Given stream and the `ParseSess`, produces a parser.
+/// Given a stream and the `ParseSess`, produces a parser.
 pub fn stream_to_parser<'a>(
     sess: &'a ParseSess,
     stream: TokenStream,
@@ -361,7 +365,7 @@ pub fn stream_to_parser<'a>(
     Parser::new(sess, stream, None, true, false, subparser_name)
 }
 
-/// Given stream, the `ParseSess` and the base directory, produces a parser.
+/// Given a stream, the `ParseSess` and the base directory, produces a parser.
 ///
 /// Use this function when you are creating a parser from the token stream
 /// and also care about the current working directory of the parser (e.g.,
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 49b05551bae86..fcebfa2996233 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -10,22 +10,22 @@ pub use path::PathStyle;
 mod stmt;
 mod generics;
 
-use crate::ast::{self, AttrStyle, Attribute, Param, BindingMode, StrStyle, SelfKind};
-use crate::ast::{FnDecl, Ident, IsAsync, MacDelimiter, Mutability, TyKind};
-use crate::ast::{Visibility, VisibilityKind, Unsafety, CrateSugar};
-use crate::source_map::{self, respan};
-use crate::parse::{SeqSep, literal, token};
+use crate::ast::{
+    self, DUMMY_NODE_ID, AttrStyle, Attribute, BindingMode, CrateSugar, FnDecl, Ident,
+    IsAsync, MacDelimiter, Mutability, Param, StrStyle, SelfKind, TyKind, Visibility,
+    VisibilityKind, Unsafety,
+};
+use crate::parse::{ParseSess, PResult, Directory, DirectoryOwnership, SeqSep, literal, token};
+use crate::parse::diagnostics::{Error, dummy_arg};
 use crate::parse::lexer::UnmatchedBrace;
 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
 use crate::parse::token::{Token, TokenKind, DelimToken};
-use crate::parse::{ParseSess, Directory, DirectoryOwnership};
 use crate::print::pprust;
 use crate::ptr::P;
-use crate::parse::PResult;
-use crate::ThinVec;
-use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
+use crate::source_map::{self, respan};
 use crate::symbol::{kw, sym, Symbol};
-use crate::parse::diagnostics::{Error, dummy_arg};
+use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
+use crate::ThinVec;
 
 use errors::{Applicability, DiagnosticId, FatalError};
 use rustc_target::spec::abi::{self, Abi};
@@ -56,7 +56,7 @@ crate enum BlockMode {
     Ignore,
 }
 
-/// As maybe_whole_expr, but for things other than expressions
+/// Like `maybe_whole_expr`, but for things other than expressions.
 #[macro_export]
 macro_rules! maybe_whole {
     ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
@@ -116,11 +116,11 @@ pub struct Parser<'a> {
     /// with non-interpolated identifier and lifetime tokens they refer to.
     /// Perhaps the normalized / non-normalized setup can be simplified somehow.
     pub token: Token,
-    /// Span of the current non-normalized token.
+    /// The span of the current non-normalized token.
     meta_var_span: Option<Span>,
-    /// Span of the previous non-normalized token.
+    /// The span of the previous non-normalized token.
     pub prev_span: Span,
-    /// Kind of the previous normalized token (in simplified form).
+    /// The kind of the previous normalized token (in simplified form).
     prev_token_kind: PrevTokenKind,
     restrictions: Restrictions,
     /// Used to determine the path to externally loaded source files.
@@ -132,7 +132,7 @@ pub struct Parser<'a> {
     /// into modules, and sub-parsers have new values for this name.
     pub root_module_name: Option<String>,
     crate expected_tokens: Vec<TokenType>,
-    crate token_cursor: TokenCursor,
+    token_cursor: TokenCursor,
     desugar_doc_comments: bool,
     /// `true` we should configure out of line modules as we parse.
     pub cfg_mods: bool,
@@ -143,7 +143,7 @@ pub struct Parser<'a> {
     /// See the comments in the `parse_path_segment` function for more details.
     crate unmatched_angle_bracket_count: u32,
     crate max_angle_bracket_count: u32,
-    /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
+    /// A list of all unclosed delimiters found by the lexer. If an entry is used for error recovery
     /// it gets removed from here. Every entry left at the end gets emitted as an independent
     /// error.
     crate unclosed_delims: Vec<UnmatchedBrace>,
@@ -161,19 +161,19 @@ impl<'a> Drop for Parser<'a> {
 }
 
 #[derive(Clone)]
-crate struct TokenCursor {
-    crate frame: TokenCursorFrame,
-    crate stack: Vec<TokenCursorFrame>,
+struct TokenCursor {
+    frame: TokenCursorFrame,
+    stack: Vec<TokenCursorFrame>,
 }
 
 #[derive(Clone)]
-crate struct TokenCursorFrame {
-    crate delim: token::DelimToken,
-    crate span: DelimSpan,
-    crate open_delim: bool,
-    crate tree_cursor: tokenstream::Cursor,
-    crate close_delim: bool,
-    crate last_token: LastToken,
+struct TokenCursorFrame {
+    delim: token::DelimToken,
+    span: DelimSpan,
+    open_delim: bool,
+    tree_cursor: tokenstream::Cursor,
+    close_delim: bool,
+    last_token: LastToken,
 }
 
 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
@@ -799,14 +799,14 @@ impl<'a> Parser<'a> {
                             break;
                         }
                         Err(mut e) => {
-                            // Attempt to keep parsing if it was a similar separator
+                            // Attempt to keep parsing if it was a similar separator.
                             if let Some(ref tokens) = t.similar_tokens() {
                                 if tokens.contains(&self.token.kind) {
                                     self.bump();
                                 }
                             }
                             e.emit();
-                            // Attempt to keep parsing if it was an omitted separator
+                            // Attempt to keep parsing if it was an omitted separator.
                             match f(self) {
                                 Ok(t) => {
                                     v.push(t);
@@ -871,7 +871,7 @@ impl<'a> Parser<'a> {
         self.parse_delim_comma_seq(token::Paren, f)
     }
 
-    /// Advance the parser by one token
+    /// Advance the parser by one token.
     pub fn bump(&mut self) {
         if self.prev_token_kind == PrevTokenKind::Eof {
             // Bumping after EOF is a bad sign, usually an infinite loop.
@@ -894,17 +894,17 @@ impl<'a> Parser<'a> {
 
         self.token = self.next_tok();
         self.expected_tokens.clear();
-        // check after each token
+        // Check after each token.
         self.process_potential_macro_variable();
     }
 
-    /// Advance the parser using provided token as a next one. Use this when
+    /// Advances the parser using provided token as a next one. Use this when
     /// consuming a part of a token. For example a single `<` from `<<`.
     fn bump_with(&mut self, next: TokenKind, span: Span) {
         self.prev_span = self.token.span.with_hi(span.lo());
         // It would be incorrect to record the kind of the current token, but
         // fortunately for tokens currently using `bump_with`, the
-        // prev_token_kind will be of no use anyway.
+        // `prev_token_kind` will be of no use anyway.
         self.prev_token_kind = PrevTokenKind::Other;
         self.token = Token::new(next, span);
         self.expected_tokens.clear();
@@ -937,8 +937,8 @@ impl<'a> Parser<'a> {
     fn parse_asyncness(&mut self) -> IsAsync {
         if self.eat_keyword(kw::Async) {
             IsAsync::Async {
-                closure_id: ast::DUMMY_NODE_ID,
-                return_impl_trait_id: ast::DUMMY_NODE_ID,
+                closure_id: DUMMY_NODE_ID,
+                return_impl_trait_id: DUMMY_NODE_ID,
             }
         } else {
             IsAsync::NotAsync
@@ -1040,7 +1040,14 @@ impl<'a> Parser<'a> {
 
         let span = lo.to(self.token.span);
 
-        Ok(Param { attrs: attrs.into(), id: ast::DUMMY_NODE_ID, pat, span, ty })
+        Ok(Param {
+            attrs: attrs.into(),
+            id: ast::DUMMY_NODE_ID,
+            is_placeholder: false,
+            pat,
+            span,
+            ty,
+        })
     }
 
     /// Parses mutability (`mut` or nothing).
@@ -1497,7 +1504,7 @@ impl<'a> Parser<'a> {
                         format!("in {}", path),
                         Applicability::MachineApplicable,
                     )
-                    .emit();  // emit diagnostic, but continue with public visibility
+                    .emit(); // Emit diagnostic, but continue with public visibility.
             }
         }
 
diff --git a/src/libsyntax/parse/parser/expr.rs b/src/libsyntax/parse/parser/expr.rs
index e502a08f4b253..31b28443abbc3 100644
--- a/src/libsyntax/parse/parser/expr.rs
+++ b/src/libsyntax/parse/parser/expr.rs
@@ -1,26 +1,26 @@
-use super::{Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle};
-use super::{BlockMode, SemiColonMode};
-use super::{SeqSep, TokenExpectType};
+use super::{
+    Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode, SemiColonMode,
+    SeqSep, TokenExpectType,
+};
 use super::pat::{GateOr, PARAM_EXPECTED};
 
+use crate::ast::{
+    self, DUMMY_NODE_ID, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode,
+    Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm, Ty, TyKind,
+    FunctionRetTy, Param, FnDecl, BinOpKind, BinOp, UnOp, Mac, AnonConst, Field,
+};
 use crate::maybe_recover_from_interpolated_ty_qpath;
-use crate::ptr::P;
-use crate::ast::{self, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode};
-use crate::ast::{Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm};
-use crate::ast::{Ty, TyKind, FunctionRetTy, Param, FnDecl};
-use crate::ast::{BinOpKind, BinOp, UnOp};
-use crate::ast::{Mac, AnonConst, Field};
-
 use crate::parse::classify;
 use crate::parse::token::{self, Token};
-use crate::parse::diagnostics::{Error};
+use crate::parse::diagnostics::Error;
 use crate::print::pprust;
+use crate::ptr::P;
 use crate::source_map::{self, Span};
 use crate::symbol::{kw, sym};
 use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
 
-use std::mem;
 use errors::Applicability;
+use std::mem;
 use rustc_data_structures::thin_vec::ThinVec;
 
 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
@@ -51,7 +51,7 @@ macro_rules! maybe_whole_expr {
                         $p.token.span, ExprKind::Block(block, None), ThinVec::new()
                     ));
                 }
-                // N.B: `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
+                // N.B., `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
                 _ => {},
             };
         }
@@ -231,7 +231,7 @@ impl<'a> Parser<'a> {
 
             self.bump();
             if op.is_comparison() {
-                self.check_no_chained_comparison(&lhs, &op);
+                self.check_no_chained_comparison(&lhs, &op)?;
             }
             // Special cases:
             if op == AssocOp::As {
@@ -340,7 +340,7 @@ impl<'a> Parser<'a> {
 
     fn is_at_start_of_range_notation_rhs(&self) -> bool {
         if self.token.can_begin_expr() {
-            // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
+            // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
             if self.token == token::OpenDelim(token::Brace) {
                 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
             }
@@ -350,12 +350,12 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
+    /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
     fn parse_prefix_range_expr(
         &mut self,
         already_parsed_attrs: Option<ThinVec<Attribute>>
     ) -> PResult<'a, P<Expr>> {
-        // Check for deprecated `...` syntax
+        // Check for deprecated `...` syntax.
         if self.token == token::DotDotDot {
             self.err_dotdotdot_syntax(self.token.span);
         }
@@ -389,7 +389,7 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(lo.to(hi), r, attrs))
     }
 
-    /// Parse a prefix-unary-operator expr
+    /// Parses a prefix-unary-operator expr.
     fn parse_prefix_expr(
         &mut self,
         already_parsed_attrs: Option<ThinVec<Attribute>>
@@ -549,7 +549,7 @@ impl<'a> Parser<'a> {
                         let expr = mk_expr(self, P(Ty {
                             span: path.span,
                             node: TyKind::Path(None, path),
-                            id: ast::DUMMY_NODE_ID
+                            id: DUMMY_NODE_ID,
                         }));
 
                         let expr_str = self.span_to_snippet(expr.span)
@@ -565,7 +565,7 @@ impl<'a> Parser<'a> {
                                 expr.span,
                                 &format!("try {} the cast value", op_verb),
                                 format!("({})", expr_str),
-                                Applicability::MachineApplicable
+                                Applicability::MachineApplicable,
                             )
                             .emit();
 
@@ -741,7 +741,6 @@ impl<'a> Parser<'a> {
         })
     }
 
-
     /// At the bottom (top?) of the precedence hierarchy,
     /// Parses things like parenthesized exprs, macros, `return`, etc.
     ///
@@ -755,7 +754,7 @@ impl<'a> Parser<'a> {
         // added to the return value after the fact.
         //
         // Therefore, prevent sub-parser from parsing
-        // attributes by giving them a empty "already parsed" list.
+        // attributes by giving them a empty "already-parsed" list.
         let mut attrs = ThinVec::new();
 
         let lo = self.token.span;
@@ -778,7 +777,7 @@ impl<'a> Parser<'a> {
             }
         }
 
-        // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
+        // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
         match self.token.kind {
             // This match arm is a special-case of the `_` match arm below and
             // could be removed without changing functionality, but it's faster
@@ -791,8 +790,8 @@ impl<'a> Parser<'a> {
 
                 attrs.extend(self.parse_inner_attributes()?);
 
-                // (e) is parenthesized e
-                // (e,) is a tuple with only one field, e
+                // `(e)` is parenthesized `e`.
+                // `(e,)` is a tuple with only one field, `e`.
                 let mut es = vec![];
                 let mut trailing_comma = false;
                 let mut recovered = false;
@@ -800,7 +799,7 @@ impl<'a> Parser<'a> {
                     es.push(match self.parse_expr() {
                         Ok(es) => es,
                         Err(mut err) => {
-                            // recover from parse error in tuple list
+                            // Recover from parse error in tuple list.
                             match self.token.kind {
                                 token::Ident(name, false)
                                 if name == kw::Underscore && self.look_ahead(1, |t| {
@@ -844,7 +843,7 @@ impl<'a> Parser<'a> {
                 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
             }
             token::BinOp(token::Or) | token::OrOr => {
-                return self.parse_lambda_expr(attrs);
+                return self.parse_closure_expr(attrs);
             }
             token::OpenDelim(token::Bracket) => {
                 self.bump();
@@ -852,21 +851,21 @@ impl<'a> Parser<'a> {
                 attrs.extend(self.parse_inner_attributes()?);
 
                 if self.eat(&token::CloseDelim(token::Bracket)) {
-                    // Empty vector.
+                    // Empty vector
                     ex = ExprKind::Array(Vec::new());
                 } else {
-                    // Nonempty vector.
+                    // Non-empty vector
                     let first_expr = self.parse_expr()?;
                     if self.eat(&token::Semi) {
-                        // Repeating array syntax: [ 0; 512 ]
+                        // Repeating array syntax: `[ 0; 512 ]`
                         let count = AnonConst {
-                            id: ast::DUMMY_NODE_ID,
+                            id: DUMMY_NODE_ID,
                             value: self.parse_expr()?,
                         };
                         self.expect(&token::CloseDelim(token::Bracket))?;
                         ex = ExprKind::Repeat(first_expr, count);
                     } else if self.eat(&token::Comma) {
-                        // Vector with two or more elements.
+                        // Vector with two or more elements
                         let remaining_exprs = self.parse_seq_to_end(
                             &token::CloseDelim(token::Bracket),
                             SeqSep::trailing_allowed(token::Comma),
@@ -876,7 +875,7 @@ impl<'a> Parser<'a> {
                         exprs.extend(remaining_exprs);
                         ex = ExprKind::Array(exprs);
                     } else {
-                        // Vector with one element.
+                        // Vector with one element
                         self.expect(&token::CloseDelim(token::Bracket))?;
                         ex = ExprKind::Array(vec![first_expr]);
                     }
@@ -892,7 +891,7 @@ impl<'a> Parser<'a> {
                 if self.token.is_path_start() {
                     let path = self.parse_path(PathStyle::Expr)?;
 
-                    // `!`, as an operator, is prefix, so we know this isn't that
+                    // `!`, as an operator, is prefix, so we know this isn't that.
                     if self.eat(&token::Not) {
                         // MACRO INVOCATION expression
                         let (delim, tts) = self.expect_delimited_token_tree()?;
@@ -920,7 +919,7 @@ impl<'a> Parser<'a> {
                     return self.maybe_recover_from_bad_qpath(expr, true);
                 }
                 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
-                    return self.parse_lambda_expr(attrs);
+                    return self.parse_closure_expr(attrs);
                 }
                 if self.eat_keyword(kw::If) {
                     return self.parse_if_expr(attrs);
@@ -982,7 +981,7 @@ impl<'a> Parser<'a> {
                 }
                 if self.is_do_catch_block() {
                     let mut db = self.fatal("found removed `do catch` syntax");
-                    db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
+                    db.help("following RFC #2388, the new non-placeholder syntax is `try`");
                     return Err(db);
                 }
                 if self.is_try_block() {
@@ -991,13 +990,13 @@ impl<'a> Parser<'a> {
                     return self.parse_try_block(lo, attrs);
                 }
 
-                // Span::rust_2018() is somewhat expensive; don't get it repeatedly.
+                // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
                 let is_span_rust_2018 = self.token.span.rust_2018();
                 if is_span_rust_2018 && self.check_keyword(kw::Async) {
-                    return if self.is_async_block() { // check for `async {` and `async move {`
+                    return if self.is_async_block() { // Check for `async {` and `async move {`.
                         self.parse_async_block(attrs)
                     } else {
-                        self.parse_lambda_expr(attrs)
+                        self.parse_closure_expr(attrs)
                     };
                 }
                 if self.eat_keyword(kw::Return) {
@@ -1043,13 +1042,12 @@ impl<'a> Parser<'a> {
                         // recovery in order to keep the error count down. Fixing the
                         // delimiters will possibly also fix the bare semicolon found in
                         // expression context. For example, silence the following error:
-                        // ```
-                        // error: expected expression, found `;`
-                        //  --> file.rs:2:13
-                        //   |
-                        // 2 |     foo(bar(;
-                        //   |             ^ expected expression
-                        // ```
+                        //
+                        //     error: expected expression, found `;`
+                        //      --> file.rs:2:13
+                        //       |
+                        //     2 |     foo(bar(;
+                        //       |             ^ expected expression
                         self.bump();
                         return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
                     }
@@ -1096,11 +1094,11 @@ impl<'a> Parser<'a> {
         attrs.extend(self.parse_inner_attributes()?);
 
         let blk = self.parse_block_tail(lo, blk_mode)?;
-        return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
+        Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
     }
 
-    /// Parses `move |args| expr`.
-    fn parse_lambda_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+    /// Parses a closure expression (e.g., `move |args| expr`).
+    fn parse_closure_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
 
         let movability = if self.eat_keyword(kw::Static) {
@@ -1115,7 +1113,7 @@ impl<'a> Parser<'a> {
             IsAsync::NotAsync
         };
         if asyncness.is_async() {
-            // Feature gate `async ||` closures.
+            // Feature-gate `async ||` closures.
             self.sess.gated_spans.async_closure.borrow_mut().push(self.prev_span);
         }
 
@@ -1128,8 +1126,7 @@ impl<'a> Parser<'a> {
                 self.parse_expr_res(restrictions, None)?
             },
             _ => {
-                // If an explicit return type is given, require a
-                // block to appear (RFC 968).
+                // If an explicit return type is given, require a block to appear (RFC 968).
                 let body_lo = self.token.span;
                 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
             }
@@ -1141,7 +1138,7 @@ impl<'a> Parser<'a> {
             attrs))
     }
 
-    /// Parse an optional `move` prefix to a closure lke construct.
+    /// Parses an optional `move` prefix to a closure lke construct.
     fn parse_capture_clause(&mut self) -> CaptureBy {
         if self.eat_keyword(kw::Move) {
             CaptureBy::Value
@@ -1176,7 +1173,7 @@ impl<'a> Parser<'a> {
         }))
     }
 
-    /// Parses a parameter in a lambda header (e.g., `|arg, arg|`).
+    /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
     fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
         let lo = self.token.span;
         let attrs = self.parse_param_attributes()?;
@@ -1185,7 +1182,7 @@ impl<'a> Parser<'a> {
             self.parse_ty()?
         } else {
             P(Ty {
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 node: TyKind::Infer,
                 span: self.prev_span,
             })
@@ -1196,7 +1193,8 @@ impl<'a> Parser<'a> {
             ty: t,
             pat,
             span,
-            id: ast::DUMMY_NODE_ID
+            id: DUMMY_NODE_ID,
+            is_placeholder: false,
         })
     }
 
@@ -1233,7 +1231,7 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
     }
 
-    /// Parse the condition of a `if`- or `while`-expression
+    /// Parses the condition of a `if` or `while` expression.
     fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
         let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
 
@@ -1250,8 +1248,7 @@ impl<'a> Parser<'a> {
     /// The `let` token has already been eaten.
     fn parse_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         let lo = self.prev_span;
-        // FIXME(or_patterns, Centril | dlrobertson): use `parse_top_pat` instead.
-        let pat = self.parse_top_pat_unpack(GateOr::No)?;
+        let pat = self.parse_top_pat(GateOr::No)?;
         self.expect(&token::Eq)?;
         let expr = self.with_res(
             Restrictions::NO_STRUCT_LITERAL,
@@ -1262,7 +1259,7 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
     }
 
-    /// `else` token already eaten
+    /// Parses an `else { ... }` expression (`else` token already eaten).
     fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
         if self.eat_keyword(kw::If) {
             return self.parse_if_expr(ThinVec::new());
@@ -1272,7 +1269,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parse a 'for' .. 'in' expression ('for' token already eaten)
+    /// Parses a `for ... in` expression (`for` token already eaten).
     fn parse_for_expr(
         &mut self,
         opt_label: Option<Label>,
@@ -1328,7 +1325,7 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs))
     }
 
-    /// Parse `loop {...}`, `loop` token already eaten.
+    /// Parses `loop { ... }` (`loop` token already eaten).
     fn parse_loop_expr(
         &mut self,
         opt_label: Option<Label>,
@@ -1351,7 +1348,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    // `match` token already eaten
+    /// Parses a `match ... { ... }` expression (`match` token already eaten).
     fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         let match_span = self.prev_span;
         let lo = self.prev_span;
@@ -1393,8 +1390,7 @@ impl<'a> Parser<'a> {
     crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
         let attrs = self.parse_outer_attributes()?;
         let lo = self.token.span;
-        // FIXME(or_patterns, Centril | dlrobertson): use `parse_top_pat` instead.
-        let pat = self.parse_top_pat_unpack(GateOr::No)?;
+        let pat = self.parse_top_pat(GateOr::No)?;
         let guard = if self.eat_keyword(kw::If) {
             Some(self.parse_expr()?)
         } else {
@@ -1455,11 +1451,12 @@ impl<'a> Parser<'a> {
 
         Ok(ast::Arm {
             attrs,
-            pats: pat, // FIXME(or_patterns, Centril | dlrobertson): this should just be `pat,`.
+            pat,
             guard,
             body: expr,
             span: lo.to(hi),
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
+            is_placeholder: false,
         })
     }
 
@@ -1493,7 +1490,7 @@ impl<'a> Parser<'a> {
         self.token.is_keyword(kw::Try) &&
         self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
         self.token.span.rust_2018() &&
-        // prevent `while try {} {}`, `if try {} {} else {}`, etc.
+        // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
         !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
     }
 
@@ -1506,7 +1503,7 @@ impl<'a> Parser<'a> {
         attrs.extend(iattrs);
         Ok(self.mk_expr(
             span_lo.to(body.span),
-            ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
+            ExprKind::Async(capture_clause, DUMMY_NODE_ID, body), attrs))
     }
 
     fn is_async_block(&self) -> bool {
@@ -1529,18 +1526,18 @@ impl<'a> Parser<'a> {
     ) -> Option<PResult<'a, P<Expr>>> {
         let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
         let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
-            // `{ ident, ` cannot start a block
+            // `{ ident, ` cannot start a block.
             self.look_ahead(2, |t| t == &token::Comma) ||
             self.look_ahead(2, |t| t == &token::Colon) && (
-                // `{ ident: token, ` cannot start a block
+                // `{ ident: token, ` cannot start a block.
                 self.look_ahead(4, |t| t == &token::Comma) ||
-                // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
+                // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
                 self.look_ahead(3, |t| !t.can_begin_type())
             )
         );
 
         if struct_allowed || certainly_not_a_block() {
-            // This is a struct literal, but we don't can't accept them here
+            // This is a struct literal, but we don't can't accept them here.
             let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
             if let (Ok(expr), false) = (&expr, struct_allowed) {
                 self.struct_span_err(
@@ -1608,14 +1605,15 @@ impl<'a> Parser<'a> {
             let mut recovery_field = None;
             if let token::Ident(name, _) = self.token.kind {
                 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
-                    // Use in case of error after field-looking code: `S { foo: () with a }`
+                    // Use in case of error after field-looking code: `S { foo: () with a }`.
                     recovery_field = Some(ast::Field {
                         ident: Ident::new(name, self.token.span),
                         span: self.token.span,
                         expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()),
                         is_shorthand: false,
                         attrs: ThinVec::new(),
-                        id: ast::DUMMY_NODE_ID,
+                        id: DUMMY_NODE_ID,
+                        is_placeholder: false,
                     });
                 }
             }
@@ -1641,7 +1639,7 @@ impl<'a> Parser<'a> {
             match self.expect_one_of(&[token::Comma],
                                      &[token::CloseDelim(token::Brace)]) {
                 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
-                    // only include the field if there's no parse error for the field name
+                    // Only include the field if there's no parse error for the field name.
                     fields.push(f);
                 }
                 Err(mut e) => {
@@ -1661,7 +1659,7 @@ impl<'a> Parser<'a> {
         return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
     }
 
-    /// Parse ident (COLON expr)?
+    /// Parses `ident (COLON expr)?`.
     fn parse_field(&mut self) -> PResult<'a, Field> {
         let attrs = self.parse_outer_attributes()?;
         let lo = self.token.span;
@@ -1701,7 +1699,8 @@ impl<'a> Parser<'a> {
             expr,
             is_shorthand,
             attrs: attrs.into(),
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
+            is_placeholder: false,
         })
     }
 
@@ -1774,6 +1773,6 @@ impl<'a> Parser<'a> {
     }
 
     crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
-        P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
+        P(Expr { node, span, attrs, id: DUMMY_NODE_ID })
     }
 }
diff --git a/src/libsyntax/parse/parser/generics.rs b/src/libsyntax/parse/parser/generics.rs
index 54f24f8ef2b21..3e6118ad86f47 100644
--- a/src/libsyntax/parse/parser/generics.rs
+++ b/src/libsyntax/parse/parser/generics.rs
@@ -49,7 +49,8 @@ impl<'a> Parser<'a> {
             bounds,
             kind: GenericParamKind::Type {
                 default,
-            }
+            },
+            is_placeholder: false
         })
     }
 
@@ -66,7 +67,8 @@ impl<'a> Parser<'a> {
             bounds: Vec::new(),
             kind: GenericParamKind::Const {
                 ty,
-            }
+            },
+            is_placeholder: false
         })
     }
 
@@ -90,6 +92,7 @@ impl<'a> Parser<'a> {
                     attrs: attrs.into(),
                     bounds,
                     kind: ast::GenericParamKind::Lifetime,
+                    is_placeholder: false
                 });
             } else if self.check_keyword(kw::Const) {
                 // Parse const parameter.
diff --git a/src/libsyntax/parse/parser/item.rs b/src/libsyntax/parse/parser/item.rs
index 59a3ade9c30e5..cf196645e4f7b 100644
--- a/src/libsyntax/parse/parser/item.rs
+++ b/src/libsyntax/parse/parser/item.rs
@@ -2,34 +2,36 @@ use super::{Parser, PResult, PathStyle, SemiColonMode, BlockMode};
 
 use crate::maybe_whole;
 use crate::ptr::P;
-use crate::ast::{self, Ident, Attribute, AttrStyle};
-use crate::ast::{Item, ItemKind, ImplItem, TraitItem, TraitItemKind};
-use crate::ast::{UseTree, UseTreeKind, PathSegment};
-use crate::ast::{IsAuto, Constness, IsAsync, Unsafety, Defaultness};
-use crate::ast::{Visibility, VisibilityKind, Mutability, FnDecl, FnHeader};
-use crate::ast::{ForeignItem, ForeignItemKind};
-use crate::ast::{Ty, TyKind, GenericBounds, TraitRef};
-use crate::ast::{EnumDef, VariantData, StructField, AnonConst};
-use crate::ast::{Mac, MacDelimiter};
+use crate::ast::{
+    self, DUMMY_NODE_ID, Ident, Attribute, AttrStyle,
+    Item, ItemKind, ImplItem, TraitItem, TraitItemKind,
+    UseTree, UseTreeKind, PathSegment,
+    IsAuto, Constness, IsAsync, Unsafety, Defaultness,
+    Visibility, VisibilityKind, Mutability, FnDecl, FnHeader,
+    ForeignItem, ForeignItemKind,
+    Ty, TyKind, Generics, GenericBounds, TraitRef,
+    EnumDef, VariantData, StructField, AnonConst,
+    Mac, MacDelimiter,
+};
 use crate::ext::base::DummyResult;
 use crate::parse::token;
 use crate::parse::parser::maybe_append;
-use crate::parse::diagnostics::{Error};
+use crate::parse::diagnostics::Error;
 use crate::tokenstream::{TokenTree, TokenStream};
 use crate::source_map::{respan, Span, Spanned};
 use crate::symbol::{kw, sym};
 
 use std::mem;
 use log::debug;
-use rustc_target::spec::abi::{Abi};
+use rustc_target::spec::abi::Abi;
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
 
-/// Whether the type alias or associated type is a concrete type or an opaque type
+/// Whether the type alias or associated type is a concrete type or an opaque type.
 #[derive(Debug)]
 pub enum AliasKind {
-    /// Just a new name for the same type
+    /// Just a new name for the same type.
     Weak(P<Ty>),
-    /// Only trait impls of the type will be usable, not the actual type itself
+    /// Only trait impls of the type will be usable, not the actual type itself.
     OpaqueTy(GenericBounds),
 }
 
@@ -200,7 +202,7 @@ impl<'a> Parser<'a> {
             return Ok(Some(item));
         }
 
-        // Parse `async unsafe? fn`.
+        // Parses `async unsafe? fn`.
         if self.check_keyword(kw::Async) {
             let async_span = self.token.span;
             if self.is_keyword_ahead(1, &[kw::Fn])
@@ -214,8 +216,8 @@ impl<'a> Parser<'a> {
                 let (ident, item_, extra_attrs) =
                     self.parse_item_fn(unsafety,
                                     respan(async_span, IsAsync::Async {
-                                        closure_id: ast::DUMMY_NODE_ID,
-                                        return_impl_trait_id: ast::DUMMY_NODE_ID,
+                                        closure_id: DUMMY_NODE_ID,
+                                        return_impl_trait_id: DUMMY_NODE_ID,
                                     }),
                                     respan(fn_span, Constness::NotConst),
                                     Abi::Rust)?;
@@ -286,7 +288,7 @@ impl<'a> Parser<'a> {
             && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
             // UNSAFE FUNCTION ITEM
             self.bump(); // `unsafe`
-            // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
+            // `{` is also expected after `unsafe`; in case of error, include it in the diagnostic.
             self.check(&token::OpenDelim(token::Brace));
             let abi = if self.eat_keyword(kw::Extern) {
                 self.parse_opt_abi()?.unwrap_or(Abi::C)
@@ -521,7 +523,7 @@ impl<'a> Parser<'a> {
 
             let mac_lo = self.token.span;
 
-            // item macro.
+            // Item macro
             let path = self.parse_path(PathStyle::Mod)?;
             self.expect(&token::Not)?;
             let (delim, tts) = self.expect_delimited_token_tree()?;
@@ -659,7 +661,7 @@ impl<'a> Parser<'a> {
         let mut generics = if self.choose_generics_over_qpath() {
             self.parse_generics()?
         } else {
-            ast::Generics::default()
+            Generics::default()
         };
 
         // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
@@ -676,7 +678,7 @@ impl<'a> Parser<'a> {
                           self.look_ahead(1, |t| t != &token::Lt) {
             let span = self.prev_span.between(self.token.span);
             self.struct_span_err(span, "missing trait in a trait impl").emit();
-            P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
+            P(Ty { node: TyKind::Path(None, err_path(span)), span, id: DUMMY_NODE_ID })
         } else {
             self.parse_ty()?
         };
@@ -798,7 +800,7 @@ impl<'a> Parser<'a> {
             self.expect(&token::Eq)?;
             let expr = self.parse_expr()?;
             self.expect(&token::Semi)?;
-            (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
+            (name, ast::ImplItemKind::Const(typ, expr), Generics::default())
         } else {
             let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
             attrs.extend(inner_attrs);
@@ -806,7 +808,7 @@ impl<'a> Parser<'a> {
         };
 
         Ok(ImplItem {
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             span: lo.to(self.prev_span),
             ident: name,
             vis,
@@ -847,14 +849,13 @@ impl<'a> Parser<'a> {
             !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
     }
 
-    /// Parse a method or a macro invocation in a trait impl.
+    /// Parses a method or a macro invocation in a trait impl.
     fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
-                         -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
-                             ast::ImplItemKind)> {
-        // code copied from parse_macro_use_or_failure... abstraction!
+                         -> PResult<'a, (Ident, Vec<Attribute>, Generics, ast::ImplItemKind)> {
+        // FIXME: code copied from `parse_macro_use_or_failure` -- use abstraction!
         if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
             // method macro
-            Ok((Ident::invalid(), vec![], ast::Generics::default(),
+            Ok((Ident::invalid(), vec![], Generics::default(),
                 ast::ImplItemKind::Macro(mac)))
         } else {
             let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
@@ -930,7 +931,7 @@ impl<'a> Parser<'a> {
         };
 
         if self.eat(&token::Eq) {
-            // it's a trait alias
+            // It's a trait alias.
             let bounds = self.parse_generic_bounds(None)?;
             tps.where_clause = self.parse_where_clause()?;
             self.expect(&token::Semi)?;
@@ -948,7 +949,7 @@ impl<'a> Parser<'a> {
             }
             Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
         } else {
-            // it's a normal trait
+            // It's a normal trait.
             tps.where_clause = self.parse_where_clause()?;
             self.expect(&token::OpenDelim(token::Brace))?;
             let mut trait_items = vec![];
@@ -1023,10 +1024,10 @@ impl<'a> Parser<'a> {
                 self.expect(&token::Semi)?;
                 None
             };
-            (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
+            (ident, TraitItemKind::Const(ty, default), Generics::default())
         } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
             // trait item macro.
-            (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
+            (Ident::invalid(), ast::TraitItemKind::Macro(mac), Generics::default())
         } else {
             let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
 
@@ -1089,7 +1090,7 @@ impl<'a> Parser<'a> {
         };
 
         Ok(TraitItem {
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             ident: name,
             attrs,
             generics,
@@ -1103,7 +1104,7 @@ impl<'a> Parser<'a> {
     ///
     ///     TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
     fn parse_trait_item_assoc_ty(&mut self)
-        -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
+        -> PResult<'a, (Ident, TraitItemKind, Generics)> {
         let ident = self.parse_ident()?;
         let mut generics = self.parse_generics()?;
 
@@ -1165,7 +1166,7 @@ impl<'a> Parser<'a> {
                     UseTreeKind::Nested(self.parse_use_tree_list()?)
                 }
             } else {
-                UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
+                UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
             }
         };
 
@@ -1178,7 +1179,7 @@ impl<'a> Parser<'a> {
     /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
     /// ```
     fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
-        self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, ast::DUMMY_NODE_ID)))
+        self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
             .map(|(r, _)| r)
     }
 
@@ -1240,9 +1241,9 @@ impl<'a> Parser<'a> {
         let mut idents = vec![];
         let mut replacement = vec![];
         let mut fixed_crate_name = false;
-        // Accept `extern crate name-like-this` for better diagnostics
+        // Accept `extern crate name-like-this` for better diagnostics.
         let dash = token::BinOp(token::BinOpToken::Minus);
-        if self.token == dash {  // Do not include `-` as part of the expected tokens list
+        if self.token == dash {  // Do not include `-` as part of the expected tokens list.
             while self.eat(&dash) {
                 fixed_crate_name = true;
                 replacement.push((self.prev_span, "_".to_string()));
@@ -1255,7 +1256,7 @@ impl<'a> Parser<'a> {
             for part in idents {
                 fixed_name.push_str(&format!("_{}", part.name));
             }
-            ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
+            ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
 
             self.struct_span_err(fixed_name_sp, error_msg)
                 .span_label(fixed_name_sp, "dash-separated idents are not valid")
@@ -1283,7 +1284,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses the name and optional generic types of a function header.
-    fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
+    fn parse_fn_header(&mut self) -> PResult<'a, (Ident, Generics)> {
         let id = self.parse_ident()?;
         let generics = self.parse_generics()?;
         Ok((id, generics))
@@ -1379,7 +1380,7 @@ impl<'a> Parser<'a> {
                     ForeignItem {
                         ident: Ident::invalid(),
                         span: lo.to(self.prev_span),
-                        id: ast::DUMMY_NODE_ID,
+                        id: DUMMY_NODE_ID,
                         attrs,
                         vis: visibility,
                         node: ForeignItemKind::Macro(mac),
@@ -1415,7 +1416,7 @@ impl<'a> Parser<'a> {
             ident,
             attrs,
             node: ForeignItemKind::Fn(decl, generics),
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             span: lo.to(hi),
             vis,
         })
@@ -1435,7 +1436,7 @@ impl<'a> Parser<'a> {
             ident,
             attrs,
             node: ForeignItemKind::Static(ty, mutbl),
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             span: lo.to(hi),
             vis,
         })
@@ -1453,7 +1454,7 @@ impl<'a> Parser<'a> {
             ident,
             attrs,
             node: ForeignItemKind::Ty,
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             span: lo.to(hi),
             vis
         })
@@ -1461,7 +1462,7 @@ impl<'a> Parser<'a> {
 
     fn is_static_global(&mut self) -> bool {
         if self.check_keyword(kw::Static) {
-            // Check if this could be a closure
+            // Check if this could be a closure.
             !self.look_ahead(1, |token| {
                 if token.is_keyword(kw::Move) {
                     return true;
@@ -1492,7 +1493,7 @@ impl<'a> Parser<'a> {
 
     /// Parses `type Foo = Bar;` or returns `None`
     /// without modifying the parser state.
-    fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
+    fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, Generics)>> {
         // This parses the grammar:
         //     Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
         if self.eat_keyword(kw::Type) {
@@ -1503,7 +1504,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a type alias or opaque type.
-    fn parse_type_alias(&mut self) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
+    fn parse_type_alias(&mut self) -> PResult<'a, (Ident, AliasKind, Generics)> {
         let ident = self.parse_ident()?;
         let mut tps = self.parse_generics()?;
         tps.where_clause = self.parse_where_clause()?;
@@ -1536,7 +1537,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses the part of an enum declaration following the `{`.
-    fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
+    fn parse_enum_def(&mut self, _generics: &Generics) -> PResult<'a, EnumDef> {
         let mut variants = Vec::new();
         while self.token != token::CloseDelim(token::Brace) {
             let variant_attrs = self.parse_outer_attributes()?;
@@ -1552,15 +1553,15 @@ impl<'a> Parser<'a> {
             } else if self.check(&token::OpenDelim(token::Paren)) {
                 VariantData::Tuple(
                     self.parse_tuple_struct_body()?,
-                    ast::DUMMY_NODE_ID,
+                    DUMMY_NODE_ID,
                 )
             } else {
-                VariantData::Unit(ast::DUMMY_NODE_ID)
+                VariantData::Unit(DUMMY_NODE_ID)
             };
 
             let disr_expr = if self.eat(&token::Eq) {
                 Some(AnonConst {
-                    id: ast::DUMMY_NODE_ID,
+                    id: DUMMY_NODE_ID,
                     value: self.parse_expr()?,
                 })
             } else {
@@ -1569,11 +1570,12 @@ impl<'a> Parser<'a> {
 
             let vr = ast::Variant {
                 ident,
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 attrs: variant_attrs,
                 data: struct_def,
                 disr_expr,
                 span: vlo.to(self.prev_span),
+                is_placeholder: false,
             };
             variants.push(vr);
 
@@ -1622,7 +1624,7 @@ impl<'a> Parser<'a> {
             generics.where_clause = self.parse_where_clause()?;
             if self.eat(&token::Semi) {
                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
-                VariantData::Unit(ast::DUMMY_NODE_ID)
+                VariantData::Unit(DUMMY_NODE_ID)
             } else {
                 // If we see: `struct Foo<T> where T: Copy { ... }`
                 let (fields, recovered) = self.parse_record_struct_body()?;
@@ -1630,14 +1632,14 @@ impl<'a> Parser<'a> {
             }
         // No `where` so: `struct Foo<T>;`
         } else if self.eat(&token::Semi) {
-            VariantData::Unit(ast::DUMMY_NODE_ID)
+            VariantData::Unit(DUMMY_NODE_ID)
         // Record-style struct definition
         } else if self.token == token::OpenDelim(token::Brace) {
             let (fields, recovered) = self.parse_record_struct_body()?;
             VariantData::Struct(fields, recovered)
         // Tuple-style struct definition with optional where-clause.
         } else if self.token == token::OpenDelim(token::Paren) {
-            let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
+            let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
             generics.where_clause = self.parse_where_clause()?;
             self.expect(&token::Semi)?;
             body
@@ -1726,9 +1728,10 @@ impl<'a> Parser<'a> {
                 span: lo.to(ty.span),
                 vis,
                 ident: None,
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 ty,
                 attrs,
+                is_placeholder: false,
             })
         }).map(|(r, _)| r)
     }
@@ -1817,9 +1820,10 @@ impl<'a> Parser<'a> {
             span: lo.to(self.prev_span),
             ident: Some(name),
             vis,
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             ty,
             attrs,
+            is_placeholder: false,
         })
     }
 
@@ -1909,7 +1913,7 @@ impl<'a> Parser<'a> {
         P(Item {
             ident,
             attrs,
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             node,
             vis,
             span,
diff --git a/src/libsyntax/parse/parser/module.rs b/src/libsyntax/parse/parser/module.rs
index 3f6f87b1c44b6..2d2fb487d7df2 100644
--- a/src/libsyntax/parse/parser/module.rs
+++ b/src/libsyntax/parse/parser/module.rs
@@ -36,12 +36,12 @@ impl<'a> Parser<'a> {
         krate
     }
 
-    /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
+    /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
     pub(super) fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
         let (in_cfg, outer_attrs) = {
             let mut strip_unconfigured = crate::config::StripUnconfigured {
                 sess: self.sess,
-                features: None, // don't perform gated feature checking
+                features: None, // Don't perform gated feature checking.
             };
             let mut outer_attrs = outer_attrs.to_owned();
             strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
@@ -57,7 +57,7 @@ impl<'a> Parser<'a> {
                     self.submod_path(id, &outer_attrs, id_span)?;
                 let (module, mut attrs) =
                     self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
-                // Record that we fetched the mod from an external file
+                // Record that we fetched the mod from an external file.
                 if warn {
                     let attr = attr::mk_attr_outer(
                         attr::mk_word_item(Ident::with_dummy_span(sym::warn_directory_ownership)));
diff --git a/src/libsyntax/parse/parser/pat.rs b/src/libsyntax/parse/parser/pat.rs
index 823f880337d13..08ee3a6bd86d4 100644
--- a/src/libsyntax/parse/parser/pat.rs
+++ b/src/libsyntax/parse/parser/pat.rs
@@ -36,16 +36,6 @@ impl<'a> Parser<'a> {
         self.parse_pat_with_range_pat(true, expected)
     }
 
-    // FIXME(or_patterns, Centril | dlrobertson):
-    // remove this and use `parse_top_pat` everywhere it is used instead.
-    pub(super) fn parse_top_pat_unpack(&mut self, gate_or: GateOr) -> PResult<'a, Vec<P<Pat>>> {
-        self.parse_top_pat(gate_or)
-            .map(|pat| pat.and_then(|pat| match pat.node {
-                PatKind::Or(pats) => pats,
-                node => vec![self.mk_pat(pat.span, node)],
-            }))
-    }
-
     /// Entry point to the main pattern parser.
     /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
     pub(super) fn parse_top_pat(&mut self, gate_or: GateOr) -> PResult<'a, P<Pat>> {
@@ -854,14 +844,14 @@ impl<'a> Parser<'a> {
         // Check if a colon exists one ahead. This means we're parsing a fieldname.
         let hi;
         let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
-            // Parsing a pattern of the form "fieldname: pat"
+            // Parsing a pattern of the form `fieldname: pat`.
             let fieldname = self.parse_field_name()?;
             self.bump();
             let pat = self.parse_pat_with_or_inner()?;
             hi = pat.span;
             (pat, fieldname, false)
         } else {
-            // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
+            // Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
             let is_box = self.eat_keyword(kw::Box);
             let boxed_span = self.token.span;
             let is_ref = self.eat_keyword(kw::Ref);
@@ -892,6 +882,7 @@ impl<'a> Parser<'a> {
             attrs: attrs.into(),
             id: ast::DUMMY_NODE_ID,
             span: lo.to(hi),
+            is_placeholder: false,
         })
     }
 
diff --git a/src/libsyntax/parse/parser/stmt.rs b/src/libsyntax/parse/parser/stmt.rs
index 651ebf6342e71..04bd61a4cfb5b 100644
--- a/src/libsyntax/parse/parser/stmt.rs
+++ b/src/libsyntax/parse/parser/stmt.rs
@@ -5,12 +5,12 @@ use super::pat::GateOr;
 
 use crate::ptr::P;
 use crate::{maybe_whole, ThinVec};
-use crate::ast::{self, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
+use crate::ast::{self, DUMMY_NODE_ID, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
 use crate::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac, MacDelimiter};
 use crate::ext::base::DummyResult;
 use crate::parse::{classify, DirectoryOwnership};
 use crate::parse::diagnostics::Error;
-use crate::parse::token::{self};
+use crate::parse::token;
 use crate::source_map::{respan, Span};
 use crate::symbol::{kw, sym};
 
@@ -18,7 +18,7 @@ use std::mem;
 use errors::Applicability;
 
 impl<'a> Parser<'a> {
-    /// Parse a statement. This stops just before trailing semicolons on everything but items.
+    /// Parses a statement. This stops just before trailing semicolons on everything but items.
     /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
     pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
         Ok(self.parse_stmt_(true))
@@ -43,7 +43,7 @@ impl<'a> Parser<'a> {
 
         Ok(Some(if self.eat_keyword(kw::Let) {
             Stmt {
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 node: StmtKind::Local(self.parse_local(attrs.into())?),
                 span: lo.to(self.prev_span),
             }
@@ -53,7 +53,7 @@ impl<'a> Parser<'a> {
             lo,
         )? {
             Stmt {
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 node: StmtKind::Item(macro_def),
                 span: lo.to(self.prev_span),
             }
@@ -85,7 +85,7 @@ impl<'a> Parser<'a> {
                 })?;
 
                 return Ok(Some(Stmt {
-                    id: ast::DUMMY_NODE_ID,
+                    id: DUMMY_NODE_ID,
                     node: StmtKind::Expr(expr),
                     span: lo.to(self.prev_span),
                 }));
@@ -114,17 +114,17 @@ impl<'a> Parser<'a> {
             // We used to incorrectly stop parsing macro-expanded statements here.
             // If the next token will be an error anyway but could have parsed with the
             // earlier behavior, stop parsing here and emit a warning to avoid breakage.
-            else if macro_legacy_warnings &&
-                    self.token.can_begin_expr() &&
-                    match self.token.kind {
-                // These can continue an expression, so we can't stop parsing and warn.
-                token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
-                token::BinOp(token::Minus) | token::BinOp(token::Star) |
-                token::BinOp(token::And) | token::BinOp(token::Or) |
-                token::AndAnd | token::OrOr |
-                token::DotDot | token::DotDotDot | token::DotDotEq => false,
-                _ => true,
-            } {
+            else if macro_legacy_warnings && self.token.can_begin_expr() &&
+                match self.token.kind {
+                    // These can continue an expression, so we can't stop parsing and warn.
+                    token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
+                    token::BinOp(token::Minus) | token::BinOp(token::Star) |
+                    token::BinOp(token::And) | token::BinOp(token::Or) |
+                    token::AndAnd | token::OrOr |
+                    token::DotDot | token::DotDotDot | token::DotDotEq => false,
+                    _ => true,
+                }
+            {
                 self.warn_missing_semicolon();
                 StmtKind::Mac(P((mac, style, attrs.into())))
             } else {
@@ -135,7 +135,7 @@ impl<'a> Parser<'a> {
                 StmtKind::Expr(e)
             };
             Stmt {
-                id: ast::DUMMY_NODE_ID,
+                id: DUMMY_NODE_ID,
                 span: lo.to(hi),
                 node,
             }
@@ -148,7 +148,7 @@ impl<'a> Parser<'a> {
 
             match item {
                 Some(i) => Stmt {
-                    id: ast::DUMMY_NODE_ID,
+                    id: DUMMY_NODE_ID,
                     span: lo.to(i.span),
                     node: StmtKind::Item(i),
                 },
@@ -178,7 +178,7 @@ impl<'a> Parser<'a> {
                         // an empty tuple that spans the excess semicolons
                         // to preserve this info until the lint stage
                         return Ok(Some(Stmt {
-                            id: ast::DUMMY_NODE_ID,
+                            id: DUMMY_NODE_ID,
                             span: lo.to(last_semi),
                             node: StmtKind::Semi(self.mk_expr(lo.to(last_semi),
                                 ExprKind::Tup(Vec::new()),
@@ -196,7 +196,7 @@ impl<'a> Parser<'a> {
                     let e = self.parse_expr_res(
                         Restrictions::STMT_EXPR, Some(attrs.into()))?;
                     Stmt {
-                        id: ast::DUMMY_NODE_ID,
+                        id: DUMMY_NODE_ID,
                         span: lo.to(e.span),
                         node: StmtKind::Expr(e),
                     }
@@ -218,7 +218,7 @@ impl<'a> Parser<'a> {
             match self.parse_ty() {
                 Ok(ty) => (None, Some(ty)),
                 Err(mut err) => {
-                    // Rewind to before attempting to parse the type and continue parsing
+                    // Rewind to before attempting to parse the type and continue parsing.
                     let parser_snapshot_after_type = self.clone();
                     mem::replace(self, parser_snapshot_before_type);
 
@@ -272,7 +272,7 @@ impl<'a> Parser<'a> {
             ty,
             pat,
             init,
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             span: lo.to(hi),
             attrs,
         }))
@@ -334,18 +334,18 @@ impl<'a> Parser<'a> {
             //    if (cond)
             //      bar;
             //
-            // Which is valid in other languages, but not Rust.
+            // which is valid in other languages, but not Rust.
             match self.parse_stmt_without_recovery(false) {
                 Ok(Some(stmt)) => {
                     if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
                         || do_not_suggest_help {
-                        // if the next token is an open brace (e.g., `if a b {`), the place-
-                        // inside-a-block suggestion would be more likely wrong than right
+                        // If the next token is an open brace (e.g., `if a b {`), the place-
+                        // inside-a-block suggestion would be more likely wrong than right.
                         e.span_label(sp, "expected `{`");
                         return Err(e);
                     }
                     let mut stmt_span = stmt.span;
-                    // expand the span to include the semicolon, if it exists
+                    // Expand the span to include the semicolon, if it exists.
                     if self.eat(&token::Semi) {
                         stmt_span = stmt_span.with_hi(self.prev_span.hi());
                     }
@@ -354,7 +354,7 @@ impl<'a> Parser<'a> {
                             stmt_span,
                             "try placing this code inside a block",
                             format!("{{ {} }}", snippet),
-                            // speculative, has been misleading in the past (#46836)
+                            // Speculative; has been misleading in the past (#46836).
                             Applicability::MaybeIncorrect,
                         );
                     }
@@ -399,7 +399,7 @@ impl<'a> Parser<'a> {
                     err.emit();
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     Some(Stmt {
-                        id: ast::DUMMY_NODE_ID,
+                        id: DUMMY_NODE_ID,
                         node: StmtKind::Expr(DummyResult::raw_expr(self.token.span, true)),
                         span: self.token.span,
                     })
@@ -415,7 +415,7 @@ impl<'a> Parser<'a> {
         }
         Ok(P(ast::Block {
             stmts,
-            id: ast::DUMMY_NODE_ID,
+            id: DUMMY_NODE_ID,
             rules: s,
             span: lo.to(self.prev_span),
         }))
@@ -423,7 +423,7 @@ impl<'a> Parser<'a> {
 
     /// Parses a statement, including the trailing semicolon.
     crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
-        // skip looking for a trailing semicolon when we have an interpolated statement
+        // Skip looking for a trailing semicolon when we have an interpolated statement.
         maybe_whole!(self, NtStmt, |x| Some(x));
 
         let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
@@ -469,7 +469,7 @@ impl<'a> Parser<'a> {
         self.diagnostic().struct_span_warn(self.token.span, {
             &format!("expected `;`, found {}", self.this_token_descr())
         }).note({
-            "This was erroneously allowed and will become a hard error in a future release"
+            "this was erroneously allowed and will become a hard error in a future release"
         }).emit();
     }
 }
diff --git a/src/libsyntax/parse/tests.rs b/src/libsyntax/parse/tests.rs
index 6a789ef99d672..5cb59b3f82790 100644
--- a/src/libsyntax/parse/tests.rs
+++ b/src/libsyntax/parse/tests.rs
@@ -25,12 +25,12 @@ fn parse_item_from_source_str(name: FileName, source: String, sess: &ParseSess)
     new_parser_from_source_str(sess, name, source).parse_item()
 }
 
-// produce a syntax_pos::span
+// Produces a `syntax_pos::span`.
 fn sp(a: u32, b: u32) -> Span {
     Span::with_root_ctxt(BytePos(a), BytePos(b))
 }
 
-/// Parse a string, return an expr
+/// Parses a string, return an expression.
 fn string_to_expr(source_str : String) -> P<ast::Expr> {
     let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
@@ -38,7 +38,7 @@ fn string_to_expr(source_str : String) -> P<ast::Expr> {
     })
 }
 
-/// Parse a string, return an item
+/// Parses a string, returns an item.
 fn string_to_item(source_str : String) -> Option<P<ast::Item>> {
     let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
@@ -53,7 +53,7 @@ fn string_to_item(source_str : String) -> Option<P<ast::Item>> {
     })
 }
 
-// check the token-tree-ization of macros
+// Checks the token-tree-ization of macros.
 #[test]
 fn string_to_tts_macro () {
     with_default_globals(|| {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 37305055e62a3..bf36c0d2f5658 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -35,6 +35,7 @@ pub enum AnnNode<'a> {
     SubItem(ast::NodeId),
     Expr(&'a ast::Expr),
     Pat(&'a ast::Pat),
+    Crate(&'a ast::Crate),
 }
 
 pub trait PpAnn {
@@ -119,23 +120,28 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
     if is_expanded && sess.injected_crate_name.try_get().is_some() {
         // We need to print `#![no_std]` (and its feature gate) so that
         // compiling pretty-printed source won't inject libstd again.
-        // However we don't want these attributes in the AST because
+        // However, we don't want these attributes in the AST because
         // of the feature gate, so we fake them up here.
 
-        // #![feature(prelude_import)]
+        // `#![feature(prelude_import)]`
         let pi_nested = attr::mk_nested_word_item(ast::Ident::with_dummy_span(sym::prelude_import));
         let list = attr::mk_list_item(ast::Ident::with_dummy_span(sym::feature), vec![pi_nested]);
         let fake_attr = attr::mk_attr_inner(list);
         s.print_attribute(&fake_attr);
 
-        // #![no_std]
-        let no_std_meta = attr::mk_word_item(ast::Ident::with_dummy_span(sym::no_std));
-        let fake_attr = attr::mk_attr_inner(no_std_meta);
-        s.print_attribute(&fake_attr);
+        // Currently, in Rust 2018 we don't have `extern crate std;` at the crate
+        // root, so this is not needed, and actually breaks things.
+        if sess.edition == syntax_pos::edition::Edition::Edition2015 {
+            // `#![no_std]`
+            let no_std_meta = attr::mk_word_item(ast::Ident::with_dummy_span(sym::no_std));
+            let fake_attr = attr::mk_attr_inner(no_std_meta);
+            s.print_attribute(&fake_attr);
+        }
     }
 
     s.print_mod(&krate.module, &krate.attrs);
     s.print_remaining_comments();
+    s.ann.post(&mut s, AnnNode::Crate(krate));
     s.s.eof()
 }
 
@@ -394,9 +400,9 @@ pub fn vis_to_string(v: &ast::Visibility) -> String {
 
 fn block_to_string(blk: &ast::Block) -> String {
     to_string(|s| {
-        // containing cbox, will be closed by print-block at }
+        // Containing cbox, will be closed by `print_block` at `}`.
         s.cbox(INDENT_UNIT);
-        // head-ibox, will be closed by print-block after {
+        // Head-ibox, will be closed by `print_block` after `{`.
         s.ibox(0);
         s.print_block(blk)
     })
@@ -439,7 +445,7 @@ impl std::ops::DerefMut for State<'_> {
     }
 }
 
-pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefMut {
+pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::DerefMut {
     fn comments(&mut self) -> &mut Option<Comments<'a>>;
     fn print_ident(&mut self, ident: ast::Ident);
     fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool);
@@ -491,7 +497,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
                 self.hardbreak_if_not_bol();
                 for line in &cmnt.lines {
                     // Don't print empty lines because they will end up as trailing
-                    // whitespace
+                    // whitespace.
                     if !line.is_empty() {
                         self.word(line.clone());
                     }
@@ -779,11 +785,11 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
 
     fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) {
         let w = w.into();
-        // outer-box is consistent
+        // Outer-box is consistent.
         self.cbox(INDENT_UNIT);
-        // head-box is inconsistent
+        // Head-box is inconsistent.
         self.ibox(w.len() + 1);
-        // keyword that starts the head
+        // Keyword that starts the head.
         if !w.is_empty() {
             self.word_nbsp(w);
         }
@@ -791,7 +797,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
 
     fn bopen(&mut self) {
         self.word("{");
-        self.end(); // close the head-box
+        self.end(); // Close the head-box.
     }
 
     fn bclose_maybe_open(&mut self, span: syntax_pos::Span, close_box: bool) {
@@ -799,7 +805,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
         self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
         self.word("}");
         if close_box {
-            self.end(); // close the outer-box
+            self.end(); // Close the outer-box.
         }
     }
 
@@ -896,8 +902,6 @@ impl<'a> State<'a> {
         self.s.word("*/")
     }
 
-
-
     crate fn commasep_cmnt<T, F, G>(&mut self,
                                   b: Breaks,
                                   elts: &[T],
@@ -924,12 +928,12 @@ impl<'a> State<'a> {
     }
 
     crate fn commasep_exprs(&mut self, b: Breaks,
-                          exprs: &[P<ast::Expr>]) {
+                            exprs: &[P<ast::Expr>]) {
         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
     }
 
     crate fn print_mod(&mut self, _mod: &ast::Mod,
-                     attrs: &[ast::Attribute]) {
+                       attrs: &[ast::Attribute]) {
         self.print_inner_attributes(attrs);
         for item in &_mod.items {
             self.print_item(item);
@@ -937,7 +941,7 @@ impl<'a> State<'a> {
     }
 
     crate fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod,
-                             attrs: &[ast::Attribute]) {
+                               attrs: &[ast::Attribute]) {
         self.print_inner_attributes(attrs);
         for item in &nmod.items {
             self.print_foreign_item(item);
@@ -1132,7 +1136,7 @@ impl<'a> State<'a> {
         self.s.word(";")
     }
 
-    /// Pretty-print an item
+    /// Pretty-prints an item.
     crate fn print_item(&mut self, item: &ast::Item) {
         self.hardbreak_if_not_bol();
         self.maybe_print_comment(item.span.lo());
@@ -1367,8 +1371,12 @@ impl<'a> State<'a> {
                 }
             }
             ast::ItemKind::MacroDef(ref macro_def) => {
-                let (kw, has_bang) =
-                    if macro_def.legacy { ("macro_rules", true) } else { ("macro", false) };
+                let (kw, has_bang) = if macro_def.legacy {
+                    ("macro_rules", true)
+                } else {
+                    self.print_visibility(&item.vis);
+                    ("macro", false)
+                };
                 self.print_mac_common(
                     Some(MacHeader::Keyword(kw)),
                     has_bang,
@@ -1485,7 +1493,7 @@ impl<'a> State<'a> {
                     self.s.word(";");
                 }
                 self.end();
-                self.end(); // close the outer-box
+                self.end(); // Close the outer-box.
             }
             ast::VariantData::Struct(..) => {
                 self.print_where_clause(&generics.where_clause);
@@ -1710,11 +1718,11 @@ impl<'a> State<'a> {
         self.ann.post(self, AnnNode::Block(blk))
     }
 
-    /// Print a `let pats = scrutinee` expression.
-    crate fn print_let(&mut self, pats: &[P<ast::Pat>], scrutinee: &ast::Expr) {
+    /// Print a `let pat = scrutinee` expression.
+    crate fn print_let(&mut self, pat: &ast::Pat, scrutinee: &ast::Expr) {
         self.s.word("let ");
 
-        self.print_pats(pats);
+        self.print_pat(pat);
         self.s.space();
 
         self.word_space("=");
@@ -1789,7 +1797,7 @@ impl<'a> State<'a> {
         self.print_expr_cond_paren(expr, expr.precedence().order() < prec)
     }
 
-    /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
+    /// Prints an expr using syntax that's acceptable in a condition position, such as the `cond` in
     /// `if cond { ... }`.
     crate fn print_expr_as_cond(&mut self, expr: &ast::Expr) {
         self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
@@ -1808,7 +1816,7 @@ impl<'a> State<'a> {
         }
     }
 
-    /// Print `expr` or `(expr)` when `needs_par` holds.
+    /// Prints `expr` or `(expr)` when `needs_par` holds.
     fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) {
         if needs_par {
             self.popen();
@@ -2040,8 +2048,8 @@ impl<'a> State<'a> {
                 self.word_space(":");
                 self.print_type(ty);
             }
-            ast::ExprKind::Let(ref pats, ref scrutinee) => {
-                self.print_let(pats, scrutinee);
+            ast::ExprKind::Let(ref pat, ref scrutinee) => {
+                self.print_let(pat, scrutinee);
             }
             ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
                 self.print_if(test, blk, elseopt.as_ref().map(|e| &**e));
@@ -2451,21 +2459,16 @@ impl<'a> State<'a> {
         self.ann.post(self, AnnNode::Pat(pat))
     }
 
-    fn print_pats(&mut self, pats: &[P<ast::Pat>]) {
-        self.strsep("|", true, Inconsistent, pats, |s, p| s.print_pat(p));
-    }
-
     fn print_arm(&mut self, arm: &ast::Arm) {
-        // I have no idea why this check is necessary, but here it
-        // is :(
+        // Note, I have no idea why this check is necessary, but here it is.
         if arm.attrs.is_empty() {
             self.s.space();
         }
         self.cbox(INDENT_UNIT);
         self.ibox(0);
-        self.maybe_print_comment(arm.pats[0].span.lo());
+        self.maybe_print_comment(arm.pat.span.lo());
         self.print_outer_attributes(&arm.attrs);
-        self.print_pats(&arm.pats);
+        self.print_pat(&arm.pat);
         self.s.space();
         if let Some(ref e) = arm.guard {
             self.word_space("if");
@@ -2481,21 +2484,21 @@ impl<'a> State<'a> {
                     self.word_space(":");
                 }
 
-                // the block will close the pattern's ibox
+                // The block will close the pattern's ibox.
                 self.print_block_unclosed_indent(blk);
 
-                // If it is a user-provided unsafe block, print a comma after it
+                // If it is a user-provided unsafe block, print a comma after it.
                 if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
                     self.s.word(",");
                 }
             }
             _ => {
-                self.end(); // close the ibox for the pattern
+                self.end(); // Close the ibox for the pattern.
                 self.print_expr(&arm.body);
                 self.s.word(",");
             }
         }
-        self.end(); // close enclosing cbox
+        self.end(); // Close enclosing cbox.
     }
 
     fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
diff --git a/src/libsyntax/print/pprust/tests.rs b/src/libsyntax/print/pprust/tests.rs
index 25214673e6935..05d78cdd87ec6 100644
--- a/src/libsyntax/print/pprust/tests.rs
+++ b/src/libsyntax/print/pprust/tests.rs
@@ -12,8 +12,8 @@ fn fun_to_string(
         s.head("");
         s.print_fn(decl, header, Some(name),
                    generics, &source_map::dummy_spanned(ast::VisibilityKind::Inherited));
-        s.end(); // Close the head box
-        s.end(); // Close the outer box
+        s.end(); // Close the head box.
+        s.end(); // Close the outer box.
     })
 }
 
@@ -58,10 +58,10 @@ fn test_variant_to_string() {
             ident,
             attrs: Vec::new(),
             id: ast::DUMMY_NODE_ID,
-            // making this up as I go.... ?
             data: ast::VariantData::Unit(ast::DUMMY_NODE_ID),
             disr_expr: None,
             span: syntax_pos::DUMMY_SP,
+            is_placeholder: false,
         };
 
         let varstr = variant_to_string(&var);
diff --git a/src/libsyntax/source_map.rs b/src/libsyntax/source_map.rs
index 7190cfd72a959..7d0d2392945e5 100644
--- a/src/libsyntax/source_map.rs
+++ b/src/libsyntax/source_map.rs
@@ -1,10 +1,10 @@
-//! The SourceMap tracks all the source code used within a single crate, mapping
+//! The `SourceMap` tracks all the source code used within a single crate, mapping
 //! from integer byte positions to the original source code location. Each bit
 //! of source parsed during crate parsing (typically files, in-memory strings,
 //! or various bits of macro expansion) cover a continuous range of bytes in the
-//! SourceMap and are represented by SourceFiles. Byte positions are stored in
-//! `spans` and used pervasively in the compiler. They are absolute positions
-//! within the SourceMap, which upon request can be converted to line and column
+//! `SourceMap` and are represented by `SourceFile`s. Byte positions are stored in
+//! `Span` and used pervasively in the compiler. They are absolute positions
+//! within the `SourceMap`, which upon request can be converted to line and column
 //! information, source code snippets, etc.
 
 pub use syntax_pos::*;
@@ -94,7 +94,7 @@ impl FileLoader for RealFileLoader {
     }
 }
 
-// This is a SourceFile identifier that is used to correlate SourceFiles between
+// This is a `SourceFile` identifier that is used to correlate `SourceFile`s between
 // subsequent compilation sessions (which is something we need to do during
 // incremental compilation).
 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
@@ -103,8 +103,8 @@ pub struct StableSourceFileId(u128);
 impl StableSourceFileId {
     pub fn new(source_file: &SourceFile) -> StableSourceFileId {
         StableSourceFileId::new_from_pieces(&source_file.name,
-                                         source_file.name_was_remapped,
-                                         source_file.unmapped_path.as_ref())
+                                            source_file.name_was_remapped,
+                                            source_file.unmapped_path.as_ref())
     }
 
     pub fn new_from_pieces(name: &FileName,
@@ -134,7 +134,7 @@ pub struct SourceMap {
     files: Lock<SourceMapFiles>,
     file_loader: Box<dyn FileLoader + Sync + Send>,
     // This is used to apply the file path remapping as specified via
-    // --remap-path-prefix to all SourceFiles allocated within this SourceMap.
+    // `--remap-path-prefix` to all `SourceFile`s allocated within this `SourceMap`.
     path_mapping: FilePathMapping,
 }
 
@@ -204,14 +204,14 @@ impl SourceMap {
         match self.files.borrow().source_files.last() {
             None => 0,
             // Add one so there is some space between files. This lets us distinguish
-            // positions in the source_map, even in the presence of zero-length files.
+            // positions in the `SourceMap`, even in the presence of zero-length files.
             Some(last) => last.end_pos.to_usize() + 1,
         }
     }
 
-    /// Creates a new source_file.
-    /// If a file already exists in the source_map with the same id, that file is returned
-    /// unmodified
+    /// Creates a new `SourceFile`.
+    /// If a file already exists in the `SourceMap` with the same ID, that file is returned
+    /// unmodified.
     pub fn new_source_file(&self, filename: FileName, src: String) -> Lrc<SourceFile> {
         self.try_new_source_file(filename, src)
             .unwrap_or_else(|OffsetOverflowError| {
@@ -268,8 +268,8 @@ impl SourceMap {
         Ok(lrc_sf)
     }
 
-    /// Allocates a new SourceFile representing a source file from an external
-    /// crate. The source code of such an "imported source_file" is not available,
+    /// Allocates a new `SourceFile` representing a source file from an external
+    /// crate. The source code of such an "imported `SourceFile`" is not available,
     /// but we still know enough to generate accurate debuginfo location
     /// information for things inlined from other crates.
     pub fn new_imported_source_file(
@@ -334,7 +334,7 @@ impl SourceMap {
                  pos.col.to_usize() + 1)
     }
 
-    // If there is a doctest_offset, apply it to the line
+    // If there is a doctest offset, applies it to the line.
     pub fn doctest_offset_line(&self, file: &FileName, orig: usize) -> usize {
         return match file {
             FileName::DocTest(_, offset) => {
@@ -348,7 +348,7 @@ impl SourceMap {
         }
     }
 
-    /// Lookup source information about a BytePos
+    /// Looks up source information about a `BytePos`.
     pub fn lookup_char_pos(&self, pos: BytePos) -> Loc {
         let chpos = self.bytepos_to_file_charpos(pos);
         match self.lookup_line(pos) {
@@ -411,7 +411,7 @@ impl SourceMap {
         }
     }
 
-    // If the relevant source_file is empty, we don't return a line number.
+    // If the corresponding `SourceFile` is empty, does not return a line number.
     pub fn lookup_line(&self, pos: BytePos) -> Result<SourceFileAndLine, Lrc<SourceFile>> {
         let idx = self.lookup_source_file_idx(pos);
 
@@ -423,15 +423,15 @@ impl SourceMap {
         }
     }
 
-    /// Returns `Some(span)`, a union of the lhs and rhs span. The lhs must precede the rhs. If
-    /// there are gaps between lhs and rhs, the resulting union will cross these gaps.
-    /// For this to work, the spans have to be:
+    /// Returns `Some(span)`, a union of the LHS and RHS span. The LHS must precede the RHS. If
+    /// there are gaps between LHS and RHS, the resulting union will cross these gaps.
+    /// For this to work,
     ///
-    ///    * the ctxt of both spans much match
-    ///    * the lhs span needs to end on the same line the rhs span begins
-    ///    * the lhs span must start at or before the rhs span
+    ///    * the syntax contexts of both spans much match,
+    ///    * the LHS span needs to end on the same line the RHS span begins,
+    ///    * the LHS span must start at or before the RHS span.
     pub fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
-        // make sure we're at the same expansion id
+        // Ensure we're at the same expansion ID.
         if sp_lhs.ctxt() != sp_rhs.ctxt() {
             return None;
         }
@@ -445,12 +445,12 @@ impl SourceMap {
             Err(_) => return None
         };
 
-        // if we must cross lines to merge, don't merge
+        // If we must cross lines to merge, don't merge.
         if lhs_end.line != rhs_begin.line {
             return None;
         }
 
-        // ensure these follow the expected order and we don't overlap
+        // Ensure these follow the expected order and that we don't overlap.
         if (sp_lhs.lo() <= sp_rhs.lo()) && (sp_lhs.hi() <= sp_rhs.lo()) {
             Some(sp_lhs.to(sp_rhs))
         } else {
@@ -466,11 +466,12 @@ impl SourceMap {
         let lo = self.lookup_char_pos(sp.lo());
         let hi = self.lookup_char_pos(sp.hi());
         format!("{}:{}:{}: {}:{}",
-                        lo.file.name,
-                        lo.line,
-                        lo.col.to_usize() + 1,
-                        hi.line,
-                        hi.col.to_usize() + 1)
+            lo.file.name,
+            lo.line,
+            lo.col.to_usize() + 1,
+            hi.line,
+            hi.col.to_usize() + 1,
+        )
     }
 
     pub fn span_to_filename(&self, sp: Span) -> FileName {
@@ -479,7 +480,7 @@ impl SourceMap {
 
     pub fn span_to_unmapped_path(&self, sp: Span) -> FileName {
         self.lookup_char_pos(sp.lo()).file.unmapped_path.clone()
-            .expect("SourceMap::span_to_unmapped_path called for imported SourceFile?")
+            .expect("`SourceMap::span_to_unmapped_path` called for imported `SourceFile`?")
     }
 
     pub fn is_multiline(&self, sp: Span) -> bool {
@@ -586,7 +587,7 @@ impl SourceMap {
         }
     }
 
-    /// Returns the source snippet as `String` corresponding to the given `Span`
+    /// Returns the source snippet as `String` corresponding to the given `Span`.
     pub fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError> {
         self.span_to_source(sp, |src, start_index, end_index| src.get(start_index..end_index)
             .map(|s| s.to_string())
@@ -602,14 +603,14 @@ impl SourceMap {
         }
     }
 
-    /// Returns the source snippet as `String` before the given `Span`
+    /// Returns the source snippet as `String` before the given `Span`.
     pub fn span_to_prev_source(&self, sp: Span) -> Result<String, SpanSnippetError> {
         self.span_to_source(sp, |src, start_index, _| src.get(..start_index)
             .map(|s| s.to_string())
             .ok_or_else(|| SpanSnippetError::IllFormedSpan(sp)))
     }
 
-    /// Extend the given `Span` to just after the previous occurrence of `c`. Return the same span
+    /// Extends the given `Span` to just after the previous occurrence of `c`. Return the same span
     /// if no character could be found or if an error occurred while retrieving the code snippet.
     pub fn span_extend_to_prev_char(&self, sp: Span, c: char) -> Span {
         if let Ok(prev_source) = self.span_to_prev_source(sp) {
@@ -622,8 +623,8 @@ impl SourceMap {
         sp
     }
 
-    /// Extend the given `Span` to just after the previous occurrence of `pat` when surrounded by
-    /// whitespace. Return the same span if no character could be found or if an error occurred
+    /// Extends the given `Span` to just after the previous occurrence of `pat` when surrounded by
+    /// whitespace. Returns the same span if no character could be found or if an error occurred
     /// while retrieving the code snippet.
     pub fn span_extend_to_prev_str(&self, sp: Span, pat: &str, accept_newlines: bool) -> Span {
         // assure that the pattern is delimited, to avoid the following
@@ -643,7 +644,8 @@ impl SourceMap {
         sp
     }
 
-    /// Given a `Span`, try to get a shorter span ending before the first occurrence of `c` `char`
+    /// Given a `Span`, tries to get a shorter span ending before the first occurrence of `char`
+    /// `c`.
     pub fn span_until_char(&self, sp: Span, c: char) -> Span {
         match self.span_to_snippet(sp) {
             Ok(snippet) => {
@@ -658,7 +660,7 @@ impl SourceMap {
         }
     }
 
-    /// Given a `Span`, try to get a shorter span ending just after the first occurrence of `char`
+    /// Given a `Span`, tries to get a shorter span ending just after the first occurrence of `char`
     /// `c`.
     pub fn span_through_char(&self, sp: Span, c: char) -> Span {
         if let Ok(snippet) = self.span_to_snippet(sp) {
@@ -669,8 +671,8 @@ impl SourceMap {
         sp
     }
 
-    /// Given a `Span`, get a new `Span` covering the first token and all its trailing whitespace or
-    /// the original `Span`.
+    /// Given a `Span`, gets a new `Span` covering the first token and all its trailing whitespace
+    /// or the original `Span`.
     ///
     /// If `sp` points to `"let mut x"`, then a span pointing at `"let "` will be returned.
     pub fn span_until_non_whitespace(&self, sp: Span) -> Span {
@@ -689,15 +691,15 @@ impl SourceMap {
         })
     }
 
-    /// Given a `Span`, get a new `Span` covering the first token without its trailing whitespace or
-    /// the original `Span` in case of error.
+    /// Given a `Span`, gets a new `Span` covering the first token without its trailing whitespace
+    /// or the original `Span` in case of error.
     ///
     /// If `sp` points to `"let mut x"`, then a span pointing at `"let"` will be returned.
     pub fn span_until_whitespace(&self, sp: Span) -> Span {
         self.span_take_while(sp, |c| !c.is_whitespace())
     }
 
-    /// Given a `Span`, get a shorter one until `predicate` yields false.
+    /// Given a `Span`, gets a shorter one until `predicate` yields `false`.
     pub fn span_take_while<P>(&self, sp: Span, predicate: P) -> Span
         where P: for <'r> FnMut(&'r char) -> bool
     {
@@ -717,7 +719,7 @@ impl SourceMap {
         self.span_until_char(sp, '{')
     }
 
-    /// Returns a new span representing just the start-point of this span
+    /// Returns a new span representing just the start point of this span.
     pub fn start_point(&self, sp: Span) -> Span {
         let pos = sp.lo().0;
         let width = self.find_width_of_character_at_span(sp, false);
@@ -726,7 +728,7 @@ impl SourceMap {
         sp.with_hi(end_point)
     }
 
-    /// Returns a new span representing just the end-point of this span
+    /// Returns a new span representing just the end point of this span.
     pub fn end_point(&self, sp: Span) -> Span {
         let pos = sp.hi().0;
 
@@ -737,7 +739,7 @@ impl SourceMap {
         sp.with_lo(end_point)
     }
 
-    /// Returns a new span representing the next character after the end-point of this span
+    /// Returns a new span representing the next character after the end-point of this span.
     pub fn next_point(&self, sp: Span) -> Span {
         let start_of_next_point = sp.hi().0;
 
@@ -840,7 +842,7 @@ impl SourceMap {
         None
     }
 
-    /// For a global BytePos compute the local offset within the containing SourceFile
+    /// For a global `BytePos`, computes the local offset within the containing `SourceFile`.
     pub fn lookup_byte_offset(&self, bpos: BytePos) -> SourceFileAndBytePos {
         let idx = self.lookup_source_file_idx(bpos);
         let sf = (*self.files.borrow().source_files)[idx].clone();
@@ -848,22 +850,22 @@ impl SourceMap {
         SourceFileAndBytePos {sf, pos: offset}
     }
 
-    /// Converts an absolute BytePos to a CharPos relative to the source_file.
+    /// Converts an absolute `BytePos` to a `CharPos` relative to the `SourceFile`.
     pub fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
         let idx = self.lookup_source_file_idx(bpos);
         let map = &(*self.files.borrow().source_files)[idx];
 
-        // The number of extra bytes due to multibyte chars in the SourceFile
+        // The number of extra bytes due to multibyte chars in the `SourceFile`.
         let mut total_extra_bytes = 0;
 
         for mbc in map.multibyte_chars.iter() {
             debug!("{}-byte char at {:?}", mbc.bytes, mbc.pos);
             if mbc.pos < bpos {
-                // every character is at least one byte, so we only
+                // Every character is at least one byte, so we only
                 // count the actual extra bytes.
                 total_extra_bytes += mbc.bytes as u32 - 1;
                 // We should never see a byte position in the middle of a
-                // character
+                // character.
                 assert!(bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32);
             } else {
                 break;
@@ -874,13 +876,13 @@ impl SourceMap {
         CharPos(bpos.to_usize() - map.start_pos.to_usize() - total_extra_bytes as usize)
     }
 
-    // Return the index of the source_file (in self.files) which contains pos.
+    // Returns the index of the `SourceFile` (in `self.files`) that contains `pos`.
     pub fn lookup_source_file_idx(&self, pos: BytePos) -> usize {
         let files = self.files.borrow();
         let files = &files.source_files;
         let count = files.len();
 
-        // Binary search for the source_file.
+        // Binary search for the `SourceFile`.
         let mut a = 0;
         let mut b = count;
         while b - a > 1 {
@@ -911,8 +913,8 @@ impl SourceMap {
         }).ok()
     }
 
-    /// Take the span of a type parameter in a function signature and try to generate a span for the
-    /// function name (with generics) and a new snippet for this span with the pointed type
+    /// Takes the span of a type parameter in a function signature and try to generate a span for
+    /// the function name (with generics) and a new snippet for this span with the pointed type
     /// parameter as a new local type parameter.
     ///
     /// For instance:
@@ -928,18 +930,18 @@ impl SourceMap {
     ///
     /// Attention: The method used is very fragile since it essentially duplicates the work of the
     /// parser. If you need to use this function or something similar, please consider updating the
-    /// source_map functions and this function to something more robust.
+    /// `SourceMap` functions and this function to something more robust.
     pub fn generate_local_type_param_snippet(&self, span: Span) -> Option<(Span, String)> {
         // Try to extend the span to the previous "fn" keyword to retrieve the function
-        // signature
+        // signature.
         let sugg_span = self.span_extend_to_prev_str(span, "fn", false);
         if sugg_span != span {
             if let Ok(snippet) = self.span_to_snippet(sugg_span) {
-                // Consume the function name
+                // Consume the function name.
                 let mut offset = snippet.find(|c: char| !c.is_alphanumeric() && c != '_')
                     .expect("no label after fn");
 
-                // Consume the generics part of the function signature
+                // Consume the generics part of the function signature.
                 let mut bracket_counter = 0;
                 let mut last_char = None;
                 for c in snippet[offset..].chars() {
@@ -953,11 +955,11 @@ impl SourceMap {
                     last_char = Some(c);
                 }
 
-                // Adjust the suggestion span to encompass the function name with its generics
+                // Adjust the suggestion span to encompass the function name with its generics.
                 let sugg_span = sugg_span.with_hi(BytePos(sugg_span.lo().0 + offset as u32));
 
                 // Prepare the new suggested snippet to append the type parameter that triggered
-                // the error in the generics of the function signature
+                // the error in the generics of the function signature.
                 let mut new_snippet = if last_char == Some('>') {
                     format!("{}, ", &snippet[..(offset - '>'.len_utf8())])
                 } else {
diff --git a/src/libsyntax/source_map/tests.rs b/src/libsyntax/source_map/tests.rs
index c7b8332c53ef7..15254336bbfa5 100644
--- a/src/libsyntax/source_map/tests.rs
+++ b/src/libsyntax/source_map/tests.rs
@@ -4,18 +4,24 @@ use rustc_data_structures::sync::Lrc;
 
 fn init_source_map() -> SourceMap {
     let sm = SourceMap::new(FilePathMapping::empty());
-    sm.new_source_file(PathBuf::from("blork.rs").into(),
-                    "first line.\nsecond line".to_string());
-    sm.new_source_file(PathBuf::from("empty.rs").into(),
-                    String::new());
-    sm.new_source_file(PathBuf::from("blork2.rs").into(),
-                    "first line.\nsecond line".to_string());
+    sm.new_source_file(
+        PathBuf::from("blork.rs").into(),
+        "first line.\nsecond line".to_string(),
+    );
+    sm.new_source_file(
+        PathBuf::from("empty.rs").into(),
+        String::new(),
+    );
+    sm.new_source_file(
+        PathBuf::from("blork2.rs").into(),
+        "first line.\nsecond line".to_string(),
+    );
     sm
 }
 
+/// Tests `lookup_byte_offset`.
 #[test]
 fn t3() {
-    // Test lookup_byte_offset
     let sm = init_source_map();
 
     let srcfbp1 = sm.lookup_byte_offset(BytePos(23));
@@ -31,9 +37,9 @@ fn t3() {
     assert_eq!(srcfbp2.pos, BytePos(0));
 }
 
+/// Tests `bytepos_to_file_charpos`.
 #[test]
 fn t4() {
-    // Test bytepos_to_file_charpos
     let sm = init_source_map();
 
     let cp1 = sm.bytepos_to_file_charpos(BytePos(22));
@@ -43,9 +49,9 @@ fn t4() {
     assert_eq!(cp2, CharPos(0));
 }
 
+/// Tests zero-length `SourceFile`s.
 #[test]
 fn t5() {
-    // Test zero-length source_files.
     let sm = init_source_map();
 
     let loc1 = sm.lookup_char_pos(BytePos(22));
@@ -61,7 +67,7 @@ fn t5() {
 
 fn init_source_map_mbc() -> SourceMap {
     let sm = SourceMap::new(FilePathMapping::empty());
-    // € is a three byte utf8 char.
+    // "€" is a three-byte UTF8 char.
     sm.new_source_file(PathBuf::from("blork.rs").into(),
                     "fir€st €€€€ line.\nsecond line".to_string());
     sm.new_source_file(PathBuf::from("blork2.rs").into(),
@@ -69,9 +75,9 @@ fn init_source_map_mbc() -> SourceMap {
     sm
 }
 
+/// Tests `bytepos_to_file_charpos` in the presence of multi-byte chars.
 #[test]
 fn t6() {
-    // Test bytepos_to_file_charpos in the presence of multi-byte chars
     let sm = init_source_map_mbc();
 
     let cp1 = sm.bytepos_to_file_charpos(BytePos(3));
@@ -87,9 +93,9 @@ fn t6() {
     assert_eq!(cp4, CharPos(15));
 }
 
+/// Test `span_to_lines` for a span ending at the end of a `SourceFile`.
 #[test]
 fn t7() {
-    // Test span_to_lines for a span ending at the end of source_file
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let file_lines = sm.span_to_lines(span).unwrap();
@@ -110,7 +116,7 @@ fn span_from_selection(input: &str, selection: &str) -> Span {
     Span::with_root_ctxt(BytePos(left_index), BytePos(right_index + 1))
 }
 
-/// Tests span_to_snippet and span_to_lines for a span converting 3
+/// Tests `span_to_snippet` and `span_to_lines` for a span converting 3
 /// lines in the middle of a file.
 #[test]
 fn span_to_snippet_and_lines_spanning_multiple_lines() {
@@ -120,10 +126,10 @@ fn span_to_snippet_and_lines_spanning_multiple_lines() {
     sm.new_source_file(Path::new("blork.rs").to_owned().into(), inputtext.to_string());
     let span = span_from_selection(inputtext, selection);
 
-    // check that we are extracting the text we thought we were extracting
+    // Check that we are extracting the text we thought we were extracting.
     assert_eq!(&sm.span_to_snippet(span).unwrap(), "BB\nCCC\nDDDDD");
 
-    // check that span_to_lines gives us the complete result with the lines/cols we expected
+    // Check that span_to_lines gives us the complete result with the lines/cols we expected.
     let lines = sm.span_to_lines(span).unwrap();
     let expected = vec![
         LineInfo { line_index: 1, start_col: CharPos(4), end_col: CharPos(6) },
@@ -133,9 +139,9 @@ fn span_to_snippet_and_lines_spanning_multiple_lines() {
     assert_eq!(lines.lines, expected);
 }
 
+/// Test span_to_snippet for a span ending at the end of a `SourceFile`.
 #[test]
 fn t8() {
-    // Test span_to_snippet for a span ending at the end of source_file
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let snippet = sm.span_to_snippet(span);
@@ -143,9 +149,9 @@ fn t8() {
     assert_eq!(snippet, Ok("second line".to_string()));
 }
 
+/// Test `span_to_str` for a span ending at the end of a `SourceFile`.
 #[test]
 fn t9() {
-    // Test span_to_str for a span ending at the end of source_file
     let sm = init_source_map();
     let span = Span::with_root_ctxt(BytePos(12), BytePos(23));
     let sstr =  sm.span_to_string(span);
@@ -153,7 +159,7 @@ fn t9() {
     assert_eq!(sstr, "blork.rs:2:1: 2:12");
 }
 
-/// Tests failing to merge two spans on different lines
+/// Tests failing to merge two spans on different lines.
 #[test]
 fn span_merging_fail() {
     let sm = SourceMap::new(FilePathMapping::empty());
@@ -167,33 +173,37 @@ fn span_merging_fail() {
     assert!(sm.merge_spans(span1, span2).is_none());
 }
 
-/// Returns the span corresponding to the `n`th occurrence of
-/// `substring` in `source_text`.
+/// Returns the span corresponding to the `n`th occurrence of `substring` in `source_text`.
 trait SourceMapExtension {
-    fn span_substr(&self,
-                file: &Lrc<SourceFile>,
-                source_text: &str,
-                substring: &str,
-                n: usize)
-                -> Span;
+    fn span_substr(
+        &self,
+        file: &Lrc<SourceFile>,
+        source_text: &str,
+        substring: &str,
+        n: usize,
+    ) -> Span;
 }
 
 impl SourceMapExtension for SourceMap {
-    fn span_substr(&self,
-                file: &Lrc<SourceFile>,
-                source_text: &str,
-                substring: &str,
-                n: usize)
-                -> Span
-    {
-        println!("span_substr(file={:?}/{:?}, substring={:?}, n={})",
-                file.name, file.start_pos, substring, n);
+    fn span_substr(
+        &self,
+        file: &Lrc<SourceFile>,
+        source_text: &str,
+        substring: &str,
+        n: usize,
+    ) -> Span {
+        println!(
+            "span_substr(file={:?}/{:?}, substring={:?}, n={})",
+            file.name, file.start_pos, substring, n
+        );
         let mut i = 0;
         let mut hi = 0;
         loop {
             let offset = source_text[hi..].find(substring).unwrap_or_else(|| {
-                panic!("source_text `{}` does not have {} occurrences of `{}`, only {}",
-                    source_text, n, substring, i);
+                panic!(
+                    "source_text `{}` does not have {} occurrences of `{}`, only {}",
+                    source_text, n, substring, i
+                );
             });
             let lo = hi + offset;
             hi = lo + substring.len();
@@ -202,8 +212,7 @@ impl SourceMapExtension for SourceMap {
                     BytePos(lo as u32 + file.start_pos.0),
                     BytePos(hi as u32 + file.start_pos.0),
                 );
-                assert_eq!(&self.span_to_snippet(span).unwrap()[..],
-                        substring);
+                assert_eq!(&self.span_to_snippet(span).unwrap()[..], substring);
                 return span;
             }
             i += 1;
diff --git a/src/libsyntax/tests.rs b/src/libsyntax/tests.rs
index 9b90b31f2d2a2..540881b0a5496 100644
--- a/src/libsyntax/tests.rs
+++ b/src/libsyntax/tests.rs
@@ -18,7 +18,7 @@ use std::path::{Path, PathBuf};
 use std::str;
 use std::sync::{Arc, Mutex};
 
-/// Map string to parser (via tts)
+/// Map string to parser (via tts).
 fn string_to_parser(ps: &ParseSess, source_str: String) -> Parser<'_> {
     new_parser_from_source_str(ps, PathBuf::from("bogofile").into(), source_str)
 }
@@ -32,7 +32,7 @@ crate fn with_error_checking_parse<'a, T, F>(s: String, ps: &'a ParseSess, f: F)
     x
 }
 
-/// Map a string to tts, using a made-up filename:
+/// Maps a string to tts, using a made-up filename.
 crate fn string_to_stream(source_str: String) -> TokenStream {
     let ps = ParseSess::new(FilePathMapping::empty());
     source_file_to_stream(
@@ -42,7 +42,7 @@ crate fn string_to_stream(source_str: String) -> TokenStream {
     ), None).0
 }
 
-/// Parse a string, return a crate.
+/// Parses a string, returns a crate.
 crate fn string_to_crate(source_str : String) -> ast::Crate {
     let ps = ParseSess::new(FilePathMapping::empty());
     with_error_checking_parse(source_str, &ps, |p| {
@@ -64,7 +64,7 @@ crate fn matches_codepattern(a : &str, b : &str) -> bool {
             (None, _) => return false,
             (Some(&a), None) => {
                 if rustc_lexer::is_whitespace(a) {
-                    break // trailing whitespace check is out of loop for borrowck
+                    break // Trailing whitespace check is out of loop for borrowck.
                 } else {
                     return false
                 }
@@ -73,11 +73,11 @@ crate fn matches_codepattern(a : &str, b : &str) -> bool {
         };
 
         if rustc_lexer::is_whitespace(a) && rustc_lexer::is_whitespace(b) {
-            // skip whitespace for a and b
+            // Skip whitespace for `a` and `b`.
             scan_for_non_ws_or_end(&mut a_iter);
             scan_for_non_ws_or_end(&mut b_iter);
         } else if rustc_lexer::is_whitespace(a) {
-            // skip whitespace for a
+            // Skip whitespace for `a`.
             scan_for_non_ws_or_end(&mut a_iter);
         } else if a == b {
             a_iter.next();
@@ -87,18 +87,18 @@ crate fn matches_codepattern(a : &str, b : &str) -> bool {
         }
     }
 
-    // check if a has *only* trailing whitespace
+    // Check if a has *only* trailing whitespace.
     a_iter.all(rustc_lexer::is_whitespace)
 }
 
-/// Advances the given peekable `Iterator` until it reaches a non-whitespace character
+/// Advances the given peekable `Iterator` until it reaches a non-whitespace character.
 fn scan_for_non_ws_or_end<I: Iterator<Item = char>>(iter: &mut Peekable<I>) {
     while iter.peek().copied().map(|c| rustc_lexer::is_whitespace(c)) == Some(true) {
         iter.next();
     }
 }
 
-/// Identify a position in the text by the Nth occurrence of a string.
+/// Identifies a position in the text by the n'th occurrence of a string.
 struct Position {
     string: &'static str,
     count: usize,
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 480553586197e..d702038f54ec3 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -6,7 +6,7 @@
 //!
 //! ## Ownership
 //!
-//! `TokenStreams` are persistent data structures constructed as ropes with reference
+//! `TokenStream`s are persistent data structures constructed as ropes with reference
 //! counted-children. In general, this means that calling an operation on a `TokenStream`
 //! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
 //! the original. This essentially coerces `TokenStream`s into 'views' of their subparts,
@@ -147,9 +147,8 @@ impl TokenTree {
     }
 }
 
-/// # Token Streams
-///
 /// A `TokenStream` is an abstract sequence of tokens, organized into `TokenTree`s.
+///
 /// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
 /// instead of a representation of the abstract syntax tree.
 /// Today's `TokenTree`s can still contain AST via `token::Interpolated` for back-compat.
@@ -304,7 +303,7 @@ impl TokenStream {
         Cursor::new(self)
     }
 
-    /// Compares two TokenStreams, checking equality without regarding span information.
+    /// Compares two `TokenStream`s, checking equality without regarding span information.
     pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
         let mut t1 = self.trees();
         let mut t2 = other.trees();
diff --git a/src/libsyntax/util/parser.rs b/src/libsyntax/util/parser.rs
index a501541c95909..fceaed360cdb4 100644
--- a/src/libsyntax/util/parser.rs
+++ b/src/libsyntax/util/parser.rs
@@ -69,7 +69,7 @@ pub enum Fixity {
 
 impl AssocOp {
     /// Creates a new AssocOP from a token
-    pub fn from_token(t: &Token) -> Option<AssocOp> {
+    crate fn from_token(t: &Token) -> Option<AssocOp> {
         use AssocOp::*;
         match t.kind {
             token::BinOpEq(k) => Some(AssignOp(k)),
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index ce1568316f8d4..d7c537be89668 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -21,13 +21,13 @@ use syntax_pos::Span;
 
 #[derive(Copy, Clone)]
 pub enum FnKind<'a> {
-    /// fn foo() or extern "Abi" fn foo()
+    /// E.g., `fn foo()` or `extern "Abi" fn foo()`.
     ItemFn(Ident, &'a FnHeader, &'a Visibility, &'a Block),
 
-    /// fn foo(&self)
+    /// E.g., `fn foo(&self)`.
     Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a Block),
 
-    /// |x, y| body
+    /// E.g., `|x, y| body`.
     Closure(&'a Expr),
 }
 
@@ -41,7 +41,7 @@ impl<'a> FnKind<'a> {
     }
 }
 
-/// Each method of the Visitor trait is a hook to be potentially
+/// Each method of the `Visitor` trait is a hook to be potentially
 /// overridden. Each method's default implementation recursively visits
 /// the substructure of the input via the corresponding `walk` method;
 /// e.g., the `visit_mod` method by default calls `visit::walk_mod`.
@@ -302,10 +302,12 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
     walk_list!(visitor, visit_attribute, &item.attrs);
 }
 
-pub fn walk_enum_def<'a, V: Visitor<'a>>(visitor: &mut V,
-                                 enum_definition: &'a EnumDef,
-                                 _: &'a Generics,
-                                 _: NodeId) {
+pub fn walk_enum_def<'a, V: Visitor<'a>>(
+    visitor: &mut V,
+    enum_definition: &'a EnumDef,
+    _: &'a Generics,
+    _: NodeId,
+) {
     walk_list!(visitor, visit_variant, &enum_definition.variants);
 }
 
@@ -342,7 +344,6 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
             walk_list!(visitor, visit_lifetime, opt_lifetime);
             visitor.visit_ty(&mutable_type.ty)
         }
-        TyKind::Never | TyKind::CVarArgs => {}
         TyKind::Tup(ref tuple_element_types) => {
             walk_list!(visitor, visit_ty, tuple_element_types);
         }
@@ -371,6 +372,8 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
         TyKind::Mac(ref mac) => {
             visitor.visit_mac(mac)
         }
+        TyKind::Never |
+        TyKind::CVarArgs => {}
     }
 }
 
@@ -386,7 +389,7 @@ pub fn walk_use_tree<'a, V: Visitor<'a>>(
     visitor.visit_path(&use_tree.prefix, id);
     match use_tree.kind {
         UseTreeKind::Simple(rename, ..) => {
-            // the extra IDs are handled during HIR lowering
+            // The extra IDs are handled during HIR lowering.
             if let Some(rename) = rename {
                 visitor.visit_ident(rename);
             }
@@ -678,9 +681,8 @@ pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonCo
 }
 
 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
-    for attr in expression.attrs.iter() {
-        visitor.visit_attribute(attr);
-    }
+    walk_list!(visitor, visit_attribute, expression.attrs.iter());
+
     match expression.node {
         ExprKind::Box(ref subexpression) => {
             visitor.visit_expr(subexpression)
@@ -719,8 +721,8 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(subexpression);
             visitor.visit_ty(typ)
         }
-        ExprKind::Let(ref pats, ref scrutinee) => {
-            walk_list!(visitor, visit_pat, pats);
+        ExprKind::Let(ref pat, ref scrutinee) => {
+            visitor.visit_pat(pat);
             visitor.visit_expr(scrutinee);
         }
         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
@@ -831,10 +833,10 @@ pub fn walk_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Param) {
 }
 
 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
-    walk_list!(visitor, visit_pat, &arm.pats);
-    if let Some(ref e) = &arm.guard {
-        visitor.visit_expr(e);
-    }
+    visitor.visit_pat(&arm.pat);
+    // NOTE(or_patterns; Centril | dlrobertson):
+    // If you change this, also change the hack in `lowering.rs`.
+    walk_list!(visitor, visit_expr, &arm.guard);
     visitor.visit_expr(&arm.body);
     walk_list!(visitor, visit_attribute, &arm.attrs);
 }
diff --git a/src/libsyntax_ext/asm.rs b/src/libsyntax_ext/asm.rs
index 328b307361d9e..75d727b9fb60b 100644
--- a/src/libsyntax_ext/asm.rs
+++ b/src/libsyntax_ext/asm.rs
@@ -62,7 +62,7 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt<'_>,
     MacEager::expr(P(ast::Expr {
         id: ast::DUMMY_NODE_ID,
         node: ast::ExprKind::InlineAsm(P(inline_asm)),
-        span: cx.with_legacy_ctxt(sp),
+        span: cx.with_def_site_ctxt(sp),
         attrs: ThinVec::new(),
     }))
 }
diff --git a/src/libsyntax_ext/assert.rs b/src/libsyntax_ext/assert.rs
index 001996e1db718..cbfe14fa439be 100644
--- a/src/libsyntax_ext/assert.rs
+++ b/src/libsyntax_ext/assert.rs
@@ -23,7 +23,9 @@ pub fn expand_assert<'cx>(
         }
     };
 
-    let sp = cx.with_legacy_ctxt(sp);
+    // `core::panic` and `std::panic` are different macros, so we use call-site
+    // context to pick up whichever is currently in scope.
+    let sp = cx.with_call_site_ctxt(sp);
     let panic_call = Mac {
         path: Path::from_ident(Ident::new(sym::panic, sp)),
         tts: custom_message.unwrap_or_else(|| {
diff --git a/src/libsyntax_ext/cfg.rs b/src/libsyntax_ext/cfg.rs
index 0342e442df2e9..3c33baf95a597 100644
--- a/src/libsyntax_ext/cfg.rs
+++ b/src/libsyntax_ext/cfg.rs
@@ -16,7 +16,7 @@ pub fn expand_cfg(
     sp: Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let sp = cx.with_legacy_ctxt(sp);
+    let sp = cx.with_def_site_ctxt(sp);
 
     match parse_cfg(cx, sp, tts) {
         Ok(cfg) => {
diff --git a/src/libsyntax_ext/cmdline_attrs.rs b/src/libsyntax_ext/cmdline_attrs.rs
new file mode 100644
index 0000000000000..bb8e3df3db921
--- /dev/null
+++ b/src/libsyntax_ext/cmdline_attrs.rs
@@ -0,0 +1,30 @@
+//! Attributes injected into the crate root from command line using `-Z crate-attr`.
+
+use syntax::ast::{self, AttrStyle};
+use syntax::attr::mk_attr;
+use syntax::panictry;
+use syntax::parse::{self, token, ParseSess};
+use syntax_pos::FileName;
+
+pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -> ast::Crate {
+    for raw_attr in attrs {
+        let mut parser = parse::new_parser_from_source_str(
+            parse_sess,
+            FileName::cli_crate_attr_source_code(&raw_attr),
+            raw_attr.clone(),
+        );
+
+        let start_span = parser.token.span;
+        let (path, tokens) = panictry!(parser.parse_meta_item_unrestricted());
+        let end_span = parser.token.span;
+        if parser.token != token::Eof {
+            parse_sess.span_diagnostic
+                .span_err(start_span.to(end_span), "invalid crate attribute");
+            continue;
+        }
+
+        krate.attrs.push(mk_attr(AttrStyle::Inner, path, tokens, start_span.to(end_span)));
+    }
+
+    krate
+}
diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index fc56dff65e4e2..16f016036ea5e 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -59,6 +59,6 @@ pub fn expand_concat(
     } else if has_errors {
         return DummyResult::any(sp);
     }
-    let sp = cx.with_legacy_ctxt(sp);
+    let sp = cx.with_def_site_ctxt(sp);
     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
 }
diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
index 6391b62b58dc9..f344706d4ebf5 100644
--- a/src/libsyntax_ext/concat_idents.rs
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -39,7 +39,7 @@ pub fn expand_concat_idents<'cx>(cx: &'cx mut ExtCtxt<'_>,
         }
     }
 
-    let ident = ast::Ident::new(Symbol::intern(&res_str), cx.with_legacy_ctxt(sp));
+    let ident = ast::Ident::new(Symbol::intern(&res_str), cx.with_call_site_ctxt(sp));
 
     struct ConcatIdentsResult { ident: ast::Ident }
 
diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 55687c3175b9d..1f4f5aa37099f 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -95,11 +95,9 @@ pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<
                     cx.expr_call_global(span, cmp_path.clone(), args)
                 };
 
-                let eq_arm = cx.arm(span,
-                                    vec![cx.pat_path(span, equals_path.clone())],
-                                    old);
+                let eq_arm = cx.arm(span, cx.pat_path(span, equals_path.clone()), old);
                 let neq_arm = cx.arm(span,
-                                     vec![cx.pat_ident(span, test_id)],
+                                     cx.pat_ident(span, test_id),
                                      cx.expr_ident(span, test_id));
 
                 cx.expr_match(span, new, vec![eq_arm, neq_arm])
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index 740b92a9b7978..13d63aaf2a80c 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -109,7 +109,7 @@ pub fn some_ordering_collapsed(
         GtOp => "gt",
         GeOp => "ge",
     };
-    cx.expr_method_call(span, lft, ast::Ident::from_str_and_span(op_str, span), vec![rgt])
+    cx.expr_method_call(span, lft, cx.ident_of(op_str, span), vec![rgt])
 }
 
 pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
@@ -160,10 +160,10 @@ pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_
                 };
 
                 let eq_arm = cx.arm(span,
-                                    vec![cx.pat_some(span, cx.pat_path(span, ordering.clone()))],
+                                    cx.pat_some(span, cx.pat_path(span, ordering.clone())),
                                     old);
                 let neq_arm = cx.arm(span,
-                                    vec![cx.pat_ident(span, test_id)],
+                                    cx.pat_ident(span, test_id),
                                     cx.expr_ident(span, test_id));
 
                 cx.expr_match(span, new, vec![eq_arm, neq_arm])
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index 781645a574e9a..088b61be8b81b 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -62,7 +62,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
     // We want to make sure we have the ctxt set so that we can use unstable methods
     let span = cx.with_def_site_ctxt(span);
     let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
-    let builder = Ident::from_str_and_span("debug_trait_builder", span);
+    let builder = cx.ident_of("debug_trait_builder", span);
     let builder_expr = cx.expr_ident(span, builder.clone());
 
     let fmt = substr.nonself_args[0].clone();
@@ -72,7 +72,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
         ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
             // tuple struct/"normal" variant
             let expr =
-                cx.expr_method_call(span, fmt, Ident::from_str("debug_tuple"), vec![name]);
+                cx.expr_method_call(span, fmt, cx.ident_of("debug_tuple", span), vec![name]);
             stmts.push(cx.stmt_let(span, true, builder, expr));
 
             for field in fields {
@@ -93,7 +93,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
         ast::VariantData::Struct(..) => {
             // normal struct/struct variant
             let expr =
-                cx.expr_method_call(span, fmt, Ident::from_str("debug_struct"), vec![name]);
+                cx.expr_method_call(span, fmt, cx.ident_of("debug_struct", span), vec![name]);
             stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
 
             for field in fields {
@@ -113,7 +113,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
         }
     }
 
-    let expr = cx.expr_method_call(span, builder_expr, Ident::from_str("finish"), vec![]);
+    let expr = cx.expr_method_call(span, builder_expr, cx.ident_of("finish", span), vec![]);
 
     stmts.push(cx.stmt_expr(expr));
     let block = cx.block(span, stmts);
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index 9b6f8518de046..cde72abbdef6a 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -66,10 +66,14 @@ fn decodable_substructure(cx: &mut ExtCtxt<'_>,
                           krate: &str)
                           -> P<Expr> {
     let decoder = substr.nonself_args[0].clone();
-    let recurse = vec![cx.ident_of(krate), cx.ident_of("Decodable"), cx.ident_of("decode")];
+    let recurse = vec![
+        cx.ident_of(krate, trait_span),
+        cx.ident_of("Decodable", trait_span),
+        cx.ident_of("decode", trait_span),
+    ];
     let exprdecode = cx.expr_path(cx.path_global(trait_span, recurse));
     // throw an underscore in front to suppress unused variable warnings
-    let blkarg = cx.ident_of("_d");
+    let blkarg = cx.ident_of("_d", trait_span);
     let blkdecoder = cx.expr_ident(trait_span, blkarg);
 
     return match *substr.fields {
@@ -78,7 +82,7 @@ fn decodable_substructure(cx: &mut ExtCtxt<'_>,
                 Unnamed(ref fields, _) => fields.len(),
                 Named(ref fields) => fields.len(),
             };
-            let read_struct_field = cx.ident_of("read_struct_field");
+            let read_struct_field = cx.ident_of("read_struct_field", trait_span);
 
             let path = cx.path_ident(trait_span, substr.type_ident);
             let result =
@@ -94,17 +98,17 @@ fn decodable_substructure(cx: &mut ExtCtxt<'_>,
             let result = cx.expr_ok(trait_span, result);
             cx.expr_method_call(trait_span,
                                 decoder,
-                                cx.ident_of("read_struct"),
+                                cx.ident_of("read_struct", trait_span),
                                 vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.expr_usize(trait_span, nfields),
                                      cx.lambda1(trait_span, result, blkarg)])
         }
         StaticEnum(_, ref fields) => {
-            let variant = cx.ident_of("i");
+            let variant = cx.ident_of("i", trait_span);
 
             let mut arms = Vec::with_capacity(fields.len() + 1);
             let mut variants = Vec::with_capacity(fields.len());
-            let rvariant_arg = cx.ident_of("read_enum_variant_arg");
+            let rvariant_arg = cx.ident_of("read_enum_variant_arg", trait_span);
 
             for (i, &(ident, v_span, ref parts)) in fields.iter().enumerate() {
                 variants.push(cx.expr_str(v_span, ident.name));
@@ -119,9 +123,7 @@ fn decodable_substructure(cx: &mut ExtCtxt<'_>,
                                                     vec![idx, exprdecode.clone()]))
                 });
 
-                arms.push(cx.arm(v_span,
-                                 vec![cx.pat_lit(v_span, cx.expr_usize(v_span, i))],
-                                 decoded));
+                arms.push(cx.arm(v_span, cx.pat_lit(v_span, cx.expr_usize(v_span, i)), decoded));
             }
 
             arms.push(cx.arm_unreachable(trait_span));
@@ -134,11 +136,11 @@ fn decodable_substructure(cx: &mut ExtCtxt<'_>,
             let variant_vec = cx.expr_addr_of(trait_span, variant_vec);
             let result = cx.expr_method_call(trait_span,
                                              blkdecoder,
-                                             cx.ident_of("read_enum_variant"),
+                                             cx.ident_of("read_enum_variant", trait_span),
                                              vec![variant_vec, lambda]);
             cx.expr_method_call(trait_span,
                                 decoder,
-                                cx.ident_of("read_enum"),
+                                cx.ident_of("read_enum", trait_span),
                                 vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.lambda1(trait_span, result, blkarg)])
         }
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index 8b18fb25e90c1..655d3bb7c4ab8 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -153,16 +153,16 @@ fn encodable_substructure(cx: &mut ExtCtxt<'_>,
                           -> P<Expr> {
     let encoder = substr.nonself_args[0].clone();
     // throw an underscore in front to suppress unused variable warnings
-    let blkarg = cx.ident_of("_e");
+    let blkarg = cx.ident_of("_e", trait_span);
     let blkencoder = cx.expr_ident(trait_span, blkarg);
     let fn_path = cx.expr_path(cx.path_global(trait_span,
-                                              vec![cx.ident_of(krate),
-                                                   cx.ident_of("Encodable"),
-                                                   cx.ident_of("encode")]));
+                                              vec![cx.ident_of(krate, trait_span),
+                                                   cx.ident_of("Encodable", trait_span),
+                                                   cx.ident_of("encode", trait_span)]));
 
     return match *substr.fields {
         Struct(_, ref fields) => {
-            let emit_struct_field = cx.ident_of("emit_struct_field");
+            let emit_struct_field = cx.ident_of("emit_struct_field", trait_span);
             let mut stmts = Vec::new();
             for (i, &FieldInfo { name, ref self_, span, .. }) in fields.iter().enumerate() {
                 let name = match name {
@@ -201,7 +201,7 @@ fn encodable_substructure(cx: &mut ExtCtxt<'_>,
 
             cx.expr_method_call(trait_span,
                                 encoder,
-                                cx.ident_of("emit_struct"),
+                                cx.ident_of("emit_struct", trait_span),
                                 vec![cx.expr_str(trait_span, substr.type_ident.name),
                                      cx.expr_usize(trait_span, fields.len()),
                                      blk])
@@ -214,7 +214,7 @@ fn encodable_substructure(cx: &mut ExtCtxt<'_>,
             // actually exist.
             let me = cx.stmt_let(trait_span, false, blkarg, encoder);
             let encoder = cx.expr_ident(trait_span, blkarg);
-            let emit_variant_arg = cx.ident_of("emit_enum_variant_arg");
+            let emit_variant_arg = cx.ident_of("emit_enum_variant_arg", trait_span);
             let mut stmts = Vec::new();
             if !fields.is_empty() {
                 let last = fields.len() - 1;
@@ -244,7 +244,7 @@ fn encodable_substructure(cx: &mut ExtCtxt<'_>,
             let name = cx.expr_str(trait_span, variant.ident.name);
             let call = cx.expr_method_call(trait_span,
                                            blkencoder,
-                                           cx.ident_of("emit_enum_variant"),
+                                           cx.ident_of("emit_enum_variant", trait_span),
                                            vec![name,
                                                 cx.expr_usize(trait_span, idx),
                                                 cx.expr_usize(trait_span, fields.len()),
@@ -252,7 +252,7 @@ fn encodable_substructure(cx: &mut ExtCtxt<'_>,
             let blk = cx.lambda1(trait_span, call, blkarg);
             let ret = cx.expr_method_call(trait_span,
                                           encoder,
-                                          cx.ident_of("emit_enum"),
+                                          cx.ident_of("emit_enum", trait_span),
                                           vec![cx.expr_str(trait_span ,substr.type_ident.name),
                                                blk]);
             cx.expr_block(cx.block(trait_span, vec![me, cx.stmt_expr(ret)]))
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 6fd763f5a9100..aceee62e89b0c 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -237,7 +237,7 @@ pub struct MethodDef<'a> {
     /// Whether there is a self argument (outer Option) i.e., whether
     /// this is a static function, and whether it is a pointer (inner
     /// Option)
-    pub explicit_self: Option<Option<PtrTy<'a>>>,
+    pub explicit_self: Option<Option<PtrTy>>,
 
     /// Arguments other than the self argument
     pub args: Vec<(Ty<'a>, &'a str)>,
@@ -843,7 +843,7 @@ impl<'a> MethodDef<'a> {
                                 -> P<Expr> {
         let substructure = Substructure {
             type_ident,
-            method_ident: cx.ident_of(self.name),
+            method_ident: cx.ident_of(self.name, trait_.span),
             self_args,
             nonself_args,
             fields,
@@ -890,7 +890,7 @@ impl<'a> MethodDef<'a> {
 
         for (ty, name) in self.args.iter() {
             let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
-            let ident = ast::Ident::from_str_and_span(name, trait_.span);
+            let ident = cx.ident_of(name, trait_.span);
             arg_tys.push((ident, ast_ty));
 
             let arg_expr = cx.expr_ident(trait_.span, ident);
@@ -938,7 +938,7 @@ impl<'a> MethodDef<'a> {
 
         let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
 
-        let method_ident = cx.ident_of(self.name);
+        let method_ident = cx.ident_of(self.name, trait_.span);
         let fn_decl = cx.fn_decl(args, ast::FunctionRetTy::Ty(ret_type));
         let body_block = cx.block_expr(body);
 
@@ -1071,7 +1071,7 @@ impl<'a> MethodDef<'a> {
         for (arg_expr, pat) in self_args.iter().zip(patterns) {
             body = cx.expr_match(trait_.span,
                                  arg_expr.clone(),
-                                 vec![cx.arm(trait_.span, vec![pat.clone()], body)])
+                                 vec![cx.arm(trait_.span, pat.clone(), body)])
         }
 
         body
@@ -1201,7 +1201,7 @@ impl<'a> MethodDef<'a> {
             ).collect::<Vec<String>>();
 
         let self_arg_idents = self_arg_names.iter()
-            .map(|name| cx.ident_of(&name[..]))
+            .map(|name| cx.ident_of(name, sp))
             .collect::<Vec<ast::Ident>>();
 
         // The `vi_idents` will be bound, solely in the catch-all, to
@@ -1210,7 +1210,7 @@ impl<'a> MethodDef<'a> {
         let vi_idents = self_arg_names.iter()
             .map(|name| {
                 let vi_suffix = format!("{}_vi", &name[..]);
-                ast::Ident::from_str_and_span(&vi_suffix[..], trait_.span)
+                cx.ident_of(&vi_suffix[..], trait_.span)
             })
             .collect::<Vec<ast::Ident>>();
 
@@ -1311,7 +1311,7 @@ impl<'a> MethodDef<'a> {
                                                              nonself_args,
                                                              &substructure);
 
-                cx.arm(sp, vec![single_pat], arm_expr)
+                cx.arm(sp, single_pat, arm_expr)
             })
             .collect();
 
@@ -1337,7 +1337,7 @@ impl<'a> MethodDef<'a> {
             _ => None,
         };
         if let Some(arm) = default {
-            match_arms.push(cx.arm(sp, vec![cx.pat_wild(sp)], arm));
+            match_arms.push(cx.arm(sp, cx.pat_wild(sp), arm));
         }
 
         // We will usually need the catch-all after matching the
@@ -1389,7 +1389,7 @@ impl<'a> MethodDef<'a> {
 
                 let target_ty = cx.ty_ident(
                     sp,
-                    ast::Ident::from_str_and_span(target_type_name, sp),
+                    cx.ident_of(target_type_name, sp),
                 );
                 let variant_disr = cx.expr_cast(sp, variant_value, target_ty);
                 let let_stmt = cx.stmt_let(sp, false, ident, variant_disr);
@@ -1591,7 +1591,7 @@ impl<'a> TraitDef<'a> {
         let mut ident_exprs = Vec::new();
         for (i, struct_field) in struct_def.fields().iter().enumerate() {
             let sp = struct_field.span.with_ctxt(self.span.ctxt());
-            let ident = ast::Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span);
+            let ident = cx.ident_of(&format!("{}_{}", prefix, i), self.span);
             paths.push(ident.with_span_pos(sp));
             let val = cx.expr_path(cx.path_ident(sp, ident));
             let val = if use_temporaries {
@@ -1620,6 +1620,7 @@ impl<'a> TraitDef<'a> {
                             id: ast::DUMMY_NODE_ID,
                             span: pat.span.with_ctxt(self.span.ctxt()),
                             pat,
+                            is_placeholder: false
                         }
                     })
                     .collect();
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index cb1c7b21fee0d..b341a07675206 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -13,9 +13,9 @@ use syntax_pos::symbol::kw;
 
 /// The types of pointers
 #[derive(Clone)]
-pub enum PtrTy<'a> {
+pub enum PtrTy {
     /// &'lifetime mut
-    Borrowed(Option<&'a str>, ast::Mutability),
+    Borrowed(Option<Ident>, ast::Mutability),
     /// *mut
     #[allow(dead_code)]
     Raw(ast::Mutability),
@@ -26,7 +26,7 @@ pub enum PtrTy<'a> {
 #[derive(Clone)]
 pub struct Path<'a> {
     path: Vec<&'a str>,
-    lifetime: Option<&'a str>,
+    lifetime: Option<Ident>,
     params: Vec<Box<Ty<'a>>>,
     kind: PathKind,
 }
@@ -46,7 +46,7 @@ impl<'a> Path<'a> {
         Path::new_(vec![path], None, Vec::new(), PathKind::Local)
     }
     pub fn new_<'r>(path: Vec<&'r str>,
-                    lifetime: Option<&'r str>,
+                    lifetime: Option<Ident>,
                     params: Vec<Box<Ty<'r>>>,
                     kind: PathKind)
                     -> Path<'r> {
@@ -72,7 +72,7 @@ impl<'a> Path<'a> {
                    self_ty: Ident,
                    self_generics: &Generics)
                    -> ast::Path {
-        let mut idents = self.path.iter().map(|s| Ident::from_str_and_span(*s, span)).collect();
+        let mut idents = self.path.iter().map(|s| cx.ident_of(*s, span)).collect();
         let lt = mk_lifetimes(cx, span, &self.lifetime);
         let tys: Vec<P<ast::Ty>> =
             self.params.iter().map(|t| t.to_ty(cx, span, self_ty, self_generics)).collect();
@@ -99,7 +99,7 @@ impl<'a> Path<'a> {
 pub enum Ty<'a> {
     Self_,
     /// &/Box/ Ty
-    Ptr(Box<Ty<'a>>, PtrTy<'a>),
+    Ptr(Box<Ty<'a>>, PtrTy),
     /// mod::mod::Type<[lifetime], [Params...]>, including a plain type
     /// parameter, and things like `i32`
     Literal(Path<'a>),
@@ -107,14 +107,14 @@ pub enum Ty<'a> {
     Tuple(Vec<Ty<'a>>),
 }
 
-pub fn borrowed_ptrty<'r>() -> PtrTy<'r> {
+pub fn borrowed_ptrty() -> PtrTy {
     Borrowed(None, ast::Mutability::Immutable)
 }
 pub fn borrowed(ty: Box<Ty<'_>>) -> Ty<'_> {
     Ptr(ty, borrowed_ptrty())
 }
 
-pub fn borrowed_explicit_self<'r>() -> Option<Option<PtrTy<'r>>> {
+pub fn borrowed_explicit_self() -> Option<Option<PtrTy>> {
     Some(Some(borrowed_ptrty()))
 }
 
@@ -126,13 +126,11 @@ pub fn nil_ty<'r>() -> Ty<'r> {
     Tuple(Vec::new())
 }
 
-fn mk_lifetime(cx: &ExtCtxt<'_>, span: Span, lt: &Option<&str>) -> Option<ast::Lifetime> {
-    lt.map(|s|
-        cx.lifetime(span, Ident::from_str(s))
-    )
+fn mk_lifetime(cx: &ExtCtxt<'_>, span: Span, lt: &Option<Ident>) -> Option<ast::Lifetime> {
+    lt.map(|ident| cx.lifetime(span, ident))
 }
 
-fn mk_lifetimes(cx: &ExtCtxt<'_>, span: Span, lt: &Option<&str>) -> Vec<ast::Lifetime> {
+fn mk_lifetimes(cx: &ExtCtxt<'_>, span: Span, lt: &Option<Ident>) -> Vec<ast::Lifetime> {
     mk_lifetime(cx, span, lt).into_iter().collect()
 }
 
@@ -209,7 +207,7 @@ fn mk_ty_param(cx: &ExtCtxt<'_>,
             cx.trait_bound(path)
         })
         .collect();
-    cx.typaram(span, ast::Ident::from_str_and_span(name, span), attrs.to_owned(), bounds, None)
+    cx.typaram(span, cx.ident_of(name, span), attrs.to_owned(), bounds, None)
 }
 
 fn mk_generics(params: Vec<ast::GenericParam>, span: Span) -> Generics {
@@ -265,7 +263,7 @@ impl<'a> LifetimeBounds<'a> {
 
 pub fn get_explicit_self(cx: &ExtCtxt<'_>,
                          span: Span,
-                         self_ptr: &Option<PtrTy<'_>>)
+                         self_ptr: &Option<PtrTy>)
                          -> (P<Expr>, ast::ExplicitSelf) {
     // this constructs a fresh `self` path
     let self_path = cx.expr_self(span);
@@ -276,7 +274,7 @@ pub fn get_explicit_self(cx: &ExtCtxt<'_>,
                 respan(span,
                        match *ptr {
                            Borrowed(ref lt, mutbl) => {
-                               let lt = lt.map(|s| cx.lifetime(span, Ident::from_str(s)));
+                               let lt = lt.map(|s| cx.lifetime(span, s));
                                SelfKind::Region(lt, mutbl)
                            }
                            Raw(_) => {
diff --git a/src/libsyntax_ext/env.rs b/src/libsyntax_ext/env.rs
index 179b7fe00a97a..70e1fbe6af78a 100644
--- a/src/libsyntax_ext/env.rs
+++ b/src/libsyntax_ext/env.rs
@@ -20,16 +20,16 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt<'_>,
         Some(v) => v,
     };
 
-    let sp = cx.with_legacy_ctxt(sp);
+    let sp = cx.with_def_site_ctxt(sp);
     let e = match env::var(&*var.as_str()) {
         Err(..) => {
-            let lt = cx.lifetime(sp, Ident::with_dummy_span(kw::StaticLifetime));
+            let lt = cx.lifetime(sp, Ident::new(kw::StaticLifetime, sp));
             cx.expr_path(cx.path_all(sp,
                                      true,
                                      cx.std_path(&[sym::option, sym::Option, sym::None]),
                                      vec![GenericArg::Type(cx.ty_rptr(sp,
                                                      cx.ty_ident(sp,
-                                                                 Ident::with_dummy_span(sym::str)),
+                                                                 Ident::new(sym::str, sp)),
                                                      Some(lt),
                                                      ast::Mutability::Immutable))],
                                      vec![]))
diff --git a/src/libsyntax_ext/error_codes.rs b/src/libsyntax_ext/error_codes.rs
index 5982a4df226c2..2bc990574f7a8 100644
--- a/src/libsyntax_ext/error_codes.rs
+++ b/src/libsyntax_ext/error_codes.rs
@@ -1,9 +1,8 @@
-use syntax::register_long_diagnostics;
-
 // Error messages for EXXXX errors.
-// Each message should start and end with a new line, and be wrapped to 80 characters.
-// In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
-register_long_diagnostics! {
+// Each message should start and end with a new line, and be wrapped to 80
+// characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use
+// `:set tw=0` to disable.
+syntax::register_diagnostics! {
 E0660: r##"
 The argument to the `asm` macro is not well-formed.
 
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index ad275f421af49..46c7cbb83de90 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -138,15 +138,23 @@ fn parse_args<'a>(
     }
 
     let fmtstr = p.parse_expr()?;
+    let mut first = true;
     let mut named = false;
 
     while p.token != token::Eof {
         if !p.eat(&token::Comma) {
-            let mut err = ecx.struct_span_err(p.token.span, "expected token: `,`");
-            err.span_label(p.token.span, "expected `,`");
-            p.maybe_annotate_with_ascription(&mut err, false);
-            return Err(err);
+            if first {
+                // After `format!(""` we always expect *only* a comma...
+                let mut err = ecx.struct_span_err(p.token.span, "expected token: `,`");
+                err.span_label(p.token.span, "expected `,`");
+                p.maybe_annotate_with_ascription(&mut err, false);
+                return Err(err);
+            } else {
+                // ...after that delegate to `expect` to also include the other expected tokens.
+                return Err(p.expect(&token::Comma).err().unwrap());
+            }
         }
+        first = false;
         if p.token == token::Eof {
             break;
         } // accept trailing commas
@@ -291,7 +299,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 &format!(
                     "{} positional argument{} in format string, but {}",
                     count,
-                    if count > 1 { "s" } else { "" },
+                    if count != 1 { "s" } else { "" },
                     self.describe_num_args(),
                 ),
             );
@@ -478,7 +486,7 @@ impl<'a, 'b> Context<'a, 'b> {
         let sp = self.macsp;
         let count = |c, arg| {
             let mut path = Context::rtpath(self.ecx, "Count");
-            path.push(self.ecx.ident_of(c));
+            path.push(self.ecx.ident_of(c, sp));
             match arg {
                 Some(arg) => self.ecx.expr_call_global(sp, path, vec![arg]),
                 None => self.ecx.expr_path(self.ecx.path_global(sp, path)),
@@ -526,7 +534,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 let pos = {
                     let pos = |c, arg| {
                         let mut path = Context::rtpath(self.ecx, "Position");
-                        path.push(self.ecx.ident_of(c));
+                        path.push(self.ecx.ident_of(c, sp));
                         match arg {
                             Some(i) => {
                                 let arg = self.ecx.expr_usize(sp, i);
@@ -595,7 +603,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 let fill = self.ecx.expr_lit(sp, ast::LitKind::Char(fill));
                 let align = |name| {
                     let mut p = Context::rtpath(self.ecx, "Alignment");
-                    p.push(self.ecx.ident_of(name));
+                    p.push(self.ecx.ident_of(name, sp));
                     self.ecx.path_global(sp, p)
                 };
                 let align = match arg.format.align {
@@ -613,11 +621,11 @@ impl<'a, 'b> Context<'a, 'b> {
                     sp,
                     path,
                     vec![
-                        self.ecx.field_imm(sp, self.ecx.ident_of("fill"), fill),
-                        self.ecx.field_imm(sp, self.ecx.ident_of("align"), align),
-                        self.ecx.field_imm(sp, self.ecx.ident_of("flags"), flags),
-                        self.ecx.field_imm(sp, self.ecx.ident_of("precision"), prec),
-                        self.ecx.field_imm(sp, self.ecx.ident_of("width"), width),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("fill", sp), fill),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("align", sp), align),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("flags", sp), flags),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("precision", sp), prec),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("width", sp), width),
                     ],
                 );
 
@@ -626,8 +634,8 @@ impl<'a, 'b> Context<'a, 'b> {
                     sp,
                                           path,
                     vec![
-                        self.ecx.field_imm(sp, self.ecx.ident_of("position"), pos),
-                        self.ecx.field_imm(sp, self.ecx.ident_of("format"), fmt),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("position", sp), pos),
+                        self.ecx.field_imm(sp, self.ecx.ident_of("format", sp), fmt),
                     ],
                 ))
             }
@@ -645,7 +653,7 @@ impl<'a, 'b> Context<'a, 'b> {
         let mut heads = Vec::with_capacity(self.args.len());
 
         let names_pos: Vec<_> = (0..self.args.len())
-            .map(|i| ast::Ident::from_str_and_span(&format!("arg{}", i), self.macsp))
+            .map(|i| self.ecx.ident_of(&format!("arg{}", i), self.macsp))
             .collect();
 
         // First, build up the static array which will become our precompiled
@@ -716,7 +724,7 @@ impl<'a, 'b> Context<'a, 'b> {
         // But the nested match expression is proved to perform not as well
         // as series of let's; the first approach does.
         let pat = self.ecx.pat_tuple(self.fmtsp, pats);
-        let arm = self.ecx.arm(self.fmtsp, vec![pat], args_array);
+        let arm = self.ecx.arm(self.fmtsp, pat, args_array);
         let head = self.ecx.expr(self.fmtsp, ast::ExprKind::Tup(heads));
         let result = self.ecx.expr_match(self.fmtsp, head, vec![arm]);
 
diff --git a/src/libsyntax_ext/global_allocator.rs b/src/libsyntax_ext/global_allocator.rs
index f4af1699cd683..19a87e6dc6d74 100644
--- a/src/libsyntax_ext/global_allocator.rs
+++ b/src/libsyntax_ext/global_allocator.rs
@@ -28,7 +28,7 @@ pub fn expand(
     };
 
     // Generate a bunch of new items using the AllocFnFactory
-    let span = ecx.with_legacy_ctxt(item.span);
+    let span = ecx.with_def_site_ctxt(item.span);
     let f = AllocFnFactory {
         span,
         kind: AllocatorKind::Global,
@@ -43,7 +43,7 @@ pub fn expand(
     let const_ty = ecx.ty(span, TyKind::Tup(Vec::new()));
     let const_body = ecx.expr_block(ecx.block(span, stmts));
     let const_item =
-        ecx.item_const(span, Ident::with_dummy_span(kw::Underscore), const_ty, const_body);
+        ecx.item_const(span, Ident::new(kw::Underscore, span), const_ty, const_body);
 
     // Return the original item and the new methods.
     vec![Annotatable::Item(item), Annotatable::Item(const_item)]
@@ -61,7 +61,7 @@ impl AllocFnFactory<'_, '_> {
         let mut abi_args = Vec::new();
         let mut i = 0;
         let ref mut mk = || {
-            let name = Ident::from_str(&format!("arg{}", i));
+            let name = self.cx.ident_of(&format!("arg{}", i), self.span);
             i += 1;
             name
         };
@@ -83,7 +83,7 @@ impl AllocFnFactory<'_, '_> {
         );
         let item = self.cx.item(
             self.span,
-            Ident::from_str(&self.kind.fn_name(method.name)),
+            self.cx.ident_of(&self.kind.fn_name(method.name), self.span),
             self.attrs(),
             kind,
         );
@@ -119,7 +119,7 @@ impl AllocFnFactory<'_, '_> {
     ) -> P<Expr> {
         match *ty {
             AllocatorTy::Layout => {
-                let usize = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::usize));
+                let usize = self.cx.path_ident(self.span, Ident::new(sym::usize, self.span));
                 let ty_usize = self.cx.ty_path(usize);
                 let size = ident();
                 let align = ident();
@@ -177,12 +177,12 @@ impl AllocFnFactory<'_, '_> {
     }
 
     fn usize(&self) -> P<Ty> {
-        let usize = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::usize));
+        let usize = self.cx.path_ident(self.span, Ident::new(sym::usize, self.span));
         self.cx.ty_path(usize)
     }
 
     fn ptr_u8(&self) -> P<Ty> {
-        let u8 = self.cx.path_ident(self.span, Ident::with_dummy_span(sym::u8));
+        let u8 = self.cx.path_ident(self.span, Ident::new(sym::u8, self.span));
         let ty_u8 = self.cx.ty_path(u8);
         self.cx.ty_ptr(self.span, ty_u8, Mutability::Mutable)
     }
diff --git a/src/libsyntax_ext/global_asm.rs b/src/libsyntax_ext/global_asm.rs
index 6140f0df58af9..c56b3f3fc808f 100644
--- a/src/libsyntax_ext/global_asm.rs
+++ b/src/libsyntax_ext/global_asm.rs
@@ -30,7 +30,7 @@ pub fn expand_global_asm<'cx>(cx: &'cx mut ExtCtxt<'_>,
                 id: ast::DUMMY_NODE_ID,
                 node: ast::ItemKind::GlobalAsm(P(global_asm)),
                 vis: respan(sp.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                span: cx.with_legacy_ctxt(sp),
+                span: cx.with_def_site_ctxt(sp),
                 tokens: None,
             })])
         }
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index 26ef80b2b06df..631ab7a33106f 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -9,7 +9,6 @@
 #![feature(nll)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]
-#![feature(rustc_diagnostic_macros)]
 
 extern crate proc_macro;
 
@@ -40,6 +39,7 @@ mod source_util;
 mod test;
 mod trace_macros;
 
+pub mod cmdline_attrs;
 pub mod plugin_macro_defs;
 pub mod proc_macro_harness;
 pub mod standard_library_imports;
diff --git a/src/libsyntax_ext/plugin_macro_defs.rs b/src/libsyntax_ext/plugin_macro_defs.rs
index dbfd8fe98f389..ccdc5bd81a04b 100644
--- a/src/libsyntax_ext/plugin_macro_defs.rs
+++ b/src/libsyntax_ext/plugin_macro_defs.rs
@@ -11,7 +11,7 @@ use syntax::source_map::respan;
 use syntax::symbol::sym;
 use syntax::tokenstream::*;
 use syntax_pos::{Span, DUMMY_SP};
-use syntax_pos::hygiene::{ExpnData, ExpnKind, MacroKind};
+use syntax_pos::hygiene::{ExpnData, ExpnKind, AstPass};
 
 use std::mem;
 
@@ -44,7 +44,7 @@ pub fn inject(
     if !named_exts.is_empty() {
         let mut extra_items = Vec::new();
         let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-            ExpnKind::Macro(MacroKind::Attr, sym::plugin), DUMMY_SP, edition,
+            ExpnKind::AstPass(AstPass::PluginMacroDefs), DUMMY_SP, edition,
             [sym::rustc_attrs][..].into(),
         ));
         for (name, ext) in named_exts {
diff --git a/src/libsyntax_ext/proc_macro_harness.rs b/src/libsyntax_ext/proc_macro_harness.rs
index e772eaf834964..f33c813d86cfe 100644
--- a/src/libsyntax_ext/proc_macro_harness.rs
+++ b/src/libsyntax_ext/proc_macro_harness.rs
@@ -3,8 +3,7 @@ use std::mem;
 use smallvec::smallvec;
 use syntax::ast::{self, Ident};
 use syntax::attr;
-use syntax::source_map::{ExpnData, ExpnKind, respan};
-use syntax::ext::base::{ExtCtxt, MacroKind};
+use syntax::ext::base::ExtCtxt;
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
 use syntax::ext::proc_macro::is_proc_macro_attr;
 use syntax::parse::ParseSess;
@@ -12,6 +11,7 @@ use syntax::ptr::P;
 use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
 use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::hygiene::AstPass;
 
 struct ProcMacroDerive {
     trait_name: ast::Name,
@@ -20,15 +20,24 @@ struct ProcMacroDerive {
     attrs: Vec<ast::Name>,
 }
 
+enum ProcMacroDefType {
+    Attr,
+    Bang
+}
+
 struct ProcMacroDef {
     function_name: Ident,
     span: Span,
+    def_type: ProcMacroDefType
+}
+
+enum ProcMacro {
+    Derive(ProcMacroDerive),
+    Def(ProcMacroDef)
 }
 
 struct CollectProcMacros<'a> {
-    derives: Vec<ProcMacroDerive>,
-    attr_macros: Vec<ProcMacroDef>,
-    bang_macros: Vec<ProcMacroDef>,
+    macros: Vec<ProcMacro>,
     in_root: bool,
     handler: &'a errors::Handler,
     is_proc_macro_crate: bool,
@@ -46,22 +55,22 @@ pub fn inject(sess: &ParseSess,
     let ecfg = ExpansionConfig::default("proc_macro".to_string());
     let mut cx = ExtCtxt::new(sess, ecfg, resolver);
 
-    let (derives, attr_macros, bang_macros) = {
-        let mut collect = CollectProcMacros {
-            derives: Vec::new(),
-            attr_macros: Vec::new(),
-            bang_macros: Vec::new(),
-            in_root: true,
-            handler,
-            is_proc_macro_crate,
-            is_test_crate,
-        };
-        if has_proc_macro_decls || is_proc_macro_crate {
-            visit::walk_crate(&mut collect, &krate);
-        }
-        (collect.derives, collect.attr_macros, collect.bang_macros)
+    let mut collect = CollectProcMacros {
+        macros: Vec::new(),
+        in_root: true,
+        handler,
+        is_proc_macro_crate,
+        is_test_crate,
     };
 
+    if has_proc_macro_decls || is_proc_macro_crate {
+        visit::walk_crate(&mut collect, &krate);
+    }
+    // NOTE: If you change the order of macros in this vec
+    // for any reason, you must also update 'raw_proc_macro'
+    // in src/librustc_metadata/decoder.rs
+    let macros = collect.macros;
+
     if !is_proc_macro_crate {
         return krate
     }
@@ -74,7 +83,7 @@ pub fn inject(sess: &ParseSess,
         return krate;
     }
 
-    krate.module.items.push(mk_decls(&mut cx, &derives, &attr_macros, &bang_macros));
+    krate.module.items.push(mk_decls(&mut cx, &macros));
 
     krate
 }
@@ -161,12 +170,12 @@ impl<'a> CollectProcMacros<'a> {
         };
 
         if self.in_root && item.vis.node.is_pub() {
-            self.derives.push(ProcMacroDerive {
+            self.macros.push(ProcMacro::Derive(ProcMacroDerive {
                 span: item.span,
                 trait_name: trait_ident.name,
                 function_name: item.ident,
                 attrs: proc_attrs,
-            });
+            }));
         } else {
             let msg = if !self.in_root {
                 "functions tagged with `#[proc_macro_derive]` must \
@@ -180,10 +189,11 @@ impl<'a> CollectProcMacros<'a> {
 
     fn collect_attr_proc_macro(&mut self, item: &'a ast::Item) {
         if self.in_root && item.vis.node.is_pub() {
-            self.attr_macros.push(ProcMacroDef {
+            self.macros.push(ProcMacro::Def(ProcMacroDef {
                 span: item.span,
                 function_name: item.ident,
-            });
+                def_type: ProcMacroDefType::Attr
+            }));
         } else {
             let msg = if !self.in_root {
                 "functions tagged with `#[proc_macro_attribute]` must \
@@ -197,10 +207,11 @@ impl<'a> CollectProcMacros<'a> {
 
     fn collect_bang_proc_macro(&mut self, item: &'a ast::Item) {
         if self.in_root && item.vis.node.is_pub() {
-            self.bang_macros.push(ProcMacroDef {
+            self.macros.push(ProcMacro::Def(ProcMacroDef {
                 span: item.span,
                 function_name: item.ident,
-            });
+                def_type: ProcMacroDefType::Bang
+            }));
         } else {
             let msg = if !self.in_root {
                 "functions tagged with `#[proc_macro]` must \
@@ -308,8 +319,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
 // Creates a new module which looks like:
 //
-//      #[doc(hidden)]
-//      mod $gensym {
+//      const _: () = {
 //          extern crate proc_macro;
 //
 //          use proc_macro::bridge::client::ProcMacro;
@@ -323,65 +333,67 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 //      }
 fn mk_decls(
     cx: &mut ExtCtxt<'_>,
-    custom_derives: &[ProcMacroDerive],
-    custom_attrs: &[ProcMacroDef],
-    custom_macros: &[ProcMacroDef],
+    macros: &[ProcMacro],
 ) -> P<ast::Item> {
-    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::proc_macro), DUMMY_SP, cx.parse_sess.edition,
-        [sym::rustc_attrs, sym::proc_macro_internals][..].into(),
-    ));
-
-    let hidden = cx.meta_list_item_word(span, sym::hidden);
-    let doc = cx.meta_list(span, sym::doc, vec![hidden]);
-    let doc_hidden = cx.attribute(doc);
-
-    let proc_macro = Ident::with_dummy_span(sym::proc_macro);
+    let expn_id = cx.resolver.expansion_for_ast_pass(
+        DUMMY_SP,
+        AstPass::ProcMacroHarness,
+        &[sym::rustc_attrs, sym::proc_macro_internals],
+        None,
+    );
+    let span = DUMMY_SP.with_def_site_ctxt(expn_id);
+
+    let proc_macro = Ident::new(sym::proc_macro, span);
     let krate = cx.item(span,
                         proc_macro,
                         Vec::new(),
                         ast::ItemKind::ExternCrate(None));
 
-    let bridge = Ident::from_str("bridge");
-    let client = Ident::from_str("client");
-    let proc_macro_ty = Ident::from_str("ProcMacro");
-    let custom_derive = Ident::from_str("custom_derive");
-    let attr = Ident::from_str("attr");
-    let bang = Ident::from_str("bang");
-    let crate_kw = Ident::with_dummy_span(kw::Crate);
+    let bridge = cx.ident_of("bridge", span);
+    let client = cx.ident_of("client", span);
+    let proc_macro_ty = cx.ident_of("ProcMacro", span);
+    let custom_derive = cx.ident_of("custom_derive", span);
+    let attr = cx.ident_of("attr", span);
+    let bang = cx.ident_of("bang", span);
 
     let decls = {
         let local_path = |sp: Span, name| {
-            cx.expr_path(cx.path(sp.with_ctxt(span.ctxt()), vec![crate_kw, name]))
+            cx.expr_path(cx.path(sp.with_ctxt(span.ctxt()), vec![name]))
         };
         let proc_macro_ty_method_path = |method| cx.expr_path(cx.path(span, vec![
             proc_macro, bridge, client, proc_macro_ty, method,
         ]));
-        custom_derives.iter().map(|cd| {
-            cx.expr_call(span, proc_macro_ty_method_path(custom_derive), vec![
-                cx.expr_str(cd.span, cd.trait_name),
-                cx.expr_vec_slice(
-                    span,
-                    cd.attrs.iter().map(|&s| cx.expr_str(cd.span, s)).collect::<Vec<_>>()
-                ),
-                local_path(cd.span, cd.function_name),
-            ])
-        }).chain(custom_attrs.iter().map(|ca| {
-            cx.expr_call(span, proc_macro_ty_method_path(attr), vec![
-                cx.expr_str(ca.span, ca.function_name.name),
-                local_path(ca.span, ca.function_name),
-            ])
-        })).chain(custom_macros.iter().map(|cm| {
-            cx.expr_call(span, proc_macro_ty_method_path(bang), vec![
-                cx.expr_str(cm.span, cm.function_name.name),
-                local_path(cm.span, cm.function_name),
-            ])
-        })).collect()
+        macros.iter().map(|m| {
+            match m {
+                ProcMacro::Derive(cd) => {
+                    cx.expr_call(span, proc_macro_ty_method_path(custom_derive), vec![
+                        cx.expr_str(cd.span, cd.trait_name),
+                        cx.expr_vec_slice(
+                            span,
+                            cd.attrs.iter().map(|&s| cx.expr_str(cd.span, s)).collect::<Vec<_>>()
+                        ),
+                        local_path(cd.span, cd.function_name),
+                    ])
+                },
+                ProcMacro::Def(ca) => {
+                    let ident = match ca.def_type {
+                        ProcMacroDefType::Attr => attr,
+                        ProcMacroDefType::Bang => bang
+                    };
+
+                    cx.expr_call(span, proc_macro_ty_method_path(ident), vec![
+                        cx.expr_str(ca.span, ca.function_name.name),
+                        local_path(ca.span, ca.function_name),
+                    ])
+
+                }
+            }
+        }).collect()
     };
 
     let decls_static = cx.item_static(
         span,
-        Ident::from_str("_DECLS"),
+        cx.ident_of("_DECLS", span),
         cx.ty_rptr(span,
             cx.ty(span, ast::TyKind::Slice(
                 cx.ty_path(cx.path(span,
@@ -392,22 +404,22 @@ fn mk_decls(
     ).map(|mut i| {
         let attr = cx.meta_word(span, sym::rustc_proc_macro_decls);
         i.attrs.push(cx.attribute(attr));
-        i.vis = respan(span, ast::VisibilityKind::Public);
         i
     });
 
-    let module = cx.item_mod(
-        span,
+    let block = cx.expr_block(cx.block(
         span,
-        ast::Ident::from_str("decls").gensym(),
-        vec![doc_hidden],
-        vec![krate, decls_static],
-    ).map(|mut i| {
-        i.vis = respan(span, ast::VisibilityKind::Public);
-        i
-    });
+        vec![cx.stmt_item(span, krate), cx.stmt_item(span, decls_static)],
+    ));
 
-    // Integrate the new module into existing module structures.
-    let module = AstFragment::Items(smallvec![module]);
-    cx.monotonic_expander().fully_expand_fragment(module).make_items().pop().unwrap()
+    let anon_constant = cx.item_const(
+        span,
+        ast::Ident::new(kw::Underscore, span),
+        cx.ty(span, ast::TyKind::Tup(Vec::new())),
+        block,
+    );
+
+    // Integrate the new item into existing module structures.
+    let items = AstFragment::Items(smallvec![anon_constant]);
+    cx.monotonic_expander().fully_expand_fragment(items).make_items().pop().unwrap()
 }
diff --git a/src/libsyntax_ext/standard_library_imports.rs b/src/libsyntax_ext/standard_library_imports.rs
index 8ca376341fcdb..c577b1e33cfeb 100644
--- a/src/libsyntax_ext/standard_library_imports.rs
+++ b/src/libsyntax_ext/standard_library_imports.rs
@@ -1,86 +1,86 @@
 use syntax::{ast, attr};
 use syntax::edition::Edition;
-use syntax::ext::hygiene::MacroKind;
+use syntax::ext::expand::ExpansionConfig;
+use syntax::ext::hygiene::AstPass;
+use syntax::ext::base::{ExtCtxt, Resolver};
+use syntax::parse::ParseSess;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned, respan};
 use syntax::symbol::{Ident, Symbol, kw, sym};
 use syntax_pos::DUMMY_SP;
 
-use std::iter;
-
 pub fn inject(
-    mut krate: ast::Crate, alt_std_name: Option<&str>, edition: Edition
+    mut krate: ast::Crate,
+    resolver: &mut dyn Resolver,
+    sess: &ParseSess,
+    alt_std_name: Option<Symbol>,
 ) -> (ast::Crate, Option<Symbol>) {
-    let rust_2018 = edition >= Edition::Edition2018;
+    let rust_2018 = sess.edition >= Edition::Edition2018;
 
     // the first name in this list is the crate name of the crate with the prelude
-    let names: &[&str] = if attr::contains_name(&krate.attrs, sym::no_core) {
+    let names: &[Symbol] = if attr::contains_name(&krate.attrs, sym::no_core) {
         return (krate, None);
     } else if attr::contains_name(&krate.attrs, sym::no_std) {
         if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
-            &["core"]
+            &[sym::core]
         } else {
-            &["core", "compiler_builtins"]
+            &[sym::core, sym::compiler_builtins]
         }
     } else {
-        &["std"]
+        &[sym::std]
     };
 
+    let expn_id = resolver.expansion_for_ast_pass(
+        DUMMY_SP,
+        AstPass::StdImports,
+        &[sym::prelude_import],
+        None,
+    );
+    let span = DUMMY_SP.with_def_site_ctxt(expn_id);
+    let call_site = DUMMY_SP.with_call_site_ctxt(expn_id);
+
+    let ecfg = ExpansionConfig::default("std_lib_injection".to_string());
+    let cx = ExtCtxt::new(sess, ecfg, resolver);
+
+
     // .rev() to preserve ordering above in combination with insert(0, ...)
-    let alt_std_name = alt_std_name.map(Symbol::intern);
-    for orig_name_str in names.iter().rev() {
-        // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
-        // so they don't accidentally interfere with the new import paths.
-        let orig_name_sym = Symbol::intern(orig_name_str);
-        let orig_name_ident = Ident::with_dummy_span(orig_name_sym);
-        let (rename, orig_name) = if rust_2018 {
-            (orig_name_ident.gensym(), Some(orig_name_sym))
+    for &name in names.iter().rev() {
+        let ident = if rust_2018 {
+            Ident::new(name, span)
         } else {
-            (orig_name_ident, None)
+            Ident::new(name, call_site)
         };
-        krate.module.items.insert(0, P(ast::Item {
-            attrs: vec![attr::mk_attr_outer(
-                attr::mk_word_item(ast::Ident::with_dummy_span(sym::macro_use))
-            )],
-            vis: dummy_spanned(ast::VisibilityKind::Inherited),
-            node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
-            ident: rename,
-            id: ast::DUMMY_NODE_ID,
-            span: DUMMY_SP,
-            tokens: None,
-        }));
+        krate.module.items.insert(0, cx.item(
+            span,
+            ident,
+            vec![cx.attribute(cx.meta_word(span, sym::macro_use))],
+            ast::ItemKind::ExternCrate(alt_std_name),
+        ));
     }
 
-    // the crates have been injected, the assumption is that the first one is the one with
-    // the prelude.
+    // The crates have been injected, the assumption is that the first one is
+    // the one with the prelude.
     let name = names[0];
 
-    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
-        [sym::prelude_import][..].into(),
-    ));
+    let import_path = if rust_2018 {
+        [name, sym::prelude, sym::v1].iter()
+            .map(|symbol| ast::Ident::new(*symbol, span)).collect()
+    } else {
+        [kw::PathRoot, name, sym::prelude, sym::v1].iter()
+            .map(|symbol| ast::Ident::new(*symbol, span)).collect()
+    };
 
-    krate.module.items.insert(0, P(ast::Item {
-        attrs: vec![attr::mk_attr_outer(
-            attr::mk_word_item(ast::Ident::new(sym::prelude_import, span)))],
-        vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
-        node: ast::ItemKind::Use(P(ast::UseTree {
-            prefix: ast::Path {
-                segments: iter::once(ast::Ident::with_dummy_span(kw::PathRoot))
-                    .chain(
-                        [name, "prelude", "v1"].iter().cloned()
-                            .map(ast::Ident::from_str)
-                    ).map(ast::PathSegment::from_ident).collect(),
-                span,
-            },
+    let use_item = cx.item(
+        span,
+        ast::Ident::invalid(),
+        vec![cx.attribute(cx.meta_word(span, sym::prelude_import))],
+        ast::ItemKind::Use(P(ast::UseTree {
+            prefix: cx.path(span, import_path),
             kind: ast::UseTreeKind::Glob,
             span,
         })),
-        id: ast::DUMMY_NODE_ID,
-        ident: ast::Ident::invalid(),
-        span,
-        tokens: None,
-    }));
+    );
+
+    krate.module.items.insert(0, use_item);
 
-    (krate, Some(Symbol::intern(name)))
+    (krate, Some(name))
 }
diff --git a/src/libsyntax_ext/test.rs b/src/libsyntax_ext/test.rs
index 5fd87d3a0e5c6..0910c00a8a2a9 100644
--- a/src/libsyntax_ext/test.rs
+++ b/src/libsyntax_ext/test.rs
@@ -28,11 +28,11 @@ pub fn expand_test_case(
 
     if !ecx.ecfg.should_test { return vec![]; }
 
-    let sp = ecx.with_legacy_ctxt(attr_sp);
+    let sp = ecx.with_def_site_ctxt(attr_sp);
     let mut item = anno_item.expect_item();
     item = item.map(|mut item| {
         item.vis = respan(item.vis.span, ast::VisibilityKind::Public);
-        item.ident = item.ident.gensym();
+        item.ident.span = item.ident.span.with_ctxt(sp.ctxt());
         item.attrs.push(
             ecx.attribute(ecx.meta_word(sp, sym::rustc_test_marker))
         );
@@ -92,27 +92,26 @@ pub fn expand_test_or_bench(
         return vec![Annotatable::Item(item)];
     }
 
-    let (sp, attr_sp) = (cx.with_legacy_ctxt(item.span), cx.with_legacy_ctxt(attr_sp));
+    let (sp, attr_sp) = (cx.with_def_site_ctxt(item.span), cx.with_def_site_ctxt(attr_sp));
 
-    // Gensym "test" so we can extern crate without conflicting with any local names
-    let test_id = cx.ident_of("test").gensym();
+    let test_id = ast::Ident::new(sym::test, attr_sp);
 
     // creates test::$name
     let test_path = |name| {
-        cx.path(sp, vec![test_id, cx.ident_of(name)])
+        cx.path(sp, vec![test_id, cx.ident_of(name, sp)])
     };
 
     // creates test::ShouldPanic::$name
     let should_panic_path = |name| {
-        cx.path(sp, vec![test_id, cx.ident_of("ShouldPanic"), cx.ident_of(name)])
+        cx.path(sp, vec![test_id, cx.ident_of("ShouldPanic", sp), cx.ident_of(name, sp)])
     };
 
     // creates $name: $expr
-    let field = |name, expr| cx.field_imm(sp, cx.ident_of(name), expr);
+    let field = |name, expr| cx.field_imm(sp, cx.ident_of(name, sp), expr);
 
     let test_fn = if is_bench {
         // A simple ident for a lambda
-        let b = cx.ident_of("b");
+        let b = cx.ident_of("b", attr_sp);
 
         cx.expr_call(sp, cx.expr_path(test_path("StaticBenchFn")), vec![
             // |b| self::test::assert_test_result(
@@ -143,7 +142,7 @@ pub fn expand_test_or_bench(
         ])
     };
 
-    let mut test_const = cx.item(sp, ast::Ident::new(item.ident.name, sp).gensym(),
+    let mut test_const = cx.item(sp, ast::Ident::new(item.ident.name, sp),
         vec![
             // #[cfg(test)]
             cx.attribute(cx.meta_list(attr_sp, sym::cfg, vec![
@@ -192,17 +191,17 @@ pub fn expand_test_or_bench(
         ));
     test_const = test_const.map(|mut tc| { tc.vis.node = ast::VisibilityKind::Public; tc});
 
-    // extern crate test as test_gensym
+    // extern crate test
     let test_extern = cx.item(sp,
         test_id,
         vec![],
-        ast::ItemKind::ExternCrate(Some(sym::test))
+        ast::ItemKind::ExternCrate(None)
     );
 
     log::debug!("synthetic test item:\n{}\n", pprust::item_to_string(&test_const));
 
     vec![
-        // Access to libtest under a gensymed name
+        // Access to libtest under a hygienic name
         Annotatable::Item(test_extern),
         // The generated test case
         Annotatable::Item(test_const),
diff --git a/src/libsyntax_ext/test_harness.rs b/src/libsyntax_ext/test_harness.rs
index 4a6ea0ebf85e5..56de0c97f81c0 100644
--- a/src/libsyntax_ext/test_harness.rs
+++ b/src/libsyntax_ext/test_harness.rs
@@ -5,32 +5,30 @@ use smallvec::{smallvec, SmallVec};
 use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::entry::{self, EntryPointType};
-use syntax::ext::base::{ExtCtxt, MacroKind, Resolver};
+use syntax::ext::base::{ExtCtxt, Resolver};
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
 use syntax::feature_gate::Features;
 use syntax::mut_visit::{*, ExpectOne};
 use syntax::parse::ParseSess;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned};
-use syntax::symbol::{kw, sym, Symbol};
+use syntax::source_map::respan;
+use syntax::symbol::{sym, Symbol};
 use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::hygiene::{AstPass, SyntaxContext, Transparency};
 
 use std::{iter, mem};
 
 struct Test {
     span: Span,
-    path: Vec<Ident>,
+    ident: Ident,
 }
 
 struct TestCtxt<'a> {
-    span_diagnostic: &'a errors::Handler,
-    path: Vec<Ident>,
     ext_cx: ExtCtxt<'a>,
+    def_site: Span,
     test_cases: Vec<Test>,
     reexport_test_harness_main: Option<Symbol>,
     test_runner: Option<ast::Path>,
-    // top-level re-export submodule, filled out after folding is finished
-    toplevel_reexport: Option<Ident>,
 }
 
 // Traverse the crate, collecting all the test functions, eliding any
@@ -43,8 +41,8 @@ pub fn inject(
     span_diagnostic: &errors::Handler,
     features: &Features,
 ) {
-    // Check for #[reexport_test_harness_main = "some_name"] which
-    // creates a `use __test::main as some_name;`. This needs to be
+    // Check for #![reexport_test_harness_main = "some_name"] which gives the
+    // main test function the name `some_name` without hygiene. This needs to be
     // unconditional, so that the attribute is still marked as used in
     // non-test builds.
     let reexport_test_harness_main =
@@ -56,16 +54,13 @@ pub fn inject(
 
     if should_test {
         generate_test_harness(sess, resolver, reexport_test_harness_main,
-                              krate, span_diagnostic, features, test_runner)
+                              krate, features, test_runner)
     }
 }
 
 struct TestHarnessGenerator<'a> {
     cx: TestCtxt<'a>,
-    tests: Vec<Ident>,
-
-    // submodule name, gensym'd identifier for re-exports
-    tested_submods: Vec<(Ident, Ident)>,
+    tests: Vec<Test>,
 }
 
 impl<'a> MutVisitor for TestHarnessGenerator<'a> {
@@ -77,49 +72,47 @@ impl<'a> MutVisitor for TestHarnessGenerator<'a> {
     }
 
     fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
-        let ident = i.ident;
-        if ident.name != kw::Invalid {
-            self.cx.path.push(ident);
-        }
-        debug!("current path: {}", path_name_i(&self.cx.path));
-
         let mut item = i.into_inner();
         if is_test_case(&item) {
             debug!("this is a test item");
 
             let test = Test {
                 span: item.span,
-                path: self.cx.path.clone(),
+                ident: item.ident,
             };
-            self.cx.test_cases.push(test);
-            self.tests.push(item.ident);
+            self.tests.push(test);
         }
 
         // We don't want to recurse into anything other than mods, since
         // mods or tests inside of functions will break things
         if let ast::ItemKind::Mod(mut module) = item.node {
             let tests = mem::take(&mut self.tests);
-            let tested_submods = mem::take(&mut self.tested_submods);
             noop_visit_mod(&mut module, self);
-            let tests = mem::replace(&mut self.tests, tests);
-            let tested_submods = mem::replace(&mut self.tested_submods, tested_submods);
+            let mut tests = mem::replace(&mut self.tests, tests);
 
-            if !tests.is_empty() || !tested_submods.is_empty() {
-                let (it, sym) = mk_reexport_mod(&mut self.cx, item.id, tests, tested_submods);
-                module.items.push(it);
-
-                if !self.cx.path.is_empty() {
-                    self.tested_submods.push((self.cx.path[self.cx.path.len()-1], sym));
+            if !tests.is_empty() {
+                let parent = if item.id == ast::DUMMY_NODE_ID {
+                    ast::CRATE_NODE_ID
                 } else {
-                    debug!("pushing nothing, sym: {:?}", sym);
-                    self.cx.toplevel_reexport = Some(sym);
+                    item.id
+                };
+                // Create an identifier that will hygienically resolve the test
+                // case name, even in another module.
+                let expn_id = self.cx.ext_cx.resolver.expansion_for_ast_pass(
+                    module.inner,
+                    AstPass::TestHarness,
+                    &[],
+                    Some(parent),
+                );
+                for test in &mut tests {
+                    // See the comment on `mk_main` for why we're using
+                    // `apply_mark` directly.
+                    test.ident.span = test.ident.span.apply_mark(expn_id, Transparency::Opaque);
                 }
+                self.cx.test_cases.extend(tests);
             }
             item.node = ast::ItemKind::Mod(module);
         }
-        if ident.name != kw::Invalid {
-            self.cx.path.pop();
-        }
         smallvec![P(item)]
     }
 
@@ -133,6 +126,7 @@ impl<'a> MutVisitor for TestHarnessGenerator<'a> {
 struct EntryPointCleaner {
     // Current depth in the ast
     depth: usize,
+    def_site: Span,
 }
 
 impl MutVisitor for EntryPointCleaner {
@@ -149,8 +143,10 @@ impl MutVisitor for EntryPointCleaner {
             EntryPointType::MainAttr |
             EntryPointType::Start =>
                 item.map(|ast::Item {id, ident, attrs, node, vis, span, tokens}| {
-                    let allow_ident = Ident::with_dummy_span(sym::allow);
-                    let dc_nested = attr::mk_nested_word_item(Ident::from_str("dead_code"));
+                    let allow_ident = Ident::new(sym::allow, self.def_site);
+                    let dc_nested = attr::mk_nested_word_item(
+                        Ident::from_str_and_span("dead_code", self.def_site),
+                    );
                     let allow_dead_code_item = attr::mk_list_item(allow_ident, vec![dc_nested]);
                     let allow_dead_code = attr::mk_attr_outer(allow_dead_code_item);
 
@@ -181,124 +177,99 @@ impl MutVisitor for EntryPointCleaner {
     }
 }
 
-/// Creates an item (specifically a module) that "pub use"s the tests passed in.
-/// Each tested submodule will contain a similar reexport module that we will export
-/// under the name of the original module. That is, `submod::__test_reexports` is
-/// reexported like so `pub use submod::__test_reexports as submod`.
-fn mk_reexport_mod(cx: &mut TestCtxt<'_>,
-                   parent: ast::NodeId,
-                   tests: Vec<Ident>,
-                   tested_submods: Vec<(Ident, Ident)>)
-                   -> (P<ast::Item>, Ident) {
-    let super_ = Ident::with_dummy_span(kw::Super);
-
-    let items = tests.into_iter().map(|r| {
-        cx.ext_cx.item_use_simple(DUMMY_SP, dummy_spanned(ast::VisibilityKind::Public),
-                                  cx.ext_cx.path(DUMMY_SP, vec![super_, r]))
-    }).chain(tested_submods.into_iter().map(|(r, sym)| {
-        let path = cx.ext_cx.path(DUMMY_SP, vec![super_, r, sym]);
-        cx.ext_cx.item_use_simple_(DUMMY_SP, dummy_spanned(ast::VisibilityKind::Public),
-                                   Some(r), path)
-    })).collect();
-
-    let reexport_mod = ast::Mod {
-        inline: true,
-        inner: DUMMY_SP,
-        items,
-    };
-
-    let name = Ident::from_str("__test_reexports").gensym();
-    let parent = if parent == ast::DUMMY_NODE_ID { ast::CRATE_NODE_ID } else { parent };
-    cx.ext_cx.current_expansion.id = cx.ext_cx.resolver.get_module_scope(parent);
-    let module = P(ast::Item {
-        ident: name,
-        attrs: Vec::new(),
-        id: ast::DUMMY_NODE_ID,
-        node: ast::ItemKind::Mod(reexport_mod),
-        vis: dummy_spanned(ast::VisibilityKind::Public),
-        span: DUMMY_SP,
-        tokens: None,
-    });
-
-    // Integrate the new module into existing module structures.
-    let module = AstFragment::Items(smallvec![module]);
-    let module =
-        cx.ext_cx.monotonic_expander().fully_expand_fragment(module).make_items().pop().unwrap();
-
-    (module, name)
-}
-
 /// Crawl over the crate, inserting test reexports and the test main function
 fn generate_test_harness(sess: &ParseSess,
                          resolver: &mut dyn Resolver,
                          reexport_test_harness_main: Option<Symbol>,
                          krate: &mut ast::Crate,
-                         sd: &errors::Handler,
                          features: &Features,
                          test_runner: Option<ast::Path>) {
-    // Remove the entry points
-    let mut cleaner = EntryPointCleaner { depth: 0 };
-    cleaner.visit_crate(krate);
-
     let mut econfig = ExpansionConfig::default("test".to_string());
     econfig.features = Some(features);
 
+    let ext_cx = ExtCtxt::new(sess, econfig, resolver);
+
+    let expn_id = ext_cx.resolver.expansion_for_ast_pass(
+        DUMMY_SP,
+        AstPass::TestHarness,
+        &[sym::main, sym::test, sym::rustc_attrs],
+        None,
+    );
+    let def_site = DUMMY_SP.with_def_site_ctxt(expn_id);
+
+    // Remove the entry points
+    let mut cleaner = EntryPointCleaner { depth: 0, def_site };
+    cleaner.visit_crate(krate);
+
     let cx = TestCtxt {
-        span_diagnostic: sd,
-        ext_cx: ExtCtxt::new(sess, econfig, resolver),
-        path: Vec::new(),
+        ext_cx,
+        def_site,
         test_cases: Vec::new(),
         reexport_test_harness_main,
-        toplevel_reexport: None,
         test_runner
     };
 
     TestHarnessGenerator {
         cx,
         tests: Vec::new(),
-        tested_submods: Vec::new(),
     }.visit_crate(krate);
 }
 
 /// Creates a function item for use as the main function of a test build.
 /// This function will call the `test_runner` as specified by the crate attribute
+///
+/// By default this expands to
+///
+/// #[main]
+/// pub fn main() {
+///     extern crate test;
+///     test::test_main_static(&[
+///         &test_const1,
+///         &test_const2,
+///         &test_const3,
+///     ]);
+/// }
+///
+/// Most of the Ident have the usual def-site hygiene for the AST pass. The
+/// exception is the `test_const`s. These have a syntax context that has two
+/// opaque marks: one from the expansion of `test` or `test_case`, and one
+/// generated  in `TestHarnessGenerator::flat_map_item`. When resolving this
+/// identifier after failing to find a matching identifier in the root module
+/// we remove the outer mark, and try resolving at its def-site, which will
+/// then resolve to `test_const`.
+///
+/// The expansion here can be controlled by two attributes:
+///
+/// `reexport_test_harness_main` provides a different name for the `main`
+/// function and `test_runner` provides a path that replaces
+/// `test::test_main_static`.
 fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
-    // Writing this out by hand:
-    //        pub fn main() {
-    //            #![main]
-    //            test::test_main_static(&[..tests]);
-    //        }
-    let sp = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, cx.ext_cx.parse_sess.edition,
-        [sym::main, sym::test, sym::rustc_attrs][..].into(),
-    ));
+    let sp = cx.def_site;
     let ecx = &cx.ext_cx;
-    let test_id = Ident::with_dummy_span(sym::test);
+    let test_id = Ident::new(sym::test, sp);
 
     // test::test_main_static(...)
     let mut test_runner = cx.test_runner.clone().unwrap_or(
-        ecx.path(sp, vec![
-            test_id, ecx.ident_of("test_main_static")
-        ]));
+        ecx.path(sp, vec![test_id, ecx.ident_of("test_main_static", sp)]));
 
     test_runner.span = sp;
 
     let test_main_path_expr = ecx.expr_path(test_runner);
     let call_test_main = ecx.expr_call(sp, test_main_path_expr,
-                                       vec![mk_tests_slice(cx)]);
+                                       vec![mk_tests_slice(cx, sp)]);
     let call_test_main = ecx.stmt_expr(call_test_main);
 
-    // #![main]
-    let main_meta = ecx.meta_word(sp, sym::main);
-    let main_attr = ecx.attribute(main_meta);
-
-    // extern crate test as test_gensym
+    // extern crate test
     let test_extern_stmt = ecx.stmt_item(sp, ecx.item(sp,
         test_id,
         vec![],
         ast::ItemKind::ExternCrate(None)
     ));
 
+    // #[main]
+    let main_meta = ecx.meta_word(sp, sym::main);
+    let main_attr = ecx.attribute(main_meta);
+
     // pub fn main() { ... }
     let main_ret_ty = ecx.ty(sp, ast::TyKind::Tup(vec![]));
 
@@ -316,8 +287,8 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 
     // Honor the reexport_test_harness_main attribute
     let main_id = match cx.reexport_test_harness_main {
-        Some(sym) => Ident::new(sym, sp),
-        None => Ident::from_str_and_span("main", sp).gensym(),
+        Some(sym) => Ident::new(sym, sp.with_ctxt(SyntaxContext::root())),
+        None => Ident::new(sym::main, sp),
     };
 
     let main = P(ast::Item {
@@ -325,7 +296,7 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
         attrs: vec![main_attr],
         id: ast::DUMMY_NODE_ID,
         node: main,
-        vis: dummy_spanned(ast::VisibilityKind::Public),
+        vis: respan(sp, ast::VisibilityKind::Public),
         span: sp,
         tokens: None,
     });
@@ -335,44 +306,20 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     cx.ext_cx.monotonic_expander().fully_expand_fragment(main).make_items().pop().unwrap()
 }
 
-fn path_name_i(idents: &[Ident]) -> String {
-    let mut path_name = "".to_string();
-    let mut idents_iter = idents.iter().peekable();
-    while let Some(ident) = idents_iter.next() {
-        path_name.push_str(&ident.as_str());
-        if idents_iter.peek().is_some() {
-            path_name.push_str("::")
-        }
-    }
-    path_name
-}
-
 /// Creates a slice containing every test like so:
-/// &[path::to::test1, path::to::test2]
-fn mk_tests_slice(cx: &TestCtxt<'_>) -> P<ast::Expr> {
+/// &[&test1, &test2]
+fn mk_tests_slice(cx: &TestCtxt<'_>, sp: Span) -> P<ast::Expr> {
     debug!("building test vector from {} tests", cx.test_cases.len());
     let ref ecx = cx.ext_cx;
 
-    ecx.expr_vec_slice(DUMMY_SP,
+
+    ecx.expr_vec_slice(sp,
         cx.test_cases.iter().map(|test| {
             ecx.expr_addr_of(test.span,
-                ecx.expr_path(ecx.path(test.span, visible_path(cx, &test.path))))
+                ecx.expr_path(ecx.path(test.span, vec![test.ident])))
         }).collect())
 }
 
-/// Creates a path from the top-level __test module to the test via __test_reexports
-fn visible_path(cx: &TestCtxt<'_>, path: &[Ident]) -> Vec<Ident>{
-    let mut visible_path = vec![];
-    match cx.toplevel_reexport {
-        Some(id) => visible_path.push(id),
-        None => {
-            cx.span_diagnostic.bug("expected to find top-level re-export name, but found None");
-        }
-    }
-    visible_path.extend_from_slice(path);
-    visible_path
-}
-
 fn is_test_case(i: &ast::Item) -> bool {
     attr::contains_name(&i.attrs, sym::rustc_test_marker)
 }
diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index 733f6f0449065..e28d93267579a 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -343,6 +343,38 @@ pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symb
     }))
 }
 
+pub fn debug_hygiene_data(verbose: bool) -> String {
+    HygieneData::with(|data| {
+        if verbose {
+            format!("{:#?}", data)
+        } else {
+            let mut s = String::from("");
+            s.push_str("Expansions:");
+            data.expn_data.iter().enumerate().for_each(|(id, expn_info)| {
+                let expn_info = expn_info.as_ref().expect("no expansion data for an expansion ID");
+                s.push_str(&format!(
+                    "\n{}: parent: {:?}, call_site_ctxt: {:?}, kind: {:?}",
+                    id,
+                    expn_info.parent,
+                    expn_info.call_site.ctxt(),
+                    expn_info.kind,
+                ));
+            });
+            s.push_str("\n\nSyntaxContexts:");
+            data.syntax_context_data.iter().enumerate().for_each(|(id, ctxt)| {
+                s.push_str(&format!(
+                    "\n#{}: parent: {:?}, outer_mark: ({:?}, {:?})",
+                    id,
+                    ctxt.parent,
+                    ctxt.outer_expn,
+                    ctxt.outer_transparency,
+                ));
+            });
+            s
+        }
+    })
+}
+
 impl SyntaxContext {
     #[inline]
     pub const fn root() -> Self {
@@ -360,7 +392,7 @@ impl SyntaxContext {
     }
 
     /// Extend a syntax context with a given expansion and transparency.
-    pub fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
+    crate fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
         HygieneData::with(|data| data.apply_mark(self, expn_id, transparency))
     }
 
@@ -550,7 +582,7 @@ impl Span {
     /// The returned span belongs to the created expansion and has the new properties,
     /// but its location is inherited from the current span.
     pub fn fresh_expansion(self, expn_data: ExpnData) -> Span {
-        self.fresh_expansion_with_transparency(expn_data, Transparency::SemiTransparent)
+        self.fresh_expansion_with_transparency(expn_data, Transparency::Transparent)
     }
 
     pub fn fresh_expansion_with_transparency(
@@ -639,8 +671,9 @@ pub enum ExpnKind {
     /// No expansion, aka root expansion. Only `ExpnId::root()` has this kind.
     Root,
     /// Expansion produced by a macro.
-    /// FIXME: Some code injected by the compiler before HIR lowering also gets this kind.
     Macro(MacroKind, Symbol),
+    /// Transform done by the compiler on the AST.
+    AstPass(AstPass),
     /// Desugaring done by the compiler during HIR lowering.
     Desugaring(DesugaringKind)
 }
@@ -650,6 +683,7 @@ impl ExpnKind {
         match *self {
             ExpnKind::Root => kw::PathRoot,
             ExpnKind::Macro(_, descr) => descr,
+            ExpnKind::AstPass(kind) => Symbol::intern(kind.descr()),
             ExpnKind::Desugaring(kind) => Symbol::intern(kind.descr()),
         }
     }
@@ -675,6 +709,13 @@ impl MacroKind {
         }
     }
 
+    pub fn descr_expected(self) -> &'static str {
+        match self {
+            MacroKind::Attr => "attribute",
+            _ => self.descr(),
+        }
+    }
+
     pub fn article(self) -> &'static str {
         match self {
             MacroKind::Attr => "an",
@@ -683,6 +724,26 @@ impl MacroKind {
     }
 }
 
+/// The kind of AST transform.
+#[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
+pub enum AstPass {
+    StdImports,
+    TestHarness,
+    ProcMacroHarness,
+    PluginMacroDefs,
+}
+
+impl AstPass {
+    fn descr(self) -> &'static str {
+        match self {
+            AstPass::StdImports => "standard library imports",
+            AstPass::TestHarness => "test harness",
+            AstPass::ProcMacroHarness => "proc macro harness",
+            AstPass::PluginMacroDefs => "plugin macro definitions",
+        }
+    }
+}
+
 /// The kind of compiler desugaring.
 #[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 pub enum DesugaringKind {
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 3d8bfc77a8950..ca177eb4a3616 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -442,6 +442,7 @@ impl Span {
                 let (pre, post) = match expn_data.kind {
                     ExpnKind::Root => break,
                     ExpnKind::Desugaring(..) => ("desugaring of ", ""),
+                    ExpnKind::AstPass(..) => ("", ""),
                     ExpnKind::Macro(macro_kind, _) => match macro_kind {
                         MacroKind::Bang => ("", "!"),
                         MacroKind::Attr => ("#[", "]"),
@@ -513,6 +514,18 @@ impl Span {
                   span.ctxt)
     }
 
+    /// Equivalent of `Span::def_site` from the proc macro API,
+    /// except that the location is taken from the `self` span.
+    pub fn with_def_site_ctxt(self, expn_id: ExpnId) -> Span {
+        self.with_ctxt_from_mark(expn_id, Transparency::Opaque)
+    }
+
+    /// Equivalent of `Span::call_site` from the proc macro API,
+    /// except that the location is taken from the `self` span.
+    pub fn with_call_site_ctxt(&self, expn_id: ExpnId) -> Span {
+        self.with_ctxt_from_mark(expn_id, Transparency::Transparent)
+    }
+
     /// Produces a span with the same location as `self` and context produced by a macro with the
     /// given ID and transparency, assuming that macro was defined directly and not produced by
     /// some other macro (which is the case for built-in and procedural macros).
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 3a4dc1f5a096b..597ae83572cee 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -626,6 +626,7 @@ symbols! {
         size,
         slice_patterns,
         slicing_syntax,
+        soft,
         Some,
         specialization,
         speed,
@@ -764,7 +765,7 @@ impl Ident {
         Ident::with_dummy_span(string.as_symbol())
     }
 
-    /// Maps a string to an identifier with an empty span.
+    /// Maps a string to an identifier with a dummy span.
     pub fn from_str(string: &str) -> Ident {
         Ident::with_dummy_span(Symbol::intern(string))
     }
@@ -801,21 +802,15 @@ impl Ident {
         Ident::new(self.name, self.span.modern_and_legacy())
     }
 
-    /// Transforms an identifier into one with the same name, but gensymed.
-    pub fn gensym(self) -> Ident {
-        let name = with_interner(|interner| interner.gensymed(self.name));
-        Ident::new(name, self.span)
-    }
-
     /// Transforms an underscore identifier into one with the same name, but
     /// gensymed. Leaves non-underscore identifiers unchanged.
     pub fn gensym_if_underscore(self) -> Ident {
-        if self.name == kw::Underscore { self.gensym() } else { self }
-    }
-
-    // WARNING: this function is deprecated and will be removed in the future.
-    pub fn is_gensymed(self) -> bool {
-        with_interner(|interner| interner.is_gensymed(self.name))
+        if self.name == kw::Underscore {
+            let name = with_interner(|interner| interner.gensymed(self.name));
+            Ident::new(name, self.span)
+        } else {
+            self
+        }
     }
 
     /// Convert the name to a `LocalInternedString`. This is a slowish
@@ -892,9 +887,12 @@ impl UseSpecializedDecodable for Ident {
 ///
 /// Examples:
 /// ```
-/// assert_eq!(Ident::from_str("x"), Ident::from_str("x"))
-/// assert_ne!(Ident::from_str("x").gensym(), Ident::from_str("x"))
-/// assert_ne!(Ident::from_str("x").gensym(), Ident::from_str("x").gensym())
+/// assert_eq!(Ident::from_str("_"), Ident::from_str("_"))
+/// assert_ne!(Ident::from_str("_").gensym_if_underscore(), Ident::from_str("_"))
+/// assert_ne!(
+///     Ident::from_str("_").gensym_if_underscore(),
+///     Ident::from_str("_").gensym_if_underscore(),
+/// )
 /// ```
 /// Internally, a symbol is implemented as an index, and all operations
 /// (including hashing, equality, and ordering) operate on that index. The use
diff --git a/src/llvm-project b/src/llvm-project
index 48818e9f5d0f2..71fe7ec06b85f 160000
--- a/src/llvm-project
+++ b/src/llvm-project
@@ -1 +1 @@
-Subproject commit 48818e9f5d0f2d5978a9b43ad1a2e8d0b83f6aa0
+Subproject commit 71fe7ec06b85f612fc0e4eb4134c7a7d0f23fac5
diff --git a/src/test/codegen/adjustments.rs b/src/test/codegen/adjustments.rs
index ae2ff9994fdf0..ded310d0aebb1 100644
--- a/src/test/codegen/adjustments.rs
+++ b/src/test/codegen/adjustments.rs
@@ -3,7 +3,7 @@
 #![crate_type = "lib"]
 
 // Hack to get the correct size for the length part in slices
-// CHECK: @helper([[USIZE:i[0-9]+]] %arg0)
+// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }
diff --git a/src/test/codegen/c-variadic.rs b/src/test/codegen/c-variadic.rs
index bb90a9653f573..2acf95de97ee8 100644
--- a/src/test/codegen/c-variadic.rs
+++ b/src/test/codegen/c-variadic.rs
@@ -1,4 +1,5 @@
 // compile-flags: -C no-prepopulate-passes
+// ignore-tidy-linelength
 
 #![crate_type = "lib"]
 #![feature(c_variadic)]
@@ -14,13 +15,13 @@ extern "C" {
 #[unwind(aborts)] // FIXME(#58794)
 pub unsafe extern "C" fn use_foreign_c_variadic_0() {
     // Ensure that we correctly call foreign C-variadic functions.
-    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0(i32 0)
+    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0([[PARAM:i32( signext)?]] 0)
     foreign_c_variadic_0(0);
-    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0(i32 0, i32 42)
+    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0([[PARAM]] 0, [[PARAM]] 42)
     foreign_c_variadic_0(0, 42i32);
-    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0(i32 0, i32 42, i32 1024)
+    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0([[PARAM]] 0, [[PARAM]] 42, [[PARAM]] 1024)
     foreign_c_variadic_0(0, 42i32, 1024i32);
-    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0(i32 0, i32 42, i32 1024, i32 0)
+    // CHECK: invoke void (i32, ...) @foreign_c_variadic_0([[PARAM]] 0, [[PARAM]] 42, [[PARAM]] 1024, [[PARAM]] 0)
     foreign_c_variadic_0(0, 42i32, 1024i32, 0i32);
 }
 
@@ -34,18 +35,18 @@ pub unsafe extern "C" fn use_foreign_c_variadic_1_0(ap: VaList) {
 
 #[unwind(aborts)] // FIXME(#58794)
 pub unsafe extern "C" fn use_foreign_c_variadic_1_1(ap: VaList) {
-    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, i32 42)
+    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, [[PARAM]] 42)
     foreign_c_variadic_1(ap, 42i32);
 }
 #[unwind(aborts)] // FIXME(#58794)
 pub unsafe extern "C" fn use_foreign_c_variadic_1_2(ap: VaList) {
-    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, i32 2, i32 42)
+    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, [[PARAM]] 2, [[PARAM]] 42)
     foreign_c_variadic_1(ap, 2i32, 42i32);
 }
 
 #[unwind(aborts)] // FIXME(#58794)
 pub unsafe extern "C" fn use_foreign_c_variadic_1_3(ap: VaList) {
-    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, i32 2, i32 42, i32 0)
+    // CHECK: invoke void ({{.*}}*, ...) @foreign_c_variadic_1({{.*}} %ap, [[PARAM]] 2, [[PARAM]] 42, [[PARAM]] 0)
     foreign_c_variadic_1(ap, 2i32, 42i32, 0i32);
 }
 
@@ -64,12 +65,12 @@ pub unsafe extern "C" fn c_variadic(n: i32, mut ap: ...) -> i32 {
 // Ensure that we generate the correct `call` signature when calling a Rust
 // defined C-variadic.
 pub unsafe fn test_c_variadic_call() {
-    // CHECK: call i32 (i32, ...) @c_variadic(i32 0)
+    // CHECK: call [[RET:(signext )?i32]] (i32, ...) @c_variadic([[PARAM]] 0)
     c_variadic(0);
-    // CHECK: call i32 (i32, ...) @c_variadic(i32 0, i32 42)
+    // CHECK: call [[RET]] (i32, ...) @c_variadic([[PARAM]] 0, [[PARAM]] 42)
     c_variadic(0, 42i32);
-    // CHECK: call i32 (i32, ...) @c_variadic(i32 0, i32 42, i32 1024)
+    // CHECK: call [[RET]] (i32, ...) @c_variadic([[PARAM]] 0, [[PARAM]] 42, [[PARAM]] 1024)
     c_variadic(0, 42i32, 1024i32);
-    // CHECK: call i32 (i32, ...) @c_variadic(i32 0, i32 42, i32 1024, i32 0)
+    // CHECK: call [[RET]] (i32, ...) @c_variadic([[PARAM]] 0, [[PARAM]] 42, [[PARAM]] 1024, [[PARAM]] 0)
     c_variadic(0, 42i32, 1024i32, 0i32);
 }
diff --git a/src/test/codegen/fastcall-inreg.rs b/src/test/codegen/fastcall-inreg.rs
index e152e6e9d1333..f67487c83ba23 100644
--- a/src/test/codegen/fastcall-inreg.rs
+++ b/src/test/codegen/fastcall-inreg.rs
@@ -49,27 +49,27 @@
 #![crate_type = "lib"]
 
 pub mod tests {
-    // CHECK: @f1(i32 inreg %arg0, i32 inreg %arg1, i32 %arg2)
+    // CHECK: @f1(i32 inreg %_1, i32 inreg %_2, i32 %_3)
     #[no_mangle]
     pub extern "fastcall" fn f1(_: i32, _: i32, _: i32) {}
 
-    // CHECK: @f2(i32* inreg %arg0, i32* inreg %arg1, i32* %arg2)
+    // CHECK: @f2(i32* inreg %_1, i32* inreg %_2, i32* %_3)
     #[no_mangle]
     pub extern "fastcall" fn f2(_: *const i32, _: *const i32, _: *const i32) {}
 
-    // CHECK: @f3(float %arg0, i32 inreg %arg1, i32 inreg %arg2, i32 %arg3)
+    // CHECK: @f3(float %_1, i32 inreg %_2, i32 inreg %_3, i32 %_4)
     #[no_mangle]
     pub extern "fastcall" fn f3(_: f32, _: i32, _: i32, _: i32) {}
 
-    // CHECK: @f4(i32 inreg %arg0, float %arg1, i32 inreg %arg2, i32 %arg3)
+    // CHECK: @f4(i32 inreg %_1, float %_2, i32 inreg %_3, i32 %_4)
     #[no_mangle]
     pub extern "fastcall" fn f4(_: i32, _: f32, _: i32, _: i32) {}
 
-    // CHECK: @f5(i64 %arg0, i32 %arg1)
+    // CHECK: @f5(i64 %_1, i32 %_2)
     #[no_mangle]
     pub extern "fastcall" fn f5(_: i64, _: i32) {}
 
-    // CHECK: @f6(i1 inreg zeroext %arg0, i32 inreg %arg1, i32 %arg2)
+    // CHECK: @f6(i1 inreg zeroext %_1, i32 inreg %_2, i32 %_3)
     #[no_mangle]
     pub extern "fastcall" fn f6(_: bool, _: i32, _: i32) {}
 }
diff --git a/src/test/codegen/function-arguments.rs b/src/test/codegen/function-arguments.rs
index bd121ef24adae..7e1791cd4f296 100644
--- a/src/test/codegen/function-arguments.rs
+++ b/src/test/codegen/function-arguments.rs
@@ -18,48 +18,48 @@ pub fn boolean(x: bool) -> bool {
   x
 }
 
-// CHECK: @readonly_borrow(i32* noalias readonly align 4 dereferenceable(4) %arg0)
+// CHECK: @readonly_borrow(i32* noalias readonly align 4 dereferenceable(4) %_1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn readonly_borrow(_: &i32) {
 }
 
-// CHECK: @static_borrow(i32* noalias readonly align 4 dereferenceable(4) %arg0)
+// CHECK: @static_borrow(i32* noalias readonly align 4 dereferenceable(4) %_1)
 // static borrow may be captured
 #[no_mangle]
 pub fn static_borrow(_: &'static i32) {
 }
 
-// CHECK: @named_borrow(i32* noalias readonly align 4 dereferenceable(4) %arg0)
+// CHECK: @named_borrow(i32* noalias readonly align 4 dereferenceable(4) %_1)
 // borrow with named lifetime may be captured
 #[no_mangle]
 pub fn named_borrow<'r>(_: &'r i32) {
 }
 
-// CHECK: @unsafe_borrow(i16* align 2 dereferenceable(2) %arg0)
+// CHECK: @unsafe_borrow(i16* align 2 dereferenceable(2) %_1)
 // unsafe interior means this isn't actually readonly and there may be aliases ...
 #[no_mangle]
 pub fn unsafe_borrow(_: &UnsafeInner) {
 }
 
-// CHECK: @mutable_unsafe_borrow(i16* align 2 dereferenceable(2) %arg0)
+// CHECK: @mutable_unsafe_borrow(i16* align 2 dereferenceable(2) %_1)
 // ... unless this is a mutable borrow, those never alias
 #[no_mangle]
 pub fn mutable_unsafe_borrow(_: &mut UnsafeInner) {
 }
 
-// CHECK: @mutable_borrow(i32* align 4 dereferenceable(4) %arg0)
+// CHECK: @mutable_borrow(i32* align 4 dereferenceable(4) %_1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn mutable_borrow(_: &mut i32) {
 }
 
-// CHECK: @indirect_struct(%S* noalias nocapture dereferenceable(32) %arg0)
+// CHECK: @indirect_struct(%S* noalias nocapture dereferenceable(32) %_1)
 #[no_mangle]
 pub fn indirect_struct(_: S) {
 }
 
-// CHECK: @borrowed_struct(%S* noalias readonly align 4 dereferenceable(32) %arg0)
+// CHECK: @borrowed_struct(%S* noalias readonly align 4 dereferenceable(32) %_1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn borrowed_struct(_: &S) {
@@ -80,36 +80,36 @@ pub fn struct_return() -> S {
 }
 
 // Hack to get the correct size for the length part in slices
-// CHECK: @helper([[USIZE:i[0-9]+]] %arg0)
+// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }
 
-// CHECK: @slice([0 x i8]* noalias nonnull readonly align 1 %arg0.0, [[USIZE]] %arg0.1)
+// CHECK: @slice([0 x i8]* noalias nonnull readonly align 1 %_1.0, [[USIZE]] %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn slice(_: &[u8]) {
 }
 
-// CHECK: @mutable_slice([0 x i8]* nonnull align 1 %arg0.0, [[USIZE]] %arg0.1)
+// CHECK: @mutable_slice([0 x i8]* nonnull align 1 %_1.0, [[USIZE]] %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn mutable_slice(_: &mut [u8]) {
 }
 
-// CHECK: @unsafe_slice([0 x i16]* nonnull align 2 %arg0.0, [[USIZE]] %arg0.1)
+// CHECK: @unsafe_slice([0 x i16]* nonnull align 2 %_1.0, [[USIZE]] %_1.1)
 // unsafe interior means this isn't actually readonly and there may be aliases ...
 #[no_mangle]
 pub fn unsafe_slice(_: &[UnsafeInner]) {
 }
 
-// CHECK: @str([0 x i8]* noalias nonnull readonly align 1 %arg0.0, [[USIZE]] %arg0.1)
+// CHECK: @str([0 x i8]* noalias nonnull readonly align 1 %_1.0, [[USIZE]] %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn str(_: &[u8]) {
 }
 
-// CHECK: @trait_borrow({}* nonnull align 1 %arg0.0, [3 x [[USIZE]]]* noalias readonly align {{.*}} dereferenceable({{.*}}) %arg0.1)
+// CHECK: @trait_borrow({}* nonnull align 1 %_1.0, [3 x [[USIZE]]]* noalias readonly align {{.*}} dereferenceable({{.*}}) %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn trait_borrow(_: &Drop) {
diff --git a/src/test/codegen/personality_lifetimes.rs b/src/test/codegen/personality_lifetimes.rs
index 0d3d537a2723d..05888c0e733ad 100644
--- a/src/test/codegen/personality_lifetimes.rs
+++ b/src/test/codegen/personality_lifetimes.rs
@@ -20,12 +20,13 @@ pub fn test() {
     let _s = S;
     // Check that the personality slot alloca gets a lifetime start in each cleanup block, not just
     // in the first one.
+    // CHECK: [[SLOT:%[0-9]+]] = alloca { i8*, i32 }
     // CHECK-LABEL: cleanup:
-    // CHECK: bitcast{{.*}}personalityslot
-    // CHECK-NEXT: call void @llvm.lifetime.start
+    // CHECK: [[BITCAST:%[0-9]+]] = bitcast { i8*, i32 }* [[SLOT]] to i8*
+    // CHECK-NEXT: call void @llvm.lifetime.start.{{.*}}({{.*}}, i8* [[BITCAST]])
     // CHECK-LABEL: cleanup1:
-    // CHECK: bitcast{{.*}}personalityslot
-    // CHECK-NEXT: call void @llvm.lifetime.start
+    // CHECK: [[BITCAST1:%[0-9]+]] = bitcast { i8*, i32 }* [[SLOT]] to i8*
+    // CHECK-NEXT: call void @llvm.lifetime.start.{{.*}}({{.*}}, i8* [[BITCAST1]])
     might_unwind();
     let _t = S;
     might_unwind();
diff --git a/src/test/codegen/refs.rs b/src/test/codegen/refs.rs
index cbb9942347673..15f99fd0c22a0 100644
--- a/src/test/codegen/refs.rs
+++ b/src/test/codegen/refs.rs
@@ -3,7 +3,7 @@
 #![crate_type = "lib"]
 
 // Hack to get the correct size for the length part in slices
-// CHECK: @helper([[USIZE:i[0-9]+]] %arg0)
+// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }
diff --git a/src/test/codegen/repeat-trusted-len.rs b/src/test/codegen/repeat-trusted-len.rs
index c348a8f7b8b8f..87f29f6047c6a 100644
--- a/src/test/codegen/repeat-trusted-len.rs
+++ b/src/test/codegen/repeat-trusted-len.rs
@@ -6,7 +6,7 @@
 
 use std::iter;
 
-// CHECK: @helper([[USIZE:i[0-9]+]] %arg0)
+// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }
diff --git a/src/test/codegen/repr-transparent.rs b/src/test/codegen/repr-transparent.rs
index c9f3837565808..e705d5ce3cd72 100644
--- a/src/test/codegen/repr-transparent.rs
+++ b/src/test/codegen/repr-transparent.rs
@@ -14,21 +14,21 @@ pub struct Zst2(());
 #[repr(transparent)]
 pub struct F32(f32);
 
-// CHECK: define float @test_F32(float %arg0)
+// CHECK: define float @test_F32(float %_1)
 #[no_mangle]
 pub extern fn test_F32(_: F32) -> F32 { loop {} }
 
 #[repr(transparent)]
 pub struct Ptr(*mut u8);
 
-// CHECK: define i8* @test_Ptr(i8* %arg0)
+// CHECK: define i8* @test_Ptr(i8* %_1)
 #[no_mangle]
 pub extern fn test_Ptr(_: Ptr) -> Ptr { loop {} }
 
 #[repr(transparent)]
 pub struct WithZst(u64, Zst1);
 
-// CHECK: define i64 @test_WithZst(i64 %arg0)
+// CHECK: define i64 @test_WithZst(i64 %_1)
 #[no_mangle]
 pub extern fn test_WithZst(_: WithZst) -> WithZst { loop {} }
 
@@ -36,14 +36,14 @@ pub extern fn test_WithZst(_: WithZst) -> WithZst { loop {} }
 pub struct WithZeroSizedArray(*const f32, [i8; 0]);
 
 // Apparently we use i32* when newtype-unwrapping f32 pointers. Whatever.
-// CHECK: define i32* @test_WithZeroSizedArray(i32* %arg0)
+// CHECK: define i32* @test_WithZeroSizedArray(i32* %_1)
 #[no_mangle]
 pub extern fn test_WithZeroSizedArray(_: WithZeroSizedArray) -> WithZeroSizedArray { loop {} }
 
 #[repr(transparent)]
 pub struct Generic<T>(T);
 
-// CHECK: define double @test_Generic(double %arg0)
+// CHECK: define double @test_Generic(double %_1)
 #[no_mangle]
 pub extern fn test_Generic(_: Generic<f64>) -> Generic<f64> { loop {} }
 
@@ -53,14 +53,14 @@ pub struct GenericPlusZst<T>(T, Zst2);
 #[repr(u8)]
 pub enum Bool { True, False, FileNotFound }
 
-// CHECK: define{{( zeroext)?}} i8 @test_Gpz(i8{{( zeroext)?}} %arg0)
+// CHECK: define{{( zeroext)?}} i8 @test_Gpz(i8{{( zeroext)?}} %_1)
 #[no_mangle]
 pub extern fn test_Gpz(_: GenericPlusZst<Bool>) -> GenericPlusZst<Bool> { loop {} }
 
 #[repr(transparent)]
 pub struct LifetimePhantom<'a, T: 'a>(*const T, PhantomData<&'a T>);
 
-// CHECK: define i16* @test_LifetimePhantom(i16* %arg0)
+// CHECK: define i16* @test_LifetimePhantom(i16* %_1)
 #[no_mangle]
 pub extern fn test_LifetimePhantom(_: LifetimePhantom<i16>) -> LifetimePhantom<i16> { loop {} }
 
@@ -70,28 +70,28 @@ pub struct UnitPhantom<T, U> { val: T, unit: PhantomData<U> }
 
 pub struct Px;
 
-// CHECK: define float @test_UnitPhantom(float %arg0)
+// CHECK: define float @test_UnitPhantom(float %_1)
 #[no_mangle]
 pub extern fn test_UnitPhantom(_: UnitPhantom<f32, Px>) -> UnitPhantom<f32, Px> { loop {} }
 
 #[repr(transparent)]
 pub struct TwoZsts(Zst1, i8, Zst2);
 
-// CHECK: define{{( signext)?}} i8 @test_TwoZsts(i8{{( signext)?}} %arg0)
+// CHECK: define{{( signext)?}} i8 @test_TwoZsts(i8{{( signext)?}} %_1)
 #[no_mangle]
 pub extern fn test_TwoZsts(_: TwoZsts) -> TwoZsts { loop {} }
 
 #[repr(transparent)]
 pub struct Nested1(Zst2, Generic<f64>);
 
-// CHECK: define double @test_Nested1(double %arg0)
+// CHECK: define double @test_Nested1(double %_1)
 #[no_mangle]
 pub extern fn test_Nested1(_: Nested1) -> Nested1 { loop {} }
 
 #[repr(transparent)]
 pub struct Nested2(Nested1, Zst1);
 
-// CHECK: define double @test_Nested2(double %arg0)
+// CHECK: define double @test_Nested2(double %_1)
 #[no_mangle]
 pub extern fn test_Nested2(_: Nested2) -> Nested2 { loop {} }
 
@@ -101,7 +101,7 @@ struct f32x4(f32, f32, f32, f32);
 #[repr(transparent)]
 pub struct Vector(f32x4);
 
-// CHECK: define <4 x float> @test_Vector(<4 x float> %arg0)
+// CHECK: define <4 x float> @test_Vector(<4 x float> %_1)
 #[no_mangle]
 pub extern fn test_Vector(_: Vector) -> Vector { loop {} }
 
@@ -111,7 +111,7 @@ impl<T: ?Sized> Mirror for T { type It = Self; }
 #[repr(transparent)]
 pub struct StructWithProjection(<f32 as Mirror>::It);
 
-// CHECK: define float @test_Projection(float %arg0)
+// CHECK: define float @test_Projection(float %_1)
 #[no_mangle]
 pub extern fn test_Projection(_: StructWithProjection) -> StructWithProjection { loop {} }
 
@@ -120,7 +120,7 @@ pub enum EnumF32 {
     Variant(F32)
 }
 
-// CHECK: define float @test_EnumF32(float %arg0)
+// CHECK: define float @test_EnumF32(float %_1)
 #[no_mangle]
 pub extern fn test_EnumF32(_: EnumF32) -> EnumF32 { loop {} }
 
@@ -129,7 +129,7 @@ pub enum EnumF32WithZsts {
     Variant(Zst1, F32, Zst2)
 }
 
-// CHECK: define float @test_EnumF32WithZsts(float %arg0)
+// CHECK: define float @test_EnumF32WithZsts(float %_1)
 #[no_mangle]
 pub extern fn test_EnumF32WithZsts(_: EnumF32WithZsts) -> EnumF32WithZsts { loop {} }
 
@@ -138,7 +138,7 @@ pub union UnionF32 {
     field: F32,
 }
 
-// CHECK: define float @test_UnionF32(float %arg0)
+// CHECK: define float @test_UnionF32(float %_1)
 #[no_mangle]
 pub extern fn test_UnionF32(_: UnionF32) -> UnionF32 { loop {} }
 
@@ -149,7 +149,7 @@ pub union UnionF32WithZsts {
     zst2: Zst2,
 }
 
-// CHECK: define float @test_UnionF32WithZsts(float %arg0)
+// CHECK: define float @test_UnionF32WithZsts(float %_1)
 #[no_mangle]
 pub extern fn test_UnionF32WithZsts(_: UnionF32WithZsts) -> UnionF32WithZsts { loop {} }
 
diff --git a/src/test/codegen/scalar-pair-bool.rs b/src/test/codegen/scalar-pair-bool.rs
index 78d1025b13c77..d91ee7f816ded 100644
--- a/src/test/codegen/scalar-pair-bool.rs
+++ b/src/test/codegen/scalar-pair-bool.rs
@@ -20,24 +20,24 @@ pub fn pair_i32_bool(pair: (i32, bool)) -> (i32, bool) {
     pair
 }
 
-// CHECK: define { i8, i8 } @pair_and_or(i1 zeroext %arg0.0, i1 zeroext %arg0.1)
+// CHECK: define { i8, i8 } @pair_and_or(i1 zeroext %_1.0, i1 zeroext %_1.1)
 #[no_mangle]
 pub fn pair_and_or((a, b): (bool, bool)) -> (bool, bool) {
     // Make sure it can operate directly on the unpacked args
-    // CHECK: and i1 %arg0.0, %arg0.1
-    // CHECK: or i1 %arg0.0, %arg0.1
+    // CHECK: and i1 %_1.0, %_1.1
+    // CHECK: or i1 %_1.0, %_1.1
     (a && b, a || b)
 }
 
-// CHECK: define void @pair_branches(i1 zeroext %arg0.0, i1 zeroext %arg0.1)
+// CHECK: define void @pair_branches(i1 zeroext %_1.0, i1 zeroext %_1.1)
 #[no_mangle]
 pub fn pair_branches((a, b): (bool, bool)) {
     // Make sure it can branch directly on the unpacked bool args
-    // CHECK: br i1 %arg0.0
+    // CHECK: br i1 %_1.0
     if a {
         println!("Hello!");
     }
-    // CHECK: br i1 %arg0.1
+    // CHECK: br i1 %_1.1
     if b {
         println!("Goodbye!");
     }
diff --git a/src/test/codegen/union-abi.rs b/src/test/codegen/union-abi.rs
index b7baffe16695a..7339df17b057a 100644
--- a/src/test/codegen/union-abi.rs
+++ b/src/test/codegen/union-abi.rs
@@ -16,38 +16,38 @@ pub struct i64x4(i64, i64, i64, i64);
 #[derive(Copy, Clone)]
 pub union UnionI64x4{ a:(), b: i64x4 }
 
-// CHECK: define void @test_UnionI64x4(<4 x i64>* {{.*}} %arg0)
+// CHECK: define void @test_UnionI64x4(<4 x i64>* {{.*}} %_1)
 #[no_mangle]
 pub fn test_UnionI64x4(_: UnionI64x4) { loop {} }
 
 pub union UnionI64x4_{ a: i64x4, b: (), c:i64x4, d: Unhab, e: ((),()), f: UnionI64x4 }
 
-// CHECK: define void @test_UnionI64x4_(<4 x i64>* {{.*}} %arg0)
+// CHECK: define void @test_UnionI64x4_(<4 x i64>* {{.*}} %_1)
 #[no_mangle]
 pub fn test_UnionI64x4_(_: UnionI64x4_) { loop {} }
 
 pub union UnionI64x4I64{ a: i64x4, b: i64 }
 
-// CHECK: define void @test_UnionI64x4I64(%UnionI64x4I64* {{.*}} %arg0)
+// CHECK: define void @test_UnionI64x4I64(%UnionI64x4I64* {{.*}} %_1)
 #[no_mangle]
 pub fn test_UnionI64x4I64(_: UnionI64x4I64) { loop {} }
 
 pub union UnionI64x4Tuple{ a: i64x4, b: (i64, i64, i64, i64) }
 
-// CHECK: define void @test_UnionI64x4Tuple(%UnionI64x4Tuple* {{.*}} %arg0)
+// CHECK: define void @test_UnionI64x4Tuple(%UnionI64x4Tuple* {{.*}} %_1)
 #[no_mangle]
 pub fn test_UnionI64x4Tuple(_: UnionI64x4Tuple) { loop {} }
 
 
 pub union UnionF32{a:f32}
 
-// CHECK: define float @test_UnionF32(float %arg0)
+// CHECK: define float @test_UnionF32(float %_1)
 #[no_mangle]
 pub fn test_UnionF32(_: UnionF32) -> UnionF32 { loop {} }
 
 pub union UnionF32F32{a:f32, b:f32}
 
-// CHECK: define float @test_UnionF32F32(float %arg0)
+// CHECK: define float @test_UnionF32F32(float %_1)
 #[no_mangle]
 pub fn test_UnionF32F32(_: UnionF32F32) -> UnionF32F32 { loop {} }
 
@@ -58,13 +58,13 @@ pub union UnionF32U32{a:f32, b:u32}
 pub fn test_UnionF32U32(_: UnionF32U32) -> UnionF32U32 { loop {} }
 
 pub union UnionU128{a:u128}
-// CHECK: define i128 @test_UnionU128(i128 %arg0)
+// CHECK: define i128 @test_UnionU128(i128 %_1)
 #[no_mangle]
 pub fn test_UnionU128(_: UnionU128) -> UnionU128 { loop {} }
 
 #[repr(C)]
 pub union CUnionU128{a:u128}
-// CHECK: define void @test_CUnionU128(%CUnionU128* {{.*}} %arg0)
+// CHECK: define void @test_CUnionU128(%CUnionU128* {{.*}} %_1)
 #[no_mangle]
 pub fn test_CUnionU128(_: CUnionU128) { loop {} }
 
diff --git a/src/test/codegen/var-names.rs b/src/test/codegen/var-names.rs
new file mode 100644
index 0000000000000..3140a7c6b6cc2
--- /dev/null
+++ b/src/test/codegen/var-names.rs
@@ -0,0 +1,15 @@
+// compile-flags: -O -C no-prepopulate-passes
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: define i32 @test(i32 %a, i32 %b)
+#[no_mangle]
+pub fn test(a: u32, b: u32) -> u32 {
+    let c = a + b;
+    // CHECK: %c = add i32 %a, %b
+    let d = c;
+    let e = d * a;
+    // CHECK-NEXT: %e = mul i32 %c, %a
+    e
+    // CHECK-NEXT: ret i32 %e
+}
diff --git a/src/test/ui/issues/issue-44415.rs b/src/test/compile-fail/issue-44415.rs
similarity index 100%
rename from src/test/ui/issues/issue-44415.rs
rename to src/test/compile-fail/issue-44415.rs
diff --git a/src/test/debuginfo/boxed-struct.rs b/src/test/debuginfo/boxed-struct.rs
index c0ff90c3ffb9b..8709fb681704b 100644
--- a/src/test/debuginfo/boxed-struct.rs
+++ b/src/test/debuginfo/boxed-struct.rs
@@ -8,11 +8,11 @@
 
 // gdb-command:run
 
-// gdb-command:print *unique
+// gdb-command:print *boxed_with_padding
 // gdbg-check:$1 = {x = 99, y = 999, z = 9999, w = 99999}
 // gdbr-check:$1 = boxed_struct::StructWithSomePadding {x: 99, y: 999, z: 9999, w: 99999}
 
-// gdb-command:print *unique_dtor
+// gdb-command:print *boxed_with_dtor
 // gdbg-check:$2 = {x = 77, y = 777, z = 7777, w = 77777}
 // gdbr-check:$2 = boxed_struct::StructWithDestructor {x: 77, y: 777, z: 7777, w: 77777}
 
@@ -21,13 +21,13 @@
 
 // lldb-command:run
 
-// lldb-command:print *unique
+// lldb-command:print *boxed_with_padding
 // lldbg-check:[...]$0 = StructWithSomePadding { x: 99, y: 999, z: 9999, w: 99999 }
-// lldbr-check:(boxed_struct::StructWithSomePadding) *unique = StructWithSomePadding { x: 99, y: 999, z: 9999, w: 99999 }
+// lldbr-check:(boxed_struct::StructWithSomePadding) *boxed_with_padding = StructWithSomePadding { x: 99, y: 999, z: 9999, w: 99999 }
 
-// lldb-command:print *unique_dtor
+// lldb-command:print *boxed_with_dtor
 // lldbg-check:[...]$1 = StructWithDestructor { x: 77, y: 777, z: 7777, w: 77777 }
-// lldbr-check:(boxed_struct::StructWithDestructor) *unique_dtor = StructWithDestructor { x: 77, y: 777, z: 7777, w: 77777 }
+// lldbr-check:(boxed_struct::StructWithDestructor) *boxed_with_dtor = StructWithDestructor { x: 77, y: 777, z: 7777, w: 77777 }
 
 #![allow(unused_variables)]
 #![feature(box_syntax)]
@@ -54,9 +54,9 @@ impl Drop for StructWithDestructor {
 
 fn main() {
 
-    let unique: Box<_> = box StructWithSomePadding { x: 99, y: 999, z: 9999, w: 99999 };
+    let boxed_with_padding: Box<_> = box StructWithSomePadding { x: 99, y: 999, z: 9999, w: 99999 };
 
-    let unique_dtor: Box<_> = box StructWithDestructor { x: 77, y: 777, z: 7777, w: 77777 };
+    let boxed_with_dtor: Box<_> = box StructWithDestructor { x: 77, y: 777, z: 7777, w: 77777 };
     zzz(); // #break
 }
 
diff --git a/src/test/debuginfo/function-arg-initialization.rs b/src/test/debuginfo/function-arg-initialization.rs
index fef62534b304d..8c86d2cf435b6 100644
--- a/src/test/debuginfo/function-arg-initialization.rs
+++ b/src/test/debuginfo/function-arg-initialization.rs
@@ -242,12 +242,12 @@ fn non_immediate_args(a: BigStruct, b: BigStruct) {
 
 fn binding(a: i64, b: u64, c: f64) {
     let x = 0; // #break
-    println!("")
+    println!()
 }
 
 fn assignment(mut a: u64, b: u64, c: f64) {
     a = b; // #break
-    println!("")
+    println!()
 }
 
 fn function_call(x: u64, y: u64, z: f64) {
diff --git a/src/test/debuginfo/issue-22656.rs b/src/test/debuginfo/issue-22656.rs
index 86d31909a0b3b..e4634d96a6f31 100644
--- a/src/test/debuginfo/issue-22656.rs
+++ b/src/test/debuginfo/issue-22656.rs
@@ -15,7 +15,7 @@
 // lldbg-check:[...]$0 = vec![1, 2, 3]
 // lldbr-check:(alloc::vec::Vec<i32>) v = vec![1, 2, 3]
 // lldb-command:print zs
-// lldbg-check:[...]$1 = StructWithZeroSizedField { x: ZeroSizedStruct, y: 123, z: ZeroSizedStruct, w: 456 }
+// lldbg-check:[...]$1 = StructWithZeroSizedField { x: ZeroSizedStruct[...], y: 123, z: ZeroSizedStruct[...], w: 456 }
 // lldbr-check:(issue_22656::StructWithZeroSizedField) zs = StructWithZeroSizedField { x: ZeroSizedStruct { }, y: 123, z: ZeroSizedStruct { }, w: 456 }
 // lldbr-command:continue
 
diff --git a/src/test/incremental/hashes/function_interfaces.rs b/src/test/incremental/hashes/function_interfaces.rs
index 4515e36166eb8..9cc2d3bcf6045 100644
--- a/src/test/incremental/hashes/function_interfaces.rs
+++ b/src/test/incremental/hashes/function_interfaces.rs
@@ -11,7 +11,6 @@
 
 
 #![allow(warnings)]
-#![feature(intrinsics)]
 #![feature(linkage)]
 #![feature(rustc_attrs)]
 #![crate_type = "rlib"]
@@ -99,17 +98,6 @@ pub fn make_extern() {}
 pub extern "C" fn make_extern() {}
 
 
-// Extern C Extern Rust-Intrinsic ----------------------------------------------
-
-#[cfg(cfail1)]
-pub extern "C" fn make_intrinsic() {}
-
-#[cfg(not(cfail1))]
-#[rustc_clean(cfg = "cfail2", except = "Hir, HirBody, typeck_tables_of, fn_sig")]
-#[rustc_clean(cfg = "cfail3")]
-pub extern "rust-intrinsic" fn make_intrinsic() {}
-
-
 // Type Parameter --------------------------------------------------------------
 
 #[cfg(cfail1)]
diff --git a/src/test/incremental/hashes/trait_defs.rs b/src/test/incremental/hashes/trait_defs.rs
index 81ff99533fc91..3006cdccfbb55 100644
--- a/src/test/incremental/hashes/trait_defs.rs
+++ b/src/test/incremental/hashes/trait_defs.rs
@@ -18,7 +18,6 @@
 #![feature(rustc_attrs)]
 #![crate_type="rlib"]
 #![feature(associated_type_defaults)]
-#![feature(intrinsics)]
 
 
 // Change trait visibility
@@ -318,7 +317,7 @@ trait TraitAddExternModifier {
 
 
 
-// Change extern "C" to extern "rust-intrinsic"
+// Change extern "C" to extern "stdcall"
 #[cfg(cfail1)]
 trait TraitChangeExternCToRustIntrinsic {
     extern "C" fn method();
@@ -330,7 +329,7 @@ trait TraitChangeExternCToRustIntrinsic {
 trait TraitChangeExternCToRustIntrinsic {
     #[rustc_dirty(label="Hir", cfg="cfail2")]
     #[rustc_clean(label="Hir", cfg="cfail3")]
-    extern "rust-intrinsic" fn method();
+    extern "stdcall" fn method();
 }
 
 
diff --git a/src/test/mir-opt/match-arm-scopes.rs b/src/test/mir-opt/match-arm-scopes.rs
index 18e0642eb3427..c898d3a6f168c 100644
--- a/src/test/mir-opt/match-arm-scopes.rs
+++ b/src/test/mir-opt/match-arm-scopes.rs
@@ -8,8 +8,6 @@
 //   all of the bindings for that scope.
 // * No drop flags are used.
 
-#![feature(nll, bind_by_move_pattern_guards)]
-
 fn complicated_match(cond: bool, items: (bool, bool, String)) -> i32 {
     match items {
         (false, a, s) | (a, false, s) if if cond { return 3 } else { a } => 1,
diff --git a/src/test/pretty/macro.rs b/src/test/pretty/macro.rs
index 39677d1dc2da3..1e1e1dbfb3ea5 100644
--- a/src/test/pretty/macro.rs
+++ b/src/test/pretty/macro.rs
@@ -2,6 +2,6 @@
 
 #![feature(decl_macro)]
 
-macro mac { ($ arg : expr) => { $ arg + $ arg } }
+pub(crate) macro mac { ($ arg : expr) => { $ arg + $ arg } }
 
 fn main() { }
diff --git a/src/test/run-pass-valgrind/cast-enum-with-dtor.rs b/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
index 42445b9056f9d..93c47d32f92a1 100644
--- a/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
+++ b/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 #![allow(dead_code)]
 
 // check dtor calling order when casting enums.
diff --git a/src/test/run-pass-valgrind/cleanup-auto-borrow-obj.rs b/src/test/run-pass-valgrind/cleanup-auto-borrow-obj.rs
index 925ffe75fe785..fb2b4d476355e 100644
--- a/src/test/run-pass-valgrind/cleanup-auto-borrow-obj.rs
+++ b/src/test/run-pass-valgrind/cleanup-auto-borrow-obj.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 // This would previously leak the Box<Trait> because we wouldn't
 // schedule cleanups when auto borrowing trait objects.
 // This program should be valgrind clean.
diff --git a/src/test/run-pass-valgrind/cleanup-stdin.rs b/src/test/run-pass-valgrind/cleanup-stdin.rs
index 3505074293264..cf8f81cf5aa7c 100644
--- a/src/test/run-pass-valgrind/cleanup-stdin.rs
+++ b/src/test/run-pass-valgrind/cleanup-stdin.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 fn main() {
     let _ = std::io::stdin();
     let _ = std::io::stdout();
diff --git a/src/test/run-pass-valgrind/down-with-thread-dtors.rs b/src/test/run-pass-valgrind/down-with-thread-dtors.rs
index c3567a9b20097..8531b8d832604 100644
--- a/src/test/run-pass-valgrind/down-with-thread-dtors.rs
+++ b/src/test/run-pass-valgrind/down-with-thread-dtors.rs
@@ -1,4 +1,3 @@
-// no-prefer-dynamic
 // ignore-emscripten
 
 thread_local!(static FOO: Foo = Foo);
diff --git a/src/test/run-pass-valgrind/dst-dtor-1.rs b/src/test/run-pass-valgrind/dst-dtor-1.rs
index 7533a7bd2353b..5b8433f614567 100644
--- a/src/test/run-pass-valgrind/dst-dtor-1.rs
+++ b/src/test/run-pass-valgrind/dst-dtor-1.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 static mut DROP_RAN: bool = false;
 
 struct Foo;
diff --git a/src/test/run-pass-valgrind/dst-dtor-2.rs b/src/test/run-pass-valgrind/dst-dtor-2.rs
index ebf0c17fecb56..991fe00950bba 100644
--- a/src/test/run-pass-valgrind/dst-dtor-2.rs
+++ b/src/test/run-pass-valgrind/dst-dtor-2.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 static mut DROP_RAN: isize = 0;
 
 struct Foo;
diff --git a/src/test/run-pass-valgrind/dst-dtor-3.rs b/src/test/run-pass-valgrind/dst-dtor-3.rs
index e15908dfcc31f..f0c2dda5ab05b 100644
--- a/src/test/run-pass-valgrind/dst-dtor-3.rs
+++ b/src/test/run-pass-valgrind/dst-dtor-3.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 #![feature(unsized_tuple_coercion)]
 
 static mut DROP_RAN: bool = false;
diff --git a/src/test/run-pass-valgrind/dst-dtor-4.rs b/src/test/run-pass-valgrind/dst-dtor-4.rs
index 52bf0c364b24d..ad6d46f7c0886 100644
--- a/src/test/run-pass-valgrind/dst-dtor-4.rs
+++ b/src/test/run-pass-valgrind/dst-dtor-4.rs
@@ -1,5 +1,3 @@
-// no-prefer-dynamic
-
 #![feature(unsized_tuple_coercion)]
 
 static mut DROP_RAN: isize = 0;
diff --git a/src/test/run-pass-valgrind/exit-flushes.rs b/src/test/run-pass-valgrind/exit-flushes.rs
index cd5edb84bdfe4..a68c6f3355644 100644
--- a/src/test/run-pass-valgrind/exit-flushes.rs
+++ b/src/test/run-pass-valgrind/exit-flushes.rs
@@ -1,4 +1,3 @@
-// no-prefer-dynamic
 // ignore-cloudabi
 // ignore-emscripten
 // ignore-sgx no processes
diff --git a/src/test/run-pass-valgrind/osx-frameworks.rs b/src/test/run-pass-valgrind/osx-frameworks.rs
index 4ea804a184474..ea1403645a515 100644
--- a/src/test/run-pass-valgrind/osx-frameworks.rs
+++ b/src/test/run-pass-valgrind/osx-frameworks.rs
@@ -1,4 +1,3 @@
-// no-prefer-dynamic
 // pretty-expanded FIXME #23616
 
 #![feature(rustc_private)]
diff --git a/src/test/rustdoc-js-std/vec-new.js b/src/test/rustdoc-js-std/vec-new.js
index e4daa5065d233..e1a3256876bde 100644
--- a/src/test/rustdoc-js-std/vec-new.js
+++ b/src/test/rustdoc-js-std/vec-new.js
@@ -4,5 +4,6 @@ const EXPECTED = {
     'others': [
         { 'path': 'std::vec::Vec', 'name': 'new' },
         { 'path': 'std::vec::Vec', 'name': 'ne' },
+        { 'path': 'std::rc::Rc', 'name': 'ne' },
     ],
 };
diff --git a/src/test/rustdoc-js/exact-match.js b/src/test/rustdoc-js/exact-match.js
new file mode 100644
index 0000000000000..b0a411bee5829
--- /dev/null
+++ b/src/test/rustdoc-js/exact-match.js
@@ -0,0 +1,9 @@
+const QUERY = 'si::pc';
+
+const EXPECTED = {
+    'others': [
+        { 'path': 'exact_match::Si', 'name': 'pc' },
+        { 'path': 'exact_match::Psi', 'name': 'pc' },
+        { 'path': 'exact_match::Si', 'name': 'pa' },
+    ],
+};
diff --git a/src/test/rustdoc-js/exact-match.rs b/src/test/rustdoc-js/exact-match.rs
new file mode 100644
index 0000000000000..2eacc0a358284
--- /dev/null
+++ b/src/test/rustdoc-js/exact-match.rs
@@ -0,0 +1,68 @@
+macro_rules! imp {
+    ($name:ident) => {
+        pub struct $name {
+            pub op: usize,
+        }
+        impl $name {
+            pub fn op() {}
+            pub fn cmp() {}
+            pub fn map() {}
+            pub fn pop() {}
+            pub fn ptr() {}
+            pub fn rpo() {}
+            pub fn drop() {}
+            pub fn copy() {}
+            pub fn zip() {}
+            pub fn sup() {}
+            pub fn pa() {}
+            pub fn pb() {}
+            pub fn pc() {}
+            pub fn pd() {}
+            pub fn pe() {}
+            pub fn pf() {}
+            pub fn pg() {}
+            pub fn ph() {}
+            pub fn pi() {}
+            pub fn pj() {}
+            pub fn pk() {}
+            pub fn pl() {}
+            pub fn pm() {}
+            pub fn pn() {}
+            pub fn po() {}
+        }
+    };
+    ($name:ident, $($names:ident),*) => {
+        imp!($name);
+        imp!($($names),*);
+    };
+}
+macro_rules! en {
+    ($name:ident) => {
+        pub enum $name {
+            Ptr,
+            Rp,
+            Rpo,
+            Pt,
+            Drop,
+            Dr,
+            Dro,
+            Sup,
+            Op,
+            Cmp,
+            Map,
+            Mp,
+        }
+    };
+    ($name:ident, $($names:ident),*) => {
+        en!($name);
+        en!($($names),*);
+    };
+}
+
+imp!(Ot, Foo, Cmp, Map, Loc, Lac, Toc, Si, Sig, Sip, Psy, Psi, Py, Pi, Pa, Pb, Pc, Pd);
+imp!(Pe, Pf, Pg, Ph, Pj, Pk, Pl, Pm, Pn, Po, Pq, Pr, Ps, Pt, Pu, Pv, Pw, Px, Pz, Ap, Bp, Cp);
+imp!(Dp, Ep, Fp, Gp, Hp, Ip, Jp, Kp, Lp, Mp, Np, Op, Pp, Qp, Rp, Sp, Tp, Up, Vp, Wp, Xp, Yp, Zp);
+
+en!(Place, Plac, Plae, Plce, Pace, Scalar, Scalr, Scaar, Sclar, Salar);
+
+pub struct P;
diff --git a/src/test/rustdoc-js/module-substring.js b/src/test/rustdoc-js/module-substring.js
new file mode 100644
index 0000000000000..a446c39ebad57
--- /dev/null
+++ b/src/test/rustdoc-js/module-substring.js
@@ -0,0 +1,9 @@
+const QUERY = 'ig::pc';
+
+const EXPECTED = {
+    'others': [
+        { 'path': 'module_substring::Sig', 'name': 'pc' },
+        { 'path': 'module_substring::Si', 'name': 'pc' },
+        { 'path': 'module_substring::Si', 'name': 'pa' },
+    ],
+};
diff --git a/src/test/rustdoc-js/module-substring.rs b/src/test/rustdoc-js/module-substring.rs
new file mode 100644
index 0000000000000..2eacc0a358284
--- /dev/null
+++ b/src/test/rustdoc-js/module-substring.rs
@@ -0,0 +1,68 @@
+macro_rules! imp {
+    ($name:ident) => {
+        pub struct $name {
+            pub op: usize,
+        }
+        impl $name {
+            pub fn op() {}
+            pub fn cmp() {}
+            pub fn map() {}
+            pub fn pop() {}
+            pub fn ptr() {}
+            pub fn rpo() {}
+            pub fn drop() {}
+            pub fn copy() {}
+            pub fn zip() {}
+            pub fn sup() {}
+            pub fn pa() {}
+            pub fn pb() {}
+            pub fn pc() {}
+            pub fn pd() {}
+            pub fn pe() {}
+            pub fn pf() {}
+            pub fn pg() {}
+            pub fn ph() {}
+            pub fn pi() {}
+            pub fn pj() {}
+            pub fn pk() {}
+            pub fn pl() {}
+            pub fn pm() {}
+            pub fn pn() {}
+            pub fn po() {}
+        }
+    };
+    ($name:ident, $($names:ident),*) => {
+        imp!($name);
+        imp!($($names),*);
+    };
+}
+macro_rules! en {
+    ($name:ident) => {
+        pub enum $name {
+            Ptr,
+            Rp,
+            Rpo,
+            Pt,
+            Drop,
+            Dr,
+            Dro,
+            Sup,
+            Op,
+            Cmp,
+            Map,
+            Mp,
+        }
+    };
+    ($name:ident, $($names:ident),*) => {
+        en!($name);
+        en!($($names),*);
+    };
+}
+
+imp!(Ot, Foo, Cmp, Map, Loc, Lac, Toc, Si, Sig, Sip, Psy, Psi, Py, Pi, Pa, Pb, Pc, Pd);
+imp!(Pe, Pf, Pg, Ph, Pj, Pk, Pl, Pm, Pn, Po, Pq, Pr, Ps, Pt, Pu, Pv, Pw, Px, Pz, Ap, Bp, Cp);
+imp!(Dp, Ep, Fp, Gp, Hp, Ip, Jp, Kp, Lp, Mp, Np, Op, Pp, Qp, Rp, Sp, Tp, Up, Vp, Wp, Xp, Yp, Zp);
+
+en!(Place, Plac, Plae, Plce, Pace, Scalar, Scalr, Scaar, Sclar, Salar);
+
+pub struct P;
diff --git a/src/test/rustdoc-js/search-short-types.js b/src/test/rustdoc-js/search-short-types.js
index 0ebf4860cfa58..d14672af71fd6 100644
--- a/src/test/rustdoc-js/search-short-types.js
+++ b/src/test/rustdoc-js/search-short-types.js
@@ -3,6 +3,8 @@ const QUERY = 'P';
 const EXPECTED = {
     'others': [
         { 'path': 'search_short_types', 'name': 'P' },
+        { 'path': 'search_short_types::VeryLongTypeName', 'name': 'p' },
         { 'path': 'search_short_types', 'name': 'Ap' },
+        { 'path': 'search_short_types::VeryLongTypeName', 'name': 'ap' },
     ],
 };
diff --git a/src/test/rustdoc-js/search-short-types.rs b/src/test/rustdoc-js/search-short-types.rs
index 2eacc0a358284..a4083f9a76401 100644
--- a/src/test/rustdoc-js/search-short-types.rs
+++ b/src/test/rustdoc-js/search-short-types.rs
@@ -66,3 +66,9 @@ imp!(Dp, Ep, Fp, Gp, Hp, Ip, Jp, Kp, Lp, Mp, Np, Op, Pp, Qp, Rp, Sp, Tp, Up, Vp,
 en!(Place, Plac, Plae, Plce, Pace, Scalar, Scalr, Scaar, Sclar, Salar);
 
 pub struct P;
+
+pub struct VeryLongTypeName;
+impl VeryLongTypeName {
+    pub fn p() {}
+    pub fn ap() {}
+}
diff --git a/src/test/rustdoc-ui/invalid-syntax.rs b/src/test/rustdoc-ui/invalid-syntax.rs
index 3ef66e273d0d0..97a0f4aaec1eb 100644
--- a/src/test/rustdoc-ui/invalid-syntax.rs
+++ b/src/test/rustdoc-ui/invalid-syntax.rs
@@ -74,3 +74,11 @@ pub fn empty_rust() {}
 ///
 /// ```
 pub fn empty_rust_with_whitespace() {}
+
+/// ```
+/// let x = 1;
+/// ```
+///
+///     \____/
+///
+pub fn indent_after_fenced() {}
diff --git a/src/test/rustdoc-ui/invalid-syntax.stderr b/src/test/rustdoc-ui/invalid-syntax.stderr
index 36209e2927771..6f50edae65034 100644
--- a/src/test/rustdoc-ui/invalid-syntax.stderr
+++ b/src/test/rustdoc-ui/invalid-syntax.stderr
@@ -201,6 +201,24 @@ help: mark blocks that do not contain Rust code as text
 LL | /// ```text
    |     ^^^^^^^
 
+error: unknown start of token: \
+ --> <doctest>:1:1
+  |
+1 | \____/
+  | ^
+
+warning: could not parse code block as Rust code
+  --> $DIR/invalid-syntax.rs:82:9
+   |
+LL | ///     \____/
+   |         ^^^^^^
+
+error: unknown start of token: \
+ --> <rustdoc-highlighting>:1:1
+  |
+1 | \____/
+  | ^
+
 error: unknown start of token: \
  --> <rustdoc-highlighting>:1:1
   |
diff --git a/src/test/rustdoc/inline_cross/proc_macro.rs b/src/test/rustdoc/inline_cross/proc_macro.rs
index 6880e303df90b..3dc8de3fe579d 100644
--- a/src/test/rustdoc/inline_cross/proc_macro.rs
+++ b/src/test/rustdoc/inline_cross/proc_macro.rs
@@ -10,8 +10,19 @@ extern crate some_macros;
 // @has proc_macro/macro.some_proc_macro.html
 // @has proc_macro/attr.some_proc_attr.html
 // @has proc_macro/derive.SomeDerive.html
-pub use some_macros::{some_proc_macro, some_proc_attr, SomeDerive};
+
+// @has proc_macro/macro.some_proc_macro.html
+// @has - 'a proc-macro that swallows its input and does nothing.'
+pub use some_macros::some_proc_macro;
 
 // @has proc_macro/macro.reexported_macro.html
 // @has - 'Doc comment from the original crate'
 pub use some_macros::reexported_macro;
+
+// @has proc_macro/attr.some_proc_attr.html
+// @has - 'a proc-macro attribute that passes its item through verbatim.'
+pub use some_macros::some_proc_attr;
+
+// @has proc_macro/derive.SomeDerive.html
+// @has - 'a derive attribute that adds nothing to its input.'
+pub use some_macros::SomeDerive;
diff --git a/src/test/ui-fulldeps/compiler-calls.rs b/src/test/ui-fulldeps/compiler-calls.rs
index ea24f5809d52a..bd9113c7079ea 100644
--- a/src/test/ui-fulldeps/compiler-calls.rs
+++ b/src/test/ui-fulldeps/compiler-calls.rs
@@ -24,7 +24,7 @@ impl rustc_driver::Callbacks for TestCalls<'_> {
 fn main() {
     let mut count = 1;
     let args = vec!["compiler-calls".to_string(), "foo.rs".to_string()];
-    rustc_driver::report_ices_to_stderr_if_any(|| {
+    rustc_driver::catch_fatal_errors(|| {
         rustc_driver::run_compiler(&args, &mut TestCalls { count: &mut count }, None, None).ok();
     }).ok();
     assert_eq!(count, 2);
diff --git a/src/test/ui-fulldeps/hash-stable-is-unstable.rs b/src/test/ui-fulldeps/hash-stable-is-unstable.rs
index 9f67f642df1ce..d79ef62c31207 100644
--- a/src/test/ui-fulldeps/hash-stable-is-unstable.rs
+++ b/src/test/ui-fulldeps/hash-stable-is-unstable.rs
@@ -13,3 +13,5 @@ use rustc_macros::HashStable;
 #[derive(HashStable)]
 //~^ use of unstable library feature 'rustc_private'
 struct Test;
+
+fn main() {}
diff --git a/src/test/ui-fulldeps/hash-stable-is-unstable.stderr b/src/test/ui-fulldeps/hash-stable-is-unstable.stderr
index 02056d30eae9c..e2dc0c3be725f 100644
--- a/src/test/ui-fulldeps/hash-stable-is-unstable.stderr
+++ b/src/test/ui-fulldeps/hash-stable-is-unstable.stderr
@@ -1,7 +1,3 @@
-error[E0601]: `main` function not found in crate `hash_stable_is_unstable`
-   |
-   = note: consider adding a `main` function to `$DIR/hash-stable-is-unstable.rs`
-
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:3:1
    |
@@ -47,7 +43,6 @@ LL | #[derive(HashStable)]
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0601, E0658.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui-fulldeps/pprust-expr-roundtrip.rs b/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
index 09f58521e5d5c..596f515da2f7f 100644
--- a/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
+++ b/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
@@ -32,13 +32,15 @@ use syntax::print::pprust;
 use syntax::ptr::P;
 
 
-fn parse_expr(ps: &ParseSess, src: &str) -> P<Expr> {
+fn parse_expr(ps: &ParseSess, src: &str) -> Option<P<Expr>> {
     let src_as_string = src.to_string();
 
-    let mut p = parse::new_parser_from_source_str(ps,
-                                                  FileName::Custom(src_as_string.clone()),
-                                                  src_as_string);
-    p.parse_expr().unwrap()
+    let mut p = parse::new_parser_from_source_str(
+        ps,
+        FileName::Custom(src_as_string.clone()),
+        src_as_string,
+    );
+    p.parse_expr().map_err(|mut e| e.cancel()).ok()
 }
 
 
@@ -150,12 +152,12 @@ fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));
             },
             19 => {
-                let ps = vec![P(Pat {
+                let pat = P(Pat {
                     id: DUMMY_NODE_ID,
                     node: PatKind::Wild,
                     span: DUMMY_SP,
-                })];
-                iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(ps.clone(), e)))
+                });
+                iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(pat.clone(), e)))
             },
             _ => panic!("bad counter value in iter_exprs"),
         }
@@ -209,22 +211,23 @@ fn run() {
         let printed = pprust::expr_to_string(&e);
         println!("printed: {}", printed);
 
-        let mut parsed = parse_expr(&ps, &printed);
-
-        // We want to know if `parsed` is structurally identical to `e`, ignoring trivial
-        // differences like placement of `Paren`s or the exact ranges of node spans.
-        // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
-        // everywhere we can, then pretty-print. This should give an unambiguous representation of
-        // each `Expr`, and it bypasses nearly all of the parenthesization logic, so we aren't
-        // relying on the correctness of the very thing we're testing.
-        RemoveParens.visit_expr(&mut e);
-        AddParens.visit_expr(&mut e);
-        let text1 = pprust::expr_to_string(&e);
-        RemoveParens.visit_expr(&mut parsed);
-        AddParens.visit_expr(&mut parsed);
-        let text2 = pprust::expr_to_string(&parsed);
-        assert!(text1 == text2,
-                "exprs are not equal:\n  e =      {:?}\n  parsed = {:?}",
-                text1, text2);
+        // Ignore expressions with chained comparisons that fail to parse
+        if let Some(mut parsed) = parse_expr(&ps, &printed) {
+            // We want to know if `parsed` is structurally identical to `e`, ignoring trivial
+            // differences like placement of `Paren`s or the exact ranges of node spans.
+            // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
+            // everywhere we can, then pretty-print. This should give an unambiguous representation
+            // of each `Expr`, and it bypasses nearly all of the parenthesization logic, so we
+            // aren't relying on the correctness of the very thing we're testing.
+            RemoveParens.visit_expr(&mut e);
+            AddParens.visit_expr(&mut e);
+            let text1 = pprust::expr_to_string(&e);
+            RemoveParens.visit_expr(&mut parsed);
+            AddParens.visit_expr(&mut parsed);
+            let text2 = pprust::expr_to_string(&parsed);
+            assert!(text1 == text2,
+                    "exprs are not equal:\n  e =      {:?}\n  parsed = {:?}",
+                    text1, text2);
+        }
     });
 }
diff --git a/src/test/ui/allocator/hygiene.rs b/src/test/ui/allocator/hygiene.rs
new file mode 100644
index 0000000000000..9bd8406a27608
--- /dev/null
+++ b/src/test/ui/allocator/hygiene.rs
@@ -0,0 +1,31 @@
+// run-pass
+// no-prefer-dynamic
+// aux-build:custom.rs
+// aux-build:helper.rs
+
+#![allow(nonstandard_style)]
+
+extern crate custom;
+extern crate helper;
+
+use custom::A;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+#[allow(dead_code)]
+struct u8;
+#[allow(dead_code)]
+struct usize;
+#[allow(dead_code)]
+static arg0: () = ();
+
+#[global_allocator]
+pub static GLOBAL: A = A(AtomicUsize::new(0));
+
+fn main() {
+    let n = GLOBAL.0.load(Ordering::SeqCst);
+    let s = Box::new(0);
+    helper::work_with(&s);
+    assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 1);
+    drop(s);
+    assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 2);
+}
diff --git a/src/test/ui/asm/asm-out-read-uninit.rs b/src/test/ui/asm/asm-out-read-uninit.rs
index 003f1fc5bb62b..78458ff60d4aa 100644
--- a/src/test/ui/asm/asm-out-read-uninit.rs
+++ b/src/test/ui/asm/asm-out-read-uninit.rs
@@ -20,7 +20,7 @@ pub fn main() {
     let x: isize;
     unsafe {
         asm!("mov $1, $0" : "=r"(x) : "r"(x));
-        //~^ ERROR use of possibly uninitialized variable: `x`
+        //~^ ERROR use of possibly-uninitialized variable: `x`
     }
     foo(x);
 }
diff --git a/src/test/ui/asm/asm-out-read-uninit.stderr b/src/test/ui/asm/asm-out-read-uninit.stderr
index 6d0445d4b7a61..71aeda2ad4d2e 100644
--- a/src/test/ui/asm/asm-out-read-uninit.stderr
+++ b/src/test/ui/asm/asm-out-read-uninit.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/asm-out-read-uninit.rs:22:43
    |
 LL |         asm!("mov $1, $0" : "=r"(x) : "r"(x));
-   |                                           ^ use of possibly uninitialized `x`
+   |                                           ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.rs b/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.rs
index 9db5233e21e57..ceca54b7cd75f 100644
--- a/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.rs
+++ b/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![feature(associated_type_bounds)]
 
diff --git a/src/test/ui/associated-type-bounds/fn-apit.rs b/src/test/ui/associated-type-bounds/fn-apit.rs
index 7e208b4e70d81..3c9f511338f69 100644
--- a/src/test/ui/associated-type-bounds/fn-apit.rs
+++ b/src/test/ui/associated-type-bounds/fn-apit.rs
@@ -1,6 +1,7 @@
 // run-pass
 // aux-build:fn-aux.rs
 
+#![allow(unused)]
 #![feature(associated_type_bounds)]
 
 extern crate fn_aux;
diff --git a/src/test/ui/associated-type-bounds/fn-dyn-apit.rs b/src/test/ui/associated-type-bounds/fn-dyn-apit.rs
index 9ff4a50e1e6e4..c4e8092c211d6 100644
--- a/src/test/ui/associated-type-bounds/fn-dyn-apit.rs
+++ b/src/test/ui/associated-type-bounds/fn-dyn-apit.rs
@@ -1,6 +1,7 @@
 // run-pass
 // aux-build:fn-dyn-aux.rs
 
+#![allow(unused)]
 #![feature(associated_type_bounds)]
 
 extern crate fn_dyn_aux;
diff --git a/src/test/ui/associated-type-bounds/fn-inline.rs b/src/test/ui/associated-type-bounds/fn-inline.rs
index 7b188763b7a5e..8fa7212d6275b 100644
--- a/src/test/ui/associated-type-bounds/fn-inline.rs
+++ b/src/test/ui/associated-type-bounds/fn-inline.rs
@@ -1,6 +1,7 @@
 // run-pass
 // aux-build:fn-aux.rs
 
+#![allow(unused)]
 #![feature(associated_type_bounds)]
 
 extern crate fn_aux;
diff --git a/src/test/ui/associated-type-bounds/fn-where.rs b/src/test/ui/associated-type-bounds/fn-where.rs
index 60d7149a56f25..9c4f82ac991c8 100644
--- a/src/test/ui/associated-type-bounds/fn-where.rs
+++ b/src/test/ui/associated-type-bounds/fn-where.rs
@@ -1,6 +1,7 @@
 // run-pass
 // aux-build:fn-aux.rs
 
+#![allow(unused)]
 #![feature(associated_type_bounds)]
 
 extern crate fn_aux;
diff --git a/src/test/ui/associated-type-bounds/fn-wrap-apit.rs b/src/test/ui/associated-type-bounds/fn-wrap-apit.rs
index 23790d416e1f7..96df13e372a24 100644
--- a/src/test/ui/associated-type-bounds/fn-wrap-apit.rs
+++ b/src/test/ui/associated-type-bounds/fn-wrap-apit.rs
@@ -2,6 +2,7 @@
 // aux-build:fn-aux.rs
 
 #![feature(associated_type_bounds)]
+#![allow(dead_code)]
 
 extern crate fn_aux;
 
diff --git a/src/test/ui/associated-type-bounds/inside-adt.rs b/src/test/ui/associated-type-bounds/inside-adt.rs
index 83a60825d84cd..59ce9496d28f0 100644
--- a/src/test/ui/associated-type-bounds/inside-adt.rs
+++ b/src/test/ui/associated-type-bounds/inside-adt.rs
@@ -31,3 +31,5 @@ union U2 { f: Box<dyn Iterator<Item: Copy>> }
 union U3 { f: dyn Iterator<Item: 'static> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
 //~| ERROR could not find defining uses
+
+fn main() {}
diff --git a/src/test/ui/associated-type-bounds/inside-adt.stderr b/src/test/ui/associated-type-bounds/inside-adt.stderr
index d0e0ceccd3725..9c4d03e900940 100644
--- a/src/test/ui/associated-type-bounds/inside-adt.stderr
+++ b/src/test/ui/associated-type-bounds/inside-adt.stderr
@@ -52,10 +52,6 @@ error: associated type bounds are not allowed within structs, enums, or unions
 LL | union U3 { f: dyn Iterator<Item: 'static> }
    |                            ^^^^^^^^^^^^^
 
-error[E0601]: `main` function not found in crate `inside_adt`
-   |
-   = note: consider adding a `main` function to `$DIR/inside-adt.rs`
-
 error: could not find defining uses
   --> $DIR/inside-adt.rs:5:29
    |
@@ -110,6 +106,5 @@ error: could not find defining uses
 LL | union U3 { f: dyn Iterator<Item: 'static> }
    |                            ^^^^^^^^^^^^^
 
-error: aborting due to 19 previous errors
+error: aborting due to 18 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/associated-type-bounds/struct-bounds.rs b/src/test/ui/associated-type-bounds/struct-bounds.rs
index 2d189cd66724a..2c1ce1c3785ae 100644
--- a/src/test/ui/associated-type-bounds/struct-bounds.rs
+++ b/src/test/ui/associated-type-bounds/struct-bounds.rs
@@ -1,5 +1,6 @@
 // run-pass
 
+#![allow(unused)]
 #![feature(associated_type_bounds)]
 
 trait Tr1 { type As1; }
diff --git a/src/test/ui/associated-types/associated-types-bound-failure.stderr b/src/test/ui/associated-types/associated-types-bound-failure.stderr
index 54654b95edd90..85acf134d51d5 100644
--- a/src/test/ui/associated-types/associated-types-bound-failure.stderr
+++ b/src/test/ui/associated-types/associated-types-bound-failure.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `<G as GetToInt>::R: ToInt` is not satisfied
-  --> $DIR/associated-types-bound-failure.rs:17:5
+  --> $DIR/associated-types-bound-failure.rs:17:19
    |
 LL |     fn to_int(&self) -> isize;
    |     -------------------------- required by `ToInt::to_int`
 ...
 LL |     ToInt::to_int(&g.get())
-   |     ^^^^^^^^^^^^^ the trait `ToInt` is not implemented for `<G as GetToInt>::R`
+   |                   ^^^^^^^^ the trait `ToInt` is not implemented for `<G as GetToInt>::R`
    |
    = help: consider adding a `where <G as GetToInt>::R: ToInt` bound
 
diff --git a/src/test/ui/async-await/argument-patterns.rs b/src/test/ui/async-await/argument-patterns.rs
index 0e42f48b8351e..b9fc1a88cee13 100644
--- a/src/test/ui/async-await/argument-patterns.rs
+++ b/src/test/ui/async-await/argument-patterns.rs
@@ -1,7 +1,6 @@
 // edition:2018
-// run-pass
+// check-pass
 
-#![allow(unused_variables)]
 #![deny(unused_mut)]
 
 type A = Vec<u32>;
diff --git a/src/test/ui/async-await/async-await.rs b/src/test/ui/async-await/async-await.rs
index bf8bf0bcce0fe..1dc7315e88c11 100644
--- a/src/test/ui/async-await/async-await.rs
+++ b/src/test/ui/async-await/async-await.rs
@@ -1,5 +1,7 @@
 // run-pass
 
+#![allow(unused)]
+
 // edition:2018
 // aux-build:arc_wake.rs
 
diff --git a/src/test/ui/async-await/async-borrowck-escaping-closure-error.polonius.stderr b/src/test/ui/async-await/async-borrowck-escaping-closure-error.polonius.stderr
new file mode 100644
index 0000000000000..5f20367b6aba9
--- /dev/null
+++ b/src/test/ui/async-await/async-borrowck-escaping-closure-error.polonius.stderr
@@ -0,0 +1,16 @@
+error[E0597]: `x` does not live long enough
+  --> $DIR/async-borrowck-escaping-closure-error.rs:5:24
+   |
+LL |     Box::new((async || x)())
+   |     -------------------^----
+   |     |         |        |
+   |     |         |        borrowed value does not live long enough
+   |     |         value captured here
+   |     borrow later used here
+LL |
+LL | }
+   | - `x` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/async-await/async-fn-nonsend.stderr b/src/test/ui/async-await/async-fn-nonsend.stderr
index fad90b29c0e6e..d2f92f04f40a7 100644
--- a/src/test/ui/async-await/async-fn-nonsend.stderr
+++ b/src/test/ui/async-await/async-fn-nonsend.stderr
@@ -9,9 +9,9 @@ LL |     assert_send(local_dropped_before_await());
    |
    = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `std::rc::Rc<()>`
    = note: required because it appears within the type `impl std::fmt::Debug`
-   = note: required because it appears within the type `{impl std::fmt::Debug, impl std::future::Future, ()}`
-   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:21:39: 26:2 {impl std::fmt::Debug, impl std::future::Future, ()}]`
-   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:21:39: 26:2 {impl std::fmt::Debug, impl std::future::Future, ()}]>`
+   = note: required because it appears within the type `{impl std::fmt::Debug, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}`
+   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:21:39: 26:2 {impl std::fmt::Debug, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]`
+   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:21:39: 26:2 {impl std::fmt::Debug, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]>`
    = note: required because it appears within the type `impl std::future::Future`
    = note: required because it appears within the type `impl std::future::Future`
 
@@ -26,9 +26,9 @@ LL |     assert_send(non_send_temporary_in_match());
    |
    = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `std::rc::Rc<()>`
    = note: required because it appears within the type `impl std::fmt::Debug`
-   = note: required because it appears within the type `{fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, impl std::future::Future, ()}`
-   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:28:40: 37:2 {fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, impl std::future::Future, ()}]`
-   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:28:40: 37:2 {fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, impl std::future::Future, ()}]>`
+   = note: required because it appears within the type `{fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}`
+   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:28:40: 37:2 {fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]`
+   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:28:40: 37:2 {fn(impl std::fmt::Debug) -> std::option::Option<impl std::fmt::Debug> {std::option::Option::<impl std::fmt::Debug>::Some}, fn() -> impl std::fmt::Debug {non_send}, impl std::fmt::Debug, std::option::Option<impl std::fmt::Debug>, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]>`
    = note: required because it appears within the type `impl std::future::Future`
    = note: required because it appears within the type `impl std::future::Future`
 
@@ -45,9 +45,9 @@ LL |     assert_send(non_sync_with_method_call());
    = note: required because of the requirements on the impl of `std::marker::Send` for `&mut dyn std::fmt::Write`
    = note: required because it appears within the type `std::fmt::Formatter<'_>`
    = note: required because of the requirements on the impl of `std::marker::Send` for `&mut std::fmt::Formatter<'_>`
-   = note: required because it appears within the type `for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}`
-   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}]`
-   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}]>`
+   = note: required because it appears within the type `for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}`
+   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]`
+   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]>`
    = note: required because it appears within the type `impl std::future::Future`
    = note: required because it appears within the type `impl std::future::Future`
 
@@ -68,9 +68,9 @@ LL |     assert_send(non_sync_with_method_call());
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::slice::Iter<'_, std::fmt::ArgumentV1<'_>>`
    = note: required because it appears within the type `std::fmt::Formatter<'_>`
    = note: required because of the requirements on the impl of `std::marker::Send` for `&mut std::fmt::Formatter<'_>`
-   = note: required because it appears within the type `for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}`
-   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}]`
-   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, impl std::future::Future, ()}]>`
+   = note: required because it appears within the type `for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}`
+   = note: required because it appears within the type `[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]`
+   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/async-fn-nonsend.rs:39:38: 45:2 for<'r, 's> {&'r mut std::fmt::Formatter<'s>, bool, fn() -> impl std::future::Future {fut}, impl std::future::Future, ()}]>`
    = note: required because it appears within the type `impl std::future::Future`
    = note: required because it appears within the type `impl std::future::Future`
 
diff --git a/src/test/ui/async-await/drop-order/drop-order-for-locals-when-cancelled.rs b/src/test/ui/async-await/drop-order/drop-order-for-locals-when-cancelled.rs
index 5d020c9a52601..15cc9fbc81fb7 100644
--- a/src/test/ui/async-await/drop-order/drop-order-for-locals-when-cancelled.rs
+++ b/src/test/ui/async-await/drop-order/drop-order-for-locals-when-cancelled.rs
@@ -3,6 +3,9 @@
 // run-pass
 
 #![deny(dead_code)]
+#![allow(unused_variables)]
+#![allow(unused_must_use)]
+#![allow(path_statements)]
 
 // Test that the drop order for locals in a fn and async fn matches up.
 extern crate arc_wake;
@@ -10,7 +13,6 @@ extern crate arc_wake;
 use arc_wake::ArcWake;
 use std::cell::RefCell;
 use std::future::Future;
-use std::marker::PhantomData;
 use std::pin::Pin;
 use std::rc::Rc;
 use std::sync::Arc;
@@ -42,7 +44,7 @@ struct NeverReady;
 
 impl Future for NeverReady {
     type Output = ();
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+    fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
         Poll::Pending
     }
 }
diff --git a/src/test/ui/async-await/drop-order/drop-order-for-temporary-in-tail-return-expr.rs b/src/test/ui/async-await/drop-order/drop-order-for-temporary-in-tail-return-expr.rs
new file mode 100644
index 0000000000000..e40acff6dc117
--- /dev/null
+++ b/src/test/ui/async-await/drop-order/drop-order-for-temporary-in-tail-return-expr.rs
@@ -0,0 +1,95 @@
+// aux-build:arc_wake.rs
+// edition:2018
+// run-pass
+
+#![allow(unused_variables)]
+
+// Test the drop order for parameters relative to local variables and
+// temporaries created in the tail return expression of the function
+// body. In particular, check that this drop order is the same between
+// a `async fn` and an ordinary `fn`. See #64512.
+
+extern crate arc_wake;
+
+use arc_wake::ArcWake;
+use std::cell::RefCell;
+use std::future::Future;
+use std::sync::Arc;
+use std::rc::Rc;
+use std::task::Context;
+
+struct EmptyWaker;
+
+impl ArcWake for EmptyWaker {
+    fn wake(self: Arc<Self>) {}
+}
+
+#[derive(Debug, Eq, PartialEq)]
+enum DropOrder {
+    Function,
+    Val(&'static str),
+}
+
+type DropOrderListPtr = Rc<RefCell<Vec<DropOrder>>>;
+
+struct D(&'static str, DropOrderListPtr);
+
+impl Drop for D {
+    fn drop(&mut self) {
+        self.1.borrow_mut().push(DropOrder::Val(self.0));
+    }
+}
+
+/// Check drop order of temporary "temp" as compared to `x`, `y`, and `z`.
+///
+/// Expected order:
+/// - `z`
+/// - temp
+/// - `y`
+/// - `x`
+async fn foo_async(x: D, _y: D) {
+    let l = x.1.clone();
+    let z = D("z", l.clone());
+    l.borrow_mut().push(DropOrder::Function);
+    helper_async(&D("temp", l)).await
+}
+
+async fn helper_async(v: &D) { }
+
+fn foo_sync(x: D, _y: D) {
+    let l = x.1.clone();
+    let z = D("z", l.clone());
+    l.borrow_mut().push(DropOrder::Function);
+    helper_sync(&D("temp", l))
+}
+
+fn helper_sync(v: &D) { }
+
+fn assert_drop_order_after_poll<Fut: Future<Output = ()>>(
+    f: impl FnOnce(DropOrderListPtr) -> Fut,
+    g: impl FnOnce(DropOrderListPtr),
+) {
+    let empty = Arc::new(EmptyWaker);
+    let waker = ArcWake::into_waker(empty);
+    let mut cx = Context::from_waker(&waker);
+
+    let actual_order = Rc::new(RefCell::new(Vec::new()));
+    let mut fut = Box::pin(f(actual_order.clone()));
+    let r = fut.as_mut().poll(&mut cx);
+
+    assert!(match r {
+        std::task::Poll::Ready(()) => true,
+        _ => false,
+    });
+
+    let expected_order = Rc::new(RefCell::new(Vec::new()));
+    g(expected_order.clone());
+
+    assert_eq!(*actual_order.borrow(), *expected_order.borrow());
+}
+
+fn main() {
+    // Free functions (see doc comment on function for what it tests).
+    assert_drop_order_after_poll(|l| foo_async(D("x", l.clone()), D("_y", l.clone())),
+                                 |l| foo_sync(D("x", l.clone()), D("_y", l.clone())));
+}
diff --git a/src/test/ui/async-await/drop-order/drop-order-when-cancelled.rs b/src/test/ui/async-await/drop-order/drop-order-when-cancelled.rs
index 84fe79348c601..9e8304935bffc 100644
--- a/src/test/ui/async-await/drop-order/drop-order-when-cancelled.rs
+++ b/src/test/ui/async-await/drop-order/drop-order-when-cancelled.rs
@@ -6,6 +6,8 @@
 // parameters (used or unused) are not dropped until the async fn is cancelled.
 // This file is mostly copy-pasted from drop-order-for-async-fn-parameters.rs
 
+#![allow(unused_variables)]
+
 extern crate arc_wake;
 
 use arc_wake::ArcWake;
@@ -43,7 +45,7 @@ struct NeverReady;
 
 impl Future for NeverReady {
     type Output = ();
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+    fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
         Poll::Pending
     }
 }
diff --git a/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime-1.rs b/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime-1.rs
new file mode 100644
index 0000000000000..54059b29f72e2
--- /dev/null
+++ b/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime-1.rs
@@ -0,0 +1,19 @@
+// check-pass
+// edition:2018
+
+struct Test(String);
+
+impl Test {
+    async fn borrow_async(&self) {}
+
+    fn with(&mut self, s: &str) -> &mut Self {
+        self.0 = s.into();
+        self
+    }
+}
+
+async fn test() {
+    Test("".to_string()).with("123").borrow_async().await;
+}
+
+fn main() { }
diff --git a/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime.rs b/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime.rs
new file mode 100644
index 0000000000000..c5ea2b821ad78
--- /dev/null
+++ b/src/test/ui/async-await/issue-63832-await-short-temporary-lifetime.rs
@@ -0,0 +1,12 @@
+// check-pass
+// edition:2018
+
+async fn foo(x: &[Vec<u32>]) -> u32 {
+    0
+}
+
+async fn bar() {
+    foo(&[vec![123]]).await;
+}
+
+fn main() { }
diff --git a/src/test/ui/async-await/issue-64391.rs b/src/test/ui/async-await/issue-64391.rs
new file mode 100644
index 0000000000000..c6faad3aad064
--- /dev/null
+++ b/src/test/ui/async-await/issue-64391.rs
@@ -0,0 +1,14 @@
+// Regression test for Issue #64391. The goal here is that this
+// function compiles. In the past, due to incorrect drop order for
+// temporaries in the tail expression, we failed to compile this
+// example. The drop order itself is directly tested in
+// `drop-order/drop-order-for-temporary-in-tail-return-expr.rs`.
+//
+// check-pass
+// edition:2018
+
+async fn add(x: u32, y: u32) -> u32 {
+    async { x + y }.await
+}
+
+fn main() { }
diff --git a/src/test/ui/async-await/issues/issue-54752-async-block.stderr b/src/test/ui/async-await/issues/issue-54752-async-block.stderr
new file mode 100644
index 0000000000000..c3b3392cfc495
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-54752-async-block.stderr
@@ -0,0 +1,8 @@
+warning: unnecessary parentheses around assigned value
+  --> $DIR/issue-54752-async-block.rs:6:22
+   |
+LL | fn main() { let _a = (async  { }); }
+   |                      ^^^^^^^^^^^^ help: remove these parentheses
+   |
+   = note: `#[warn(unused_parens)]` on by default
+
diff --git a/src/test/ui/async-await/issues/issue-59972.rs b/src/test/ui/async-await/issues/issue-59972.rs
index 154226e8bb88f..c2e24a96b1d93 100644
--- a/src/test/ui/async-await/issues/issue-59972.rs
+++ b/src/test/ui/async-await/issues/issue-59972.rs
@@ -4,7 +4,7 @@
 
 // run-pass
 
-// compile-flags: --edition=2018
+// compile-flags: --edition=2018 -Aunused
 
 pub enum Uninhabited { }
 
diff --git a/src/test/ui/async-await/multiple-lifetimes/hrtb.rs b/src/test/ui/async-await/multiple-lifetimes/hrtb.rs
index 31d0736ba63c8..e788ca5ff49c3 100644
--- a/src/test/ui/async-await/multiple-lifetimes/hrtb.rs
+++ b/src/test/ui/async-await/multiple-lifetimes/hrtb.rs
@@ -1,5 +1,5 @@
 // edition:2018
-// run-pass
+// check-pass
 
 // Test that we can use async fns with multiple arbitrary lifetimes.
 
diff --git a/src/test/ui/async-await/no-non-guaranteed-initialization.rs b/src/test/ui/async-await/no-non-guaranteed-initialization.rs
index 0afbf4cee1d3c..6a34209d55289 100644
--- a/src/test/ui/async-await/no-non-guaranteed-initialization.rs
+++ b/src/test/ui/async-await/no-non-guaranteed-initialization.rs
@@ -8,7 +8,7 @@ async fn no_non_guaranteed_initialization(x: usize) -> usize {
         y = echo(10).await;
     }
     y
-    //~^ use of possibly uninitialized variable: `y`
+    //~^ use of possibly-uninitialized variable: `y`
 }
 
 async fn echo(x: usize) -> usize { x + 1 }
diff --git a/src/test/ui/async-await/no-non-guaranteed-initialization.stderr b/src/test/ui/async-await/no-non-guaranteed-initialization.stderr
index 91d7994654f37..b9aa9924bb815 100644
--- a/src/test/ui/async-await/no-non-guaranteed-initialization.stderr
+++ b/src/test/ui/async-await/no-non-guaranteed-initialization.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `y`
+error[E0381]: use of possibly-uninitialized variable: `y`
   --> $DIR/no-non-guaranteed-initialization.rs:10:5
    |
 LL |     y
-   |     ^ use of possibly uninitialized `y`
+   |     ^ use of possibly-uninitialized `y`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/async-await/partial-initialization-across-await.rs b/src/test/ui/async-await/partial-initialization-across-await.rs
index 1785fb7f29947..8a98a4b0f6bb4 100644
--- a/src/test/ui/async-await/partial-initialization-across-await.rs
+++ b/src/test/ui/async-await/partial-initialization-across-await.rs
@@ -11,7 +11,7 @@ async fn noop() {}
 async fn test_tuple() {
     let mut t: (i32, i32);
     t.0 = 42;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     noop().await;
     t.1 = 88;
     let _ = t;
@@ -20,7 +20,7 @@ async fn test_tuple() {
 async fn test_tuple_struct() {
     let mut t: T;
     t.0 = 42;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     noop().await;
     t.1 = 88;
     let _ = t;
@@ -29,7 +29,7 @@ async fn test_tuple_struct() {
 async fn test_struct() {
     let mut t: S;
     t.x = 42;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     noop().await;
     t.y = 88;
     let _ = t;
diff --git a/src/test/ui/async-await/partial-initialization-across-await.stderr b/src/test/ui/async-await/partial-initialization-across-await.stderr
index d9a2db985e54d..9a510c22c4b1e 100644
--- a/src/test/ui/async-await/partial-initialization-across-await.stderr
+++ b/src/test/ui/async-await/partial-initialization-across-await.stderr
@@ -1,20 +1,20 @@
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-await.rs:13:5
    |
 LL |     t.0 = 42;
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-await.rs:22:5
    |
 LL |     t.0 = 42;
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-await.rs:31:5
    |
 LL |     t.x = 42;
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/attributes/item-attributes.rs b/src/test/ui/attributes/item-attributes.rs
index c760a28ecf0ba..79cd0f5fbc358 100644
--- a/src/test/ui/attributes/item-attributes.rs
+++ b/src/test/ui/attributes/item-attributes.rs
@@ -11,8 +11,6 @@
 #![rustc_dummy]
 #![rustc_dummy(attr5)]
 
-#![crate_id="foobar#0.1"]
-
 // These are attributes of the following mod
 #[rustc_dummy = "val"]
 #[rustc_dummy = "val"]
diff --git a/src/test/ui/attributes/obsolete-attr.rs b/src/test/ui/attributes/obsolete-attr.rs
index 8759344e6f820..42f90eda166b6 100644
--- a/src/test/ui/attributes/obsolete-attr.rs
+++ b/src/test/ui/attributes/obsolete-attr.rs
@@ -1,9 +1,9 @@
-// Obsolete attributes fall back to feature gated custom attributes.
+// Obsolete attributes fall back to unstable custom attributes.
 
 #[ab_isize="stdcall"] extern {}
-//~^ ERROR cannot find attribute macro `ab_isize` in this scope
+//~^ ERROR cannot find attribute `ab_isize` in this scope
 
 #[fixed_stack_segment] fn f() {}
-//~^ ERROR cannot find attribute macro `fixed_stack_segment` in this scope
+//~^ ERROR cannot find attribute `fixed_stack_segment` in this scope
 
 fn main() {}
diff --git a/src/test/ui/attributes/obsolete-attr.stderr b/src/test/ui/attributes/obsolete-attr.stderr
index 9c6909f65f3ea..2d7c257c6208c 100644
--- a/src/test/ui/attributes/obsolete-attr.stderr
+++ b/src/test/ui/attributes/obsolete-attr.stderr
@@ -1,10 +1,10 @@
-error: cannot find attribute macro `fixed_stack_segment` in this scope
+error: cannot find attribute `fixed_stack_segment` in this scope
   --> $DIR/obsolete-attr.rs:6:3
    |
 LL | #[fixed_stack_segment] fn f() {}
    |   ^^^^^^^^^^^^^^^^^^^
 
-error: cannot find attribute macro `ab_isize` in this scope
+error: cannot find attribute `ab_isize` in this scope
   --> $DIR/obsolete-attr.rs:3:3
    |
 LL | #[ab_isize="stdcall"] extern {}
diff --git a/src/test/ui/attributes/unknown-attr.rs b/src/test/ui/attributes/unknown-attr.rs
index 140a1fc3f93e5..70fef04e95c67 100644
--- a/src/test/ui/attributes/unknown-attr.rs
+++ b/src/test/ui/attributes/unknown-attr.rs
@@ -1,12 +1,12 @@
-// Unknown attributes fall back to feature gated custom attributes.
+// Unknown attributes fall back to unstable custom attributes.
 
 #![feature(custom_inner_attributes)]
 
 #![mutable_doc]
-//~^ ERROR cannot find attribute macro `mutable_doc` in this scope
+//~^ ERROR cannot find attribute `mutable_doc` in this scope
 
 #[dance] mod a {}
-//~^ ERROR cannot find attribute macro `dance` in this scope
+//~^ ERROR cannot find attribute `dance` in this scope
 
 #[dance] fn main() {}
-//~^ ERROR cannot find attribute macro `dance` in this scope
+//~^ ERROR cannot find attribute `dance` in this scope
diff --git a/src/test/ui/attributes/unknown-attr.stderr b/src/test/ui/attributes/unknown-attr.stderr
index 4d463874d669e..85c227dc83aa6 100644
--- a/src/test/ui/attributes/unknown-attr.stderr
+++ b/src/test/ui/attributes/unknown-attr.stderr
@@ -1,16 +1,16 @@
-error: cannot find attribute macro `mutable_doc` in this scope
+error: cannot find attribute `mutable_doc` in this scope
   --> $DIR/unknown-attr.rs:5:4
    |
 LL | #![mutable_doc]
    |    ^^^^^^^^^^^
 
-error: cannot find attribute macro `dance` in this scope
+error: cannot find attribute `dance` in this scope
   --> $DIR/unknown-attr.rs:8:3
    |
 LL | #[dance] mod a {}
    |   ^^^^^
 
-error: cannot find attribute macro `dance` in this scope
+error: cannot find attribute `dance` in this scope
   --> $DIR/unknown-attr.rs:11:3
    |
 LL | #[dance] fn main() {}
diff --git a/src/test/ui/attributes/unnamed-field-attributes.rs b/src/test/ui/attributes/unnamed-field-attributes.rs
new file mode 100644
index 0000000000000..93f364047e9a5
--- /dev/null
+++ b/src/test/ui/attributes/unnamed-field-attributes.rs
@@ -0,0 +1,9 @@
+// check-pass
+
+struct S(
+    #[rustfmt::skip] u8,
+    u16,
+    #[rustfmt::skip] u32,
+);
+
+fn main() {}
diff --git a/src/test/ui/attrs-resolution-errors.rs b/src/test/ui/attrs-resolution-errors.rs
new file mode 100644
index 0000000000000..a38b3cfa6665e
--- /dev/null
+++ b/src/test/ui/attrs-resolution-errors.rs
@@ -0,0 +1,40 @@
+enum FooEnum {
+    #[test]
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    Bar(i32),
+}
+
+struct FooStruct {
+    #[test]
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    bar: i32,
+}
+
+fn main() {
+    let foo_enum_bar = FooEnum::Bar(1);
+    match foo_enum_bar {
+        FooEnum::Bar(x) => {},
+        _ => {}
+    }
+
+    let foo_struct = FooStruct { bar: 1 };
+    match foo_struct {
+        FooStruct {
+            #[test] bar
+            //~^ ERROR expected an inert attribute, found an attribute macro
+        } => {}
+    }
+
+    match 1 {
+        0 => {}
+        #[test]
+        //~^ ERROR expected an inert attribute, found an attribute macro
+        _ => {}
+    }
+
+    let _another_foo_strunct = FooStruct {
+        #[test]
+        //~^ ERROR expected an inert attribute, found an attribute macro
+        bar: 1,
+    };
+}
diff --git a/src/test/ui/attrs-resolution-errors.stderr b/src/test/ui/attrs-resolution-errors.stderr
new file mode 100644
index 0000000000000..31f2a74edb333
--- /dev/null
+++ b/src/test/ui/attrs-resolution-errors.stderr
@@ -0,0 +1,32 @@
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/attrs-resolution-errors.rs:2:5
+   |
+LL |     #[test]
+   |     ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/attrs-resolution-errors.rs:8:5
+   |
+LL |     #[test]
+   |     ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/attrs-resolution-errors.rs:23:13
+   |
+LL |             #[test] bar
+   |             ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/attrs-resolution-errors.rs:30:9
+   |
+LL |         #[test]
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/attrs-resolution-errors.rs:36:9
+   |
+LL |         #[test]
+   |         ^^^^^^^
+
+error: aborting due to 5 previous errors
+
diff --git a/src/test/ui/attrs-resolution.rs b/src/test/ui/attrs-resolution.rs
new file mode 100644
index 0000000000000..6809773237d2c
--- /dev/null
+++ b/src/test/ui/attrs-resolution.rs
@@ -0,0 +1,37 @@
+// check-pass
+
+enum FooEnum {
+    #[rustfmt::skip]
+    Bar(i32),
+}
+
+struct FooStruct {
+    #[rustfmt::skip]
+    bar: i32,
+}
+
+fn main() {
+    let foo_enum_bar = FooEnum::Bar(1);
+    match foo_enum_bar {
+        FooEnum::Bar(x) => {}
+        _ => {}
+    }
+
+    let foo_struct = FooStruct { bar: 1 };
+    match foo_struct {
+        FooStruct {
+            #[rustfmt::skip] bar
+        } => {}
+    }
+
+    match 1 {
+        0 => {}
+        #[rustfmt::skip]
+        _ => {}
+    }
+
+    let _another_foo_strunct = FooStruct {
+        #[rustfmt::skip]
+        bar: 1,
+    };
+}
diff --git a/src/test/ui/auto-ref-slice-plus-ref.stderr b/src/test/ui/auto-ref-slice-plus-ref.stderr
index f2e0d379d1b30..3e36f2402a990 100644
--- a/src/test/ui/auto-ref-slice-plus-ref.stderr
+++ b/src/test/ui/auto-ref-slice-plus-ref.stderr
@@ -12,7 +12,7 @@ error[E0599]: no method named `test` found for type `std::vec::Vec<{integer}>` i
   --> $DIR/auto-ref-slice-plus-ref.rs:8:7
    |
 LL |     a.test();
-   |       ^^^^
+   |       ^^^^ method not found in `std::vec::Vec<{integer}>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `test`, perhaps you need to implement it:
@@ -22,7 +22,7 @@ error[E0599]: no method named `test` found for type `[{integer}; 1]` in the curr
   --> $DIR/auto-ref-slice-plus-ref.rs:10:11
    |
 LL |     ([1]).test();
-   |           ^^^^
+   |           ^^^^ method not found in `[{integer}; 1]`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `test`, perhaps you need to implement it:
@@ -32,7 +32,7 @@ error[E0599]: no method named `test` found for type `&[{integer}; 1]` in the cur
   --> $DIR/auto-ref-slice-plus-ref.rs:11:12
    |
 LL |     (&[1]).test();
-   |            ^^^^
+   |            ^^^^ method not found in `&[{integer}; 1]`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `test`, perhaps you need to implement it:
diff --git a/src/test/ui/bind-by-move/bind-by-move-no-guards.rs b/src/test/ui/bind-by-move/bind-by-move-no-guards.rs
deleted file mode 100644
index bc9b3a8de4ef5..0000000000000
--- a/src/test/ui/bind-by-move/bind-by-move-no-guards.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-use std::sync::mpsc::channel;
-
-fn main() {
-    let (tx, rx) = channel();
-    let x = Some(rx);
-    tx.send(false);
-    match x {
-        Some(z) if z.recv().unwrap() => { panic!() },
-            //~^ ERROR cannot bind by-move into a pattern guard
-        Some(z) => { assert!(!z.recv().unwrap()); },
-        None => panic!()
-    }
-}
diff --git a/src/test/ui/bind-by-move/bind-by-move-no-guards.stderr b/src/test/ui/bind-by-move/bind-by-move-no-guards.stderr
deleted file mode 100644
index c5f0256c2c92f..0000000000000
--- a/src/test/ui/bind-by-move/bind-by-move-no-guards.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0008]: cannot bind by-move into a pattern guard
-  --> $DIR/bind-by-move-no-guards.rs:8:14
-   |
-LL |         Some(z) if z.recv().unwrap() => { panic!() },
-   |              ^ moves value into pattern guard
-   |
-   = help: add `#![feature(bind_by_move_pattern_guards)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0008`.
diff --git a/src/test/ui/borrowck/assign_mutable_fields.stderr b/src/test/ui/borrowck/assign_mutable_fields.stderr
index 35101df4e0a6e..40f1aae092dc6 100644
--- a/src/test/ui/borrowck/assign_mutable_fields.stderr
+++ b/src/test/ui/borrowck/assign_mutable_fields.stderr
@@ -1,14 +1,14 @@
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/assign_mutable_fields.rs:9:5
    |
 LL |     x.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/assign_mutable_fields.rs:17:5
    |
 LL |     x.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-and-init.rs b/src/test/ui/borrowck/borrowck-and-init.rs
index 4427e25186103..f11d44e2217ba 100644
--- a/src/test/ui/borrowck/borrowck-and-init.rs
+++ b/src/test/ui/borrowck/borrowck-and-init.rs
@@ -2,5 +2,5 @@ fn main() {
     let i: isize;
 
     println!("{}", false && { i = 5; true });
-    println!("{}", i); //~ ERROR borrow of possibly uninitialized variable: `i`
+    println!("{}", i); //~ ERROR borrow of possibly-uninitialized variable: `i`
 }
diff --git a/src/test/ui/borrowck/borrowck-and-init.stderr b/src/test/ui/borrowck/borrowck-and-init.stderr
index 2db075194810e..c7e357d4604f7 100644
--- a/src/test/ui/borrowck/borrowck-and-init.stderr
+++ b/src/test/ui/borrowck/borrowck-and-init.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `i`
+error[E0381]: borrow of possibly-uninitialized variable: `i`
   --> $DIR/borrowck-and-init.rs:5:20
    |
 LL |     println!("{}", i);
-   |                    ^ use of possibly uninitialized `i`
+   |                    ^ use of possibly-uninitialized `i`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-asm.rs b/src/test/ui/borrowck/borrowck-asm.rs
index 9c9cc04baafee..c1b0f39f9366c 100644
--- a/src/test/ui/borrowck/borrowck-asm.rs
+++ b/src/test/ui/borrowck/borrowck-asm.rs
@@ -57,7 +57,7 @@ mod test_cases {
     fn indirect_is_not_init() {
         let x: i32;
         unsafe {
-            asm!("nop" : "=*r"(x)); //~ ERROR use of possibly uninitialized variable
+            asm!("nop" : "=*r"(x)); //~ ERROR use of possibly-uninitialized variable
         }
     }
 
diff --git a/src/test/ui/borrowck/borrowck-asm.stderr b/src/test/ui/borrowck/borrowck-asm.stderr
index c771373022ac4..f85b5983acced 100644
--- a/src/test/ui/borrowck/borrowck-asm.stderr
+++ b/src/test/ui/borrowck/borrowck-asm.stderr
@@ -46,11 +46,11 @@ LL |         unsafe {
 LL |             asm!("nop" : "+r"(x));
    |                               ^ cannot assign twice to immutable variable
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-asm.rs:60:32
    |
 LL |             asm!("nop" : "=*r"(x));
-   |                                ^ use of possibly uninitialized `x`
+   |                                ^ use of possibly-uninitialized `x`
 
 error[E0506]: cannot assign to `x` because it is borrowed
   --> $DIR/borrowck-asm.rs:68:31
diff --git a/src/test/ui/borrowck/borrowck-block-unint.rs b/src/test/ui/borrowck/borrowck-block-unint.rs
index 1fed2d503bd35..1e7306acaee98 100644
--- a/src/test/ui/borrowck/borrowck-block-unint.rs
+++ b/src/test/ui/borrowck/borrowck-block-unint.rs
@@ -1,7 +1,7 @@
 fn force<F>(f: F) where F: FnOnce() { f(); }
 fn main() {
     let x: isize;
-    force(|| {  //~ ERROR borrow of possibly uninitialized variable: `x`
+    force(|| {  //~ ERROR borrow of possibly-uninitialized variable: `x`
         println!("{}", x);
     });
 }
diff --git a/src/test/ui/borrowck/borrowck-block-unint.stderr b/src/test/ui/borrowck/borrowck-block-unint.stderr
index d2a49962bafca..578f89df46ce1 100644
--- a/src/test/ui/borrowck/borrowck-block-unint.stderr
+++ b/src/test/ui/borrowck/borrowck-block-unint.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-block-unint.rs:4:11
    |
 LL |     force(|| {
-   |           ^^ use of possibly uninitialized `x`
+   |           ^^ use of possibly-uninitialized `x`
 LL |         println!("{}", x);
    |                        - borrow occurs due to use in closure
 
diff --git a/src/test/ui/borrowck/borrowck-break-uninit-2.rs b/src/test/ui/borrowck/borrowck-break-uninit-2.rs
index dad5325cb8750..126d991a51c6e 100644
--- a/src/test/ui/borrowck/borrowck-break-uninit-2.rs
+++ b/src/test/ui/borrowck/borrowck-break-uninit-2.rs
@@ -6,7 +6,7 @@ fn foo() -> isize {
         x = 0;
     }
 
-    println!("{}", x); //~ ERROR borrow of possibly uninitialized variable: `x`
+    println!("{}", x); //~ ERROR borrow of possibly-uninitialized variable: `x`
 
     return 17;
 }
diff --git a/src/test/ui/borrowck/borrowck-break-uninit-2.stderr b/src/test/ui/borrowck/borrowck-break-uninit-2.stderr
index e40d8d9dfccb9..bc9b25c0221fc 100644
--- a/src/test/ui/borrowck/borrowck-break-uninit-2.stderr
+++ b/src/test/ui/borrowck/borrowck-break-uninit-2.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-break-uninit-2.rs:9:20
    |
 LL |     println!("{}", x);
-   |                    ^ use of possibly uninitialized `x`
+   |                    ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-break-uninit.rs b/src/test/ui/borrowck/borrowck-break-uninit.rs
index 9af02b387d8b0..8ccb21ae8eebf 100644
--- a/src/test/ui/borrowck/borrowck-break-uninit.rs
+++ b/src/test/ui/borrowck/borrowck-break-uninit.rs
@@ -6,7 +6,7 @@ fn foo() -> isize {
         x = 0;
     }
 
-    println!("{}", x); //~ ERROR borrow of possibly uninitialized variable: `x`
+    println!("{}", x); //~ ERROR borrow of possibly-uninitialized variable: `x`
 
     return 17;
 }
diff --git a/src/test/ui/borrowck/borrowck-break-uninit.stderr b/src/test/ui/borrowck/borrowck-break-uninit.stderr
index bbf9b9f1241a2..766d5cfd6348c 100644
--- a/src/test/ui/borrowck/borrowck-break-uninit.stderr
+++ b/src/test/ui/borrowck/borrowck-break-uninit.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-break-uninit.rs:9:20
    |
 LL |     println!("{}", x);
-   |                    ^ use of possibly uninitialized `x`
+   |                    ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-field-sensitivity.rs b/src/test/ui/borrowck/borrowck-field-sensitivity.rs
index 88f74d1ed3300..ab607c2acbd4b 100644
--- a/src/test/ui/borrowck/borrowck-field-sensitivity.rs
+++ b/src/test/ui/borrowck/borrowck-field-sensitivity.rs
@@ -78,20 +78,20 @@ fn fu_move_after_fu_move() {
 
 fn copy_after_field_assign_after_uninit() {
     let mut x: A;
-    x.a = 1; //~ ERROR assign to part of possibly uninitialized variable: `x`
+    x.a = 1; //~ ERROR assign to part of possibly-uninitialized variable: `x`
     drop(x.a);
 }
 
 fn borrow_after_field_assign_after_uninit() {
     let mut x: A;
-    x.a = 1; //~ ERROR assign to part of possibly uninitialized variable: `x`
+    x.a = 1; //~ ERROR assign to part of possibly-uninitialized variable: `x`
     let p = &x.a;
     drop(*p);
 }
 
 fn move_after_field_assign_after_uninit() {
     let mut x: A;
-    x.b = box 1; //~ ERROR assign to part of possibly uninitialized variable: `x`
+    x.b = box 1; //~ ERROR assign to part of possibly-uninitialized variable: `x`
     drop(x.b);
 }
 
diff --git a/src/test/ui/borrowck/borrowck-field-sensitivity.stderr b/src/test/ui/borrowck/borrowck-field-sensitivity.stderr
index 89523235481ad..158b2e42f2ddf 100644
--- a/src/test/ui/borrowck/borrowck-field-sensitivity.stderr
+++ b/src/test/ui/borrowck/borrowck-field-sensitivity.stderr
@@ -108,23 +108,23 @@ LL |     let _z = A { a: 4, .. x };
    |
    = note: move occurs because `x.b` has type `std::boxed::Box<isize>`, which does not implement the `Copy` trait
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-field-sensitivity.rs:81:5
    |
 LL |     x.a = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-field-sensitivity.rs:87:5
    |
 LL |     x.a = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-field-sensitivity.rs:94:5
    |
 LL |     x.b = box 1;
-   |     ^^^ use of possibly uninitialized `x`
+   |     ^^^ use of possibly-uninitialized `x`
 
 error: aborting due to 14 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-if-no-else.rs b/src/test/ui/borrowck/borrowck-if-no-else.rs
index 044db99d54c1f..f59bcad6f61d7 100644
--- a/src/test/ui/borrowck/borrowck-if-no-else.rs
+++ b/src/test/ui/borrowck/borrowck-if-no-else.rs
@@ -2,5 +2,5 @@ fn foo(x: isize) { println!("{}", x); }
 
 fn main() {
     let x: isize; if 1 > 2 { x = 10; }
-    foo(x); //~ ERROR use of possibly uninitialized variable: `x`
+    foo(x); //~ ERROR use of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/borrowck/borrowck-if-no-else.stderr b/src/test/ui/borrowck/borrowck-if-no-else.stderr
index 1223e409d4df6..3e9d3d4f6d513 100644
--- a/src/test/ui/borrowck/borrowck-if-no-else.stderr
+++ b/src/test/ui/borrowck/borrowck-if-no-else.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-if-no-else.rs:5:9
    |
 LL |     foo(x);
-   |         ^ use of possibly uninitialized `x`
+   |         ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-if-with-else.rs b/src/test/ui/borrowck/borrowck-if-with-else.rs
index f632d61a6c3c1..c13318b16c2fa 100644
--- a/src/test/ui/borrowck/borrowck-if-with-else.rs
+++ b/src/test/ui/borrowck/borrowck-if-with-else.rs
@@ -7,5 +7,5 @@ fn main() {
     } else {
         x = 10;
     }
-    foo(x); //~ ERROR use of possibly uninitialized variable: `x`
+    foo(x); //~ ERROR use of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/borrowck/borrowck-if-with-else.stderr b/src/test/ui/borrowck/borrowck-if-with-else.stderr
index d11f29b05f565..53b8a6bba2c76 100644
--- a/src/test/ui/borrowck/borrowck-if-with-else.stderr
+++ b/src/test/ui/borrowck/borrowck-if-with-else.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-if-with-else.rs:10:9
    |
 LL |     foo(x);
-   |         ^ use of possibly uninitialized `x`
+   |         ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.rs b/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.rs
index f7457781adc3e..9905e420f948d 100644
--- a/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.rs
+++ b/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.rs
@@ -1,7 +1,7 @@
 fn main() {
     let j = || -> isize {
         let i: isize;
-        i //~ ERROR use of possibly uninitialized variable: `i`
+        i //~ ERROR use of possibly-uninitialized variable: `i`
     };
     j();
 }
diff --git a/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.stderr b/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.stderr
index 82a602c6359c1..2d1d9bc8fa41d 100644
--- a/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.stderr
+++ b/src/test/ui/borrowck/borrowck-init-in-called-fn-expr.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `i`
+error[E0381]: use of possibly-uninitialized variable: `i`
   --> $DIR/borrowck-init-in-called-fn-expr.rs:4:9
    |
 LL |         i
-   |         ^ use of possibly uninitialized `i`
+   |         ^ use of possibly-uninitialized `i`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-init-in-fn-expr.rs b/src/test/ui/borrowck/borrowck-init-in-fn-expr.rs
index 5055814625539..7dd3396c8c2cb 100644
--- a/src/test/ui/borrowck/borrowck-init-in-fn-expr.rs
+++ b/src/test/ui/borrowck/borrowck-init-in-fn-expr.rs
@@ -1,7 +1,7 @@
 fn main() {
     let f  = || -> isize {
         let i: isize;
-        i //~ ERROR use of possibly uninitialized variable: `i`
+        i //~ ERROR use of possibly-uninitialized variable: `i`
     };
     println!("{}", f());
 }
diff --git a/src/test/ui/borrowck/borrowck-init-in-fn-expr.stderr b/src/test/ui/borrowck/borrowck-init-in-fn-expr.stderr
index 899739378524c..fd8b90eda6032 100644
--- a/src/test/ui/borrowck/borrowck-init-in-fn-expr.stderr
+++ b/src/test/ui/borrowck/borrowck-init-in-fn-expr.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `i`
+error[E0381]: use of possibly-uninitialized variable: `i`
   --> $DIR/borrowck-init-in-fn-expr.rs:4:9
    |
 LL |         i
-   |         ^ use of possibly uninitialized `i`
+   |         ^ use of possibly-uninitialized `i`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-init-in-fru.rs b/src/test/ui/borrowck/borrowck-init-in-fru.rs
index 6da3098dc9336..d7ec2ed75c85c 100644
--- a/src/test/ui/borrowck/borrowck-init-in-fru.rs
+++ b/src/test/ui/borrowck/borrowck-init-in-fru.rs
@@ -7,6 +7,6 @@ struct Point {
 fn main() {
     let mut origin: Point;
     origin = Point { x: 10, ..origin };
-    //~^ ERROR use of possibly uninitialized variable: `origin` [E0381]
+    //~^ ERROR use of possibly-uninitialized variable: `origin` [E0381]
     origin.clone();
 }
diff --git a/src/test/ui/borrowck/borrowck-init-in-fru.stderr b/src/test/ui/borrowck/borrowck-init-in-fru.stderr
index fe55bc2fd95c0..a4c042d1c125f 100644
--- a/src/test/ui/borrowck/borrowck-init-in-fru.stderr
+++ b/src/test/ui/borrowck/borrowck-init-in-fru.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `origin`
+error[E0381]: use of possibly-uninitialized variable: `origin`
   --> $DIR/borrowck-init-in-fru.rs:9:5
    |
 LL |     origin = Point { x: 10, ..origin };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ use of possibly uninitialized `origin.y`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ use of possibly-uninitialized `origin.y`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-init-op-equal.rs b/src/test/ui/borrowck/borrowck-init-op-equal.rs
index d3fa852ac91ba..784eb8cf85b8a 100644
--- a/src/test/ui/borrowck/borrowck-init-op-equal.rs
+++ b/src/test/ui/borrowck/borrowck-init-op-equal.rs
@@ -1,6 +1,6 @@
 fn test() {
     let v: isize;
-    v += 1; //~ ERROR use of possibly uninitialized variable: `v`
+    v += 1; //~ ERROR use of possibly-uninitialized variable: `v`
     v.clone();
 }
 
diff --git a/src/test/ui/borrowck/borrowck-init-op-equal.stderr b/src/test/ui/borrowck/borrowck-init-op-equal.stderr
index 9863ceb14240f..6c88778ae0e5a 100644
--- a/src/test/ui/borrowck/borrowck-init-op-equal.stderr
+++ b/src/test/ui/borrowck/borrowck-init-op-equal.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `v`
+error[E0381]: use of possibly-uninitialized variable: `v`
   --> $DIR/borrowck-init-op-equal.rs:3:5
    |
 LL |     v += 1;
-   |     ^^^^^^ use of possibly uninitialized `v`
+   |     ^^^^^^ use of possibly-uninitialized `v`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-init-plus-equal.rs b/src/test/ui/borrowck/borrowck-init-plus-equal.rs
index d895a2e16b537..d9d20a2a9c148 100644
--- a/src/test/ui/borrowck/borrowck-init-plus-equal.rs
+++ b/src/test/ui/borrowck/borrowck-init-plus-equal.rs
@@ -1,6 +1,6 @@
 fn test() {
     let mut v: isize;
-    v = v + 1; //~ ERROR use of possibly uninitialized variable: `v`
+    v = v + 1; //~ ERROR use of possibly-uninitialized variable: `v`
     v.clone();
 }
 
diff --git a/src/test/ui/borrowck/borrowck-init-plus-equal.stderr b/src/test/ui/borrowck/borrowck-init-plus-equal.stderr
index 80c4e0c80483d..fe09c8581df0e 100644
--- a/src/test/ui/borrowck/borrowck-init-plus-equal.stderr
+++ b/src/test/ui/borrowck/borrowck-init-plus-equal.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `v`
+error[E0381]: use of possibly-uninitialized variable: `v`
   --> $DIR/borrowck-init-plus-equal.rs:3:9
    |
 LL |     v = v + 1;
-   |         ^ use of possibly uninitialized `v`
+   |         ^ use of possibly-uninitialized `v`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr b/src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr
index a33a1d00a5786..58f2cadcc6573 100644
--- a/src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr
+++ b/src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr
@@ -1,15 +1,14 @@
-warning[E0502]: cannot borrow `*block.current` as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-migrate-to-nll.rs:28:21
+error[E0502]: cannot borrow `*block.current` as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-migrate-to-nll.rs:29:21
    |
 LL |     let x = &mut block;
    |             ---------- mutable borrow occurs here
 LL |     let p: &'a u8 = &*block.current;
    |                     ^^^^^^^^^^^^^^^ immutable borrow occurs here
-LL |     // (use `x` and `p` so enabling NLL doesn't assign overly short lifetimes)
+...
 LL |     drop(x);
    |          - mutable borrow later used here
-   |
-   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
-   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
-   = note: for more information, try `rustc --explain E0729`
 
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0502`.
diff --git a/src/test/ui/borrowck/borrowck-migrate-to-nll.rs b/src/test/ui/borrowck/borrowck-migrate-to-nll.rs
index 6dda317e57efe..6587dfdbc03f3 100644
--- a/src/test/ui/borrowck/borrowck-migrate-to-nll.rs
+++ b/src/test/ui/borrowck/borrowck-migrate-to-nll.rs
@@ -4,6 +4,8 @@
 //
 // Therefore, for backwards-compatiblity, under borrowck=migrate the
 // NLL checks will be emitted as *warnings*.
+//
+// In Rust 2018, no errors will be downgraded to warnings.
 
 // NLL mode makes this compile-fail; we cannot currently encode a
 // test that is run-pass or compile-fail based on compare-mode. So
@@ -15,8 +17,7 @@
 // revisions: zflag edition
 //[zflag]compile-flags: -Z borrowck=migrate
 //[edition]edition:2018
-//[zflag] run-pass
-//[edition] run-pass
+//[zflag] check-pass
 
 pub struct Block<'a> {
     current: &'a u8,
@@ -26,6 +27,7 @@ pub struct Block<'a> {
 fn bump<'a>(mut block: &mut Block<'a>) {
     let x = &mut block;
     let p: &'a u8 = &*block.current;
+    //[edition]~^ ERROR cannot borrow `*block.current` as immutable
     // (use `x` and `p` so enabling NLL doesn't assign overly short lifetimes)
     drop(x);
     drop(p);
diff --git a/src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr b/src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr
index a33a1d00a5786..ace336a3bf32a 100644
--- a/src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr
+++ b/src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr
@@ -1,11 +1,11 @@
 warning[E0502]: cannot borrow `*block.current` as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-migrate-to-nll.rs:28:21
+  --> $DIR/borrowck-migrate-to-nll.rs:29:21
    |
 LL |     let x = &mut block;
    |             ---------- mutable borrow occurs here
 LL |     let p: &'a u8 = &*block.current;
    |                     ^^^^^^^^^^^^^^^ immutable borrow occurs here
-LL |     // (use `x` and `p` so enabling NLL doesn't assign overly short lifetimes)
+...
 LL |     drop(x);
    |          - mutable borrow later used here
    |
diff --git a/src/test/ui/borrowck/borrowck-mutate-in-guard.rs b/src/test/ui/borrowck/borrowck-mutate-in-guard.rs
index 5b6aa7a979be5..9cbceeb945ccc 100644
--- a/src/test/ui/borrowck/borrowck-mutate-in-guard.rs
+++ b/src/test/ui/borrowck/borrowck-mutate-in-guard.rs
@@ -8,12 +8,9 @@ fn foo() -> isize {
     let mut x = Enum::A(&mut n);
     match x {
         Enum::A(_) if { x = Enum::B(false); false } => 1,
-        //~^ ERROR cannot assign in a pattern guard
-        //~| ERROR cannot assign `x` in match guard
+        //~^ ERROR cannot assign `x` in match guard
         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
-        //~^ ERROR cannot mutably borrow in a pattern guard
-        //~| ERROR cannot assign in a pattern guard
-        //~| ERROR cannot mutably borrow `x` in match guard
+        //~^ ERROR cannot mutably borrow `x` in match guard
         Enum::A(p) => *p,
         Enum::B(_) => 2,
     }
diff --git a/src/test/ui/borrowck/borrowck-mutate-in-guard.stderr b/src/test/ui/borrowck/borrowck-mutate-in-guard.stderr
index 674f137dbb043..6d05e97252d92 100644
--- a/src/test/ui/borrowck/borrowck-mutate-in-guard.stderr
+++ b/src/test/ui/borrowck/borrowck-mutate-in-guard.stderr
@@ -1,23 +1,3 @@
-error[E0302]: cannot assign in a pattern guard
-  --> $DIR/borrowck-mutate-in-guard.rs:10:25
-   |
-LL |         Enum::A(_) if { x = Enum::B(false); false } => 1,
-   |                         ^^^^^^^^^^^^^^^^^^ assignment in pattern guard
-
-error[E0301]: cannot mutably borrow in a pattern guard
-  --> $DIR/borrowck-mutate-in-guard.rs:13:38
-   |
-LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
-   |                                      ^ borrowed mutably in pattern guard
-   |
-   = help: add `#![feature(bind_by_move_pattern_guards)]` to the crate attributes to enable
-
-error[E0302]: cannot assign in a pattern guard
-  --> $DIR/borrowck-mutate-in-guard.rs:13:41
-   |
-LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
-   |                                         ^^^^^^^^^^^^^^^^^^^ assignment in pattern guard
-
 error[E0510]: cannot assign `x` in match guard
   --> $DIR/borrowck-mutate-in-guard.rs:10:25
    |
@@ -27,7 +7,7 @@ LL |         Enum::A(_) if { x = Enum::B(false); false } => 1,
    |                         ^^^^^^^^^^^^^^^^^^ cannot assign
 
 error[E0510]: cannot mutably borrow `x` in match guard
-  --> $DIR/borrowck-mutate-in-guard.rs:13:33
+  --> $DIR/borrowck-mutate-in-guard.rs:12:33
    |
 LL |     match x {
    |           - value is immutable in match guard
@@ -35,7 +15,6 @@ LL |     match x {
 LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
    |                                 ^^^^^^ cannot mutably borrow
 
-error: aborting due to 5 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0301, E0302, E0510.
-For more information about an error, try `rustc --explain E0301`.
+For more information about this error, try `rustc --explain E0510`.
diff --git a/src/test/ui/borrowck/borrowck-or-init.rs b/src/test/ui/borrowck/borrowck-or-init.rs
index c0d6c9c2739b2..81b0b80bf11b5 100644
--- a/src/test/ui/borrowck/borrowck-or-init.rs
+++ b/src/test/ui/borrowck/borrowck-or-init.rs
@@ -2,5 +2,5 @@ fn main() {
     let i: isize;
 
     println!("{}", false || { i = 5; true });
-    println!("{}", i); //~ ERROR borrow of possibly uninitialized variable: `i`
+    println!("{}", i); //~ ERROR borrow of possibly-uninitialized variable: `i`
 }
diff --git a/src/test/ui/borrowck/borrowck-or-init.stderr b/src/test/ui/borrowck/borrowck-or-init.stderr
index 122f5192720cc..3fe8d9eededc5 100644
--- a/src/test/ui/borrowck/borrowck-or-init.stderr
+++ b/src/test/ui/borrowck/borrowck-or-init.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `i`
+error[E0381]: borrow of possibly-uninitialized variable: `i`
   --> $DIR/borrowck-or-init.rs:5:20
    |
 LL |     println!("{}", i);
-   |                    ^ use of possibly uninitialized `i`
+   |                    ^ use of possibly-uninitialized `i`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-partial-reinit-4.rs b/src/test/ui/borrowck/borrowck-partial-reinit-4.rs
index 0fb955d201d03..5e5a8cdf4232b 100644
--- a/src/test/ui/borrowck/borrowck-partial-reinit-4.rs
+++ b/src/test/ui/borrowck/borrowck-partial-reinit-4.rs
@@ -15,7 +15,7 @@ impl Drop for Test2 {
 fn stuff() {
     let mut x : (Test2, Test2);
     (x.0).0 = Some(Test);
-    //~^ ERROR assign of possibly uninitialized variable: `x.0`
+    //~^ ERROR assign of possibly-uninitialized variable: `x.0`
 }
 
 fn main() {
diff --git a/src/test/ui/borrowck/borrowck-partial-reinit-4.stderr b/src/test/ui/borrowck/borrowck-partial-reinit-4.stderr
index f0a9a7dd5e243..218c4f2de5bc7 100644
--- a/src/test/ui/borrowck/borrowck-partial-reinit-4.stderr
+++ b/src/test/ui/borrowck/borrowck-partial-reinit-4.stderr
@@ -1,8 +1,8 @@
-error[E0381]: assign of possibly uninitialized variable: `x.0`
+error[E0381]: assign of possibly-uninitialized variable: `x.0`
   --> $DIR/borrowck-partial-reinit-4.rs:17:5
    |
 LL |     (x.0).0 = Some(Test);
-   |     ^^^^^^^ use of possibly uninitialized `x.0`
+   |     ^^^^^^^ use of possibly-uninitialized `x.0`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-return.rs b/src/test/ui/borrowck/borrowck-return.rs
index e5bee2ca4bfeb..8c623356f6c6b 100644
--- a/src/test/ui/borrowck/borrowck-return.rs
+++ b/src/test/ui/borrowck/borrowck-return.rs
@@ -1,6 +1,6 @@
 fn f() -> isize {
     let x: isize;
-    return x; //~ ERROR use of possibly uninitialized variable: `x`
+    return x; //~ ERROR use of possibly-uninitialized variable: `x`
 }
 
 fn main() { f(); }
diff --git a/src/test/ui/borrowck/borrowck-return.stderr b/src/test/ui/borrowck/borrowck-return.stderr
index a2b65af5dbfcd..bc74e8e343848 100644
--- a/src/test/ui/borrowck/borrowck-return.stderr
+++ b/src/test/ui/borrowck/borrowck-return.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-return.rs:3:12
    |
 LL |     return x;
-   |            ^ use of possibly uninitialized `x`
+   |            ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-storage-dead.stderr b/src/test/ui/borrowck/borrowck-storage-dead.stderr
index 5b9f49c2e7c92..8e4932142f0db 100644
--- a/src/test/ui/borrowck/borrowck-storage-dead.stderr
+++ b/src/test/ui/borrowck/borrowck-storage-dead.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-storage-dead.rs:16:17
    |
 LL |         let _ = x + 1;
-   |                 ^ use of possibly uninitialized `x`
+   |                 ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-uninit-after-item.rs b/src/test/ui/borrowck/borrowck-uninit-after-item.rs
index 83f3752a1a850..e9a389657c8fd 100644
--- a/src/test/ui/borrowck/borrowck-uninit-after-item.rs
+++ b/src/test/ui/borrowck/borrowck-uninit-after-item.rs
@@ -1,5 +1,5 @@
 fn main() {
     let bar;
     fn baz(_x: isize) { }
-    baz(bar); //~ ERROR use of possibly uninitialized variable: `bar`
+    baz(bar); //~ ERROR use of possibly-uninitialized variable: `bar`
 }
diff --git a/src/test/ui/borrowck/borrowck-uninit-after-item.stderr b/src/test/ui/borrowck/borrowck-uninit-after-item.stderr
index 2d0b21dd0d6fb..f7f069b81be02 100644
--- a/src/test/ui/borrowck/borrowck-uninit-after-item.stderr
+++ b/src/test/ui/borrowck/borrowck-uninit-after-item.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `bar`
+error[E0381]: use of possibly-uninitialized variable: `bar`
   --> $DIR/borrowck-uninit-after-item.rs:4:9
    |
 LL |     baz(bar);
-   |         ^^^ use of possibly uninitialized `bar`
+   |         ^^^ use of possibly-uninitialized `bar`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-uninit-field-access.stderr b/src/test/ui/borrowck/borrowck-uninit-field-access.stderr
index aa214f9c2f590..9f35a4a8d83bd 100644
--- a/src/test/ui/borrowck/borrowck-uninit-field-access.stderr
+++ b/src/test/ui/borrowck/borrowck-uninit-field-access.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `a`
+error[E0381]: use of possibly-uninitialized variable: `a`
   --> $DIR/borrowck-uninit-field-access.rs:21:13
    |
 LL |     let _ = a.x + 1;
-   |             ^^^ use of possibly uninitialized `a.x`
+   |             ^^^ use of possibly-uninitialized `a.x`
 
 error[E0382]: use of moved value: `line1.origin`
   --> $DIR/borrowck-uninit-field-access.rs:25:13
diff --git a/src/test/ui/borrowck/borrowck-uninit-in-assignop.rs b/src/test/ui/borrowck/borrowck-uninit-in-assignop.rs
index bfb0dd4301dd1..20350d61d5bb6 100644
--- a/src/test/ui/borrowck/borrowck-uninit-in-assignop.rs
+++ b/src/test/ui/borrowck/borrowck-uninit-in-assignop.rs
@@ -3,32 +3,32 @@
 
 pub fn main() {
     let x: isize;
-    x += 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x += 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x -= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x -= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x *= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x *= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x /= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x /= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x %= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x %= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x ^= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x ^= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x &= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x &= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x |= 1; //~ ERROR use of possibly uninitialized variable: `x`
+    x |= 1; //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x <<= 1;    //~ ERROR use of possibly uninitialized variable: `x`
+    x <<= 1;    //~ ERROR use of possibly-uninitialized variable: `x`
 
     let x: isize;
-    x >>= 1;    //~ ERROR use of possibly uninitialized variable: `x`
+    x >>= 1;    //~ ERROR use of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/borrowck/borrowck-uninit-in-assignop.stderr b/src/test/ui/borrowck/borrowck-uninit-in-assignop.stderr
index 163395e42d252..f2036df3ce92a 100644
--- a/src/test/ui/borrowck/borrowck-uninit-in-assignop.stderr
+++ b/src/test/ui/borrowck/borrowck-uninit-in-assignop.stderr
@@ -1,62 +1,62 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:6:5
    |
 LL |     x += 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:9:5
    |
 LL |     x -= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:12:5
    |
 LL |     x *= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:15:5
    |
 LL |     x /= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:18:5
    |
 LL |     x %= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:21:5
    |
 LL |     x ^= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:24:5
    |
 LL |     x &= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:27:5
    |
 LL |     x |= 1;
-   |     ^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:30:5
    |
 LL |     x <<= 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-in-assignop.rs:33:5
    |
 LL |     x >>= 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
 error: aborting due to 10 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-uninit-ref-chain.rs b/src/test/ui/borrowck/borrowck-uninit-ref-chain.rs
index fa9148f984077..0ccea49f329bb 100644
--- a/src/test/ui/borrowck/borrowck-uninit-ref-chain.rs
+++ b/src/test/ui/borrowck/borrowck-uninit-ref-chain.rs
@@ -15,19 +15,19 @@ fn main() {
 
 
     let mut a: S<i32, i32>;
-    a.x = 0;            //~ ERROR assign to part of possibly uninitialized variable: `a` [E0381]
+    a.x = 0;            //~ ERROR assign to part of possibly-uninitialized variable: `a` [E0381]
     let _b = &a.x;
 
     let mut a: S<&&i32, &&i32>;
-    a.x = &&0;          //~ ERROR assign to part of possibly uninitialized variable: `a` [E0381]
+    a.x = &&0;          //~ ERROR assign to part of possibly-uninitialized variable: `a` [E0381]
     let _b = &**a.x;
 
 
     let mut a: S<i32, i32>;
-    a.x = 0;            //~ ERROR assign to part of possibly uninitialized variable: `a` [E0381]
+    a.x = 0;            //~ ERROR assign to part of possibly-uninitialized variable: `a` [E0381]
     let _b = &a.y;
 
     let mut a: S<&&i32, &&i32>;
-    a.x = &&0;          //~ assign to part of possibly uninitialized variable: `a` [E0381]
+    a.x = &&0;          //~ assign to part of possibly-uninitialized variable: `a` [E0381]
     let _b = &**a.y;
 }
diff --git a/src/test/ui/borrowck/borrowck-uninit-ref-chain.stderr b/src/test/ui/borrowck/borrowck-uninit-ref-chain.stderr
index d87621f04d653..d99a50df75b8c 100644
--- a/src/test/ui/borrowck/borrowck-uninit-ref-chain.stderr
+++ b/src/test/ui/borrowck/borrowck-uninit-ref-chain.stderr
@@ -1,44 +1,44 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-ref-chain.rs:8:14
    |
 LL |     let _y = &**x;
-   |              ^^^^ use of possibly uninitialized `**x`
+   |              ^^^^ use of possibly-uninitialized `**x`
 
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-ref-chain.rs:11:14
    |
 LL |     let _y = &**x;
-   |              ^^^^ use of possibly uninitialized `**x`
+   |              ^^^^ use of possibly-uninitialized `**x`
 
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit-ref-chain.rs:14:14
    |
 LL |     let _y = &**x;
-   |              ^^^^ use of possibly uninitialized `**x`
+   |              ^^^^ use of possibly-uninitialized `**x`
 
-error[E0381]: assign to part of possibly uninitialized variable: `a`
+error[E0381]: assign to part of possibly-uninitialized variable: `a`
   --> $DIR/borrowck-uninit-ref-chain.rs:18:5
    |
 LL |     a.x = 0;
-   |     ^^^^^^^ use of possibly uninitialized `a`
+   |     ^^^^^^^ use of possibly-uninitialized `a`
 
-error[E0381]: assign to part of possibly uninitialized variable: `a`
+error[E0381]: assign to part of possibly-uninitialized variable: `a`
   --> $DIR/borrowck-uninit-ref-chain.rs:22:5
    |
 LL |     a.x = &&0;
-   |     ^^^^^^^^^ use of possibly uninitialized `a`
+   |     ^^^^^^^^^ use of possibly-uninitialized `a`
 
-error[E0381]: assign to part of possibly uninitialized variable: `a`
+error[E0381]: assign to part of possibly-uninitialized variable: `a`
   --> $DIR/borrowck-uninit-ref-chain.rs:27:5
    |
 LL |     a.x = 0;
-   |     ^^^^^^^ use of possibly uninitialized `a`
+   |     ^^^^^^^ use of possibly-uninitialized `a`
 
-error[E0381]: assign to part of possibly uninitialized variable: `a`
+error[E0381]: assign to part of possibly-uninitialized variable: `a`
   --> $DIR/borrowck-uninit-ref-chain.rs:31:5
    |
 LL |     a.x = &&0;
-   |     ^^^^^^^^^ use of possibly uninitialized `a`
+   |     ^^^^^^^^^ use of possibly-uninitialized `a`
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-uninit.rs b/src/test/ui/borrowck/borrowck-uninit.rs
index 71c1f596fa21b..017b955a39535 100644
--- a/src/test/ui/borrowck/borrowck-uninit.rs
+++ b/src/test/ui/borrowck/borrowck-uninit.rs
@@ -2,5 +2,5 @@ fn foo(x: isize) { println!("{}", x); }
 
 fn main() {
     let x: isize;
-    foo(x); //~ ERROR use of possibly uninitialized variable: `x`
+    foo(x); //~ ERROR use of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/borrowck/borrowck-uninit.stderr b/src/test/ui/borrowck/borrowck-uninit.stderr
index 5db9c1b250cc2..effc209e81659 100644
--- a/src/test/ui/borrowck/borrowck-uninit.stderr
+++ b/src/test/ui/borrowck/borrowck-uninit.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-uninit.rs:5:9
    |
 LL |     foo(x);
-   |         ^ use of possibly uninitialized `x`
+   |         ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-union-uninitialized.rs b/src/test/ui/borrowck/borrowck-union-uninitialized.rs
index 9cab0b19202a0..3cc71e7cece0e 100644
--- a/src/test/ui/borrowck/borrowck-union-uninitialized.rs
+++ b/src/test/ui/borrowck/borrowck-union-uninitialized.rs
@@ -10,8 +10,8 @@ fn main() {
     unsafe {
         let mut s: S;
         let mut u: U;
-        s.a = 0; //~ ERROR assign to part of possibly uninitialized variable: `s`
-        u.a = 0; //~ ERROR assign to part of possibly uninitialized variable: `u`
+        s.a = 0; //~ ERROR assign to part of possibly-uninitialized variable: `s`
+        u.a = 0; //~ ERROR assign to part of possibly-uninitialized variable: `u`
         let sa = s.a;
         let ua = u.a;
     }
diff --git a/src/test/ui/borrowck/borrowck-union-uninitialized.stderr b/src/test/ui/borrowck/borrowck-union-uninitialized.stderr
index 06c884e244667..bd9ec5e579ca9 100644
--- a/src/test/ui/borrowck/borrowck-union-uninitialized.stderr
+++ b/src/test/ui/borrowck/borrowck-union-uninitialized.stderr
@@ -1,14 +1,14 @@
-error[E0381]: assign to part of possibly uninitialized variable: `s`
+error[E0381]: assign to part of possibly-uninitialized variable: `s`
   --> $DIR/borrowck-union-uninitialized.rs:13:9
    |
 LL |         s.a = 0;
-   |         ^^^^^^^ use of possibly uninitialized `s`
+   |         ^^^^^^^ use of possibly-uninitialized `s`
 
-error[E0381]: assign to part of possibly uninitialized variable: `u`
+error[E0381]: assign to part of possibly-uninitialized variable: `u`
   --> $DIR/borrowck-union-uninitialized.rs:14:9
    |
 LL |         u.a = 0;
-   |         ^^^^^^^ use of possibly uninitialized `u`
+   |         ^^^^^^^ use of possibly-uninitialized `u`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-use-in-index-lvalue.stderr b/src/test/ui/borrowck/borrowck-use-in-index-lvalue.stderr
index c03ef759f570a..d1b396aba8257 100644
--- a/src/test/ui/borrowck/borrowck-use-in-index-lvalue.stderr
+++ b/src/test/ui/borrowck/borrowck-use-in-index-lvalue.stderr
@@ -1,14 +1,14 @@
-error[E0381]: use of possibly uninitialized variable: `w`
+error[E0381]: use of possibly-uninitialized variable: `w`
   --> $DIR/borrowck-use-in-index-lvalue.rs:3:5
    |
 LL |     w[5] = 0;
-   |     ^^^^ use of possibly uninitialized `*w`
+   |     ^^^^ use of possibly-uninitialized `*w`
 
-error[E0381]: use of possibly uninitialized variable: `w`
+error[E0381]: use of possibly-uninitialized variable: `w`
   --> $DIR/borrowck-use-in-index-lvalue.rs:6:5
    |
 LL |     w[5] = 0;
-   |     ^^^^ use of possibly uninitialized `*w`
+   |     ^^^^ use of possibly-uninitialized `*w`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.stderr b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.stderr
index 2b80140c6b376..ca5227c98c862 100644
--- a/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.stderr
+++ b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-use-uninitialized-in-cast-trait.rs:9:13
    |
 LL |     let y = x as *const dyn Foo;
-   |             ^ use of possibly uninitialized `*x`
+   |             ^ use of possibly-uninitialized `*x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast.stderr b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast.stderr
index 84e717a4639cd..24897a0f2dc9c 100644
--- a/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast.stderr
+++ b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-use-uninitialized-in-cast.rs:7:13
    |
 LL |     let y = x as *const i32;
-   |             ^ use of possibly uninitialized `*x`
+   |             ^ use of possibly-uninitialized `*x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-while-break.rs b/src/test/ui/borrowck/borrowck-while-break.rs
index e16bc58656d81..48e4221470221 100644
--- a/src/test/ui/borrowck/borrowck-while-break.rs
+++ b/src/test/ui/borrowck/borrowck-while-break.rs
@@ -4,7 +4,7 @@ fn test(cond: bool) {
         v = 3;
         break;
     }
-    println!("{}", v); //~ ERROR borrow of possibly uninitialized variable: `v`
+    println!("{}", v); //~ ERROR borrow of possibly-uninitialized variable: `v`
 }
 
 fn main() {
diff --git a/src/test/ui/borrowck/borrowck-while-break.stderr b/src/test/ui/borrowck/borrowck-while-break.stderr
index 0fe3cdc96a874..3eaaf8d7df08d 100644
--- a/src/test/ui/borrowck/borrowck-while-break.stderr
+++ b/src/test/ui/borrowck/borrowck-while-break.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `v`
+error[E0381]: borrow of possibly-uninitialized variable: `v`
   --> $DIR/borrowck-while-break.rs:7:20
    |
 LL |     println!("{}", v);
-   |                    ^ use of possibly uninitialized `v`
+   |                    ^ use of possibly-uninitialized `v`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-while-cond.rs b/src/test/ui/borrowck/borrowck-while-cond.rs
index 28a5fb18a7f1d..b3ec20711c12b 100644
--- a/src/test/ui/borrowck/borrowck-while-cond.rs
+++ b/src/test/ui/borrowck/borrowck-while-cond.rs
@@ -1,4 +1,4 @@
 fn main() {
     let x: bool;
-    while x { } //~ ERROR use of possibly uninitialized variable: `x`
+    while x { } //~ ERROR use of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/borrowck/borrowck-while-cond.stderr b/src/test/ui/borrowck/borrowck-while-cond.stderr
index 06deae345ab60..92937a9c5730e 100644
--- a/src/test/ui/borrowck/borrowck-while-cond.stderr
+++ b/src/test/ui/borrowck/borrowck-while-cond.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-while-cond.rs:3:11
    |
 LL |     while x { }
-   |           ^ use of possibly uninitialized `x`
+   |           ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-while.rs b/src/test/ui/borrowck/borrowck-while.rs
index 4274fa997a0ab..6b3220c7d8591 100644
--- a/src/test/ui/borrowck/borrowck-while.rs
+++ b/src/test/ui/borrowck/borrowck-while.rs
@@ -1,7 +1,7 @@
 fn f() -> isize {
     let mut x: isize;
     while 1 == 1 { x = 10; }
-    return x; //~ ERROR use of possibly uninitialized variable: `x`
+    return x; //~ ERROR use of possibly-uninitialized variable: `x`
 }
 
 fn main() { f(); }
diff --git a/src/test/ui/borrowck/borrowck-while.stderr b/src/test/ui/borrowck/borrowck-while.stderr
index 60622d648dd23..a1f8f64725dcd 100644
--- a/src/test/ui/borrowck/borrowck-while.stderr
+++ b/src/test/ui/borrowck/borrowck-while.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/borrowck-while.rs:4:12
    |
 LL |     return x;
-   |            ^ use of possibly uninitialized `x`
+   |            ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/disallow-possibly-uninitialized.rs b/src/test/ui/borrowck/disallow-possibly-uninitialized.rs
index a987c00b09191..7043cb3a164e7 100644
--- a/src/test/ui/borrowck/disallow-possibly-uninitialized.rs
+++ b/src/test/ui/borrowck/disallow-possibly-uninitialized.rs
@@ -4,19 +4,19 @@
 fn main() {
     let mut t: (u64, u64);
     t.0 = 1;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     t.1 = 1;
 
     let mut t: (u64, u64);
     t.1 = 1;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     t.0 = 1;
 
     let mut t: (u64, u64);
     t.0 = 1;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
 
     let mut t: (u64,);
     t.0 = 1;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
 }
diff --git a/src/test/ui/borrowck/disallow-possibly-uninitialized.stderr b/src/test/ui/borrowck/disallow-possibly-uninitialized.stderr
index a32b17b165934..8d5b39341c109 100644
--- a/src/test/ui/borrowck/disallow-possibly-uninitialized.stderr
+++ b/src/test/ui/borrowck/disallow-possibly-uninitialized.stderr
@@ -1,26 +1,26 @@
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/disallow-possibly-uninitialized.rs:6:5
    |
 LL |     t.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/disallow-possibly-uninitialized.rs:11:5
    |
 LL |     t.1 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/disallow-possibly-uninitialized.rs:16:5
    |
 LL |     t.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/disallow-possibly-uninitialized.rs:20:5
    |
 LL |     t.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^ use of possibly-uninitialized `t`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/borrowck/issue-10876.rs b/src/test/ui/borrowck/issue-10876.rs
index 20ab905fec46e..22eaa119f2467 100644
--- a/src/test/ui/borrowck/issue-10876.rs
+++ b/src/test/ui/borrowck/issue-10876.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 enum Nat {
     S(Box<Nat>),
diff --git a/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.rs b/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.rs
index 8d8ac279b23a8..f031a144443b3 100644
--- a/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.rs
+++ b/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.rs
@@ -10,7 +10,7 @@ fn main() {
     {
         let mut t: Tuple;
         t.0 = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
         t.1 = 2;
         println!("{:?} {:?}", t.0, t.1);
     }
@@ -18,7 +18,7 @@ fn main() {
     {
         let mut u: Tpair;
         u.0 = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `u` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `u` [E0381]
         u.1 = 2;
         println!("{:?} {:?}", u.0, u.1);
     }
@@ -26,7 +26,7 @@ fn main() {
     {
         let mut v: Spair;
         v.x = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `v` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `v` [E0381]
         v.y = 2;
         println!("{:?} {:?}", v.x, v.y);
     }
diff --git a/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.stderr b/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.stderr
index 6f18ff161372a..22c6c3964edc1 100644
--- a/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.stderr
+++ b/src/test/ui/borrowck/issue-54499-field-mutation-marks-mut-as-used.stderr
@@ -1,20 +1,20 @@
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:12:9
    |
 LL |         t.0 = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `t`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `u`
+error[E0381]: assign to part of possibly-uninitialized variable: `u`
   --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:20:9
    |
 LL |         u.0 = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `u`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `u`
 
-error[E0381]: assign to part of possibly uninitialized variable: `v`
+error[E0381]: assign to part of possibly-uninitialized variable: `v`
   --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:28:9
    |
 LL |         v.x = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `v`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `v`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.rs b/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.rs
index 1a1b376bf9bcf..660d9e85ef54e 100644
--- a/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.rs
+++ b/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.rs
@@ -10,7 +10,7 @@ fn main() {
     {
         let t: Tuple;
         t.0 = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
         t.1 = 2;
         println!("{:?} {:?}", t.0, t.1);
     }
@@ -18,7 +18,7 @@ fn main() {
     {
         let u: Tpair;
         u.0 = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `u` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `u` [E0381]
         u.1 = 2;
         println!("{:?} {:?}", u.0, u.1);
     }
@@ -26,7 +26,7 @@ fn main() {
     {
         let v: Spair;
         v.x = S(1);
-        //~^ ERROR assign to part of possibly uninitialized variable: `v` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `v` [E0381]
         v.y = 2;
         println!("{:?} {:?}", v.x, v.y);
     }
diff --git a/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.stderr b/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.stderr
index 68873ac5c02e2..5f9c978c342f6 100644
--- a/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.stderr
+++ b/src/test/ui/borrowck/issue-54499-field-mutation-of-never-init.stderr
@@ -1,20 +1,20 @@
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/issue-54499-field-mutation-of-never-init.rs:12:9
    |
 LL |         t.0 = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `t`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `u`
+error[E0381]: assign to part of possibly-uninitialized variable: `u`
   --> $DIR/issue-54499-field-mutation-of-never-init.rs:20:9
    |
 LL |         u.0 = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `u`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `u`
 
-error[E0381]: assign to part of possibly uninitialized variable: `v`
+error[E0381]: assign to part of possibly-uninitialized variable: `v`
   --> $DIR/issue-54499-field-mutation-of-never-init.rs:28:9
    |
 LL |         v.x = S(1);
-   |         ^^^^^^^^^^ use of possibly uninitialized `v`
+   |         ^^^^^^^^^^ use of possibly-uninitialized `v`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/borrowck/issue-62107-match-arm-scopes.rs b/src/test/ui/borrowck/issue-62107-match-arm-scopes.rs
index 220b2ecf04d38..f8efa8c891eb3 100644
--- a/src/test/ui/borrowck/issue-62107-match-arm-scopes.rs
+++ b/src/test/ui/borrowck/issue-62107-match-arm-scopes.rs
@@ -1,7 +1,7 @@
 fn main() {
     let e: i32;
     match e {
-        //~^ ERROR use of possibly uninitialized variable
+        //~^ ERROR use of possibly-uninitialized variable
         ref u if true => {}
         ref v if true => {
             let tx = 0;
diff --git a/src/test/ui/borrowck/issue-62107-match-arm-scopes.stderr b/src/test/ui/borrowck/issue-62107-match-arm-scopes.stderr
index 9701343d2b1dd..0eca447b55159 100644
--- a/src/test/ui/borrowck/issue-62107-match-arm-scopes.stderr
+++ b/src/test/ui/borrowck/issue-62107-match-arm-scopes.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `e`
+error[E0381]: use of possibly-uninitialized variable: `e`
   --> $DIR/issue-62107-match-arm-scopes.rs:3:11
    |
 LL |     match e {
-   |           ^ use of possibly uninitialized `e`
+   |           ^ use of possibly-uninitialized `e`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/reassignment_immutable_fields.stderr b/src/test/ui/borrowck/reassignment_immutable_fields.stderr
index d455a8f078743..f09db378a75b4 100644
--- a/src/test/ui/borrowck/reassignment_immutable_fields.stderr
+++ b/src/test/ui/borrowck/reassignment_immutable_fields.stderr
@@ -1,14 +1,14 @@
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/reassignment_immutable_fields.rs:7:5
    |
 LL |     x.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/reassignment_immutable_fields.rs:15:5
    |
 LL |     x.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.stderr b/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.stderr
index 649c127dcc9d4..5f346708eb610 100644
--- a/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.stderr
+++ b/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.stderr
@@ -1,8 +1,8 @@
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/reassignment_immutable_fields_overlapping.rs:12:5
    |
 LL |     x.a = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
 error[E0594]: cannot assign to `x.b`, as `x` is not declared as mutable
   --> $DIR/reassignment_immutable_fields_overlapping.rs:13:5
diff --git a/src/test/ui/borrowck/reassignment_immutable_fields_twice.stderr b/src/test/ui/borrowck/reassignment_immutable_fields_twice.stderr
index 9a2824ccb3cd2..14f0fee84c9aa 100644
--- a/src/test/ui/borrowck/reassignment_immutable_fields_twice.stderr
+++ b/src/test/ui/borrowck/reassignment_immutable_fields_twice.stderr
@@ -7,11 +7,11 @@ LL |     x = (22, 44);
 LL |     x.0 = 1;
    |     ^^^^^^^ cannot assign
 
-error[E0381]: assign to part of possibly uninitialized variable: `x`
+error[E0381]: assign to part of possibly-uninitialized variable: `x`
   --> $DIR/reassignment_immutable_fields_twice.rs:12:5
    |
 LL |     x.0 = 1;
-   |     ^^^^^^^ use of possibly uninitialized `x`
+   |     ^^^^^^^ use of possibly-uninitialized `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/return-local-binding-from-desugaring.polonius.stderr b/src/test/ui/borrowck/return-local-binding-from-desugaring.polonius.stderr
new file mode 100644
index 0000000000000..c818379762c9d
--- /dev/null
+++ b/src/test/ui/borrowck/return-local-binding-from-desugaring.polonius.stderr
@@ -0,0 +1,16 @@
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/return-local-binding-from-desugaring.rs:26:18
+   |
+LL |     for ref x in xs {
+   |                  ^^ creates a temporary which is freed while still in use
+...
+LL |     }
+   |     - temporary value is freed at the end of this statement
+LL |     result
+   |     ------ borrow later used here
+   |
+   = note: consider using a `let` binding to create a longer lived value
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0716`.
diff --git a/src/test/ui/borrowck/two-phase-across-loop.rs b/src/test/ui/borrowck/two-phase-across-loop.rs
index 12222342c95a1..3fcea7d171349 100644
--- a/src/test/ui/borrowck/two-phase-across-loop.rs
+++ b/src/test/ui/borrowck/two-phase-across-loop.rs
@@ -1,4 +1,4 @@
-// Test that a borrow which starts as a 2-phase borrow and gets
+// Test that a borrow which starts as a two-phase borrow and gets
 // carried around a loop winds up conflicting with itself.
 
 struct Foo { x: String }
diff --git a/src/test/ui/borrowck/two-phase-multiple-activations.rs b/src/test/ui/borrowck/two-phase-multiple-activations.rs
index a7fa7fac13e73..599138a9ce0f1 100644
--- a/src/test/ui/borrowck/two-phase-multiple-activations.rs
+++ b/src/test/ui/borrowck/two-phase-multiple-activations.rs
@@ -11,7 +11,7 @@ pub trait FakeRead {
 }
 
 impl FakeRead for Foo {
-    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
+    fn read_to_end(&mut self, _buf: &mut Vec<u8>) -> Result<usize> {
         Ok(4)
     }
 }
@@ -19,5 +19,5 @@ impl FakeRead for Foo {
 fn main() {
     let mut a = Foo {};
     let mut v = Vec::new();
-    a.read_to_end(&mut v);
+    a.read_to_end(&mut v).unwrap();
 }
diff --git a/src/test/ui/borrowck/two-phase-surprise-no-conflict.rs b/src/test/ui/borrowck/two-phase-surprise-no-conflict.rs
index 3fd24bbf290b5..6d37d1ded6400 100644
--- a/src/test/ui/borrowck/two-phase-surprise-no-conflict.rs
+++ b/src/test/ui/borrowck/two-phase-surprise-no-conflict.rs
@@ -31,7 +31,7 @@ impl <'a> SpanlessHash<'a> {
                 //
                 // Not okay without two-phase borrows: the implicit
                 // `&mut self` of the receiver is evaluated first, and
-                // that conflicts with the `self.cx`` access during
+                // that conflicts with the `self.cx` access during
                 // argument evaluation, as demonstrated in `fn demo`
                 // above.
                 //
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr b/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
index 4947d6e529108..ab8398ec5e935 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
+++ b/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
@@ -37,11 +37,11 @@ error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:20:5
    |
 LL | pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-   |                                               -------                   ------- has type `core::ffi::VaListImpl<'1>`
+   |                                               -------                   ------- has type `core::ffi::VaListImpl<'2>`
    |                                               |
-   |                                               has type `&mut core::ffi::VaListImpl<'2>`
+   |                                               has type `&mut core::ffi::VaListImpl<'1>`
 LL |     *ap0 = ap1;
-   |     ^^^^ assignment requires that `'1` must outlive `'2`
+   |     ^^^^ assignment requires that `'2` must outlive `'1`
 
 error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:25:5
@@ -57,11 +57,11 @@ error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:25:5
    |
 LL | pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
-   |                                               ---                   ------- has type `core::ffi::VaListImpl<'1>`
+   |                                               ---                   ------- has type `core::ffi::VaListImpl<'2>`
    |                                               |
-   |                                               has type `&mut core::ffi::VaListImpl<'2>`
+   |                                               has type `&mut core::ffi::VaListImpl<'1>`
 LL |     ap0 = &mut ap1;
-   |     ^^^^^^^^^^^^^^ assignment requires that `'1` must outlive `'2`
+   |     ^^^^^^^^^^^^^^ assignment requires that `'2` must outlive `'1`
 
 error[E0384]: cannot assign to immutable argument `ap0`
   --> $DIR/variadic-ffi-4.rs:25:5
@@ -99,11 +99,11 @@ error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:33:12
    |
 LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-   |                                               -------                   ------- has type `core::ffi::VaListImpl<'1>`
+   |                                               -------                   ------- has type `core::ffi::VaListImpl<'2>`
    |                                               |
-   |                                               has type `&mut core::ffi::VaListImpl<'2>`
+   |                                               has type `&mut core::ffi::VaListImpl<'1>`
 LL |     *ap0 = ap1.clone();
-   |            ^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |            ^^^^^^^^^^^ argument requires that `'2` must outlive `'1`
 
 error: aborting due to 11 previous errors
 
diff --git a/src/test/ui/class-cast-to-trait.stderr b/src/test/ui/class-cast-to-trait.stderr
index 39f308cdfd490..4cab52e3e974c 100644
--- a/src/test/ui/class-cast-to-trait.stderr
+++ b/src/test/ui/class-cast-to-trait.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `eat` found for type `std::boxed::Box<dyn Noisy>`
   --> $DIR/class-cast-to-trait.rs:53:8
    |
 LL |   nyan.eat();
-   |        ^^^
+   |        ^^^ method not found in `std::boxed::Box<dyn Noisy>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/closure-expected.stderr b/src/test/ui/closure-expected.stderr
index ff77423577db6..ae4f4d69b5ef5 100644
--- a/src/test/ui/closure-expected.stderr
+++ b/src/test/ui/closure-expected.stderr
@@ -1,8 +1,8 @@
 error[E0277]: expected a `std::ops::FnOnce<()>` closure, found `{integer}`
-  --> $DIR/closure-expected.rs:3:15
+  --> $DIR/closure-expected.rs:3:23
    |
 LL |     let y = x.or_else(4);
-   |               ^^^^^^^ expected an `FnOnce<()>` closure, found `{integer}`
+   |                       ^ expected an `FnOnce<()>` closure, found `{integer}`
    |
    = help: the trait `std::ops::FnOnce<()>` is not implemented for `{integer}`
    = note: wrap the `{integer}` in a closure with no arguments: `|| { /* code */ }
diff --git a/src/test/ui/closures/closure-bounds-subtype.stderr b/src/test/ui/closures/closure-bounds-subtype.stderr
index 4958bd06d9b16..e9b34e05ac2e2 100644
--- a/src/test/ui/closures/closure-bounds-subtype.stderr
+++ b/src/test/ui/closures/closure-bounds-subtype.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `F` cannot be shared between threads safely
-  --> $DIR/closure-bounds-subtype.rs:13:5
+  --> $DIR/closure-bounds-subtype.rs:13:22
    |
 LL | fn take_const_owned<F>(_: F) where F: FnOnce() + Sync + Send {
    | ------------------------------------------------------------ required by `take_const_owned`
 ...
 LL |     take_const_owned(f);
-   |     ^^^^^^^^^^^^^^^^ `F` cannot be shared between threads safely
+   |                      ^ `F` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `F`
    = help: consider adding a `where F: std::marker::Sync` bound
diff --git a/src/test/ui/codemap_tests/bad-format-args.rs b/src/test/ui/codemap_tests/bad-format-args.rs
index 9f90185774467..dff248344a53d 100644
--- a/src/test/ui/codemap_tests/bad-format-args.rs
+++ b/src/test/ui/codemap_tests/bad-format-args.rs
@@ -1,5 +1,5 @@
 fn main() {
     format!(); //~ ERROR requires at least a format string argument
     format!("" 1); //~ ERROR expected token: `,`
-    format!("", 1 1); //~ ERROR expected token: `,`
+    format!("", 1 1); //~ ERROR expected one of
 }
diff --git a/src/test/ui/codemap_tests/bad-format-args.stderr b/src/test/ui/codemap_tests/bad-format-args.stderr
index 5b01314d8ad4f..3372ef6dea1fc 100644
--- a/src/test/ui/codemap_tests/bad-format-args.stderr
+++ b/src/test/ui/codemap_tests/bad-format-args.stderr
@@ -12,11 +12,11 @@ error: expected token: `,`
 LL |     format!("" 1);
    |                ^ expected `,`
 
-error: expected token: `,`
+error: expected one of `,`, `.`, `?`, or an operator, found `1`
   --> $DIR/bad-format-args.rs:4:19
    |
 LL |     format!("", 1 1);
-   |                   ^ expected `,`
+   |                   ^ expected one of `,`, `.`, `?`, or an operator here
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/codemap_tests/overlapping_inherent_impls.stderr b/src/test/ui/codemap_tests/overlapping_inherent_impls.stderr
index 70c1093e9ed48..8fe24bae7c6ca 100644
--- a/src/test/ui/codemap_tests/overlapping_inherent_impls.stderr
+++ b/src/test/ui/codemap_tests/overlapping_inherent_impls.stderr
@@ -25,7 +25,7 @@ LL |     fn baz(&self) {}
 LL |     fn baz(&self) {}
    |     ---------------- other definition for `baz`
    |
-   = note: upstream crates may add new impl of trait `std::marker::Copy` for type `std::vec::Vec<_>` in future versions
+   = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::vec::Vec<_>` in future versions
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/coercion/coercion-slice.rs b/src/test/ui/coercion/coercion-slice.rs
index 312b634c9fd0b..b69edcf260637 100644
--- a/src/test/ui/coercion/coercion-slice.rs
+++ b/src/test/ui/coercion/coercion-slice.rs
@@ -4,5 +4,5 @@ fn main() {
     let _: &[i32] = [0];
     //~^ ERROR mismatched types
     //~| expected type `&[i32]`
-    //~| expected &[i32], found array of 1 elements
+    //~| expected &[i32], found array of 1 element
 }
diff --git a/src/test/ui/coercion/coercion-slice.stderr b/src/test/ui/coercion/coercion-slice.stderr
index 6fa712371178b..ccd776e987938 100644
--- a/src/test/ui/coercion/coercion-slice.stderr
+++ b/src/test/ui/coercion/coercion-slice.stderr
@@ -4,7 +4,7 @@ error[E0308]: mismatched types
 LL |     let _: &[i32] = [0];
    |                     ^^^
    |                     |
-   |                     expected &[i32], found array of 1 elements
+   |                     expected &[i32], found array of 1 element
    |                     help: consider borrowing here: `&[0]`
    |
    = note: expected type `&[i32]`
diff --git a/src/test/ui/coherence/coherence-overlap-upstream-inherent.old.stderr b/src/test/ui/coherence/coherence-overlap-upstream-inherent.old.stderr
index 928b65e003918..3a3e1a4afc3bb 100644
--- a/src/test/ui/coherence/coherence-overlap-upstream-inherent.old.stderr
+++ b/src/test/ui/coherence/coherence-overlap-upstream-inherent.old.stderr
@@ -7,7 +7,7 @@ LL | impl<T> A<T> where T: Remote { fn dummy(&self) { } }
 LL | impl A<i16> { fn dummy(&self) { } }
    |               ------------------- other definition for `dummy`
    |
-   = note: upstream crates may add new impl of trait `coherence_lib::Remote` for type `i16` in future versions
+   = note: upstream crates may add a new impl of trait `coherence_lib::Remote` for type `i16` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-overlap-upstream-inherent.re.stderr b/src/test/ui/coherence/coherence-overlap-upstream-inherent.re.stderr
index 928b65e003918..3a3e1a4afc3bb 100644
--- a/src/test/ui/coherence/coherence-overlap-upstream-inherent.re.stderr
+++ b/src/test/ui/coherence/coherence-overlap-upstream-inherent.re.stderr
@@ -7,7 +7,7 @@ LL | impl<T> A<T> where T: Remote { fn dummy(&self) { } }
 LL | impl A<i16> { fn dummy(&self) { } }
    |               ------------------- other definition for `dummy`
    |
-   = note: upstream crates may add new impl of trait `coherence_lib::Remote` for type `i16` in future versions
+   = note: upstream crates may add a new impl of trait `coherence_lib::Remote` for type `i16` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-overlap-upstream.old.stderr b/src/test/ui/coherence/coherence-overlap-upstream.old.stderr
index 6c3484c2d8c4d..bd6f59f346b6d 100644
--- a/src/test/ui/coherence/coherence-overlap-upstream.old.stderr
+++ b/src/test/ui/coherence/coherence-overlap-upstream.old.stderr
@@ -6,7 +6,7 @@ LL | impl<T> Foo for T where T: Remote {}
 LL | impl Foo for i16 {}
    | ^^^^^^^^^^^^^^^^ conflicting implementation for `i16`
    |
-   = note: upstream crates may add new impl of trait `coherence_lib::Remote` for type `i16` in future versions
+   = note: upstream crates may add a new impl of trait `coherence_lib::Remote` for type `i16` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-overlap-upstream.re.stderr b/src/test/ui/coherence/coherence-overlap-upstream.re.stderr
index 6c3484c2d8c4d..bd6f59f346b6d 100644
--- a/src/test/ui/coherence/coherence-overlap-upstream.re.stderr
+++ b/src/test/ui/coherence/coherence-overlap-upstream.re.stderr
@@ -6,7 +6,7 @@ LL | impl<T> Foo for T where T: Remote {}
 LL | impl Foo for i16 {}
    | ^^^^^^^^^^^^^^^^ conflicting implementation for `i16`
    |
-   = note: upstream crates may add new impl of trait `coherence_lib::Remote` for type `i16` in future versions
+   = note: upstream crates may add a new impl of trait `coherence_lib::Remote` for type `i16` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-projection-conflict-orphan.old.stderr b/src/test/ui/coherence/coherence-projection-conflict-orphan.old.stderr
index cde9360ddf2c8..728eae5e547da 100644
--- a/src/test/ui/coherence/coherence-projection-conflict-orphan.old.stderr
+++ b/src/test/ui/coherence/coherence-projection-conflict-orphan.old.stderr
@@ -7,7 +7,7 @@ LL |
 LL | impl<A:Iterator> Foo<A::Item> for A { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
    |
-   = note: upstream crates may add new impl of trait `std::iter::Iterator` for type `i32` in future versions
+   = note: upstream crates may add a new impl of trait `std::iter::Iterator` for type `i32` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-projection-conflict-orphan.re.stderr b/src/test/ui/coherence/coherence-projection-conflict-orphan.re.stderr
index cde9360ddf2c8..728eae5e547da 100644
--- a/src/test/ui/coherence/coherence-projection-conflict-orphan.re.stderr
+++ b/src/test/ui/coherence/coherence-projection-conflict-orphan.re.stderr
@@ -7,7 +7,7 @@ LL |
 LL | impl<A:Iterator> Foo<A::Item> for A { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
    |
-   = note: upstream crates may add new impl of trait `std::iter::Iterator` for type `i32` in future versions
+   = note: upstream crates may add a new impl of trait `std::iter::Iterator` for type `i32` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.old.stderr b/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.old.stderr
index 12c7a1f977c3f..4d9f55c121547 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.old.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.old.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for lib::MyFundamentalStruct<(MyType,)> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `lib::MyFundamentalStruct<(MyType,)>`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `lib::MyFundamentalStruct<(MyType,)>` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `lib::MyFundamentalStruct<(MyType,)>` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.re.stderr b/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.re.stderr
index 12c7a1f977c3f..4d9f55c121547 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.re.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_fundamental_struct_tuple.re.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for lib::MyFundamentalStruct<(MyType,)> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `lib::MyFundamentalStruct<(MyType,)>`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `lib::MyFundamentalStruct<(MyType,)>` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `lib::MyFundamentalStruct<(MyType,)>` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_struct.old.stderr b/src/test/ui/coherence/coherence_copy_like_err_struct.old.stderr
index 1b6c62e9bf3a8..f0bcf659bb696 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_struct.old.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_struct.old.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for lib::MyStruct<MyType> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `lib::MyStruct<MyType>`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `lib::MyStruct<MyType>` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `lib::MyStruct<MyType>` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_struct.re.stderr b/src/test/ui/coherence/coherence_copy_like_err_struct.re.stderr
index 1b6c62e9bf3a8..f0bcf659bb696 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_struct.re.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_struct.re.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for lib::MyStruct<MyType> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `lib::MyStruct<MyType>`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `lib::MyStruct<MyType>` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `lib::MyStruct<MyType>` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_tuple.old.stderr b/src/test/ui/coherence/coherence_copy_like_err_tuple.old.stderr
index 11bd788c76153..a40153af2cf30 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_tuple.old.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_tuple.old.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for (MyType,) { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(MyType,)`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `(MyType,)` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `(MyType,)` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_copy_like_err_tuple.re.stderr b/src/test/ui/coherence/coherence_copy_like_err_tuple.re.stderr
index 11bd788c76153..a40153af2cf30 100644
--- a/src/test/ui/coherence/coherence_copy_like_err_tuple.re.stderr
+++ b/src/test/ui/coherence/coherence_copy_like_err_tuple.re.stderr
@@ -7,7 +7,7 @@ LL | impl<T: lib::MyCopy> MyTrait for T { }
 LL | impl MyTrait for (MyType,) { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(MyType,)`
    |
-   = note: upstream crates may add new impl of trait `lib::MyCopy` for type `(MyType,)` in future versions
+   = note: upstream crates may add a new impl of trait `lib::MyCopy` for type `(MyType,)` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence_inherent.old.stderr b/src/test/ui/coherence/coherence_inherent.old.stderr
index fa564459b2133..750d243480638 100644
--- a/src/test/ui/coherence/coherence_inherent.old.stderr
+++ b/src/test/ui/coherence/coherence_inherent.old.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `the_fn` found for type `&Lib::TheStruct` in the c
   --> $DIR/coherence_inherent.rs:35:11
    |
 LL |         s.the_fn();
-   |           ^^^^^^
+   |           ^^^^^^ method not found in `&Lib::TheStruct`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/coherence/coherence_inherent.re.stderr b/src/test/ui/coherence/coherence_inherent.re.stderr
index fa564459b2133..750d243480638 100644
--- a/src/test/ui/coherence/coherence_inherent.re.stderr
+++ b/src/test/ui/coherence/coherence_inherent.re.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `the_fn` found for type `&Lib::TheStruct` in the c
   --> $DIR/coherence_inherent.rs:35:11
    |
 LL |         s.the_fn();
-   |           ^^^^^^
+   |           ^^^^^^ method not found in `&Lib::TheStruct`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/coherence/coherence_inherent_cc.old.stderr b/src/test/ui/coherence/coherence_inherent_cc.old.stderr
index 4d93e699031f3..59166a4609406 100644
--- a/src/test/ui/coherence/coherence_inherent_cc.old.stderr
+++ b/src/test/ui/coherence/coherence_inherent_cc.old.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `the_fn` found for type `&coherence_inherent_cc_li
   --> $DIR/coherence_inherent_cc.rs:26:11
    |
 LL |         s.the_fn();
-   |           ^^^^^^
+   |           ^^^^^^ method not found in `&coherence_inherent_cc_lib::TheStruct`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/coherence/coherence_inherent_cc.re.stderr b/src/test/ui/coherence/coherence_inherent_cc.re.stderr
index 4d93e699031f3..59166a4609406 100644
--- a/src/test/ui/coherence/coherence_inherent_cc.re.stderr
+++ b/src/test/ui/coherence/coherence_inherent_cc.re.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `the_fn` found for type `&coherence_inherent_cc_li
   --> $DIR/coherence_inherent_cc.rs:26:11
    |
 LL |         s.the_fn();
-   |           ^^^^^^
+   |           ^^^^^^ method not found in `&coherence_inherent_cc_lib::TheStruct`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/coherence/conflicting-impl-with-err.rs b/src/test/ui/coherence/conflicting-impl-with-err.rs
new file mode 100644
index 0000000000000..3e0234b874d7b
--- /dev/null
+++ b/src/test/ui/coherence/conflicting-impl-with-err.rs
@@ -0,0 +1,16 @@
+struct ErrorKind;
+struct Error(ErrorKind);
+
+impl From<nope::Thing> for Error { //~ ERROR failed to resolve
+    fn from(_: nope::Thing) -> Self { //~ ERROR failed to resolve
+        unimplemented!()
+    }
+}
+
+impl From<ErrorKind> for Error {
+    fn from(_: ErrorKind) -> Self {
+        unimplemented!()
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/coherence/conflicting-impl-with-err.stderr b/src/test/ui/coherence/conflicting-impl-with-err.stderr
new file mode 100644
index 0000000000000..a8a5730accdd8
--- /dev/null
+++ b/src/test/ui/coherence/conflicting-impl-with-err.stderr
@@ -0,0 +1,15 @@
+error[E0433]: failed to resolve: use of undeclared type or module `nope`
+  --> $DIR/conflicting-impl-with-err.rs:4:11
+   |
+LL | impl From<nope::Thing> for Error {
+   |           ^^^^ use of undeclared type or module `nope`
+
+error[E0433]: failed to resolve: use of undeclared type or module `nope`
+  --> $DIR/conflicting-impl-with-err.rs:5:16
+   |
+LL |     fn from(_: nope::Thing) -> Self {
+   |                ^^^^ use of undeclared type or module `nope`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0433`.
diff --git a/src/test/ui/collections-const-new.rs b/src/test/ui/collections-const-new.rs
index e01b0dfa14d6e..a93f9a136db23 100644
--- a/src/test/ui/collections-const-new.rs
+++ b/src/test/ui/collections-const-new.rs
@@ -1,15 +1,11 @@
-// run-pass
+// check-pass
 
-#![allow(dead_code)]
 // Test several functions can be used for constants
 // 1. Vec::new()
 // 2. String::new()
 
-#![feature(const_vec_new)]
-#![feature(const_string_new)]
-
 const MY_VEC: Vec<usize> = Vec::new();
 
 const MY_STRING: String = String::new();
 
-pub fn main() {}
+fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
new file mode 100644
index 0000000000000..9fa726f93e3ea
--- /dev/null
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
@@ -0,0 +1,3 @@
+// compile-flags: --cfg a{
+// error-pattern: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
+fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
new file mode 100644
index 0000000000000..7d2087b4b71f7
--- /dev/null
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
@@ -0,0 +1,2 @@
+error: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
+
diff --git a/src/test/ui/conditional-compilation/cfg-attr-cfg-2.stderr b/src/test/ui/conditional-compilation/cfg-attr-cfg-2.stderr
index db3c7acff151c..e9df780def5df 100644
--- a/src/test/ui/conditional-compilation/cfg-attr-cfg-2.stderr
+++ b/src/test/ui/conditional-compilation/cfg-attr-cfg-2.stderr
@@ -1,6 +1,9 @@
 error[E0601]: `main` function not found in crate `cfg_attr_cfg_2`
+  --> $DIR/cfg-attr-cfg-2.rs:8:1
    |
-   = note: consider adding a `main` function to `$DIR/cfg-attr-cfg-2.rs`
+LL | / #[cfg_attr(foo, cfg(bar))]
+LL | | fn main() { }
+   | |_____________^ consider adding a `main` function to `$DIR/cfg-attr-cfg-2.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
index 22dbac766707d..45b757e928302 100644
--- a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
+++ b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
@@ -1,7 +1,7 @@
 macro_rules! foo {
     () => {
         #[cfg_attr(all(), unknown)]
-        //~^ ERROR cannot find attribute macro `unknown` in this scope
+        //~^ ERROR cannot find attribute `unknown` in this scope
         fn foo() {}
     }
 }
diff --git a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
index c7c52a2923a59..ef434ec82610e 100644
--- a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
+++ b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
@@ -1,4 +1,4 @@
-error: cannot find attribute macro `unknown` in this scope
+error: cannot find attribute `unknown` in this scope
   --> $DIR/cfg-attr-unknown-attribute-macro-expansion.rs:3:27
    |
 LL |         #[cfg_attr(all(), unknown)]
diff --git a/src/test/ui/conditional-compilation/cfg-generic-params.rs b/src/test/ui/conditional-compilation/cfg-generic-params.rs
index d80d3ea7b7fe9..53aa3556362f9 100644
--- a/src/test/ui/conditional-compilation/cfg-generic-params.rs
+++ b/src/test/ui/conditional-compilation/cfg-generic-params.rs
@@ -16,21 +16,23 @@ struct WhereBad where for<#[cfg(no)] 'a, #[cfg(yes)] T> u8: Copy;
 //~^ ERROR only lifetime parameters can be used in this context
 
 fn f_lt_no<#[cfg_attr(no, unknown)] 'a>() {} // OK
-fn f_lt_yes<#[cfg_attr(yes, unknown)] 'a>() {} //~ ERROR attribute `unknown` is currently unknown
+fn f_lt_yes<#[cfg_attr(yes, unknown)] 'a>() {}
+//~^ ERROR cannot find attribute `unknown` in this scope
 fn f_ty_no<#[cfg_attr(no, unknown)] T>() {} // OK
-fn f_ty_yes<#[cfg_attr(yes, unknown)] T>() {} //~ ERROR attribute `unknown` is currently unknown
+fn f_ty_yes<#[cfg_attr(yes, unknown)] T>() {}
+//~^ ERROR cannot find attribute `unknown` in this scope
 
 type FnNo = for<#[cfg_attr(no, unknown)] 'a> fn(); // OK
 type FnYes = for<#[cfg_attr(yes, unknown)] 'a> fn();
-//~^ ERROR attribute `unknown` is currently unknown
+//~^ ERROR cannot find attribute `unknown` in this scope
 
 type PolyNo = dyn for<#[cfg_attr(no, unknown)] 'a> Copy; // OK
 type PolyYes = dyn for<#[cfg_attr(yes, unknown)] 'a> Copy;
-//~^ ERROR attribute `unknown` is currently unknown
+//~^ ERROR cannot find attribute `unknown` in this scope
 
 struct WhereNo where for<#[cfg_attr(no, unknown)] 'a> u8: Copy; // OK
 struct WhereYes where for<#[cfg_attr(yes, unknown)] 'a> u8: Copy;
-//~^ ERROR attribute `unknown` is currently unknown
+//~^ ERROR cannot find attribute `unknown` in this scope
 
 fn main() {
     f_lt::<'static>();
diff --git a/src/test/ui/conditional-compilation/cfg-generic-params.stderr b/src/test/ui/conditional-compilation/cfg-generic-params.stderr
index 1f9731fcfbefb..d9e29c8262c63 100644
--- a/src/test/ui/conditional-compilation/cfg-generic-params.stderr
+++ b/src/test/ui/conditional-compilation/cfg-generic-params.stderr
@@ -16,51 +16,35 @@ error: only lifetime parameters can be used in this context
 LL | struct WhereBad where for<#[cfg(no)] 'a, #[cfg(yes)] T> u8: Copy;
    |                                                      ^
 
-error[E0658]: the attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/cfg-generic-params.rs:19:29
-   |
-LL | fn f_lt_yes<#[cfg_attr(yes, unknown)] 'a>() {}
-   |                             ^^^^^^^
+error: cannot find attribute `unknown` in this scope
+  --> $DIR/cfg-generic-params.rs:34:43
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | struct WhereYes where for<#[cfg_attr(yes, unknown)] 'a> u8: Copy;
+   |                                           ^^^^^^^
 
-error[E0658]: the attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/cfg-generic-params.rs:21:29
+error: cannot find attribute `unknown` in this scope
+  --> $DIR/cfg-generic-params.rs:30:40
    |
-LL | fn f_ty_yes<#[cfg_attr(yes, unknown)] T>() {}
-   |                             ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | type PolyYes = dyn for<#[cfg_attr(yes, unknown)] 'a> Copy;
+   |                                        ^^^^^^^
 
-error[E0658]: the attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/cfg-generic-params.rs:24:34
+error: cannot find attribute `unknown` in this scope
+  --> $DIR/cfg-generic-params.rs:26:34
    |
 LL | type FnYes = for<#[cfg_attr(yes, unknown)] 'a> fn();
    |                                  ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/cfg-generic-params.rs:28:40
+error: cannot find attribute `unknown` in this scope
+  --> $DIR/cfg-generic-params.rs:22:29
    |
-LL | type PolyYes = dyn for<#[cfg_attr(yes, unknown)] 'a> Copy;
-   |                                        ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | fn f_ty_yes<#[cfg_attr(yes, unknown)] T>() {}
+   |                             ^^^^^^^
 
-error[E0658]: the attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/cfg-generic-params.rs:32:43
-   |
-LL | struct WhereYes where for<#[cfg_attr(yes, unknown)] 'a> u8: Copy;
-   |                                           ^^^^^^^
+error: cannot find attribute `unknown` in this scope
+  --> $DIR/cfg-generic-params.rs:19:29
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | fn f_lt_yes<#[cfg_attr(yes, unknown)] 'a>() {}
+   |                             ^^^^^^^
 
 error: aborting due to 8 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/conditional-compilation/cfg-in-crate-1.stderr b/src/test/ui/conditional-compilation/cfg-in-crate-1.stderr
index c6d42c732c934..0b5c3e0335586 100644
--- a/src/test/ui/conditional-compilation/cfg-in-crate-1.stderr
+++ b/src/test/ui/conditional-compilation/cfg-in-crate-1.stderr
@@ -1,6 +1,8 @@
 error[E0601]: `main` function not found in crate `cfg_in_crate_1`
+  --> $DIR/cfg-in-crate-1.rs:3:1
    |
-   = note: consider adding a `main` function to `$DIR/cfg-in-crate-1.rs`
+LL | #![cfg(bar)]
+   | ^^^^^^^^^^^^ consider adding a `main` function to `$DIR/cfg-in-crate-1.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/apit-with-const-param.rs b/src/test/ui/const-generics/apit-with-const-param.rs
index 70e718d889029..7acc50819a6ad 100644
--- a/src/test/ui/const-generics/apit-with-const-param.rs
+++ b/src/test/ui/const-generics/apit-with-const-param.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
diff --git a/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.stderr b/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.stderr
index 09652d99e8ea5..594a0d4b5d844 100644
--- a/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.stderr
+++ b/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.stderr
@@ -8,10 +8,10 @@ LL |     println!("{:?}", [0_usize; 33]);
    = note: required by `std::fmt::Debug::fmt`
 
 error[E0277]: arrays only have std trait implementations for lengths 0..=32
-  --> $DIR/core-traits-no-impls-length-33.rs:9:9
+  --> $DIR/core-traits-no-impls-length-33.rs:9:16
    |
 LL |     set.insert([0_usize; 33]);
-   |         ^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[usize; 33]`
+   |                ^^^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[usize; 33]`
    |
    = note: required because of the requirements on the impl of `std::cmp::Eq` for `[usize; 33]`
 
diff --git a/src/test/ui/const-generics/array-wrapper-struct-ctor.rs b/src/test/ui/const-generics/array-wrapper-struct-ctor.rs
index d83846fcf88d4..2d1a405ebdd80 100644
--- a/src/test/ui/const-generics/array-wrapper-struct-ctor.rs
+++ b/src/test/ui/const-generics/array-wrapper-struct-ctor.rs
@@ -3,6 +3,8 @@
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
+#![allow(dead_code)]
+
 struct ArrayStruct<T, const N: usize> {
     data: [T; N],
 }
diff --git a/src/test/ui/const-generics/const-types.rs b/src/test/ui/const-generics/const-types.rs
index 11757cd588dab..bc5188133d7f1 100644
--- a/src/test/ui/const-generics/const-types.rs
+++ b/src/test/ui/const-generics/const-types.rs
@@ -3,7 +3,7 @@
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
-#[allow(dead_code)]
+#![allow(dead_code, unused_variables)]
 
 struct ConstArray<T, const LEN: usize> {
     array: [T; LEN],
diff --git a/src/test/ui/const-generics/foreign-item-const-parameter.rs b/src/test/ui/const-generics/foreign-item-const-parameter.rs
new file mode 100644
index 0000000000000..4673c8606c393
--- /dev/null
+++ b/src/test/ui/const-generics/foreign-item-const-parameter.rs
@@ -0,0 +1,10 @@
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+extern "C" {
+    fn foo<const X: usize>(); //~ ERROR foreign items may not have const parameters
+
+    fn bar<T, const X: usize>(_: T); //~ ERROR foreign items may not have type or const parameters
+}
+
+fn main() {}
diff --git a/src/test/ui/const-generics/foreign-item-const-parameter.stderr b/src/test/ui/const-generics/foreign-item-const-parameter.stderr
new file mode 100644
index 0000000000000..999feed2d3b20
--- /dev/null
+++ b/src/test/ui/const-generics/foreign-item-const-parameter.stderr
@@ -0,0 +1,27 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/foreign-item-const-parameter.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0044]: foreign items may not have const parameters
+  --> $DIR/foreign-item-const-parameter.rs:5:5
+   |
+LL |     fn foo<const X: usize>();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ can't have const parameters
+   |
+   = help: replace the const parameters with concrete consts
+
+error[E0044]: foreign items may not have type or const parameters
+  --> $DIR/foreign-item-const-parameter.rs:7:5
+   |
+LL |     fn bar<T, const X: usize>(_: T);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't have type or const parameters
+   |
+   = help: replace the type or const parameters with concrete types or consts
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0044`.
diff --git a/src/test/ui/const-generics/invalid-const-arg-for-type-param.stderr b/src/test/ui/const-generics/invalid-const-arg-for-type-param.stderr
index 8f3f91651edfb..47b090cb88678 100644
--- a/src/test/ui/const-generics/invalid-const-arg-for-type-param.stderr
+++ b/src/test/ui/const-generics/invalid-const-arg-for-type-param.stderr
@@ -11,7 +11,7 @@ LL | struct S;
    | --------- method `f` not found for this
 ...
 LL |     S.f::<0>();
-   |       ^
+   |       ^ method not found in `S`
 
 error[E0107]: wrong number of const arguments: expected 0, found 1
   --> $DIR/invalid-const-arg-for-type-param.rs:8:9
diff --git a/src/test/ui/const-generics/issue-61422.rs b/src/test/ui/const-generics/issue-61422.rs
index 68e5a52e0ac5c..45d37b6a2f3c5 100644
--- a/src/test/ui/const-generics/issue-61422.rs
+++ b/src/test/ui/const-generics/issue-61422.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
@@ -8,7 +8,7 @@ use std::mem;
 fn foo<const SIZE: usize>() {
     let arr: [u8; SIZE] = unsafe {
         #[allow(deprecated)]
-        let mut array: [u8; SIZE] = mem::uninitialized();
+        let array: [u8; SIZE] = mem::uninitialized();
         array
     };
 }
diff --git a/src/test/ui/const-generics/unused-const-param.rs b/src/test/ui/const-generics/unused-const-param.rs
index ee98e5eb4a01f..8025b3af8f1bf 100644
--- a/src/test/ui/const-generics/unused-const-param.rs
+++ b/src/test/ui/const-generics/unused-const-param.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
diff --git a/src/test/ui/consts/const-err4.stderr b/src/test/ui/consts/const-err4.stderr
index 1feec3c21c0a5..081b09e33006f 100644
--- a/src/test/ui/consts/const-err4.stderr
+++ b/src/test/ui/consts/const-err4.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr b/src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr
index 3333ffac4c9b0..e0df787f80a44 100644
--- a/src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr
+++ b/src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_USIZE_UNION: usize = unsafe { Nonsense { int_32_ref: &3 }.u };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:28:43
@@ -38,7 +38,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_U64_UNION: u64 = unsafe { Nonsense { int_32_ref: &3 }.uint_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/const-pointer-values-in-various-types.rs:40:5
@@ -46,7 +46,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_U128_UNION: u128 = unsafe { Nonsense { int_32_ref: &3 }.uint_128 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:43:43
@@ -78,7 +78,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_I64_UNION: i64 = unsafe { Nonsense { int_32_ref: &3 }.int_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/const-pointer-values-in-various-types.rs:55:5
@@ -86,7 +86,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_I128_UNION: i128 = unsafe { Nonsense { int_32_ref: &3 }.int_128 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:58:45
@@ -102,7 +102,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const I32_REF_F64_UNION: f64 = unsafe { Nonsense { int_32_ref: &3 }.float_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:64:47
@@ -150,7 +150,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const STR_U64_UNION: u64 = unsafe { Nonsense { stringy: "3" }.uint_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:82:43
@@ -190,7 +190,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const STR_I64_UNION: i64 = unsafe { Nonsense { stringy: "3" }.int_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:97:43
@@ -214,7 +214,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const STR_F64_UNION: f64 = unsafe { Nonsense { stringy: "3" }.float_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:106:43
diff --git a/src/test/ui/consts/const-eval/const_transmute.rs b/src/test/ui/consts/const-eval/const_transmute.rs
index 4a7d8490ef25f..f0e1d8263022b 100644
--- a/src/test/ui/consts/const-eval/const_transmute.rs
+++ b/src/test/ui/consts/const-eval/const_transmute.rs
@@ -1,6 +1,7 @@
 // run-pass
 
 #![feature(const_fn_union)]
+#![allow(dead_code)]
 
 #[repr(C)]
 union Transmute<T: Copy, U: Copy> {
diff --git a/src/test/ui/consts/const-eval/double_check2.stderr b/src/test/ui/consts/const-eval/double_check2.stderr
index 9c56f1995208f..28e0922ecafa6 100644
--- a/src/test/ui/consts/const-eval/double_check2.stderr
+++ b/src/test/ui/consts/const-eval/double_check2.stderr
@@ -7,7 +7,7 @@ LL | |     Union { u8: &BAR }.bar,
 LL | | )};
    | |___^ type validation failed: encountered 5 at .1.<deref>, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/ref_to_int_match.stderr b/src/test/ui/consts/const-eval/ref_to_int_match.stderr
index 0be82e3434142..b72a5b80afa8d 100644
--- a/src/test/ui/consts/const-eval/ref_to_int_match.stderr
+++ b/src/test/ui/consts/const-eval/ref_to_int_match.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAR: Int = unsafe { Foo { r: &42 }.f };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: could not evaluate constant pattern
   --> $DIR/ref_to_int_match.rs:7:14
diff --git a/src/test/ui/consts/const-eval/transmute-const.stderr b/src/test/ui/consts/const-eval/transmute-const.stderr
index cacf86364796f..47f89fccf7a81 100644
--- a/src/test/ui/consts/const-eval/transmute-const.stderr
+++ b/src/test/ui/consts/const-eval/transmute-const.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | static FOO: bool = unsafe { mem::transmute(3u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3, but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/ub-enum.stderr b/src/test/ui/consts/const-eval/ub-enum.stderr
index 30dd86592d469..8ebc9dbec8ab2 100644
--- a/src/test/ui/consts/const-eval/ub-enum.stderr
+++ b/src/test/ui/consts/const-eval/ub-enum.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM: Enum = unsafe { TransmuteEnum { in2: 1 }.out1 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 1, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:26:1
@@ -12,7 +12,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM_PTR: Enum = unsafe { TransmuteEnum { in1: &1 }.out1 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:29:1
@@ -20,7 +20,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM_WRAPPED: Wrap<Enum> = unsafe { TransmuteEnum { in1: &1 }.out2 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected something that cannot possibly fail to be equal to 0
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:48:1
@@ -28,7 +28,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM2: Enum2 = unsafe { TransmuteEnum2 { in1: 0 }.out1 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:50:1
@@ -36,7 +36,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM2_PTR: Enum2 = unsafe { TransmuteEnum2 { in2: &0 }.out1 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:52:1
@@ -44,7 +44,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM2_WRAPPED: Wrap<Enum2> = unsafe { TransmuteEnum2 { in2: &0 }.out2 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected something that cannot possibly fail to be equal to 2
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:56:1
@@ -52,7 +52,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM2_UNDEF : Enum2 = unsafe { TransmuteEnum2 { in3: () }.out1 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:60:1
@@ -60,7 +60,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_ENUM2_OPTION_PTR: Option<Enum2> = unsafe { TransmuteEnum2 { in2: &0 }.out3 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:71:1
@@ -68,7 +68,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_OPTION_CHAR: Option<(char, char)> = Some(('x', unsafe { TransmuteChar { a: !0 }.b }));
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 4294967295 at .<downcast-variant(Some)>.0.1, but expected something less or equal to 1114111
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/consts/const-eval/ub-nonnull.stderr b/src/test/ui/consts/const-eval/ub-nonnull.stderr
index de20c3d0b8cfe..80d80a986751e 100644
--- a/src/test/ui/consts/const-eval/ub-nonnull.stderr
+++ b/src/test/ui/consts/const-eval/ub-nonnull.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const NULL_PTR: NonNull<u8> = unsafe { mem::transmute(0usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: any use of this value will cause an error
   --> $DIR/ub-nonnull.rs:18:29
@@ -30,7 +30,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const NULL_U8: NonZeroU8 = unsafe { mem::transmute(0u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:24:1
@@ -38,7 +38,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const NULL_USIZE: NonZeroUsize = unsafe { mem::transmute(0usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:32:1
@@ -46,7 +46,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const UNINIT: NonZeroU8 = unsafe { Transmute { uninit: () }.out };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:40:1
@@ -54,7 +54,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_RANGE1: RestrictedRange1 = unsafe { RestrictedRange1(42) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 42, but expected something in the range 10..=30
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:46:1
@@ -62,7 +62,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_RANGE2: RestrictedRange2 = unsafe { RestrictedRange2(20) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 20, but expected something less or equal to 10, or greater or equal to 30
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/consts/const-eval/ub-ref.stderr b/src/test/ui/consts/const-eval/ub-ref.stderr
index cd3cc38467c36..01bde413c0d9c 100644
--- a/src/test/ui/consts/const-eval/ub-ref.stderr
+++ b/src/test/ui/consts/const-eval/ub-ref.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered unaligned reference (required 2 byte alignment but found 1)
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:11:1
@@ -12,7 +12,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const NULL: &u16 = unsafe { mem::transmute(0usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:17:1
@@ -20,7 +20,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:20:1
@@ -28,7 +28,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const REF_AS_USIZE_SLICE: &[usize] = &[unsafe { mem::transmute(&0) }];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<deref>, but expected plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:23:1
@@ -36,7 +36,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (created from integer)
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/consts/const-eval/ub-uninhabit.stderr b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
index 43d91483797bf..3877f3cab6d44 100644
--- a/src/test/ui/consts/const-eval/ub-uninhabit.stderr
+++ b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_BAD_BAD: Bar = unsafe { (TransmuteUnion::<(), Bar> { a: () }).b };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:18:1
@@ -12,7 +12,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:21:1
@@ -20,7 +20,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_BAD_ARRAY: [Bar; 1] = unsafe { (TransmuteUnion::<(), [Bar; 1]> { a: () }).b };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/consts/const-eval/ub-upvars.stderr b/src/test/ui/consts/const-eval/ub-upvars.stderr
index f8273ba902a88..ea6ab3ae5b5ba 100644
--- a/src/test/ui/consts/const-eval/ub-upvars.stderr
+++ b/src/test/ui/consts/const-eval/ub-upvars.stderr
@@ -8,7 +8,7 @@ LL | |     move || { let _ = bad_ref; let _ = another_var; }
 LL | | };
    | |__^ type validation failed: encountered 0 at .<deref>.<dyn-downcast>.<closure-var(bad_ref)>, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
index aadabc323fbd4..9134ef5a31ad9 100644
--- a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
+++ b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const STR_TOO_LONG: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (not entirely in bounds)
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:90:1
@@ -12,7 +12,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const STR_LENGTH_PTR: &str = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.str};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:93:1
@@ -20,7 +20,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const MY_STR_LENGTH_PTR: &MyStr = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.my_str};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:97:1
@@ -28,7 +28,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const STR_NO_UTF8: &str = unsafe { SliceTransmute { slice: &[0xFF] }.str };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized or non-UTF-8 data in str at .<deref>
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:100:1
@@ -36,7 +36,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const MYSTR_NO_UTF8: &MyStr = unsafe { SliceTransmute { slice: &[0xFF] }.my_str };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized or non-UTF-8 data in str at .<deref>.0
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:107:1
@@ -44,7 +44,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const SLICE_LENGTH_UNINIT: &[u8] = unsafe { SliceTransmute { addr: 42 }.slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in wide pointer metadata
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:110:1
@@ -52,7 +52,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const SLICE_TOO_LONG: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (not entirely in bounds)
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:113:1
@@ -60,7 +60,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const SLICE_LENGTH_PTR: &[u8] = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:117:1
@@ -68,7 +68,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const SLICE_CONTENT_INVALID: &[bool] = &[unsafe { BoolTransmute { val: 3 }.bl }];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>[0], but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:123:1
@@ -76,7 +76,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const MYSLICE_PREFIX_BAD: &MySliceBool = &MySlice(unsafe { BoolTransmute { val: 3 }.bl }, [false]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.0, but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:126:1
@@ -84,7 +84,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const MYSLICE_SUFFIX_BAD: &MySliceBool = &MySlice(true, [unsafe { BoolTransmute { val: 3 }.bl }]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.1[0], but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:133:1
@@ -92,7 +92,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const RAW_SLICE_LENGTH_UNINIT: *const [u8] = unsafe { SliceTransmute { addr: 42 }.raw_slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in wide pointer metadata
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:138:1
@@ -100,7 +100,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const TRAIT_OBJ_SHORT_VTABLE_1: &dyn Trait = unsafe { DynTransmute { repr: DynRepr { ptr: &92, vtable: &3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:141:1
@@ -108,7 +108,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const TRAIT_OBJ_SHORT_VTABLE_2: &dyn Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:144:1
@@ -116,7 +116,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:148:1
@@ -124,7 +124,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.<dyn-downcast>, but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:152:1
@@ -132,7 +132,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const RAW_TRAIT_OBJ_VTABLE_NULL: *const dyn Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 0 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:154:1
@@ -140,7 +140,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const RAW_TRAIT_OBJ_VTABLE_INVALID: *const dyn Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.raw_rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 18 previous errors
 
diff --git a/src/test/ui/consts/const-eval/union-const-eval-field.stderr b/src/test/ui/consts/const-eval/union-const-eval-field.stderr
index 4d008a0e02ad7..9193bd9dea189 100644
--- a/src/test/ui/consts/const-eval/union-const-eval-field.stderr
+++ b/src/test/ui/consts/const-eval/union-const-eval-field.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL |     const FIELD3: Field3 = unsafe { UNION.field3 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/union-ice.stderr b/src/test/ui/consts/const-eval/union-ice.stderr
index 8d950e86d27fc..476f3651740ab 100644
--- a/src/test/ui/consts/const-eval/union-ice.stderr
+++ b/src/test/ui/consts/const-eval/union-ice.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const FIELD3: Field3 = unsafe { UNION.field3 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/union-ice.rs:16:1
@@ -15,7 +15,7 @@ LL | |     b: unsafe { UNION.field3 },
 LL | | };
    | |__^ type validation failed: encountered uninitialized bytes at .b, but expected initialized plain (non-pointer) bytes
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/union-ice.rs:26:1
@@ -29,7 +29,7 @@ LL | |     a: 42,
 LL | | };
    | |__^ type validation failed: encountered undefined bytes at .b[1]
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/consts/const-eval/union-ub.stderr b/src/test/ui/consts/const-eval/union-ub.stderr
index 6a3a397585c89..fa67bc0d8e7b5 100644
--- a/src/test/ui/consts/const-eval/union-ub.stderr
+++ b/src/test/ui/consts/const-eval/union-ub.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const BAD_BOOL: bool = unsafe { DummyUnion { u8: 42 }.bool};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 42, but expected something less or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-int-overflowing-rpass.rs b/src/test/ui/consts/const-int-overflowing-rpass.rs
index b619c7908aa22..9be87a6447cda 100644
--- a/src/test/ui/consts/const-int-overflowing-rpass.rs
+++ b/src/test/ui/consts/const-int-overflowing-rpass.rs
@@ -18,6 +18,10 @@ const SHR_B: (u32, bool) = 0x10u32.overflowing_shr(132);
 const NEG_A: (u32, bool) = 0u32.overflowing_neg();
 const NEG_B: (u32, bool) = core::u32::MAX.overflowing_neg();
 
+const ABS_POS: (i32, bool) = 10i32.overflowing_abs();
+const ABS_NEG: (i32, bool) = (-10i32).overflowing_abs();
+const ABS_MIN: (i32, bool) = i32::min_value().overflowing_abs();
+
 fn main() {
     assert_eq!(ADD_A, (7, false));
     assert_eq!(ADD_B, (0, true));
@@ -36,4 +40,8 @@ fn main() {
 
     assert_eq!(NEG_A, (0, false));
     assert_eq!(NEG_B, (1, true));
+
+    assert_eq!(ABS_POS, (10, false));
+    assert_eq!(ABS_NEG, (10, false));
+    assert_eq!(ABS_MIN, (i32::min_value(), true));
 }
diff --git a/src/test/ui/consts/const-int-sign-rpass.rs b/src/test/ui/consts/const-int-sign-rpass.rs
index 05726cb228647..dc46fce39a93c 100644
--- a/src/test/ui/consts/const-int-sign-rpass.rs
+++ b/src/test/ui/consts/const-int-sign-rpass.rs
@@ -11,6 +11,9 @@ const SIGNUM_POS: i32 = 10i32.signum();
 const SIGNUM_NIL: i32 = 0i32.signum();
 const SIGNUM_NEG: i32 = (-42i32).signum();
 
+const ABS_A: i32 = 10i32.abs();
+const ABS_B: i32 = (-10i32).abs();
+
 fn main() {
     assert!(NEGATIVE_A);
     assert!(!NEGATIVE_B);
@@ -20,4 +23,7 @@ fn main() {
     assert_eq!(SIGNUM_POS, 1);
     assert_eq!(SIGNUM_NIL, 0);
     assert_eq!(SIGNUM_NEG, -1);
+
+    assert_eq!(ABS_A, 10);
+    assert_eq!(ABS_B, 10);
 }
diff --git a/src/test/ui/consts/const-int-wrapping-rpass.rs b/src/test/ui/consts/const-int-wrapping-rpass.rs
index 73147d7912d19..2bbad99a52a90 100644
--- a/src/test/ui/consts/const-int-wrapping-rpass.rs
+++ b/src/test/ui/consts/const-int-wrapping-rpass.rs
@@ -18,6 +18,10 @@ const SHR_B: u32 = 128u32.wrapping_shr(128);
 const NEG_A: u32 = 5u32.wrapping_neg();
 const NEG_B: u32 = 1234567890u32.wrapping_neg();
 
+const ABS_POS: i32 = 10i32.wrapping_abs();
+const ABS_NEG: i32 = (-10i32).wrapping_abs();
+const ABS_MIN: i32 = i32::min_value().wrapping_abs();
+
 fn main() {
     assert_eq!(ADD_A, 255);
     assert_eq!(ADD_B, 199);
@@ -36,4 +40,8 @@ fn main() {
 
     assert_eq!(NEG_A, 4294967291);
     assert_eq!(NEG_B, 3060399406);
+
+    assert_eq!(ABS_POS, 10);
+    assert_eq!(ABS_NEG, 10);
+    assert_eq!(ABS_MIN, i32::min_value());
 }
diff --git a/src/test/ui/consts/const-labeled-break.rs b/src/test/ui/consts/const-labeled-break.rs
index 36e308ade9c54..7cdbb22f92459 100644
--- a/src/test/ui/consts/const-labeled-break.rs
+++ b/src/test/ui/consts/const-labeled-break.rs
@@ -1,4 +1,4 @@
-// run-pass
+// build-pass
 
 // Using labeled break in a while loop has caused an illegal instruction being
 // generated, and an ICE later.
diff --git a/src/test/ui/consts/const-match-check.eval1.stderr b/src/test/ui/consts/const-match-check.eval1.stderr
index 3bcb50c6dcf6f..24d2e3ce53937 100644
--- a/src/test/ui/consts/const-match-check.eval1.stderr
+++ b/src/test/ui/consts/const-match-check.eval1.stderr
@@ -1,8 +1,8 @@
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:25:15
    |
 LL |     A = { let 0 = 0; 0 },
-   |               ^ pattern `std::i32::MIN..=-1i32` not covered
+   |               ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-match-check.eval2.stderr b/src/test/ui/consts/const-match-check.eval2.stderr
index e292e1cc16585..5d59d06f7982a 100644
--- a/src/test/ui/consts/const-match-check.eval2.stderr
+++ b/src/test/ui/consts/const-match-check.eval2.stderr
@@ -1,8 +1,8 @@
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:31:24
    |
 LL |     let x: [i32; { let 0 = 0; 0 }] = [];
-   |                        ^ pattern `std::i32::MIN..=-1i32` not covered
+   |                        ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-match-check.matchck.stderr b/src/test/ui/consts/const-match-check.matchck.stderr
index 8a9fbde8537bf..6d74c26f9f7a5 100644
--- a/src/test/ui/consts/const-match-check.matchck.stderr
+++ b/src/test/ui/consts/const-match-check.matchck.stderr
@@ -1,26 +1,26 @@
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:4:22
    |
 LL | const X: i32 = { let 0 = 0; 0 };
-   |                      ^ pattern `std::i32::MIN..=-1i32` not covered
+   |                      ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:8:23
    |
 LL | static Y: i32 = { let 0 = 0; 0 };
-   |                       ^ pattern `std::i32::MIN..=-1i32` not covered
+   |                       ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:13:26
    |
 LL |     const X: i32 = { let 0 = 0; 0 };
-   |                          ^ pattern `std::i32::MIN..=-1i32` not covered
+   |                          ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
-error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` not covered
+error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:19:26
    |
 LL |     const X: i32 = { let 0 = 0; 0 };
-   |                          ^ pattern `std::i32::MIN..=-1i32` not covered
+   |                          ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/consts/const-pattern-irrefutable.rs b/src/test/ui/consts/const-pattern-irrefutable.rs
index d3f7be18a9839..60e16aaf89532 100644
--- a/src/test/ui/consts/const-pattern-irrefutable.rs
+++ b/src/test/ui/consts/const-pattern-irrefutable.rs
@@ -9,8 +9,8 @@ use foo::d;
 const a: u8 = 2;
 
 fn main() {
-    let a = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` not covered
-    let c = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` not covered
-    let d = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` not covered
+    let a = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX
+    let c = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX
+    let d = 4; //~ ERROR refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX
     fn f() {} // Check that the `NOTE`s still work with an item here (cf. issue #35115).
 }
diff --git a/src/test/ui/consts/const-pattern-irrefutable.stderr b/src/test/ui/consts/const-pattern-irrefutable.stderr
index 48fe24df4d044..06f5e90d2f1f7 100644
--- a/src/test/ui/consts/const-pattern-irrefutable.stderr
+++ b/src/test/ui/consts/const-pattern-irrefutable.stderr
@@ -1,16 +1,16 @@
-error[E0005]: refutable pattern in local binding: `0u8..=1u8` not covered
+error[E0005]: refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX` not covered
   --> $DIR/const-pattern-irrefutable.rs:12:9
    |
 LL |     let a = 4;
    |         ^ interpreted as a constant pattern, not new variable
 
-error[E0005]: refutable pattern in local binding: `0u8..=1u8` not covered
+error[E0005]: refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX` not covered
   --> $DIR/const-pattern-irrefutable.rs:13:9
    |
 LL |     let c = 4;
    |         ^ interpreted as a constant pattern, not new variable
 
-error[E0005]: refutable pattern in local binding: `0u8..=1u8` not covered
+error[E0005]: refutable pattern in local binding: `0u8..=1u8` and `3u8..=std::u8::MAX` not covered
   --> $DIR/const-pattern-irrefutable.rs:14:9
    |
 LL |     let d = 4;
diff --git a/src/test/ui/consts/const-size_of-cycle.stderr b/src/test/ui/consts/const-size_of-cycle.stderr
index fdba359e7464a..1ae39e7563a82 100644
--- a/src/test/ui/consts/const-size_of-cycle.stderr
+++ b/src/test/ui/consts/const-size_of-cycle.stderr
@@ -14,6 +14,11 @@ note: ...which requires const-evaluating `Foo::bytes::{{constant}}#0`...
    |
 LL |     intrinsics::size_of::<T>()
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires const-evaluating + checking `std::intrinsics::size_of`...
+  --> $SRC_DIR/libcore/intrinsics.rs:LL:COL
+   |
+LL |     pub fn size_of<T>() -> usize;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: ...which requires computing layout of `Foo`...
    = note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
    = note: ...which again requires const-evaluating + checking `Foo::bytes::{{constant}}#0`, completing the cycle
diff --git a/src/test/ui/consts/const_let_refutable.rs b/src/test/ui/consts/const_let_refutable.rs
index 7b3a591223025..d48d5945e7da9 100644
--- a/src/test/ui/consts/const_let_refutable.rs
+++ b/src/test/ui/consts/const_let_refutable.rs
@@ -2,6 +2,6 @@ fn main() {}
 
 const fn slice([a, b]: &[i32]) -> i32 { //~ ERROR refutable pattern in function argument
     a + b //~ ERROR can only call other `const fn` within a `const fn`
-    //~^ ERROR use of possibly uninitialized variable: `a`
-    //~| ERROR use of possibly uninitialized variable: `b`
+    //~^ ERROR use of possibly-uninitialized variable: `a`
+    //~| ERROR use of possibly-uninitialized variable: `b`
 }
diff --git a/src/test/ui/consts/const_let_refutable.stderr b/src/test/ui/consts/const_let_refutable.stderr
index a61c9b0c9fef9..7f15f02d4d37b 100644
--- a/src/test/ui/consts/const_let_refutable.stderr
+++ b/src/test/ui/consts/const_let_refutable.stderr
@@ -1,8 +1,8 @@
-error[E0005]: refutable pattern in function argument: `&[]` not covered
+error[E0005]: refutable pattern in function argument: `&[]`, `&[_]` and `&[_, _, _]` not covered
   --> $DIR/const_let_refutable.rs:3:16
    |
 LL | const fn slice([a, b]: &[i32]) -> i32 {
-   |                ^^^^^^ pattern `&[]` not covered
+   |                ^^^^^^ patterns `&[]`, `&[_]` and `&[_, _, _]` not covered
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const <&i32 as std::ops::Add>::add` is not stable as `const fn`
   --> $DIR/const_let_refutable.rs:4:5
@@ -13,17 +13,17 @@ LL |     a + b
    = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
-error[E0381]: use of possibly uninitialized variable: `a`
+error[E0381]: use of possibly-uninitialized variable: `a`
   --> $DIR/const_let_refutable.rs:4:5
    |
 LL |     a + b
-   |     ^ use of possibly uninitialized `a`
+   |     ^ use of possibly-uninitialized `a`
 
-error[E0381]: use of possibly uninitialized variable: `b`
+error[E0381]: use of possibly-uninitialized variable: `b`
   --> $DIR/const_let_refutable.rs:4:9
    |
 LL |     a + b
-   |         ^ use of possibly uninitialized `b`
+   |         ^ use of possibly-uninitialized `b`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/consts/match_ice.stderr b/src/test/ui/consts/match_ice.stderr
index 158581fcb1599..bf0bd3aca97a4 100644
--- a/src/test/ui/consts/match_ice.stderr
+++ b/src/test/ui/consts/match_ice.stderr
@@ -7,6 +7,9 @@ LL |         C => {}
 error[E0004]: non-exhaustive patterns: `&T` not covered
   --> $DIR/match_ice.rs:15:11
    |
+LL | struct T;
+   | --------- `T` defined here
+...
 LL |     match K {
    |           ^ pattern `&T` not covered
    |
diff --git a/src/test/ui/consts/miri_unleashed/enum_discriminants.rs b/src/test/ui/consts/miri_unleashed/enum_discriminants.rs
new file mode 100644
index 0000000000000..9f34fc73953a4
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/enum_discriminants.rs
@@ -0,0 +1,110 @@
+// compile-flags: -Zunleash-the-miri-inside-of-you
+// run-pass
+
+//! Make sure that we read and write enum discriminants correctly for corner cases caused
+//! by layout optimizations.
+
+const OVERFLOW: usize = {
+    // Tests for https://github.com/rust-lang/rust/issues/62138.
+    #[repr(u8)]
+    #[allow(dead_code)]
+    enum WithWraparoundInvalidValues {
+        X = 1,
+        Y = 254,
+    }
+
+    #[allow(dead_code)]
+    enum Foo {
+        A,
+        B,
+        C(WithWraparoundInvalidValues),
+    }
+
+    let x = Foo::B;
+    match x {
+        Foo::B => 0,
+        _ => panic!(),
+    }
+};
+
+const MORE_OVERFLOW: usize = {
+    pub enum Infallible {}
+
+    // The check that the `bool` field of `V1` is encoding a "niche variant"
+    // (i.e. not `V1`, so `V3` or `V4`) used to be mathematically incorrect,
+    // causing valid `V1` values to be interpreted as other variants.
+    #[allow(dead_code)]
+    pub enum E1 {
+        V1 { f: bool },
+        V2 { f: Infallible },
+        V3,
+        V4,
+    }
+
+    // Computing the discriminant used to be done using the niche type (here `u8`,
+    // from the `bool` field of `V1`), overflowing for variants with large enough
+    // indices (`V3` and `V4`), causing them to be interpreted as other variants.
+    #[allow(dead_code)]
+    pub enum E2<X> {
+        V1 { f: bool },
+
+        /*_00*/ _01(X), _02(X), _03(X), _04(X), _05(X), _06(X), _07(X),
+        _08(X), _09(X), _0A(X), _0B(X), _0C(X), _0D(X), _0E(X), _0F(X),
+        _10(X), _11(X), _12(X), _13(X), _14(X), _15(X), _16(X), _17(X),
+        _18(X), _19(X), _1A(X), _1B(X), _1C(X), _1D(X), _1E(X), _1F(X),
+        _20(X), _21(X), _22(X), _23(X), _24(X), _25(X), _26(X), _27(X),
+        _28(X), _29(X), _2A(X), _2B(X), _2C(X), _2D(X), _2E(X), _2F(X),
+        _30(X), _31(X), _32(X), _33(X), _34(X), _35(X), _36(X), _37(X),
+        _38(X), _39(X), _3A(X), _3B(X), _3C(X), _3D(X), _3E(X), _3F(X),
+        _40(X), _41(X), _42(X), _43(X), _44(X), _45(X), _46(X), _47(X),
+        _48(X), _49(X), _4A(X), _4B(X), _4C(X), _4D(X), _4E(X), _4F(X),
+        _50(X), _51(X), _52(X), _53(X), _54(X), _55(X), _56(X), _57(X),
+        _58(X), _59(X), _5A(X), _5B(X), _5C(X), _5D(X), _5E(X), _5F(X),
+        _60(X), _61(X), _62(X), _63(X), _64(X), _65(X), _66(X), _67(X),
+        _68(X), _69(X), _6A(X), _6B(X), _6C(X), _6D(X), _6E(X), _6F(X),
+        _70(X), _71(X), _72(X), _73(X), _74(X), _75(X), _76(X), _77(X),
+        _78(X), _79(X), _7A(X), _7B(X), _7C(X), _7D(X), _7E(X), _7F(X),
+        _80(X), _81(X), _82(X), _83(X), _84(X), _85(X), _86(X), _87(X),
+        _88(X), _89(X), _8A(X), _8B(X), _8C(X), _8D(X), _8E(X), _8F(X),
+        _90(X), _91(X), _92(X), _93(X), _94(X), _95(X), _96(X), _97(X),
+        _98(X), _99(X), _9A(X), _9B(X), _9C(X), _9D(X), _9E(X), _9F(X),
+        _A0(X), _A1(X), _A2(X), _A3(X), _A4(X), _A5(X), _A6(X), _A7(X),
+        _A8(X), _A9(X), _AA(X), _AB(X), _AC(X), _AD(X), _AE(X), _AF(X),
+        _B0(X), _B1(X), _B2(X), _B3(X), _B4(X), _B5(X), _B6(X), _B7(X),
+        _B8(X), _B9(X), _BA(X), _BB(X), _BC(X), _BD(X), _BE(X), _BF(X),
+        _C0(X), _C1(X), _C2(X), _C3(X), _C4(X), _C5(X), _C6(X), _C7(X),
+        _C8(X), _C9(X), _CA(X), _CB(X), _CC(X), _CD(X), _CE(X), _CF(X),
+        _D0(X), _D1(X), _D2(X), _D3(X), _D4(X), _D5(X), _D6(X), _D7(X),
+        _D8(X), _D9(X), _DA(X), _DB(X), _DC(X), _DD(X), _DE(X), _DF(X),
+        _E0(X), _E1(X), _E2(X), _E3(X), _E4(X), _E5(X), _E6(X), _E7(X),
+        _E8(X), _E9(X), _EA(X), _EB(X), _EC(X), _ED(X), _EE(X), _EF(X),
+        _F0(X), _F1(X), _F2(X), _F3(X), _F4(X), _F5(X), _F6(X), _F7(X),
+        _F8(X), _F9(X), _FA(X), _FB(X), _FC(X), _FD(X), _FE(X), _FF(X),
+
+        V3,
+        V4,
+    }
+
+    if let E1::V2 { .. } = (E1::V1 { f: true }) {
+        unreachable!()
+    }
+    if let E1::V1 { .. } = (E1::V1 { f: true }) {
+    } else {
+        unreachable!()
+    }
+
+    if let E2::V1 { .. } = E2::V3::<Infallible> {
+        unreachable!()
+    }
+    if let E2::V3 { .. } = E2::V3::<Infallible> {
+    } else {
+        unreachable!()
+    }
+
+    0
+};
+
+fn main() {
+    assert_eq!(OVERFLOW, 0);
+    assert_eq!(MORE_OVERFLOW, 0);
+}
diff --git a/src/test/ui/consts/miri_unleashed/enum_discriminants.stderr b/src/test/ui/consts/miri_unleashed/enum_discriminants.stderr
new file mode 100644
index 0000000000000..8ca81ad22b72b
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/enum_discriminants.stderr
@@ -0,0 +1,72 @@
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:23:13
+   |
+LL |     let x = Foo::B;
+   |             ^^^^^^
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:25:9
+   |
+LL |         Foo::B => 0,
+   |         ^^^^^^
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:88:28
+   |
+LL |     if let E1::V2 { .. } = (E1::V1 { f: true }) {
+   |                            ^^^^^^^^^^^^^^^^^^^^
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:88:12
+   |
+LL |     if let E1::V2 { .. } = (E1::V1 { f: true }) {
+   |            ^^^^^^^^^^^^^
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:108:5
+   |
+LL |     assert_eq!(OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:108:5
+   |
+LL |     assert_eq!(OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:108:5
+   |
+LL |     assert_eq!(OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:109:5
+   |
+LL |     assert_eq!(MORE_OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:109:5
+   |
+LL |     assert_eq!(MORE_OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+warning: skipping const checks
+  --> $DIR/enum_discriminants.rs:109:5
+   |
+LL |     assert_eq!(MORE_OVERFLOW, 0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
diff --git a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
index 5fb92535502a5..8b17f6885ad3e 100644
--- a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
+++ b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
@@ -14,8 +14,9 @@ trait Bar<T, U: Foo<T>> {
 impl Foo<u32> for () {
     const X: u32 = 42;
 }
+
 impl Foo<Vec<u32>> for String {
-    const X: Vec<u32> = Vec::new(); //~ ERROR not yet stable as a const fn
+    const X: Vec<u32> = Vec::new();
 }
 
 impl Bar<u32, ()> for () {}
diff --git a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
index c56ebf60df481..5bc7b70638c80 100644
--- a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
+++ b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
@@ -4,13 +4,5 @@ error[E0493]: destructors cannot be evaluated at compile-time
 LL |     const F: u32 = (U::X, 42).1;
    |                    ^^^^^^^^^^ constants cannot evaluate destructors
 
-error: `std::vec::Vec::<T>::new` is not yet stable as a const fn
-  --> $DIR/feature-gate-unleash_the_miri_inside_of_you.rs:18:25
-   |
-LL |     const X: Vec<u32> = Vec::new();
-   |                         ^^^^^^^^^^
-   |
-   = help: add `#![feature(const_vec_new)]` to the crate attributes to enable
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
diff --git a/src/test/ui/consts/miri_unleashed/mutable_const.rs b/src/test/ui/consts/miri_unleashed/mutable_const.rs
new file mode 100644
index 0000000000000..b476e04529a52
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/mutable_const.rs
@@ -0,0 +1,20 @@
+// compile-flags: -Zunleash-the-miri-inside-of-you
+
+#![feature(const_raw_ptr_deref)]
+#![deny(const_err)]
+
+use std::cell::UnsafeCell;
+
+// make sure we do not just intern this as mutable
+const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+
+const MUTATING_BEHIND_RAW: () = {
+    // Test that `MUTABLE_BEHIND_RAW` is actually immutable, by doing this at const time.
+    unsafe {
+        *MUTABLE_BEHIND_RAW = 99 //~ WARN skipping const checks
+        //~^ ERROR any use of this value will cause an error
+        //~^^ tried to modify constant memory
+    }
+};
+
+fn main() {}
diff --git a/src/test/ui/consts/miri_unleashed/mutable_const.stderr b/src/test/ui/consts/miri_unleashed/mutable_const.stderr
new file mode 100644
index 0000000000000..507d4823a111d
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/mutable_const.stderr
@@ -0,0 +1,27 @@
+warning: skipping const checks
+  --> $DIR/mutable_const.rs:14:9
+   |
+LL |         *MUTABLE_BEHIND_RAW = 99
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: any use of this value will cause an error
+  --> $DIR/mutable_const.rs:14:9
+   |
+LL | / const MUTATING_BEHIND_RAW: () = {
+LL | |     // Test that `MUTABLE_BEHIND_RAW` is actually immutable, by doing this at const time.
+LL | |     unsafe {
+LL | |         *MUTABLE_BEHIND_RAW = 99
+   | |         ^^^^^^^^^^^^^^^^^^^^^^^^ tried to modify constant memory
+...  |
+LL | |     }
+LL | | };
+   | |__-
+   |
+note: lint level defined here
+  --> $DIR/mutable_const.rs:4:9
+   |
+LL | #![deny(const_err)]
+   |         ^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/consts/miri_unleashed/mutable_references_ice.stderr b/src/test/ui/consts/miri_unleashed/mutable_references_ice.stderr
index 82569e260143c..28cf3537d605a 100644
--- a/src/test/ui/consts/miri_unleashed/mutable_references_ice.stderr
+++ b/src/test/ui/consts/miri_unleashed/mutable_references_ice.stderr
@@ -6,7 +6,7 @@ LL |         *MUH.x.get() = 99;
 
 thread 'rustc' panicked at 'assertion failed: `(left != right)`
   left: `Const`,
- right: `Const`: UnsafeCells are not allowed behind references in constants. This should have been prevented statically by const qualification. If this were allowed one would be able to change a constant at one use site and other use sites may arbitrarily decide to change, too.', src/librustc_mir/interpret/intern.rs:LL:CC
+ right: `Const`: UnsafeCells are not allowed behind references in constants. This should have been prevented statically by const qualification. If this were allowed one would be able to change a constant at one use site and other use sites could observe that mutation.', src/librustc_mir/interpret/intern.rs:LL:CC
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
 error: internal compiler error: unexpected panic
diff --git a/src/test/ui/consts/packed_pattern.stderr b/src/test/ui/consts/packed_pattern.stderr
new file mode 100644
index 0000000000000..9b7daf2e674fb
--- /dev/null
+++ b/src/test/ui/consts/packed_pattern.stderr
@@ -0,0 +1,8 @@
+warning: unreachable pattern
+  --> $DIR/packed_pattern.rs:16:9
+   |
+LL |         FOO => unreachable!(),
+   |         ^^^
+   |
+   = note: `#[warn(unreachable_patterns)]` on by default
+
diff --git a/src/test/ui/consts/packed_pattern2.stderr b/src/test/ui/consts/packed_pattern2.stderr
new file mode 100644
index 0000000000000..6cc0225d3043d
--- /dev/null
+++ b/src/test/ui/consts/packed_pattern2.stderr
@@ -0,0 +1,8 @@
+warning: unreachable pattern
+  --> $DIR/packed_pattern2.rs:24:9
+   |
+LL |         FOO => unreachable!(),
+   |         ^^^
+   |
+   = note: `#[warn(unreachable_patterns)]` on by default
+
diff --git a/src/test/ui/consts/std/alloc.stderr b/src/test/ui/consts/std/alloc.stderr
index 74a8f3daf6aaa..26b7a24ebfa6f 100644
--- a/src/test/ui/consts/std/alloc.stderr
+++ b/src/test/ui/consts/std/alloc.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const LAYOUT_INVALID: Layout = unsafe { Layout::from_size_align_unchecked(0x1000, 0x00) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0 at .align_, but expected something greater or equal to 1
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/validate_never_arrays.stderr b/src/test/ui/consts/validate_never_arrays.stderr
index 7a7d816873350..c4c7a33718279 100644
--- a/src/test/ui/consts/validate_never_arrays.stderr
+++ b/src/test/ui/consts/validate_never_arrays.stderr
@@ -4,7 +4,7 @@ error[E0080]: it is undefined behavior to use this value
 LL | const FOO: &[!; 1] = unsafe { &*(1_usize as *const [!; 1]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/continue-after-missing-main.nll.stderr b/src/test/ui/continue-after-missing-main.nll.stderr
index aceabf3316479..b94c365f2539a 100644
--- a/src/test/ui/continue-after-missing-main.nll.stderr
+++ b/src/test/ui/continue-after-missing-main.nll.stderr
@@ -1,6 +1,14 @@
 error[E0601]: `main` function not found in crate `continue_after_missing_main`
+  --> $DIR/continue-after-missing-main.rs:1:1
    |
-   = note: consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
+LL | / #![allow(dead_code)]
+LL | |
+LL | | // error-pattern:`main` function not found in crate
+LL | |
+...  |
+LL | |
+LL | | }
+   | |_^ consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/continue-after-missing-main.stderr b/src/test/ui/continue-after-missing-main.stderr
index cc5f87659079e..d764e7d860af6 100644
--- a/src/test/ui/continue-after-missing-main.stderr
+++ b/src/test/ui/continue-after-missing-main.stderr
@@ -1,6 +1,14 @@
 error[E0601]: `main` function not found in crate `continue_after_missing_main`
+  --> $DIR/continue-after-missing-main.rs:1:1
    |
-   = note: consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
+LL | / #![allow(dead_code)]
+LL | |
+LL | | // error-pattern:`main` function not found in crate
+LL | |
+...  |
+LL | |
+LL | | }
+   | |_^ consider adding a `main` function to `$DIR/continue-after-missing-main.rs`
 
 error[E0623]: lifetime mismatch
   --> $DIR/continue-after-missing-main.rs:30:56
diff --git a/src/test/ui/copy-a-resource.stderr b/src/test/ui/copy-a-resource.stderr
index cceb9e328b676..054bd0914d31c 100644
--- a/src/test/ui/copy-a-resource.stderr
+++ b/src/test/ui/copy-a-resource.stderr
@@ -5,7 +5,7 @@ LL | struct Foo {
    | ---------- method `clone` not found for this
 ...
 LL |     let _y = x.clone();
-   |                ^^^^^
+   |                ^^^^^ method not found in `Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `clone`, perhaps you need to implement it:
diff --git a/src/test/ui/custom_attribute.rs b/src/test/ui/custom_attribute.rs
index 13c873c3b7e48..4957184229da0 100644
--- a/src/test/ui/custom_attribute.rs
+++ b/src/test/ui/custom_attribute.rs
@@ -1,9 +1,9 @@
 #![feature(stmt_expr_attributes)]
 
-#[foo] //~ ERROR cannot find attribute macro `foo` in this scope
+#[foo] //~ ERROR cannot find attribute `foo` in this scope
 fn main() {
-    #[foo] //~ ERROR cannot find attribute macro `foo` in this scope
+    #[foo] //~ ERROR cannot find attribute `foo` in this scope
     let x = ();
-    #[foo] //~ ERROR cannot find attribute macro `foo` in this scope
+    #[foo] //~ ERROR cannot find attribute `foo` in this scope
     x
 }
diff --git a/src/test/ui/custom_attribute.stderr b/src/test/ui/custom_attribute.stderr
index b4f9f3f49b235..4023892d29466 100644
--- a/src/test/ui/custom_attribute.stderr
+++ b/src/test/ui/custom_attribute.stderr
@@ -1,16 +1,16 @@
-error: cannot find attribute macro `foo` in this scope
+error: cannot find attribute `foo` in this scope
   --> $DIR/custom_attribute.rs:3:3
    |
 LL | #[foo]
    |   ^^^
 
-error: cannot find attribute macro `foo` in this scope
+error: cannot find attribute `foo` in this scope
   --> $DIR/custom_attribute.rs:5:7
    |
 LL |     #[foo]
    |       ^^^
 
-error: cannot find attribute macro `foo` in this scope
+error: cannot find attribute `foo` in this scope
   --> $DIR/custom_attribute.rs:7:7
    |
 LL |     #[foo]
diff --git a/src/test/ui/dead-code-ret.stderr b/src/test/ui/dead-code-ret.stderr
index 092a176f443b2..0ce31ea40ddbb 100644
--- a/src/test/ui/dead-code-ret.stderr
+++ b/src/test/ui/dead-code-ret.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/dead-code-ret.rs:6:5
+   |
+LL |     return;
+   |     ^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to previous error
diff --git a/src/test/ui/deprecation/deprecation-in-future.rs b/src/test/ui/deprecation/deprecation-in-future.rs
index c4f9fdce74907..464ddcc4cdb94 100644
--- a/src/test/ui/deprecation/deprecation-in-future.rs
+++ b/src/test/ui/deprecation/deprecation-in-future.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![deny(deprecated_in_future)]
 
diff --git a/src/test/ui/derives/derive-assoc-type-not-impl.stderr b/src/test/ui/derives/derive-assoc-type-not-impl.stderr
index b9e175e43d1cf..038de80508ac2 100644
--- a/src/test/ui/derives/derive-assoc-type-not-impl.stderr
+++ b/src/test/ui/derives/derive-assoc-type-not-impl.stderr
@@ -5,7 +5,7 @@ LL | struct Bar<T: Foo> {
    | ------------------ method `clone` not found for this
 ...
 LL |     Bar::<NotClone> { x: 1 }.clone();
-   |                              ^^^^^
+   |                              ^^^^^ method not found in `Bar<NotClone>`
    |
    = note: the method `clone` exists but the following trait bounds were not satisfied:
            `Bar<NotClone> : std::clone::Clone`
diff --git a/src/test/ui/derives/deriving-copyclone.stderr b/src/test/ui/derives/deriving-copyclone.stderr
index 46b6a0d337695..f142257604cc8 100644
--- a/src/test/ui/derives/deriving-copyclone.stderr
+++ b/src/test/ui/derives/deriving-copyclone.stderr
@@ -1,33 +1,33 @@
 error[E0277]: the trait bound `C: std::marker::Copy` is not satisfied
-  --> $DIR/deriving-copyclone.rs:31:5
+  --> $DIR/deriving-copyclone.rs:31:13
    |
 LL | fn is_copy<T: Copy>(_: T) {}
    | ------------------------- required by `is_copy`
 ...
 LL |     is_copy(B { a: 1, b: C });
-   |     ^^^^^^^ the trait `std::marker::Copy` is not implemented for `C`
+   |             ^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `C`
    |
    = note: required because of the requirements on the impl of `std::marker::Copy` for `B<C>`
 
 error[E0277]: the trait bound `C: std::clone::Clone` is not satisfied
-  --> $DIR/deriving-copyclone.rs:32:5
+  --> $DIR/deriving-copyclone.rs:32:14
    |
 LL | fn is_clone<T: Clone>(_: T) {}
    | --------------------------- required by `is_clone`
 ...
 LL |     is_clone(B { a: 1, b: C });
-   |     ^^^^^^^^ the trait `std::clone::Clone` is not implemented for `C`
+   |              ^^^^^^^^^^^^^^^^ the trait `std::clone::Clone` is not implemented for `C`
    |
    = note: required because of the requirements on the impl of `std::clone::Clone` for `B<C>`
 
 error[E0277]: the trait bound `D: std::marker::Copy` is not satisfied
-  --> $DIR/deriving-copyclone.rs:35:5
+  --> $DIR/deriving-copyclone.rs:35:13
    |
 LL | fn is_copy<T: Copy>(_: T) {}
    | ------------------------- required by `is_copy`
 ...
 LL |     is_copy(B { a: 1, b: D });
-   |     ^^^^^^^ the trait `std::marker::Copy` is not implemented for `D`
+   |             ^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `D`
    |
    = note: required because of the requirements on the impl of `std::marker::Copy` for `B<D>`
 
diff --git a/src/test/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr b/src/test/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr
index ea2017f485a7b..1bd4543f2316c 100644
--- a/src/test/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr
+++ b/src/test/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `i8: Foo<i32>` is not satisfied
-  --> $DIR/issue-39802-show-5-trait-impls.rs:24:5
+  --> $DIR/issue-39802-show-5-trait-impls.rs:24:21
    |
 LL |     fn bar(&self){}
    |     ------------- required by `Foo::bar`
 ...
 LL |     Foo::<i32>::bar(&1i8);
-   |     ^^^^^^^^^^^^^^^ the trait `Foo<i32>` is not implemented for `i8`
+   |                     ^^^^ the trait `Foo<i32>` is not implemented for `i8`
    |
    = help: the following implementations were found:
              <i8 as Foo<bool>>
@@ -15,13 +15,13 @@ LL |     Foo::<i32>::bar(&1i8);
              <i8 as Foo<u8>>
 
 error[E0277]: the trait bound `u8: Foo<i32>` is not satisfied
-  --> $DIR/issue-39802-show-5-trait-impls.rs:25:5
+  --> $DIR/issue-39802-show-5-trait-impls.rs:25:21
    |
 LL |     fn bar(&self){}
    |     ------------- required by `Foo::bar`
 ...
 LL |     Foo::<i32>::bar(&1u8);
-   |     ^^^^^^^^^^^^^^^ the trait `Foo<i32>` is not implemented for `u8`
+   |                     ^^^^ the trait `Foo<i32>` is not implemented for `u8`
    |
    = help: the following implementations were found:
              <u8 as Foo<bool>>
@@ -30,13 +30,13 @@ LL |     Foo::<i32>::bar(&1u8);
              <u8 as Foo<u64>>
 
 error[E0277]: the trait bound `bool: Foo<i32>` is not satisfied
-  --> $DIR/issue-39802-show-5-trait-impls.rs:26:5
+  --> $DIR/issue-39802-show-5-trait-impls.rs:26:21
    |
 LL |     fn bar(&self){}
    |     ------------- required by `Foo::bar`
 ...
 LL |     Foo::<i32>::bar(&true);
-   |     ^^^^^^^^^^^^^^^ the trait `Foo<i32>` is not implemented for `bool`
+   |                     ^^^^^ the trait `Foo<i32>` is not implemented for `bool`
    |
    = help: the following implementations were found:
              <bool as Foo<bool>>
diff --git a/src/test/ui/did_you_mean/issue-40396.rs b/src/test/ui/did_you_mean/issue-40396.rs
index 63eec50c2d29f..6902779f33d23 100644
--- a/src/test/ui/did_you_mean/issue-40396.rs
+++ b/src/test/ui/did_you_mean/issue-40396.rs
@@ -1,27 +1,16 @@
 fn foo() {
     (0..13).collect<Vec<i32>>();
     //~^ ERROR chained comparison
-    //~| ERROR expected value, found struct `Vec`
-    //~| ERROR expected value, found builtin type `i32`
-    //~| ERROR attempted to take value of method `collect`
 }
 
 fn bar() {
     Vec<i32>::new();
     //~^ ERROR chained comparison
-    //~| ERROR expected value, found struct `Vec`
-    //~| ERROR expected value, found builtin type `i32`
-    //~| ERROR cannot find function `new` in the crate root
 }
 
 fn qux() {
     (0..13).collect<Vec<i32>();
     //~^ ERROR chained comparison
-    //~| ERROR chained comparison
-    //~| ERROR expected value, found struct `Vec`
-    //~| ERROR expected value, found builtin type `i32`
-    //~| ERROR attempted to take value of method `collect`
-    //~| ERROR mismatched types
 }
 
 fn main() {}
diff --git a/src/test/ui/did_you_mean/issue-40396.stderr b/src/test/ui/did_you_mean/issue-40396.stderr
index fe517ee34949d..7a08fda27e355 100644
--- a/src/test/ui/did_you_mean/issue-40396.stderr
+++ b/src/test/ui/did_you_mean/issue-40396.stderr
@@ -8,7 +8,7 @@ LL |     (0..13).collect<Vec<i32>>();
    = help: or use `(...)` if you meant to specify fn arguments
 
 error: chained comparison operators require parentheses
-  --> $DIR/issue-40396.rs:10:8
+  --> $DIR/issue-40396.rs:7:8
    |
 LL |     Vec<i32>::new();
    |        ^^^^^^^
@@ -17,7 +17,7 @@ LL |     Vec<i32>::new();
    = help: or use `(...)` if you meant to specify fn arguments
 
 error: chained comparison operators require parentheses
-  --> $DIR/issue-40396.rs:18:20
+  --> $DIR/issue-40396.rs:12:20
    |
 LL |     (0..13).collect<Vec<i32>();
    |                    ^^^^^^^^
@@ -25,79 +25,5 @@ LL |     (0..13).collect<Vec<i32>();
    = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
    = help: or use `(...)` if you meant to specify fn arguments
 
-error: chained comparison operators require parentheses
-  --> $DIR/issue-40396.rs:18:24
-   |
-LL |     (0..13).collect<Vec<i32>();
-   |                        ^^^^^^
-   |
-   = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
-   = help: or use `(...)` if you meant to specify fn arguments
-
-error[E0423]: expected value, found struct `Vec`
-  --> $DIR/issue-40396.rs:2:21
-   |
-LL |     (0..13).collect<Vec<i32>>();
-   |                     ^^^ did you mean `Vec { /* fields */ }`?
-
-error[E0423]: expected value, found builtin type `i32`
-  --> $DIR/issue-40396.rs:2:25
-   |
-LL |     (0..13).collect<Vec<i32>>();
-   |                         ^^^ not a value
-
-error[E0423]: expected value, found struct `Vec`
-  --> $DIR/issue-40396.rs:10:5
-   |
-LL |     Vec<i32>::new();
-   |     ^^^ did you mean `Vec { /* fields */ }`?
-
-error[E0423]: expected value, found builtin type `i32`
-  --> $DIR/issue-40396.rs:10:9
-   |
-LL |     Vec<i32>::new();
-   |         ^^^ not a value
-
-error[E0425]: cannot find function `new` in the crate root
-  --> $DIR/issue-40396.rs:10:15
-   |
-LL |     Vec<i32>::new();
-   |               ^^^ not found in the crate root
-
-error[E0423]: expected value, found struct `Vec`
-  --> $DIR/issue-40396.rs:18:21
-   |
-LL |     (0..13).collect<Vec<i32>();
-   |                     ^^^ did you mean `Vec { /* fields */ }`?
-
-error[E0423]: expected value, found builtin type `i32`
-  --> $DIR/issue-40396.rs:18:25
-   |
-LL |     (0..13).collect<Vec<i32>();
-   |                         ^^^ not a value
-
-error[E0615]: attempted to take value of method `collect` on type `std::ops::Range<{integer}>`
-  --> $DIR/issue-40396.rs:2:13
-   |
-LL |     (0..13).collect<Vec<i32>>();
-   |             ^^^^^^^ help: use parentheses to call the method: `collect()`
-
-error[E0615]: attempted to take value of method `collect` on type `std::ops::Range<{integer}>`
-  --> $DIR/issue-40396.rs:18:13
-   |
-LL |     (0..13).collect<Vec<i32>();
-   |             ^^^^^^^ help: use parentheses to call the method: `collect()`
-
-error[E0308]: mismatched types
-  --> $DIR/issue-40396.rs:18:29
-   |
-LL |     (0..13).collect<Vec<i32>();
-   |                             ^^ expected bool, found ()
-   |
-   = note: expected type `bool`
-              found type `()`
-
-error: aborting due to 14 previous errors
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0308, E0423, E0425, E0615.
-For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/drop/dropck_legal_cycles.rs b/src/test/ui/drop/dropck_legal_cycles.rs
index a4f4c2666ac9a..fb13fd764bfaf 100644
--- a/src/test/ui/drop/dropck_legal_cycles.rs
+++ b/src/test/ui/drop/dropck_legal_cycles.rs
@@ -143,7 +143,7 @@ pub fn main() {
     v[0].descend_into_self(&mut c);
     assert!(!c.saw_prev_marked); // <-- different from below, b/c acyclic above
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 1: { v[0] -> v[1], v[1] -> v[0] };
     // does not exercise `v` itself
@@ -158,7 +158,7 @@ pub fn main() {
     v[0].descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 2: { v[0] -> v, v[1] -> v }
     let v: V = Named::new("v");
@@ -171,7 +171,7 @@ pub fn main() {
     v.descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 3: { hk0 -> hv0, hv0 -> hk0, hk1 -> hv1, hv1 -> hk1 };
     // does not exercise `h` itself
@@ -193,7 +193,7 @@ pub fn main() {
         assert!(c.saw_prev_marked);
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 4: { h -> (hmk0,hmv0,hmk1,hmv1), {hmk0,hmv0,hmk1,hmv1} -> h }
 
@@ -216,7 +216,7 @@ pub fn main() {
         // break;
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 5: { vd[0] -> vd[1], vd[1] -> vd[0] };
     // does not exercise vd itself
@@ -232,7 +232,7 @@ pub fn main() {
     vd[0].descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 6: { vd -> (vd0, vd1), {vd0, vd1} -> vd }
     let mut vd: VecDeque<VD> = VecDeque::new();
@@ -247,7 +247,7 @@ pub fn main() {
     vd[0].descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 7: { vm -> (vm0, vm1), {vm0, vm1} -> vm }
     let mut vm: HashMap<usize, VM> = HashMap::new();
@@ -262,7 +262,7 @@ pub fn main() {
     vm[&0].descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 8: { ll -> (ll0, ll1), {ll0, ll1} -> ll }
     let mut ll: LinkedList<LL> = LinkedList::new();
@@ -282,7 +282,7 @@ pub fn main() {
         // break;
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 9: { bh -> (bh0, bh1), {bh0, bh1} -> bh }
     let mut bh: BinaryHeap<BH> = BinaryHeap::new();
@@ -302,7 +302,7 @@ pub fn main() {
         // break;
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 10: { btm -> (btk0, btv1), {bt0, bt1} -> btm }
     let mut btm: BTreeMap<BTM, BTM> = BTreeMap::new();
@@ -323,7 +323,7 @@ pub fn main() {
         // break;
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 10: { bts -> (bts0, bts1), {bts0, bts1} -> btm }
     let mut bts: BTreeSet<BTS> = BTreeSet::new();
@@ -343,7 +343,7 @@ pub fn main() {
         // break;
     }
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 11: { rc0 -> (rc1, rc2), rc1 -> (), rc2 -> rc0 }
     let (rc0, rc1, rc2): (RCRC, RCRC, RCRC);
@@ -361,7 +361,7 @@ pub fn main() {
     rc0.descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // We want to take the previous Rc case and generalize it to Arc.
     //
@@ -395,7 +395,7 @@ pub fn main() {
     arc0.descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 13: { arc0 -> (arc1, arc2), arc1 -> (), arc2 -> arc0 }, rwlocks
     let (arc0, arc1, arc2): (ARCRW, ARCRW, ARCRW);
@@ -413,7 +413,7 @@ pub fn main() {
     arc0.descend_into_self(&mut c);
     assert!(c.saw_prev_marked);
 
-    if PRINT { println!(""); }
+    if PRINT { println!(); }
 
     // Cycle 14: { arc0 -> (arc1, arc2), arc1 -> (), arc2 -> arc0 }, mutexs
     let (arc0, arc1, arc2): (ARCM, ARCM, ARCM);
diff --git a/src/test/ui/drop/dynamic-drop-async.rs b/src/test/ui/drop/dynamic-drop-async.rs
index 79d09d1817601..91063edf0f6c4 100644
--- a/src/test/ui/drop/dynamic-drop-async.rs
+++ b/src/test/ui/drop/dynamic-drop-async.rs
@@ -8,6 +8,7 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(slice_patterns)]
+#![allow(unused)]
 
 use std::{
     cell::{Cell, RefCell},
diff --git a/src/test/ui/dropck/dropck_trait_cycle_checked.polonius.stderr b/src/test/ui/dropck/dropck_trait_cycle_checked.polonius.stderr
index dbcb0fcebb73d..5e93a0234259c 100644
--- a/src/test/ui/dropck/dropck_trait_cycle_checked.polonius.stderr
+++ b/src/test/ui/dropck/dropck_trait_cycle_checked.polonius.stderr
@@ -8,7 +8,9 @@ LL | }
    | -
    | |
    | `o2` dropped here while still borrowed
-   | borrow might be used here, when `o2` is dropped and runs the destructor for type `std::boxed::Box<dyn Obj<'_>>`
+   | borrow might be used here, when `o1` is dropped and runs the destructor for type `std::boxed::Box<dyn Obj<'_>>`
+   |
+   = note: values in a scope are dropped in the opposite order they are defined
 
 error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:112:13
@@ -20,7 +22,9 @@ LL | }
    | -
    | |
    | `o3` dropped here while still borrowed
-   | borrow might be used here, when `o3` is dropped and runs the destructor for type `std::boxed::Box<dyn Obj<'_>>`
+   | borrow might be used here, when `o1` is dropped and runs the destructor for type `std::boxed::Box<dyn Obj<'_>>`
+   |
+   = note: values in a scope are dropped in the opposite order they are defined
 
 error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:113:13
@@ -38,7 +42,7 @@ error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:114:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                                                                                         -------- cast requires that `o3` is borrowed for `'static`
+   |                                                                               -------- cast requires that `o3` is borrowed for `'static`
 ...
 LL |     o2.set1(&o3);
    |             ^^^ borrowed value does not live long enough
@@ -62,7 +66,7 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:116:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                                                                               -------- cast requires that `o2` is borrowed for `'static`
+   |                                                                                         -------- cast requires that `o2` is borrowed for `'static`
 ...
 LL |     o3.set1(&o2);
    |             ^^^ borrowed value does not live long enough
diff --git a/src/test/ui/elided-test.stderr b/src/test/ui/elided-test.stderr
index d22eee4e8bde7..175bd033067bc 100644
--- a/src/test/ui/elided-test.stderr
+++ b/src/test/ui/elided-test.stderr
@@ -1,6 +1,10 @@
 error[E0601]: `main` function not found in crate `elided_test`
+  --> $DIR/elided-test.rs:5:1
    |
-   = note: consider adding a `main` function to `$DIR/elided-test.rs`
+LL | / #[test]
+LL | | fn main() {
+LL | | }
+   | |_^ consider adding a `main` function to `$DIR/elided-test.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/empty/empty-macro-use.stderr b/src/test/ui/empty/empty-macro-use.stderr
index 16300411c8cef..8e3e06896ee78 100644
--- a/src/test/ui/empty/empty-macro-use.stderr
+++ b/src/test/ui/empty/empty-macro-use.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `macro_two!` in this scope
+error: cannot find macro `macro_two` in this scope
   --> $DIR/empty-macro-use.rs:7:5
    |
 LL |     macro_two!();
diff --git a/src/test/ui/empty/empty-never-array.rs b/src/test/ui/empty/empty-never-array.rs
index ffd2545b291e2..f0ecea42f39c8 100644
--- a/src/test/ui/empty/empty-never-array.rs
+++ b/src/test/ui/empty/empty-never-array.rs
@@ -10,7 +10,7 @@ fn transmute<T, U>(t: T) -> U {
     let Helper::U(u) = Helper::T(t, []);
     //~^ ERROR refutable pattern in local binding: `T(_, _)` not covered
     u
-    //~^ ERROR use of possibly uninitialized variable: `u`
+    //~^ ERROR use of possibly-uninitialized variable: `u`
 }
 
 fn main() {
diff --git a/src/test/ui/empty/empty-never-array.stderr b/src/test/ui/empty/empty-never-array.stderr
index 01ee1c3a4d7fa..7d59d553d88fd 100644
--- a/src/test/ui/empty/empty-never-array.stderr
+++ b/src/test/ui/empty/empty-never-array.stderr
@@ -3,6 +3,7 @@ error[E0005]: refutable pattern in local binding: `T(_, _)` not covered
    |
 LL | / enum Helper<T, U> {
 LL | |     T(T, [!; 0]),
+   | |     - not covered
 LL | |     #[allow(dead_code)]
 LL | |     U(U),
 LL | | }
@@ -11,11 +12,11 @@ LL | | }
 LL |       let Helper::U(u) = Helper::T(t, []);
    |           ^^^^^^^^^^^^ pattern `T(_, _)` not covered
 
-error[E0381]: use of possibly uninitialized variable: `u`
+error[E0381]: use of possibly-uninitialized variable: `u`
   --> $DIR/empty-never-array.rs:12:5
    |
 LL |     u
-   |     ^ use of possibly uninitialized `u`
+   |     ^ use of possibly-uninitialized `u`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/error-codes/E0008.rs b/src/test/ui/error-codes/E0008.rs
deleted file mode 100644
index c87ef4cb8541f..0000000000000
--- a/src/test/ui/error-codes/E0008.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-fn main() {
-    match Some("hi".to_string()) {
-        Some(s) if s.len() == 0 => {},
-        //~^ ERROR E0008
-        _ => {},
-    }
-}
diff --git a/src/test/ui/error-codes/E0008.stderr b/src/test/ui/error-codes/E0008.stderr
deleted file mode 100644
index 6b45439c4b587..0000000000000
--- a/src/test/ui/error-codes/E0008.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0008]: cannot bind by-move into a pattern guard
-  --> $DIR/E0008.rs:3:14
-   |
-LL |         Some(s) if s.len() == 0 => {},
-   |              ^ moves value into pattern guard
-   |
-   = help: add `#![feature(bind_by_move_pattern_guards)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0008`.
diff --git a/src/test/ui/error-codes/E0023.stderr b/src/test/ui/error-codes/E0023.stderr
index 1bc90a995fe30..d04e494c2585c 100644
--- a/src/test/ui/error-codes/E0023.stderr
+++ b/src/test/ui/error-codes/E0023.stderr
@@ -1,18 +1,27 @@
 error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
   --> $DIR/E0023.rs:10:9
    |
+LL |     Apple(String, String),
+   |     --------------------- tuple variant defined here
+...
 LL |         Fruit::Apple(a) => {},
    |         ^^^^^^^^^^^^^^^ expected 2 fields, found 1
 
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/E0023.rs:11:9
    |
+LL |     Apple(String, String),
+   |     --------------------- tuple variant defined here
+...
 LL |         Fruit::Apple(a, b, c) => {},
    |         ^^^^^^^^^^^^^^^^^^^^^ expected 2 fields, found 3
 
 error[E0023]: this pattern has 2 fields, but the corresponding tuple variant has 1 field
   --> $DIR/E0023.rs:12:9
    |
+LL |     Pear(u32),
+   |     --------- tuple variant defined here
+...
 LL |         Fruit::Pear(1, 2) => {},
    |         ^^^^^^^^^^^^^^^^^ expected 1 field, found 2
 
diff --git a/src/test/ui/error-codes/E0044.rs b/src/test/ui/error-codes/E0044.rs
index a5265e7dc1708..9eee9c31d3c38 100644
--- a/src/test/ui/error-codes/E0044.rs
+++ b/src/test/ui/error-codes/E0044.rs
@@ -1,7 +1,7 @@
 extern {
     fn sqrt<T>(f: T) -> T;
     //~^ ERROR foreign items may not have type parameters [E0044]
-    //~| HELP use specialization instead of type parameters by replacing them with concrete types
+    //~| HELP replace the type parameters with concrete types
     //~| NOTE can't have type parameters
 }
 
diff --git a/src/test/ui/error-codes/E0044.stderr b/src/test/ui/error-codes/E0044.stderr
index 57c21116b2856..e889c167b98d2 100644
--- a/src/test/ui/error-codes/E0044.stderr
+++ b/src/test/ui/error-codes/E0044.stderr
@@ -4,7 +4,7 @@ error[E0044]: foreign items may not have type parameters
 LL |     fn sqrt<T>(f: T) -> T;
    |     ^^^^^^^^^^^^^^^^^^^^^^ can't have type parameters
    |
-   = help: use specialization instead of type parameters by replacing them with concrete types like `u32`
+   = help: replace the type parameters with concrete types like `u32`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/error-codes/E0138.stderr b/src/test/ui/error-codes/E0138.stderr
index 745dccfb17571..445053a4a89e3 100644
--- a/src/test/ui/error-codes/E0138.stderr
+++ b/src/test/ui/error-codes/E0138.stderr
@@ -1,4 +1,4 @@
-error[E0138]: multiple 'start' functions
+error[E0138]: multiple `start` functions
   --> $DIR/E0138.rs:7:1
    |
 LL | fn foo(argc: isize, argv: *const *const u8) -> isize { 0 }
diff --git a/src/test/ui/error-codes/E0277.stderr b/src/test/ui/error-codes/E0277.stderr
index 352102dd38629..9cd0dc7a68e7c 100644
--- a/src/test/ui/error-codes/E0277.stderr
+++ b/src/test/ui/error-codes/E0277.stderr
@@ -11,13 +11,13 @@ LL | fn f(p: Path) { }
    = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the trait bound `i32: Foo` is not satisfied
-  --> $DIR/E0277.rs:17:5
+  --> $DIR/E0277.rs:17:15
    |
 LL | fn some_func<T: Foo>(foo: T) {
    | ---------------------------- required by `some_func`
 ...
 LL |     some_func(5i32);
-   |     ^^^^^^^^^ the trait `Foo` is not implemented for `i32`
+   |               ^^^^ the trait `Foo` is not implemented for `i32`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/error-codes/E0301.rs b/src/test/ui/error-codes/E0301.rs
deleted file mode 100644
index 3b451801c99df..0000000000000
--- a/src/test/ui/error-codes/E0301.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-fn main() {
-    match Some(()) {
-        None => { },
-        option if option.take().is_none() => {}, //~ ERROR E0301
-        Some(_) => { } //~^ ERROR E0596
-    }
-}
diff --git a/src/test/ui/error-codes/E0301.stderr b/src/test/ui/error-codes/E0301.stderr
deleted file mode 100644
index 4f12fd3850e33..0000000000000
--- a/src/test/ui/error-codes/E0301.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error[E0301]: cannot mutably borrow in a pattern guard
-  --> $DIR/E0301.rs:4:19
-   |
-LL |         option if option.take().is_none() => {},
-   |                   ^^^^^^ borrowed mutably in pattern guard
-   |
-   = help: add `#![feature(bind_by_move_pattern_guards)]` to the crate attributes to enable
-
-error[E0596]: cannot borrow `option` as mutable, as it is immutable for the pattern guard
-  --> $DIR/E0301.rs:4:19
-   |
-LL |         option if option.take().is_none() => {},
-   |                   ^^^^^^ cannot borrow as mutable
-   |
-   = note: variables bound in patterns are immutable until the end of the pattern guard
-
-error: aborting due to 2 previous errors
-
-Some errors have detailed explanations: E0301, E0596.
-For more information about an error, try `rustc --explain E0301`.
diff --git a/src/test/ui/error-codes/E0302.rs b/src/test/ui/error-codes/E0302.rs
deleted file mode 100644
index 69f5953deb223..0000000000000
--- a/src/test/ui/error-codes/E0302.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-fn main() {
-    match Some(()) {
-        None => { },
-        option if { option = None; false } => { }, //~ ERROR E0302
-        //~^ ERROR cannot assign to `option`, as it is immutable for the pattern guard
-        Some(_) => { }
-    }
-}
diff --git a/src/test/ui/error-codes/E0302.stderr b/src/test/ui/error-codes/E0302.stderr
deleted file mode 100644
index a077fcaea4101..0000000000000
--- a/src/test/ui/error-codes/E0302.stderr
+++ /dev/null
@@ -1,17 +0,0 @@
-error[E0302]: cannot assign in a pattern guard
-  --> $DIR/E0302.rs:4:21
-   |
-LL |         option if { option = None; false } => { },
-   |                     ^^^^^^^^^^^^^ assignment in pattern guard
-
-error[E0594]: cannot assign to `option`, as it is immutable for the pattern guard
-  --> $DIR/E0302.rs:4:21
-   |
-LL |         option if { option = None; false } => { },
-   |                     ^^^^^^^^^^^^^ cannot assign
-   |
-   = note: variables bound in patterns are immutable until the end of the pattern guard
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0302`.
diff --git a/src/test/ui/error-codes/E0601.rs b/src/test/ui/error-codes/E0601.rs
index 47feb7f836722..4380ddeac0aac 100644
--- a/src/test/ui/error-codes/E0601.rs
+++ b/src/test/ui/error-codes/E0601.rs
@@ -1 +1 @@
-// Test for main function not found.
+//~ ERROR `main` function not found
diff --git a/src/test/ui/error-codes/E0601.stderr b/src/test/ui/error-codes/E0601.stderr
index cbc20db35da77..a687f575615d7 100644
--- a/src/test/ui/error-codes/E0601.stderr
+++ b/src/test/ui/error-codes/E0601.stderr
@@ -1,6 +1,8 @@
 error[E0601]: `main` function not found in crate `E0601`
+  --> $DIR/E0601.rs:1:37
    |
-   = note: consider adding a `main` function to `$DIR/E0601.rs`
+LL |
+   |                                     ^ consider adding a `main` function to `$DIR/E0601.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/error-festival.stderr b/src/test/ui/error-festival.stderr
index 8808e95d81b18..73571a375b5f6 100644
--- a/src/test/ui/error-festival.stderr
+++ b/src/test/ui/error-festival.stderr
@@ -24,7 +24,7 @@ error[E0599]: no method named `z` found for type `&str` in the current scope
   --> $DIR/error-festival.rs:16:7
    |
 LL |     x.z();
-   |       ^
+   |       ^ method not found in `&str`
 
 error[E0600]: cannot apply unary operator `!` to type `Question`
   --> $DIR/error-festival.rs:19:5
diff --git a/src/test/ui/error-should-say-copy-not-pod.stderr b/src/test/ui/error-should-say-copy-not-pod.stderr
index 78d54c3836db4..df79aeea054ca 100644
--- a/src/test/ui/error-should-say-copy-not-pod.stderr
+++ b/src/test/ui/error-should-say-copy-not-pod.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
-  --> $DIR/error-should-say-copy-not-pod.rs:6:5
+  --> $DIR/error-should-say-copy-not-pod.rs:6:17
    |
 LL | fn check_bound<T:Copy>(_: T) {}
    | ---------------------------- required by `check_bound`
 ...
 LL |     check_bound("nocopy".to_string());
-   |     ^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
+   |                 ^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/ext-nonexistent.stderr b/src/test/ui/ext-nonexistent.stderr
index 3fbbb4952649f..f3aa83fd50806 100644
--- a/src/test/ui/ext-nonexistent.stderr
+++ b/src/test/ui/ext-nonexistent.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `iamnotanextensionthatexists!` in this scope
+error: cannot find macro `iamnotanextensionthatexists` in this scope
   --> $DIR/ext-nonexistent.rs:2:13
    |
 LL | fn main() { iamnotanextensionthatexists!(""); }
diff --git a/src/test/ui/extenv/issue-55897.rs b/src/test/ui/extenv/issue-55897.rs
index c3975f6b9255e..64c4107e89875 100644
--- a/src/test/ui/extenv/issue-55897.rs
+++ b/src/test/ui/extenv/issue-55897.rs
@@ -1,7 +1,7 @@
 use prelude::*; //~ ERROR unresolved import `prelude`
 
 mod unresolved_env {
-    use env;
+    use env; //~ ERROR unresolved import `env`
 
     include!(concat!(env!("NON_EXISTENT"), "/data.rs"));
     //~^ ERROR cannot determine resolution for the macro `env`
diff --git a/src/test/ui/extenv/issue-55897.stderr b/src/test/ui/extenv/issue-55897.stderr
index 9d68131beabd7..c57a467cdba56 100644
--- a/src/test/ui/extenv/issue-55897.stderr
+++ b/src/test/ui/extenv/issue-55897.stderr
@@ -19,6 +19,12 @@ LL | use prelude::*;
    |     unresolved import
    |     help: a similar path exists: `std::prelude`
 
+error[E0432]: unresolved import `env`
+  --> $DIR/issue-55897.rs:4:9
+   |
+LL |     use env;
+   |         ^^^ no `env` in the root
+
 error: cannot determine resolution for the macro `env`
   --> $DIR/issue-55897.rs:6:22
    |
@@ -27,6 +33,6 @@ LL |     include!(concat!(env!("NON_EXISTENT"), "/data.rs"));
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0432`.
diff --git a/src/test/ui/extern/extern-wrong-value-type.stderr b/src/test/ui/extern/extern-wrong-value-type.stderr
index 52fcb90e6de0c..f2468895d21d1 100644
--- a/src/test/ui/extern/extern-wrong-value-type.stderr
+++ b/src/test/ui/extern/extern-wrong-value-type.stderr
@@ -1,11 +1,11 @@
 error[E0277]: expected a `std::ops::Fn<()>` closure, found `extern "C" fn() {f}`
-  --> $DIR/extern-wrong-value-type.rs:9:5
+  --> $DIR/extern-wrong-value-type.rs:9:11
    |
 LL | fn is_fn<F>(_: F) where F: Fn() {}
    | ------------------------------- required by `is_fn`
 ...
 LL |     is_fn(f);
-   |     ^^^^^ expected an `Fn<()>` closure, found `extern "C" fn() {f}`
+   |           ^ expected an `Fn<()>` closure, found `extern "C" fn() {f}`
    |
    = help: the trait `std::ops::Fn<()>` is not implemented for `extern "C" fn() {f}`
    = note: wrap the `extern "C" fn() {f}` in a closure with no arguments: `|| { /* code */ }
diff --git a/src/test/ui/feature-gate/allow-features-empty.rs b/src/test/ui/feature-gate/allow-features-empty.rs
index 784a1d2697d67..641e4b852e79f 100644
--- a/src/test/ui/feature-gate/allow-features-empty.rs
+++ b/src/test/ui/feature-gate/allow-features-empty.rs
@@ -1,8 +1,6 @@
 // compile-flags: -Z allow_features=
 // Note: This test uses rustc internal flags because they will never stabilize.
 
-#![feature(rustc_diagnostic_macros)] //~ ERROR
-
 #![feature(rustc_const_unstable)] //~ ERROR
 
 #![feature(lang_items)] //~ ERROR
diff --git a/src/test/ui/feature-gate/allow-features-empty.stderr b/src/test/ui/feature-gate/allow-features-empty.stderr
index ab41422ed05b8..a87d105850327 100644
--- a/src/test/ui/feature-gate/allow-features-empty.stderr
+++ b/src/test/ui/feature-gate/allow-features-empty.stderr
@@ -1,27 +1,21 @@
-error[E0725]: the feature `rustc_diagnostic_macros` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:4:12
-   |
-LL | #![feature(rustc_diagnostic_macros)]
-   |            ^^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0725]: the feature `rustc_const_unstable` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:6:12
+  --> $DIR/allow-features-empty.rs:4:12
    |
 LL | #![feature(rustc_const_unstable)]
    |            ^^^^^^^^^^^^^^^^^^^^
 
 error[E0725]: the feature `lang_items` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:8:12
+  --> $DIR/allow-features-empty.rs:6:12
    |
 LL | #![feature(lang_items)]
    |            ^^^^^^^^^^
 
 error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:10:12
+  --> $DIR/allow-features-empty.rs:8:12
    |
 LL | #![feature(unknown_stdlib_feature)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0725`.
diff --git a/src/test/ui/feature-gate/allow-features.rs b/src/test/ui/feature-gate/allow-features.rs
index de3439a5b628f..de69e48a65fdf 100644
--- a/src/test/ui/feature-gate/allow-features.rs
+++ b/src/test/ui/feature-gate/allow-features.rs
@@ -1,8 +1,6 @@
-// compile-flags: -Z allow_features=rustc_diagnostic_macros,lang_items
+// compile-flags: -Z allow_features=lang_items
 // Note: This test uses rustc internal flags because they will never stabilize.
 
-#![feature(rustc_diagnostic_macros)]
-
 #![feature(rustc_const_unstable)] //~ ERROR
 
 #![feature(lang_items)]
diff --git a/src/test/ui/feature-gate/allow-features.stderr b/src/test/ui/feature-gate/allow-features.stderr
index 5b39a6f053bde..157dddf06ad1d 100644
--- a/src/test/ui/feature-gate/allow-features.stderr
+++ b/src/test/ui/feature-gate/allow-features.stderr
@@ -1,11 +1,11 @@
 error[E0725]: the feature `rustc_const_unstable` is not in the list of allowed features
-  --> $DIR/allow-features.rs:6:12
+  --> $DIR/allow-features.rs:4:12
    |
 LL | #![feature(rustc_const_unstable)]
    |            ^^^^^^^^^^^^^^^^^^^^
 
 error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
-  --> $DIR/allow-features.rs:10:12
+  --> $DIR/allow-features.rs:8:12
    |
 LL | #![feature(unknown_stdlib_feature)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/feature-gate/feature-gate-static-nobundle-2.rs b/src/test/ui/feature-gate/feature-gate-static-nobundle-2.rs
index 92844f9306d28..b6c8648a7d03d 100644
--- a/src/test/ui/feature-gate/feature-gate-static-nobundle-2.rs
+++ b/src/test/ui/feature-gate/feature-gate-static-nobundle-2.rs
@@ -1,4 +1,4 @@
-//~ ERROR kind="static-nobundle" is feature gated
+//~ ERROR kind="static-nobundle" is unstable
 // Test the behavior of rustc when non-existent library is statically linked
 
 // compile-flags: -l static-nobundle=nonexistent
diff --git a/src/test/ui/feature-gate/feature-gate-static-nobundle-2.stderr b/src/test/ui/feature-gate/feature-gate-static-nobundle-2.stderr
index 059559dd92831..cfff4c36a6d7b 100644
--- a/src/test/ui/feature-gate/feature-gate-static-nobundle-2.stderr
+++ b/src/test/ui/feature-gate/feature-gate-static-nobundle-2.stderr
@@ -1,4 +1,4 @@
-error[E0658]: kind="static-nobundle" is feature gated
+error[E0658]: kind="static-nobundle" is unstable
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/37403
    = help: add `#![feature(static_nobundle)]` to the crate attributes to enable
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
index 6d51bb3f8ada8..68ff95e420895 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
@@ -84,12 +84,12 @@
 #![crate_name = "0900"]
 #![crate_type = "bin"] // cannot pass "0800" here
 
-// For #![crate_id], see issue #43142. (I cannot bear to enshrine current behavior in a test)
+#![crate_id = "10"] //~ WARN use of deprecated attribute
 
 // FIXME(#44232) we should warn that this isn't used.
 #![feature(rust1)]
 
-// For #![no_start], see issue #43144. (I cannot bear to enshrine current behavior in a test)
+#![no_start] //~ WARN use of deprecated attribute
 
 // (cannot easily gating state of crate-level #[no_main]; but non crate-level is below at "0400")
 #![no_builtins]
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index 864df35a79fe3..b2a6018b5354d 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -186,6 +186,20 @@ LL |     mod inner { #![macro_escape] }
    |
    = help: consider an outer attribute, `#[macro_use]` mod ...
 
+warning: use of deprecated attribute `crate_id`: no longer used.
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:87:1
+   |
+LL | #![crate_id = "10"]
+   | ^^^^^^^^^^^^^^^^^^^ help: remove this attribute
+   |
+   = note: `#[warn(deprecated)]` on by default
+
+warning: use of deprecated attribute `no_start`: no longer used.
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:92:1
+   |
+LL | #![no_start]
+   | ^^^^^^^^^^^^ help: remove this attribute
+
 warning: the feature `rust1` has been stable since 1.0.0 and no longer requires an attribute to enable
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:90:12
    |
diff --git a/src/test/ui/feature-gates/bench.rs b/src/test/ui/feature-gates/bench.rs
new file mode 100644
index 0000000000000..afe4dc7d54c9b
--- /dev/null
+++ b/src/test/ui/feature-gates/bench.rs
@@ -0,0 +1,5 @@
+#[bench] //~ ERROR use of unstable library feature 'test'
+         //~| WARN this was previously accepted
+fn bench() {}
+
+fn main() {}
diff --git a/src/test/ui/feature-gates/bench.stderr b/src/test/ui/feature-gates/bench.stderr
new file mode 100644
index 0000000000000..b9e24e931d42b
--- /dev/null
+++ b/src/test/ui/feature-gates/bench.stderr
@@ -0,0 +1,12 @@
+error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+  --> $DIR/bench.rs:1:3
+   |
+LL | #[bench]
+   |   ^^^^^
+   |
+   = note: `#[deny(soft_unstable)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #64266 <https://github.com/rust-lang/rust/issues/64266>
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/feature-gates/feature-gate-abi.rs b/src/test/ui/feature-gates/feature-gate-abi.rs
index 41c9f79bfe3ed..61da38eea74b3 100644
--- a/src/test/ui/feature-gates/feature-gate-abi.rs
+++ b/src/test/ui/feature-gates/feature-gate-abi.rs
@@ -10,7 +10,9 @@
 
 // Functions
 extern "rust-intrinsic" fn f1() {} //~ ERROR intrinsics are subject to change
+//~^ ERROR intrinsic must be in
 extern "platform-intrinsic" fn f2() {} //~ ERROR platform intrinsics are experimental
+//~^ ERROR intrinsic must be in
 extern "vectorcall" fn f3() {} //~ ERROR vectorcall is experimental and subject to change
 extern "rust-call" fn f4() {} //~ ERROR rust-call ABI is subject to change
 extern "msp430-interrupt" fn f5() {} //~ ERROR msp430-interrupt ABI is experimental
@@ -22,7 +24,9 @@ extern "amdgpu-kernel" fn f9() {} //~ ERROR amdgpu-kernel ABI is experimental an
 // Methods in trait definition
 trait Tr {
     extern "rust-intrinsic" fn m1(); //~ ERROR intrinsics are subject to change
+    //~^ ERROR intrinsic must be in
     extern "platform-intrinsic" fn m2(); //~ ERROR platform intrinsics are experimental
+    //~^ ERROR intrinsic must be in
     extern "vectorcall" fn m3(); //~ ERROR vectorcall is experimental and subject to change
     extern "rust-call" fn m4(); //~ ERROR rust-call ABI is subject to change
     extern "msp430-interrupt" fn m5(); //~ ERROR msp430-interrupt ABI is experimental
@@ -31,8 +35,6 @@ trait Tr {
     extern "thiscall" fn m8(); //~ ERROR thiscall is experimental and subject to change
     extern "amdgpu-kernel" fn m9(); //~ ERROR amdgpu-kernel ABI is experimental and subject to change
 
-    extern "rust-intrinsic" fn dm1() {} //~ ERROR intrinsics are subject to change
-    extern "platform-intrinsic" fn dm2() {} //~ ERROR platform intrinsics are experimental
     extern "vectorcall" fn dm3() {} //~ ERROR vectorcall is experimental and subject to change
     extern "rust-call" fn dm4() {} //~ ERROR rust-call ABI is subject to change
     extern "msp430-interrupt" fn dm5() {} //~ ERROR msp430-interrupt ABI is experimental
@@ -47,7 +49,9 @@ struct S;
 // Methods in trait impl
 impl Tr for S {
     extern "rust-intrinsic" fn m1() {} //~ ERROR intrinsics are subject to change
+    //~^ ERROR intrinsic must be in
     extern "platform-intrinsic" fn m2() {} //~ ERROR platform intrinsics are experimental
+    //~^ ERROR intrinsic must be in
     extern "vectorcall" fn m3() {} //~ ERROR vectorcall is experimental and subject to change
     extern "rust-call" fn m4() {} //~ ERROR rust-call ABI is subject to change
     extern "msp430-interrupt" fn m5() {} //~ ERROR msp430-interrupt ABI is experimental
@@ -60,7 +64,9 @@ impl Tr for S {
 // Methods in inherent impl
 impl S {
     extern "rust-intrinsic" fn im1() {} //~ ERROR intrinsics are subject to change
+    //~^ ERROR intrinsic must be in
     extern "platform-intrinsic" fn im2() {} //~ ERROR platform intrinsics are experimental
+    //~^ ERROR intrinsic must be in
     extern "vectorcall" fn im3() {} //~ ERROR vectorcall is experimental and subject to change
     extern "rust-call" fn im4() {} //~ ERROR rust-call ABI is subject to change
     extern "msp430-interrupt" fn im5() {} //~ ERROR msp430-interrupt ABI is experimental
diff --git a/src/test/ui/feature-gates/feature-gate-abi.stderr b/src/test/ui/feature-gates/feature-gate-abi.stderr
index 88e0b8667be54..afda76dc2b0aa 100644
--- a/src/test/ui/feature-gates/feature-gate-abi.stderr
+++ b/src/test/ui/feature-gates/feature-gate-abi.stderr
@@ -7,7 +7,7 @@ LL | extern "rust-intrinsic" fn f1() {}
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:13:1
+  --> $DIR/feature-gate-abi.rs:14:1
    |
 LL | extern "platform-intrinsic" fn f2() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -16,7 +16,7 @@ LL | extern "platform-intrinsic" fn f2() {}
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:14:1
+  --> $DIR/feature-gate-abi.rs:16:1
    |
 LL | extern "vectorcall" fn f3() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -24,7 +24,7 @@ LL | extern "vectorcall" fn f3() {}
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:15:1
+  --> $DIR/feature-gate-abi.rs:17:1
    |
 LL | extern "rust-call" fn f4() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -33,7 +33,7 @@ LL | extern "rust-call" fn f4() {}
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:16:1
+  --> $DIR/feature-gate-abi.rs:18:1
    |
 LL | extern "msp430-interrupt" fn f5() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -42,7 +42,7 @@ LL | extern "msp430-interrupt" fn f5() {}
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:17:1
+  --> $DIR/feature-gate-abi.rs:19:1
    |
 LL | extern "ptx-kernel" fn f6() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -51,7 +51,7 @@ LL | extern "ptx-kernel" fn f6() {}
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:18:1
+  --> $DIR/feature-gate-abi.rs:20:1
    |
 LL | extern "x86-interrupt" fn f7() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -60,7 +60,7 @@ LL | extern "x86-interrupt" fn f7() {}
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:19:1
+  --> $DIR/feature-gate-abi.rs:21:1
    |
 LL | extern "thiscall" fn f8() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -68,7 +68,7 @@ LL | extern "thiscall" fn f8() {}
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:20:1
+  --> $DIR/feature-gate-abi.rs:22:1
    |
 LL | extern "amdgpu-kernel" fn f9() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -77,7 +77,7 @@ LL | extern "amdgpu-kernel" fn f9() {}
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
 error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:24:5
+  --> $DIR/feature-gate-abi.rs:26:5
    |
 LL |     extern "rust-intrinsic" fn m1();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -85,7 +85,7 @@ LL |     extern "rust-intrinsic" fn m1();
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:25:5
+  --> $DIR/feature-gate-abi.rs:28:5
    |
 LL |     extern "platform-intrinsic" fn m2();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -94,7 +94,7 @@ LL |     extern "platform-intrinsic" fn m2();
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:26:5
+  --> $DIR/feature-gate-abi.rs:30:5
    |
 LL |     extern "vectorcall" fn m3();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -102,7 +102,7 @@ LL |     extern "vectorcall" fn m3();
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:27:5
+  --> $DIR/feature-gate-abi.rs:31:5
    |
 LL |     extern "rust-call" fn m4();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -111,7 +111,7 @@ LL |     extern "rust-call" fn m4();
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:28:5
+  --> $DIR/feature-gate-abi.rs:32:5
    |
 LL |     extern "msp430-interrupt" fn m5();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -120,7 +120,7 @@ LL |     extern "msp430-interrupt" fn m5();
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:29:5
+  --> $DIR/feature-gate-abi.rs:33:5
    |
 LL |     extern "ptx-kernel" fn m6();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -129,7 +129,7 @@ LL |     extern "ptx-kernel" fn m6();
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:30:5
+  --> $DIR/feature-gate-abi.rs:34:5
    |
 LL |     extern "x86-interrupt" fn m7();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -138,7 +138,7 @@ LL |     extern "x86-interrupt" fn m7();
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:31:5
+  --> $DIR/feature-gate-abi.rs:35:5
    |
 LL |     extern "thiscall" fn m8();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -146,7 +146,7 @@ LL |     extern "thiscall" fn m8();
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:32:5
+  --> $DIR/feature-gate-abi.rs:36:5
    |
 LL |     extern "amdgpu-kernel" fn m9();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -154,25 +154,8 @@ LL |     extern "amdgpu-kernel" fn m9();
    = note: for more information, see https://github.com/rust-lang/rust/issues/51575
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
-error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:34:5
-   |
-LL |     extern "rust-intrinsic" fn dm1() {}
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(intrinsics)]` to the crate attributes to enable
-
-error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:35:5
-   |
-LL |     extern "platform-intrinsic" fn dm2() {}
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/27731
-   = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
-
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:36:5
+  --> $DIR/feature-gate-abi.rs:38:5
    |
 LL |     extern "vectorcall" fn dm3() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -180,7 +163,7 @@ LL |     extern "vectorcall" fn dm3() {}
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:37:5
+  --> $DIR/feature-gate-abi.rs:39:5
    |
 LL |     extern "rust-call" fn dm4() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -189,7 +172,7 @@ LL |     extern "rust-call" fn dm4() {}
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:38:5
+  --> $DIR/feature-gate-abi.rs:40:5
    |
 LL |     extern "msp430-interrupt" fn dm5() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -198,7 +181,7 @@ LL |     extern "msp430-interrupt" fn dm5() {}
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:39:5
+  --> $DIR/feature-gate-abi.rs:41:5
    |
 LL |     extern "ptx-kernel" fn dm6() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -207,7 +190,7 @@ LL |     extern "ptx-kernel" fn dm6() {}
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:40:5
+  --> $DIR/feature-gate-abi.rs:42:5
    |
 LL |     extern "x86-interrupt" fn dm7() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -216,7 +199,7 @@ LL |     extern "x86-interrupt" fn dm7() {}
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:41:5
+  --> $DIR/feature-gate-abi.rs:43:5
    |
 LL |     extern "thiscall" fn dm8() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -224,7 +207,7 @@ LL |     extern "thiscall" fn dm8() {}
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:42:5
+  --> $DIR/feature-gate-abi.rs:44:5
    |
 LL |     extern "amdgpu-kernel" fn dm9() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -233,7 +216,7 @@ LL |     extern "amdgpu-kernel" fn dm9() {}
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
 error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:49:5
+  --> $DIR/feature-gate-abi.rs:51:5
    |
 LL |     extern "rust-intrinsic" fn m1() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -241,7 +224,7 @@ LL |     extern "rust-intrinsic" fn m1() {}
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:50:5
+  --> $DIR/feature-gate-abi.rs:53:5
    |
 LL |     extern "platform-intrinsic" fn m2() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -250,7 +233,7 @@ LL |     extern "platform-intrinsic" fn m2() {}
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:51:5
+  --> $DIR/feature-gate-abi.rs:55:5
    |
 LL |     extern "vectorcall" fn m3() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -258,7 +241,7 @@ LL |     extern "vectorcall" fn m3() {}
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:52:5
+  --> $DIR/feature-gate-abi.rs:56:5
    |
 LL |     extern "rust-call" fn m4() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -267,7 +250,7 @@ LL |     extern "rust-call" fn m4() {}
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:53:5
+  --> $DIR/feature-gate-abi.rs:57:5
    |
 LL |     extern "msp430-interrupt" fn m5() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -276,7 +259,7 @@ LL |     extern "msp430-interrupt" fn m5() {}
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:54:5
+  --> $DIR/feature-gate-abi.rs:58:5
    |
 LL |     extern "ptx-kernel" fn m6() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -285,7 +268,7 @@ LL |     extern "ptx-kernel" fn m6() {}
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:55:5
+  --> $DIR/feature-gate-abi.rs:59:5
    |
 LL |     extern "x86-interrupt" fn m7() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -294,7 +277,7 @@ LL |     extern "x86-interrupt" fn m7() {}
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:56:5
+  --> $DIR/feature-gate-abi.rs:60:5
    |
 LL |     extern "thiscall" fn m8() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -302,7 +285,7 @@ LL |     extern "thiscall" fn m8() {}
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:57:5
+  --> $DIR/feature-gate-abi.rs:61:5
    |
 LL |     extern "amdgpu-kernel" fn m9() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -311,7 +294,7 @@ LL |     extern "amdgpu-kernel" fn m9() {}
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
 error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:62:5
+  --> $DIR/feature-gate-abi.rs:66:5
    |
 LL |     extern "rust-intrinsic" fn im1() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -319,7 +302,7 @@ LL |     extern "rust-intrinsic" fn im1() {}
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:63:5
+  --> $DIR/feature-gate-abi.rs:68:5
    |
 LL |     extern "platform-intrinsic" fn im2() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -328,7 +311,7 @@ LL |     extern "platform-intrinsic" fn im2() {}
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:64:5
+  --> $DIR/feature-gate-abi.rs:70:5
    |
 LL |     extern "vectorcall" fn im3() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -336,7 +319,7 @@ LL |     extern "vectorcall" fn im3() {}
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:65:5
+  --> $DIR/feature-gate-abi.rs:71:5
    |
 LL |     extern "rust-call" fn im4() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -345,7 +328,7 @@ LL |     extern "rust-call" fn im4() {}
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:66:5
+  --> $DIR/feature-gate-abi.rs:72:5
    |
 LL |     extern "msp430-interrupt" fn im5() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -354,7 +337,7 @@ LL |     extern "msp430-interrupt" fn im5() {}
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:67:5
+  --> $DIR/feature-gate-abi.rs:73:5
    |
 LL |     extern "ptx-kernel" fn im6() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -363,7 +346,7 @@ LL |     extern "ptx-kernel" fn im6() {}
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:68:5
+  --> $DIR/feature-gate-abi.rs:74:5
    |
 LL |     extern "x86-interrupt" fn im7() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -372,7 +355,7 @@ LL |     extern "x86-interrupt" fn im7() {}
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:69:5
+  --> $DIR/feature-gate-abi.rs:75:5
    |
 LL |     extern "thiscall" fn im8() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -380,7 +363,7 @@ LL |     extern "thiscall" fn im8() {}
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:70:5
+  --> $DIR/feature-gate-abi.rs:76:5
    |
 LL |     extern "amdgpu-kernel" fn im9() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -389,7 +372,7 @@ LL |     extern "amdgpu-kernel" fn im9() {}
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
 error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:74:11
+  --> $DIR/feature-gate-abi.rs:80:11
    |
 LL | type A1 = extern "rust-intrinsic" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -397,7 +380,7 @@ LL | type A1 = extern "rust-intrinsic" fn();
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:75:11
+  --> $DIR/feature-gate-abi.rs:81:11
    |
 LL | type A2 = extern "platform-intrinsic" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -406,7 +389,7 @@ LL | type A2 = extern "platform-intrinsic" fn();
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:76:11
+  --> $DIR/feature-gate-abi.rs:82:11
    |
 LL | type A3 = extern "vectorcall" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -414,7 +397,7 @@ LL | type A3 = extern "vectorcall" fn();
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:77:11
+  --> $DIR/feature-gate-abi.rs:83:11
    |
 LL | type A4 = extern "rust-call" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^
@@ -423,7 +406,7 @@ LL | type A4 = extern "rust-call" fn();
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:78:11
+  --> $DIR/feature-gate-abi.rs:84:11
    |
 LL | type A5 = extern "msp430-interrupt" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -432,7 +415,7 @@ LL | type A5 = extern "msp430-interrupt" fn();
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:79:11
+  --> $DIR/feature-gate-abi.rs:85:11
    |
 LL | type A6 = extern "ptx-kernel" fn ();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -441,7 +424,7 @@ LL | type A6 = extern "ptx-kernel" fn ();
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:80:11
+  --> $DIR/feature-gate-abi.rs:86:11
    |
 LL | type A7 = extern "x86-interrupt" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -450,7 +433,7 @@ LL | type A7 = extern "x86-interrupt" fn();
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:81:11
+  --> $DIR/feature-gate-abi.rs:87:11
    |
 LL | type A8 = extern "thiscall" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^
@@ -458,7 +441,7 @@ LL | type A8 = extern "thiscall" fn();
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:82:11
+  --> $DIR/feature-gate-abi.rs:88:11
    |
 LL | type A9 = extern "amdgpu-kernel" fn();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -467,7 +450,7 @@ LL | type A9 = extern "amdgpu-kernel" fn();
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
 error[E0658]: intrinsics are subject to change
-  --> $DIR/feature-gate-abi.rs:85:1
+  --> $DIR/feature-gate-abi.rs:91:1
    |
 LL | extern "rust-intrinsic" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -475,7 +458,7 @@ LL | extern "rust-intrinsic" {}
    = help: add `#![feature(intrinsics)]` to the crate attributes to enable
 
 error[E0658]: platform intrinsics are experimental and possibly buggy
-  --> $DIR/feature-gate-abi.rs:86:1
+  --> $DIR/feature-gate-abi.rs:92:1
    |
 LL | extern "platform-intrinsic" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -484,7 +467,7 @@ LL | extern "platform-intrinsic" {}
    = help: add `#![feature(platform_intrinsics)]` to the crate attributes to enable
 
 error[E0658]: vectorcall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:87:1
+  --> $DIR/feature-gate-abi.rs:93:1
    |
 LL | extern "vectorcall" {}
    | ^^^^^^^^^^^^^^^^^^^^^^
@@ -492,7 +475,7 @@ LL | extern "vectorcall" {}
    = help: add `#![feature(abi_vectorcall)]` to the crate attributes to enable
 
 error[E0658]: rust-call ABI is subject to change
-  --> $DIR/feature-gate-abi.rs:88:1
+  --> $DIR/feature-gate-abi.rs:94:1
    |
 LL | extern "rust-call" {}
    | ^^^^^^^^^^^^^^^^^^^^^
@@ -501,7 +484,7 @@ LL | extern "rust-call" {}
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
 error[E0658]: msp430-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:89:1
+  --> $DIR/feature-gate-abi.rs:95:1
    |
 LL | extern "msp430-interrupt" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -510,7 +493,7 @@ LL | extern "msp430-interrupt" {}
    = help: add `#![feature(abi_msp430_interrupt)]` to the crate attributes to enable
 
 error[E0658]: PTX ABIs are experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:90:1
+  --> $DIR/feature-gate-abi.rs:96:1
    |
 LL | extern "ptx-kernel" {}
    | ^^^^^^^^^^^^^^^^^^^^^^
@@ -519,7 +502,7 @@ LL | extern "ptx-kernel" {}
    = help: add `#![feature(abi_ptx)]` to the crate attributes to enable
 
 error[E0658]: x86-interrupt ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:91:1
+  --> $DIR/feature-gate-abi.rs:97:1
    |
 LL | extern "x86-interrupt" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -528,7 +511,7 @@ LL | extern "x86-interrupt" {}
    = help: add `#![feature(abi_x86_interrupt)]` to the crate attributes to enable
 
 error[E0658]: thiscall is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:92:1
+  --> $DIR/feature-gate-abi.rs:98:1
    |
 LL | extern "thiscall" {}
    | ^^^^^^^^^^^^^^^^^^^^
@@ -536,7 +519,7 @@ LL | extern "thiscall" {}
    = help: add `#![feature(abi_thiscall)]` to the crate attributes to enable
 
 error[E0658]: amdgpu-kernel ABI is experimental and subject to change
-  --> $DIR/feature-gate-abi.rs:93:1
+  --> $DIR/feature-gate-abi.rs:99:1
    |
 LL | extern "amdgpu-kernel" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -544,6 +527,54 @@ LL | extern "amdgpu-kernel" {}
    = note: for more information, see https://github.com/rust-lang/rust/issues/51575
    = help: add `#![feature(abi_amdgpu_kernel)]` to the crate attributes to enable
 
-error: aborting due to 63 previous errors
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:26:32
+   |
+LL |     extern "rust-intrinsic" fn m1();
+   |                                ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:28:36
+   |
+LL |     extern "platform-intrinsic" fn m2();
+   |                                    ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:12:33
+   |
+LL | extern "rust-intrinsic" fn f1() {}
+   |                                 ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:14:37
+   |
+LL | extern "platform-intrinsic" fn f2() {}
+   |                                     ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:51:37
+   |
+LL |     extern "rust-intrinsic" fn m1() {}
+   |                                     ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:53:41
+   |
+LL |     extern "platform-intrinsic" fn m2() {}
+   |                                         ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:66:38
+   |
+LL |     extern "rust-intrinsic" fn im1() {}
+   |                                      ^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-abi.rs:68:42
+   |
+LL |     extern "platform-intrinsic" fn im2() {}
+   |                                          ^^
+
+error: aborting due to 69 previous errors
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute.rs b/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
index d34936b42a6ff..936cab268d2c9 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
@@ -1,18 +1,18 @@
 // Check that literals in attributes parse just fine.
 
-#[fake_attr] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(100)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(1, 2, 3)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr("hello")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(name = "hello")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(1, "hi", key = 12, true, false)] //~ ERROR cannot find attribute macro `fake_attr` in th
-#[fake_attr(key = "hello", val = 10)] //~ ERROR cannot find attribute macro `fake_attr` in this scop
-#[fake_attr(key("hello"), val(10))] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(enabled = true, disabled = false)] //~ ERROR cannot find attribute macro `fake_attr` in
-#[fake_attr(true)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(pi = 3.14159)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_attr(b"hi")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
-#[fake_doc(r"doc")] //~ ERROR cannot find attribute macro `fake_doc` in this scope
+#[fake_attr] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(100)] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(1, 2, 3)] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr("hello")] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(name = "hello")] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(1, "hi", key = 12, true, false)] //~ ERROR cannot find attribute `fake_attr` in th
+#[fake_attr(key = "hello", val = 10)] //~ ERROR cannot find attribute `fake_attr` in this scop
+#[fake_attr(key("hello"), val(10))] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(enabled = true, disabled = false)] //~ ERROR cannot find attribute `fake_attr` in
+#[fake_attr(true)] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(pi = 3.14159)] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_attr(b"hi")] //~ ERROR cannot find attribute `fake_attr` in this scope
+#[fake_doc(r"doc")] //~ ERROR cannot find attribute `fake_doc` in this scope
 struct Q {}
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr b/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
index efdc2d1cd31ed..b7c45ec1fb7ea 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
@@ -1,76 +1,76 @@
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:3:3
    |
 LL | #[fake_attr]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:4:3
    |
 LL | #[fake_attr(100)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:5:3
    |
 LL | #[fake_attr(1, 2, 3)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:6:3
    |
 LL | #[fake_attr("hello")]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:7:3
    |
 LL | #[fake_attr(name = "hello")]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:8:3
    |
 LL | #[fake_attr(1, "hi", key = 12, true, false)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:9:3
    |
 LL | #[fake_attr(key = "hello", val = 10)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:10:3
    |
 LL | #[fake_attr(key("hello"), val(10))]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:11:3
    |
 LL | #[fake_attr(enabled = true, disabled = false)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:12:3
    |
 LL | #[fake_attr(true)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:13:3
    |
 LL | #[fake_attr(pi = 3.14159)]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_attr` in this scope
+error: cannot find attribute `fake_attr` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:14:3
    |
 LL | #[fake_attr(b"hi")]
    |   ^^^^^^^^^
 
-error: cannot find attribute macro `fake_doc` in this scope
+error: cannot find attribute `fake_doc` in this scope
   --> $DIR/feature-gate-custom_attribute.rs:15:3
    |
 LL | #[fake_doc(r"doc")]
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute2.rs b/src/test/ui/feature-gates/feature-gate-custom_attribute2.rs
index 8fe11cb02a021..e4c80141aa2a5 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute2.rs
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute2.rs
@@ -4,54 +4,54 @@
 // gate-test-custom_attribute
 
 struct StLt<#[lt_struct] 'a>(&'a u32);
-//~^ ERROR the attribute `lt_struct` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_struct` in this scope
 struct StTy<#[ty_struct] I>(I);
-//~^ ERROR the attribute `ty_struct` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_struct` in this scope
 
 enum EnLt<#[lt_enum] 'b> { A(&'b u32), B }
-//~^ ERROR the attribute `lt_enum` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_enum` in this scope
 enum EnTy<#[ty_enum] J> { A(J), B }
-//~^ ERROR the attribute `ty_enum` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_enum` in this scope
 
 trait TrLt<#[lt_trait] 'c> { fn foo(&self, _: &'c [u32]) -> &'c u32; }
-//~^ ERROR the attribute `lt_trait` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_trait` in this scope
 trait TrTy<#[ty_trait] K> { fn foo(&self, _: K); }
-//~^ ERROR the attribute `ty_trait` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_trait` in this scope
 
 type TyLt<#[lt_type] 'd> = &'d u32;
-//~^ ERROR the attribute `lt_type` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_type` in this scope
 type TyTy<#[ty_type] L> = (L, );
-//~^ ERROR the attribute `ty_type` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_type` in this scope
 
 impl<#[lt_inherent] 'e> StLt<'e> { }
-//~^ ERROR the attribute `lt_inherent` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_inherent` in this scope
 impl<#[ty_inherent] M> StTy<M> { }
-//~^ ERROR the attribute `ty_inherent` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_inherent` in this scope
 
 impl<#[lt_impl_for] 'f> TrLt<'f> for StLt<'f> {
-    //~^ ERROR the attribute `lt_impl_for` is currently unknown to the compiler
+    //~^ ERROR cannot find attribute `lt_impl_for` in this scope
     fn foo(&self, _: &'f [u32]) -> &'f u32 { loop { } }
 }
 impl<#[ty_impl_for] N> TrTy<N> for StTy<N> {
-    //~^ ERROR the attribute `ty_impl_for` is currently unknown to the compiler
+    //~^ ERROR cannot find attribute `ty_impl_for` in this scope
     fn foo(&self, _: N) { }
 }
 
 fn f_lt<#[lt_fn] 'g>(_: &'g [u32]) -> &'g u32 { loop { } }
-//~^ ERROR the attribute `lt_fn` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `lt_fn` in this scope
 fn f_ty<#[ty_fn] O>(_: O) { }
-//~^ ERROR the attribute `ty_fn` is currently unknown to the compiler
+//~^ ERROR cannot find attribute `ty_fn` in this scope
 
 impl<I> StTy<I> {
     fn m_lt<#[lt_meth] 'h>(_: &'h [u32]) -> &'h u32 { loop { } }
-    //~^ ERROR the attribute `lt_meth` is currently unknown to the compiler
+    //~^ ERROR cannot find attribute `lt_meth` in this scope
     fn m_ty<#[ty_meth] P>(_: P) { }
-    //~^ ERROR the attribute `ty_meth` is currently unknown to the compiler
+    //~^ ERROR cannot find attribute `ty_meth` in this scope
 }
 
 fn hof_lt<Q>(_: Q)
     where Q: for <#[lt_hof] 'i> Fn(&'i [u32]) -> &'i u32
-    //~^ ERROR the attribute `lt_hof` is currently unknown to the compiler
+    //~^ ERROR cannot find attribute `lt_hof` in this scope
 {
 }
 
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute2.stderr b/src/test/ui/feature-gates/feature-gate-custom_attribute2.stderr
index 15e0c41b90637..bc89caddb4439 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute2.stderr
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute2.stderr
@@ -1,156 +1,104 @@
-error[E0658]: the attribute `lt_struct` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:6:13
+error: cannot find attribute `lt_hof` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:53:21
    |
-LL | struct StLt<#[lt_struct] 'a>(&'a u32);
-   |             ^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL |     where Q: for <#[lt_hof] 'i> Fn(&'i [u32]) -> &'i u32
+   |                     ^^^^^^
 
-error[E0658]: the attribute `ty_struct` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:8:13
+error: cannot find attribute `ty_meth` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:48:15
    |
-LL | struct StTy<#[ty_struct] I>(I);
-   |             ^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL |     fn m_ty<#[ty_meth] P>(_: P) { }
+   |               ^^^^^^^
 
-error[E0658]: the attribute `lt_enum` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:11:11
+error: cannot find attribute `lt_meth` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:46:15
    |
-LL | enum EnLt<#[lt_enum] 'b> { A(&'b u32), B }
-   |           ^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL |     fn m_lt<#[lt_meth] 'h>(_: &'h [u32]) -> &'h u32 { loop { } }
+   |               ^^^^^^^
 
-error[E0658]: the attribute `ty_enum` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:13:11
-   |
-LL | enum EnTy<#[ty_enum] J> { A(J), B }
-   |           ^^^^^^^^^^
+error: cannot find attribute `ty_fn` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:42:11
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | fn f_ty<#[ty_fn] O>(_: O) { }
+   |           ^^^^^
 
-error[E0658]: the attribute `lt_trait` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:16:12
+error: cannot find attribute `lt_fn` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:40:11
    |
-LL | trait TrLt<#[lt_trait] 'c> { fn foo(&self, _: &'c [u32]) -> &'c u32; }
-   |            ^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | fn f_lt<#[lt_fn] 'g>(_: &'g [u32]) -> &'g u32 { loop { } }
+   |           ^^^^^
 
-error[E0658]: the attribute `ty_trait` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:18:12
-   |
-LL | trait TrTy<#[ty_trait] K> { fn foo(&self, _: K); }
-   |            ^^^^^^^^^^^
+error: cannot find attribute `ty_impl_for` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:35:8
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | impl<#[ty_impl_for] N> TrTy<N> for StTy<N> {
+   |        ^^^^^^^^^^^
 
-error[E0658]: the attribute `lt_type` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:21:11
-   |
-LL | type TyLt<#[lt_type] 'd> = &'d u32;
-   |           ^^^^^^^^^^
+error: cannot find attribute `lt_impl_for` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:31:8
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | impl<#[lt_impl_for] 'f> TrLt<'f> for StLt<'f> {
+   |        ^^^^^^^^^^^
 
-error[E0658]: the attribute `ty_type` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:23:11
-   |
-LL | type TyTy<#[ty_type] L> = (L, );
-   |           ^^^^^^^^^^
+error: cannot find attribute `ty_inherent` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:28:8
    |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | impl<#[ty_inherent] M> StTy<M> { }
+   |        ^^^^^^^^^^^
 
-error[E0658]: the attribute `lt_inherent` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:26:6
+error: cannot find attribute `lt_inherent` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:26:8
    |
 LL | impl<#[lt_inherent] 'e> StLt<'e> { }
-   |      ^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |        ^^^^^^^^^^^
 
-error[E0658]: the attribute `ty_inherent` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:28:6
+error: cannot find attribute `ty_type` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:23:13
    |
-LL | impl<#[ty_inherent] M> StTy<M> { }
-   |      ^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | type TyTy<#[ty_type] L> = (L, );
+   |             ^^^^^^^
 
-error[E0658]: the attribute `lt_impl_for` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:31:6
+error: cannot find attribute `lt_type` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:21:13
    |
-LL | impl<#[lt_impl_for] 'f> TrLt<'f> for StLt<'f> {
-   |      ^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | type TyLt<#[lt_type] 'd> = &'d u32;
+   |             ^^^^^^^
 
-error[E0658]: the attribute `ty_impl_for` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:35:6
+error: cannot find attribute `ty_trait` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:18:14
    |
-LL | impl<#[ty_impl_for] N> TrTy<N> for StTy<N> {
-   |      ^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | trait TrTy<#[ty_trait] K> { fn foo(&self, _: K); }
+   |              ^^^^^^^^
 
-error[E0658]: the attribute `lt_fn` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:40:9
+error: cannot find attribute `lt_trait` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:16:14
    |
-LL | fn f_lt<#[lt_fn] 'g>(_: &'g [u32]) -> &'g u32 { loop { } }
-   |         ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | trait TrLt<#[lt_trait] 'c> { fn foo(&self, _: &'c [u32]) -> &'c u32; }
+   |              ^^^^^^^^
 
-error[E0658]: the attribute `ty_fn` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:42:9
+error: cannot find attribute `ty_enum` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:13:13
    |
-LL | fn f_ty<#[ty_fn] O>(_: O) { }
-   |         ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | enum EnTy<#[ty_enum] J> { A(J), B }
+   |             ^^^^^^^
 
-error[E0658]: the attribute `lt_meth` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:46:13
+error: cannot find attribute `lt_enum` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:11:13
    |
-LL |     fn m_lt<#[lt_meth] 'h>(_: &'h [u32]) -> &'h u32 { loop { } }
-   |             ^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | enum EnLt<#[lt_enum] 'b> { A(&'b u32), B }
+   |             ^^^^^^^
 
-error[E0658]: the attribute `ty_meth` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:48:13
+error: cannot find attribute `ty_struct` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:8:15
    |
-LL |     fn m_ty<#[ty_meth] P>(_: P) { }
-   |             ^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | struct StTy<#[ty_struct] I>(I);
+   |               ^^^^^^^^^
 
-error[E0658]: the attribute `lt_hof` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute2.rs:53:19
+error: cannot find attribute `lt_struct` in this scope
+  --> $DIR/feature-gate-custom_attribute2.rs:6:15
    |
-LL |     where Q: for <#[lt_hof] 'i> Fn(&'i [u32]) -> &'i u32
-   |                   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+LL | struct StLt<#[lt_struct] 'a>(&'a u32);
+   |               ^^^^^^^^^
 
 error: aborting due to 17 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/feature-gates/feature-gate-doc_alias.rs b/src/test/ui/feature-gates/feature-gate-doc_alias.rs
index adb6fc217a329..c95722102d9b6 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_alias.rs
+++ b/src/test/ui/feature-gates/feature-gate-doc_alias.rs
@@ -1,4 +1,4 @@
-#[doc(alias = "foo")] //~ ERROR: `#[doc(alias = "...")]` is experimental
+#[doc(alias = "foo")] //~ ERROR: `#[doc(alias)]` is experimental
 pub struct Foo;
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-doc_alias.stderr b/src/test/ui/feature-gates/feature-gate-doc_alias.stderr
index dddaa45de8ff8..540b1f5ccbe43 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_alias.stderr
+++ b/src/test/ui/feature-gates/feature-gate-doc_alias.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `#[doc(alias = "...")]` is experimental
+error[E0658]: `#[doc(alias)]` is experimental
   --> $DIR/feature-gate-doc_alias.rs:1:1
    |
 LL | #[doc(alias = "foo")]
diff --git a/src/test/ui/feature-gates/feature-gate-doc_cfg.rs b/src/test/ui/feature-gates/feature-gate-doc_cfg.rs
index bb3846e7f6b55..b12b8a1057182 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_cfg.rs
+++ b/src/test/ui/feature-gates/feature-gate-doc_cfg.rs
@@ -1,2 +1,2 @@
-#[doc(cfg(unix))] //~ ERROR: `#[doc(cfg(...))]` is experimental
+#[doc(cfg(unix))] //~ ERROR: `#[doc(cfg)]` is experimental
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-doc_cfg.stderr b/src/test/ui/feature-gates/feature-gate-doc_cfg.stderr
index 7b0a231df4c3e..eaa908d0037ae 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_cfg.stderr
+++ b/src/test/ui/feature-gates/feature-gate-doc_cfg.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `#[doc(cfg(...))]` is experimental
+error[E0658]: `#[doc(cfg)]` is experimental
   --> $DIR/feature-gate-doc_cfg.rs:1:1
    |
 LL | #[doc(cfg(unix))]
diff --git a/src/test/ui/feature-gates/feature-gate-doc_keyword.rs b/src/test/ui/feature-gates/feature-gate-doc_keyword.rs
index 6cdcfa67c3a9b..4bb9a40deb0dd 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_keyword.rs
+++ b/src/test/ui/feature-gates/feature-gate-doc_keyword.rs
@@ -1,4 +1,4 @@
-#[doc(keyword = "match")] //~ ERROR: `#[doc(keyword = "...")]` is experimental
+#[doc(keyword = "match")] //~ ERROR: `#[doc(keyword)]` is experimental
 /// wonderful
 mod foo{}
 
diff --git a/src/test/ui/feature-gates/feature-gate-doc_keyword.stderr b/src/test/ui/feature-gates/feature-gate-doc_keyword.stderr
index abde0bea9b230..15a41d9ffa4ea 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_keyword.stderr
+++ b/src/test/ui/feature-gates/feature-gate-doc_keyword.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `#[doc(keyword = "...")]` is experimental
+error[E0658]: `#[doc(keyword)]` is experimental
   --> $DIR/feature-gate-doc_keyword.rs:1:1
    |
 LL | #[doc(keyword = "match")]
diff --git a/src/test/ui/feature-gates/feature-gate-external_doc.rs b/src/test/ui/feature-gates/feature-gate-external_doc.rs
index dec3fa185791c..9d68d3ec4f52a 100644
--- a/src/test/ui/feature-gates/feature-gate-external_doc.rs
+++ b/src/test/ui/feature-gates/feature-gate-external_doc.rs
@@ -1,2 +1,2 @@
-#[doc(include="asdf.md")] //~ ERROR: `#[doc(include = "...")]` is experimental
+#[doc(include="asdf.md")] //~ ERROR: `#[doc(include)]` is experimental
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-external_doc.stderr b/src/test/ui/feature-gates/feature-gate-external_doc.stderr
index a5a874374d1eb..683c0ad217426 100644
--- a/src/test/ui/feature-gates/feature-gate-external_doc.stderr
+++ b/src/test/ui/feature-gates/feature-gate-external_doc.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `#[doc(include = "...")]` is experimental
+error[E0658]: `#[doc(include)]` is experimental
   --> $DIR/feature-gate-external_doc.rs:1:1
    |
 LL | #[doc(include="asdf.md")]
diff --git a/src/test/ui/feature-gates/feature-gate-intrinsics.rs b/src/test/ui/feature-gates/feature-gate-intrinsics.rs
index d1da94338283b..e0dc3cc579d79 100644
--- a/src/test/ui/feature-gates/feature-gate-intrinsics.rs
+++ b/src/test/ui/feature-gates/feature-gate-intrinsics.rs
@@ -3,5 +3,6 @@ extern "rust-intrinsic" {   //~ ERROR intrinsics are subject to change
 }
 
 extern "rust-intrinsic" fn baz() {} //~ ERROR intrinsics are subject to change
+//~^ ERROR intrinsic must be in
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-intrinsics.stderr b/src/test/ui/feature-gates/feature-gate-intrinsics.stderr
index 09843f05af1b9..101a10e8df71f 100644
--- a/src/test/ui/feature-gates/feature-gate-intrinsics.stderr
+++ b/src/test/ui/feature-gates/feature-gate-intrinsics.stderr
@@ -22,7 +22,13 @@ error[E0093]: unrecognized intrinsic function: `bar`
 LL |     fn bar();
    |     ^^^^^^^^^ unrecognized intrinsic
 
-error: aborting due to 3 previous errors
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/feature-gate-intrinsics.rs:5:34
+   |
+LL | extern "rust-intrinsic" fn baz() {}
+   |                                  ^^
+
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0093, E0658.
 For more information about an error, try `rustc --explain E0093`.
diff --git a/src/test/ui/feature-gates/feature-gate-is_sorted.rs b/src/test/ui/feature-gates/feature-gate-is_sorted.rs
index 078ecc577610b..359ed835bcbb2 100644
--- a/src/test/ui/feature-gates/feature-gate-is_sorted.rs
+++ b/src/test/ui/feature-gates/feature-gate-is_sorted.rs
@@ -1,11 +1,11 @@
 fn main() {
-    // Assert `Iterator` methods are feature gated
+    // Assert `Iterator` methods are unstable
     assert!([1, 2, 2, 9].iter().is_sorted());
     //~^ ERROR: use of unstable library feature 'is_sorted': new API
     assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
     //~^ ERROR: use of unstable library feature 'is_sorted': new API
 
-    // Assert `[T]` methods are feature gated
+    // Assert `[T]` methods are unstable
     assert!([1, 2, 2, 9].is_sorted());
     //~^ ERROR: use of unstable library feature 'is_sorted': new API
     assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
diff --git a/src/test/ui/feature-gates/feature-gate-link_cfg.rs b/src/test/ui/feature-gates/feature-gate-link_cfg.rs
index 1905346e2b5d7..27ec2e98eb68b 100644
--- a/src/test/ui/feature-gates/feature-gate-link_cfg.rs
+++ b/src/test/ui/feature-gates/feature-gate-link_cfg.rs
@@ -1,5 +1,5 @@
 #[link(name = "foo", cfg(foo))]
-//~^ ERROR: is feature gated
+//~^ ERROR: is unstable
 extern {}
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-link_cfg.stderr b/src/test/ui/feature-gates/feature-gate-link_cfg.stderr
index 58aa4ed7497ce..f6c5061546438 100644
--- a/src/test/ui/feature-gates/feature-gate-link_cfg.stderr
+++ b/src/test/ui/feature-gates/feature-gate-link_cfg.stderr
@@ -1,4 +1,4 @@
-error[E0658]: is feature gated
+error[E0658]: is unstable
   --> $DIR/feature-gate-link_cfg.rs:1:1
    |
 LL | #[link(name = "foo", cfg(foo))]
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs b/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
index 4044fd2b895e4..c985298a30aed 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
@@ -19,5 +19,5 @@ fn g() {}
 //~^ ERROR the `#[rustc_dummy]` attribute is just used for rustc unit tests
 #[rustc_unknown]
 //~^ ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
-//~| ERROR cannot find attribute macro `rustc_unknown` in this scope
+//~| ERROR cannot find attribute `rustc_unknown` in this scope
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr b/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
index c1063027fa444..d6fdab2b0412d 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
@@ -37,7 +37,7 @@ LL | #[rustc_unknown]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error: cannot find attribute macro `rustc_unknown` in this scope
+error: cannot find attribute `rustc_unknown` in this scope
   --> $DIR/feature-gate-rustc-attrs.rs:20:3
    |
 LL | #[rustc_unknown]
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.rs b/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.rs
deleted file mode 100644
index 63c2c31fd30e6..0000000000000
--- a/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-// Test that diagnostic macros are gated by `rustc_diagnostic_macros` feature
-// gate
-
-__register_diagnostic!(E0001);
-//~^ ERROR cannot find macro `__register_diagnostic!` in this scope
-
-fn main() {
-    __diagnostic_used!(E0001);
-    //~^ ERROR cannot find macro `__diagnostic_used!` in this scope
-}
-
-__build_diagnostic_array!(DIAGNOSTICS);
-//~^ ERROR cannot find macro `__build_diagnostic_array!` in this scope
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.stderr b/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.stderr
deleted file mode 100644
index 676b8b9f056c1..0000000000000
--- a/src/test/ui/feature-gates/feature-gate-rustc-diagnostic-macros.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error: cannot find macro `__build_diagnostic_array!` in this scope
-  --> $DIR/feature-gate-rustc-diagnostic-macros.rs:12:1
-   |
-LL | __build_diagnostic_array!(DIAGNOSTICS);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: cannot find macro `__diagnostic_used!` in this scope
-  --> $DIR/feature-gate-rustc-diagnostic-macros.rs:8:5
-   |
-LL |     __diagnostic_used!(E0001);
-   |     ^^^^^^^^^^^^^^^^^
-
-error: cannot find macro `__register_diagnostic!` in this scope
-  --> $DIR/feature-gate-rustc-diagnostic-macros.rs:4:1
-   |
-LL | __register_diagnostic!(E0001);
-   | ^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
-
diff --git a/src/test/ui/feature-gates/feature-gate-static-nobundle.rs b/src/test/ui/feature-gates/feature-gate-static-nobundle.rs
index 1ce6c54aa4dc2..644b1f964a059 100644
--- a/src/test/ui/feature-gates/feature-gate-static-nobundle.rs
+++ b/src/test/ui/feature-gates/feature-gate-static-nobundle.rs
@@ -1,5 +1,5 @@
 #[link(name="foo", kind="static-nobundle")]
-//~^ ERROR: kind="static-nobundle" is feature gated
+//~^ ERROR: kind="static-nobundle" is unstable
 extern {}
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-static-nobundle.stderr b/src/test/ui/feature-gates/feature-gate-static-nobundle.stderr
index f2e29cf0678ae..cc0d426d6cf9a 100644
--- a/src/test/ui/feature-gates/feature-gate-static-nobundle.stderr
+++ b/src/test/ui/feature-gates/feature-gate-static-nobundle.stderr
@@ -1,4 +1,4 @@
-error[E0658]: kind="static-nobundle" is feature gated
+error[E0658]: kind="static-nobundle" is unstable
   --> $DIR/feature-gate-static-nobundle.rs:1:1
    |
 LL | #[link(name="foo", kind="static-nobundle")]
diff --git a/src/test/ui/feature-gates/feature-gate-type_ascription.rs b/src/test/ui/feature-gates/feature-gate-type_ascription.rs
index e42e340550681..7a597157300ed 100644
--- a/src/test/ui/feature-gates/feature-gate-type_ascription.rs
+++ b/src/test/ui/feature-gates/feature-gate-type_ascription.rs
@@ -1,4 +1,4 @@
-// Type ascription is feature gated
+// Type ascription is unstable
 
 fn main() {
     let a = 10: u8; //~ ERROR type ascription is experimental
diff --git a/src/test/ui/fn/fn-trait-formatting.stderr b/src/test/ui/fn/fn-trait-formatting.stderr
index 20d7d9ea5b7a8..4d610b49dff8e 100644
--- a/src/test/ui/fn/fn-trait-formatting.stderr
+++ b/src/test/ui/fn/fn-trait-formatting.stderr
@@ -26,13 +26,13 @@ LL |     let _: () = (box || -> isize { unimplemented!() }) as Box<dyn FnMut() -
               found type `std::boxed::Box<dyn std::ops::FnMut() -> isize>`
 
 error[E0277]: expected a `std::ops::Fn<(isize,)>` closure, found `{integer}`
-  --> $DIR/fn-trait-formatting.rs:19:5
+  --> $DIR/fn-trait-formatting.rs:19:14
    |
 LL | fn needs_fn<F>(x: F) where F: Fn(isize) -> isize {}
    | ------------------------------------------------ required by `needs_fn`
 ...
 LL |     needs_fn(1);
-   |     ^^^^^^^^ expected an `Fn<(isize,)>` closure, found `{integer}`
+   |              ^ expected an `Fn<(isize,)>` closure, found `{integer}`
    |
    = help: the trait `std::ops::Fn<(isize,)>` is not implemented for `{integer}`
 
diff --git a/src/test/ui/for/for-c-in-str.rs b/src/test/ui/for/for-c-in-str.rs
index 43b1a04c22d04..1871cf9d2386e 100644
--- a/src/test/ui/for/for-c-in-str.rs
+++ b/src/test/ui/for/for-c-in-str.rs
@@ -6,6 +6,9 @@ fn main() {
     //~| NOTE `&str` is not an iterator
     //~| HELP the trait `std::iter::Iterator` is not implemented for `&str`
     //~| NOTE required by `std::iter::IntoIterator::into_iter`
-        println!("");
+    //~| NOTE in this expansion of desugaring of `for` loop
+    //~| NOTE in this expansion of desugaring of `for` loop
+    //~| NOTE in this expansion of desugaring of `for` loop
+        println!();
     }
 }
diff --git a/src/test/ui/for/for-loop-refutable-pattern-error-message.stderr b/src/test/ui/for/for-loop-refutable-pattern-error-message.stderr
index 0d77fd4efdb82..14aea2dc27eea 100644
--- a/src/test/ui/for/for-loop-refutable-pattern-error-message.stderr
+++ b/src/test/ui/for/for-loop-refutable-pattern-error-message.stderr
@@ -1,8 +1,8 @@
-error[E0005]: refutable pattern in `for` loop binding: `&std::i32::MIN..=0i32` not covered
+error[E0005]: refutable pattern in `for` loop binding: `&std::i32::MIN..=0i32` and `&2i32..=std::i32::MAX` not covered
   --> $DIR/for-loop-refutable-pattern-error-message.rs:2:9
    |
 LL |     for &1 in [1].iter() {}
-   |         ^^ pattern `&std::i32::MIN..=0i32` not covered
+   |         ^^ patterns `&std::i32::MIN..=0i32` and `&2i32..=std::i32::MAX` not covered
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/generator/auto-trait-regions.stderr b/src/test/ui/generator/auto-trait-regions.stderr
index 92f92e2a32a36..dab4d348ceb60 100644
--- a/src/test/ui/generator/auto-trait-regions.stderr
+++ b/src/test/ui/generator/auto-trait-regions.stderr
@@ -1,20 +1,26 @@
 error: implementation of `Foo` is not general enough
   --> $DIR/auto-trait-regions.rs:30:5
    |
+LL | auto trait Foo {}
+   | ----------------- trait `Foo` defined here
+...
 LL |     assert_foo(gen);
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo` would have to be implemented for the type `&'0 OnlyFooIfStaticRef`, for any lifetime `'0`
-   = note: but `Foo` is actually implemented for the type `&'1 OnlyFooIfStaticRef`, for some specific lifetime `'1`
+   = note: `Foo` would have to be implemented for the type `&'0 OnlyFooIfStaticRef`, for any lifetime `'0`...
+   = note: ...but `Foo` is actually implemented for the type `&'1 OnlyFooIfStaticRef`, for some specific lifetime `'1`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/auto-trait-regions.rs:48:5
    |
+LL | auto trait Foo {}
+   | ----------------- trait `Foo` defined here
+...
 LL |     assert_foo(gen);
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo` would have to be implemented for the type `A<'0, '1>`, for any two lifetimes `'0` and `'1`
-   = note: but `Foo` is actually implemented for the type `A<'_, '2>`, for some specific lifetime `'2`
+   = note: `Foo` would have to be implemented for the type `A<'0, '1>`, for any two lifetimes `'0` and `'1`...
+   = note: ...but `Foo` is actually implemented for the type `A<'_, '2>`, for some specific lifetime `'2`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/generator/partial-initialization-across-yield.rs b/src/test/ui/generator/partial-initialization-across-yield.rs
index 1e4593002cb9a..8b75721420351 100644
--- a/src/test/ui/generator/partial-initialization-across-yield.rs
+++ b/src/test/ui/generator/partial-initialization-across-yield.rs
@@ -10,7 +10,7 @@ fn test_tuple() {
     let _ = || {
         let mut t: (i32, i32);
         t.0 = 42;
-        //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
         yield;
         t.1 = 88;
         let _ = t;
@@ -21,7 +21,7 @@ fn test_tuple_struct() {
     let _ = || {
         let mut t: T;
         t.0 = 42;
-        //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
         yield;
         t.1 = 88;
         let _ = t;
@@ -32,7 +32,7 @@ fn test_struct() {
     let _ = || {
         let mut t: S;
         t.x = 42;
-        //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+        //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
         yield;
         t.y = 88;
         let _ = t;
diff --git a/src/test/ui/generator/partial-initialization-across-yield.stderr b/src/test/ui/generator/partial-initialization-across-yield.stderr
index 8bf0037e07009..66b86488eaec7 100644
--- a/src/test/ui/generator/partial-initialization-across-yield.stderr
+++ b/src/test/ui/generator/partial-initialization-across-yield.stderr
@@ -1,20 +1,20 @@
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-yield.rs:12:9
    |
 LL |         t.0 = 42;
-   |         ^^^^^^^^ use of possibly uninitialized `t`
+   |         ^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-yield.rs:23:9
    |
 LL |         t.0 = 42;
-   |         ^^^^^^^^ use of possibly uninitialized `t`
+   |         ^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/partial-initialization-across-yield.rs:34:9
    |
 LL |         t.x = 42;
-   |         ^^^^^^^^ use of possibly uninitialized `t`
+   |         ^^^^^^^^ use of possibly-uninitialized `t`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/generator/static-not-unpin.stderr b/src/test/ui/generator/static-not-unpin.stderr
index 28a6fac5b85e3..b7871ee3478a4 100644
--- a/src/test/ui/generator/static-not-unpin.stderr
+++ b/src/test/ui/generator/static-not-unpin.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `[static generator@$DIR/static-not-unpin.rs:11:25: 13:6 _]: std::marker::Unpin` is not satisfied
-  --> $DIR/static-not-unpin.rs:14:5
+  --> $DIR/static-not-unpin.rs:14:18
    |
 LL | fn assert_unpin<T: Unpin>(_: T) {
    | ------------------------------- required by `assert_unpin`
 ...
 LL |     assert_unpin(generator);
-   |     ^^^^^^^^^^^^ the trait `std::marker::Unpin` is not implemented for `[static generator@$DIR/static-not-unpin.rs:11:25: 13:6 _]`
+   |                  ^^^^^^^^^ the trait `std::marker::Unpin` is not implemented for `[static generator@$DIR/static-not-unpin.rs:11:25: 13:6 _]`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/generic/generic-extern.stderr b/src/test/ui/generic/generic-extern.stderr
index e7625abb1c831..c90215b612d4c 100644
--- a/src/test/ui/generic/generic-extern.stderr
+++ b/src/test/ui/generic/generic-extern.stderr
@@ -4,7 +4,7 @@ error[E0044]: foreign items may not have type parameters
 LL |     fn foo<T>();
    |     ^^^^^^^^^^^^ can't have type parameters
    |
-   = help: use specialization instead of type parameters by replacing them with concrete types like `u32`
+   = help: replace the type parameters with concrete types like `u32`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/hrtb/due-to-where-clause.rs b/src/test/ui/hrtb/due-to-where-clause.rs
new file mode 100644
index 0000000000000..04e2ddd4a6090
--- /dev/null
+++ b/src/test/ui/hrtb/due-to-where-clause.rs
@@ -0,0 +1,16 @@
+// ignore-compare-mode-nll
+// ^ This code works in nll mode.
+
+fn main() {
+    test::<FooS>(&mut 42); //~ ERROR implementation of `Foo` is not general enough
+}
+
+trait Foo<'a> {}
+
+struct FooS<'a> {
+    data: &'a mut u32,
+}
+
+impl<'a, 'b: 'a> Foo<'b> for FooS<'a> {}
+
+fn test<'a, F>(data: &'a mut u32) where F: for<'b> Foo<'b> {}
diff --git a/src/test/ui/hrtb/due-to-where-clause.stderr b/src/test/ui/hrtb/due-to-where-clause.stderr
new file mode 100644
index 0000000000000..e698584bb716f
--- /dev/null
+++ b/src/test/ui/hrtb/due-to-where-clause.stderr
@@ -0,0 +1,17 @@
+error: implementation of `Foo` is not general enough
+  --> $DIR/due-to-where-clause.rs:5:5
+   |
+LL |     test::<FooS>(&mut 42);
+   |     ^^^^^^^^^^^^ doesn't satisfy where-clause
+...
+LL | trait Foo<'a> {}
+   | ---------------- trait `Foo` defined here
+...
+LL | fn test<'a, F>(data: &'a mut u32) where F: for<'b> Foo<'b> {}
+   | ------------------------------------------------------------- due to a where-clause on `test`...
+   |
+   = note: ...`FooS<'_>` must implement `Foo<'0>`, for any lifetime `'0`...
+   = note: ...but `FooS<'_>` actually implements `Foo<'1>`, for some specific lifetime `'1`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/hrtb/hrtb-cache-issue-54302.stderr b/src/test/ui/hrtb/hrtb-cache-issue-54302.stderr
index 77a5491cb63a7..003f32659351f 100644
--- a/src/test/ui/hrtb/hrtb-cache-issue-54302.stderr
+++ b/src/test/ui/hrtb/hrtb-cache-issue-54302.stderr
@@ -1,11 +1,14 @@
 error: implementation of `Deserialize` is not general enough
   --> $DIR/hrtb-cache-issue-54302.rs:19:5
    |
+LL | trait Deserialize<'de> {}
+   | ------------------------- trait `Deserialize` defined here
+...
 LL |     assert_deserialize_owned::<&'static str>();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Deserialize` is not general enough
    |
-   = note: `&'static str` must implement `Deserialize<'0>`, for any lifetime `'0`
-   = note: but `&str` actually implements `Deserialize<'1>`, for some specific lifetime `'1`
+   = note: `&'static str` must implement `Deserialize<'0>`, for any lifetime `'0`...
+   = note: ...but `&str` actually implements `Deserialize<'1>`, for some specific lifetime `'1`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/hrtb/hrtb-higher-ranker-supertraits-transitive.stderr b/src/test/ui/hrtb/hrtb-higher-ranker-supertraits-transitive.stderr
index 0cddd353d679e..18f49089302e5 100644
--- a/src/test/ui/hrtb/hrtb-higher-ranker-supertraits-transitive.stderr
+++ b/src/test/ui/hrtb/hrtb-higher-ranker-supertraits-transitive.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `for<'ccx> B: Bar<'ccx>` is not satisfied
-  --> $DIR/hrtb-higher-ranker-supertraits-transitive.rs:47:5
+  --> $DIR/hrtb-higher-ranker-supertraits-transitive.rs:47:26
    |
 LL | / fn want_bar_for_any_ccx<B>(b: &B)
 LL | |     where B : for<'ccx> Bar<'ccx>
@@ -8,7 +8,7 @@ LL | | }
    | |_- required by `want_bar_for_any_ccx`
 ...
 LL |       want_bar_for_any_ccx(b);
-   |       ^^^^^^^^^^^^^^^^^^^^ the trait `for<'ccx> Bar<'ccx>` is not implemented for `B`
+   |                            ^ the trait `for<'ccx> Bar<'ccx>` is not implemented for `B`
    |
    = help: consider adding a `where for<'ccx> B: Bar<'ccx>` bound
 
diff --git a/src/test/ui/hrtb/hrtb-higher-ranker-supertraits.stderr b/src/test/ui/hrtb/hrtb-higher-ranker-supertraits.stderr
index 6df486ebaff38..7857ab6e86a20 100644
--- a/src/test/ui/hrtb/hrtb-higher-ranker-supertraits.stderr
+++ b/src/test/ui/hrtb/hrtb-higher-ranker-supertraits.stderr
@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `for<'tcx> F: Foo<'tcx>` is not satisfied
-  --> $DIR/hrtb-higher-ranker-supertraits.rs:18:5
+  --> $DIR/hrtb-higher-ranker-supertraits.rs:18:26
    |
 LL |       want_foo_for_any_tcx(f);
-   |       ^^^^^^^^^^^^^^^^^^^^ the trait `for<'tcx> Foo<'tcx>` is not implemented for `F`
+   |                            ^ the trait `for<'tcx> Foo<'tcx>` is not implemented for `F`
 ...
 LL | / fn want_foo_for_any_tcx<F>(f: &F)
 LL | |     where F : for<'tcx> Foo<'tcx>
@@ -15,10 +15,10 @@ LL | | }
    = help: consider adding a `where for<'tcx> F: Foo<'tcx>` bound
 
 error[E0277]: the trait bound `for<'ccx> B: Bar<'ccx>` is not satisfied
-  --> $DIR/hrtb-higher-ranker-supertraits.rs:35:5
+  --> $DIR/hrtb-higher-ranker-supertraits.rs:35:26
    |
 LL |       want_bar_for_any_ccx(b);
-   |       ^^^^^^^^^^^^^^^^^^^^ the trait `for<'ccx> Bar<'ccx>` is not implemented for `B`
+   |                            ^ the trait `for<'ccx> Bar<'ccx>` is not implemented for `B`
 ...
 LL | / fn want_bar_for_any_ccx<B>(b: &B)
 LL | |     where B : for<'ccx> Bar<'ccx>
diff --git a/src/test/ui/hrtb/issue-30786.migrate.stderr b/src/test/ui/hrtb/issue-30786.migrate.stderr
index e7deca7644b0e..c0e3fd3cf4679 100644
--- a/src/test/ui/hrtb/issue-30786.migrate.stderr
+++ b/src/test/ui/hrtb/issue-30786.migrate.stderr
@@ -1,11 +1,17 @@
 error: implementation of `Stream` is not general enough
   --> $DIR/issue-30786.rs:108:22
    |
-LL |     let map = source.map(|x: &_| x);
-   |                      ^^^
+LL | / pub trait Stream {
+LL | |     type Item;
+LL | |     fn next(self) -> Option<Self::Item>;
+LL | | }
+   | |_- trait `Stream` defined here
+...
+LL |       let map = source.map(|x: &_| x);
+   |                        ^^^ implementation of `Stream` is not general enough
    |
-   = note: `Stream` would have to be implemented for the type `&'0 mut Map<Repeat, [closure@$DIR/issue-30786.rs:108:26: 108:35]>`, for any lifetime `'0`
-   = note: but `Stream` is actually implemented for the type `&'1 mut Map<Repeat, [closure@$DIR/issue-30786.rs:108:26: 108:35]>`, for some specific lifetime `'1`
+   = note: `Stream` would have to be implemented for the type `&'0 mut Map<Repeat, [closure@$DIR/issue-30786.rs:108:26: 108:35]>`, for any lifetime `'0`...
+   = note: ...but `Stream` is actually implemented for the type `&'1 mut Map<Repeat, [closure@$DIR/issue-30786.rs:108:26: 108:35]>`, for some specific lifetime `'1`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/hrtb/issue-30786.nll.stderr b/src/test/ui/hrtb/issue-30786.nll.stderr
index 8614d86d93ac3..1cfd93e59d935 100644
--- a/src/test/ui/hrtb/issue-30786.nll.stderr
+++ b/src/test/ui/hrtb/issue-30786.nll.stderr
@@ -1,11 +1,11 @@
 error: higher-ranked subtype error
-  --> $DIR/issue-30786.rs:112:18
+  --> $DIR/issue-30786.rs:113:18
    |
 LL |     let filter = map.filter(|x: &_| true);
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: higher-ranked subtype error
-  --> $DIR/issue-30786.rs:114:17
+  --> $DIR/issue-30786.rs:115:17
    |
 LL |     let count = filter.count(); // Assert that we still have a valid stream.
    |                 ^^^^^^^^^^^^^^
diff --git a/src/test/ui/hrtb/issue-30786.rs b/src/test/ui/hrtb/issue-30786.rs
index b9920a1950498..c42297ca68346 100644
--- a/src/test/ui/hrtb/issue-30786.rs
+++ b/src/test/ui/hrtb/issue-30786.rs
@@ -16,7 +16,7 @@
 
 //[nll]compile-flags: -Z borrowck=mir
 
-pub trait Stream {
+pub trait Stream { //[migrate]~ NOTE trait `Stream` defined here
     type Item;
     fn next(self) -> Option<Self::Item>;
 }
@@ -109,6 +109,7 @@ fn main() {
     //[migrate]~^ ERROR implementation of `Stream` is not general enough
     //[migrate]~| NOTE  `Stream` would have to be implemented for the type `&'0 mut Map
     //[migrate]~| NOTE  but `Stream` is actually implemented for the type `&'1
+    //[migrate]~| NOTE  implementation of `Stream` is not general enough
     let filter = map.filter(|x: &_| true);
     //[nll]~^ ERROR higher-ranked subtype error
     let count = filter.count(); // Assert that we still have a valid stream.
diff --git a/src/test/ui/hrtb/issue-57639.rs b/src/test/ui/hrtb/issue-57639.rs
index 4bcaef3616bd5..392e7233b567a 100644
--- a/src/test/ui/hrtb/issue-57639.rs
+++ b/src/test/ui/hrtb/issue-57639.rs
@@ -10,7 +10,7 @@
 //
 // See [this comment on GitHub][c] for more details.
 //
-// run-pass
+// check-pass
 //
 // [c]: https://github.com/rust-lang/rust/issues/57639#issuecomment-455685861
 
diff --git a/src/test/ui/hygiene/auxiliary/not-libstd.rs b/src/test/ui/hygiene/auxiliary/not-libstd.rs
new file mode 100644
index 0000000000000..babba293d03bd
--- /dev/null
+++ b/src/test/ui/hygiene/auxiliary/not-libstd.rs
@@ -0,0 +1 @@
+pub fn not_in_lib_std() {}
diff --git a/src/test/ui/hygiene/no_implicit_prelude-2018.rs b/src/test/ui/hygiene/no_implicit_prelude-2018.rs
index 3ad7435fecf29..83ca28167a468 100644
--- a/src/test/ui/hygiene/no_implicit_prelude-2018.rs
+++ b/src/test/ui/hygiene/no_implicit_prelude-2018.rs
@@ -4,7 +4,7 @@
 mod bar {
     fn f() {
         ::std::print!(""); // OK
-        print!(); //~ ERROR cannot find macro `print!` in this scope
+        print!(); //~ ERROR cannot find macro `print` in this scope
     }
 }
 
diff --git a/src/test/ui/hygiene/no_implicit_prelude-2018.stderr b/src/test/ui/hygiene/no_implicit_prelude-2018.stderr
index 0fdb18d967a6c..f31b75238dffe 100644
--- a/src/test/ui/hygiene/no_implicit_prelude-2018.stderr
+++ b/src/test/ui/hygiene/no_implicit_prelude-2018.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `print!` in this scope
+error: cannot find macro `print` in this scope
   --> $DIR/no_implicit_prelude-2018.rs:7:9
    |
 LL |         print!();
diff --git a/src/test/ui/hygiene/no_implicit_prelude.rs b/src/test/ui/hygiene/no_implicit_prelude.rs
index 890c8307543f3..204e7b248797a 100644
--- a/src/test/ui/hygiene/no_implicit_prelude.rs
+++ b/src/test/ui/hygiene/no_implicit_prelude.rs
@@ -13,7 +13,7 @@ mod bar {
     }
     fn f() {
         ::foo::m!();
-        assert_eq!(0, 0); //~ ERROR cannot find macro `panic!` in this scope
+        assert_eq!(0, 0); //~ ERROR cannot find macro `panic` in this scope
     }
 }
 
diff --git a/src/test/ui/hygiene/no_implicit_prelude.stderr b/src/test/ui/hygiene/no_implicit_prelude.stderr
index 643f803f62049..bc0ce746be925 100644
--- a/src/test/ui/hygiene/no_implicit_prelude.stderr
+++ b/src/test/ui/hygiene/no_implicit_prelude.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `panic!` in this scope
+error: cannot find macro `panic` in this scope
   --> $DIR/no_implicit_prelude.rs:16:9
    |
 LL |         assert_eq!(0, 0);
@@ -22,7 +22,7 @@ LL |     fn f() { ::bar::m!(); }
    |              ------------ in this macro invocation
 ...
 LL |         ().clone()
-   |            ^^^^^
+   |            ^^^^^ method not found in `()`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/hygiene/prelude-import-hygiene.rs b/src/test/ui/hygiene/prelude-import-hygiene.rs
new file mode 100644
index 0000000000000..51e7bed6580b3
--- /dev/null
+++ b/src/test/ui/hygiene/prelude-import-hygiene.rs
@@ -0,0 +1,29 @@
+// Make sure that attribute used when injecting the prelude are resolved
+// hygienically.
+
+// check-pass
+// aux-build:not-libstd.rs
+
+//revisions: rust2015 rust2018
+//[rust2018] edition:2018
+
+// The prelude import shouldn't see these as candidates for when it's trying to
+// use the built-in macros.
+extern crate core;
+use core::prelude::v1::test as prelude_import;
+use core::prelude::v1::test as macro_use;
+
+// Should not be used for the prelude import - not a concern in the 2015 edition
+// because `std` is already declared in the crate root.
+#[cfg(rust2018)]
+extern crate not_libstd as std;
+
+#[cfg(rust2018)]
+mod x {
+    // The extern crate item should override `std` in the extern prelude.
+    fn f() {
+        std::not_in_lib_std();
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/hygiene/trait_items.stderr b/src/test/ui/hygiene/trait_items.stderr
index 4192b97e75069..39e32522c7a76 100644
--- a/src/test/ui/hygiene/trait_items.stderr
+++ b/src/test/ui/hygiene/trait_items.stderr
@@ -5,7 +5,7 @@ LL |     fn f() { ::baz::m!(); }
    |              ------------ in this macro invocation
 ...
 LL |     pub macro m() { ().f() }
-   |                        ^
+   |                        ^ method not found in `()`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/hygiene/unpretty-debug.stdout b/src/test/ui/hygiene/unpretty-debug.stdout
index beac4c17abf9c..6971873ba601e 100644
--- a/src/test/ui/hygiene/unpretty-debug.stdout
+++ b/src/test/ui/hygiene/unpretty-debug.stdout
@@ -13,3 +13,13 @@ macro_rules! foo /* 0#0 */ { ($ x : ident) => { y + $ x } }
 fn bar /* 0#0 */() { let x /* 0#0 */ = 1; y /* 0#1 */ + x /* 0#0 */ }
 
 fn y /* 0#0 */() { }
+
+/*
+Expansions:
+0: parent: ExpnId(0), call_site_ctxt: #0, kind: Root
+1: parent: ExpnId(0), call_site_ctxt: #0, kind: Macro(Bang, foo)
+
+SyntaxContexts:
+#0: parent: #0, outer_mark: (ExpnId(0), Opaque)
+#1: parent: #0, outer_mark: (ExpnId(1), SemiTransparent)
+*/
diff --git a/src/test/ui/if-ret.stderr b/src/test/ui/if-ret.stderr
new file mode 100644
index 0000000000000..2df8f22944ee8
--- /dev/null
+++ b/src/test/ui/if-ret.stderr
@@ -0,0 +1,13 @@
+warning: unreachable block in `if` expression
+  --> $DIR/if-ret.rs:6:24
+   |
+LL | fn foo() { if (return) { } }
+   |                        ^^^
+   |
+   = note: `#[warn(unreachable_code)]` on by default
+note: any code following this expression is unreachable
+  --> $DIR/if-ret.rs:6:15
+   |
+LL | fn foo() { if (return) { } }
+   |               ^^^^^^^^
+
diff --git a/src/test/ui/impl-trait/bindings-opaque.stderr b/src/test/ui/impl-trait/bindings-opaque.stderr
index ad108173a7a1e..644d26b34060c 100644
--- a/src/test/ui/impl-trait/bindings-opaque.stderr
+++ b/src/test/ui/impl-trait/bindings-opaque.stderr
@@ -10,19 +10,19 @@ error[E0599]: no method named `count_ones` found for type `impl std::marker::Cop
   --> $DIR/bindings-opaque.rs:11:17
    |
 LL |     let _ = FOO.count_ones();
-   |                 ^^^^^^^^^^
+   |                 ^^^^^^^^^^ method not found in `impl std::marker::Copy`
 
 error[E0599]: no method named `count_ones` found for type `impl std::marker::Copy` in the current scope
   --> $DIR/bindings-opaque.rs:13:17
    |
 LL |     let _ = BAR.count_ones();
-   |                 ^^^^^^^^^^
+   |                 ^^^^^^^^^^ method not found in `impl std::marker::Copy`
 
 error[E0599]: no method named `count_ones` found for type `impl std::marker::Copy` in the current scope
   --> $DIR/bindings-opaque.rs:15:17
    |
 LL |     let _ = foo.count_ones();
-   |                 ^^^^^^^^^^
+   |                 ^^^^^^^^^^ method not found in `impl std::marker::Copy`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/impl-trait/closure-calling-parent-fn.rs b/src/test/ui/impl-trait/closure-calling-parent-fn.rs
index 58d7875ccd034..9dab334a217c2 100644
--- a/src/test/ui/impl-trait/closure-calling-parent-fn.rs
+++ b/src/test/ui/impl-trait/closure-calling-parent-fn.rs
@@ -5,7 +5,7 @@
 // `foo` and hence is treated opaquely within the closure body.  This
 // resulted in a failed subtype relationship.
 //
-// run-pass
+// check-pass
 
 fn foo() -> impl Copy { || foo(); }
 fn bar() -> impl Copy { || bar(); }
diff --git a/src/test/ui/impl-trait/issues/issue-21659-show-relevant-trait-impls-3.stderr b/src/test/ui/impl-trait/issues/issue-21659-show-relevant-trait-impls-3.stderr
index 666418f6ee2c1..441191beaf588 100644
--- a/src/test/ui/impl-trait/issues/issue-21659-show-relevant-trait-impls-3.stderr
+++ b/src/test/ui/impl-trait/issues/issue-21659-show-relevant-trait-impls-3.stderr
@@ -5,7 +5,7 @@ LL | struct Bar;
    | ----------- method `foo` not found for this
 ...
 LL |     f1.foo(1usize);
-   |        ^^^
+   |        ^^^ method not found in `Bar`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `foo`, perhaps you need to implement it:
diff --git a/src/test/ui/impl-trait/issues/issue-53457.rs b/src/test/ui/impl-trait/issues/issue-53457.rs
index de8c579743fc0..3f97502492506 100644
--- a/src/test/ui/impl-trait/issues/issue-53457.rs
+++ b/src/test/ui/impl-trait/issues/issue-53457.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![feature(type_alias_impl_trait)]
 
@@ -9,7 +9,7 @@ fn bar<F: Fn(&i32) + Clone>(f: F) -> F {
 }
 
 fn foo() -> X {
-    bar(|x| ())
+    bar(|_| ())
 }
 
 fn main() {}
diff --git a/src/test/ui/impl-trait/method-suggestion-no-duplication.stderr b/src/test/ui/impl-trait/method-suggestion-no-duplication.stderr
index afb3376638a96..fb870d6c6f076 100644
--- a/src/test/ui/impl-trait/method-suggestion-no-duplication.stderr
+++ b/src/test/ui/impl-trait/method-suggestion-no-duplication.stderr
@@ -5,7 +5,7 @@ LL | struct Foo;
    | ----------- method `is_empty` not found for this
 ...
 LL |     foo(|s| s.is_empty());
-   |               ^^^^^^^^
+   |               ^^^^^^^^ method not found in `Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `is_empty`, perhaps you need to implement it:
diff --git a/src/test/ui/impl-trait/multiple-lifetimes/inverse-bounds.rs b/src/test/ui/impl-trait/multiple-lifetimes/inverse-bounds.rs
index 2da3886bb552b..3911769b0c63d 100644
--- a/src/test/ui/impl-trait/multiple-lifetimes/inverse-bounds.rs
+++ b/src/test/ui/impl-trait/multiple-lifetimes/inverse-bounds.rs
@@ -1,5 +1,5 @@
 // edition:2018
-// run-pass
+// check-pass
 // revisions: migrate mir
 //[mir]compile-flags: -Z borrowck=mir
 
diff --git a/src/test/ui/impl-trait/needs_least_region_or_bound.rs b/src/test/ui/impl-trait/needs_least_region_or_bound.rs
index 52475f65a8353..3c8682bb62aa5 100644
--- a/src/test/ui/impl-trait/needs_least_region_or_bound.rs
+++ b/src/test/ui/impl-trait/needs_least_region_or_bound.rs
@@ -1,9 +1,7 @@
-// run-pass
+// check-pass
 
 #![feature(member_constraints)]
 
-use std::fmt::Debug;
-
 trait MultiRegionTrait<'a, 'b> {}
 impl<'a, 'b> MultiRegionTrait<'a, 'b> for (&'a u32, &'b u32) {}
 
diff --git a/src/test/ui/impl-trait/no-method-suggested-traits.stderr b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
index 002b60f9f258d..be8f3ab1b72e8 100644
--- a/src/test/ui/impl-trait/no-method-suggested-traits.stderr
+++ b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `method` found for type `u32` in the current scope
   --> $DIR/no-method-suggested-traits.rs:23:10
    |
 LL |     1u32.method();
-   |          ^^^^^^
+   |          ^^^^^^ method not found in `u32`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following traits are implemented but not in scope, perhaps add a `use` for one of them:
@@ -20,7 +20,7 @@ error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::box
   --> $DIR/no-method-suggested-traits.rs:26:44
    |
 LL |     std::rc::Rc::new(&mut Box::new(&1u32)).method();
-   |                                            ^^^^^^
+   |                                            ^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&u32>>`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following traits are implemented but not in scope, perhaps add a `use` for one of them:
@@ -38,7 +38,7 @@ error[E0599]: no method named `method` found for type `char` in the current scop
   --> $DIR/no-method-suggested-traits.rs:30:9
    |
 LL |     'a'.method();
-   |         ^^^^^^
+   |         ^^^^^^ method not found in `char`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -58,7 +58,7 @@ LL |         fn method(&self) {}
    |            the method is available for `std::rc::Rc<std::rc::Rc<&mut std::boxed::Box<&char>>>` here
 ...
 LL |     std::rc::Rc::new(&mut Box::new(&'a')).method();
-   |                                           ^^^^^^
+   |                                           ^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&char>>`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -70,7 +70,7 @@ error[E0599]: no method named `method` found for type `i32` in the current scope
   --> $DIR/no-method-suggested-traits.rs:35:10
    |
 LL |     1i32.method();
-   |          ^^^^^^
+   |          ^^^^^^ method not found in `i32`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -82,7 +82,7 @@ error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::box
   --> $DIR/no-method-suggested-traits.rs:37:44
    |
 LL |     std::rc::Rc::new(&mut Box::new(&1i32)).method();
-   |                                            ^^^^^^
+   |                                            ^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&i32>>`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -97,7 +97,7 @@ LL | struct Foo;
    | ----------- method `method` not found for this
 ...
 LL |     Foo.method();
-   |         ^^^^^^
+   |         ^^^^^^ method not found in `Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following traits define an item `method`, perhaps you need to implement one of them:
@@ -110,7 +110,7 @@ error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::box
   --> $DIR/no-method-suggested-traits.rs:42:43
    |
 LL |     std::rc::Rc::new(&mut Box::new(&Foo)).method();
-   |                                           ^^^^^^
+   |                                           ^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&Foo>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following traits define an item `method`, perhaps you need to implement one of them:
@@ -123,7 +123,7 @@ error[E0599]: no method named `method2` found for type `u64` in the current scop
   --> $DIR/no-method-suggested-traits.rs:45:10
    |
 LL |     1u64.method2();
-   |          ^^^^^^^
+   |          ^^^^^^^ method not found in `u64`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -133,7 +133,7 @@ error[E0599]: no method named `method2` found for type `std::rc::Rc<&mut std::bo
   --> $DIR/no-method-suggested-traits.rs:47:44
    |
 LL |     std::rc::Rc::new(&mut Box::new(&1u64)).method2();
-   |                                            ^^^^^^^
+   |                                            ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&u64>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -143,7 +143,7 @@ error[E0599]: no method named `method2` found for type `no_method_suggested_trai
   --> $DIR/no-method-suggested-traits.rs:50:37
    |
 LL |     no_method_suggested_traits::Foo.method2();
-   |                                     ^^^^^^^
+   |                                     ^^^^^^^ method not found in `no_method_suggested_traits::Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -153,7 +153,7 @@ error[E0599]: no method named `method2` found for type `std::rc::Rc<&mut std::bo
   --> $DIR/no-method-suggested-traits.rs:52:71
    |
 LL |     std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method2();
-   |                                                                       ^^^^^^^
+   |                                                                       ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Foo>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -163,7 +163,7 @@ error[E0599]: no method named `method2` found for type `no_method_suggested_trai
   --> $DIR/no-method-suggested-traits.rs:54:40
    |
 LL |     no_method_suggested_traits::Bar::X.method2();
-   |                                        ^^^^^^^
+   |                                        ^^^^^^^ method not found in `no_method_suggested_traits::Bar`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -173,7 +173,7 @@ error[E0599]: no method named `method2` found for type `std::rc::Rc<&mut std::bo
   --> $DIR/no-method-suggested-traits.rs:56:74
    |
 LL |     std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method2();
-   |                                                                          ^^^^^^^
+   |                                                                          ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Bar>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method2`, perhaps you need to implement it:
@@ -186,7 +186,7 @@ LL | struct Foo;
    | ----------- method `method3` not found for this
 ...
 LL |     Foo.method3();
-   |         ^^^^^^^
+   |         ^^^^^^^ method not found in `Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method3`, perhaps you need to implement it:
@@ -196,7 +196,7 @@ error[E0599]: no method named `method3` found for type `std::rc::Rc<&mut std::bo
   --> $DIR/no-method-suggested-traits.rs:61:43
    |
 LL |     std::rc::Rc::new(&mut Box::new(&Foo)).method3();
-   |                                           ^^^^^^^
+   |                                           ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&Foo>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method3`, perhaps you need to implement it:
@@ -209,7 +209,7 @@ LL | enum Bar { X }
    | -------- method `method3` not found for this
 ...
 LL |     Bar::X.method3();
-   |            ^^^^^^^
+   |            ^^^^^^^ method not found in `Bar`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method3`, perhaps you need to implement it:
@@ -219,7 +219,7 @@ error[E0599]: no method named `method3` found for type `std::rc::Rc<&mut std::bo
   --> $DIR/no-method-suggested-traits.rs:65:46
    |
 LL |     std::rc::Rc::new(&mut Box::new(&Bar::X)).method3();
-   |                                              ^^^^^^^
+   |                                              ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&Bar>>`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `method3`, perhaps you need to implement it:
@@ -229,37 +229,37 @@ error[E0599]: no method named `method3` found for type `usize` in the current sc
   --> $DIR/no-method-suggested-traits.rs:69:13
    |
 LL |     1_usize.method3();
-   |             ^^^^^^^
+   |             ^^^^^^^ method not found in `usize`
 
 error[E0599]: no method named `method3` found for type `std::rc::Rc<&mut std::boxed::Box<&usize>>` in the current scope
   --> $DIR/no-method-suggested-traits.rs:70:47
    |
 LL |     std::rc::Rc::new(&mut Box::new(&1_usize)).method3();
-   |                                               ^^^^^^^
+   |                                               ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&usize>>`
 
 error[E0599]: no method named `method3` found for type `no_method_suggested_traits::Foo` in the current scope
   --> $DIR/no-method-suggested-traits.rs:71:37
    |
 LL |     no_method_suggested_traits::Foo.method3();
-   |                                     ^^^^^^^
+   |                                     ^^^^^^^ method not found in `no_method_suggested_traits::Foo`
 
 error[E0599]: no method named `method3` found for type `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Foo>>` in the current scope
   --> $DIR/no-method-suggested-traits.rs:72:71
    |
 LL |     std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method3();
-   |                                                                       ^^^^^^^
+   |                                                                       ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Foo>>`
 
 error[E0599]: no method named `method3` found for type `no_method_suggested_traits::Bar` in the current scope
   --> $DIR/no-method-suggested-traits.rs:74:40
    |
 LL |     no_method_suggested_traits::Bar::X.method3();
-   |                                        ^^^^^^^
+   |                                        ^^^^^^^ method not found in `no_method_suggested_traits::Bar`
 
 error[E0599]: no method named `method3` found for type `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Bar>>` in the current scope
   --> $DIR/no-method-suggested-traits.rs:75:74
    |
 LL |     std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method3();
-   |                                                                          ^^^^^^^
+   |                                                                          ^^^^^^^ method not found in `std::rc::Rc<&mut std::boxed::Box<&no_method_suggested_traits::Bar>>`
 
 error: aborting due to 24 previous errors
 
diff --git a/src/test/ui/imports/gensymed.rs b/src/test/ui/imports/gensymed.rs
index 613ccc0b24234..7b53f0c536ad9 100644
--- a/src/test/ui/imports/gensymed.rs
+++ b/src/test/ui/imports/gensymed.rs
@@ -1,7 +1,9 @@
-// build-pass (FIXME(62277): could be check-pass?)
+// check-pass
 // edition:2018
 // aux-build:gensymed.rs
 
 extern crate gensymed;
 
+use gensymed::*;
+
 fn main() {}
diff --git a/src/test/ui/imports/unresolved-imports-used.rs b/src/test/ui/imports/unresolved-imports-used.rs
index d1461e7b041c5..75cf880192c8e 100644
--- a/src/test/ui/imports/unresolved-imports-used.rs
+++ b/src/test/ui/imports/unresolved-imports-used.rs
@@ -1,12 +1,18 @@
-// There should be *no* unused import errors.
+// There should be *one* unused import error.
 #![deny(unused_imports)]
 
 mod qux {
    fn quz() {}
+   pub fn quy() {}
 }
 
-use qux::quz; //~ ERROR function `quz` is private
-use qux::bar; //~ ERROR unresolved import `qux::bar`
-use foo::bar; //~ ERROR unresolved import `foo`
+use qux::quz;  //~ ERROR function `quz` is private
+use qux::bar;  //~ ERROR unresolved import `qux::bar`
+use foo::bar;  //~ ERROR unresolved import `foo`
+use baz::*;    //~ ERROR unresolved import `baz`
+use qux::bar2; //~ ERROR unresolved import `qux::bar2`
+use foo2::bar2;//~ ERROR unresolved import `foo2`
+use baz2::*;   //~ ERROR unresolved import `baz2`
+use qux::quy;  //~ ERROR unused import
 
 fn main() {}
diff --git a/src/test/ui/imports/unresolved-imports-used.stderr b/src/test/ui/imports/unresolved-imports-used.stderr
index e8c827a6179bb..b341e8e059288 100644
--- a/src/test/ui/imports/unresolved-imports-used.stderr
+++ b/src/test/ui/imports/unresolved-imports-used.stderr
@@ -1,22 +1,58 @@
 error[E0432]: unresolved import `qux::bar`
-  --> $DIR/unresolved-imports-used.rs:9:5
+  --> $DIR/unresolved-imports-used.rs:10:5
    |
 LL | use qux::bar;
    |     ^^^^^^^^ no `bar` in `qux`
 
+error[E0432]: unresolved import `qux::bar2`
+  --> $DIR/unresolved-imports-used.rs:13:5
+   |
+LL | use qux::bar2;
+   |     ^^^^^^^^^ no `bar2` in `qux`
+
 error[E0432]: unresolved import `foo`
-  --> $DIR/unresolved-imports-used.rs:10:5
+  --> $DIR/unresolved-imports-used.rs:11:5
    |
 LL | use foo::bar;
    |     ^^^ maybe a missing crate `foo`?
 
+error[E0432]: unresolved import `baz`
+  --> $DIR/unresolved-imports-used.rs:12:5
+   |
+LL | use baz::*;
+   |     ^^^ maybe a missing crate `baz`?
+
+error[E0432]: unresolved import `foo2`
+  --> $DIR/unresolved-imports-used.rs:14:5
+   |
+LL | use foo2::bar2;
+   |     ^^^^ maybe a missing crate `foo2`?
+
+error[E0432]: unresolved import `baz2`
+  --> $DIR/unresolved-imports-used.rs:15:5
+   |
+LL | use baz2::*;
+   |     ^^^^ maybe a missing crate `baz2`?
+
 error[E0603]: function `quz` is private
-  --> $DIR/unresolved-imports-used.rs:8:10
+  --> $DIR/unresolved-imports-used.rs:9:10
    |
 LL | use qux::quz;
    |          ^^^
 
-error: aborting due to 3 previous errors
+error: unused import: `qux::quy`
+  --> $DIR/unresolved-imports-used.rs:16:5
+   |
+LL | use qux::quy;
+   |     ^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/unresolved-imports-used.rs:2:9
+   |
+LL | #![deny(unused_imports)]
+   |         ^^^^^^^^^^^^^^
+
+error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0432, E0603.
 For more information about an error, try `rustc --explain E0432`.
diff --git a/src/test/ui/inaccessible-test-modules.stderr b/src/test/ui/inaccessible-test-modules.stderr
deleted file mode 100644
index b6a817e6b1d30..0000000000000
--- a/src/test/ui/inaccessible-test-modules.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0432]: unresolved import `__test`
-  --> $DIR/inaccessible-test-modules.rs:5:5
-   |
-LL | use __test as x;
-   |     ------^^^^^
-   |     |
-   |     no `__test` in the root
-   |     help: a similar name exists in the module: `test`
-
-error[E0432]: unresolved import `__test_reexports`
-  --> $DIR/inaccessible-test-modules.rs:6:5
-   |
-LL | use __test_reexports as y;
-   |     ----------------^^^^^
-   |     |
-   |     no `__test_reexports` in the root
-   |     help: a similar name exists in the module: `__test_reexports`
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/src/test/ui/infinite/infinite-autoderef.stderr b/src/test/ui/infinite/infinite-autoderef.stderr
index 3159a4b67dae5..a2ad58a7e46fc 100644
--- a/src/test/ui/infinite/infinite-autoderef.stderr
+++ b/src/test/ui/infinite/infinite-autoderef.stderr
@@ -44,7 +44,7 @@ LL | struct Foo;
    | ----------- method `bar` not found for this
 ...
 LL |     Foo.bar();
-   |         ^^^
+   |         ^^^ method not found in `Foo`
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/intrinsics-always-extern.rs b/src/test/ui/intrinsics-always-extern.rs
new file mode 100644
index 0000000000000..22951147d7d87
--- /dev/null
+++ b/src/test/ui/intrinsics-always-extern.rs
@@ -0,0 +1,16 @@
+#![feature(intrinsics)]
+
+trait Foo {
+    extern "rust-intrinsic" fn foo(&self); //~ ERROR intrinsic must
+}
+
+impl Foo for () {
+    extern "rust-intrinsic" fn foo(&self) { //~ ERROR intrinsic must
+    }
+}
+
+extern "rust-intrinsic" fn hello() {//~ ERROR intrinsic must
+}
+
+fn main() {
+}
diff --git a/src/test/ui/intrinsics-always-extern.stderr b/src/test/ui/intrinsics-always-extern.stderr
new file mode 100644
index 0000000000000..24b6da16096e6
--- /dev/null
+++ b/src/test/ui/intrinsics-always-extern.stderr
@@ -0,0 +1,24 @@
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/intrinsics-always-extern.rs:4:32
+   |
+LL |     extern "rust-intrinsic" fn foo(&self);
+   |                                ^^^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/intrinsics-always-extern.rs:8:43
+   |
+LL |       extern "rust-intrinsic" fn foo(&self) {
+   |  ___________________________________________^
+LL | |     }
+   | |_____^
+
+error: intrinsic must be in `extern "rust-intrinsic" { ... }` block
+  --> $DIR/intrinsics-always-extern.rs:12:36
+   |
+LL |   extern "rust-intrinsic" fn hello() {
+   |  ____________________________________^
+LL | | }
+   | |_^
+
+error: aborting due to 3 previous errors
+
diff --git a/src/test/ui/issues/issue-10465.stderr b/src/test/ui/issues/issue-10465.stderr
index 6efbd8e40ef64..413daa6db6787 100644
--- a/src/test/ui/issues/issue-10465.stderr
+++ b/src/test/ui/issues/issue-10465.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `foo` found for type `&b::B` in the current scope
   --> $DIR/issue-10465.rs:17:15
    |
 LL |             b.foo();
-   |               ^^^
+   |               ^^^ method not found in `&b::B`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/issues/issue-11692-1.rs b/src/test/ui/issues/issue-11692-1.rs
index 70b712c560830..b6f3bb8ef0549 100644
--- a/src/test/ui/issues/issue-11692-1.rs
+++ b/src/test/ui/issues/issue-11692-1.rs
@@ -1,3 +1,3 @@
 fn main() {
-    print!(testo!()); //~ ERROR cannot find macro `testo!` in this scope
+    print!(testo!()); //~ ERROR cannot find macro `testo` in this scope
 }
diff --git a/src/test/ui/issues/issue-11692-1.stderr b/src/test/ui/issues/issue-11692-1.stderr
index bfd1647e8bee4..386463436b8e6 100644
--- a/src/test/ui/issues/issue-11692-1.stderr
+++ b/src/test/ui/issues/issue-11692-1.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `testo!` in this scope
+error: cannot find macro `testo` in this scope
   --> $DIR/issue-11692-1.rs:2:12
    |
 LL |     print!(testo!());
diff --git a/src/test/ui/issues/issue-11692-2.rs b/src/test/ui/issues/issue-11692-2.rs
index 61be284d7320e..5957ed338f4e7 100644
--- a/src/test/ui/issues/issue-11692-2.rs
+++ b/src/test/ui/issues/issue-11692-2.rs
@@ -1,3 +1,3 @@
 fn main() {
-    concat!(test!()); //~ ERROR cannot find macro `test!` in this scope
+    concat!(test!()); //~ ERROR cannot find macro `test` in this scope
 }
diff --git a/src/test/ui/issues/issue-11692-2.stderr b/src/test/ui/issues/issue-11692-2.stderr
index 740c3555e52f0..f021943da32da 100644
--- a/src/test/ui/issues/issue-11692-2.stderr
+++ b/src/test/ui/issues/issue-11692-2.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `test!` in this scope
+error: cannot find macro `test` in this scope
   --> $DIR/issue-11692-2.rs:2:13
    |
 LL |     concat!(test!());
diff --git a/src/test/ui/issues/issue-1251.rs b/src/test/ui/issues/issue-1251.rs
index 63b5a4dd1b31a..77278ecda6ecb 100644
--- a/src/test/ui/issues/issue-1251.rs
+++ b/src/test/ui/issues/issue-1251.rs
@@ -6,8 +6,6 @@
 
 #![feature(rustc_private)]
 
-#![crate_id="rust_get_test_int"]
-
 mod rustrt {
     extern crate libc;
 
diff --git a/src/test/ui/issues/issue-13853.stderr b/src/test/ui/issues/issue-13853.stderr
index 9026845b4ed86..c57ca3e25d99f 100644
--- a/src/test/ui/issues/issue-13853.stderr
+++ b/src/test/ui/issues/issue-13853.stderr
@@ -14,7 +14,7 @@ error[E0599]: no method named `iter` found for type `&G` in the current scope
   --> $DIR/issue-13853.rs:27:23
    |
 LL |     for node in graph.iter() {
-   |                       ^^^^
+   |                       ^^^^ method not found in `&G`
 
 error[E0308]: mismatched types
   --> $DIR/issue-13853.rs:37:13
diff --git a/src/test/ui/issues/issue-14309.rs b/src/test/ui/issues/issue-14309.rs
index d0e532a264656..328a4c982b81e 100644
--- a/src/test/ui/issues/issue-14309.rs
+++ b/src/test/ui/issues/issue-14309.rs
@@ -27,7 +27,7 @@ struct D {
 }
 
 extern "C" {
-    fn foo(x: A); //~ ERROR type `A` which is not FFI-safe
+    fn foo(x: A); //~ ERROR type `A`, which is not FFI-safe
     fn bar(x: B); //~ ERROR type `A`
     fn baz(x: C);
     fn qux(x: A2); //~ ERROR type `A`
diff --git a/src/test/ui/issues/issue-14309.stderr b/src/test/ui/issues/issue-14309.stderr
index e0491093a722a..f598e1f9e2f6d 100644
--- a/src/test/ui/issues/issue-14309.stderr
+++ b/src/test/ui/issues/issue-14309.stderr
@@ -1,8 +1,8 @@
-error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `A`, which is not FFI-safe
   --> $DIR/issue-14309.rs:30:15
    |
 LL |     fn foo(x: A);
-   |               ^
+   |               ^ not FFI-safe
    |
 note: lint level defined here
   --> $DIR/issue-14309.rs:1:9
@@ -10,6 +10,7 @@ note: lint level defined here
 LL | #![deny(improper_ctypes)]
    |         ^^^^^^^^^^^^^^^
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-14309.rs:4:1
    |
@@ -18,13 +19,14 @@ LL | |     x: i32
 LL | | }
    | |_^
 
-error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `A`, which is not FFI-safe
   --> $DIR/issue-14309.rs:31:15
    |
 LL |     fn bar(x: B);
-   |               ^
+   |               ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-14309.rs:4:1
    |
@@ -33,13 +35,14 @@ LL | |     x: i32
 LL | | }
    | |_^
 
-error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `A`, which is not FFI-safe
   --> $DIR/issue-14309.rs:33:15
    |
 LL |     fn qux(x: A2);
-   |               ^^
+   |               ^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-14309.rs:4:1
    |
@@ -48,13 +51,14 @@ LL | |     x: i32
 LL | | }
    | |_^
 
-error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `A`, which is not FFI-safe
   --> $DIR/issue-14309.rs:34:16
    |
 LL |     fn quux(x: B2);
-   |                ^^
+   |                ^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-14309.rs:4:1
    |
@@ -63,13 +67,14 @@ LL | |     x: i32
 LL | | }
    | |_^
 
-error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `A`, which is not FFI-safe
   --> $DIR/issue-14309.rs:36:16
    |
 LL |     fn fred(x: D);
-   |                ^
+   |                ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-14309.rs:4:1
    |
diff --git a/src/test/ui/issues/issue-15207.stderr b/src/test/ui/issues/issue-15207.stderr
index 2d90eb80fc54c..25ce7cb5cc069 100644
--- a/src/test/ui/issues/issue-15207.stderr
+++ b/src/test/ui/issues/issue-15207.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `push` found for type `!` in the current scope
   --> $DIR/issue-15207.rs:3:15
    |
 LL |         break.push(1)
-   |               ^^^^
+   |               ^^^^ method not found in `!`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-15381.rs b/src/test/ui/issues/issue-15381.rs
index d21c321b09399..5307153cb4403 100644
--- a/src/test/ui/issues/issue-15381.rs
+++ b/src/test/ui/issues/issue-15381.rs
@@ -2,8 +2,8 @@ fn main() {
     let values: Vec<u8> = vec![1,2,3,4,5,6,7,8];
 
     for &[x,y,z] in values.chunks(3).filter(|&xs| xs.len() == 3) {
-        //~^ ERROR refutable pattern in `for` loop binding: `&[]` not covered
+        //~^ ERROR refutable pattern in `for` loop binding: `&[]`, `&[_]`, `&[_, _]` and 1 more not
         println!("y={}", y);
-        //~^ ERROR borrow of possibly uninitialized variable: `y`
+        //~^ ERROR borrow of possibly-uninitialized variable: `y`
     }
 }
diff --git a/src/test/ui/issues/issue-15381.stderr b/src/test/ui/issues/issue-15381.stderr
index a8495846b3610..47a0d514ad873 100644
--- a/src/test/ui/issues/issue-15381.stderr
+++ b/src/test/ui/issues/issue-15381.stderr
@@ -1,14 +1,14 @@
-error[E0005]: refutable pattern in `for` loop binding: `&[]` not covered
+error[E0005]: refutable pattern in `for` loop binding: `&[]`, `&[_]`, `&[_, _]` and 1 more not covered
   --> $DIR/issue-15381.rs:4:9
    |
 LL |     for &[x,y,z] in values.chunks(3).filter(|&xs| xs.len() == 3) {
-   |         ^^^^^^^^ pattern `&[]` not covered
+   |         ^^^^^^^^ patterns `&[]`, `&[_]`, `&[_, _]` and 1 more not covered
 
-error[E0381]: borrow of possibly uninitialized variable: `y`
+error[E0381]: borrow of possibly-uninitialized variable: `y`
   --> $DIR/issue-15381.rs:6:26
    |
 LL |         println!("y={}", y);
-   |                          ^ use of possibly uninitialized `y`
+   |                          ^ use of possibly-uninitialized `y`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-15783.rs b/src/test/ui/issues/issue-15783.rs
index 77eae914fa1ca..5189f550cfbd6 100644
--- a/src/test/ui/issues/issue-15783.rs
+++ b/src/test/ui/issues/issue-15783.rs
@@ -6,9 +6,9 @@ fn main() {
     let name = "Foo";
     let x = Some(&[name]);
     let msg = foo(x);
-//~^ ERROR mismatched types
-//~| expected type `std::option::Option<&[&str]>`
-//~| found type `std::option::Option<&[&str; 1]>`
-//~| expected slice, found array of 1 elements
+    //~^ ERROR mismatched types
+    //~| expected type `std::option::Option<&[&str]>`
+    //~| found type `std::option::Option<&[&str; 1]>`
+    //~| expected slice, found array of 1 element
     assert_eq!(msg, 3);
 }
diff --git a/src/test/ui/issues/issue-15783.stderr b/src/test/ui/issues/issue-15783.stderr
index 595fe4025ad48..1d54b2830d6c5 100644
--- a/src/test/ui/issues/issue-15783.stderr
+++ b/src/test/ui/issues/issue-15783.stderr
@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-15783.rs:8:19
    |
 LL |     let msg = foo(x);
-   |                   ^ expected slice, found array of 1 elements
+   |                   ^ expected slice, found array of 1 element
    |
    = note: expected type `std::option::Option<&[&str]>`
               found type `std::option::Option<&[&str; 1]>`
diff --git a/src/test/ui/issues/issue-16250.rs b/src/test/ui/issues/issue-16250.rs
index bf01627adfc1f..a3c6751ad897c 100644
--- a/src/test/ui/issues/issue-16250.rs
+++ b/src/test/ui/issues/issue-16250.rs
@@ -3,7 +3,7 @@
 pub struct Foo;
 
 extern {
-    pub fn foo(x: (Foo)); //~ ERROR unspecified layout
+    pub fn foo(x: (Foo)); //~ ERROR `extern` block uses type `Foo`
 }
 
 fn main() {
diff --git a/src/test/ui/issues/issue-16250.stderr b/src/test/ui/issues/issue-16250.stderr
index f3686e82b05a4..5686ac3774215 100644
--- a/src/test/ui/issues/issue-16250.stderr
+++ b/src/test/ui/issues/issue-16250.stderr
@@ -1,8 +1,8 @@
-error: `extern` block uses type `Foo` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `Foo`, which is not FFI-safe
   --> $DIR/issue-16250.rs:6:20
    |
 LL |     pub fn foo(x: (Foo));
-   |                    ^^^
+   |                    ^^^ not FFI-safe
    |
 note: lint level defined here
   --> $DIR/issue-16250.rs:1:9
@@ -11,6 +11,7 @@ LL | #![deny(warnings)]
    |         ^^^^^^^^
    = note: `#[deny(improper_ctypes)]` implied by `#[deny(warnings)]`
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/issue-16250.rs:3:1
    |
diff --git a/src/test/ui/issues/issue-17651.rs b/src/test/ui/issues/issue-17651.rs
index 7629a5a3be1ea..08f352c11fa12 100644
--- a/src/test/ui/issues/issue-17651.rs
+++ b/src/test/ui/issues/issue-17651.rs
@@ -4,4 +4,5 @@
 fn main() {
     (|| Box::new(*(&[0][..])))();
     //~^ ERROR the size for values of type
+    //~| ERROR the size for values of type
 }
diff --git a/src/test/ui/issues/issue-17651.stderr b/src/test/ui/issues/issue-17651.stderr
index ce9af1524b087..c3445024c3752 100644
--- a/src/test/ui/issues/issue-17651.stderr
+++ b/src/test/ui/issues/issue-17651.stderr
@@ -1,3 +1,13 @@
+error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
+  --> $DIR/issue-17651.rs:5:18
+   |
+LL |     (|| Box::new(*(&[0][..])))();
+   |                  ^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `std::marker::Sized` is not implemented for `[{integer}]`
+   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+   = note: required by `std::boxed::Box::<T>::new`
+
 error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
   --> $DIR/issue-17651.rs:5:9
    |
@@ -6,8 +16,9 @@ LL |     (|| Box::new(*(&[0][..])))();
    |
    = help: the trait `std::marker::Sized` is not implemented for `[{integer}]`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required by `std::boxed::Box::<T>::new`
+   = note: all function arguments must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/issues/issue-1871.stderr b/src/test/ui/issues/issue-1871.stderr
index fecd689251b32..b774ca22dd72a 100644
--- a/src/test/ui/issues/issue-1871.stderr
+++ b/src/test/ui/issues/issue-1871.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `honk` found for type `{integer}` in the current s
   --> $DIR/issue-1871.rs:7:9
    |
 LL |       f.honk()
-   |         ^^^^
+   |         ^^^^ method not found in `{integer}`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-19521.stderr b/src/test/ui/issues/issue-19521.stderr
index a43368be58339..c15c5392fac25 100644
--- a/src/test/ui/issues/issue-19521.stderr
+++ b/src/test/ui/issues/issue-19521.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `homura` found for type `&'static str` in the curr
   --> $DIR/issue-19521.rs:2:8
    |
 LL |     "".homura()();
-   |        ^^^^^^
+   |        ^^^^^^ method not found in `&'static str`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-19692.stderr b/src/test/ui/issues/issue-19692.stderr
index 5e576f11583eb..fe920c1693982 100644
--- a/src/test/ui/issues/issue-19692.stderr
+++ b/src/test/ui/issues/issue-19692.stderr
@@ -5,7 +5,7 @@ LL | struct Homura;
    | -------------- method `kaname` not found for this
 ...
 LL |     let Some(ref madoka) = Some(homura.kaname());
-   |                                        ^^^^^^
+   |                                        ^^^^^^ method not found in `Homura`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-19734.rs b/src/test/ui/issues/issue-19734.rs
index b730e19a1e632..fe4a327aef49c 100644
--- a/src/test/ui/issues/issue-19734.rs
+++ b/src/test/ui/issues/issue-19734.rs
@@ -4,5 +4,5 @@ struct Type;
 
 impl Type {
     undef!();
-    //~^ ERROR cannot find macro `undef!` in this scope
+    //~^ ERROR cannot find macro `undef` in this scope
 }
diff --git a/src/test/ui/issues/issue-19734.stderr b/src/test/ui/issues/issue-19734.stderr
index fc1a7d0381be2..81757974de9dd 100644
--- a/src/test/ui/issues/issue-19734.stderr
+++ b/src/test/ui/issues/issue-19734.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `undef!` in this scope
+error: cannot find macro `undef` in this scope
   --> $DIR/issue-19734.rs:6:5
    |
 LL |     undef!();
diff --git a/src/test/ui/issues/issue-2149.stderr b/src/test/ui/issues/issue-2149.stderr
index 1df32aafa79c8..8ce2ba033321e 100644
--- a/src/test/ui/issues/issue-2149.stderr
+++ b/src/test/ui/issues/issue-2149.stderr
@@ -10,7 +10,7 @@ error[E0599]: no method named `bind` found for type `[&str; 1]` in the current s
   --> $DIR/issue-2149.rs:13:12
    |
 LL |     ["hi"].bind(|x| [x] );
-   |            ^^^^
+   |            ^^^^ method not found in `[&str; 1]`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `bind`, perhaps you need to implement it:
diff --git a/src/test/ui/issues/issue-2150.stderr b/src/test/ui/issues/issue-2150.stderr
index 59000f3dd5338..623f098d0b337 100644
--- a/src/test/ui/issues/issue-2150.stderr
+++ b/src/test/ui/issues/issue-2150.stderr
@@ -9,6 +9,12 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/issue-2150.rs:7:5
+   |
+LL |     panic!();
+   |     ^^^^^^^^^
+   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-21596.stderr b/src/test/ui/issues/issue-21596.stderr
index 8e4e09b13a9bd..4e5cace525787 100644
--- a/src/test/ui/issues/issue-21596.stderr
+++ b/src/test/ui/issues/issue-21596.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `to_string` found for type `*const u8` in the curr
   --> $DIR/issue-21596.rs:4:22
    |
 LL |     println!("{}", z.to_string());
-   |                      ^^^^^^^^^
+   |                      ^^^^^^^^^ method not found in `*const u8`
    |
    = note: try using `<*const T>::as_ref()` to get a reference to the type behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref
    = note: using `<*const T>::as_ref()` on a pointer which is unaligned or points to invalid or uninitialized memory is undefined behavior
diff --git a/src/test/ui/issues/issue-23966.stderr b/src/test/ui/issues/issue-23966.stderr
index ac64067db1099..c2fe6d92b910a 100644
--- a/src/test/ui/issues/issue-23966.stderr
+++ b/src/test/ui/issues/issue-23966.stderr
@@ -1,8 +1,8 @@
 error[E0277]: expected a `std::ops::FnMut<(_, char)>` closure, found `()`
-  --> $DIR/issue-23966.rs:2:16
+  --> $DIR/issue-23966.rs:2:32
    |
 LL |     "".chars().fold(|_, _| (), ());
-   |                ^^^^ expected an `FnMut<(_, char)>` closure, found `()`
+   |                                ^^ expected an `FnMut<(_, char)>` closure, found `()`
    |
    = help: the trait `std::ops::FnMut<(_, char)>` is not implemented for `()`
 
diff --git a/src/test/ui/issues/issue-24267-flow-exit.rs b/src/test/ui/issues/issue-24267-flow-exit.rs
index a1b4d75d4048f..d6809ee4143b0 100644
--- a/src/test/ui/issues/issue-24267-flow-exit.rs
+++ b/src/test/ui/issues/issue-24267-flow-exit.rs
@@ -9,11 +9,11 @@ pub fn main() {
 pub fn foo1() {
     let x: i32;
     loop { x = break; }
-    println!("{}", x); //~ ERROR borrow of possibly uninitialized variable: `x`
+    println!("{}", x); //~ ERROR borrow of possibly-uninitialized variable: `x`
 }
 
 pub fn foo2() {
     let x: i32;
     for _ in 0..10 { x = continue; }
-    println!("{}", x); //~ ERROR borrow of possibly uninitialized variable: `x`
+    println!("{}", x); //~ ERROR borrow of possibly-uninitialized variable: `x`
 }
diff --git a/src/test/ui/issues/issue-24267-flow-exit.stderr b/src/test/ui/issues/issue-24267-flow-exit.stderr
index 3b4f27621f696..4eb41ca24ddfe 100644
--- a/src/test/ui/issues/issue-24267-flow-exit.stderr
+++ b/src/test/ui/issues/issue-24267-flow-exit.stderr
@@ -1,14 +1,14 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/issue-24267-flow-exit.rs:12:20
    |
 LL |     println!("{}", x);
-   |                    ^ use of possibly uninitialized `x`
+   |                    ^ use of possibly-uninitialized `x`
 
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/issue-24267-flow-exit.rs:18:20
    |
 LL |     println!("{}", x);
-   |                    ^ use of possibly uninitialized `x`
+   |                    ^ use of possibly-uninitialized `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-24535-allow-mutable-borrow-in-match-guard.rs b/src/test/ui/issues/issue-24535-allow-mutable-borrow-in-match-guard.rs
index 48362d0bb6282..7253d35ed2d4f 100644
--- a/src/test/ui/issues/issue-24535-allow-mutable-borrow-in-match-guard.rs
+++ b/src/test/ui/issues/issue-24535-allow-mutable-borrow-in-match-guard.rs
@@ -5,8 +5,6 @@
 // See further discussion on rust-lang/rust#24535,
 // rust-lang/rfcs#1006, and rust-lang/rfcs#107
 
-#![feature(bind_by_move_pattern_guards)]
-
 fn main() {
     rust_issue_24535();
     rfcs_issue_1006_1();
diff --git a/src/test/ui/issues/issue-25076.stderr b/src/test/ui/issues/issue-25076.stderr
index b583a6b54bf9f..a7b6626b16a1c 100644
--- a/src/test/ui/issues/issue-25076.stderr
+++ b/src/test/ui/issues/issue-25076.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `(): InOut<_>` is not satisfied
-  --> $DIR/issue-25076.rs:10:5
+  --> $DIR/issue-25076.rs:10:20
    |
 LL | fn do_fold<B, F: InOut<B, Out=B>>(init: B, f: F) {}
    | ------------------------------------------------ required by `do_fold`
 ...
 LL |     do_fold(bot(), ());
-   |     ^^^^^^^ the trait `InOut<_>` is not implemented for `()`
+   |                    ^^ the trait `InOut<_>` is not implemented for `()`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-25385.stderr b/src/test/ui/issues/issue-25385.stderr
index e170a9d383b0e..ab4db7e42a4b9 100644
--- a/src/test/ui/issues/issue-25385.stderr
+++ b/src/test/ui/issues/issue-25385.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `foo` found for type `i32` in the current scope
   --> $DIR/issue-25385.rs:2:23
    |
 LL |     ($e:expr) => { $e.foo() }
-   |                       ^^^
+   |                       ^^^ method not found in `i32`
 ...
 LL |     foo!(a);
    |     -------- in this macro invocation
@@ -11,7 +11,7 @@ error[E0599]: no method named `foo` found for type `i32` in the current scope
   --> $DIR/issue-25385.rs:10:15
    |
 LL |     foo!(1i32.foo());
-   |               ^^^
+   |               ^^^ method not found in `i32`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-26448-2.rs b/src/test/ui/issues/issue-26448-2.rs
index 17e7c1f977a6d..c60e06c3ceb35 100644
--- a/src/test/ui/issues/issue-26448-2.rs
+++ b/src/test/ui/issues/issue-26448-2.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 pub struct Bar<T> {
     items: Vec<&'static str>,
diff --git a/src/test/ui/issues/issue-26448-3.rs b/src/test/ui/issues/issue-26448-3.rs
index e57352e57f4fc..d48022c09fee3 100644
--- a/src/test/ui/issues/issue-26448-3.rs
+++ b/src/test/ui/issues/issue-26448-3.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 pub struct Item {
     _inner: &'static str,
diff --git a/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.rs b/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.rs
index 1ffb7f6fd4acd..82d8b9e9ed977 100644
--- a/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.rs
+++ b/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.rs
@@ -5,8 +5,6 @@
 // reject it. But I want to make sure that we continue to reject it
 // (under NLL) even when that conservaive check goes away.
 
-#![feature(bind_by_move_pattern_guards)]
-
 fn main() {
     let mut b = &mut true;
     match b {
diff --git a/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.stderr b/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.stderr
index a8eb78b7cc007..f0264b56ea569 100644
--- a/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.stderr
+++ b/src/test/ui/issues/issue-27282-reborrow-ref-mut-in-guard.stderr
@@ -1,5 +1,5 @@
 error[E0596]: cannot borrow `r` as mutable, as it is immutable for the pattern guard
-  --> $DIR/issue-27282-reborrow-ref-mut-in-guard.rs:14:25
+  --> $DIR/issue-27282-reborrow-ref-mut-in-guard.rs:12:25
    |
 LL |         ref mut r if { (|| { let bar = &mut *r; **bar = false; })();
    |                         ^^                   - mutable borrow occurs due to use of `r` in closure
diff --git a/src/test/ui/issues/issue-27697.rs b/src/test/ui/issues/issue-27697.rs
index 83070012f5f04..12af8a8e875af 100644
--- a/src/test/ui/issues/issue-27697.rs
+++ b/src/test/ui/issues/issue-27697.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 use std::ops::Deref;
 
diff --git a/src/test/ui/issues/issue-28098.rs b/src/test/ui/issues/issue-28098.rs
index c4addaccefc10..62a90d90d12de 100644
--- a/src/test/ui/issues/issue-28098.rs
+++ b/src/test/ui/issues/issue-28098.rs
@@ -1,6 +1,7 @@
 fn main() {
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
+    //~| ERROR `()` is not an iterator
 
     for _ in false {}
     //~^ ERROR `bool` is not an iterator
@@ -16,6 +17,7 @@ pub fn other() {
 
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
+    //~| ERROR `()` is not an iterator
 
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
diff --git a/src/test/ui/issues/issue-28098.stderr b/src/test/ui/issues/issue-28098.stderr
index 30f7819b96daf..8b724b9331dd6 100644
--- a/src/test/ui/issues/issue-28098.stderr
+++ b/src/test/ui/issues/issue-28098.stderr
@@ -1,14 +1,14 @@
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:2:13
+  --> $DIR/issue-28098.rs:2:28
    |
 LL |     let _ = Iterator::next(&mut ());
-   |             ^^^^^^^^^^^^^^ `()` is not an iterator
+   |                            ^^^^^^^ `()` is not an iterator
    |
    = help: the trait `std::iter::Iterator` is not implemented for `()`
    = note: required by `std::iter::Iterator::next`
 
 error[E0277]: `bool` is not an iterator
-  --> $DIR/issue-28098.rs:5:14
+  --> $DIR/issue-28098.rs:6:14
    |
 LL |     for _ in false {}
    |              ^^^^^ `bool` is not an iterator
@@ -17,34 +17,42 @@ LL |     for _ in false {}
    = note: required by `std::iter::IntoIterator::into_iter`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:8:13
+  --> $DIR/issue-28098.rs:9:28
    |
 LL |     let _ = Iterator::next(&mut ());
-   |             ^^^^^^^^^^^^^^ `()` is not an iterator
+   |                            ^^^^^^^ `()` is not an iterator
    |
    = help: the trait `std::iter::Iterator` is not implemented for `()`
    = note: required by `std::iter::Iterator::next`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:17:13
+  --> $DIR/issue-28098.rs:2:13
    |
 LL |     let _ = Iterator::next(&mut ());
    |             ^^^^^^^^^^^^^^ `()` is not an iterator
    |
    = help: the trait `std::iter::Iterator` is not implemented for `()`
+
+error[E0277]: `()` is not an iterator
+  --> $DIR/issue-28098.rs:18:28
+   |
+LL |     let _ = Iterator::next(&mut ());
+   |                            ^^^^^^^ `()` is not an iterator
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `()`
    = note: required by `std::iter::Iterator::next`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:20:13
+  --> $DIR/issue-28098.rs:22:28
    |
 LL |     let _ = Iterator::next(&mut ());
-   |             ^^^^^^^^^^^^^^ `()` is not an iterator
+   |                            ^^^^^^^ `()` is not an iterator
    |
    = help: the trait `std::iter::Iterator` is not implemented for `()`
    = note: required by `std::iter::Iterator::next`
 
 error[E0277]: `bool` is not an iterator
-  --> $DIR/issue-28098.rs:23:14
+  --> $DIR/issue-28098.rs:25:14
    |
 LL |     for _ in false {}
    |              ^^^^^ `bool` is not an iterator
@@ -52,6 +60,14 @@ LL |     for _ in false {}
    = help: the trait `std::iter::Iterator` is not implemented for `bool`
    = note: required by `std::iter::IntoIterator::into_iter`
 
-error: aborting due to 6 previous errors
+error[E0277]: `()` is not an iterator
+  --> $DIR/issue-28098.rs:18:13
+   |
+LL |     let _ = Iterator::next(&mut ());
+   |             ^^^^^^^^^^^^^^ `()` is not an iterator
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `()`
+
+error: aborting due to 8 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/issues/issue-2823.stderr b/src/test/ui/issues/issue-2823.stderr
index 4c1dfb8501a91..c9ede03003434 100644
--- a/src/test/ui/issues/issue-2823.stderr
+++ b/src/test/ui/issues/issue-2823.stderr
@@ -5,7 +5,7 @@ LL | struct C {
    | -------- method `clone` not found for this
 ...
 LL |     let _d = c.clone();
-   |                ^^^^^
+   |                ^^^^^ method not found in `C`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `clone`, perhaps you need to implement it:
diff --git a/src/test/ui/issues/issue-29124.stderr b/src/test/ui/issues/issue-29124.stderr
index 3beb728978884..c537c6118f3a8 100644
--- a/src/test/ui/issues/issue-29124.stderr
+++ b/src/test/ui/issues/issue-29124.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `x` found for type `fn() -> Ret {Obj::func}` in th
   --> $DIR/issue-29124.rs:15:15
    |
 LL |     Obj::func.x();
-   |               ^
+   |               ^ method not found in `fn() -> Ret {Obj::func}`
    |
    = note: Obj::func is a function, perhaps you wish to call it
 
@@ -10,7 +10,7 @@ error[E0599]: no method named `x` found for type `fn() -> Ret {func}` in the cur
   --> $DIR/issue-29124.rs:17:10
    |
 LL |     func.x();
-   |          ^
+   |          ^ method not found in `fn() -> Ret {func}`
    |
    = note: func is a function, perhaps you wish to call it
 
diff --git a/src/test/ui/issues/issue-29181.stderr b/src/test/ui/issues/issue-29181.stderr
index 092014281546f..250b158ab8e33 100644
--- a/src/test/ui/issues/issue-29181.stderr
+++ b/src/test/ui/issues/issue-29181.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `homura` found for type `{integer}` in the current
   --> $DIR/issue-29181.rs:6:7
    |
 LL |     0.homura();
-   |       ^^^^^^
+   |       ^^^^^^ method not found in `{integer}`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-31173.stderr b/src/test/ui/issues/issue-31173.stderr
index 3ca8338882681..6d03b7810939a 100644
--- a/src/test/ui/issues/issue-31173.stderr
+++ b/src/test/ui/issues/issue-31173.stderr
@@ -11,7 +11,7 @@ error[E0599]: no method named `collect` found for type `std::iter::Cloned<std::i
   --> $DIR/issue-31173.rs:14:10
    |
 LL |         .collect();
-   |          ^^^^^^^
+   |          ^^^^^^^ method not found in `std::iter::Cloned<std::iter::TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6 found_e:_]>>`
    |
    = note: the method `collect` exists but the following trait bounds were not satisfied:
            `&mut std::iter::Cloned<std::iter::TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6 found_e:_]>> : std::iter::Iterator`
diff --git a/src/test/ui/issues/issue-31561.rs b/src/test/ui/issues/issue-31561.rs
index 87b19fe5ea7cb..813b2409cc8e1 100644
--- a/src/test/ui/issues/issue-31561.rs
+++ b/src/test/ui/issues/issue-31561.rs
@@ -6,5 +6,5 @@ enum Thing {
 
 fn main() {
     let Thing::Foo(y) = Thing::Foo(1);
-    //~^ ERROR refutable pattern in local binding: `Bar` not covered
+    //~^ ERROR refutable pattern in local binding: `Bar` and `Baz` not covered
 }
diff --git a/src/test/ui/issues/issue-31561.stderr b/src/test/ui/issues/issue-31561.stderr
index 246137aeee05c..9ec26b024bce2 100644
--- a/src/test/ui/issues/issue-31561.stderr
+++ b/src/test/ui/issues/issue-31561.stderr
@@ -1,15 +1,17 @@
-error[E0005]: refutable pattern in local binding: `Bar` not covered
+error[E0005]: refutable pattern in local binding: `Bar` and `Baz` not covered
   --> $DIR/issue-31561.rs:8:9
    |
 LL | / enum Thing {
 LL | |     Foo(u8),
 LL | |     Bar,
+   | |     --- not covered
 LL | |     Baz
+   | |     --- not covered
 LL | | }
    | |_- `Thing` defined here
 ...
 LL |       let Thing::Foo(y) = Thing::Foo(1);
-   |           ^^^^^^^^^^^^^ pattern `Bar` not covered
+   |           ^^^^^^^^^^^^^ patterns `Bar` and `Baz` not covered
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-32655.rs b/src/test/ui/issues/issue-32655.rs
index fad7bf55cf4ea..f52e092312968 100644
--- a/src/test/ui/issues/issue-32655.rs
+++ b/src/test/ui/issues/issue-32655.rs
@@ -1,6 +1,6 @@
 macro_rules! foo (
     () => (
-        #[derive_Clone] //~ ERROR cannot find attribute macro `derive_Clone` in this scope
+        #[derive_Clone] //~ ERROR cannot find attribute `derive_Clone` in this scope
         struct T;
     );
 );
@@ -12,7 +12,7 @@ macro_rules! bar (
 foo!();
 
 bar!(
-    #[derive_Clone] //~ ERROR cannot find attribute macro `derive_Clone` in this scope
+    #[derive_Clone] //~ ERROR cannot find attribute `derive_Clone` in this scope
     struct S;
 );
 
diff --git a/src/test/ui/issues/issue-32655.stderr b/src/test/ui/issues/issue-32655.stderr
index e13bed0fbfd66..ca085b25c2ddf 100644
--- a/src/test/ui/issues/issue-32655.stderr
+++ b/src/test/ui/issues/issue-32655.stderr
@@ -1,4 +1,4 @@
-error: cannot find attribute macro `derive_Clone` in this scope
+error: cannot find attribute `derive_Clone` in this scope
   --> $DIR/issue-32655.rs:3:11
    |
 LL |         #[derive_Clone]
@@ -7,7 +7,7 @@ LL |         #[derive_Clone]
 LL | foo!();
    | ------- in this macro invocation
 
-error: cannot find attribute macro `derive_Clone` in this scope
+error: cannot find attribute `derive_Clone` in this scope
   --> $DIR/issue-32655.rs:15:7
    |
 LL |     #[derive_Clone]
diff --git a/src/test/ui/issues/issue-34334.stderr b/src/test/ui/issues/issue-34334.stderr
index 7f89caf92abe1..8d52e08374ac7 100644
--- a/src/test/ui/issues/issue-34334.stderr
+++ b/src/test/ui/issues/issue-34334.stderr
@@ -45,7 +45,7 @@ error[E0599]: no method named `iter` found for type `()` in the current scope
   --> $DIR/issue-34334.rs:9:36
    |
 LL |     let sr2: Vec<(u32, _, _)> = sr.iter().map(|(faction, th_sender, th_receiver)| {}).collect();
-   |                                    ^^^^
+   |                                    ^^^^ method not found in `()`
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/issues/issue-35677.stderr b/src/test/ui/issues/issue-35677.stderr
index 99d99db93f3e3..b381203856e92 100644
--- a/src/test/ui/issues/issue-35677.stderr
+++ b/src/test/ui/issues/issue-35677.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `is_subset` found for type `&std::collections::Has
   --> $DIR/issue-35677.rs:4:10
    |
 LL |     this.is_subset(other)
-   |          ^^^^^^^^^
+   |          ^^^^^^^^^ method not found in `&std::collections::HashSet<T>`
    |
    = note: the method `is_subset` exists but the following trait bounds were not satisfied:
            `T : std::cmp::Eq`
diff --git a/src/test/ui/issues/issue-36836.rs b/src/test/ui/issues/issue-36836.rs
new file mode 100644
index 0000000000000..99c56213153e4
--- /dev/null
+++ b/src/test/ui/issues/issue-36836.rs
@@ -0,0 +1,15 @@
+// Previously, in addition to the real cause of the problem as seen below,
+// the compiler would tell the user:
+//
+// ```
+// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or
+// predicates
+// ```
+//
+// With this test, we check that only the relevant error is emitted.
+
+trait Foo {}
+
+impl<T> Foo for Bar<T> {} //~ ERROR cannot find type `Bar` in this scope
+
+fn main() {}
diff --git a/src/test/ui/issues/issue-36836.stderr b/src/test/ui/issues/issue-36836.stderr
new file mode 100644
index 0000000000000..418194fac9923
--- /dev/null
+++ b/src/test/ui/issues/issue-36836.stderr
@@ -0,0 +1,9 @@
+error[E0412]: cannot find type `Bar` in this scope
+  --> $DIR/issue-36836.rs:13:17
+   |
+LL | impl<T> Foo for Bar<T> {}
+   |                 ^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0412`.
diff --git a/src/test/ui/issues/issue-38591.rs b/src/test/ui/issues/issue-38591.rs
index 7aa71f8b9eb9b..2f594b48e697f 100644
--- a/src/test/ui/issues/issue-38591.rs
+++ b/src/test/ui/issues/issue-38591.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 struct S<T> {
     t : T,
diff --git a/src/test/ui/issues/issue-39175.stderr b/src/test/ui/issues/issue-39175.stderr
index 108c969cdadde..66680b9936e68 100644
--- a/src/test/ui/issues/issue-39175.stderr
+++ b/src/test/ui/issues/issue-39175.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `exec` found for type `&mut std::process::Command`
   --> $DIR/issue-39175.rs:15:39
    |
 LL |     Command::new("echo").arg("hello").exec();
-   |                                       ^^^^
+   |                                       ^^^^ method not found in `&mut std::process::Command`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/issues/issue-40845.rs b/src/test/ui/issues/issue-40845.rs
index c9102f4417c17..a4ede6adfa3c2 100644
--- a/src/test/ui/issues/issue-40845.rs
+++ b/src/test/ui/issues/issue-40845.rs
@@ -1,6 +1,6 @@
-trait T { m!(); } //~ ERROR cannot find macro `m!` in this scope
+trait T { m!(); } //~ ERROR cannot find macro `m` in this scope
 
 struct S;
-impl S { m!(); } //~ ERROR cannot find macro `m!` in this scope
+impl S { m!(); } //~ ERROR cannot find macro `m` in this scope
 
 fn main() {}
diff --git a/src/test/ui/issues/issue-40845.stderr b/src/test/ui/issues/issue-40845.stderr
index a8be38ebf0657..2744330a4e58e 100644
--- a/src/test/ui/issues/issue-40845.stderr
+++ b/src/test/ui/issues/issue-40845.stderr
@@ -1,10 +1,10 @@
-error: cannot find macro `m!` in this scope
+error: cannot find macro `m` in this scope
   --> $DIR/issue-40845.rs:4:10
    |
 LL | impl S { m!(); }
    |          ^
 
-error: cannot find macro `m!` in this scope
+error: cannot find macro `m` in this scope
   --> $DIR/issue-40845.rs:1:11
    |
 LL | trait T { m!(); }
diff --git a/src/test/ui/issues/issue-41880.stderr b/src/test/ui/issues/issue-41880.stderr
index 359a2340240a7..0e1d55c339eb4 100644
--- a/src/test/ui/issues/issue-41880.stderr
+++ b/src/test/ui/issues/issue-41880.stderr
@@ -5,7 +5,7 @@ LL | pub struct Iterate<T, F> {
    | ------------------------ method `iter` not found for this
 ...
 LL |     println!("{:?}", a.iter().take(10).collect::<Vec<usize>>());
-   |                        ^^^^
+   |                        ^^^^ method not found in `Iterate<{integer}, [closure@$DIR/issue-41880.rs:26:24: 26:31]>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-43189.stderr b/src/test/ui/issues/issue-43189.stderr
index e364650da40a1..33c3f18650a80 100644
--- a/src/test/ui/issues/issue-43189.stderr
+++ b/src/test/ui/issues/issue-43189.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `a` found for type `()` in the current scope
   --> $DIR/issue-43189.rs:10:8
    |
 LL |     ().a();
-   |        ^
+   |        ^ method not found in `()`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/issues/issue-43806.rs b/src/test/ui/issues/issue-43806.rs
index cbfbfa35afbd9..8c8cccfb2bb82 100644
--- a/src/test/ui/issues/issue-43806.rs
+++ b/src/test/ui/issues/issue-43806.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 #![deny(unused_results)]
 
diff --git a/src/test/ui/issues/issue-44415.stderr b/src/test/ui/issues/issue-44415.stderr
deleted file mode 100644
index 8008e53f65f4d..0000000000000
--- a/src/test/ui/issues/issue-44415.stderr
+++ /dev/null
@@ -1,28 +0,0 @@
-error[E0391]: cycle detected when const-evaluating + checking `Foo::bytes::{{constant}}#0`
-  --> $DIR/issue-44415.rs:6:17
-   |
-LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
-   |                 ^^^^^^
-   |
-note: ...which requires const-evaluating + checking `Foo::bytes::{{constant}}#0`...
-  --> $DIR/issue-44415.rs:6:17
-   |
-LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
-   |                 ^^^^^^
-note: ...which requires const-evaluating `Foo::bytes::{{constant}}#0`...
-  --> $DIR/issue-44415.rs:6:26
-   |
-LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
-   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: ...which requires computing layout of `Foo`...
-   = note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
-   = note: ...which again requires const-evaluating + checking `Foo::bytes::{{constant}}#0`, completing the cycle
-note: cycle used when processing `Foo`
-  --> $DIR/issue-44415.rs:5:1
-   |
-LL | struct Foo {
-   | ^^^^^^^^^^
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0391`.
diff --git a/src/test/ui/issues/issue-46101.rs b/src/test/ui/issues/issue-46101.rs
index 2d9111e9b3a98..8b1343b1326b4 100644
--- a/src/test/ui/issues/issue-46101.rs
+++ b/src/test/ui/issues/issue-46101.rs
@@ -2,3 +2,5 @@
 trait Foo {}
 #[derive(Foo::Anything)] //~ ERROR failed to resolve: partially resolved path in a derive macro
 struct S;
+
+fn main() {}
diff --git a/src/test/ui/issues/issue-46101.stderr b/src/test/ui/issues/issue-46101.stderr
index 772d4bfeb30a7..9c88d3b87c907 100644
--- a/src/test/ui/issues/issue-46101.stderr
+++ b/src/test/ui/issues/issue-46101.stderr
@@ -4,11 +4,6 @@ error[E0433]: failed to resolve: partially resolved path in a derive macro
 LL | #[derive(Foo::Anything)]
    |          ^^^^^^^^^^^^^ partially resolved path in a derive macro
 
-error[E0601]: `main` function not found in crate `issue_46101`
-   |
-   = note: consider adding a `main` function to `$DIR/issue-46101.rs`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0433, E0601.
-For more information about an error, try `rustc --explain E0433`.
+For more information about this error, try `rustc --explain E0433`.
diff --git a/src/test/ui/issues/issue-47706-trait.stderr b/src/test/ui/issues/issue-47706-trait.stderr
index 5f8f8564249c8..8a6a199148c39 100644
--- a/src/test/ui/issues/issue-47706-trait.stderr
+++ b/src/test/ui/issues/issue-47706-trait.stderr
@@ -1,10 +1,10 @@
 error[E0593]: function is expected to take a single 0-tuple as argument, but it takes 2 distinct arguments
-  --> $DIR/issue-47706-trait.rs:3:20
+  --> $DIR/issue-47706-trait.rs:3:24
    |
 LL |     fn f(&self, _: ()) {
    |     ------------------ takes 2 distinct arguments
 LL |         None::<()>.map(Self::f);
-   |                    ^^^ expected function that takes a single 0-tuple as argument
+   |                        ^^^^^^^ expected function that takes a single 0-tuple as argument
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-47706.stderr b/src/test/ui/issues/issue-47706.stderr
index c47eebb8e5c07..4f64a643fe57d 100644
--- a/src/test/ui/issues/issue-47706.stderr
+++ b/src/test/ui/issues/issue-47706.stderr
@@ -1,14 +1,14 @@
 error[E0593]: function is expected to take 1 argument, but it takes 2 arguments
-  --> $DIR/issue-47706.rs:11:18
+  --> $DIR/issue-47706.rs:11:22
    |
 LL |     pub fn new(foo: Option<i32>, _: ()) -> Foo {
    |     ------------------------------------------ takes 2 arguments
 ...
 LL |         self.foo.map(Foo::new)
-   |                  ^^^ expected function that takes 1 argument
+   |                      ^^^^^^^^ expected function that takes 1 argument
 
 error[E0593]: function is expected to take 0 arguments, but it takes 1 argument
-  --> $DIR/issue-47706.rs:27:5
+  --> $DIR/issue-47706.rs:27:9
    |
 LL |       Bar(i32),
    |       -------- takes 1 argument
@@ -21,7 +21,7 @@ LL | | }
    | |_- required by `foo`
 ...
 LL |       foo(Qux::Bar);
-   |       ^^^ expected function that takes 0 arguments
+   |           ^^^^^^^^ expected function that takes 0 arguments
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-48132.rs b/src/test/ui/issues/issue-48132.rs
index ea325ea695f66..f564aefe78ced 100644
--- a/src/test/ui/issues/issue-48132.rs
+++ b/src/test/ui/issues/issue-48132.rs
@@ -3,6 +3,8 @@
 
 // run-pass
 
+#![allow(dead_code)]
+
 struct Inner<I, V> {
     iterator: I,
     item: V,
diff --git a/src/test/ui/issues/issue-48179.rs b/src/test/ui/issues/issue-48179.rs
index 90e9858d74197..f81203dc41299 100644
--- a/src/test/ui/issues/issue-48179.rs
+++ b/src/test/ui/issues/issue-48179.rs
@@ -1,7 +1,7 @@
 // Regression test for #48132. This was failing due to problems around
 // the projection caching and dropck type enumeration.
 
-// run-pass
+// check-pass
 
 pub struct Container<T: Iterator> {
     value: Option<T::Item>,
diff --git a/src/test/ui/issues/issue-48728.stderr b/src/test/ui/issues/issue-48728.stderr
index 99a9bf9903e25..84c10d8fbc477 100644
--- a/src/test/ui/issues/issue-48728.stderr
+++ b/src/test/ui/issues/issue-48728.stderr
@@ -7,7 +7,7 @@ LL | #[derive(Clone)]
 LL | impl<T: Clone + ?Sized> Clone for Node<[T]> {
    | ------------------------------------------- first implementation here
    |
-   = note: upstream crates may add new impl of trait `std::clone::Clone` for type `[_]` in future versions
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `[_]` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-49040.rs b/src/test/ui/issues/issue-49040.rs
index a5f05d2824eb8..b7a541dd6642a 100644
--- a/src/test/ui/issues/issue-49040.rs
+++ b/src/test/ui/issues/issue-49040.rs
@@ -1,2 +1,3 @@
 #![allow(unused_variables)]; //~ ERROR expected item, found `;`
+//~^ ERROR `main` function
 fn foo() {}
diff --git a/src/test/ui/issues/issue-49040.stderr b/src/test/ui/issues/issue-49040.stderr
index de78b8d3c14af..4134d6aa54468 100644
--- a/src/test/ui/issues/issue-49040.stderr
+++ b/src/test/ui/issues/issue-49040.stderr
@@ -5,8 +5,12 @@ LL | #![allow(unused_variables)];
    |                            ^ help: remove this semicolon
 
 error[E0601]: `main` function not found in crate `issue_49040`
+  --> $DIR/issue-49040.rs:1:1
    |
-   = note: consider adding a `main` function to `$DIR/issue-49040.rs`
+LL | / #![allow(unused_variables)];
+LL | |
+LL | | fn foo() {}
+   | |__^ consider adding a `main` function to `$DIR/issue-49040.rs`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-49074.rs b/src/test/ui/issues/issue-49074.rs
index 38074d5b05ca2..752bb345b703e 100644
--- a/src/test/ui/issues/issue-49074.rs
+++ b/src/test/ui/issues/issue-49074.rs
@@ -1,7 +1,7 @@
 // Check that unknown attribute error is shown even if there are unresolved macros.
 
 #[marco_use] // typo
-//~^ ERROR cannot find attribute macro `marco_use` in this scope
+//~^ ERROR cannot find attribute `marco_use` in this scope
 mod foo {
     macro_rules! bar {
         () => ();
@@ -9,5 +9,5 @@ mod foo {
 }
 
 fn main() {
-   bar!(); //~ ERROR cannot find macro `bar!` in this scope
+   bar!(); //~ ERROR cannot find macro `bar` in this scope
 }
diff --git a/src/test/ui/issues/issue-49074.stderr b/src/test/ui/issues/issue-49074.stderr
index e0d3bb3ecc2e1..bbfeb4ea9483a 100644
--- a/src/test/ui/issues/issue-49074.stderr
+++ b/src/test/ui/issues/issue-49074.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `bar!` in this scope
+error: cannot find macro `bar` in this scope
   --> $DIR/issue-49074.rs:12:4
    |
 LL |    bar!();
@@ -6,7 +6,7 @@ LL |    bar!();
    |
    = help: have you added the `#[macro_use]` on the module/import?
 
-error: cannot find attribute macro `marco_use` in this scope
+error: cannot find attribute `marco_use` in this scope
   --> $DIR/issue-49074.rs:3:3
    |
 LL | #[marco_use] // typo
diff --git a/src/test/ui/issues/issue-49934-errors.rs b/src/test/ui/issues/issue-49934-errors.rs
new file mode 100644
index 0000000000000..6fa5f01ffd926
--- /dev/null
+++ b/src/test/ui/issues/issue-49934-errors.rs
@@ -0,0 +1,13 @@
+fn foo<#[derive(Debug)] T>() {
+//~^ ERROR `derive` may only be applied to structs, enums and unions
+//~| ERROR expected an inert attribute, found a derive macro
+    match 0 {
+        #[derive(Debug)]
+        //~^ ERROR `derive` may only be applied to structs, enums and unions
+        //~| ERROR expected an inert attribute, found a derive macro
+        _ => (),
+    }
+}
+
+fn main() {
+}
diff --git a/src/test/ui/issues/issue-49934-errors.stderr b/src/test/ui/issues/issue-49934-errors.stderr
new file mode 100644
index 0000000000000..8778d88d0ebec
--- /dev/null
+++ b/src/test/ui/issues/issue-49934-errors.stderr
@@ -0,0 +1,26 @@
+error: `derive` may only be applied to structs, enums and unions
+  --> $DIR/issue-49934-errors.rs:1:8
+   |
+LL | fn foo<#[derive(Debug)] T>() {
+   |        ^^^^^^^^^^^^^^^^
+
+error: expected an inert attribute, found a derive macro
+  --> $DIR/issue-49934-errors.rs:1:17
+   |
+LL | fn foo<#[derive(Debug)] T>() {
+   |                 ^^^^^
+
+error: `derive` may only be applied to structs, enums and unions
+  --> $DIR/issue-49934-errors.rs:5:9
+   |
+LL |         #[derive(Debug)]
+   |         ^^^^^^^^^^^^^^^^
+
+error: expected an inert attribute, found a derive macro
+  --> $DIR/issue-49934-errors.rs:5:18
+   |
+LL |         #[derive(Debug)]
+   |                  ^^^^^
+
+error: aborting due to 4 previous errors
+
diff --git a/src/test/ui/issues/issue-49934.rs b/src/test/ui/issues/issue-49934.rs
index e75381afae9ae..262f4931d42d4 100644
--- a/src/test/ui/issues/issue-49934.rs
+++ b/src/test/ui/issues/issue-49934.rs
@@ -1,15 +1,8 @@
-// build-pass (FIXME(62277): could be check-pass?)
+// check-pass
 
 #![feature(stmt_expr_attributes)]
 #![warn(unused_attributes)] //~ NOTE lint level defined here
 
-fn foo<#[derive(Debug)] T>() { //~ WARN unused attribute
-    match 0 {
-        #[derive(Debug)] //~ WARN unused attribute
-        _ => (),
-    }
-}
-
 fn main() {
     // fold_stmt (Item)
     #[allow(dead_code)]
diff --git a/src/test/ui/issues/issue-49934.stderr b/src/test/ui/issues/issue-49934.stderr
index 6ca751a47c47d..dbec379e3c55b 100644
--- a/src/test/ui/issues/issue-49934.stderr
+++ b/src/test/ui/issues/issue-49934.stderr
@@ -1,5 +1,5 @@
 warning: `#[derive]` does nothing on macro invocations
-  --> $DIR/issue-49934.rs:20:5
+  --> $DIR/issue-49934.rs:13:5
    |
 LL |     #[derive(Debug)]
    |     ^^^^^^^^^^^^^^^^
@@ -7,10 +7,10 @@ LL |     #[derive(Debug)]
    = note: this may become a hard error in a future release
 
 warning: unused attribute
-  --> $DIR/issue-49934.rs:6:8
+  --> $DIR/issue-49934.rs:19:5
    |
-LL | fn foo<#[derive(Debug)] T>() {
-   |        ^^^^^^^^^^^^^^^^
+LL |     #[derive(Debug)]
+   |     ^^^^^^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/issue-49934.rs:4:9
@@ -19,31 +19,19 @@ LL | #![warn(unused_attributes)]
    |         ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-49934.rs:8:9
-   |
-LL |         #[derive(Debug)]
-   |         ^^^^^^^^^^^^^^^^
-
-warning: unused attribute
-  --> $DIR/issue-49934.rs:26:5
-   |
-LL |     #[derive(Debug)]
-   |     ^^^^^^^^^^^^^^^^
-
-warning: unused attribute
-  --> $DIR/issue-49934.rs:30:5
+  --> $DIR/issue-49934.rs:23:5
    |
 LL |     #[derive(Debug)]
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-49934.rs:34:13
+  --> $DIR/issue-49934.rs:27:13
    |
 LL |     let _ = #[derive(Debug)] "Hello, world!";
    |             ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-49934.rs:39:9
+  --> $DIR/issue-49934.rs:32:9
    |
 LL |         #[derive(Debug)]
    |         ^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.stderr b/src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.stderr
index 2c3a18be67c8f..29fd15fb396e9 100644
--- a/src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.stderr
+++ b/src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `as_deref_mut` found for type `std::option::Option
   --> $DIR/option-as_deref_mut.rs:4:33
    |
 LL |     let _result = &mut Some(42).as_deref_mut();
-   |                                 ^^^^^^^^^^^^
+   |                                 ^^^^^^^^^^^^ method not found in `std::option::Option<{integer}>`
    |
    = note: the method `as_deref_mut` exists but the following trait bounds were not satisfied:
            `{integer} : std::ops::DerefMut`
diff --git a/src/test/ui/issues/issue-5153.stderr b/src/test/ui/issues/issue-5153.stderr
index 97214fbdc52d4..5034e6d538e3e 100644
--- a/src/test/ui/issues/issue-5153.stderr
+++ b/src/test/ui/issues/issue-5153.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `foo` found for type `&dyn Foo` in the current sco
   --> $DIR/issue-5153.rs:10:27
    |
 LL |     (&5isize as &dyn Foo).foo();
-   |                           ^^^
+   |                           ^^^ method not found in `&dyn Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `foo`, perhaps you need to implement it:
diff --git a/src/test/ui/issues/issue-54062.stderr b/src/test/ui/issues/issue-54062.stderr
index 082ac91edb1c4..3830ad4b1e3ae 100644
--- a/src/test/ui/issues/issue-54062.stderr
+++ b/src/test/ui/issues/issue-54062.stderr
@@ -8,7 +8,7 @@ error[E0599]: no method named `unwrap` found for type `std::sys_common::mutex::M
   --> $DIR/issue-54062.rs:10:37
    |
 LL |     let _ = test.comps.inner.lock().unwrap();
-   |                                     ^^^^^^
+   |                                     ^^^^^^ method not found in `std::sys_common::mutex::MutexGuard<'_>`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-54302-cases.stderr b/src/test/ui/issues/issue-54302-cases.stderr
index 98637611b79fe..3ed2779164301 100644
--- a/src/test/ui/issues/issue-54302-cases.stderr
+++ b/src/test/ui/issues/issue-54302-cases.stderr
@@ -1,38 +1,58 @@
 error: implementation of `Foo` is not general enough
   --> $DIR/issue-54302-cases.rs:63:5
    |
-LL |     <u32 as RefFoo<u32>>::ref_foo(a)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `Foo<'static, u32>` would have to be implemented for the type `&'0 u32`, for any lifetime `'0`
-   = note: but `Foo<'_, u32>` is actually implemented for the type `&'1 u32`, for some specific lifetime `'1`
+LL | / trait Foo<'x, T> {
+LL | |     fn foo(self) -> &'x T;
+LL | | }
+   | |_- trait `Foo` defined here
+...
+LL |       <u32 as RefFoo<u32>>::ref_foo(a)
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
+   |
+   = note: `Foo<'static, u32>` would have to be implemented for the type `&'0 u32`, for any lifetime `'0`...
+   = note: ...but `Foo<'_, u32>` is actually implemented for the type `&'1 u32`, for some specific lifetime `'1`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/issue-54302-cases.rs:69:5
    |
-LL |     <i32 as RefFoo<i32>>::ref_foo(a)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / trait Foo<'x, T> {
+LL | |     fn foo(self) -> &'x T;
+LL | | }
+   | |_- trait `Foo` defined here
+...
+LL |       <i32 as RefFoo<i32>>::ref_foo(a)
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo<'static, i32>` would have to be implemented for the type `&'0 i32`, for any lifetime `'0`
-   = note: but `Foo<'_, i32>` is actually implemented for the type `&'1 i32`, for some specific lifetime `'1`
+   = note: `Foo<'static, i32>` would have to be implemented for the type `&'0 i32`, for any lifetime `'0`...
+   = note: ...but `Foo<'_, i32>` is actually implemented for the type `&'1 i32`, for some specific lifetime `'1`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/issue-54302-cases.rs:75:5
    |
-LL |     <u64 as RefFoo<u64>>::ref_foo(a)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / trait Foo<'x, T> {
+LL | |     fn foo(self) -> &'x T;
+LL | | }
+   | |_- trait `Foo` defined here
+...
+LL |       <u64 as RefFoo<u64>>::ref_foo(a)
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo<'static, u64>` would have to be implemented for the type `&'0 u64`, for any lifetime `'0`
-   = note: but `Foo<'_, u64>` is actually implemented for the type `&'1 u64`, for some specific lifetime `'1`
+   = note: `Foo<'static, u64>` would have to be implemented for the type `&'0 u64`, for any lifetime `'0`...
+   = note: ...but `Foo<'_, u64>` is actually implemented for the type `&'1 u64`, for some specific lifetime `'1`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/issue-54302-cases.rs:81:5
    |
-LL |     <i64 as RefFoo<i64>>::ref_foo(a)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / trait Foo<'x, T> {
+LL | |     fn foo(self) -> &'x T;
+LL | | }
+   | |_- trait `Foo` defined here
+...
+LL |       <i64 as RefFoo<i64>>::ref_foo(a)
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo<'static, i64>` would have to be implemented for the type `&'0 i64`, for any lifetime `'0`
-   = note: but `Foo<'_, i64>` is actually implemented for the type `&'1 i64`, for some specific lifetime `'1`
+   = note: `Foo<'static, i64>` would have to be implemented for the type `&'0 i64`, for any lifetime `'0`...
+   = note: ...but `Foo<'_, i64>` is actually implemented for the type `&'1 i64`, for some specific lifetime `'1`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/issues/issue-54302.stderr b/src/test/ui/issues/issue-54302.stderr
index c6d0805f3ab2a..1b3f57ba188a3 100644
--- a/src/test/ui/issues/issue-54302.stderr
+++ b/src/test/ui/issues/issue-54302.stderr
@@ -1,11 +1,14 @@
 error: implementation of `Deserialize` is not general enough
   --> $DIR/issue-54302.rs:13:5
    |
+LL | trait Deserialize<'de> {}
+   | ------------------------- trait `Deserialize` defined here
+...
 LL |     assert_deserialize_owned::<&'static str>();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Deserialize` is not general enough
    |
-   = note: `&'static str` must implement `Deserialize<'0>`, for any lifetime `'0`
-   = note: but `&str` actually implements `Deserialize<'1>`, for some specific lifetime `'1`
+   = note: `&'static str` must implement `Deserialize<'0>`, for any lifetime `'0`...
+   = note: ...but `&str` actually implements `Deserialize<'1>`, for some specific lifetime `'1`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-55731.stderr b/src/test/ui/issues/issue-55731.stderr
index f25e18e5d90cb..f44c842187cc2 100644
--- a/src/test/ui/issues/issue-55731.stderr
+++ b/src/test/ui/issues/issue-55731.stderr
@@ -1,11 +1,16 @@
 error: implementation of `DistributedIteratorMulti` is not general enough
   --> $DIR/issue-55731.rs:48:5
    |
-LL |     multi(Map {
-   |     ^^^^^
+LL | / trait DistributedIteratorMulti<Source> {
+LL | |     type Item;
+LL | | }
+   | |_- trait `DistributedIteratorMulti` defined here
+...
+LL |       multi(Map {
+   |       ^^^^^ implementation of `DistributedIteratorMulti` is not general enough
    |
-   = note: `DistributedIteratorMulti<&'0 ()>` would have to be implemented for the type `Cloned<&()>`, for any lifetime `'0`
-   = note: but `DistributedIteratorMulti<&'1 ()>` is actually implemented for the type `Cloned<&'1 ()>`, for some specific lifetime `'1`
+   = note: `DistributedIteratorMulti<&'0 ()>` would have to be implemented for the type `Cloned<&()>`, for any lifetime `'0`...
+   = note: ...but `DistributedIteratorMulti<&'1 ()>` is actually implemented for the type `Cloned<&'1 ()>`, for some specific lifetime `'1`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-57362-1.stderr b/src/test/ui/issues/issue-57362-1.stderr
index 1d2ff7669c093..c4000c8a9d41e 100644
--- a/src/test/ui/issues/issue-57362-1.stderr
+++ b/src/test/ui/issues/issue-57362-1.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `f` found for type `fn(&u8)` in the current scope
   --> $DIR/issue-57362-1.rs:20:7
    |
 LL |     a.f();
-   |       ^
+   |       ^ method not found in `fn(&u8)`
    |
    = note: a is a function, perhaps you wish to call it
    = help: items from traits can only be used if the trait is implemented and in scope
diff --git a/src/test/ui/issues/issue-60057.rs b/src/test/ui/issues/issue-60057.rs
index 3027d01c5325b..b52343adaee71 100644
--- a/src/test/ui/issues/issue-60057.rs
+++ b/src/test/ui/issues/issue-60057.rs
@@ -15,3 +15,5 @@ impl A {
         }
     }
 }
+
+fn main() {}
diff --git a/src/test/ui/issues/issue-60057.stderr b/src/test/ui/issues/issue-60057.stderr
index 6b967204ce6fb..4d915fcd9fe3d 100644
--- a/src/test/ui/issues/issue-60057.stderr
+++ b/src/test/ui/issues/issue-60057.stderr
@@ -10,11 +10,6 @@ error[E0425]: cannot find value `banana` in this scope
 LL |             banana: banana
    |                     ^^^^^^ help: you might have meant to use the available field: `self.banana`
 
-error[E0601]: `main` function not found in crate `issue_60057`
-   |
-   = note: consider adding a `main` function to `$DIR/issue-60057.rs`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0425, E0601.
-For more information about an error, try `rustc --explain E0425`.
+For more information about this error, try `rustc --explain E0425`.
diff --git a/src/test/ui/issues/issue-60283.stderr b/src/test/ui/issues/issue-60283.stderr
index a977ba392769f..2b01a64d39a9b 100644
--- a/src/test/ui/issues/issue-60283.stderr
+++ b/src/test/ui/issues/issue-60283.stderr
@@ -1,5 +1,5 @@
 error[E0631]: type mismatch in function arguments
-  --> $DIR/issue-60283.rs:14:5
+  --> $DIR/issue-60283.rs:14:13
    |
 LL | / pub fn foo<T, F>(_: T, _: F)
 LL | | where T: for<'a> Trait<'a>,
@@ -7,10 +7,10 @@ LL | |       F: for<'a> FnMut(<T as Trait<'a>>::Item) {}
    | |_________________________________________________- required by `foo`
 ...
 LL |       foo((), drop)
-   |       ^^^
-   |       |
-   |       expected signature of `for<'a> fn(<() as Trait<'a>>::Item) -> _`
-   |       found signature of `fn(_) -> _`
+   |               ^^^^
+   |               |
+   |               expected signature of `for<'a> fn(<() as Trait<'a>>::Item) -> _`
+   |               found signature of `fn(_) -> _`
 
 error[E0271]: type mismatch resolving `for<'a> <fn(_) {std::mem::drop::<_>} as std::ops::FnOnce<(<() as Trait<'a>>::Item,)>>::Output == ()`
   --> $DIR/issue-60283.rs:14:5
diff --git a/src/test/ui/issues/issue-61711-once-caused-rustc-inf-loop.rs b/src/test/ui/issues/issue-61711-once-caused-rustc-inf-loop.rs
index 8fc09c89f786b..de7d6a0d80c9e 100644
--- a/src/test/ui/issues/issue-61711-once-caused-rustc-inf-loop.rs
+++ b/src/test/ui/issues/issue-61711-once-caused-rustc-inf-loop.rs
@@ -5,7 +5,7 @@
 // aux-build:xcrate-issue-61711-b.rs
 // compile-flags:--extern xcrate_issue_61711_b
 
-// run-pass
+// build-pass
 
 fn f<F: Fn(xcrate_issue_61711_b::Struct)>(_: F) { }
 fn main() { }
diff --git a/src/test/ui/issues/issue-64430.rs b/src/test/ui/issues/issue-64430.rs
new file mode 100644
index 0000000000000..0bc66e06e6731
--- /dev/null
+++ b/src/test/ui/issues/issue-64430.rs
@@ -0,0 +1,14 @@
+// compile-flags:-C panic=abort
+
+#![no_std]
+pub struct Foo;
+
+fn main() {
+    Foo.bar()
+    //~^ ERROR E0599
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop{}
+}
diff --git a/src/test/ui/issues/issue-64430.stderr b/src/test/ui/issues/issue-64430.stderr
new file mode 100644
index 0000000000000..f1b2de8d8b36f
--- /dev/null
+++ b/src/test/ui/issues/issue-64430.stderr
@@ -0,0 +1,12 @@
+error[E0599]: no method named `bar` found for type `Foo` in the current scope
+  --> $DIR/issue-64430.rs:7:9
+   |
+LL | pub struct Foo;
+   | --------------- method `bar` not found for this
+...
+LL |     Foo.bar()
+   |         ^^^ method not found in `Foo`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/src/test/ui/issues/issue-6919.rs b/src/test/ui/issues/issue-6919.rs
index 11aed12087313..6f1e1f97708ef 100644
--- a/src/test/ui/issues/issue-6919.rs
+++ b/src/test/ui/issues/issue-6919.rs
@@ -4,7 +4,6 @@
 
 // pretty-expanded FIXME #23616
 
-#![crate_id="issue-6919"]
 extern crate issue6919_3;
 
 pub fn main() {
diff --git a/src/test/ui/issues/issue-7246.stderr b/src/test/ui/issues/issue-7246.stderr
index e049295e9136f..d1b23672dc7f4 100644
--- a/src/test/ui/issues/issue-7246.stderr
+++ b/src/test/ui/issues/issue-7246.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/issue-7246.rs:6:5
+   |
+LL |     return;
+   |     ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/json-multiple.polonius.stderr b/src/test/ui/json-multiple.polonius.stderr
new file mode 100644
index 0000000000000..0e4d442f299c3
--- /dev/null
+++ b/src/test/ui/json-multiple.polonius.stderr
@@ -0,0 +1 @@
+{"artifact":"$TEST_BUILD_DIR/json-multiple.polonius/libjson_multiple.rlib","emit":"link"}
diff --git a/src/test/ui/json-options.polonius.stderr b/src/test/ui/json-options.polonius.stderr
new file mode 100644
index 0000000000000..e21f6f85d162d
--- /dev/null
+++ b/src/test/ui/json-options.polonius.stderr
@@ -0,0 +1 @@
+{"artifact":"$TEST_BUILD_DIR/json-options.polonius/libjson_options.rlib","emit":"link"}
diff --git a/src/test/ui/json-short.stderr b/src/test/ui/json-short.stderr
index dffbdb7e4802d..0a1fb567714fb 100644
--- a/src/test/ui/json-short.stderr
+++ b/src/test/ui/json-short.stderr
@@ -11,9 +11,9 @@ fn main() {
 
 If you don't know the basics of Rust, you can go look to the Rust Book to get
 started: https://doc.rust-lang.org/book/
-"},"level":"error","spans":[],"children":[{"message":"consider adding a `main` function to `$DIR/json-short.rs`","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0601]: `main` function not found in crate `json_short`
+"},"level":"error","spans":[{"file_name":"$DIR/json-short.rs","byte_start":76,"byte_end":76,"line_start":2,"line_end":2,"column_start":63,"column_end":63,"is_primary":true,"text":[{"text":"// compile-flags: --json=diagnostic-short --error-format=json","highlight_start":63,"highlight_end":63}],"label":"consider adding a `main` function to `$DIR/json-short.rs`","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":"$DIR/json-short.rs:2:63: error[E0601]: `main` function not found in crate `json_short`
 "}
 {"message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
 "}
-{"message":"For more information about this error, try `rustc --explain E0601`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0601`.
+{"message":"For more information about this error, try `rustc --explain E0601`.","code":null,"level":"failure-note","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0601`.
 "}
diff --git a/src/test/ui/kindck/kindck-impl-type-params-2.stderr b/src/test/ui/kindck/kindck-impl-type-params-2.stderr
index 6d599423d2548..5e6eca6f0571b 100644
--- a/src/test/ui/kindck/kindck-impl-type-params-2.stderr
+++ b/src/test/ui/kindck/kindck-impl-type-params-2.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `std::boxed::Box<{integer}>: std::marker::Copy` is not satisfied
-  --> $DIR/kindck-impl-type-params-2.rs:13:5
+  --> $DIR/kindck-impl-type-params-2.rs:13:16
    |
 LL | fn take_param<T:Foo>(foo: &T) { }
    | ----------------------------- required by `take_param`
 ...
 LL |     take_param(&x);
-   |     ^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::boxed::Box<{integer}>`
+   |                ^^ the trait `std::marker::Copy` is not implemented for `std::boxed::Box<{integer}>`
    |
    = note: required because of the requirements on the impl of `Foo` for `std::boxed::Box<{integer}>`
 
diff --git a/src/test/ui/kindck/kindck-inherited-copy-bound.stderr b/src/test/ui/kindck/kindck-inherited-copy-bound.stderr
index a53063157fc8e..9f548083e73d1 100644
--- a/src/test/ui/kindck/kindck-inherited-copy-bound.stderr
+++ b/src/test/ui/kindck/kindck-inherited-copy-bound.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `std::boxed::Box<{integer}>: std::marker::Copy` is not satisfied
-  --> $DIR/kindck-inherited-copy-bound.rs:18:5
+  --> $DIR/kindck-inherited-copy-bound.rs:18:16
    |
 LL | fn take_param<T:Foo>(foo: &T) { }
    | ----------------------------- required by `take_param`
 ...
 LL |     take_param(&x);
-   |     ^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::boxed::Box<{integer}>`
+   |                ^^ the trait `std::marker::Copy` is not implemented for `std::boxed::Box<{integer}>`
    |
    = note: required because of the requirements on the impl of `Foo` for `std::boxed::Box<{integer}>`
 
diff --git a/src/test/ui/lifetime-before-type-params.rs b/src/test/ui/lifetime-before-type-params.rs
index 9b905d4883a16..5a71d6efeda62 100644
--- a/src/test/ui/lifetime-before-type-params.rs
+++ b/src/test/ui/lifetime-before-type-params.rs
@@ -7,3 +7,5 @@ fn third<T, U, 'a>() {}
 //~^ ERROR lifetime parameters must be declared prior to type parameters
 fn fourth<'a, T, 'b, U, 'c, V>() {}
 //~^ ERROR lifetime parameters must be declared prior to type parameters
+
+fn main() {}
diff --git a/src/test/ui/lifetime-before-type-params.stderr b/src/test/ui/lifetime-before-type-params.stderr
index ffc6784bafed8..76d7d0f024d65 100644
--- a/src/test/ui/lifetime-before-type-params.stderr
+++ b/src/test/ui/lifetime-before-type-params.stderr
@@ -22,10 +22,5 @@ error: lifetime parameters must be declared prior to type parameters
 LL | fn fourth<'a, T, 'b, U, 'c, V>() {}
    |          --------^^-----^^---- help: reorder the parameters: lifetimes, then types: `<'a, 'b, 'c, T, U, V>`
 
-error[E0601]: `main` function not found in crate `lifetime_before_type_params`
-   |
-   = note: consider adding a `main` function to `$DIR/lifetime-before-type-params.rs`
-
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
index 779e2eb8b9205..2ed4d6d4401aa 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
@@ -12,11 +12,11 @@ error: lifetime may not live long enough
   --> $DIR/ex3-both-anon-regions-3.rs:2:5
    |
 LL | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
-   |                         -                    - let's call the lifetime of this reference `'1`
+   |                         -                    - let's call the lifetime of this reference `'3`
    |                         |
-   |                         let's call the lifetime of this reference `'2`
+   |                         let's call the lifetime of this reference `'4`
 LL |     z.push((x,y));
-   |     ^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |     ^^^^^^^^^^^^^ argument requires that `'3` must outlive `'4`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/lint/empty-lint-attributes.rs b/src/test/ui/lint/empty-lint-attributes.rs
index 1f0a9538d88b1..9a0ec253322e4 100644
--- a/src/test/ui/lint/empty-lint-attributes.rs
+++ b/src/test/ui/lint/empty-lint-attributes.rs
@@ -1,6 +1,6 @@
 #![feature(lint_reasons)]
 
-// run-pass
+// check-pass
 
 // Empty (and reason-only) lint attributes are legal—although we may want to
 // lint them in the future (Issue #55112).
diff --git a/src/test/ui/lint/issue-54538-unused-parens-lint.rs b/src/test/ui/lint/issue-54538-unused-parens-lint.rs
index c442c39fe010e..7dcbdd0863cbd 100644
--- a/src/test/ui/lint/issue-54538-unused-parens-lint.rs
+++ b/src/test/ui/lint/issue-54538-unused-parens-lint.rs
@@ -1,4 +1,4 @@
-#![feature(box_patterns)]
+#![feature(box_patterns, stmt_expr_attributes)]
 
 #![feature(or_patterns)]
 //~^ WARN the feature `or_patterns` is incomplete
@@ -17,6 +17,10 @@ fn lint_on_top_level() {
     let _ = |(a): u8| 0; //~ ERROR unnecessary parentheses around pattern
 }
 
+fn _no_lint_attr() {
+    let _x = #[allow(dead_code)] (1 + 2);
+}
+
 // Don't lint in these cases (#64106).
 fn or_patterns_no_lint() {
     match Box::new(0) {
@@ -33,10 +37,8 @@ fn or_patterns_no_lint() {
     if let &mut (0 | 1) = &mut 0 {} // Same.
 
     fn foo((Ok(a) | Err(a)): Result<u8, u8>) {} // Doesn't parse if we remove parens for now.
-    //~^ ERROR identifier `a` is bound more than once
 
     let _ = |(Ok(a) | Err(a)): Result<u8, u8>| 1; // `|Ok(a) | Err(a)| 1` parses as bit-or.
-    //~^ ERROR identifier `a` is bound more than once
 }
 
 fn or_patterns_will_lint() {
diff --git a/src/test/ui/lint/issue-54538-unused-parens-lint.stderr b/src/test/ui/lint/issue-54538-unused-parens-lint.stderr
index a3e0fb938b3c6..675dd4f07def6 100644
--- a/src/test/ui/lint/issue-54538-unused-parens-lint.stderr
+++ b/src/test/ui/lint/issue-54538-unused-parens-lint.stderr
@@ -1,15 +1,3 @@
-error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:35:25
-   |
-LL |     fn foo((Ok(a) | Err(a)): Result<u8, u8>) {} // Doesn't parse if we remove parens for now.
-   |                         ^ used in a pattern more than once
-
-error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:38:27
-   |
-LL |     let _ = |(Ok(a) | Err(a)): Result<u8, u8>| 1; // `|Ok(a) | Err(a)| 1` parses as bit-or.
-   |                           ^ used in a pattern more than once
-
 warning: the feature `or_patterns` is incomplete and may cause the compiler to crash
   --> $DIR/issue-54538-unused-parens-lint.rs:3:12
    |
@@ -61,113 +49,112 @@ LL |     let _ = |(a): u8| 0;
    |              ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:43:12
+  --> $DIR/issue-54538-unused-parens-lint.rs:45:12
    |
 LL |     if let (0 | 1) = 0 {}
    |            ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:44:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:46:13
    |
 LL |     if let ((0 | 1),) = (0,) {}
    |             ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:45:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:47:13
    |
 LL |     if let [(0 | 1)] = [0] {}
    |             ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:46:16
+  --> $DIR/issue-54538-unused-parens-lint.rs:48:16
    |
 LL |     if let 0 | (1 | 2) = 0 {}
    |                ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:48:15
+  --> $DIR/issue-54538-unused-parens-lint.rs:50:15
    |
 LL |     if let TS((0 | 1)) = TS(0) {}
    |               ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:50:20
+  --> $DIR/issue-54538-unused-parens-lint.rs:52:20
    |
 LL |     if let NS { f: (0 | 1) } = (NS { f: 0 }) {}
    |                    ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:60:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:62:9
    |
 LL |         (_) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:61:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:63:9
    |
 LL |         (y) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:62:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:64:9
    |
 LL |         (ref r) => {}
    |         ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:63:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:65:9
    |
 LL |         (e @ 1...2) => {}
    |         ^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:69:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:71:9
    |
 LL |         (e @ &(1...2)) => {}
    |         ^^^^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:70:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:72:10
    |
 LL |         &(_) => {}
    |          ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:81:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:83:9
    |
 LL |         (_) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:82:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:84:9
    |
 LL |         (y) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:83:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:85:9
    |
 LL |         (ref r) => {}
    |         ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:84:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:86:9
    |
 LL |         (e @ 1..=2) => {}
    |         ^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:90:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:92:9
    |
 LL |         (e @ &(1..=2)) => {}
    |         ^^^^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:91:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:93:10
    |
 LL |         &(_) => {}
    |          ^^^ help: remove these parentheses
 
-error: aborting due to 26 previous errors
+error: aborting due to 24 previous errors
 
-For more information about this error, try `rustc --explain E0416`.
diff --git a/src/test/ui/lint/lint-attr-non-item-node.stderr b/src/test/ui/lint/lint-attr-non-item-node.stderr
index 6eb72c098df5c..e6c76c24c9110 100644
--- a/src/test/ui/lint/lint-attr-non-item-node.stderr
+++ b/src/test/ui/lint/lint-attr-non-item-node.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL |     #[deny(unreachable_code)]
    |            ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/lint-attr-non-item-node.rs:6:9
+   |
+LL |         break;
+   |         ^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lint/lint-ctypes-enum.rs b/src/test/ui/lint/lint-ctypes-enum.rs
index e1f4b0b34ebaa..3898e67a07f7e 100644
--- a/src/test/ui/lint/lint-ctypes-enum.rs
+++ b/src/test/ui/lint/lint-ctypes-enum.rs
@@ -36,36 +36,37 @@ struct Rust<T>(T);
 
 extern {
    fn zf(x: Z);
-   fn uf(x: U); //~ ERROR enum has no representation hint
-   fn bf(x: B); //~ ERROR enum has no representation hint
-   fn tf(x: T); //~ ERROR enum has no representation hint
+   fn uf(x: U); //~ ERROR `extern` block uses type `U`
+   fn bf(x: B); //~ ERROR `extern` block uses type `B`
+   fn tf(x: T); //~ ERROR `extern` block uses type `T`
    fn repr_c(x: ReprC);
    fn repr_u8(x: U8);
    fn repr_isize(x: Isize);
    fn option_ref(x: Option<&'static u8>);
    fn option_fn(x: Option<extern "C" fn()>);
    fn nonnull(x: Option<std::ptr::NonNull<u8>>);
-   fn unique(x: Option<std::ptr::Unique<u8>>); //~ ERROR enum has no representation hint
+   fn unique(x: Option<std::ptr::Unique<u8>>);
+   //~^ ERROR `extern` block uses type `std::option::Option<std::ptr::Unique<u8>>`
    fn nonzero_u8(x: Option<num::NonZeroU8>);
    fn nonzero_u16(x: Option<num::NonZeroU16>);
    fn nonzero_u32(x: Option<num::NonZeroU32>);
    fn nonzero_u64(x: Option<num::NonZeroU64>);
    fn nonzero_u128(x: Option<num::NonZeroU128>);
-   //~^ ERROR 128-bit integers don't currently have a known stable ABI
+   //~^ ERROR `extern` block uses type `u128`
    fn nonzero_usize(x: Option<num::NonZeroUsize>);
    fn nonzero_i8(x: Option<num::NonZeroI8>);
    fn nonzero_i16(x: Option<num::NonZeroI16>);
    fn nonzero_i32(x: Option<num::NonZeroI32>);
    fn nonzero_i64(x: Option<num::NonZeroI64>);
    fn nonzero_i128(x: Option<num::NonZeroI128>);
-   //~^ ERROR 128-bit integers don't currently have a known stable ABI
+   //~^ ERROR `extern` block uses type `i128`
    fn nonzero_isize(x: Option<num::NonZeroIsize>);
    fn transparent_struct(x: Option<TransparentStruct<num::NonZeroU8>>);
    fn transparent_enum(x: Option<TransparentEnum<num::NonZeroU8>>);
    fn transparent_union(x: Option<TransparentUnion<num::NonZeroU8>>);
-   //~^ ERROR enum has no representation hint
-   fn repr_rust(x: Option<Rust<num::NonZeroU8>>); //~ ERROR enum has no representation hint
-   fn no_result(x: Result<(), num::NonZeroI32>); //~ ERROR enum has no representation hint
+   //~^ ERROR `extern` block uses type
+   fn repr_rust(x: Option<Rust<num::NonZeroU8>>); //~ ERROR `extern` block uses type
+   fn no_result(x: Result<(), num::NonZeroI32>); //~ ERROR `extern` block uses type
 }
 
-pub fn main() { }
+pub fn main() {}
diff --git a/src/test/ui/lint/lint-ctypes-enum.stderr b/src/test/ui/lint/lint-ctypes-enum.stderr
index 20e438606642c..81939e6ee206c 100644
--- a/src/test/ui/lint/lint-ctypes-enum.stderr
+++ b/src/test/ui/lint/lint-ctypes-enum.stderr
@@ -1,8 +1,8 @@
-error: `extern` block uses type `U` which is not FFI-safe: enum has no representation hint
+error: `extern` block uses type `U`, which is not FFI-safe
   --> $DIR/lint-ctypes-enum.rs:39:13
    |
 LL |    fn uf(x: U);
-   |             ^
+   |             ^ not FFI-safe
    |
 note: lint level defined here
   --> $DIR/lint-ctypes-enum.rs:3:9
@@ -10,81 +10,92 @@ note: lint level defined here
 LL | #![deny(improper_ctypes)]
    |         ^^^^^^^^^^^^^^^
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 note: type defined here
   --> $DIR/lint-ctypes-enum.rs:9:1
    |
 LL | enum U { A }
    | ^^^^^^^^^^^^
 
-error: `extern` block uses type `B` which is not FFI-safe: enum has no representation hint
+error: `extern` block uses type `B`, which is not FFI-safe
   --> $DIR/lint-ctypes-enum.rs:40:13
    |
 LL |    fn bf(x: B);
-   |             ^
+   |             ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 note: type defined here
   --> $DIR/lint-ctypes-enum.rs:10:1
    |
 LL | enum B { C, D }
    | ^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `T` which is not FFI-safe: enum has no representation hint
+error: `extern` block uses type `T`, which is not FFI-safe
   --> $DIR/lint-ctypes-enum.rs:41:13
    |
 LL |    fn tf(x: T);
-   |             ^
+   |             ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 note: type defined here
   --> $DIR/lint-ctypes-enum.rs:11:1
    |
 LL | enum T { E, F, G }
    | ^^^^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `std::option::Option<std::ptr::Unique<u8>>` which is not FFI-safe: enum has no representation hint
+error: `extern` block uses type `std::option::Option<std::ptr::Unique<u8>>`, which is not FFI-safe
   --> $DIR/lint-ctypes-enum.rs:48:17
    |
 LL |    fn unique(x: Option<std::ptr::Unique<u8>>);
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 
-error: `extern` block uses type `u128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
-  --> $DIR/lint-ctypes-enum.rs:53:23
+error: `extern` block uses type `u128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:54:23
    |
 LL |    fn nonzero_u128(x: Option<num::NonZeroU128>);
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
 
-error: `extern` block uses type `i128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
-  --> $DIR/lint-ctypes-enum.rs:60:23
+error: `extern` block uses type `i128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:61:23
    |
 LL |    fn nonzero_i128(x: Option<num::NonZeroI128>);
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
 
-error: `extern` block uses type `std::option::Option<TransparentUnion<std::num::NonZeroU8>>` which is not FFI-safe: enum has no representation hint
-  --> $DIR/lint-ctypes-enum.rs:65:28
+error: `extern` block uses type `std::option::Option<TransparentUnion<std::num::NonZeroU8>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:66:28
    |
 LL |    fn transparent_union(x: Option<TransparentUnion<num::NonZeroU8>>);
-   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 
-error: `extern` block uses type `std::option::Option<Rust<std::num::NonZeroU8>>` which is not FFI-safe: enum has no representation hint
-  --> $DIR/lint-ctypes-enum.rs:67:20
+error: `extern` block uses type `std::option::Option<Rust<std::num::NonZeroU8>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:68:20
    |
 LL |    fn repr_rust(x: Option<Rust<num::NonZeroU8>>);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 
-error: `extern` block uses type `std::result::Result<(), std::num::NonZeroI32>` which is not FFI-safe: enum has no representation hint
-  --> $DIR/lint-ctypes-enum.rs:68:20
+error: `extern` block uses type `std::result::Result<(), std::num::NonZeroI32>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:69:20
    |
 LL |    fn no_result(x: Result<(), num::NonZeroI32>);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/lint/lint-ctypes.rs b/src/test/ui/lint/lint-ctypes.rs
index a3d9b6febdbb7..e20503a395c89 100644
--- a/src/test/ui/lint/lint-ctypes.rs
+++ b/src/test/ui/lint/lint-ctypes.rs
@@ -1,7 +1,7 @@
-#![deny(improper_ctypes)]
 #![feature(rustc_private)]
 
 #![allow(private_in_public)]
+#![deny(improper_ctypes)]
 
 extern crate libc;
 
@@ -54,12 +54,13 @@ extern {
     pub fn trait_type(p: &dyn Clone); //~ ERROR uses type `dyn std::clone::Clone`
     pub fn tuple_type(p: (i32, i32)); //~ ERROR uses type `(i32, i32)`
     pub fn tuple_type2(p: I32Pair); //~ ERROR uses type `(i32, i32)`
-    pub fn zero_size(p: ZeroSize); //~ ERROR struct has no fields
-    pub fn zero_size_phantom(p: ZeroSizeWithPhantomData); //~ ERROR composed only of PhantomData
+    pub fn zero_size(p: ZeroSize); //~ ERROR uses type `ZeroSize`
+    pub fn zero_size_phantom(p: ZeroSizeWithPhantomData);
+    //~^ ERROR uses type `ZeroSizeWithPhantomData`
     pub fn zero_size_phantom_toplevel()
-        -> ::std::marker::PhantomData<bool>; //~ ERROR: composed only of PhantomData
-    pub fn fn_type(p: RustFn); //~ ERROR function pointer has Rust-specific
-    pub fn fn_type2(p: fn()); //~ ERROR function pointer has Rust-specific
+        -> ::std::marker::PhantomData<bool>; //~ ERROR uses type `std::marker::PhantomData<bool>`
+    pub fn fn_type(p: RustFn); //~ ERROR uses type `fn()`
+    pub fn fn_type2(p: fn()); //~ ERROR uses type `fn()`
     pub fn fn_contained(p: RustBadRet); //~ ERROR: uses type `std::boxed::Box<u32>`
     pub fn transparent_i128(p: TransparentI128); //~ ERROR: uses type `i128`
     pub fn transparent_str(p: TransparentStr); //~ ERROR: uses type `str`
diff --git a/src/test/ui/lint/lint-ctypes.stderr b/src/test/ui/lint/lint-ctypes.stderr
index c78463beb6559..e533a767b317f 100644
--- a/src/test/ui/lint/lint-ctypes.stderr
+++ b/src/test/ui/lint/lint-ctypes.stderr
@@ -1,170 +1,201 @@
-error: `extern` block uses type `Foo` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `Foo`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:46:28
    |
 LL |     pub fn ptr_type1(size: *const Foo);
-   |                            ^^^^^^^^^^
+   |                            ^^^^^^^^^^ not FFI-safe
    |
 note: lint level defined here
-  --> $DIR/lint-ctypes.rs:1:9
+  --> $DIR/lint-ctypes.rs:4:9
    |
 LL | #![deny(improper_ctypes)]
    |         ^^^^^^^^^^^^^^^
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/lint-ctypes.rs:24:1
    |
 LL | pub struct Foo;
    | ^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `Foo` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `Foo`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:47:28
    |
 LL |     pub fn ptr_type2(size: *const Foo);
-   |                            ^^^^^^^^^^
+   |                            ^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 note: type defined here
   --> $DIR/lint-ctypes.rs:24:1
    |
 LL | pub struct Foo;
    | ^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `[u32]` which is not FFI-safe: slices have no C equivalent
+error: `extern` block uses type `[u32]`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:48:26
    |
 LL |     pub fn slice_type(p: &[u32]);
-   |                          ^^^^^^
+   |                          ^^^^^^ not FFI-safe
    |
    = help: consider using a raw pointer instead
+   = note: slices have no C equivalent
 
-error: `extern` block uses type `str` which is not FFI-safe: string slices have no C equivalent
+error: `extern` block uses type `str`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:49:24
    |
 LL |     pub fn str_type(p: &str);
-   |                        ^^^^
+   |                        ^^^^ not FFI-safe
    |
    = help: consider using `*const u8` and a length instead
+   = note: string slices have no C equivalent
 
-error: `extern` block uses type `std::boxed::Box<u32>` which is not FFI-safe: this struct has unspecified layout
+error: `extern` block uses type `std::boxed::Box<u32>`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:50:24
    |
 LL |     pub fn box_type(p: Box<u32>);
-   |                        ^^^^^^^^
+   |                        ^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 
-error: `extern` block uses type `char` which is not FFI-safe: the `char` type has no C equivalent
+error: `extern` block uses type `char`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:51:25
    |
 LL |     pub fn char_type(p: char);
-   |                         ^^^^
+   |                         ^^^^ not FFI-safe
    |
    = help: consider using `u32` or `libc::wchar_t` instead
+   = note: the `char` type has no C equivalent
 
-error: `extern` block uses type `i128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
+error: `extern` block uses type `i128`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:52:25
    |
 LL |     pub fn i128_type(p: i128);
-   |                         ^^^^
+   |                         ^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
 
-error: `extern` block uses type `u128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
+error: `extern` block uses type `u128`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:53:25
    |
 LL |     pub fn u128_type(p: u128);
-   |                         ^^^^
+   |                         ^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
 
-error: `extern` block uses type `dyn std::clone::Clone` which is not FFI-safe: trait objects have no C equivalent
+error: `extern` block uses type `dyn std::clone::Clone`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:54:26
    |
 LL |     pub fn trait_type(p: &dyn Clone);
-   |                          ^^^^^^^^^^
+   |                          ^^^^^^^^^^ not FFI-safe
+   |
+   = note: trait objects have no C equivalent
 
-error: `extern` block uses type `(i32, i32)` which is not FFI-safe: tuples have unspecified layout
+error: `extern` block uses type `(i32, i32)`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:55:26
    |
 LL |     pub fn tuple_type(p: (i32, i32));
-   |                          ^^^^^^^^^^
+   |                          ^^^^^^^^^^ not FFI-safe
    |
    = help: consider using a struct instead
+   = note: tuples have unspecified layout
 
-error: `extern` block uses type `(i32, i32)` which is not FFI-safe: tuples have unspecified layout
+error: `extern` block uses type `(i32, i32)`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:56:27
    |
 LL |     pub fn tuple_type2(p: I32Pair);
-   |                           ^^^^^^^
+   |                           ^^^^^^^ not FFI-safe
    |
    = help: consider using a struct instead
+   = note: tuples have unspecified layout
 
-error: `extern` block uses type `ZeroSize` which is not FFI-safe: this struct has no fields
+error: `extern` block uses type `ZeroSize`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:57:25
    |
 LL |     pub fn zero_size(p: ZeroSize);
-   |                         ^^^^^^^^
+   |                         ^^^^^^^^ not FFI-safe
    |
    = help: consider adding a member to this struct
+   = note: this struct has no fields
 note: type defined here
   --> $DIR/lint-ctypes.rs:20:1
    |
 LL | pub struct ZeroSize;
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `ZeroSizeWithPhantomData` which is not FFI-safe: composed only of PhantomData
+error: `extern` block uses type `ZeroSizeWithPhantomData`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:58:33
    |
 LL |     pub fn zero_size_phantom(p: ZeroSizeWithPhantomData);
-   |                                 ^^^^^^^^^^^^^^^^^^^^^^^
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: composed only of `PhantomData`
+note: type defined here
+  --> $DIR/lint-ctypes.rs:43:1
+   |
+LL | pub struct ZeroSizeWithPhantomData(::std::marker::PhantomData<i32>);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: `extern` block uses type `std::marker::PhantomData<bool>` which is not FFI-safe: composed only of PhantomData
-  --> $DIR/lint-ctypes.rs:60:12
+error: `extern` block uses type `std::marker::PhantomData<bool>`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:61:12
    |
 LL |         -> ::std::marker::PhantomData<bool>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: composed only of `PhantomData`
 
-error: `extern` block uses type `fn()` which is not FFI-safe: this function pointer has Rust-specific calling convention
-  --> $DIR/lint-ctypes.rs:61:23
+error: `extern` block uses type `fn()`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:62:23
    |
 LL |     pub fn fn_type(p: RustFn);
-   |                       ^^^^^^
+   |                       ^^^^^^ not FFI-safe
    |
    = help: consider using an `extern fn(...) -> ...` function pointer instead
+   = note: this function pointer has Rust-specific calling convention
 
-error: `extern` block uses type `fn()` which is not FFI-safe: this function pointer has Rust-specific calling convention
-  --> $DIR/lint-ctypes.rs:62:24
+error: `extern` block uses type `fn()`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:63:24
    |
 LL |     pub fn fn_type2(p: fn());
-   |                        ^^^^
+   |                        ^^^^ not FFI-safe
    |
    = help: consider using an `extern fn(...) -> ...` function pointer instead
+   = note: this function pointer has Rust-specific calling convention
 
-error: `extern` block uses type `std::boxed::Box<u32>` which is not FFI-safe: this struct has unspecified layout
-  --> $DIR/lint-ctypes.rs:63:28
+error: `extern` block uses type `std::boxed::Box<u32>`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:64:28
    |
 LL |     pub fn fn_contained(p: RustBadRet);
-   |                            ^^^^^^^^^^
+   |                            ^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 
-error: `extern` block uses type `i128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
-  --> $DIR/lint-ctypes.rs:64:32
+error: `extern` block uses type `i128`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:65:32
    |
 LL |     pub fn transparent_i128(p: TransparentI128);
-   |                                ^^^^^^^^^^^^^^^
+   |                                ^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
 
-error: `extern` block uses type `str` which is not FFI-safe: string slices have no C equivalent
-  --> $DIR/lint-ctypes.rs:65:31
+error: `extern` block uses type `str`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:66:31
    |
 LL |     pub fn transparent_str(p: TransparentStr);
-   |                               ^^^^^^^^^^^^^^
+   |                               ^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider using `*const u8` and a length instead
+   = note: string slices have no C equivalent
 
-error: `extern` block uses type `std::boxed::Box<u32>` which is not FFI-safe: this struct has unspecified layout
-  --> $DIR/lint-ctypes.rs:66:30
+error: `extern` block uses type `std::boxed::Box<u32>`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:67:30
    |
 LL |     pub fn transparent_fn(p: TransparentBadFn);
-   |                              ^^^^^^^^^^^^^^^^
+   |                              ^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
+   = note: this struct has unspecified layout
 
 error: aborting due to 20 previous errors
 
diff --git a/src/test/ui/lint/opaque-ty-ffi-unsafe.rs b/src/test/ui/lint/opaque-ty-ffi-unsafe.rs
new file mode 100644
index 0000000000000..25d5f8ec68aa0
--- /dev/null
+++ b/src/test/ui/lint/opaque-ty-ffi-unsafe.rs
@@ -0,0 +1,16 @@
+#![feature(type_alias_impl_trait)]
+
+#![deny(improper_ctypes)]
+
+type A = impl Fn();
+
+pub fn ret_closure() -> A {
+    || {}
+}
+
+extern "C" {
+    pub fn a(_: A);
+    //~^ ERROR `extern` block uses type `A`, which is not FFI-safe
+}
+
+fn main() {}
diff --git a/src/test/ui/lint/opaque-ty-ffi-unsafe.stderr b/src/test/ui/lint/opaque-ty-ffi-unsafe.stderr
new file mode 100644
index 0000000000000..136d564d1ab3d
--- /dev/null
+++ b/src/test/ui/lint/opaque-ty-ffi-unsafe.stderr
@@ -0,0 +1,15 @@
+error: `extern` block uses type `A`, which is not FFI-safe
+  --> $DIR/opaque-ty-ffi-unsafe.rs:12:17
+   |
+LL |     pub fn a(_: A);
+   |                 ^ not FFI-safe
+   |
+note: lint level defined here
+  --> $DIR/opaque-ty-ffi-unsafe.rs:3:9
+   |
+LL | #![deny(improper_ctypes)]
+   |         ^^^^^^^^^^^^^^^
+   = note: opaque types have no C equivalent
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/lint/use_suggestion_json.stderr b/src/test/ui/lint/use_suggestion_json.stderr
index c7c53abcf4406..678c88849b561 100644
--- a/src/test/ui/lint/use_suggestion_json.stderr
+++ b/src/test/ui/lint/use_suggestion_json.stderr
@@ -412,7 +412,7 @@ mod foo {
 {
   "message": "For more information about this error, try `rustc --explain E0412`.",
   "code": null,
-  "level": "",
+  "level": "failure-note",
   "spans": [],
   "children": [],
   "rendered": "\u001b[0m\u001b[1mFor more information about this error, try `rustc --explain E0412`.\u001b[0m
diff --git a/src/test/ui/liveness/liveness-unused.stderr b/src/test/ui/liveness/liveness-unused.stderr
index 40a677c08f2b0..84e9b5bab99ff 100644
--- a/src/test/ui/liveness/liveness-unused.stderr
+++ b/src/test/ui/liveness/liveness-unused.stderr
@@ -10,6 +10,11 @@ note: lint level defined here
 LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unreachable_code)]` implied by `#[warn(unused)]`
+note: any code following this expression is unreachable
+  --> $DIR/liveness-unused.rs:91:9
+   |
+LL |         continue;
+   |         ^^^^^^^^
 
 error: unused variable: `x`
   --> $DIR/liveness-unused.rs:8:7
diff --git a/src/test/ui/loops/loop-proper-liveness.rs b/src/test/ui/loops/loop-proper-liveness.rs
index b8f76fbe57ba3..b242ec4296d66 100644
--- a/src/test/ui/loops/loop-proper-liveness.rs
+++ b/src/test/ui/loops/loop-proper-liveness.rs
@@ -6,7 +6,7 @@ fn test1() {
     'a: loop {
         x = loop { break 'a };
     }
-    println!("{:?}", x); //~ ERROR borrow of possibly uninitialized variable
+    println!("{:?}", x); //~ ERROR borrow of possibly-uninitialized variable
 }
 
 // test2 and test3 should not fail.
diff --git a/src/test/ui/loops/loop-proper-liveness.stderr b/src/test/ui/loops/loop-proper-liveness.stderr
index c87720659fd78..d55f9ff31e3ee 100644
--- a/src/test/ui/loops/loop-proper-liveness.stderr
+++ b/src/test/ui/loops/loop-proper-liveness.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `x`
+error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/loop-proper-liveness.rs:9:22
    |
 LL |     println!("{:?}", x);
-   |                      ^ use of possibly uninitialized `x`
+   |                      ^ use of possibly-uninitialized `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/macros/macro-backtrace-invalid-internals.stderr b/src/test/ui/macros/macro-backtrace-invalid-internals.stderr
index 015e05ed9bf61..96054de801c1f 100644
--- a/src/test/ui/macros/macro-backtrace-invalid-internals.stderr
+++ b/src/test/ui/macros/macro-backtrace-invalid-internals.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `fake` found for type `{integer}` in the current s
   --> $DIR/macro-backtrace-invalid-internals.rs:5:13
    |
 LL |           1.fake()
-   |             ^^^^
+   |             ^^^^ method not found in `{integer}`
 ...
 LL |     fake_method_stmt!();
    |     -------------------- in this macro invocation
@@ -42,7 +42,7 @@ error[E0599]: no method named `fake` found for type `{integer}` in the current s
   --> $DIR/macro-backtrace-invalid-internals.rs:23:13
    |
 LL |           1.fake()
-   |             ^^^^
+   |             ^^^^ method not found in `{integer}`
 ...
 LL |     let _ = fake_method_expr!();
    |             ------------------- in this macro invocation
diff --git a/src/test/ui/macros/macro-expansion-tests.stderr b/src/test/ui/macros/macro-expansion-tests.stderr
index 4ad9ade95a052..8b3f7ca88171c 100644
--- a/src/test/ui/macros/macro-expansion-tests.stderr
+++ b/src/test/ui/macros/macro-expansion-tests.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `m!` in this scope
+error: cannot find macro `m` in this scope
   --> $DIR/macro-expansion-tests.rs:7:21
    |
 LL |     fn g() -> i32 { m!() }
@@ -6,7 +6,7 @@ LL |     fn g() -> i32 { m!() }
    |
    = help: have you added the `#[macro_use]` on the module/import?
 
-error: cannot find macro `m!` in this scope
+error: cannot find macro `m` in this scope
   --> $DIR/macro-expansion-tests.rs:15:21
    |
 LL |     fn g() -> i32 { m!() }
diff --git a/src/test/ui/macros/macro-name-typo.stderr b/src/test/ui/macros/macro-name-typo.stderr
index 967f4f3c4ac4a..ce2e1985b38ce 100644
--- a/src/test/ui/macros/macro-name-typo.stderr
+++ b/src/test/ui/macros/macro-name-typo.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `printlx!` in this scope
+error: cannot find macro `printlx` in this scope
   --> $DIR/macro-name-typo.rs:2:5
    |
 LL |     printlx!("oh noes!");
diff --git a/src/test/ui/macros/macro-path-prelude-fail-3.rs b/src/test/ui/macros/macro-path-prelude-fail-3.rs
index 597053d625134..68eb350a95614 100644
--- a/src/test/ui/macros/macro-path-prelude-fail-3.rs
+++ b/src/test/ui/macros/macro-path-prelude-fail-3.rs
@@ -1,3 +1,3 @@
 fn main() {
-    inline!(); //~ ERROR cannot find macro `inline!` in this scope
+    inline!(); //~ ERROR cannot find macro `inline` in this scope
 }
diff --git a/src/test/ui/macros/macro-path-prelude-fail-3.stderr b/src/test/ui/macros/macro-path-prelude-fail-3.stderr
index 96b8a24cff293..ec00760de6c6f 100644
--- a/src/test/ui/macros/macro-path-prelude-fail-3.stderr
+++ b/src/test/ui/macros/macro-path-prelude-fail-3.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `inline!` in this scope
+error: cannot find macro `inline` in this scope
   --> $DIR/macro-path-prelude-fail-3.rs:2:5
    |
 LL |     inline!();
diff --git a/src/test/ui/macros/macro-reexport-removed.rs b/src/test/ui/macros/macro-reexport-removed.rs
index b69a1fa4df08a..874c94d08e06a 100644
--- a/src/test/ui/macros/macro-reexport-removed.rs
+++ b/src/test/ui/macros/macro-reexport-removed.rs
@@ -2,7 +2,7 @@
 
 #![feature(macro_reexport)] //~ ERROR feature has been removed
 
-#[macro_reexport(macro_one)] //~ ERROR cannot find attribute macro `macro_reexport` in this scope
+#[macro_reexport(macro_one)] //~ ERROR cannot find attribute `macro_reexport` in this scope
 extern crate two_macros;
 
 fn main() {}
diff --git a/src/test/ui/macros/macro-reexport-removed.stderr b/src/test/ui/macros/macro-reexport-removed.stderr
index 25778fba68f7c..4bec70850aff7 100644
--- a/src/test/ui/macros/macro-reexport-removed.stderr
+++ b/src/test/ui/macros/macro-reexport-removed.stderr
@@ -10,7 +10,7 @@ note: subsumed by `pub use`
 LL | #![feature(macro_reexport)]
    |            ^^^^^^^^^^^^^^
 
-error: cannot find attribute macro `macro_reexport` in this scope
+error: cannot find attribute `macro_reexport` in this scope
   --> $DIR/macro-reexport-removed.rs:5:3
    |
 LL | #[macro_reexport(macro_one)]
diff --git a/src/test/ui/macros/macro-use-wrong-name.stderr b/src/test/ui/macros/macro-use-wrong-name.stderr
index 28f727d6a5808..8b4e90a5798f1 100644
--- a/src/test/ui/macros/macro-use-wrong-name.stderr
+++ b/src/test/ui/macros/macro-use-wrong-name.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `macro_two!` in this scope
+error: cannot find macro `macro_two` in this scope
   --> $DIR/macro-use-wrong-name.rs:7:5
    |
 LL |     macro_two!();
diff --git a/src/test/ui/macros/macro_undefined.stderr b/src/test/ui/macros/macro_undefined.stderr
index 9239b2a51e62b..01c8ebea62a2c 100644
--- a/src/test/ui/macros/macro_undefined.stderr
+++ b/src/test/ui/macros/macro_undefined.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `k!` in this scope
+error: cannot find macro `k` in this scope
   --> $DIR/macro_undefined.rs:11:5
    |
 LL |     k!();
diff --git a/src/test/ui/main-wrong-location.rs b/src/test/ui/main-wrong-location.rs
index d7ed5128195e9..f75d08813cdcd 100644
--- a/src/test/ui/main-wrong-location.rs
+++ b/src/test/ui/main-wrong-location.rs
@@ -1,4 +1,5 @@
 mod m {
+//~^ ERROR `main` function not found
     // An inferred main entry point (that doesn't use #[main])
     // must appear at the top of the crate
     fn main() { }
diff --git a/src/test/ui/main-wrong-location.stderr b/src/test/ui/main-wrong-location.stderr
index b30931f2f2301..e301c2ff09ad7 100644
--- a/src/test/ui/main-wrong-location.stderr
+++ b/src/test/ui/main-wrong-location.stderr
@@ -1,11 +1,21 @@
 error[E0601]: `main` function not found in crate `main_wrong_location`
+  --> $DIR/main-wrong-location.rs:1:1
    |
-   = note: the main function must be defined at the crate level but you have one or more functions named 'main' that are not defined at the crate level. Either move the definition or attach the `#[main]` attribute to override this behavior.
-note: here is a function named 'main'
-  --> $DIR/main-wrong-location.rs:4:5
+LL | / mod m {
+LL | |
+LL | |     // An inferred main entry point (that doesn't use #[main])
+LL | |     // must appear at the top of the crate
+LL | |     fn main() { }
+LL | | }
+   | |_^ the main function must be defined at the crate level (in `$DIR/main-wrong-location.rs`)
+   |
+note: here is a function named `main`
+  --> $DIR/main-wrong-location.rs:5:5
    |
 LL |     fn main() { }
    |     ^^^^^^^^^^^^^
+   = note: you have one or more functions named `main` not defined at the crate level
+   = help: either move the `main` function definitions or attach the `#[main]` attribute to one of them
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/match/match-no-arms-unreachable-after.stderr b/src/test/ui/match/match-no-arms-unreachable-after.stderr
index 65dcc6ee46554..6c46b2473cce6 100644
--- a/src/test/ui/match/match-no-arms-unreachable-after.stderr
+++ b/src/test/ui/match/match-no-arms-unreachable-after.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/match-no-arms-unreachable-after.rs:7:5
+   |
+LL |     match v { }
+   |     ^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/match/match-pattern-field-mismatch.stderr b/src/test/ui/match/match-pattern-field-mismatch.stderr
index 663cd2cd24d56..c2298d6fbbf02 100644
--- a/src/test/ui/match/match-pattern-field-mismatch.stderr
+++ b/src/test/ui/match/match-pattern-field-mismatch.stderr
@@ -1,6 +1,9 @@
 error[E0023]: this pattern has 2 fields, but the corresponding tuple variant has 3 fields
   --> $DIR/match-pattern-field-mismatch.rs:10:11
    |
+LL |         Rgb(usize, usize, usize),
+   |         ------------------------ tuple variant defined here
+...
 LL |           Color::Rgb(_, _) => { }
    |           ^^^^^^^^^^^^^^^^ expected 3 fields, found 2
 
diff --git a/src/test/ui/match/match-ref-mut-stability.rs b/src/test/ui/match/match-ref-mut-stability.rs
index 49e0dfaa3eb84..52120360be71e 100644
--- a/src/test/ui/match/match-ref-mut-stability.rs
+++ b/src/test/ui/match/match-ref-mut-stability.rs
@@ -3,8 +3,6 @@
 
 // run-pass
 
-#![feature(bind_by_move_pattern_guards)]
-
 // Test that z always point to the same temporary.
 fn referent_stability() {
     let p;
diff --git a/src/test/ui/match/match-vec-mismatch.stderr b/src/test/ui/match/match-vec-mismatch.stderr
index 2f1bbb7621659..a3523bb689e6b 100644
--- a/src/test/ui/match/match-vec-mismatch.stderr
+++ b/src/test/ui/match/match-vec-mismatch.stderr
@@ -10,7 +10,7 @@ error[E0529]: expected an array or slice, found `std::string::String`
 LL |         ['f', 'o', ..] => {}
    |         ^^^^^^^^^^^^^^ pattern cannot match with input type `std::string::String`
 
-error[E0527]: pattern requires 1 elements but array has 3
+error[E0527]: pattern requires 1 element but array has 3
   --> $DIR/match-vec-mismatch.rs:20:9
    |
 LL |         [0] => {},
diff --git a/src/test/ui/match/non-exhaustive-defined-here.rs b/src/test/ui/match/non-exhaustive-defined-here.rs
new file mode 100644
index 0000000000000..6f009acbdfe18
--- /dev/null
+++ b/src/test/ui/match/non-exhaustive-defined-here.rs
@@ -0,0 +1,72 @@
+// Test the "defined here" and "not covered" diagnostic hints.
+// We also make sure that references are peeled off from the scrutinee type
+// so that the diagnostics work better with default binding modes.
+
+#[derive(Clone)]
+enum E {
+//~^ `E` defined here
+//~| `E` defined here
+//~| `E` defined here
+//~| `E` defined here
+//~| `E` defined here
+//~| `E` defined here
+    A,
+    B,
+    //~^ not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+    C
+    //~^ not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+    //~| not covered
+}
+
+fn by_val(e: E) {
+    let e1 = e.clone();
+    match e1 { //~ ERROR non-exhaustive patterns: `B` and `C` not covered
+        E::A => {}
+    }
+
+    let E::A = e; //~ ERROR refutable pattern in local binding: `B` and `C` not covered
+}
+
+fn by_ref_once(e: &E) {
+    match e { //~ ERROR non-exhaustive patterns: `&B` and `&C` not covered
+        E::A => {}
+    }
+
+    let E::A = e; //~ ERROR refutable pattern in local binding: `&B` and `&C` not covered
+}
+
+fn by_ref_thrice(e: & &mut &E) {
+    match e { //~ ERROR non-exhaustive patterns: `&&mut &B` and `&&mut &C` not covered
+        E::A => {}
+    }
+
+    let E::A = e;
+    //~^ ERROR refutable pattern in local binding: `&&mut &B` and `&&mut &C` not covered
+}
+
+enum Opt {
+//~^ `Opt` defined here
+//~| `Opt` defined here
+    Some(u8),
+    None,
+    //~^ not covered
+}
+
+fn ref_pat(e: Opt) {
+    match e {//~ ERROR non-exhaustive patterns: `None` not covered
+        Opt::Some(ref _x) => {}
+    }
+
+    let Opt::Some(ref _x) = e; //~ ERROR refutable pattern in local binding: `None` not covered
+}
+
+fn main() {}
diff --git a/src/test/ui/match/non-exhaustive-defined-here.stderr b/src/test/ui/match/non-exhaustive-defined-here.stderr
new file mode 100644
index 0000000000000..25b8bbdab2d8e
--- /dev/null
+++ b/src/test/ui/match/non-exhaustive-defined-here.stderr
@@ -0,0 +1,170 @@
+error[E0004]: non-exhaustive patterns: `B` and `C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:32:11
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       match e1 {
+   |             ^^ patterns `B` and `C` not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+
+error[E0005]: refutable pattern in local binding: `B` and `C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:36:9
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       let E::A = e;
+   |           ^^^^ patterns `B` and `C` not covered
+
+error[E0004]: non-exhaustive patterns: `&B` and `&C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:40:11
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       match e {
+   |             ^ patterns `&B` and `&C` not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+
+error[E0005]: refutable pattern in local binding: `&B` and `&C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:44:9
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       let E::A = e;
+   |           ^^^^ patterns `&B` and `&C` not covered
+
+error[E0004]: non-exhaustive patterns: `&&mut &B` and `&&mut &C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:48:11
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       match e {
+   |             ^ patterns `&&mut &B` and `&&mut &C` not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+
+error[E0005]: refutable pattern in local binding: `&&mut &B` and `&&mut &C` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:52:9
+   |
+LL | / enum E {
+LL | |
+LL | |
+LL | |
+...  |
+LL | |     B,
+   | |     - not covered
+...  |
+LL | |     C
+   | |     - not covered
+...  |
+LL | |
+LL | | }
+   | |_- `E` defined here
+...
+LL |       let E::A = e;
+   |           ^^^^ patterns `&&mut &B` and `&&mut &C` not covered
+
+error[E0004]: non-exhaustive patterns: `None` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:65:11
+   |
+LL | / enum Opt {
+LL | |
+LL | |
+LL | |     Some(u8),
+LL | |     None,
+   | |     ---- not covered
+LL | |
+LL | | }
+   | |_- `Opt` defined here
+...
+LL |       match e {
+   |             ^ pattern `None` not covered
+   |
+   = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
+
+error[E0005]: refutable pattern in local binding: `None` not covered
+  --> $DIR/non-exhaustive-defined-here.rs:69:9
+   |
+LL | / enum Opt {
+LL | |
+LL | |
+LL | |     Some(u8),
+LL | |     None,
+   | |     ---- not covered
+LL | |
+LL | | }
+   | |_- `Opt` defined here
+...
+LL |       let Opt::Some(ref _x) = e;
+   |           ^^^^^^^^^^^^^^^^^ pattern `None` not covered
+
+error: aborting due to 8 previous errors
+
+Some errors have detailed explanations: E0004, E0005.
+For more information about an error, try `rustc --explain E0004`.
diff --git a/src/test/ui/methods/method-call-err-msg.stderr b/src/test/ui/methods/method-call-err-msg.stderr
index b8ae4c34dc155..94c27b7d17865 100644
--- a/src/test/ui/methods/method-call-err-msg.stderr
+++ b/src/test/ui/methods/method-call-err-msg.stderr
@@ -32,7 +32,7 @@ LL | pub struct Foo;
    | --------------- method `take` not found for this
 ...
 LL |      .take()
-   |       ^^^^
+   |       ^^^^ method not found in `Foo`
    |
    = note: the method `take` exists but the following trait bounds were not satisfied:
            `&mut Foo : std::iter::Iterator`
diff --git a/src/test/ui/mismatched_types/E0631.stderr b/src/test/ui/mismatched_types/E0631.stderr
index 319eb86480af5..64ddf1deb0639 100644
--- a/src/test/ui/mismatched_types/E0631.stderr
+++ b/src/test/ui/mismatched_types/E0631.stderr
@@ -21,7 +21,7 @@ LL |     bar(|_: isize| {});
    |     expected signature of `fn(usize) -> _`
 
 error[E0631]: type mismatch in function arguments
-  --> $DIR/E0631.rs:9:5
+  --> $DIR/E0631.rs:9:9
    |
 LL | fn foo<F: Fn(usize)>(_: F) {}
    | -------------------------- required by `foo`
@@ -30,10 +30,10 @@ LL |     fn f(_: u64) {}
    |     ------------ found signature of `fn(u64) -> _`
 ...
 LL |     foo(f);
-   |     ^^^ expected signature of `fn(usize) -> _`
+   |         ^ expected signature of `fn(usize) -> _`
 
 error[E0631]: type mismatch in function arguments
-  --> $DIR/E0631.rs:10:5
+  --> $DIR/E0631.rs:10:9
    |
 LL | fn bar<F: Fn<usize>>(_: F) {}
    | -------------------------- required by `bar`
@@ -42,7 +42,7 @@ LL |     fn f(_: u64) {}
    |     ------------ found signature of `fn(u64) -> _`
 ...
 LL |     bar(f);
-   |     ^^^ expected signature of `fn(usize) -> _`
+   |         ^ expected signature of `fn(usize) -> _`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/mismatched_types/closure-arg-count.stderr b/src/test/ui/mismatched_types/closure-arg-count.stderr
index b7b5b50b0b4e4..12ae8acaee5cf 100644
--- a/src/test/ui/mismatched_types/closure-arg-count.stderr
+++ b/src/test/ui/mismatched_types/closure-arg-count.stderr
@@ -105,42 +105,42 @@ LL |     let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x, y| i);
    |                                                     expected closure that takes a single 2-tuple as argument
 
 error[E0593]: function is expected to take a single 2-tuple as argument, but it takes 0 arguments
-  --> $DIR/closure-arg-count.rs:24:53
+  --> $DIR/closure-arg-count.rs:24:57
    |
 LL |     let _it = vec![1, 2, 3].into_iter().enumerate().map(foo);
-   |                                                     ^^^ expected function that takes a single 2-tuple as argument
+   |                                                         ^^^ expected function that takes a single 2-tuple as argument
 ...
 LL | fn foo() {}
    | -------- takes 0 arguments
 
 error[E0593]: closure is expected to take a single 2-tuple as argument, but it takes 3 distinct arguments
-  --> $DIR/closure-arg-count.rs:27:53
+  --> $DIR/closure-arg-count.rs:27:57
    |
 LL |     let bar = |i, x, y| i;
    |               --------- takes 3 distinct arguments
 LL |     let _it = vec![1, 2, 3].into_iter().enumerate().map(bar);
-   |                                                     ^^^ expected closure that takes a single 2-tuple as argument
+   |                                                         ^^^ expected closure that takes a single 2-tuple as argument
 
 error[E0593]: function is expected to take a single 2-tuple as argument, but it takes 2 distinct arguments
-  --> $DIR/closure-arg-count.rs:29:53
+  --> $DIR/closure-arg-count.rs:29:57
    |
 LL |     let _it = vec![1, 2, 3].into_iter().enumerate().map(qux);
-   |                                                     ^^^ expected function that takes a single 2-tuple as argument
+   |                                                         ^^^ expected function that takes a single 2-tuple as argument
 ...
 LL | fn qux(x: usize, y: usize) {}
    | -------------------------- takes 2 distinct arguments
 
 error[E0593]: function is expected to take 1 argument, but it takes 2 arguments
-  --> $DIR/closure-arg-count.rs:32:41
+  --> $DIR/closure-arg-count.rs:32:45
    |
 LL |     let _it = vec![1, 2, 3].into_iter().map(usize::checked_add);
-   |                                         ^^^ expected function that takes 1 argument
+   |                                             ^^^^^^^^^^^^^^^^^^ expected function that takes 1 argument
 
 error[E0593]: function is expected to take 0 arguments, but it takes 1 argument
-  --> $DIR/closure-arg-count.rs:35:5
+  --> $DIR/closure-arg-count.rs:35:10
    |
 LL |     call(Foo);
-   |     ^^^^ expected function that takes 0 arguments
+   |          ^^^ expected function that takes 0 arguments
 ...
 LL | fn call<F, R>(_: F) where F: FnOnce() -> R {}
    | ------------------------------------------ required by `call`
diff --git a/src/test/ui/mismatched_types/closure-arg-type-mismatch.stderr b/src/test/ui/mismatched_types/closure-arg-type-mismatch.stderr
index 2a65759dd17f8..68bc17b4966f1 100644
--- a/src/test/ui/mismatched_types/closure-arg-type-mismatch.stderr
+++ b/src/test/ui/mismatched_types/closure-arg-type-mismatch.stderr
@@ -23,16 +23,16 @@ LL |     a.iter().map(|_: (u16, u16)| 45);
    |              expected signature of `fn(&(u32, u32)) -> _`
 
 error[E0631]: type mismatch in function arguments
-  --> $DIR/closure-arg-type-mismatch.rs:10:5
+  --> $DIR/closure-arg-type-mismatch.rs:10:9
    |
 LL | fn baz<F: Fn(*mut &u32)>(_: F) {}
    | ------------------------------ required by `baz`
 LL | fn _test<'a>(f: fn(*mut &'a u32)) {
 LL |     baz(f);
-   |     ^^^
-   |     |
-   |     expected signature of `for<'r> fn(*mut &'r u32) -> _`
-   |     found signature of `fn(*mut &'a u32) -> _`
+   |         ^
+   |         |
+   |         expected signature of `for<'r> fn(*mut &'r u32) -> _`
+   |         found signature of `fn(*mut &'a u32) -> _`
 
 error[E0271]: type mismatch resolving `for<'r> <fn(*mut &'a u32) as std::ops::FnOnce<(*mut &'r u32,)>>::Output == ()`
   --> $DIR/closure-arg-type-mismatch.rs:10:5
diff --git a/src/test/ui/mismatched_types/fn-variance-1.stderr b/src/test/ui/mismatched_types/fn-variance-1.stderr
index d4db7bda06e7e..6342ee770ddaf 100644
--- a/src/test/ui/mismatched_types/fn-variance-1.stderr
+++ b/src/test/ui/mismatched_types/fn-variance-1.stderr
@@ -1,5 +1,5 @@
 error[E0631]: type mismatch in function arguments
-  --> $DIR/fn-variance-1.rs:11:5
+  --> $DIR/fn-variance-1.rs:11:15
    |
 LL | fn takes_mut(x: &mut isize) { }
    | --------------------------- found signature of `for<'r> fn(&'r mut isize) -> _`
@@ -8,10 +8,10 @@ LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) {
    | --------------------------------------------- required by `apply`
 ...
 LL |     apply(&3, takes_mut);
-   |     ^^^^^ expected signature of `fn(&{integer}) -> _`
+   |               ^^^^^^^^^ expected signature of `fn(&{integer}) -> _`
 
 error[E0631]: type mismatch in function arguments
-  --> $DIR/fn-variance-1.rs:15:5
+  --> $DIR/fn-variance-1.rs:15:19
    |
 LL | fn takes_imm(x: &isize) { }
    | ----------------------- found signature of `for<'r> fn(&'r isize) -> _`
@@ -20,7 +20,7 @@ LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) {
    | --------------------------------------------- required by `apply`
 ...
 LL |     apply(&mut 3, takes_imm);
-   |     ^^^^^ expected signature of `fn(&mut {integer}) -> _`
+   |                   ^^^^^^^^^ expected signature of `fn(&mut {integer}) -> _`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/mismatched_types/issue-36053-2.stderr b/src/test/ui/mismatched_types/issue-36053-2.stderr
index 3f87ef74b8ea3..89c7b0981158a 100644
--- a/src/test/ui/mismatched_types/issue-36053-2.stderr
+++ b/src/test/ui/mismatched_types/issue-36053-2.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `count` found for type `std::iter::Filter<std::ite
   --> $DIR/issue-36053-2.rs:7:55
    |
 LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
-   |                                                       ^^^^^
+   |                                                       ^^^^^ method not found in `std::iter::Filter<std::iter::Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:53]>`
    |
    = note: the method `count` exists but the following trait bounds were not satisfied:
            `&mut std::iter::Filter<std::iter::Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:53]> : std::iter::Iterator`
diff --git a/src/test/ui/mismatched_types/method-help-unsatisfied-bound.stderr b/src/test/ui/mismatched_types/method-help-unsatisfied-bound.stderr
index 9721dc8ba4e6c..865092e4e9ccc 100644
--- a/src/test/ui/mismatched_types/method-help-unsatisfied-bound.stderr
+++ b/src/test/ui/mismatched_types/method-help-unsatisfied-bound.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `unwrap` found for type `std::result::Result<(), F
   --> $DIR/method-help-unsatisfied-bound.rs:5:7
    |
 LL |     a.unwrap();
-   |       ^^^^^^
+   |       ^^^^^^ method not found in `std::result::Result<(), Foo>`
    |
    = note: the method `unwrap` exists but the following trait bounds were not satisfied:
            `Foo : std::fmt::Debug`
diff --git a/src/test/ui/mismatched_types/unboxed-closures-vtable-mismatch.stderr b/src/test/ui/mismatched_types/unboxed-closures-vtable-mismatch.stderr
index 53c9fcd70a23d..139d87d58b640 100644
--- a/src/test/ui/mismatched_types/unboxed-closures-vtable-mismatch.stderr
+++ b/src/test/ui/mismatched_types/unboxed-closures-vtable-mismatch.stderr
@@ -1,5 +1,5 @@
 error[E0631]: type mismatch in closure arguments
-  --> $DIR/unboxed-closures-vtable-mismatch.rs:15:13
+  --> $DIR/unboxed-closures-vtable-mismatch.rs:15:24
    |
 LL | fn call_it<F:FnMut(isize,isize)->isize>(y: isize, mut f: F) -> isize {
    | -------------------------------------------------------------------- required by `call_it`
@@ -8,7 +8,7 @@ LL |     let f = to_fn_mut(|x: usize, y: isize| -> isize { (x as isize) + y });
    |                       ----------------------------- found signature of `fn(usize, isize) -> _`
 LL |
 LL |     let z = call_it(3, f);
-   |             ^^^^^^^ expected signature of `fn(isize, isize) -> _`
+   |                        ^ expected signature of `fn(isize, isize) -> _`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/missing/missing-macro-use.rs b/src/test/ui/missing/missing-macro-use.rs
index dff4c94fcf413..d494c4471a31c 100644
--- a/src/test/ui/missing/missing-macro-use.rs
+++ b/src/test/ui/missing/missing-macro-use.rs
@@ -4,5 +4,5 @@ extern crate two_macros;
 
 pub fn main() {
     macro_two!();
-    //~^ ERROR cannot find macro `macro_two!` in this scope
+    //~^ ERROR cannot find macro `macro_two` in this scope
 }
diff --git a/src/test/ui/missing/missing-macro-use.stderr b/src/test/ui/missing/missing-macro-use.stderr
index 01a7beb3b0502..711e249d2bca1 100644
--- a/src/test/ui/missing/missing-macro-use.stderr
+++ b/src/test/ui/missing/missing-macro-use.stderr
@@ -1,4 +1,4 @@
-error: cannot find macro `macro_two!` in this scope
+error: cannot find macro `macro_two` in this scope
   --> $DIR/missing-macro-use.rs:6:5
    |
 LL |     macro_two!();
diff --git a/src/test/ui/missing/missing-main.stderr b/src/test/ui/missing/missing-main.stderr
index 34b03ada3d295..6a35f5117efd6 100644
--- a/src/test/ui/missing/missing-main.stderr
+++ b/src/test/ui/missing/missing-main.stderr
@@ -1,6 +1,8 @@
 error[E0601]: `main` function not found in crate `missing_main`
+  --> $DIR/missing-main.rs:2:1
    |
-   = note: consider adding a `main` function to `$DIR/missing-main.rs`
+LL | fn mian() { }
+   | ^^^^^^^^^^^^^ consider adding a `main` function to `$DIR/missing-main.rs`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/missing/missing-semicolon-warning.stderr b/src/test/ui/missing/missing-semicolon-warning.stderr
index b3f3ebc855daa..b4001aba2882c 100644
--- a/src/test/ui/missing/missing-semicolon-warning.stderr
+++ b/src/test/ui/missing/missing-semicolon-warning.stderr
@@ -7,7 +7,7 @@ LL |         $( let x = $e1 )*;
 LL | fn main() { m!(0, 0; 0, 0); }
    |             --------------- in this macro invocation
    |
-   = note: This was erroneously allowed and will become a hard error in a future release
+   = note: this was erroneously allowed and will become a hard error in a future release
 
 warning: expected `;`, found `println`
   --> $DIR/missing-semicolon-warning.rs:7:12
@@ -18,5 +18,5 @@ LL |         $( println!("{}", $e2) )*;
 LL | fn main() { m!(0, 0; 0, 0); }
    |             --------------- in this macro invocation
    |
-   = note: This was erroneously allowed and will become a hard error in a future release
+   = note: this was erroneously allowed and will become a hard error in a future release
 
diff --git a/src/test/ui/moves/move-into-dead-array-1.rs b/src/test/ui/moves/move-into-dead-array-1.rs
index 16a18da4a44a3..2d0ff58526393 100644
--- a/src/test/ui/moves/move-into-dead-array-1.rs
+++ b/src/test/ui/moves/move-into-dead-array-1.rs
@@ -11,5 +11,5 @@ fn main() {
 
 fn foo(i: usize) {
     let mut a: [D; 4];
-    a[i] = d();        //~ ERROR use of possibly uninitialized variable: `a`
+    a[i] = d();        //~ ERROR use of possibly-uninitialized variable: `a`
 }
diff --git a/src/test/ui/moves/move-into-dead-array-1.stderr b/src/test/ui/moves/move-into-dead-array-1.stderr
index 33da0e54a1e4c..5f20ccfeddf48 100644
--- a/src/test/ui/moves/move-into-dead-array-1.stderr
+++ b/src/test/ui/moves/move-into-dead-array-1.stderr
@@ -1,8 +1,8 @@
-error[E0381]: use of possibly uninitialized variable: `a`
+error[E0381]: use of possibly-uninitialized variable: `a`
   --> $DIR/move-into-dead-array-1.rs:14:5
    |
 LL |     a[i] = d();
-   |     ^^^^ use of possibly uninitialized `a`
+   |     ^^^^ use of possibly-uninitialized `a`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/mutexguard-sync.stderr b/src/test/ui/mutexguard-sync.stderr
index 4a93c9f09b788..1cda2da5061a5 100644
--- a/src/test/ui/mutexguard-sync.stderr
+++ b/src/test/ui/mutexguard-sync.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `std::cell::Cell<i32>` cannot be shared between threads safely
-  --> $DIR/mutexguard-sync.rs:11:5
+  --> $DIR/mutexguard-sync.rs:11:15
    |
 LL | fn test_sync<T: Sync>(_t: T) {}
    | ---------------------------- required by `test_sync`
 ...
 LL |     test_sync(guard);
-   |     ^^^^^^^^^ `std::cell::Cell<i32>` cannot be shared between threads safely
+   |               ^^^^^ `std::cell::Cell<i32>` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `std::cell::Cell<i32>`
    = note: required because of the requirements on the impl of `std::marker::Sync` for `std::sync::MutexGuard<'_, std::cell::Cell<i32>>`
diff --git a/src/test/ui/namespace/namespace-mix.stderr b/src/test/ui/namespace/namespace-mix.stderr
index 39aaddb390caa..249ad1c584421 100644
--- a/src/test/ui/namespace/namespace-mix.stderr
+++ b/src/test/ui/namespace/namespace-mix.stderr
@@ -67,400 +67,400 @@ LL | use namespace_mix::xm8::V;
    |
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:33:5
+  --> $DIR/namespace-mix.rs:33:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m1::S{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `c::S: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:35:5
+  --> $DIR/namespace-mix.rs:35:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m2::S{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::S`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `c::S`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:36:5
+  --> $DIR/namespace-mix.rs:36:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m2::S);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:39:5
+  --> $DIR/namespace-mix.rs:39:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm1::S{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::S: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:41:5
+  --> $DIR/namespace-mix.rs:41:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm2::S{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::S`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::S`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:42:5
+  --> $DIR/namespace-mix.rs:42:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm2::S);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:55:5
+  --> $DIR/namespace-mix.rs:55:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m3::TS{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `fn() -> c::TS {c::TS}: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:56:5
+  --> $DIR/namespace-mix.rs:56:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m3::TS);
-   |     ^^^^^ the trait `Impossible` is not implemented for `fn() -> c::TS {c::TS}`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `fn() -> c::TS {c::TS}`
 
 error[E0277]: the trait bound `c::TS: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:57:5
+  --> $DIR/namespace-mix.rs:57:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m4::TS{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::TS`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::TS`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:58:5
+  --> $DIR/namespace-mix.rs:58:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m4::TS);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:61:5
+  --> $DIR/namespace-mix.rs:61:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm3::TS{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `fn() -> namespace_mix::c::TS {namespace_mix::c::TS}: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:62:5
+  --> $DIR/namespace-mix.rs:62:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm3::TS);
-   |     ^^^^^ the trait `Impossible` is not implemented for `fn() -> namespace_mix::c::TS {namespace_mix::c::TS}`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `fn() -> namespace_mix::c::TS {namespace_mix::c::TS}`
 
 error[E0277]: the trait bound `namespace_mix::c::TS: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:63:5
+  --> $DIR/namespace-mix.rs:63:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm4::TS{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::TS`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::TS`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:64:5
+  --> $DIR/namespace-mix.rs:64:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm4::TS);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:77:5
+  --> $DIR/namespace-mix.rs:77:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m5::US{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `c::US: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:78:5
+  --> $DIR/namespace-mix.rs:78:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m5::US);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::US`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::US`
 
 error[E0277]: the trait bound `c::US: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:79:5
+  --> $DIR/namespace-mix.rs:79:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m6::US{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::US`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::US`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:80:5
+  --> $DIR/namespace-mix.rs:80:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m6::US);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:83:5
+  --> $DIR/namespace-mix.rs:83:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm5::US{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::US: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:84:5
+  --> $DIR/namespace-mix.rs:84:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm5::US);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::US`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::US`
 
 error[E0277]: the trait bound `namespace_mix::c::US: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:85:5
+  --> $DIR/namespace-mix.rs:85:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm6::US{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::US`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::US`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:86:5
+  --> $DIR/namespace-mix.rs:86:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm6::US);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:99:5
+  --> $DIR/namespace-mix.rs:99:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m7::V{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:101:5
+  --> $DIR/namespace-mix.rs:101:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m8::V{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::E`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `c::E`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:102:5
+  --> $DIR/namespace-mix.rs:102:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m8::V);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:105:5
+  --> $DIR/namespace-mix.rs:105:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm7::V{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:107:5
+  --> $DIR/namespace-mix.rs:107:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm8::V{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:108:5
+  --> $DIR/namespace-mix.rs:108:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm8::V);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:121:5
+  --> $DIR/namespace-mix.rs:121:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m9::TV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `fn() -> c::E {c::E::TV}: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:122:5
+  --> $DIR/namespace-mix.rs:122:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(m9::TV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `fn() -> c::E {c::E::TV}`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `fn() -> c::E {c::E::TV}`
 
 error[E0277]: the trait bound `c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:123:5
+  --> $DIR/namespace-mix.rs:123:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mA::TV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::E`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::E`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:124:5
+  --> $DIR/namespace-mix.rs:124:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mA::TV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:127:5
+  --> $DIR/namespace-mix.rs:127:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm9::TV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `fn() -> namespace_mix::c::E {namespace_mix::xm7::TV}: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:128:5
+  --> $DIR/namespace-mix.rs:128:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xm9::TV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `fn() -> namespace_mix::c::E {namespace_mix::xm7::TV}`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `fn() -> namespace_mix::c::E {namespace_mix::xm7::TV}`
 
 error[E0277]: the trait bound `namespace_mix::c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:129:5
+  --> $DIR/namespace-mix.rs:129:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmA::TV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:130:5
+  --> $DIR/namespace-mix.rs:130:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmA::TV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:143:5
+  --> $DIR/namespace-mix.rs:143:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mB::UV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:144:5
+  --> $DIR/namespace-mix.rs:144:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mB::UV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::E`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::E`
 
 error[E0277]: the trait bound `c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:145:5
+  --> $DIR/namespace-mix.rs:145:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mC::UV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::E`
+   |           ^^^^^^^^ the trait `Impossible` is not implemented for `c::E`
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:146:5
+  --> $DIR/namespace-mix.rs:146:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(mC::UV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `c::Item`
+   |           ^^^^^^ the trait `Impossible` is not implemented for `c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:149:5
+  --> $DIR/namespace-mix.rs:149:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmB::UV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error[E0277]: the trait bound `namespace_mix::c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:150:5
+  --> $DIR/namespace-mix.rs:150:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmB::UV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
 
 error[E0277]: the trait bound `namespace_mix::c::E: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:151:5
+  --> $DIR/namespace-mix.rs:151:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmC::UV{});
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
+   |           ^^^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::E`
 
 error[E0277]: the trait bound `namespace_mix::c::Item: Impossible` is not satisfied
-  --> $DIR/namespace-mix.rs:152:5
+  --> $DIR/namespace-mix.rs:152:11
    |
 LL | fn check<T: Impossible>(_: T) {}
    | ----------------------------- required by `check`
 ...
 LL |     check(xmC::UV);
-   |     ^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
+   |           ^^^^^^^ the trait `Impossible` is not implemented for `namespace_mix::c::Item`
 
 error: aborting due to 48 previous errors
 
diff --git a/src/test/ui/never-assign-dead-code.stderr b/src/test/ui/never-assign-dead-code.stderr
index 779780a90a81d..436c703e4b6b9 100644
--- a/src/test/ui/never-assign-dead-code.stderr
+++ b/src/test/ui/never-assign-dead-code.stderr
@@ -10,12 +10,24 @@ note: lint level defined here
 LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unreachable_code)]` implied by `#[warn(unused)]`
+note: any code following this expression is unreachable
+  --> $DIR/never-assign-dead-code.rs:9:16
+   |
+LL |     let x: ! = panic!("aah");
+   |                ^^^^^^^^^^^^^
+   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
-warning: unreachable expression
+warning: unreachable call
   --> $DIR/never-assign-dead-code.rs:10:5
    |
 LL |     drop(x);
-   |     ^^^^^^^
+   |     ^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/never-assign-dead-code.rs:10:10
+   |
+LL |     drop(x);
+   |          ^
 
 warning: unused variable: `x`
   --> $DIR/never-assign-dead-code.rs:9:9
diff --git a/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.rs b/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.rs
index 906ea32b9c42d..1983e13db0afd 100644
--- a/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.rs
+++ b/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.rs
@@ -26,13 +26,13 @@ impl Drop for D {
 fn cannot_partially_init_adt_with_drop() {
     let d: D;
     d.x = 10;
-    //~^ ERROR assign of possibly uninitialized variable: `d` [E0381]
+    //~^ ERROR assign of possibly-uninitialized variable: `d` [E0381]
 }
 
 fn cannot_partially_init_mutable_adt_with_drop() {
     let mut d: D;
     d.x = 10;
-    //~^ ERROR assign of possibly uninitialized variable: `d` [E0381]
+    //~^ ERROR assign of possibly-uninitialized variable: `d` [E0381]
 }
 
 fn cannot_partially_reinit_adt_with_drop() {
@@ -45,13 +45,13 @@ fn cannot_partially_reinit_adt_with_drop() {
 fn cannot_partially_init_inner_adt_via_outer_with_drop() {
     let d: D;
     d.s.y = 20;
-    //~^ ERROR assign to part of possibly uninitialized variable: `d` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `d` [E0381]
 }
 
 fn cannot_partially_init_inner_adt_via_mutable_outer_with_drop() {
     let mut d: D;
     d.s.y = 20;
-    //~^ ERROR assign to part of possibly uninitialized variable: `d` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `d` [E0381]
 }
 
 fn cannot_partially_reinit_inner_adt_via_outer_with_drop() {
diff --git a/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.stderr b/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.stderr
index 153d9bdf3215d..1b66e034d3785 100644
--- a/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.stderr
+++ b/src/test/ui/nll/issue-21232-partial-init-and-erroneous-use.stderr
@@ -1,14 +1,14 @@
-error[E0381]: assign of possibly uninitialized variable: `d`
+error[E0381]: assign of possibly-uninitialized variable: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:28:5
    |
 LL |     d.x = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `d`
+   |     ^^^^^^^^ use of possibly-uninitialized `d`
 
-error[E0381]: assign of possibly uninitialized variable: `d`
+error[E0381]: assign of possibly-uninitialized variable: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:34:5
    |
 LL |     d.x = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `d`
+   |     ^^^^^^^^ use of possibly-uninitialized `d`
 
 error[E0382]: assign of moved value: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:41:5
@@ -20,17 +20,17 @@ LL |     drop(d);
 LL |     d.x = 10;
    |     ^^^^^^^^ value assigned here after move
 
-error[E0381]: assign to part of possibly uninitialized variable: `d`
+error[E0381]: assign to part of possibly-uninitialized variable: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:47:5
    |
 LL |     d.s.y = 20;
-   |     ^^^^^^^^^^ use of possibly uninitialized `d.s`
+   |     ^^^^^^^^^^ use of possibly-uninitialized `d.s`
 
-error[E0381]: assign to part of possibly uninitialized variable: `d`
+error[E0381]: assign to part of possibly-uninitialized variable: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:53:5
    |
 LL |     d.s.y = 20;
-   |     ^^^^^^^^^^ use of possibly uninitialized `d.s`
+   |     ^^^^^^^^^^ use of possibly-uninitialized `d.s`
 
 error[E0382]: assign to part of moved value: `d`
   --> $DIR/issue-21232-partial-init-and-erroneous-use.rs:60:5
diff --git a/src/test/ui/nll/issue-21232-partial-init-and-use.rs b/src/test/ui/nll/issue-21232-partial-init-and-use.rs
index 633cbdba2d40e..7da47c85f5450 100644
--- a/src/test/ui/nll/issue-21232-partial-init-and-use.rs
+++ b/src/test/ui/nll/issue-21232-partial-init-and-use.rs
@@ -97,14 +97,14 @@ macro_rules! use_part {
 fn test_0000_local_fully_init_and_use_struct() {
     let s: S<B>;
     s.x = 10; s.y = Box::new(20);
-    //~^ ERROR assign to part of possibly uninitialized variable: `s` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `s` [E0381]
     use_fully!(struct s);
 }
 
 fn test_0001_local_fully_init_and_use_tuple() {
     let t: T;
     t.0 = 10; t.1 = Box::new(20);
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     use_fully!(tuple t);
 }
 
@@ -125,14 +125,14 @@ fn test_0011_local_fully_reinit_and_use_tuple() {
 fn test_0100_local_partial_init_and_use_struct() {
     let s: S<B>;
     s.x = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `s` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `s` [E0381]
     use_part!(struct s);
 }
 
 fn test_0101_local_partial_init_and_use_tuple() {
     let t: T;
     t.0 = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     use_part!(tuple t);
 }
 
@@ -153,14 +153,14 @@ fn test_0111_local_partial_reinit_and_use_tuple() {
 fn test_0200_local_void_init_and_use_struct() {
     let s: S<Void>;
     s.x = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `s` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `s` [E0381]
     use_part!(struct s);
 }
 
 fn test_0201_local_void_init_and_use_tuple() {
     let t: Tvoid;
     t.0 = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `t` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `t` [E0381]
     use_part!(tuple t);
 }
 
@@ -176,14 +176,14 @@ fn test_0201_local_void_init_and_use_tuple() {
 fn test_1000_field_fully_init_and_use_struct() {
     let q: Q<S<B>>;
     q.r.f.x = 10; q.r.f.y = Box::new(20);
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_fully!(struct q.r.f);
 }
 
 fn test_1001_field_fully_init_and_use_tuple() {
     let q: Q<T>;
     q.r.f.0 = 10; q.r.f.1 = Box::new(20);
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_fully!(tuple q.r.f);
 }
 
@@ -204,14 +204,14 @@ fn test_1011_field_fully_reinit_and_use_tuple() {
 fn test_1100_field_partial_init_and_use_struct() {
     let q: Q<S<B>>;
     q.r.f.x = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_part!(struct q.r.f);
 }
 
 fn test_1101_field_partial_init_and_use_tuple() {
     let q: Q<T>;
     q.r.f.0 = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_part!(tuple q.r.f);
 }
 
@@ -232,14 +232,14 @@ fn test_1111_field_partial_reinit_and_use_tuple() {
 fn test_1200_field_void_init_and_use_struct() {
     let mut q: Q<S<Void>>;
     q.r.f.x = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_part!(struct q.r.f);
 }
 
 fn test_1201_field_void_init_and_use_tuple() {
     let mut q: Q<Tvoid>;
     q.r.f.0 = 10;
-    //~^ ERROR assign to part of possibly uninitialized variable: `q` [E0381]
+    //~^ ERROR assign to part of possibly-uninitialized variable: `q` [E0381]
     use_part!(tuple q.r.f);
 }
 
diff --git a/src/test/ui/nll/issue-21232-partial-init-and-use.stderr b/src/test/ui/nll/issue-21232-partial-init-and-use.stderr
index 1cdf728a5e604..32147898320c0 100644
--- a/src/test/ui/nll/issue-21232-partial-init-and-use.stderr
+++ b/src/test/ui/nll/issue-21232-partial-init-and-use.stderr
@@ -1,14 +1,14 @@
-error[E0381]: assign to part of possibly uninitialized variable: `s`
+error[E0381]: assign to part of possibly-uninitialized variable: `s`
   --> $DIR/issue-21232-partial-init-and-use.rs:99:5
    |
 LL |     s.x = 10; s.y = Box::new(20);
-   |     ^^^^^^^^ use of possibly uninitialized `s`
+   |     ^^^^^^^^ use of possibly-uninitialized `s`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/issue-21232-partial-init-and-use.rs:106:5
    |
 LL |     t.0 = 10; t.1 = Box::new(20);
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
 error[E0382]: assign to part of moved value: `s`
   --> $DIR/issue-21232-partial-init-and-use.rs:113:5
@@ -30,17 +30,17 @@ LL |     let mut t: T = (0, Box::new(0)); drop(t);
 LL |     t.0 = 10; t.1 = Box::new(20);
    |     ^^^^^^^^ value partially assigned here after move
 
-error[E0381]: assign to part of possibly uninitialized variable: `s`
+error[E0381]: assign to part of possibly-uninitialized variable: `s`
   --> $DIR/issue-21232-partial-init-and-use.rs:127:5
    |
 LL |     s.x = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `s`
+   |     ^^^^^^^^ use of possibly-uninitialized `s`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/issue-21232-partial-init-and-use.rs:134:5
    |
 LL |     t.0 = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
 error[E0382]: assign to part of moved value: `s`
   --> $DIR/issue-21232-partial-init-and-use.rs:141:5
@@ -62,29 +62,29 @@ LL |     let mut t: T = (0, Box::new(0)); drop(t);
 LL |     t.0 = 10;
    |     ^^^^^^^^ value partially assigned here after move
 
-error[E0381]: assign to part of possibly uninitialized variable: `s`
+error[E0381]: assign to part of possibly-uninitialized variable: `s`
   --> $DIR/issue-21232-partial-init-and-use.rs:155:5
    |
 LL |     s.x = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `s`
+   |     ^^^^^^^^ use of possibly-uninitialized `s`
 
-error[E0381]: assign to part of possibly uninitialized variable: `t`
+error[E0381]: assign to part of possibly-uninitialized variable: `t`
   --> $DIR/issue-21232-partial-init-and-use.rs:162:5
    |
 LL |     t.0 = 10;
-   |     ^^^^^^^^ use of possibly uninitialized `t`
+   |     ^^^^^^^^ use of possibly-uninitialized `t`
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:178:5
    |
 LL |     q.r.f.x = 10; q.r.f.y = Box::new(20);
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:185:5
    |
 LL |     q.r.f.0 = 10; q.r.f.1 = Box::new(20);
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
 error[E0382]: assign to part of moved value: `q.r`
   --> $DIR/issue-21232-partial-init-and-use.rs:192:5
@@ -106,17 +106,17 @@ LL |     q.r.f.0 = 10; q.r.f.1 = Box::new(20);
    |
    = note: move occurs because `q.r` has type `R<(u32, std::boxed::Box<u32>)>`, which does not implement the `Copy` trait
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:206:5
    |
 LL |     q.r.f.x = 10;
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:213:5
    |
 LL |     q.r.f.0 = 10;
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
 error[E0382]: assign to part of moved value: `q.r`
   --> $DIR/issue-21232-partial-init-and-use.rs:220:5
@@ -138,17 +138,17 @@ LL |     q.r.f.0 = 10;
    |
    = note: move occurs because `q.r` has type `R<(u32, std::boxed::Box<u32>)>`, which does not implement the `Copy` trait
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:234:5
    |
 LL |     q.r.f.x = 10;
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
-error[E0381]: assign to part of possibly uninitialized variable: `q`
+error[E0381]: assign to part of possibly-uninitialized variable: `q`
   --> $DIR/issue-21232-partial-init-and-use.rs:241:5
    |
 LL |     q.r.f.0 = 10;
-   |     ^^^^^^^^^^^^ use of possibly uninitialized `q.r.f`
+   |     ^^^^^^^^^^^^ use of possibly-uninitialized `q.r.f`
 
 error[E0382]: assign to part of moved value: `c`
   --> $DIR/issue-21232-partial-init-and-use.rs:259:13
diff --git a/src/test/ui/nll/issue-55288.rs b/src/test/ui/nll/issue-55288.rs
index c7b6ac5924837..aab2dc267d594 100644
--- a/src/test/ui/nll/issue-55288.rs
+++ b/src/test/ui/nll/issue-55288.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 struct Slice(&'static [&'static [u8]]);
 
diff --git a/src/test/ui/nll/issue-57960.rs b/src/test/ui/nll/issue-57960.rs
index 1399694a79b6a..32e45184a9195 100644
--- a/src/test/ui/nll/issue-57960.rs
+++ b/src/test/ui/nll/issue-57960.rs
@@ -30,7 +30,6 @@ fn digits(x: u8) -> u32 {
         OneDigit::FIRST..=OneDigit::LAST => 1,
         TwoDigits::FIRST..=TwoDigits::LAST => 2,
         ThreeDigits::FIRST..=ThreeDigits::LAST => 3,
-        _ => unreachable!(),
     }
 }
 
diff --git a/src/test/ui/nll/match-cfg-fake-edges.rs b/src/test/ui/nll/match-cfg-fake-edges.rs
index 94e4a763866f6..2e6d675fb641e 100644
--- a/src/test/ui/nll/match-cfg-fake-edges.rs
+++ b/src/test/ui/nll/match-cfg-fake-edges.rs
@@ -1,8 +1,6 @@
 // Test that we have enough false edges to avoid exposing the exact matching
 // algorithm in borrow checking.
 
-#![feature(bind_by_move_pattern_guards)]
-
 fn guard_always_precedes_arm(y: i32) {
     let mut x;
     // x should always be initialized, as the only way to reach the arm is
@@ -20,7 +18,7 @@ fn guard_may_be_skipped(y: i32) {
     match y {
         _ if { x = 2; true } => 1,
         _ if {
-            x; //~ ERROR use of possibly uninitialized variable: `x`
+            x; //~ ERROR use of possibly-uninitialized variable: `x`
             false
         } => 2,
         _ => 3,
diff --git a/src/test/ui/nll/match-cfg-fake-edges.stderr b/src/test/ui/nll/match-cfg-fake-edges.stderr
index b1e0fa739769a..06fe564ac69e3 100644
--- a/src/test/ui/nll/match-cfg-fake-edges.stderr
+++ b/src/test/ui/nll/match-cfg-fake-edges.stderr
@@ -1,11 +1,11 @@
-error[E0381]: use of possibly uninitialized variable: `x`
-  --> $DIR/match-cfg-fake-edges.rs:23:13
+error[E0381]: use of possibly-uninitialized variable: `x`
+  --> $DIR/match-cfg-fake-edges.rs:21:13
    |
 LL |             x;
-   |             ^ use of possibly uninitialized `x`
+   |             ^ use of possibly-uninitialized `x`
 
 error[E0382]: use of moved value: `x`
-  --> $DIR/match-cfg-fake-edges.rs:37:13
+  --> $DIR/match-cfg-fake-edges.rs:35:13
    |
 LL |     let x = String::new();
    |         - move occurs because `x` has type `std::string::String`, which does not implement the `Copy` trait
diff --git a/src/test/ui/nll/match-guards-partially-borrow.rs b/src/test/ui/nll/match-guards-partially-borrow.rs
index 601c46ff86cc7..81ae19ebf8a72 100644
--- a/src/test/ui/nll/match-guards-partially-borrow.rs
+++ b/src/test/ui/nll/match-guards-partially-borrow.rs
@@ -5,8 +5,6 @@
 // Test that we don't allow mutating the value being matched on in a way that
 // changes which patterns it matches, until we have chosen an arm.
 
-#![feature(bind_by_move_pattern_guards)]
-
 fn ok_mutation_in_guard(mut q: i32) {
     match q {
         // OK, mutation doesn't change which patterns g matches
diff --git a/src/test/ui/nll/match-guards-partially-borrow.stderr b/src/test/ui/nll/match-guards-partially-borrow.stderr
index b2951fd339da4..48e3a7c699318 100644
--- a/src/test/ui/nll/match-guards-partially-borrow.stderr
+++ b/src/test/ui/nll/match-guards-partially-borrow.stderr
@@ -1,5 +1,5 @@
 error[E0510]: cannot assign `q` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:57:13
+  --> $DIR/match-guards-partially-borrow.rs:55:13
    |
 LL |     match q {
    |           - value is immutable in match guard
@@ -8,7 +8,7 @@ LL |             q = true;
    |             ^^^^^^^^ cannot assign
 
 error[E0510]: cannot assign `r` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:69:13
+  --> $DIR/match-guards-partially-borrow.rs:67:13
    |
 LL |     match r {
    |           - value is immutable in match guard
@@ -17,7 +17,7 @@ LL |             r = true;
    |             ^^^^^^^^ cannot assign
 
 error[E0510]: cannot assign `t` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:93:13
+  --> $DIR/match-guards-partially-borrow.rs:91:13
    |
 LL |     match t {
    |           - value is immutable in match guard
@@ -26,7 +26,7 @@ LL |             t = true;
    |             ^^^^^^^^ cannot assign
 
 error[E0510]: cannot mutably borrow `x.0` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:107:22
+  --> $DIR/match-guards-partially-borrow.rs:105:22
    |
 LL |     match x {
    |           - value is immutable in match guard
@@ -35,7 +35,7 @@ LL |                 Some(ref mut r) => *r = None,
    |                      ^^^^^^^^^ cannot mutably borrow
 
 error[E0506]: cannot assign to `t` because it is borrowed
-  --> $DIR/match-guards-partially-borrow.rs:119:13
+  --> $DIR/match-guards-partially-borrow.rs:117:13
    |
 LL |         s if {
    |         - borrow of `t` occurs here
@@ -46,7 +46,7 @@ LL |         } => (), // What value should `s` have in the arm?
    |         - borrow later used here
 
 error[E0510]: cannot assign `y` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:130:13
+  --> $DIR/match-guards-partially-borrow.rs:128:13
    |
 LL |     match *y {
    |           -- value is immutable in match guard
@@ -55,7 +55,7 @@ LL |             y = &true;
    |             ^^^^^^^^^ cannot assign
 
 error[E0510]: cannot assign `z` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:141:13
+  --> $DIR/match-guards-partially-borrow.rs:139:13
    |
 LL |     match z {
    |           - value is immutable in match guard
@@ -64,7 +64,7 @@ LL |             z = &true;
    |             ^^^^^^^^^ cannot assign
 
 error[E0510]: cannot assign `a` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:153:13
+  --> $DIR/match-guards-partially-borrow.rs:151:13
    |
 LL |     match a {
    |           - value is immutable in match guard
@@ -73,7 +73,7 @@ LL |             a = &true;
    |             ^^^^^^^^^ cannot assign
 
 error[E0510]: cannot assign `b` in match guard
-  --> $DIR/match-guards-partially-borrow.rs:164:13
+  --> $DIR/match-guards-partially-borrow.rs:162:13
    |
 LL |     match b {
    |           - value is immutable in match guard
diff --git a/src/test/ui/nll/match-on-borrowed.stderr b/src/test/ui/nll/match-on-borrowed.stderr
index 9f804dfb3d7be..284a910a01b8a 100644
--- a/src/test/ui/nll/match-on-borrowed.stderr
+++ b/src/test/ui/nll/match-on-borrowed.stderr
@@ -34,11 +34,11 @@ LL |         true => (),
 LL |     x;
    |     - borrow later used here
 
-error[E0381]: use of possibly uninitialized variable: `n`
+error[E0381]: use of possibly-uninitialized variable: `n`
   --> $DIR/match-on-borrowed.rs:92:11
    |
 LL |     match n {}
-   |           ^ use of possibly uninitialized `n`
+   |           ^ use of possibly-uninitialized `n`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/nll/normalization-bounds.rs b/src/test/ui/nll/normalization-bounds.rs
index 5d2825ef2d670..bb6d981e0133f 100644
--- a/src/test/ui/nll/normalization-bounds.rs
+++ b/src/test/ui/nll/normalization-bounds.rs
@@ -1,6 +1,6 @@
 // Check that lifetime bounds get checked the right way around with NLL enabled.
 
-//run-pass
+// check-pass
 
 trait Visitor<'d> {
     type Value;
diff --git a/src/test/ui/nll/promotable-mutable-zst-doesnt-conflict.rs b/src/test/ui/nll/promotable-mutable-zst-doesnt-conflict.rs
index 6d5bdfa4da2f0..3b06b0db37065 100644
--- a/src/test/ui/nll/promotable-mutable-zst-doesnt-conflict.rs
+++ b/src/test/ui/nll/promotable-mutable-zst-doesnt-conflict.rs
@@ -1,11 +1,11 @@
 // Check that mutable promoted length zero arrays don't check for conflicting
 // access
 
-// run-pass
+// check-pass
 
 pub fn main() {
     let mut x: Vec<&[i32; 0]> = Vec::new();
-    for i in 0..10 {
+    for _ in 0..10 {
         x.push(&[]);
     }
 }
diff --git a/src/test/ui/nll/user-annotations/issue-55219.rs b/src/test/ui/nll/user-annotations/issue-55219.rs
index 4d18e96cc1543..147413663897d 100644
--- a/src/test/ui/nll/user-annotations/issue-55219.rs
+++ b/src/test/ui/nll/user-annotations/issue-55219.rs
@@ -3,7 +3,7 @@
 // The `Self::HASH_LEN` here expands to a "self-type" where `T` is not
 // known. This unbound inference variable was causing an ICE.
 //
-// run-pass
+// check-pass
 
 pub struct Foo<T>(T);
 
diff --git a/src/test/ui/nll/user-annotations/normalize-self-ty.rs b/src/test/ui/nll/user-annotations/normalize-self-ty.rs
index a06229a02032a..df905c8786a18 100644
--- a/src/test/ui/nll/user-annotations/normalize-self-ty.rs
+++ b/src/test/ui/nll/user-annotations/normalize-self-ty.rs
@@ -2,7 +2,7 @@
 // the inherent impl requires normalization to be equal to the
 // user-provided type.
 //
-// run-pass
+// check-pass
 
 trait Mirror {
     type Me;
@@ -15,7 +15,7 @@ impl<T> Mirror for T {
 struct Foo<A, B>(A, B);
 
 impl<A> Foo<A, <A as Mirror>::Me> {
-    fn m(b: A) { }
+    fn m(_: A) { }
 }
 
 fn main() {
diff --git a/src/test/ui/no_send-rc.stderr b/src/test/ui/no_send-rc.stderr
index eaf3103060eff..de08634e16ac4 100644
--- a/src/test/ui/no_send-rc.stderr
+++ b/src/test/ui/no_send-rc.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `std::rc::Rc<{integer}>` cannot be sent between threads safely
-  --> $DIR/no_send-rc.rs:7:5
+  --> $DIR/no_send-rc.rs:7:9
    |
 LL | fn bar<T: Send>(_: T) {}
    | --------------------- required by `bar`
 ...
 LL |     bar(x);
-   |     ^^^ `std::rc::Rc<{integer}>` cannot be sent between threads safely
+   |         ^ `std::rc::Rc<{integer}>` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `std::rc::Rc<{integer}>`
 
diff --git a/src/test/ui/no_send-struct.stderr b/src/test/ui/no_send-struct.stderr
index 1808cef45f184..3865971fcfdd1 100644
--- a/src/test/ui/no_send-struct.stderr
+++ b/src/test/ui/no_send-struct.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `Foo` cannot be sent between threads safely
-  --> $DIR/no_send-struct.rs:15:5
+  --> $DIR/no_send-struct.rs:15:9
    |
 LL | fn bar<T: Send>(_: T) {}
    | --------------------- required by `bar`
 ...
 LL |     bar(x);
-   |     ^^^ `Foo` cannot be sent between threads safely
+   |         ^ `Foo` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `Foo`
 
diff --git a/src/test/ui/no_share-struct.stderr b/src/test/ui/no_share-struct.stderr
index c12ee7c5eae85..13de5bd6fe84b 100644
--- a/src/test/ui/no_share-struct.stderr
+++ b/src/test/ui/no_share-struct.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `Foo` cannot be shared between threads safely
-  --> $DIR/no_share-struct.rs:12:5
+  --> $DIR/no_share-struct.rs:12:9
    |
 LL | fn bar<T: Sync>(_: T) {}
    | --------------------- required by `bar`
 ...
 LL |     bar(x);
-   |     ^^^ `Foo` cannot be shared between threads safely
+   |         ^ `Foo` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `Foo`
 
diff --git a/src/test/ui/non-copyable-void.stderr b/src/test/ui/non-copyable-void.stderr
index 4041e1935dcb7..b05c29c0d4036 100644
--- a/src/test/ui/non-copyable-void.stderr
+++ b/src/test/ui/non-copyable-void.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `clone` found for type `libc::c_void` in the curre
   --> $DIR/non-copyable-void.rs:11:23
    |
 LL |         let _z = (*y).clone();
-   |                       ^^^^^
+   |                       ^^^^^ method not found in `libc::c_void`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/noncopyable-class.stderr b/src/test/ui/noncopyable-class.stderr
index eb47a33a7292b..c1c5021138189 100644
--- a/src/test/ui/noncopyable-class.stderr
+++ b/src/test/ui/noncopyable-class.stderr
@@ -5,7 +5,7 @@ LL | struct Foo {
    | ---------- method `clone` not found for this
 ...
 LL |     let _y = x.clone();
-   |                ^^^^^
+   |                ^^^^^ method not found in `Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `clone`, perhaps you need to implement it:
diff --git a/src/test/ui/object-does-not-impl-trait.stderr b/src/test/ui/object-does-not-impl-trait.stderr
index d3add6398bd98..83ca9a7212b22 100644
--- a/src/test/ui/object-does-not-impl-trait.stderr
+++ b/src/test/ui/object-does-not-impl-trait.stderr
@@ -1,10 +1,10 @@
 error[E0277]: the trait bound `std::boxed::Box<dyn Foo>: Foo` is not satisfied
-  --> $DIR/object-does-not-impl-trait.rs:6:35
+  --> $DIR/object-does-not-impl-trait.rs:6:44
    |
 LL | fn take_foo<F:Foo>(f: F) {}
    | ------------------------ required by `take_foo`
 LL | fn take_object(f: Box<dyn Foo>) { take_foo(f); }
-   |                                   ^^^^^^^^ the trait `Foo` is not implemented for `std::boxed::Box<dyn Foo>`
+   |                                            ^ the trait `Foo` is not implemented for `std::boxed::Box<dyn Foo>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/object-pointer-types.stderr b/src/test/ui/object-pointer-types.stderr
index 0c7e4e991a51d..2df628ecf8e50 100644
--- a/src/test/ui/object-pointer-types.stderr
+++ b/src/test/ui/object-pointer-types.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `owned` found for type `&dyn Foo` in the current s
   --> $DIR/object-pointer-types.rs:11:7
    |
 LL |     x.owned();
-   |       ^^^^^
+   |       ^^^^^ method not found in `&dyn Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `owned`, perhaps you need to implement it:
@@ -12,7 +12,7 @@ error[E0599]: no method named `owned` found for type `&mut dyn Foo` in the curre
   --> $DIR/object-pointer-types.rs:17:7
    |
 LL |     x.owned();
-   |       ^^^^^
+   |       ^^^^^ method not found in `&mut dyn Foo`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `owned`, perhaps you need to implement it:
@@ -22,7 +22,7 @@ error[E0599]: no method named `managed` found for type `std::boxed::Box<(dyn Foo
   --> $DIR/object-pointer-types.rs:23:7
    |
 LL |     x.managed();
-   |       ^^^^^^^
+   |       ^^^^^^^ method not found in `std::boxed::Box<(dyn Foo + 'static)>`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/on-unimplemented/multiple-impls.stderr b/src/test/ui/on-unimplemented/multiple-impls.stderr
index b286265bf01c0..f0651c4cdef0e 100644
--- a/src/test/ui/on-unimplemented/multiple-impls.stderr
+++ b/src/test/ui/on-unimplemented/multiple-impls.stderr
@@ -1,57 +1,57 @@
 error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
-  --> $DIR/multiple-impls.rs:33:5
+  --> $DIR/multiple-impls.rs:33:18
    |
 LL |     fn index(&self, index: Idx) -> &Self::Output;
    |     --------------------------------------------- required by `Index::index`
 ...
 LL |     Index::index(&[] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^ trait message
-   |
-   = help: the trait `Index<u32>` is not implemented for `[i32]`
-
-error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
-  --> $DIR/multiple-impls.rs:33:5
-   |
-LL |     Index::index(&[] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ trait message
+   |                  ^^^^^^^^^^^^^ trait message
    |
    = help: the trait `Index<u32>` is not implemented for `[i32]`
 
 error[E0277]: the trait bound `[i32]: Index<Foo<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:36:5
+  --> $DIR/multiple-impls.rs:36:18
    |
 LL |     fn index(&self, index: Idx) -> &Self::Output;
    |     --------------------------------------------- required by `Index::index`
 ...
 LL |     Index::index(&[] as &[i32], Foo(2u32));
-   |     ^^^^^^^^^^^^ on impl for Foo
-   |
-   = help: the trait `Index<Foo<u32>>` is not implemented for `[i32]`
-
-error[E0277]: the trait bound `[i32]: Index<Foo<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:36:5
-   |
-LL |     Index::index(&[] as &[i32], Foo(2u32));
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ on impl for Foo
+   |                  ^^^^^^^^^^^^^ on impl for Foo
    |
    = help: the trait `Index<Foo<u32>>` is not implemented for `[i32]`
 
 error[E0277]: the trait bound `[i32]: Index<Bar<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:39:5
+  --> $DIR/multiple-impls.rs:39:18
    |
 LL |     fn index(&self, index: Idx) -> &Self::Output;
    |     --------------------------------------------- required by `Index::index`
 ...
 LL |     Index::index(&[] as &[i32], Bar(2u32));
-   |     ^^^^^^^^^^^^ on impl for Bar
+   |                  ^^^^^^^^^^^^^ on impl for Bar
    |
    = help: the trait `Index<Bar<u32>>` is not implemented for `[i32]`
 
+error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
+  --> $DIR/multiple-impls.rs:33:5
+   |
+LL |     Index::index(&[] as &[i32], 2u32);
+   |     ^^^^^^^^^^^^ trait message
+   |
+   = help: the trait `Index<u32>` is not implemented for `[i32]`
+
+error[E0277]: the trait bound `[i32]: Index<Foo<u32>>` is not satisfied
+  --> $DIR/multiple-impls.rs:36:5
+   |
+LL |     Index::index(&[] as &[i32], Foo(2u32));
+   |     ^^^^^^^^^^^^ on impl for Foo
+   |
+   = help: the trait `Index<Foo<u32>>` is not implemented for `[i32]`
+
 error[E0277]: the trait bound `[i32]: Index<Bar<u32>>` is not satisfied
   --> $DIR/multiple-impls.rs:39:5
    |
 LL |     Index::index(&[] as &[i32], Bar(2u32));
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ on impl for Bar
+   |     ^^^^^^^^^^^^ on impl for Bar
    |
    = help: the trait `Index<Bar<u32>>` is not implemented for `[i32]`
 
diff --git a/src/test/ui/on-unimplemented/on-impl.stderr b/src/test/ui/on-unimplemented/on-impl.stderr
index 78dc9a53761c5..f19fa8a07fe64 100644
--- a/src/test/ui/on-unimplemented/on-impl.stderr
+++ b/src/test/ui/on-unimplemented/on-impl.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
-  --> $DIR/on-impl.rs:22:5
+  --> $DIR/on-impl.rs:22:25
    |
 LL |     fn index(&self, index: Idx) -> &Self::Output;
    |     --------------------------------------------- required by `Index::index`
 ...
 LL |     Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^^^^^^^^ a usize is required to index into a slice
+   |                         ^^^^^^^^^^^^^^^^^^^^ a usize is required to index into a slice
    |
    = help: the trait `Index<u32>` is not implemented for `[i32]`
 
@@ -13,7 +13,7 @@ error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
   --> $DIR/on-impl.rs:22:5
    |
 LL |     Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ a usize is required to index into a slice
+   |     ^^^^^^^^^^^^^^^^^^^ a usize is required to index into a slice
    |
    = help: the trait `Index<u32>` is not implemented for `[i32]`
 
diff --git a/src/test/ui/or-patterns/already-bound-name.rs b/src/test/ui/or-patterns/already-bound-name.rs
new file mode 100644
index 0000000000000..3ebf59c643735
--- /dev/null
+++ b/src/test/ui/or-patterns/already-bound-name.rs
@@ -0,0 +1,46 @@
+// This test ensures that the "already bound identifier in a product pattern"
+// correctly accounts for or-patterns.
+
+#![feature(or_patterns)]
+//~^ WARN the feature `or_patterns` is incomplete
+
+enum E<T> { A(T, T), B(T) }
+
+use E::*;
+
+fn main() {
+    let (a, a) = (0, 1); // Standard duplication without an or-pattern.
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+
+    let (a, A(a, _) | B(a)) = (0, A(1, 2));
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR identifier `a` is bound more than once in the same pattern
+
+    let (A(a, _) | B(a), a) = (A(0, 1), 2);
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+
+    let A(a, a) | B(a) = A(0, 1);
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+
+    let B(a) | A(a, a) = A(0, 1);
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+
+    match A(0, 1) {
+        B(a) | A(a, a) => {} // Let's ensure `match` has no funny business.
+        //~^ ERROR identifier `a` is bound more than once in the same pattern
+    }
+
+    let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR mismatched types
+
+    let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR variable `a` is not bound in all patterns
+
+    let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+    //~^ ERROR identifier `a` is bound more than once in the same pattern
+    //~| ERROR identifier `a` is bound more than once in the same pattern
+}
diff --git a/src/test/ui/or-patterns/already-bound-name.stderr b/src/test/ui/or-patterns/already-bound-name.stderr
new file mode 100644
index 0000000000000..360699a873938
--- /dev/null
+++ b/src/test/ui/or-patterns/already-bound-name.stderr
@@ -0,0 +1,105 @@
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:12:13
+   |
+LL |     let (a, a) = (0, 1); // Standard duplication without an or-pattern.
+   |             ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:15:15
+   |
+LL |     let (a, A(a, _) | B(a)) = (0, A(1, 2));
+   |               ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:15:25
+   |
+LL |     let (a, A(a, _) | B(a)) = (0, A(1, 2));
+   |                         ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:19:26
+   |
+LL |     let (A(a, _) | B(a), a) = (A(0, 1), 2);
+   |                          ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:22:14
+   |
+LL |     let A(a, a) | B(a) = A(0, 1);
+   |              ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:25:21
+   |
+LL |     let B(a) | A(a, a) = A(0, 1);
+   |                     ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:29:21
+   |
+LL |         B(a) | A(a, a) => {} // Let's ensure `match` has no funny business.
+   |                     ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:33:36
+   |
+LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
+   |                                    ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:33:46
+   |
+LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
+   |                                              ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:38:36
+   |
+LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+   |                                    ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:38:46
+   |
+LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+   |                                              ^ used in a pattern more than once
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/already-bound-name.rs:38:9
+   |
+LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+   |         ^^^^ pattern doesn't bind `a`        - variable not in all patterns
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:43:49
+   |
+LL |     let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+   |                                                 ^ used in a pattern more than once
+
+error[E0416]: identifier `a` is bound more than once in the same pattern
+  --> $DIR/already-bound-name.rs:43:59
+   |
+LL |     let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+   |                                                           ^ used in a pattern more than once
+
+warning: the feature `or_patterns` is incomplete and may cause the compiler to crash
+  --> $DIR/already-bound-name.rs:4:12
+   |
+LL | #![feature(or_patterns)]
+   |            ^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/already-bound-name.rs:33:31
+   |
+LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
+   |                               ^ expected integer, found enum `E`
+   |
+   = note: expected type `{integer}`
+              found type `E<{integer}>`
+
+error: aborting due to 15 previous errors
+
+Some errors have detailed explanations: E0308, E0408, E0416.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/or-patterns/consistent-bindings.rs b/src/test/ui/or-patterns/consistent-bindings.rs
new file mode 100644
index 0000000000000..0eb539dca4cba
--- /dev/null
+++ b/src/test/ui/or-patterns/consistent-bindings.rs
@@ -0,0 +1,46 @@
+// Check that or-patterns with consistent bindings across arms are allowed.
+
+// edition:2018
+
+#![feature(or_patterns)]
+//~^ WARN the feature `or_patterns` is incomplete
+
+fn main() {
+    // One level:
+    let Ok(a) | Err(a) = Ok(0);
+    let Ok(ref a) | Err(ref a) = Ok(0);
+    let Ok(ref mut a) | Err(ref mut a) = Ok(0);
+
+    // Two levels:
+    enum Tri<S, T, U> { V1(S), V2(T), V3(U) }
+    use Tri::*;
+
+    let Ok((V1(a) | V2(a) | V3(a), b)) | Err(Ok((a, b)) | Err((a, b)))
+        : Result<_, Result<_, _>>
+        = Ok((V1(1), 1));
+
+    let Ok((V1(a) | V2(a) | V3(a), ref b)) | Err(Ok((a, ref b)) | Err((a, ref b)))
+        : Result<_, Result<_, _>>
+        = Ok((V1(1), 1));
+
+    // Three levels:
+    let (
+            a,
+            Err((ref mut b, ref c, d)) |
+            Ok((
+                Ok(
+                    V1((ref c, d)) |
+                    V2((d, ref c)) |
+                    V3((ref c, Ok((_, d)) | Err((d, _))))
+                ) |
+                Err((ref c, d)),
+                ref mut b
+            ))
+        ) =
+        (1, Ok((Ok(V3((1, Ok((1, 1))))), 1)));
+
+    // FIXME(or_patterns; Centril | dlrobertson): remove this line below and
+    // change this test to check-pass once MIR can handle or-patterns with bindings.
+    let () = 0;
+    //~^ ERROR mismatched types
+}
diff --git a/src/test/ui/or-patterns/consistent-bindings.stderr b/src/test/ui/or-patterns/consistent-bindings.stderr
new file mode 100644
index 0000000000000..7f5e670c257ce
--- /dev/null
+++ b/src/test/ui/or-patterns/consistent-bindings.stderr
@@ -0,0 +1,20 @@
+warning: the feature `or_patterns` is incomplete and may cause the compiler to crash
+  --> $DIR/consistent-bindings.rs:5:12
+   |
+LL | #![feature(or_patterns)]
+   |            ^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/consistent-bindings.rs:44:9
+   |
+LL |     let () = 0;
+   |         ^^ expected integer, found ()
+   |
+   = note: expected type `{integer}`
+              found type `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/or-patterns/inconsistent-modes.rs b/src/test/ui/or-patterns/inconsistent-modes.rs
new file mode 100644
index 0000000000000..44836893ea2b2
--- /dev/null
+++ b/src/test/ui/or-patterns/inconsistent-modes.rs
@@ -0,0 +1,28 @@
+// This test ensures that or patterns require binding mode consistency across arms.
+
+#![feature(or_patterns)]
+//~^ WARN the feature `or_patterns` is incomplete
+
+#![allow(non_camel_case_types)]
+fn main() {
+    // One level:
+    let Ok(a) | Err(ref a): Result<&u8, u8> = Ok(&0);
+    //~^ ERROR variable `a` is bound in inconsistent ways
+    let Ok(ref mut a) | Err(a): Result<u8, &mut u8> = Ok(0);
+    //~^ ERROR variable `a` is bound in inconsistent ways
+    let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
+    //~^ ERROR variable `a` is bound in inconsistent ways
+    //~| ERROR mismatched types
+    let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
+    //~^ ERROR variable `a` is bound in inconsistent ways
+    //~| ERROR variable `b` is bound in inconsistent ways
+    //~| ERROR mismatched types
+
+    // Two levels:
+    let Ok(Ok(a) | Err(a)) | Err(ref a) = Err(0);
+    //~^ ERROR variable `a` is bound in inconsistent ways
+
+    // Three levels:
+    let Ok([ Ok((Ok(ref a) | Err(a),)) | Err(a) ]) | Err(a) = Err(&1);
+    //~^ ERROR variable `a` is bound in inconsistent ways
+}
diff --git a/src/test/ui/or-patterns/inconsistent-modes.stderr b/src/test/ui/or-patterns/inconsistent-modes.stderr
new file mode 100644
index 0000000000000..0a36ed5548e5b
--- /dev/null
+++ b/src/test/ui/or-patterns/inconsistent-modes.stderr
@@ -0,0 +1,80 @@
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:9:25
+   |
+LL |     let Ok(a) | Err(ref a): Result<&u8, u8> = Ok(&0);
+   |            -            ^ bound in different ways
+   |            |
+   |            first binding
+
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:11:29
+   |
+LL |     let Ok(ref mut a) | Err(a): Result<u8, &mut u8> = Ok(0);
+   |                    -        ^ bound in different ways
+   |                    |
+   |                    first binding
+
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:13:33
+   |
+LL |     let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
+   |                - first binding  ^ bound in different ways
+
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:16:39
+   |
+LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
+   |                 - first binding       ^ bound in different ways
+
+error[E0409]: variable `b` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:16:46
+   |
+LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
+   |                    - first binding           ^ bound in different ways
+
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:22:38
+   |
+LL |     let Ok(Ok(a) | Err(a)) | Err(ref a) = Err(0);
+   |                        -             ^ bound in different ways
+   |                        |
+   |                        first binding
+
+error[E0409]: variable `a` is bound in inconsistent ways within the same match arm
+  --> $DIR/inconsistent-modes.rs:26:34
+   |
+LL |     let Ok([ Ok((Ok(ref a) | Err(a),)) | Err(a) ]) | Err(a) = Err(&1);
+   |                         -        ^ bound in different ways
+   |                         |
+   |                         first binding
+
+warning: the feature `or_patterns` is incomplete and may cause the compiler to crash
+  --> $DIR/inconsistent-modes.rs:3:12
+   |
+LL | #![feature(or_patterns)]
+   |            ^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/inconsistent-modes.rs:13:25
+   |
+LL |     let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
+   |                         ^^^^^^^^^ types differ in mutability
+   |
+   = note: expected type `&&u8`
+              found type `&mut &mut u8`
+
+error[E0308]: mismatched types
+  --> $DIR/inconsistent-modes.rs:16:31
+   |
+LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
+   |                               ^^^^^^^^^ types differ in mutability
+   |
+   = note: expected type `&{integer}`
+              found type `&mut _`
+
+error: aborting due to 9 previous errors
+
+Some errors have detailed explanations: E0308, E0409.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/or-patterns/missing-bindings.rs b/src/test/ui/or-patterns/missing-bindings.rs
new file mode 100644
index 0000000000000..b065028e7a5a4
--- /dev/null
+++ b/src/test/ui/or-patterns/missing-bindings.rs
@@ -0,0 +1,84 @@
+// This test ensures that or patterns do not allow missing bindings in any of the arms.
+
+// edition:2018
+
+#![feature(or_patterns)]
+//~^ WARN the feature `or_patterns` is incomplete
+
+#![allow(non_camel_case_types)]
+
+fn main() {}
+
+fn check_handling_of_paths() {
+    mod bar {
+        pub enum foo {
+            alpha,
+            beta,
+            charlie
+        }
+    }
+
+    use bar::foo::{alpha, charlie};
+    let alpha | beta | charlie = alpha; //~  ERROR variable `beta` is not bound in all patterns
+    match Some(alpha) {
+        Some(alpha | beta) => {} //~ ERROR variable `beta` is not bound in all patterns
+    }
+}
+
+fn check_misc_nesting() {
+    enum E<T> { A(T, T), B(T) }
+    use E::*;
+    enum Vars3<S, T, U> { V1(S), V2(T), V3(U) }
+    use Vars3::*;
+
+    // One level:
+    const X: E<u8> = B(0);
+    let A(a, _) | _ = X; //~ ERROR variable `a` is not bound in all patterns
+    let _ | B(a) = X; //~ ERROR variable `a` is not bound in all patterns
+    let A(..) | B(a) = X; //~ ERROR variable `a` is not bound in all patterns
+    let A(a, _) | B(_) = X; //~ ERROR variable `a` is not bound in all patterns
+    let A(_, a) | B(_) = X; //~ ERROR variable `a` is not bound in all patterns
+    let A(a, b) | B(a) = X; //~ ERROR variable `b` is not bound in all patterns
+
+    // Two levels:
+    const Y: E<E<u8>> = B(B(0));
+    let A(A(..) | B(_), _) | B(a) = Y; //~ ERROR variable `a` is not bound in all patterns
+    let A(A(..) | B(a), _) | B(A(a, _) | B(a)) = Y;
+    //~^ ERROR variable `a` is not bound in all patterns
+    let A(A(a, b) | B(c), d) | B(e) = Y;
+    //~^ ERROR variable `a` is not bound in all patterns
+    //~| ERROR variable `a` is not bound in all patterns
+    //~| ERROR variable `b` is not bound in all patterns
+    //~| ERROR variable `b` is not bound in all patterns
+    //~| ERROR variable `c` is not bound in all patterns
+    //~| ERROR variable `c` is not bound in all patterns
+    //~| ERROR variable `d` is not bound in all patterns
+    //~| ERROR variable `e` is not bound in all patterns
+
+    // Three levels:
+    let (
+            V1(
+            //~^ ERROR variable `b` is not bound in all patterns
+            //~| ERROR variable `c` is not bound in all patterns
+                A(
+                    Ok(a) | Err(_), //~ ERROR variable `a` is not bound in all patterns
+                    _
+                ) |
+                B(Ok(a) | Err(a))
+            ) |
+            V2(
+                A(
+                    A(_, a) | //~ ERROR variable `b` is not bound in all patterns
+                    B(b), //~ ERROR variable `a` is not bound in all patterns
+                    _
+                ) |
+                B(_)
+                //~^ ERROR variable `a` is not bound in all patterns
+                //~| ERROR variable `b` is not bound in all patterns
+            ) |
+            V3(c),
+            //~^ ERROR variable `a` is not bound in all patterns
+        )
+        : (Vars3<E<Result<u8, u8>>, E<E<u8>>, u8>,)
+        = (V3(0),);
+}
diff --git a/src/test/ui/or-patterns/missing-bindings.stderr b/src/test/ui/or-patterns/missing-bindings.stderr
new file mode 100644
index 0000000000000..c73af7a42eec0
--- /dev/null
+++ b/src/test/ui/or-patterns/missing-bindings.stderr
@@ -0,0 +1,250 @@
+error[E0408]: variable `beta` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:22:9
+   |
+LL |     let alpha | beta | charlie = alpha;
+   |         ^^^^^   ----   ^^^^^^^ pattern doesn't bind `beta`
+   |         |       |
+   |         |       variable not in all patterns
+   |         pattern doesn't bind `beta`
+
+error[E0408]: variable `beta` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:24:14
+   |
+LL |         Some(alpha | beta) => {}
+   |              ^^^^^   ---- variable not in all patterns
+   |              |
+   |              pattern doesn't bind `beta`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:36:19
+   |
+LL |     let A(a, _) | _ = X;
+   |           -       ^ pattern doesn't bind `a`
+   |           |
+   |           variable not in all patterns
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:37:9
+   |
+LL |     let _ | B(a) = X;
+   |         ^     - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `a`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:38:9
+   |
+LL |     let A(..) | B(a) = X;
+   |         ^^^^^     - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `a`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:39:19
+   |
+LL |     let A(a, _) | B(_) = X;
+   |           -       ^^^^ pattern doesn't bind `a`
+   |           |
+   |           variable not in all patterns
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:40:19
+   |
+LL |     let A(_, a) | B(_) = X;
+   |              -    ^^^^ pattern doesn't bind `a`
+   |              |
+   |              variable not in all patterns
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:41:19
+   |
+LL |     let A(a, b) | B(a) = X;
+   |              -    ^^^^ pattern doesn't bind `b`
+   |              |
+   |              variable not in all patterns
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:45:9
+   |
+LL |     let A(A(..) | B(_), _) | B(a) = Y;
+   |         ^^^^^^^^^^^^^^^^^^     - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `a`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:46:11
+   |
+LL |     let A(A(..) | B(a), _) | B(A(a, _) | B(a)) = Y;
+   |           ^^^^^     - variable not in all patterns
+   |           |
+   |           pattern doesn't bind `a`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:21
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |             -       ^^^^ pattern doesn't bind `a`
+   |             |
+   |             variable not in all patterns
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:21
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |                -    ^^^^ pattern doesn't bind `b`
+   |                |
+   |                variable not in all patterns
+
+error[E0408]: variable `c` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:11
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |           ^^^^^^^     - variable not in all patterns
+   |           |
+   |           pattern doesn't bind `c`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:32
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |             -                  ^^^^ pattern doesn't bind `a`
+   |             |
+   |             variable not in all patterns
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:32
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |                -               ^^^^ pattern doesn't bind `b`
+   |                |
+   |                variable not in all patterns
+
+error[E0408]: variable `c` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:32
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |                       -        ^^^^ pattern doesn't bind `c`
+   |                       |
+   |                       variable not in all patterns
+
+error[E0408]: variable `d` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:32
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |                           -    ^^^^ pattern doesn't bind `d`
+   |                           |
+   |                           variable not in all patterns
+
+error[E0408]: variable `e` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:48:9
+   |
+LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
+   |         ^^^^^^^^^^^^^^^^^^^^     - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `e`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:64:29
+   |
+LL |                     Ok(a) | Err(_),
+   |                        -    ^^^^^^ pattern doesn't bind `a`
+   |                        |
+   |                        variable not in all patterns
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:72:21
+   |
+LL |                     A(_, a) |
+   |                          - variable not in all patterns
+LL |                     B(b),
+   |                     ^^^^ pattern doesn't bind `a`
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:71:21
+   |
+LL |                     A(_, a) |
+   |                     ^^^^^^^ pattern doesn't bind `b`
+LL |                     B(b),
+   |                       - variable not in all patterns
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:75:17
+   |
+LL |                     A(_, a) |
+   |                          - variable not in all patterns
+...
+LL |                 B(_)
+   |                 ^^^^ pattern doesn't bind `a`
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:75:17
+   |
+LL |                     B(b),
+   |                       - variable not in all patterns
+...
+LL |                 B(_)
+   |                 ^^^^ pattern doesn't bind `b`
+
+error[E0408]: variable `a` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:79:13
+   |
+LL |                 B(Ok(a) | Err(a))
+   |                               - variable not in all patterns
+...
+LL |                     A(_, a) |
+   |                          - variable not in all patterns
+...
+LL |             V3(c),
+   |             ^^^^^ pattern doesn't bind `a`
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:60:13
+   |
+LL | /             V1(
+LL | |
+LL | |
+LL | |                 A(
+...  |
+LL | |                 B(Ok(a) | Err(a))
+LL | |             ) |
+   | |_____________^ pattern doesn't bind `b`
+...
+LL |                       B(b),
+   |                         - variable not in all patterns
+...
+LL |               V3(c),
+   |               ^^^^^ pattern doesn't bind `b`
+
+error[E0408]: variable `c` is not bound in all patterns
+  --> $DIR/missing-bindings.rs:60:13
+   |
+LL | /             V1(
+LL | |
+LL | |
+LL | |                 A(
+...  |
+LL | |                 B(Ok(a) | Err(a))
+LL | |             ) |
+   | |_____________^ pattern doesn't bind `c`
+LL | /             V2(
+LL | |                 A(
+LL | |                     A(_, a) |
+LL | |                     B(b),
+...  |
+LL | |
+LL | |             ) |
+   | |_____________^ pattern doesn't bind `c`
+LL |               V3(c),
+   |                  - variable not in all patterns
+
+warning: the feature `or_patterns` is incomplete and may cause the compiler to crash
+  --> $DIR/missing-bindings.rs:5:12
+   |
+LL | #![feature(or_patterns)]
+   |            ^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: aborting due to 26 previous errors
+
+For more information about this error, try `rustc --explain E0408`.
diff --git a/src/test/ui/parser-recovery-1.rs b/src/test/ui/parser-recovery-1.rs
index 21d36048e6703..8126525c34f95 100644
--- a/src/test/ui/parser-recovery-1.rs
+++ b/src/test/ui/parser-recovery-1.rs
@@ -3,6 +3,7 @@
 // Test that we can recover from missing braces in the parser.
 
 trait Foo {
+//~^ ERROR `main` function not found
     fn bar() {
         let x = foo();
         //~^ ERROR cannot find function `foo` in this scope
diff --git a/src/test/ui/parser-recovery-1.stderr b/src/test/ui/parser-recovery-1.stderr
index c29f42759178e..ffe2b3322fc81 100644
--- a/src/test/ui/parser-recovery-1.stderr
+++ b/src/test/ui/parser-recovery-1.stderr
@@ -1,8 +1,9 @@
 error: this file contains an un-closed delimiter
-  --> $DIR/parser-recovery-1.rs:15:55
+  --> $DIR/parser-recovery-1.rs:16:55
    |
 LL | trait Foo {
    |           - un-closed delimiter
+LL |
 LL |     fn bar() {
    |              - this delimiter might not be properly closed...
 ...
@@ -13,26 +14,34 @@ LL | }
    |                                                       ^
 
 error: unexpected token: `;`
-  --> $DIR/parser-recovery-1.rs:12:15
+  --> $DIR/parser-recovery-1.rs:13:15
    |
 LL |     let x = y.;
    |               ^
 
 error[E0425]: cannot find function `foo` in this scope
-  --> $DIR/parser-recovery-1.rs:7:17
+  --> $DIR/parser-recovery-1.rs:8:17
    |
 LL |         let x = foo();
    |                 ^^^ not found in this scope
 
 error[E0425]: cannot find value `y` in this scope
-  --> $DIR/parser-recovery-1.rs:12:13
+  --> $DIR/parser-recovery-1.rs:13:13
    |
 LL |     let x = y.;
    |             ^ not found in this scope
 
 error[E0601]: `main` function not found in crate `parser_recovery_1`
+  --> $DIR/parser-recovery-1.rs:5:1
    |
-   = note: consider adding a `main` function to `$DIR/parser-recovery-1.rs`
+LL | / trait Foo {
+LL | |
+LL | |     fn bar() {
+LL | |         let x = foo();
+...  |
+LL | |
+LL | | }
+   | |______________________________________________________^ consider adding a `main` function to `$DIR/parser-recovery-1.rs`
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/parser/do-catch-suggests-try.rs b/src/test/ui/parser/do-catch-suggests-try.rs
index 61fae721ffbde..d805ab75882dd 100644
--- a/src/test/ui/parser/do-catch-suggests-try.rs
+++ b/src/test/ui/parser/do-catch-suggests-try.rs
@@ -1,5 +1,5 @@
 fn main() {
     let _: Option<()> = do catch {};
     //~^ ERROR found removed `do catch` syntax
-    //~^^ HELP Following RFC #2388, the new non-placeholder syntax is `try`
+    //~^^ HELP following RFC #2388, the new non-placeholder syntax is `try`
 }
diff --git a/src/test/ui/parser/do-catch-suggests-try.stderr b/src/test/ui/parser/do-catch-suggests-try.stderr
index 6d13b0f1cc872..e151d4cf8a6aa 100644
--- a/src/test/ui/parser/do-catch-suggests-try.stderr
+++ b/src/test/ui/parser/do-catch-suggests-try.stderr
@@ -4,7 +4,7 @@ error: found removed `do catch` syntax
 LL |     let _: Option<()> = do catch {};
    |                         ^^
    |
-   = help: Following RFC #2388, the new non-placeholder syntax is `try`
+   = help: following RFC #2388, the new non-placeholder syntax is `try`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/issue-2354.rs b/src/test/ui/parser/issue-2354.rs
index 565f84822f7d6..a14eb6e32fc91 100644
--- a/src/test/ui/parser/issue-2354.rs
+++ b/src/test/ui/parser/issue-2354.rs
@@ -1,4 +1,7 @@
 fn foo() { //~ NOTE un-closed delimiter
+//~^ ERROR `main` function not found
+//~^^ NOTE main function must be defined
+//~^^^ NOTE you have one or more functions
   match Some(10) {
   //~^ NOTE this delimiter might not be properly closed...
       Some(y) => { panic!(); }
@@ -11,5 +14,5 @@ fn bar() {
     while (i < 1000) {}
 }
 
-fn main() {} //~ NOTE here is a function named 'main'
+fn main() {} //~ NOTE here is a function named `main`
              //~ ERROR this file contains an un-closed delimiter
diff --git a/src/test/ui/parser/issue-2354.stderr b/src/test/ui/parser/issue-2354.stderr
index 7098da738b8df..038e3dcfa40a9 100644
--- a/src/test/ui/parser/issue-2354.stderr
+++ b/src/test/ui/parser/issue-2354.stderr
@@ -1,8 +1,9 @@
 error: this file contains an un-closed delimiter
-  --> $DIR/issue-2354.rs:15:66
+  --> $DIR/issue-2354.rs:18:66
    |
 LL | fn foo() {
    |          - un-closed delimiter
+...
 LL |   match Some(10) {
    |                  - this delimiter might not be properly closed...
 ...
@@ -13,13 +14,24 @@ LL |
    |                                                                  ^
 
 error[E0601]: `main` function not found in crate `issue_2354`
+  --> $DIR/issue-2354.rs:1:1
+   |
+LL | / fn foo() {
+LL | |
+LL | |
+LL | |
+...  |
+LL | | fn main() {}
+LL | |
+   | |_________________________________________________________________^ the main function must be defined at the crate level (in `$DIR/issue-2354.rs`)
    |
-   = note: the main function must be defined at the crate level but you have one or more functions named 'main' that are not defined at the crate level. Either move the definition or attach the `#[main]` attribute to override this behavior.
-note: here is a function named 'main'
-  --> $DIR/issue-2354.rs:14:1
+note: here is a function named `main`
+  --> $DIR/issue-2354.rs:17:1
    |
 LL | fn main() {}
    | ^^^^^^^^^^^^
+   = note: you have one or more functions named `main` not defined at the crate level
+   = help: either move the `main` function definitions or attach the `#[main]` attribute to one of them
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/lex-bad-char-literals-2.rs b/src/test/ui/parser/lex-bad-char-literals-2.rs
index 1e180f87fc186..d35dafd9a3443 100644
--- a/src/test/ui/parser/lex-bad-char-literals-2.rs
+++ b/src/test/ui/parser/lex-bad-char-literals-2.rs
@@ -2,3 +2,5 @@
 static c: char =
     'nope' //~ ERROR: character literal may only contain one codepoint
 ;
+
+fn main() {}
diff --git a/src/test/ui/parser/lex-bad-char-literals-2.stderr b/src/test/ui/parser/lex-bad-char-literals-2.stderr
index b0a4ed02434b4..5653d4ea672af 100644
--- a/src/test/ui/parser/lex-bad-char-literals-2.stderr
+++ b/src/test/ui/parser/lex-bad-char-literals-2.stderr
@@ -8,10 +8,5 @@ help: if you meant to write a `str` literal, use double quotes
 LL |     "nope"
    |     ^^^^^^
 
-error[E0601]: `main` function not found in crate `lex_bad_char_literals_2`
-   |
-   = note: consider adding a `main` function to `$DIR/lex-bad-char-literals-2.rs`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/parser/require-parens-for-chained-comparison.rs b/src/test/ui/parser/require-parens-for-chained-comparison.rs
index 525be5d20e27f..3dcc0c8f3d496 100644
--- a/src/test/ui/parser/require-parens-for-chained-comparison.rs
+++ b/src/test/ui/parser/require-parens-for-chained-comparison.rs
@@ -11,8 +11,7 @@ fn main() {
     //~| ERROR: mismatched types
 
     f<X>();
-    //~^ ERROR: chained comparison operators require parentheses
-    //~| ERROR: binary operation `<` cannot be applied to type `fn() {f::<_>}`
+    //~^ ERROR chained comparison operators require parentheses
     //~| HELP: use `::<...>` instead of `<...>`
     //~| HELP: or use `(...)`
 }
diff --git a/src/test/ui/parser/require-parens-for-chained-comparison.stderr b/src/test/ui/parser/require-parens-for-chained-comparison.stderr
index 76e548de045aa..e927f4c32484e 100644
--- a/src/test/ui/parser/require-parens-for-chained-comparison.stderr
+++ b/src/test/ui/parser/require-parens-for-chained-comparison.stderr
@@ -37,17 +37,6 @@ LL |     false == 0 < 2;
    = note: expected type `bool`
               found type `{integer}`
 
-error[E0369]: binary operation `<` cannot be applied to type `fn() {f::<_>}`
-  --> $DIR/require-parens-for-chained-comparison.rs:13:6
-   |
-LL |     f<X>();
-   |     -^- X
-   |     |
-   |     fn() {f::<_>}
-   |
-   = note: an implementation of `std::cmp::PartialOrd` might be missing for `fn() {f::<_>}`
-
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0308, E0369.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/parser/trait-object-lifetime-parens.rs b/src/test/ui/parser/trait-object-lifetime-parens.rs
index 5bbda4296ca7e..c8b0eb684f33d 100644
--- a/src/test/ui/parser/trait-object-lifetime-parens.rs
+++ b/src/test/ui/parser/trait-object-lifetime-parens.rs
@@ -9,7 +9,6 @@ fn check<'a>() {
     let _: Box<('a) + Trait>;
     //~^ ERROR expected type, found `'a`
     //~| ERROR expected `:`, found `)`
-    //~| ERROR chained comparison operators require parentheses
 }
 
 fn main() {}
diff --git a/src/test/ui/parser/trait-object-lifetime-parens.stderr b/src/test/ui/parser/trait-object-lifetime-parens.stderr
index 7ffc26e9edead..319a308c0137c 100644
--- a/src/test/ui/parser/trait-object-lifetime-parens.stderr
+++ b/src/test/ui/parser/trait-object-lifetime-parens.stderr
@@ -16,15 +16,6 @@ error: expected `:`, found `)`
 LL |     let _: Box<('a) + Trait>;
    |                   ^ expected `:`
 
-error: chained comparison operators require parentheses
-  --> $DIR/trait-object-lifetime-parens.rs:9:15
-   |
-LL |     let _: Box<('a) + Trait>;
-   |               ^^^^^^^^^^^^^^^
-   |
-   = help: use `::<...>` instead of `<...>` if you meant to specify type arguments
-   = help: or use `(...)` if you meant to specify fn arguments
-
 error: expected type, found `'a`
   --> $DIR/trait-object-lifetime-parens.rs:9:17
    |
@@ -33,5 +24,5 @@ LL |     let _: Box<('a) + Trait>;
    |         |
    |         while parsing the type for `_`
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/parser/unclosed-delimiter-in-dep.stderr b/src/test/ui/parser/unclosed-delimiter-in-dep.stderr
index 633c63bea9105..818f61b4d2229 100644
--- a/src/test/ui/parser/unclosed-delimiter-in-dep.stderr
+++ b/src/test/ui/parser/unclosed-delimiter-in-dep.stderr
@@ -1,5 +1,5 @@
 error: incorrect close delimiter: `}`
-  --> $DIR/unclosed_delim_mod.rs:5:1
+  --> $DIR/unclosed_delim_mod.rs:7:1
    |
 LL | pub fn new() -> Result<Value, ()> {
    |                                   - close delimiter possibly meant for this
diff --git a/src/test/ui/parser/unclosed_delim_mod.rs b/src/test/ui/parser/unclosed_delim_mod.rs
index b1664f49dc591..486e23312819d 100644
--- a/src/test/ui/parser/unclosed_delim_mod.rs
+++ b/src/test/ui/parser/unclosed_delim_mod.rs
@@ -1,3 +1,5 @@
+fn main() {}
+
 pub struct Value {}
 pub fn new() -> Result<Value, ()> {
     Ok(Value {
diff --git a/src/test/ui/parser/unclosed_delim_mod.stderr b/src/test/ui/parser/unclosed_delim_mod.stderr
index cc04eb531cbea..fe2d968af0f32 100644
--- a/src/test/ui/parser/unclosed_delim_mod.stderr
+++ b/src/test/ui/parser/unclosed_delim_mod.stderr
@@ -1,5 +1,5 @@
 error: incorrect close delimiter: `}`
-  --> $DIR/unclosed_delim_mod.rs:5:1
+  --> $DIR/unclosed_delim_mod.rs:7:1
    |
 LL | pub fn new() -> Result<Value, ()> {
    |                                   - close delimiter possibly meant for this
@@ -9,10 +9,5 @@ LL |     }
 LL | }
    | ^ incorrect close delimiter
 
-error[E0601]: `main` function not found in crate `unclosed_delim_mod`
-   |
-   = note: consider adding a `main` function to `$DIR/unclosed_delim_mod.rs`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/pattern/pat-tuple-overfield.stderr b/src/test/ui/pattern/pat-tuple-overfield.stderr
index 0430897510b85..e64b6efb08da8 100644
--- a/src/test/ui/pattern/pat-tuple-overfield.stderr
+++ b/src/test/ui/pattern/pat-tuple-overfield.stderr
@@ -19,12 +19,18 @@ LL |         (1, 2, .., 3, 4) => {}
 error[E0023]: this pattern has 4 fields, but the corresponding tuple struct has 3 fields
   --> $DIR/pat-tuple-overfield.rs:10:9
    |
+LL | struct S(u8, u8, u8);
+   | --------------------- tuple struct defined here
+...
 LL |         S(1, 2, 3, 4) => {}
    |         ^^^^^^^^^^^^^ expected 3 fields, found 4
 
 error[E0023]: this pattern has 4 fields, but the corresponding tuple struct has 3 fields
   --> $DIR/pat-tuple-overfield.rs:12:9
    |
+LL | struct S(u8, u8, u8);
+   | --------------------- tuple struct defined here
+...
 LL |         S(1, 2, .., 3, 4) => {}
    |         ^^^^^^^^^^^^^^^^^ expected 3 fields, found 4
 
diff --git a/src/test/ui/pattern/pattern-error-continue.stderr b/src/test/ui/pattern/pattern-error-continue.stderr
index a581f07496e6c..4fbc630644baa 100644
--- a/src/test/ui/pattern/pattern-error-continue.stderr
+++ b/src/test/ui/pattern/pattern-error-continue.stderr
@@ -15,6 +15,9 @@ LL |         A::D(_) => (),
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/pattern-error-continue.rs:17:9
    |
+LL |     B(isize, isize),
+   |     --------------- tuple variant defined here
+...
 LL |         A::B(_, _, _) => (),
    |         ^^^^^^^^^^^^^ expected 2 fields, found 3
 
diff --git a/src/test/ui/phantom-oibit.stderr b/src/test/ui/phantom-oibit.stderr
index 284102a6df028..c1b60e0823fd4 100644
--- a/src/test/ui/phantom-oibit.stderr
+++ b/src/test/ui/phantom-oibit.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `T` cannot be shared between threads safely
-  --> $DIR/phantom-oibit.rs:21:5
+  --> $DIR/phantom-oibit.rs:21:12
    |
 LL | fn is_zen<T: Zen>(_: T) {}
    | ----------------------- required by `is_zen`
 ...
 LL |     is_zen(x)
-   |     ^^^^^^ `T` cannot be shared between threads safely
+   |            ^ `T` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `T`
    = help: consider adding a `where T: std::marker::Sync` bound
@@ -14,13 +14,13 @@ LL |     is_zen(x)
    = note: required because it appears within the type `Guard<'_, T>`
 
 error[E0277]: `T` cannot be shared between threads safely
-  --> $DIR/phantom-oibit.rs:26:5
+  --> $DIR/phantom-oibit.rs:26:12
    |
 LL | fn is_zen<T: Zen>(_: T) {}
    | ----------------------- required by `is_zen`
 ...
 LL |     is_zen(x)
-   |     ^^^^^^ `T` cannot be shared between threads safely
+   |            ^ `T` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `T`
    = help: consider adding a `where T: std::marker::Sync` bound
diff --git a/src/test/ui/proc-macro/derive-still-gated.rs b/src/test/ui/proc-macro/derive-still-gated.rs
index 4e6f9b072205d..3f8d6f0716b3a 100644
--- a/src/test/ui/proc-macro/derive-still-gated.rs
+++ b/src/test/ui/proc-macro/derive-still-gated.rs
@@ -3,7 +3,7 @@
 #[macro_use]
 extern crate test_macros;
 
-#[derive_Empty] //~ ERROR cannot find attribute macro `derive_Empty` in this scope
+#[derive_Empty] //~ ERROR cannot find attribute `derive_Empty` in this scope
 struct A;
 
 fn main() {}
diff --git a/src/test/ui/proc-macro/derive-still-gated.stderr b/src/test/ui/proc-macro/derive-still-gated.stderr
index 4df1715db9467..99289fdfe7fd5 100644
--- a/src/test/ui/proc-macro/derive-still-gated.stderr
+++ b/src/test/ui/proc-macro/derive-still-gated.stderr
@@ -1,4 +1,4 @@
-error: cannot find attribute macro `derive_Empty` in this scope
+error: cannot find attribute `derive_Empty` in this scope
   --> $DIR/derive-still-gated.rs:6:3
    |
 LL | #[derive_Empty]
diff --git a/src/test/ui/proc-macro/dollar-crate-issue-57089.stdout b/src/test/ui/proc-macro/dollar-crate-issue-57089.stdout
index 0fe02a9a34d18..ea06f6c1acaf9 100644
--- a/src/test/ui/proc-macro/dollar-crate-issue-57089.stdout
+++ b/src/test/ui/proc-macro/dollar-crate-issue-57089.stdout
@@ -2,40 +2,40 @@ PRINT-BANG INPUT (DISPLAY): struct M ($crate :: S) ;
 PRINT-BANG INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "M",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
 PRINT-ATTR INPUT (DISPLAY): struct A(crate::S);
@@ -43,39 +43,39 @@ PRINT-ATTR RE-COLLECTED (DISPLAY): struct A ($crate :: S) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "A",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
diff --git a/src/test/ui/proc-macro/dollar-crate-issue-62325.stdout b/src/test/ui/proc-macro/dollar-crate-issue-62325.stdout
index a499e1362ec0b..7ee8078b2c5d2 100644
--- a/src/test/ui/proc-macro/dollar-crate-issue-62325.stdout
+++ b/src/test/ui/proc-macro/dollar-crate-issue-62325.stdout
@@ -3,55 +3,55 @@ PRINT-ATTR RE-COLLECTED (DISPLAY): struct A (identity ! ($crate :: S)) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "A",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "identity",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: '!',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Group {
                 delimiter: Parenthesis,
                 stream: TokenStream [
                     Ident {
                         ident: "$crate",
-                        span: #2 bytes(LO..HI),
+                        span: #3 bytes(LO..HI),
                     },
                     Punct {
                         ch: ':',
                         spacing: Joint,
-                        span: #2 bytes(LO..HI),
+                        span: #3 bytes(LO..HI),
                     },
                     Punct {
                         ch: ':',
                         spacing: Alone,
-                        span: #2 bytes(LO..HI),
+                        span: #3 bytes(LO..HI),
                     },
                     Ident {
                         ident: "S",
-                        span: #2 bytes(LO..HI),
+                        span: #3 bytes(LO..HI),
                     },
                 ],
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
 PRINT-ATTR INPUT (DISPLAY): struct B(identity!(::dollar_crate_external :: S));
@@ -59,54 +59,54 @@ PRINT-ATTR RE-COLLECTED (DISPLAY): struct B (identity ! ($crate :: S)) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #7 bytes(LO..HI),
+        span: #8 bytes(LO..HI),
     },
     Ident {
         ident: "B",
-        span: #7 bytes(LO..HI),
+        span: #8 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "identity",
-                span: #7 bytes(LO..HI),
+                span: #8 bytes(LO..HI),
             },
             Punct {
                 ch: '!',
                 spacing: Alone,
-                span: #7 bytes(LO..HI),
+                span: #8 bytes(LO..HI),
             },
             Group {
                 delimiter: Parenthesis,
                 stream: TokenStream [
                     Ident {
                         ident: "$crate",
-                        span: #7 bytes(LO..HI),
+                        span: #8 bytes(LO..HI),
                     },
                     Punct {
                         ch: ':',
                         spacing: Joint,
-                        span: #7 bytes(LO..HI),
+                        span: #8 bytes(LO..HI),
                     },
                     Punct {
                         ch: ':',
                         spacing: Alone,
-                        span: #7 bytes(LO..HI),
+                        span: #8 bytes(LO..HI),
                     },
                     Ident {
                         ident: "S",
-                        span: #7 bytes(LO..HI),
+                        span: #8 bytes(LO..HI),
                     },
                 ],
-                span: #7 bytes(LO..HI),
+                span: #8 bytes(LO..HI),
             },
         ],
-        span: #7 bytes(LO..HI),
+        span: #8 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #7 bytes(LO..HI),
+        span: #8 bytes(LO..HI),
     },
 ]
diff --git a/src/test/ui/proc-macro/dollar-crate.stdout b/src/test/ui/proc-macro/dollar-crate.stdout
index da1d7549d0750..4f7e000265eb0 100644
--- a/src/test/ui/proc-macro/dollar-crate.stdout
+++ b/src/test/ui/proc-macro/dollar-crate.stdout
@@ -2,40 +2,40 @@ PRINT-BANG INPUT (DISPLAY): struct M ($crate :: S) ;
 PRINT-BANG INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "M",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
 PRINT-ATTR INPUT (DISPLAY): struct A(crate::S);
@@ -43,40 +43,40 @@ PRINT-ATTR RE-COLLECTED (DISPLAY): struct A ($crate :: S) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "A",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
 PRINT-DERIVE INPUT (DISPLAY): struct D(crate::S);
@@ -84,80 +84,80 @@ PRINT-DERIVE RE-COLLECTED (DISPLAY): struct D ($crate :: S) ;
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Ident {
         ident: "D",
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #2 bytes(LO..HI),
+                span: #3 bytes(LO..HI),
             },
         ],
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #2 bytes(LO..HI),
+        span: #3 bytes(LO..HI),
     },
 ]
 PRINT-BANG INPUT (DISPLAY): struct M ($crate :: S) ;
 PRINT-BANG INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Ident {
         ident: "M",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
         ],
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
 ]
 PRINT-ATTR INPUT (DISPLAY): struct A(::dollar_crate_external::S);
@@ -165,40 +165,40 @@ PRINT-ATTR RE-COLLECTED (DISPLAY): struct A ($crate :: S) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Ident {
         ident: "A",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
         ],
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
 ]
 PRINT-DERIVE INPUT (DISPLAY): struct D(::dollar_crate_external::S);
@@ -206,39 +206,39 @@ PRINT-DERIVE RE-COLLECTED (DISPLAY): struct D ($crate :: S) ;
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Ident {
         ident: "D",
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Group {
         delimiter: Parenthesis,
         stream: TokenStream [
             Ident {
                 ident: "$crate",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Joint,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Punct {
                 ch: ':',
                 spacing: Alone,
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
             Ident {
                 ident: "S",
-                span: #9 bytes(LO..HI),
+                span: #10 bytes(LO..HI),
             },
         ],
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
     Punct {
         ch: ';',
         spacing: Alone,
-        span: #9 bytes(LO..HI),
+        span: #10 bytes(LO..HI),
     },
 ]
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-1.rs b/src/test/ui/proc-macro/invalid-punct-ident-1.rs
index c9881ad2c38af..94a4b403d5a3f 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-1.rs
+++ b/src/test/ui/proc-macro/invalid-punct-ident-1.rs
@@ -3,6 +3,11 @@
 // FIXME https://github.com/rust-lang/rust/issues/59998
 // normalize-stderr-test "thread.*panicked.*proc_macro_server.rs.*\n" -> ""
 // normalize-stderr-test "note:.*RUST_BACKTRACE=1.*\n" -> ""
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-1.stderr b/src/test/ui/proc-macro/invalid-punct-ident-1.stderr
index 40333a3f4c211..107f5fb515b1c 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-1.stderr
+++ b/src/test/ui/proc-macro/invalid-punct-ident-1.stderr
@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-1.rs:10:1
+  --> $DIR/invalid-punct-ident-1.rs:15:1
    |
 LL | invalid_punct!();
    | ^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-2.rs b/src/test/ui/proc-macro/invalid-punct-ident-2.rs
index 15e2286a65049..778b7eeecd7a9 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-2.rs
+++ b/src/test/ui/proc-macro/invalid-punct-ident-2.rs
@@ -3,6 +3,11 @@
 // FIXME https://github.com/rust-lang/rust/issues/59998
 // normalize-stderr-test "thread.*panicked.*proc_macro_server.rs.*\n" -> ""
 // normalize-stderr-test "note:.*RUST_BACKTRACE=1.*\n" -> ""
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-2.stderr b/src/test/ui/proc-macro/invalid-punct-ident-2.stderr
index ec97e265c3fcd..f1b9ecc6cbfe4 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-2.stderr
+++ b/src/test/ui/proc-macro/invalid-punct-ident-2.stderr
@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-2.rs:10:1
+  --> $DIR/invalid-punct-ident-2.rs:15:1
    |
 LL | invalid_ident!();
    | ^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-3.rs b/src/test/ui/proc-macro/invalid-punct-ident-3.rs
index 629bbaa9e3888..f68ee3de7f456 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-3.rs
+++ b/src/test/ui/proc-macro/invalid-punct-ident-3.rs
@@ -3,6 +3,11 @@
 // FIXME https://github.com/rust-lang/rust/issues/59998
 // normalize-stderr-test "thread.*panicked.*proc_macro_server.rs.*\n" -> ""
 // normalize-stderr-test "note:.*RUST_BACKTRACE=1.*\n" -> ""
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;
diff --git a/src/test/ui/proc-macro/invalid-punct-ident-3.stderr b/src/test/ui/proc-macro/invalid-punct-ident-3.stderr
index a5e5ded65333a..6044b9887401e 100644
--- a/src/test/ui/proc-macro/invalid-punct-ident-3.stderr
+++ b/src/test/ui/proc-macro/invalid-punct-ident-3.stderr
@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-3.rs:10:1
+  --> $DIR/invalid-punct-ident-3.rs:15:1
    |
 LL | invalid_raw_ident!();
    | ^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/proc-macro/macro-namespace-reserved-2.rs b/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
index 8a26df9e76ade..b17c0565932fd 100644
--- a/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
+++ b/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
@@ -25,17 +25,17 @@ fn check_bang1() {
     my_macro!(); //~ ERROR can't use a procedural macro from the same crate that defines it
 }
 fn check_bang2() {
-    my_macro_attr!(); //~ ERROR cannot find macro `my_macro_attr!` in this scope
+    my_macro_attr!(); //~ ERROR cannot find macro `my_macro_attr` in this scope
     crate::my_macro_attr!(); //~ ERROR can't use a procedural macro from the same crate that defines
                              //~| ERROR expected macro, found attribute macro `crate::my_macro_attr`
 }
 fn check_bang3() {
-    MyTrait!(); //~ ERROR cannot find macro `MyTrait!` in this scope
+    MyTrait!(); //~ ERROR cannot find macro `MyTrait` in this scope
     crate::MyTrait!(); //~ ERROR can't use a procedural macro from the same crate that defines it
                        //~| ERROR expected macro, found derive macro `crate::MyTrait`
 }
 
-#[my_macro] //~ ERROR cannot find attribute macro `my_macro` in this scope
+#[my_macro] //~ ERROR cannot find attribute `my_macro` in this scope
 #[crate::my_macro] //~ ERROR can't use a procedural macro from the same crate that defines it
                    //~| ERROR expected attribute, found macro `crate::my_macro`
 fn check_attr1() {}
diff --git a/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr b/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
index 0c863e919670d..c011a70cd0c84 100644
--- a/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
+++ b/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
@@ -88,19 +88,19 @@ error: expected derive macro, found macro `crate::my_macro`
 LL | #[derive(crate::my_macro)]
    |          ^^^^^^^^^^^^^^^ not a derive macro
 
-error: cannot find macro `my_macro_attr!` in this scope
+error: cannot find macro `my_macro_attr` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:28:5
    |
 LL |     my_macro_attr!();
    |     ^^^^^^^^^^^^^
 
-error: cannot find macro `MyTrait!` in this scope
+error: cannot find macro `MyTrait` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:33:5
    |
 LL |     MyTrait!();
    |     ^^^^^^^
 
-error: cannot find attribute macro `my_macro` in this scope
+error: cannot find attribute `my_macro` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:38:3
    |
 LL | #[my_macro]
diff --git a/src/test/ui/proc-macro/proc-macro-attributes.rs b/src/test/ui/proc-macro/proc-macro-attributes.rs
index 04215226c6d41..6401522bdf89c 100644
--- a/src/test/ui/proc-macro/proc-macro-attributes.rs
+++ b/src/test/ui/proc-macro/proc-macro-attributes.rs
@@ -4,7 +4,7 @@
 extern crate derive_b;
 
 #[B] //~ ERROR `B` is ambiguous
-#[C] //~ ERROR cannot find attribute macro `C` in this scope
+#[C] //~ ERROR cannot find attribute `C` in this scope
 #[B(D)] //~ ERROR `B` is ambiguous
 #[B(E = "foo")] //~ ERROR `B` is ambiguous
 #[B(arbitrary tokens)] //~ ERROR `B` is ambiguous
diff --git a/src/test/ui/proc-macro/proc-macro-attributes.stderr b/src/test/ui/proc-macro/proc-macro-attributes.stderr
index b068c6bc83bf3..3ac93a748523a 100644
--- a/src/test/ui/proc-macro/proc-macro-attributes.stderr
+++ b/src/test/ui/proc-macro/proc-macro-attributes.stderr
@@ -1,4 +1,4 @@
-error: cannot find attribute macro `C` in this scope
+error: cannot find attribute `C` in this scope
   --> $DIR/proc-macro-attributes.rs:7:3
    |
 LL | #[C]
diff --git a/src/test/ui/proc-macro/proc-macro-gates2.rs b/src/test/ui/proc-macro/proc-macro-gates2.rs
index 35d7fc8042a3d..2fd5efd71f041 100644
--- a/src/test/ui/proc-macro/proc-macro-gates2.rs
+++ b/src/test/ui/proc-macro/proc-macro-gates2.rs
@@ -10,11 +10,11 @@ extern crate test_macros;
 // should either require a feature gate or not be allowed on stable.
 
 fn _test6<#[empty_attr] T>() {}
-//~^ ERROR: unknown to the compiler
+//~^ ERROR: expected an inert attribute, found an attribute macro
 
 fn _test7() {
     match 1 {
-        #[empty_attr] //~ ERROR: unknown to the compiler
+        #[empty_attr] //~ ERROR: expected an inert attribute, found an attribute macro
         0 => {}
         _ => {}
     }
diff --git a/src/test/ui/proc-macro/proc-macro-gates2.stderr b/src/test/ui/proc-macro/proc-macro-gates2.stderr
index a7f6f8bfb13d6..fd271da61553a 100644
--- a/src/test/ui/proc-macro/proc-macro-gates2.stderr
+++ b/src/test/ui/proc-macro/proc-macro-gates2.stderr
@@ -1,21 +1,14 @@
-error[E0658]: the attribute `empty_attr` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-gates2.rs:12:11
    |
 LL | fn _test6<#[empty_attr] T>() {}
    |           ^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `empty_attr` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-gates2.rs:17:9
    |
 LL |         #[empty_attr]
    |         ^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/proc-macro/resolve-error.rs b/src/test/ui/proc-macro/resolve-error.rs
index 0a7861aba6ebb..d2282af27f543 100644
--- a/src/test/ui/proc-macro/resolve-error.rs
+++ b/src/test/ui/proc-macro/resolve-error.rs
@@ -23,12 +23,12 @@ macro_rules! attr_proc_mac {
 //~^ ERROR cannot find
 struct Foo;
 
-// Interpreted as a feature gated custom attribute
-#[attr_proc_macra] //~ ERROR cannot find attribute macro `attr_proc_macra` in this scope
+// Interpreted as an unstable custom attribute
+#[attr_proc_macra] //~ ERROR cannot find attribute `attr_proc_macra` in this scope
 struct Bar;
 
-// Interpreted as a feature gated custom attribute
-#[FooWithLongNan] //~ ERROR cannot find attribute macro `FooWithLongNan` in this scope
+// Interpreted as an unstable custom attribute
+#[FooWithLongNan] //~ ERROR cannot find attribute `FooWithLongNan` in this scope
 struct Asdf;
 
 #[derive(Dlone)]
diff --git a/src/test/ui/proc-macro/resolve-error.stderr b/src/test/ui/proc-macro/resolve-error.stderr
index 2a5f2b883813d..3dca5cee63caa 100644
--- a/src/test/ui/proc-macro/resolve-error.stderr
+++ b/src/test/ui/proc-macro/resolve-error.stderr
@@ -1,22 +1,22 @@
-error: cannot find macro `bang_proc_macrp!` in this scope
+error: cannot find macro `bang_proc_macrp` in this scope
   --> $DIR/resolve-error.rs:56:5
    |
 LL |     bang_proc_macrp!();
    |     ^^^^^^^^^^^^^^^ help: a macro with a similar name exists: `bang_proc_macro`
 
-error: cannot find macro `Dlona!` in this scope
+error: cannot find macro `Dlona` in this scope
   --> $DIR/resolve-error.rs:53:5
    |
 LL |     Dlona!();
    |     ^^^^^
 
-error: cannot find macro `attr_proc_macra!` in this scope
+error: cannot find macro `attr_proc_macra` in this scope
   --> $DIR/resolve-error.rs:50:5
    |
 LL |     attr_proc_macra!();
    |     ^^^^^^^^^^^^^^^ help: a macro with a similar name exists: `attr_proc_mac`
 
-error: cannot find macro `FooWithLongNama!` in this scope
+error: cannot find macro `FooWithLongNama` in this scope
   --> $DIR/resolve-error.rs:47:5
    |
 LL |     FooWithLongNama!();
@@ -40,13 +40,13 @@ error: cannot find derive macro `Dlone` in this scope
 LL | #[derive(Dlone)]
    |          ^^^^^ help: a derive macro with a similar name exists: `Clone`
 
-error: cannot find attribute macro `FooWithLongNan` in this scope
+error: cannot find attribute `FooWithLongNan` in this scope
   --> $DIR/resolve-error.rs:31:3
    |
 LL | #[FooWithLongNan]
    |   ^^^^^^^^^^^^^^
 
-error: cannot find attribute macro `attr_proc_macra` in this scope
+error: cannot find attribute `attr_proc_macra` in this scope
   --> $DIR/resolve-error.rs:27:3
    |
 LL | #[attr_proc_macra]
diff --git a/src/test/ui/reachable/expr_add.stderr b/src/test/ui/reachable/expr_add.stderr
index 02b29021cb61a..47b4e467abecb 100644
--- a/src/test/ui/reachable/expr_add.stderr
+++ b/src/test/ui/reachable/expr_add.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_add.rs:17:19
+   |
+LL |     let x = Foo + return;
+   |                   ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_again.stderr b/src/test/ui/reachable/expr_again.stderr
index bdc3d143ea57e..8e246d940fd8d 100644
--- a/src/test/ui/reachable/expr_again.stderr
+++ b/src/test/ui/reachable/expr_again.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_again.rs:7:9
+   |
+LL |         continue;
+   |         ^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to previous error
diff --git a/src/test/ui/reachable/expr_array.stderr b/src/test/ui/reachable/expr_array.stderr
index 18d7ffe74bd18..419a332e632f3 100644
--- a/src/test/ui/reachable/expr_array.stderr
+++ b/src/test/ui/reachable/expr_array.stderr
@@ -9,12 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_array.rs:9:26
+   |
+LL |     let x: [usize; 2] = [return, 22];
+   |                          ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_array.rs:14:25
    |
 LL |     let x: [usize; 2] = [22, return];
    |                         ^^^^^^^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_array.rs:14:30
+   |
+LL |     let x: [usize; 2] = [22, return];
+   |                              ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reachable/expr_assign.stderr b/src/test/ui/reachable/expr_assign.stderr
index def16d90a7490..7388fb4a6b9b2 100644
--- a/src/test/ui/reachable/expr_assign.stderr
+++ b/src/test/ui/reachable/expr_assign.stderr
@@ -9,18 +9,35 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_assign.rs:10:9
+   |
+LL |     x = return;
+   |         ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_assign.rs:20:14
    |
 LL |         *p = return;
    |              ^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_assign.rs:20:9
+   |
+LL |         *p = return;
+   |         ^^
 
 error: unreachable expression
   --> $DIR/expr_assign.rs:26:15
    |
 LL |     *{return; &mut i} = 22;
    |               ^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_assign.rs:26:7
+   |
+LL |     *{return; &mut i} = 22;
+   |       ^^^^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/reachable/expr_block.stderr b/src/test/ui/reachable/expr_block.stderr
index a498502e6cb1a..03a6139d688bb 100644
--- a/src/test/ui/reachable/expr_block.stderr
+++ b/src/test/ui/reachable/expr_block.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_block.rs:9:9
+   |
+LL |         return;
+   |         ^^^^^^
 
 error: unreachable statement
   --> $DIR/expr_block.rs:25:9
@@ -16,6 +21,11 @@ error: unreachable statement
 LL |         println!("foo");
    |         ^^^^^^^^^^^^^^^^
    |
+note: any code following this expression is unreachable
+  --> $DIR/expr_block.rs:24:9
+   |
+LL |         return;
+   |         ^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/reachable/expr_box.stderr b/src/test/ui/reachable/expr_box.stderr
index 63137ce3da180..d0f666d2be44b 100644
--- a/src/test/ui/reachable/expr_box.stderr
+++ b/src/test/ui/reachable/expr_box.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_box.rs:6:17
+   |
+LL |     let x = box return;
+   |                 ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_call.stderr b/src/test/ui/reachable/expr_call.stderr
index df5cff16f9a46..3fcea90e7cd87 100644
--- a/src/test/ui/reachable/expr_call.stderr
+++ b/src/test/ui/reachable/expr_call.stderr
@@ -9,12 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_call.rs:13:9
+   |
+LL |     foo(return, 22);
+   |         ^^^^^^
 
-error: unreachable expression
+error: unreachable call
   --> $DIR/expr_call.rs:18:5
    |
 LL |     bar(return);
-   |     ^^^^^^^^^^^
+   |     ^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_call.rs:18:9
+   |
+LL |     bar(return);
+   |         ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reachable/expr_cast.stderr b/src/test/ui/reachable/expr_cast.stderr
index 3086745d28ed4..d3ce0ca079f90 100644
--- a/src/test/ui/reachable/expr_cast.stderr
+++ b/src/test/ui/reachable/expr_cast.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_cast.rs:9:14
+   |
+LL |     let x = {return} as !;
+   |              ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_if.stderr b/src/test/ui/reachable/expr_if.stderr
index f1690e595e5d1..03284576086a7 100644
--- a/src/test/ui/reachable/expr_if.stderr
+++ b/src/test/ui/reachable/expr_if.stderr
@@ -12,6 +12,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_if.rs:7:9
+   |
+LL |     if {return} {
+   |         ^^^^^^
 
 error: unreachable statement
   --> $DIR/expr_if.rs:27:5
@@ -19,6 +24,11 @@ error: unreachable statement
 LL |     println!("But I am.");
    |     ^^^^^^^^^^^^^^^^^^^^^^
    |
+note: any code following this expression is unreachable
+  --> $DIR/expr_if.rs:21:9
+   |
+LL |         return;
+   |         ^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/reachable/expr_loop.stderr b/src/test/ui/reachable/expr_loop.stderr
index 4d3e06c93a376..a4cf8cfcfd9e6 100644
--- a/src/test/ui/reachable/expr_loop.stderr
+++ b/src/test/ui/reachable/expr_loop.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_loop.rs:7:12
+   |
+LL |     loop { return; }
+   |            ^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
@@ -17,6 +22,11 @@ error: unreachable statement
 LL |     println!("I am dead.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^
    |
+note: any code following this expression is unreachable
+  --> $DIR/expr_loop.rs:20:12
+   |
+LL |     loop { return; }
+   |            ^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
@@ -25,6 +35,11 @@ error: unreachable statement
 LL |     println!("I am dead.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^
    |
+note: any code following this expression is unreachable
+  --> $DIR/expr_loop.rs:31:5
+   |
+LL |     loop { 'middle: loop { loop { break 'middle; } } }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to 3 previous errors
diff --git a/src/test/ui/reachable/expr_match.stderr b/src/test/ui/reachable/expr_match.stderr
index 1aef06aec5ba6..f587e524d350d 100644
--- a/src/test/ui/reachable/expr_match.stderr
+++ b/src/test/ui/reachable/expr_match.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this `match` expression is unreachable, as all arms diverge
+  --> $DIR/expr_match.rs:7:5
+   |
+LL |     match () { () => return }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
@@ -17,6 +22,11 @@ error: unreachable statement
 LL |     println!("I am dead");
    |     ^^^^^^^^^^^^^^^^^^^^^^
    |
+note: any code following this `match` expression is unreachable, as all arms diverge
+  --> $DIR/expr_match.rs:18:5
+   |
+LL |     match () { () if false => return, () => return }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/reachable/expr_method.stderr b/src/test/ui/reachable/expr_method.stderr
index bbfa2ef529add..7ad279c9f487a 100644
--- a/src/test/ui/reachable/expr_method.stderr
+++ b/src/test/ui/reachable/expr_method.stderr
@@ -9,12 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_method.rs:16:13
+   |
+LL |     Foo.foo(return, 22);
+   |             ^^^^^^
 
-error: unreachable expression
-  --> $DIR/expr_method.rs:21:5
+error: unreachable call
+  --> $DIR/expr_method.rs:21:9
+   |
+LL |     Foo.bar(return);
+   |         ^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_method.rs:21:13
    |
 LL |     Foo.bar(return);
-   |     ^^^^^^^^^^^^^^^
+   |             ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reachable/expr_repeat.stderr b/src/test/ui/reachable/expr_repeat.stderr
index 0536cdef72128..3ff6be76daea5 100644
--- a/src/test/ui/reachable/expr_repeat.stderr
+++ b/src/test/ui/reachable/expr_repeat.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_repeat.rs:9:26
+   |
+LL |     let x: [usize; 2] = [return; 2];
+   |                          ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_return.stderr b/src/test/ui/reachable/expr_return.stderr
index 3317da58aba1c..31f7ebe7618ea 100644
--- a/src/test/ui/reachable/expr_return.stderr
+++ b/src/test/ui/reachable/expr_return.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_return.rs:10:30
+   |
+LL |     let x = {return {return {return;}}};
+   |                              ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_return_in_macro.rs b/src/test/ui/reachable/expr_return_in_macro.rs
new file mode 100644
index 0000000000000..4e57618bf5e77
--- /dev/null
+++ b/src/test/ui/reachable/expr_return_in_macro.rs
@@ -0,0 +1,15 @@
+// Tests that we generate nice error messages
+// when an expression is unreachble due to control
+// flow inside of a macro expansion.
+#![deny(unreachable_code)]
+
+macro_rules! early_return {
+    () => {
+        return ()
+    }
+}
+
+fn main() {
+    return early_return!();
+    //~^ ERROR unreachable expression
+}
diff --git a/src/test/ui/reachable/expr_return_in_macro.stderr b/src/test/ui/reachable/expr_return_in_macro.stderr
new file mode 100644
index 0000000000000..ff3abb5551f92
--- /dev/null
+++ b/src/test/ui/reachable/expr_return_in_macro.stderr
@@ -0,0 +1,22 @@
+error: unreachable expression
+  --> $DIR/expr_return_in_macro.rs:13:5
+   |
+LL |     return early_return!();
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/expr_return_in_macro.rs:4:9
+   |
+LL | #![deny(unreachable_code)]
+   |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_return_in_macro.rs:8:9
+   |
+LL |         return ()
+   |         ^^^^^^^^^
+...
+LL |     return early_return!();
+   |            --------------- in this macro invocation
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/reachable/expr_struct.stderr b/src/test/ui/reachable/expr_struct.stderr
index dcccb7a4db307..d08bcc4f0d1ae 100644
--- a/src/test/ui/reachable/expr_struct.stderr
+++ b/src/test/ui/reachable/expr_struct.stderr
@@ -9,24 +9,47 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_struct.rs:14:35
+   |
+LL |     let x = Foo { a: 22, b: 33, ..return };
+   |                                   ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_struct.rs:19:33
    |
 LL |     let x = Foo { a: return, b: 33, ..return };
    |                                 ^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_struct.rs:19:22
+   |
+LL |     let x = Foo { a: return, b: 33, ..return };
+   |                      ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_struct.rs:24:39
    |
 LL |     let x = Foo { a: 22, b: return, ..return };
    |                                       ^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_struct.rs:24:29
+   |
+LL |     let x = Foo { a: 22, b: return, ..return };
+   |                             ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_struct.rs:29:13
    |
 LL |     let x = Foo { a: 22, b: return };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_struct.rs:29:29
+   |
+LL |     let x = Foo { a: 22, b: return };
+   |                             ^^^^^^
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/reachable/expr_tup.stderr b/src/test/ui/reachable/expr_tup.stderr
index 1837031107d59..788499533db33 100644
--- a/src/test/ui/reachable/expr_tup.stderr
+++ b/src/test/ui/reachable/expr_tup.stderr
@@ -9,12 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_tup.rs:9:30
+   |
+LL |     let x: (usize, usize) = (return, 2);
+   |                              ^^^^^^
 
 error: unreachable expression
   --> $DIR/expr_tup.rs:14:29
    |
 LL |     let x: (usize, usize) = (2, return);
    |                             ^^^^^^^^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_tup.rs:14:33
+   |
+LL |     let x: (usize, usize) = (2, return);
+   |                                 ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reachable/expr_type.stderr b/src/test/ui/reachable/expr_type.stderr
index f867c89163415..15eb735da75d8 100644
--- a/src/test/ui/reachable/expr_type.stderr
+++ b/src/test/ui/reachable/expr_type.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_type.rs:9:14
+   |
+LL |     let x = {return}: !;
+   |              ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/reachable/expr_unary.stderr b/src/test/ui/reachable/expr_unary.stderr
index 61982289cdc6e..7f86519616639 100644
--- a/src/test/ui/reachable/expr_unary.stderr
+++ b/src/test/ui/reachable/expr_unary.stderr
@@ -15,6 +15,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_unary.rs:8:20
+   |
+LL |     let x: ! = ! { return; };
+   |                    ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reachable/expr_while.stderr b/src/test/ui/reachable/expr_while.stderr
index fc528926b4c97..b6d6d11ac691e 100644
--- a/src/test/ui/reachable/expr_while.stderr
+++ b/src/test/ui/reachable/expr_while.stderr
@@ -13,6 +13,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/expr_while.rs:7:12
+   |
+LL |     while {return} {
+   |            ^^^^^^
 
 error: unreachable block in `while` expression
   --> $DIR/expr_while.rs:22:20
@@ -23,6 +28,12 @@ LL | |
 LL | |         println!("I am dead.");
 LL | |     }
    | |_____^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/expr_while.rs:22:12
+   |
+LL |     while {return} {
+   |            ^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/recursion/recursive-types-are-not-uninhabited.rs b/src/test/ui/recursion/recursive-types-are-not-uninhabited.rs
index 45910c3c3a8c6..f6b317886bfad 100644
--- a/src/test/ui/recursion/recursive-types-are-not-uninhabited.rs
+++ b/src/test/ui/recursion/recursive-types-are-not-uninhabited.rs
@@ -6,7 +6,7 @@ fn foo(res: Result<u32, &R>) -> u32 {
     let Ok(x) = res;
     //~^ ERROR refutable pattern
     x
-    //~^ ERROR use of possibly uninitialized variable: `x`
+    //~^ ERROR use of possibly-uninitialized variable: `x`
 }
 
 fn main() {
diff --git a/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr b/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
index eee331d95b9bc..b9385952fafa3 100644
--- a/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
+++ b/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
@@ -4,11 +4,11 @@ error[E0005]: refutable pattern in local binding: `Err(_)` not covered
 LL |     let Ok(x) = res;
    |         ^^^^^ pattern `Err(_)` not covered
 
-error[E0381]: use of possibly uninitialized variable: `x`
+error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/recursive-types-are-not-uninhabited.rs:8:5
    |
 LL |     x
-   |     ^ use of possibly uninitialized `x`
+   |     ^ use of possibly-uninitialized `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/refutable-pattern-errors.rs b/src/test/ui/refutable-pattern-errors.rs
index aa5fa76bb8cff..d4afe17ca748c 100644
--- a/src/test/ui/refutable-pattern-errors.rs
+++ b/src/test/ui/refutable-pattern-errors.rs
@@ -1,7 +1,9 @@
+// ignore-tidy-linelength
+
 fn func((1, (Some(1), 2..=3)): (isize, (Option<isize>, isize))) { }
 //~^ ERROR refutable pattern in function argument: `(_, _)` not covered
 
 fn main() {
     let (1, (Some(1), 2..=3)) = (1, (None, 2));
-    //~^ ERROR refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` not covered
+    //~^ ERROR refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
 }
diff --git a/src/test/ui/refutable-pattern-errors.stderr b/src/test/ui/refutable-pattern-errors.stderr
index c67ae7c6d48d2..3b13e25293d58 100644
--- a/src/test/ui/refutable-pattern-errors.stderr
+++ b/src/test/ui/refutable-pattern-errors.stderr
@@ -1,14 +1,14 @@
 error[E0005]: refutable pattern in function argument: `(_, _)` not covered
-  --> $DIR/refutable-pattern-errors.rs:1:9
+  --> $DIR/refutable-pattern-errors.rs:3:9
    |
 LL | fn func((1, (Some(1), 2..=3)): (isize, (Option<isize>, isize))) { }
    |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(_, _)` not covered
 
-error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` not covered
-  --> $DIR/refutable-pattern-errors.rs:5:9
+error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
+  --> $DIR/refutable-pattern-errors.rs:7:9
    |
 LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
-   |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(std::i32::MIN..=0i32, _)` not covered
+   |         ^^^^^^^^^^^^^^^^^^^^^ patterns `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/reserved/reserved-attr-on-macro.rs b/src/test/ui/reserved/reserved-attr-on-macro.rs
index fddb991da822c..2630db0d09785 100644
--- a/src/test/ui/reserved/reserved-attr-on-macro.rs
+++ b/src/test/ui/reserved/reserved-attr-on-macro.rs
@@ -1,5 +1,5 @@
 #[rustc_attribute_should_be_reserved]
-//~^ ERROR cannot find attribute macro `rustc_attribute_should_be_reserved` in this scope
+//~^ ERROR cannot find attribute `rustc_attribute_should_be_reserved` in this scope
 //~| ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
 
 macro_rules! foo {
diff --git a/src/test/ui/reserved/reserved-attr-on-macro.stderr b/src/test/ui/reserved/reserved-attr-on-macro.stderr
index 856162b318dea..685960588a2cb 100644
--- a/src/test/ui/reserved/reserved-attr-on-macro.stderr
+++ b/src/test/ui/reserved/reserved-attr-on-macro.stderr
@@ -15,7 +15,7 @@ LL |     foo!();
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: cannot find attribute macro `rustc_attribute_should_be_reserved` in this scope
+error: cannot find attribute `rustc_attribute_should_be_reserved` in this scope
   --> $DIR/reserved-attr-on-macro.rs:1:3
    |
 LL | #[rustc_attribute_should_be_reserved]
diff --git a/src/test/ui/resolve/block-with-trait-parent.rs b/src/test/ui/resolve/block-with-trait-parent.rs
new file mode 100644
index 0000000000000..bc86f94e921cb
--- /dev/null
+++ b/src/test/ui/resolve/block-with-trait-parent.rs
@@ -0,0 +1,14 @@
+// check-pass
+
+trait Trait {
+    fn method(&self) {
+        // Items inside a block turn it into a module internally.
+        struct S;
+        impl Trait for S {}
+
+        // OK, `Trait` is in scope here from method resolution point of view.
+        S.method();
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/resolve/visibility-indeterminate.rs b/src/test/ui/resolve/visibility-indeterminate.rs
index 595eaf440c9f4..0e1142db37d2d 100644
--- a/src/test/ui/resolve/visibility-indeterminate.rs
+++ b/src/test/ui/resolve/visibility-indeterminate.rs
@@ -1,5 +1,7 @@
 // edition:2018
 
-foo!(); //~ ERROR cannot find macro `foo!` in this scope
+foo!(); //~ ERROR cannot find macro `foo` in this scope
 
 pub(in ::bar) struct Baz {} //~ ERROR cannot determine resolution for the visibility
+
+fn main() {}
diff --git a/src/test/ui/resolve/visibility-indeterminate.stderr b/src/test/ui/resolve/visibility-indeterminate.stderr
index a259c8090b35d..b9678291ee40b 100644
--- a/src/test/ui/resolve/visibility-indeterminate.stderr
+++ b/src/test/ui/resolve/visibility-indeterminate.stderr
@@ -4,16 +4,11 @@ error[E0578]: cannot determine resolution for the visibility
 LL | pub(in ::bar) struct Baz {}
    |        ^^^^^
 
-error: cannot find macro `foo!` in this scope
+error: cannot find macro `foo` in this scope
   --> $DIR/visibility-indeterminate.rs:3:1
    |
 LL | foo!();
    | ^^^
 
-error[E0601]: `main` function not found in crate `visibility_indeterminate`
-   |
-   = note: consider adding a `main` function to `$DIR/visibility-indeterminate.rs`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/bind-by-move-no-guards.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/bind-by-move-no-guards.rs
index e43c8541e6d6d..1e086160f3f34 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/bind-by-move-no-guards.rs
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/bind-by-move-no-guards.rs
@@ -4,15 +4,13 @@
 
 // run-pass
 
-#![feature(bind_by_move_pattern_guards)]
-
 use std::sync::mpsc::channel;
 
 fn main() {
     let (tx, rx) = channel();
     let x = Some(rx);
-    tx.send(false);
-    tx.send(false);
+    tx.send(false).unwrap();
+    tx.send(false).unwrap();
     match x {
         Some(z) if z.recv().unwrap() => { panic!() },
         Some(z) => { assert!(!z.recv().unwrap()); },
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2015.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2015.stderr
deleted file mode 100644
index fe1f699074735..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2015.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: compilation successful
-  --> $DIR/feature-gate.rs:36:1
-   |
-LL | / fn main() {
-LL | |     foo(107)
-LL | | }
-   | |_^
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2018.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2018.stderr
deleted file mode 100644
index fe1f699074735..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_2018.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: compilation successful
-  --> $DIR/feature-gate.rs:36:1
-   |
-LL | / fn main() {
-LL | |     foo(107)
-LL | | }
-   | |_^
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_feature_nll.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_feature_nll.stderr
deleted file mode 100644
index 34e8b0e14399e..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_feature_nll.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: compilation successful
-  --> $DIR/feature-gate.rs:41:1
-   |
-LL | / fn main() {
-LL | |     foo(107)
-LL | | }
-   | |_^
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_znll.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_znll.stderr
deleted file mode 100644
index 34e8b0e14399e..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.gate_and_znll.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: compilation successful
-  --> $DIR/feature-gate.rs:41:1
-   |
-LL | / fn main() {
-LL | |     foo(107)
-LL | | }
-   | |_^
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.no_gate.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.no_gate.stderr
deleted file mode 100644
index 7a7b1c253528f..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.no_gate.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0008]: cannot bind by-move into a pattern guard
-  --> $DIR/feature-gate.rs:28:16
-   |
-LL |         A { a: v } if *v == 42 => v,
-   |                ^ moves value into pattern guard
-   |
-   = help: add `#![feature(bind_by_move_pattern_guards)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0008`.
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.rs
deleted file mode 100644
index 69fce0bc775f7..0000000000000
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/feature-gate.rs
+++ /dev/null
@@ -1,40 +0,0 @@
-// Check that pattern-guards with move-bound variables is only allowed
-// with the appropriate set of feature gates. (Note that we require
-// the code to opt into MIR-borrowck in *some* way before the feature
-// will work; we use the revision system here to enumerate a number of
-// ways that opt-in could occur.)
-
-// gate-test-bind_by_move_pattern_guards
-
-// revisions: no_gate gate_and_2015 gate_and_2018
-
-// (We're already testing NLL behavior quite explicitly, no need for compare-mode=nll.)
-// ignore-compare-mode-nll
-
-#![feature(rustc_attrs)]
-
-#![cfg_attr(gate_and_2015, feature(bind_by_move_pattern_guards))]
-#![cfg_attr(gate_and_2018, feature(bind_by_move_pattern_guards))]
-
-//[gate_and_2015] edition:2015
-//[gate_and_2018] edition:2018
-
-struct A { a: Box<i32> }
-
-fn foo(n: i32) {
-    let x = A { a: Box::new(n) };
-    let _y = match x {
-
-        A { a: v } if *v == 42 => v,
-        //[no_gate]~^ ERROR cannot bind by-move into a pattern guard
-
-        _ => Box::new(0)
-    };
-}
-
-#[rustc_error]
-fn main() {
-    foo(107)
-}
-//[gate_and_2015]~^^^ ERROR compilation successful
-//[gate_and_2018]~^^^^ ERROR compilation successful
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/former-E0008-now-pass.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/former-E0008-now-pass.rs
new file mode 100644
index 0000000000000..3161d6fbbe647
--- /dev/null
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/former-E0008-now-pass.rs
@@ -0,0 +1,11 @@
+// This test used to emit E0008 but now passed since `bind_by_move_pattern_guards`
+// have been stabilized.
+
+// check-pass
+
+fn main() {
+    match Some("hi".to_string()) {
+        Some(s) if s.len() == 0 => {},
+        _ => {},
+    }
+}
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-basic-examples.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-basic-examples.rs
index eccb4e417b694..b716fc870e071 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-basic-examples.rs
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-basic-examples.rs
@@ -1,5 +1,3 @@
-#![feature(bind_by_move_pattern_guards)]
-
 // run-pass
 
 struct A { a: Box<i32> }
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.rs
index 602a8e15cb180..d1f685f3e7a6d 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.rs
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.rs
@@ -1,5 +1,3 @@
-#![feature(bind_by_move_pattern_guards)]
-
 enum VecWrapper { A(Vec<i32>) }
 
 fn foo(x: VecWrapper) -> usize {
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.stderr
index c9e8fc8ee532b..7becd013249d4 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.stderr
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-across-arms.stderr
@@ -1,5 +1,5 @@
 error[E0507]: cannot move out of `v` in pattern guard
-  --> $DIR/rfc-reject-double-move-across-arms.rs:7:36
+  --> $DIR/rfc-reject-double-move-across-arms.rs:5:36
    |
 LL |         VecWrapper::A(v) if { drop(v); false } => 1,
    |                                    ^ move occurs because `v` has type `std::vec::Vec<i32>`, which does not implement the `Copy` trait
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.rs b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.rs
index 77252a1ce1569..571f51c900120 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.rs
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.rs
@@ -1,5 +1,3 @@
-#![feature(bind_by_move_pattern_guards)]
-
 struct A { a: Box<i32> }
 
 fn foo(n: i32) {
diff --git a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.stderr b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.stderr
index a345022cee7c5..b93e72190680d 100644
--- a/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.stderr
+++ b/src/test/ui/rfc-0107-bind-by-move-pattern-guards/rfc-reject-double-move-in-first-arm.stderr
@@ -1,5 +1,5 @@
 error[E0507]: cannot move out of `v` in pattern guard
-  --> $DIR/rfc-reject-double-move-in-first-arm.rs:8:30
+  --> $DIR/rfc-reject-double-move-in-first-arm.rs:6:30
    |
 LL |         A { a: v } if { drop(v); true } => v,
    |                              ^ move occurs because `v` has type `std::boxed::Box<i32>`, which does not implement the `Copy` trait
diff --git a/src/test/ui/rfc-2008-non-exhaustive/variants_same_crate.rs b/src/test/ui/rfc-2008-non-exhaustive/variants_same_crate.rs
index 470a5ea9833ad..fe7df44590b8d 100644
--- a/src/test/ui/rfc-2008-non-exhaustive/variants_same_crate.rs
+++ b/src/test/ui/rfc-2008-non-exhaustive/variants_same_crate.rs
@@ -10,11 +10,11 @@ pub enum NonExhaustiveVariants {
 
 fn main() {
     let variant_tuple = NonExhaustiveVariants::Tuple(340);
-    let variant_struct = NonExhaustiveVariants::Struct { field: 340 };
+    let _variant_struct = NonExhaustiveVariants::Struct { field: 340 };
 
     match variant_tuple {
         NonExhaustiveVariants::Unit => "",
-        NonExhaustiveVariants::Tuple(fe_tpl) => "",
-        NonExhaustiveVariants::Struct { field } => ""
+        NonExhaustiveVariants::Tuple(_fe_tpl) => "",
+        NonExhaustiveVariants::Struct { field: _ } => ""
     };
 }
diff --git a/src/test/ui/rfc-2497-if-let-chains/protect-precedences.rs b/src/test/ui/rfc-2497-if-let-chains/protect-precedences.rs
index 1de4e5bcebee9..b95105b59eddb 100644
--- a/src/test/ui/rfc-2497-if-let-chains/protect-precedences.rs
+++ b/src/test/ui/rfc-2497-if-let-chains/protect-precedences.rs
@@ -2,8 +2,6 @@
 
 #![allow(irrefutable_let_patterns)]
 
-use std::ops::Range;
-
 fn main() {
     let x: bool;
     // This should associate as: `(x = (true && false));`.
diff --git a/src/test/ui/rfc-2497-if-let-chains/protect-precedences.stderr b/src/test/ui/rfc-2497-if-let-chains/protect-precedences.stderr
new file mode 100644
index 0000000000000..ca98a3947146e
--- /dev/null
+++ b/src/test/ui/rfc-2497-if-let-chains/protect-precedences.stderr
@@ -0,0 +1,13 @@
+warning: unreachable block in `if` expression
+  --> $DIR/protect-precedences.rs:13:41
+   |
+LL |         if let _ = return true && false {};
+   |                                         ^^
+   |
+   = note: `#[warn(unreachable_code)]` on by default
+note: any code following this expression is unreachable
+  --> $DIR/protect-precedences.rs:13:20
+   |
+LL |         if let _ = return true && false {};
+   |                    ^^^^^^^^^^^^^^^^^^^^
+
diff --git a/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs b/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs
index b957c673a41f1..a8fe5d6c1f60e 100644
--- a/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs
+++ b/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs
@@ -5,7 +5,7 @@ extern "C" {
         /// Foo
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: i32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
@@ -21,7 +21,7 @@ type FnType = fn(
     /// Foo
     //~^ ERROR documentation comments cannot be applied to function
     #[test] a: u32,
-    //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+    //~^ ERROR expected an inert attribute, found an attribute macro
     /// Bar
     //~^ ERROR documentation comments cannot be applied to function
     #[must_use]
@@ -36,7 +36,7 @@ pub fn foo(
     /// Foo
     //~^ ERROR documentation comments cannot be applied to function
     #[test] a: u32,
-    //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+    //~^ ERROR expected an inert attribute, found an attribute macro
     /// Bar
     //~^ ERROR documentation comments cannot be applied to function
     #[must_use]
@@ -56,7 +56,7 @@ impl SelfStruct {
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: i32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Baz
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
@@ -77,7 +77,7 @@ impl RefStruct {
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: i32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Baz
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
@@ -96,7 +96,7 @@ trait RefTrait {
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: i32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Baz
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
@@ -115,7 +115,7 @@ impl RefTrait for RefStruct {
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: i32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Baz
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
@@ -132,7 +132,7 @@ fn main() {
         /// Foo
         //~^ ERROR documentation comments cannot be applied to function
         #[test] a: u32,
-        //~^ ERROR the attribute `test` is currently unknown to the compiler and may have
+        //~^ ERROR expected an inert attribute, found an attribute macro
         /// Bar
         //~^ ERROR documentation comments cannot be applied to function
         #[must_use]
diff --git a/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.stderr b/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.stderr
index a57572abb3513..8ab3fc39a0ccb 100644
--- a/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.stderr
+++ b/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.stderr
@@ -1,3 +1,51 @@
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:7:9
+   |
+LL |         #[test] a: i32,
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:23:5
+   |
+LL |     #[test] a: u32,
+   |     ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:38:5
+   |
+LL |     #[test] a: u32,
+   |     ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:58:9
+   |
+LL |         #[test] a: i32,
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:79:9
+   |
+LL |         #[test] a: i32,
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:98:9
+   |
+LL |         #[test] a: i32,
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:117:9
+   |
+LL |         #[test] a: i32,
+   |         ^^^^^^^
+
+error: expected an inert attribute, found an attribute macro
+  --> $DIR/param-attrs-builtin-attrs.rs:134:9
+   |
+LL |         #[test] a: u32,
+   |         ^^^^^^^
+
 error: documentation comments cannot be applied to function parameters
   --> $DIR/param-attrs-builtin-attrs.rs:5:9
    |
@@ -262,78 +310,5 @@ error: allow, cfg, cfg_attr, deny, forbid, and warn are the only allowed built-i
 LL |         #[no_mangle] b: i32
    |         ^^^^^^^^^^^^
 
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:7:9
-   |
-LL |         #[test] a: i32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:23:5
-   |
-LL |     #[test] a: u32,
-   |     ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:38:5
-   |
-LL |     #[test] a: u32,
-   |     ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:58:9
-   |
-LL |         #[test] a: i32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:79:9
-   |
-LL |         #[test] a: i32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:98:9
-   |
-LL |         #[test] a: i32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:117:9
-   |
-LL |         #[test] a: i32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error[E0658]: the attribute `test` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/param-attrs-builtin-attrs.rs:134:9
-   |
-LL |         #[test] a: u32,
-   |         ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
 error: aborting due to 52 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.rs b/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.rs
index 8defa26e48d8d..7f00308925442 100644
--- a/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.rs
+++ b/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.rs
@@ -9,52 +9,52 @@ use ident_mac::id;
 struct W(u8);
 
 extern "C" { fn ffi(#[id] arg1: i32, #[id] ...); }
-//~^ ERROR the attribute `id` is currently unknown to the compiler
-//~| ERROR the attribute `id` is currently unknown to the compiler
+//~^ ERROR expected an inert attribute, found an attribute macro
+//~| ERROR expected an inert attribute, found an attribute macro
 
 unsafe extern "C" fn cvar(arg1: i32, #[id] mut args: ...) {}
-//~^ ERROR the attribute `id` is currently unknown to the compiler
+//~^ ERROR expected an inert attribute, found an attribute macro
 
 type Alias = extern "C" fn(#[id] u8, #[id] ...);
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
 
 fn free(#[id] arg1: u8) {
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
     let lam = |#[id] W(x), #[id] y| ();
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
 }
 
 impl W {
     fn inherent1(#[id] self, #[id] arg1: u8) {}
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn inherent2(#[id] &self, #[id] arg1: u8) {}
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn inherent3<'a>(#[id] &'a mut self, #[id] arg1: u8) {}
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn inherent4<'a>(#[id] self: Box<Self>, #[id] arg1: u8) {}
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
 }
 
 trait A {
     fn trait1(#[id] self, #[id] arg1: u8);
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn trait2(#[id] &self, #[id] arg1: u8);
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn trait3<'a>(#[id] &'a mut self, #[id] arg1: u8);
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
     fn trait4<'a>(#[id] self: Box<Self>, #[id] arg1: u8, #[id] Vec<u8>);
-    //~^ ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
-    //~| ERROR the attribute `id` is currently unknown to the compiler
+    //~^ ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
+    //~| ERROR expected an inert attribute, found an attribute macro
 }
 
 fn main() {}
diff --git a/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.stderr b/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.stderr
index 69b9a46b3d502..3b72e8ab4bdf9 100644
--- a/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.stderr
+++ b/src/test/ui/rfc-2565-param-attrs/proc-macro-cannot-be-used.stderr
@@ -1,228 +1,152 @@
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:11:21
    |
 LL | extern "C" { fn ffi(#[id] arg1: i32, #[id] ...); }
    |                     ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:11:38
    |
 LL | extern "C" { fn ffi(#[id] arg1: i32, #[id] ...); }
    |                                      ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:15:38
    |
 LL | unsafe extern "C" fn cvar(arg1: i32, #[id] mut args: ...) {}
    |                                      ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:18:28
    |
 LL | type Alias = extern "C" fn(#[id] u8, #[id] ...);
    |                            ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:18:38
    |
 LL | type Alias = extern "C" fn(#[id] u8, #[id] ...);
    |                                      ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:22:9
    |
 LL | fn free(#[id] arg1: u8) {
    |         ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:24:16
    |
 LL |     let lam = |#[id] W(x), #[id] y| ();
    |                ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:24:28
    |
 LL |     let lam = |#[id] W(x), #[id] y| ();
    |                            ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:30:18
    |
 LL |     fn inherent1(#[id] self, #[id] arg1: u8) {}
    |                  ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:30:30
    |
 LL |     fn inherent1(#[id] self, #[id] arg1: u8) {}
    |                              ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:33:18
    |
 LL |     fn inherent2(#[id] &self, #[id] arg1: u8) {}
    |                  ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:33:31
    |
 LL |     fn inherent2(#[id] &self, #[id] arg1: u8) {}
    |                               ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:36:22
    |
 LL |     fn inherent3<'a>(#[id] &'a mut self, #[id] arg1: u8) {}
    |                      ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:36:42
    |
 LL |     fn inherent3<'a>(#[id] &'a mut self, #[id] arg1: u8) {}
    |                                          ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:39:22
    |
 LL |     fn inherent4<'a>(#[id] self: Box<Self>, #[id] arg1: u8) {}
    |                      ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:39:45
    |
 LL |     fn inherent4<'a>(#[id] self: Box<Self>, #[id] arg1: u8) {}
    |                                             ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:45:15
    |
 LL |     fn trait1(#[id] self, #[id] arg1: u8);
    |               ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:45:27
    |
 LL |     fn trait1(#[id] self, #[id] arg1: u8);
    |                           ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:48:15
    |
 LL |     fn trait2(#[id] &self, #[id] arg1: u8);
    |               ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:48:28
    |
 LL |     fn trait2(#[id] &self, #[id] arg1: u8);
    |                            ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:51:19
    |
 LL |     fn trait3<'a>(#[id] &'a mut self, #[id] arg1: u8);
    |                   ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:51:39
    |
 LL |     fn trait3<'a>(#[id] &'a mut self, #[id] arg1: u8);
    |                                       ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:54:19
    |
 LL |     fn trait4<'a>(#[id] self: Box<Self>, #[id] arg1: u8, #[id] Vec<u8>);
    |                   ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:54:42
    |
 LL |     fn trait4<'a>(#[id] self: Box<Self>, #[id] arg1: u8, #[id] Vec<u8>);
    |                                          ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: the attribute `id` is currently unknown to the compiler and may have meaning added to it in the future
+error: expected an inert attribute, found an attribute macro
   --> $DIR/proc-macro-cannot-be-used.rs:54:58
    |
 LL |     fn trait4<'a>(#[id] self: Box<Self>, #[id] arg1: u8, #[id] Vec<u8>);
    |                                                          ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 25 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/rfc1445/fn-ptr-is-structurally-matchable.rs b/src/test/ui/rfc1445/fn-ptr-is-structurally-matchable.rs
new file mode 100644
index 0000000000000..5b378fb2a5928
--- /dev/null
+++ b/src/test/ui/rfc1445/fn-ptr-is-structurally-matchable.rs
@@ -0,0 +1,135 @@
+// run-pass
+
+// This file checks that fn ptrs are considered structurally matchable.
+// See also rust-lang/rust#63479.
+
+fn main() {
+    let mut count = 0;
+
+    // A type which is not structurally matchable:
+    struct NotSM;
+
+    // And one that is:
+    #[derive(PartialEq, Eq)]
+    struct SM;
+
+    fn trivial() {}
+
+    fn sm_to(_: SM) {}
+    fn not_sm_to(_: NotSM) {}
+    fn to_sm() -> SM { SM }
+    fn to_not_sm() -> NotSM { NotSM }
+
+    // To recreate the scenario of interest in #63479, we need to add
+    // a ref-level-of-indirection so that we descend into the type.
+
+    fn r_sm_to(_: &SM) {}
+    fn r_not_sm_to(_: &NotSM) {}
+    fn r_to_r_sm(_: &()) -> &SM { &SM }
+    fn r_to_r_not_sm(_: &()) -> &NotSM { &NotSM }
+
+    #[derive(PartialEq, Eq)]
+    struct Wrap<T>(T);
+
+    // In the code below, we put the match input into a local so that
+    // we can assign it an explicit type that is an fn ptr instead of
+    // a singleton type of the fn itself that the type inference would
+    // otherwise assign.
+
+    // Check that fn() is #[structural_match]
+    const CFN1: Wrap<fn()> = Wrap(trivial);
+    let input: Wrap<fn()> = Wrap(trivial);
+    match Wrap(input) {
+        Wrap(CFN1) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn(T) is #[structural_match] when T is too.
+    const CFN2: Wrap<fn(SM)> = Wrap(sm_to);
+    let input: Wrap<fn(SM)> = Wrap(sm_to);
+    match Wrap(input) {
+        Wrap(CFN2) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn() -> T is #[structural_match] when T is too.
+    const CFN3: Wrap<fn() -> SM> = Wrap(to_sm);
+    let input: Wrap<fn() -> SM> = Wrap(to_sm);
+    match Wrap(input) {
+        Wrap(CFN3) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn(T) is #[structural_match] even if T is not.
+    const CFN4: Wrap<fn(NotSM)> = Wrap(not_sm_to);
+    let input: Wrap<fn(NotSM)> = Wrap(not_sm_to);
+    match Wrap(input) {
+        Wrap(CFN4) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn() -> T is #[structural_match] even if T is not.
+    const CFN5: Wrap<fn() -> NotSM> = Wrap(to_not_sm);
+    let input: Wrap<fn() -> NotSM> = Wrap(to_not_sm);
+    match Wrap(input) {
+        Wrap(CFN5) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn(&T) is #[structural_match] when T is too.
+    const CFN6: Wrap<fn(&SM)> = Wrap(r_sm_to);
+    let input: Wrap<fn(&SM)> = Wrap(r_sm_to);
+    match Wrap(input) {
+        Wrap(CFN6) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn() -> &T is #[structural_match] when T is too.
+    const CFN7: Wrap<fn(&()) -> &SM> = Wrap(r_to_r_sm);
+    let input: Wrap<fn(&()) -> &SM> = Wrap(r_to_r_sm);
+    match Wrap(input) {
+        Wrap(CFN7) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn(T) is #[structural_match] even if T is not.
+    const CFN8: Wrap<fn(&NotSM)> = Wrap(r_not_sm_to);
+    let input: Wrap<fn(&NotSM)> = Wrap(r_not_sm_to);
+    match Wrap(input) {
+        Wrap(CFN8) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that fn() -> T is #[structural_match] even if T is not.
+    const CFN9: Wrap<fn(&()) -> &NotSM> = Wrap(r_to_r_not_sm);
+    let input: Wrap<fn(&()) -> &NotSM> = Wrap(r_to_r_not_sm);
+    match Wrap(input) {
+        Wrap(CFN9) => count += 1,
+        Wrap(_) => {}
+    };
+
+    // Check that a type which has fn ptrs is `#[structural_match]`.
+    #[derive(PartialEq, Eq)]
+    struct Foo {
+        alpha: fn(NotSM),
+        beta: fn() -> NotSM,
+        gamma: fn(SM),
+        delta: fn() -> SM,
+    }
+
+    const CFOO: Foo = Foo {
+        alpha: not_sm_to,
+        beta: to_not_sm,
+        gamma: sm_to,
+        delta: to_sm,
+    };
+
+    let input = Foo { alpha: not_sm_to, beta: to_not_sm, gamma: sm_to, delta: to_sm };
+    match input {
+        CFOO => count += 1,
+        Foo { .. } => {}
+    };
+
+    // Final count must be 10 now if all
+    assert_eq!(count, 10);
+}
diff --git a/src/test/ui/rfc1445/issue-63479-match-fnptr.rs b/src/test/ui/rfc1445/issue-63479-match-fnptr.rs
new file mode 100644
index 0000000000000..b3c91cec580bf
--- /dev/null
+++ b/src/test/ui/rfc1445/issue-63479-match-fnptr.rs
@@ -0,0 +1,36 @@
+// run-pass
+
+// The actual regression test from #63479. (Including this because my
+// first draft at fn-ptr-is-structurally-matchable.rs failed to actually
+// cover the case this hit; I've since expanded it accordingly, but the
+// experience left me wary of leaving this regression test out.)
+
+#[derive(Eq)]
+struct A {
+  a: i64
+}
+
+impl PartialEq for A {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.a.eq(&other.a)
+    }
+}
+
+type Fn = fn(&[A]);
+
+fn my_fn(_args: &[A]) {
+  println!("hello world");
+}
+
+const TEST: Fn = my_fn;
+
+struct B(Fn);
+
+fn main() {
+  let s = B(my_fn);
+  match s {
+    B(TEST) => println!("matched"),
+    _ => panic!("didn't match")
+  };
+}
diff --git a/src/test/ui/rust-2018/trait-import-suggestions.stderr b/src/test/ui/rust-2018/trait-import-suggestions.stderr
index a81181228dfda..19f758fd8da77 100644
--- a/src/test/ui/rust-2018/trait-import-suggestions.stderr
+++ b/src/test/ui/rust-2018/trait-import-suggestions.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `foobar` found for type `u32` in the current scope
   --> $DIR/trait-import-suggestions.rs:22:11
    |
 LL |         x.foobar();
-   |           ^^^^^^
+   |           ^^^^^^ method not found in `u32`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -12,7 +12,7 @@ error[E0599]: no method named `bar` found for type `u32` in the current scope
   --> $DIR/trait-import-suggestions.rs:28:7
    |
 LL |     x.bar();
-   |       ^^^
+   |       ^^^ method not found in `u32`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
@@ -24,7 +24,7 @@ error[E0599]: no method named `baz` found for type `u32` in the current scope
   --> $DIR/trait-import-suggestions.rs:29:7
    |
 LL |     x.baz();
-   |       ^^^
+   |       ^^^ method not found in `u32`
 
 error[E0599]: no function or associated item named `from_str` found for type `u32` in the current scope
   --> $DIR/trait-import-suggestions.rs:30:18
diff --git a/src/test/ui/rust-2018/uniform-paths/deadlock.rs b/src/test/ui/rust-2018/uniform-paths/deadlock.rs
index 3228d799083fb..83ed70a0459a8 100644
--- a/src/test/ui/rust-2018/uniform-paths/deadlock.rs
+++ b/src/test/ui/rust-2018/uniform-paths/deadlock.rs
@@ -1,7 +1,7 @@
 // edition:2018
 // compile-flags:--extern foo --extern bar
 
-use foo::bar; //~ ERROR unresolved import
+use foo::bar; //~ ERROR can't find crate for `foo`
 use bar::foo;
 
 fn main() {}
diff --git a/src/test/ui/rust-2018/uniform-paths/deadlock.stderr b/src/test/ui/rust-2018/uniform-paths/deadlock.stderr
index b4ac15c588ebd..9336e90afb71d 100644
--- a/src/test/ui/rust-2018/uniform-paths/deadlock.stderr
+++ b/src/test/ui/rust-2018/uniform-paths/deadlock.stderr
@@ -1,9 +1,9 @@
-error[E0432]: unresolved import
+error[E0463]: can't find crate for `foo`
   --> $DIR/deadlock.rs:4:5
    |
 LL | use foo::bar;
-   |     ^^^^^^^^
+   |     ^^^ can't find crate
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0432`.
+For more information about this error, try `rustc --explain E0463`.
diff --git a/src/test/ui/save-analysis/issue-63663.rs b/src/test/ui/save-analysis/issue-63663.rs
new file mode 100644
index 0000000000000..92e85884f664d
--- /dev/null
+++ b/src/test/ui/save-analysis/issue-63663.rs
@@ -0,0 +1,28 @@
+// check-pass
+// compile-flags: -Zsave-analysis
+
+pub trait Trait {
+    type Assoc;
+}
+
+pub struct A;
+
+trait Generic<T> {}
+impl<T> Generic<T> for () {}
+
+// Don't ICE when resolving type paths in return type `impl Trait`
+fn assoc_in_opaque_type_bounds<U: Trait>() -> impl Generic<U::Assoc> {}
+
+// Check that this doesn't ICE when processing associated const in formal
+// argument and return type of functions defined inside function/method scope.
+pub fn func() {
+    fn _inner1<U: Trait>(_: U::Assoc) {}
+    fn _inner2<U: Trait>() -> U::Assoc { unimplemented!() }
+
+    impl A {
+        fn _inner1<U: Trait>(self, _: U::Assoc) {}
+        fn _inner2<U: Trait>(self) -> U::Assoc { unimplemented!() }
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-method.stderr b/src/test/ui/self/point-at-arbitrary-self-type-method.stderr
index 06dad7caa6735..dec5809f1539b 100644
--- a/src/test/ui/self/point-at-arbitrary-self-type-method.stderr
+++ b/src/test/ui/self/point-at-arbitrary-self-type-method.stderr
@@ -8,7 +8,7 @@ LL |     fn foo(self: Box<Self>) {}
    |        --- the method is available for `std::boxed::Box<A>` here
 ...
 LL |     A.foo();
-   |       ^^^
+   |       ^^^ method not found in `A`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr
index 90cd3b8074580..e93c4da9dfc85 100644
--- a/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr
+++ b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr
@@ -7,7 +7,7 @@ LL | struct A;
    | --------- method `foo` not found for this
 ...
 LL |     A.foo()
-   |       ^^^
+   |       ^^^ method not found in `A`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `foo`, perhaps you need to implement it:
diff --git a/src/test/ui/self/self_type_keyword.rs b/src/test/ui/self/self_type_keyword.rs
index 844f13c2f896a..dfb7d6583d9dd 100644
--- a/src/test/ui/self/self_type_keyword.rs
+++ b/src/test/ui/self/self_type_keyword.rs
@@ -19,7 +19,7 @@ pub fn main() {
         ref mut Self => (),
         //~^ ERROR expected identifier, found keyword `Self`
         Self!() => (),
-        //~^ ERROR cannot find macro `Self!` in this scope
+        //~^ ERROR cannot find macro `Self` in this scope
         Foo { Self } => (),
         //~^ ERROR expected identifier, found keyword `Self`
     }
diff --git a/src/test/ui/self/self_type_keyword.stderr b/src/test/ui/self/self_type_keyword.stderr
index bb631194bf3df..11b3b012c5f5e 100644
--- a/src/test/ui/self/self_type_keyword.stderr
+++ b/src/test/ui/self/self_type_keyword.stderr
@@ -54,7 +54,7 @@ error: lifetimes cannot use keyword names
 LL | struct Bar<'Self>;
    |            ^^^^^
 
-error: cannot find macro `Self!` in this scope
+error: cannot find macro `Self` in this scope
   --> $DIR/self_type_keyword.rs:21:9
    |
 LL |         Self!() => (),
diff --git a/src/test/ui/shadowed/shadowed-trait-methods.stderr b/src/test/ui/shadowed/shadowed-trait-methods.stderr
index e05da17983f83..190159ec7b88d 100644
--- a/src/test/ui/shadowed/shadowed-trait-methods.stderr
+++ b/src/test/ui/shadowed/shadowed-trait-methods.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `f` found for type `()` in the current scope
   --> $DIR/shadowed-trait-methods.rs:13:8
    |
 LL |     ().f()
-   |        ^
+   |        ^ method not found in `()`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/shadowed/shadowing-in-the-same-pattern.stderr b/src/test/ui/shadowed/shadowing-in-the-same-pattern.stderr
index 71197efcaba54..1c51653db6abf 100644
--- a/src/test/ui/shadowed/shadowing-in-the-same-pattern.stderr
+++ b/src/test/ui/shadowed/shadowing-in-the-same-pattern.stderr
@@ -1,8 +1,8 @@
-error[E0416]: identifier `a` is bound more than once in the same pattern
+error[E0415]: identifier `a` is bound more than once in this parameter list
   --> $DIR/shadowing-in-the-same-pattern.rs:3:10
    |
 LL | fn f((a, a): (isize, isize)) {}
-   |          ^ used in a pattern more than once
+   |          ^ used as parameter more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
   --> $DIR/shadowing-in-the-same-pattern.rs:6:13
@@ -12,4 +12,5 @@ LL |     let (a, a) = (1, 1);
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0416`.
+Some errors have detailed explanations: E0415, E0416.
+For more information about an error, try `rustc --explain E0415`.
diff --git a/src/test/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr b/src/test/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr
index c14fc04f631fc..bbfe4c3d59dcf 100644
--- a/src/test/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr
+++ b/src/test/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr
@@ -5,7 +5,7 @@ LL | struct MyStruct;
    | ---------------- method `foo_one` not found for this
 ...
 LL |     println!("{}", MyStruct.foo_one());
-   |                             ^^^^^^^
+   |                             ^^^^^^^ method not found in `MyStruct`
    |
    = note: the method `foo_one` exists but the following trait bounds were not satisfied:
            `MyStruct : Foo`
diff --git a/src/test/ui/specialization/issue-52050.stderr b/src/test/ui/specialization/issue-52050.stderr
index dcb34f3ad4836..36f96b011983f 100644
--- a/src/test/ui/specialization/issue-52050.stderr
+++ b/src/test/ui/specialization/issue-52050.stderr
@@ -11,7 +11,7 @@ LL |
 LL |   impl IntoPyDictPointer for ()
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `()`
    |
-   = note: upstream crates may add new impl of trait `std::iter::Iterator` for type `()` in future versions
+   = note: upstream crates may add a new impl of trait `std::iter::Iterator` for type `()` in future versions
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/std-backtrace.rs b/src/test/ui/std-backtrace.rs
new file mode 100644
index 0000000000000..d84c493d53523
--- /dev/null
+++ b/src/test/ui/std-backtrace.rs
@@ -0,0 +1,75 @@
+// run-pass
+// ignore-android FIXME #17520
+// ignore-cloudabi spawning processes is not supported
+// ignore-emscripten spawning processes is not supported
+// ignore-openbsd no support for libbacktrace without filename
+// ignore-sgx no processes
+// ignore-msvc see #62897 and `backtrace-debuginfo.rs` test
+// compile-flags:-g
+
+#![feature(backtrace)]
+
+use std::env;
+use std::process::Command;
+use std::str;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() >= 2 && args[1] == "force" {
+        println!("{}", std::backtrace::Backtrace::force_capture());
+    } else if args.len() >= 2 {
+        println!("{}", std::backtrace::Backtrace::capture());
+    } else {
+        runtest(&args[0]);
+        println!("test ok");
+    }
+}
+
+fn runtest(me: &str) {
+    env::remove_var("RUST_BACKTRACE");
+    env::remove_var("RUST_LIB_BACKTRACE");
+
+    let p = Command::new(me).arg("a").env("RUST_BACKTRACE", "1").output().unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("stack backtrace:\n"));
+    assert!(String::from_utf8_lossy(&p.stdout).contains("backtrace::main"));
+
+    let p = Command::new(me).arg("a").env("RUST_BACKTRACE", "0").output().unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("disabled backtrace\n"));
+
+    let p = Command::new(me).arg("a").output().unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("disabled backtrace\n"));
+
+    let p = Command::new(me)
+        .arg("a")
+        .env("RUST_LIB_BACKTRACE", "1")
+        .env("RUST_BACKTRACE", "1")
+        .output()
+        .unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("stack backtrace:\n"));
+
+    let p = Command::new(me)
+        .arg("a")
+        .env("RUST_LIB_BACKTRACE", "0")
+        .env("RUST_BACKTRACE", "1")
+        .output()
+        .unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("disabled backtrace\n"));
+
+    let p = Command::new(me)
+        .arg("force")
+        .env("RUST_LIB_BACKTRACE", "0")
+        .env("RUST_BACKTRACE", "0")
+        .output()
+        .unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("stack backtrace:\n"));
+
+    let p = Command::new(me).arg("force").output().unwrap();
+    assert!(p.status.success());
+    assert!(String::from_utf8_lossy(&p.stdout).contains("stack backtrace:\n"));
+}
diff --git a/src/test/ui/str/str-idx.stderr b/src/test/ui/str/str-idx.stderr
index e388534f132d2..9f21aaaebad58 100644
--- a/src/test/ui/str/str-idx.stderr
+++ b/src/test/ui/str/str-idx.stderr
@@ -10,20 +10,20 @@ LL |     let _: u8 = s[4];
    = note: required because of the requirements on the impl of `std::ops::Index<{integer}>` for `str`
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-idx.rs:4:15
+  --> $DIR/str-idx.rs:4:19
    |
 LL |     let _ = s.get(4);
-   |               ^^^ string indices are ranges of `usize`
+   |                   ^ string indices are ranges of `usize`
    |
    = help: the trait `std::slice::SliceIndex<str>` is not implemented for `{integer}`
    = note: you can use `.chars().nth()` or `.bytes().nth()`
            see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-idx.rs:5:15
+  --> $DIR/str-idx.rs:5:29
    |
 LL |     let _ = s.get_unchecked(4);
-   |               ^^^^^^^^^^^^^ string indices are ranges of `usize`
+   |                             ^ string indices are ranges of `usize`
    |
    = help: the trait `std::slice::SliceIndex<str>` is not implemented for `{integer}`
    = note: you can use `.chars().nth()` or `.bytes().nth()`
diff --git a/src/test/ui/str/str-mut-idx.stderr b/src/test/ui/str/str-mut-idx.stderr
index 08baa478b8bfa..372077a465e4a 100644
--- a/src/test/ui/str/str-mut-idx.stderr
+++ b/src/test/ui/str/str-mut-idx.stderr
@@ -30,20 +30,20 @@ LL |     s[1usize] = bot();
    = note: required because of the requirements on the impl of `std::ops::Index<usize>` for `str`
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-mut-idx.rs:9:7
+  --> $DIR/str-mut-idx.rs:9:15
    |
 LL |     s.get_mut(1);
-   |       ^^^^^^^ string indices are ranges of `usize`
+   |               ^ string indices are ranges of `usize`
    |
    = help: the trait `std::slice::SliceIndex<str>` is not implemented for `{integer}`
    = note: you can use `.chars().nth()` or `.bytes().nth()`
            see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>
 
 error[E0277]: the type `str` cannot be indexed by `{integer}`
-  --> $DIR/str-mut-idx.rs:11:7
+  --> $DIR/str-mut-idx.rs:11:25
    |
 LL |     s.get_unchecked_mut(1);
-   |       ^^^^^^^^^^^^^^^^^ string indices are ranges of `usize`
+   |                         ^ string indices are ranges of `usize`
    |
    = help: the trait `std::slice::SliceIndex<str>` is not implemented for `{integer}`
    = note: you can use `.chars().nth()` or `.bytes().nth()`
diff --git a/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr b/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
index 3141b1b65f9ba..6bb6533899669 100644
--- a/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
+++ b/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
@@ -1,13 +1,14 @@
 error[E0277]: the trait bound `fn() -> impl std::future::Future {foo}: std::future::Future` is not satisfied
-  --> $DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:9:5
+  --> $DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:9:9
    |
 LL | fn bar(f: impl Future<Output=()>) {}
    | --------------------------------- required by `bar`
 ...
 LL |     bar(foo);
-   |     ^^^ the trait `std::future::Future` is not implemented for `fn() -> impl std::future::Future {foo}`
-   |
-   = help: use parentheses to call the function: `foo()`
+   |         ^^^
+   |         |
+   |         the trait `std::future::Future` is not implemented for `fn() -> impl std::future::Future {foo}`
+   |         help: use parentheses to call the function: `foo()`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/attribute-typos.rs b/src/test/ui/suggestions/attribute-typos.rs
index 74f63f2b0ed07..7c8231bbb24f8 100644
--- a/src/test/ui/suggestions/attribute-typos.rs
+++ b/src/test/ui/suggestions/attribute-typos.rs
@@ -1,11 +1,11 @@
-#[deprcated] //~ ERROR cannot find attribute macro `deprcated` in this scope
+#[deprcated] //~ ERROR cannot find attribute `deprcated` in this scope
 fn foo() {}
 
-#[tests] //~ ERROR cannot find attribute macro `tests` in this scope
+#[tests] //~ ERROR cannot find attribute `tests` in this scope
 fn bar() {}
 
 #[rustc_err]
-//~^ ERROR cannot find attribute macro `rustc_err` in this scope
+//~^ ERROR cannot find attribute `rustc_err` in this scope
 //~| ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
 
 fn main() {}
diff --git a/src/test/ui/suggestions/attribute-typos.stderr b/src/test/ui/suggestions/attribute-typos.stderr
index 6b2f591b9e7d9..e40329382fd40 100644
--- a/src/test/ui/suggestions/attribute-typos.stderr
+++ b/src/test/ui/suggestions/attribute-typos.stderr
@@ -7,19 +7,19 @@ LL | #[rustc_err]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error: cannot find attribute macro `rustc_err` in this scope
+error: cannot find attribute `rustc_err` in this scope
   --> $DIR/attribute-typos.rs:7:3
    |
 LL | #[rustc_err]
    |   ^^^^^^^^^ help: a built-in attribute with a similar name exists: `rustc_error`
 
-error: cannot find attribute macro `tests` in this scope
+error: cannot find attribute `tests` in this scope
   --> $DIR/attribute-typos.rs:4:3
    |
 LL | #[tests]
    |   ^^^^^ help: an attribute macro with a similar name exists: `test`
 
-error: cannot find attribute macro `deprcated` in this scope
+error: cannot find attribute `deprcated` in this scope
   --> $DIR/attribute-typos.rs:1:3
    |
 LL | #[deprcated]
diff --git a/src/test/ui/suggestions/fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr b/src/test/ui/suggestions/fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
index 2cc4653fabe2d..59726c82c2377 100644
--- a/src/test/ui/suggestions/fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
+++ b/src/test/ui/suggestions/fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
@@ -1,13 +1,14 @@
 error[E0277]: the trait bound `fn() -> impl T {foo}: T` is not satisfied
-  --> $DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:17:5
+  --> $DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:17:9
    |
 LL | fn bar(f: impl T<O=()>) {}
    | ----------------------- required by `bar`
 ...
 LL |     bar(foo);
-   |     ^^^ the trait `T` is not implemented for `fn() -> impl T {foo}`
-   |
-   = help: use parentheses to call the function: `foo()`
+   |         ^^^
+   |         |
+   |         the trait `T` is not implemented for `fn() -> impl T {foo}`
+   |         help: use parentheses to call the function: `foo()`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/impl-trait-with-missing-trait-bounds-in-arg.stderr b/src/test/ui/suggestions/impl-trait-with-missing-trait-bounds-in-arg.stderr
index 48c2503e8eb32..4aec72006eef0 100644
--- a/src/test/ui/suggestions/impl-trait-with-missing-trait-bounds-in-arg.stderr
+++ b/src/test/ui/suggestions/impl-trait-with-missing-trait-bounds-in-arg.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `hello` found for type `impl Foo` in the current s
   --> $DIR/impl-trait-with-missing-trait-bounds-in-arg.rs:15:9
    |
 LL |     foo.hello();
-   |         ^^^^^
+   |         ^^^^^ method not found in `impl Foo`
    |
    = help: items from traits can only be used if the type parameter is bounded by the trait
 help: the following trait defines an item `hello`, perhaps you need to restrict type parameter `impl Foo` with it:
diff --git a/src/test/ui/suggestions/issue-21673.stderr b/src/test/ui/suggestions/issue-21673.stderr
index 6cf71c8b7c53b..f2496f696d698 100644
--- a/src/test/ui/suggestions/issue-21673.stderr
+++ b/src/test/ui/suggestions/issue-21673.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `method` found for type `&T` in the current scope
   --> $DIR/issue-21673.rs:6:7
    |
 LL |     x.method()
-   |       ^^^^^^
+   |       ^^^^^^ method not found in `&T`
    |
    = help: items from traits can only be used if the type parameter is bounded by the trait
 help: the following trait defines an item `method`, perhaps you need to restrict type parameter `T` with it:
@@ -14,7 +14,7 @@ error[E0599]: no method named `method` found for type `T` in the current scope
   --> $DIR/issue-21673.rs:10:7
    |
 LL |     x.method()
-   |       ^^^^^^
+   |       ^^^^^^ method not found in `T`
    |
    = help: items from traits can only be used if the type parameter is bounded by the trait
 help: the following trait defines an item `method`, perhaps you need to restrict type parameter `T` with it:
diff --git a/src/test/ui/suggestions/issue-62843.stderr b/src/test/ui/suggestions/issue-62843.stderr
index cc27b5b49b67d..b5801e9162fb3 100644
--- a/src/test/ui/suggestions/issue-62843.stderr
+++ b/src/test/ui/suggestions/issue-62843.stderr
@@ -1,8 +1,8 @@
 error[E0277]: expected a `std::ops::FnMut<(char,)>` closure, found `std::string::String`
-  --> $DIR/issue-62843.rs:4:27
+  --> $DIR/issue-62843.rs:4:32
    |
 LL |     println!("{:?}", line.find(pattern));
-   |                           ^^^^ expected an `FnMut<(char,)>` closure, found `std::string::String`
+   |                                ^^^^^^^ expected an `FnMut<(char,)>` closure, found `std::string::String`
    |
    = help: the trait `std::ops::FnMut<(char,)>` is not implemented for `std::string::String`
    = note: borrowing the `std::string::String` might fix the problem
diff --git a/src/test/ui/suggestions/suggest-methods.stderr b/src/test/ui/suggestions/suggest-methods.stderr
index ad4a4deb5a886..4678410eb4859 100644
--- a/src/test/ui/suggestions/suggest-methods.stderr
+++ b/src/test/ui/suggestions/suggest-methods.stderr
@@ -23,7 +23,7 @@ error[E0599]: no method named `count_o` found for type `u32` in the current scop
   --> $DIR/suggest-methods.rs:28:19
    |
 LL |     let _ = 63u32.count_o();
-   |                   ^^^^^^^
+   |                   ^^^^^^^ method not found in `u32`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/syntax-extension-minor.rs b/src/test/ui/syntax-extension-minor.rs
index 0206a769937e4..2d6710af39270 100644
--- a/src/test/ui/syntax-extension-minor.rs
+++ b/src/test/ui/syntax-extension-minor.rs
@@ -1,3 +1,5 @@
+// run-pass
+
 #![feature(concat_idents)]
 
 pub fn main() {
@@ -5,10 +7,8 @@ pub fn main() {
     let _: concat_idents!(F, oo) = Foo; // Test that `concat_idents!` can be used in type positions
 
     let asdf_fdsa = "<.<".to_string();
-    // this now fails (correctly, I claim) because hygiene prevents
-    // the assembled identifier from being a reference to the binding.
+    // concat_idents should have call-site hygiene.
     assert!(concat_idents!(asd, f_f, dsa) == "<.<".to_string());
-    //~^ ERROR cannot find value `asdf_fdsa` in this scope
 
     assert_eq!(stringify!(use_mention_distinction), "use_mention_distinction");
 }
diff --git a/src/test/ui/syntax-extension-minor.stderr b/src/test/ui/syntax-extension-minor.stderr
deleted file mode 100644
index 2d8056da527c6..0000000000000
--- a/src/test/ui/syntax-extension-minor.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-error[E0425]: cannot find value `asdf_fdsa` in this scope
-  --> $DIR/syntax-extension-minor.rs:10:13
-   |
-LL |     assert!(concat_idents!(asd, f_f, dsa) == "<.<".to_string());
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0425`.
diff --git a/src/test/ui/test-shadowing/auxiliary/test_macro.rs b/src/test/ui/test-attrs/auxiliary/test_macro.rs
similarity index 100%
rename from src/test/ui/test-shadowing/auxiliary/test_macro.rs
rename to src/test/ui/test-attrs/auxiliary/test_macro.rs
diff --git a/src/test/ui/test-attrs/decl-macro-test.rs b/src/test/ui/test-attrs/decl-macro-test.rs
new file mode 100644
index 0000000000000..fcbe9f49e5564
--- /dev/null
+++ b/src/test/ui/test-attrs/decl-macro-test.rs
@@ -0,0 +1,22 @@
+// Check that declarative macros can declare tests
+
+// check-pass
+// compile-flags: --test
+
+#![feature(decl_macro)]
+
+macro create_test() {
+    #[test]
+    fn test() {}
+}
+
+macro create_module_test() {
+    mod x {
+        #[test]
+        fn test() {}
+    }
+}
+
+create_test!();
+create_test!();
+create_module_test!();
diff --git a/src/test/ui/inaccessible-test-modules.rs b/src/test/ui/test-attrs/inaccessible-test-modules.rs
similarity index 56%
rename from src/test/ui/inaccessible-test-modules.rs
rename to src/test/ui/test-attrs/inaccessible-test-modules.rs
index 7095ec290f8f2..f5b3479379480 100644
--- a/src/test/ui/inaccessible-test-modules.rs
+++ b/src/test/ui/test-attrs/inaccessible-test-modules.rs
@@ -2,8 +2,8 @@
 
 // the `--test` harness creates modules with these textual names, but
 // they should be inaccessible from normal code.
-use __test as x; //~ ERROR unresolved import `__test`
-use __test_reexports as y; //~ ERROR unresolved import `__test_reexports`
+use main as x; //~ ERROR unresolved import `main`
+use test as y; //~ ERROR unresolved import `test`
 
 #[test]
 fn baz() {}
diff --git a/src/test/ui/test-attrs/inaccessible-test-modules.stderr b/src/test/ui/test-attrs/inaccessible-test-modules.stderr
new file mode 100644
index 0000000000000..a94ea1e79bc51
--- /dev/null
+++ b/src/test/ui/test-attrs/inaccessible-test-modules.stderr
@@ -0,0 +1,21 @@
+error[E0432]: unresolved import `main`
+  --> $DIR/inaccessible-test-modules.rs:5:5
+   |
+LL | use main as x;
+   |     ----^^^^^
+   |     |
+   |     no `main` in the root
+   |     help: a similar name exists in the module: `main`
+
+error[E0432]: unresolved import `test`
+  --> $DIR/inaccessible-test-modules.rs:6:5
+   |
+LL | use test as y;
+   |     ----^^^^^
+   |     |
+   |     no `test` in the root
+   |     help: a similar name exists in the module: `test`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0432`.
diff --git a/src/test/ui/test-allow-fail-attr.rs b/src/test/ui/test-attrs/test-allow-fail-attr.rs
similarity index 100%
rename from src/test/ui/test-allow-fail-attr.rs
rename to src/test/ui/test-attrs/test-allow-fail-attr.rs
diff --git a/src/test/ui/test-attr-non-associated-functions.rs b/src/test/ui/test-attrs/test-attr-non-associated-functions.rs
similarity index 100%
rename from src/test/ui/test-attr-non-associated-functions.rs
rename to src/test/ui/test-attrs/test-attr-non-associated-functions.rs
diff --git a/src/test/ui/test-attr-non-associated-functions.stderr b/src/test/ui/test-attrs/test-attr-non-associated-functions.stderr
similarity index 100%
rename from src/test/ui/test-attr-non-associated-functions.stderr
rename to src/test/ui/test-attrs/test-attr-non-associated-functions.stderr
diff --git a/src/test/ui/test-shadowing/test-cant-be-shadowed.rs b/src/test/ui/test-attrs/test-cant-be-shadowed.rs
similarity index 100%
rename from src/test/ui/test-shadowing/test-cant-be-shadowed.rs
rename to src/test/ui/test-attrs/test-cant-be-shadowed.rs
diff --git a/src/test/ui/test-fn-signature-verification-for-explicit-return-type.rs b/src/test/ui/test-attrs/test-fn-signature-verification-for-explicit-return-type.rs
similarity index 100%
rename from src/test/ui/test-fn-signature-verification-for-explicit-return-type.rs
rename to src/test/ui/test-attrs/test-fn-signature-verification-for-explicit-return-type.rs
diff --git a/src/test/ui/test-main-not-dead-attr.rs b/src/test/ui/test-attrs/test-main-not-dead-attr.rs
similarity index 100%
rename from src/test/ui/test-main-not-dead-attr.rs
rename to src/test/ui/test-attrs/test-main-not-dead-attr.rs
diff --git a/src/test/ui/test-main-not-dead.rs b/src/test/ui/test-attrs/test-main-not-dead.rs
similarity index 100%
rename from src/test/ui/test-main-not-dead.rs
rename to src/test/ui/test-attrs/test-main-not-dead.rs
diff --git a/src/test/ui/test-on-macro.rs b/src/test/ui/test-attrs/test-on-macro.rs
similarity index 100%
rename from src/test/ui/test-on-macro.rs
rename to src/test/ui/test-attrs/test-on-macro.rs
diff --git a/src/test/ui/test-on-macro.stderr b/src/test/ui/test-attrs/test-on-macro.stderr
similarity index 100%
rename from src/test/ui/test-on-macro.stderr
rename to src/test/ui/test-attrs/test-on-macro.stderr
diff --git a/src/test/ui/test-runner-hides-buried-main.rs b/src/test/ui/test-attrs/test-runner-hides-buried-main.rs
similarity index 100%
rename from src/test/ui/test-runner-hides-buried-main.rs
rename to src/test/ui/test-attrs/test-runner-hides-buried-main.rs
diff --git a/src/test/ui/test-runner-hides-main.rs b/src/test/ui/test-attrs/test-runner-hides-main.rs
similarity index 100%
rename from src/test/ui/test-runner-hides-main.rs
rename to src/test/ui/test-attrs/test-runner-hides-main.rs
diff --git a/src/test/ui/test-runner-hides-start.rs b/src/test/ui/test-attrs/test-runner-hides-start.rs
similarity index 100%
rename from src/test/ui/test-runner-hides-start.rs
rename to src/test/ui/test-attrs/test-runner-hides-start.rs
diff --git a/src/test/ui/test-should-fail-good-message.rs b/src/test/ui/test-attrs/test-should-fail-good-message.rs
similarity index 100%
rename from src/test/ui/test-should-fail-good-message.rs
rename to src/test/ui/test-attrs/test-should-fail-good-message.rs
diff --git a/src/test/ui/test-should-panic-attr.rs b/src/test/ui/test-attrs/test-should-panic-attr.rs
similarity index 100%
rename from src/test/ui/test-should-panic-attr.rs
rename to src/test/ui/test-attrs/test-should-panic-attr.rs
diff --git a/src/test/ui/test-should-panic-attr.stderr b/src/test/ui/test-attrs/test-should-panic-attr.stderr
similarity index 100%
rename from src/test/ui/test-should-panic-attr.stderr
rename to src/test/ui/test-attrs/test-should-panic-attr.stderr
diff --git a/src/test/ui/test-vs-cfg-test.rs b/src/test/ui/test-attrs/test-vs-cfg-test.rs
similarity index 100%
rename from src/test/ui/test-vs-cfg-test.rs
rename to src/test/ui/test-attrs/test-vs-cfg-test.rs
diff --git a/src/test/ui/test-warns-dead-code.rs b/src/test/ui/test-attrs/test-warns-dead-code.rs
similarity index 100%
rename from src/test/ui/test-warns-dead-code.rs
rename to src/test/ui/test-attrs/test-warns-dead-code.rs
diff --git a/src/test/ui/test-warns-dead-code.stderr b/src/test/ui/test-attrs/test-warns-dead-code.stderr
similarity index 100%
rename from src/test/ui/test-warns-dead-code.stderr
rename to src/test/ui/test-attrs/test-warns-dead-code.stderr
diff --git a/src/test/ui/tool-attributes/diagnostic_item.rs b/src/test/ui/tool-attributes/diagnostic_item.rs
index 1d35422ed6241..26a52ce60cfd8 100644
--- a/src/test/ui/tool-attributes/diagnostic_item.rs
+++ b/src/test/ui/tool-attributes/diagnostic_item.rs
@@ -1,2 +1,3 @@
 #[rustc_diagnostic_item = "foomp"] //~ ERROR compiler internal support for linting
 struct Foomp;
+fn main() {}
diff --git a/src/test/ui/tool-attributes/diagnostic_item.stderr b/src/test/ui/tool-attributes/diagnostic_item.stderr
index deff4da6b8052..5432f8dea8606 100644
--- a/src/test/ui/tool-attributes/diagnostic_item.stderr
+++ b/src/test/ui/tool-attributes/diagnostic_item.stderr
@@ -7,11 +7,6 @@ LL | #[rustc_diagnostic_item = "foomp"]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0601]: `main` function not found in crate `diagnostic_item`
-   |
-   = note: consider adding a `main` function to `$DIR/diagnostic_item.rs`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0601, E0658.
-For more information about an error, try `rustc --explain E0601`.
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
index 8c62b34bd9ea5..d5698be8d4c57 100644
--- a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
+++ b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
@@ -4,14 +4,14 @@ type B = rustfmt::skip; //~ ERROR expected type, found tool attribute `rustfmt::
 #[derive(rustfmt)] //~ ERROR cannot find derive macro `rustfmt` in this scope
 struct S;
 
-// Interpreted as a feature gated custom attribute
-#[rustfmt] //~ ERROR cannot find attribute macro `rustfmt` in this scope
+// Interpreted as an unstable custom attribute
+#[rustfmt] //~ ERROR cannot find attribute `rustfmt` in this scope
 fn check() {}
 
 #[rustfmt::skip] // OK
 fn main() {
     rustfmt; //~ ERROR expected value, found tool module `rustfmt`
-    rustfmt!(); //~ ERROR cannot find macro `rustfmt!` in this scope
+    rustfmt!(); //~ ERROR cannot find macro `rustfmt` in this scope
 
     rustfmt::skip; //~ ERROR expected value, found tool attribute `rustfmt::skip`
 }
diff --git a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
index 33581a170822b..6bef793e0e71b 100644
--- a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
+++ b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
@@ -4,13 +4,13 @@ error: cannot find derive macro `rustfmt` in this scope
 LL | #[derive(rustfmt)]
    |          ^^^^^^^
 
-error: cannot find attribute macro `rustfmt` in this scope
+error: cannot find attribute `rustfmt` in this scope
   --> $DIR/tool-attributes-misplaced-1.rs:8:3
    |
 LL | #[rustfmt]
    |   ^^^^^^^
 
-error: cannot find macro `rustfmt!` in this scope
+error: cannot find macro `rustfmt` in this scope
   --> $DIR/tool-attributes-misplaced-1.rs:14:5
    |
 LL |     rustfmt!();
diff --git a/src/test/ui/traits/trait-alias/trait-alias-object-wf.rs b/src/test/ui/traits/trait-alias/trait-alias-object-wf.rs
index fb26b7e2df7cb..1440f02df1df8 100644
--- a/src/test/ui/traits/trait-alias/trait-alias-object-wf.rs
+++ b/src/test/ui/traits/trait-alias/trait-alias-object-wf.rs
@@ -1,4 +1,4 @@
-// run-pass
+// check-pass
 
 // This test checks that trait objects involving trait aliases are well-formed.
 
diff --git a/src/test/ui/traits/trait-impl-1.stderr b/src/test/ui/traits/trait-impl-1.stderr
index 71d5cc26bf141..0d61c3ed00d90 100644
--- a/src/test/ui/traits/trait-impl-1.stderr
+++ b/src/test/ui/traits/trait-impl-1.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `foo` found for type `&i32` in the current scope
   --> $DIR/trait-impl-1.rs:15:7
    |
 LL |     x.foo();
-   |       ^^^
+   |       ^^^ method not found in `&i32`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/traits/trait-item-privacy.stderr b/src/test/ui/traits/trait-item-privacy.stderr
index 16ea7bdb0807d..39cc66d275c24 100644
--- a/src/test/ui/traits/trait-item-privacy.stderr
+++ b/src/test/ui/traits/trait-item-privacy.stderr
@@ -5,7 +5,7 @@ LL | struct S;
    | --------- method `a` not found for this
 ...
 LL |     S.a();
-   |       ^
+   |       ^ method not found in `S`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `a`, perhaps you need to implement it:
@@ -25,7 +25,7 @@ LL |         fn b(&self) { }
    |            the method is available for `std::rc::Rc<S>` here
 ...
 LL |     S.b();
-   |       ^
+   |       ^ method not found in `S`
    |
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.stderr b/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.stderr
index 0b543616d7c9a..76d486a51e5cc 100644
--- a/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.stderr
+++ b/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.stderr
@@ -5,13 +5,13 @@ LL | auto trait Magic: Copy {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `NoClone: std::marker::Copy` is not satisfied
-  --> $DIR/traits-inductive-overflow-supertrait-oibit.rs:15:18
+  --> $DIR/traits-inductive-overflow-supertrait-oibit.rs:15:23
    |
 LL | fn copy<T: Magic>(x: T) -> (T, T) { (x, x) }
    | --------------------------------- required by `copy`
 ...
 LL |     let (a, b) = copy(NoClone);
-   |                  ^^^^ the trait `std::marker::Copy` is not implemented for `NoClone`
+   |                       ^^^^^^^ the trait `std::marker::Copy` is not implemented for `NoClone`
    |
    = note: required because of the requirements on the impl of `Magic` for `NoClone`
 
diff --git a/src/test/ui/traits/traits-negative-impls.stderr b/src/test/ui/traits/traits-negative-impls.stderr
index 23bd334a3e776..022b12d256cc3 100644
--- a/src/test/ui/traits/traits-negative-impls.stderr
+++ b/src/test/ui/traits/traits-negative-impls.stderr
@@ -1,11 +1,11 @@
 error[E0277]: `dummy::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:23:5
+  --> $DIR/traits-negative-impls.rs:23:11
    |
 LL | struct Outer<T: Send>(T);
    | ------------------------- required by `Outer`
 ...
 LL |     Outer(TestType);
-   |     ^^^^^ `dummy::TestType` cannot be sent between threads safely
+   |           ^^^^^^^^ `dummy::TestType` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `dummy::TestType`
 
@@ -21,49 +21,49 @@ LL |     Outer(TestType);
    = help: the trait `std::marker::Send` is not implemented for `dummy::TestType`
 
 error[E0277]: `dummy1b::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:32:5
+  --> $DIR/traits-negative-impls.rs:32:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    | ------------------------- required by `is_send`
 ...
 LL |     is_send(TestType);
-   |     ^^^^^^^ `dummy1b::TestType` cannot be sent between threads safely
+   |             ^^^^^^^^ `dummy1b::TestType` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `dummy1b::TestType`
 
 error[E0277]: `dummy1c::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:40:5
+  --> $DIR/traits-negative-impls.rs:40:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    | ------------------------- required by `is_send`
 ...
 LL |     is_send((8, TestType));
-   |     ^^^^^^^ `dummy1c::TestType` cannot be sent between threads safely
+   |             ^^^^^^^^^^^^^ `dummy1c::TestType` cannot be sent between threads safely
    |
    = help: within `({integer}, dummy1c::TestType)`, the trait `std::marker::Send` is not implemented for `dummy1c::TestType`
    = note: required because it appears within the type `({integer}, dummy1c::TestType)`
 
 error[E0277]: `dummy2::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:48:5
+  --> $DIR/traits-negative-impls.rs:48:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    | ------------------------- required by `is_send`
 ...
 LL |     is_send(Box::new(TestType));
-   |     ^^^^^^^ `dummy2::TestType` cannot be sent between threads safely
+   |             ^^^^^^^^^^^^^^^^^^ `dummy2::TestType` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `dummy2::TestType`
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::ptr::Unique<dummy2::TestType>`
    = note: required because it appears within the type `std::boxed::Box<dummy2::TestType>`
 
 error[E0277]: `dummy3::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:56:5
+  --> $DIR/traits-negative-impls.rs:56:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    | ------------------------- required by `is_send`
 ...
 LL |     is_send(Box::new(Outer2(TestType)));
-   |     ^^^^^^^ `dummy3::TestType` cannot be sent between threads safely
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ `dummy3::TestType` cannot be sent between threads safely
    |
    = help: within `Outer2<dummy3::TestType>`, the trait `std::marker::Send` is not implemented for `dummy3::TestType`
    = note: required because it appears within the type `Outer2<dummy3::TestType>`
@@ -71,13 +71,13 @@ LL |     is_send(Box::new(Outer2(TestType)));
    = note: required because it appears within the type `std::boxed::Box<Outer2<dummy3::TestType>>`
 
 error[E0277]: `main::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:66:5
+  --> $DIR/traits-negative-impls.rs:66:13
    |
 LL | fn is_sync<T: Sync>(_: T) {}
    | ------------------------- required by `is_sync`
 ...
 LL |     is_sync(Outer2(TestType));
-   |     ^^^^^^^ `main::TestType` cannot be sent between threads safely
+   |             ^^^^^^^^^^^^^^^^ `main::TestType` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `main::TestType`
    = note: required because of the requirements on the impl of `std::marker::Sync` for `Outer2<main::TestType>`
diff --git a/src/test/ui/trivial-bounds/trivial-bounds-leak.stderr b/src/test/ui/trivial-bounds/trivial-bounds-leak.stderr
index f0f048159ec73..49393a8678ef8 100644
--- a/src/test/ui/trivial-bounds/trivial-bounds-leak.stderr
+++ b/src/test/ui/trivial-bounds/trivial-bounds-leak.stderr
@@ -12,26 +12,26 @@ error[E0599]: no method named `test` found for type `i32` in the current scope
   --> $DIR/trivial-bounds-leak.rs:24:10
    |
 LL |     3i32.test();
-   |          ^^^^
+   |          ^^^^ method not found in `i32`
    |
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `test`, perhaps you need to implement it:
            candidate #1: `Foo`
 
 error[E0277]: the trait bound `i32: Foo` is not satisfied
-  --> $DIR/trivial-bounds-leak.rs:25:5
+  --> $DIR/trivial-bounds-leak.rs:25:15
    |
 LL |     fn test(&self);
    |     --------------- required by `Foo::test`
 ...
 LL |     Foo::test(&4i32);
-   |     ^^^^^^^^^ the trait `Foo` is not implemented for `i32`
+   |               ^^^^^ the trait `Foo` is not implemented for `i32`
 
 error[E0277]: the trait bound `i32: Foo` is not satisfied
-  --> $DIR/trivial-bounds-leak.rs:26:5
+  --> $DIR/trivial-bounds-leak.rs:26:22
    |
 LL |     generic_function(5i32);
-   |     ^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `i32`
+   |                      ^^^^ the trait `Foo` is not implemented for `i32`
 ...
 LL | fn generic_function<T: Foo>(t: T) {}
    | --------------------------------- required by `generic_function`
diff --git a/src/test/ui/try-block/try-block-opt-init.rs b/src/test/ui/try-block/try-block-opt-init.rs
index 2387db8de4d6a..ef10b47fd1305 100644
--- a/src/test/ui/try-block/try-block-opt-init.rs
+++ b/src/test/ui/try-block/try-block-opt-init.rs
@@ -12,5 +12,5 @@ pub fn main() {
         Ok::<(), ()>(())?;
         use_val(cfg_res);
     };
-    assert_eq!(cfg_res, 5); //~ ERROR borrow of possibly uninitialized variable: `cfg_res`
+    assert_eq!(cfg_res, 5); //~ ERROR borrow of possibly-uninitialized variable: `cfg_res`
 }
diff --git a/src/test/ui/try-block/try-block-opt-init.stderr b/src/test/ui/try-block/try-block-opt-init.stderr
index ec0128dbdf0fc..308906477d914 100644
--- a/src/test/ui/try-block/try-block-opt-init.stderr
+++ b/src/test/ui/try-block/try-block-opt-init.stderr
@@ -1,8 +1,8 @@
-error[E0381]: borrow of possibly uninitialized variable: `cfg_res`
+error[E0381]: borrow of possibly-uninitialized variable: `cfg_res`
   --> $DIR/try-block-opt-init.rs:15:5
    |
 LL |     assert_eq!(cfg_res, 5);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^ use of possibly uninitialized `cfg_res`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ use of possibly-uninitialized `cfg_res`
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
diff --git a/src/test/ui/try-operator-on-main.rs b/src/test/ui/try-operator-on-main.rs
index 3b48194eb44fd..602c3c5c3593b 100644
--- a/src/test/ui/try-operator-on-main.rs
+++ b/src/test/ui/try-operator-on-main.rs
@@ -19,7 +19,7 @@ fn main() {
 
 fn try_trait_generic<T: Try>() -> T {
     // and a non-`Try` object on a `Try` fn.
-    ()?; //~ ERROR the `?` operator can only
+    ()?; //~ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
 
     loop {}
 }
diff --git a/src/test/ui/type-alias-enum-variants/enum-variant-generic-args-pass.rs b/src/test/ui/type-alias-enum-variants/enum-variant-generic-args-pass.rs
index 0c212096f9234..19fcc78721ab1 100644
--- a/src/test/ui/type-alias-enum-variants/enum-variant-generic-args-pass.rs
+++ b/src/test/ui/type-alias-enum-variants/enum-variant-generic-args-pass.rs
@@ -9,13 +9,13 @@
 
 #![allow(irrefutable_let_patterns)]
 
-enum Enum<T> { TSVariant(T), SVariant { v: T }, UVariant }
+enum Enum<T> { TSVariant(T), SVariant { _v: T }, UVariant }
 type Alias<T> = Enum<T>;
 type AliasFixed = Enum<()>;
 
 macro_rules! is_variant {
     (TSVariant, $expr:expr) => (is_variant!(@check TSVariant, (_), $expr));
-    (SVariant, $expr:expr) => (is_variant!(@check SVariant, { v: _ }, $expr));
+    (SVariant, $expr:expr) => (is_variant!(@check SVariant, { _v: _ }, $expr));
     (UVariant, $expr:expr) => (is_variant!(@check UVariant, {}, $expr));
     (@check $variant:ident, $matcher:tt, $expr:expr) => (
         assert!(if let Enum::$variant::<()> $matcher = $expr { true } else { false },
@@ -37,14 +37,14 @@ fn main() {
 
     // Struct variant
 
-    is_variant!(SVariant, Enum::SVariant { v: () });
-    is_variant!(SVariant, Enum::SVariant::<()> { v: () });
-    is_variant!(SVariant, Enum::<()>::SVariant { v: () });
+    is_variant!(SVariant, Enum::SVariant { _v: () });
+    is_variant!(SVariant, Enum::SVariant::<()> { _v: () });
+    is_variant!(SVariant, Enum::<()>::SVariant { _v: () });
 
-    is_variant!(SVariant, Alias::SVariant { v: () });
-    is_variant!(SVariant, Alias::<()>::SVariant { v: () });
+    is_variant!(SVariant, Alias::SVariant { _v: () });
+    is_variant!(SVariant, Alias::<()>::SVariant { _v: () });
 
-    is_variant!(SVariant, AliasFixed::SVariant { v: () });
+    is_variant!(SVariant, AliasFixed::SVariant { _v: () });
 
     // Unit variant
 
diff --git a/src/test/ui/type-alias-impl-trait/issue-60564.rs b/src/test/ui/type-alias-impl-trait/issue-60564.rs
index 91c4576597ea4..9e96b1cf7b05f 100644
--- a/src/test/ui/type-alias-impl-trait/issue-60564.rs
+++ b/src/test/ui/type-alias-impl-trait/issue-60564.rs
@@ -24,3 +24,5 @@ where
             .map(move |shift| ((self >> T::from(shift)) & T::from(1)).try_into().unwrap())
     }
 }
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/issue-60564.stderr b/src/test/ui/type-alias-impl-trait/issue-60564.stderr
index ebb13fca1da92..b838c06cadee3 100644
--- a/src/test/ui/type-alias-impl-trait/issue-60564.stderr
+++ b/src/test/ui/type-alias-impl-trait/issue-60564.stderr
@@ -1,7 +1,3 @@
-error[E0601]: `main` function not found in crate `issue_60564`
-   |
-   = note: consider adding a `main` function to `$DIR/issue-60564.rs`
-
 error: type parameter `E` is part of concrete type but not used in parameter list for the `impl Trait` type alias
   --> $DIR/issue-60564.rs:20:49
    |
@@ -20,6 +16,5 @@ error: could not find defining uses
 LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
diff --git a/src/test/ui/type/ascription/issue-34255-1.rs b/src/test/ui/type/ascription/issue-34255-1.rs
index c11a248d3c7d1..c21d9f3d97cbb 100644
--- a/src/test/ui/type/ascription/issue-34255-1.rs
+++ b/src/test/ui/type/ascription/issue-34255-1.rs
@@ -13,3 +13,4 @@ impl Reactor {
 }
 
 // This case isn't currently being handled gracefully, including for completeness.
+fn main() {}
diff --git a/src/test/ui/type/ascription/issue-34255-1.stderr b/src/test/ui/type/ascription/issue-34255-1.stderr
index 531455b82b424..195b393b2f609 100644
--- a/src/test/ui/type/ascription/issue-34255-1.stderr
+++ b/src/test/ui/type/ascription/issue-34255-1.stderr
@@ -14,17 +14,13 @@ LL |         input_cells: Vec::new()
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>
 
-error[E0601]: `main` function not found in crate `issue_34255_1`
-   |
-   = note: consider adding a `main` function to `$DIR/issue-34255-1.rs`
-
 error[E0107]: wrong number of type arguments: expected 1, found 0
   --> $DIR/issue-34255-1.rs:7:22
    |
 LL |         input_cells: Vec::new()
    |                      ^^^^^^^^^^ expected 1 type argument
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0107, E0425, E0601.
+Some errors have detailed explanations: E0107, E0425.
 For more information about an error, try `rustc --explain E0107`.
diff --git a/src/test/ui/type/ascription/issue-54516.rs b/src/test/ui/type/ascription/issue-54516.rs
index 6d65760e299b5..b53bfe5df03f3 100644
--- a/src/test/ui/type/ascription/issue-54516.rs
+++ b/src/test/ui/type/ascription/issue-54516.rs
@@ -2,5 +2,5 @@ use std::collections::BTreeMap;
 
 fn main() {
     println!("{}", std::mem:size_of::<BTreeMap<u32, u32>>());
-    //~^ ERROR expected token: `,`
+    //~^ ERROR expected one of
 }
diff --git a/src/test/ui/type/ascription/issue-54516.stderr b/src/test/ui/type/ascription/issue-54516.stderr
index a846f3bc320e6..97942904a0ffa 100644
--- a/src/test/ui/type/ascription/issue-54516.stderr
+++ b/src/test/ui/type/ascription/issue-54516.stderr
@@ -1,8 +1,8 @@
-error: expected token: `,`
+error: expected one of `!`, `,`, or `::`, found `(`
   --> $DIR/issue-54516.rs:4:58
    |
 LL |     println!("{}", std::mem:size_of::<BTreeMap<u32, u32>>());
-   |                            -                             ^ expected `,`
+   |                            -                             ^ expected one of `!`, `,`, or `::` here
    |                            |
    |                            help: maybe write a path separator here: `::`
    |
diff --git a/src/test/ui/type/type-check-defaults.stderr b/src/test/ui/type/type-check-defaults.stderr
index 42cca76451fd1..742a709958fa0 100644
--- a/src/test/ui/type/type-check-defaults.stderr
+++ b/src/test/ui/type/type-check-defaults.stderr
@@ -20,30 +20,30 @@ LL | struct WellFormedNoBounds<Z:?Sized = Foo<i32, i32>>(Z);
    = help: the trait `std::iter::FromIterator<i32>` is not implemented for `i32`
 
 error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
-  --> $DIR/type-check-defaults.rs:11:1
+  --> $DIR/type-check-defaults.rs:11:17
    |
 LL | struct Bounds<T:Copy=String>(T);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   | |
-   | the trait `std::marker::Copy` is not implemented for `std::string::String`
+   | ----------------^^^^------------
+   | |               |
+   | |               the trait `std::marker::Copy` is not implemented for `std::string::String`
    | required by `Bounds`
 
 error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
-  --> $DIR/type-check-defaults.rs:14:1
+  --> $DIR/type-check-defaults.rs:14:42
    |
 LL | struct WhereClause<T=String>(T) where T: Copy;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   | |
-   | the trait `std::marker::Copy` is not implemented for `std::string::String`
+   | -----------------------------------------^^^^-
+   | |                                        |
+   | |                                        the trait `std::marker::Copy` is not implemented for `std::string::String`
    | required by `WhereClause`
 
 error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
-  --> $DIR/type-check-defaults.rs:17:1
+  --> $DIR/type-check-defaults.rs:17:20
    |
 LL | trait TraitBound<T:Copy=String> {}
-   | -------------------------------^^^
-   | |
-   | the trait `std::marker::Copy` is not implemented for `std::string::String`
+   | -------------------^^^^--------
+   | |                  |
+   | |                  the trait `std::marker::Copy` is not implemented for `std::string::String`
    | required by `TraitBound`
 
 error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
@@ -57,12 +57,12 @@ LL | trait Base<T = String>: Super<T> { }
    = help: consider adding a `where T: std::marker::Copy` bound
 
 error[E0277]: cannot add `u8` to `i32`
-  --> $DIR/type-check-defaults.rs:24:1
+  --> $DIR/type-check-defaults.rs:24:66
    |
 LL | trait ProjectionPred<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
-   | ------------------------------------------------------------------------^^^
-   | |
-   | no implementation for `i32 + u8`
+   | -----------------------------------------------------------------^^^^^^^
+   | |                                                                |
+   | |                                                                no implementation for `i32 + u8`
    | required by `ProjectionPred`
    |
    = help: the trait `std::ops::Add<u8>` is not implemented for `i32`
diff --git a/src/test/ui/typeck/typeck-unsafe-always-share.stderr b/src/test/ui/typeck/typeck-unsafe-always-share.stderr
index 7ed85a14259aa..8b3032b088d0e 100644
--- a/src/test/ui/typeck/typeck-unsafe-always-share.stderr
+++ b/src/test/ui/typeck/typeck-unsafe-always-share.stderr
@@ -1,22 +1,22 @@
 error[E0277]: `std::cell::UnsafeCell<MySync<{integer}>>` cannot be shared between threads safely
-  --> $DIR/typeck-unsafe-always-share.rs:19:5
+  --> $DIR/typeck-unsafe-always-share.rs:19:10
    |
 LL | fn test<T: Sync>(s: T) {}
    | ---------------------- required by `test`
 ...
 LL |     test(us);
-   |     ^^^^ `std::cell::UnsafeCell<MySync<{integer}>>` cannot be shared between threads safely
+   |          ^^ `std::cell::UnsafeCell<MySync<{integer}>>` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `std::cell::UnsafeCell<MySync<{integer}>>`
 
 error[E0277]: `std::cell::UnsafeCell<NoSync>` cannot be shared between threads safely
-  --> $DIR/typeck-unsafe-always-share.rs:23:5
+  --> $DIR/typeck-unsafe-always-share.rs:23:10
    |
 LL | fn test<T: Sync>(s: T) {}
    | ---------------------- required by `test`
 ...
 LL |     test(uns);
-   |     ^^^^ `std::cell::UnsafeCell<NoSync>` cannot be shared between threads safely
+   |          ^^^ `std::cell::UnsafeCell<NoSync>` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `std::cell::UnsafeCell<NoSync>`
 
@@ -33,13 +33,13 @@ LL |     test(ms);
    = note: required because it appears within the type `MySync<NoSync>`
 
 error[E0277]: `NoSync` cannot be shared between threads safely
-  --> $DIR/typeck-unsafe-always-share.rs:30:5
+  --> $DIR/typeck-unsafe-always-share.rs:30:10
    |
 LL | fn test<T: Sync>(s: T) {}
    | ---------------------- required by `test`
 ...
 LL |     test(NoSync);
-   |     ^^^^ `NoSync` cannot be shared between threads safely
+   |          ^^^^^^ `NoSync` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `NoSync`
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
index d64e54a548442..d03397e42445c 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
@@ -1,11 +1,11 @@
 error[E0277]: expected a `std::ops::Fn<(isize,)>` closure, found `S`
-  --> $DIR/unboxed-closures-fnmut-as-fn.rs:28:13
+  --> $DIR/unboxed-closures-fnmut-as-fn.rs:28:21
    |
 LL | fn call_it<F:Fn(isize)->isize>(f: &F, x: isize) -> isize {
    | -------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&S, 22);
-   |             ^^^^^^^ expected an `Fn<(isize,)>` closure, found `S`
+   |                     ^^ expected an `Fn<(isize,)>` closure, found `S`
    |
    = help: the trait `std::ops::Fn<(isize,)>` is not implemented for `S`
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-static-call-wrong-trait.stderr b/src/test/ui/unboxed-closures/unboxed-closures-static-call-wrong-trait.stderr
index 2e1845888a2f7..18276d5710cf8 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-static-call-wrong-trait.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-static-call-wrong-trait.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `call` found for type `[closure@$DIR/unboxed-closu
   --> $DIR/unboxed-closures-static-call-wrong-trait.rs:7:10
    |
 LL |     mut_.call((0, ));
-   |          ^^^^
+   |          ^^^^ method not found in `[closure@$DIR/unboxed-closures-static-call-wrong-trait.rs:6:26: 6:31]`
    |
    = note: mut_ is a function, perhaps you wish to call it
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
index 3d20b5df1e3f3..bde30729a3ca3 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
@@ -1,55 +1,55 @@
 error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:12:13
+  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:12:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:12:13
+  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:12:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:18:13
+  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:18:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:18:13
+  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:18:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:24:13
+  --> $DIR/unboxed-closures-unsafe-extern-fn.rs:24:26
    |
 LL | fn call_it_once<F:FnOnce(&isize)->isize>(_: F, _: isize) -> isize { 0 }
    | ----------------------------------------------------------------- required by `call_it_once`
 ...
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |                          ^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr b/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
index f435a05e04901..7b393b35f298d 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
@@ -1,55 +1,55 @@
 error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-abi.rs:12:13
+  --> $DIR/unboxed-closures-wrong-abi.rs:12:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-abi.rs:12:13
+  --> $DIR/unboxed-closures-wrong-abi.rs:12:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-abi.rs:18:13
+  --> $DIR/unboxed-closures-wrong-abi.rs:18:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-abi.rs:18:13
+  --> $DIR/unboxed-closures-wrong-abi.rs:18:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-abi.rs:24:13
+  --> $DIR/unboxed-closures-wrong-abi.rs:24:26
    |
 LL | fn call_it_once<F:FnOnce(&isize)->isize>(_: F, _: isize) -> isize { 0 }
    | ----------------------------------------------------------------- required by `call_it_once`
 ...
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |                          ^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
index efdb2e8efa4e8..68fc0d45b9a8c 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
@@ -1,55 +1,55 @@
 error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:13:13
+  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:13:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:13:13
+  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:13:21
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | --------------------------------------------------------- required by `call_it`
 ...
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
+   |                     ^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:19:13
+  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:19:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
    = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:19:13
+  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:19:25
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | -------------------------------------------------------------------- required by `call_it_mut`
 ...
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
+   |                         ^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 
 error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
-  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:25:13
+  --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:25:26
    |
 LL | fn call_it_once<F:FnOnce(&isize)->isize>(_: F, _: isize) -> isize { 0 }
    | ----------------------------------------------------------------- required by `call_it_once`
 ...
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
+   |                          ^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
    = help: the trait `std::ops::FnOnce<(&isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 
diff --git a/src/test/ui/underscore-imports/shadow.stderr b/src/test/ui/underscore-imports/shadow.stderr
index 92adca2c70490..63262d0dc326d 100644
--- a/src/test/ui/underscore-imports/shadow.stderr
+++ b/src/test/ui/underscore-imports/shadow.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `deref` found for type `&()` in the current scope
   --> $DIR/shadow.rs:19:11
    |
 LL |         x.deref();
-   |           ^^^^^
+   |           ^^^^^ method not found in `&()`
    |
    = help: items from traits can only be used if the trait is in scope
    = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
diff --git a/src/test/ui/uninhabited/uninhabited-irrefutable.stderr b/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
index 45976f8ac56ad..29ff1dc376089 100644
--- a/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
+++ b/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
@@ -3,6 +3,7 @@ error[E0005]: refutable pattern in local binding: `A(_)` not covered
    |
 LL | / enum Foo {
 LL | |     A(foo::SecretlyEmpty),
+   | |     - not covered
 LL | |     B(foo::NotSoSecretlyEmpty),
 LL | |     C(NotSoSecretlyEmpty),
 LL | |     D(u32),
diff --git a/src/test/ui/union/union-derive-clone.stderr b/src/test/ui/union/union-derive-clone.stderr
index 37a0093784048..4f4c779b12bb3 100644
--- a/src/test/ui/union/union-derive-clone.stderr
+++ b/src/test/ui/union/union-derive-clone.stderr
@@ -13,7 +13,7 @@ LL | union U4<T> {
    | ----------- method `clone` not found for this
 ...
 LL |     let w = u.clone();
-   |               ^^^^^
+   |               ^^^^^ method not found in `U4<CloneNoCopy>`
    |
    = note: the method `clone` exists but the following trait bounds were not satisfied:
            `U4<CloneNoCopy> : std::clone::Clone`
diff --git a/src/test/ui/union/union-repr-c.rs b/src/test/ui/union/union-repr-c.rs
index 658452d57f748..1367835e67781 100644
--- a/src/test/ui/union/union-repr-c.rs
+++ b/src/test/ui/union/union-repr-c.rs
@@ -12,7 +12,7 @@ union W {
 
 extern "C" {
     static FOREIGN1: U; // OK
-    static FOREIGN2: W; //~ ERROR union has unspecified layout
+    static FOREIGN2: W; //~ ERROR `extern` block uses type `W`
 }
 
 fn main() {}
diff --git a/src/test/ui/union/union-repr-c.stderr b/src/test/ui/union/union-repr-c.stderr
index c60817a849a3b..c8bc0380dee68 100644
--- a/src/test/ui/union/union-repr-c.stderr
+++ b/src/test/ui/union/union-repr-c.stderr
@@ -1,8 +1,8 @@
-error: `extern` block uses type `W` which is not FFI-safe: this union has unspecified layout
+error: `extern` block uses type `W`, which is not FFI-safe
   --> $DIR/union-repr-c.rs:15:22
    |
 LL |     static FOREIGN2: W;
-   |                      ^
+   |                      ^ not FFI-safe
    |
 note: lint level defined here
   --> $DIR/union-repr-c.rs:2:9
@@ -10,6 +10,7 @@ note: lint level defined here
 LL | #![deny(improper_ctypes)]
    |         ^^^^^^^^^^^^^^^
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this union
+   = note: this union has unspecified layout
 note: type defined here
   --> $DIR/union-repr-c.rs:9:1
    |
diff --git a/src/test/ui/unique-object-noncopyable.stderr b/src/test/ui/unique-object-noncopyable.stderr
index 407905f52e750..cd46878c19be4 100644
--- a/src/test/ui/unique-object-noncopyable.stderr
+++ b/src/test/ui/unique-object-noncopyable.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `clone` found for type `std::boxed::Box<dyn Foo>`
   --> $DIR/unique-object-noncopyable.rs:24:16
    |
 LL |     let _z = y.clone();
-   |                ^^^^^
+   |                ^^^^^ method not found in `std::boxed::Box<dyn Foo>`
    |
    = note: the method `clone` exists but the following trait bounds were not satisfied:
            `std::boxed::Box<dyn Foo> : std::clone::Clone`
diff --git a/src/test/ui/unique-pinned-nocopy.stderr b/src/test/ui/unique-pinned-nocopy.stderr
index 0f6ba90afacf4..19ef2b21c2685 100644
--- a/src/test/ui/unique-pinned-nocopy.stderr
+++ b/src/test/ui/unique-pinned-nocopy.stderr
@@ -2,7 +2,7 @@ error[E0599]: no method named `clone` found for type `std::boxed::Box<R>` in the
   --> $DIR/unique-pinned-nocopy.rs:12:16
    |
 LL |     let _j = i.clone();
-   |                ^^^^^
+   |                ^^^^^ method not found in `std::boxed::Box<R>`
    |
    = note: the method `clone` exists but the following trait bounds were not satisfied:
            `std::boxed::Box<R> : std::clone::Clone`
diff --git a/src/test/ui/unreachable/unreachable-code.stderr b/src/test/ui/unreachable/unreachable-code.stderr
index 803bb966be8fc..226f088c63a5e 100644
--- a/src/test/ui/unreachable/unreachable-code.stderr
+++ b/src/test/ui/unreachable/unreachable-code.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/unreachable-code.rs:5:3
+   |
+LL |   loop{}
+   |   ^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/unreachable/unreachable-in-call.rs b/src/test/ui/unreachable/unreachable-in-call.rs
index 25f849d7a0a91..dd94e79f4d84c 100644
--- a/src/test/ui/unreachable/unreachable-in-call.rs
+++ b/src/test/ui/unreachable/unreachable-in-call.rs
@@ -14,7 +14,7 @@ fn diverge_first() {
          get_u8()); //~ ERROR unreachable expression
 }
 fn diverge_second() {
-    call( //~ ERROR unreachable expression
+    call( //~ ERROR unreachable call
         get_u8(),
         diverge());
 }
diff --git a/src/test/ui/unreachable/unreachable-in-call.stderr b/src/test/ui/unreachable/unreachable-in-call.stderr
index f8dd54590f6ae..928f5634a1248 100644
--- a/src/test/ui/unreachable/unreachable-in-call.stderr
+++ b/src/test/ui/unreachable/unreachable-in-call.stderr
@@ -9,14 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/unreachable-in-call.rs:13:10
+   |
+LL |     call(diverge(),
+   |          ^^^^^^^^^
 
-error: unreachable expression
+error: unreachable call
   --> $DIR/unreachable-in-call.rs:17:5
    |
-LL | /     call(
-LL | |         get_u8(),
-LL | |         diverge());
-   | |__________________^
+LL |     call(
+   |     ^^^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/unreachable-in-call.rs:19:9
+   |
+LL |         diverge());
+   |         ^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/unreachable/unreachable-try-pattern.stderr b/src/test/ui/unreachable/unreachable-try-pattern.stderr
index 758aa5a45bc17..889df790124da 100644
--- a/src/test/ui/unreachable/unreachable-try-pattern.stderr
+++ b/src/test/ui/unreachable/unreachable-try-pattern.stderr
@@ -9,6 +9,11 @@ note: lint level defined here
    |
 LL | #![warn(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/unreachable-try-pattern.rs:19:36
+   |
+LL |     let y = (match x { Ok(n) => Ok(n as u32), Err(e) => Err(e) })?;
+   |                                    ^
 
 warning: unreachable pattern
   --> $DIR/unreachable-try-pattern.rs:19:24
diff --git a/src/test/ui/unreachable/unwarned-match-on-never.stderr b/src/test/ui/unreachable/unwarned-match-on-never.stderr
index ccb70d7431145..9ce6e3df8046e 100644
--- a/src/test/ui/unreachable/unwarned-match-on-never.stderr
+++ b/src/test/ui/unreachable/unwarned-match-on-never.stderr
@@ -9,12 +9,23 @@ note: lint level defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+note: any code following this expression is unreachable
+  --> $DIR/unwarned-match-on-never.rs:8:11
+   |
+LL |     match x {}
+   |           ^
 
 error: unreachable arm
   --> $DIR/unwarned-match-on-never.rs:15:15
    |
 LL |         () => ()
    |               ^^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/unwarned-match-on-never.rs:14:11
+   |
+LL |     match (return) {
+   |           ^^^^^^^^
 
 error: unreachable expression
   --> $DIR/unwarned-match-on-never.rs:21:5
@@ -23,6 +34,12 @@ LL | /     match () {
 LL | |         () => (),
 LL | |     }
    | |_____^
+   |
+note: any code following this expression is unreachable
+  --> $DIR/unwarned-match-on-never.rs:20:5
+   |
+LL |     return;
+   |     ^^^^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/unsized3.stderr b/src/test/ui/unsized3.stderr
index 9064aa14d429f..f381cacadf9c0 100644
--- a/src/test/ui/unsized3.stderr
+++ b/src/test/ui/unsized3.stderr
@@ -1,8 +1,8 @@
 error[E0277]: the size for values of type `X` cannot be known at compilation time
-  --> $DIR/unsized3.rs:7:5
+  --> $DIR/unsized3.rs:7:13
    |
 LL |     f2::<X>(x);
-   |     ^^^^^^^ doesn't have a size known at compile-time
+   |             ^ doesn't have a size known at compile-time
 ...
 LL | fn f2<X>(x: &X) {
    | --------------- required by `f2`
@@ -12,10 +12,10 @@ LL | fn f2<X>(x: &X) {
    = help: consider adding a `where X: std::marker::Sized` bound
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
-  --> $DIR/unsized3.rs:18:5
+  --> $DIR/unsized3.rs:18:13
    |
 LL |     f4::<X>(x);
-   |     ^^^^^^^ doesn't have a size known at compile-time
+   |             ^ doesn't have a size known at compile-time
 ...
 LL | fn f4<X: T>(x: &X) {
    | ------------------ required by `f4`
@@ -25,13 +25,13 @@ LL | fn f4<X: T>(x: &X) {
    = help: consider adding a `where X: std::marker::Sized` bound
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
-  --> $DIR/unsized3.rs:33:5
+  --> $DIR/unsized3.rs:33:8
    |
 LL | fn f5<Y>(x: &Y) {}
    | --------------- required by `f5`
 ...
 LL |     f5(x1);
-   |     ^^ doesn't have a size known at compile-time
+   |        ^^ doesn't have a size known at compile-time
    |
    = help: within `S<X>`, the trait `std::marker::Sized` is not implemented for `X`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
@@ -39,10 +39,10 @@ LL |     f5(x1);
    = note: required because it appears within the type `S<X>`
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
-  --> $DIR/unsized3.rs:40:5
+  --> $DIR/unsized3.rs:40:8
    |
 LL |     f5(&(*x1, 34));
-   |     ^^ doesn't have a size known at compile-time
+   |        ^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: within `S<X>`, the trait `std::marker::Sized` is not implemented for `X`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
@@ -64,13 +64,13 @@ LL |     f5(&(32, *x1));
    = note: tuples must have a statically known size to be initialized
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
-  --> $DIR/unsized3.rs:45:5
+  --> $DIR/unsized3.rs:45:8
    |
 LL | fn f5<Y>(x: &Y) {}
    | --------------- required by `f5`
 ...
 LL |     f5(&(32, *x1));
-   |     ^^ doesn't have a size known at compile-time
+   |        ^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: within `({integer}, S<X>)`, the trait `std::marker::Sized` is not implemented for `X`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
diff --git a/src/test/ui/vtable-res-trait-param.stderr b/src/test/ui/vtable-res-trait-param.stderr
index 58a88979b2faf..bff64813268ce 100644
--- a/src/test/ui/vtable-res-trait-param.stderr
+++ b/src/test/ui/vtable-res-trait-param.stderr
@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `{integer}: TraitA` is not satisfied
-  --> $DIR/vtable-res-trait-param.rs:17:7
+  --> $DIR/vtable-res-trait-param.rs:17:18
    |
 LL |     b.gimme_an_a(y)
-   |       ^^^^^^^^^^ the trait `TraitA` is not implemented for `{integer}`
+   |                  ^ the trait `TraitA` is not implemented for `{integer}`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/where-clauses/where-clause-constraints-are-local-for-inherent-impl.stderr b/src/test/ui/where-clauses/where-clause-constraints-are-local-for-inherent-impl.stderr
index f923c6798829f..118caf8cccec7 100644
--- a/src/test/ui/where-clauses/where-clause-constraints-are-local-for-inherent-impl.stderr
+++ b/src/test/ui/where-clauses/where-clause-constraints-are-local-for-inherent-impl.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
-  --> $DIR/where-clause-constraints-are-local-for-inherent-impl.rs:13:9
+  --> $DIR/where-clause-constraints-are-local-for-inherent-impl.rs:13:22
    |
 LL | fn require_copy<T: Copy>(x: T) {}
    | ------------------------------ required by `require_copy`
 ...
 LL |         require_copy(self.x);
-   |         ^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
+   |                      ^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
    |
    = help: consider adding a `where T: std::marker::Copy` bound
 
diff --git a/src/test/ui/where-clauses/where-clause-constraints-are-local-for-trait-impl.stderr b/src/test/ui/where-clauses/where-clause-constraints-are-local-for-trait-impl.stderr
index 32736836ef8a3..d1cb4e1cc7d1d 100644
--- a/src/test/ui/where-clauses/where-clause-constraints-are-local-for-trait-impl.stderr
+++ b/src/test/ui/where-clauses/where-clause-constraints-are-local-for-trait-impl.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
-  --> $DIR/where-clause-constraints-are-local-for-trait-impl.rs:18:9
+  --> $DIR/where-clause-constraints-are-local-for-trait-impl.rs:18:22
    |
 LL | fn require_copy<T: Copy>(x: T) {}
    | ------------------------------ required by `require_copy`
 ...
 LL |         require_copy(self.x);
-   |         ^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
+   |                      ^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
    |
    = help: consider adding a `where T: std::marker::Copy` bound
 
diff --git a/src/test/ui/where-clauses/where-clauses-method-unsatisfied.stderr b/src/test/ui/where-clauses/where-clauses-method-unsatisfied.stderr
index 60bcba09e976c..6fd38728777e4 100644
--- a/src/test/ui/where-clauses/where-clauses-method-unsatisfied.stderr
+++ b/src/test/ui/where-clauses/where-clauses-method-unsatisfied.stderr
@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `Bar: std::cmp::Eq` is not satisfied
-  --> $DIR/where-clauses-method-unsatisfied.rs:18:7
+  --> $DIR/where-clauses-method-unsatisfied.rs:18:14
    |
 LL |     x.equals(&x);
-   |       ^^^^^^ the trait `std::cmp::Eq` is not implemented for `Bar`
+   |              ^^ the trait `std::cmp::Eq` is not implemented for `Bar`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/while-let.rs b/src/test/ui/while-let.rs
index 69f9de9497740..53babefae81c0 100644
--- a/src/test/ui/while-let.rs
+++ b/src/test/ui/while-let.rs
@@ -1,5 +1,6 @@
 // run-pass
 
+#[allow(dead_code)]
 fn macros() {
     macro_rules! foo{
         ($p:pat, $e:expr, $b:block) => {{
@@ -12,16 +13,16 @@ fn macros() {
         }}
     }
 
-    foo!(a, 1, { //~ WARN irrefutable while-let
+    foo!(_a, 1, { //~ WARN irrefutable while-let
         println!("irrefutable pattern");
     });
-    bar!(a, 1, { //~ WARN irrefutable while-let
+    bar!(_a, 1, { //~ WARN irrefutable while-let
         println!("irrefutable pattern");
     });
 }
 
 pub fn main() {
-    while let a = 1 { //~ WARN irrefutable while-let
+    while let _a = 1 { //~ WARN irrefutable while-let
         println!("irrefutable pattern");
         break;
     }
diff --git a/src/test/ui/while-let.stderr b/src/test/ui/while-let.stderr
index 348925aa9702c..30307ecaeadf2 100644
--- a/src/test/ui/while-let.stderr
+++ b/src/test/ui/while-let.stderr
@@ -1,10 +1,10 @@
 warning: irrefutable while-let pattern
-  --> $DIR/while-let.rs:6:13
+  --> $DIR/while-let.rs:7:13
    |
 LL |               while let $p = $e $b
    |               ^^^^^
 ...
-LL | /     foo!(a, 1, {
+LL | /     foo!(_a, 1, {
 LL | |         println!("irrefutable pattern");
 LL | |     });
    | |_______- in this macro invocation
@@ -12,20 +12,20 @@ LL | |     });
    = note: `#[warn(irrefutable_let_patterns)]` on by default
 
 warning: irrefutable while-let pattern
-  --> $DIR/while-let.rs:6:13
+  --> $DIR/while-let.rs:7:13
    |
 LL |               while let $p = $e $b
    |               ^^^^^
 ...
-LL | /     bar!(a, 1, {
+LL | /     bar!(_a, 1, {
 LL | |         println!("irrefutable pattern");
 LL | |     });
    | |_______- in this macro invocation
 
 warning: irrefutable while-let pattern
-  --> $DIR/while-let.rs:24:5
+  --> $DIR/while-let.rs:25:5
    |
-LL | /     while let a = 1 {
+LL | /     while let _a = 1 {
 LL | |         println!("irrefutable pattern");
 LL | |         break;
 LL | |     }
diff --git a/src/tools/build-manifest/src/main.rs b/src/tools/build-manifest/src/main.rs
index 9ffa9391c820b..eab23f3cfffc4 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -1,3 +1,9 @@
+//! Build a dist manifest, hash and sign everything.
+//! This gets called by `promote-release`
+//! (https://github.com/rust-lang/rust-central-station/tree/master/promote-release)
+//! via `x.py dist hash-and-sign`; the cmdline arguments are set up
+//! by rustbuild (in `src/bootstrap/dist.rs`).
+
 use toml;
 use serde::Serialize;
 
@@ -270,6 +276,7 @@ fn main() {
     // Do not ask for a passphrase while manually testing
     let mut passphrase = String::new();
     if should_sign {
+        // `x.py` passes the passphrase via stdin.
         t!(io::stdin().read_to_string(&mut passphrase));
     }
 
@@ -362,6 +369,7 @@ impl Builder {
         }
     }
 
+    /// Hash all files, compute their signatures, and collect the hashes in `self.digests`.
     fn digest_and_sign(&mut self) {
         for file in t!(self.input.read_dir()).map(|e| t!(e).path()) {
             let filename = file.file_name().unwrap().to_str().unwrap();
@@ -532,19 +540,20 @@ impl Builder {
             .as_ref()
             .cloned()
             .map(|version| (version, true))
-            .unwrap_or_default();
+            .unwrap_or_default(); // `is_present` defaults to `false` here.
 
-        // miri needs to build std with xargo, which doesn't allow stable/beta:
-        // <https://github.com/japaric/xargo/pull/204#issuecomment-374888868>
+        // Miri is nightly-only; never ship it for other trains.
         if pkgname == "miri-preview" && self.rust_release != "nightly" {
-            is_present = false; // ignore it
+            is_present = false; // Pretend the component is entirely missing.
         }
 
         let targets = targets.iter().map(|name| {
             if is_present {
+                // The component generally exists, but it might still be missing for this target.
                 let filename = self.filename(pkgname, name);
                 let digest = match self.digests.remove(&filename) {
                     Some(digest) => digest,
+                    // This component does not exist for this target -- skip it.
                     None => return (name.to_string(), Target::unavailable()),
                 };
                 let xz_filename = filename.replace(".tar.gz", ".tar.xz");
diff --git a/src/tools/cargo b/src/tools/cargo
index fe0e5a48b75da..3596cb86b2e87 160000
--- a/src/tools/cargo
+++ b/src/tools/cargo
@@ -1 +1 @@
-Subproject commit fe0e5a48b75da2b405c8ce1ba2674e174ae11d5d
+Subproject commit 3596cb86b2e87dd9b9c1bb90d4a9d73ec2c1512f
diff --git a/src/tools/clippy b/src/tools/clippy
index aeadf1562c024..58e01ea4d7df6 160000
--- a/src/tools/clippy
+++ b/src/tools/clippy
@@ -1 +1 @@
-Subproject commit aeadf1562c024d3c5421e61dc6b8d48c2d7902f5
+Subproject commit 58e01ea4d7df69e658c034afbfa6d0abd90808ed
diff --git a/src/tools/compiletest/Cargo.toml b/src/tools/compiletest/Cargo.toml
index e759ad1f35dde..745233c151cd6 100644
--- a/src/tools/compiletest/Cargo.toml
+++ b/src/tools/compiletest/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 diff = "0.1.10"
-env_logger = { version = "0.5", default-features = false }
+env_logger = { version = "0.6", default-features = false }
 getopts = "0.2"
 log = "0.4"
 regex = "1.0"
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index 3ba8cffe2b559..48dd68d0f61ee 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -628,6 +628,11 @@ impl TestProps {
         }
         self.pass_mode
     }
+
+    // does not consider CLI override for pass mode
+    pub fn local_pass_mode(&self) -> Option<PassMode> {
+        self.pass_mode
+    }
 }
 
 fn iter_header(testfile: &Path, cfg: Option<&str>, it: &mut dyn FnMut(&str)) {
@@ -835,10 +840,10 @@ impl Config {
 
             if name == "test" ||
                 util::matches_os(&self.target, name) ||             // target
+                util::matches_env(&self.target, name) ||            // env
                 name == util::get_arch(&self.target) ||             // architecture
                 name == util::get_pointer_width(&self.target) ||    // pointer width
                 name == self.stage_id.split('-').next().unwrap() || // stage
-                Some(name) == util::get_env(&self.target) ||        // env
                 (self.target != self.host && name == "cross-compile") ||
                 match self.compare_mode {
                     Some(CompareMode::Nll) => name == "compare-mode-nll",
diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index 467b7771c152e..7c51de5df2267 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -253,7 +253,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
     if args.len() == 1 || args[1] == "-h" || args[1] == "--help" {
         let message = format!("Usage: {} [OPTIONS] [TESTNAME...]", argv0);
         println!("{}", opts.usage(&message));
-        println!("");
+        println!();
         panic!()
     }
 
@@ -265,7 +265,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
     if matches.opt_present("h") || matches.opt_present("help") {
         let message = format!("Usage: {} [OPTIONS]  [TESTNAME...]", argv0);
         println!("{}", opts.usage(&message));
-        println!("");
+        println!();
         panic!()
     }
 
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 9a3d24facc2c8..baed27dd15152 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -1557,7 +1557,11 @@ impl<'test> TestCx<'test> {
                 // want to actually assert warnings about all this code. Instead
                 // let's just ignore unused code warnings by defaults and tests
                 // can turn it back on if needed.
-                if !self.config.src_base.ends_with("rustdoc-ui") {
+                if !self.config.src_base.ends_with("rustdoc-ui") &&
+                    // Note that we don't call pass_mode() here as we don't want
+                    // to set unused to allow if we've overriden the pass mode
+                    // via command line flags.
+                    self.props.local_pass_mode() != Some(PassMode::Run) {
                     rustc.args(&["-A", "unused"]);
                 }
             }
@@ -2589,7 +2593,7 @@ impl<'test> TestCx<'test> {
                     "  actual:   {}",
                     codegen_units_to_str(&actual_item.codegen_units)
                 );
-                println!("");
+                println!();
             }
         }
 
@@ -3522,7 +3526,7 @@ impl<'test> TestCx<'test> {
                             }
                         }
                     }
-                    println!("");
+                    println!();
                 }
             }
         }
diff --git a/src/tools/compiletest/src/util.rs b/src/tools/compiletest/src/util.rs
index 56ebea7c20f36..3a2ee445087d5 100644
--- a/src/tools/compiletest/src/util.rs
+++ b/src/tools/compiletest/src/util.rs
@@ -105,8 +105,12 @@ pub fn get_arch(triple: &str) -> &'static str {
     panic!("Cannot determine Architecture from triple");
 }
 
-pub fn get_env(triple: &str) -> Option<&str> {
-    triple.split('-').nth(3)
+pub fn matches_env(triple: &str, name: &str) -> bool {
+    if let Some(env) = triple.split('-').nth(3) {
+        env.starts_with(name)
+    } else {
+        false
+    }
 }
 
 pub fn get_pointer_width(triple: &str) -> &'static str {
diff --git a/src/tools/error_index_generator/build.rs b/src/tools/error_index_generator/build.rs
index 2ac7351fce469..592b3f14c85af 100644
--- a/src/tools/error_index_generator/build.rs
+++ b/src/tools/error_index_generator/build.rs
@@ -14,9 +14,7 @@ fn main() {
         if entry.file_name() == "error_codes.rs" {
             println!("cargo:rerun-if-changed={}", entry.path().to_str().unwrap());
             let file = fs::read_to_string(entry.path()).unwrap()
-                .replace("use syntax::{register_diagnostics, register_long_diagnostics};", "")
-                .replace("use syntax::register_diagnostics;", "")
-                .replace("use syntax::register_long_diagnostics;", "");
+                .replace("syntax::register_diagnostics!", "register_diagnostics!");
             let contents = format!("(|| {{\n{}\n}})();", file);
 
             fs::write(&out_dir.join(&format!("error_{}.rs", idx)), &contents).unwrap();
@@ -26,36 +24,31 @@ fn main() {
     }
 
     let mut all = String::new();
-    all.push_str("fn register_all() -> Vec<(&'static str, Option<&'static str>)> {\n");
-    all.push_str("let mut long_codes: Vec<(&'static str, Option<&'static str>)> = Vec::new();\n");
-    all.push_str(r#"
-macro_rules! register_diagnostics {
-    ($($code:tt),*) => {{
-        long_codes.extend([$(
-            stringify!($code),
-        )*].iter().cloned().map(|s| (s, None)).collect::<Vec<_>>());
-    }};
-    ($($code:tt),*,) => {{
-        long_codes.extend([$(
-            stringify!($code),
-        )*].iter().cloned().map(|s| (s, None)));
-    }}
-}
+    all.push_str(r###"
+fn register_all() -> Vec<(&'static str, Option<&'static str>)> {
+    let mut long_codes: Vec<(&'static str, Option<&'static str>)> = Vec::new();
+    macro_rules! register_diagnostics {
+        ($($ecode:ident: $message:expr,)*) => (
+            register_diagnostics!{$($ecode:$message,)* ;}
+        );
 
-macro_rules! register_long_diagnostics {
-    ($($code:tt: $description:tt),*) => {
-        {long_codes.extend([$(
-            (stringify!($code), Some(stringify!($description))),
-        )*].iter());}
-    };
-    ($($code:tt: $description:tt),*,) => {
-        {long_codes.extend([$(
-            (stringify!($code), Some(stringify!($description))),
-        )*].iter());}
+        ($($ecode:ident: $message:expr,)* ; $($code:ident,)*) => (
+            $(
+                {long_codes.extend([
+                    (stringify!($ecode), Some($message)),
+                ].iter());}
+            )*
+            $(
+                {long_codes.extend([
+                    stringify!($code),
+                ].iter().cloned().map(|s| (s, None)).collect::<Vec<_>>());}
+            )*
+        )
     }
-}"#);
+"###);
     for idx in 0..idx {
         all.push_str(&format!(r#"include!(concat!(env!("OUT_DIR"), "/error_{}.rs"));"#, idx));
+        all.push_str("\n");
     }
     all.push_str("\nlong_codes\n");
     all.push_str("}\n");
diff --git a/src/tools/miri b/src/tools/miri
index 69268fb75fdb4..130f9488d3b86 160000
--- a/src/tools/miri
+++ b/src/tools/miri
@@ -1 +1 @@
-Subproject commit 69268fb75fdb452296caa9bc4aaeff1674279de2
+Subproject commit 130f9488d3b861e02c9282b686eec717e30912cf
diff --git a/src/tools/publish_toolstate.py b/src/tools/publish_toolstate.py
index 1411f4c0b05a2..7cf3cc7663b47 100755
--- a/src/tools/publish_toolstate.py
+++ b/src/tools/publish_toolstate.py
@@ -7,6 +7,8 @@
 ## It is set as callback for `src/ci/docker/x86_64-gnu-tools/repo.sh` by the CI scripts
 ## when a new commit lands on `master` (i.e., after it passed all checks on `auto`).
 
+from __future__ import print_function
+
 import sys
 import re
 import os
@@ -20,21 +22,26 @@
     import urllib.request as urllib2
 
 # List of people to ping when the status of a tool or a book changed.
+# These should be collaborators of the rust-lang/rust repository (with at least
+# read privileges on it). CI will fail otherwise.
 MAINTAINERS = {
-    'miri': '@oli-obk @RalfJung @eddyb',
-    'clippy-driver': '@Manishearth @llogiq @mcarton @oli-obk @phansch @flip1995',
-    'rls': '@Xanewok',
-    'rustfmt': '@topecongiro',
-    'book': '@carols10cents @steveklabnik',
-    'nomicon': '@frewsxcv @Gankro',
-    'reference': '@steveklabnik @Havvy @matthewjasper @ehuss',
-    'rust-by-example': '@steveklabnik @marioidival @projektir',
-    'embedded-book': (
-        '@adamgreig @andre-richter @jamesmunns @korken89 '
-        '@ryankurte @thejpster @therealprof'
-    ),
-    'edition-guide': '@ehuss @Centril @steveklabnik',
-    'rustc-guide': '@mark-i-m @spastorino @amanjeev'
+    'miri': {'oli-obk', 'RalfJung', 'eddyb'},
+    'clippy-driver': {
+        'Manishearth', 'llogiq', 'mcarton', 'oli-obk', 'phansch', 'flip1995',
+        'yaahc',
+    },
+    'rls': {'Xanewok'},
+    'rustfmt': {'topecongiro'},
+    'book': {'carols10cents', 'steveklabnik'},
+    'nomicon': {'frewsxcv', 'Gankra'},
+    'reference': {'steveklabnik', 'Havvy', 'matthewjasper', 'ehuss'},
+    'rust-by-example': {'steveklabnik', 'marioidival'},
+    'embedded-book': {
+        'adamgreig', 'andre-richter', 'jamesmunns', 'korken89',
+        'ryankurte', 'thejpster', 'therealprof',
+    },
+    'edition-guide': {'ehuss', 'Centril', 'steveklabnik'},
+    'rustc-guide': {'mark-i-m', 'spastorino', 'amanjeev'},
 }
 
 REPOS = {
@@ -52,6 +59,50 @@
 }
 
 
+def validate_maintainers(repo, github_token):
+    '''Ensure all maintainers are assignable on a GitHub repo'''
+    next_link_re = re.compile(r'<([^>]+)>; rel="next"')
+
+    # Load the list of assignable people in the GitHub repo
+    assignable = []
+    url = 'https://api.github.com/repos/%s/collaborators?per_page=100' % repo
+    while url is not None:
+        response = urllib2.urlopen(urllib2.Request(url, headers={
+            'Authorization': 'token ' + github_token,
+            # Properly load nested teams.
+            'Accept': 'application/vnd.github.hellcat-preview+json',
+        }))
+        assignable.extend(user['login'] for user in json.load(response))
+        # Load the next page if available
+        url = None
+        link_header = response.headers.get('Link')
+        if link_header:
+            matches = next_link_re.match(link_header)
+            if matches is not None:
+                url = matches.group(1)
+
+    errors = False
+    for tool, maintainers in MAINTAINERS.items():
+        for maintainer in maintainers:
+            if maintainer not in assignable:
+                errors = True
+                print(
+                    "error: %s maintainer @%s is not assignable in the %s repo"
+                    % (tool, maintainer, repo),
+                )
+
+    if errors:
+        print()
+        print("  To be assignable, a person needs to be explicitly listed as a")
+        print("  collaborator in the repository settings. The simple way to")
+        print("  fix this is to ask someone with 'admin' privileges on the repo")
+        print("  to add the person or whole team as a collaborator with 'read'")
+        print("  privileges. Those privileges don't grant any extra permissions")
+        print("  so it's safe to apply them.")
+        print()
+        print("The build will fail due to this.")
+        exit(1)
+
 def read_current_status(current_commit, path):
     '''Reads build status of `current_commit` from content of `history/*.tsv`
     '''
@@ -73,13 +124,12 @@ def maybe_delink(message):
 def issue(
     tool,
     status,
-    maintainers,
+    assignees,
     relevant_pr_number,
     relevant_pr_user,
     pr_reviewer,
 ):
     # Open an issue about the toolstate failure.
-    assignees = [x.strip() for x in maintainers.split('@') if x != '']
     if status == 'test-fail':
         status_description = 'has failing tests'
     else:
@@ -100,7 +150,7 @@ def issue(
             REPOS.get(tool), relevant_pr_user, pr_reviewer
         )),
         'title': '`{}` no longer builds after {}'.format(tool, relevant_pr_number),
-        'assignees': assignees,
+        'assignees': list(assignees),
         'labels': ['T-compiler', 'I-nominated'],
     })
     print("Creating issue:\n{}".format(request))
@@ -150,22 +200,32 @@ def update_latest(
                 old = status[os]
                 new = s.get(tool, old)
                 status[os] = new
-                if new > old: # comparing the strings, but they are ordered appropriately!
+                maintainers = ' '.join('@'+name for name in MAINTAINERS[tool])
+                # comparing the strings, but they are ordered appropriately:
+                # "test-pass" > "test-fail" > "build-fail"
+                if new > old:
                     # things got fixed or at least the status quo improved
                     changed = True
                     message += '🎉 {} on {}: {} → {} (cc {}, @rust-lang/infra).\n' \
-                        .format(tool, os, old, new, MAINTAINERS.get(tool))
+                        .format(tool, os, old, new, maintainers)
                 elif new < old:
                     # tests or builds are failing and were not failing before
                     changed = True
                     title = '💔 {} on {}: {} → {}' \
                         .format(tool, os, old, new)
                     message += '{} (cc {}, @rust-lang/infra).\n' \
-                        .format(title, MAINTAINERS.get(tool))
-                    # Most tools only create issues for build failures.
-                    # Other failures can be spurious.
-                    if new == 'build-fail' or (tool == 'miri' and new == 'test-fail'):
-                        create_issue_for_status = new
+                        .format(title, maintainers)
+                    # See if we need to create an issue.
+                    if tool == 'miri':
+                        # Create issue if tests used to pass before. Don't open a *second*
+                        # issue when we regress from "test-fail" to "build-fail".
+                        if old == 'test-pass':
+                            create_issue_for_status = new
+                    else:
+                        # Create issue if things no longer build.
+                        # (No issue for mere test failures to avoid spurious issues.)
+                        if new == 'build-fail':
+                            create_issue_for_status = new
 
             if create_issue_for_status is not None:
                 try:
@@ -200,6 +260,16 @@ def update_latest(
 
 
 if __name__ == '__main__':
+    repo = os.environ.get('TOOLSTATE_VALIDATE_MAINTAINERS_REPO')
+    if repo:
+        github_token = os.environ.get('TOOLSTATE_REPO_ACCESS_TOKEN')
+        if github_token:
+            validate_maintainers(repo, github_token)
+        else:
+            print('skipping toolstate maintainers validation since no GitHub token is present')
+        # When validating maintainers don't run the full script.
+        exit(0)
+
     cur_commit = sys.argv[1]
     cur_datetime = datetime.datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%SZ')
     cur_commit_msg = sys.argv[2]
diff --git a/src/tools/rls b/src/tools/rls
index 496c892752213..d9aa23a43ad29 160000
--- a/src/tools/rls
+++ b/src/tools/rls
@@ -1 +1 @@
-Subproject commit 496c89275221303a4b0c2779cb8203fb3ce2a136
+Subproject commit d9aa23a43ad29e3a10551a1425ef5d5baef28d70
diff --git a/src/tools/rustbook/src/main.rs b/src/tools/rustbook/src/main.rs
index 95530b210afd6..d5dc9a79b5acb 100644
--- a/src/tools/rustbook/src/main.rs
+++ b/src/tools/rustbook/src/main.rs
@@ -1,18 +1,19 @@
-use clap::{crate_version};
+use clap::crate_version;
 
 use std::env;
 use std::path::{Path, PathBuf};
 
-use clap::{App, ArgMatches, SubCommand, AppSettings};
+use clap::{App, AppSettings, ArgMatches, SubCommand};
 
+use mdbook::errors::Result as Result3;
 use mdbook::MDBook;
-use mdbook::errors::{Result as Result3};
 
+#[cfg(feature = "linkcheck")]
+use failure::Error;
 #[cfg(feature = "linkcheck")]
 use mdbook::renderer::RenderContext;
 #[cfg(feature = "linkcheck")]
 use mdbook_linkcheck::{self, errors::BrokenLinks};
-use failure::Error;
 
 fn main() {
     let d_message = "-d, --dest-dir=[dest-dir]
@@ -21,18 +22,22 @@ fn main() {
 'A directory for your book{n}(Defaults to Current Directory when omitted)'";
 
     let matches = App::new("rustbook")
-                    .about("Build a book with mdBook")
-                    .author("Steve Klabnik <steve@steveklabnik.com>")
-                    .version(&*format!("v{}", crate_version!()))
-                    .setting(AppSettings::SubcommandRequired)
-                    .subcommand(SubCommand::with_name("build")
-                        .about("Build the book from the markdown files")
-                        .arg_from_usage(d_message)
-                        .arg_from_usage(dir_message))
-                    .subcommand(SubCommand::with_name("linkcheck")
-                        .about("Run linkcheck with mdBook 3")
-                        .arg_from_usage(dir_message))
-                    .get_matches();
+        .about("Build a book with mdBook")
+        .author("Steve Klabnik <steve@steveklabnik.com>")
+        .version(&*format!("v{}", crate_version!()))
+        .setting(AppSettings::SubcommandRequired)
+        .subcommand(
+            SubCommand::with_name("build")
+                .about("Build the book from the markdown files")
+                .arg_from_usage(d_message)
+                .arg_from_usage(dir_message),
+        )
+        .subcommand(
+            SubCommand::with_name("linkcheck")
+                .about("Run linkcheck with mdBook 3")
+                .arg_from_usage(dir_message),
+        )
+        .get_matches();
 
     // Check which subcomamnd the user ran...
     match matches.subcommand() {
@@ -46,23 +51,44 @@ fn main() {
 
                 ::std::process::exit(101);
             }
-        },
+        }
         ("linkcheck", Some(sub_matches)) => {
-            if let Err(err) = linkcheck(sub_matches) {
-                eprintln!("Error: {}", err);
-
-                #[cfg(feature = "linkcheck")]
-                {
-                    if let Ok(broken_links) = err.downcast::<BrokenLinks>() {
-                        for cause in broken_links.links().iter() {
-                            eprintln!("\tCaused By: {}", cause);
-                        }
+            #[cfg(feature = "linkcheck")]
+            {
+                if let Err(err) = linkcheck(sub_matches) {
+                    eprintln!("Error: {}", err);
+
+                    // HACK: ignore timeouts
+                    let actually_broken = err
+                        .downcast::<BrokenLinks>()
+                        .map(|broken_links| {
+                            broken_links
+                                .links()
+                                .iter()
+                                .inspect(|cause| eprintln!("\tCaused By: {}", cause))
+                                .fold(false, |already_broken, cause| {
+                                    already_broken || !format!("{}", cause).contains("timed out")
+                                })
+                        })
+                        .unwrap_or(false);
+
+                    if actually_broken {
+                        std::process::exit(101);
+                    } else {
+                        std::process::exit(0);
                     }
                 }
+            }
 
-                ::std::process::exit(101);
+            #[cfg(not(feature = "linkcheck"))]
+            {
+                // This avoids the `unused_binding` lint.
+                println!(
+                    "mdbook-linkcheck is disabled, but arguments were passed: {:?}",
+                    sub_matches
+                );
             }
-        },
+        }
         (_, _) => unreachable!(),
     };
 }
@@ -77,12 +103,6 @@ pub fn linkcheck(args: &ArgMatches<'_>) -> Result<(), Error> {
     mdbook_linkcheck::check_links(&render_ctx)
 }
 
-#[cfg(not(feature = "linkcheck"))]
-pub fn linkcheck(_args: &ArgMatches<'_>) -> Result<(), Error> {
-    println!("mdbook-linkcheck is disabled.");
-    Ok(())
-}
-
 // Build command implementation
 pub fn build(args: &ArgMatches<'_>) -> Result3<()> {
     let book_dir = get_book_dir(args);
diff --git a/src/tools/rustc-std-workspace-alloc/Cargo.toml b/src/tools/rustc-std-workspace-alloc/Cargo.toml
index ef7dc812af9d4..9e04b14756e06 100644
--- a/src/tools/rustc-std-workspace-alloc/Cargo.toml
+++ b/src/tools/rustc-std-workspace-alloc/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rustc-std-workspace-alloc"
-version = "1.0.0"
+version = "1.99.0"
 authors = ["Alex Crichton <alex@alexcrichton.com>"]
 license = 'MIT OR Apache-2.0'
 description = """
diff --git a/src/tools/rustc-std-workspace-core/Cargo.toml b/src/tools/rustc-std-workspace-core/Cargo.toml
index 38ca56a557be6..6b4e7540affc9 100644
--- a/src/tools/rustc-std-workspace-core/Cargo.toml
+++ b/src/tools/rustc-std-workspace-core/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rustc-std-workspace-core"
-version = "1.0.0"
+version = "1.99.0"
 authors = ["Alex Crichton <alex@alexcrichton.com>"]
 license = 'MIT OR Apache-2.0'
 description = """
diff --git a/src/tools/rustc-std-workspace-std/Cargo.toml b/src/tools/rustc-std-workspace-std/Cargo.toml
index ce1644809dbe6..e41554b74affd 100644
--- a/src/tools/rustc-std-workspace-std/Cargo.toml
+++ b/src/tools/rustc-std-workspace-std/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rustc-std-workspace-std"
-version = "1.0.0"
+version = "1.99.0"
 authors = ["Alex Crichton <alex@alexcrichton.com>"]
 license = 'MIT OR Apache-2.0'
 description = """
diff --git a/src/tools/rustc-workspace-hack/Cargo.toml b/src/tools/rustc-workspace-hack/Cargo.toml
index 4ce411223de43..980c9753761ed 100644
--- a/src/tools/rustc-workspace-hack/Cargo.toml
+++ b/src/tools/rustc-workspace-hack/Cargo.toml
@@ -14,12 +14,6 @@ path = "lib.rs"
 # For documentation about what this is and why in the world these dependencies
 # are appearing, see `README.md`.
 
-[build-dependencies]
-# Currently Cargo/RLS depend on `failure` which depends on `synstructure` which
-# enables this feature. Clippy, however, does not depend on anything that
-# enables this feature. Enable it unconditionally.
-syn = { version = "0.15", features = ['extra-traits'] }
-
 [target.'cfg(windows)'.dependencies.winapi]
 version = "0.3"
 features = [
@@ -65,14 +59,10 @@ features = [
 [dependencies]
 curl-sys = { version = "0.4.13", features = ["http2", "libnghttp2-sys"], optional = true }
 crossbeam-utils = { version = "0.6.5", features = ["nightly"] }
-parking_lot = { version = "0.7", features = ['nightly'] }
-rand = { version = "0.6.1", features = ["i128_support"] }
 serde = { version = "1.0.82", features = ['derive'] }
 serde_json = { version = "1.0.31", features = ["raw_value"] }
 smallvec = { version = "0.6", features = ['union', 'may_dangle'] }
-scopeguard = { version = "0.3.3", features = ["use_std", "default"] }
-byteorder = { version = "1.2.7", features = ["i128"] }
-syn = { version = "0.15.35", features = ["extra-traits", "full"] }
+url = { version = "2.0", features = ['serde'] }
 
 
 [target.'cfg(not(windows))'.dependencies]
diff --git a/src/tools/rustfmt b/src/tools/rustfmt
index f800ce47d1da2..afb1ee1c14594 160000
--- a/src/tools/rustfmt
+++ b/src/tools/rustfmt
@@ -1 +1 @@
-Subproject commit f800ce47d1da2a1c02ffd260deca8b7445f7facf
+Subproject commit afb1ee1c14594aed5bb4a762b357b01f13c9de10
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index a564b991c404b..1ed39f45d3e70 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -15,6 +15,7 @@ const LICENSES: &[&str] = &[
     "Apache-2.0 / MIT",
     "MIT OR Apache-2.0",
     "Apache-2.0 OR MIT",
+    "Apache-2.0 WITH LLVM-exception OR Apache-2.0 OR MIT", // wasi license
     "MIT",
     "Unlicense/MIT",
     "Unlicense OR MIT",
@@ -172,6 +173,7 @@ const WHITELIST: &[Crate<'_>] = &[
     Crate("vcpkg"),
     Crate("version_check"),
     Crate("void"),
+    Crate("wasi"),
     Crate("winapi"),
     Crate("winapi-build"),
     Crate("winapi-i686-pc-windows-gnu"),
diff --git a/src/tools/tidy/src/style.rs b/src/tools/tidy/src/style.rs
index 6a0d530e2362a..9302909968615 100644
--- a/src/tools/tidy/src/style.rs
+++ b/src/tools/tidy/src/style.rs
@@ -15,6 +15,7 @@
 
 use std::path::Path;
 
+const ERROR_CODE_COLS: usize = 80;
 const COLS: usize = 100;
 
 const LINES: usize = 3000;
@@ -51,7 +52,13 @@ enum LIUState {
 /// Lines of this form are allowed to be overlength, because Markdown
 /// offers no way to split a line in the middle of a URL, and the lengths
 /// of URLs to external references are beyond our control.
-fn line_is_url(line: &str) -> bool {
+fn line_is_url(columns: usize, line: &str) -> bool {
+    // more basic check for error_codes.rs, to avoid complexity in implementing two state machines
+    if columns == ERROR_CODE_COLS {
+        return line.starts_with("[") &&
+            line.contains("]:") && line.contains("http");
+    }
+
     use self::LIUState::*;
     let mut state: LIUState = EXP_COMMENT_START;
     let is_url = |w: &str| w.starts_with("http://") || w.starts_with("https://");
@@ -75,7 +82,7 @@ fn line_is_url(line: &str) -> bool {
                 => state = EXP_END,
 
             (_, w)
-                if w.len() > COLS && is_url(w)
+                if w.len() > columns && is_url(w)
                 => state = EXP_END,
 
             (_, _) => {}
@@ -88,8 +95,8 @@ fn line_is_url(line: &str) -> bool {
 /// Returns `true` if `line` is allowed to be longer than the normal limit.
 /// Currently there is only one exception, for long URLs, but more
 /// may be added in the future.
-fn long_line_is_ok(line: &str) -> bool {
-    if line_is_url(line) {
+fn long_line_is_ok(max_columns: usize, line: &str) -> bool {
+    if line_is_url(max_columns, line) {
         return true;
     }
 
@@ -144,6 +151,12 @@ pub fn check(path: &Path, bad: &mut bool) {
             tidy_error!(bad, "{}: empty file", file.display());
         }
 
+        let max_columns = if filename == "error_codes.rs" {
+            ERROR_CODE_COLS
+        } else {
+            COLS
+        };
+
         let can_contain = contents.contains("// ignore-tidy-") ||
             contents.contains("# ignore-tidy-");
         let mut skip_cr = contains_ignore_directive(can_contain, &contents, "cr");
@@ -162,11 +175,12 @@ pub fn check(path: &Path, bad: &mut bool) {
             let mut err = |msg: &str| {
                 tidy_error!(bad, "{}:{}: {}", file.display(), i + 1, msg);
             };
-            if line.chars().count() > COLS && !long_line_is_ok(line) {
+            if line.chars().count() > max_columns &&
+                !long_line_is_ok(max_columns, line) {
                 suppressible_tidy_err!(
                     err,
                     skip_line_length,
-                    &format!("line longer than {} chars", COLS)
+                    &format!("line longer than {} chars", max_columns)
                 );
             }
             if line.contains('\t') {