From 2ac89ff994c9ddcc49eed2b06ff5327bc09f4118 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Mon, 7 Sep 2020 18:42:29 -0700
Subject: [PATCH 01/21] Point at named argument not found when using
 `format_args_capture` instead of whole format string

---
 compiler/rustc_builtin_macros/src/format.rs   |  9 ++++--
 .../format-args-capture-missing-variables.rs  |  6 ++--
 ...rmat-args-capture-missing-variables.stderr | 31 ++++++++-----------
 3 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 5d6f791f13719..550524e652af7 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -543,9 +543,12 @@ impl<'a, 'b> Context<'a, 'b> {
                             let idx = self.args.len();
                             self.arg_types.push(Vec::new());
                             self.arg_unique_types.push(Vec::new());
-                            self.args.push(
-                                self.ecx.expr_ident(self.fmtsp, Ident::new(name, self.fmtsp)),
-                            );
+                            let span = if self.is_literal {
+                                *self.arg_spans.get(self.curpiece).unwrap_or(&self.fmtsp)
+                            } else {
+                                self.fmtsp
+                            };
+                            self.args.push(self.ecx.expr_ident(span, Ident::new(name, span)));
                             self.names.insert(name, idx);
                             self.verify_arg_type(Exact(idx), ty)
                         } else {
diff --git a/src/test/ui/fmt/format-args-capture-missing-variables.rs b/src/test/ui/fmt/format-args-capture-missing-variables.rs
index 3c596ae3bb899..3a4b6144b04db 100644
--- a/src/test/ui/fmt/format-args-capture-missing-variables.rs
+++ b/src/test/ui/fmt/format-args-capture-missing-variables.rs
@@ -5,7 +5,7 @@ fn main() {
     //~^ ERROR: cannot find value `foo` in this scope
     //~^^ ERROR: cannot find value `bar` in this scope
 
-    format!("{foo}");                //~ ERROR: cannot find value `foo` in this scope
+    format!("{foo}"); //~ ERROR: cannot find value `foo` in this scope
 
     format!("{valuea} {valueb}", valuea=5, valuec=7);
     //~^ ERROR cannot find value `valueb` in this scope
@@ -16,7 +16,7 @@ fn main() {
         {foo}
 
     "##);
-    //~^^^^^ ERROR: cannot find value `foo` in this scope
+    //~^^^ ERROR: cannot find value `foo` in this scope
 
-    panic!("{foo} {bar}", bar=1);    //~ ERROR: cannot find value `foo` in this scope
+    panic!("{foo} {bar}", bar=1); //~ ERROR: cannot find value `foo` in this scope
 }
diff --git a/src/test/ui/fmt/format-args-capture-missing-variables.stderr b/src/test/ui/fmt/format-args-capture-missing-variables.stderr
index c3d740eef9d3c..ec2faa4185b3e 100644
--- a/src/test/ui/fmt/format-args-capture-missing-variables.stderr
+++ b/src/test/ui/fmt/format-args-capture-missing-variables.stderr
@@ -7,45 +7,40 @@ LL |     format!("{valuea} {valueb}", valuea=5, valuec=7);
    |             formatting specifier missing
 
 error[E0425]: cannot find value `foo` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:4:13
+  --> $DIR/format-args-capture-missing-variables.rs:4:17
    |
 LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
-   |             ^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |                 ^^^^^ not found in this scope
 
 error[E0425]: cannot find value `bar` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:4:13
+  --> $DIR/format-args-capture-missing-variables.rs:4:26
    |
 LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
-   |             ^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |                          ^^^^^ not found in this scope
 
 error[E0425]: cannot find value `foo` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:8:13
+  --> $DIR/format-args-capture-missing-variables.rs:8:14
    |
 LL |     format!("{foo}");
-   |             ^^^^^^^ not found in this scope
+   |              ^^^^^ not found in this scope
 
 error[E0425]: cannot find value `valueb` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:10:13
+  --> $DIR/format-args-capture-missing-variables.rs:10:23
    |
 LL |     format!("{valuea} {valueb}", valuea=5, valuec=7);
-   |             ^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |                       ^^^^^^^^ not found in this scope
 
 error[E0425]: cannot find value `foo` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:14:13
+  --> $DIR/format-args-capture-missing-variables.rs:16:9
    |
-LL |       format!(r##"
-   |  _____________^
-LL | |
-LL | |         {foo}
-LL | |
-LL | |     "##);
-   | |_______^ not found in this scope
+LL |         {foo}
+   |         ^^^^^ not found in this scope
 
 error[E0425]: cannot find value `foo` in this scope
-  --> $DIR/format-args-capture-missing-variables.rs:21:12
+  --> $DIR/format-args-capture-missing-variables.rs:21:13
    |
 LL |     panic!("{foo} {bar}", bar=1);
-   |            ^^^^^^^^^^^^^ not found in this scope
+   |             ^^^^^ not found in this scope
 
 error: aborting due to 7 previous errors
 

From 094d67ae0587def6c23dec05a39685ed4f096739 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Mon, 21 Sep 2020 11:32:06 -0700
Subject: [PATCH 02/21] Add accessors to Command.

---
 library/std/src/process.rs                    | 125 ++++++++++++++++++
 library/std/src/sys/unix/process/mod.rs       |   3 +-
 .../src/sys/unix/process/process_common.rs    |  53 +++++++-
 .../std/src/sys/unix/process/process_unix.rs  |   4 +-
 library/std/src/sys/unsupported/process.rs    |  39 +++++-
 library/std/src/sys/windows/process.rs        |  48 ++++++-
 library/std/src/sys_common/process.rs         |  37 ++++++
 7 files changed, 302 insertions(+), 7 deletions(-)

diff --git a/library/std/src/process.rs b/library/std/src/process.rs
index 00e2dbc9c1dbf..6299cf02eedd1 100644
--- a/library/std/src/process.rs
+++ b/library/std/src/process.rs
@@ -110,6 +110,8 @@ use crate::path::Path;
 use crate::str;
 use crate::sys::pipe::{read2, AnonPipe};
 use crate::sys::process as imp;
+#[unstable(feature = "command_access", issue = "44434")]
+pub use crate::sys_common::process::CommandEnvs;
 use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
 
 /// Representation of a running or exited child process.
@@ -875,6 +877,98 @@ impl Command {
             .map(Child::from_inner)
             .and_then(|mut p| p.wait())
     }
+
+    /// Returns the path to the program that was given to [`Command::new`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #![feature(command_access)]
+    /// use std::process::Command;
+    ///
+    /// let cmd = Command::new("echo");
+    /// assert_eq!(cmd.get_program(), "echo");
+    /// ```
+    #[unstable(feature = "command_access", issue = "44434")]
+    pub fn get_program(&self) -> &OsStr {
+        self.inner.get_program()
+    }
+
+    /// Returns an iterator of the arguments that will be passed to the program.
+    ///
+    /// This does not include the path to the program as the first argument;
+    /// it only includes the arguments specified with [`Command::arg`] and
+    /// [`Command::args`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #![feature(command_access)]
+    /// use std::ffi::OsStr;
+    /// use std::process::Command;
+    ///
+    /// let mut cmd = Command::new("echo");
+    /// cmd.arg("first").arg("second");
+    /// let args: Vec<&OsStr> = cmd.get_args().collect();
+    /// assert_eq!(args, &["first", "second"]);
+    /// ```
+    #[unstable(feature = "command_access", issue = "44434")]
+    pub fn get_args(&self) -> CommandArgs<'_> {
+        CommandArgs { inner: self.inner.get_args() }
+    }
+
+    /// Returns an iterator of the environment variables that will be set when
+    /// the process is spawned.
+    ///
+    /// Each element is a tuple `(&OsStr, Option<&OsStr>)`, where the first
+    /// value is the key, and the second is the value, which is [`None`] if
+    /// the environment variable is to be explicitly removed.
+    ///
+    /// This only includes environment variables explicitly set with
+    /// [`Command::env`], [`Command::envs`], and [`Command::env_remove`]. It
+    /// does not include environment variables that will be inherited by the
+    /// child process.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #![feature(command_access)]
+    /// use std::ffi::OsStr;
+    /// use std::process::Command;
+    ///
+    /// let mut cmd = Command::new("ls");
+    /// cmd.env("TERM", "dumb").env_remove("TZ");
+    /// let envs: Vec<(&OsStr, Option<&OsStr>)> = cmd.get_envs().collect();
+    /// assert_eq!(envs, &[
+    ///     (OsStr::new("TERM"), Some(OsStr::new("dumb"))),
+    ///     (OsStr::new("TZ"), None)
+    /// ]);
+    /// ```
+    #[unstable(feature = "command_access", issue = "44434")]
+    pub fn get_envs(&self) -> CommandEnvs<'_> {
+        self.inner.get_envs()
+    }
+
+    /// Returns the working directory for the child process.
+    ///
+    /// This returns [`None`] if the working directory will not be changed.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #![feature(command_access)]
+    /// use std::path::Path;
+    /// use std::process::Command;
+    ///
+    /// let mut cmd = Command::new("ls");
+    /// assert_eq!(cmd.get_current_dir(), None);
+    /// cmd.current_dir("/bin");
+    /// assert_eq!(cmd.get_current_dir(), Some(Path::new("/bin")));
+    /// ```
+    #[unstable(feature = "command_access", issue = "44434")]
+    pub fn get_current_dir(&self) -> Option<&Path> {
+        self.inner.get_current_dir()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -899,6 +993,37 @@ impl AsInnerMut<imp::Command> for Command {
     }
 }
 
+/// An iterator over the command arguments.
+///
+/// This struct is created by [`Command::get_args`]. See its documentation for
+/// more.
+#[unstable(feature = "command_access", issue = "44434")]
+#[derive(Debug)]
+pub struct CommandArgs<'a> {
+    inner: imp::CommandArgs<'a>,
+}
+
+#[unstable(feature = "command_access", issue = "44434")]
+impl<'a> Iterator for CommandArgs<'a> {
+    type Item = &'a OsStr;
+    fn next(&mut self) -> Option<&'a OsStr> {
+        self.inner.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+}
+
+#[unstable(feature = "command_access", issue = "44434")]
+impl<'a> ExactSizeIterator for CommandArgs<'a> {
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
+    fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+}
+
 /// The output of a finished process.
 ///
 /// This is returned in a Result by either the [`output`] method of a
diff --git a/library/std/src/sys/unix/process/mod.rs b/library/std/src/sys/unix/process/mod.rs
index 553e980f08e97..1b7b93f9d4a5f 100644
--- a/library/std/src/sys/unix/process/mod.rs
+++ b/library/std/src/sys/unix/process/mod.rs
@@ -1,6 +1,7 @@
-pub use self::process_common::{Command, ExitCode, Stdio, StdioPipes};
+pub use self::process_common::{Command, CommandArgs, ExitCode, Stdio, StdioPipes};
 pub use self::process_inner::{ExitStatus, Process};
 pub use crate::ffi::OsString as EnvKey;
+pub use crate::sys_common::process::CommandEnvs;
 
 mod process_common;
 #[cfg(not(target_os = "fuchsia"))]
diff --git a/library/std/src/sys/unix/process/process_common.rs b/library/std/src/sys/unix/process/process_common.rs
index f8666485eeccb..9ddd4ad4000ef 100644
--- a/library/std/src/sys/unix/process/process_common.rs
+++ b/library/std/src/sys/unix/process/process_common.rs
@@ -7,11 +7,12 @@ use crate::collections::BTreeMap;
 use crate::ffi::{CStr, CString, OsStr, OsString};
 use crate::fmt;
 use crate::io;
+use crate::path::Path;
 use crate::ptr;
 use crate::sys::fd::FileDesc;
 use crate::sys::fs::File;
 use crate::sys::pipe::{self, AnonPipe};
-use crate::sys_common::process::CommandEnv;
+use crate::sys_common::process::{CommandEnv, CommandEnvs};
 
 #[cfg(not(target_os = "fuchsia"))]
 use crate::sys::fs::OpenOptions;
@@ -184,11 +185,30 @@ impl Command {
     pub fn saw_nul(&self) -> bool {
         self.saw_nul
     }
+
+    pub fn get_program(&self) -> &OsStr {
+        OsStr::from_bytes(self.program.as_bytes())
+    }
+
+    pub fn get_args(&self) -> CommandArgs<'_> {
+        let mut iter = self.args.iter();
+        iter.next();
+        CommandArgs { iter }
+    }
+
+    pub fn get_envs(&self) -> CommandEnvs<'_> {
+        self.env.iter()
+    }
+
+    pub fn get_current_dir(&self) -> Option<&Path> {
+        self.cwd.as_ref().map(|cs| Path::new(OsStr::from_bytes(cs.as_bytes())))
+    }
+
     pub fn get_argv(&self) -> &Vec<*const c_char> {
         &self.argv.0
     }
 
-    pub fn get_program(&self) -> &CStr {
+    pub fn get_program_cstr(&self) -> &CStr {
         &*self.program
     }
 
@@ -402,3 +422,32 @@ impl ExitCode {
         self.0 as i32
     }
 }
+
+pub struct CommandArgs<'a> {
+    iter: crate::slice::Iter<'a, CString>,
+}
+
+impl<'a> Iterator for CommandArgs<'a> {
+    type Item = &'a OsStr;
+    fn next(&mut self) -> Option<&'a OsStr> {
+        self.iter.next().map(|cs| OsStr::from_bytes(cs.as_bytes()))
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> ExactSizeIterator for CommandArgs<'a> {
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
+
+impl<'a> fmt::Debug for CommandArgs<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_list().entries(self.iter.clone()).finish()
+    }
+}
diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs
index 08efe154e4c3b..50f5e78cf2a88 100644
--- a/library/std/src/sys/unix/process/process_unix.rs
+++ b/library/std/src/sys/unix/process/process_unix.rs
@@ -245,7 +245,7 @@ impl Command {
             *sys::os::environ() = envp.as_ptr();
         }
 
-        libc::execvp(self.get_program().as_ptr(), self.get_argv().as_ptr());
+        libc::execvp(self.get_program_cstr().as_ptr(), self.get_argv().as_ptr());
         Err(io::Error::last_os_error())
     }
 
@@ -383,7 +383,7 @@ impl Command {
             let envp = envp.map(|c| c.as_ptr()).unwrap_or_else(|| *sys::os::environ() as *const _);
             let ret = libc::posix_spawnp(
                 &mut p.pid,
-                self.get_program().as_ptr(),
+                self.get_program_cstr().as_ptr(),
                 file_actions.0.as_ptr(),
                 attrs.0.as_ptr(),
                 self.get_argv().as_ptr() as *const _,
diff --git a/library/std/src/sys/unsupported/process.rs b/library/std/src/sys/unsupported/process.rs
index 7156c9ab92f2b..3ede2291d5a91 100644
--- a/library/std/src/sys/unsupported/process.rs
+++ b/library/std/src/sys/unsupported/process.rs
@@ -1,10 +1,12 @@
 use crate::ffi::OsStr;
 use crate::fmt;
 use crate::io;
+use crate::marker::PhantomData;
+use crate::path::Path;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::{unsupported, Void};
-use crate::sys_common::process::CommandEnv;
+use crate::sys_common::process::{CommandEnv, CommandEnvs};
 
 pub use crate::ffi::OsString as EnvKey;
 
@@ -49,6 +51,22 @@ impl Command {
 
     pub fn stderr(&mut self, _stderr: Stdio) {}
 
+    pub fn get_program(&self) -> &OsStr {
+        panic!("unsupported")
+    }
+
+    pub fn get_args(&self) -> CommandArgs<'_> {
+        CommandArgs { _p: PhantomData }
+    }
+
+    pub fn get_envs(&self) -> CommandEnvs<'_> {
+        self.env.iter()
+    }
+
+    pub fn get_current_dir(&self) -> Option<&Path> {
+        None
+    }
+
     pub fn spawn(
         &mut self,
         _default: Stdio,
@@ -147,3 +165,22 @@ impl Process {
         match self.0 {}
     }
 }
+
+pub struct CommandArgs<'a> {
+    _p: PhantomData<&'a ()>,
+}
+
+impl<'a> Iterator for CommandArgs<'a> {
+    type Item = &'a OsStr;
+    fn next(&mut self) -> Option<&'a OsStr> {
+        None
+    }
+}
+
+impl<'a> ExactSizeIterator for CommandArgs<'a> {}
+
+impl<'a> fmt::Debug for CommandArgs<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_list().finish()
+    }
+}
diff --git a/library/std/src/sys/windows/process.rs b/library/std/src/sys/windows/process.rs
index e18521bb30d91..243065b94b125 100644
--- a/library/std/src/sys/windows/process.rs
+++ b/library/std/src/sys/windows/process.rs
@@ -22,7 +22,7 @@ use crate::sys::handle::Handle;
 use crate::sys::mutex::Mutex;
 use crate::sys::pipe::{self, AnonPipe};
 use crate::sys::stdio;
-use crate::sys_common::process::CommandEnv;
+use crate::sys_common::process::{CommandEnv, CommandEnvs};
 use crate::sys_common::AsInner;
 
 use libc::{c_void, EXIT_FAILURE, EXIT_SUCCESS};
@@ -134,6 +134,23 @@ impl Command {
         self.flags = flags;
     }
 
+    pub fn get_program(&self) -> &OsStr {
+        &self.program
+    }
+
+    pub fn get_args(&self) -> CommandArgs<'_> {
+        let iter = self.args.iter();
+        CommandArgs { iter }
+    }
+
+    pub fn get_envs(&self) -> CommandEnvs<'_> {
+        self.env.iter()
+    }
+
+    pub fn get_current_dir(&self) -> Option<&Path> {
+        self.cwd.as_ref().map(|cwd| Path::new(cwd))
+    }
+
     pub fn spawn(
         &mut self,
         default: Stdio,
@@ -529,3 +546,32 @@ fn make_dirp(d: Option<&OsString>) -> io::Result<(*const u16, Vec<u16>)> {
         None => Ok((ptr::null(), Vec::new())),
     }
 }
+
+pub struct CommandArgs<'a> {
+    iter: crate::slice::Iter<'a, OsString>,
+}
+
+impl<'a> Iterator for CommandArgs<'a> {
+    type Item = &'a OsStr;
+    fn next(&mut self) -> Option<&'a OsStr> {
+        self.iter.next().map(|s| s.as_ref())
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> ExactSizeIterator for CommandArgs<'a> {
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
+
+impl<'a> fmt::Debug for CommandArgs<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_list().entries(self.iter.clone()).finish()
+    }
+}
diff --git a/library/std/src/sys_common/process.rs b/library/std/src/sys_common/process.rs
index f3a2962098b4d..fe89b11043c0f 100644
--- a/library/std/src/sys_common/process.rs
+++ b/library/std/src/sys_common/process.rs
@@ -92,4 +92,41 @@ impl CommandEnv {
             self.saw_path = true;
         }
     }
+
+    pub fn iter(&self) -> CommandEnvs<'_> {
+        let iter = self.vars.iter();
+        CommandEnvs { iter }
+    }
+}
+
+/// An iterator over the command environment variables.
+///
+/// This struct is created by
+/// [`Command::get_envs`][crate::process::Command::get_envs]. See its
+/// documentation for more.
+#[unstable(feature = "command_access", issue = "44434")]
+#[derive(Debug)]
+pub struct CommandEnvs<'a> {
+    iter: crate::collections::btree_map::Iter<'a, EnvKey, Option<OsString>>,
+}
+
+#[unstable(feature = "command_access", issue = "44434")]
+impl<'a> Iterator for CommandEnvs<'a> {
+    type Item = (&'a OsStr, Option<&'a OsStr>);
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|(key, value)| (key.as_ref(), value.as_deref()))
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[unstable(feature = "command_access", issue = "44434")]
+impl<'a> ExactSizeIterator for CommandEnvs<'a> {
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
 }

From 945a732dd6c3928e0219a862066c92bde45d26bf Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Wed, 23 Sep 2020 16:18:59 -0700
Subject: [PATCH 03/21] Update mdBook

0.4.2 -> 0.4.3
---
 Cargo.lock                    | 4 ++--
 src/tools/rustbook/Cargo.toml | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 68288916e6d12..3727e3d20f86b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1848,9 +1848,9 @@ dependencies = [
 
 [[package]]
 name = "mdbook"
-version = "0.4.2"
+version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b75e31ae4eaa0e45e17ee2b6b9e3ed969c3c6ff12bb4c2e352c42493f4ebb706"
+checksum = "29be448fcafb00c5a8966c4020c2a5ffbbc333e5b96d0bb5ef54b5bd0524d9ff"
 dependencies = [
  "ammonia",
  "anyhow",
diff --git a/src/tools/rustbook/Cargo.toml b/src/tools/rustbook/Cargo.toml
index f0a6ce2fa06c2..f5e5c0867b48a 100644
--- a/src/tools/rustbook/Cargo.toml
+++ b/src/tools/rustbook/Cargo.toml
@@ -9,6 +9,6 @@ edition = "2018"
 clap = "2.25.0"
 
 [dependencies.mdbook]
-version = "0.4.0"
+version = "0.4.3"
 default-features = false
 features = ["search"]

From 50d96635872b0625da84b7f2e2556b1804cc9de7 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Wed, 23 Sep 2020 17:06:56 -0700
Subject: [PATCH 04/21] Update cargo

---
 src/tools/cargo | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tools/cargo b/src/tools/cargo
index 8777a6b1e8834..05c611ae3c425 160000
--- a/src/tools/cargo
+++ b/src/tools/cargo
@@ -1 +1 @@
-Subproject commit 8777a6b1e8834899f51b7e09cc9b8d85b2417110
+Subproject commit 05c611ae3c4255b7a2bcf4fcfa65b20286a07839

From ecf389547cf4ef5d8b7b18de5264426617e824d3 Mon Sep 17 00:00:00 2001
From: Lzu Tao <taolzu@gmail.com>
Date: Wed, 16 Sep 2020 15:35:58 +0000
Subject: [PATCH 05/21] Add MIPS asm! support

This patch also:
* Add soft-float supports: only f32
* zero-extend i8/i16 to i32 because MIPS only supports register-length
  arithmetic.
* Update table in asm! chapter in unstable book.
---
 compiler/rustc_codegen_llvm/src/asm.rs        |  25 +++
 compiler/rustc_target/src/asm/mips.rs         | 132 ++++++++++++
 compiler/rustc_target/src/asm/mod.rs          |  25 +++
 .../unstable-book/src/library-features/asm.md |  17 +-
 src/test/assembly/asm/mips-types.rs           | 191 ++++++++++++++++++
 5 files changed, 389 insertions(+), 1 deletion(-)
 create mode 100644 compiler/rustc_target/src/asm/mips.rs
 create mode 100644 src/test/assembly/asm/mips-types.rs

diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index a468d09c2d93d..f801f845ac16c 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -259,6 +259,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 InlineAsmArch::RiscV32 | InlineAsmArch::RiscV64 => {}
                 InlineAsmArch::Nvptx64 => {}
                 InlineAsmArch::Hexagon => {}
+                InlineAsmArch::Mips => {}
             }
         }
         if !options.contains(InlineAsmOptions::NOMEM) {
@@ -505,6 +506,8 @@ fn reg_to_llvm(reg: InlineAsmRegOrRegClass, layout: Option<&TyAndLayout<'tcx>>)
             InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg)
             | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg) => "w",
             InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => "r",
+            InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg) => "r",
+            InlineAsmRegClass::Mips(MipsInlineAsmRegClass::freg) => "f",
             InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg16) => "h",
             InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg32) => "r",
             InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg64) => "l",
@@ -551,6 +554,7 @@ fn modifier_to_llvm(
             }
         }
         InlineAsmRegClass::Hexagon(_) => None,
+        InlineAsmRegClass::Mips(_) => None,
         InlineAsmRegClass::Nvptx(_) => None,
         InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg)
         | InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => None,
@@ -603,6 +607,8 @@ fn dummy_output_type(cx: &CodegenCx<'ll, 'tcx>, reg: InlineAsmRegClass) -> &'ll
             cx.type_vector(cx.type_i64(), 2)
         }
         InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => cx.type_i32(),
+        InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg) => cx.type_i32(),
+        InlineAsmRegClass::Mips(MipsInlineAsmRegClass::freg) => cx.type_f32(),
         InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg16) => cx.type_i16(),
         InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg32) => cx.type_i32(),
         InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg64) => cx.type_i64(),
@@ -700,6 +706,12 @@ fn llvm_fixup_input(
                 value
             }
         }
+        (InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg), Abi::Scalar(s)) => match s.value {
+            // MIPS only supports register-length arithmetics.
+            Primitive::Int(Integer::I8 | Integer::I16, _) => bx.zext(value, bx.cx.type_i32()),
+            Primitive::F32 => bx.bitcast(value, bx.cx.type_i32()),
+            _ => value,
+        },
         _ => value,
     }
 }
@@ -768,6 +780,13 @@ fn llvm_fixup_output(
                 value
             }
         }
+        (InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg), Abi::Scalar(s)) => match s.value {
+            // MIPS only supports register-length arithmetics.
+            Primitive::Int(Integer::I8, _) => bx.trunc(value, bx.cx.type_i8()),
+            Primitive::Int(Integer::I16, _) => bx.trunc(value, bx.cx.type_i16()),
+            Primitive::F32 => bx.bitcast(value, bx.cx.type_f32()),
+            _ => value,
+        },
         _ => value,
     }
 }
@@ -831,6 +850,12 @@ fn llvm_fixup_output_type(
                 layout.llvm_type(cx)
             }
         }
+        (InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg), Abi::Scalar(s)) => match s.value {
+            // MIPS only supports register-length arithmetics.
+            Primitive::Int(Integer::I8 | Integer::I16, _) => cx.type_i32(),
+            Primitive::F32 => cx.type_i32(),
+            _ => layout.llvm_type(cx),
+        },
         _ => layout.llvm_type(cx),
     }
 }
diff --git a/compiler/rustc_target/src/asm/mips.rs b/compiler/rustc_target/src/asm/mips.rs
new file mode 100644
index 0000000000000..638c52d97f1e3
--- /dev/null
+++ b/compiler/rustc_target/src/asm/mips.rs
@@ -0,0 +1,132 @@
+use super::{InlineAsmArch, InlineAsmType};
+use rustc_macros::HashStable_Generic;
+use std::fmt;
+
+def_reg_class! {
+    Mips MipsInlineAsmRegClass {
+        reg,
+        freg,
+    }
+}
+
+impl MipsInlineAsmRegClass {
+    pub fn valid_modifiers(self, _arch: super::InlineAsmArch) -> &'static [char] {
+        &[]
+    }
+
+    pub fn suggest_class(self, _arch: InlineAsmArch, _ty: InlineAsmType) -> Option<Self> {
+        None
+    }
+
+    pub fn suggest_modifier(
+        self,
+        _arch: InlineAsmArch,
+        _ty: InlineAsmType,
+    ) -> Option<(char, &'static str)> {
+        None
+    }
+
+    pub fn default_modifier(self, _arch: InlineAsmArch) -> Option<(char, &'static str)> {
+        None
+    }
+
+    pub fn supported_types(
+        self,
+        _arch: InlineAsmArch,
+    ) -> &'static [(InlineAsmType, Option<&'static str>)] {
+        match self {
+            Self::reg => types! { _: I8, I16, I32, F32; },
+            Self::freg => types! { _: F32; },
+        }
+    }
+}
+
+// The reserved registers are somewhat taken from <https://git.io/JUR1k#L150>.
+def_regs! {
+    Mips MipsInlineAsmReg MipsInlineAsmRegClass {
+        v0: reg = ["$2", "$v0"],
+        v1: reg = ["$3", "$v1"],
+        a0: reg = ["$4", "$a0"],
+        a1: reg = ["$5", "$a1"],
+        a2: reg = ["$6", "$a2"],
+        a3: reg = ["$7", "$a3"],
+        // FIXME: Reserve $t0, $t1 if in mips16 mode.
+        t0: reg = ["$8", "$t0"],
+        t1: reg = ["$9", "$t1"],
+        t2: reg = ["$10", "$t2"],
+        t3: reg = ["$11", "$t3"],
+        t4: reg = ["$12", "$t4"],
+        t5: reg = ["$13", "$t5"],
+        t6: reg = ["$14", "$t6"],
+        t7: reg = ["$15", "$t7"],
+        s0: reg = ["$16", "$s0"],
+        s1: reg = ["$17", "$s1"],
+        s2: reg = ["$18", "$s2"],
+        s3: reg = ["$19", "$s3"],
+        s4: reg = ["$20", "$s4"],
+        s5: reg = ["$21", "$s5"],
+        s6: reg = ["$22", "$s6"],
+        s7: reg = ["$23", "$s7"],
+        t8: reg = ["$24", "$t8"],
+        t9: reg = ["$25", "$t9"],
+        f0: freg = ["$f0"],
+        f1: freg = ["$f1"],
+        f2: freg = ["$f2"],
+        f3: freg = ["$f3"],
+        f4: freg = ["$f4"],
+        f5: freg = ["$f5"],
+        f6: freg = ["$f6"],
+        f7: freg = ["$f7"],
+        f8: freg = ["$f8"],
+        f9: freg = ["$f9"],
+        f10: freg = ["$f10"],
+        f11: freg = ["$f11"],
+        f12: freg = ["$f12"],
+        f13: freg = ["$f13"],
+        f14: freg = ["$f14"],
+        f15: freg = ["$f15"],
+        f16: freg = ["$f16"],
+        f17: freg = ["$f17"],
+        f18: freg = ["$f18"],
+        f19: freg = ["$f19"],
+        f20: freg = ["$f20"],
+        f21: freg = ["$f21"],
+        f22: freg = ["$f22"],
+        f23: freg = ["$f23"],
+        f24: freg = ["$f24"],
+        f25: freg = ["$f25"],
+        f26: freg = ["$f26"],
+        f27: freg = ["$f27"],
+        f28: freg = ["$f28"],
+        f29: freg = ["$f29"],
+        f30: freg = ["$f30"],
+        f31: freg = ["$f31"],
+        #error = ["$0", "$zero"] =>
+            "constant zero cannot be used as an operand for inline asm",
+        #error = ["$1", "$at"] =>
+            "reserved for assembler (Assembler Temp)",
+        #error = ["$26", "$k0"] =>
+            "OS-reserved register cannot be used as an operand for inline asm",
+        #error = ["$27", "$k1"] =>
+            "OS-reserved register cannot be used as an operand for inline asm",
+        #error = ["$28", "$gp"] =>
+            "the global pointer cannot be used as an operand for inline asm",
+        #error = ["$29", "$sp"] =>
+            "the stack pointer cannot be used as an operand for inline asm",
+        #error = ["$30", "$s8", "$fp"] =>
+            "the frame pointer cannot be used as an operand for inline asm",
+        #error = ["$31", "$ra"] =>
+            "the return address register cannot be used as an operand for inline asm",
+    }
+}
+
+impl MipsInlineAsmReg {
+    pub fn emit(
+        self,
+        out: &mut dyn fmt::Write,
+        _arch: InlineAsmArch,
+        _modifier: Option<char>,
+    ) -> fmt::Result {
+        out.write_str(self.name())
+    }
+}
diff --git a/compiler/rustc_target/src/asm/mod.rs b/compiler/rustc_target/src/asm/mod.rs
index c22644bf813a4..e2f8e91fa9574 100644
--- a/compiler/rustc_target/src/asm/mod.rs
+++ b/compiler/rustc_target/src/asm/mod.rs
@@ -152,6 +152,7 @@ macro_rules! types {
 mod aarch64;
 mod arm;
 mod hexagon;
+mod mips;
 mod nvptx;
 mod riscv;
 mod x86;
@@ -159,6 +160,7 @@ mod x86;
 pub use aarch64::{AArch64InlineAsmReg, AArch64InlineAsmRegClass};
 pub use arm::{ArmInlineAsmReg, ArmInlineAsmRegClass};
 pub use hexagon::{HexagonInlineAsmReg, HexagonInlineAsmRegClass};
+pub use mips::{MipsInlineAsmReg, MipsInlineAsmRegClass};
 pub use nvptx::{NvptxInlineAsmReg, NvptxInlineAsmRegClass};
 pub use riscv::{RiscVInlineAsmReg, RiscVInlineAsmRegClass};
 pub use x86::{X86InlineAsmReg, X86InlineAsmRegClass};
@@ -173,6 +175,7 @@ pub enum InlineAsmArch {
     RiscV64,
     Nvptx64,
     Hexagon,
+    Mips,
 }
 
 impl FromStr for InlineAsmArch {
@@ -188,6 +191,7 @@ impl FromStr for InlineAsmArch {
             "riscv64" => Ok(Self::RiscV64),
             "nvptx64" => Ok(Self::Nvptx64),
             "hexagon" => Ok(Self::Hexagon),
+            "mips" => Ok(Self::Mips),
             _ => Err(()),
         }
     }
@@ -201,6 +205,7 @@ pub enum InlineAsmReg {
     RiscV(RiscVInlineAsmReg),
     Nvptx(NvptxInlineAsmReg),
     Hexagon(HexagonInlineAsmReg),
+    Mips(MipsInlineAsmReg),
 }
 
 impl InlineAsmReg {
@@ -211,6 +216,7 @@ impl InlineAsmReg {
             Self::AArch64(r) => r.name(),
             Self::RiscV(r) => r.name(),
             Self::Hexagon(r) => r.name(),
+            Self::Mips(r) => r.name(),
         }
     }
 
@@ -221,6 +227,7 @@ impl InlineAsmReg {
             Self::AArch64(r) => InlineAsmRegClass::AArch64(r.reg_class()),
             Self::RiscV(r) => InlineAsmRegClass::RiscV(r.reg_class()),
             Self::Hexagon(r) => InlineAsmRegClass::Hexagon(r.reg_class()),
+            Self::Mips(r) => InlineAsmRegClass::Mips(r.reg_class()),
         }
     }
 
@@ -252,6 +259,9 @@ impl InlineAsmReg {
             InlineAsmArch::Hexagon => {
                 Self::Hexagon(HexagonInlineAsmReg::parse(arch, has_feature, target, &name)?)
             }
+            InlineAsmArch::Mips => {
+                Self::Mips(MipsInlineAsmReg::parse(arch, has_feature, target, &name)?)
+            }
         })
     }
 
@@ -269,6 +279,7 @@ impl InlineAsmReg {
             Self::AArch64(r) => r.emit(out, arch, modifier),
             Self::RiscV(r) => r.emit(out, arch, modifier),
             Self::Hexagon(r) => r.emit(out, arch, modifier),
+            Self::Mips(r) => r.emit(out, arch, modifier),
         }
     }
 
@@ -279,6 +290,7 @@ impl InlineAsmReg {
             Self::AArch64(_) => cb(self),
             Self::RiscV(_) => cb(self),
             Self::Hexagon(r) => r.overlapping_regs(|r| cb(Self::Hexagon(r))),
+            Self::Mips(_) => cb(self),
         }
     }
 }
@@ -291,6 +303,7 @@ pub enum InlineAsmRegClass {
     RiscV(RiscVInlineAsmRegClass),
     Nvptx(NvptxInlineAsmRegClass),
     Hexagon(HexagonInlineAsmRegClass),
+    Mips(MipsInlineAsmRegClass),
 }
 
 impl InlineAsmRegClass {
@@ -302,6 +315,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.name(),
             Self::Nvptx(r) => r.name(),
             Self::Hexagon(r) => r.name(),
+            Self::Mips(r) => r.name(),
         }
     }
 
@@ -316,6 +330,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.suggest_class(arch, ty).map(InlineAsmRegClass::RiscV),
             Self::Nvptx(r) => r.suggest_class(arch, ty).map(InlineAsmRegClass::Nvptx),
             Self::Hexagon(r) => r.suggest_class(arch, ty).map(InlineAsmRegClass::Hexagon),
+            Self::Mips(r) => r.suggest_class(arch, ty).map(InlineAsmRegClass::Mips),
         }
     }
 
@@ -337,6 +352,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.suggest_modifier(arch, ty),
             Self::Nvptx(r) => r.suggest_modifier(arch, ty),
             Self::Hexagon(r) => r.suggest_modifier(arch, ty),
+            Self::Mips(r) => r.suggest_modifier(arch, ty),
         }
     }
 
@@ -354,6 +370,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.default_modifier(arch),
             Self::Nvptx(r) => r.default_modifier(arch),
             Self::Hexagon(r) => r.default_modifier(arch),
+            Self::Mips(r) => r.default_modifier(arch),
         }
     }
 
@@ -370,6 +387,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.supported_types(arch),
             Self::Nvptx(r) => r.supported_types(arch),
             Self::Hexagon(r) => r.supported_types(arch),
+            Self::Mips(r) => r.supported_types(arch),
         }
     }
 
@@ -391,6 +409,7 @@ impl InlineAsmRegClass {
                 InlineAsmArch::Hexagon => {
                     Self::Hexagon(HexagonInlineAsmRegClass::parse(arch, name)?)
                 }
+                InlineAsmArch::Mips => Self::Mips(MipsInlineAsmRegClass::parse(arch, name)?),
             })
         })
     }
@@ -405,6 +424,7 @@ impl InlineAsmRegClass {
             Self::RiscV(r) => r.valid_modifiers(arch),
             Self::Nvptx(r) => r.valid_modifiers(arch),
             Self::Hexagon(r) => r.valid_modifiers(arch),
+            Self::Mips(r) => r.valid_modifiers(arch),
         }
     }
 }
@@ -545,5 +565,10 @@ pub fn allocatable_registers(
             hexagon::fill_reg_map(arch, has_feature, target, &mut map);
             map
         }
+        InlineAsmArch::Mips => {
+            let mut map = mips::regclass_map();
+            mips::fill_reg_map(arch, has_feature, target, &mut map);
+            map
+        }
     }
 }
diff --git a/src/doc/unstable-book/src/library-features/asm.md b/src/doc/unstable-book/src/library-features/asm.md
index 28a5fe31fc4b5..9b68f462dca70 100644
--- a/src/doc/unstable-book/src/library-features/asm.md
+++ b/src/doc/unstable-book/src/library-features/asm.md
@@ -27,6 +27,7 @@ Inline assembly is currently supported on the following architectures:
 - RISC-V
 - NVPTX
 - Hexagon
+- MIPS32
 
 ## Basic usage
 
@@ -493,6 +494,8 @@ Here is the list of currently supported register classes:
 | ARM | `qreg` | `q[0-15]` | `w` |
 | ARM | `qreg_low8` | `q[0-7]` | `t` |
 | ARM | `qreg_low4` | `q[0-3]` | `x` |
+| MIPS32 | `reg` | `$[2-25]` | `r` |
+| MIPS32 | `freg` | `$f[0-31]` | `f` |
 | NVPTX | `reg16` | None\* | `h` |
 | NVPTX | `reg32` | None\* | `r` |
 | NVPTX | `reg64` | None\* | `l` |
@@ -528,6 +531,8 @@ Each register class has constraints on which value types they can be used with.
 | ARM | `sreg` | `vfp2` | `i32`, `f32` |
 | ARM | `dreg` | `vfp2` | `i64`, `f64`, `i8x8`, `i16x4`, `i32x2`, `i64x1`, `f32x2` |
 | ARM | `qreg` | `neon` | `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4` |
+| MIPS32 | `reg` | None | `i8`, `i16`, `i32`, `f32` |
+| MIPS32 | `freg` | None | `f32` |
 | NVPTX | `reg16` | None | `i8`, `i16` |
 | NVPTX | `reg32` | None | `i8`, `i16`, `i32`, `f32` |
 | NVPTX | `reg64` | None | `i8`, `i16`, `i32`, `f32`, `i64`, `f64` |
@@ -576,6 +581,7 @@ Some registers have multiple names. These are all treated by the compiler as ide
 | ARM | `r13` | `sp` |
 | ARM | `r14` | `lr` |
 | ARM | `r15` | `pc` |
+| MIPS32 | `$[2-25]` | Please [see the Wikipedia page][mips-regs] |
 | RISC-V | `x0` | `zero` |
 | RISC-V | `x1` | `ra` |
 | RISC-V | `x2` | `sp` |
@@ -596,12 +602,14 @@ Some registers have multiple names. These are all treated by the compiler as ide
 | Hexagon | `r30` | `fr` |
 | Hexagon | `r31` | `lr` |
 
+[mips-regs]: https://en.wikibooks.org/wiki/MIPS_Assembly/Register_File#Registers
+
 Some registers cannot be used for input or output operands:
 
 | Architecture | Unsupported register | Reason |
 | ------------ | -------------------- | ------ |
 | All | `sp` | The stack pointer must be restored to its original value at the end of an asm code block. |
-| All | `bp` (x86), `x29` (AArch64), `x8` (RISC-V), `fr` (Hexagon) | The frame pointer cannot be used as an input or output. |
+| All | `bp` (x86), `x29` (AArch64), `x8` (RISC-V), `fr` (Hexagon), `$fp` (MIPS) | The frame pointer cannot be used as an input or output. |
 | ARM | `r7` or `r11` | On ARM the frame pointer can be either `r7` or `r11` depending on the target. The frame pointer cannot be used as an input or output. |
 | ARM | `r6` | `r6` is used internally by LLVM as a base pointer and therefore cannot be used as an input or output. |
 | x86 | `k0` | This is a constant zero register which can't be modified. |
@@ -610,6 +618,11 @@ Some registers cannot be used for input or output operands:
 | x86 | `st([0-7])` | x87 registers are not currently supported (but may be in the future). |
 | AArch64 | `xzr` | This is a constant zero register which can't be modified. |
 | ARM | `pc` | This is the program counter, not a real register. |
+| MIPS32 | `$0` or `$zero` | This is a constant zero register which can't be modified. |
+| MIPS32 | `$1` or `$at` | Reserved for assembler. |
+| MIPS32 | `$26`/`$k0`, `$27`/`$k1` | OS-reserved registers. |
+| MIPS32 | `$28`/`$gp` | Global pointer cannot be used as inputs or outputs. |
+| MIPS32 | `$ra` | Return address cannot be used as inputs or outputs. |
 | RISC-V | `x0` | This is a constant zero register which can't be modified. |
 | RISC-V | `gp`, `tp` | These registers are reserved and cannot be used as inputs or outputs. |
 | Hexagon | `lr` | This is the link register which cannot be used as an input or output. |
@@ -657,6 +670,8 @@ The supported modifiers are a subset of LLVM's (and GCC's) [asm template argumen
 | ARM | `dreg` | None | `d0` | `P` |
 | ARM | `qreg` | None | `q0` | `q` |
 | ARM | `qreg` | `e` / `f` | `d0` / `d1` | `e` / `f` |
+| MIPS32 | `reg` | None | `$2` | None |
+| MIPS32 | `freg` | None | `$f0` | None |
 | NVPTX | `reg16` | None | `rs0` | None |
 | NVPTX | `reg32` | None | `r0` | None |
 | NVPTX | `reg64` | None | `rd0` | None |
diff --git a/src/test/assembly/asm/mips-types.rs b/src/test/assembly/asm/mips-types.rs
new file mode 100644
index 0000000000000..d23bcedd1fa3a
--- /dev/null
+++ b/src/test/assembly/asm/mips-types.rs
@@ -0,0 +1,191 @@
+// no-system-llvm
+// assembly-output: emit-asm
+// compile-flags: --target mips-unknown-linux-gnu
+// needs-llvm-components: mips
+
+#![feature(no_core, lang_items, rustc_attrs, repr_simd)]
+#![crate_type = "rlib"]
+#![no_core]
+#![allow(asm_sub_register, non_camel_case_types)]
+
+#[rustc_builtin_macro]
+macro_rules! asm {
+    () => {};
+}
+#[rustc_builtin_macro]
+macro_rules! concat {
+    () => {};
+}
+#[rustc_builtin_macro]
+macro_rules! stringify {
+    () => {};
+}
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
+
+type ptr = *const i32;
+
+impl Copy for i8 {}
+impl Copy for u8 {}
+impl Copy for i16 {}
+impl Copy for i32 {}
+impl Copy for f32 {}
+impl Copy for ptr {}
+extern "C" {
+    fn extern_func();
+    static extern_static: u8;
+}
+
+// Hack to avoid function merging
+extern "Rust" {
+    fn dont_merge(s: &str);
+}
+
+macro_rules! check { ($func:ident, $ty:ty, $class:ident) => {
+    #[no_mangle]
+    pub unsafe fn $func(x: $ty) -> $ty {
+        dont_merge(stringify!($func));
+
+        let y;
+        asm!("move {}, {}", out($class) y, in($class) x);
+        y
+    }
+};}
+
+macro_rules! check_reg { ($func:ident, $ty:ty, $reg:tt) => {
+    #[no_mangle]
+    pub unsafe fn $func(x: $ty) -> $ty {
+        dont_merge(stringify!($func));
+
+        let y;
+        asm!(concat!("move ", $reg, ", ", $reg), lateout($reg) y, in($reg) x);
+        y
+    }
+};}
+
+// CHECK-LABEL: sym_static:
+// CHECK: #APP
+// CHECK: lw $3, %got(extern_static)
+// CHECK: #NO_APP
+#[no_mangle]
+pub unsafe fn sym_static() {
+    dont_merge(stringify!($func));
+
+    asm!("la $v1, {}", sym extern_static);
+}
+
+// CHECK-LABEL: sym_fn:
+// CHECK: #APP
+// CHECK: lw $3, %got(extern_func)
+// CHECK: #NO_APP
+#[no_mangle]
+pub unsafe fn sym_fn() {
+    dont_merge(stringify!($func));
+
+    asm!("la $v1, {}", sym extern_func);
+}
+
+// CHECK-LABEL: reg_f32:
+// CHECK: #APP
+// CHECK: mov.s $f0, $f{{(2[0-9])|(3[0-1])}}
+// CHECK: #NO_APP
+#[no_mangle]
+pub unsafe fn reg_f32(x: f32) -> f32 {
+    dont_merge("reg_f32");
+    let y;
+    asm!("mov.s {}, {}", out(freg) y, in(freg) x);
+    y
+}
+
+// CHECK-LABEL: f0_f32:
+// CHECK: #APP
+// CHECK: mov.s $f0, $f0
+// CHECK: #NO_APP
+#[no_mangle]
+pub unsafe fn f0_f32(x: f32) -> f32 {
+    dont_merge("f0_f32");
+    let y;
+    asm!("mov.s $f0, $f0", lateout("$f0") y, in("$f0") x);
+    y
+}
+
+// CHECK-LABEL: reg_ptr:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, ${{(1[6-9])|(2[0-3])}}
+// CHECK: #NO_APP
+check!(reg_ptr, ptr, reg);
+
+// CHECK-LABEL: reg_i32:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, ${{(1[6-9])|(2[0-3])}}
+// CHECK: #NO_APP
+check!(reg_i32, i32, reg);
+
+// CHECK-LABEL: reg_f32_soft:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, $1
+// CHECK: #NO_APP
+check!(reg_f32_soft, f32, reg);
+
+// CHECK-LABEL: reg_i8:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, $1
+// CHECK: #NO_APP
+check!(reg_i8, i8, reg);
+
+// CHECK-LABEL: reg_u8:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, $1
+// CHECK: #NO_APP
+check!(reg_u8, u8, reg);
+
+// CHECK-LABEL: reg_i16:
+// CHECK: #APP
+// CHECK: move ${{[2-3]}}, $1
+// CHECK: #NO_APP
+check!(reg_i16, i16, reg);
+
+// CHECK-LABEL: t0_ptr:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_ptr, ptr, "$t0");
+
+// CHECK-LABEL: t0_i32:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_i32, i32, "$t0");
+
+// CHECK-LABEL: t0_f32:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_f32, f32, "$t0");
+
+// CHECK-LABEL: t0_i8:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_i8, i8, "$t0");
+
+// CHECK-LABEL: t0_u8:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_u8, u8, "$t0");
+
+// CHECK-LABEL: t0_i16:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(t0_i16, i16, "$t0");
+
+// CHECK-LABEL: r8_i16:
+// CHECK: #APP
+// CHECK: move $8, $8
+// CHECK: #NO_APP
+check_reg!(r8_i16, i16, "$8");

From 9baa601afd50f57655be9eb7e5e2892c2ea9f005 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 12 Sep 2020 02:32:43 -0400
Subject: [PATCH 06/21] Add `x.py setup`

- Suggest `x.py setup` if config.toml doesn't exist yet (twice, once
before and once after the build)
- Prompt for a profile if not given on the command line
- Print the configuration file that will be used
- Print helpful starting commands after setup
- Link to the dev-guide after finishing
- Note that distro maintainers will see the changelog warning
---
 src/bootstrap/CHANGELOG.md |  1 +
 src/bootstrap/bin/main.rs  | 19 ++++++--
 src/bootstrap/builder.rs   |  4 +-
 src/bootstrap/config.rs    |  7 ++-
 src/bootstrap/flags.rs     | 32 +++++++++++++-
 src/bootstrap/lib.rs       |  7 ++-
 src/bootstrap/run.rs       |  2 +-
 src/bootstrap/setup.rs     | 88 ++++++++++++++++++++++++++++++++++++++
 8 files changed, 152 insertions(+), 8 deletions(-)
 create mode 100644 src/bootstrap/setup.rs

diff --git a/src/bootstrap/CHANGELOG.md b/src/bootstrap/CHANGELOG.md
index 5fcaafab959e9..aa398f25020f1 100644
--- a/src/bootstrap/CHANGELOG.md
+++ b/src/bootstrap/CHANGELOG.md
@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Non-breaking changes since the last major version]
 
+- Add `x.py setup` [#76631](https://github.com/rust-lang/rust/pull/76631)
 - Add a changelog for x.py [#76626](https://github.com/rust-lang/rust/pull/76626)
 - Optionally, download LLVM from CI on Linux and NixOS
   + [#76439](https://github.com/rust-lang/rust/pull/76349)
diff --git a/src/bootstrap/bin/main.rs b/src/bootstrap/bin/main.rs
index f7512aa9fcebd..669dd7a33de18 100644
--- a/src/bootstrap/bin/main.rs
+++ b/src/bootstrap/bin/main.rs
@@ -7,21 +7,34 @@
 
 use std::env;
 
-use bootstrap::{Build, Config};
+use bootstrap::{Build, Config, Subcommand};
 
 fn main() {
     let args = env::args().skip(1).collect::<Vec<_>>();
     let config = Config::parse(&args);
 
     let changelog_suggestion = check_version(&config);
-    if let Some(suggestion) = &changelog_suggestion {
+
+    // NOTE: Since `./configure` generates a `config.toml`, distro maintainers will see the
+    // changelog warning, not the `x.py setup` message.
+    let suggest_setup = !config.config.exists() && !matches!(config.cmd, Subcommand::Setup { .. });
+    if suggest_setup {
+        println!("warning: you have not made a `config.toml`");
+        println!("help: consider running `x.py setup` or copying `config.toml.example`");
+    } else if let Some(suggestion) = &changelog_suggestion {
         println!("{}", suggestion);
     }
 
     Build::new(config).build();
 
-    if let Some(suggestion) = changelog_suggestion {
+    if suggest_setup {
+        println!("warning: you have not made a `config.toml`");
+        println!("help: consider running `x.py setup` or copying `config.toml.example`");
+    } else if let Some(suggestion) = &changelog_suggestion {
         println!("{}", suggestion);
+    }
+
+    if suggest_setup || changelog_suggestion.is_some() {
         println!("note: this message was printed twice to make it more likely to be seen");
     }
 }
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index d2537d65e67f5..4aaaeb8a93bda 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -549,7 +549,9 @@ impl<'a> Builder<'a> {
             Subcommand::Dist { ref paths } => (Kind::Dist, &paths[..]),
             Subcommand::Install { ref paths } => (Kind::Install, &paths[..]),
             Subcommand::Run { ref paths } => (Kind::Run, &paths[..]),
-            Subcommand::Format { .. } | Subcommand::Clean { .. } => panic!(),
+            Subcommand::Format { .. } | Subcommand::Clean { .. } | Subcommand::Setup { .. } => {
+                panic!()
+            }
         };
 
         Self::new_internal(build, kind, paths.to_owned())
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index c74501979f0ec..46a9d989652e9 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -72,6 +72,8 @@ pub struct Config {
     pub stage: u32,
     pub keep_stage: Vec<u32>,
     pub src: PathBuf,
+    // defaults to `config.toml`
+    pub config: PathBuf,
     pub jobs: Option<u32>,
     pub cmd: Subcommand,
     pub incremental: bool,
@@ -512,6 +514,7 @@ impl Config {
         config.rust_codegen_backends = vec![INTERNER.intern_str("llvm")];
         config.deny_warnings = true;
         config.missing_tools = false;
+        config.config = PathBuf::from("config.toml");
 
         // set by bootstrap.py
         config.build = TargetSelection::from_user(&env!("BUILD_TRIPLE"));
@@ -556,7 +559,7 @@ impl Config {
         let get_toml = |file: PathBuf| {
             use std::process;
 
-            let contents = t!(fs::read_to_string(&file), "configuration file did not exist");
+            let contents = t!(fs::read_to_string(&file), "`include` config not found");
             match toml::from_str(&contents) {
                 Ok(table) => table,
                 Err(err) => {
@@ -642,6 +645,7 @@ impl Config {
             | Subcommand::Clippy { .. }
             | Subcommand::Fix { .. }
             | Subcommand::Run { .. }
+            | Subcommand::Setup { .. }
             | Subcommand::Format { .. } => flags.stage.unwrap_or(0),
         };
 
@@ -666,6 +670,7 @@ impl Config {
                 | Subcommand::Clippy { .. }
                 | Subcommand::Fix { .. }
                 | Subcommand::Run { .. }
+                | Subcommand::Setup { .. }
                 | Subcommand::Format { .. } => {}
             }
         }
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index 842c84a3e5cd6..643edeb8321ba 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -7,6 +7,7 @@ use std::env;
 use std::path::PathBuf;
 use std::process;
 
+use build_helper::t;
 use getopts::Options;
 
 use crate::builder::Builder;
@@ -88,6 +89,9 @@ pub enum Subcommand {
     Run {
         paths: Vec<PathBuf>,
     },
+    Setup {
+        path: String,
+    },
 }
 
 impl Default for Subcommand {
@@ -191,6 +195,7 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
                 || (s == "install")
                 || (s == "run")
                 || (s == "r")
+                || (s == "setup")
         });
         let subcommand = match subcommand {
             Some(s) => s,
@@ -445,10 +450,21 @@ Arguments:
     At least a tool needs to be called.",
                 );
             }
+            "setup" => {
+                subcommand_help.push_str(
+                    "\n
+Arguments:
+    This subcommand accepts a 'profile' to use for builds. For example:
+
+        ./x.py setup library
+
+    The profile is optional and you will be prompted interactively if it is not given.",
+                );
+            }
             _ => {}
         };
         // Get any optional paths which occur after the subcommand
-        let paths = matches.free[1..].iter().map(|p| p.into()).collect::<Vec<PathBuf>>();
+        let mut paths = matches.free[1..].iter().map(|p| p.into()).collect::<Vec<PathBuf>>();
 
         let cfg_file = env::var_os("BOOTSTRAP_CONFIG").map(PathBuf::from);
         let verbose = matches.opt_present("verbose");
@@ -500,6 +516,20 @@ Arguments:
                 }
                 Subcommand::Run { paths }
             }
+            "setup" => {
+                let path = if paths.len() > 1 {
+                    println!("\nat most one profile can be passed to setup\n");
+                    usage(1, &opts, verbose, &subcommand_help)
+                } else if let Some(path) = paths.pop() {
+                    t!(path.into_os_string().into_string().map_err(|path| format!(
+                        "{} is not a valid UTF8 string",
+                        path.to_string_lossy()
+                    )))
+                } else {
+                    t!(crate::setup::interactive_path())
+                };
+                Subcommand::Setup { path }
+            }
             _ => {
                 usage(1, &opts, verbose, &subcommand_help);
             }
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 3f7aeae0ed495..4cc72f5f39c97 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -141,6 +141,7 @@ mod metadata;
 mod native;
 mod run;
 mod sanity;
+mod setup;
 mod test;
 mod tool;
 mod toolstate;
@@ -165,7 +166,7 @@ mod job {
 
 use crate::cache::{Interned, INTERNER};
 pub use crate::config::Config;
-use crate::flags::Subcommand;
+pub use crate::flags::Subcommand;
 
 const LLVM_TOOLS: &[&str] = &[
     "llvm-nm", // used to inspect binaries; it shows symbol names, their sizes and visibility
@@ -470,6 +471,10 @@ impl Build {
             return clean::clean(self, all);
         }
 
+        if let Subcommand::Setup { path: include_name } = &self.config.cmd {
+            return setup::setup(&self.config.src, include_name);
+        }
+
         {
             let builder = builder::Builder::new(&self);
             if let Some(path) = builder.paths.get(0) {
diff --git a/src/bootstrap/run.rs b/src/bootstrap/run.rs
index 900534714277c..ba593cadbad81 100644
--- a/src/bootstrap/run.rs
+++ b/src/bootstrap/run.rs
@@ -10,7 +10,7 @@ impl Step for ExpandYamlAnchors {
 
     /// Runs the `expand-yaml_anchors` tool.
     ///
-    /// This tool in `src/tools` read the CI configuration files written in YAML and expands the
+    /// This tool in `src/tools` reads the CI configuration files written in YAML and expands the
     /// anchors in them, since GitHub Actions doesn't support them.
     fn run(self, builder: &Builder<'_>) {
         builder.info("Expanding YAML anchors in the GitHub Actions configuration");
diff --git a/src/bootstrap/setup.rs b/src/bootstrap/setup.rs
new file mode 100644
index 0000000000000..9d3a889aa008e
--- /dev/null
+++ b/src/bootstrap/setup.rs
@@ -0,0 +1,88 @@
+use crate::t;
+use std::path::{Path, PathBuf};
+use std::{
+    env, fs,
+    io::{self, Write},
+};
+
+pub fn setup(src_path: &Path, include_name: &str) {
+    let cfg_file = env::var_os("BOOTSTRAP_CONFIG").map(PathBuf::from);
+
+    if cfg_file.as_ref().map_or(false, |f| f.exists()) {
+        let file = cfg_file.unwrap();
+        println!(
+            "error: you asked `x.py` to setup a new config file, but one already exists at `{}`",
+            file.display()
+        );
+        println!(
+            "help: try adding `profile = \"{}\"` at the top of {}",
+            include_name,
+            file.display()
+        );
+        println!(
+            "note: this will use the configuration in {}/src/bootstrap/defaults/config.toml.{}",
+            src_path.display(),
+            include_name
+        );
+        std::process::exit(1);
+    }
+
+    let path = cfg_file.unwrap_or_else(|| src_path.join("config.toml"));
+    let settings = format!(
+        "# Includes one of the default files in src/bootstrap/defaults\n\
+    profile = \"{}\"\n",
+        include_name
+    );
+    t!(fs::write(path, settings));
+
+    let include_path =
+        format!("{}/src/bootstrap/defaults/config.toml.{}", src_path.display(), include_name);
+    println!("`x.py` will now use the configuration at {}", include_path);
+
+    let suggestions = match include_name {
+        "codegen" | "compiler" => &["check", "build", "test"][..],
+        "library" => &["check", "build", "test library/std", "doc"],
+        "user" => &["dist", "build"],
+        _ => return,
+    };
+
+    println!("To get started, try one of the following commands:");
+    for cmd in suggestions {
+        println!("- `x.py {}`", cmd);
+    }
+
+    if include_name != "user" {
+        println!(
+            "For more suggestions, see https://rustc-dev-guide.rust-lang.org/building/suggested.html"
+        );
+    }
+}
+
+// Used to get the path for `Subcommand::Setup`
+pub fn interactive_path() -> io::Result<String> {
+    let mut input = String::new();
+    println!(
+        "Welcome to the Rust project! What do you want to do with x.py?
+a) Contribute to the standard library
+b) Contribute to the compiler
+c) Contribute to the compiler, and also modify LLVM or codegen
+d) Install Rust from source"
+    );
+    let template = loop {
+        print!("Please choose one (a/b/c/d): ");
+        io::stdout().flush()?;
+        io::stdin().read_line(&mut input)?;
+        break match input.trim().to_lowercase().as_str() {
+            "a" | "lib" | "library" => "library",
+            "b" | "compiler" => "compiler",
+            "c" | "llvm" => "llvm",
+            "d" | "user" | "maintainer" => "maintainer",
+            _ => {
+                println!("error: unrecognized option '{}'", input.trim());
+                println!("note: press Ctrl+C to exit");
+                continue;
+            }
+        };
+    };
+    Ok(template.to_owned())
+}

From bab15f773afd5724023d9a065b5af276e2468ff5 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 24 Sep 2020 17:45:50 +0200
Subject: [PATCH 07/21] Remove std::io::lazy::Lazy in favour of SyncOnceCell

The (internal) std::io::lazy::Lazy was used to lazily initialize the
stdout and stdin buffers (and mutexes). It uses atexit() to register a
destructor to flush the streams on exit, and mark the streams as
'closed'. Using the stream afterwards would result in a panic.

Stdout uses a LineWriter which contains a BufWriter that will flush the
buffer on drop. This one is important to be executed during shutdown,
to make sure no buffered output is lost. It also forbids access to
stdout afterwards, since the buffer is already flushed and gone.

Stdin uses a BufReader, which does not implement Drop. It simply forgets
any previously read data that was not read from the buffer yet. This
means that in the case of stdin, the atexit() function's only effect is
making stdin inaccessible to the program, such that later accesses
result in a panic. This is uncessary, as it'd have been safe to access
stdin during shutdown of the program.

---

This change removes the entire io::lazy module in favour of
SyncOnceCell. SyncOnceCell's fast path is much faster (a single atomic
operation) than locking a sys_common::Mutex on every access like Lazy
did.

However, SyncOnceCell does not use atexit() to drop the contained object
during shutdown.

As noted above, this is not a problem for stdin. It simply means stdin
is now usable during shutdown.

The atexit() call for stdout is moved to the stdio module. Unlike the
now-removed Lazy struct, SyncOnceCell does not have a 'gone and
unusable' state that panics. Instead of adding this again, this simply
replaces the buffer with one with zero capacity. This effectively
flushes the old buffer *and* makes any writes afterwards pass through
directly without touching a buffer, making print!() available during
shutdown without panicking.
---
 library/std/src/io/lazy.rs  | 63 -------------------------------
 library/std/src/io/mod.rs   |  1 -
 library/std/src/io/stdio.rs | 74 ++++++++++++++++++++-----------------
 3 files changed, 40 insertions(+), 98 deletions(-)
 delete mode 100644 library/std/src/io/lazy.rs

diff --git a/library/std/src/io/lazy.rs b/library/std/src/io/lazy.rs
deleted file mode 100644
index 1968d498bbed4..0000000000000
--- a/library/std/src/io/lazy.rs
+++ /dev/null
@@ -1,63 +0,0 @@
-use crate::cell::Cell;
-use crate::ptr;
-use crate::sync::Arc;
-use crate::sys_common;
-use crate::sys_common::mutex::Mutex;
-
-pub struct Lazy<T> {
-    // We never call `lock.init()`, so it is UB to attempt to acquire this mutex reentrantly!
-    lock: Mutex,
-    ptr: Cell<*mut Arc<T>>,
-}
-
-#[inline]
-const fn done<T>() -> *mut Arc<T> {
-    1_usize as *mut _
-}
-
-unsafe impl<T> Sync for Lazy<T> {}
-
-impl<T> Lazy<T> {
-    pub const fn new() -> Lazy<T> {
-        Lazy { lock: Mutex::new(), ptr: Cell::new(ptr::null_mut()) }
-    }
-}
-
-impl<T: Send + Sync + 'static> Lazy<T> {
-    /// Safety: `init` must not call `get` on the variable that is being
-    /// initialized.
-    pub unsafe fn get(&'static self, init: fn() -> Arc<T>) -> Option<Arc<T>> {
-        let _guard = self.lock.lock();
-        let ptr = self.ptr.get();
-        if ptr.is_null() {
-            Some(self.init(init))
-        } else if ptr == done() {
-            None
-        } else {
-            Some((*ptr).clone())
-        }
-    }
-
-    // Must only be called with `lock` held
-    unsafe fn init(&'static self, init: fn() -> Arc<T>) -> Arc<T> {
-        // If we successfully register an at exit handler, then we cache the
-        // `Arc` allocation in our own internal box (it will get deallocated by
-        // the at exit handler). Otherwise we just return the freshly allocated
-        // `Arc`.
-        let registered = sys_common::at_exit(move || {
-            let ptr = {
-                let _guard = self.lock.lock();
-                self.ptr.replace(done())
-            };
-            drop(Box::from_raw(ptr))
-        });
-        // This could reentrantly call `init` again, which is a problem
-        // because our `lock` allows reentrancy!
-        // That's why `get` is unsafe and requires the caller to ensure no reentrancy happens.
-        let ret = init();
-        if registered.is_ok() {
-            self.ptr.set(Box::into_raw(Box::new(ret.clone())));
-        }
-        ret
-    }
-}
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index adea8a804e3ca..d9d0380781925 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -285,7 +285,6 @@ mod buffered;
 mod cursor;
 mod error;
 mod impls;
-mod lazy;
 pub mod prelude;
 mod stdio;
 mod util;
diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
index 9974b65f1e164..e0e5ccd062533 100644
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -7,10 +7,11 @@ use crate::io::prelude::*;
 
 use crate::cell::RefCell;
 use crate::fmt;
-use crate::io::lazy::Lazy;
 use crate::io::{self, BufReader, Initializer, IoSlice, IoSliceMut, LineWriter};
-use crate::sync::{Arc, Mutex, MutexGuard, Once};
+use crate::lazy::SyncOnceCell;
+use crate::sync::{Arc, Mutex, MutexGuard};
 use crate::sys::stdio;
+use crate::sys_common;
 use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 use crate::thread::LocalKey;
 
@@ -292,15 +293,13 @@ pub struct StdinLock<'a> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdin() -> Stdin {
-    static INSTANCE: Lazy<Mutex<BufReader<StdinRaw>>> = Lazy::new();
-    return Stdin {
-        inner: unsafe { INSTANCE.get(stdin_init).expect("cannot access stdin during shutdown") },
-    };
-
-    fn stdin_init() -> Arc<Mutex<BufReader<StdinRaw>>> {
-        // This must not reentrantly access `INSTANCE`
-        let stdin = stdin_raw();
-        Arc::new(Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin)))
+    static INSTANCE: SyncOnceCell<Arc<Mutex<BufReader<StdinRaw>>>> = SyncOnceCell::new();
+    Stdin {
+        inner: INSTANCE
+            .get_or_init(|| {
+                Arc::new(Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin_raw())))
+            })
+            .clone(),
     }
 }
 
@@ -534,19 +533,27 @@ pub struct StdoutLock<'a> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdout() -> Stdout {
-    static INSTANCE: Lazy<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = Lazy::new();
-    return Stdout {
-        inner: unsafe { INSTANCE.get(stdout_init).expect("cannot access stdout during shutdown") },
-    };
-
-    fn stdout_init() -> Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> {
-        // This must not reentrantly access `INSTANCE`
-        let stdout = stdout_raw();
-        unsafe {
-            let ret = Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout))));
-            ret.init();
-            ret
-        }
+    static INSTANCE: SyncOnceCell<Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>>> =
+        SyncOnceCell::new();
+    Stdout {
+        inner: INSTANCE
+            .get_or_init(|| unsafe {
+                let _ = sys_common::at_exit(|| {
+                    if let Some(instance) = INSTANCE.get() {
+                        // Flush the data and disable buffering during shutdown
+                        // by replacing the line writer by one with zero
+                        // buffering capacity.
+                        // We use try_lock() instead of lock(), because someone
+                        // might have leaked a StdoutLock, which would
+                        // otherwise cause a deadlock here.
+                        if let Some(lock) = instance.try_lock() {
+                            *lock.borrow_mut() = LineWriter::with_capacity(0, stdout_raw());
+                        }
+                    }
+                });
+                Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw()))))
+            })
+            .clone(),
     }
 }
 
@@ -714,16 +721,15 @@ pub fn stderr() -> Stderr {
     //
     // This has the added benefit of allowing `stderr` to be usable during
     // process shutdown as well!
-    static INSTANCE: ReentrantMutex<RefCell<StderrRaw>> =
-        unsafe { ReentrantMutex::new(RefCell::new(stderr_raw())) };
-
-    // When accessing stderr we need one-time initialization of the reentrant
-    // mutex. Afterwards we can just always use the now-filled-in `INSTANCE` value.
-    static INIT: Once = Once::new();
-    INIT.call_once(|| unsafe {
-        INSTANCE.init();
-    });
-    Stderr { inner: &INSTANCE }
+    static INSTANCE: SyncOnceCell<ReentrantMutex<RefCell<StderrRaw>>> = SyncOnceCell::new();
+
+    Stderr {
+        inner: INSTANCE.get_or_init(|| unsafe {
+            let r = ReentrantMutex::new(RefCell::new(stderr_raw()));
+            r.init();
+            r
+        }),
+    }
 }
 
 impl Stderr {

From e9b25f520bd2e3687213aa1162e631b08b9bf7ed Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 24 Sep 2020 18:10:26 +0200
Subject: [PATCH 08/21] Add test to check stdout flushing during shutdown.

---
 src/test/ui/stdout-during-shutdown.rs         | 14 ++++++++++++++
 src/test/ui/stdout-during-shutdown.run.stdout |  1 +
 2 files changed, 15 insertions(+)
 create mode 100644 src/test/ui/stdout-during-shutdown.rs
 create mode 100644 src/test/ui/stdout-during-shutdown.run.stdout

diff --git a/src/test/ui/stdout-during-shutdown.rs b/src/test/ui/stdout-during-shutdown.rs
new file mode 100644
index 0000000000000..c785fc0869610
--- /dev/null
+++ b/src/test/ui/stdout-during-shutdown.rs
@@ -0,0 +1,14 @@
+// run-pass
+// check-run-results
+
+#![feature(rustc_private)]
+
+extern crate libc;
+
+fn main() {
+    extern "C" fn bye() {
+        print!(", world!");
+    }
+    unsafe { libc::atexit(bye) };
+    print!("hello");
+}
diff --git a/src/test/ui/stdout-during-shutdown.run.stdout b/src/test/ui/stdout-during-shutdown.run.stdout
new file mode 100644
index 0000000000000..30f51a3fba527
--- /dev/null
+++ b/src/test/ui/stdout-during-shutdown.run.stdout
@@ -0,0 +1 @@
+hello, world!
\ No newline at end of file

From 45700a9d58679131a628ddc95dd8ce0fcf1f2430 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 24 Sep 2020 19:09:33 +0200
Subject: [PATCH 09/21] Drop use of Arc from Stdin and Stdout.

---
 library/std/src/io/stdio.rs | 50 +++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 27 deletions(-)

diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
index e0e5ccd062533..05bdbe0f563c6 100644
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -9,7 +9,7 @@ use crate::cell::RefCell;
 use crate::fmt;
 use crate::io::{self, BufReader, Initializer, IoSlice, IoSliceMut, LineWriter};
 use crate::lazy::SyncOnceCell;
-use crate::sync::{Arc, Mutex, MutexGuard};
+use crate::sync::{Mutex, MutexGuard};
 use crate::sys::stdio;
 use crate::sys_common;
 use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
@@ -218,7 +218,7 @@ fn handle_ebadf<T>(r: io::Result<T>, default: T) -> io::Result<T> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Stdin {
-    inner: Arc<Mutex<BufReader<StdinRaw>>>,
+    inner: &'static Mutex<BufReader<StdinRaw>>,
 }
 
 /// A locked reference to the `Stdin` handle.
@@ -293,13 +293,11 @@ pub struct StdinLock<'a> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdin() -> Stdin {
-    static INSTANCE: SyncOnceCell<Arc<Mutex<BufReader<StdinRaw>>>> = SyncOnceCell::new();
+    static INSTANCE: SyncOnceCell<Mutex<BufReader<StdinRaw>>> = SyncOnceCell::new();
     Stdin {
-        inner: INSTANCE
-            .get_or_init(|| {
-                Arc::new(Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin_raw())))
-            })
-            .clone(),
+        inner: INSTANCE.get_or_init(|| {
+            Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin_raw()))
+        }),
     }
 }
 
@@ -475,7 +473,7 @@ pub struct Stdout {
     // FIXME: this should be LineWriter or BufWriter depending on the state of
     //        stdout (tty or not). Note that if this is not line buffered it
     //        should also flush-on-panic or some form of flush-on-abort.
-    inner: Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>>,
+    inner: &'static ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>,
 }
 
 /// A locked reference to the `Stdout` handle.
@@ -533,27 +531,25 @@ pub struct StdoutLock<'a> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdout() -> Stdout {
-    static INSTANCE: SyncOnceCell<Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>>> =
+    static INSTANCE: SyncOnceCell<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> =
         SyncOnceCell::new();
     Stdout {
-        inner: INSTANCE
-            .get_or_init(|| unsafe {
-                let _ = sys_common::at_exit(|| {
-                    if let Some(instance) = INSTANCE.get() {
-                        // Flush the data and disable buffering during shutdown
-                        // by replacing the line writer by one with zero
-                        // buffering capacity.
-                        // We use try_lock() instead of lock(), because someone
-                        // might have leaked a StdoutLock, which would
-                        // otherwise cause a deadlock here.
-                        if let Some(lock) = instance.try_lock() {
-                            *lock.borrow_mut() = LineWriter::with_capacity(0, stdout_raw());
-                        }
+        inner: INSTANCE.get_or_init(|| unsafe {
+            let _ = sys_common::at_exit(|| {
+                if let Some(instance) = INSTANCE.get() {
+                    // Flush the data and disable buffering during shutdown
+                    // by replacing the line writer by one with zero
+                    // buffering capacity.
+                    // We use try_lock() instead of lock(), because someone
+                    // might have leaked a StdoutLock, which would
+                    // otherwise cause a deadlock here.
+                    if let Some(lock) = instance.try_lock() {
+                        *lock.borrow_mut() = LineWriter::with_capacity(0, stdout_raw());
                     }
-                });
-                Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw()))))
-            })
-            .clone(),
+                }
+            });
+            ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw())))
+        }),
     }
 }
 

From 12ada5cf4bebabd7dc240a3a993eaebbdf2ed3d3 Mon Sep 17 00:00:00 2001
From: est31 <MTest31@outlook.com>
Date: Thu, 24 Sep 2020 19:10:34 +0200
Subject: [PATCH 10/21] Remove TrustedLen requirement from
 BuilderMethods::switch

The main use case of TrustedLen is allowing APIs to specialize on it,
but no use of it uses that specialization. Instead, only the .len()
function provided by ExactSizeIterator is used, which is already
required to be accurate.

Thus, the TrustedLen requirement on BuilderMethods::switch is redundant.
---
 compiler/rustc_codegen_llvm/src/builder.rs       | 3 +--
 compiler/rustc_codegen_llvm/src/lib.rs           | 1 -
 compiler/rustc_codegen_ssa/src/lib.rs            | 1 -
 compiler/rustc_codegen_ssa/src/traits/builder.rs | 3 +--
 4 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 23a3be1a2f2e8..27061acd5afd4 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -21,7 +21,6 @@ use rustc_target::abi::{self, Align, Size};
 use rustc_target::spec::{HasTargetSpec, Target};
 use std::borrow::Cow;
 use std::ffi::CStr;
-use std::iter::TrustedLen;
 use std::ops::{Deref, Range};
 use std::ptr;
 use tracing::debug;
@@ -179,7 +178,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         &mut self,
         v: &'ll Value,
         else_llbb: &'ll BasicBlock,
-        cases: impl ExactSizeIterator<Item = (u128, &'ll BasicBlock)> + TrustedLen,
+        cases: impl ExactSizeIterator<Item = (u128, &'ll BasicBlock)>,
     ) {
         let switch =
             unsafe { llvm::LLVMBuildSwitch(self.llbuilder, v, else_llbb, cases.len() as c_uint) };
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 2e2abe9fb30f8..2751481535c41 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -12,7 +12,6 @@
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(or_patterns)]
-#![feature(trusted_len)]
 #![recursion_limit = "256"]
 
 use back::write::{create_informational_target_machine, create_target_machine};
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index a87ce1446ba14..ee0778490eeda 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -6,7 +6,6 @@
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(or_patterns)]
-#![feature(trusted_len)]
 #![feature(associated_type_bounds)]
 #![recursion_limit = "256"]
 
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 5142922260a57..b35b0f24208b2 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -18,7 +18,6 @@ use rustc_middle::ty::Ty;
 use rustc_target::abi::{Abi, Align, Scalar, Size};
 use rustc_target::spec::HasTargetSpec;
 
-use std::iter::TrustedLen;
 use std::ops::Range;
 
 #[derive(Copy, Clone)]
@@ -60,7 +59,7 @@ pub trait BuilderMethods<'a, 'tcx>:
         &mut self,
         v: Self::Value,
         else_llbb: Self::BasicBlock,
-        cases: impl ExactSizeIterator<Item = (u128, Self::BasicBlock)> + TrustedLen,
+        cases: impl ExactSizeIterator<Item = (u128, Self::BasicBlock)>,
     );
     fn invoke(
         &mut self,

From 6f9c1323a7a0fe162a5642e229d54afec7ccb299 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 24 Sep 2020 19:25:21 +0200
Subject: [PATCH 11/21] Call ReentrantMutex::init() in stdout().

---
 library/std/src/io/stdio.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
index 05bdbe0f563c6..b7d3c47e24b09 100644
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -548,7 +548,9 @@ pub fn stdout() -> Stdout {
                     }
                 }
             });
-            ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw())))
+            let r = ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw())));
+            r.init();
+            r
         }),
     }
 }

From 47843f52d3f3a99f8f6fb64c434341838670f371 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Thu, 24 Sep 2020 21:53:07 +0200
Subject: [PATCH 12/21] update Miri

---
 src/tools/miri | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tools/miri b/src/tools/miri
index 02a33d411d8e3..2f84bfc57dd0e 160000
--- a/src/tools/miri
+++ b/src/tools/miri
@@ -1 +1 @@
-Subproject commit 02a33d411d8e385942776760a99535d69826349b
+Subproject commit 2f84bfc57dd0ef22269bb84dae10f71e5e23e85d

From 257f6e5f745c25b66e432f5222d1b746469fcdb0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomasz=20Mi=C4=85sko?= <tomasz.miasko@gmail.com>
Date: Fri, 25 Sep 2020 00:00:00 +0000
Subject: [PATCH 13/21] Reopen standard streams when they are closed on Unix

The syscalls returning a new file descriptors generally use
lowest-numbered file descriptor not currently opened, without any
exceptions for those corresponding to the standard streams.

Previously when any of standard streams has been closed before starting
the application, operations on std::io::{stderr,stdin,stdout} objects
were likely to operate on other logically unrelated file resources
opened afterwards.

Avoid the issue by reopening the standard streams when they are closed.
---
 library/std/src/sys/unix/mod.rs | 62 +++++++++++++++++++++++++++++
 src/test/ui/closed-std-fds.rs   | 69 +++++++++++++++++++++++++++++++++
 2 files changed, 131 insertions(+)
 create mode 100644 src/test/ui/closed-std-fds.rs

diff --git a/library/std/src/sys/unix/mod.rs b/library/std/src/sys/unix/mod.rs
index eddf00d3979f5..b48d2162eca92 100644
--- a/library/std/src/sys/unix/mod.rs
+++ b/library/std/src/sys/unix/mod.rs
@@ -75,6 +75,13 @@ pub use crate::sys_common::os_str_bytes as os_str;
 
 #[cfg(not(test))]
 pub fn init() {
+    // The standard streams might be closed on application startup. To prevent
+    // std::io::{stdin, stdout,stderr} objects from using other unrelated file
+    // resources opened later, we reopen standards streams when they are closed.
+    unsafe {
+        sanitize_standard_fds();
+    }
+
     // By default, some platforms will send a *signal* when an EPIPE error
     // would otherwise be delivered. This runtime doesn't install a SIGPIPE
     // handler, causing it to kill the program, which isn't exactly what we
@@ -86,6 +93,61 @@ pub fn init() {
         reset_sigpipe();
     }
 
+    // In the case when all file descriptors are open, the poll has been
+    // observed to perform better than fcntl (on GNU/Linux).
+    #[cfg(not(any(
+        miri,
+        target_os = "emscripten",
+        target_os = "fuchsia",
+        // The poll on Darwin doesn't set POLLNVAL for closed fds.
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "redox",
+    )))]
+    unsafe fn sanitize_standard_fds() {
+        use crate::sys::os::errno;
+        let pfds: &mut [_] = &mut [
+            libc::pollfd { fd: 0, events: 0, revents: 0 },
+            libc::pollfd { fd: 1, events: 0, revents: 0 },
+            libc::pollfd { fd: 2, events: 0, revents: 0 },
+        ];
+        while libc::poll(pfds.as_mut_ptr(), 3, 0) == -1 {
+            if errno() == libc::EINTR {
+                continue;
+            }
+            libc::abort();
+        }
+        for pfd in pfds {
+            if pfd.revents & libc::POLLNVAL == 0 {
+                continue;
+            }
+            if libc::open("/dev/null\0".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                // If the stream is closed but we failed to reopen it, abort the
+                // process. Otherwise we wouldn't preserve the safety of
+                // operations on the corresponding Rust object Stdin, Stdout, or
+                // Stderr.
+                libc::abort();
+            }
+        }
+    }
+    #[cfg(any(target_os = "macos", target_os = "ios", target_os = "redox"))]
+    unsafe fn sanitize_standard_fds() {
+        use crate::sys::os::errno;
+        for fd in 0..3 {
+            if libc::fcntl(fd, libc::F_GETFD) == -1 && errno() == libc::EBADF {
+                if libc::open("/dev/null\0".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                    libc::abort();
+                }
+            }
+        }
+    }
+    #[cfg(any(
+        // The standard fds are always available in Miri.
+        miri,
+        target_os = "emscripten",
+        target_os = "fuchsia"))]
+    unsafe fn sanitize_standard_fds() {}
+
     #[cfg(not(any(target_os = "emscripten", target_os = "fuchsia")))]
     unsafe fn reset_sigpipe() {
         assert!(signal(libc::SIGPIPE, libc::SIG_IGN) != libc::SIG_ERR);
diff --git a/src/test/ui/closed-std-fds.rs b/src/test/ui/closed-std-fds.rs
new file mode 100644
index 0000000000000..906da94433455
--- /dev/null
+++ b/src/test/ui/closed-std-fds.rs
@@ -0,0 +1,69 @@
+// Verifies that std provides replacement for the standard file descriptors when they are missing.
+//
+// run-pass
+// ignore-windows unix specific test
+// ignore-cloudabi no processes
+// ignore-emscripten no processes
+// ignore-sgx no processes
+
+#![feature(rustc_private)]
+extern crate libc;
+
+use std::io::{self, Read};
+use std::os::unix::process::CommandExt;
+use std::process::Command;
+
+fn main() {
+    let mut args = std::env::args();
+    let argv0 = args.next().expect("argv0");
+    match args.next().as_deref() {
+        Some("child") => child(),
+        None => parent(&argv0),
+        _ => unreachable!(),
+    }
+}
+
+fn parent(argv0: &str) {
+    let status = unsafe { Command::new(argv0)
+        .arg("child")
+        .pre_exec(close_std_fds_on_exec)
+        .status()
+        .expect("failed to execute child process")
+    };
+    if !status.success() {
+        panic!("child failed with {}", status);
+    }
+}
+
+fn close_std_fds_on_exec() -> io::Result<()> {
+    for fd in 0..3 {
+        if unsafe { libc::fcntl(fd, libc::F_SETFD, libc::FD_CLOEXEC) == -1 } {
+            return Err(io::Error::last_os_error())
+        }
+    }
+    Ok(())
+}
+
+fn child() {
+    // Standard file descriptors should be valid.
+    assert_fd_is_valid(0);
+    assert_fd_is_valid(1);
+    assert_fd_is_valid(2);
+
+    // Writing to stdout & stderr should not panic.
+    println!("a");
+    println!("b");
+    eprintln!("c");
+    eprintln!("d");
+
+    // Stdin should be at EOF.
+    let mut buffer = Vec::new();
+    let n = io::stdin().read_to_end(&mut buffer).unwrap();
+    assert_eq!(n, 0);
+}
+
+fn assert_fd_is_valid(fd: libc::c_int) {
+    if unsafe { libc::fcntl(fd, libc::F_GETFD) == -1 } {
+        panic!("file descriptor {} is not valid {}", fd, io::Error::last_os_error());
+    }
+}

From 0d2521aaf7548f0de6c227ef68eae76df4420c03 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 11:53:58 -0700
Subject: [PATCH 14/21] Add `const_fn_floating_point_arithmetic`

---
 compiler/rustc_feature/src/active.rs          |  3 +++
 .../src/transform/check_consts/ops.rs         | 24 +++++++++++++++++++
 compiler/rustc_span/src/symbol.rs             |  1 +
 3 files changed, 28 insertions(+)

diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 6452bda293ef5..720fa9939f399 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -584,6 +584,9 @@ declare_features! (
     /// Allows non trivial generic constants which have to be manually propageted upwards.
     (active, const_evaluatable_checked, "1.48.0", Some(76560), None),
 
+    /// Allows basic arithmetic on floating point types in a `const fn`.
+    (active, const_fn_floating_point_arithmetic, "1.48.0", Some(57563), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------
diff --git a/compiler/rustc_mir/src/transform/check_consts/ops.rs b/compiler/rustc_mir/src/transform/check_consts/ops.rs
index 496e620dd9df6..1d74108585360 100644
--- a/compiler/rustc_mir/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_mir/src/transform/check_consts/ops.rs
@@ -112,6 +112,30 @@ impl NonConstOp for Abort {
     }
 }
 
+#[derive(Debug)]
+pub struct FloatingPointOp;
+impl NonConstOp for FloatingPointOp {
+    const STOPS_CONST_CHECKING: bool = true;
+
+    fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status {
+        if ccx.const_kind() == hir::ConstContext::ConstFn {
+            Status::Unstable(sym::const_fn_floating_point_arithmetic)
+        } else {
+            Status::Allowed
+        }
+    }
+
+    fn emit_error(&self, ccx: &ConstCx<'_, '_>, span: Span) {
+        feature_err(
+            &ccx.tcx.sess.parse_sess,
+            sym::const_fn_floating_point_arithmetic,
+            span,
+            &format!("floating point arithmetic is not allowed in {}s", ccx.const_kind()),
+        )
+        .emit();
+    }
+}
+
 #[derive(Debug)]
 pub struct NonPrimitiveOp;
 impl NonConstOp for NonPrimitiveOp {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 2d5c6451d1a52..4447564c8b4c5 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -351,6 +351,7 @@ symbols! {
         const_evaluatable_checked,
         const_extern_fn,
         const_fn,
+        const_fn_floating_point_arithmetic,
         const_fn_transmute,
         const_fn_union,
         const_generics,

From 2049052cb9880c97bb289a086815576f5aabc6c9 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 11:54:11 -0700
Subject: [PATCH 15/21] Put floating point arithmetic behind its own feature
 gate

This refactors handling of `Rvalue::{Unary,Binary}Op` in the
const-checker. Now we `span_bug` if there's an unexpected type in a
primitive operation. This also allows unary negation on
`char` values through the const-checker because it makes the code a bit
cleaner. `char` does not actually support these operations, and if it
did, we could evaluate them at compile-time.
---
 .../src/transform/check_consts/validation.rs  | 31 +++++++++++++------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_mir/src/transform/check_consts/validation.rs b/compiler/rustc_mir/src/transform/check_consts/validation.rs
index dc28ba46d7cbb..73725c7b98eee 100644
--- a/compiler/rustc_mir/src/transform/check_consts/validation.rs
+++ b/compiler/rustc_mir/src/transform/check_consts/validation.rs
@@ -540,8 +540,12 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
 
             Rvalue::UnaryOp(_, ref operand) => {
                 let ty = operand.ty(self.body, self.tcx);
-                if !(ty.is_integral() || ty.is_bool()) {
-                    self.check_op(ops::NonPrimitiveOp)
+                if is_int_bool_or_char(ty) {
+                    // Int, bool, and char operations are fine.
+                } else if ty.is_floating_point() {
+                    self.check_op(ops::FloatingPointOp);
+                } else {
+                    span_bug!(self.span, "non-primitive type in `Rvalue::UnaryOp`: {:?}", ty);
                 }
             }
 
@@ -550,7 +554,9 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
                 let lhs_ty = lhs.ty(self.body, self.tcx);
                 let rhs_ty = rhs.ty(self.body, self.tcx);
 
-                if let ty::RawPtr(_) | ty::FnPtr(..) = lhs_ty.kind() {
+                if is_int_bool_or_char(lhs_ty) && is_int_bool_or_char(rhs_ty) {
+                    // Int, bool, and char operations are fine.
+                } else if lhs_ty.is_fn_ptr() || lhs_ty.is_unsafe_ptr() {
                     assert_eq!(lhs_ty, rhs_ty);
                     assert!(
                         op == BinOp::Eq
@@ -563,12 +569,15 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
                     );
 
                     self.check_op(ops::RawPtrComparison);
-                }
-
-                if !(lhs_ty.is_integral() || lhs_ty.is_bool() || lhs_ty.is_char())
-                    || !(rhs_ty.is_integral() || rhs_ty.is_bool() || rhs_ty.is_char())
-                {
-                    self.check_op(ops::NonPrimitiveOp)
+                } else if lhs_ty.is_floating_point() || rhs_ty.is_floating_point() {
+                    self.check_op(ops::FloatingPointOp);
+                } else {
+                    span_bug!(
+                        self.span,
+                        "non-primitive type in `Rvalue::BinaryOp`: {:?} ⚬ {:?}",
+                        lhs_ty,
+                        rhs_ty
+                    );
                 }
             }
         }
@@ -867,3 +876,7 @@ fn place_as_reborrow(
         }
     })
 }
+
+fn is_int_bool_or_char(ty: Ty<'_>) -> bool {
+    ty.is_bool() || ty.is_integral() || ty.is_char()
+}

From 6a52c094408370a3bd60ed0976211995ef52fc23 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 11:58:22 -0700
Subject: [PATCH 16/21] Add new feature gate to standard library

---
 library/core/src/lib.rs | 1 +
 library/std/src/lib.rs  | 1 +
 2 files changed, 2 insertions(+)

diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 63ca6e517d214..30fb87b022645 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -82,6 +82,7 @@
 #![feature(const_pin)]
 #![feature(const_fn_union)]
 #![feature(const_fn)]
+#![cfg_attr(not(bootstrap), feature(const_fn_floating_point_arithmetic))]
 #![feature(const_generics)]
 #![feature(const_option)]
 #![feature(const_precise_live_drops)]
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index ac0075ad129c5..d03428dd08282 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -236,6 +236,7 @@
 #![feature(clamp)]
 #![feature(concat_idents)]
 #![feature(const_cstr_unchecked)]
+#![cfg_attr(not(bootstrap), feature(const_fn_floating_point_arithmetic))]
 #![feature(const_fn_transmute)]
 #![feature(const_fn)]
 #![feature(const_ip)]

From b428f287c3ddb951450bc5f94cf3a5e38a59e3d6 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 11:58:41 -0700
Subject: [PATCH 17/21] Bless tests

---
 .../const-extern-fn-min-const-fn.rs              |  2 +-
 .../const-extern-fn-min-const-fn.stderr          |  4 ++--
 src/test/ui/consts/const_let_eq_float.rs         |  4 ++--
 src/test/ui/consts/min_const_fn/min_const_fn.rs  |  8 ++++----
 .../ui/consts/min_const_fn/min_const_fn.stderr   | 16 ++++++++--------
 .../min_const_fn_libstd_stability.rs             |  6 +++---
 .../min_const_fn_libstd_stability.stderr         |  2 +-
 .../min_const_unsafe_fn_libstd_stability.rs      |  4 ++--
 .../min_const_unsafe_fn_libstd_stability.stderr  |  2 +-
 9 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
index e0b9e5f33759e..094ae7378bce8 100644
--- a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
+++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
@@ -4,7 +4,7 @@ const extern fn unsize(x: &[u8; 3]) -> &[u8] { x }
 const unsafe extern "C" fn closure() -> fn() { || {} }
 //~^ ERROR function pointers in const fn are unstable
 const unsafe extern fn use_float() { 1.0 + 1.0; }
-//~^ ERROR only int, `bool` and `char` operations are stable in const fn
+//~^ ERROR floating point arithmetic
 const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
 //~^ ERROR casting pointers to integers
 
diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
index 5ca44b3fa7e65..49caac00ca884 100644
--- a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
+++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
@@ -7,14 +7,14 @@ LL | const unsafe extern "C" fn closure() -> fn() { || {} }
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
-error[E0723]: only int, `bool` and `char` operations are stable in const fn
+error[E0658]: floating point arithmetic is not allowed in constant functions
   --> $DIR/const-extern-fn-min-const-fn.rs:6:38
    |
 LL | const unsafe extern fn use_float() { 1.0 + 1.0; }
    |                                      ^^^^^^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: casting pointers to integers in constant functions is unstable
   --> $DIR/const-extern-fn-min-const-fn.rs:8:48
diff --git a/src/test/ui/consts/const_let_eq_float.rs b/src/test/ui/consts/const_let_eq_float.rs
index bc0ef26eb2fe5..e15f4b804f716 100644
--- a/src/test/ui/consts/const_let_eq_float.rs
+++ b/src/test/ui/consts/const_let_eq_float.rs
@@ -1,6 +1,6 @@
-// build-pass (FIXME(62277): could be check-pass?)
+// run-pass
 
-#![feature(const_fn)]
+#![feature(const_fn_floating_point_arithmetic)]
 
 struct Foo<T>(T);
 struct Bar<T> { x: T }
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.rs b/src/test/ui/consts/min_const_fn/min_const_fn.rs
index 336d754b06a73..86b26a53371d8 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_fn.rs
@@ -78,13 +78,13 @@ const fn foo11<T: std::fmt::Display>(t: T) -> T { t }
 const fn foo11_2<T: Send>(t: T) -> T { t }
 //~^ ERROR trait bounds other than `Sized` on const fn parameters are unstable
 const fn foo19(f: f32) -> f32 { f * 2.0 }
-//~^ ERROR int, `bool` and `char` operations
+//~^ ERROR floating point arithmetic
 const fn foo19_2(f: f32) -> f32 { 2.0 - f }
-//~^ ERROR int, `bool` and `char` operations
+//~^ ERROR floating point arithmetic
 const fn foo19_3(f: f32) -> f32 { -f }
-//~^ ERROR int, `bool` and `char` operations
+//~^ ERROR floating point arithmetic
 const fn foo19_4(f: f32, g: f32) -> f32 { f / g }
-//~^ ERROR int, `bool` and `char` operations
+//~^ ERROR floating point arithmetic
 
 static BAR: u32 = 42;
 const fn foo25() -> u32 { BAR } //~ ERROR cannot refer to statics
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.stderr b/src/test/ui/consts/min_const_fn/min_const_fn.stderr
index c96500e38ec83..60c4eef795359 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_fn.stderr
@@ -76,41 +76,41 @@ LL | const fn foo11_2<T: Send>(t: T) -> T { t }
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
-error[E0723]: only int, `bool` and `char` operations are stable in const fn
+error[E0658]: floating point arithmetic is not allowed in constant functions
   --> $DIR/min_const_fn.rs:80:33
    |
 LL | const fn foo19(f: f32) -> f32 { f * 2.0 }
    |                                 ^^^^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
-error[E0723]: only int, `bool` and `char` operations are stable in const fn
+error[E0658]: floating point arithmetic is not allowed in constant functions
   --> $DIR/min_const_fn.rs:82:35
    |
 LL | const fn foo19_2(f: f32) -> f32 { 2.0 - f }
    |                                   ^^^^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
-error[E0723]: only int, `bool` and `char` operations are stable in const fn
+error[E0658]: floating point arithmetic is not allowed in constant functions
   --> $DIR/min_const_fn.rs:84:35
    |
 LL | const fn foo19_3(f: f32) -> f32 { -f }
    |                                   ^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
-error[E0723]: only int, `bool` and `char` operations are stable in const fn
+error[E0658]: floating point arithmetic is not allowed in constant functions
   --> $DIR/min_const_fn.rs:86:43
    |
 LL | const fn foo19_4(f: f32, g: f32) -> f32 { f / g }
    |                                           ^^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0013]: constant functions cannot refer to statics
   --> $DIR/min_const_fn.rs:90:27
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
index b83fdf7c656cd..292e2dd167c91 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
@@ -3,7 +3,7 @@
             we're apparently really bad at it",
             issue = "none")]
 
-#![feature(const_fn, foo, foo2)]
+#![feature(const_fn, const_fn_floating_point_arithmetic, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -25,9 +25,9 @@ const fn bar2() -> u32 { foo2() } //~ ERROR not yet stable as a const fn
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "rust1", since = "1.0.0")]
-// conformity is required, even with `const_fn` feature gate
+// Const-stable functions cannot rely on unstable const-eval features.
 const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-//~^ ERROR const-stable function cannot use `#[feature(const_fn)]`
+//~^ ERROR const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
 
 // check whether this function cannot be called even with the feature gate active
 #[unstable(feature = "foo2", issue = "none")]
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
index a1f1f6f52ab2a..fa2260b40d19f 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
@@ -14,7 +14,7 @@ LL | const fn bar2() -> u32 { foo2() }
    |
    = help: Const-stable functions can only call other const-stable functions
 
-error: const-stable function cannot use `#[feature(const_fn)]`
+error: const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
   --> $DIR/min_const_fn_libstd_stability.rs:29:26
    |
 LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
index 902ed435e31bc..0f48341ddf3ec 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
@@ -3,7 +3,7 @@
             we're apparently really bad at it",
             issue = "none")]
 
-#![feature(const_fn, foo, foo2)]
+#![feature(const_fn, const_fn_floating_point_arithmetic, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -27,7 +27,7 @@ const unsafe fn bar2() -> u32 { unsafe { foo2() } } //~ ERROR not yet stable as
 #[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // conformity is required, even with `const_fn` feature gate
 const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-//~^ ERROR const-stable function cannot use `#[feature(const_fn)]`
+//~^ ERROR const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
 
 // check whether this function cannot be called even with the feature gate active
 #[unstable(feature = "foo2", issue = "none")]
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
index 2741a86440487..1ca5964ce0fc4 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
@@ -14,7 +14,7 @@ LL | const unsafe fn bar2() -> u32 { unsafe { foo2() } }
    |
    = help: Const-stable functions can only call other const-stable functions
 
-error: const-stable function cannot use `#[feature(const_fn)]`
+error: const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
   --> $DIR/min_const_unsafe_fn_libstd_stability.rs:29:33
    |
 LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }

From 4cac90c968774b799697d5ce18da75483dc2f15b Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 12:38:21 -0700
Subject: [PATCH 18/21] Move const fn floating point test out of `min_const_fn`

---
 ..._fn_floating_point_arithmetic.gated.stderr |  8 +++
 .../const_fn_floating_point_arithmetic.rs     | 20 ++++++
 ..._fn_floating_point_arithmetic.stock.stderr | 48 +++++++++++++
 .../ui/consts/min_const_fn/min_const_fn.rs    |  8 ---
 .../consts/min_const_fn/min_const_fn.stderr   | 72 +++++--------------
 5 files changed, 94 insertions(+), 62 deletions(-)
 create mode 100644 src/test/ui/consts/const_fn_floating_point_arithmetic.gated.stderr
 create mode 100644 src/test/ui/consts/const_fn_floating_point_arithmetic.rs
 create mode 100644 src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr

diff --git a/src/test/ui/consts/const_fn_floating_point_arithmetic.gated.stderr b/src/test/ui/consts/const_fn_floating_point_arithmetic.gated.stderr
new file mode 100644
index 0000000000000..ae24f8f65009a
--- /dev/null
+++ b/src/test/ui/consts/const_fn_floating_point_arithmetic.gated.stderr
@@ -0,0 +1,8 @@
+error: fatal error triggered by #[rustc_error]
+  --> $DIR/const_fn_floating_point_arithmetic.rs:20:1
+   |
+LL | fn main() {}
+   | ^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/consts/const_fn_floating_point_arithmetic.rs b/src/test/ui/consts/const_fn_floating_point_arithmetic.rs
new file mode 100644
index 0000000000000..5e32482b21a52
--- /dev/null
+++ b/src/test/ui/consts/const_fn_floating_point_arithmetic.rs
@@ -0,0 +1,20 @@
+// gate-test-const_fn_floating_point_arithmetic
+
+// revisions: stock gated
+
+#![feature(rustc_attrs)]
+#![cfg_attr(gated, feature(const_fn_floating_point_arithmetic))]
+
+const fn add(f: f32) -> f32 { f + 2.0 }
+//[stock]~^ floating point arithmetic
+const fn sub(f: f32) -> f32 { 2.0 - f }
+//[stock]~^ floating point arithmetic
+const fn mul(f: f32, g: f32) -> f32 { f * g }
+//[stock]~^ floating point arithmetic
+const fn div(f: f32, g: f32) -> f32 { f / g }
+//[stock]~^ floating point arithmetic
+const fn neg(f: f32) -> f32 { -f }
+//[stock]~^ floating point arithmetic
+
+#[rustc_error]
+fn main() {} //[gated]~ fatal error triggered by #[rustc_error]
diff --git a/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr b/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
new file mode 100644
index 0000000000000..7461007fc2aa5
--- /dev/null
+++ b/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
@@ -0,0 +1,48 @@
+error[E0658]: floating point arithmetic is not allowed in constant functions
+  --> $DIR/const_fn_floating_point_arithmetic.rs:8:31
+   |
+LL | const fn add(f: f32) -> f32 { f + 2.0 }
+   |                               ^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
+
+error[E0658]: floating point arithmetic is not allowed in constant functions
+  --> $DIR/const_fn_floating_point_arithmetic.rs:10:31
+   |
+LL | const fn sub(f: f32) -> f32 { 2.0 - f }
+   |                               ^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
+
+error[E0658]: floating point arithmetic is not allowed in constant functions
+  --> $DIR/const_fn_floating_point_arithmetic.rs:12:39
+   |
+LL | const fn mul(f: f32, g: f32) -> f32 { f * g }
+   |                                       ^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
+
+error[E0658]: floating point arithmetic is not allowed in constant functions
+  --> $DIR/const_fn_floating_point_arithmetic.rs:14:39
+   |
+LL | const fn div(f: f32, g: f32) -> f32 { f / g }
+   |                                       ^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
+
+error[E0658]: floating point arithmetic is not allowed in constant functions
+  --> $DIR/const_fn_floating_point_arithmetic.rs:16:31
+   |
+LL | const fn neg(f: f32) -> f32 { -f }
+   |                               ^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.rs b/src/test/ui/consts/min_const_fn/min_const_fn.rs
index 86b26a53371d8..55a999d5cdc04 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_fn.rs
@@ -77,14 +77,6 @@ const fn foo11<T: std::fmt::Display>(t: T) -> T { t }
 //~^ ERROR trait bounds other than `Sized` on const fn parameters are unstable
 const fn foo11_2<T: Send>(t: T) -> T { t }
 //~^ ERROR trait bounds other than `Sized` on const fn parameters are unstable
-const fn foo19(f: f32) -> f32 { f * 2.0 }
-//~^ ERROR floating point arithmetic
-const fn foo19_2(f: f32) -> f32 { 2.0 - f }
-//~^ ERROR floating point arithmetic
-const fn foo19_3(f: f32) -> f32 { -f }
-//~^ ERROR floating point arithmetic
-const fn foo19_4(f: f32, g: f32) -> f32 { f / g }
-//~^ ERROR floating point arithmetic
 
 static BAR: u32 = 42;
 const fn foo25() -> u32 { BAR } //~ ERROR cannot refer to statics
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.stderr b/src/test/ui/consts/min_const_fn/min_const_fn.stderr
index 60c4eef795359..a37e5203eeef4 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_fn.stderr
@@ -76,44 +76,8 @@ LL | const fn foo11_2<T: Send>(t: T) -> T { t }
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/min_const_fn.rs:80:33
-   |
-LL | const fn foo19(f: f32) -> f32 { f * 2.0 }
-   |                                 ^^^^^^^
-   |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/min_const_fn.rs:82:35
-   |
-LL | const fn foo19_2(f: f32) -> f32 { 2.0 - f }
-   |                                   ^^^^^^^
-   |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/min_const_fn.rs:84:35
-   |
-LL | const fn foo19_3(f: f32) -> f32 { -f }
-   |                                   ^^
-   |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/min_const_fn.rs:86:43
-   |
-LL | const fn foo19_4(f: f32, g: f32) -> f32 { f / g }
-   |                                           ^^^^^
-   |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-
 error[E0013]: constant functions cannot refer to statics
-  --> $DIR/min_const_fn.rs:90:27
+  --> $DIR/min_const_fn.rs:82:27
    |
 LL | const fn foo25() -> u32 { BAR }
    |                           ^^^
@@ -121,7 +85,7 @@ LL | const fn foo25() -> u32 { BAR }
    = help: consider extracting the value of the `static` to a `const`, and referring to that
 
 error[E0013]: constant functions cannot refer to statics
-  --> $DIR/min_const_fn.rs:91:37
+  --> $DIR/min_const_fn.rs:83:37
    |
 LL | const fn foo26() -> &'static u32 { &BAR }
    |                                     ^^^
@@ -129,7 +93,7 @@ LL | const fn foo26() -> &'static u32 { &BAR }
    = help: consider extracting the value of the `static` to a `const`, and referring to that
 
 error[E0658]: casting pointers to integers in constant functions is unstable
-  --> $DIR/min_const_fn.rs:92:42
+  --> $DIR/min_const_fn.rs:84:42
    |
 LL | const fn foo30(x: *const u32) -> usize { x as usize }
    |                                          ^^^^^^^^^^
@@ -138,7 +102,7 @@ LL | const fn foo30(x: *const u32) -> usize { x as usize }
    = help: add `#![feature(const_raw_ptr_to_usize_cast)]` to the crate attributes to enable
 
 error[E0658]: casting pointers to integers in constant functions is unstable
-  --> $DIR/min_const_fn.rs:94:63
+  --> $DIR/min_const_fn.rs:86:63
    |
 LL | const fn foo30_with_unsafe(x: *const u32) -> usize { unsafe { x as usize } }
    |                                                               ^^^^^^^^^^
@@ -147,7 +111,7 @@ LL | const fn foo30_with_unsafe(x: *const u32) -> usize { unsafe { x as usize }
    = help: add `#![feature(const_raw_ptr_to_usize_cast)]` to the crate attributes to enable
 
 error[E0658]: casting pointers to integers in constant functions is unstable
-  --> $DIR/min_const_fn.rs:96:42
+  --> $DIR/min_const_fn.rs:88:42
    |
 LL | const fn foo30_2(x: *mut u32) -> usize { x as usize }
    |                                          ^^^^^^^^^^
@@ -156,7 +120,7 @@ LL | const fn foo30_2(x: *mut u32) -> usize { x as usize }
    = help: add `#![feature(const_raw_ptr_to_usize_cast)]` to the crate attributes to enable
 
 error[E0658]: casting pointers to integers in constant functions is unstable
-  --> $DIR/min_const_fn.rs:98:63
+  --> $DIR/min_const_fn.rs:90:63
    |
 LL | const fn foo30_2_with_unsafe(x: *mut u32) -> usize { unsafe { x as usize } }
    |                                                               ^^^^^^^^^^
@@ -165,7 +129,7 @@ LL | const fn foo30_2_with_unsafe(x: *mut u32) -> usize { unsafe { x as usize }
    = help: add `#![feature(const_raw_ptr_to_usize_cast)]` to the crate attributes to enable
 
 error[E0658]: mutable references are not allowed in constant functions
-  --> $DIR/min_const_fn.rs:101:14
+  --> $DIR/min_const_fn.rs:93:14
    |
 LL | const fn inc(x: &mut i32) { *x += 1 }
    |              ^
@@ -174,7 +138,7 @@ LL | const fn inc(x: &mut i32) { *x += 1 }
    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:110:6
+  --> $DIR/min_const_fn.rs:102:6
    |
 LL | impl<T: std::fmt::Debug> Foo<T> {
    |      ^
@@ -183,7 +147,7 @@ LL | impl<T: std::fmt::Debug> Foo<T> {
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:115:6
+  --> $DIR/min_const_fn.rs:107:6
    |
 LL | impl<T: std::fmt::Debug + Sized> Foo<T> {
    |      ^
@@ -192,7 +156,7 @@ LL | impl<T: std::fmt::Debug + Sized> Foo<T> {
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:120:6
+  --> $DIR/min_const_fn.rs:112:6
    |
 LL | impl<T: Sync + Sized> Foo<T> {
    |      ^
@@ -201,7 +165,7 @@ LL | impl<T: Sync + Sized> Foo<T> {
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:126:34
+  --> $DIR/min_const_fn.rs:118:34
    |
 LL | const fn no_apit2(_x: AlanTuring<impl std::fmt::Debug>) {}
    |                                  ^^^^^^^^^^^^^^^^^^^^
@@ -210,7 +174,7 @@ LL | const fn no_apit2(_x: AlanTuring<impl std::fmt::Debug>) {}
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:128:22
+  --> $DIR/min_const_fn.rs:120:22
    |
 LL | const fn no_apit(_x: impl std::fmt::Debug) {}
    |                      ^^^^^^^^^^^^^^^^^^^^
@@ -219,7 +183,7 @@ LL | const fn no_apit(_x: impl std::fmt::Debug) {}
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:129:23
+  --> $DIR/min_const_fn.rs:121:23
    |
 LL | const fn no_dyn_trait(_x: &dyn std::fmt::Debug) {}
    |                       ^^
@@ -228,7 +192,7 @@ LL | const fn no_dyn_trait(_x: &dyn std::fmt::Debug) {}
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:130:32
+  --> $DIR/min_const_fn.rs:122:32
    |
 LL | const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() }
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -237,7 +201,7 @@ LL | const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable
-  --> $DIR/min_const_fn.rs:135:41
+  --> $DIR/min_const_fn.rs:127:41
    |
 LL | const fn really_no_traits_i_mean_it() { (&() as &dyn std::fmt::Debug, ()).1 }
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -246,7 +210,7 @@ LL | const fn really_no_traits_i_mean_it() { (&() as &dyn std::fmt::Debug, ()).1
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: function pointers in const fn are unstable
-  --> $DIR/min_const_fn.rs:138:21
+  --> $DIR/min_const_fn.rs:130:21
    |
 LL | const fn no_fn_ptrs(_x: fn()) {}
    |                     ^^
@@ -255,7 +219,7 @@ LL | const fn no_fn_ptrs(_x: fn()) {}
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: function pointers in const fn are unstable
-  --> $DIR/min_const_fn.rs:140:27
+  --> $DIR/min_const_fn.rs:132:27
    |
 LL | const fn no_fn_ptrs2() -> fn() { fn foo() {} foo }
    |                           ^^^^
@@ -263,7 +227,7 @@ LL | const fn no_fn_ptrs2() -> fn() { fn foo() {} foo }
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
-error: aborting due to 30 previous errors
+error: aborting due to 26 previous errors
 
 Some errors have detailed explanations: E0013, E0493, E0658, E0723.
 For more information about an error, try `rustc --explain E0013`.

From 659028f48b7b47ee3e16a4d110b1379ed8524121 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Wed, 23 Sep 2020 13:08:20 -0700
Subject: [PATCH 19/21] Use proper issue for
 `const_fn_floating_point_arithmetic`

---
 compiler/rustc_feature/src/active.rs                   |  2 +-
 .../const-extern-fn-min-const-fn.stderr                |  2 +-
 .../const_fn_floating_point_arithmetic.stock.stderr    | 10 +++++-----
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 720fa9939f399..17b9e1ee7e8ba 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -585,7 +585,7 @@ declare_features! (
     (active, const_evaluatable_checked, "1.48.0", Some(76560), None),
 
     /// Allows basic arithmetic on floating point types in a `const fn`.
-    (active, const_fn_floating_point_arithmetic, "1.48.0", Some(57563), None),
+    (active, const_fn_floating_point_arithmetic, "1.48.0", Some(57241), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
index 49caac00ca884..fcc34f358f9f9 100644
--- a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
+++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
@@ -13,7 +13,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const unsafe extern fn use_float() { 1.0 + 1.0; }
    |                                      ^^^^^^^^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: casting pointers to integers in constant functions is unstable
diff --git a/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr b/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
index 7461007fc2aa5..ef7a60faf3f5c 100644
--- a/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
+++ b/src/test/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
@@ -4,7 +4,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const fn add(f: f32) -> f32 { f + 2.0 }
    |                               ^^^^^^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: floating point arithmetic is not allowed in constant functions
@@ -13,7 +13,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const fn sub(f: f32) -> f32 { 2.0 - f }
    |                               ^^^^^^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: floating point arithmetic is not allowed in constant functions
@@ -22,7 +22,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const fn mul(f: f32, g: f32) -> f32 { f * g }
    |                                       ^^^^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: floating point arithmetic is not allowed in constant functions
@@ -31,7 +31,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const fn div(f: f32, g: f32) -> f32 { f / g }
    |                                       ^^^^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error[E0658]: floating point arithmetic is not allowed in constant functions
@@ -40,7 +40,7 @@ error[E0658]: floating point arithmetic is not allowed in constant functions
 LL | const fn neg(f: f32) -> f32 { -f }
    |                               ^^
    |
-   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
    = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
 
 error: aborting due to 5 previous errors

From 187162e9917b6255c5eb12434362e6c4cc9c6976 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Tue, 22 Sep 2020 22:27:18 +0200
Subject: [PATCH 20/21] Add missing code examples on slice iter types

---
 library/core/src/slice/iter.rs | 164 +++++++++++++++++++++++++++++++++
 1 file changed, 164 insertions(+)

diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index 84fa34c75e3a2..1bac35845dff0 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -270,6 +270,13 @@ pub(super) trait SplitIter: DoubleEndedIterator {
 ///
 /// This struct is created by the [`split`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = [10, 40, 33, 20];
+/// let mut iter = slice.split(|num| num % 3 == 0);
+/// ```
+///
 /// [`split`]: ../../std/primitive.slice.html#method.split
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -378,6 +385,15 @@ impl<T, P> FusedIterator for Split<'_, T, P> where P: FnMut(&T) -> bool {}
 ///
 /// This struct is created by the [`split_inclusive`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// #![feature(split_inclusive)]
+///
+/// let slice = [10, 40, 33, 20];
+/// let mut iter = slice.split_inclusive(|num| num % 3 == 0);
+/// ```
+///
 /// [`split_inclusive`]: ../../std/primitive.slice.html#method.split_inclusive
 /// [slices]: ../../std/primitive.slice.html
 #[unstable(feature = "split_inclusive", issue = "72360")]
@@ -476,6 +492,13 @@ impl<T, P> FusedIterator for SplitInclusive<'_, T, P> where P: FnMut(&T) -> bool
 ///
 /// This struct is created by the [`split_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut v = [10, 40, 30, 20, 60, 50];
+/// let iter = v.split_mut(|num| *num % 3 == 0);
+/// ```
+///
 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -591,6 +614,15 @@ impl<T, P> FusedIterator for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
 ///
 /// This struct is created by the [`split_inclusive_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// #![feature(split_inclusive)]
+///
+/// let mut v = [10, 40, 30, 20, 60, 50];
+/// let iter = v.split_inclusive_mut(|num| *num % 3 == 0);
+/// ```
+///
 /// [`split_inclusive_mut`]: ../../std/primitive.slice.html#method.split_inclusive_mut
 /// [slices]: ../../std/primitive.slice.html
 #[unstable(feature = "split_inclusive", issue = "72360")]
@@ -698,6 +730,13 @@ impl<T, P> FusedIterator for SplitInclusiveMut<'_, T, P> where P: FnMut(&T) -> b
 ///
 /// This struct is created by the [`rsplit`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = [11, 22, 33, 0, 44, 55];
+/// let iter = slice.rsplit(|num| *num == 0);
+/// ```
+///
 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "slice_rsplit", since = "1.27.0")]
@@ -770,6 +809,13 @@ impl<T, P> FusedIterator for RSplit<'_, T, P> where P: FnMut(&T) -> bool {}
 ///
 /// This struct is created by the [`rsplit_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = [11, 22, 33, 0, 44, 55];
+/// let iter = slice.rsplit_mut(|num| *num == 0);
+/// ```
+///
 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "slice_rsplit", since = "1.27.0")]
@@ -875,6 +921,13 @@ impl<T, I: SplitIter<Item = T>> Iterator for GenericSplitN<I> {
 ///
 /// This struct is created by the [`splitn`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = [10, 40, 30, 20, 60, 50];
+/// let iter = slice.splitn(2, |num| *num % 3 == 0);
+/// ```
+///
 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -901,6 +954,13 @@ where
 ///
 /// This struct is created by the [`rsplitn`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = [10, 40, 30, 20, 60, 50];
+/// let iter = slice.rsplitn(2, |num| *num % 3 == 0);
+/// ```
+///
 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -926,6 +986,13 @@ where
 ///
 /// This struct is created by the [`splitn_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = [10, 40, 30, 20, 60, 50];
+/// let iter = slice.splitn_mut(2, |num| *num % 3 == 0);
+/// ```
+///
 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -952,6 +1019,13 @@ where
 ///
 /// This struct is created by the [`rsplitn_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = [10, 40, 30, 20, 60, 50];
+/// let iter = slice.rsplitn_mut(2, |num| *num % 3 == 0);
+/// ```
+///
 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -981,6 +1055,13 @@ forward_iterator! { RSplitNMut: T, &'a mut [T] }
 ///
 /// This struct is created by the [`windows`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = ['r', 'u', 's', 't'];
+/// let iter = slice.windows(2);
+/// ```
+///
 /// [`windows`]: ../../std/primitive.slice.html#method.windows
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug)]
@@ -1113,6 +1194,13 @@ unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
 ///
 /// This struct is created by the [`chunks`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.chunks(2);
+/// ```
+///
 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug)]
@@ -1267,6 +1355,13 @@ unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
 ///
 /// This struct is created by the [`chunks_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.chunks_mut(2);
+/// ```
+///
 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug)]
@@ -1419,6 +1514,13 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
 ///
 /// This struct is created by the [`chunks_exact`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.chunks_exact(2);
+/// ```
+///
 /// [`chunks_exact`]: ../../std/primitive.slice.html#method.chunks_exact
 /// [`remainder`]: ChunksExact::remainder
 /// [slices]: ../../std/primitive.slice.html
@@ -1559,6 +1661,13 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> {
 ///
 /// This struct is created by the [`chunks_exact_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.chunks_exact_mut(2);
+/// ```
+///
 /// [`chunks_exact_mut`]: ../../std/primitive.slice.html#method.chunks_exact_mut
 /// [`into_remainder`]: ChunksExactMut::into_remainder
 /// [slices]: ../../std/primitive.slice.html
@@ -1692,6 +1801,15 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {
 ///
 /// This struct is created by the [`array_windows`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// #![feature(array_windows)]
+///
+/// let slice = [0, 1, 2, 3];
+/// let iter = slice.array_windows::<2>();
+/// ```
+///
 /// [`array_windows`]: ../../std/primitive.slice.html#method.array_windows
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug, Clone, Copy)]
@@ -1796,6 +1914,15 @@ impl<T, const N: usize> ExactSizeIterator for ArrayWindows<'_, T, N> {
 ///
 /// This struct is created by the [`array_chunks`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// #![feature(array_chunks)]
+///
+/// let slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.array_chunks::<2>();
+/// ```
+///
 /// [`array_chunks`]: ../../std/primitive.slice.html#method.array_chunks
 /// [`remainder`]: ArrayChunks::remainder
 /// [slices]: ../../std/primitive.slice.html
@@ -1903,6 +2030,15 @@ unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunks<'a, T, N>
 ///
 /// This struct is created by the [`array_chunks_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// #![feature(array_chunks)]
+///
+/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.array_chunks_mut::<2>();
+/// ```
+///
 /// [`array_chunks_mut`]: ../../std/primitive.slice.html#method.array_chunks_mut
 /// [`into_remainder`]: ../../std/slice/struct.ArrayChunksMut.html#method.into_remainder
 /// [slices]: ../../std/primitive.slice.html
@@ -2001,6 +2137,13 @@ unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunksMut<'a, T,
 ///
 /// This struct is created by the [`rchunks`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.rchunks(2);
+/// ```
+///
 /// [`rchunks`]: ../../std/primitive.slice.html#method.rchunks
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug)]
@@ -2151,6 +2294,13 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunks<'a, T> {
 ///
 /// This struct is created by the [`rchunks_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.rchunks_mut(2);
+/// ```
+///
 /// [`rchunks_mut`]: ../../std/primitive.slice.html#method.rchunks_mut
 /// [slices]: ../../std/primitive.slice.html
 #[derive(Debug)]
@@ -2300,6 +2450,13 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunksMut<'a, T> {
 ///
 /// This struct is created by the [`rchunks_exact`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.rchunks_exact(2);
+/// ```
+///
 /// [`rchunks_exact`]: ../../std/primitive.slice.html#method.rchunks_exact
 /// [`remainder`]: ChunksExact::remainder
 /// [slices]: ../../std/primitive.slice.html
@@ -2445,6 +2602,13 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunksExact<'a, T> {
 ///
 /// This struct is created by the [`rchunks_exact_mut`] method on [slices].
 ///
+/// # Example
+///
+/// ```
+/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
+/// let iter = slice.rchunks_exact_mut(2);
+/// ```
+///
 /// [`rchunks_exact_mut`]: ../../std/primitive.slice.html#method.rchunks_exact_mut
 /// [`into_remainder`]: ChunksExactMut::into_remainder
 /// [slices]: ../../std/primitive.slice.html

From 900daba2cbcc077f26b45c31c6a853ef5d4d6e9f Mon Sep 17 00:00:00 2001
From: LingMan <LingMan@users.noreply.github.com>
Date: Fri, 25 Sep 2020 23:35:07 +0200
Subject: [PATCH 21/21] Remove stray word from `ClosureKind::extends` docs

---
 compiler/rustc_middle/src/ty/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 637ef4c17ebc8..492afa54445bc 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2675,7 +2675,7 @@ impl<'tcx> ClosureKind {
         }
     }
 
-    /// Returns `true` if this a type that impls this closure kind
+    /// Returns `true` if a type that impls this closure kind
     /// must also implement `other`.
     pub fn extends(self, other: ty::ClosureKind) -> bool {
         match (self, other) {