Tweak unstable diagnostic output

src/libsyntax/feature_gate.rs

@@ -903,7 +903,7 @@ pub const BUILTIN_ATTRIBUTES: &[(&str, AttributeType, AttributeTemplate, Attribu
     ("thread_local", Whitelisted, template!(Word), Gated(Stability::Unstable,
                                         "thread_local",
                                         "`#[thread_local]` is an experimental feature, and does \
-                                         not currently handle destructors.",
+                                         not currently handle destructors",
                                         cfg_fn!(thread_local))),
 
     ("rustc_on_unimplemented", Whitelisted, template!(List:
@@ -1438,42 +1438,61 @@ pub enum GateStrength {
     Soft,
 }
 
-pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
-                        explain: &str) {
+pub fn emit_feature_err(
+    sess: &ParseSess,
+    feature: &str,
+    span: Span,
+    issue: GateIssue,
+    explain: &str,
+) {
     feature_err(sess, feature, span, issue, explain).emit();
 }
 
-pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
-                       explain: &str) -> DiagnosticBuilder<'a> {
+pub fn feature_err<'a>(
+    sess: &'a ParseSess,
+    feature: &str,
+    span: Span,
+    issue: GateIssue,
+    explain: &str,
+) -> DiagnosticBuilder<'a> {
     leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
 }
 
-fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
-                           explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
+fn leveled_feature_err<'a>(
+    sess: &'a ParseSess,
+    feature: &str,
+    span: Span,
+    issue: GateIssue,
+    explain: &str,
+    level: GateStrength,
+) -> DiagnosticBuilder<'a> {
     let diag = &sess.span_diagnostic;
 
     let issue = match issue {
         GateIssue::Language => find_lang_feature_issue(feature),
         GateIssue::Library(lib) => lib,
     };
 
-    let explanation = match issue {
-        None | Some(0) => explain.to_owned(),
-        Some(n) => format!("{} (see issue #{})", explain, n)
-    };
-
     let mut err = match level {
         GateStrength::Hard => {
-            diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
+            diag.struct_span_err_with_code(span, explain, stringify_error_code!(E0658))
         }
-        GateStrength::Soft => diag.struct_span_warn(span, &explanation),
+        GateStrength::Soft => diag.struct_span_warn(span, explain),
     };
 
+    match issue {
+        None | Some(0) => {}  // We still accept `0` as a stand-in for backwards compatibility
+        Some(n) => {
+            err.note(&format!(
+                "for more information, see https://github.com/rust-lang/rust/issues/{}",
+                n,
+            ));
+        }
+    }
+
     // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
     if sess.unstable_features.is_nightly_build() {
-        err.help(&format!("add #![feature({})] to the \
-                           crate attributes to enable",
-                          feature));
+        err.help(&format!("add #![feature({})] to the crate attributes to enable", feature));
     }
 
     // If we're on stable and only emitting a "soft" warning, add a note to
@@ -1488,10 +1507,10 @@ fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue
 }
 
 const EXPLAIN_BOX_SYNTAX: &str =
-    "box expression syntax is experimental; you can call `Box::new` instead.";
+    "box expression syntax is experimental; you can call `Box::new` instead";
 
 pub const EXPLAIN_STMT_ATTR_SYNTAX: &str =
-    "attributes on expressions are experimental.";
+    "attributes on expressions are experimental";
 
 pub const EXPLAIN_ASM: &str =
     "inline assembly is not stable enough for use and is subject to change";
@@ -1685,10 +1704,12 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
     fn visit_name(&mut self, sp: Span, name: ast::Name) {
         if !name.as_str().is_ascii() {
-            gate_feature_post!(&self,
-                               non_ascii_idents,
-                               self.context.parse_sess.source_map().def_span(sp),
-                               "non-ascii idents are not fully supported.");
+            gate_feature_post!(
+                &self,
+                non_ascii_idents,
+                self.context.parse_sess.source_map().def_span(sp),
+                "non-ascii idents are not fully supported"
+            );
         }
     }
 

src/libsyntax/json.rs

@@ -348,19 +348,17 @@ impl DiagnosticSpanLine {
     /// `span` within the line.
     fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
         je.sm.span_to_lines(span)
-             .map(|lines| {
-                 let fm = &*lines.file;
-                 lines.lines
-                      .iter()
-                      .map(|line| {
-                          DiagnosticSpanLine::line_from_source_file(fm,
-                                                                line.line_index,
-                                                                line.start_col.0 + 1,
-                                                                line.end_col.0 + 1)
-                      })
-                     .collect()
-             })
-            .unwrap_or_else(|_| vec![])
+            .map(|lines| {
+                let fm = &*lines.file;
+                lines.lines
+                    .iter()
+                    .map(|line| DiagnosticSpanLine::line_from_source_file(
+                        fm,
+                        line.line_index,
+                        line.start_col.0 + 1,
+                        line.end_col.0 + 1,
+                    )).collect()
+            }).unwrap_or_else(|_| vec![])
     }
 }
 

src/test/ui-fulldeps/gated-plugin.stderr

@@ -1,9 +1,10 @@
-error[E0658]: compiler plugins are experimental and possibly buggy (see issue #29597)
+error[E0658]: compiler plugins are experimental and possibly buggy
   --> $DIR/gated-plugin.rs:3:1
    |
 LL | #![plugin(attr_plugin_test)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/29597
    = help: add #![feature(plugin)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui-fulldeps/hash-stable-is-unstable.stderr

@@ -2,44 +2,49 @@ error[E0601]: `main` function not found in crate `hash_stable_is_unstable`
    |
    = note: consider adding a `main` function to `$DIR/hash-stable-is-unstable.rs`
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:3:1
    |
 LL | extern crate rustc_data_structures;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add #![feature(rustc_private)] to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:5:1
    |
 LL | extern crate rustc;
    | ^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add #![feature(rustc_private)] to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:7:1
    |
 LL | extern crate rustc_macros;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add #![feature(rustc_private)] to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:10:5
    |
 LL | use rustc_macros::HashStable;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add #![feature(rustc_private)] to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> $DIR/hash-stable-is-unstable.rs:13:10
    |
 LL | #[derive(HashStable)]
    |          ^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add #![feature(rustc_private)] to the crate attributes to enable
 
 error: aborting due to 6 previous errors

src/test/ui/cast/cast-ptr-to-int-const.stderr

@@ -1,17 +1,19 @@
-error[E0658]: casting pointers to integers in constants is unstable (see issue #51910)
+error[E0658]: casting pointers to integers in constants is unstable
   --> $DIR/cast-ptr-to-int-const.rs:5:9
    |
 LL |         main as u32
    |         ^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51910
    = help: add #![feature(const_raw_ptr_to_usize_cast)] to the crate attributes to enable
 
-error[E0658]: casting pointers to integers in constants is unstable (see issue #51910)
+error[E0658]: casting pointers to integers in constants is unstable
   --> $DIR/cast-ptr-to-int-const.rs:9:9
    |
 LL |         &Y as *const u32 as u32
    |         ^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51910
    = help: add #![feature(const_raw_ptr_to_usize_cast)] to the crate attributes to enable
 
 error: aborting due to 2 previous errors

src/test/ui/conditional-compilation/cfg-attr-crate-2.stderr

@@ -1,9 +1,10 @@
-error[E0658]: no_core is experimental (see issue #29639)
+error[E0658]: no_core is experimental
   --> $DIR/cfg-attr-crate-2.rs:6:21
    |
 LL | #![cfg_attr(broken, no_core)]
    |                     ^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/29639
    = help: add #![feature(no_core)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/conditional-compilation/cfg-attr-multi-invalid-1.stderr

@@ -1,9 +1,10 @@
-error[E0658]: no_core is experimental (see issue #29639)
+error[E0658]: no_core is experimental
   --> $DIR/cfg-attr-multi-invalid-1.rs:4:21
    |
 LL | #![cfg_attr(broken, no_core, no_std)]
    |                     ^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/29639
    = help: add #![feature(no_core)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/conditional-compilation/cfg-attr-multi-invalid-2.stderr

@@ -1,9 +1,10 @@
-error[E0658]: no_core is experimental (see issue #29639)
+error[E0658]: no_core is experimental
   --> $DIR/cfg-attr-multi-invalid-2.rs:4:29
    |
 LL | #![cfg_attr(broken, no_std, no_core)]
    |                             ^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/29639
    = help: add #![feature(no_core)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr

@@ -1,4 +1,4 @@
-error[E0658]: The attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
+error[E0658]: The attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
   --> $DIR/cfg-attr-unknown-attribute-macro-expansion.rs:3:27
    |
 LL |         #[cfg_attr(all(), unknown)]
@@ -7,6 +7,7 @@ LL |         #[cfg_attr(all(), unknown)]
 LL | foo!();
    | ------- in this macro invocation
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add #![feature(custom_attribute)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/consts/const-deref-ptr.stderr

@@ -1,9 +1,10 @@
-error[E0658]: dereferencing raw pointers in statics is unstable (see issue #51911)
+error[E0658]: dereferencing raw pointers in statics is unstable
   --> $DIR/const-deref-ptr.rs:4:29
    |
 LL |     static C: u64 = unsafe {*(0xdeadbeef as *const u64)};
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51911
    = help: add #![feature(const_raw_ptr_deref)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/consts/const-eval/feature-gate-const_fn_union.stderr

@@ -1,9 +1,10 @@
-error[E0658]: unions in const fn are unstable (see issue #51909)
+error[E0658]: unions in const fn are unstable
   --> $DIR/feature-gate-const_fn_union.rs:11:5
    |
 LL |     Foo { u }.i
    |     ^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51909
    = help: add #![feature(const_fn_union)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/consts/const-eval/feature-gate-const_panic.stderr

@@ -1,27 +1,30 @@
-error[E0658]: panicking in constants is unstable (see issue #51999)
+error[E0658]: panicking in constants is unstable
   --> $DIR/feature-gate-const_panic.rs:3:15
    |
 LL | const Z: () = panic!("cheese");
    |               ^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51999
    = help: add #![feature(const_panic)] to the crate attributes to enable
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
-error[E0658]: panicking in constants is unstable (see issue #51999)
+error[E0658]: panicking in constants is unstable
   --> $DIR/feature-gate-const_panic.rs:9:15
    |
 LL | const X: () = unimplemented!();
    |               ^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51999
    = help: add #![feature(const_panic)] to the crate attributes to enable
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
-error[E0658]: panicking in constants is unstable (see issue #51999)
+error[E0658]: panicking in constants is unstable
   --> $DIR/feature-gate-const_panic.rs:6:15
    |
 LL | const Y: () = unreachable!();
    |               ^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51999
    = help: add #![feature(const_panic)] to the crate attributes to enable
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 

src/test/ui/consts/const-eval/match-test-ptr-null.rs

@@ -3,7 +3,9 @@ fn main() {
     // that pointer comparison is disallowed, not that parts of a pointer are accessed as raw
     // bytes.
     let _: [u8; 0] = [4; {
-        match &1 as *const i32 as usize { //~ ERROR casting pointers to integers in constants
+        match &1 as *const i32 as usize {
+            //~^ ERROR casting pointers to integers in constants
+            //~| NOTE for more information, see
             0 => 42, //~ ERROR constant contains unimplemented expression type
             //~^ NOTE "pointer arithmetic or comparison" needs an rfc before being allowed
             //~| ERROR evaluation of constant value failed

src/test/ui/consts/const-eval/match-test-ptr-null.stderr

@@ -1,19 +1,20 @@
-error[E0658]: casting pointers to integers in constants is unstable (see issue #51910)
+error[E0658]: casting pointers to integers in constants is unstable
   --> $DIR/match-test-ptr-null.rs:6:15
    |
 LL |         match &1 as *const i32 as usize {
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/51910
    = help: add #![feature(const_raw_ptr_to_usize_cast)] to the crate attributes to enable
 
 error[E0019]: constant contains unimplemented expression type
-  --> $DIR/match-test-ptr-null.rs:7:13
+  --> $DIR/match-test-ptr-null.rs:9:13
    |
 LL |             0 => 42,
    |             ^
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/match-test-ptr-null.rs:7:13
+  --> $DIR/match-test-ptr-null.rs:9:13
    |
 LL |             0 => 42,
    |             ^ "pointer arithmetic or comparison" needs an rfc before being allowed inside constants