Don't gate the feature twice

Author: Nadrieril

compiler/rustc_ast/src/ast.rs

@@ -676,6 +676,19 @@ impl Pat {
  });
  could_be_never_pattern
  }
+
+ /// Whether this contains a `!` pattern. This in particular means that a feature gate error will
+ /// be raised if the feature is off. Used to avoid gating the feature twice.
+ pub fn contains_never_pattern(&self) -> bool {
+ let mut contains_never_pattern = false;
+ self.walk(&mut |pat| {
+ if matches!(pat.kind, PatKind::Never) {
+ contains_never_pattern = true;
+ }
+ true
+ });
+ contains_never_pattern
+ }
 }
 
 /// A single field in a struct pattern.

compiler/rustc_parse/src/parser/expr.rs

@@ -2920,7 +2920,10 @@ impl<'a> Parser<'a> {
  arm_body = None;
  this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)]).map(
  |x| {
- this.sess.gated_spans.gate(sym::never_patterns, pat.span);
+ // Don't gate twice
+ if !pat.contains_never_pattern() {
+ this.sess.gated_spans.gate(sym::never_patterns, pat.span);
+ }
  x
  },
  )

tests/ui/feature-gates/feature-gate-never_patterns.rs

@@ -14,14 +14,12 @@ fn main() {
  match *ptr {
  !
  //~^ ERROR `!` patterns are experimental
- //~| ERROR `!` patterns are experimental
  }
  // Check that the gate operates even behind `cfg`.
  #[cfg(FALSE)]
  match *ptr {
  !
  //~^ ERROR `!` patterns are experimental
- //~| ERROR `!` patterns are experimental
  }
  #[cfg(FALSE)]
  match *ptr {
@@ -51,14 +49,12 @@ fn main() {
  match res {
  Ok(_) => {}
  Err(!),
- //~^ ERROR `match` arm with no body
- //~| ERROR `!` patterns are experimental
+ //~^ ERROR `!` patterns are experimental
  }
  match res {
  Err(!) if false,
- //~^ ERROR `match` arm with no body
+ //~^ ERROR `!` patterns are experimental
  //~| ERROR a guard on a never pattern will never be run
- //~| ERROR `!` patterns are experimental
  _ => {}
  }
 

tests/ui/feature-gates/feature-gate-never_patterns.stderr

@@ -1,5 +1,5 @@
 error: unexpected `,` in pattern
- --> $DIR/feature-gate-never_patterns.rs:36:16
+ --> $DIR/feature-gate-never_patterns.rs:34:16
  |
 LL | Some(_),
  | ^
@@ -40,17 +40,7 @@ LL | !
  = help: add `#![feature(never_patterns)]` to the crate attributes to enable
 
 error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:15:13
- |
-LL | !
- | ^
- |
- = note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
- = help: add `#![feature(never_patterns)]` to the crate attributes to enable
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:22:13
+ --> $DIR/feature-gate-never_patterns.rs:21:13
  |
 LL | !
  | ^
@@ -59,17 +49,7 @@ LL | !
  = help: add `#![feature(never_patterns)]` to the crate attributes to enable
 
 error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:22:13
- |
-LL | !
- | ^
- |
- = note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
- = help: add `#![feature(never_patterns)]` to the crate attributes to enable
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:28:13
+ --> $DIR/feature-gate-never_patterns.rs:26:13
  |
 LL | ! => {}
  | ^
@@ -78,40 +58,34 @@ LL | ! => {}
  = help: add `#![feature(never_patterns)]` to the crate attributes to enable
 
 error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:41:9
+ --> $DIR/feature-gate-never_patterns.rs:39:9
  |
 LL | Some(_)
  | ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
 
 error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:46:9
+ --> $DIR/feature-gate-never_patterns.rs:44:9
  |
 LL | Some(_) if false,
  | ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
 
 error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:48:9
+ --> $DIR/feature-gate-never_patterns.rs:46:9
  |
 LL | Some(_) if false
  | ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
 
 error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:53:13
+ --> $DIR/feature-gate-never_patterns.rs:51:13
  |
 LL | Err(!),
  | ^
  |
  = note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
  = help: add `#![feature(never_patterns)]` to the crate attributes to enable
 
-error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:53:9
- |
-LL | Err(!),
- | ^^^^^^- help: add a body after the pattern: `=> todo!(),`
-
 error[E0658]: `!` patterns are experimental
- --> $DIR/feature-gate-never_patterns.rs:58:13
+ --> $DIR/feature-gate-never_patterns.rs:55:13
  |
 LL | Err(!) if false,
  | ^
@@ -120,30 +94,24 @@ LL | Err(!) if false,
  = help: add `#![feature(never_patterns)]` to the crate attributes to enable
 
 error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:58:9
- |
-LL | Err(!) if false,
- | ^^^^^^- help: add a body after the pattern: `=> todo!(),`
-
-error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:69:9
+ --> $DIR/feature-gate-never_patterns.rs:65:9
  |
 LL | Some(_)
  | ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
 
 error: `match` arm with no body
- --> $DIR/feature-gate-never_patterns.rs:75:9
+ --> $DIR/feature-gate-never_patterns.rs:71:9
  |
 LL | Some(_) if false
  | ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
 
 error: a guard on a never pattern will never be run
- --> $DIR/feature-gate-never_patterns.rs:58:19
+ --> $DIR/feature-gate-never_patterns.rs:55:19
  |
 LL | Err(!) if false,
  | ^^^^^ help: remove this guard
 
-error: aborting due to 18 previous errors
+error: aborting due to 14 previous errors
 
 Some errors have detailed explanations: E0408, E0658.
 For more information about an error, try `rustc --explain E0408`.