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Rollup merge of #118868 - Nadrieril:correctly-gate-never_patterns-parsing, r=petrochenkov

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Correctly gate the parsing of match arms without body

https://github.com/rust-lang/rust/pull/118527 accidentally allowed the following to parse on stable:
```rust
match Some(0) {
    None => { foo(); }
    #[cfg(FALSE)]
    Some(_)
}
```

This fixes that oversight. The way I choose which error to emit is the best I could think of, I'm open if you know a better way.

r? `@petrochenkov` since you're the one who noticed
This commit is contained in:
Matthias Krüger 2023-12-12 17:40:56 +01:00 • committed by GitHub
commit d661974017
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10 changed files with 207 additions and 26 deletions
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10
compiler/rustc_parse/src/parser/expr.rs
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@ -2918,7 +2918,15 @@ impl<'a> Parser<'a> {
let mut result = if !is_fat_arrow && !is_almost_fat_arrow {
// A pattern without a body, allowed for never patterns.
arm_body = None;
this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)]).map(
|x| {
// Don't gate twice
if !pat.contains_never_pattern() {
this.sess.gated_spans.gate(sym::never_patterns, pat.span);
}
x
},
)
} else {
if let Err(mut err) = this.expect(&token::FatArrow) {
// We might have a `=>` -> `=` or `->` typo (issue #89396).