bjoernager/rust
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Auto merge of #118527 - Nadrieril:never_patterns_parse, r=compiler-errors

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never_patterns: Parse match arms with no body

Never patterns are meant to signal unreachable cases, and thus don't take bodies:
```rust
let ptr: *const Option<!> = ...;
match *ptr {
    None => { foo(); }
    Some(!),
}
```
This PR makes rustc accept the above, and enforces that an arm has a body xor is a never pattern. This affects parsing of match arms even with the feature off, so this is delicate. (Plus this is my first non-trivial change to the parser).

~~The last commit is optional; it introduces a bit of churn to allow the new suggestions to be machine-applicable. There may be a better solution? I'm not sure.~~ EDIT: I removed that commit

r? `@compiler-errors`
This commit is contained in:
bors 2023-12-08 17:08:52 +00:00
commit 2b399b5275
47 changed files with 777 additions and 241 deletions
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12
compiler/rustc_parse/src/parser/pat.rs
View file

@ -154,12 +154,8 @@ impl<'a> Parser<'a> {
}
Err(err) => return Err(err),
};
if rc == RecoverComma::Yes {
self.maybe_recover_unexpected_comma(
first_pat.span,
matches!(first_pat.kind, PatKind::MacCall(_)),
rt,
)?;
if rc == RecoverComma::Yes && !first_pat.could_be_never_pattern() {
self.maybe_recover_unexpected_comma(first_pat.span, rt)?;
}
// If the next token is not a `|`,
@ -200,8 +196,8 @@ impl<'a> Parser<'a> {
err.span_label(lo, WHILE_PARSING_OR_MSG);
err
})?;
if rc == RecoverComma::Yes {
self.maybe_recover_unexpected_comma(pat.span, false, rt)?;
if rc == RecoverComma::Yes && !pat.could_be_never_pattern() {
self.maybe_recover_unexpected_comma(pat.span, rt)?;
}
pats.push(pat);
}