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Properly recover from parenthesized use-bounds (precise capturing)

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This commit is contained in:
León Orell Valerian Liehr
2025-08-15 22:14:37 +02:00
parent 577166503a
commit eb3e0d4c8a
3 changed files with 48 additions and 16 deletions
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42
compiler/rustc_parse/src/parser/ty.rs
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@@ -849,8 +849,9 @@ impl<'a> Parser<'a> {
fn parse_precise_capturing_args(
&mut self,
) -> PResult<'a, (ThinVec<PreciseCapturingArg>, Span)> {
let lo = self.token.span;
lo: Span,
parens: ast::Parens,
) -> PResult<'a, GenericBound> {
self.expect_lt()?;
let (args, _, _) = self.parse_seq_to_before_tokens(
&[exp!(Gt)],
@@ -876,7 +877,22 @@ impl<'a> Parser<'a> {
},
)?;
self.expect_gt()?;
Ok((args, lo.to(self.prev_token.span)))
if let ast::Parens::Yes = parens {
self.expect(exp!(CloseParen))?;
let hi = self.prev_token.span;
let mut diag = self
.dcx()
.struct_span_err(lo.to(hi), "precise capturing lists may not be parenthesized");
diag.multipart_suggestion(
"remove the parentheses",
vec![(lo, String::new()), (hi, String::new())],
Applicability::MachineApplicable,
);
diag.emit();
}
Ok(GenericBound::Use(args, lo.to(self.prev_token.span)))
}
/// Is a `dyn B0 + ... + Bn` type allowed here?
@@ -987,24 +1003,18 @@ impl<'a> Parser<'a> {
/// BOUND = TY_BOUND | LT_BOUND
/// ```
fn parse_generic_bound(&mut self) -> PResult<'a, GenericBound> {
let lo = self.token.span;
let leading_token = self.prev_token;
let lo = self.token.span;
let parens = if self.eat(exp!(OpenParen)) { ast::Parens::Yes } else { ast::Parens::No };
let bound = if self.token.is_lifetime() {
self.parse_generic_lt_bound(lo, parens)?
if self.token.is_lifetime() {
self.parse_generic_lt_bound(lo, parens)
} else if self.eat_keyword(exp!(Use)) {
// parse precise captures, if any. This is `use<'lt, 'lt, P, P>`; a list of
// lifetimes and ident params (including SelfUpper). These are validated later
// for order, duplication, and whether they actually reference params.
let use_span = self.prev_token.span;
let (args, args_span) = self.parse_precise_capturing_args()?;
GenericBound::Use(args, use_span.to(args_span))
self.parse_precise_capturing_args(lo, parens)
} else {
self.parse_generic_ty_bound(lo, parens, &leading_token)?
};
Ok(bound)
self.parse_generic_ty_bound(lo, parens, &leading_token)
}
}
/// Parses a lifetime ("outlives") bound, e.g. `'a`, according to: