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Recover impl<T ?Sized> correctly

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This commit is contained in:
Michael Goulet 2023-05-10 23:00:47 +00:00
parent 2913ad6db0
commit a5763ff8d3
3 changed files with 19 additions and 0 deletions
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5
compiler/rustc_parse/src/parser/generics.rs
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@ -453,6 +453,8 @@ impl<'a> Parser<'a> {
// `<` (LIFETIME|IDENT) `:` - generic parameter with bounds // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
// `<` (LIFETIME|IDENT) `=` - generic parameter with a default // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
// `<` const - generic const parameter // `<` const - generic const parameter
// `<` IDENT `?` - RECOVERY for `impl<T ?Bound` missing a `:`, meant to
// avoid the `T?` to `Option<T>` recovery for types.
// The only truly ambiguous case is // The only truly ambiguous case is
// `<` IDENT `>` `::` IDENT ... // `<` IDENT `>` `::` IDENT ...
// we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`) // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
@ -463,6 +465,9 @@ impl<'a> Parser<'a> {
|| self.look_ahead(start + 1, |t| t.is_lifetime() || t.is_ident()) || self.look_ahead(start + 1, |t| t.is_lifetime() || t.is_ident())
&& self.look_ahead(start + 2, |t| { && self.look_ahead(start + 2, |t| {
matches!(t.kind, token::Gt | token::Comma | token::Colon | token::Eq) matches!(t.kind, token::Gt | token::Comma | token::Colon | token::Eq)
// Recovery-only branch -- this could be removed,
// since it only affects diagnostics currently.
|| matches!(t.kind, token::Question)
}) })
|| self.is_keyword_ahead(start + 1, &[kw::Const])) || self.is_keyword_ahead(start + 1, &[kw::Const]))
} }

6
tests/ui/parser/impl-on-unsized-typo.rs Normal file
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@ -0,0 +1,6 @@
trait Tr {}
impl<T ?Sized> Tr for T {}
//~^ ERROR expected one of `,`, `:`, `=`, or `>`, found `?`
fn main() {}

8
tests/ui/parser/impl-on-unsized-typo.stderr Normal file
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@ -0,0 +1,8 @@
error: expected one of `,`, `:`, `=`, or `>`, found `?`
--> $DIR/impl-on-unsized-typo.rs:3:8
|
LL | impl<T ?Sized> Tr for T {}
| ^ expected one of `,`, `:`, `=`, or `>`
error: aborting due to previous error