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Parse impl const Trait for Ty syntax

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This commit is contained in:
Dylan MacKenzie 2020-01-02 15:49:45 -08:00
parent fd4a6a1213
commit 1c3fe9de4e
1 changed files with 11 additions and 3 deletions
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14
src/librustc_parse/parser/item.rs
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@ -542,10 +542,11 @@ impl<'a> Parser<'a> {
/// impl<'a, T> TYPE { /* impl items */ }
/// impl<'a, T> TRAIT for TYPE { /* impl items */ }
/// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
/// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
///
/// We actually parse slightly more relaxed grammar for better error reporting and recovery.
/// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
/// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
/// `impl` GENERICS `const`? `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
/// `impl` GENERICS `const`? `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
fn parse_item_impl(
&mut self,
unsafety: Unsafety,
@ -558,6 +559,13 @@ impl<'a> Parser<'a> {
Generics::default()
};
let constness = if self.eat_keyword(kw::Const) {
self.sess.gated_spans.gate(sym::const_trait_impl, self.prev_span);
Some(Constness::Const)
} else {
None
};
// Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
self.bump(); // `!`
@ -618,7 +626,7 @@ impl<'a> Parser<'a> {
err_path(ty_first.span)
}
};
let trait_ref = TraitRef { path, ref_id: ty_first.id };
let trait_ref = TraitRef { path, constness, ref_id: ty_first.id };
ItemKind::Impl(
unsafety,