bjoernager/rust
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Auto merge of #79668 - coolreader18:recover-const-impl, r=petrochenkov

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Recover on `const impl<> X for Y`

`@leonardo-m` mentioned that `const impl Foo for Bar` could be recovered from in #79287.

I'm not sure about the error strings as they are, I think it should probably be something like the error that `expected_one_of_not_found` makes + the suggestion to flip the keywords, but I'm not sure how exactly to do that. Also, I decided not to try to handle `const unsafe impl` or `unsafe const impl` cause I figured that `unsafe impl const` would be pretty rare anyway (if it's even valid?), and it wouldn't be worth making the code more messy.
This commit is contained in:
bors 2020-12-13 10:52:29 +00:00
commit 057937bdda
5 changed files with 99 additions and 3 deletions
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41
compiler/rustc_parse/src/parser/item.rs
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@ -247,9 +247,14 @@ impl<'a> Parser<'a> {
(ident, ItemKind::Static(ty, m, expr))
} else if let Const::Yes(const_span) = self.parse_constness() {
// CONST ITEM
self.recover_const_mut(const_span);
let (ident, ty, expr) = self.parse_item_global(None)?;
(ident, ItemKind::Const(def(), ty, expr))
if self.token.is_keyword(kw::Impl) {
// recover from `const impl`, suggest `impl const`
self.recover_const_impl(const_span, attrs, def())?
} else {
self.recover_const_mut(const_span);
let (ident, ty, expr) = self.parse_item_global(None)?;
(ident, ItemKind::Const(def(), ty, expr))
}
} else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
// TRAIT ITEM
self.parse_item_trait(attrs, lo)?
@ -988,6 +993,36 @@ impl<'a> Parser<'a> {
}
}
/// Recover on `const impl` with `const` already eaten.
fn recover_const_impl(
&mut self,
const_span: Span,
attrs: &mut Vec<Attribute>,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
let impl_span = self.token.span;
let mut err = self.expected_ident_found();
let mut impl_info = self.parse_item_impl(attrs, defaultness)?;
match impl_info.1 {
// only try to recover if this is implementing a trait for a type
ItemKind::Impl { of_trait: Some(ref trai), ref mut constness, .. } => {
*constness = Const::Yes(const_span);
let before_trait = trai.path.span.shrink_to_lo();
let const_up_to_impl = const_span.with_hi(impl_span.lo());
err.multipart_suggestion(
"you might have meant to write a const trait impl",
vec![(const_up_to_impl, "".to_owned()), (before_trait, "const ".to_owned())],
Applicability::MaybeIncorrect,
)
.emit();
}
ItemKind::Impl { .. } => return Err(err),
_ => unreachable!(),
}
Ok(impl_info)
}
/// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
/// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
///