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parser: Fix panic in 'const impl' recovery

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The panic happens when in recovery parsing a full `impl`
(`parse_item_impl`) fails and we drop the `DiagnosticBuilder` for the
recovery suggestion and return the `parse_item_impl` error.

We now raise the original error "expected identifier found `impl`" when
parsing the `impl` fails.

Note that the regression test is slightly simplified version of the
original repro in #81806, to make the error output smaller and more
resilient to unrelated changes in parser error messages.

Fixes #81806
This commit is contained in:
Ömer Sinan Ağacan 2021-02-08 10:43:54 +03:00
parent 0b7a598e12
commit 6eb1bd4c3e
3 changed files with 34 additions and 2 deletions
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14
compiler/rustc_parse/src/parser/item.rs
View file

@ -1010,9 +1010,18 @@ impl<'a> Parser<'a> {
) -> 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)?;
// Only try to recover if this is implementing a trait for a type
let mut impl_info = match self.parse_item_impl(attrs, defaultness) {
Ok(impl_info) => impl_info,
Err(mut recovery_error) => {
// Recovery failed, raise the "expected identifier" error
recovery_error.cancel();
return Err(err);
}
};
match impl_info.1 {
// only try to recover if this is implementing a trait for a type
ItemKind::Impl(box ImplKind {
of_trait: Some(ref trai), ref mut constness, ..
}) => {
@ -1030,6 +1039,7 @@ impl<'a> Parser<'a> {
ItemKind::Impl { .. } => return Err(err),
_ => unreachable!(),
}
Ok(impl_info)
}