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Improve recovery for missing trait in a trait impl

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This commit is contained in:
Vadim Petrochenkov 2019-03-07 23:18:03 +03:00
parent 00887f39d1
commit e19b228959
3 changed files with 15 additions and 16 deletions
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22
src/libsyntax/parse/parser.rs
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@ -6716,16 +6716,16 @@ impl<'a> Parser<'a> {
ast::ImplPolarity::Positive
};
let possible_missing_trait = self.look_ahead(0, |t| t.is_keyword(keywords::For));
// Parse both types and traits as a type, then reinterpret if necessary.
let ty_first = self.parse_ty().map_err(|mut err| {
if possible_missing_trait {
err.help("did you forget a trait name after `impl`?");
}
err
})?;
let err_path = |span| ast::Path::from_ident(Ident::new(keywords::Invalid.name(), span));
let ty_first = if self.token.is_keyword(keywords::For) &&
self.look_ahead(1, |t| t != &token::Lt) {
let span = self.prev_span.between(self.span);
self.struct_span_err(span, "missing trait in a trait impl").emit();
P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
} else {
self.parse_ty()?
};
// If `for` is missing we try to recover.
let has_for = self.eat_keyword(keywords::For);
@ -6734,7 +6734,7 @@ impl<'a> Parser<'a> {
let ty_second = if self.token == token::DotDot {
// We need to report this error after `cfg` expansion for compatibility reasons
self.bump(); // `..`, do not add it to expected tokens
Some(P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID }))
Some(DummyResult::raw_ty(self.prev_span, true))
} else if has_for || self.token.can_begin_type() {
Some(self.parse_ty()?)
} else {
@ -6764,7 +6764,7 @@ impl<'a> Parser<'a> {
TyKind::Path(None, path) => path,
_ => {
self.span_err(ty_first.span, "expected a trait, found type");
ast::Path::from_ident(Ident::new(keywords::Invalid.name(), ty_first.span))
err_path(ty_first.span)
}
};
let trait_ref = TraitRef { path, ref_id: ty_first.id };