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Recover from &dyn mut ... parse errors

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This commit is contained in:
Fabian Wolff
2021-07-02 17:07:32 +02:00
parent ce331ee6ee
commit c692896ba2
3 changed files with 45 additions and 1 deletions
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22
compiler/rustc_parse/src/parser/ty.rs
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@@ -393,7 +393,7 @@ impl<'a> Parser<'a> {
let and_span = self.prev_token.span;
let mut opt_lifetime =
if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
let mutbl = self.parse_mutability();
let mut mutbl = self.parse_mutability();
if self.token.is_lifetime() && mutbl == Mutability::Mut && opt_lifetime.is_none() {
// A lifetime is invalid here: it would be part of a bare trait bound, which requires
// it to be followed by a plus, but we disallow plus in the pointee type.
@@ -417,6 +417,26 @@ impl<'a> Parser<'a> {
opt_lifetime = Some(self.expect_lifetime());
}
} else if self.token.is_keyword(kw::Dyn)
&& mutbl == Mutability::Not
&& self.look_ahead(1, |t| t.is_keyword(kw::Mut))
{
// We have `&dyn mut ...`, which is invalid and should be `&mut dyn ...`.
let span = and_span.to(self.look_ahead(1, |t| t.span));
let mut err = self.struct_span_err(span, "`mut` must precede `dyn`");
err.span_suggestion(
span,
"place `mut` before `dyn`",
"&mut dyn".to_string(),
Applicability::MachineApplicable,
);
err.emit();
// Recovery
mutbl = Mutability::Mut;
let (dyn_tok, dyn_tok_sp) = (self.token.clone(), self.token_spacing);
self.bump();
self.bump_with((dyn_tok, dyn_tok_sp));
}
let ty = self.parse_ty_no_plus()?;
Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))