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feat(rustc_parse): recover from pre-RFC-2000 const generics syntax

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Fixes #89013
This commit is contained in:
Michael Howell 2021-09-16 13:05:14 -07:00
parent 2b5ddf36fd
commit d8e9db0dcf
9 changed files with 197 additions and 1 deletions
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20
compiler/rustc_parse/src/parser/path.rs
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@ -495,11 +495,16 @@ impl<'a> Parser<'a> {
None => {
let after_eq = eq.shrink_to_hi();
let before_next = self.token.span.shrink_to_lo();
let the_type_placeholder = if matches!(self.token.kind, token::Comma | token::Gt) {
" TheType"
} else {
" TheType "
};
self.struct_span_err(after_eq.to(before_next), "missing type to the right of `=`")
.span_suggestion(
self.sess.source_map().next_point(eq).to(before_next),
"to constrain the associated type, add a type after `=`",
" TheType".to_string(),
the_type_placeholder.to_string(),
Applicability::HasPlaceholders,
)
.span_suggestion(
@ -572,6 +577,19 @@ impl<'a> Parser<'a> {
return self.recover_const_arg(start, err).map(Some);
}
}
} else if self.eat_keyword_noexpect(kw::Const) {
// Detect and recover from the old, pre-RFC2000 syntax for const generics.
let mut err = self.struct_span_err(
start,
"expected lifetime, type, or constant, found keyword `const`",
);
if self.check_const_arg() {
err.emit();
GenericArg::Const(self.parse_const_arg()?)
} else {
let after_kw_const = self.token.span;
return self.recover_const_arg(after_kw_const, err).map(Some);
}
} else {
return Ok(None);
};