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Auto merge of #71846 - petrochenkov:fresh2, r=davidtwco

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resolve: Relax fresh binding disambiguation slightly to fix regression

Fixes https://github.com/rust-lang/rust/issues/71765
This commit is contained in:
bors 2020-05-05 06:01:08 +00:00
commit de27cd7649
2 changed files with 11 additions and 6 deletions
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16
src/librustc_resolve/late.rs
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@ -1522,11 +1522,20 @@ impl<'a, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
ident: Ident,
has_sub: bool,
) -> Option<Res> {
// An immutable (no `mut`) by-value (no `ref`) binding pattern without
// a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
// also be interpreted as a path to e.g. a constant, variant, etc.
let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Not);
let ls_binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?;
let (res, binding) = match ls_binding {
LexicalScopeBinding::Item(binding) if binding.is_ambiguity() => {
LexicalScopeBinding::Item(binding)
if is_syntactic_ambiguity && binding.is_ambiguity() =>
{
// For ambiguous bindings we don't know all their definitions and cannot check
// whether they can be shadowed by fresh bindings or not, so force an error.
// issues/33118#issuecomment-233962221 (see below) still applies here,
// but we have to ignore it for backward compatibility.
self.r.record_use(ident, ValueNS, binding, false);
return None;
}
@ -1534,11 +1543,6 @@ impl<'a, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
LexicalScopeBinding::Res(res) => (res, None),
};
// An immutable (no `mut`) by-value (no `ref`) binding pattern without
// a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
// also be interpreted as a path to e.g. a constant, variant, etc.
let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Not);
match res {
Res::SelfCtor(_) // See #70549.
| Res::Def(

1
src/test/ui/binding/ambiguity-item.rs
View File

@ -14,5 +14,6 @@ fn main() {
let v = f; //~ ERROR `f` is ambiguous
match v {
f => {} //~ ERROR `f` is ambiguous
mut f => {} // OK, unambiguously a fresh binding due to `mut`
}
}