bjoernager/rust
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Show note for type ascription interpreted as a constant pattern, not a new variable

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Given the code

```rust
pub fn main() {
    const y: i32 = 4;
    let y: i32 = 3;
}
```

`y` in the let binding is actually interpreted as a constant pattern
and is not a new variable, causing confusing diagnostics about
refutable patterns in local binding.

This commit extends the note for type ascription as a constant pattern
to `AscribeUserType` patterns as well.
This commit is contained in:
许杰友 Jieyou Xu (Joe) 2023-06-04 20:33:33 +08:00
parent 9eee230cd0
commit 55b4549602
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GPG key ID: C5FD5D32014FDB47
3 changed files with 46 additions and 1 deletions
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7
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -443,7 +443,12 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let mut let_suggestion = None;
let mut misc_suggestion = None;
let mut interpreted_as_const = None;
if let PatKind::Constant { .. } = pat.kind
if let PatKind::Constant { .. }
| PatKind::AscribeUserType {
subpattern: box Pat { kind: PatKind::Constant { .. }, .. },
..
} = pat.kind
&& let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(pat.span)
{
// If the pattern to match is an integer literal: