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Rollup merge of #132708 - estebank:const-as-binding, r=Nadrieril

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Point at `const` definition when used instead of a binding in a `let` statement

Modify `PatKind::InlineConstant` to be `ExpandedConstant` standing in not only for inline `const` blocks but also for `const` items. This allows us to track named `const`s used in patterns when the pattern is a single binding. When we detect that there is a refutable pattern involving a `const` that could have been a binding instead, we point at the `const` item, and suggest renaming. We do this for both `let` bindings and `match` expressions missing a catch-all arm if there's at least one single binding pattern referenced.

After:

```
error[E0005]: refutable pattern in local binding
  --> $DIR/bad-pattern.rs:19:13
   |
LL |     const PAT: u32 = 0;
   |     -------------- missing patterns are not covered because `PAT` is interpreted as a constant pattern, not a new variable
...
LL |         let PAT = v1;
   |             ^^^ pattern `1_u32..=u32::MAX` not covered
   |
   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
   = note: the matched value is of type `u32`
help: introduce a variable instead
   |
LL |         let PAT_var = v1;
   |             ~~~~~~~
```

Before:

```
error[E0005]: refutable pattern in local binding
  --> $DIR/bad-pattern.rs:19:13
   |
LL |         let PAT = v1;
   |             ^^^
   |             |
   |             pattern `1_u32..=u32::MAX` not covered
   |             missing patterns are not covered because `PAT` is interpreted as a constant pattern, not a new variable
   |             help: introduce a variable instead: `PAT_var`
   |
   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
   = note: the matched value is of type `u32`
```

CC #132582.
This commit is contained in:
Matthias Krüger 2024-11-20 20:10:12 +01:00 • committed by GitHub
commit 7fc2b33722
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22 changed files with 365 additions and 94 deletions
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2
compiler/rustc_pattern_analysis/src/rustc.rs
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@ -465,7 +465,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
let fields: Vec<_>;
match &pat.kind {
PatKind::AscribeUserType { subpattern, .. }
| PatKind::InlineConstant { subpattern, .. } => return self.lower_pat(subpattern),
| PatKind::ExpandedConstant { subpattern, .. } => return self.lower_pat(subpattern),
PatKind::Binding { subpattern: Some(subpat), .. } => return self.lower_pat(subpat),
PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
ctor = Wildcard;