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Rollup merge of #112019 - jieyouxu:issue-111554, r=compiler-errors

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Don't suggest changing `&self` and `&mut self` in function signature to be mutable when taking `&mut self` in closure

Current suggestion for when taking a mutable reference to `self` in a closure (as an upvar) will produce a machine-applicable suggestion to change the `self` in the function signature to `mut self`, but does not account for the specialness of implicit self in that it can already have `&` and `&mut` (see #111554). This causes the function signature to become `test(&mut mut self)` which does not seem desirable.

```
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
   --> src/sound_player.rs:870:11
    |
869 |     pub fn test(&mut self) {
    |                      ---- help: consider changing this to be mutable: `mut self`
870 |     || test2(&mut self);
    |              ^^^^^^^^^ cannot borrow as mutable
```

This PR suppresses the "changing this to be mutable" suggestion if the implicit self is either `ImplicitSelfKind::ImmRef` or `ImplicitSelfKind::MutRef`.

Fixes #111554.
This commit is contained in:
Matthias Krüger 2023-06-06 12:00:33 +02:00 • committed by GitHub
commit 21e7463bf8
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3 changed files with 79 additions and 6 deletions
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28
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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@ -416,12 +416,28 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
_,
) = pat.kind
{
err.span_suggestion(
upvar_ident.span,
"consider changing this to be mutable",
format!("mut {}", upvar_ident.name),
Applicability::MachineApplicable,
);
if upvar_ident.name == kw::SelfLower {
for (_, node) in self.infcx.tcx.hir().parent_iter(upvar_hir_id) {
if let Some(fn_decl) = node.fn_decl() {
if !matches!(fn_decl.implicit_self, hir::ImplicitSelfKind::ImmRef | hir::ImplicitSelfKind::MutRef) {
err.span_suggestion(
upvar_ident.span,
"consider changing this to be mutable",
format!("mut {}", upvar_ident.name),
Applicability::MachineApplicable,
);
break;
}
}
}
} else {
err.span_suggestion(
upvar_ident.span,
"consider changing this to be mutable",
format!("mut {}", upvar_ident.name),
Applicability::MachineApplicable,
);
}
}
let tcx = self.infcx.tcx;