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Rollup merge of #106410 - clubby789:borrow-mut-self-mut-self-diag, r=compiler-errors

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Suggest `mut self: &mut Self` for `?Sized` impls

Closes #106325
Closes #93078

The suggestion is _probably_ not what the user wants (hence `MaybeIncorrect`) but at least makes the problem in the above issues clearer. It might be better to add a note explaining why this is the case, but I'm not sure how best to word that so this is a start.

``@rustbot`` label +A-diagnostics
This commit is contained in:
Yuki Okushi 2023-01-08 17:01:46 +09:00 • committed by GitHub
commit fe075319e6
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3 changed files with 43 additions and 11 deletions
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27
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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@ -344,20 +344,25 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
} else {
err.span_help(source_info.span, "try removing `&mut` here");
}
} else if decl.mutability == Mutability::Not
&& !matches!(
} else if decl.mutability == Mutability::Not {
if matches!(
decl.local_info,
Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::ImplicitSelf(
hir::ImplicitSelfKind::MutRef
))))
)
{
err.span_suggestion_verbose(
decl.source_info.span.shrink_to_lo(),
"consider making the binding mutable",
"mut ",
Applicability::MachineApplicable,
);
),)))
) {
err.note(
"as `Self` may be unsized, this call attempts to take `&mut &mut self`",
);
err.note("however, `&mut self` expands to `self: &mut Self`, therefore `self` cannot be borrowed mutably");
} else {
err.span_suggestion_verbose(
decl.source_info.span.shrink_to_lo(),
"consider making the binding mutable",
"mut ",
Applicability::MachineApplicable,
);
};
}
}