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Merge multiple mutable borrows of immutable binding errors

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Fix #53466.
This commit is contained in:
Esteban Küber
2022-12-29 22:46:17 -08:00
parent bb6e76df06
commit 5bfcfeee2a
14 changed files with 199 additions and 93 deletions
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90
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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@@ -180,6 +180,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
// the verbs used in some diagnostic messages.
let act;
let acted_on;
let mut suggest = true;
let mut mut_error = None;
let mut count = 1;
let span = match error_access {
AccessKind::Mutate => {
@@ -194,15 +197,50 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let borrow_spans = self.borrow_spans(span, location);
let borrow_span = borrow_spans.args_or_use();
err = self.cannot_borrow_path_as_mutable_because(borrow_span, &item_msg, &reason);
borrow_spans.var_span_label(
&mut err,
format!(
"mutable borrow occurs due to use of {} in closure",
self.describe_any_place(access_place.as_ref()),
),
"mutable",
);
match the_place_err {
PlaceRef { local, projection: [] }
if self.body.local_decls[local].can_be_made_mutable() =>
{
let span = self.body.local_decls[local].source_info.span;
mut_error = Some(span);
if let Some((buffer, c)) = self.get_buffered_mut_error(span) {
// We've encountered a second (or more) attempt to mutably borrow an
// immutable binding, so the likely problem is with the binding
// declaration, not the use. We collect these in a single diagnostic
// and make the binding the primary span of the error.
err = buffer;
count = c + 1;
if count == 2 {
err.replace_span_with(span, false);
err.span_label(span, "not mutable");
}
suggest = false;
} else {
err = self.cannot_borrow_path_as_mutable_because(
borrow_span,
&item_msg,
&reason,
);
}
}
_ => {
err = self.cannot_borrow_path_as_mutable_because(
borrow_span,
&item_msg,
&reason,
);
}
}
if suggest {
borrow_spans.var_span_label(
&mut err,
format!(
"mutable borrow occurs due to use of {} in closure",
self.describe_any_place(access_place.as_ref()),
),
"mutable",
);
}
borrow_span
}
};
@@ -276,7 +314,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
pat_span: _,
},
)))) => {
err.span_note(sp, "the binding is already a mutable borrow");
if suggest {
err.span_note(sp, "the binding is already a mutable borrow");
}
}
_ => {
err.span_note(
@@ -333,16 +373,20 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let local_decl = &self.body.local_decls[local];
assert_eq!(local_decl.mutability, Mutability::Not);
err.span_label(span, format!("cannot {act}"));
err.span_suggestion(
local_decl.source_info.span,
"consider changing this to be mutable",
format!("mut {}", self.local_names[local].unwrap()),
Applicability::MachineApplicable,
);
let tcx = self.infcx.tcx;
if let ty::Closure(id, _) = *the_place_err.ty(self.body, tcx).ty.kind() {
self.show_mutating_upvar(tcx, id.expect_local(), the_place_err, &mut err);
if count < 10 {
err.span_label(span, format!("cannot {act}"));
}
if suggest {
err.span_suggestion(
local_decl.source_info.span,
"consider changing this to be mutable",
format!("mut {}", self.local_names[local].unwrap()),
Applicability::MachineApplicable,
);
let tcx = self.infcx.tcx;
if let ty::Closure(id, _) = *the_place_err.ty(self.body, tcx).ty.kind() {
self.show_mutating_upvar(tcx, id.expect_local(), the_place_err, &mut err);
}
}
}
@@ -615,7 +659,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
}
}
self.buffer_error(err);
if let Some(span) = mut_error {
self.buffer_mut_error(span, err, count);
} else {
self.buffer_error(err);
}
}
fn suggest_map_index_mut_alternatives(&self, ty: Ty<'tcx>, err: &mut Diagnostic, span: Span) {