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Rollup merge of #83945 - SkiFire13:fix-83924, r=estebank

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Add suggestion to reborrow mutable references when they're moved in a for loop

Address #83924
This commit is contained in:
Dylan DPC 2021-04-07 13:07:17 +02:00 • committed by GitHub
commit d7d42ccfd2
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4 changed files with 83 additions and 1 deletions
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19
compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs
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@ -264,7 +264,24 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
if let Some(DesugaringKind::ForLoop(_)) = move_span.desugaring_kind() {
let sess = self.infcx.tcx.sess;
if let Ok(snippet) = sess.source_map().span_to_snippet(move_span) {
let ty = used_place.ty(self.body, self.infcx.tcx).ty;
// If we have a `&mut` ref, we need to reborrow.
if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() {
// If we are in a loop this will be suggested later.
if !is_loop_move {
err.span_suggestion_verbose(
move_span.shrink_to_lo(),
&format!(
"consider creating a fresh reborrow of {} here",
self.describe_place(moved_place.as_ref())
.map(|n| format!("`{}`", n))
.unwrap_or_else(|| "the mutable reference".to_string()),
),
format!("&mut *"),
Applicability::MachineApplicable,
);
}
} else if let Ok(snippet) = sess.source_map().span_to_snippet(move_span) {
err.span_suggestion(
move_span,
"consider borrowing to avoid moving into the for loop",