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If the moved value is a mut reference, it is used in a generic function and it's type is a generic param, it can be reborrowed to avoid moving.
for example: ```rust struct Y(u32); // x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`. fn generic<T>(x: T) {} ``` fixes #127285
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7d356ebde3
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4821b84b92
@ -205,9 +205,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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is_loop_move = true;
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}
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let mut has_suggest_reborrow = false;
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if !seen_spans.contains(&move_span) {
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if !closure {
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self.suggest_ref_or_clone(mpi, &mut err, &mut in_pattern, move_spans);
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self.suggest_ref_or_clone(
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mpi,
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&mut err,
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&mut in_pattern,
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move_spans,
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moved_place.as_ref(),
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&mut has_suggest_reborrow,
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);
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}
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let msg_opt = CapturedMessageOpt {
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@ -215,6 +223,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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is_loop_message,
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is_move_msg,
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is_loop_move,
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has_suggest_reborrow,
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maybe_reinitialized_locations_is_empty: maybe_reinitialized_locations
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.is_empty(),
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};
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@ -259,17 +268,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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if is_loop_move & !in_pattern && !matches!(use_spans, UseSpans::ClosureUse { .. }) {
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if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() {
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// We have a `&mut` ref, we need to reborrow on each iteration (#62112).
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err.span_suggestion_verbose(
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span.shrink_to_lo(),
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format!(
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"consider creating a fresh reborrow of {} here",
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self.describe_place(moved_place)
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.map(|n| format!("`{n}`"))
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.unwrap_or_else(|| "the mutable reference".to_string()),
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),
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"&mut *",
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Applicability::MachineApplicable,
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);
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self.suggest_reborrow(&mut err, span, moved_place);
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}
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}
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@ -346,6 +345,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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err: &mut Diag<'infcx>,
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in_pattern: &mut bool,
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move_spans: UseSpans<'tcx>,
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moved_place: PlaceRef<'tcx>,
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has_suggest_reborrow: &mut bool,
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) {
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let move_span = match move_spans {
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UseSpans::ClosureUse { capture_kind_span, .. } => capture_kind_span,
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@ -435,20 +436,44 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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let parent = self.infcx.tcx.parent_hir_node(expr.hir_id);
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let (def_id, args, offset) = if let hir::Node::Expr(parent_expr) = parent
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&& let hir::ExprKind::MethodCall(_, _, args, _) = parent_expr.kind
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&& let Some(def_id) = typeck.type_dependent_def_id(parent_expr.hir_id)
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{
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(def_id.as_local(), args, 1)
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(typeck.type_dependent_def_id(parent_expr.hir_id), args, 1)
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} else if let hir::Node::Expr(parent_expr) = parent
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&& let hir::ExprKind::Call(call, args) = parent_expr.kind
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&& let ty::FnDef(def_id, _) = typeck.node_type(call.hir_id).kind()
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{
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(def_id.as_local(), args, 0)
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(Some(*def_id), args, 0)
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} else {
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(None, &[][..], 0)
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};
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// If the moved value is a mut reference, it is used in a
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// generic function and it's type is a generic param, it can be
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// reborrowed to avoid moving.
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// for example:
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// struct Y(u32);
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// x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`.
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if let Some(def_id) = def_id
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&& self.infcx.tcx.def_kind(def_id).is_fn_like()
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&& let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
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&& let ty::Param(_) =
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self.infcx.tcx.fn_sig(def_id).skip_binder().skip_binder().inputs()
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[pos + offset]
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.kind()
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{
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let place = &self.move_data.move_paths[mpi].place;
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let ty = place.ty(self.body, self.infcx.tcx).ty;
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if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() {
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*has_suggest_reborrow = true;
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self.suggest_reborrow(err, expr.span, moved_place);
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return;
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}
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}
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let mut can_suggest_clone = true;
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if let Some(def_id) = def_id
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&& let node = self.infcx.tcx.hir_node_by_def_id(def_id)
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&& let Some(local_def_id) = def_id.as_local()
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&& let node = self.infcx.tcx.hir_node_by_def_id(local_def_id)
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&& let Some(fn_sig) = node.fn_sig()
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&& let Some(ident) = node.ident()
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&& let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
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@ -622,6 +647,25 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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}
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}
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pub fn suggest_reborrow(
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&self,
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err: &mut Diag<'infcx>,
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span: Span,
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moved_place: PlaceRef<'tcx>,
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) {
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err.span_suggestion_verbose(
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span.shrink_to_lo(),
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format!(
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"consider creating a fresh reborrow of {} here",
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self.describe_place(moved_place)
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.map(|n| format!("`{n}`"))
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.unwrap_or_else(|| "the mutable reference".to_string()),
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),
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"&mut *",
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Applicability::MachineApplicable,
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);
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}
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fn report_use_of_uninitialized(
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&self,
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mpi: MovePathIndex,
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@ -768,10 +768,11 @@ struct CapturedMessageOpt {
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is_loop_message: bool,
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is_move_msg: bool,
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is_loop_move: bool,
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has_suggest_reborrow: bool,
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maybe_reinitialized_locations_is_empty: bool,
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}
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impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
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impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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/// Finds the spans associated to a move or copy of move_place at location.
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pub(super) fn move_spans(
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&self,
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@ -997,7 +998,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
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#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
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fn explain_captures(
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&mut self,
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err: &mut Diag<'_>,
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err: &mut Diag<'infcx>,
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span: Span,
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move_span: Span,
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move_spans: UseSpans<'tcx>,
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@ -1009,6 +1010,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
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is_loop_message,
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is_move_msg,
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is_loop_move,
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has_suggest_reborrow,
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maybe_reinitialized_locations_is_empty,
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} = msg_opt;
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if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
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@ -1182,18 +1184,15 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
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if let ty::Ref(_, _, hir::Mutability::Mut) =
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moved_place.ty(self.body, self.infcx.tcx).ty.kind()
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{
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// If we are in a loop this will be suggested later.
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if !is_loop_move {
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err.span_suggestion_verbose(
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// Suggest `reborrow` in other place for following situations:
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// 1. If we are in a loop this will be suggested later.
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// 2. If the moved value is a mut reference, it is used in a
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// generic function and the corresponding arg's type is generic param.
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if !is_loop_move && !has_suggest_reborrow {
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self.suggest_reborrow(
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err,
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move_span.shrink_to_lo(),
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format!(
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"consider creating a fresh reborrow of {} here",
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self.describe_place(moved_place.as_ref())
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.map(|n| format!("`{n}`"))
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.unwrap_or_else(|| "the mutable reference".to_string()),
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),
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"&mut *",
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Applicability::MachineApplicable,
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moved_place.as_ref(),
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);
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}
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}
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@ -554,6 +554,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
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is_loop_message: false,
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is_move_msg: false,
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is_loop_move: false,
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has_suggest_reborrow: false,
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maybe_reinitialized_locations_is_empty: true,
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};
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if let Some(use_spans) = use_spans {
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@ -0,0 +1,17 @@
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//@ run-rustfix
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#![allow(dead_code)]
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struct X(u32);
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impl X {
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fn f(&mut self) {
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generic(&mut *self);
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self.0 += 1;
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//~^ ERROR: use of moved value: `self` [E0382]
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}
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}
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fn generic<T>(_x: T) {}
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fn main() {}
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@ -0,0 +1,17 @@
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//@ run-rustfix
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#![allow(dead_code)]
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struct X(u32);
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impl X {
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fn f(&mut self) {
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generic(self);
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self.0 += 1;
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//~^ ERROR: use of moved value: `self` [E0382]
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}
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}
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fn generic<T>(_x: T) {}
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fn main() {}
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@ -0,0 +1,18 @@
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error[E0382]: use of moved value: `self`
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--> $DIR/moved-value-suggest-reborrow-issue-127285.rs:10:9
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LL | fn f(&mut self) {
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| --------- move occurs because `self` has type `&mut X`, which does not implement the `Copy` trait
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LL | generic(self);
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| ---- value moved here
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LL | self.0 += 1;
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| ^^^^^^^^^^^ value used here after move
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help: consider creating a fresh reborrow of `self` here
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LL | generic(&mut *self);
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| ++++++
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error: aborting due to 1 previous error
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For more information about this error, try `rustc --explain E0382`.
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@ -8,19 +8,10 @@ LL | for _ in 0..3 {
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LL | Other::handle(value);
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| ^^^^^ value moved here, in previous iteration of loop
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note: consider changing this parameter type in function `handle` to borrow instead if owning the value isn't necessary
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--> $DIR/mut-borrow-in-loop-2.rs:8:22
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LL | fn handle(value: T) -> Self;
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| ------ ^ this parameter takes ownership of the value
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| |
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| in this function
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help: consider moving the expression out of the loop so it is only moved once
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LL ~ let mut value = Other::handle(value);
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LL ~ for _ in 0..3 {
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LL ~ value;
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help: consider creating a fresh reborrow of `value` here
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LL | Other::handle(&mut *value);
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| ++++++
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help: consider creating a fresh reborrow of `value` here
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LL | Other::handle(&mut *value);
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