Determine unused mutable variables based on the 'root' place
This commit is contained in:
Keith Yeung
parent
e3b372f67d
commit
71d221f294
1 changed files with 111 additions and 86 deletions
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@ -241,7 +241,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
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access_place_error_reported: FxHashSet(),
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reservation_error_reported: FxHashSet(),
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moved_error_reported: FxHashSet(),
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nonlexical_regioncx: opt_regioncx,
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nonlexical_regioncx: regioncx,
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used_mut: FxHashSet(),
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used_mut_upvars: SmallVec::new(),
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nonlexical_cause_info: None,
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@ -276,7 +276,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
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tcx.struct_span_lint_node(
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UNUSED_MUT,
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vsi[source_info.scope].lint_root,
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vsi[local_decl.syntactic_scope].lint_root,
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source_info.span,
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"variable does not need to be mutable"
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)
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@ -1366,7 +1366,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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) {
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debug!("check_if_reassignment_to_immutable_state({:?})", place);
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// determine if this path has a non-mut owner (and thus needs checking).
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if let Ok(()) = self.is_mutable(place, LocalMutationIsAllowed::No) {
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if let Ok(_) = self.is_mutable(place, LocalMutationIsAllowed::No) {
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return;
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}
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debug!(
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@ -1679,27 +1679,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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}
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}
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Reservation(WriteKind::MutableBorrow(BorrowKind::Mut { .. }))
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| Write(WriteKind::MutableBorrow(BorrowKind::Mut { .. })) => if let Err(place_err) =
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self.is_mutable(place, is_local_mutation_allowed)
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{
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error_reported = true;
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let item_msg = self.get_default_err_msg(place);
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let mut err = self.tcx
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.cannot_borrow_path_as_mutable(span, &item_msg, Origin::Mir);
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err.span_label(span, "cannot borrow as mutable");
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if place != place_err {
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if let Some(name) = self.describe_place(place_err) {
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err.note(&format!("the value which is causing this path not to be mutable \
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is...: `{}`", name));
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}
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}
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err.emit();
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},
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Reservation(WriteKind::Mutate) | Write(WriteKind::Mutate) => {
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match place {
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Place::Local(local) => {
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| Write(WriteKind::MutableBorrow(BorrowKind::Mut { .. })) => {
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match self.is_mutable(place, is_local_mutation_allowed) {
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Ok(Place::Local(local))
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if is_local_mutation_allowed != LocalMutationIsAllowed::Yes =>
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{
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// If the local may be initialized, and it is now currently being
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// mutated, then it is justified to be annotated with the `mut` keyword,
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// since the mutation may be a possible reassignment.
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@ -1708,77 +1692,118 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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self.used_mut.insert(*local);
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}
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}
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Place::Projection(ref proj) => {
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Ok(Place::Projection(ref proj)) => {
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if let Some(field) = self.is_upvar_field_projection(&proj.base) {
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self.used_mut_upvars.push(field);
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}
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}
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Place::Static(..) => {}
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}
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if let Err(place_err) = self.is_mutable(place, is_local_mutation_allowed) {
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error_reported = true;
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let mut err_info = None;
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match *place_err {
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Ok(Place::Local(_)) |
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Ok(Place::Static(..)) => {}
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Err(place_err) => {
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error_reported = true;
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let item_msg = self.get_default_err_msg(place);
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let mut err = self.tcx
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.cannot_borrow_path_as_mutable(span, &item_msg, Origin::Mir);
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err.span_label(span, "cannot borrow as mutable");
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Place::Projection(box Projection {
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ref base, elem:ProjectionElem::Deref}) => {
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match *base {
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Place::Local(local) => {
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let locations = self.mir.find_assignments(local);
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if locations.len() > 0 {
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let item_msg = if error_reported {
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self.get_secondary_err_msg(base)
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} else {
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self.get_default_err_msg(place)
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};
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let sp = self.mir.source_info(locations[0]).span;
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let mut to_suggest_span = String::new();
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if let Ok(src) =
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self.tcx.sess.codemap().span_to_snippet(sp) {
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to_suggest_span = src[1..].to_string();
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};
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err_info = Some((
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sp,
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"consider changing this to be a \
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mutable reference",
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to_suggest_span,
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item_msg,
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self.get_primary_err_msg(base)));
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}
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},
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_ => {},
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}
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},
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_ => {},
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}
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if let Some((err_help_span,
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err_help_stmt,
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to_suggest_span,
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item_msg,
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sec_span)) = err_info {
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let mut err = self.tcx.cannot_assign(span, &item_msg, Origin::Mir);
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err.span_suggestion(err_help_span,
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err_help_stmt,
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format!("&mut {}", to_suggest_span));
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if place != place_err {
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err.span_label(span, sec_span);
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}
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err.emit()
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} else {
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let item_msg_ = self.get_default_err_msg(place);
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let mut err = self.tcx.cannot_assign(span, &item_msg_, Origin::Mir);
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err.span_label(span, "cannot mutate");
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if place != place_err {
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if let Some(name) = self.describe_place(place_err) {
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err.note(&format!("the value which is causing this path not to be \
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mutable is...: `{}`", name));
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mutable is...: `{}`", name));
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}
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}
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err.emit();
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}
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}
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}
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Reservation(WriteKind::Mutate) | Write(WriteKind::Mutate) => {
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match self.is_mutable(place, is_local_mutation_allowed) {
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Ok(Place::Local(local))
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if is_local_mutation_allowed != LocalMutationIsAllowed::Yes =>
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{
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// If the local may be initialized, and it is now currently being
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// mutated, then it is justified to be annotated with the `mut` keyword,
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// since the mutation may be a possible reassignment.
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let mpi = self.move_data.rev_lookup.find_local(*local);
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if flow_state.inits.contains(&mpi) {
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self.used_mut.insert(*local);
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}
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}
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Ok(Place::Projection(ref proj)) => {
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if let Some(field) = self.is_upvar_field_projection(&proj.base) {
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self.used_mut_upvars.push(field);
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}
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}
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Ok(Place::Local(_)) |
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Ok(Place::Static(..)) => {}
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Err(place_err) => {
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error_reported = true;
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let err_info = if let Place::Projection(
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box Projection {
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ref base,
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elem: ProjectionElem::Deref
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}
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) = *place_err {
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if let Place::Local(local) = *base {
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let locations = self.mir.find_assignments(local);
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if locations.len() > 0 {
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let item_msg = if error_reported {
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self.get_secondary_err_msg(base)
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} else {
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self.get_default_err_msg(place)
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};
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let sp = self.mir.source_info(locations[0]).span;
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let mut to_suggest_span = String::new();
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if let Ok(src) =
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self.tcx.sess.codemap().span_to_snippet(sp) {
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to_suggest_span = src[1..].to_string();
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};
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Some((sp,
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"consider changing this to be a \
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mutable reference",
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to_suggest_span,
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item_msg,
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self.get_primary_err_msg(base)))
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} else {
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None
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}
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} else {
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None
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}
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} else {
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None
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};
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if let Some((err_help_span,
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err_help_stmt,
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to_suggest_span,
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item_msg,
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sec_span)) = err_info {
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let mut err = self.tcx.cannot_assign(span, &item_msg, Origin::Mir);
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err.span_suggestion(err_help_span,
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err_help_stmt,
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format!("&mut {}", to_suggest_span));
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if place != place_err {
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err.span_label(span, sec_span);
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}
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err.emit()
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} else {
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let item_msg = self.get_default_err_msg(place);
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let mut err = self.tcx.cannot_assign(span, &item_msg, Origin::Mir);
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err.span_label(span, "cannot mutate");
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if place != place_err {
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if let Some(name) = self.describe_place(place_err) {
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err.note(&format!("the value which is causing this path not \
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to be mutable is...: `{}`", name));
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}
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}
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err.emit();
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}
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}
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}
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}
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Reservation(WriteKind::Move)
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| Reservation(WriteKind::StorageDeadOrDrop)
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| Reservation(WriteKind::MutableBorrow(BorrowKind::Shared))
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@ -1810,25 +1835,25 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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&self,
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place: &'d Place<'tcx>,
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is_local_mutation_allowed: LocalMutationIsAllowed,
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) -> Result<(), &'d Place<'tcx>> {
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) -> Result<&'d Place<'tcx>, &'d Place<'tcx>> {
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match *place {
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Place::Local(local) => {
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let local = &self.mir.local_decls[local];
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match local.mutability {
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Mutability::Not => match is_local_mutation_allowed {
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LocalMutationIsAllowed::Yes | LocalMutationIsAllowed::ExceptUpvars => {
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Ok(())
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Ok(place)
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}
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LocalMutationIsAllowed::No => Err(place),
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},
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Mutability::Mut => Ok(()),
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Mutability::Mut => Ok(place),
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}
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}
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Place::Static(ref static_) =>
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if self.tcx.is_static(static_.def_id) != Some(hir::Mutability::MutMutable) {
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Err(place)
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} else {
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Ok(())
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Ok(place)
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},
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Place::Projection(ref proj) => {
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match proj.elem {
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@ -1866,7 +1891,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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hir::MutImmutable => return Err(place),
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// `*mut` raw pointers are always mutable, regardless of context
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// The users have to check by themselve.
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hir::MutMutable => return Ok(()),
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hir::MutMutable => return Ok(place),
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}
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}
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// `Box<T>` owns its content, so mutable if its location is mutable
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