Fixed nits from PR review #49392

src/librustc_mir/borrow_check/mod.rs

@@ -1306,7 +1306,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  }
  }
 
- fn check_if_path_is_moved(
+ fn check_if_full_path_is_moved(
  &mut self,
  context: Context,
  desired_action: InitializationRequiringAction,
@@ -1355,7 +1355,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  //
  // This code covers scenarios 1, 2, and 3.
 
- debug!("check_if_path_is_moved place: {:?}", place);
+ debug!("check_if_full_path_is_moved place: {:?}", place);
  match self.move_path_closest_to(place) {
  Ok(mpi) => {
  if maybe_uninits.contains(&mpi) {
@@ -1399,7 +1399,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  // 1. Move of `a.b.c`, use of `a` or `a.b`
  // partial initialization support, one might have `a.x`
  // initialized but not `a.b`.
- // 2. All bad scenarios from `check_if_path_is_moved`
+ // 2. All bad scenarios from `check_if_full_path_is_moved`
  //
  // OK scenarios:
  //
@@ -1409,7 +1409,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  // must have been initialized for the use to be sound.
  // 6. Move of `a.b.c` then reinit of `a.b.c.d`, use of `a.b.c.d`
 
- self.check_if_path_is_moved(context, desired_action, place_span, flow_state);
+ self.check_if_full_path_is_moved(context, desired_action, place_span, flow_state);
 
  // A move of any shallow suffix of `place` also interferes
  // with an attempt to use `place`. This is scenario 3 above.
@@ -1494,17 +1494,21 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  match *elem {
  ProjectionElem::Index(_/*operand*/) |
  ProjectionElem::ConstantIndex { .. } |
- // assigning to P[i] requires `P` initialized.
+ // assigning to P[i] requires P to be valid.
  ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) =>
  // assigning to (P->variant) is okay if assigning to `P` is okay
  //
  // FIXME: is this true even if P is a adt with a dtor?
  { }
 
+ // assigning to (*P) requires P to be initialized
  ProjectionElem::Deref => {
- self.check_if_path_is_moved(
+ self.check_if_full_path_is_moved(
  context, InitializationRequiringAction::Use,
  (base, span), flow_state);
+ // (base initialized; no need to
+ // recur further)
+ break;
  }
 
  ProjectionElem::Subslice { .. } => {