1 use crate::elaborate_drops::DropFlagState;
2 use rustc_middle::mir::{self, Body, Location};
3 use rustc_middle::ty::{self, TyCtxt};
4 use rustc_target::abi::VariantIdx;
6 use super::indexes::MovePathIndex;
7 use super::move_paths::{InitKind, LookupResult, MoveData};
8 use super::MoveDataParamEnv;
10 pub fn move_path_children_matching<'tcx, F>(
11 move_data: &MoveData<'tcx>,
14 ) -> Option<MovePathIndex>
16 F: FnMut(mir::PlaceElem<'tcx>) -> bool,
18 let mut next_child = move_data.move_paths[path].first_child;
19 while let Some(child_index) = next_child {
20 let move_path_children = &move_data.move_paths[child_index];
21 if let Some(&elem) = move_path_children.place.projection.last() {
23 return Some(child_index);
26 next_child = move_path_children.next_sibling;
32 pub fn on_lookup_result_bits<'tcx, F>(
35 move_data: &MoveData<'tcx>,
36 lookup_result: LookupResult,
39 F: FnMut(MovePathIndex),
42 LookupResult::Parent(..) => {
43 // access to untracked value - do not touch children
45 LookupResult::Exact(e) => on_all_children_bits(tcx, body, move_data, e, each_child),
49 pub fn on_all_children_bits<'tcx, F>(
52 move_data: &MoveData<'tcx>,
53 move_path_index: MovePathIndex,
56 F: FnMut(MovePathIndex),
59 fn is_terminal_path<'tcx>(
62 move_data: &MoveData<'tcx>,
65 let place = move_data.move_paths[path].place;
67 // When enumerating the child fragments of a path, don't recurse into
68 // paths (1.) past arrays, slices, and pointers, nor (2.) into a type
69 // that implements `Drop`.
71 // Places behind references or arrays are not tracked by elaboration
72 // and are always assumed to be initialized when accessible. As
73 // references and indexes can be reseated, trying to track them can
74 // only lead to trouble.
76 // Places behind ADT's with a Drop impl are not tracked by
77 // elaboration since they can never have a drop-flag state that
78 // differs from that of the parent with the Drop impl.
80 // In both cases, the contents can only be accessed if and only if
81 // their parents are initialized. This implies for example that there
82 // is no need to maintain separate drop flags to track such state.
84 // FIXME: we have to do something for moving slice patterns.
85 let ty = place.ty(body, tcx).ty;
87 ty::Adt(def, _) if (def.has_dtor(tcx) && !def.is_box()) || def.is_union() => {
89 "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} Drop => true",
96 "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} => false",
101 ty::Slice(..) | ty::Ref(..) | ty::RawPtr(..) => {
103 "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} refd => true",
112 fn on_all_children_bits<'tcx, F>(
115 move_data: &MoveData<'tcx>,
116 move_path_index: MovePathIndex,
119 F: FnMut(MovePathIndex),
121 each_child(move_path_index);
123 if is_terminal_path(tcx, body, move_data, move_path_index) {
127 let mut next_child_index = move_data.move_paths[move_path_index].first_child;
128 while let Some(child_index) = next_child_index {
129 on_all_children_bits(tcx, body, move_data, child_index, each_child);
130 next_child_index = move_data.move_paths[child_index].next_sibling;
133 on_all_children_bits(tcx, body, move_data, move_path_index, &mut each_child);
136 pub fn on_all_drop_children_bits<'tcx, F>(
139 ctxt: &MoveDataParamEnv<'tcx>,
143 F: FnMut(MovePathIndex),
145 on_all_children_bits(tcx, body, &ctxt.move_data, path, |child| {
146 let place = &ctxt.move_data.move_paths[path].place;
147 let ty = place.ty(body, tcx).ty;
148 debug!("on_all_drop_children_bits({:?}, {:?} : {:?})", path, place, ty);
150 let erased_ty = tcx.erase_regions(ty);
151 if erased_ty.needs_drop(tcx, ctxt.param_env) {
154 debug!("on_all_drop_children_bits - skipping")
159 pub fn drop_flag_effects_for_function_entry<'tcx, F>(
162 ctxt: &MoveDataParamEnv<'tcx>,
165 F: FnMut(MovePathIndex, DropFlagState),
167 let move_data = &ctxt.move_data;
168 for arg in body.args_iter() {
169 let place = mir::Place::from(arg);
170 let lookup_result = move_data.rev_lookup.find(place.as_ref());
171 on_lookup_result_bits(tcx, body, move_data, lookup_result, |mpi| {
172 callback(mpi, DropFlagState::Present)
177 pub fn drop_flag_effects_for_location<'tcx, F>(
180 ctxt: &MoveDataParamEnv<'tcx>,
184 F: FnMut(MovePathIndex, DropFlagState),
186 let move_data = &ctxt.move_data;
187 debug!("drop_flag_effects_for_location({:?})", loc);
189 // first, move out of the RHS
190 for mi in &move_data.loc_map[loc] {
191 let path = mi.move_path_index(move_data);
192 debug!("moving out of path {:?}", move_data.move_paths[path]);
194 on_all_children_bits(tcx, body, move_data, path, |mpi| callback(mpi, DropFlagState::Absent))
197 debug!("drop_flag_effects: assignment for location({:?})", loc);
199 for_location_inits(tcx, body, move_data, loc, |mpi| callback(mpi, DropFlagState::Present));
202 pub fn for_location_inits<'tcx, F>(
205 move_data: &MoveData<'tcx>,
209 F: FnMut(MovePathIndex),
211 for ii in &move_data.init_loc_map[loc] {
212 let init = move_data.inits[*ii];
215 let path = init.path;
217 on_all_children_bits(tcx, body, move_data, path, &mut callback)
219 InitKind::Shallow => {
223 InitKind::NonPanicPathOnly => (),
228 /// Calls `handle_inactive_variant` for each descendant move path of `enum_place` that contains a
229 /// `Downcast` to a variant besides the `active_variant`.
231 /// NOTE: If there are no move paths corresponding to an inactive variant,
232 /// `handle_inactive_variant` will not be called for that variant.
233 pub(crate) fn on_all_inactive_variants<'tcx>(
235 body: &mir::Body<'tcx>,
236 move_data: &MoveData<'tcx>,
237 enum_place: mir::Place<'tcx>,
238 active_variant: VariantIdx,
239 mut handle_inactive_variant: impl FnMut(MovePathIndex),
241 let LookupResult::Exact(enum_mpi) = move_data.rev_lookup.find(enum_place.as_ref()) else {
245 let enum_path = &move_data.move_paths[enum_mpi];
246 for (variant_mpi, variant_path) in enum_path.children(&move_data.move_paths) {
247 // Because of the way we build the `MoveData` tree, each child should have exactly one more
248 // projection than `enum_place`. This additional projection must be a downcast since the
250 let (downcast, base_proj) = variant_path.place.projection.split_last().unwrap();
251 assert_eq!(enum_place.projection.len(), base_proj.len());
253 let mir::ProjectionElem::Downcast(_, variant_idx) = *downcast else {
257 if variant_idx != active_variant {
258 on_all_children_bits(tcx, body, move_data, variant_mpi, |mpi| {
259 handle_inactive_variant(mpi)