| use crate::util::elaborate_drops::DropFlagState; |
| use rustc_middle::mir::{self, Body, Location}; |
| use rustc_middle::ty::{self, TyCtxt}; |
| use rustc_target::abi::VariantIdx; |
| |
| use super::indexes::MovePathIndex; |
| use super::move_paths::{InitKind, LookupResult, MoveData}; |
| use super::MoveDataParamEnv; |
| |
| pub fn move_path_children_matching<'tcx, F>( |
| move_data: &MoveData<'tcx>, |
| path: MovePathIndex, |
| mut cond: F, |
| ) -> Option<MovePathIndex> |
| where |
| F: FnMut(mir::PlaceElem<'tcx>) -> bool, |
| { |
| let mut next_child = move_data.move_paths[path].first_child; |
| while let Some(child_index) = next_child { |
| let move_path_children = &move_data.move_paths[child_index]; |
| if let Some(&elem) = move_path_children.place.projection.last() { |
| if cond(elem) { |
| return Some(child_index); |
| } |
| } |
| next_child = move_path_children.next_sibling; |
| } |
| |
| None |
| } |
| |
| /// When enumerating the child fragments of a path, don't recurse into |
| /// paths (1.) past arrays, slices, and pointers, nor (2.) into a type |
| /// that implements `Drop`. |
| /// |
| /// Places behind references or arrays are not tracked by elaboration |
| /// and are always assumed to be initialized when accessible. As |
| /// references and indexes can be reseated, trying to track them can |
| /// only lead to trouble. |
| /// |
| /// Places behind ADT's with a Drop impl are not tracked by |
| /// elaboration since they can never have a drop-flag state that |
| /// differs from that of the parent with the Drop impl. |
| /// |
| /// In both cases, the contents can only be accessed if and only if |
| /// their parents are initialized. This implies for example that there |
| /// is no need to maintain separate drop flags to track such state. |
| // |
| // FIXME: we have to do something for moving slice patterns. |
| fn place_contents_drop_state_cannot_differ<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| place: mir::Place<'tcx>, |
| ) -> bool { |
| let ty = place.ty(body, tcx).ty; |
| match ty.kind { |
| ty::Array(..) => { |
| debug!( |
| "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} => false", |
| place, ty |
| ); |
| false |
| } |
| ty::Slice(..) | ty::Ref(..) | ty::RawPtr(..) => { |
| debug!( |
| "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} refd => true", |
| place, ty |
| ); |
| true |
| } |
| ty::Adt(def, _) if (def.has_dtor(tcx) && !def.is_box()) || def.is_union() => { |
| debug!( |
| "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} Drop => true", |
| place, ty |
| ); |
| true |
| } |
| _ => false, |
| } |
| } |
| |
| pub(crate) fn on_lookup_result_bits<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| lookup_result: LookupResult, |
| each_child: F, |
| ) where |
| F: FnMut(MovePathIndex), |
| { |
| match lookup_result { |
| LookupResult::Parent(..) => { |
| // access to untracked value - do not touch children |
| } |
| LookupResult::Exact(e) => on_all_children_bits(tcx, body, move_data, e, each_child), |
| } |
| } |
| |
| pub(crate) fn on_all_children_bits<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| move_path_index: MovePathIndex, |
| mut each_child: F, |
| ) where |
| F: FnMut(MovePathIndex), |
| { |
| fn is_terminal_path<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| path: MovePathIndex, |
| ) -> bool { |
| place_contents_drop_state_cannot_differ(tcx, body, move_data.move_paths[path].place) |
| } |
| |
| fn on_all_children_bits<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| move_path_index: MovePathIndex, |
| each_child: &mut F, |
| ) where |
| F: FnMut(MovePathIndex), |
| { |
| each_child(move_path_index); |
| |
| if is_terminal_path(tcx, body, move_data, move_path_index) { |
| return; |
| } |
| |
| let mut next_child_index = move_data.move_paths[move_path_index].first_child; |
| while let Some(child_index) = next_child_index { |
| on_all_children_bits(tcx, body, move_data, child_index, each_child); |
| next_child_index = move_data.move_paths[child_index].next_sibling; |
| } |
| } |
| on_all_children_bits(tcx, body, move_data, move_path_index, &mut each_child); |
| } |
| |
| pub(crate) fn on_all_drop_children_bits<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| ctxt: &MoveDataParamEnv<'tcx>, |
| path: MovePathIndex, |
| mut each_child: F, |
| ) where |
| F: FnMut(MovePathIndex), |
| { |
| on_all_children_bits(tcx, body, &ctxt.move_data, path, |child| { |
| let place = &ctxt.move_data.move_paths[path].place; |
| let ty = place.ty(body, tcx).ty; |
| debug!("on_all_drop_children_bits({:?}, {:?} : {:?})", path, place, ty); |
| |
| let erased_ty = tcx.erase_regions(&ty); |
| if erased_ty.needs_drop(tcx, ctxt.param_env) { |
| each_child(child); |
| } else { |
| debug!("on_all_drop_children_bits - skipping") |
| } |
| }) |
| } |
| |
| pub(crate) fn drop_flag_effects_for_function_entry<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| ctxt: &MoveDataParamEnv<'tcx>, |
| mut callback: F, |
| ) where |
| F: FnMut(MovePathIndex, DropFlagState), |
| { |
| let move_data = &ctxt.move_data; |
| for arg in body.args_iter() { |
| let place = mir::Place::from(arg); |
| let lookup_result = move_data.rev_lookup.find(place.as_ref()); |
| on_lookup_result_bits(tcx, body, move_data, lookup_result, |mpi| { |
| callback(mpi, DropFlagState::Present) |
| }); |
| } |
| } |
| |
| pub(crate) fn drop_flag_effects_for_location<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| ctxt: &MoveDataParamEnv<'tcx>, |
| loc: Location, |
| mut callback: F, |
| ) where |
| F: FnMut(MovePathIndex, DropFlagState), |
| { |
| let move_data = &ctxt.move_data; |
| debug!("drop_flag_effects_for_location({:?})", loc); |
| |
| // first, move out of the RHS |
| for mi in &move_data.loc_map[loc] { |
| let path = mi.move_path_index(move_data); |
| debug!("moving out of path {:?}", move_data.move_paths[path]); |
| |
| on_all_children_bits(tcx, body, move_data, path, |mpi| callback(mpi, DropFlagState::Absent)) |
| } |
| |
| debug!("drop_flag_effects: assignment for location({:?})", loc); |
| |
| for_location_inits(tcx, body, move_data, loc, |mpi| callback(mpi, DropFlagState::Present)); |
| } |
| |
| pub(crate) fn for_location_inits<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| body: &Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| loc: Location, |
| mut callback: F, |
| ) where |
| F: FnMut(MovePathIndex), |
| { |
| for ii in &move_data.init_loc_map[loc] { |
| let init = move_data.inits[*ii]; |
| match init.kind { |
| InitKind::Deep => { |
| let path = init.path; |
| |
| on_all_children_bits(tcx, body, move_data, path, &mut callback) |
| } |
| InitKind::Shallow => { |
| let mpi = init.path; |
| callback(mpi); |
| } |
| InitKind::NonPanicPathOnly => (), |
| } |
| } |
| } |
| |
| /// Calls `handle_inactive_variant` for each descendant move path of `enum_place` that contains a |
| /// `Downcast` to a variant besides the `active_variant`. |
| /// |
| /// NOTE: If there are no move paths corresponding to an inactive variant, |
| /// `handle_inactive_variant` will not be called for that variant. |
| pub(crate) fn on_all_inactive_variants<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| body: &mir::Body<'tcx>, |
| move_data: &MoveData<'tcx>, |
| enum_place: mir::Place<'tcx>, |
| active_variant: VariantIdx, |
| mut handle_inactive_variant: impl FnMut(MovePathIndex), |
| ) { |
| let enum_mpi = match move_data.rev_lookup.find(enum_place.as_ref()) { |
| LookupResult::Exact(mpi) => mpi, |
| LookupResult::Parent(_) => return, |
| }; |
| |
| let enum_path = &move_data.move_paths[enum_mpi]; |
| for (variant_mpi, variant_path) in enum_path.children(&move_data.move_paths) { |
| // Because of the way we build the `MoveData` tree, each child should have exactly one more |
| // projection than `enum_place`. This additional projection must be a downcast since the |
| // base is an enum. |
| let (downcast, base_proj) = variant_path.place.projection.split_last().unwrap(); |
| assert_eq!(enum_place.projection.len(), base_proj.len()); |
| |
| let variant_idx = match *downcast { |
| mir::ProjectionElem::Downcast(_, idx) => idx, |
| _ => unreachable!(), |
| }; |
| |
| if variant_idx != active_variant { |
| on_all_children_bits(tcx, body, move_data, variant_mpi, |mpi| { |
| handle_inactive_variant(mpi) |
| }); |
| } |
| } |
| } |