bjoernager/rust
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dropck_outlives check generator witness needs_drop

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This commit is contained in:
lcnr 2023-10-24 19:16:15 +02:00
parent f0df3d2dfb
commit 57253552de
8 changed files with 69 additions and 58 deletions
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32
compiler/rustc_ty_utils/src/needs_drop.rs
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@ -66,6 +66,9 @@ fn has_significant_drop_raw<'tcx>(
struct NeedsDropTypes<'tcx, F> {
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
// Whether to reveal coroutine witnesses, this is set
// to `false` unless we compute `needs_drop` for a generator witness.
reveal_coroutine_witnesses: bool,
query_ty: Ty<'tcx>,
seen_tys: FxHashSet<Ty<'tcx>>,
/// A stack of types left to process, and the recursion depth when we
@ -89,6 +92,7 @@ impl<'tcx, F> NeedsDropTypes<'tcx, F> {
Self {
tcx,
param_env,
reveal_coroutine_witnesses: false,
seen_tys,
query_ty: ty,
unchecked_tys: vec![(ty, 0)],
@ -133,8 +137,31 @@ where
// The information required to determine whether a coroutine has drop is
// computed on MIR, while this very method is used to build MIR.
// To avoid cycles, we consider that coroutines always require drop.
ty::Coroutine(..) => {
return Some(Err(AlwaysRequiresDrop));
//
// HACK: Because we erase regions contained in the generator witness, we
// have to conservatively assume that every region captured by the
// generator has to be live when dropped. This results in a lot of
// undesirable borrowck errors. During borrowck, we call `needs_drop`
// for the generator witness and check whether any of the contained types
// need to be dropped, and only require the captured types to be live
// if they do.
ty::Coroutine(_, args, _) => {
if self.reveal_coroutine_witnesses {
queue_type(self, args.as_coroutine().witness());
} else {
return Some(Err(AlwaysRequiresDrop));
}
}
ty::CoroutineWitness(def_id, args) => {
if let Some(witness) = tcx.mir_coroutine_witnesses(def_id) {
self.reveal_coroutine_witnesses = true;
for field_ty in &witness.field_tys {
queue_type(
self,
EarlyBinder::bind(field_ty.ty).instantiate(tcx, args),
);
}
}
}
_ if component.is_copy_modulo_regions(tcx, self.param_env) => (),
@ -191,7 +218,6 @@ where
| ty::FnPtr(..)
| ty::Tuple(_)
| ty::Bound(..)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Infer(_)
| ty::Error(_) => {