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relax adt unsizing requirements

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This commit is contained in:
Bastian Kauschke 2021-01-05 16:33:10 +01:00
parent 120b2a704a
commit 50e394a05e
3 changed files with 28 additions and 8 deletions
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13
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@ -829,16 +829,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let tail_field_ty = tcx.type_of(tail_field.did);
let mut unsizing_params = GrowableBitSet::new_empty();
let mut found = false;
for arg in tail_field_ty.walk() {
if let Some(i) = maybe_unsizing_param_idx(arg) {
unsizing_params.insert(i);
found = true;
}
}
if !found {
return Err(Unimplemented);
}
// Ensure none of the other fields mention the parameters used
// in unsizing.
@ -848,13 +843,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
for field in prefix_fields {
for arg in tcx.type_of(field.did).walk() {
if let Some(i) = maybe_unsizing_param_idx(arg) {
if unsizing_params.contains(i) {
return Err(Unimplemented);
}
unsizing_params.remove(i);
}
}
}
if unsizing_params.is_empty() {
return Err(Unimplemented);
}
// Extract `TailField<T>` and `TailField<U>` from `Struct<T>` and `Struct<U>`.
let source_tail = tail_field_ty.subst(tcx, substs_a);
let target_tail = tail_field_ty.subst(tcx, substs_b);