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Rollup merge of #90417 - lcnr:stabilize-relaxed-struct-unsizing, r=wesleywiser

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stabilize `relaxed_struct_unsize`

closes #81793

the fcp is already complete.
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Matthias Krüger 2021-11-02 23:48:47 +01:00 • committed by GitHub
commit bc487f7dd2
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6 changed files with 16 additions and 70 deletions
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56
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@ -948,52 +948,24 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let tail_field_ty = tcx.type_of(tail_field.did);
let mut unsizing_params = GrowableBitSet::new_empty();
if tcx.features().relaxed_struct_unsize {
for arg in tail_field_ty.walk(tcx) {
for arg in tail_field_ty.walk(tcx) {
if let Some(i) = maybe_unsizing_param_idx(arg) {
unsizing_params.insert(i);
}
}
// Ensure none of the other fields mention the parameters used
// in unsizing.
for field in prefix_fields {
for arg in tcx.type_of(field.did).walk(tcx) {
if let Some(i) = maybe_unsizing_param_idx(arg) {
unsizing_params.insert(i);
unsizing_params.remove(i);
}
}
}
// Ensure none of the other fields mention the parameters used
// in unsizing.
for field in prefix_fields {
for arg in tcx.type_of(field.did).walk(tcx) {
if let Some(i) = maybe_unsizing_param_idx(arg) {
unsizing_params.remove(i);
}
}
}
if unsizing_params.is_empty() {
return Err(Unimplemented);
}
} else {
let mut found = false;
for arg in tail_field_ty.walk(tcx) {
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.
// FIXME(eddyb) cache this (including computing `unsizing_params`)
// by putting it in a query; it would only need the `DefId` as it
// looks at declared field types, not anything substituted.
for field in prefix_fields {
for arg in tcx.type_of(field.did).walk(tcx) {
if let Some(i) = maybe_unsizing_param_idx(arg) {
if unsizing_params.contains(i) {
return Err(Unimplemented);
}
}
}
}
if unsizing_params.is_empty() {
return Err(Unimplemented);
}
// Extract `TailField<T>` and `TailField<U>` from `Struct<T>` and `Struct<U>`.