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For a rigid projection, recursively look at the self type's item bounds

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This commit is contained in:
Michael Goulet
2024-02-01 23:48:04 +00:00
parent 98aa3624be
commit 22d582a38d
23 changed files with 273 additions and 431 deletions
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29
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@@ -162,20 +162,26 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.infcx.enter_forall_and_leak_universe(trait_predicate).trait_ref;
let placeholder_self_ty = placeholder_trait_predicate.self_ty();
let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
let (def_id, args) = match *placeholder_self_ty.kind() {
// Excluding IATs and type aliases here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
(def_id, args)
}
_ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
};
let candidate_predicate =
tcx.item_bounds(def_id).map_bound(|i| i[idx]).instantiate(tcx, args);
let candidate_predicate = self
.for_each_item_bound(
placeholder_self_ty,
|_, clause, clause_idx| {
if clause_idx == idx {
ControlFlow::Break(clause)
} else {
ControlFlow::Continue(())
}
},
|| unreachable!(),
)
.break_value()
.expect("expected to index into clause that exists");
let candidate = candidate_predicate
.as_trait_clause()
.expect("projection candidate is not a trait predicate")
.map_bound(|t| t.trait_ref);
let mut obligations = Vec::new();
let candidate = normalize_with_depth_to(
self,
@@ -194,8 +200,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.map_err(|_| Unimplemented)
})?);
if let ty::Alias(ty::Projection, ..) = placeholder_self_ty.kind() {
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, args);
// FIXME(compiler-errors): I don't think this is needed.
if let ty::Alias(ty::Projection, alias_ty) = placeholder_self_ty.kind() {
let predicates = tcx.predicates_of(alias_ty.def_id).instantiate_own(tcx, alias_ty.args);
for (predicate, _) in predicates {
let normalized = normalize_with_depth_to(
self,