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Don't match any projection predicates when the obligation has inference types or consts in GAT substs

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This commit is contained in:
Jack Huey 2022-01-14 20:51:30 -05:00
parent c5e414843e
commit 3602e0e262
4 changed files with 64 additions and 2 deletions
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4
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
View file

@ -2470,8 +2470,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
let projection_ty = ty::ProjectionTy {
// `T`
substs: self.tcx.mk_substs_trait(
trait_pred.self_ty().skip_binder(),
self.fresh_substs_for_item(span, item_def_id),
trait_ref.self_ty().skip_binder(),
&self.fresh_substs_for_item(span, item_def_id)[1..],
),
// `Future::Output`
item_def_id,

10
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -1521,6 +1521,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
infer_predicate.projection_ty
};
// If the obligation contains any inference types or consts in associated
// type substs, then we don't match any projection candidates against it.
// This isn't really correct, but otherwise we can end up in a case where
// we constrain inference variables by selecting a single predicate, when
// we need to stay general. See issue #91762.
let (_, predicate_own_substs) =
obligation.predicate.trait_ref_and_own_substs(self.infcx.tcx);
if predicate_own_substs.iter().any(|g| g.has_infer_types_or_consts()) {
return false;
}
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(obligation.predicate, infer_projection)