Exclude inherent projections from some alias ty matches

4 files changed, 13 insertions, 4 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 8e684b7ac23..79ecbabb5f7 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1543,7 +1543,10 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
     // Check whether the self-type is itself a projection.
     // If so, extract what we know from the trait and try to come up with a good answer.
     let bounds = match *obligation.predicate.self_ty().kind() {
-        ty::Alias(_, ref data) => tcx.item_bounds(data.def_id).subst(tcx, data.substs),
+        // Excluding IATs here as they don't have meaningful item bounds.
+        ty::Alias(ty::Projection | ty::Opaque, ref data) => {
+            tcx.item_bounds(data.def_id).subst(tcx, data.substs)
+        }
         ty::Infer(ty::TyVar(_)) => {
             // If the self-type is an inference variable, then it MAY wind up
             // being a projected type, so induce an ambiguity.
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index a8fb55df2d3..aa230936903 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -143,7 +143,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // Before we go into the whole placeholder thing, just
         // quickly check if the self-type is a projection at all.
         match obligation.predicate.skip_binder().trait_ref.self_ty().kind() {
-            ty::Alias(..) => {}
+            // Excluding IATs here as they don't have meaningful item bounds.
+            ty::Alias(ty::Projection | ty::Opaque, _) => {}
             ty::Infer(ty::TyVar(_)) => {
                 span_bug!(
                     obligation.cause.span,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 6a648294efd..de023501f9e 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -156,7 +156,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let placeholder_self_ty = placeholder_trait_predicate.self_ty();
         let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
         let (def_id, substs) = match *placeholder_self_ty.kind() {
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
+            // Excluding IATs here as they don't have meaningful item bounds.
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+                (def_id, substs)
+            }
             _ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
         };
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index b72ff5b78e4..f1bd9f5bbf8 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1645,7 +1645,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         let tcx = self.infcx.tcx;
         let (def_id, substs) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+                (def_id, substs)
+            }
             _ => {
                 span_bug!(
                     obligation.cause.span,