Ignore non-self item bounds for rigid projections

Author: compiler-errors

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1619,16 +1619,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             for bound in
                 self.tcx().item_bounds(alias_ty.def_id).instantiate(self.tcx(), alias_ty.args)
             {
-                // HACK: On subsequent recursions, we only care about bounds that don't
+                // HACK: In the initial recursion, we only care about bounds for the
+                // `self_ty`. On subsequent recursions, we care about bounds that don't
                 // share the same type as `self_ty`. This is because for truly rigid
                 // projections, we will never be able to equate, e.g. `<T as Tr>::A`
                 // with `<<T as Tr>::A as Tr>::A`.
-                if in_parent_alias_type {
-                    match bound.kind().skip_binder() {
-                        ty::ClauseKind::Trait(tr) if tr.self_ty() == self_ty => continue,
-                        ty::ClauseKind::Projection(p) if p.self_ty() == self_ty => continue,
-                        _ => {}
+                match bound.kind().skip_binder() {
+                    ty::ClauseKind::Trait(tr)
+                        if (tr.self_ty() == self_ty) ^ !in_parent_alias_type =>
+                    {
+                        continue;
+                    }
+                    ty::ClauseKind::Projection(p)
+                        if (p.self_ty() == self_ty) ^ !in_parent_alias_type =>
+                    {
+                        continue;
                     }
+                    _ => {}
                 }
 
                 for_each(self, bound, idx)?;