Use elaborated item bounds for alias types

compiler/rustc_trait_selection/src/solve/assembly.rs

@@ -399,10 +399,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             ty::Alias(_, alias_ty) => alias_ty,
         };
 
-        for (assumption, _) in self
+        for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
-            .tcx()
-            .bound_explicit_item_bounds(alias_ty.def_id)
-            .subst_iter_copied(self.tcx(), alias_ty.substs)
         {
             match G::consider_assumption(self, goal, assumption) {
                 Ok(result) => {

tests/ui/traits/new-solver/elaborate-item-bounds.rs

@@ -0,0 +1,12 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+trait Foo {
+    type Bar: Bar;
+}
+
+trait Bar: Baz {}
+
+trait Baz {}
+
+fn main() {}