Make sure the new solver agrees

Author: oli-obk

tests/ui/type-alias-impl-trait/nested_inference_failure.rs

@@ -1,4 +1,6 @@
 // check-pass
+// revisions: new old
+//[new] compile-flags: -Znext-solver
 
 //! This test checks that we can successfully infer
 //! the hidden type of `FooImpl` to be `Foo<i32, {closure}>`