rust/tests/ui/type-alias-impl-trait/nested-tait-inference3.stderr

error: unconstrained opaque type
  --> $DIR/nested-tait-inference3.rs:6:13
   |
LL | type FooX = impl Debug;
   |             ^^^^^^^^^^
   |
   = note: `FooX` must be used in combination with a concrete type within the same module

error: aborting due to 1 previous error