error: non-defining opaque type use in defining scope
  --> $DIR/generic_duplicate_param_use4.rs:10:27
   |
LL | fn one<T: Debug>(t: T) -> Two<T, T> {
   |                           ^^^^^^^^^
   |
note: type used multiple times
  --> $DIR/generic_duplicate_param_use4.rs:8:10
   |
LL | type Two<T, U> = impl Debug;
   |          ^  ^

error: aborting due to previous error