error: defining opaque type use does not fully define opaque type: generic parameter `U` is specified as concrete type `u32`
  --> $DIR/not_a_defining_use.rs:9:1
   |
LL | / fn two<T: Debug>(t: T) -> Two<T, u32> {
LL | |
LL | |     (t, 4i8)
LL | | }
   | |_^

error: concrete type differs from previous defining opaque type use
  --> $DIR/not_a_defining_use.rs:30:1
   |
LL | / fn four<T: Debug, U: Bar>(t: T) -> Two<T, U> {
LL | |     (t, <U as Bar>::FOO)
LL | | }
   | |_^ expected `(T, i8)`, got `(T, <U as Bar>::Blub)`
   |
note: previous use here
  --> $DIR/not_a_defining_use.rs:14:1
   |
LL | / fn three<T: Debug, U>(t: T) -> Two<T, U> {
LL | |     (t, 5i8)
LL | | }
   | |_^

error: aborting due to 2 previous errors