error: concrete type differs from previous defining opaque type use
  --> $DIR/hidden_type_mismatch.rs:11:20
   |
LL |     pub type Sep = impl Sized + std::fmt::Display;
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, got `String`
   |
note: previous use here
  --> $DIR/hidden_type_mismatch.rs:37:21
   |
LL |     pub type Tait = impl Copy + From<Bar<()>> + Into<Bar<()>>;
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error