error[E0271]: type mismatch resolving `<() as Proj>::Assoc == i32`
  --> $DIR/hidden_type_mismatch.rs:43:9
   |
LL |     pub type Sep = impl Sized + std::fmt::Display;
   |                    ------------------------------ the expected opaque type
...
LL |         Bar { inner: 1i32, _marker: () }
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type mismatch resolving `<() as Proj>::Assoc == i32`
   |
note: expected this to be `Sep`
  --> $DIR/hidden_type_mismatch.rs:20:22
   |
LL |         type Assoc = sus::Sep;
   |                      ^^^^^^^^
   = note: expected opaque type `Sep`
                     found type `i32`
note: required for `Bar<()>` to implement `Copy`
  --> $DIR/hidden_type_mismatch.rs:32:39
   |
LL |     impl<T: Proj<Assoc = i32> + Copy> Copy for Bar<T> {}
   |                  -----------          ^^^^     ^^^^^^
   |                  |
   |                  unsatisfied trait bound introduced here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0271`.