error[E0271]: type mismatch resolving `<std::vec::IntoIter<i32> as Iterator>::Item == u32`
  --> $DIR/assoc-type-in-superbad.rs:12:16
   |
LL |     type Key = u32;
   |                ^^^ expected `u32`, found `i32`
   |
note: required by a bound in `Foo`
  --> $DIR/assoc-type-in-superbad.rs:7:25
   |
LL | pub trait Foo: Iterator<Item=<Self as Foo>::Key> {
   |                         ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Foo`

error: aborting due to previous error

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