error[E0046]: not all trait items implemented, missing: `Assoc`
  --> $DIR/specialize_on_type_error.rs:14:1
   |
LL |     type Assoc: Y;
   |     ------------- `Assoc` from trait
...
LL | impl<T: X> Z for A<T> {}
   | ^^^^^^^^^^^^^^^^^^^^^ missing `Assoc` in implementation

error: aborting due to previous error

For more information about this error, try `rustc --explain E0046`.