error[E0277]: the trait bound `u8: Identity` is not satisfied
  --> $DIR/projection-as-union-type-error.rs:12:9
   |
LL |     a:  <Foo as Identity>::Identity,
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Identity` is not implemented for `u8`
   |
help: this trait has no implementations, consider adding one
  --> $DIR/projection-as-union-type-error.rs:5:1
   |
LL | pub trait Identity {
   | ^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.