error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/dont-project-to-specializable-projection.rs:13:5
   |
LL |     default async fn foo(_: T) -> &'static str {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected associated type, found future
   |
note: type in trait
  --> $DIR/dont-project-to-specializable-projection.rs:9:5
   |
LL |     async fn foo(_: T) -> &'static str;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: expected signature `fn(_) -> impl Future<Output = &'static str>`
              found signature `fn(_) -> impl Future<Output = &'static str>`

error: async associated function in trait cannot be specialized
  --> $DIR/dont-project-to-specializable-projection.rs:13:5
   |
LL |     default async fn foo(_: T) -> &'static str {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: specialization behaves in inconsistent and surprising ways with async functions in traits, and for now is disallowed

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0053`.