error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/dont-project-to-specializable-projection.rs:14:35
   |
LL |     default async fn foo(_: T) -> &'static str {
   |                                   ^^^^^^^^^^^^ expected associated type, found future
   |
note: type in trait
  --> $DIR/dont-project-to-specializable-projection.rs:10:27
   |
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:14:5
   |
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[E0599]: no method named `poll` found for struct `Pin<&mut impl Future<Output = ()>>` in the current scope
  --> $DIR/dont-project-to-specializable-projection.rs:49:28
   |
LL |         match fut.as_mut().poll(ctx) {
   |                            ^^^^ method not found in `Pin<&mut impl Future<Output = ()>>`
   |
  --> $SRC_DIR/core/src/future/future.rs:LL:COL
   |
   = note: the method is available for `Pin<&mut impl Future<Output = ()>>` here
   |
   = help: items from traits can only be used if the trait is in scope
help: trait `Future` which provides `poll` is implemented but not in scope; perhaps you want to import it
   |
LL + use std::future::Future;
   |

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0053, E0599.
For more information about an error, try `rustc --explain E0053`.