error[E0038]: the trait `AsyncFnMut` is not dyn compatible
  --> $DIR/dyn-pos.rs:3:16
   |
LL | fn foo(x: &dyn AsyncFn()) {}
   |                ^^^^^^^^^ `AsyncFnMut` is not dyn compatible
   |
note: for a trait to be dyn compatible it needs to allow building a vtable
      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
  --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
   |
   = note: the trait is not dyn compatible because it contains the generic associated type `CallRefFuture`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0038`.