error[E0321]: cross-crate traits with a default impl, like `Unpin`, can only be implemented for a struct/enum type, not `(dyn MyUnpinTrait + 'static)`
  --> $DIR/pin-dyn-dispatch-sound.rs:12:1
   |
LL | impl Unpin for dyn MyUnpinTrait {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0321`.