error[E0308]: mismatched types
  --> $DIR/suggest-missing-await-closure.rs:16:18
   |
LL | async fn make_u32() -> u32 {
   |                        --- the `Output` of this `async fn`'s found opaque type
...
LL |         take_u32(x)
   |                  ^
   |                  |
   |                  expected `u32`, found opaque type
   |                  help: consider using `.await` here: `x.await`
   |
   = note:     expected type `u32`
           found opaque type `impl std::future::Future`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.