message: use Wake trait for async-fn driver
diff: #![feature(never_type)]
  +#![feature(wake_trait)]
  -use std::{future::Future, pin::Pin, task::Poll, ptr};
  -use std::task::{Waker, RawWaker, RawWakerVTable, Context};
  +use std::{future::Future, pin::Pin, task::Poll};
  +use std::task::{Wake, Waker, Context};
  +use std::sync::Arc;
  // See if we can run a basic `async fn`
  pub async fn foo(x: &u32, y: u32) -> u32 {
  @@ -47,25 +49,14 @@ async fn partial_init(x: u32) -> u32 {
  }
  fn run_fut(mut fut: impl Future<Output=u32>, output: u32) {
  - fn raw_waker_clone(_this: *const ()) -> RawWaker {
  - panic!("unimplemented");
  + struct MyWaker;
  + impl Wake for MyWaker {
  + fn wake(self: Arc<Self>) {
  + unimplemented!()
  }
  - fn raw_waker_wake(_this: *const ()) {
  - panic!("unimplemented");
  }
  - fn raw_waker_wake_by_ref(_this: *const ()) {
  - panic!("unimplemented");
  - }
  - fn raw_waker_drop(_this: *const ()) {}
  -
  - static RAW_WAKER: RawWakerVTable = RawWakerVTable::new(
  - raw_waker_clone,
  - raw_waker_wake,
  - raw_waker_wake_by_ref,
  - raw_waker_drop,
  - );
  - let waker = unsafe { Waker::from_raw(RawWaker::new(ptr::null(), &RAW_WAKER)) };
  + let waker = Waker::from(Arc::new(MyWaker));
  let mut context = Context::from_waker(&waker);
  assert_eq!(unsafe { Pin::new_unchecked(&mut fut) }.poll(&mut context), Poll::Ready(output));
  }
  