src/test/ui/async-await/issues/issue-53249.rs

   1 // check-pass
   2 // edition:2018
   3
   4 #![feature(arbitrary_self_types)]
   5
   6 use std::task::{self, Poll};
   7 use std::future::Future;
   8 use std::marker::Unpin;
   9 use std::pin::Pin;
  10
  11 // This is a regression test for a ICE/unbounded recursion issue relating to async-await.
  12
  13 #[derive(Debug)]
  14 #[must_use = "futures do nothing unless polled"]
  15 pub struct Lazy<F> {
  16     f: Option<F>
  17 }
  18
  19 impl<F> Unpin for Lazy<F> {}
  20
  21 pub fn lazy<F, R>(f: F) -> Lazy<F>
  22     where F: FnOnce(&mut task::Context) -> R,
  23 {
  24     Lazy { f: Some(f) }
  25 }
  26
  27 impl<R, F> Future for Lazy<F>
  28     where F: FnOnce(&mut task::Context) -> R,
  29 {
  30     type Output = R;
  31
  32     fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<R> {
  33         Poll::Ready((self.f.take().unwrap())(cx))
  34     }
  35 }
  36
  37 async fn __receive<WantFn, Fut>(want: WantFn) -> ()
  38     where Fut: Future<Output = ()>, WantFn: Fn(&Box<dyn Send + 'static>) -> Fut,
  39 {
  40     lazy(|_| ()).await;
  41 }
  42
  43 pub fn basic_spawn_receive() {
  44     async { __receive(|_| async { () }).await };
  45 }
  46
  47 fn main() {}