| // edition:2021 |
| // run-pass |
| |
| #![feature(never_type)] |
| |
| use std::future::Future; |
| |
| // See if we can run a basic `async fn` |
| pub async fn foo(x: &u32, y: u32) -> u32 { |
| let y = &y; |
| let z = 9; |
| let z = &z; |
| let y = async { *y + *z }.await; |
| let a = 10; |
| let a = &a; |
| *x + y + *a |
| } |
| |
| async fn add(x: u32, y: u32) -> u32 { |
| let a = async { x + y }; |
| a.await |
| } |
| |
| async fn build_aggregate(a: u32, b: u32, c: u32, d: u32) -> u32 { |
| let x = (add(a, b).await, add(c, d).await); |
| x.0 + x.1 |
| } |
| |
| enum Never {} |
| fn never() -> Never { |
| panic!() |
| } |
| |
| async fn includes_never(crash: bool, x: u32) -> u32 { |
| let result = async { x * x }.await; |
| if !crash { |
| return result; |
| } |
| #[allow(unused)] |
| let bad = never(); |
| result *= async { x + x }.await; |
| drop(bad); |
| result |
| } |
| |
| async fn partial_init(x: u32) -> u32 { |
| #[allow(unreachable_code)] |
| let _x: (String, !) = (String::new(), return async { x + x }.await); |
| } |
| |
| async fn read_exact(_from: &mut &[u8], _to: &mut [u8]) -> Option<()> { |
| Some(()) |
| } |
| |
| async fn hello_world() { |
| let data = [0u8; 1]; |
| let mut reader = &data[..]; |
| |
| let mut marker = [0u8; 1]; |
| read_exact(&mut reader, &mut marker).await.unwrap(); |
| } |
| |
| fn run_fut<T>(fut: impl Future<Output = T>) -> T { |
| use std::sync::Arc; |
| use std::task::{Context, Poll, Wake, Waker}; |
| |
| struct MyWaker; |
| impl Wake for MyWaker { |
| fn wake(self: Arc<Self>) { |
| unimplemented!() |
| } |
| } |
| |
| let waker = Waker::from(Arc::new(MyWaker)); |
| let mut context = Context::from_waker(&waker); |
| |
| let mut pinned = Box::pin(fut); |
| loop { |
| match pinned.as_mut().poll(&mut context) { |
| Poll::Pending => continue, |
| Poll::Ready(v) => return v, |
| } |
| } |
| } |
| |
| fn main() { |
| let x = 5; |
| assert_eq!(run_fut(foo(&x, 7)), 31); |
| assert_eq!(run_fut(build_aggregate(1, 2, 3, 4)), 10); |
| assert_eq!(run_fut(includes_never(false, 4)), 16); |
| assert_eq!(run_fut(partial_init(4)), 8); |
| run_fut(hello_world()); |
| } |