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