mirror of https://github.com/rust-lang/rust.git
53 lines
1.3 KiB
Rust
53 lines
1.3 KiB
Rust
// run-pass
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// edition:2021
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// check-run-results
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#![feature(dyn_star)]
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//~^ WARN the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
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use std::future::Future;
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async fn foo(f: dyn* Future<Output = i32>) {
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println!("value: {}", f.await);
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}
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async fn async_main() {
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foo(Box::pin(async { 1 })).await
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}
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// ------------------------------------------------------------------------- //
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// Implementation Details Below...
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use std::pin::Pin;
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use std::task::*;
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pub fn noop_waker() -> Waker {
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let raw = RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE);
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// SAFETY: the contracts for RawWaker and RawWakerVTable are upheld
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unsafe { Waker::from_raw(raw) }
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}
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const NOOP_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(noop_clone, noop, noop, noop);
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unsafe fn noop_clone(_p: *const ()) -> RawWaker {
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RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE)
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}
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unsafe fn noop(_p: *const ()) {}
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fn main() {
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let mut fut = async_main();
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// Poll loop, just to test the future...
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let waker = noop_waker();
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let ctx = &mut Context::from_waker(&waker);
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loop {
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match unsafe { Pin::new_unchecked(&mut fut).poll(ctx) } {
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Poll::Pending => {}
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Poll::Ready(()) => break,
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}
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}
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}
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