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//@ run-pass
//@ check-run-results
// Test async drop of coroutine `bar` (with internal async drop),
// stopped at the middle of execution, with AsyncDrop object Foo active.
#![feature(async_drop)]
#![allow(incomplete_features)]
//@ edition: 2021
use std::mem::ManuallyDrop;
use std::{
future::{Future, async_drop_in_place, AsyncDrop},
pin::{pin, Pin},
sync::{mpsc, Arc},
task::{Context, Poll, Wake, Waker},
};
struct Foo {
my_resource_handle: usize,
}
impl Foo {
fn new(my_resource_handle: usize) -> Self {
let out = Foo {
my_resource_handle,
};
println!("Foo::new({})", my_resource_handle);
out
}
}
impl Drop for Foo {
fn drop(&mut self) {
println!("Foo::drop({})", self.my_resource_handle);
}
}
impl AsyncDrop for Foo {
async fn drop(self: Pin<&mut Self>) {
println!("Foo::async drop({})", self.my_resource_handle);
}
}
fn main() {
block_on_and_drop_in_the_middle(bar(10));
println!("done")
}
pub struct MiddleFuture {
first_call: bool,
}
impl Future for MiddleFuture {
type Output = ();
fn poll(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
if self.first_call {
println!("MiddleFuture first poll");
self.first_call = false;
Poll::Pending
} else {
println!("MiddleFuture Ready");
Poll::Ready(())
}
}
}
async fn bar(ident_base: usize) {
let middle = MiddleFuture { first_call: true };
let mut _first = Foo::new(ident_base);
middle.await; // Hanging `bar` future before Foo drop
}
fn block_on_and_drop_in_the_middle<F>(fut_unpin: F) -> F::Output
where
F: Future<Output = ()>,
{
let mut fut_pin = pin!(ManuallyDrop::new(fut_unpin));
let mut fut: Pin<&mut F> = unsafe {
Pin::map_unchecked_mut(fut_pin.as_mut(), |x| &mut **x)
};
let (waker, rx) = simple_waker();
let mut context = Context::from_waker(&waker);
let poll1 = fut.as_mut().poll(&mut context);
assert!(poll1.is_pending());
let drop_fut_unpin = unsafe { async_drop_in_place(fut.get_unchecked_mut()) };
let mut drop_fut: Pin<&mut _> = pin!(drop_fut_unpin);
loop {
match drop_fut.as_mut().poll(&mut context) {
Poll::Ready(()) => break,
Poll::Pending => rx.try_recv().unwrap(),
}
}
}
fn simple_waker() -> (Waker, mpsc::Receiver<()>) {
struct SimpleWaker {
tx: std::sync::mpsc::Sender<()>,
}
impl Wake for SimpleWaker {
fn wake(self: Arc<Self>) {
self.tx.send(()).unwrap();
}
}
let (tx, rx) = mpsc::channel();
(Waker::from(Arc::new(SimpleWaker { tx })), rx)
}
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