1use anyhow::{anyhow, Result};
2use async_task::Runnable;
3use futures::channel::mpsc;
4use smol::{channel, prelude::*, Executor};
5use std::{
6 any::Any,
7 fmt::{self, Display},
8 marker::PhantomData,
9 mem,
10 pin::Pin,
11 rc::Rc,
12 sync::Arc,
13 task::{Context, Poll},
14 thread,
15 time::Duration,
16};
17
18use crate::{
19 platform::{self, Dispatcher},
20 util, MutableAppContext,
21};
22
23pub enum Foreground {
24 Platform {
25 dispatcher: Arc<dyn platform::Dispatcher>,
26 _not_send_or_sync: PhantomData<Rc<()>>,
27 },
28 #[cfg(any(test, feature = "test-support"))]
29 Deterministic {
30 cx_id: usize,
31 executor: Arc<Deterministic>,
32 },
33}
34
35pub enum Background {
36 #[cfg(any(test, feature = "test-support"))]
37 Deterministic { executor: Arc<Deterministic> },
38 Production {
39 executor: Arc<smol::Executor<'static>>,
40 _stop: channel::Sender<()>,
41 },
42}
43
44type AnyLocalFuture = Pin<Box<dyn 'static + Future<Output = Box<dyn Any + 'static>>>>;
45type AnyFuture = Pin<Box<dyn 'static + Send + Future<Output = Box<dyn Any + Send + 'static>>>>;
46type AnyTask = async_task::Task<Box<dyn Any + Send + 'static>>;
47type AnyLocalTask = async_task::Task<Box<dyn Any + 'static>>;
48
49#[must_use]
50pub enum Task<T> {
51 Ready(Option<T>),
52 Local {
53 any_task: AnyLocalTask,
54 result_type: PhantomData<T>,
55 },
56 Send {
57 any_task: AnyTask,
58 result_type: PhantomData<T>,
59 },
60}
61
62unsafe impl<T: Send> Send for Task<T> {}
63
64#[cfg(any(test, feature = "test-support"))]
65struct DeterministicState {
66 rng: rand::prelude::StdRng,
67 seed: u64,
68 scheduled_from_foreground: collections::HashMap<usize, Vec<ForegroundRunnable>>,
69 scheduled_from_background: Vec<Runnable>,
70 forbid_parking: bool,
71 block_on_ticks: std::ops::RangeInclusive<usize>,
72 now: std::time::Instant,
73 next_timer_id: usize,
74 pending_timers: Vec<(usize, std::time::Instant, postage::barrier::Sender)>,
75 waiting_backtrace: Option<backtrace::Backtrace>,
76}
77
78#[cfg(any(test, feature = "test-support"))]
79struct ForegroundRunnable {
80 runnable: Runnable,
81 main: bool,
82}
83
84#[cfg(any(test, feature = "test-support"))]
85pub struct Deterministic {
86 state: Arc<parking_lot::Mutex<DeterministicState>>,
87 parker: parking_lot::Mutex<parking::Parker>,
88}
89
90pub enum Timer {
91 Production(smol::Timer),
92 #[cfg(any(test, feature = "test-support"))]
93 Deterministic(DeterministicTimer),
94}
95
96#[cfg(any(test, feature = "test-support"))]
97pub struct DeterministicTimer {
98 rx: postage::barrier::Receiver,
99 id: usize,
100 state: Arc<parking_lot::Mutex<DeterministicState>>,
101}
102
103#[cfg(any(test, feature = "test-support"))]
104impl Deterministic {
105 pub fn new(seed: u64) -> Arc<Self> {
106 use rand::prelude::*;
107
108 Arc::new(Self {
109 state: Arc::new(parking_lot::Mutex::new(DeterministicState {
110 rng: StdRng::seed_from_u64(seed),
111 seed,
112 scheduled_from_foreground: Default::default(),
113 scheduled_from_background: Default::default(),
114 forbid_parking: false,
115 block_on_ticks: 0..=1000,
116 now: std::time::Instant::now(),
117 next_timer_id: Default::default(),
118 pending_timers: Default::default(),
119 waiting_backtrace: None,
120 })),
121 parker: Default::default(),
122 })
123 }
124
125 pub fn build_background(self: &Arc<Self>) -> Arc<Background> {
126 Arc::new(Background::Deterministic {
127 executor: self.clone(),
128 })
129 }
130
131 pub fn build_foreground(self: &Arc<Self>, id: usize) -> Rc<Foreground> {
132 Rc::new(Foreground::Deterministic {
133 cx_id: id,
134 executor: self.clone(),
135 })
136 }
137
138 fn spawn_from_foreground(
139 &self,
140 cx_id: usize,
141 future: AnyLocalFuture,
142 main: bool,
143 ) -> AnyLocalTask {
144 let state = self.state.clone();
145 let unparker = self.parker.lock().unparker();
146 let (runnable, task) = async_task::spawn_local(future, move |runnable| {
147 let mut state = state.lock();
148 state
149 .scheduled_from_foreground
150 .entry(cx_id)
151 .or_default()
152 .push(ForegroundRunnable { runnable, main });
153 unparker.unpark();
154 });
155 runnable.schedule();
156 task
157 }
158
159 fn spawn(&self, future: AnyFuture) -> AnyTask {
160 let state = self.state.clone();
161 let unparker = self.parker.lock().unparker();
162 let (runnable, task) = async_task::spawn(future, move |runnable| {
163 let mut state = state.lock();
164 state.scheduled_from_background.push(runnable);
165 unparker.unpark();
166 });
167 runnable.schedule();
168 task
169 }
170
171 fn run<'a>(
172 &self,
173 cx_id: usize,
174 main_future: Pin<Box<dyn 'a + Future<Output = Box<dyn Any>>>>,
175 ) -> Box<dyn Any> {
176 use std::sync::atomic::{AtomicBool, Ordering::SeqCst};
177
178 let woken = Arc::new(AtomicBool::new(false));
179
180 let state = self.state.clone();
181 let unparker = self.parker.lock().unparker();
182 let (runnable, mut main_task) = unsafe {
183 async_task::spawn_unchecked(main_future, move |runnable| {
184 let mut state = state.lock();
185 state
186 .scheduled_from_foreground
187 .entry(cx_id)
188 .or_default()
189 .push(ForegroundRunnable {
190 runnable,
191 main: true,
192 });
193 unparker.unpark();
194 })
195 };
196 runnable.schedule();
197
198 loop {
199 if let Some(result) = self.run_internal(woken.clone(), Some(&mut main_task)) {
200 return result;
201 }
202
203 if !woken.load(SeqCst) {
204 self.state.lock().will_park();
205 }
206
207 woken.store(false, SeqCst);
208 self.parker.lock().park();
209 }
210 }
211
212 pub fn run_until_parked(&self) {
213 use std::sync::atomic::AtomicBool;
214 let woken = Arc::new(AtomicBool::new(false));
215 self.run_internal(woken, None);
216 }
217
218 fn run_internal(
219 &self,
220 woken: Arc<std::sync::atomic::AtomicBool>,
221 mut main_task: Option<&mut AnyLocalTask>,
222 ) -> Option<Box<dyn Any>> {
223 use rand::prelude::*;
224 use std::sync::atomic::Ordering::SeqCst;
225
226 let unparker = self.parker.lock().unparker();
227 let waker = waker_fn::waker_fn(move || {
228 woken.store(true, SeqCst);
229 unparker.unpark();
230 });
231
232 let mut cx = Context::from_waker(&waker);
233 loop {
234 let mut state = self.state.lock();
235
236 if state.scheduled_from_foreground.is_empty()
237 && state.scheduled_from_background.is_empty()
238 {
239 if let Some(main_task) = main_task {
240 if let Poll::Ready(result) = main_task.poll(&mut cx) {
241 return Some(result);
242 }
243 }
244
245 return None;
246 }
247
248 if !state.scheduled_from_background.is_empty() && state.rng.gen() {
249 let background_len = state.scheduled_from_background.len();
250 let ix = state.rng.gen_range(0..background_len);
251 let runnable = state.scheduled_from_background.remove(ix);
252 drop(state);
253 runnable.run();
254 } else if !state.scheduled_from_foreground.is_empty() {
255 let available_cx_ids = state
256 .scheduled_from_foreground
257 .keys()
258 .copied()
259 .collect::<Vec<_>>();
260 let cx_id_to_run = *available_cx_ids.iter().choose(&mut state.rng).unwrap();
261 let scheduled_from_cx = state
262 .scheduled_from_foreground
263 .get_mut(&cx_id_to_run)
264 .unwrap();
265 let foreground_runnable = scheduled_from_cx.remove(0);
266 if scheduled_from_cx.is_empty() {
267 state.scheduled_from_foreground.remove(&cx_id_to_run);
268 }
269
270 drop(state);
271
272 foreground_runnable.runnable.run();
273 if let Some(main_task) = main_task.as_mut() {
274 if foreground_runnable.main {
275 if let Poll::Ready(result) = main_task.poll(&mut cx) {
276 return Some(result);
277 }
278 }
279 }
280 }
281 }
282 }
283
284 fn block<F, T>(&self, future: &mut F, max_ticks: usize) -> Option<T>
285 where
286 F: Unpin + Future<Output = T>,
287 {
288 use rand::prelude::*;
289
290 let unparker = self.parker.lock().unparker();
291 let waker = waker_fn::waker_fn(move || {
292 unparker.unpark();
293 });
294
295 let mut cx = Context::from_waker(&waker);
296 for _ in 0..max_ticks {
297 let mut state = self.state.lock();
298 let runnable_count = state.scheduled_from_background.len();
299 let ix = state.rng.gen_range(0..=runnable_count);
300 if ix < state.scheduled_from_background.len() {
301 let runnable = state.scheduled_from_background.remove(ix);
302 drop(state);
303 runnable.run();
304 } else {
305 drop(state);
306 if let Poll::Ready(result) = future.poll(&mut cx) {
307 return Some(result);
308 }
309 let mut state = self.state.lock();
310 if state.scheduled_from_background.is_empty() {
311 state.will_park();
312 drop(state);
313 self.parker.lock().park();
314 }
315
316 continue;
317 }
318 }
319
320 None
321 }
322
323 pub fn timer(&self, duration: Duration) -> Timer {
324 let (tx, rx) = postage::barrier::channel();
325 let mut state = self.state.lock();
326 let wakeup_at = state.now + duration;
327 let id = util::post_inc(&mut state.next_timer_id);
328 state.pending_timers.push((id, wakeup_at, tx));
329 let state = self.state.clone();
330 Timer::Deterministic(DeterministicTimer { rx, id, state })
331 }
332
333 pub fn now(&self) -> std::time::Instant {
334 let state = self.state.lock();
335 state.now
336 }
337
338 pub fn advance_clock(&self, duration: Duration) {
339 let new_now = self.state.lock().now + duration;
340 loop {
341 self.run_until_parked();
342 let mut state = self.state.lock();
343
344 if let Some((_, wakeup_time, _)) = state.pending_timers.first() {
345 let wakeup_time = *wakeup_time;
346 if wakeup_time <= new_now {
347 let timer_count = state
348 .pending_timers
349 .iter()
350 .take_while(|(_, t, _)| *t == wakeup_time)
351 .count();
352 state.now = wakeup_time;
353 let timers_to_wake = state
354 .pending_timers
355 .drain(0..timer_count)
356 .collect::<Vec<_>>();
357 drop(state);
358 drop(timers_to_wake);
359 continue;
360 }
361 }
362
363 break;
364 }
365
366 self.state.lock().now = new_now;
367 }
368
369 pub fn start_waiting(&self) {
370 self.state.lock().waiting_backtrace = Some(backtrace::Backtrace::new_unresolved());
371 }
372
373 pub fn finish_waiting(&self) {
374 self.state.lock().waiting_backtrace.take();
375 }
376
377 pub fn forbid_parking(&self) {
378 use rand::prelude::*;
379
380 let mut state = self.state.lock();
381 state.forbid_parking = true;
382 state.rng = StdRng::seed_from_u64(state.seed);
383 }
384
385 pub async fn simulate_random_delay(&self) {
386 use rand::prelude::*;
387 use smol::future::yield_now;
388 if self.state.lock().rng.gen_bool(0.2) {
389 let yields = self.state.lock().rng.gen_range(1..=10);
390 for _ in 0..yields {
391 yield_now().await;
392 }
393 }
394 }
395}
396
397impl Drop for Timer {
398 fn drop(&mut self) {
399 #[cfg(any(test, feature = "test-support"))]
400 if let Timer::Deterministic(DeterministicTimer { state, id, .. }) = self {
401 state
402 .lock()
403 .pending_timers
404 .retain(|(timer_id, _, _)| timer_id != id)
405 }
406 }
407}
408
409impl Future for Timer {
410 type Output = ();
411
412 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
413 match &mut *self {
414 #[cfg(any(test, feature = "test-support"))]
415 Self::Deterministic(DeterministicTimer { rx, .. }) => {
416 use postage::stream::{PollRecv, Stream as _};
417 smol::pin!(rx);
418 match rx.poll_recv(&mut postage::Context::from_waker(cx.waker())) {
419 PollRecv::Ready(()) | PollRecv::Closed => Poll::Ready(()),
420 PollRecv::Pending => Poll::Pending,
421 }
422 }
423 Self::Production(timer) => {
424 smol::pin!(timer);
425 match timer.poll(cx) {
426 Poll::Ready(_) => Poll::Ready(()),
427 Poll::Pending => Poll::Pending,
428 }
429 }
430 }
431 }
432}
433
434#[cfg(any(test, feature = "test-support"))]
435impl DeterministicState {
436 fn will_park(&mut self) {
437 if self.forbid_parking {
438 let mut backtrace_message = String::new();
439 #[cfg(any(test, feature = "test-support"))]
440 if let Some(backtrace) = self.waiting_backtrace.as_mut() {
441 backtrace.resolve();
442 backtrace_message = format!(
443 "\nbacktrace of waiting future:\n{:?}",
444 util::CwdBacktrace(backtrace)
445 );
446 }
447
448 panic!(
449 "deterministic executor parked after a call to forbid_parking{}",
450 backtrace_message
451 );
452 }
453 }
454}
455
456impl Foreground {
457 pub fn platform(dispatcher: Arc<dyn platform::Dispatcher>) -> Result<Self> {
458 if dispatcher.is_main_thread() {
459 Ok(Self::Platform {
460 dispatcher,
461 _not_send_or_sync: PhantomData,
462 })
463 } else {
464 Err(anyhow!("must be constructed on main thread"))
465 }
466 }
467
468 pub fn spawn<T: 'static>(&self, future: impl Future<Output = T> + 'static) -> Task<T> {
469 let future = any_local_future(future);
470 let any_task = match self {
471 #[cfg(any(test, feature = "test-support"))]
472 Self::Deterministic { cx_id, executor } => {
473 executor.spawn_from_foreground(*cx_id, future, false)
474 }
475 Self::Platform { dispatcher, .. } => {
476 fn spawn_inner(
477 future: AnyLocalFuture,
478 dispatcher: &Arc<dyn Dispatcher>,
479 ) -> AnyLocalTask {
480 let dispatcher = dispatcher.clone();
481 let schedule =
482 move |runnable: Runnable| dispatcher.run_on_main_thread(runnable);
483 let (runnable, task) = async_task::spawn_local(future, schedule);
484 runnable.schedule();
485 task
486 }
487 spawn_inner(future, dispatcher)
488 }
489 };
490 Task::local(any_task)
491 }
492
493 #[cfg(any(test, feature = "test-support"))]
494 pub fn run<T: 'static>(&self, future: impl Future<Output = T>) -> T {
495 let future = async move { Box::new(future.await) as Box<dyn Any> }.boxed_local();
496 let result = match self {
497 Self::Deterministic { cx_id, executor } => executor.run(*cx_id, future),
498 Self::Platform { .. } => panic!("you can't call run on a platform foreground executor"),
499 };
500 *result.downcast().unwrap()
501 }
502
503 #[cfg(any(test, feature = "test-support"))]
504 pub fn run_until_parked(&self) {
505 match self {
506 Self::Deterministic { executor, .. } => executor.run_until_parked(),
507 _ => panic!("this method can only be called on a deterministic executor"),
508 }
509 }
510
511 #[cfg(any(test, feature = "test-support"))]
512 pub fn parking_forbidden(&self) -> bool {
513 match self {
514 Self::Deterministic { executor, .. } => executor.state.lock().forbid_parking,
515 _ => panic!("this method can only be called on a deterministic executor"),
516 }
517 }
518
519 #[cfg(any(test, feature = "test-support"))]
520 pub fn start_waiting(&self) {
521 match self {
522 Self::Deterministic { executor, .. } => executor.start_waiting(),
523 _ => panic!("this method can only be called on a deterministic executor"),
524 }
525 }
526
527 #[cfg(any(test, feature = "test-support"))]
528 pub fn finish_waiting(&self) {
529 match self {
530 Self::Deterministic { executor, .. } => executor.finish_waiting(),
531 _ => panic!("this method can only be called on a deterministic executor"),
532 }
533 }
534
535 #[cfg(any(test, feature = "test-support"))]
536 pub fn forbid_parking(&self) {
537 match self {
538 Self::Deterministic { executor, .. } => executor.forbid_parking(),
539 _ => panic!("this method can only be called on a deterministic executor"),
540 }
541 }
542
543 #[cfg(any(test, feature = "test-support"))]
544 pub fn advance_clock(&self, duration: Duration) {
545 match self {
546 Self::Deterministic { executor, .. } => executor.advance_clock(duration),
547 _ => panic!("this method can only be called on a deterministic executor"),
548 }
549 }
550
551 #[cfg(any(test, feature = "test-support"))]
552 pub fn set_block_on_ticks(&self, range: std::ops::RangeInclusive<usize>) {
553 match self {
554 Self::Deterministic { executor, .. } => executor.state.lock().block_on_ticks = range,
555 _ => panic!("this method can only be called on a deterministic executor"),
556 }
557 }
558}
559
560impl Background {
561 pub fn new() -> Self {
562 let executor = Arc::new(Executor::new());
563 let stop = channel::unbounded::<()>();
564
565 for i in 0..2 * num_cpus::get() {
566 let executor = executor.clone();
567 let stop = stop.1.clone();
568 thread::Builder::new()
569 .name(format!("background-executor-{}", i))
570 .spawn(move || smol::block_on(executor.run(stop.recv())))
571 .unwrap();
572 }
573
574 Self::Production {
575 executor,
576 _stop: stop.0,
577 }
578 }
579
580 pub fn num_cpus(&self) -> usize {
581 num_cpus::get()
582 }
583
584 pub fn spawn<T, F>(&self, future: F) -> Task<T>
585 where
586 T: 'static + Send,
587 F: Send + Future<Output = T> + 'static,
588 {
589 let future = any_future(future);
590 let any_task = match self {
591 Self::Production { executor, .. } => executor.spawn(future),
592 #[cfg(any(test, feature = "test-support"))]
593 Self::Deterministic { executor } => executor.spawn(future),
594 };
595 Task::send(any_task)
596 }
597
598 pub fn block<F, T>(&self, future: F) -> T
599 where
600 F: Future<Output = T>,
601 {
602 smol::pin!(future);
603 match self {
604 Self::Production { .. } => smol::block_on(&mut future),
605 #[cfg(any(test, feature = "test-support"))]
606 Self::Deterministic { executor, .. } => {
607 executor.block(&mut future, usize::MAX).unwrap()
608 }
609 }
610 }
611
612 pub fn block_with_timeout<F, T>(
613 &self,
614 timeout: Duration,
615 future: F,
616 ) -> Result<T, impl Future<Output = T>>
617 where
618 T: 'static,
619 F: 'static + Unpin + Future<Output = T>,
620 {
621 let mut future = any_local_future(future);
622 if !timeout.is_zero() {
623 let output = match self {
624 Self::Production { .. } => smol::block_on(util::timeout(timeout, &mut future)).ok(),
625 #[cfg(any(test, feature = "test-support"))]
626 Self::Deterministic { executor, .. } => {
627 use rand::prelude::*;
628 let max_ticks = {
629 let mut state = executor.state.lock();
630 let range = state.block_on_ticks.clone();
631 state.rng.gen_range(range)
632 };
633 executor.block(&mut future, max_ticks)
634 }
635 };
636 if let Some(output) = output {
637 return Ok(*output.downcast().unwrap());
638 }
639 }
640 Err(async { *future.await.downcast().unwrap() })
641 }
642
643 pub async fn scoped<'scope, F>(self: &Arc<Self>, scheduler: F)
644 where
645 F: FnOnce(&mut Scope<'scope>),
646 {
647 let mut scope = Scope::new(self.clone());
648 (scheduler)(&mut scope);
649 let spawned = mem::take(&mut scope.futures)
650 .into_iter()
651 .map(|f| self.spawn(f))
652 .collect::<Vec<_>>();
653 for task in spawned {
654 task.await;
655 }
656 }
657
658 pub fn timer(&self, duration: Duration) -> Timer {
659 match self {
660 Background::Production { .. } => Timer::Production(smol::Timer::after(duration)),
661 #[cfg(any(test, feature = "test-support"))]
662 Background::Deterministic { executor } => executor.timer(duration),
663 }
664 }
665
666 pub fn now(&self) -> std::time::Instant {
667 match self {
668 Background::Production { .. } => std::time::Instant::now(),
669 #[cfg(any(test, feature = "test-support"))]
670 Background::Deterministic { executor } => executor.now(),
671 }
672 }
673
674 #[cfg(any(test, feature = "test-support"))]
675 pub async fn simulate_random_delay(&self) {
676 match self {
677 Self::Deterministic { executor, .. } => {
678 executor.simulate_random_delay().await;
679 }
680 _ => {
681 panic!("this method can only be called on a deterministic executor")
682 }
683 }
684 }
685}
686
687impl Default for Background {
688 fn default() -> Self {
689 Self::new()
690 }
691}
692
693pub struct Scope<'a> {
694 executor: Arc<Background>,
695 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
696 tx: Option<mpsc::Sender<()>>,
697 rx: mpsc::Receiver<()>,
698 _phantom: PhantomData<&'a ()>,
699}
700
701impl<'a> Scope<'a> {
702 fn new(executor: Arc<Background>) -> Self {
703 let (tx, rx) = mpsc::channel(1);
704 Self {
705 executor,
706 tx: Some(tx),
707 rx,
708 futures: Default::default(),
709 _phantom: PhantomData,
710 }
711 }
712
713 pub fn spawn<F>(&mut self, f: F)
714 where
715 F: Future<Output = ()> + Send + 'a,
716 {
717 let tx = self.tx.clone().unwrap();
718
719 // Safety: The 'a lifetime is guaranteed to outlive any of these futures because
720 // dropping this `Scope` blocks until all of the futures have resolved.
721 let f = unsafe {
722 mem::transmute::<
723 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
724 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
725 >(Box::pin(async move {
726 f.await;
727 drop(tx);
728 }))
729 };
730 self.futures.push(f);
731 }
732}
733
734impl<'a> Drop for Scope<'a> {
735 fn drop(&mut self) {
736 self.tx.take().unwrap();
737
738 // Wait until the channel is closed, which means that all of the spawned
739 // futures have resolved.
740 self.executor.block(self.rx.next());
741 }
742}
743
744impl<T> Task<T> {
745 pub fn ready(value: T) -> Self {
746 Self::Ready(Some(value))
747 }
748
749 fn local(any_task: AnyLocalTask) -> Self {
750 Self::Local {
751 any_task,
752 result_type: PhantomData,
753 }
754 }
755
756 pub fn detach(self) {
757 match self {
758 Task::Ready(_) => {}
759 Task::Local { any_task, .. } => any_task.detach(),
760 Task::Send { any_task, .. } => any_task.detach(),
761 }
762 }
763}
764
765impl<T: 'static, E: 'static + Display> Task<Result<T, E>> {
766 pub fn detach_and_log_err(self, cx: &mut MutableAppContext) {
767 cx.spawn(|_| async move {
768 if let Err(err) = self.await {
769 log::error!("{}", err);
770 }
771 })
772 .detach();
773 }
774}
775
776impl<T: Send> Task<T> {
777 fn send(any_task: AnyTask) -> Self {
778 Self::Send {
779 any_task,
780 result_type: PhantomData,
781 }
782 }
783}
784
785impl<T: fmt::Debug> fmt::Debug for Task<T> {
786 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
787 match self {
788 Task::Ready(value) => value.fmt(f),
789 Task::Local { any_task, .. } => any_task.fmt(f),
790 Task::Send { any_task, .. } => any_task.fmt(f),
791 }
792 }
793}
794
795impl<T: 'static> Future for Task<T> {
796 type Output = T;
797
798 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
799 match unsafe { self.get_unchecked_mut() } {
800 Task::Ready(value) => Poll::Ready(value.take().unwrap()),
801 Task::Local { any_task, .. } => {
802 any_task.poll(cx).map(|value| *value.downcast().unwrap())
803 }
804 Task::Send { any_task, .. } => {
805 any_task.poll(cx).map(|value| *value.downcast().unwrap())
806 }
807 }
808 }
809}
810
811fn any_future<T, F>(future: F) -> AnyFuture
812where
813 T: 'static + Send,
814 F: Future<Output = T> + Send + 'static,
815{
816 async { Box::new(future.await) as Box<dyn Any + Send> }.boxed()
817}
818
819fn any_local_future<T, F>(future: F) -> AnyLocalFuture
820where
821 T: 'static,
822 F: Future<Output = T> + 'static,
823{
824 async { Box::new(future.await) as Box<dyn Any> }.boxed_local()
825}