d67fa511c1
- the borrowck USER_TYPES buffer grows in the kept heap, not the compiler generation the zone swap destroys (Calculator crashed after the swap) - tools/run/fixture/zone_swap.sh forces a swap and fails on a fault, a use-after-destroy, a panic or a nonzero kept-scan - Box::pin(f(n-1)).await in an async fn lowers (no false E0733) Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
58 lines
1.7 KiB
Rust
58 lines
1.7 KiB
Rust
// A recursive async fn through Box::pin: the boxed future is a pointer, so the future type does
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// not contain itself (rustc accepts it; E0733 is only for recursion by value). The poll function
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// builds the callee future as a temporary and moves it into the box, which needs the future's
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// layout before its own saved locals are known.
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use std::future::Future;
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use std::pin::Pin;
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use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
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fn noop_raw() -> RawWaker {
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fn clone(_: *const ()) -> RawWaker { noop_raw() }
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fn noop(_: *const ()) {}
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static VT: RawWakerVTable = RawWakerVTable::new(clone, noop, noop, noop);
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RawWaker::new(std::ptr::null(), &VT)
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}
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fn block_on<F: Future>(mut f: F) -> F::Output {
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let waker = unsafe { Waker::from_raw(noop_raw()) };
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let mut cx = Context::from_waker(&waker);
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let mut f = unsafe { Pin::new_unchecked(&mut f) };
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loop {
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if let Poll::Ready(v) = f.as_mut().poll(&mut cx) {
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return v;
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}
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}
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}
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struct Yield(bool);
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impl Future for Yield {
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type Output = ();
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fn poll(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<()> {
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if self.0 { Poll::Ready(()) } else { self.0 = true; Poll::Pending }
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}
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}
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async fn sum(n: u32) -> u32 {
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if n == 0 {
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0
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} else {
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Yield(false).await;
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n + Box::pin(sum(n - 1)).await
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}
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}
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async fn tree(depth: u32) -> u32 {
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if depth == 0 {
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return 1;
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}
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let left = Box::pin(tree(depth - 1)).await;
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Yield(false).await;
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let right = Box::pin(tree(depth - 1)).await;
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left + right
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}
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#[test]
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fn boxed_self_recursion() {
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assert_eq!(block_on(sum(10)), 55);
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assert_eq!(block_on(tree(5)), 32);
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}
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