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poll_recv was previously unimplemented. The new implementation stores a persistent Acquire future in ReceiverInternal so the semaphore waiter stays registered across polls. When the channel is empty, the caller is properly suspended via the semaphore waiter queue until a message arrives or the channel closes. recv, try_recv, and blocking_recv are reimplemented atop poll_recv so that semaphore interaction is centralized in a single code path. try_recv polls once with a noop waker and clears the pending acquire on Pending; recv uses poll_fn; blocking_recv uses block_on(recv). The Acquire future borrows recv_semaphore behind Arc<Channel>, with the lifetime transmuted to 'static. This is sound because pending_acquire is always cleared before chan is dropped. Add parity tests for bounded and unbounded poll_recv, plus a test that interleaves poll_recv with recv to verify no permit leak. 🤖 Assisted by AI Cherry-picked from ShuttleTokio commit fb6e01b7, with poll_recv_then_recv_no_leak changed to use a capacity-1 channel so that a leaked permit is actually observable (it would deadlock the send) rather than being masked by the spare capacity.
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poll_recv was previously unimplemented. The new implementation
stores a persistent Acquire future in ReceiverInternal so the
semaphore waiter stays registered across polls. When the channel
is empty, the caller is properly suspended via the semaphore
waiter queue until a message arrives or the channel closes.
recv, try_recv, and blocking_recv are reimplemented atop poll_recv
so that semaphore interaction is centralized in a single code path.
try_recv polls once with a noop waker and clears the pending acquire
on Pending; recv uses poll_fn; blocking_recv uses block_on(recv).
The Acquire future borrows recv_semaphore behind Arc,
with the lifetime transmuted to 'static. This is sound because
pending_acquire is always cleared before chan is dropped.
Add parity tests for bounded and unbounded poll_recv, plus a test
that interleaves poll_recv with recv to verify no permit leak.
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.