Unified implementation for withTimeout family#63
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On platforms with SwiftStdlib 6.2 (macOS/iOS/macCatalyst 26+), delegate to withTaskPriorityEscalationHandler. The new API is event-driven (no polling) and integrated with the runtime, so it reacts immediately to escalations. Mark the wrapper @available(..., deprecated: 26.0). Once the min deployment target reaches 26, the deprecation warning fires at every call site, prompting migration to withTaskPriorityEscalationHandler and removal of this wrapper. Change the function from `throws` to `rethrows` following the stdlib version. Also, use `RefBox<Atomic<_>>` for the previous priority storage. Atomic is lighter, and actually simplifies the code. The old codepath is extracted as a function and kept tested even on platforms with built-in withTaskPriorityEscalationHandler.
rintaro
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May 29, 2026
| if didHitTimeout.value { | ||
| await resultReceivedAfterTimeout(result) | ||
| } | ||
| continuation.yield(result) |
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I think there was actually a correctness issue here.
After didHitTimeout.value check passes but before continuation.yield(result), the timeout task might have set didHitTimeout and continuation.yield(nil). So the result is timeout but resultReceivedAfterTimeout never get called.
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Introduce `withTimeoutResult(_:body:resultReceivedAfterTimeout:)` as a unified core of the `withTimeout` family. The existing `withTimeout` overloads become thin `@inlinable` switches over `WithTimeoutResult`, forwarding errors via `rethrows`. `withTimeoutResult` supports an optional late-result callback. Late errors after the timeout are dropped silently because the callback signature accepts only the success value, so errors have nowhere to go. Implementation note: `bodyTask` itself yields its outcome onto the internal `AsyncStream` instead of a separate forwarder task. Adding a forwarder that awaits `bodyTask.result` proved unreliable — priority escalation through the await chain didn't always reach `bodyTask`, leaving `Task.currentPriority` inside `body` stuck at the original priority.
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Introduce
withTimeoutResult(_:body:resultReceivedAfterTimeout:)returning aWithTimeoutResult<T>enum (.result(Result<T>)/.timedOut). ExistingwithTimeoutoverloads become thin switches over it. The optional late-result callback receives successful late results only.withTaskPriorityChangedHandlernow delegates to stdlib'swithTaskPriorityEscalationHandleron macOS 26+, giving event-driven priority reaction instead of polling.Also
withTaskPriorityChangedHandlerand all thewithTimeoutoverloads are nowrethrows.Added some test cases to ensure old
withTaskPriorityChangedHandlerimplementation keep working even when testing withwithTaskPriorityEscalationHandler.