[Observations] Prevent duplicate emissions on re-iterating Observations after cancellation #86145
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…ns after cancellation Fix swiftlang#85683: avoid duplicated values when re-iterating `Observations` after cancelling a prior iteration. This changes `Observations` to allocate its internal `_ManagedCriticalState<State>` per iterator (in `makeAsyncIterator()`), rather than sharing a single state across all iterations. Sharing state allowed change notifications from a cancelled iteration to interfere with subsequent iterations, resulting in duplicated emissions.
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Fix duplicated emissions when re-iterating
Observationsafter cancelling a prior iteration by allocating internal state per iterator (instead of sharing state across iterations).Stdlib Observation change; alters internal iteration-state lifetime (sequence-scoped → iterator-scoped). No API surface change, but behavior changes for code that (implicitly) relied on cross-iterator state sharing.
Resolves [Observations] Subsequent iteration on Observations receives double values #85683
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Low–medium. Changes internal state sharing semantics between iterators; could affect any undocumented reliance on shared
dirty/continuationbookkeeping across multiple iterators.Not tested on any platform.
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