[6.0] Teach #isolation to respect the flow-sensitive nature of actor initializers #74245
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…ializers Actor initializers have a flow-sensitive property where they are isolated to the actor being initialized only after the actor instance itself is fully-initialized. However, this behavior was not being reflected in the expansion of `#isolation`, which was always expanding to `self`, even before `self` is fully formed. This led to a source compatibility issue with code that used the async for..in loop within an actor initializer *prior* to the point where the actor was fully initialized, because the type checker is introducing the `#isolation` (SE-0421) but Definite Initialization properly rejects the use of `self` before it is initialized. Address this issue by delaying the expansion of `#isolation` until after the actor is fully initialized. In SILGen, we introduce a new builtin for this case (and *just* this case) called `flowSensitiveSelfIsolation`, which takes in `self` as its argument and produces an `(any Actor)?`. Definite initialization does not treat this as a use of `self`. Rather, it tracks these builtins and replaces them either with `self` (if it is fully-initialized at this point) or `nil` (if it is not fully-initialized at this point), mirroring the flow-sensitive isolation semantics described in SE-0327. Fixes rdar://127080037.
Distributed actors can be treated as actors by accessing the `asLocalActor` property. When lowering `#isolation` in a distributed actor initializer, use a separate builtin `flowSensitiveDistributedSelfIsolation` to capture the conformance to `DistributedActor`, and have Definite Initialization introduce the call to the `asLocalActor` getter when needed.
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@swift-ci please test |
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Hmph, failures are unrelated to this change. |
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@swift-ci please test Windows |
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@swift-ci please test macOS |
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@swift-ci please test Windows |
hborla
approved these changes
Jun 11, 2024
ktoso
approved these changes
Jun 11, 2024
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@swift-ci please test |
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@swift-ci please test |
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Explanation: Perform flow-sensitive lowering of
#isolationwithin actor initializers so that it lowers tonilbefore the actor is fully-initialized andself(orself.asLocalActorin the distributed case) after the actor is fully-initialized.Original PR: #74225
Radar/issue: rdar://127080037
Reviewed by: @ktoso
Risk: Low. Only affects actor initializers that use
#isolationor the asynchronous for-in loop on new-enough platforms (where the newAsyncIteratorProtocol.next(isolation:)is present).