[pull] swiftwasm from main #4350
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During actor isolation inference, we would unconditionally choose the isolation of the overridden decl (when, say, there is no attribute on the decl). The overridden decl is identified with `getOverriddenDecl`. This works mostly fine, but initializers have some unusual overridden decls returned by that method. For example, in the following code: ```swift @objc class PictureFrame: NSObject { init(size: Int) { } } @mainactor class FooFrame: PictureFrame { init() { super.init(size: 0) } } ``` that method claims that `FooFrame.init()` overrides `PictureFrame.init()`, when it really does not! So, if we were to unconditionally take the isolation from `PictureFrame.init()` (and thus `NSObject.init()`), then we'd infer that `FooFrame.init()` has unspecified isolation, despite the nominal it resides in being marked as `MainActor`. This is in essence the problem in SR-15694, where placing the isolation directly on the initializer fixes this issue. If `FooFrame.init()` really does override, then why can it be `MainActor`? Well, we have a rule in one part of the type-checker saying that if an ObjC-imported decl has unspecified isolation, then overriding it with isolation is permitted. But the other part of the type-checker dealing with the isolation inference was not permitting that. So, this patch unifies how actor-isolation inference is conducted to reuse that same logic. In addition, the inference now effectively says that, if the decl has no inferred isolation, or the inferred isolation is invalid according to the overriding rules, then we use the isolation of the overridden decl. This preserves the old behavior of the inference, while also fixing this issue with ObjC declarations by expanding where isolation is allowed. For example, as a consequence of this change, in the following code: ```swift @mainactor class FooFrame: NotIsolatedPictureFrame { override func rotate() { mainActorFn() } } ``` if `NotIsolatedPictureFrame` is a plain-old not-isolated class imported from Objective-C, then `rotate` will now have `MainActor` isolation, instead of having unspecified isolation like it was inferred to have previously. This helps make things consistent, because `rotate` is allowed to be `@MainActor` if it were explicitly marked as such. resolves rdar://87217618 / SR-15694
This reverts commit c194d1c.
[SR-15694] make isolation inference + override more consistent
Revert "visualc: clean up the module definition"
Fix error in MutableCollection.shuffle() docs
MaxDesiatov
approved these changes
Mar 8, 2022
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