Obj-C class metatypes should never satisfy Obj-C existentials #69435
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Given this ``` @objc protocol P { func f() } class C: P { func f() {} } ``` the casts `C.self is any P` and `C.self as? any P` should always fail, because the metatype of `C.self` does not have an `f()` implementation. These casts previously succeeded because the runtime implementation deferred to Obj-C's `[o conformsToProtocol:p]`, and that behaves differently depending on whether `o` is a class instance or a Class itself. Since these casts should never succeed, I've just modified the Swift runtime logic to fail whenever the source of the cast is an Obj-C Class and the target is a protocol existential. Resolves: rdar://106973771
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@swift-ci Please test |
mikeash
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Oct 26, 2023
tbkka
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Jan 23, 2024
Revert "Obj-C class metatypes should never satisfy Obj-C existentials" (#69435)
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Given this
the casts
C.self is any PandC.self as? any Pshould always fail, because the metatype ofC.selfdoes not have anf()implementation.These casts previously succeeded because the runtime implementation deferred to Obj-C's
[o conformsToProtocol:p], and that behaves differently depending on whetherois a class instance or a Class itself.Since these casts should never succeed, I've just modified the Swift runtime logic to fail whenever the source of the cast is an Obj-C Class and the target is a protocol existential.
Resolves: rdar://106973771