Hi all, swift_dynamicCastClassUnconditional <https://github.com/apple/swift/blob/3d2b5bcc5350e1dea2ed8a0a95cd12ff5c760f24/stdlib/public/runtime/Casting.cpp#L508> and swift_dynamicCastObjCClassUnconditional <https://github.com/apple/swift/blob/2daa1400cf79a2965eb07034b48ef7fae02459fd/stdlib/public/runtime/SwiftObject.mm#L1155> methods behave differently while verifying casting.
swift_dynamicCastObjCClassUnconditional <https://github.com/apple/swift/blob/2daa1400cf79a2965eb07034b48ef7fae02459fd/stdlib/public/runtime/SwiftObject.mm#L1155> method calls *-isKindOfClass:* method before falling back to *object_getClass* function. swift_dynamicCastClassUnconditional <https://github.com/apple/swift/blob/3d2b5bcc5350e1dea2ed8a0a95cd12ff5c760f24/stdlib/public/runtime/Casting.cpp#L508> method calls *swift_dynamicCastClass* method which calls *_swift_getClassOfAllocated <https://github.com/apple/swift/blob/82509cbd7451e72fb99d22556ad259ceb335cb1f/stdlib/public/runtime/Private.h#L80>* method which calls directly *object_getClass* function. This causes problems if underlying object is an NSProxy subclass. NSProxy class does not implement *-isKindOfClass:* method, so calls to this method are forwarded to the real object through *-forwardInvocation:* method, which causes *-isKindOfClass:* method to return answer according to the real object's class. However, *object_getClass* function directly accesses to the metadata of the given object, so it returns NSProxy subclass. I think this is a conflicting behavior, and I think swift_dynamicCastClassUnconditional <https://github.com/apple/swift/blob/3d2b5bcc5350e1dea2ed8a0a95cd12ff5c760f24/stdlib/public/runtime/Casting.cpp#L508> method should also verify first using *-isKindOfClass:* method, in order to provide consistency. What do you think? Best
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