[SR-12529] @NSCopying attribute not working in final class

[swift-ci]

Previous ID	SR-12529
Radar	rdar://problem/62201660
Original Reporter	sh-a-n (JIRA User)
Type	Bug

Attachment: Download

Environment

xCode 11.4

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | Bug, PropertyWrappers | |Assignee | None | |Priority | Medium | md5: 0a3413c9b5880fdad2a5640dfab27de7

Issue Description:

Marking class as final makes @NSCopying attribute not working at all.

Example of bug in attachments.

//
import UIKit

class MyClass: NSCopying {
    var a: Int

    init(a: Int) {
        self.a = a
    }

    func copy(with zone: NSZone? = nil) -> Any {
        print(#function)
        return MyClass(a: self.a)
    }
}

class CopyingContainerWithoutFinal {
    @NSCopying var value: MyClass?
}

final class CopyingContainerWithFinal {
    @NSCopying var value: MyClass?
}

class ContainerWithoutNSCopying {
    var value: MyClass?
}

let c1 = MyClass(a: 0)

let container1 = CopyingContainerWithoutFinal()
let container2 = CopyingContainerWithFinal()
let container3 = ContainerWithoutNSCopying()

container1.value = c1
container2.value = c1
container3.value = c1

let value1 = container1.value
let value2 = container2.value

c1.a = 1

print(container1.value!.a) // Must print 0.
print(container2.value!.a) // Must print 0, but actually prints 1. Bug?
print(container3.value!.a) // Must print 1.

[beccadax]

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