rdar://127199021, fix compatibility with apps that accidentally do [[[aSwiftArray class] new] mutableCopy] #73755

Catfish-Man merged 1 commit intoswiftlang:release/6.0swiftlang/swift:release/6.0from

Catfish-Man:when-is-an-array-not-an-array-6.0Catfish-Man/swift:when-is-an-array-not-an-array-6.0Copy head branch name to clipboard