@swift-4.2.4
class Animal : Hashable { static func ==(a: Animal, b: Animal) -> Bool { return a === b } func hash(into hasher: inout Hasher) { hasher.combine(ObjectIdentifier(self)) } } class Cat : Animal {} class Dog : Animal {} let a = Cat() let b: Animal = a let c: Animal = Dog() print(AnyHashable(a) == AnyHashable(c), 3)
(edited)