rintaro

protocol AnimalProtocol {} extension AnimalProtocol { init(_with obj: Self) { self = obj } } class AnimalBase : AnimalProtocol { convenience init(with obj: AnimalBase) { self.init(_with: obj) } } class Cat: AnimalBase {} class Dog: AnimalBase {} var cat: Cat = Cat(with: Dog()) print(type(of: cat))

Version:

swift-4.1.1-RELEASE

Output:

Dog

Error: