struct Cat { subscript(ex ex: Void) -> Ex<Cat> { get { return Ex(self) } set { self = newValue.t } } var age: Int = 3 } struct Ex<T> { init(_ t: T) { self.t = t } var t: T } var cat = Cat() cat[ex: ()].t.age = 6 print(cat) // Cat(age: 6)struct Cat { subscript(ex ex: Void) -> Ex<Cat> { get { return Ex(self) } set { self = newValue.t } } var age: Int = 3 } struct Ex<T> { init(_ t: T) { self.t = t } var t: T } var cat = Cat() cat[ex: ()].t.age = 6 print(cat) // Cat(age: 6)