One more thing, this idea has not to ship in the first implementation or ever, but I'd like to explore it at least here publicly. Can we potentially improve the way how we can have a 'safer' property delegate that will have a non-optional value, but the delegating computed property can stay optional?
For example UIApplicationDelegate requires a var window: UIWindow? { get set } member, but in reality most application have a non-optional root window. It would be cool to have a property delegate that implements the optional delegating property with a non-optional value (potentially delayed).