On Sat, Jan 7, 2017 at 5:33 PM, Braeden Profile <[email protected]>
wrote:
>
>> Of course, I would love being able to use an initializer setup, but there
>> are serious bugs in the implementation.
>>
>> protocol Clonable
>> {
>> init(other: Self)
>> }
>>
>> extension Clonable
>> {
>> func clone() -> Self
>> { return type(of: self).init(other: self) }
>> }
>>
>>
>> class Base: Clonable
>> {
>> var x: Int
>>
>> init(x: Int)
>> { self.x = x }
>>
>> required init(other: Base)
>> { self.x = other.x }
>> }
>>
>> class Derived: Base
>> {
>> var y: String
>>
>> init(x: Int, y: String)
>> {
>> self.y = y
>> super.init(x: x)
>> }
>>
>> // Should be required by the Clonable protocol, but it isn't.
>> required init(other: Derived)
>> {
>> self.y = other.y
>> super.init(other: other)
>> }
>>
>> // Required because it was `required` in Base. Even a `Derived` calls
>> this initializer to clone, which is wrong. Bugs abound.
>> required init(other: Base)
>> { fatalError("init(other:) is wrong.") }
>> }
>>
>>
>>
>> let me = Derived(x: 1, y: "food")
>> let alienClone = me.clone() // "init(other:) is wrong."
>>
>>
> Agree. That seems wrong. Great example.
>
>
> So, is this odd behavior intentional, a bug, or a design deficiency? I
> would think that when a protocol has a method or initializer has `Self`
> parameters—like in Clonable—every subclass would be required to implement
> its own specialized version (much like a required initializer). That would
> be a special case of the protocol system, though.
>
> As it sits, even fixing the calling behavior of my example leaves us with
> the problem of subclasses inheriting inapplicable required initializers
> from superclasses that actually don’t make any sense.
>
> Does this deserve its own thread?
>
Dunno, maybe best to have its own thread. It's not mentioned as part of
SE-0068, but IMO a complete design that respects the spirit of that
proposal *should* involve allowing you to write:
```
class Base : Clonable {
required init(other: Self) { ... }
}
class Derived : Base {
required init(other: Self) { ... }
}
```
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