Issue Description:

The following code will crash when you instantiate (or in some cases use) C:

class S {
    let x: Int
    init(s: S) {
        self.x = s.x
    }
}

class C: S {
    init() {
        super.init(s: self)
    }
}

let c = C() // malloc: *** error for object 0x600000031244: Invalid pointer dequeued from free list

The compiler is allowing self to be passed to super.init, which should not be allowed.

If this is changed to init(s: AnyObject) (using type AnyObject rather than S), the compiler will generate the correct error. It seems specific to an init that accepts a parameter of the class's own type.