Why are default arguments not allowed in protocols?

[tera]

But you may make a bug, for example, somone changes signature:

protocol A {
    func myFunction(argument: Int)
}
extension A {
    // this will cause stack overflow:
    func myFunc(arg: Int = 1) {
        myFunc(arg: arg)
    }
}

This is how to overcome stack overflow: (snipped)

the proper fix (not in swift currently).