relates to:

• SR-11688 Swift should consider functions with default args ambiguous when there is another function with an identical signature

Issue Description:

When a method in a class that has arguments with default values clashes with other methods in a superclass, the compiler should warn the user that the method won't ever be called with those default arguments.

A common scenario is with init in UIKit code.

class Subview: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        print("init frame")
    }
    
    init(other: Int = 0) {
        super.init(frame: .zero)
        print("init other \(other)")
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

let sub = Subview()

In the above example the second init won't ever be called with the default argument, as Swift will always prefer the superclass (UIView) init with zero arguments. This can be misleading and a cause of bugs.

As Jordan pointed out on Twitter the general case is tricky but it may be worth adding some diagnostics to the simple case.