In Swift, how do I add a setter to immutable GLKit vector structs?

In Swift GLKit vectors are immutable structs:

public struct _GLKVector2 {


    public var v: (Float, Float)

    public init(v: (Float, Float))

    public init()
}

extension GLKVector2 {

    public var x: Float { get }

    public var y: Float { get }

    public var s: Float { get }

    public var t: Float { get }

    public subscript(i: Int) -> Float { get }
}
public typealias GLKVector2 = _GLKVector2

I find this a bit restrictive and would like to extend GLKVector2 to include corresponding setters. How do I do this?

You could create a mutating func that replaces the whole self.

extension GLKVector2 {
    mutating func setX(_ x: Float) {
        self = GLKVector2Make(x, y)
    }
}

...

v2.setX(123)

You could create a property as well, but be careful you will need to write your own getter as well, and you can't return self.x there.

var x: Float {
    get {
        return v.0
        // Note:
        //  1. you need to use a getter
        //  2. you cannot `return x`, otherwise it will be an infinite recursion
    }
    set {
        self = GLKVector2Make(newValue, y)
    }
}