Mutating self (struct/enum) inside escaping closure in Swift 3.0

Question

In swift 2.2, We could mutate a struct or enum within a closure, when it was inside a mutating function. But in swift 3.0 its no longer possible. I get the following error

Answer 1

Struct is value type. So when use as Model or ModelView, you can make up a closure with new Value to VC.

struct Point {
    var x = 0.0, y = 0.0

    mutating func moveBy(x deltaX: Double, y deltaY: Double) {
        x += deltaX
        y += deltaY

        test { [x, y](a) -> Point in
            // Get the Error in the below line.
            return Point(x: Double(a), y: y)
        }

    }

    mutating func test(myClosure: @escaping (_ a: Double) -> Point) {
        self = myClosure(3)
    }
}