Nil cannot be assigned to type ()->()?

Question

So this is a function from a class that lets you have a double tap and a single tap gesture. It\'s working fine in Swift 2.3, but after converting to Swift 3 it\'s throwing

Answer 1

From another topic:

func someFunction(someParameter: someType, completionClosure: @escaping @autoclosure () -> ()? = nil)

The use of @autoclosure allowed me to assign nil to the optional closure.

The full details of how exactly @autoclosure helps escape me (why "my" closure is "not good" but the Swift_generated_one_that_simply_wraps_mine is?) . But, it helped me get rid of ... ...and call my function in either of two ways:

someFunction(x, { ... }) 

OR

someFunction(x)