What is a Function-local static in Swift?

[Martin (Martin R)]

I do not know for sure if that is what the article refers to, but you can define a function-local struct with a static property:

func f () {
    struct S {
        static var u: Int = 7
    }
}

See also:

Why can't functions have static variables?

I'm sure this has been brought up before but as I couldn't find any previous discussion on it: The following is not allowed: func next() -> Int { static var v = 0 // ERROR: Static properties may only be declared on a type v += 1 return v } But it is trivial to work around this: func next() -> Int { struct S { static var v = 0 } S.v += 1 return S.v } print(next()) // 1 print(next()) // 2 print(next()) // 3 So what is the rationale behind not allowing static variables …