function_obj.kt

class S {
    fun f(v: Int): String = "f"
}

fun main() {
    var sf: (S, Int) -> String = S::f
    var _sf: S.(Int) -> String = sf
    val sf1: String = sf(S(), 1)
    val sf2: String = _sf(S(), 1)
}

function_obj.swift

class S {
    func f(_ v: Int) -> String { return "f" }
}
var sf: (S) -> (Int) -> String = S.f
//var _sf: (S, Int) -> String = sf