trait Iface[B, C] {
    def meth(b: B): C
}

def polish[B, C](f: (Iface[B, C], B) => C): (Iface[B, C], B) => C = { (a, b) =>
    f(a, b)
}

object IfaceImpl extends Iface[String, String] {
    override def meth(b: String): String = b.reverse
}

polish((a: Iface[String, String], b: String) => a meth b)(IfaceImpl, "hello")