case and call-by-name?

desired.scala

receive("hallo") {
  case "hallo" => "selber" // selber should not be evaluated at this point
} // result Some(selber)

working.scala

def receive[T](data: String)(fun: PartialFunction[String, Function0[T]]): Option[T] = {
  val action = fun orElse new PartialFunction[String, Function0[T]] {
    def isDefinedAt(str: String) = true
    def apply(str: String) = () => {
      println("no match :(")
      null.asInstanceOf[T]
    }
  } apply data
  Some(action()).filter(null ne)
}

receive("hallo") {
  case "hallo" => () => { "selber" }
} // result: Some(selber)

receive("test") {
  case "hallo" => () => { "selber" }
} // result: None