def mySetCookie = if(cookies.length == 1) setCookie(cookies(0)) else if(cookies.length > 1) setCookie(cookies(0), cookies.tail: _*) else pass
def mySetHeader = if(headers.length > 0) respondWithHeaders(headers: _*) else pass

mySetCookie
{
  mySetHeader
  {
    complete(StatusCodes.OK)
  }
}

mySetCookie & mySetHeader
{
  complete(StatusCodes.OK)
}

Error:(116, 21) type mismatch;
found   : akka.http.scaladsl.server.Route
(which expands to)  akka.http.scaladsl.server.RequestContext => scala.concurrent.Future[akka.http.scaladsl.server.RouteResult]
required: akka.http.scaladsl.server.ConjunctionMagnet[Unit]