static PopupMenu makePopupMenu(O... x) {
  if (l(x) == 1 && x[0] instanceof PopupMenu)
    ret (PopupMenu) x[0];
  new PopupMenu m;
  for (O o : x)
    if (eqOneOf(o, "***", "---", "===", ""))
      m.addSeparator();
    else if (o instanceof S || o instanceof Menu || o instanceof MenuItem)
      call(m, "add", o);
    else
      print("Unknown menu item: " + o);
  ret m;
}