static void checkrepeated (LexState *ls, TString *name) {
  Labeldesc *lb = findlabel(ls, name);
  if (l_unlikely(lb != NULL)) {  /* already defined? */
    const char *msg = "label '%s' already defined on line %d";
    msg = luaO_pushfstring(ls->L, msg, getstr(name), lb->line);
    luaK_semerror(ls, msg);  /* error */
  }
}