  void visit(Repetition &ope) override {
    if (ope.min_ == 0) {
      set_error();
    } else {
      ope.ope_->accept(*this);
    }
  }
  void visit(Repetition &ope) override {
    if (ope.min_ == 0) {
      set_error();
    } else {
      ope.ope_->accept(*this);
    }
  }