Method operator()

cpp/src/arrow/type.cc:1929–1931

  // flatten children
  struct Visitor {
    void operator()(std::string&& name, std::vector<FieldRef>* out) {
      out->push_back(FieldRef(std::move(name)));
    }

    void operator()(FieldPath&& path, std::vector<FieldRef>* out) {
      if (path.indices().empty()) {