Function FindOneOrNone

cpp/src/arrow/type.h:2225–2232

  /// will be returned if none match.
  template <typename T>
  Result<FieldPath> FindOneOrNone(const T& root) const {
    auto matches = FindAll(root);
    ARROW_RETURN_NOT_OK(CheckNonMultiple(matches, root));
    if (matches.empty()) {
      return FieldPath();
    }
    return std::move(matches[0]);
  }

  template <typename T>
  using GetType = decltype(std::declval<FieldPath>().Get(std::declval<T>()).ValueOrDie());