Function ExtensionScalar

cpp/src/arrow/scalar.h:899–901

  using ValueType = std::shared_ptr<Scalar>;

  ExtensionScalar(std::shared_ptr<Scalar> storage, std::shared_ptr<DataType> type,
                  bool is_valid = true)
      : Scalar(std::move(type), is_valid), value(std::move(storage)) {}

  template <typename Storage,
            typename = enable_if_t<std::is_base_of<Scalar, Storage>::value>>