template<class OtherElementType, size_t OtherByteAlignment>
  constexpr aligned_accessor(aligned_accessor<OtherElementType, OtherByteAlignment>) noexcept;
template<class OtherElementType>
  constexpr explicit aligned_accessor(default_accessor<OtherElementType>) noexcept;
constexpr reference access(data_handle_type p, size_t i) const noexcept;
template<class OtherElementType>
  constexpr operator default_accessor<OtherElementType>() const noexcept;
constexpr typename offset_policy::data_handle_type
  offset(data_handle_type p, size_t i) const noexcept;