Method subspan

test/buffer.cpp:80–81

  std::size_t size() const { return 0; }
  friend span<const T, Extent> as_bytes(const span&) { return {}; }
  span<T, static_cast<std::size_t>(-1)>
    subspan(std::size_t, std::size_t = 0) const { return {}; }
};

template <typename T, std::size_t Extent>