{ // with boost optional

basic_multi_buffer const* b_;

friend class basic_multi_buffer;

explicit

const_buffers_type(basic_multi_buffer const& b);

const_buffers_type() = delete;

const_buffers_type(const_buffers_type const&) = default;

const_buffers_type& operator=(const_buffers_type const&) = default;

{

// test if it even compiles

boost::optional< std::pair<const_buffers_type, int> > opt, opt2;

opt = opt2;

(void)opt;

{

// test if it even compiles

boost::optional<NotDefaultConstructible> opt, opt2;

opt = opt2;

(void)opt;

{

test_beast_example();

test_assign_for_non_default_constructible();