id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12802	optional<recursive_wrapper> is broken in 1.63	pal666@…	Fernando Cacciola	"{{{
boost::optional<boost::recursive_wrapper<int> > o;
o = 1;
}}}
gcc says error: no match for 'operator=' (operand types are 'boost::optional<boost::recursive_wrapper<int> >' and 'int')

i found the reason for failure:
is_convertible_to_T_or_factory checks is_constructinble<T, U&&>, which means <recursive_wrapper<U>, U'''&&'''>, while recursive wrapper specializes only <recursive_wrapper<T>,T> (no '''&&''') as true and <recursive_wrapper<T>,U> (catches U=T'''&&''') as false

i don't know who is wrong - recursive_wrapper or optional
it can be fixed either by adding
{{{
template <class T> struct is_constructible < recursive_wrapper < T>, T &&> : boost::true_type{};
}}}
to recursive_wrapper or by changing boost::is_constructible<T, U'''&&'''> to boost::is_constructible<T, U> in is_convertible_to_T_or_factory
"	Bugs	new	To Be Determined	optional	Boost 1.63.0	Regression