id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12652	boost::optional<DefaultConstructable>::operator= chooses wrong overload for {}	mathias@…	Fernando Cacciola	"{{{
boost::optional<int> op = 5; // creates engaged optional
op = {}; // currently does op = 0;
}}}

For most types operator={} assigns from a value-constructed value of that type. That is the behavior of std::experimental::optional but not boost::optional<T>. It chooses the T&& overload. I think the standard avoids it by having the assign-from-T operator= be templated on U instead, which doesn't match {}.

"	Bugs	closed	Boost 1.63.0	optional	Boost 1.63.0	Problem	fixed