bsl::optional::operator=

Assign to this object the value of the specified rhs object converted to t_TYPE, and return a reference providing modifiable access to this object. Note that this method may invoke assignment from rhs, or construction from rhs, depending on whether this object is engaged. This assignment operator does not participate in overload resolution if t_ANY_TYPE is possibly cv‐qualified bsl::optional<t_TYPE>. Also note that an assignment of the form o = {};, where o is of type optional, will always assign to o the empty state, and never call this overload (see implementation notes). This assignment operator can be called in constant expressions only when t_TYPE is not allocator‐aware.