of ‘void boost::optional_detail::optional_base<T>::assign_value(boost::optional_detail::optional_base&]’
/stuff/boost/optional/optional.hpp:606:9: required from ‘boost::optio
\boost\dist\include\boost-1_66\boost\optional\optional.hpp(384): error C2280: 'Foo::Foo(const Foo &)'\boost\dist\include\boost-1_66\boost\optional\optional.hpp(383): note: while compiling class te
我尝试了下面的第一种方法,因为返回的是boost::optional。/optional/optional.hpp: In instantiation of ‘void boost::optional_detail::optional_base<T>::construct(boost::optional_detail::optional_base<T>::argument_