https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99692
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #1) > Right the problem is here (and not with the compiler itself if there is a > problem): > /home/ubuntu/upstream-gcc/include/c++/11.0.1/ostream:747:46: error: no match > for ‘operator<<’ (operand types are ‘std::basic_ostream<char>’ and ‘const > std::vector<int>’) > 746 | __void_t<decltype(declval<_Ostream&>() > | ~~~~~~~~~~~~~~~~~~~~ > 747 | << declval<const > _Tp&>())>> > | ^~~~~~~~~~~~~~~~~~~~~~~~ > > > But by definition at this point operator << does not exist and is not > considered as it is not found via ADL because both std::basic_ostream<char> > and std::vector<int> are in the std namespace and the global namespace is > not considered. > > /home/ubuntu/upstream-gcc/include/c++/11.0.1/ostream:773:5: required by > substitution of ‘template<class _Ostream, class _Tp> typename > std::enable_if<std::__and_<std::__not_<std::is_lvalue_reference<_Tp> >, > std::__is_convertible_to_basic_ostream<_Ostream>, > std::__is_insertable<typename > std::__is_convertible_to_basic_ostream<_Tp>::__ostream_type, const _Tp&, > void> >::value, typename > std::__is_convertible_to_basic_ostream<_Tp>::__ostream_type>::type > std::operator<<(_Ostream&&, const _Tp&) [with _Ostream = CustomStream; _Tp = > std::vector<int>]’ > t78.cc:21:41: required from here > template<typename _Ostream, typename _Tp> > inline > typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>, > __is_convertible_to_basic_ostream<_Ostream>, > __is_insertable< > __rvalue_ostream_type<_Ostream>, > const _Tp&>>::value, > __rvalue_ostream_type<_Ostream>>::type > operator<<(_Ostream&& __os, const _Tp& __x) > > It is the __is_insertable in the above. > So it might be the wrong type being used to check __is_insertable .... If anything it is the __rvalue_ostream_type<_Ostream> part if I am reading this code correctly.
