/home/dac/CLion/bin/cmake/bin/cmake --build /home/dac/boost_variant_apply_visitor_error/cmake-build-debug --target boost_visitor_error -- -j 2 Scanning dependencies of target boost_visitor_error [ 50%] Building CXX object CMakeFiles/boost_visitor_error.dir/main.cpp.o In file included from /usr/include/boost/variant/apply_visitor.hpp:16:0, from /home/dac/boost_variant_apply_visitor_error/main.cpp:2: /usr/include/boost/variant/detail/apply_visitor_unary.hpp: In instantiation of ‘static decltype(auto) boost::detail::variant::result_multideduce1::deduce_impl(boost::detail::variant::result_multideduce1::last_it, unsigned int) [with Visitor = const main(int, char**)::; Variant = boost::variant; boost::detail::variant::result_multideduce1::last_it = boost::mpl::l_iter, double, boost::mpl::l_end> >]’: /usr/include/boost/variant/detail/apply_visitor_unary.hpp:120:31: required from ‘static decltype(auto) boost::detail::variant::result_multideduce1::deduce_impl(It, unsigned int) [with It = boost::mpl::l_iter, int, boost::mpl::l_item, double, boost::mpl::l_end> > >; Visitor = const main(int, char**)::; Variant = boost::variant]’ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:127:27: required from ‘static decltype(auto) boost::detail::variant::result_multideduce1::deduce() [with Visitor = const main(int, char**)::; Variant = boost::variant]’ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:134:67: required from ‘struct boost::detail::variant::result_wrapper1, boost::variant >’ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:165:71: required from ‘decltype(auto) boost::apply_visitor(const Visitor&, Visitable&, typename boost::disable_if >::type*) [with Visitor = main(int, char**)::; Visitable = boost::variant; typename boost::disable_if >::type = void]’ /home/dac/boost_variant_apply_visitor_error/main.cpp:34:21: required from here /usr/include/boost/variant/detail/apply_visitor_unary.hpp:112:21: error: no match for call to ‘(const main(int, char**)::) (double&)’ return vis()( boost::declval< value_t& >() ); ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /home/dac/boost_variant_apply_visitor_error/main.cpp:31:78: note: candidate: main(int, char**):: mutable [with auto:2 = double] [capturedNumber = std::move(number)](const auto& msg) mutable -> auto { ^~~~ /home/dac/boost_variant_apply_visitor_error/main.cpp:31:78: note: passing ‘const main(int, char**)::*’ as ‘this’ argument discards qualifiers In file included from /usr/include/boost/variant/apply_visitor.hpp:16:0, from /home/dac/boost_variant_apply_visitor_error/main.cpp:2: /usr/include/boost/variant/detail/apply_visitor_unary.hpp: In instantiation of ‘static decltype(auto) boost::detail::variant::result_multideduce1::deduce_impl(It, unsigned int) [with It = boost::mpl::l_iter, int, boost::mpl::l_item, double, boost::mpl::l_end> > >; Visitor = const main(int, char**)::; Variant = boost::variant]’: /usr/include/boost/variant/detail/apply_visitor_unary.hpp:127:27: required from ‘static decltype(auto) boost::detail::variant::result_multideduce1::deduce() [with Visitor = const main(int, char**)::; Variant = boost::variant]’ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:134:67: required from ‘struct boost::detail::variant::result_wrapper1, boost::variant >’ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:165:71: required from ‘decltype(auto) boost::apply_visitor(const Visitor&, Visitable&, typename boost::disable_if >::type*) [with Visitor = main(int, char**)::; Visitable = boost::variant; typename boost::disable_if >::type = void]’ /home/dac/boost_variant_apply_visitor_error/main.cpp:34:21: required from here /usr/include/boost/variant/detail/apply_visitor_unary.hpp:123:21: error: no match for call to ‘(const main(int, char**)::) (int&)’ return vis()( boost::declval< value_t& >() ); ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /home/dac/boost_variant_apply_visitor_error/main.cpp:31:78: note: candidate: main(int, char**):: mutable [with auto:2 = int] [capturedNumber = std::move(number)](const auto& msg) mutable -> auto { ^~~~ /home/dac/boost_variant_apply_visitor_error/main.cpp:31:78: note: passing ‘const main(int, char**)::*’ as ‘this’ argument discards qualifiers In file included from /usr/include/boost/variant/apply_visitor.hpp:16:0, from /home/dac/boost_variant_apply_visitor_error/main.cpp:2: /usr/include/boost/variant/detail/apply_visitor_unary.hpp:123:52: error: return-statement with a value, in function returning 'void' [-fpermissive] return vis()( boost::declval< value_t& >() ); ^ /usr/include/boost/variant/detail/apply_visitor_unary.hpp:137:14: error: ‘boost::detail::variant::result_wrapper1::result_wrapper1(Visitor&) [with Visitor = const main(int, char**)::; Variant = boost::variant]’, declared using local type ‘const main(int, char**)::’, is used but never defined [-fpermissive] explicit result_wrapper1(Visitor& visitor) BOOST_NOEXCEPT ^~~~~~~~~~~~~~~ In file included from /home/dac/boost_variant_apply_visitor_error/main.cpp:3:0: /usr/include/boost/variant/variant.hpp:2428:5: warning: ‘typename Visitor::result_type boost::variant::apply_visitor(Visitor&) [with Visitor = boost::detail::variant::result_wrapper1, boost::variant >; T0_ = int; TN = {double}]’ used but never defined apply_visitor(Visitor& visitor) ^~~~~~~~~~~~~ In file included from /usr/include/boost/variant/apply_visitor.hpp:16:0, from /home/dac/boost_variant_apply_visitor_error/main.cpp:2: /usr/include/boost/variant/detail/apply_visitor_unary.hpp:137:14: warning: ‘boost::detail::variant::result_wrapper1::result_wrapper1(Visitor&) noexcept [with Visitor = const main(int, char**)::; Variant = boost::variant]’ used but never defined explicit result_wrapper1(Visitor& visitor) BOOST_NOEXCEPT ^~~~~~~~~~~~~~~ make[3]: *** [CMakeFiles/boost_visitor_error.dir/build.make:63: CMakeFiles/boost_visitor_error.dir/main.cpp.o] Error 1 make[2]: *** [CMakeFiles/Makefile2:68: CMakeFiles/boost_visitor_error.dir/all] Error 2 make[1]: *** [CMakeFiles/Makefile2:80: CMakeFiles/boost_visitor_error.dir/rule] Error 2 make: *** [Makefile:118: boost_visitor_error] Error 2