json: Qt6: Break changes

I have a large Qt C++ application that’s uses this nlohmann json library everywhere. Well, Qt has release the new Qt6 version in this week. So I just switch from Qt 5.15.0 to the Qt6 and tried to compile my C++ project and I got some compile time warnings and errors related with nlohmann json library.

Warning message 1:

/home/nyck/Qt6/6.0.0/gcc_64/include/QtCore/qglobal.h:1126: warning: ‘void QtPrivate::warnIfContainerIsNotShared(...) [with T = std::__cxx11::list<QString>]’ is deprecated: Do not use foreach/Q_FOREACH with containers which are not implicitly shared. Prefer using a range-based for loop with these containers: `for (const auto &it : container)`, keeping in mind that range-based for doesn't copy the container as Q_FOREACH does [-Wdeprecated-declarations]
In file included from ../../../../Qt6/6.0.0/gcc_64/include/QtGui/qtguiglobal.h:43,
                 from ../../../../Qt6/6.0.0/gcc_64/include/QtWidgets/qtwidgetsglobal.h:43,
                 from ../../../../Qt6/6.0.0/gcc_64/include/QtWidgets/qmainwindow.h:43,
                 from ../../../../Qt6/6.0.0/gcc_64/include/QtWidgets/QMainWindow:1,
                 from ../../rotortest/App/app.h:4,
                 from ../../rotortest/App/app.cpp:1:
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qglobal.h: In instantiation of ‘QtPrivate::QForeachContainer<typename std::decay<_Tp>::type> QtPrivate::qMakeForeachContainer(T&&) [with T = const std::__cxx11::list<QString>&; typename std::decay<_Tp>::type = std::__cxx11::list<QString>]’:
../../rotortest/App/app.cpp:320:5:   required from here
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qglobal.h:1126:61: warning: ‘void QtPrivate::warnIfContainerIsNotShared(...) [with T = std::__cxx11::list<QString>]’ is deprecated: Do not use foreach/Q_FOREACH with containers which are not implicitly shared. Prefer using a range-based for loop with these containers: `for (const auto &it : container)`, keeping in mind that range-based for doesn't copy the container as Q_FOREACH does [-Wdeprecated-declarations]
 1126 |     warnIfContainerIsNotShared<typename std::decay<T>::type>(0);
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qglobal.h:1120:13: note: declared here
 1120 | inline void warnIfContainerIsNotShared(...) {}
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~

Error message 1:

/usr/include/c++/9/type_traits:131: error: incomplete type ‘QTypeTraits::detail::expand_operator_equal_container<nlohmann::basic_json<>, true>’ used in nested name specifier
In file included from /usr/include/c++/9/bits/move.h:55,
                 from /usr/include/c++/9/bits/stl_pair.h:59,
                 from /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/memory:62,
                 from moc_form_pipeline.cpp:9:
/usr/include/c++/9/type_traits: In instantiation of ‘struct std::__and_<QTypeTraits::detail::expand_operator_equal_container<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >, true>, QTypeTraits::detail::expand_operator_equal_tuple<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > > > >’:
/usr/include/c++/9/type_traits:155:12:   required from ‘struct std::conjunction<QTypeTraits::detail::expand_operator_equal_container<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >, true>, QTypeTraits::detail::expand_operator_equal_tuple<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > > > >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:260:8:   required from ‘struct QTypeTraits::detail::expand_operator_equal_container<nlohmann::basic_json<>, true>’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:324:8:   required from ‘struct QTypeTraits::has_operator_equal<nlohmann::basic_json<> >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:326:23:   required from ‘constexpr const bool QTypeTraits::has_operator_equal_v<nlohmann::basic_json<> >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2123:67:   required from ‘constexpr const QtPrivate::QMetaTypeInterface QtPrivate::QMetaTypeInterfaceWrapper<nlohmann::basic_json<> >::metaType’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2377:16:   required from ‘constexpr const QtPrivate::QMetaTypeInterface* QtPrivate::qTryMetaTypeInterfaceForType() [with Unique = qt_meta_stringdata_Form_Pipeline_t; TypeCompletePair = QtPrivate::TypeAndForceComplete<const nlohmann::basic_json<>&, std::integral_constant<bool, false> >]’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2421:55:   required from ‘constexpr const QtPrivate::QMetaTypeInterface* const qt_incomplete_metaTypeArray [14]<qt_meta_stringdata_Form_Pipeline_t, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const QString&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const MSG_TYPE, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const QString&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> > >’
moc_form_pipeline.cpp:155:1:   required from here
/usr/include/c++/9/type_traits:131:12: error: incomplete type ‘QTypeTraits::detail::expand_operator_equal_container<nlohmann::basic_json<>, true>’ used in nested name specifier
  131 |     struct __and_<_B1, _B2>
      |            ^~~~~~~~~~~~~~~~

Error message 2:

/usr/include/c++/9/type_traits:131: error: incomplete type ‘QTypeTraits::detail::expand_operator_less_than_container<nlohmann::basic_json<>, true>’ used in nested name specifier
In file included from /usr/include/c++/9/bits/move.h:55,
                 from /usr/include/c++/9/bits/stl_pair.h:59,
                 from /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/memory:62,
                 from moc_form_pipeline.cpp:9:
/usr/include/c++/9/type_traits: In instantiation of ‘struct std::__and_<QTypeTraits::detail::expand_operator_less_than_container<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >, true>, QTypeTraits::detail::expand_operator_less_than_tuple<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > > > >’:
/usr/include/c++/9/type_traits:155:12:   required from ‘struct std::conjunction<QTypeTraits::detail::expand_operator_less_than_container<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >, true>, QTypeTraits::detail::expand_operator_less_than_tuple<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > > > >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:296:8:   required from ‘struct QTypeTraits::detail::expand_operator_less_than_container<nlohmann::basic_json<>, true>’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:329:8:   required from ‘struct QTypeTraits::has_operator_less_than<nlohmann::basic_json<> >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qtypeinfo.h:331:23:   required from ‘constexpr const bool QTypeTraits::has_operator_less_than_v<nlohmann::basic_json<> >’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2139:71:   required from ‘constexpr const QtPrivate::QMetaTypeInterface QtPrivate::QMetaTypeInterfaceWrapper<nlohmann::basic_json<> >::metaType’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2377:16:   required from ‘constexpr const QtPrivate::QMetaTypeInterface* QtPrivate::qTryMetaTypeInterfaceForType() [with Unique = qt_meta_stringdata_Form_Pipeline_t; TypeCompletePair = QtPrivate::TypeAndForceComplete<const nlohmann::basic_json<>&, std::integral_constant<bool, false> >]’
../../../../Qt6/6.0.0/gcc_64/include/QtCore/qmetatype.h:2421:55:   required from ‘constexpr const QtPrivate::QMetaTypeInterface* const qt_incomplete_metaTypeArray [14]<qt_meta_stringdata_Form_Pipeline_t, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer, std::vector<unsigned char, std::allocator<unsigned char> > >&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const QString&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const MSG_TYPE, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<const QString&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> > >’
moc_form_pipeline.cpp:155:1:   required from here
/usr/include/c++/9/type_traits:131:12: error: incomplete type ‘QTypeTraits::detail::expand_operator_less_than_container<nlohmann::basic_json<>, true>’ used in nested name specifier
  131 |     struct __and_<_B1, _B2>
      |            ^~~~~~~~~~~~~~~~

What can I do? How to fix it?

Thank you,

My system:

• Ubuntu 20.04 x64
• Qt 5.15.0 and Qt 6.0.0
• nlohmann JSON version 3.8.0
• Qt Creator IDE 4.13.3