[Reg 5.15->6.0] Recursive QMap as MetaType cannot have key with custom operator==

class Input {
public:
    bool operator==(const Input &a) const
    {
        return false;
    }
    bool operator!=(const Input &a) const { return !(*this == a); }
};

class ModeMapping : public QMap<Input, ModeMapping>
{
};

Q_DECLARE_METATYPE(ModeMapping)

C:\PROGRA~2\MICROS~1\2019\BUILDT~1\VC\Tools\MSVC\1427~1.291\bin\HostX86\x64\cl.exe  /nologo /TP -DQT_CORE_LIB -DWIN32 -DWIN64 -D_ENABLE_EXTENDED_ALIGNED_STORAGE -D_WIN64 -I. -IC:\Users\ziller\Documents\untitled2 -Iuntitled2_autogen\include -IC:\Qt\6.1.0\msvc2019_64\include\QtCore -IC:\Qt\6.1.0\msvc2019_64\include -IC:\Qt\6.1.0\msvc2019_64\mkspecs\win32-msvc /DWIN32 /D_WINDOWS /W3 /GR /EHsc /MDd /Zi /Ob0 /Od /RTC1   -Zc:__cplusplus -permissive- -utf-8 -std:c++17 /showIncludes /FoCMakeFiles\untitled2.dir\main.cpp.obj /FdCMakeFiles\untitled2.dir\ /FS -c C:\Users\ziller\Documents\untitled2\main.cpp
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(54): error C2039: 'value': is not a member of 'QTypeTraits::has_operator_equal<T>'
        with
        [
            T=Ty
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): note: see declaration of 'QTypeTraits::has_operator_equal<T>'
        with
        [
            T=Ty
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(61): note: see reference to class template instantiation 'std::_Conjunction<true,_First,QTypeTraits::has_operator_equal<T>>' being compiled
        with
        [
            _First=QTypeTraits::has_operator_equal<Input>,
            T=Ty
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): note: see reference to class template instantiation 'std::conjunction<QTypeTraits::has_operator_equal<Key>,QTypeTraits::has_operator_equal<T>>' being compiled
        with
        [
            Key=Input,
            T=Ty
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(334): note: see reference to variable template 'const bool conjunction_v<QTypeTraits::has_operator_equal<Input>,QTypeTraits::has_operator_equal<ModeMapping> >' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmap.h(280): note: see reference to alias template instantiation 'QTypeTraits::compare_eq_result<Input,ModeMapping>' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmap.h(291): note: see reference to function template instantiation 'enable_if<std::conjunction_v<QTypeTraits::has_operator_equal<T>,QTypeTraits::has_operator_equal<AT>>,bool>::type operator !=(const QMap<Input,ModeMapping> &,const QMap<Input,ModeMapping> &)' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(324): note: see reference to alias template instantiation 'QTypeTraits::detail::expand_operator_equal<Ty>' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): note: see reference to class template instantiation 'QTypeTraits::has_operator_equal<T>' being compiled
        with
        [
            T=Ty
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2126): note: see reference to variable template 'const bool has_operator_equal_v<ModeMapping>' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2328): note: see reference to class template instantiation 'QtPrivate::QMetaTypeInterfaceWrapper<Ty>' being compiled
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2389): note: see reference to function template instantiation 'const QtPrivate::QMetaTypeInterface *QtPrivate::qMetaTypeInterfaceForType<T>(void)' being compiled
        with
        [
            T=ModeMapping
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(1146): note: see reference to function template instantiation 'QMetaType QMetaType::fromType<T>(void)' being compiled
        with
        [
            T=ModeMapping
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(1170): note: see reference to function template instantiation 'int qRegisterNormalizedMetaType<T>(const QByteArray &)' being compiled
        with
        [
            T=ModeMapping
        ]
C:\Users\ziller\Documents\untitled2\main.cpp(18): note: see reference to function template instantiation 'int qRegisterMetaType<ModeMapping>(const char *)' being compiled
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(54): error C2065: 'value': undeclared identifier
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(54): error C2975: '_First_value': invalid template argument for 'std::_Conjunction', expected compile-time constant expression
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(47): note: see declaration of '_First_value'
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(61): error C2504: 'QTypeTraits::has_operator_equal<T>': base class undefined
        with
        [
            T=Ty
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): error C2039: 'value': is not a member of 'std::conjunction<QTypeTraits::has_operator_equal<Key>,QTypeTraits::has_operator_equal<T>>'
        with
        [
            Key=Input,
            T=Ty
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): note: see declaration of 'std::conjunction<QTypeTraits::has_operator_equal<Key>,QTypeTraits::has_operator_equal<T>>'
        with
        [
            Key=Input,
            T=Ty
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): error C2065: 'value': undeclared identifier
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): error C2131: expression did not evaluate to a constant
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.27.29110\include\type_traits(66): note: a non-constant (sub-)expression was encountered
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(253): error C2976: 'QTypeTraits::detail::expand_operator_equal_container': too few template arguments
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(257): note: see declaration of 'QTypeTraits::detail::expand_operator_equal_container'
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(324): error C3770: 'unknown-type': is not a valid base class
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): error C2039: 'value': is not a member of 'QTypeTraits::has_operator_equal<T>'
        with
        [
            T=Ty
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): note: see declaration of 'QTypeTraits::has_operator_equal<T>'
        with
        [
            T=Ty
        ]
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): error C2065: 'value': undeclared identifier
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): error C2131: expression did not evaluate to a constant
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qtypeinfo.h(326): note: a non-constant (sub-)expression was encountered
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2265): error C2976: 'QtPrivate::QEqualityOperatorForType': too few template arguments
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2128): note: see declaration of 'QtPrivate::QEqualityOperatorForType'
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2265): error C2975: 'unnamed-parameter': invalid template argument for 'QtPrivate::QEqualityOperatorForType', expected compile-time constant expression
C:\Qt\6.1.0\msvc2019_64\include\QtCore/qmetatype.h(2126): note: see declaration of 'unnamed-parameter'
ninja: build stopped: subcommand failed.