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Details

Type: Bug
Resolution: Invalid
Priority: Not Evaluated
Fix Version/s: None
Affects Version/s: 6.0.0 Alpha
Component/s: Core: Containers and Algorithms
Labels:
None
Environment:
Qt 6.0.0-202010060504 from installer (MSVC 2019 64-bit)
MSVC 2019 - Microsoft (R) C/C++ Optimizing Compiler Version 19.27.29112 for x64
Windows 10 x64 2004

Platform/s:

Windows

Description

Simple example:

#include <QCoreApplication>
#include <QMap>
#include <QVariant>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QMap<QVariant, QVariant> map;
    map.insert(QVariant("test"), QVariant("test"));
    qDebug() << map.first();

    return a.exec();
}

Leads to compilation error on Qt 6 alpha:

C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xstddef(127): error C2678: binary '<': no operator found which takes a left-hand operand of type 'const _Ty' (or there is no acceptable conversion)
        with
        [
            _Ty=QVariant
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\variant(1697): note: could be 'bool std::operator <(std::monostate,std::monostate) noexcept'
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qchar.h(67): note: or       'bool operator <(char,QLatin1Char) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qchar.h(74): note: or       'bool operator <(QLatin1Char,char) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qchar.h(612): note: or       'bool operator <(QChar,QChar) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qchar.h(621): note: or       'bool operator <(QChar,std::nullptr_t) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qchar.h(623): note: or       'bool operator <(std::nullptr_t,QChar) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qbytearrayview.h(307): note: or       'bool operator <(QByteArrayView,QByteArrayView) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qbytearray.h(589): note: or       'bool operator <(const QByteArray &,const QByteArray &) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qbytearray.h(591): note: or       'bool operator <(const QByteArray &,const char *) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qbytearray.h(593): note: or       'bool operator <(const char *,const QByteArray &) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qanystringview.h(290): note: or       'bool operator <(QAnyStringView,QAnyStringView) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(783): note: or       'bool operator <(const QString &,const QString &) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1259): note: or       'bool operator <(const char *,const QString &)' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1407): note: or       'bool operator <(QChar,const QString &) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1426): note: or       'bool operator <(QChar,QLatin1String) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1215): note: or       'bool operator <(QLatin1String,QLatin1String) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1272): note: or       'bool operator <(const char *,QLatin1String)' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1418): note: or       'bool operator <(const QString &,QChar) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1437): note: or       'bool operator <(QLatin1String,QChar) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1455): note: or       'bool operator <(QStringView,QChar) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1462): note: or       'bool operator <(QChar,QStringView) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1470): note: or       'bool operator <(QStringView,QLatin1String) noexcept' [found using argument-dependent lookup]
..\..\..\qt\official\6.0.0\msvc2019_64\include\QtCore/qstring.h(1477): note: or       'bool operator <(QLatin1String,QStringView) noexcept' [found using argument-dependent lookup]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xstddef(127): note: while trying to match the argument list '(const _Ty, const _Ty)'
        with
        [
            _Ty=QVariant
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xstddef(126): note: while compiling class template member function 'bool std::less<Key>::operator ()(const _Ty &,const _Ty &) const'
        with
        [
            Key=QVariant,
            _Ty=QVariant
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xtree(1705): note: see reference to function template instantiation 'bool std::less<Key>::operator ()(const _Ty &,const _Ty &) const' being compiled
        with
        [
            Key=QVariant,
            _Ty=QVariant
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xmemory(1326): note: see reference to class template instantiation 'std::less<Key>' being compiled
        with
        [
            Key=QVariant
        ]
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\xmemory(1326): note: see reference to variable template 'const bool is_empty_v<std::less<QVariant> >' being compiled
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\map(75): note: see reference to class template instantiation 'std::_Tree<std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,false>>' being compiled
        with
        [
            _Kty=QVariant,
            _Ty=QVariant,
            _Pr=std::less<QVariant>,
            _Alloc=std::allocator<std::pair<const QVariant,QVariant>>
        ]
F:\qt\official\6.0.0\msvc2019_64\include\QtCore\qmap.h(64): note: see reference to class template instantiation 'std::map<Key,T,std::less<Key>,std::allocator<std::pair<const Key,T>>>' being compiled
        with
        [
            Key=QVariant,
            T=QVariant
        ]
F:\qt\official\6.0.0\msvc2019_64\include\QtCore\qmap.h(439): note: see reference to class template instantiation 'QMapData<std::map<Key,T,std::less<Key>,std::allocator<std::pair<const Key,T>>>>' being compiled
        with
        [
            Key=QVariant,
            T=QVariant
        ]
..\maptest\main.cpp(11): note: see reference to class template instantiation 'QMap<QVariant,QVariant>::iterator' being compiled

Works on 5.15.1.