I'm porting my code to Qt6 (6.4.2) (from 5.15) and ran into this mysterious problem; this code doesn't compile:

    const auto connections = QSqlDatabase::connectionNames();
    qDebug() << "Closing open connections:" << connections;


claiming that

../../../src/server/server_database.cpp:691:45: error: invalid operands to binary expression ('QDebug' and 'const QList<QString>')

It then lists all the candidates, of which there are many.  I have a simple test program that compiles OK though.

The same occurs on both Visual Studio/Windows and gcc 10/Linux.

Am I missing an include or something?


Hamish



../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:398:1: note: 
candidate function template not viable: no known conversion from 'QDebug' to 
'QDataStream &' for 1st argument
operator<<(QDataStream &s, const T &t)
^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:415:63: note: 
candidate function template not viable: no known conversion from 'QDebug' to 
'QDataStream &' for 1st argument
inline QDataStreamIfHasOStreamOperatorsContainer<QList<T>, T> operator<<(QDataStream &s, 
const QList<T> &v)
                                                              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qobject.h:491:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QObject *' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, const QObject *);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtSql/qsqldatabase.h:105:21: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QSqlDatabase' for 2nd argument
Q_SQL_EXPORT QDebug operator<<(QDebug, const QSqlDatabase &);
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:447:15: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QKeyCombination' for 2nd argument
inline QDebug operator<<(QDebug debug, QKeyCombination combination)
              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qiodevice.h:143:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QIODevice::OpenMode' (aka 'QFlags<QIODeviceBase::OpenModeFlag>') for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, QIODevice::OpenMode modes);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qvariant.h:560:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &s, const QVariant &p);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qvariant.h:622:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QVariant::Type' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, const QVariant::Type);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qlocale.h:1142:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QLocale' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, const QLocale &);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:540:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'QDate' 
for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, QDate);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:541:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'QTime' 
for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, QTime);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:542:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QDateTime' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, const QDateTime &);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qfileinfo.h:175:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QFileInfo' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug, const QFileInfo &);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdir.h:244:22: note: candidate function not 
viable: no known conversion from 'const QList<QString>' to 'QDir::Filters' (aka 
'QFlags<QDir::Filter>') for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, QDir::Filters filters);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdir.h:245:22: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QDir' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, const QDir &dir);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qregularexpression.h:166:22: note: 
candidate function not viable: no known conversion from 'const QList<QString>' 
to 'const QRegularExpression' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, const QRegularExpression &re);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qregularexpression.h:167:22: note: 
candidate function not viable: no known conversion from 'const QList<QString>' to 
'QRegularExpression::PatternOptions' (aka 
'QFlags<QRegularExpression::PatternOption>') for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, 
QRegularExpression::PatternOptions patternOptions);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qregularexpression.h:238:22: note: 
candidate function not viable: no known conversion from 'const QList<QString>' 
to 'const QRegularExpressionMatch' for 2nd argument
Q_CORE_EXPORT QDebug operator<<(QDebug debug, const QRegularExpressionMatch 
&match);
                     ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtSql/qsqlerror.h:53:21: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QSqlError' for 2nd argument
Q_SQL_EXPORT QDebug operator<<(QDebug, const QSqlError &);
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtSql/qsqlrecord.h:67:21: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QSqlRecord' for 2nd argument
Q_SQL_EXPORT QDebug operator<<(QDebug, const QSqlRecord &);
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qchar.h:617:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, QChar);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qbytearray.h:579:28: note: 
candidate function not viable: no known conversion from 'QDebug' to 'QDataStream 
&' for 1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QByteArray &);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qstring.h:1512:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QString &);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:549:21: note: 
candidate function not viable: no known conversion from 'QDebug' to 'QDataStream 
&' for 1st argument
inline QDataStream &operator<<(QDataStream &s, QKeyCombination combination)
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qtextstream.h:192:21: note: 
candidate function not viable: no known conversion from 'QDebug' to 'QTextStream 
&' for 1st argument
inline QTextStream &operator<<(QTextStream &s, QTextStreamFunction f)
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qtextstream.h:195:21: note: 
candidate function not viable: no known conversion from 'QDebug' to 'QTextStream 
&' for 1st argument
inline QTextStream &operator<<(QTextStream &s, QTextStreamManipulator m)
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qvariant.h:574:21: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
inline QDataStream &operator<<(QDataStream &s, const QVariant::Type p)
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qlocale.h:1137:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QLocale &);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:531:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, QDate);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:533:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, QTime);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatetime.h:535:28: note: candidate 
function not viable: no known conversion from 'QDebug' to 'QDataStream &' for 
1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QDateTime &);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qregularexpression.h:161:28: note: 
candidate function not viable: no known conversion from 'QDebug' to 'QDataStream 
&' for 1st argument
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &out, const QRegularExpression 
&re);
                           ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:384:21: note: 
candidate template ignored: could not match 'QFlags' against 'QList'
inline QDataStream &operator<<(QDataStream &s, QFlags<Enum> e)
                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:427:62: note: 
candidate template ignored: could not match 'QSet' against 'QList'
inline QDataStreamIfHasOStreamOperatorsContainer<QSet<T>, T> operator<<(QDataStream &s, 
const QSet<T> &set)
                                                             ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:440:73: note: 
candidate template ignored: could not match 'QHash' against 'QList'
inline QDataStreamIfHasOStreamOperatorsContainer<QHash<Key, T>, Key, T> 
operator<<(QDataStream &s, const QHash<Key, T> &hash)
                                                                        ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:452:78: note: 
candidate template ignored: could not match 'QMultiHash' against 'QList'
inline QDataStreamIfHasOStreamOperatorsContainer<QMultiHash<Key, T>, Key, T> 
operator<<(QDataStream &s, const QMultiHash<Key, T> &hash)
                                                                             ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:464:72: note: 
candidate template ignored: could not match 'QMap' against 'QList'
inline QDataStreamIfHasOStreamOperatorsContainer<QMap<Key, T>, Key, T> operator<<(QDataStream 
&s, const QMap<Key, T> &map)
                                                                       ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:476:77: note: 
candidate template ignored: could not match 'QMultiMap' against 'QList'
inline QDataStreamIfHasOStreamOperatorsContainer<QMultiMap<Key, T>, Key, T> 
operator<<(QDataStream &s, const QMultiMap<Key, T> &map)
                                                                            ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdatastream.h:489:49: note: 
candidate template ignored: could not match 'pair' against 'QList'
inline QDataStreamIfHasOStreamOperators<T1, T2> operator<<(QDataStream& s, const 
std::pair<T1, T2> &p)
                                                ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:223:34: note: 
candidate template ignored: could not match 'QVarLengthArray' against 'QList'
inline QDebugIfHasDebugStream<T> operator<<(QDebug debug, const QVarLengthArray<T, 
P> &vec)
                                 ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:229:34: note: 
candidate template ignored: could not match 'vector' against 'QList'
inline QDebugIfHasDebugStream<T> operator<<(QDebug debug, const std::vector<T, 
Alloc> &vec)
                                 ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:235:34: note: 
candidate template ignored: could not match 'list' against 'QList'
inline QDebugIfHasDebugStream<T> operator<<(QDebug debug, const std::list<T, Alloc> 
&vec)
                                 ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:241:39: note: 
candidate template ignored: could not match 'map' against 'QList'
inline QDebugIfHasDebugStream<Key, T> operator<<(QDebug debug, const std::map<Key, T, 
Compare, Alloc> &map)
                                      ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:247:39: note: 
candidate template ignored: could not match 'multimap' against 'QList'
inline QDebugIfHasDebugStream<Key, T> operator<<(QDebug debug, const 
std::multimap<Key, T, Compare, Alloc> &map)
                                      ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:253:62: note: 
candidate template ignored: could not match 'QMap' against 'QList'
inline QDebugIfHasDebugStreamContainer<QMap<Key, T>, Key, T> operator<<(QDebug debug, 
const QMap<Key, T> &map)
                                                             ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:259:67: note: 
candidate template ignored: could not match 'QMultiMap' against 'QList'
inline QDebugIfHasDebugStreamContainer<QMultiMap<Key, T>, Key, T> operator<<(QDebug 
debug, const QMultiMap<Key, T> &map)
                                                                  ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:265:63: note: 
candidate template ignored: could not match 'QHash' against 'QList'
inline QDebugIfHasDebugStreamContainer<QHash<Key, T>, Key, T> operator<<(QDebug debug, 
const QHash<Key, T> &hash)
                                                              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:271:68: note: 
candidate template ignored: could not match 'QMultiHash' against 'QList'
inline QDebugIfHasDebugStreamContainer<QMultiHash<Key, T>, Key, T> operator<<(QDebug 
debug, const QMultiHash<Key, T> &hash)
                                                                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:277:39: note: 
candidate template ignored: could not match 'pair' against 'QList'
inline QDebugIfHasDebugStream<T1, T2> operator<<(QDebug debug, const std::pair<T1, 
T2> &pair)
                                      ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:285:52: note: 
candidate template ignored: could not match 'QSet' against 'QList'
inline QDebugIfHasDebugStreamContainer<QSet<T>, T> operator<<(QDebug debug, const 
QSet<T> &set)
                                                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:440:15: note: 
candidate template ignored: could not match 'QFlags' against 'QList'
inline QDebug operator<<(QDebug debug, const QFlags<T> &flags)
              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:217:53: note: candidate template ignored: 
requirement 'std::conjunction_v<std::disjunction<std::is_base_of<QList<QString>, QString>, 
QTypeTraits::has_ostream_operator<QDebug, QString, void>>>' was not satisfied [with T = QString]
inline QDebugIfHasDebugStreamContainer<QList<T>, T> operator<<(QDebug debug, const 
QList<T> &vec)
                                                    ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:394:1: note: candidate template ignored: 
requirement 'QtPrivate::IsQEnumHelper<QList<QString>>::Value' was not satisfied [with 
T = QList<QString>]
operator<<(QDebug dbg, T value)
^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:406:15: note: candidate template 
ignored: requirement 'std::is_enum<QList<QString>>::value' was not satisfied [with T 
= QList<QString>]
inline QDebug operator<<(QDebug dbg, T value)
              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:291:34: note: 
candidate template ignored: could not match 'QContiguousCache' against 'QList'
inline QDebugIfHasDebugStream<T> operator<<(QDebug debug, const QContiguousCache<T> 
&cache)
                                 ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:350:15: note: 
candidate template ignored: could not match 'QSharedPointer' against 'QList'
inline QDebug operator<<(QDebug debug, const QSharedPointer<T> &ptr)
              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:360:15: note: 
candidate template ignored: could not match 'QTaggedPointer' against 'QList'
inline QDebug operator<<(QDebug debug, const QTaggedPointer<T, Tag> &ptr)
              ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:92:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'QChar' 
for 1st argument
    inline QDebug &operator<<(QChar t) { putUcs4(t.unicode()); return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:93:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'bool' 
for 1st argument
    inline QDebug &operator<<(bool t) { stream->ts << (t ? "true" : "false"); 
return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:94:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'char' 
for 1st argument
    inline QDebug &operator<<(char t) { stream->ts << t; return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:95:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'short' 
for 1st argument
    inline QDebug &operator<<(signed short t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:96:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'unsigned short' for 1st argument
    inline QDebug &operator<<(unsigned short t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:97:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'char16_t' for 1st argument
    inline QDebug &operator<<(char16_t t) { return *this << QChar(ushort(t)); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:98:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'char32_t' for 1st argument
    inline QDebug &operator<<(char32_t t) { putUcs4(t); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:99:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'int' 
for 1st argument
    inline QDebug &operator<<(signed int t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:100:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'unsigned int' for 1st argument
    inline QDebug &operator<<(unsigned int t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:101:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'long' 
for 1st argument
    inline QDebug &operator<<(signed long t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:102:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'unsigned long' for 1st argument
    inline QDebug &operator<<(unsigned long t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:103:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'qint64' (aka 'long long') for 1st argument
    inline QDebug &operator<<(qint64 t) { stream->ts << t; return maybeSpace(); 
}
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:104:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'quint64' (aka 'unsigned long long') for 1st argument
    inline QDebug &operator<<(quint64 t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:105:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'float' 
for 1st argument
    inline QDebug &operator<<(float t) { stream->ts << t; return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:106:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'double' for 1st argument
    inline QDebug &operator<<(double t) { stream->ts << t; return maybeSpace(); 
}
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:107:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
char *' for 1st argument
    inline QDebug &operator<<(const char* t) { stream->ts << 
QString::fromUtf8(t); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:108:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
char16_t *' for 1st argument
    inline QDebug &operator<<(const char16_t *t)  { stream->ts << 
QStringView(t); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:109:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QString' for 1st argument
    inline QDebug &operator<<(const QString & t) { putString(t.constData(), 
size_t(t.size())); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:110:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QStringView' for 1st argument
    inline QDebug &operator<<(QStringView s) { putString(s.data(), 
size_t(s.size())); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:111:20: note: candidate function 
not viable: no known conversion from 'const QList<QString>' to 
'q_no_char8_t::QUtf8StringView' (aka 'QBasicUtf8StringView<false>') for 1st argument
    inline QDebug &operator<<(QUtf8StringView s) { 
putByteArray(reinterpret_cast<const char*>(s.data()), s.size(), ContainsBinary); return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:112:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QLatin1StringView' (aka 'QLatin1String') for 1st argument
    inline QDebug &operator<<(QLatin1StringView t) { putByteArray(t.latin1(), 
t.size(), ContainsLatin1); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:113:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 'const 
QByteArray' for 1st argument
    inline QDebug &operator<<(const QByteArray & t) { 
putByteArray(t.constData(), t.size(), ContainsBinary); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:114:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QByteArrayView' for 1st argument
    inline QDebug &operator<<(QByteArrayView t) { putByteArray(t.constData(), 
t.size(), ContainsBinary); return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:115:20: note: candidate function 
not viable: no known conversion from 'const QList<QString>' to 'const void *' for 
1st argument; take the address of the argument with &
    inline QDebug &operator<<(const void * t) { stream->ts << t; return 
maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:116:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'std::nullptr_t' (aka 'nullptr_t') for 1st argument
    inline QDebug &operator<<(std::nullptr_t) { stream->ts << "(nullptr)"; 
return maybeSpace(); }
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:117:20: note: candidate function not 
viable: no known conversion from 'const QList<QString>' to 'QTextStreamFunction' (aka 
'QTextStream &(*)(QTextStream &)') for 1st argument
    inline QDebug &operator<<(QTextStreamFunction f) {
                   ^
../../../../Qt6.4.2/6.4.2/gcc_64/include/QtCore/qdebug.h:122:20: note: candidate 
function not viable: no known conversion from 'const QList<QString>' to 
'QTextStreamManipulator' for 1st argument
    inline QDebug &operator<<(QTextStreamManipulator m)
                   ^
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