QStringList is a QList<QString>. But it is not possible cast it to QList<QVariant>. That's two template containers containing different types.
Edit: BTW, see qCopy. Maybe it suits for your need:
stringList << "one" << "two" << "three";
QVector<QVariant> vector(strings.size());
qCopy(stringList.begin(), stringList.end(), vector.begin()); // works because QVariant has
// a constructor taking QString
QList<QVariant> variantList = vector.toList(); // if you really need a list
QStringList stringList;
stringList << "one" << "two" << "three";
QVector<QVariant> vector(strings.size());
qCopy(stringList.begin(), stringList.end(), vector.begin()); // works because QVariant has
// a constructor taking QString
QList<QVariant> variantList = vector.toList(); // if you really need a list
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