QImageWriter has confusing docs

QImageWriter::UnknownError

An unknown error occurred. If you get this value after calling write(), it is most likely caused by a bug in QImageWriter. 

#include <QtGui/QImage>
#include <QtGui/QImageWriter>int main()
{
    QImage img(10, 10, QImage::Format_ARGB32);
    img.fill(Qt::red);    QImageWriter w("out.png");
    Q_ASSERT(w.canWrite());
    w.write(img);
    // Write succeeded, but we still have UnknownError which is bad according to the docs
    qDebug() << "Error: " << (w.error() == QImageWriter::UnknownError) << w.errorString();    return 0;
}