QPolygonF created from QRectF has five(?!) points

[Asperamanca]

In order to use QTransform::quadToQuad, I convert two rectangles to QPolygonF.

void GenericScale::paintGrid(QPainter *painter,
                             QRectF logicalRect)
{
    QPolygonF drawRect(logicalRect);
 
    qDebug() << drawRect;
}

void GenericScale::paintGrid(QPainter *painter,
                             QRectF logicalRect)
{
    QPolygonF drawRect(logicalRect);

    qDebug() << drawRect;
}

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The resulting QPolygonF has - according to watch window and qDebug output - 5 points:

QPolygonF(QPointF(0, 1) QPointF(57, 1) QPointF(57, 2) QPointF(0, 2) QPointF(0, 1) )

QPolygonF(QPointF(0, 1) QPointF(57, 1) QPointF(57, 2) QPointF(0, 2) QPointF(0, 1) )

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Naturally, quadToQuad fails.

Why would the constructor of QPolygonF taking a QRectF as an argument create a QPolygonF with five instead of four points?