QML syntax/semantic oddity

The following  code creates  a warning about "file:///tmp/test.qml:4:2: Unable to assign QQuickItem_QML_0 to QQuickRectangle", however the line with Item does not.

import QtQuick 2.14
Item {
	property Rectangle r: Rectangle
	property Item i: Item
}

It is unclear to me what exactly happens here, but we most likely want to reject such a program.