qmltc/qmllint issues with size value type

import QtQuick

Item {
    id: _control

    implicitWidth: 640
    implicitHeight: 480

    property size leftIconSize: "150x50"

    Image {
        sourceSize: _control.leftIconSize
    }
}

Warning: MyComponent.qml:12:21: Cannot assign binding of type QSizeF to QSize [incompatible-type]
        sourceSize: _control.leftIconSize
                    ^^^^^^^^^^^^^^^^^^^^^
Warning: MyComponent.qml:12:42: Could not compile binding for sourceSize: cannot convert from QSizeF of (component in MyComponent.qml)::leftIconSize with type QSizeF to QSize of QSize [compiler] 

...
this->m_leftIconSize = QStringLiteral("150x50"); 
...