V4 error: "conditional function or closure declaration"

import QtQuick 2.1

Rectangle {
    width: 360
    height: 360

    color: testFunc()

    function testFunc() {
        if (true) {
            // 'conditional function or closure declaration'
            function nestedFunc() { return "mediumseagreen" }
            return nestedFunc()
        }
    }
}