setMonth() and other setXXX() javascript function doesn't work on the date QML object

[Didier Roche-Tolomelli]

From http://doc.qt.io/qt-5/qml-qtqml-date.html, "The QML Date object extends the JS Date object with locale aware functions.".

Some of them indeed works, like getMonth(), getDate(), returning expected value.

However, when change a date property on a object with setMonth() and other functions, they don't do anything (and worse, fails silently):

Item {
  id: foo
  property date currentDate
}

foo.currentDate having no databinding.

On a click event handler:
console.log("Before setMonth " + foo.currentDate);
currentDate.setMonth(4);
console.log("After setMonth " + foo.currentDate);

returns:
Before setMonth Sat Mar 7 08:13:50 2015 GMT+0100
After setMonth Sat Mar 7 08:13:50 2015 GMT+0100

The date has been unchanged