Xtend, JavaFX-Properties and operator overloading

JavaFX has properties you can bind to each other to keep them insync. Watch this video for a very minimal example which scales a text by dragging a slider. Video Now let's look at the Xtend code used to write this small sample The important lines are:

// Bidirectional binding between sliders
sl_1.valueProperty .. sl_2.valueProperty;

// Unidirectional binding from slider to scaleX/Y
l.scaleXProperty -> sl_2.valueProperty;
l.scaleYProperty -> sl_2.valueProperty;

The trick here to make this code not as verbose as it's java counterpart is that Xtend allows to overload operators (+, -, ->, .., ...). What I don't fully understand is why I can't define my operator overloading like this:

def static <T> operator_mappedTo(Property<T> x, ObservableValue<? extends T> y) {
  x.bind(y);
}

which should work when looking at the inheritance hierarchy of DoubleProperty, maybe some Xtend guru can explain it to me ;-)