num y

The y-coordinate of this display object relative to the local coordinates of the parent DisplayObjectContainer.

If the object is inside a DisplayObjectContainer that has transformations, it is in the local coordinate system of the enclosing DisplayObjectContainer.

Source 

@override
num get y => _y;
void y=(num value)

Source 

@override
set y(num value) {
  if (value is num) _y = value;
  _transformationMatrixRefresh = true;
}