SizedOverflowBox({Key key, @required Size size, FractionalOffset alignment: FractionalOffset.center, Widget child })

Creates a widget of a given size that lets its child overflow.

The size argument must not be null.

Source 

SizedOverflowBox({
  Key key,
  @required this.size,
  this.alignment: FractionalOffset.center,
  Widget child
}) : super(key: key, child: child) {
  assert(size != null);
  assert(alignment != null && alignment.dx != null && alignment.dy != null);
}