as演算子でキャストされた物って参照渡しだったっけ？

/**
 * Copyright yasurageruheya ( http://wonderfl.net/user/yasurageruheya )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/ePjt
 */

package {
	import flash.display.DisplayObject;
    import flash.display.Sprite;
	import flash.geom.Matrix;
	import flash.text.TextField;
    public class FlashTest extends Sprite {
		private var txt:TextField;
		private var spr:Sprite;
        public function FlashTest() {
            // write as3 code here..
            txt = new TextField();
			txt.autoSize = "left";
			addChild(txt);
			
			spr = new Sprite();
			
			txt.text = test(spr);
        }
		
		private function test(display:DisplayObject):String
		{
			var tmp:Sprite = display as Sprite;
			
			tmp.mouseChildren = false;
			
			var str:String = "tmp.mouseChildren : " + tmp.mouseChildren;
			str += "\nspr.mouseChildren : " + spr.mouseChildren;
			str += "\ndisplay.mouseChildren : " + (display as Sprite).mouseChildren;
			
			tmp.mouseChildren = true;
			
			str += "\n======================";
			str += "\ntmp.mouseChildren : " + tmp.mouseChildren;
			str += "\nspr.mouseChildren : " + spr.mouseChildren;
			str += "\ndisplay.mouseChildren : " + (display as Sprite).mouseChildren;
			return str;
		}
    }
}