width < 0 の Rectangle は union() できるか

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

// forked from yprops's DebugText
package {
    import flash.geom.Rectangle;
    import flash.display.Sprite;
    import flash.text.TextField;
    public class RectangleUnionTest extends Sprite {
        public function RectangleUnionTest() {
            addDeb(300, 300);
            
            //以下本文
            addDebLine("width < 0 の Rectangle は union() できるか\n");
            var r0 :Rectangle;
            var r1 :Rectangle;
            
            r0 = new Rectangle(0,0,100,100);
            r1 = new Rectangle(0,100,100,100);
            addDebLine("r0 ... " + r0);
            addDebLine("r1 ... " + r1);
            addDebLine("r0.union(r1) = " + r0.union(r1) );
            addDebLine("(`・ω・´) 合成された矩形！\n");
            
            r0 = new Rectangle(0,0,100,100);
            r1 = new Rectangle(0,100,-100,100);
            addDebLine("r0 ... " + r0);
            addDebLine("r1 ... " + r1);
            addDebLine("r0.union(r1) = " + r0.union(r1) );
            addDebLine("(´・ω・`) r0と同じ矩形？\n");
            
            r0 = new Rectangle(0,0,-100,100);
            r1 = new Rectangle(100,100,-100,100);
            addDebLine("r0 ... " + r0);
            addDebLine("r1 ... " + r1);
            addDebLine("r0.union(r1) = " + r0.union(r1) );
            addDebLine("(´；ω；`) r1と同じ矩形？？\n");
            
        }
        
        
        
        //-------------------------------
        private var deb :TextField;
        private function addDeb(w:uint, h:uint) :void{
                deb = new TextField();
                deb.wordWrap = true;
                deb.width = w;
                deb.height = h;
                deb.border = true;
                deb.borderColor = 0;
                deb.background = true;
                deb.backgroundColor = 0x99ffffff;
                deb.text = "beginDebugText-------\n";
                addChild(deb);
        }
        private function addDebLine(str :String) :void{
                deb.appendText(str + "\n");
                deb.scrollV = deb.maxScrollV;
        }
    }
}