What's wrong here?

 
package {
 import flash.display.*;
 public class Test extends Sprite {
  private var m1:Number=99;
  public var m2:Number=88;
  public override function toString():String {
   return m1 + ", " + m2;
  }
 }
}

when I use it as the main class of a .fla file, it generate the error:
Test, line1 1180: call to a possibly undefined method addFrameScript