Error 1119 when class extends another class that extends movieclip

Question

hiya
i came across this problem and i have no clue why it's happening. basically, consider 2 nested movieclips on the stage, something like stage -> main -> filler.  both movieclips have instance names (main and filler).
in the library, i set main to export for actionscript, using class A:
package {
    import flash.display.MovieClip;
    public class A extends MovieClip {     
        public function A ():void {
            trace ('construct A');
            trace (this.filler); // should trace [movieclip] etc
it works fine. now i change it's export settings to use class B, that extends A, and it breaks:
package {
    import flash.display.MovieClip;
    public class B extends A {
        public function B ():void {
            trace ('construct B');
this throws an error 1119: Access of possibly undefined property filler through a reference with static type A.
can anyone give me a hint on that, as it works with class A, but not B extending A? i understand it was meant to work?
many thanks

Answer 1

afaik, if you dont declare super(), flash will make a call for you (but best practice is to call it always).
but i found the "solution" in another forum.
it seems that flash implicitly generates variables if you have instance names/symbols on the stage. there is an option to disable that under publish settings -> Actionscript version -> Settings -> automatically declare stage instances. by disabling that, we were able to declare public var filler:MovieClip; on class A, and that worked.
although, that solution doesnt look attractive to me. the other solution posted on another forum was to make calls to this ["filler"] instead of this.filler. that seems to work fine. i guess it has to do with the automatic variable generated thing.. who knows?
i hope that helps someone else too