Accessing compile-time constants

on the stage I have a movie clip that is tied to class Test, inside it I have another movie clip that I named “child”. Since under publish settings I have it checked to “Automatically declare stage instances” I was hoping to just access it… here’s my Test class:

package {
    import flash.display.MovieClip;
    
    public class Test extends MovieClip {
        
        public function Test() {
            this.addEventListener("load", movieLoaded);
        }
        
        public function movieLoaded() {
            child.visible = false;
        }
    }
}

And here’s my compiler error:
1046: Type was not found or was not a compile-time constant: child.

I was looking through AS3 tips of the day, and a whole bunch of sites talking about this error, but found nothing similar to my situation…

How to access “stage instances” if they have been “automatically declared”?