Need help creating simple component

I’m trying to create a simple component that extends the MovieClip class. It’s just a basic component… no live preview, no extending UIComponent, etc.

What is giving me problems is that I am trying to include a prebuilt Flash component within my own custom component, and it’s throwing errors. Here is my stripped down code.

    import flash.display.MovieClip;
    import fl.controls.Slider;
    public class Foo extends MovieClip
        private var _mySlider:Slider;

        public function Foo()
        { }

On stage I have the component built from various MovieClips, and it also includes a prebuilt Slider component. Now, if I try to right click my main MovieClip in the Library to give it its linkage name and component definition, I am greeted with weird errors. The weirdest error is:

Actionscript 2.0 class scripts may only define class or interface constructs.
The offending line seems to be the _mySlider variable declaration. If I comment that out the errors go away, but then I can’t do anything with the Slider on stage. Can anybody help? This is driving me mad. Thanks.