I had hoped that the compiler/AVM might be able to infer that the interface is valid.

ICompoundInterface.as

public interface ICompoundInterface extends IDrawable, IEdible 
{
}

public class SomethingConcrete implements IDrawable, IEdible
{
}

// throws type conversion error
var concreteThing:ICompoundInterface = ICompoundInterface(new SomethingConcrete());

// no error but concreteThing is null
var concreteThing:ICompoundInterface = new SomethingConcrete() as ICompoundInterface;