aspect OverridesCrossRefs {
	
    // Fill in cross-references for
	// - overrides -> overriders
	// - TODO: handle implements relation
	// - TODO: handle sub/super-interfaces
	
	public Collection MethodDecl.overriders() {
		Program root = getProgram();
		if (!root.overridesCrossRefsFilledIn) {
			root.overridesCrossRefs();
			root.overridesCrossRefsFilledIn = true;
		}
		return privateOverriders;
	}
	
	private LinkedList MethodDecl.privateOverriders = new LinkedList();
	
	boolean Program.overridesCrossRefsFilledIn = false;
	
	void ASTNode.overridesCrossRefs() {
		for(int i=0; i<getNumChild(); i++) {
			getChild(i).overridesCrossRefs();
		}
	}

	void MethodDecl.overridesCrossRefs() {
		for (Iterator iter = overrides().iterator(); iter.hasNext();) {
			MethodDecl m = (MethodDecl) iter.next();
			m.privateOverriders.add(this);
		}
		super.overridesCrossRefs();		
	}

  syn lazy HashSet MethodDecl.overrides() {
    HashSet set = new HashSet();
    for(Iterator iter = hostType().ancestorMethods(signature()).iterator(); iter.hasNext(); ) {
      MethodDecl m = (MethodDecl)iter.next();
      if(overrides(m)) {
        set.add(m);
        set.addAll(m.overrides());
      }
    }
    return set;
  }
	
}