michael@0: interface EventTarget {
michael@0:   void addEventListener();
michael@0: };
michael@0: 
michael@0: interface Event {};
michael@0: 
michael@0: callback EventHandlerNonNull = any (Event event);
michael@0: typedef EventHandlerNonNull? EventHandler;
michael@0: 
michael@0: [NoInterfaceObject]
michael@0: interface TestEvent : EventTarget {
michael@0:   attribute EventHandler onfoo;
michael@0: };