public Parser classIs() {
        if (classIsParser == null) {
           FutureParser future = scoped("classIs");
           classIsParser = future;
           future.setParser(
               sequence(
                   token("CLASS"),
                   identifier(),
                   optional(
                       token("IS")
                   ),
                   plus(
                       choice(
                           literalRange(),
                           literal()
                       )
                   )
               )
           );
        }

        return classIsParser;
    }