Experimental parser: remove some dead code

tools/lexer_generator/rule_parser.py

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 288 matching lines @@
           action = Action(entry_action, match_action, precedence)
           graph = NfaBuilder.add_action(graph, action)
         if not transition:
           pass
         elif transition == 'continue':
           assert not subgraph == 'default'
           continues += 1
           graph = NfaBuilder.add_continue(graph)
         else:
           assert subgraph == 'default'
-          subgraph_modifier = None
           graph = NfaBuilder.join_subgraph(
-            graph, transition, rule_map[transition], subgraph_modifier)
+            graph, transition, rule_map[transition])
         graphs.append(graph)
       if continues == len(graphs):
         graphs.append(NfaBuilder.epsilon())
       if v['catch_all']:
         (precedence, catch_all) = v['catch_all']
         assert catch_all == (None, None, 'continue'), "unimplemented"
         graphs.append(NfaBuilder.add_continue(NfaBuilder.catch_all()))
       graph = NfaBuilder.or_graphs(graphs)
       rule_map[subgraph] = graph
     # process first the subgraphs, then the default graph
     for k, v in parser_state.rules.items():
       if k == 'default': continue
       process(k, v)
     process('default', parser_state.rules['default'])
     # build the automata
     for rule_name, graph in rule_map.items():
       self.__automata[rule_name] = RuleProcessor.Automata(builder, graph)
     # process default_action
     default_action = parser_state.rules['default']['default_action']
     self.default_action = Action(None, default_action[1]) if default_action else None