Experimental parser: use sentinal values for actions

tools/lexer_generator/code_generator.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 43 matching lines @@
     self.__inline = inline
     self.__switching = switching
     self.__jump_table = []
 
   __jump_labels = ['state_entry', 'after_entry_code']
 
   @staticmethod
   def __transform_state(encoding, state):
     # action data
     action = state.action()
-    entry_action = None if not action else action.entry_action()
-    match_action = None if not action else action.match_action()
+    entry_action = action.entry_action()
+    match_action = action.match_action()
     # generate ordered transitions
     transitions = map(lambda (k, v) : (k, v.node_number()),
                       state.transitions().items())
     def cmp(left, right):
       return TransitionKey.canonical_compare(left[0], right[0])
     transitions = sorted(transitions, cmp)
     # map transition keys to disjoint ranges and collect stats
     disjoint_keys = []
     unique_transitions = {}
     old_transitions = transitions
@@ skipping 214 matching lines @@
     assert id_map[self.__start_node_number]['node_number'] == 0
     assert len(dfa_states) == self.__dfa.node_count()
     # mark eos states
     self.__mark_eos_states(dfa_states, eos_states)
     self.__dfa_states = dfa_states
 
   def __rewrite_gotos(self):
     goto_map = {}
     states = self.__dfa_states
     for state in states:
-      if (state['match_action'] and
-          state['match_action'].name() == 'do_stored_token'):
+      if (state['match_action'].name() == 'do_stored_token'):
         assert not state['match_action'].args()[0] in goto_map
         goto_map[state['match_action'].args()[0]] = state['node_number']
     mapped_actions = set([
       'store_harmony_token_and_goto',
       'store_token_and_goto',
       'goto_start'])
     for state in states:
       if not state['match_action']:
         continue
       action = state['match_action'].name()
@@ skipping 112 matching lines @@
 
     return template.render(
       start_node_number = 0,
       debug_print = self.__debug_print,
       default_action = default_action,
       dfa_states = dfa_states,
       jump_table = self.__jump_table,
       encoding = encoding.name(),
       char_type = char_type,
       upper_bound = encoding.primary_range()[1])