anchor.diff:  def ANS (issignal, identifier): # assert non-signal decl
     if issignal:
       raise TypeError ('non-method invalidly declared as \'signal\': %s' % identifier)
  +def ASC (collkind): # assert signal collector
  +  if not collkind in collectors:
  +    raise TypeError ('invalid signal collector: %s' % collkind)
   
   class Error (Exception):
     def __init__ (self, msg, ecaret = None):
  
positive.code: import AuxData
  
  reservedwords = ('class', 'signal', 'void')
  keywords = ('TRUE', 'True', 'true', 'FALSE', 'False', 'false',
              'namespace', 'enum', 'enumeration', 'Const', 'typedef', 'interface',
              'record', 'sequence', 'Bool', 'Num', 'Real', 'String')
  
negative.code: 
  rule field_or_method_or_signal_decl:
                                                  {{ signal = false; fargs = []; daux = () }}
          [ 'signal'                              {{ signal = true; coll = 'void' }}
            [ '<' IDENT '>'                       {{ coll = IDENT; ASC (coll) }}
            ] ]
          ( 'void'                                {{ dtname = 'void' }}
          | typename                              {{ dtname = typename }}
          )
  