         @identifierError id
 
     unless forcedIdentifier
-      id  = COFFEE_ALIASES[id] if COFFEE_ALIASES[id] and not [][id]
+      id  = COFFEE_ALIAS_MAP[id] if id in COFFEE_ALIASES
       tag = switch id
         when '!'                                  then 'UNARY'
         when '==', '!='                           then 'COMPARE'


# CoffeeScript-only keywords.
COFFEE_KEYWORDS = ['undefined', 'then', 'unless', 'until', 'loop', 'of', 'by', 'when']
COFFEE_KEYWORDS.push op for op of COFFEE_ALIASES =
  and  : '&&'
  or   : '||'
  is   : '=='

  no   : 'false'
  on   : 'true'
  off  : 'false'
  
COFFEE_ALIASES  = (key for key of COFFEE_ALIAS_MAP)
COFFEE_KEYWORDS = COFFEE_KEYWORDS.concat COFFEE_ALIASES

# The list of keywords that are reserved by JavaScript, but not used, or are
# used by CoffeeScript internally. We throw an error when these are encountered,
