anchor.diff:      ;
   
   expressions
  -    :   expression ( (NL | ',') expression)*
  +    :   expression ( (NL | COMMA) expression)*
       ;
   
   expression
  
positive.code: RETURN  :   'return';
  THIS    :   'this';
  TRACE   :   'trace';
  TYPE    :   'Type' | 'type';
  WITH    :   'with';
  WHILE   :   'while';
  
negative.code:     |   expression
      ;
  
  enumeration
      :   Identifier ASSIGN 
          (   elements
          |   INDENT elements DEDENT
          )
      ;
  
  elements
      :   PIPE element (NL? PIPE element)* NL*
      ;
  
  element
      :   Identifier (ASSIGN expression)?
      ;
  
  if_block
  