anchor.diff:  
   THIS
       :   'this'
  +    ;
  +
  +OUTER
  +    :   'outer'
       ;
   
   SUBTYPE
  
positive.code:     | '#' 
      | LIDENTIFIER 
      | UIDENTIFIER 
      | specialValue 
      | nonstringLiteral
      | prefixOperator
      ;
  
negative.code:     : '$' | '-' |'++' | '--' | '~'
      ;
  
  selfReference
      : 'this' //typeName?
      | 'super'
      | 'outer'
      ;
  
  enumeration
  