anchor.diff:  
   OF
       :   'of'
  +    ;
  +
  +OUT
  +    :   'out'
       ;
   
   SUBTYPE
  
positive.code: 
  enumeration
      : '{' expressions '}'
      -> ^(ENUM_LIST expressions?)
      ;
      
  primary
  
negative.code: 
  classBody
      : '{' declarationOrStatement* '}'
      -> ^(BLOCK declarationOrStatement*)
   //    -> ^(CLASS_BODY ^(STMT_LIST $stmts))
      ;
  
  