anchor.diff:      :   IdentifierStart IdentifierPart*
           { int cp = $text.codePointAt(0);
             if (cp=='_' || Character.isLowerCase(cp)) $type=LIDENTIFIER; }
  +    |   UIdentifierPrefix name=IdentifierPart+
  +        { $text = $name; /* FIXME this is unlikely to work */ }
       ;
   
   fragment
  
positive.code:           //TODO: error!
          } }
      ;       
               
  fragment 
  IdentifierPart
      :   '_'
  
negative.code:     ;
  
  fragment
  LIDENTIFIER
      :   LIdentifierPrefix name=IdentifierPart+
          {$text = $name; /* FIXME this is unlikely to work */ }
      // also see UIDENTIFIER    
      ;
  
  fragment
  PIDENTIFIER :;
  fragment
  