anchor.diff:      ;
   
   fragment
  +ASTRING_LITERAL:;
  +
  +fragment
   QuotedLiteralPart
       : ~('\'')*
       ;
  
positive.code:       { $positionalArgument = new PositionalArgument(null);
          Expression e = new Expression(null);
          e.setTerm($stringLiteral.stringLiteral);
          $positionalArgument.setExpression(e); }
      ;
  
  //special rule for syntactic predicate
  
negative.code: 
  packageName returns [Identifier identifier]
      : LIDENTIFIER
        { $identifier = new Identifier($LIDENTIFIER); 
          $LIDENTIFIER.setType(PIDENTIFIER);}
      ;
  
  typeName returns [Identifier identifier]
  