anchor.diff:  
           if (next(TokenType.COLON)) {
             var COLON = current;
  -          var val = parseValueOrVariable();
  +          var val = parseInputValue();
             if (val != null)
               return new DirectiveContext(
                   ARROBA, NAME, COLON, null, null, null, val);
  
positive.code: 
        if (next(TokenType.COLON)) {
          var COLON = current;
          var value = parseValue();
  
          if (value != null) {
            return new ObjectFieldContext(NAME, COLON, value);
  
negative.code:       var NAME = current;
        if (next(TokenType.COLON)) {
          var COLON = current;
          var val = parseInputValue();
          if (val != null)
            return new ArgumentContext(NAME, COLON, val);
          else {
  