anchor.diff:            span: scanner.spanFrom(start));
       }
   
  -    var first = _spaceListOrValue();
  +    var first = _spaceListOrExpression();
       if (scanner.scanChar($colon)) {
         whitespace();
         return _map(first, start);
  
positive.code:       }
  
        if (!_lookingAtExpression()) break;
        commaExpressions.add(_spaceListOrValue());
      } while (scanner.scanChar($comma));
  
      scanner.error("Expected $name.");
  
negative.code:     do {
        whitespace();
        if (!_lookingAtExpression()) break;
        commaExpressions.add(_spaceListOrExpression());
      } while (scanner.scanChar($comma));
  
      return new ListExpression(commaExpressions, ListSeparator.comma);
  