anchor.diff:        _inContentBlock = true;
         children = this.children(_ruleChild);
         _inContentBlock = false;
  +    } else {
  +      _expectStatementSeparator();
       }
   
       return new IncludeRule(name, arguments, scanner.spanFrom(start),
  
positive.code:     var value = _almostAnyValue();
      var optional = scanner.scanChar($exclamation);
      if (optional) expectIdentifier("optional");
      return new ExtendRule(value, scanner.spanFrom(start), optional: optional);
    }
  
  
negative.code:   /// Consumes an `@error` rule.
    ///
    /// [start] should point before the `@`.
    ErrorRule _errorRule(LineScannerState start) {
      var expression = _expression();
      _expectStatementSeparator();
      return new ErrorRule(expression, scanner.spanFrom(start));
    }
  
    /// Consumes an `@extend` rule.
    ///
  