anchor.diff:    var styleSheet = parse(css, errors: errors);
   
     if (errors.isNotEmpty) {
  -    logger.warning('Errors parsing CSS:\n${errors.join('\n')}');
  +    logger.severe('Errors parsing CSS:\n${errors.join('\n')}');
     }
   
     var shadowTransformer = useLegacyEncapsulation
  
positive.code: 
      if (x.runtimeType == y.runtimeType) {
        if (x is ElementSelector || x is NamespaceSelector) {
          logger.warning('Compound selector contains multiple type selectors:\n'
              '${x.span.message('')}\n'
              '${y.span.message('')}');
        } else if (x is PseudoElementSelector) {
          logger.warning(
              'Compound selector contains multiple pseudo element selectors:\n'
              '${x.span.message('')}\n'
              '${y.span.message('')}');
  
negative.code: 
    var selectorGroup = parseSelectorGroupFrom(declaration);
    if (selectorGroup == null) {
      logger.severe(declaration.expression.span.message('Not a valid selector'));
      return null;
    }
  
  