anchor.diff:   */
   class PageLoader {
     final WebDriver _driver;
  -  final Map<ClassMirror, _ClassInfo> _classInfoCache =
  -      <ClassMirror, _ClassInfo>{};
   
     PageLoader(this._driver);
   
  
positive.code:   }
  
    _getInstance(ClassMirror type, SearchContext context) =>
        _classInfoCache.putIfAbsent(type, () => new _ClassInfo(type))
            .getInstance(context, this);
  }
  
  class _ClassInfo {
    final ClassMirror _class;
    final List<_FieldInfo> _fields;
    final Finder _finder;
  
negative.code:   final bool _finderIsOptional;
  
    factory _ClassInfo(ClassMirror type) {
      if (_classInfoCache.containsKey(type)) {
        return _classInfoCache[type];
      }
      Finder finder = null;
      List<Filter> filters = <Filter>[];
      bool finderIsOptional = false;
  