Catergorized classes to abstract, class, typedef, and error/exception

pkg/docgen/test/single_library_test.dart

Index: pkg/docgen/test/single_library_test.dart
diff --git a/pkg/docgen/test/single_library_test.dart b/pkg/docgen/test/single_library_test.dart
index f00ddc4d2f40f6fd14723f493208212aae702fa4..6ff153985dd11b6f93fecf6594a9c88860c435a1 100644
--- a/pkg/docgen/test/single_library_test.dart
+++ b/pkg/docgen/test/single_library_test.dart
@@ -54,7 +54,11 @@ main() {
               includePrivate: true);
           expect(library is Library, isTrue);
           
-          var classes = library.classes.values;
+          var classTypes = library.classes.values;
+          expect(classTypes.every((e) => e is Map), isTrue);
+          
+          var classes = [];
+          classTypes.forEach((e) => classes.addAll(e.values));
           expect(classes.every((e) => e is Class), isTrue);
           
           var classMethodTypes = [];