patch 9.0.2078: several problems with type aliases

Problem:  several problems with type aliases
Solution: Check for more error conditions, add tests,
          fix issues

Check for more error conditions and add additional tests

fixes  #13434
fixes  #13437
fixes  #13438
closes #13441

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index db8f94e..3f577ad 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -52,6 +52,7 @@
 int check_for_list_or_dict_or_blob_or_string_arg(typval_T *args, int idx);
 int check_for_opt_buffer_or_dict_arg(typval_T *args, int idx);
 int check_for_object_arg(typval_T *args, int idx);
+int tv_class_alias(typval_T *tv);
 int check_for_class_or_list_arg(typval_T *args, int idx);
 char_u *tv_get_string(typval_T *varp);
 char_u *tv_get_string_strict(typval_T *varp);