Fix for bug #1109
Warning required when calling register() on an ABCMeta subclass.
diff --git a/Lib/abc.py b/Lib/abc.py
index 54dc8e2..30bb6b0 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -137,8 +137,11 @@
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
return cls
- def register(cls, subclass):
+ def register(cls, subclass=None):
"""Register a virtual subclass of an ABC."""
+ if subclass is None:
+ raise TypeError("register() cannot be called on an ABCMeta "
+ "subclass, use class Example(metaclass=abc.ABCMeta) instead.")
if not isinstance(cls, type):
raise TypeError("Can only register classes")
if issubclass(subclass, cls):