Make isinstance(OldstyleClass, NewstyleClass) return False instead of raising
an exception. Issue reported by Joseph Armbruster.
diff --git a/Lib/abc.py b/Lib/abc.py
index 5da2590..5e90bf5 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -116,18 +116,18 @@
def __instancecheck__(cls, instance):
"""Override for isinstance(instance, cls)."""
- # Inline the cache checking for new-style classes.
- subclass = instance.__class__
+ # Inline the cache checking when it's simple.
+ subclass = getattr(instance, '__class__', None)
if subclass in cls._abc_cache:
return True
subtype = type(instance)
- if subtype is subclass:
+ if subtype is subclass or subclass is None:
if (cls._abc_negative_cache_version ==
ABCMeta._abc_invalidation_counter and
- subclass in cls._abc_negative_cache):
+ subtype in cls._abc_negative_cache):
return False
# Fall back to the subclass check.
- return cls.__subclasscheck__(subclass)
+ return cls.__subclasscheck__(subtype)
return (cls.__subclasscheck__(subclass) or
cls.__subclasscheck__(subtype))