classmethod(classmethod(foo)) -> SystemError

[anthonybaxter]

BPO	770465
Nosy	@rhettinger

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2003-07-13.13:58:40.000>
created_at = <Date 2003-07-13.08:54:09.000>
labels = []
title = 'classmethod(classmethod(foo)) -> SystemError'
updated_at = <Date 2003-07-13.13:58:40.000>
user = 'https://bugs.python.org/anthonybaxter'

bugs.python.org fields:

activity = <Date 2003-07-13.13:58:40.000>
actor = 'anthonybaxter'
assignee = 'anthonybaxter'
closed = True
closed_date = None
closer = None
components = ['None']
creation = <Date 2003-07-13.08:54:09.000>
creator = 'anthonybaxter'
dependencies = []
files = []
hgrepos = []
issue_num = 770465
keywords = []
message_count = 4.0
messages = ['17045', '17046', '17047', '17048']
nosy_count = 2.0
nosy_names = ['anthonybaxter', 'rhettinger']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue770465'
versions = ['Python 2.2']

[anthonybaxter]

Using 2.2.3 or current release22-maint:

>>> classmethod(classmethod(None)).__get__(1) 
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
SystemError: Objects/classobject.c:2022: bad argument
to internal function
(thanks to Steve Alexander for the one-line example)

This produces the error "classmethod is not callable"
in 2.3,
but no systemerror - dunno if 2.3 could provide a
better error message here.

A more realistic example (derived from the code that
originally tripped me up):

>>> class a:
...     def foo(self):
...         print "self is", self, type(self)
...     foo=classmethod(foo)
...     foo=classmethod(foo)
... 
>>> b=a()
>>> b.foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
SystemError: Objects/classobject.c:2022: bad argument
to internal function

[rhettinger]

Logged In: YES
user_id=80475

This was fixed in revision 2.63 on Jun 18, 2003
and marked as a backport candidate. See SF bug bpo-753451.

[anthonybaxter]

Logged In: YES
user_id=29957

Re-opening, assigning to myself to remind me to do the backport.

[anthonybaxter]

Logged In: YES
user_id=29957

Backported. Thanks for the pointer!
(also fixed identical bug in Zope3's ContextMethod)

Checking in Objects/funcobject.c;
/cvsroot/python/python/dist/src/Objects/funcobject.c,v <--
funcobject.c
new revision: 2.50.4.4; previous revision: 2.50.4.3
done
Checking in Lib/test/test_descr.py;
/cvsroot/python/python/dist/src/Lib/test/test_descr.py,v
<-- test_descr.py
new revision: 1.113.4.35; previous revision: 1.113.4.34
done