Mark Shannon <[email protected]> added the comment:
This failure appears to be a symptom of recursively traversing __bases__ rather
scanning __mro__ in the implementation of type.__subclasses__
The MCACHE depends on type.__subclasses__ being correct and it is not correct
for weird.py
python -i weird.py
>>> C = Meta("C", (), {})
>>> C.__mro__
(<class '__main__.C'>, <class '__main__.Foo'>, <class 'object'>)
>>> Foo.__subclasses__()
[]
>>> C.__bases__
(<class 'object'>,)
Fixing this may need a change in the API for type.__subclasses__() to return
all subclasses, as defined by __mro__, not just the bases.
A simpler, temporary fix might be to set Py_TPFLAGS_HAVE_VERSION_TAG to 0 for
any class that has a custom mro()
----------
nosy: +Mark.Shannon
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Python tracker <[email protected]>
<https://bugs.python.org/issue28866>
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