Bug report

Bug description:

Generic classes that are instantiated with the Class[Type](...) syntax have an undocumented(?) __orig_class__ attribute defined on them that contains a reference to the type passed in the brackets. This attribute is pickled along with the class as usual, and in the cases when that type is well-behaved this works fine. However, PEP695-defined TypeVars have their __module__ set to typing, and so pickling fails as it is not a true member of the typing module. This prevents the usage of either Class[Type](...) syntax or PEP695 syntax in code near anything that must be pickled.

import pickle
from typing import Generic, TypeVar

T = TypeVar('T')

class Foo(Generic[T]): # equivalently class Foo[Anything]:
    pass

def bar[Baz]():
    return Foo[Baz]()

pickle.dumps(bar())
#    pickle.dumps(bar())
#    ~~~~~~~~~~~~^^^^^^^
# _pickle.PicklingError: Can't pickle Baz: attribute lookup Baz on typing failed

print(bar().__dict__)
# {'__orig_class__': __main__.Foo[Baz]}
print(bar().__orig_class__.__parameters__[0])
# Baz
print(bar().__orig_class__.__parameters__[0].__module__)
# typing

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-129250: allow pickle instances of generic classes #129446