"""

conftest.py - builtin classes generics shim for python < 3.9

"""

from sys import version_info

if version_info < (3, 9):

# For each of the following types, add a

# new class function called `__class_getitem__`.

# This is called when the type is subscripted,

# such as in:

#

# list[str]

# dict[int, list[int]]

#

# This will make these typing expressions work

# seamlessly on python versions >= 3.7 and < 3.9

# (support was added, but not used out-of-the-box),

# in python 3.7).

import gc, types, typing

from typing import _GenericAlias as GenericAlias

for t in (list, dict, set, tuple, frozenset):

r = gc.get_referents(t.__dict__)[0]

r.update({

"__class_getitem__": classmethod(GenericAlias),

})