Success(None) and Some(None) fails to load from pickle

[yukiisbored]

Bug report

What's wrong

It appears returns containers fail to load from serialized pickle form when the inner value is None.

I wrote a quick test script:

import pickle

from returns.result import Success, Failure
from returns.maybe import Some

assert(pickle.loads(pickle.dumps(Success(None))) == Success(None))
assert(pickle.loads(pickle.dumps(Failure(None))) == Failure(None))
assert(pickle.loads(pickle.dumps(Some(None)))    == Some(None))

Here's the stacktrace

$ python ./test.py
Traceback (most recent call last):
  File "/home/yuki/cum/./test.py", line 6, in <module>
    assert(pickle.loads(pickle.dumps(Success(None))) == Success(None))
  File "/nix/store/rsyzznrv5jg9dx7yj26lf4yjybmafba2-python3-3.9.12-env/lib/python3.9/site-packages/returns/primitives/container.py", line 34, in __eq__
    return container_equality(self, other)  # type: ignore
  File "/nix/store/rsyzznrv5jg9dx7yj26lf4yjybmafba2-python3-3.9.12-env/lib/python3.9/site-packages/returns/primitives/container.py", line 61, in container_equality
    self._inner_value == other._inner_value,  # type: ignore # noqa: WPS437
AttributeError: _inner_value

So far I've tested Success, Failure, Some and all three of them fail the same way.

How is that should be

As shown in the test script, returns container should be "recreated" properly including its None inner value from the pickled form.

System information

• python version: 3.9.12
• returns version: 0.19.0
• mypy version: 0.950