Undefined variable __class__ as return type when using annotations

[mattclay]

Steps to reproduce

Using __class__ as a method return type results in an undefined variable error, unless the type is also used in the arguments. Using it only for arguments works as expected.

#!/usr/bin/env python3.7

from __future__ import annotations


class Demo:
    def __init__(self, number):
        self.number = number

    # OK
    def become(self, demo: __class__) -> None:
        self.number = demo.number

    # OK
    def combine(self, demo: __class__) -> __class__:
        return Demo(self.number + demo.number)

    # demo.py:19:27: E0602: Undefined variable '__class__' (undefined-variable)
    def increment(self) -> __class__:
        return Demo(self.number + 1)

Current behavior

demo.py:19:27: E0602: Undefined variable '__class__' (undefined-variable)

Expected behavior

No undefined variable error.

pylint --version output

__main__.py 2.2.2
astroid 2.1.0
Python 3.7.0 (default, Sep  5 2018, 11:18:59) 
[Clang 9.1.0 (clang-902.0.39.2)]

[mattclay]

May be related to #1976

[PCManticore]

Right, this makes sense and it's a bug, but it's quite an edge case with __class__.

[PCManticore]

This no longer reproduces with the unreleased version:

pylint 2.5.0-dev1
astroid 2.4.0
Python 3.8.1 (default, Feb 13 2020, 10:17:07)
[Clang 8.1.0 (clang-802.0.42)]