self incorrectly marked as unsubscriptable in list subclass

[pauladams8]

Steps to reproduce

1. Subclass the builtin list class
2. Slice self from within the class

Example

class CustomList(list):
    def first(self):
        # for example
        return self[0]

Current behavior

pylint produces error

Value 'self' is unsubscriptable

Expected behavior

No alert from pylint

pylint --version output

pylint 2.6.0
astroid 2.4.2
Python 3.8.5 (default, Jul 21 2020, 10:48:26)
[Clang 11.0.3 (clang-1103.0.32.62)]

[hippo91]

@pauladams8 thanks for your report.
I'm unable to reproduce it.
Linting the following code:

#pylint:disable=missing-module-docstring
#pylint:disable=missing-class-docstring
#pylint:disable=missing-function-docstring
class CustomList(list):
    def first(self):
        # for example
        return self[0]

gives no message.

pylint 2.6.0
astroid 2.4.3
Python 3.8.2 (default, Sep 28 2020, 21:24:28) 
[GCC 8.3.0]

[pauladams8]

Sorry, should have been clearer. Upon further testing, the problem occurs only when I subclass the List alias in typing and with a type hint.

Try this:

from typing import List

class TypeHint:
    pass

class CustomList(List[TypeHint]):
    def first(self):
        # pylint alerts me "Value 'self' is unsubscriptable", which is incorrect
        return self[0]

Additionally, pylint incorrectly reports errors when List is subclassed without a type hint.

Inheriting 'List', which is not a class.

When getting and setting custom properties:

Instance of '_GenericAlias' has no '{any member}' member

It seems these errors are not present with a type hint.

To reproduce this, use the sample above but without the [TypeHint].

[pauladams8]

pylint also reports incorrectly on List[TypeHint] subclasses

Value 'self' doesn't support membership test

Test sample as above, with additional method

def has_foo(self):
    return 'foo' in self

[hippo91]

@pauladams8 thanks for this update. I can now reproduce it.
While it is not linked to python3.9 maybe the current work on supporting typing module under python3.9 (#3890 #3905) may improve the situation.

[cdce8p]

@pauladams8 I wasn't able to reproduce any of the errors with the latest version of pylint. We improved the handling of the typing module quite a bit in recent versions so I would assume this has been fixed. Going to close this issue.

If you still experience issues, please report back and I'll reopen it.