False positive too-few-public-methods for TypedDict in Python 3.9

[wshanks]

This is a follow up to #1927, #2607, and #4072. In Python 3.9, TypedDict was changed from a class to a function with metaclass magic. This change caused worse problems initially (fixed by #4072), but now pylint gives a warning about too few public methods when subclassing TypedDict to create a new type as suggested in the documentation (https://docs.python.org/3/library/typing.html#typing.TypedDict). A work around is to use one of the alternate TypedDict syntax forms in which TypedDict is used as a function instead of a class.

Steps to reproduce

Given a file a.py:

"Demo"
import typing


class Coordinate(typing.TypedDict):
    "This is my type"
    x: float
    y: float

Current behavior

Result of pylint a.py:

************* Module test
test.py:5:0: R0903: Too few public methods (0/2) (too-few-public-methods)

------------------------------------------------------------------
Your code has been rated at 7.50/10 (previous run: 7.50/10, +0.00)

Expected behavior

No warnings.

pylint --version output

Result of pylint --version output:

pylint 2.7.2                                                                                  
astroid 2.5.1                                                                                 
Python 3.9.2

[cdce8p]

Yeah, with pylint-dev/astroid#915 TypedDicts are now inferred as classes and thus all default class checks do apply. It might indeed make sense to disable too-few-public-methods if the class inherits from TypedDict.

[cdce8p]

Opened #4191 to fix it