When implementing __new__, you usually create an instance of the class in which the __new__ is defined. pylint currently does not allow setting protected and private attributes inside __new__.

Steps to reproduce

Lint the follwing code

# pylint: disable=blacklisted-name, missing-docstring

class MyObj:

    def __new__(cls, foo, bar):
        obj = object.__new__(cls)
        obj._foo = foo   # <-- warning reported here
        obj.__bar = bar   # <-- warning reported here
        return obj

    @property
    def foo(self):
        return self._foo

    @property
    def bar(self):
        return self.__bar



def main():
    instance = MyObj(1, 2)
    print(instance.foo)
    print(instance.bar)


main()

Current behavior

This currently returns the following:

************* Module example
W:  7, 8: Access to a protected member _foo of a client class (protected-access)
W:  8, 8: Access to a protected member __bar of a client class (protected-access)

------------------------------------------------------------------
Your code has been rated at 8.67/10 (previous run: 7.69/10, +0.97)

Expected behavior

No warning should be reported.

This may be controversial, but I wonder if it would make sense to silence the warnings in this case. just like they are inside of __init__. While __new__ is used really rarely, it does not strike me as wrong to access private/protected members in there unless I am missing something. Would that really be a bad practice?

pylint --version output

pylint 1.8.1,
astroid 1.6.0
Python 3.5.2 (default, Nov 23 2017, 16:37:01)
[GCC 5.4.0 20160609]

This is also somewhat related to #1801 as I noticed this error with that enum, but it turns out that the warning is also emitted for normal objects.