AttributeError: 'Call' object has no attribute 'name'

[gtristan]

Bug description

This is similar but distinct from issue #4439.

Here is a reduced test case, I was able to concoct this after running pylint with modified checkers/classes.py and tracing the asteroid nodes being checked in _check_unused_private_attributes().

class Pony:
    __defaults = {}
    __defaults_set = False

    def __init__(self, value):
        self.value = value

    def __init_defaults(self):

        if not self.__defaults_set:
            type(self).__defaults = { "fur": "pink" }
            type(self).__defaults_set = True


    def __get_fur_color(self):
        color = lookup_attribute(self.__defaults, "fur")
        return color


def lookup_attribute(mapping, key):
    return mapping[key]

Possible fix

I think the crash is essentially caused by NodeNG.node_of_classes() yielding attributes passed through function calls, and it seems that pylint's _check_unused_private_attributes() is unprepared for this outcome.

The yielded astroid.AssignAttr and astroid.Attribute should have the type of the expr object checked before expecting the expression to be a named expression.

Command used

pylint test.py

Pylint output

Here is the stack trace generated by linting the test case:

Exception on node <ClassDef.Pony l.2 at 0x7f4029878280> in file '/home/tristan/linting-issue.py'
Traceback (most recent call last):
  File "/home/tristan/.local/bin/pylint", line 8, in <module>
    sys.exit(run_pylint())
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/__init__.py", line 24, in run_pylint
    PylintRun(sys.argv[1:])
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/run.py", line 384, in __init__
    linter.check(args)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/pylinter.py", line 975, in check
    self._check_files(
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/pylinter.py", line 1009, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/pylinter.py", line 1035, in _check_file
    check_astroid_module(ast_node)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/pylinter.py", line 1172, in check_astroid_module
    retval = self._check_astroid_module(
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/lint/pylinter.py", line 1217, in _check_astroid_module
    walker.walk(ast_node)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/utils/ast_walker.py", line 79, in walk
    callback(astroid)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/checkers/classes.py", line 904, in leave_classdef
    self._check_unused_private_attributes(node)
  File "/home/tristan/.local/lib/python3.9/site-packages/pylint/checkers/classes.py", line 983, in _check_unused_private_attributes
    assign_attr.expr.name == "cls"
AttributeError: 'Call' object has no attribute 'name'

Expected behavior

No crash, properly report if private class attributes are unused.

Pylint version

pylint 2.9.6
astroid 2.6.6
Python 3.9.2 (default, Feb 28 2021, 17:03:44) 

I've also tested this with python 3.8 and had the same results.

OS / Environment

I've seen this on fedora 32 and on debian 11.

Additional dependencies

No response

[Pierre-Sassoulas]

Thank you for taking the time to report this. Love the example with default pink ponyz.