Crash "Fatal error while checking" with metaclass

[bersbersbers]

Bug description

When parsing the following file:

"""Fatal error while checking."""
class Meta(type(object), type(object)):
    pass

class Class(metaclass=Meta):
    pass

pylint crashed with a AstroidError and with the following stacktrace:

Traceback (most recent call last):
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 811, in _lint_file
    check_astroid_module(module)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 1085, in check_astroid_module
    retval = self._check_astroid_module(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 1135, in _check_astroid_module
    walker.walk(node)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\utils\ast_walker.py", line 94, in walk
    self.walk(child)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\utils\ast_walker.py", line 91, in walk
    callback(astroid)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 1040, in visit_classdef
    if _is_invalid_metaclass(metaclass):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 748, in _is_invalid_metaclass
    mro = metaclass.mro()
          ^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3066, in mro
    return self._compute_mro(context=context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3054, in _compute_mro
    unmerged_mro = list(clean_duplicates_mro(unmerged_mro, self, context))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 155, in clean_duplicates_mro
    raise DuplicateBasesError(
astroid.exceptions.DuplicateBasesError: Duplicates found in MROs (Meta), (type, object), (type, object), (type, type) for <ClassDef.Meta l.2 at 0x26ca8902bd0>.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 775, in _lint_files
    self._lint_file(fileitem, module, check_astroid_module)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 813, in _lint_file
    raise astroid.AstroidError from e
astroid.exceptions.AstroidError

Configuration

No response

Command used

pylint bug.py

Pylint output

************* Module bug
bug.py:2:0: C0115: Missing class docstring (missing-class-docstring)
bug.py:2:0: E0241: Duplicate bases for class 'Meta' (duplicate-bases)
bug.py:5:0: C0115: Missing class docstring (missing-class-docstring)
Exception on node <ClassDef.Class l.5 at 0x26ca8903410> in file 'C:\Code\Bug\bug.py'
Traceback (most recent call last):
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\utils\ast_walker.py", line 91, in walk
    callback(astroid)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 1040, in visit_classdef
    if _is_invalid_metaclass(metaclass):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 748, in _is_invalid_metaclass
    mro = metaclass.mro()
          ^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3066, in mro
    return self._compute_mro(context=context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3054, in _compute_mro
    unmerged_mro = list(clean_duplicates_mro(unmerged_mro, self, context))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 155, in clean_duplicates_mro
    raise DuplicateBasesError(
astroid.exceptions.DuplicateBasesError: Duplicates found in MROs (Meta), (type, object), (type, object), (type, type) for <ClassDef.Meta l.2 at 0x26ca8902bd0>.
bug.py:1:0: F0002: bug.py: Fatal error while checking 'bug.py'. Please open an issue in our bug tracker so we address this. There is a pre-filled template that you can use in 'C:\Users\bers\AppData\Local\pylint\pylint\Cache\pylint-crash-2023-05-18-09-05-35.txt'. (astroid-error)

------------------------------------------------------------------
Your code has been rated at 0.00/10 (previous run: 7.14/10, -7.14)

Expected behavior

I have no idea if the code examples makes any sense, but pylint should not crash.

Pylint version

pylint 2.17.4
astroid 2.15.5
Python 3.11.3 (tags/v3.11.3:f3909b8, Apr  4 2023, 23:49:59) [MSC v.1934 64 bit (AMD64)]

OS / Environment

Windows 10 21H2

Additional dependencies

No response

[bersbersbers]

Probably related:

When parsing the following file:

from pathlib import Path
from typing import Protocol

class Proto(Protocol):
    ...

class Meta(type(Path), type(Proto)):
    pass

class Class(Path, Proto, metaclass=Meta):
    pass

pylint crashed with a AstroidError and with the following stacktrace:

Traceback (most recent call last):
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 811, in _lint_file
    check_astroid_module(module)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 1085, in check_astroid_module
    retval = self._check_astroid_module(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 1135, in _check_astroid_module
    walker.walk(node)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\utils\ast_walker.py", line 94, in walk
    self.walk(child)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\utils\ast_walker.py", line 91, in walk
    callback(astroid)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 1040, in visit_classdef
    if _is_invalid_metaclass(metaclass):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\checkers\typecheck.py", line 748, in _is_invalid_metaclass
    mro = metaclass.mro()
          ^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3066, in mro
    return self._compute_mro(context=context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 3056, in _compute_mro
    return _c3_merge(unmerged_mro, self, context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\astroid\nodes\scoped_nodes\scoped_nodes.py", line 96, in _c3_merge
    raise InconsistentMroError(
astroid.exceptions.InconsistentMroError: Cannot create a consistent method resolution order for MROs (type, object), (_ProtocolMeta, ABCMeta, type, object), (type, _ProtocolMeta) of class <ClassDef.Meta l.9 at 0x21e4765e790>.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 775, in _lint_files
    self._lint_file(fileitem, module, check_astroid_module)
  File "C:\Users\bers\.pyenv-win-venv\envs\project_3.11\Lib\site-packages\pylint\lint\pylinter.py", line 813, in _lint_file
    raise astroid.AstroidError from e
astroid.exceptions.AstroidError

[Pierre-Sassoulas]

Thank you for opening the bug, I can reproduce on main.