Not reporting W0621 redefined-outer-name when the outer name is redefined by except .. as ..

[chucklin]

Steps to reproduce

Given a file a.py:

"""Test pylint W0621"""
class CustomException(Exception):
    """Customized Exception"""

def func():
    """Override CustomException by except .. as .."""
    try:
        raise CustomException('Test')
    except IOError as CustomException:
        pass

Current behavior

Result of pylint a.py:

************* Module test
test.py:8:14: E0601: Using variable 'CustomException' before assignment (used-before-assignment)

------------------------------------------------------------------
Your code has been rated at 1.67/10 (previous run: 1.67/10, +0.00)

Expected behavior

Expecting pylint reports W0621 redefined-outer-name on line except IOError as CustomException

I tested overriding the outer name by with .. as .., and the W0621 reported without problems.
In my opinion, W0621 should also be reported when the outer name gets redefined by except .. as .. .

pylint --version output

Result of pylint --version output:

pylint 2.8.2
astroid 2.5.6
Python 3.9.2 (default, Apr 12 2021, 14:14:14)
[Clang 12.0.0 (clang-1200.0.32.29)]

[Pierre-Sassoulas]

Thank you for opening the issue, this is a strange behavior indeed.

[jacobtylerwalls]

In my opinion, W0621 should also be reported when the outer name gets redefined by except .. as .. .

This bit on line 9 (the false negative for redefined-outer-name) is fixed in #5630. I'll add a regression test.

The false positive on line 8 for used-before-assignment is weird.

[jacobtylerwalls]

The false positive on line 8 for used-before-assignment is weird.

Oooh, no -- that's just how the python interpreter works!

"""Test pylint W0621"""
class CustomException(Exception):
    """Customized Exception"""

def func():
    """Override CustomException by except .. as .."""
    try:
        raise CustomException('Test')
    except IOError as CustomException:
        pass

if __name__ == "__main__":
    func()

Gives
UnboundLocalError: local variable 'CustomException' referenced before assignment.

---

So I think ultimately this is a duplicate of #5370, but I can add the smart test case.