E0601 false positive when nested try block exhaustively defines name, raises, or returns

[AndersMunch]

Bug description

This produces a using 'x' before assignment error:

"""pylint_false_positive.py"""
def test():
    try:
        try:
            x = None
        except:
            x = None
            raise
    finally:
        print("x", x)

Configuration

No response

Command used

pylint -E pylint_false_positive.py

Pylint output

************* Module pylint_false_positive
pylint_false_positive.py:10: [E0601(used-before-assignment), test] Using variable 'x' before assignment

Expected behavior

Expected no error, x is assigned in all branches.

Pylint version

pylint 2.14.5
astroid 2.11.7
Python 3.10.6 (tags/v3.10.6:9c7b4bd, Aug  1 2022, 21:53:49) [MSC v.1932 64 bit (AMD64)]

OS / Environment

No response

Additional dependencies

No response

[DanielNoord]

I think this is correct? Pinging @jacobtylerwalls for an opinion.

If you change this to:

"""pylint_false_positive.py"""


def test():
    try:
        try:
            x = 1 / 0
        except:
            x = 1 / 0
            raise
    finally:
        print("x", x)


test()

This won't run and an UnboundLocalError will be raised. Is that we are guarding against here @jacobtylerwalls?

[jacobtylerwalls]

Yes, or even:

"""pylint_false_positive.py"""


def test():
    try:
        1 / 0
        try:
            x = None
        except:
            x = None
            raise
    finally:
        print("x", x)


test()

We just currently lack a "comprehensivity" check that "nothing else is being done in the outer try". Theoretically we could, so I'm happy to leave the issue open for now, but it could be that ultimately we determine it doesn't bring enough value for the effort involved.