false positive (used-before-assignment) due to assignment expression within a tuple

[msladecek]

Steps to reproduce

1. Create file examples/tuple.py

values = (
    a := 1,
    b := 2,
    c := a + b,
)
print(values)

function = lambda: (
    a := 1,
    b := 2,
    c := a + b,
)
print(function())

2. Run pylint

$ pylint examples/tuple.py
************* Module tuple
examples/tuple.py:4:9: E0601: Using variable 'a' before assignment (used-before-assignment)
examples/tuple.py:4:13: E0601: Using variable 'b' before assignment (used-before-assignment)
examples/tuple.py:11:9: E0602: Undefined variable 'a' (undefined-variable)
examples/tuple.py:11:13: E0602: Undefined variable 'b' (undefined-variable)

Current behavior

Pylint returns error E0601 (used-before-assignment) when the left side of an assignment expression is used within the same tuple it was created in.

Pylint returns error E0602 (undefined-variable) when the left side of an assignment expression is used within the same tuple it was created in, in a lambda.

Expected behavior

Pylint shouldn't detect E0601 & E0602 on these expressions because they are valid python3.8 code.

$ python examples/tuple.py
(1, 2, 3)
(1, 2, 3)

pylint --version output

pylint 2.4.4
astroid 2.3.3
Python 3.8.0 (default, Nov  2 2019, 00:46:27) 
[GCC 9.2.0]

[PCManticore]

Thanks for the report. While assignment expressions is part of the language, supporting it is not a priority right now.

[bjtho08]

I also get Undefined variable 'match' in this otherwise elegant piece of code:

import os
from re import search
...
log_path = "/path/to/log/dir/
if any((match := search(r"\.csv$", file)) for file in os.listdir(log_path)):
        log_id = match.string

In my opinion this is a good example of how to properly utilize the assignment operator and it should not result in an obvious false positive, regardless of what some people might think of the assignment operator in general.