False positive 'undefined-variable' with assignment expression in decorator

[Jasha10]

Bug description

When using an assignment expression in a decorator, a false positive 'undefined-variable' and 'unused-variable' may be raised.

Reproducible Example

# example.py
def preprocess(bar: str) -> str:
    return bar + "xyz"

def condition1(foo):
    return foo.startswith("abc")

def condition2(foo):
    return "bcdef" in foo

def postprocess(foo):
    return foo

data = ["abcdef", "qwerty"]

def decorator(arg):
    print(f"{arg=}")
    return lambda x: x

@decorator(
    [postprocess(foo) for string in data if condition1(foo := preprocess(string)) and condition2(foo)],
)
def decorated() -> None:
    pass

Pylint output

$ pylint example.py
************* Module example
tmp2.py:32:17: E0602: Undefined variable 'foo' (undefined-variable)
tmp2.py:32:97: E0602: Undefined variable 'foo' (undefined-variable)
tmp2.py:32:55: W0612: Unused variable 'foo' (unused-variable)

------------------------------------------------------------------
Your code has been rated at 3.12/10 (previous run: 3.12/10, +0.00)

$ # Demonstrating that the python code runs as expected:
$ python example.py
arg=['abcdefxyz']

Expected behavior

No errors

Pylint version

$ pylint --version
pylint 2.12.2
astroid 2.9.3
Python 3.9.9 | packaged by conda-forge | (main, Dec 20 2021, 02:40:17)
[GCC 9.4.0]