False positive undefined-loop-variable with pylint 2.5.3

[lukasoyen]

Steps to reproduce

1. Save code as false-positive.py
2. Run python3 -m pylint --disable=all --enable=undefined-loop-variable false-positive.py

def test(content):
    def handle_line(line):
        if "X" in line:
            line = line.replace("X", "Y")
        elif "Y" in line:  # line 5
            line = '{}'.format(line)
        elif "Z" in line:  # line 7
            line = f'{line}'
        else:
            line = '%s' % line  # line 10

    for line in content.split('\n'):
        handle_line(line)

Current behavior

This prints:

false-positive.py:5:20: W0631: Using possibly undefined loop variable 'line' (undefined-loop-variable)
false-positive.py:7:20: W0631: Using possibly undefined loop variable 'line' (undefined-loop-variable)
false-positive.py:10:26: W0631: Using possibly undefined loop variable 'line' (undefined-loop-variable)

Expected behavior

No undefined-loop-variable violations.

pylint --version output

pylint 2.5.3
astroid 2.4.2
Python 3.7.7 (default, Mar 10 2020, 06:34:06) 
[GCC 9.3.0]

[bodograumann]

I am seeing a similar issue here:

lst = []
lst2 = [1, 2, 3]

for item in lst:
    pass

bigger = [
    [
        x for x in lst2 if x > item
    ]
    for item in lst
]

pylint complains:

pylint-test.py:9:31: W0631: Using possibly undefined loop variable 'item' (undefined-loop-variable)

Removing the first for loop makes it vanish.
When pylint determines that lst definitely contains items, the warning also disappears, but it does not apply even for an empty lst, because then the outer list comprehension is simply empty as well.