Unexpected error 'already defined' in function

[TiesWestendorp]

Bug Report

Unexpected error: error: Name "*" already defined in combination with assignment expression and list comprehension.

To Reproduce

Execute mypy on the following snippet:

def func(input: List[int]) -> List[int]:
    running_maximum = input[0] if len(input) > 0 else 0
    return [running_maximum := max(running_maximum, item) for item in input]

Expected Behavior

Since running_maximum is being returned implicitly during each step in the list comprehension, the assignment expression doesn't hide the value of the initial assignment. Hence, there should be no errors.

Actual Behavior

error: Name "running_maximum" already defined

Your Environment

• Mypy version used: 0.910
• Python version used: 3.10
• Operating system and version: Windows 10

[hauntsaninja]

Thanks, I already fixed this on master in #11153

[TiesWestendorp]

Nice, great work in that case. :)

[TiesWestendorp]

How do mypy releases work? When will this be shipped?

[hauntsaninja]

No idea. The people with the ability to make releases are very busy.

It looks like this landed one or two days after the cutoff for #11158, so I'd post on there asking for it to be cherry-picked.