Spurious used-before-def in a specific situation using walrus

[tzaffi]

Bug Report

I'm getting the following mypy error used-before-def on the code snippet below:

I played around a bit trying to simplify, but there could be other scenarios I haven't explored.

Generalizing what I deem the problem to be:

WHEN:

• A function is defined whereby
• it calls a callable object
• AND inside the call there an assignment to a new variable
• AND the call returns another callable object
• AND the other callable object is supplied the new variable defined in the previous call

THEN:

the used-before-def error is generated even though there is nothing at all incorrect in this scenario since the new variable would ALWAYS be available.

To Reproduce

run mypy version 1.0 on the following:

from typing import Any


class Reporter:
    def __init__(self, x: Any):
        self.x: Any = x

    def report(self, y: Any = None):
        print(self.x)
        if y is not None:
            print(y)


def foo(z: Any):
    Reporter(x := z).report(x)


for i in range(10):
    foo(i)

Expected Behavior

No error should be generated.

Actual Behavior

pyteal/walrus.py:15 error: Name "x" is used before definition  [used-before-def]

Your Environment

Python 3.11.1 running on mac Ventura 13.1

• Mypy version used: 1.0
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): not relevant IMO
• Python version used: 3.11.1

[AlexWaygood]

Duplicate of #14626

[AlexWaygood]

A patch release with the fix should hopefully be coming soon! :)