[Python] Why does MyPy fail to narrow types when comparing Enum members in this way?

Given a simple enumerator:

from enum import Enum
from typing import assert_never

class Day(Enum):
MONDAY = 1
TUESDAY = 2
WEDNESDAY = 3


And some code that handles members:

a_day = Day(1) # simplified version of larger code base
if a_day == a_day.MONDAY:
print("MONDAY")
elif a_day == a_day.TUESDAY:
print("TUESDAY")
elif a_day == a_day.WEDNESDAY:
print("WEDNESDAY")
else:
assert_never(a_day)
# MyPy revealed type is "Day", but linter revealed type is "Never"


MyPy complains that assert_never is reachable.

I'm expecting MyPy to understand that a_day is Never here. The linter does.

I know that I can change it to:

a_day = Day(1) # simplified version of larger code base
if a_day == Day.MONDAY:
print("MONDAY")
elif a_day == Day.TUESDAY:
print("TUESDAY")
elif a_day == Day.WEDNESDAY:
print("WEDNESDAY")
else:
assert_never(a_day)
# MyPy revealed type is "Never"


However, i'm trying to avoid referring to the Enum class directly ("Day"), as this causes issues whenever I use iPython with Autoreload: the instance "a_day" becomes a different type to Day after reloading from a separate module.

I'm aware that I can restart the Python kernel to resolve, but this is impractical in my use case (Python opens other software that takes a lot of time to restart). I'm also aware of %reset -f --aggressive in iPython would also resolve, but this breaks other functions in our code base too, and is also frustrating when we forget until after the code fails.

I have found a "hacky workaround" (problem being to remember to do it):

a_day = Day(1) # simplified version of larger code base
enum_type = type(a_day)
if a_day == enum_type.MONDAY:
print("MONDAY")
elif a_day == enum_type.TUESDAY:
print("TUESDAY")
elif a_day == enum_type.WEDNESDAY:
print("WEDNESDAY")
else:
assert_never(a_day)
# MyPy revealed type is "Never", and continues to work through iPython Autoreload

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