Final not honored when applied post-hoc

Bug Report

The behavior of Final is a bit inconsistent. It can be applied post-hoc, but then it won't be honored.

To Reproduce

import platform
import sys

from typing import Final

SERIES_STD = ' ▌█' if platform.system() == 'Windows' else ' ▏▎▍▌▋▊▉█'
if sys.__stdout__ and sys.__stdout__.encoding:
    try:
        SERIES_STD.encode(sys.__stdout__.encoding)
    except UnicodeEncodeError:
        SERIES_STD = ' |'

SERIES_STD: Final = SERIES_STD
SERIES_STD = '| '

Expected Behavior

I expect an assignment error for the final line to raise an error.

error: Cannot assign to final name "SERIES_STD"  [misc]

Some people might argue applying Final post-hoc itself should raise an error, but I'm not one of them.

Actual Behavior

Success: no issues found in 1 source file

Your Environment

• Mypy version used: 1.18.2
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): No Config
• Python version used: 3.13.9

Commencez par exécuter le reproducer fourni avec mypy 1.18.2 et suivez la manière dont les annotations Final postérieures sont traitées. Identifiez le chemin pertinent de vérification des types, ajoutez une couverture pour cet exemple et confirmez que la réaffectation signale "Cannot assign to final name", tandis que le reste du comportement de Final reste inchangé.