@final is not allowed on non-method functions

What it does

Checks for @final decorators applied to non-method functions.

Why is this bad?

The @final decorator is only meaningful on methods and classes. Applying it to a module-level function or a nested function has no effect and is likely a mistake.

Example

from typing import final


# @final is not allowed on non-method functions
@final  # error
def my_function() -> int:
    return 0