Fails to flag `None` passed to constructor of `enum.Enum`-based classes

Bug Report

Mypy fails to flag None passed to constructor of enum.Enum-based classes.

To Reproduce

import enum


class Foo(enum.Enum):
    one = 1


Foo(None)

Note that changing to class Foo(int, enum.Enum) does make mypy flag the error. However, the two aren't equivalent as the latter lets you do Foo.one + 1 while the former requires Foo.one.value + 1.

Edit: In fact, in both forms it fails to flag invalid arguments such as Foo(2). I do realize this is a slightly different case, which is why I'm focusing on None which has different behavior between the two.

Expected Behavior

I would expect mypy to flag the last line as an error:

error: No overload variant of "Foo" matches argument type "None"  [call-overload]

Actual Behavior

Mypy reports no errors.

Your Environment

Tested on

• Mypy 1.13.0 and 1.15.0
• CPython 3.11.10

Used mypy --strict file.py and just mypy file.py.

Contents of mypy.ini (I actually use a pyproject.toml file, but have tested with only this ini-file):

[mypy]
check_untyped_defs = true
disallow_any_generics = false
disallow_incomplete_defs = false
disallow_subclassing_any = false
disallow_untyped_calls = false
disallow_untyped_decorators = true
disallow_untyped_defs = false
enable_error_code = truthy-bool, truthy-iterable
extra_checks = true
ignore_missing_imports = false
local_partial_types = true
no_implicit_optional = true
no_implicit_reexport = false
no_namespace_packages = true
python_version = 3.11
strict_equality = true
warn_redundant_casts = true
warn_return_any = false
warn_unused_configs = true
warn_unused_ignores = true

Inizia con il riproduttore enum.Enum fornito e confrontalo con il caso int, enum.Enum che segnala già un errore. Traccia il modo in cui mypy controlla le chiamate al costruttore per le classi basate su enum, quindi aggiungi la copertura per Foo(None) e per valori non validi come Foo(2); il lavoro è completo quando viene segnalato l’errore call-overload previsto.