Not detecting enum.auto vs enum.auto()

[jamesbraza]

Bug Report

mypy is not detecting forgetting to call enum.auto() in IntEnum and StrEnum.

To Reproduce

from enum import IntEnum, StrEnum, auto

class SomeIntEnum(IntEnum):
    CORRECT_AUTO = auto()
    INCORRECT_AUTO = auto

reveal_type(SomeIntEnum.CORRECT_AUTO.value)
reveal_type(SomeIntEnum.INCORRECT_AUTO.value)

class SomeStrEnum(StrEnum):
    CORRECT_AUTO = auto()
    INCORRECT_AUTO = auto

reveal_type(SomeStrEnum.CORRECT_AUTO.value)
reveal_type(SomeStrEnum.INCORRECT_AUTO.value)

Running this code will actually crash with a TypeError, but mypy will pass:

• For the IntEnum.INCORRECT_AUTO: TypeError: int() argument must be a string, a bytes-like object or a real number, not 'type'
• For the StrEnum.INCORRECT_AUTO: TypeError: <class 'enum.auto'> is not a string

Expected Behavior

I expect mypy to error when one forgets to call auto, as:

1. The code doesn't run
2. Even if it did run, the enum's value wouldn't be a primitive as intended

Actual Behavior

mypy passes with the below output:

a.py:7:13: note: Revealed type is "builtins.int"
a.py:8:13: note: Revealed type is "def () -> enum.auto"
a.py:14:13: note: Revealed type is "builtins.str"
a.py:15:13: note: Revealed type is "def () -> enum.auto"

Your Environment

• Mypy version used: 1.11.1
• Mypy command-line flags: n/a
• Mypy configuration options from mypy.ini (and other config files): n/a
• Python version used: 3.12.4

[jamesbraza]

The issue may be related to typeshed currently typing auto with Any: https://github.com/python/typeshed/blob/8a7f09e3511f3a1d04281c60167b8dcc3b78938b/stdlib/enum.pyi#L323