Bug report

Bug description:

I observed different behavior for Enum __contains__ in 3.13.2 and 3.13.3 if there is _missing_ method implemented:

from enum import Enum

class Color(Enum):
    RED = 1
    
    @classmethod
    def _missing_(cls, value):
        return cls.RED

# 3.13.2
>>> "blue" in Color
False

# 3.13.3
>>> "blue" in Color
True

IMO _missing_ should only influence the __call__ method:

# both 3.13.2 and 3.13.3
>>> Color("blue")
<Color.RED: 1>

CPython versions tested on:

3.13

Operating systems tested on:

macOS

Linked PRs

• gh-132684: [Enum] only call _missing_ in __contains__ for Flags #132790
• [3.13] gh-132684: [Enum] only call _missing_ in __contains__ for Flags (GH-132790) #132896