New enum features in Python 3.11

[AlexWaygood]

There's a ton of new enum features in Python 3.11 that mypy doesn't yet support:

• enum.property
• enum.verify
• enum.(non)member
• ReprEnum
• StrEnum

---

enum.property is not yet supported:

• (🐞) Enum.name is Any in 3.11 / support enum.property #12483

---

The new enum.verify decorator isn't supported: the following snippet will raise an exception at runtime on 3.11 due to not all values being unique, but it passes mypy:

from enum import Enum, verify, UNIQUE

@verify(UNIQUE)
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
    CRIMSON = 1

---

enum.member/enum.nonmember. The docs are a bit thin on these, but it looks like in the following enum, BAR is converted to become a member, but BAZ
is not:

from enum import Enum, nonmember

class Foo(Enum):
    BAR = 1
    BAZ = nonmember(2)

(These two can also be used as decorators)

---

ReprEnum: this doesn't need any special support by mypy, but the following mypy bug but means that it can't really be used idiomatically at the moment:

• Enums: false-positive "No base classes allowed after ReprEnum" error #12787

---

StrEnum: I didn't think this required any special treatment from mypy, but there's a weird bug here in mypy's handling of StrEnum:

• Invalid typing assumption over variable with list(StrEnum) on python 3.11 #14688

[electric-coder]

There are 83 open Enum mypy issues at the the time of this writing.

Getting the Enum datatype to work with mypy is becoming impossible as I find myself having to use cast() in at least every other line.

[electric-coder]

@AlexWaygood there's also Enum's _new_member_ that hasn't been mentioned in the docs nor in the mypy repository.

[CoolCat467]

With #17376 being merged we should be able to check off enum.nonmember, no?

[AlexWaygood]

With #17376 being merged we should be able to check off enum.nonmember, no?

Done