New enum features in Python 3.11

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:

• #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:

• #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:

• #14688

Start by reviewing mypy's existing handling of Python enums and the Python 3.11 enum documentation. Use the issue's examples for enum.verify and enum.member/nonmember to determine the expected behavior, then verify that the listed unsupported features are handled consistently while accounting for the separately linked issues.