Private property in subclass of Enum is not indexable

[jcrada]

Hi,

• Are you reporting a bug, or opening a feature request?
  Reporting a minor bug in --strict mode when adding private property to Enum subclass.

import operator
import enum
from typing import Callable

@enum.unique
class Comparator(enum.Enum):
    LessThan = "<"
    LessThanOrEqualTo = "<="
    EqualTo = "=="
    NotEqualTo = "!="
    GreaterThanOrEqualTo = ">="
    GreaterThan = ">"

    __operator__ = {
        LessThan: operator.lt,
        LessThanOrEqualTo: operator.le,
        EqualTo: operator.eq,
        NotEqualTo: operator.ne,
        GreaterThanOrEqualTo: operator.ge,
        GreaterThan: operator.gt
    }

    @property
    def operator(self) -> Callable[[object, object], bool]:
        return Comparator.__operator__[self.value]

Comparator.LessThan.operator(1,2)
Comparator("<").operator(1,2)

• What is the actual behavior/output?
  The output is the following, where the first line is a missing stub for operator, and the second is the error in this report:

<string>:26: warning: Returning Any from function declared to return "Callable[[object, object], bool]"
<string>:26: error: Value of type "Comparator" is not indexable

• What is the behavior/output you expect?
  <string>:26: error: Value of type "Comparator" is not indexable should not appear.

• What are the versions of mypy and Python you are using?
  mypy: 0.610
  python: 3.6.5
  Could not run mypy from master

• What are the mypy flags you are using? (For example --strict-optional)
  --strict

[JelleZijlstra]

Probably what's happening here is that mypy doesn't implement the enum feature where names surrounded by underscores don't turn into enum members. This should be relatively easy to fix.