Example:

from typing import Dict
from enum import Enum
class E(Enum):
    V = 'V'
d = {}  # type: Dict[E, int]
def f(s: str):
    e = E[s]  # type: ignore
    d[e] = 0  # Still error here

We have to use # type: ignore on the line e = E[s] because of #741. But somehow the type of e, when ignoring the error, is not Any but something else. So on the last line we get

__tmp__.py: note: In function "f":
__tmp__.py:8: error: Invalid index type "E" for "dict"

The weird thing is that if e had type E, d[e] would be valid, so the error is also somehow lying...

UPDATE: When trying to repro this, don't try E['V'] -- mypy sees the literal and gives some other error, probably also because of #741.