Find the test case below:

----
from typing import NamedTuple

class Foo(NamedTuple):
    alpha: int
    index: int
----

This results in the following error when run through type-checking with mypy:

----
% mypy --version
mypy 0.620
% mypy go.py
go.py:5: error: Incompatible types in assignment (expression has type "int", base class "tuple" defined the type as "Callable[[Tuple[int, ...], Any, int, int], int]")
----

When I instantiate this class in the python interpreter, I have no problem accessing the "index" member, so I suspect this is a bug in the type checker.