Hello,

Python 3.5, but I'm using typing.py from this repo, master branch. (Trying to port a library.)

I realize this is not really the intended use of typing.

I'm not really sure if this is an issue in typing or singledispatch, but it used to work before. Here's a small test case. Note that typing.Tuple[int] is a subclass of typing.Tuple, and typing.Tuple is a subclass of typing.Sequence.

import typing
from functools import singledispatch

s = singledispatch(lambda: 'default')
s.register(typing.Sequence, lambda: 'sequence')
s.register(typing.Tuple, lambda: 'tuple')

print(s.dispatch(typing.Tuple[int])())

If you run it a number of times, the results are either 'tuple' or 'sequence', based on the ordering of an internal dict in singledispatch. This is a bug in singledispatch, right?