typing.Generic-based type annotations cannot be loaded

[marcbllv]

Cloud pickle 0.5.5 now supports pickling of type annotations, but some of them cannot be pickled and loaded. Especially generic types that are based on base class Generic, like Sequence, Tuple, List, ...

Here is the issue:

import typing
import cloudpickle

cloudpickle.loads(cloudpickle.dumps(typing.Sequence[int]))

Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/Users/marcbeillevaire/anaconda/envs/test/lib/python3.6/typing.py", line 948, in __new__
 raise TypeError("Cannot inherit from plain Generic")
TypeError: Cannot inherit from plain Generic

Note that this works fine:

import typing
import cloudpickle
cloudpickle.loads(cloudpickle.dumps(typing.Sequence)) # Sequence, not Sequence[int]

It looks like the arguments of __getitem__ get lost, and only the generic class is pickled -- here: Sequence, and not Sequence[int].

This leads to loading a class that inherits from typing.Generic, not typing.Generic[int] which raises the error (see typing.py line 948 where the error above is raised).

[marcbllv]

Issue #193 may be related (pickling typing class with brackets)