pyi parser crashes on file that imports typing.Literal inside version check

[rchen152]

See python/typeshed#4807. The pytype test failed with the following error:

free(): invalid pointer
/home/runner/work/_temp/c2a28e77-7168-488e-8f26-da1cbba538c8.sh: line 1:  2734 Aborted                 (core dumped) ./tests/pytype_test.py

srittau fixed the failure with the following change: python/typeshed@02dfcc6, which modified:

if sys.version_info >= (3, 9):
    from typing import Literal

to:

from typing_extensions import Literal

[Solumin]

I was able to reproduce this with:

git clone http://github.com/python/typeshed
cd typeshed
python3 tests/pytype_test.py

That is, with a completely fresh install, I'm still seeing the double free error.

Python version: 3.6.6
Pytype version: 2020.02.20
Typeshed commit: 3d1401

Edit: Unsurprisingly, updating to the latest release made it go away. Reverting srittau's fix for abc.pyi makes it reappear. Still investigating -- I have a sneaking suspicion it's not abc.pyi that's at fault, but something to do with the number of breakages.

[Solumin]

Every time there are 10 or more errors found, the double free error appears.

I don't think this is a crash, because no crash appears in the logs. It might be some kind of post-test clean up that's failing.

Ideally, we'd hook up Asan, but I don't see an easy way to do that.

[rchen152]

Is this still an issue with the new parser?

[rchen152]

I introduced an error to typeshed that causes pytype to report 56 errors and didn't manage to trigger this issue, so I think it's fixed...? I suggest we close it unless it comes up again.