Add more error checking in subclass creation (#64746)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64746
This extracts the error checking that used to be in the PR above.
We are not going to land the proposed fix there, but I think we want this error checking in right now as these would lead to respectively a memory leak and arbitrary memory read/write.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D30867569
Pulled By: albanD
fbshipit-source-id: bf468033fb8b49fcb26eed423f5fad82b4a46c56
