Deduplication of type casting codes (#32730)
Summary:
These codes are implemented twice at different places by different people, we should merge them together.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32730
Differential Revision: D19622023
Pulled By: ezyang
fbshipit-source-id: a9cbda31428b335bf28a7e4050f51f58e787b94f
