Back out "Revert D21986243: TORCH_FN" (#40110)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40110
Original commit changeset: 72c690c2b4c2
ghstack-source-id: 105993222
Test Plan: waitforsandcastle
Differential Revision: D22072829
fbshipit-source-id: 0bc1a3e389e2afb05688c472793d34eaddb67f2a
