Prevent VS from emitting errors when using swap in Optional.h (#22182)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/21706
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22182
Differential Revision: D15981740
Pulled By: ezyang
fbshipit-source-id: d58b3ca3aea8d3d383150208b87fa4bbd4f6fe33
