some behavior-preserving simplifications [easy]
some behavior-preserving simplifications [easy]

Reviewed By: Feng23

Differential Revision: D29698630

fbshipit-source-id: 6f148ba336fff23bbe5f122fd860cdd861f58425

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex