Summary:
An attempt to use these resulted in an error like:

[1 of 1] Compiling Main             ( p.hs, p.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.4 for x86_64-unknown-linux):
	emitPrimOp: can't translate PrimOp  parAt#{v}

Test Plan: validate

Reviewers: thomie, austin

Reviewed By: thomie, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D758