It would be good to have a clear problem statement, plus an example of a program that runs more slowly than it “should”. Simon From: ghc-devs On Behalf Of Ryan Scott Sent: 04 September 2018 14:02 To: ghc-devs@haskell.org Subject: Re: Unpacking coercions If we can gain some performance from this, then I'm generally supportive of this idea. I'm still of the belief that we could teach GHC to unpack boxed equality constraints, but your idea would definitely be the simpler one to implement. Ryan S.