Do a bit more CSE
Do a bit more CSE

I discovered that in

   let x = MkT y in ....(MKT y |> co)....

we weren't CSE'ing the (MkT y).  The fix is easy.

ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc