#14691: Replace EvTerm with CoreExpr -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.3 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nomeata): Hmpf, no matter how I shake it, it converges back to having many constructors for `EvTerm`. At first I added only `EvTypeable`, because we have determined that we cannot create the Core for that during constraint solving. But then I find code like this: {{{ rewriteEvidence ev@(CtWanted { ctev_dest = dest , ctev_loc = loc }) new_pred co = do { mb_new_ev <- newWanted loc new_pred ; MASSERT( tcCoercionRole co == ctEvRole ev ) ; setWantedEvTerm dest (mkEvCast (getEvTerm mb_new_ev) (tcDowngradeRole Representational (ctEvRole ev) co)) ; case mb_new_ev of Fresh new_ev -> continueWith new_ev Cached _ -> stopWith ev "Cached wanted" } }}} where an arbitrary `EvTerm`, the result of `getEvTerm` needs to be casted. I cannot use Core’s `Cast` for that, because the `EvTerm` may be a `EvTypeable`. So seems that I need to add the `EvCast` constructor back to `EvTerm` … and bit by bit I am undoing the refactoring that I was hoping to do here… Maybe the better thing to do is to leave all the existing constructors in place, and just add `EvExpr :: CoreExpr -> EvTerm` as an additional leaf constructor. This way, the existing code structure can remain. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14691#comment:23 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler