#11785: Merge types and kinds in Template Haskell -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 8.1 Resolution: | Keywords: TypeInType 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 RyanGlScott): Actually, there's another way to go about this. Instead of making more things pure, we could make more things monadic. This can be accomplished with the following combinator: {{{#!hs bindCore :: DsM (Core (TH.Q a)) -> (Core a -> DsM (Core (TH.Q b))) -> DsM (Core (TH.Q b)) bindCore dsma f = do { cqa@(MkC qa) <- dsma ; loc <- getSrcSpanDs ; a_name <- newNameAt (mkVarOccFS (fsLit "a")) loc ; let [a_ty] = tcTyConAppArgs (exprType qa) ; let a_id = mkLocalId (localiseName a_name) a_ty ca = MkC (Var a_id) ; MkC qb <- f ca ; let [b_ty] = tcTyConAppArgs (exprType qb) ; repBindQ a_ty b_ty cqa (MkC (Lam a_id qb)) } }}} With `bindCore`, we can retrofit existing uses of `repLKind` with `repLTy`. Here's one example: {{{#!diff diff --git a/compiler/deSugar/DsMeta.hs b/compiler/deSugar/DsMeta.hs index c679981..8acc6eb 100644 --- a/compiler/deSugar/DsMeta.hs +++ b/compiler/deSugar/DsMeta.hs @@ -1043,8 +1044,9 @@ repTy (HsEqTy t1 t2) = do repTapps eq [t1', t2'] repTy (HsKindSig t k) = do t1 <- repLTy t - k1 <- repLKind k - repTSig t1 k1 + bindCore (repLTy k) $ repTSig t1 + -- k1 <- repLKind k + -- repTSig t1 k1 repTy (HsSpliceTy splice _) = repSplice splice repTy (HsExplicitListTy _ _ tys) = do tys1 <- repLTys tys }}} It's somewhat unsavory, but it prevents us from having to change a truckload of combinators in `Language.Haskell.TH.Lib` to take `KindQ` as an argument instead of `Kind`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11785#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler