X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=fa5190101b0d1bfa7e87b1145d6bb9364b1bd595;hb=435c21ed6a0f4be11e4e94055fc4b8bc3deff08f;hp=7d667e3872694c3387d49c3f6dc24a312925664a;hpb=6c2585f8d52b7d1a879154bbcc5e62f4e9f1af99;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index 7d667e3..fa51901 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -1,74 +1,62 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcDeriv]{Deriving} Handles @deriving@ clauses on @data@ declarations. \begin{code} -#include "HsVersions.h" - module TcDeriv ( tcDeriving ) where -IMP_Ubiq() +#include "HsVersions.h" -import HsSyn ( HsDecl, FixityDecl, Fixity, InstDecl, - Sig, HsBinds(..), MonoBinds(..), - GRHSsAndBinds, Match, HsExpr, HsLit, InPat, - ArithSeqInfo, Fake, HsType, - collectMonoBinders - ) -import HsPragmas ( InstancePragmas(..) ) -import RdrHsSyn ( RdrName, SYN_IE(RdrNameMonoBinds) ) -import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedMonoBinds), SYN_IE(RenamedFixityDecl) ) +import HsSyn ( HsBinds(..), MonoBinds(..), collectMonoBinders ) +import RdrHsSyn ( RdrNameMonoBinds ) +import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds ) +import CmdLineOpts ( opt_D_dump_deriv ) import TcMonad -import Inst ( SYN_IE(InstanceMapper) ) -import TcEnv ( getEnv_TyCons, tcLookupClassByKey ) -import SpecEnv ( SpecEnv ) -import TcKind ( TcKind ) +import Inst ( InstanceMapper ) +import TcEnv ( getEnvTyCons ) import TcGenDeriv -- Deriv stuff -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) +import TcInstUtil ( InstInfo(..), buildInstanceEnvs ) import TcSimplify ( tcSimplifyThetas ) -import TcType ( TcIdOcc ) import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( newDfunName, bindLocatedLocalsRn ) -import RnMonad ( SYN_IE(RnM), RnDown, GDown, SDown, RnNameSupply(..), - setNameSupplyRn, renameSourceCode, thenRn, mapRn, returnRn ) - -import Bag ( Bag, isEmptyBag, unionBags, listToBag ) -import Class ( classKey, GenClass, SYN_IE(Class) ) -import ErrUtils ( addErrLoc, SYN_IE(Error) ) -import Id ( dataConArgTys, isNullaryDataCon, mkDictFunId ) +import RnEnv ( newDFunName, bindLocatedLocalsRn ) +import RnMonad ( RnNameSupply, + renameSourceCode, thenRn, mapRn, returnRn ) + +import Bag ( Bag, emptyBag, unionBags, listToBag ) +import Class ( classKey, Class ) +import ErrUtils ( dumpIfSet, Message ) +import MkId ( mkDictFunId ) +import Id ( mkVanillaId ) +import DataCon ( dataConArgTys, isNullaryDataCon ) import PrelInfo ( needsDataDeclCtxtClassKeys ) import Maybes ( maybeToBool ) -import Name ( isLocallyDefined, getSrcLoc, ExportFlag(..), Provenance, - Name{--O only-}, SYN_IE(Module) +import Module ( Module ) +import Name ( isLocallyDefined, getSrcLoc, + Name, NamedThing(..), + OccName, nameOccName ) -import Outputable ( PprStyle(..), Outputable(..){-instances e.g., (,)-} ) -import PprType ( GenType, GenTyVar, GenClass, TyCon ) -import Pretty ( ($$), vcat, hsep, hcat, parens, - ptext, char, hang, Doc ) +import RdrName ( RdrName ) +import RnMonad ( Fixities ) import SrcLoc ( mkGeneratedSrcLoc, SrcLoc ) import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings, tyConTheta, maybeTyConSingleCon, isDataTyCon, isEnumerationTyCon, isAlgTyCon, TyCon ) -import Type ( GenType(..), SYN_IE(TauType), mkTyVarTys, applyTyCon, - mkSigmaTy, mkDictTy, isPrimType, instantiateTy, - getAppDataTyCon, getAppTyCon +import Type ( TauType, mkTyVarTys, mkTyConApp, + mkSigmaTy, mkDictTy, isUnboxedType, + splitAlgTyConApp ) -import TysPrim ( voidTy ) -import TyVar ( GenTyVar, SYN_IE(TyVar) ) -import UniqFM ( emptyUFM ) +import TysWiredIn ( voidTy ) +import Var ( TyVar ) import Unique -- Keys stuff import Bag ( bagToList ) -import Util ( zipWithEqual, zipEqual, sortLt, removeDups, assoc, - thenCmp, cmpList, panic, panic#, pprPanic, pprPanic#, - Ord3(..), assertPanic-- , pprTrace{-ToDo:rm-} - - ) +import Util ( zipWithEqual, sortLt, removeDups, assoc, thenCmp ) +import Outputable \end{code} %************************************************************************ @@ -161,7 +149,7 @@ type DerivEqn = (Class, TyCon, [TyVar], DerivRhs) -- NEW: it's convenient to re-use InstInfo -- We'll "panic" out some fields... -type DerivRhs = [(Class, TauType)] -- Same as a ThetaType! +type DerivRhs = [(Class, [TauType])] -- Same as a ThetaType! type DerivSoln = DerivRhs \end{code} @@ -199,17 +187,21 @@ context to the instance decl. The "offending classes" are \begin{code} tcDeriving :: Module -- name of module under scrutiny + -> Fixities -- for the deriving code (Show/Read.) -> RnNameSupply -- for "renaming" bits of generated code -> Bag InstInfo -- What we already know about instances -> TcM s (Bag InstInfo, -- The generated "instance decls". - RenamedHsBinds, -- Extra generated bindings - PprStyle -> Doc) -- Printable derived instance decls; - -- for debugging via -ddump-derivings. + RenamedHsBinds) -- Extra generated bindings -tcDeriving modname rn_name_supply inst_decl_infos_in - = -- Fish the "deriving"-related information out of the TcEnv +tcDeriving modname fixs rn_name_supply inst_decl_infos_in + = recoverTc (returnTc (emptyBag, EmptyBinds)) $ + + -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". makeDerivEqns `thenTc` \ eqns -> + if null eqns then + returnTc (emptyBag, EmptyBinds) + else -- Take the equation list and solve it, to deliver a list of -- solutions, a.k.a. the contexts for the instance decls @@ -228,7 +220,7 @@ tcDeriving modname rn_name_supply inst_decl_infos_in let extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list - method_binds_s = map gen_bind new_inst_infos + method_binds_s = map (gen_bind fixs) new_inst_infos mbinders = bagToList (collectMonoBinders extra_mbinds) -- Rename to get RenamedBinds. @@ -236,34 +228,34 @@ tcDeriving modname rn_name_supply inst_decl_infos_in -- method bindings for the instances. (dfun_names_w_method_binds, rn_extra_binds) = renameSourceCode modname rn_name_supply ( - bindLocatedLocalsRn (\_ -> ptext (SLIT("deriving"))) mbinders $ \ _ -> - rnTopMonoBinds extra_mbinds [] `thenRn` \ rn_extra_binds -> + bindLocatedLocalsRn (ptext (SLIT("deriving"))) mbinders $ \ _ -> + rnTopMonoBinds extra_mbinds [] `thenRn` \ (rn_extra_binds, _) -> mapRn rn_one method_binds_s `thenRn` \ dfun_names_w_method_binds -> returnRn (dfun_names_w_method_binds, rn_extra_binds) ) - rn_one meth_binds = newDfunName Nothing mkGeneratedSrcLoc `thenRn` \ dfun_name -> - rnMethodBinds meth_binds `thenRn` \ rn_meth_binds -> - returnRn (dfun_name, rn_meth_binds) + rn_one (cl_nm, tycon_nm, meth_binds) + = newDFunName cl_nm tycon_nm + Nothing mkGeneratedSrcLoc `thenRn` \ dfun_name -> + rnMethodBinds meth_binds `thenRn` \ (rn_meth_binds, _) -> + returnRn (dfun_name, rn_meth_binds) really_new_inst_infos = map (gen_inst_info modname) (new_inst_infos `zip` dfun_names_w_method_binds) ddump_deriv = ddump_deriving really_new_inst_infos rn_extra_binds in - --pprTrace "derived:\n" (ddump_deriv PprDebug) $ + ioToTc (dumpIfSet opt_D_dump_deriv "Derived instances" ddump_deriv) `thenTc_` - returnTc (listToBag really_new_inst_infos, - rn_extra_binds, - ddump_deriv) + returnTc (listToBag really_new_inst_infos, rn_extra_binds) where - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> (PprStyle -> Doc) - - ddump_deriving inst_infos extra_binds sty - = vcat ((map pp_info inst_infos) ++ [ppr sty extra_binds]) + ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc + ddump_deriving inst_infos extra_binds + = vcat (map pp_info inst_infos) $$ ppr extra_binds where - pp_info (InstInfo clas tvs ty inst_decl_theta _ _ mbinds _ _) - = ($$) (ppr sty (mkSigmaTy tvs inst_decl_theta (mkDictTy clas ty))) - (ppr sty mbinds) + pp_info (InstInfo clas tvs [ty] inst_decl_theta _ mbinds _ _) + = ppr (mkSigmaTy tvs inst_decl_theta (mkDictTy clas [ty])) + $$ + ppr mbinds \end{code} @@ -295,38 +287,24 @@ makeDerivEqns = tcGetEnv `thenNF_Tc` \ env -> let local_data_tycons = filter (\tc -> isLocallyDefined tc && isAlgTyCon tc) - (getEnv_TyCons env) - in - if null local_data_tycons then - -- Bale out now; evalClass may not be loaded if there aren't any - returnTc [] - else - tcLookupClassByKey evalClassKey `thenNF_Tc` \ eval_clas -> - let - think_about_deriving = need_deriving eval_clas local_data_tycons + (getEnvTyCons env) + + think_about_deriving = need_deriving local_data_tycons (derive_these, _) = removeDups cmp_deriv think_about_deriving eqns = map mk_eqn derive_these in + if null local_data_tycons then + returnTc [] -- Bale out now + else mapTc chk_out think_about_deriving `thenTc_` returnTc eqns where ------------------------------------------------------------------ - need_deriving :: Class -> [TyCon] -> [(Class, TyCon)] + need_deriving :: [TyCon] -> [(Class, TyCon)] -- find the tycons that have `deriving' clauses; - -- we handle the "every datatype in Eval" by - -- doing a dummy "deriving" for it. - - need_deriving eval_clas tycons_to_consider - = foldr ( \ tycon acc -> - let - acc_plus = if isLocallyDefined tycon - then (eval_clas, tycon) : acc - else acc - in - case (tyConDerivings tycon) of - [] -> acc_plus - cs -> [ (clas,tycon) | clas <- cs ] ++ acc_plus - ) + + need_deriving tycons_to_consider + = foldr (\ tycon acc -> [(clas,tycon) | clas <- tyConDerivings tycon] ++ acc) [] tycons_to_consider @@ -359,9 +337,9 @@ makeDerivEqns (is_enumeration || is_single_con) ------------------------------------------------------------------ - cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> TAG_ + cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> Ordering cmp_deriv (c1, t1) (c2, t2) - = (c1 `cmp` c2) `thenCmp` (t1 `cmp` t2) + = (c1 `compare` c2) `thenCmp` (t1 `compare` t2) ------------------------------------------------------------------ mk_eqn :: (Class, TyCon) -> DerivEqn @@ -369,15 +347,13 @@ makeDerivEqns -- to make the rest of the equation mk_eqn (clas, tycon) - = (clas, tycon, tyvars, if_not_Eval constraints) + = (clas, tycon, tyvars, constraints) where clas_key = classKey clas tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ??? tyvar_tys = mkTyVarTys tyvars data_cons = tyConDataCons tycon - if_not_Eval cs = if clas_key == evalClassKey then [] else cs - constraints = extra_constraints ++ concat (map mk_constraints data_cons) -- "extra_constraints": see notes above about contexts on data decls @@ -388,9 +364,9 @@ makeDerivEqns offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys mk_constraints data_con - = [ (clas, arg_ty) + = [ (clas, [arg_ty]) | arg_ty <- instd_arg_tys, - not (isPrimType arg_ty) -- No constraints for primitive types + not (isUnboxedType arg_ty) -- No constraints for unboxed types? ] where instd_arg_tys = dataConArgTys data_con tyvar_tys @@ -431,81 +407,73 @@ solveDerivEqns inst_decl_infos_in orig_eqns initial_solutions :: [DerivSoln] initial_solutions = [ [] | _ <- orig_eqns ] + ------------------------------------------------------------------ -- iterateDeriv calculates the next batch of solutions, -- compares it with the current one; finishes if they are the -- same, otherwise recurses with the new solutions. - + -- It fails if any iteration fails iterateDeriv :: [DerivSoln] ->TcM s [InstInfo] - iterateDeriv current_solns + = checkNoErrsTc (iterateOnce current_solns) `thenTc` \ (new_inst_infos, new_solns) -> + if (current_solns == new_solns) then + returnTc new_inst_infos + else + iterateDeriv new_solns + + ------------------------------------------------------------------ + iterateOnce current_solns = -- Extend the inst info from the explicit instance decls -- with the current set of solutions, giving a add_solns inst_decl_infos_in orig_eqns current_solns - `thenTc` \ (new_inst_infos, inst_mapper) -> + `thenNF_Tc` \ (new_inst_infos, inst_mapper) -> let class_to_inst_env cls = inst_mapper cls in -- Simplify each RHS - listTc [ tcSimplifyThetas class_to_inst_env [{-Nothing "given"-}] deriv_rhs - | (_,_,_,deriv_rhs) <- orig_eqns ] `thenTc` \ next_solns -> + listTc [ tcAddErrCtxt (derivCtxt tc) $ + tcSimplifyThetas class_to_inst_env deriv_rhs + | (_,tc,_,deriv_rhs) <- orig_eqns ] `thenTc` \ next_solns -> -- Canonicalise the solutions, so they compare nicely let canonicalised_next_solns - = [ sortLt lt_rhs next_soln | next_soln <- next_solns ] in - - if (current_solns `eq_solns` canonicalised_next_solns) then - returnTc new_inst_infos - else - iterateDeriv canonicalised_next_solns - - where - ------------------------------------------------------------------ - lt_rhs r1 r2 = case cmp_rhs r1 r2 of { LT_ -> True; _ -> False } - eq_solns s1 s2 = case cmp_solns s1 s2 of { EQ_ -> True; _ -> False } - cmp_solns s1 s2 = cmpList (cmpList cmp_rhs) s1 s2 - cmp_rhs (c1, TyVarTy tv1) (c2, TyVarTy tv2) - = (tv1 `cmp` tv2) `thenCmp` (c1 `cmp` c2) -#ifdef DEBUG - cmp_rhs other_1 other_2 - = panic# "tcDeriv:cmp_rhs:" --(hsep [ppr PprDebug other_1, ppr PprDebug other_2]) -#endif - + = [ sortLt (<) next_soln | next_soln <- next_solns ] + in + returnTc (new_inst_infos, canonicalised_next_solns) \end{code} \begin{code} add_solns :: Bag InstInfo -- The global, non-derived ones -> [DerivEqn] -> [DerivSoln] - -> TcM s ([InstInfo], -- The new, derived ones - InstanceMapper) + -> NF_TcM s ([InstInfo], -- The new, derived ones + InstanceMapper) -- the eqns and solns move "in lockstep"; we have the eqns -- because we need the LHS info for addClassInstance. add_solns inst_infos_in eqns solns - = discardErrsTc (buildInstanceEnvs all_inst_infos) `thenTc` \ inst_mapper -> + + = discardErrsTc (buildInstanceEnvs all_inst_infos) `thenNF_Tc` \ inst_mapper -> -- We do the discard-errs so that we don't get repeated error messages - -- about missing or duplicate instances. - returnTc (new_inst_infos, inst_mapper) + -- about duplicate instances. + -- They'll appear later, when we do the top-level buildInstanceEnvs. + + returnNF_Tc (new_inst_infos, inst_mapper) where new_inst_infos = zipWithEqual "add_solns" mk_deriv_inst_info eqns solns all_inst_infos = inst_infos_in `unionBags` listToBag new_inst_infos mk_deriv_inst_info (clas, tycon, tyvars, _) theta - = InstInfo clas tyvars (applyTyCon tycon (mkTyVarTys tyvars)) + = InstInfo clas tyvars [mkTyConApp tycon (mkTyVarTys tyvars)] theta - (my_panic "dfun_theta") - dummy_dfun_id - (my_panic "binds") (getSrcLoc tycon) (my_panic "upragmas") where dummy_dfun_id - = mkDictFunId bottom dummy_dfun_ty bottom bottom - where - bottom = panic "dummy_dfun_id" + = mkVanillaId (getName tycon) dummy_dfun_ty + -- The name is getSrcLoc'd in an error message dummy_dfun_ty = mkSigmaTy tyvars theta voidTy -- All we need from the dfun is its "theta" part, used during @@ -519,7 +487,7 @@ add_solns inst_infos_in eqns solns -- We can't leave it as a panic because to get the theta part we -- have to run down the type! - my_panic str = panic "add_soln" -- pprPanic ("add_soln:"++str) (hsep [char ':', ppr PprDebug clas, ppr PprDebug tycon]) + my_panic str = panic "add_soln" -- pprPanic ("add_soln:"++str) (hsep [char ':', ppr clas, ppr tycon]) \end{code} %************************************************************************ @@ -586,26 +554,33 @@ the renamer. What a great hack! \begin{code} -- Generate the method bindings for the required instance -gen_bind :: InstInfo -> RdrNameMonoBinds -gen_bind (InstInfo clas _ ty _ _ _ _ _ _) +-- (paired with class name, as we need that when generating dict +-- names.) +gen_bind :: Fixities -> InstInfo -> ({-class-}OccName, {-tyCon-}OccName, RdrNameMonoBinds) +gen_bind fixities (InstInfo clas _ [ty] _ _ _ _ _) | not from_here - = EmptyMonoBinds + = (clas_nm, tycon_nm, EmptyMonoBinds) + | ckey == showClassKey + = (clas_nm, tycon_nm, gen_Show_binds fixities tycon) + | ckey == readClassKey + = (clas_nm, tycon_nm, gen_Read_binds fixities tycon) | otherwise - = assoc "gen_inst_info:bad derived class" - [(eqClassKey, gen_Eq_binds) - ,(ordClassKey, gen_Ord_binds) - ,(enumClassKey, gen_Enum_binds) - ,(evalClassKey, gen_Eval_binds) - ,(boundedClassKey, gen_Bounded_binds) - ,(showClassKey, gen_Show_binds) - ,(readClassKey, gen_Read_binds) - ,(ixClassKey, gen_Ix_binds) - ] - (classKey clas) - tycon + = (clas_nm, tycon_nm, + assoc "gen_bind:bad derived class" + [(eqClassKey, gen_Eq_binds) + ,(ordClassKey, gen_Ord_binds) + ,(enumClassKey, gen_Enum_binds) + ,(boundedClassKey, gen_Bounded_binds) + ,(ixClassKey, gen_Ix_binds) + ] + ckey + tycon) where + clas_nm = nameOccName (getName clas) + tycon_nm = nameOccName (getName tycon) from_here = isLocallyDefined tycon - (tycon,_,_) = getAppDataTyCon ty + (tycon,_,_) = splitAlgTyConApp ty + ckey = classKey clas gen_inst_info :: Module -- Module name @@ -613,21 +588,18 @@ gen_inst_info :: Module -- Module name -> InstInfo -- the gen'd (filled-in) "instance decl" gen_inst_info modname - (InstInfo clas tyvars ty inst_decl_theta _ _ _ locn _, (dfun_name, meth_binds)) + (InstInfo clas tyvars tys@(ty:_) inst_decl_theta _ _ locn _, (dfun_name, meth_binds)) = -- Generate the various instance-related Ids - InstInfo clas tyvars ty inst_decl_theta - dfun_theta dfun_id + InstInfo clas tyvars tys inst_decl_theta + dfun_id meth_binds locn [] where - (dfun_id, dfun_theta) = mkInstanceRelatedIds - dfun_name - clas tyvars ty - inst_decl_theta + dfun_id = mkDictFunId dfun_name clas tyvars tys inst_decl_theta from_here = isLocallyDefined tycon - (tycon,_,_) = getAppDataTyCon ty + (tycon,_,_) = splitAlgTyConApp ty \end{code} @@ -670,25 +642,25 @@ gen_taggery_Names :: [InstInfo] TagThingWanted)] gen_taggery_Names inst_infos - = --pprTrace "gen_taggery:\n" (vcat [hsep [ppr PprDebug c, ppr PprDebug t] | (c,t) <- all_CTs]) $ + = --pprTrace "gen_taggery:\n" (vcat [hsep [ppr c, ppr t] | (c,t) <- all_CTs]) $ foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far -> foldlTc do_tag2con names_so_far tycons_of_interest where - all_CTs = [ mk_CT c ty | (InstInfo c _ ty _ _ _ _ _ _) <- inst_infos ] + all_CTs = [ (c, get_tycon ty) | (InstInfo c _ [ty] _ _ _ _ _) <- inst_infos ] - mk_CT c ty = (c, fst (getAppTyCon ty)) + get_tycon ty = case splitAlgTyConApp ty of { (tc, _, _) -> tc } all_tycons = map snd all_CTs - (tycons_of_interest, _) = removeDups cmp all_tycons + (tycons_of_interest, _) = removeDups compare all_tycons do_con2tag acc_Names tycon | isDataTyCon tycon && - (we_are_deriving eqClassKey tycon + ((we_are_deriving eqClassKey tycon && any isNullaryDataCon (tyConDataCons tycon)) || (we_are_deriving ordClassKey tycon && not (maybeToBool (maybeTyConSingleCon tycon))) || (we_are_deriving enumClassKey tycon) - || (we_are_deriving ixClassKey tycon) + || (we_are_deriving ixClassKey tycon)) = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag) : acc_Names) @@ -696,14 +668,15 @@ gen_taggery_Names inst_infos = returnTc acc_Names do_tag2con acc_Names tycon - = if (we_are_deriving enumClassKey tycon) - || (we_are_deriving ixClassKey tycon) - then - returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con) - : (maxtag_RDR tycon, tycon, GenMaxTag) - : acc_Names) - else - returnTc acc_Names + | isDataTyCon tycon && + (we_are_deriving enumClassKey tycon || + we_are_deriving ixClassKey tycon + && isEnumerationTyCon tycon) + = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con) + : (maxtag_RDR tycon, tycon, GenMaxTag) + : acc_Names) + | otherwise + = returnTc acc_Names we_are_deriving clas_key tycon = is_in_eqns clas_key tycon all_CTs @@ -716,10 +689,13 @@ gen_taggery_Names inst_infos \end{code} \begin{code} -derivingThingErr :: FAST_STRING -> FAST_STRING -> TyCon -> Error +derivingThingErr :: FAST_STRING -> FAST_STRING -> TyCon -> Message -derivingThingErr thing why tycon sty +derivingThingErr thing why tycon = hang (hsep [ptext SLIT("Can't make a derived instance of"), ptext thing]) - 0 (hang (hsep [ptext SLIT("for the type"), ppr sty tycon]) + 0 (hang (hsep [ptext SLIT("for the type"), quotes (ppr tycon)]) 0 (parens (ptext why))) + +derivCtxt tycon + = ptext SLIT("When deriving classes for") <+> quotes (ppr tycon) \end{code}