X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcTyDecls.lhs;h=b5973f722c3f7d7c850ceeea84ca3e61b045c8ea;hb=1b91b7e5adb10bb9d9c6bfe6112f3ef03ab47e31;hp=a36845c32aad1d36b3c59bbb83ca175ce624899b;hpb=1fb1ab5d53a09607e7f6d2450806760688396387;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcTyDecls.lhs b/ghc/compiler/typecheck/TcTyDecls.lhs index a36845c..b5973f7 100644 --- a/ghc/compiler/typecheck/TcTyDecls.lhs +++ b/ghc/compiler/typecheck/TcTyDecls.lhs @@ -1,201 +1,249 @@ % -% (c) The AQUA Project, Glasgow University, 1996 +% (c) The AQUA Project, Glasgow University, 1996-1998 % \section[TcTyDecls]{Typecheck type declarations} \begin{code} -#include "HsVersions.h" - module TcTyDecls ( - tcTyDecl, - tcConDecl, - mkDataBinds + tcTyDecl1, + kcConDetails, + mkImplicitDataBinds, mkNewTyConRep ) where -IMP_Ubiq(){-uitous-} +#include "HsVersions.h" -import HsSyn ( TyDecl(..), ConDecl(..), BangType(..), HsExpr(..), - Match(..), GRHSsAndBinds(..), GRHS(..), OutPat(..), - HsBinds(..), HsLit, Stmt, DoOrListComp, ArithSeqInfo, - HsType, Fake, InPat, HsTyVar, Fixity, - Bind(..), MonoBinds(..), Sig +import HsSyn ( MonoBinds(..), + TyClDecl(..), ConDecl(..), ConDetails(..), BangType(..), + getBangType ) -import HsTypes ( getTyVarName ) -import RnHsSyn ( RenamedTyDecl(..), RenamedConDecl(..) ) -import TcHsSyn ( mkHsTyLam, mkHsDictLam, tcIdType, - SYN_IE(TcHsBinds), TcIdOcc(..) +import RnHsSyn ( RenamedTyClDecl, RenamedConDecl, RenamedContext ) +import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) +import BasicTypes ( NewOrData(..) ) + +import TcMonoType ( tcHsType, tcHsSigType, tcHsBoxedSigType, tcHsTyVars, tcClassContext, + kcHsContext, kcHsSigType ) -import Inst ( newDicts, InstOrigin(..), Inst ) -import TcMonoType ( tcHsTypeKind, tcHsType, tcContext ) -import TcSimplify ( tcSimplifyThetas ) -import TcType ( tcInstTyVars, tcInstType, tcInstId ) -import TcEnv ( tcLookupTyCon, tcLookupTyVar, tcLookupClass, - newLocalId, newLocalIds, tcLookupClassByKey +import TcEnv ( tcExtendTyVarEnv, + tcLookupTyCon, tcLookupClass, tcLookupGlobalId, + TyThing(..), TyThingDetails(..) ) import TcMonad -import TcKind ( TcKind, unifyKind, mkTcArrowKind, mkTcTypeKind ) -import PprType ( GenClass, GenType{-instance Outputable-}, - GenTyVar{-instance Outputable-}{-ToDo:possibly rm-} - ) -import CoreUnfold ( getUnfoldingTemplate ) -import Class ( GenClass{-instance Eq-}, classInstEnv ) -import Id ( mkDataCon, dataConSig, mkRecordSelId, idType, - dataConFieldLabels, dataConStrictMarks, - StrictnessMark(..), getIdUnfolding, - GenId{-instance NamedThing-} +import Class ( ClassContext ) +import DataCon ( DataCon, mkDataCon, + dataConFieldLabels, dataConId, dataConWrapId, + markedStrict, notMarkedStrict, markedUnboxed, dataConRepType ) +import MkId ( mkDataConId, mkDataConWrapId, mkRecordSelId ) import FieldLabel -import Kind ( Kind, mkArrowKind, mkBoxedTypeKind ) -import SpecEnv ( SpecEnv, nullSpecEnv ) -import Name ( nameSrcLoc, isLocallyDefined, getSrcLoc, - OccName(..), Name{-instance Ord3-} +import Var ( Id, TyVar ) +import Name ( Name, isLocallyDefined, NamedThing(..) ) +import Outputable +import TyCon ( TyCon, isSynTyCon, isNewTyCon, + tyConDataConsIfAvailable, tyConTyVars, tyConGenIds ) -import Outputable ( Outputable(..), interpp'SP ) -import Pretty -import TyCon ( TyCon, NewOrData(..), mkSynTyCon, mkDataTyCon, isDataTyCon, - isNewTyCon, isSynTyCon, tyConDataCons +import Type ( tyVarsOfTypes, splitFunTy, applyTys, + mkTyConApp, mkTyVarTys, mkForAllTys, + splitAlgTyConApp_maybe, Type ) -import Type ( GenType, -- instances - typeKind, getTyVar, tyVarsOfTypes, eqTy, splitSigmaTy, - applyTyCon, mkTyVarTys, mkForAllTys, mkFunTy, - splitFunTy, mkTyVarTy, getTyVar_maybe - ) -import TyVar ( tyVarKind, elementOfTyVarSet, GenTyVar{-instance Eq-} ) -import Unique ( Unique {- instance Eq -}, evalClassKey ) -import UniqSet ( emptyUniqSet, mkUniqSet, uniqSetToList, unionManyUniqSets, SYN_IE(UniqSet) ) -import Util ( equivClasses, zipEqual, nOfThem, panic, assertPanic ) -\end{code} - -\begin{code} -tcTyDecl :: RenamedTyDecl -> TcM s TyCon +import TysWiredIn ( unitTy ) +import VarSet ( intersectVarSet, isEmptyVarSet ) +import PrelNames ( unpackCStringName, unpackCStringUtf8Name ) +import ListSetOps ( equivClasses ) \end{code} -Type synonym decls -~~~~~~~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ \begin{code} -tcTyDecl (TySynonym tycon_name tyvar_names rhs src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (tySynCtxt tycon_name) $ - - -- Look up the pieces - tcLookupTyCon tycon_name `thenTc` \ (tycon_kind, _, rec_tycon) -> - mapAndUnzipNF_Tc (tcLookupTyVar.getTyVarName) tyvar_names - `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) -> - - -- Look at the rhs - tcHsTypeKind rhs `thenTc` \ (rhs_kind, rhs_ty) -> - - -- Unify tycon kind with (k1->...->kn->rhs) - unifyKind tycon_kind - (foldr mkTcArrowKind rhs_kind tyvar_kinds) - `thenTc_` +tcTyDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcTyDecl1 (TySynonym tycon_name tyvar_names rhs src_loc) + = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> + tcExtendTyVarEnv (tyConTyVars tycon) $ + tcHsType rhs `thenTc` \ rhs_ty -> + -- Note tcHsType not tcHsSigType; we allow type synonyms + -- that aren't types; e.g. type List = [] + -- + -- If the RHS mentions tyvars that aren't in scope, we'll + -- quantify over them: + -- e.g. type T = a->a + -- will become type T = forall a. a->a + -- + -- With gla-exts that's right, but for H98 we should complain. + -- We can now do that here without falling into + -- a black hole, we still do it in rnDecl (TySynonym case) + + returnTc (tycon_name, SynTyDetails rhs_ty) + +tcTyDecl1 (TyData new_or_data context tycon_name _ con_decls _ derivings _ src_loc name1 name2) + = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> let - -- Getting the TyCon's kind is a bit of a nuisance. We can't use the tycon_kind, - -- because that's a TcKind and may not yet be fully unified with other kinds. - -- We could have augmented the tycon environment with a knot-tied kind, - -- but the simplest thing to do seems to be to get the Kind by (lazily) - -- looking at the tyvars and rhs_ty. - result_kind, final_tycon_kind :: Kind -- NB not TcKind! - result_kind = typeKind rhs_ty - final_tycon_kind = foldr (mkArrowKind . tyVarKind) result_kind rec_tyvars - - -- Construct the tycon - tycon = mkSynTyCon (getName tycon_name) - final_tycon_kind - (length tyvar_names) - rec_tyvars - rhs_ty + tyvars = tyConTyVars tycon in - returnTc tycon -\end{code} + tcExtendTyVarEnv tyvars $ -Algebraic data and newtype decls -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + -- Typecheck the pieces + tcClassContext context `thenTc` \ ctxt -> + tc_derivs derivings `thenTc` \ derived_classes -> + mapTc (tcConDecl new_or_data tycon tyvars ctxt) con_decls `thenTc` \ data_cons -> + + returnTc (tycon_name, DataTyDetails ctxt data_cons derived_classes) + where + tc_derivs Nothing = returnTc [] + tc_derivs (Just ds) = mapTc tcLookupClass ds +\end{code} \begin{code} -tcTyDecl (TyData context tycon_name tyvar_names con_decls derivings pragmas src_loc) - = tcTyDataOrNew DataType context tycon_name tyvar_names con_decls derivings pragmas src_loc +mkNewTyConRep :: TyCon -> Type +-- Find the representation type for this newtype TyCon +-- The trick is to to deal correctly with recursive newtypes +-- such as newtype T = MkT T -tcTyDecl (TyNew context tycon_name tyvar_names con_decl derivings pragmas src_loc) - = tcTyDataOrNew NewType context tycon_name tyvar_names [con_decl] derivings pragmas src_loc +mkNewTyConRep tc + = mkForAllTys tvs (loop [] (mkTyConApp tc (mkTyVarTys tvs))) + where + tvs = tyConTyVars tc + loop tcs ty = case splitAlgTyConApp_maybe ty of { + Nothing -> ty ; + Just (tc, tys, data_cons) | not (isNewTyCon tc) -> ty + | tc `elem` tcs -> unitTy + | otherwise -> + + case splitFunTy (applyTys (dataConRepType (head data_cons)) tys) of + (rep_ty, _) -> loop (tc:tcs) rep_ty + } +\end{code} -tcTyDataOrNew data_or_new context tycon_name tyvar_names con_decls derivings pragmas src_loc - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (tyDataCtxt tycon_name) $ +%************************************************************************ +%* * +\subsection{Kind and type check constructors} +%* * +%************************************************************************ - -- Lookup the pieces - tcLookupTyCon tycon_name `thenTc` \ (tycon_kind, _, rec_tycon) -> - mapAndUnzipNF_Tc (tcLookupTyVar.getTyVarName) - tyvar_names `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) -> - tc_derivs derivings `thenTc` \ derived_classes -> +\begin{code} +kcConDetails :: RenamedContext -> ConDetails Name -> TcM () +kcConDetails ex_ctxt details + = kcHsContext ex_ctxt `thenTc_` + kc_con_details details + where + kc_con_details (VanillaCon btys) = mapTc_ kc_bty btys + kc_con_details (InfixCon bty1 bty2) = mapTc_ kc_bty [bty1,bty2] + kc_con_details (RecCon flds) = mapTc_ kc_field flds - -- Typecheck the context - tcContext context `thenTc` \ ctxt -> + kc_field (_, bty) = kc_bty bty - -- Unify tycon kind with (k1->...->kn->Type) - unifyKind tycon_kind - (foldr mkTcArrowKind mkTcTypeKind tyvar_kinds) - `thenTc_` + kc_bty bty = kcHsSigType (getBangType bty) - -- Walk the condecls - mapTc (tcConDecl rec_tycon rec_tyvars ctxt) con_decls - `thenTc` \ con_ids -> - let - -- Construct the tycon - final_tycon_kind :: Kind -- NB not TcKind! - final_tycon_kind = foldr (mkArrowKind . tyVarKind) mkBoxedTypeKind rec_tyvars - - tycon = mkDataTyCon (getName tycon_name) - final_tycon_kind - rec_tyvars - ctxt - con_ids - derived_classes - data_or_new - in - returnTc tycon +tcConDecl :: NewOrData -> TyCon -> [TyVar] -> ClassContext -> RenamedConDecl -> TcM DataCon -tc_derivs Nothing = returnTc [] -tc_derivs (Just ds) = mapTc tc_deriv ds +tcConDecl new_or_data tycon tyvars ctxt (ConDecl name wkr_name ex_tvs ex_ctxt details src_loc) + = tcAddSrcLoc src_loc $ + tcHsTyVars ex_tvs (kcConDetails ex_ctxt details) $ \ ex_tyvars -> + tcClassContext ex_ctxt `thenTc` \ ex_theta -> + case details of + VanillaCon btys -> tc_datacon ex_tyvars ex_theta btys + InfixCon bty1 bty2 -> tc_datacon ex_tyvars ex_theta [bty1,bty2] + RecCon fields -> tc_rec_con ex_tyvars ex_theta fields + where + tc_sig_type = case new_or_data of + DataType -> tcHsSigType + NewType -> tcHsBoxedSigType + -- Can't allow an unboxed type here, because we're effectively + -- going to remove the constructor while coercing it to a boxed type. + + tc_datacon ex_tyvars ex_theta btys + = let + arg_stricts = map getBangStrictness btys + tys = map getBangType btys + in + mapTc tc_sig_type tys `thenTc` \ arg_tys -> + mk_data_con ex_tyvars ex_theta arg_stricts arg_tys [] + + tc_rec_con ex_tyvars ex_theta fields + = checkTc (null ex_tyvars) (exRecConErr name) `thenTc_` + mapTc tc_field (fields `zip` allFieldLabelTags) `thenTc` \ field_labels_s -> + let + field_labels = concat field_labels_s + arg_stricts = [str | (ns, bty) <- fields, + let str = getBangStrictness bty, + n <- ns -- One for each. E.g x,y,z :: !Int + ] + in + mk_data_con ex_tyvars ex_theta arg_stricts + (map fieldLabelType field_labels) field_labels + + tc_field ((field_label_names, bty), tag) + = tc_sig_type (getBangType bty) `thenTc` \ field_ty -> + returnTc [mkFieldLabel (getName name) tycon field_ty tag | name <- field_label_names] + + mk_data_con ex_tyvars ex_theta arg_stricts arg_tys fields + = let + data_con = mkDataCon name arg_stricts fields + tyvars (thinContext arg_tys ctxt) + ex_tyvars ex_theta + arg_tys + tycon data_con_id data_con_wrap_id -tc_deriv name - = tcLookupClass name `thenTc` \ (_, clas) -> - returnTc clas + data_con_id = mkDataConId wkr_name data_con + data_con_wrap_id = mkDataConWrapId data_con + in + returnNF_Tc data_con + +-- The context for a data constructor should be limited to +-- the type variables mentioned in the arg_tys +thinContext arg_tys ctxt + = filter in_arg_tys ctxt + where + arg_tyvars = tyVarsOfTypes arg_tys + in_arg_tys (clas,tys) = not $ isEmptyVarSet $ + tyVarsOfTypes tys `intersectVarSet` arg_tyvars + +getBangStrictness (Banged _) = markedStrict +getBangStrictness (Unbanged _) = notMarkedStrict +getBangStrictness (Unpacked _) = markedUnboxed \end{code} -Generating constructor/selector bindings for data declarations -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + +%************************************************************************ +%* * +\subsection{Generating constructor/selector bindings for data declarations} +%* * +%************************************************************************ \begin{code} -mkDataBinds :: [TyCon] -> TcM s ([Id], TcHsBinds s) -mkDataBinds [] = returnTc ([], EmptyBinds) -mkDataBinds (tycon : tycons) - | isSynTyCon tycon = mkDataBinds tycons - | otherwise = mkDataBinds_one tycon `thenTc` \ (ids1, b1) -> - mkDataBinds tycons `thenTc` \ (ids2, b2) -> - returnTc (ids1++ids2, b1 `ThenBinds` b2) - -mkDataBinds_one tycon - = ASSERT( isDataTyCon tycon || isNewTyCon tycon ) - mapTc checkConstructorContext data_cons `thenTc_` - mapTc (mkRecordSelector tycon) groups `thenTc` \ sel_ids -> +mkImplicitDataBinds :: [TyCon] -> TcM ([Id], TcMonoBinds) +mkImplicitDataBinds [] = returnTc ([], EmptyMonoBinds) +mkImplicitDataBinds (tycon : tycons) + | isSynTyCon tycon = mkImplicitDataBinds tycons + | otherwise = mkImplicitDataBinds_one tycon `thenTc` \ (ids1, b1) -> + mkImplicitDataBinds tycons `thenTc` \ (ids2, b2) -> + returnTc (ids1++ids2, b1 `AndMonoBinds` b2) + +mkImplicitDataBinds_one tycon + = mapTc (mkRecordSelector tycon) groups `thenTc` \ sel_ids -> let - data_ids = data_cons ++ sel_ids + unf_ids = sel_ids ++ data_con_wrapper_ids ++ gen_ids + all_ids = map dataConId data_cons ++ unf_ids -- For the locally-defined things - -- we need to turn the unfoldings inside the Ids into bindings, - binds = [ CoreMonoBind (RealId data_id) (getUnfoldingTemplate (getIdUnfolding data_id)) - | data_id <- data_ids, isLocallyDefined data_id - ] + -- we need to turn the unfoldings inside the selector Ids into bindings, + -- and build bindigns for the constructor wrappers + binds | isLocallyDefined tycon = idsToMonoBinds unf_ids + | otherwise = EmptyMonoBinds in - returnTc (data_ids, - SingleBind (NonRecBind (foldr AndMonoBinds EmptyMonoBinds binds)) - ) + returnTc (all_ids, binds) where - data_cons = tyConDataCons tycon + data_cons = tyConDataConsIfAvailable tycon + -- Abstract types mean we don't bring the + -- data cons into scope, which should be fine + gen_ids = tyConGenIds tycon + data_con_wrapper_ids = map dataConWrapId data_cons + fields = [ (con, field) | con <- data_cons, field <- dataConFieldLabels con ] @@ -203,31 +251,7 @@ mkDataBinds_one tycon -- groups is list of fields that share a common name groups = equivClasses cmp_name fields cmp_name (_, field1) (_, field2) - = fieldLabelName field1 `cmp` fieldLabelName field2 -\end{code} - --- Check that all the types of all the strict arguments are in Eval - -\begin{code} -checkConstructorContext con_id - | not (isLocallyDefined con_id) - = returnTc () - - | otherwise -- It is locally defined - = tcLookupClassByKey evalClassKey `thenNF_Tc` \ eval_clas -> - let - strict_marks = dataConStrictMarks con_id - (tyvars,theta,tau) = splitSigmaTy (idType con_id) - (arg_tys, result_ty) = splitFunTy tau - - eval_theta = [ (eval_clas,arg_ty) - | (arg_ty, MarkedStrict) <- zipEqual "strict_args" - arg_tys strict_marks - ] - in - tcSimplifyThetas classInstEnv theta eval_theta `thenTc` \ eval_theta' -> - checkTc (null eval_theta') - (missingEvalErr con_id eval_theta') + = fieldLabelName field1 `compare` fieldLabelName field2 \end{code} \begin{code} @@ -237,132 +261,26 @@ mkRecordSelector tycon fields@((first_con, first_field_label) : other_fields) -- Check that all the fields in the group have the same type -- This check assumes that all the constructors of a given -- data type use the same type variables - = checkTc (all (eqTy field_ty) other_tys) + = checkTc (all (== field_ty) other_tys) (fieldTypeMisMatch field_name) `thenTc_` - returnTc selector_id + tcLookupGlobalId unpackCStringName `thenTc` \ unpack_id -> + tcLookupGlobalId unpackCStringUtf8Name `thenTc` \ unpackUtf8_id -> + returnTc (mkRecordSelId tycon first_field_label unpack_id unpackUtf8_id) where field_ty = fieldLabelType first_field_label field_name = fieldLabelName first_field_label other_tys = [fieldLabelType fl | (_, fl) <- other_fields] - (tyvars, _, _, _) = dataConSig first_con - data_ty = applyTyCon tycon (mkTyVarTys tyvars) - -- tyvars of first_con may be free in field_ty - -- Now build the selector - - selector_ty :: Type - selector_ty = mkForAllTys tyvars $ - mkFunTy data_ty $ - field_ty - - selector_id :: Id - selector_id = mkRecordSelId first_field_label selector_ty \end{code} -Constructors -~~~~~~~~~~~~ -\begin{code} -tcConDecl :: TyCon -> [TyVar] -> [(Class,Type)] -> RenamedConDecl -> TcM s Id - -tcConDecl tycon tyvars ctxt (ConDecl name btys src_loc) - = tcDataCon tycon tyvars ctxt name btys src_loc - -tcConDecl tycon tyvars ctxt (ConOpDecl bty1 op bty2 src_loc) - = tcDataCon tycon tyvars ctxt op [bty1,bty2] src_loc - -tcConDecl tycon tyvars ctxt (NewConDecl name ty src_loc) - = tcAddSrcLoc src_loc $ - tcHsType ty `thenTc` \ arg_ty -> - let - data_con = mkDataCon (getName name) - [NotMarkedStrict] - [{- No labelled fields -}] - tyvars - ctxt - [arg_ty] - tycon - -- nullSpecEnv - in - returnTc data_con - -tcConDecl tycon tyvars ctxt (RecConDecl name fields src_loc) - = tcAddSrcLoc src_loc $ - mapTc tcField fields `thenTc` \ field_label_infos_s -> - let - field_label_infos = concat field_label_infos_s - stricts = [strict | (_, _, strict) <- field_label_infos] - arg_tys = [ty | (_, ty, _) <- field_label_infos] - - field_labels = [ mkFieldLabel (getName name) ty tag - | ((name, ty, _), tag) <- field_label_infos `zip` allFieldLabelTags ] - - data_con = mkDataCon (getName name) - stricts - field_labels - tyvars - (thinContext arg_tys ctxt) - arg_tys - tycon - -- nullSpecEnv - in - returnTc data_con - -tcField (field_label_names, bty) - = tcHsType (get_pty bty) `thenTc` \ field_ty -> - returnTc [(name, field_ty, get_strictness bty) | name <- field_label_names] - -tcDataCon tycon tyvars ctxt name btys src_loc - = tcAddSrcLoc src_loc $ - let - stricts = map get_strictness btys - tys = map get_pty btys - in - mapTc tcHsType tys `thenTc` \ arg_tys -> - let - data_con = mkDataCon (getName name) - stricts - [{- No field labels -}] - tyvars - (thinContext arg_tys ctxt) - arg_tys - tycon - -- nullSpecEnv - in - returnTc data_con - --- The context for a data constructor should be limited to --- the type variables mentioned in the arg_tys -thinContext arg_tys ctxt - = filter in_arg_tys ctxt - where - arg_tyvars = tyVarsOfTypes arg_tys - in_arg_tys (clas,ty) = getTyVar "tcDataCon" ty `elementOfTyVarSet` arg_tyvars - -get_strictness (Banged _) = MarkedStrict -get_strictness (Unbanged _) = NotMarkedStrict - -get_pty (Banged ty) = ty -get_pty (Unbanged ty) = ty -\end{code} - - Errors and contexts ~~~~~~~~~~~~~~~~~~~ \begin{code} -tySynCtxt tycon_name sty - = ppCat [ppPStr SLIT("In the type declaration for"), ppr sty tycon_name] - -tyDataCtxt tycon_name sty - = ppCat [ppPStr SLIT("In the data declaration for"), ppr sty tycon_name] - -tyNewCtxt tycon_name sty - = ppCat [ppPStr SLIT("In the newtype declaration for"), ppr sty tycon_name] - -fieldTypeMisMatch field_name sty - = ppSep [ppPStr SLIT("Declared types differ for field"), ppr sty field_name] +fieldTypeMisMatch field_name + = sep [ptext SLIT("Declared types differ for field"), quotes (ppr field_name)] -missingEvalErr con eval_theta sty - = ppCat [ppPStr SLIT("Missing Eval context for constructor"), - ppQuote (ppr sty con), - ppChar ':', ppr sty eval_theta] +exRecConErr name + = ptext SLIT("Can't combine named fields with locally-quantified type variables") + $$ + (ptext SLIT("In the declaration of data constructor") <+> ppr name) \end{code}