X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=ghc%2Fcompiler%2Ftypecheck%2FTcTyDecls.lhs;h=b7c891039dfe48fe97481158bd210ea5e31b430d;hb=3d88a73157a15627dcc2385148d9af66a80157ac;hp=3ad7b060b7318a0b58c30ae0350abb528ab25a14;hpb=68a1f0233996ed79824d11d946e9801473f6946c;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcTyDecls.lhs b/ghc/compiler/typecheck/TcTyDecls.lhs index 3ad7b06..b7c8910 100644 --- a/ghc/compiler/typecheck/TcTyDecls.lhs +++ b/ghc/compiler/typecheck/TcTyDecls.lhs @@ -1,280 +1,367 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The AQUA Project, Glasgow University, 1996 % -\section[TcTyDecls]{Typecheck algebraic datatypes and type synonyms} +\section[TcTyDecls]{Typecheck type declarations} \begin{code} -#include "HsVersions.h" - -module TcTyDecls ( tcTyDecls ) where +module TcTyDecls ( + tcTyDecl, + tcConDecl, + mkDataBinds + ) where -import TcMonad -- typechecking monad machinery -import AbsSyn -- the stuff being typechecked +#include "HsVersions.h" -import AbsUniType ( applyTyCon, mkDataTyCon, mkSynonymTyCon, - getUniDataTyCon, isUnboxedDataType, - isTyVarTemplateTy, cmpUniTypeMaybeList, - pprMaybeTy +import HsSyn ( MonoBinds(..), + TyDecl(..), ConDecl(..), ConDetails(..), BangType(..), + andMonoBinds + ) +import HsTypes ( getTyVarName ) +import RnHsSyn ( RenamedTyDecl(..), RenamedConDecl(..) ) +import TcHsSyn ( mkHsTyLam, mkHsDictLam, tcIdType, + TcHsBinds, TcMonoBinds + ) +import BasicTypes ( RecFlag(..), NewOrData(..) ) + +import Inst ( newDicts, InstOrigin(..), Inst ) +import TcMonoType ( tcHsTypeKind, tcHsType, tcContext ) +import TcSimplify ( tcSimplifyCheckThetas ) +import TcType ( tcInstTyVars ) +import TcEnv ( TcIdOcc(..), tcInstId, + tcLookupTyCon, tcLookupTyVar, tcLookupClass, + newLocalId, newLocalIds, tcLookupClassByKey + ) +import TcMonad +import TcKind ( TcKind, unifyKind, mkArrowKind, mkBoxedTypeKind ) + +import Class ( classInstEnv, Class ) +import Id ( mkDataCon, dataConSig, mkRecordSelId, idType, + dataConFieldLabels, dataConStrictMarks, + StrictnessMark(..), getIdUnfolding, + Id + ) +import CoreUnfold ( getUnfoldingTemplate ) +import FieldLabel +import Kind ( Kind, mkArrowKind, mkBoxedTypeKind ) +import Name ( nameSrcLoc, isLocallyDefined, getSrcLoc, + OccName(..), + NamedThing(..) ) -import CE ( lookupCE, CE(..) ) -import CmdLineOpts ( GlobalSwitch(..) ) -import E ( getE_TCE, getE_CE, plusGVE, nullGVE, GVE(..), E ) -import ErrUtils ( addShortErrLocLine ) -import Errors ( confusedNameErr, specDataNoSpecErr, specDataUnboxedErr ) -import FiniteMap ( FiniteMap, emptyFM, plusFM, singletonFM ) -import IdInfo ( SpecEnv, mkSpecEnv, SpecInfo(..) ) -import Pretty -import SpecTyFuns ( specialiseConstrTys ) -import TCE -- ( nullTCE, unitTCE, lookupTCE, plusTCE, TCE(..), UniqFM ) -import TVE ( mkTVE, TVE(..) ) -import TcConDecls ( tcConDecls ) -import TcMonoType ( tcMonoType ) -import TcPragmas ( tcDataPragmas, tcTypePragmas ) -import Util +import Outputable +import TyCon ( TyCon, mkSynTyCon, mkDataTyCon, isAlgTyCon, + isSynTyCon, tyConDataCons + ) +import Type ( typeKind, getTyVar, tyVarsOfTypes, splitSigmaTy, + mkTyConApp, mkTyVarTys, mkForAllTys, mkFunTy, + splitFunTys, mkTyVarTy, getTyVar_maybe, + isUnboxedType, Type, ThetaType + ) +import TyVar ( tyVarKind, elementOfTyVarSet, intersectTyVarSets, isEmptyTyVarSet, + TyVar ) +import Unique ( evalClassKey ) +import UniqSet ( emptyUniqSet, mkUniqSet, uniqSetToList, unionManyUniqSets, UniqSet ) +import Util ( equivClasses, zipEqual, nOfThem, panic, assertPanic ) \end{code} -We consult the @CE@/@TCE@ arguments {\em only} to build knots! +\begin{code} +tcTyDecl :: RecFlag -> RenamedTyDecl -> TcM s TyCon +\end{code} -The resulting @TCE@ has info about the type constructors in it; the -@GVE@ has info about their data constructors. +Type synonym decls +~~~~~~~~~~~~~~~~~~ \begin{code} -tcTyDecls :: E - -> (Name -> Bool) -- given Name, is it an abstract synonym? - -> (Name -> [RenamedDataTypeSig]) -- given Name, get specialisation pragmas - -> [RenamedTyDecl] - -> Baby_TcM (TCE, GVE, - FiniteMap TyCon [(Bool, [Maybe UniType])]) - -- specialisations: - -- True => imported data types i.e. from interface file - -- False => local data types i.e. requsted by source pragmas - -tcTyDecls e _ _ [] = returnB_Tc (nullTCE, nullGVE, emptyFM) - -tcTyDecls e is_abs_syn get_spec_sigs (tyd: tyds) - = tc_decl tyd `thenB_Tc` \ (tce1, gve1, specs1) -> - tcTyDecls e is_abs_syn get_spec_sigs tyds - `thenB_Tc` \ (tce2, gve2, specs2) -> +tcTyDecl is_rec (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 mkArrowKind rhs_kind tyvar_kinds) + `thenTc_` let - tce3 = tce1 `plusTCE` tce2 - gve3 = gve1 `plusGVE` gve2 - specs3 = specs1 `plusFM` specs2 + -- 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 in - returnB_Tc (tce3, gve3, specs3) - where - rec_ce = getE_CE e - rec_tce = getE_TCE e - - -- continued... + returnTc tycon \end{code} -We don't need to substitute here, because the @TCE@s -(which are at the top level) cannot contain free type variables. +Algebraic data and newtype decls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Gather relevant info: \begin{code} - tc_decl (TyData context name@(PreludeTyCon uniq full_name arity True{-"data"-}) - tyvars con_decls derivings pragmas src_loc) - -- ToDo: context - = tc_data_decl uniq name full_name arity tyvars con_decls - derivings pragmas src_loc - - tc_decl (TyData context name@(OtherTyCon uniq full_name arity True{-"data"-} _) - tyvars con_decls derivings pragmas src_loc) - -- ToDo: context - = tc_data_decl uniq name full_name arity tyvars con_decls - derivings pragmas src_loc - - tc_decl (TyData _ bad_name _ _ _ _ src_loc) - = failB_Tc (confusedNameErr "Bad name on a datatype constructor (a Prelude name?)" - bad_name src_loc) - - tc_decl (TySynonym name@(PreludeTyCon uniq full_name arity False{-"type"-}) - tyvars mono_ty pragmas src_loc) - = tc_syn_decl uniq name full_name arity tyvars mono_ty pragmas src_loc - - tc_decl (TySynonym name@(OtherTyCon uniq full_name arity False{-"type"-} _) - tyvars mono_ty pragmas src_loc) - = tc_syn_decl uniq name full_name arity tyvars mono_ty pragmas src_loc - - tc_decl (TySynonym bad_name _ _ _ src_loc) - = failB_Tc (confusedNameErr "Bad name on a type-synonym constructor (a Prelude name?)" - bad_name src_loc) -\end{code} +tcTyDecl is_rec (TyData data_or_new context tycon_name tyvar_names con_decls derivings pragmas src_loc) + = tcAddSrcLoc src_loc $ + let ctxt = case data_or_new of + NewType -> tyNewCtxt tycon_name + DataType -> tyDataCtxt tycon_name + in + tcAddErrCtxt ctxt $ -Real work for @data@ declarations: -\begin{code} - tc_data_decl uniq name full_name arity tyvars con_decls derivings pragmas src_loc - = addSrcLocB_Tc src_loc ( - let - (tve, new_tyvars, _) = mkTVE tyvars - rec_tycon = lookupTCE rec_tce name - -- We know the lookup will succeed, because we are just - -- about to put it in the outgoing TCE! - - spec_sigs = get_spec_sigs name - in - tcSpecDataSigs rec_tce spec_sigs [] `thenB_Tc` \ user_spec_infos -> - - recoverIgnoreErrorsB_Tc ([], []) ( - tcDataPragmas rec_tce tve rec_tycon new_tyvars pragmas - ) `thenB_Tc` \ (pragma_con_decls, pragma_spec_infos) -> - let - (condecls_to_use, ignore_condecl_errors_if_pragma) - = if null pragma_con_decls then - (con_decls, id) - else - if null con_decls - then (pragma_con_decls, recoverIgnoreErrorsB_Tc nullGVE) - else panic "tcTyDecls:data: user and pragma condecls!" - - (imported_specs, specinfos_to_use) - = if null pragma_spec_infos then - (False, user_spec_infos) - else - if null user_spec_infos - then (True, pragma_spec_infos) - else panic "tcTyDecls:data: user and pragma specinfos!" - - specenv_to_use = mkSpecEnv specinfos_to_use - in - ignore_condecl_errors_if_pragma - (tcConDecls rec_tce tve rec_tycon new_tyvars specenv_to_use condecls_to_use) - `thenB_Tc` \ gve -> - let - condecls = map snd gve - - derived_classes = map (lookupCE rec_ce) derivings - - new_tycon - = mkDataTyCon uniq - full_name arity new_tyvars condecls + -- 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 -> + + -- Typecheck the context + tcContext context `thenTc` \ ctxt -> + + -- Unify tycon kind with (k1->...->kn->Type) + unifyKind tycon_kind + (foldr mkArrowKind mkBoxedTypeKind tyvar_kinds) + `thenTc_` + + -- 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 - (null pragma_con_decls) - -- if constrs are from pragma we are *abstract* - - spec_list - = [(imported_specs, maybe_tys) | (SpecInfo maybe_tys _ _) <- specinfos_to_use] - - spec_map - = if null spec_list then - emptyFM - else - singletonFM rec_tycon spec_list - in - returnB_Tc (unitTCE uniq new_tycon, gve, spec_map) - -- It's OK to return pragma condecls in gve, even - -- though some of those names should be "invisible", - -- because the *renamer* is supposed to have dealt with - -- naming/scope issues already. - ) + Nothing -- Not a dictionary + data_or_new + is_rec + in + returnTc tycon + +tc_derivs Nothing = returnTc [] +tc_derivs (Just ds) = mapTc tc_deriv ds + +tc_deriv name + = tcLookupClass name `thenTc` \ (_, clas) -> + returnTc clas \end{code} -Real work for @type@ (synonym) declarations: +Generating constructor/selector bindings for data declarations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + \begin{code} - tc_syn_decl uniq name full_name arity tyvars mono_ty pragmas src_loc - = addSrcLocB_Tc src_loc ( - - let (tve, new_tyvars, _) = mkTVE tyvars - in - tcMonoType rec_ce rec_tce tve mono_ty `thenB_Tc` \ expansion -> - let - -- abstractness info either comes from the interface pragmas - -- (tcTypePragmas) or from a user-pragma in this module - -- (is_abs_syn) - abstract = tcTypePragmas pragmas - || is_abs_syn name - - new_tycon = mkSynonymTyCon uniq full_name - arity new_tyvars expansion (not abstract) - in - returnB_Tc (unitTCE uniq new_tycon, nullGVE, emptyFM) - ) +mkDataBinds :: [TyCon] -> TcM s ([Id], TcMonoBinds s) +mkDataBinds [] = returnTc ([], EmptyMonoBinds) +mkDataBinds (tycon : tycons) + | isSynTyCon tycon = mkDataBinds tycons + | otherwise = mkDataBinds_one tycon `thenTc` \ (ids1, b1) -> + mkDataBinds tycons `thenTc` \ (ids2, b2) -> + returnTc (ids1++ids2, b1 `AndMonoBinds` b2) + +mkDataBinds_one tycon + = ASSERT( isAlgTyCon tycon ) + mapTc checkConstructorContext data_cons `thenTc_` + mapTc (mkRecordSelector tycon) groups `thenTc` \ sel_ids -> + let + data_ids = data_cons ++ sel_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 + ] + in + returnTc (data_ids, andMonoBinds binds) + where + data_cons = tyConDataCons tycon + fields = [ (con, field) | con <- data_cons, + field <- dataConFieldLabels con + ] + + -- groups is list of fields that share a common name + groups = equivClasses cmp_name fields + cmp_name (_, field1) (_, field2) + = fieldLabelName field1 `compare` fieldLabelName field2 \end{code} -%************************************************************************ -%* * -\subsection{Specialisation Signatures for Data Type declarations} -%* * -%************************************************************************ +-- Check that all the types of all the strict arguments are in Eval -@tcSpecDataSigs@ checks data type specialisation signatures for -validity, and returns the list of specialisation requests. +\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, ext_tyvars, ext_theta, arg_tys, _) = dataConSig con_id + + eval_theta = [ (eval_clas, [arg_ty]) + | (arg_ty, MarkedStrict) <- zipEqual "strict_args" + arg_tys strict_marks + ] + in + tcAddErrCtxt (evalCtxt con_id eval_theta) $ + tcSimplifyCheckThetas theta eval_theta +\end{code} \begin{code} -tcSpecDataSigs :: TCE - -> [RenamedDataTypeSig] - -> [(RenamedDataTypeSig,SpecInfo)] - -> Baby_TcM [SpecInfo] - -tcSpecDataSigs tce (s:ss) accum - = tc_sig s `thenB_Tc` \ info -> - tcSpecDataSigs tce ss ((s,info):accum) +mkRecordSelector tycon fields@((first_con, first_field_label) : other_fields) + -- These fields all have the same name, but are from + -- different constructors in the data type + -- 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 (== field_ty) other_tys) + (fieldTypeMisMatch field_name) `thenTc_` + returnTc selector_id where - tc_sig (SpecDataSig n ty src_loc) - = addSrcLocB_Tc src_loc ( - let - ty_names = extractMonoTyNames (==) ty - (tve,_,_) = mkTVE ty_names - fake_CE = panic "tcSpecDataSigs:CE" - in - -- Typecheck specialising type (includes arity check) - tcMonoType fake_CE tce tve ty `thenB_Tc` \ tau_ty -> - let - (_,ty_args,_) = getUniDataTyCon tau_ty - is_unboxed_or_tyvar ty = isUnboxedDataType ty || isTyVarTemplateTy ty - in - -- Check at least one unboxed type in specialisation - checkB_Tc (not (any isUnboxedDataType ty_args)) - (specDataNoSpecErr n ty_args src_loc) `thenB_Tc_` - - -- Check all types are unboxed or tyvars - -- (specific boxed types are redundant) - checkB_Tc (not (all is_unboxed_or_tyvar ty_args)) - (specDataUnboxedErr n ty_args src_loc) `thenB_Tc_` - - let - maybe_tys = specialiseConstrTys ty_args - in - returnB_Tc (SpecInfo maybe_tys 0 (panic "SpecData:SpecInfo:SpecId")) - ) - -tcSpecDataSigs tce [] accum - = -- Remove any duplicates from accumulated specinfos - getSwitchCheckerB_Tc `thenB_Tc` \ sw_chkr -> - - (if sw_chkr SpecialiseTrace && not (null duplicates) then - pprTrace "Duplicate SPECIALIZE data pragmas:\n" - (ppAboves (map specmsg sep_dups)) - else id)( - - (if sw_chkr SpecialiseTrace && not (null spec_infos) then - pprTrace "Specialising " - (ppHang (ppCat [ppr PprDebug name, ppStr "at types:"]) - 4 (ppAboves (map pp_spec spec_infos))) - - else id) ( - - returnB_Tc (spec_infos) - )) + 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 = mkTyConApp 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] -> ThetaType -> RenamedConDecl -> TcM s Id + +tcConDecl tycon tyvars ctxt (ConDecl name ex_ctxt (VanillaCon btys) src_loc) + = tcDataCon tycon tyvars ctxt name btys src_loc + +tcConDecl tycon tyvars ctxt (ConDecl op ex_ctxt (InfixCon bty1 bty2) src_loc) + = tcDataCon tycon tyvars ctxt op [bty1,bty2] src_loc + +tcConDecl tycon tyvars ctxt (ConDecl name ex_ctxt (NewCon ty) src_loc) + = tcAddSrcLoc src_loc $ + tcHsType ty `thenTc` \ arg_ty -> + -- can't allow an unboxed type here, because we're effectively + -- going to remove the constructor while coercing it to a boxed type. + checkTc (not (isUnboxedType arg_ty)) (newTypeUnboxedField ty) `thenTc_` + let + data_con = mkDataCon (getName name) + [NotMarkedStrict] + [{- No labelled fields -}] + tyvars + ctxt + [] [] -- Temporary; existential chaps + [arg_ty] + tycon + in + returnTc data_con + +tcConDecl tycon tyvars ctxt (ConDecl name ex_ctxt (RecCon 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) + [] [] -- Temporary; existential chaps + arg_tys + tycon + 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) + [] [] -- Temporary existential chaps + arg_tys + tycon + 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 - spec_infos = map (snd . head) equiv + arg_tyvars = tyVarsOfTypes arg_tys + in_arg_tys (clas,tys) = not $ isEmptyTyVarSet $ + tyVarsOfTypes tys `intersectTyVarSets` 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 + = hsep [ptext SLIT("In the type declaration for"), quotes (ppr tycon_name)] - equiv = equivClasses cmp_info accum - duplicates = filter (not . singleton) equiv +tyDataCtxt tycon_name + = hsep [ptext SLIT("In the data declaration for"), quotes (ppr tycon_name)] - cmp_info (_, SpecInfo tys1 _ _) (_, SpecInfo tys2 _ _) - = cmpUniTypeMaybeList tys1 tys2 +tyNewCtxt tycon_name + = hsep [ptext SLIT("In the newtype declaration for"), quotes (ppr tycon_name)] - singleton [_] = True - singleton _ = False +fieldTypeMisMatch field_name + = sep [ptext SLIT("Declared types differ for field"), quotes (ppr field_name)] - sep_dups = tail (concat (map ((:) Nothing . map Just) duplicates)) - specmsg (Just (SpecDataSig _ ty locn, _)) - = addShortErrLocLine locn ( \ sty -> ppr sty ty ) PprDebug - specmsg Nothing - = ppStr "***" +newTypeUnboxedField ty + = sep [ptext SLIT("Newtype constructor field has an unboxed type:"), + quotes (ppr ty)] - ((SpecDataSig name _ _, _):_) = accum - pp_spec (SpecInfo tys _ _) = ppInterleave ppNil [pprMaybeTy PprDebug ty | ty <- tys] +evalCtxt con eval_theta + = hsep [ptext SLIT("When checking the Eval context for constructor:"), + ppr con, + text "::", ppr eval_theta] \end{code}