----------------------------------------------------------------------------- -- -- Pretty-printing TyThings -- -- (c) The GHC Team 2005 -- ----------------------------------------------------------------------------- module PprTyThing ( PrintExplicitForalls, pprTyThing, pprTyThingInContext, pprTyThingLoc, pprTyThingInContextLoc, pprTyThingHdr, pprTypeForUser ) where import qualified GHC import GHC ( TyThing(..) ) import TyCon import Type ( TyThing(..), tidyTopType, pprTypeApp ) import TcType import Var import Name import Outputable import FastString -- ----------------------------------------------------------------------------- -- Pretty-printing entities that we get from the GHC API -- This should be a good source of sample code for using the GHC API to -- inspect source code entities. type PrintExplicitForalls = Bool -- | Pretty-prints a 'TyThing' with its defining location. pprTyThingLoc :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingLoc pefas tyThing = showWithLoc loc (pprTyThing pefas tyThing) where loc = pprNameLoc (GHC.getName tyThing) -- | Pretty-prints a 'TyThing'. pprTyThing :: PrintExplicitForalls -> TyThing -> SDoc pprTyThing pefas (AnId id) = pprId pefas id pprTyThing pefas (ADataCon dataCon) = pprDataConSig pefas dataCon pprTyThing pefas (ATyCon tyCon) = pprTyCon pefas tyCon pprTyThing pefas (AClass cls) = pprClass pefas cls -- | Like 'pprTyThingInContext', but adds the defining location. pprTyThingInContextLoc :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingInContextLoc pefas tyThing = showWithLoc loc (pprTyThingInContext pefas tyThing) where loc = pprNameLoc (GHC.getName tyThing) -- | Pretty-prints a 'TyThing' in context: that is, if the entity -- is a data constructor, record selector, or class method, then -- the entity's parent declaration is pretty-printed with irrelevant -- parts omitted. pprTyThingInContext :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingInContext pefas (AnId id) = pprIdInContext pefas id pprTyThingInContext pefas (ADataCon dataCon) = pprDataCon pefas dataCon pprTyThingInContext pefas (ATyCon tyCon) = pprTyCon pefas tyCon pprTyThingInContext pefas (AClass cls) = pprClass pefas cls -- | Pretty-prints the 'TyThing' header. For functions and data constructors -- the function is equivalent to 'pprTyThing' but for type constructors -- and classes it prints only the header part of the declaration. pprTyThingHdr :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingHdr pefas (AnId id) = pprId pefas id pprTyThingHdr pefas (ADataCon dataCon) = pprDataConSig pefas dataCon pprTyThingHdr pefas (ATyCon tyCon) = pprTyConHdr pefas tyCon pprTyThingHdr pefas (AClass cls) = pprClassHdr pefas cls pprTyConHdr :: PrintExplicitForalls -> TyCon -> SDoc pprTyConHdr _ tyCon | Just (_fam_tc, tys) <- tyConFamInst_maybe tyCon = ptext keyword <+> ptext (sLit "instance") <+> pprTypeApp tyCon tys | otherwise = ptext keyword <+> opt_family <+> opt_stupid <+> ppr_bndr tyCon <+> hsep (map ppr vars) where vars | GHC.isPrimTyCon tyCon || GHC.isFunTyCon tyCon = take (GHC.tyConArity tyCon) GHC.alphaTyVars | otherwise = GHC.tyConTyVars tyCon keyword | GHC.isSynTyCon tyCon = sLit "type" | GHC.isNewTyCon tyCon = sLit "newtype" | otherwise = sLit "data" opt_family | GHC.isOpenTyCon tyCon = ptext (sLit "family") | otherwise = empty opt_stupid -- The "stupid theta" part of the declaration | isAlgTyCon tyCon = GHC.pprThetaArrow (tyConStupidTheta tyCon) | otherwise = empty -- Returns 'empty' if null theta pprDataConSig :: PrintExplicitForalls -> GHC.DataCon -> SDoc pprDataConSig pefas dataCon = ppr_bndr dataCon <+> dcolon <+> pprTypeForUser pefas (GHC.dataConType dataCon) pprClassHdr :: PrintExplicitForalls -> GHC.Class -> SDoc pprClassHdr _ cls = let (tyVars, funDeps) = GHC.classTvsFds cls in ptext (sLit "class") <+> GHC.pprThetaArrow (GHC.classSCTheta cls) <+> ppr_bndr cls <+> hsep (map ppr tyVars) <+> GHC.pprFundeps funDeps pprIdInContext :: PrintExplicitForalls -> Var -> SDoc pprIdInContext pefas id | GHC.isRecordSelector id = pprRecordSelector pefas id | Just cls <- GHC.isClassOpId_maybe id = pprClassOneMethod pefas cls id | otherwise = pprId pefas id pprRecordSelector :: PrintExplicitForalls -> Id -> SDoc pprRecordSelector pefas id = pprAlgTyCon pefas tyCon show_con show_label where (tyCon,label) = GHC.recordSelectorFieldLabel id show_con dataCon = label `elem` GHC.dataConFieldLabels dataCon show_label label' = label == label' pprId :: PrintExplicitForalls -> Var -> SDoc pprId pefas ident = hang (ppr_bndr ident <+> dcolon) 2 (pprTypeForUser pefas (GHC.idType ident)) pprTypeForUser :: PrintExplicitForalls -> GHC.Type -> SDoc -- We do two things here. -- a) We tidy the type, regardless -- b) If PrintExplicitForAlls is True, we discard the foralls -- but we do so `deeply' -- Prime example: a class op might have type -- forall a. C a => forall b. Ord b => stuff -- Then we want to display -- (C a, Ord b) => stuff pprTypeForUser print_foralls ty | print_foralls = ppr tidy_ty | otherwise = ppr (mkPhiTy [p | (_tvs, ps) <- ctxt, p <- ps] ty') where tidy_ty = tidyTopType ty (ctxt, ty') = tcMultiSplitSigmaTy tidy_ty pprTyCon :: PrintExplicitForalls -> TyCon -> SDoc pprTyCon pefas tyCon | GHC.isSynTyCon tyCon = if GHC.isOpenTyCon tyCon then pprTyConHdr pefas tyCon <+> dcolon <+> pprTypeForUser pefas (GHC.synTyConResKind tyCon) else let rhs_type = GHC.synTyConType tyCon in hang (pprTyConHdr pefas tyCon <+> equals) 2 (pprTypeForUser pefas rhs_type) | otherwise = pprAlgTyCon pefas tyCon (const True) (const True) pprAlgTyCon :: PrintExplicitForalls -> TyCon -> (GHC.DataCon -> Bool) -> (FieldLabel -> Bool) -> SDoc pprAlgTyCon pefas tyCon ok_con ok_label | gadt = pprTyConHdr pefas tyCon <+> ptext (sLit "where") $$ nest 2 (vcat (ppr_trim show_con datacons)) | otherwise = hang (pprTyConHdr pefas tyCon) 2 (add_bars (ppr_trim show_con datacons)) where datacons = GHC.tyConDataCons tyCon gadt = any (not . GHC.isVanillaDataCon) datacons show_con dataCon | ok_con dataCon = Just (pprDataConDecl pefas gadt ok_label dataCon) | otherwise = Nothing pprDataCon :: PrintExplicitForalls -> GHC.DataCon -> SDoc pprDataCon pefas dataCon = pprAlgTyCon pefas tyCon (== dataCon) (const True) where tyCon = GHC.dataConTyCon dataCon pprDataConDecl :: PrintExplicitForalls -> Bool -> (FieldLabel -> Bool) -> GHC.DataCon -> SDoc pprDataConDecl _ gadt_style show_label dataCon | not gadt_style = ppr_fields tys_w_strs | otherwise = ppr_bndr dataCon <+> dcolon <+> sep [ ppr_tvs, GHC.pprThetaArrow theta, pp_tau ] where (tyvars, theta, argTypes, res_ty) = GHC.dataConSig dataCon tyCon = GHC.dataConTyCon dataCon labels = GHC.dataConFieldLabels dataCon qualVars = filter (flip notElem (GHC.tyConTyVars tyCon)) tyvars stricts = GHC.dataConStrictMarks dataCon tys_w_strs = zip stricts argTypes ppr_tvs | null qualVars = empty | otherwise = ptext (sLit "forall") <+> hsep (map ppr qualVars) <> dot -- printing out the dataCon as a type signature, in GADT style pp_tau = foldr add (ppr res_ty) tys_w_strs add str_ty pp_ty = pprParendBangTy str_ty <+> arrow <+> pp_ty pprParendBangTy (strict,ty) | GHC.isMarkedStrict strict = char '!' <> GHC.pprParendType ty | otherwise = GHC.pprParendType ty pprBangTy strict ty | GHC.isMarkedStrict strict = char '!' <> ppr ty | otherwise = ppr ty maybe_show_label (lbl,(strict,tp)) | show_label lbl = Just (ppr lbl <+> dcolon <+> pprBangTy strict tp) | otherwise = Nothing ppr_fields [ty1, ty2] | GHC.dataConIsInfix dataCon && null labels = sep [pprParendBangTy ty1, pprInfixName dataCon, pprParendBangTy ty2] ppr_fields fields | null labels = ppr_bndr dataCon <+> sep (map pprParendBangTy fields) | otherwise = ppr_bndr dataCon <+> braces (sep (punctuate comma (ppr_trim maybe_show_label (zip labels fields)))) pprClass :: PrintExplicitForalls -> GHC.Class -> SDoc pprClass pefas cls | null methods = pprClassHdr pefas cls | otherwise = hang (pprClassHdr pefas cls <+> ptext (sLit "where")) 2 (vcat (map (pprClassMethod pefas) methods)) where methods = GHC.classMethods cls pprClassOneMethod :: PrintExplicitForalls -> GHC.Class -> Id -> SDoc pprClassOneMethod pefas cls this_one = hang (pprClassHdr pefas cls <+> ptext (sLit "where")) 2 (vcat (ppr_trim show_meth methods)) where methods = GHC.classMethods cls show_meth id | id == this_one = Just (pprClassMethod pefas id) | otherwise = Nothing pprClassMethod :: PrintExplicitForalls -> Id -> SDoc pprClassMethod pefas id = hang (ppr_bndr id <+> dcolon) 2 (pprTypeForUser pefas op_ty) where -- Here's the magic incantation to strip off the dictionary -- from the class op type. Stolen from IfaceSyn.tyThingToIfaceDecl. -- -- It's important to tidy it *before* splitting it up, so that if -- we have class C a b where -- op :: forall a. a -> b -- then the inner forall on op gets renamed to a1, and we print -- (when dropping foralls) -- class C a b where -- op :: a1 -> b tidy_sel_ty = tidyTopType (GHC.idType id) (_sel_tyvars, rho_ty) = GHC.splitForAllTys tidy_sel_ty op_ty = GHC.funResultTy rho_ty ppr_trim :: (a -> Maybe SDoc) -> [a] -> [SDoc] ppr_trim show xs = snd (foldr go (False, []) xs) where go x (eliding, so_far) | Just doc <- show x = (False, doc : so_far) | otherwise = if eliding then (True, so_far) else (True, ptext (sLit "...") : so_far) add_bars :: [SDoc] -> SDoc add_bars [] = empty add_bars [c] = equals <+> c add_bars (c:cs) = sep ((equals <+> c) : map (char '|' <+>) cs) -- Wrap operators in () ppr_bndr :: GHC.NamedThing a => a -> SDoc ppr_bndr a = GHC.pprParenSymName a showWithLoc :: SDoc -> SDoc -> SDoc showWithLoc loc doc = hang doc 2 (char '\t' <> comment <+> loc) -- The tab tries to make them line up a bit where comment = ptext (sLit "--")