----------------------------------------------------------------------------- -- -- Pretty-printing TyThings -- -- (c) The GHC Team 2005 -- ----------------------------------------------------------------------------- module PprTyThing ( PrintExplicitForalls, pprTyThing, pprTyThingInContext, pprTyThingParent_maybe, pprTyThingLoc, pprTyThingInContextLoc, pprTyThingHdr, pprTypeForUser ) where import qualified GHC import GHC ( TyThing(..) ) import DataCon import Id import IdInfo import TyCon 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 type ShowMe = Name -> Bool -- The ShowMe function says which sub-components to print -- True <=> print -- False <=> elide to "..." ---------------------------- -- | 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 thing = ppr_ty_thing pefas (const True) thing ppr_ty_thing :: PrintExplicitForalls -> ShowMe -> TyThing -> SDoc ppr_ty_thing pefas _ (AnId id) = pprId pefas id ppr_ty_thing pefas _ (ADataCon dataCon) = pprDataConSig pefas dataCon ppr_ty_thing pefas show_me (ATyCon tyCon) = pprTyCon pefas show_me tyCon ppr_ty_thing pefas show_me (AClass cls) = pprClass pefas show_me cls -- | 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 thing | Just parent <- pprTyThingParent_maybe thing = ppr_ty_thing pefas (== GHC.getName thing) parent | otherwise = pprTyThing pefas thing -- | Like 'pprTyThingInContext', but adds the defining location. pprTyThingInContextLoc :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingInContextLoc pefas tyThing = showWithLoc (pprNameLoc (GHC.getName tyThing)) (pprTyThingInContext pefas tyThing) pprTyThingParent_maybe :: TyThing -> Maybe TyThing -- (pprTyThingParent_maybe x) returns (Just p) -- when pprTyThingInContext sould print a declaration for p -- (albeit with some "..." in it) when asked to show x pprTyThingParent_maybe (ADataCon dc) = Just (ATyCon (dataConTyCon dc)) pprTyThingParent_maybe (AnId id) = case idDetails id of RecSelId { sel_tycon = tc } -> Just (ATyCon tc) ClassOpId cls -> Just (AClass cls) _other -> Nothing pprTyThingParent_maybe _other = Nothing -- | 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.isFamilyTyCon 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 = ptext (sLit "class") <+> GHC.pprThetaArrow (GHC.classSCTheta cls) <+> ppr_bndr cls <+> hsep (map ppr tyVars) <+> GHC.pprFundeps funDeps where (tyVars, funDeps) = GHC.classTvsFds cls 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 ctxt ty') where tidy_ty = tidyTopType ty (_, ctxt, ty') = tcSplitSigmaTy tidy_ty pprTyCon :: PrintExplicitForalls -> ShowMe -> TyCon -> SDoc pprTyCon pefas show_me tyCon | GHC.isSynTyCon tyCon = if GHC.isFamilyTyCon 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 show_me tyCon pprAlgTyCon :: PrintExplicitForalls -> ShowMe -> TyCon -> SDoc pprAlgTyCon pefas show_me tyCon | 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 ok_con dc = show_me (dataConName dc) || any show_me (dataConFieldLabels dc) show_con dc | ok_con dc = Just (pprDataConDecl pefas show_me gadt dc) | otherwise = Nothing pprDataConDecl :: PrintExplicitForalls -> ShowMe -> Bool -> GHC.DataCon -> SDoc pprDataConDecl pefas show_me gadt_style dataCon | not gadt_style = ppr_fields tys_w_strs | otherwise = ppr_bndr dataCon <+> dcolon <+> sep [ pp_foralls, GHC.pprThetaArrow theta, pp_tau ] -- Printing out the dataCon as a type signature, in GADT style where (forall_tvs, theta, tau) = tcSplitSigmaTy (GHC.dataConUserType dataCon) (arg_tys, res_ty) = tcSplitFunTys tau labels = GHC.dataConFieldLabels dataCon stricts = GHC.dataConStrictMarks dataCon tys_w_strs = zip stricts arg_tys pp_foralls | pefas = GHC.pprForAll forall_tvs | otherwise = empty pp_tau = foldr add (ppr res_ty) tys_w_strs add str_ty pp_ty = pprParendBangTy str_ty <+> arrow <+> pp_ty pprParendBangTy (bang,ty) = ppr bang <> GHC.pprParendType ty pprBangTy bang ty = ppr bang <> ppr ty maybe_show_label (lbl,(strict,tp)) | show_me 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 -> ShowMe -> GHC.Class -> SDoc pprClass pefas show_me cls | null methods = pprClassHdr pefas cls | otherwise = hang (pprClassHdr pefas cls <+> ptext (sLit "where")) 2 (vcat (ppr_trim show_meth methods)) where methods = GHC.classMethods cls show_meth id | show_me (idName id) = 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 "--")