----------------------------------------------------------------------------- -- -- Pretty-printing TyThings -- -- (c) The GHC Team 2005 -- ----------------------------------------------------------------------------- {-# OPTIONS -fno-warn-tabs #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and -- detab the module (please do the detabbing in a separate patch). See -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces -- for details module PprTyThing ( PrintExplicitForalls, pprTyThing, pprTyThingInContext, pprTyThingLoc, pprTyThingInContextLoc, pprTyThingHdr, pprTypeForUser ) where import qualified GHC import GHC ( TyThing(..) ) import DataCon import Id import TyCon import Coercion( pprCoAxiom ) import HscTypes( tyThingParent_maybe ) import TcType 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 ShowSub = [Name] -- [] <=> print all sub-components of the current thing -- (n:ns) <=> print sub-component 'n' with ShowSub=ns -- elide other sub-components to "..." showAll :: ShowSub showAll = [] showSub :: NamedThing n => ShowSub -> n -> Bool showSub [] _ = True showSub (n:_) thing = n == getName thing showSub_maybe :: NamedThing n => ShowSub -> n -> Maybe ShowSub showSub_maybe [] _ = Just [] showSub_maybe (n:ns) thing = if n == getName thing then Just ns else Nothing ---------------------------- -- | Pretty-prints a 'TyThing' with its defining location. pprTyThingLoc :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingLoc pefas tyThing = showWithLoc (pprDefinedAt (GHC.getName tyThing)) (pprTyThing pefas tyThing) -- | Pretty-prints a 'TyThing'. pprTyThing :: PrintExplicitForalls -> TyThing -> SDoc pprTyThing pefas thing = ppr_ty_thing pefas showAll thing -- | 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 = go [] thing where go ss thing = case tyThingParent_maybe thing of Just parent -> go (getName thing : ss) parent Nothing -> ppr_ty_thing pefas ss thing -- | Like 'pprTyThingInContext', but adds the defining location. pprTyThingInContextLoc :: PrintExplicitForalls -> TyThing -> SDoc pprTyThingInContextLoc pefas tyThing = showWithLoc (pprDefinedAt (GHC.getName tyThing)) (pprTyThingInContext pefas tyThing) -- | 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 _ (ACoAxiom ax) = pprCoAxiom ax ------------------------ ppr_ty_thing :: PrintExplicitForalls -> ShowSub -> TyThing -> SDoc ppr_ty_thing pefas _ (AnId id) = pprId pefas id ppr_ty_thing pefas _ (ADataCon dataCon) = pprDataConSig pefas dataCon ppr_ty_thing pefas ss (ATyCon tyCon) = pprTyCon pefas ss tyCon ppr_ty_thing _ _ (ACoAxiom ax) = pprCoAxiom ax pprTyConHdr :: PrintExplicitForalls -> TyCon -> SDoc pprTyConHdr pefas tyCon | Just (fam_tc, tys) <- tyConFamInst_maybe tyCon = ptext keyword <+> ptext (sLit "instance") <+> pprTypeApp fam_tc tys | Just cls <- tyConClass_maybe tyCon = pprClassHdr pefas cls | 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.pprThetaArrowTy (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.pprThetaArrowTy (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 -> ShowSub -> TyCon -> SDoc pprTyCon pefas ss 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) | Just cls <- GHC.tyConClass_maybe tyCon = pprClass pefas ss cls | otherwise = pprAlgTyCon pefas ss tyCon pprAlgTyCon :: PrintExplicitForalls -> ShowSub -> TyCon -> SDoc pprAlgTyCon pefas ss tyCon | gadt = pprTyConHdr pefas tyCon <+> ptext (sLit "where") $$ nest 2 (vcat (ppr_trim (map show_con datacons))) | otherwise = hang (pprTyConHdr pefas tyCon) 2 (add_bars (ppr_trim (map show_con datacons))) where datacons = GHC.tyConDataCons tyCon gadt = any (not . GHC.isVanillaDataCon) datacons ok_con dc = showSub ss dc || any (showSub ss) (dataConFieldLabels dc) show_con dc | ok_con dc = Just (pprDataConDecl pefas ss gadt dc) | otherwise = Nothing pprDataConDecl :: PrintExplicitForalls -> ShowSub -> Bool -> GHC.DataCon -> SDoc pprDataConDecl pefas ss gadt_style dataCon | not gadt_style = ppr_fields tys_w_strs | otherwise = ppr_bndr dataCon <+> dcolon <+> sep [ pp_foralls, GHC.pprThetaArrowTy 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)) | showSub ss 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 $ map maybe_show_label (zip labels fields)) pprClass :: PrintExplicitForalls -> ShowSub -> GHC.Class -> SDoc pprClass pefas ss cls | null methods && null assoc_ts = pprClassHdr pefas cls | otherwise = vcat [ pprClassHdr pefas cls <+> ptext (sLit "where") , nest 2 (vcat $ ppr_trim $ map show_at assoc_ts ++ map show_meth methods)] where methods = GHC.classMethods cls assoc_ts = GHC.classATs cls show_meth id | showSub ss id = Just (pprClassMethod pefas id) | otherwise = Nothing show_at tc = case showSub_maybe ss tc of Just ss' -> Just (pprTyCon pefas ss' tc) Nothing -> 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 :: [Maybe SDoc] -> [SDoc] -- Collapse a group of Nothings to a single "..." ppr_trim xs = snd (foldr go (False, []) xs) where go (Just doc) (_, so_far) = (False, doc : so_far) go Nothing (True, so_far) = (True, so_far) go Nothing (False, so_far) = (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 "--")