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+-----------------------------------------------------------------------------
+--
+-- Pretty-printing TyThings
+--
+-- (c) The GHC Team 2005
+--
+-----------------------------------------------------------------------------
+
+module PprTyThing (
+ pprTyThing,
+ pprTyThingInContext,
+ pprTyThingLoc,
+ pprTyThingInContextLoc,
+ pprTyThingHdr
+ ) where
+
+#include "HsVersions.h"
+
+import qualified GHC
+import GHC ( TyThing(..), SrcLoc )
+import Outputable
+
+-- -----------------------------------------------------------------------------
+-- 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.
+
+-- | Pretty-prints a 'TyThing' with its defining location.
+pprTyThingLoc :: Bool -> TyThing -> SDoc
+pprTyThingLoc exts tyThing
+ = showWithLoc loc (pprTyThing exts tyThing)
+ where loc = GHC.nameSrcLoc (GHC.getName tyThing)
+
+-- | Pretty-prints a 'TyThing'.
+pprTyThing :: Bool -> TyThing -> SDoc
+pprTyThing exts (AnId id) = pprId exts id
+pprTyThing exts (ADataCon dataCon) = pprDataConSig exts dataCon
+pprTyThing exts (ATyCon tyCon) = pprTyCon exts tyCon
+pprTyThing exts (AClass cls) = pprClass exts cls
+
+-- | Like 'pprTyThingInContext', but adds the defining location.
+pprTyThingInContextLoc :: Bool -> TyThing -> SDoc
+pprTyThingInContextLoc exts tyThing
+ = showWithLoc loc (pprTyThingInContext exts tyThing)
+ where loc = GHC.nameSrcLoc (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 :: Bool -> TyThing -> SDoc
+pprTyThingInContext exts (AnId id) = pprIdInContext exts id
+pprTyThingInContext exts (ADataCon dataCon) = pprDataCon exts dataCon
+pprTyThingInContext exts (ATyCon tyCon) = pprTyCon exts tyCon
+pprTyThingInContext exts (AClass cls) = pprClass exts 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 :: Bool -> TyThing -> SDoc
+pprTyThingHdr exts (AnId id) = pprId exts id
+pprTyThingHdr exts (ADataCon dataCon) = pprDataConSig exts dataCon
+pprTyThingHdr exts (ATyCon tyCon) = pprTyConHdr exts tyCon
+pprTyThingHdr exts (AClass cls) = pprClassHdr exts cls
+
+pprTyConHdr exts tyCon =
+ ptext keyword <+> 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")
+
+pprDataConSig exts dataCon =
+ ppr_bndr dataCon <+> dcolon <+> pprType exts (GHC.dataConType dataCon)
+
+pprClassHdr exts 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 exts id
+ | GHC.isRecordSelector id = pprRecordSelector exts id
+ | Just cls <- GHC.isClassOpId_maybe id = pprClassOneMethod exts cls id
+ | otherwise = pprId exts id
+
+pprRecordSelector exts id
+ = pprAlgTyCon exts 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 exts id
+ = hang (ppr_bndr id <+> dcolon) 2
+ (pprType exts (GHC.idType id))
+
+pprType True ty = ppr ty
+pprType False ty = ppr (GHC.dropForAlls ty)
+
+pprTyCon exts tyCon
+ | GHC.isSynTyCon tyCon
+ = let rhs_type = GHC.synTyConRhs tyCon
+ in hang (pprTyConHdr exts tyCon <+> equals) 2 (pprType exts rhs_type)
+ | otherwise
+ = pprAlgTyCon exts tyCon (const True) (const True)
+
+pprAlgTyCon exts tyCon ok_con ok_label
+ | gadt = pprTyConHdr exts tyCon <+> ptext SLIT("where") $$
+ nest 2 (vcat (ppr_trim show_con datacons))
+ | otherwise = hang (pprTyConHdr exts 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 exts gadt ok_label dataCon)
+ | otherwise = Nothing
+
+pprDataCon exts dataCon = pprAlgTyCon exts tyCon (== dataCon) (const True)
+ where tyCon = GHC.dataConTyCon dataCon
+
+pprDataConDecl exts 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, tyCon, res_tys) = GHC.dataConSig 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 pp_res_ty tys_w_strs
+ pp_res_ty = ppr_bndr tyCon <+> hsep (map GHC.pprParendType res_tys)
+ add (str,ty) pp_ty = pprBangTy 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, ppr 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 exts cls
+ | null methods =
+ pprClassHdr exts cls
+ | otherwise =
+ hang (pprClassHdr exts cls <+> ptext SLIT("where"))
+ 2 (vcat (map (pprClassMethod exts) methods))
+ where
+ methods = GHC.classMethods cls
+
+pprClassOneMethod exts cls this_one =
+ hang (pprClassHdr exts cls <+> ptext SLIT("where"))
+ 2 (vcat (ppr_trim show_meth methods))
+ where
+ methods = GHC.classMethods cls
+ show_meth id | id == this_one = Just (pprClassMethod exts id)
+ | otherwise = Nothing
+
+pprClassMethod exts id =
+ hang (ppr_bndr id <+> dcolon) 2 (pprType exts (classOpType id))
+ where
+ -- Here's the magic incantation to strip off the dictionary
+ -- from the class op type. Stolen from IfaceSyn.tyThingToIfaceDecl.
+ classOpType id = GHC.funResultTy rho_ty
+ where (_sel_tyvars, rho_ty) = GHC.splitForAllTys (GHC.idType id)
+
+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 [] = 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 :: SrcLoc -> SDoc -> SDoc
+showWithLoc loc doc
+ = hang doc 2 (char '\t' <> comment <+> GHC.pprDefnLoc loc)
+ -- The tab tries to make them line up a bit
+ where
+ comment = ptext SLIT("--")
+
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