Language/Haskell/TH/Ppr.hs

    -- | contains a prettyprinter for the
    -- Template Haskell datatypes

    module Language.Haskell.TH.Ppr where
        -- All of the exports from this module should
        -- be "public" functions.  The main module TH
        -- re-exports them all.

    import Text.PrettyPrint (render)
    import Language.Haskell.TH.PprLib
    import Language.Haskell.TH.Syntax
    import Data.Word ( Word8 )
    import Data.Char ( toLower, chr)
    import GHC.Show  ( showMultiLineString )
    import GHC.Lexeme( startsVarSym )
    import Data.Ratio ( numerator, denominator )
    import Prelude hiding ((<>))

    nestDepth :: Int
    nestDepth = 4

    type Precedence = Int
    appPrec, opPrec, unopPrec, sigPrec, noPrec :: Precedence
    appPrec  = 4    -- Argument of a function application
    opPrec   = 3    -- Argument of an infix operator
    unopPrec = 2    -- Argument of an unresolved infix operator
    sigPrec  = 1    -- Argument of an explicit type signature
    noPrec   = 0    -- Others

    parensIf :: Bool -> Doc -> Doc
    parensIf True d = parens d
    parensIf False d = d

    ------------------------------

    pprint :: Ppr a => a -> String
    pprint x = render $ to_HPJ_Doc $ ppr x

    class Ppr a where
        ppr :: a -> Doc
        ppr_list :: [a] -> Doc
        ppr_list = vcat . map ppr

    instance Ppr a => Ppr [a] where
        ppr x = ppr_list x

    ------------------------------
    instance Ppr Name where
        ppr v = pprName v

    ------------------------------
    instance Ppr Info where
        ppr (TyConI d)     = ppr d
        ppr (ClassI d is)  = ppr d $$ vcat (map ppr is)
        ppr (FamilyI d is) = ppr d $$ vcat (map ppr is)
        ppr (PrimTyConI name arity is_unlifted)
          = text "Primitive"
            <+> (if is_unlifted then text "unlifted" else empty)
            <+> text "type constructor" <+> quotes (ppr name)
            <+> parens (text "arity" <+> int arity)
        ppr (ClassOpI v ty cls)
          = text "Class op from" <+> ppr cls <> colon <+> ppr_sig v ty
        ppr (DataConI v ty tc)
          = text "Constructor from" <+> ppr tc <> colon <+> ppr_sig v ty
        ppr (PatSynI nm ty) = pprPatSynSig nm ty
        ppr (TyVarI v ty)
          = text "Type variable" <+> ppr v <+> equals <+> ppr ty
        ppr (VarI v ty mb_d)
          = vcat [ppr_sig v ty,
                  case mb_d of { Nothing -> empty; Just d -> ppr d }]

    ppr_sig :: Name -> Type -> Doc
    ppr_sig v ty = pprName' Applied v <+> dcolon <+> ppr ty

    pprFixity :: Name -> Fixity -> Doc
    pprFixity _ f | f == defaultFixity = empty
    pprFixity v (Fixity i d) = ppr_fix d <+> int i <+> ppr v
        where ppr_fix InfixR = text "infixr"
              ppr_fix InfixL = text "infixl"
              ppr_fix InfixN = text "infix"

    -- | Pretty prints a pattern synonym type signature
    pprPatSynSig :: Name -> PatSynType -> Doc
    pprPatSynSig nm ty
      = text "pattern" <+> pprPrefixOcc nm <+> dcolon <+> pprPatSynType ty

    -- | Pretty prints a pattern synonym's type; follows the usual
    -- conventions to print a pattern synonym type compactly, yet
    -- unambiguously. See the note on 'PatSynType' and the section on
    -- pattern synonyms in the GHC user's guide for more information.
    pprPatSynType :: PatSynType -> Doc
    pprPatSynType ty@(ForallT uniTys reqs ty'@(ForallT exTys provs ty''))
      | null exTys,  null provs = ppr (ForallT uniTys reqs ty'')
      | null uniTys, null reqs  = noreqs <+> ppr ty'
      | null reqs               = forall uniTys <+> noreqs <+> ppr ty'
      | otherwise               = ppr ty
      where noreqs     = text "() =>"
            forall tvs = text "forall" <+> (hsep (map ppr tvs)) <+> text "."
    pprPatSynType ty            = ppr ty

    ------------------------------
    instance Ppr Module where
      ppr (Module pkg m) = text (pkgString pkg) <+> text (modString m)

    instance Ppr ModuleInfo where
      ppr (ModuleInfo imps) = text "Module" <+> vcat (map ppr imps)

    ------------------------------
    instance Ppr Exp where
        ppr = pprExp noPrec

    pprPrefixOcc :: Name -> Doc
    -- Print operators with parens around them
    pprPrefixOcc n = parensIf (isSymOcc n) (ppr n)

    isSymOcc :: Name -> Bool
    isSymOcc n
      = case nameBase n of
          []    -> True  -- Empty name; weird
          (c:_) -> startsVarSym c
                       -- c.f. OccName.startsVarSym in GHC itself

    pprInfixExp :: Exp -> Doc
    pprInfixExp (VarE v) = pprName' Infix v
    pprInfixExp (ConE v) = pprName' Infix v
    pprInfixExp _        = text "<<Non-variable/constructor in infix context>>"

    pprExp :: Precedence -> Exp -> Doc
    pprExp _ (VarE v)     = pprName' Applied v
    pprExp _ (ConE c)     = pprName' Applied c
    pprExp i (LitE l)     = pprLit i l
    pprExp i (AppE e1 e2) = parensIf (i >= appPrec) $ pprExp opPrec e1
                                                  <+> pprExp appPrec e2
    pprExp i (AppTypeE e t)
     = parensIf (i >= appPrec) $ pprExp opPrec e <+> char '@' <> pprParendType t
    pprExp _ (ParensE e)  = parens (pprExp noPrec e)
    pprExp i (UInfixE e1 op e2)
     = parensIf (i > unopPrec) $ pprExp unopPrec e1
                             <+> pprInfixExp op
                             <+> pprExp unopPrec e2
    pprExp i (InfixE (Just e1) op (Just e2))
     = parensIf (i >= opPrec) $ pprExp opPrec e1
                            <+> pprInfixExp op
                            <+> pprExp opPrec e2
    pprExp _ (InfixE me1 op me2) = parens $ pprMaybeExp noPrec me1
                                        <+> pprInfixExp op
                                        <+> pprMaybeExp noPrec me2
    pprExp i (LamE [] e) = pprExp i e -- #13856
    pprExp i (LamE ps e) = parensIf (i > noPrec) $ char '\\' <> hsep (map (pprPat appPrec) ps)
                                               <+> text "->" <+> ppr e
    pprExp i (LamCaseE ms) = parensIf (i > noPrec)
                           $ text "\\case" $$ nest nestDepth (ppr ms)
    pprExp _ (TupE es) = parens (commaSep es)
    pprExp _ (UnboxedTupE es) = hashParens (commaSep es)
    pprExp _ (UnboxedSumE e alt arity) = unboxedSumBars (ppr e) alt arity
    -- Nesting in Cond is to avoid potential problems in do statements
    pprExp i (CondE guard true false)
     = parensIf (i > noPrec) $ sep [text "if"   <+> ppr guard,
                           nest 1 $ text "then" <+> ppr true,
                           nest 1 $ text "else" <+> ppr false]
    pprExp i (MultiIfE alts)
      = parensIf (i > noPrec) $ vcat $
          case alts of
            []            -> [text "if {}"]
            (alt : alts') -> text "if" <+> pprGuarded arrow alt
                             : map (nest 3 . pprGuarded arrow) alts'
    pprExp i (LetE ds_ e) = parensIf (i > noPrec) $ text "let" <+> pprDecs ds_
                                                 $$ text " in" <+> ppr e
      where
        pprDecs []  = empty
        pprDecs [d] = ppr d
        pprDecs ds  = braces (semiSep ds)

    pprExp i (CaseE e ms)
     = parensIf (i > noPrec) $ text "case" <+> ppr e <+> text "of"
                            $$ nest nestDepth (ppr ms)
    pprExp i (DoE ss_) = parensIf (i > noPrec) $ text "do" <+> pprStms ss_
      where
        pprStms []  = empty
        pprStms [s] = ppr s
        pprStms ss  = braces (semiSep ss)
    pprExp i (MDoE ss_) = parensIf (i > noPrec) $ text "mdo" <+> pprStms ss_
      where
        pprStms []  = empty
        pprStms [s] = ppr s
        pprStms ss  = braces (semiSep ss)

    pprExp _ (CompE []) = text "<<Empty CompExp>>"
    -- This will probably break with fixity declarations - would need a ';'
    pprExp _ (CompE ss) =
        if null ss'
           -- If there are no statements in a list comprehension besides the last
           -- one, we simply treat it like a normal list.
           then text "[" <> ppr s <> text "]"
           else text "[" <> ppr s
            <+> bar
            <+> commaSep ss'
             <> text "]"
      where s = last ss
            ss' = init ss
    pprExp _ (ArithSeqE d) = ppr d
    pprExp _ (ListE es) = brackets (commaSep es)
    pprExp i (SigE e t) = parensIf (i > noPrec) $ pprExp sigPrec e
                                              <+> dcolon <+> ppr t
    pprExp _ (RecConE nm fs) = ppr nm <> braces (pprFields fs)
    pprExp _ (RecUpdE e fs) = pprExp appPrec e <> braces (pprFields fs)
    pprExp i (StaticE e) = parensIf (i >= appPrec) $
                             text "static"<+> pprExp appPrec e
    pprExp _ (UnboundVarE v) = pprName' Applied v
    pprExp _ (LabelE s) = text "#" <> text s
    pprExp _ (ImplicitParamVarE n) = text ('?' : n)

    pprFields :: [(Name,Exp)] -> Doc
    pprFields = sep . punctuate comma . map (\(s,e) -> ppr s <+> equals <+> ppr e)

    pprMaybeExp :: Precedence -> Maybe Exp -> Doc
    pprMaybeExp _ Nothing = empty
    pprMaybeExp i (Just e) = pprExp i e

    ------------------------------
    instance Ppr Stmt where
        ppr (BindS p e) = ppr p <+> text "<-" <+> ppr e
        ppr (LetS ds) = text "let" <+> (braces (semiSep ds))
        ppr (NoBindS e) = ppr e
        ppr (ParS sss) = sep $ punctuate bar
                             $ map commaSep sss
        ppr (RecS ss) = text "rec" <+> (braces (semiSep ss))

    ------------------------------
    instance Ppr Match where
        ppr (Match p rhs ds) = pprMatchPat p <+> pprBody False rhs
                            $$ where_clause ds

    pprMatchPat :: Pat -> Doc
    -- Everything except pattern signatures bind more tightly than (->)
    pprMatchPat p@(SigP {}) = parens (ppr p)
    pprMatchPat p           = ppr p

    ------------------------------
    pprGuarded :: Doc -> (Guard, Exp) -> Doc
    pprGuarded eqDoc (guard, expr) = case guard of
      NormalG guardExpr -> bar <+> ppr guardExpr <+> eqDoc <+> ppr expr
      PatG    stmts     -> bar <+> vcat (punctuate comma $ map ppr stmts) $$
                             nest nestDepth (eqDoc <+> ppr expr)

    ------------------------------
    pprBody :: Bool -> Body -> Doc
    pprBody eq body = case body of
        GuardedB xs -> nest nestDepth $ vcat $ map (pprGuarded eqDoc) xs
        NormalB  e  -> eqDoc <+> ppr e
      where eqDoc | eq        = equals
                  | otherwise = arrow

    ------------------------------
    instance Ppr Lit where
      ppr = pprLit noPrec

    pprLit :: Precedence -> Lit -> Doc
    pprLit i (IntPrimL x)    = parensIf (i > noPrec && x < 0)
                                        (integer x <> char '#')
    pprLit _ (WordPrimL x)    = integer x <> text "##"
    pprLit i (FloatPrimL x)  = parensIf (i > noPrec && x < 0)
                                        (float (fromRational x) <> char '#')
    pprLit i (DoublePrimL x) = parensIf (i > noPrec && x < 0)
                                        (double (fromRational x) <> text "##")
    pprLit i (IntegerL x)    = parensIf (i > noPrec && x < 0) (integer x)
    pprLit _ (CharL c)       = text (show c)
    pprLit _ (CharPrimL c)   = text (show c) <> char '#'
    pprLit _ (StringL s)     = pprString s
    pprLit _ (StringPrimL s) = pprString (bytesToString s) <> char '#'
    pprLit i (RationalL rat) = parensIf (i > noPrec) $
                               integer (numerator rat) <+> char '/'
                                  <+> integer (denominator rat)

    bytesToString :: [Word8] -> String
    bytesToString = map (chr . fromIntegral)

    pprString :: String -> Doc
    -- Print newlines as newlines with Haskell string escape notation,
    -- not as '\n'.  For other non-printables use regular escape notation.
    pprString s = vcat (map text (showMultiLineString s))

    ------------------------------
    instance Ppr Pat where
        ppr = pprPat noPrec

    pprPat :: Precedence -> Pat -> Doc
    pprPat i (LitP l)     = pprLit i l
    pprPat _ (VarP v)     = pprName' Applied v
    pprPat _ (TupP ps)    = parens (commaSep ps)
    pprPat _ (UnboxedTupP ps) = hashParens (commaSep ps)
    pprPat _ (UnboxedSumP p alt arity) = unboxedSumBars (ppr p) alt arity
    pprPat i (ConP s ps)  = parensIf (i >= appPrec) $ pprName' Applied s
                                                  <+> sep (map (pprPat appPrec) ps)
    pprPat _ (ParensP p)  = parens $ pprPat noPrec p
    pprPat i (UInfixP p1 n p2)
                          = parensIf (i > unopPrec) (pprPat unopPrec p1 <+>
                                                     pprName' Infix n   <+>
                                                     pprPat unopPrec p2)
    pprPat i (InfixP p1 n p2)
                          = parensIf (i >= opPrec) (pprPat opPrec p1 <+>
                                                    pprName' Infix n <+>
                                                    pprPat opPrec p2)
    pprPat i (TildeP p)   = parensIf (i > noPrec) $ char '~' <> pprPat appPrec p
    pprPat i (BangP p)    = parensIf (i > noPrec) $ char '!' <> pprPat appPrec p
    pprPat i (AsP v p)    = parensIf (i > noPrec) $ ppr v <> text "@"
                                                          <> pprPat appPrec p
    pprPat _ WildP        = text "_"
    pprPat _ (RecP nm fs)
     = parens $     ppr nm
                <+> braces (sep $ punctuate comma $
                            map (\(s,p) -> ppr s <+> equals <+> ppr p) fs)
    pprPat _ (ListP ps) = brackets (commaSep ps)
    pprPat i (SigP p t) = parensIf (i > noPrec) $ ppr p <+> dcolon <+> ppr t
    pprPat _ (ViewP e p) = parens $ pprExp noPrec e <+> text "->" <+> pprPat noPrec p

    ------------------------------
    instance Ppr Dec where
        ppr = ppr_dec True

    ppr_dec :: Bool     -- declaration on the toplevel?
            -> Dec
            -> Doc
    ppr_dec _ (FunD f cs)   = vcat $ map (\c -> pprPrefixOcc f <+> ppr c) cs
    ppr_dec _ (ValD p r ds) = ppr p <+> pprBody True r
                              $$ where_clause ds
    ppr_dec _ (TySynD t xs rhs)
      = ppr_tySyn empty (Just t) (hsep (map ppr xs)) rhs
    ppr_dec _ (DataD ctxt t xs ksig cs decs)
      = ppr_data empty ctxt (Just t) (hsep (map ppr xs)) ksig cs decs
    ppr_dec _ (NewtypeD ctxt t xs ksig c decs)
      = ppr_newtype empty ctxt (Just t) (sep (map ppr xs)) ksig c decs
    ppr_dec _  (ClassD ctxt c xs fds ds)
      = text "class" <+> pprCxt ctxt <+> ppr c <+> hsep (map ppr xs) <+> ppr fds
        $$ where_clause ds
    ppr_dec _ (InstanceD o ctxt i ds) =
            text "instance" <+> maybe empty ppr_overlap o <+> pprCxt ctxt <+> ppr i
                                      $$ where_clause ds
    ppr_dec _ (SigD f t)    = pprPrefixOcc f <+> dcolon <+> ppr t
    ppr_dec _ (ForeignD f)  = ppr f
    ppr_dec _ (InfixD fx n) = pprFixity n fx
    ppr_dec _ (PragmaD p)   = ppr p
    ppr_dec isTop (DataFamilyD tc tvs kind)
      = text "data" <+> maybeFamily <+> ppr tc <+> hsep (map ppr tvs) <+> maybeKind
      where
        maybeFamily | isTop     = text "family"
                    | otherwise = empty
        maybeKind | (Just k') <- kind = dcolon <+> ppr k'
                  | otherwise = empty
    ppr_dec isTop (DataInstD ctxt bndrs ty ksig cs decs)
      = ppr_data (maybeInst <+> ppr_bndrs bndrs)
                 ctxt Nothing (ppr ty) ksig cs decs
      where
        maybeInst | isTop     = text "instance"
                  | otherwise = empty
    ppr_dec isTop (NewtypeInstD ctxt bndrs ty ksig c decs)
      = ppr_newtype (maybeInst <+> ppr_bndrs bndrs)
                    ctxt Nothing (ppr ty) ksig c decs
      where
        maybeInst | isTop     = text "instance"
                  | otherwise = empty
    ppr_dec isTop (TySynInstD (TySynEqn mb_bndrs ty rhs))
      = ppr_tySyn (maybeInst <+> ppr_bndrs mb_bndrs)
                  Nothing (ppr ty) rhs
      where
        maybeInst | isTop     = text "instance"
                  | otherwise = empty
    ppr_dec isTop (OpenTypeFamilyD tfhead)
      = text "type" <+> maybeFamily <+> ppr_tf_head tfhead
      where
        maybeFamily | isTop     = text "family"
                    | otherwise = empty
    ppr_dec _ (ClosedTypeFamilyD tfhead eqns)
      = hang (text "type family" <+> ppr_tf_head tfhead <+> text "where")
          nestDepth (vcat (map ppr_eqn eqns))
      where
        ppr_eqn (TySynEqn mb_bndrs lhs rhs)
          = ppr_bndrs mb_bndrs <+> ppr lhs <+> text "=" <+> ppr rhs
    ppr_dec _ (RoleAnnotD name roles)
      = hsep [ text "type role", ppr name ] <+> hsep (map ppr roles)
    ppr_dec _ (StandaloneDerivD ds cxt ty)
      = hsep [ text "deriving"
             , maybe empty ppr_deriv_strategy ds
             , text "instance"
             , pprCxt cxt
             , ppr ty ]
    ppr_dec _ (DefaultSigD n ty)
      = hsep [ text "default", pprPrefixOcc n, dcolon, ppr ty ]
    ppr_dec _ (PatSynD name args dir pat)
      = text "pattern" <+> pprNameArgs <+> ppr dir <+> pprPatRHS
      where
        pprNameArgs | InfixPatSyn a1 a2 <- args = ppr a1 <+> ppr name <+> ppr a2
                    | otherwise                 = ppr name <+> ppr args
        pprPatRHS   | ExplBidir cls <- dir = hang (ppr pat <+> text "where")
                                               nestDepth (ppr name <+> ppr cls)
                    | otherwise            = ppr pat
    ppr_dec _ (PatSynSigD name ty)
      = pprPatSynSig name ty
    ppr_dec _ (ImplicitParamBindD n e)
      = hsep [text ('?' : n), text "=", ppr e]

    ppr_deriv_strategy :: DerivStrategy -> Doc
    ppr_deriv_strategy ds =
      case ds of
        StockStrategy    -> text "stock"
        AnyclassStrategy -> text "anyclass"
        NewtypeStrategy  -> text "newtype"
        ViaStrategy ty   -> text "via" <+> pprParendType ty

    ppr_overlap :: Overlap -> Doc
    ppr_overlap o = text $
      case o of
        Overlaps      -> "{-# OVERLAPS #-}"
        Overlappable  -> "{-# OVERLAPPABLE #-}"
        Overlapping   -> "{-# OVERLAPPING #-}"
        Incoherent    -> "{-# INCOHERENT #-}"

    ppr_data :: Doc -> Cxt -> Maybe Name -> Doc -> Maybe Kind -> [Con] -> [DerivClause]
             -> Doc
    ppr_data maybeInst ctxt t argsDoc ksig cs decs
      = sep [text "data" <+> maybeInst
                <+> pprCxt ctxt
                <+> case t of
                     Just n -> pprName' Applied n <+> argsDoc
                     Nothing -> argsDoc
                <+> ksigDoc <+> maybeWhere,
             nest nestDepth (sep (pref $ map ppr cs)),
             if null decs
               then empty
               else nest nestDepth
                  $ vcat $ map ppr_deriv_clause decs]
      where
        pref :: [Doc] -> [Doc]
        pref xs | isGadtDecl = xs
        pref []              = []      -- No constructors; can't happen in H98
        pref (d:ds)          = (char '=' <+> d):map (bar <+>) ds

        maybeWhere :: Doc
        maybeWhere | isGadtDecl = text "where"
                   | otherwise  = empty

        isGadtDecl :: Bool
        isGadtDecl = not (null cs) && all isGadtCon cs
            where isGadtCon (GadtC _ _ _   ) = True
                  isGadtCon (RecGadtC _ _ _) = True
                  isGadtCon (ForallC _ _ x ) = isGadtCon x
                  isGadtCon  _               = False

        ksigDoc = case ksig of
                    Nothing -> empty
                    Just k  -> dcolon <+> ppr k

    ppr_newtype :: Doc -> Cxt -> Maybe Name -> Doc -> Maybe Kind -> Con -> [DerivClause]
                -> Doc
    ppr_newtype maybeInst ctxt t argsDoc ksig c decs
      = sep [text "newtype" <+> maybeInst
                <+> pprCxt ctxt
                <+> case t of
                     Just n -> ppr n <+> argsDoc
                     Nothing -> argsDoc
                <+> ksigDoc,
             nest 2 (char '=' <+> ppr c),
             if null decs
               then empty
               else nest nestDepth
                    $ vcat $ map ppr_deriv_clause decs]
      where
        ksigDoc = case ksig of
                    Nothing -> empty
                    Just k  -> dcolon <+> ppr k

    ppr_deriv_clause :: DerivClause -> Doc
    ppr_deriv_clause (DerivClause ds ctxt)
      = text "deriving" <+> pp_strat_before
                        <+> ppr_cxt_preds ctxt
                        <+> pp_strat_after
      where
        -- @via@ is unique in that in comes /after/ the class being derived,
        -- so we must special-case it.
        (pp_strat_before, pp_strat_after) =
          case ds of
            Just (via@ViaStrategy{}) -> (empty, ppr_deriv_strategy via)
            _                        -> (maybe empty ppr_deriv_strategy ds, empty)

    ppr_tySyn :: Doc -> Maybe Name -> Doc -> Type -> Doc
    ppr_tySyn maybeInst t argsDoc rhs
      = text "type" <+> maybeInst
        <+> case t of
             Just n -> ppr n <+> argsDoc
             Nothing -> argsDoc
        <+> text "=" <+> ppr rhs

    ppr_tf_head :: TypeFamilyHead -> Doc
    ppr_tf_head (TypeFamilyHead tc tvs res inj)
      = ppr tc <+> hsep (map ppr tvs) <+> ppr res <+> maybeInj
      where
        maybeInj | (Just inj') <- inj = ppr inj'
                 | otherwise          = empty

    ppr_bndrs :: Maybe [TyVarBndr] -> Doc
    ppr_bndrs (Just bndrs) = text "forall" <+> sep (map ppr bndrs) <> text "."
    ppr_bndrs Nothing = empty

    ------------------------------
    instance Ppr FunDep where
        ppr (FunDep xs ys) = hsep (map ppr xs) <+> text "->" <+> hsep (map ppr ys)
        ppr_list [] = empty
        ppr_list xs = bar <+> commaSep xs

    ------------------------------
    instance Ppr FamilyResultSig where
        ppr NoSig           = empty
        ppr (KindSig k)     = dcolon <+> ppr k
        ppr (TyVarSig bndr) = text "=" <+> ppr bndr

    ------------------------------
    instance Ppr InjectivityAnn where
        ppr (InjectivityAnn lhs rhs) =
            bar <+> ppr lhs <+> text "->" <+> hsep (map ppr rhs)

    ------------------------------
    instance Ppr Foreign where
        ppr (ImportF callconv safety impent as typ)
           = text "foreign import"
         <+> showtextl callconv
         <+> showtextl safety
         <+> text (show impent)
         <+> ppr as
         <+> dcolon <+> ppr typ
        ppr (ExportF callconv expent as typ)
            = text "foreign export"
          <+> showtextl callconv
          <+> text (show expent)
          <+> ppr as
          <+> dcolon <+> ppr typ

    ------------------------------
    instance Ppr Pragma where
        ppr (InlineP n inline rm phases)
           = text "{-#"
         <+> ppr inline
         <+> ppr rm
         <+> ppr phases
         <+> ppr n
         <+> text "#-}"
        ppr (SpecialiseP n ty inline phases)
           =   text "{-# SPECIALISE"
           <+> maybe empty ppr inline
           <+> ppr phases
           <+> sep [ ppr n <+> dcolon
                   , nest 2 $ ppr ty ]
           <+> text "#-}"
        ppr (SpecialiseInstP inst)
           = text "{-# SPECIALISE instance" <+> ppr inst <+> text "#-}"
        ppr (RuleP n ty_bndrs tm_bndrs lhs rhs phases)
           = sep [ text "{-# RULES" <+> pprString n <+> ppr phases
                 , nest 4 $ ppr_ty_forall ty_bndrs <+> ppr_tm_forall ty_bndrs
                                                   <+> ppr lhs
                 , nest 4 $ char '=' <+> ppr rhs <+> text "#-}" ]
          where ppr_ty_forall Nothing      = empty
                ppr_ty_forall (Just bndrs) = text "forall"
                                             <+> fsep (map ppr bndrs)
                                             <+> char '.'
                ppr_tm_forall Nothing | null tm_bndrs = empty
                ppr_tm_forall _ = text "forall"
                                  <+> fsep (map ppr tm_bndrs)
                                  <+> char '.'
        ppr (AnnP tgt expr)
           = text "{-# ANN" <+> target1 tgt <+> ppr expr <+> text "#-}"
          where target1 ModuleAnnotation    = text "module"
                target1 (TypeAnnotation t)  = text "type" <+> ppr t
                target1 (ValueAnnotation v) = ppr v
        ppr (LineP line file)
           = text "{-# LINE" <+> int line <+> text (show file) <+> text "#-}"
        ppr (CompleteP cls mty)
           = text "{-# COMPLETE" <+> (fsep $ punctuate comma $ map ppr cls)
                    <+> maybe empty (\ty -> dcolon <+> ppr ty) mty

    ------------------------------
    instance Ppr Inline where
        ppr NoInline  = text "NOINLINE"
        ppr Inline    = text "INLINE"
        ppr Inlinable = text "INLINABLE"

    ------------------------------
    instance Ppr RuleMatch where
        ppr ConLike = text "CONLIKE"
        ppr FunLike = empty

    ------------------------------
    instance Ppr Phases where
        ppr AllPhases       = empty
        ppr (FromPhase i)   = brackets $ int i
        ppr (BeforePhase i) = brackets $ char '~' <> int i

    ------------------------------
    instance Ppr RuleBndr where
        ppr (RuleVar n)         = ppr n
        ppr (TypedRuleVar n ty) = parens $ ppr n <+> dcolon <+> ppr ty

    ------------------------------
    instance Ppr Clause where
        ppr (Clause ps rhs ds) = hsep (map (pprPat appPrec) ps) <+> pprBody True rhs
                                 $$ where_clause ds

    ------------------------------
    instance Ppr Con where
        ppr (NormalC c sts) = ppr c <+> sep (map pprBangType sts)

        ppr (RecC c vsts)
            = ppr c <+> braces (sep (punctuate comma $ map pprVarBangType vsts))

        ppr (InfixC st1 c st2) = pprBangType st1
                             <+> pprName' Infix c
                             <+> pprBangType st2

        ppr (ForallC ns ctxt (GadtC c sts ty))
            = commaSepApplied c <+> dcolon <+> pprForall ns ctxt
          <+> pprGadtRHS sts ty

        ppr (ForallC ns ctxt (RecGadtC c vsts ty))
            = commaSepApplied c <+> dcolon <+> pprForall ns ctxt
          <+> pprRecFields vsts ty

        ppr (ForallC ns ctxt con)
            = pprForall ns ctxt <+> ppr con

        ppr (GadtC c sts ty)
            = commaSepApplied c <+> dcolon <+> pprGadtRHS sts ty

        ppr (RecGadtC c vsts ty)
            = commaSepApplied c <+> dcolon <+> pprRecFields vsts ty

    instance Ppr PatSynDir where
      ppr Unidir        = text "<-"
      ppr ImplBidir     = text "="
      ppr (ExplBidir _) = text "<-"
        -- the ExplBidir's clauses are pretty printed together with the
        -- entire pattern synonym; so only print the direction here.

    instance Ppr PatSynArgs where
      ppr (PrefixPatSyn args) = sep $ map ppr args
      ppr (InfixPatSyn a1 a2) = ppr a1 <+> ppr a2
      ppr (RecordPatSyn sels) = braces $ sep (punctuate comma (map ppr sels))

    commaSepApplied :: [Name] -> Doc
    commaSepApplied = commaSepWith (pprName' Applied)

    pprForall :: [TyVarBndr] -> Cxt -> Doc
    pprForall tvs cxt
      -- even in the case without any tvs, there could be a non-empty
      -- context cxt (e.g., in the case of pattern synonyms, where there
      -- are multiple forall binders and contexts).
      | [] <- tvs = pprCxt cxt
      | otherwise = text "forall" <+> hsep (map ppr tvs) <+> char '.' <+> pprCxt cxt

    pprRecFields :: [(Name, Strict, Type)] -> Type -> Doc
    pprRecFields vsts ty
        = braces (sep (punctuate comma $ map pprVarBangType vsts))
      <+> arrow <+> ppr ty

    pprGadtRHS :: [(Strict, Type)] -> Type -> Doc
    pprGadtRHS [] ty
        = ppr ty
    pprGadtRHS sts ty
        = sep (punctuate (space <> arrow) (map pprBangType sts))
      <+> arrow <+> ppr ty

    ------------------------------
    pprVarBangType :: VarBangType -> Doc
    -- Slight infelicity: with print non-atomic type with parens
    pprVarBangType (v, bang, t) = ppr v <+> dcolon <+> pprBangType (bang, t)

    ------------------------------
    pprBangType :: BangType -> Doc
    -- Make sure we print
    --
    -- Con {-# UNPACK #-} a
    --
    -- rather than
    --
    -- Con {-# UNPACK #-}a
    --
    -- when there's no strictness annotation. If there is a strictness annotation,
    -- it's okay to not put a space between it and the type.
    pprBangType (bt@(Bang _ NoSourceStrictness), t) = ppr bt <+> pprParendType t
    pprBangType (bt, t) = ppr bt <> pprParendType t

    ------------------------------
    instance Ppr Bang where
        ppr (Bang su ss) = ppr su <+> ppr ss

    ------------------------------
    instance Ppr SourceUnpackedness where
        ppr NoSourceUnpackedness = empty
        ppr SourceNoUnpack       = text "{-# NOUNPACK #-}"
        ppr SourceUnpack         = text "{-# UNPACK #-}"

    ------------------------------
    instance Ppr SourceStrictness where
        ppr NoSourceStrictness = empty
        ppr SourceLazy         = char '~'
        ppr SourceStrict       = char '!'

    ------------------------------
    instance Ppr DecidedStrictness where
        ppr DecidedLazy   = empty
        ppr DecidedStrict = char '!'
        ppr DecidedUnpack = text "{-# UNPACK #-} !"

    ------------------------------
    {-# DEPRECATED pprVarStrictType
                   "As of @template-haskell-2.11.0.0@, 'VarStrictType' has been replaced by 'VarBangType'. Please use 'pprVarBangType' instead." #-}
    pprVarStrictType :: (Name, Strict, Type) -> Doc
    pprVarStrictType = pprVarBangType

    ------------------------------
    {-# DEPRECATED pprStrictType
                   "As of @template-haskell-2.11.0.0@, 'StrictType' has been replaced by 'BangType'. Please use 'pprBangType' instead." #-}
    pprStrictType :: (Strict, Type) -> Doc
    pprStrictType = pprBangType

    ------------------------------
    pprParendType :: Type -> Doc
    pprParendType (VarT v)            = pprName' Applied v
    -- `Applied` is used here instead of `ppr` because of infix names (#13887)
    pprParendType (ConT c)            = pprName' Applied c
    pprParendType (TupleT 0)          = text "()"
    pprParendType (TupleT n)          = parens (hcat (replicate (n-1) comma))
    pprParendType (UnboxedTupleT n)   = hashParens $ hcat $ replicate (n-1) comma
    pprParendType (UnboxedSumT arity) = hashParens $ hcat $ replicate (arity-1) bar
    pprParendType ArrowT              = parens (text "->")
    pprParendType ListT               = text "[]"
    pprParendType (LitT l)            = pprTyLit l
    pprParendType (PromotedT c)       = text "'" <> pprName' Applied c
    pprParendType (PromotedTupleT 0)  = text "'()"
    pprParendType (PromotedTupleT n)  = quoteParens (hcat (replicate (n-1) comma))
    pprParendType PromotedNilT        = text "'[]"
    pprParendType PromotedConsT       = text "'(:)"
    pprParendType StarT               = char '*'
    pprParendType ConstraintT         = text "Constraint"
    pprParendType (SigT ty k)         = parens (ppr ty <+> text "::" <+> ppr k)
    pprParendType WildCardT           = char '_'
    pprParendType (InfixT x n y)      = parens (ppr x <+> pprName' Infix n <+> ppr y)
    pprParendType t@(UInfixT {})      = parens (pprUInfixT t)
    pprParendType (ParensT t)         = ppr t
    pprParendType tuple | (TupleT n, args) <- split tuple
                        , length args == n
                        = parens (commaSep args)
    pprParendType (ImplicitParamT n t)= text ('?':n) <+> text "::" <+> ppr t
    pprParendType EqualityT           = text "(~)"
    pprParendType t@(ForallT {})      = parens (ppr t)
    pprParendType t@(AppT {})         = parens (ppr t)
    pprParendType t@(AppKindT {})     = parens (ppr t)

    pprUInfixT :: Type -> Doc
    pprUInfixT (UInfixT x n y) = pprUInfixT x <+> pprName' Infix n <+> pprUInfixT y
    pprUInfixT t               = ppr t

    instance Ppr Type where
        ppr (ForallT tvars ctxt ty) = sep [pprForall tvars ctxt, ppr ty]
        ppr ty = pprTyApp (split ty)
           -- Works, in a degnerate way, for SigT, and puts parens round (ty :: kind)
           -- See Note [Pretty-printing kind signatures]
    instance Ppr TypeArg where
        ppr (TANormal ty) = ppr ty
        ppr (TyArg ki) = char '@' <> ppr ki

    pprParendTypeArg :: TypeArg -> Doc
    pprParendTypeArg (TANormal ty) = pprParendType ty
    pprParendTypeArg (TyArg ki) = char '@' <> pprParendType ki
    {- Note [Pretty-printing kind signatures]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    GHC's parser only recognises a kind signature in a type when there are
    parens around it.  E.g. the parens are required here:
       f :: (Int :: *)
       type instance F Int = (Bool :: *)
    So we always print a SigT with parens (see Trac #10050). -}

    pprTyApp :: (Type, [TypeArg]) -> Doc
    pprTyApp (ArrowT, [TANormal arg1, TANormal arg2]) = sep [pprFunArgType arg1 <+> text "->", ppr arg2]
    pprTyApp (EqualityT, [TANormal arg1, TANormal arg2]) =
        sep [pprFunArgType arg1 <+> text "~", ppr arg2]
    pprTyApp (ListT, [TANormal arg]) = brackets (ppr arg)
    pprTyApp (TupleT n, args)
     | length args == n = parens (commaSep args)
    pprTyApp (PromotedTupleT n, args)
     | length args == n = quoteParens (commaSep args)
    pprTyApp (fun, args) = pprParendType fun <+> sep (map pprParendTypeArg args)

    pprFunArgType :: Type -> Doc    -- Should really use a precedence argument
    -- Everything except forall and (->) binds more tightly than (->)
    pprFunArgType ty@(ForallT {})                 = parens (ppr ty)
    pprFunArgType ty@((ArrowT `AppT` _) `AppT` _) = parens (ppr ty)
    pprFunArgType ty@(SigT _ _)                   = parens (ppr ty)
    pprFunArgType ty                              = ppr ty

    data TypeArg = TANormal Type
                 | TyArg Kind

    split :: Type -> (Type, [TypeArg])    -- Split into function and args
    split t = go t []
        where go (AppT t1 t2) args = go t1 (TANormal t2:args)
              go (AppKindT ty ki) args = go ty (TyArg ki:args)
              go ty           args = (ty, args)

    pprTyLit :: TyLit -> Doc
    pprTyLit (NumTyLit n) = integer n
    pprTyLit (StrTyLit s) = text (show s)

    instance Ppr TyLit where
      ppr = pprTyLit

    ------------------------------
    instance Ppr TyVarBndr where
        ppr (PlainTV nm)    = ppr nm
        ppr (KindedTV nm k) = parens (ppr nm <+> dcolon <+> ppr k)

    instance Ppr Role where
        ppr NominalR          = text "nominal"
        ppr RepresentationalR = text "representational"
        ppr PhantomR          = text "phantom"
        ppr InferR            = text "_"

    ------------------------------
    pprCxt :: Cxt -> Doc
    pprCxt [] = empty
    pprCxt ts = ppr_cxt_preds ts <+> text "=>"

    ppr_cxt_preds :: Cxt -> Doc
    ppr_cxt_preds [] = empty
    ppr_cxt_preds [t@ImplicitParamT{}] = parens (ppr t)
    ppr_cxt_preds [t@ForallT{}] = parens (ppr t)
    ppr_cxt_preds [t] = ppr t
    ppr_cxt_preds ts = parens (commaSep ts)

    ------------------------------
    instance Ppr Range where
        ppr = brackets . pprRange
            where pprRange :: Range -> Doc
                  pprRange (FromR e) = ppr e <> text ".."
                  pprRange (FromThenR e1 e2) = ppr e1 <> text ","
                                            <> ppr e2 <> text ".."
                  pprRange (FromToR e1 e2) = ppr e1 <> text ".." <> ppr e2
                  pprRange (FromThenToR e1 e2 e3) = ppr e1 <> text ","
                                                 <> ppr e2 <> text ".."
                                                 <> ppr e3

    ------------------------------
    where_clause :: [Dec] -> Doc
    where_clause [] = empty
    where_clause ds = nest nestDepth $ text "where" <+> vcat (map (ppr_dec False) ds)

    showtextl :: Show a => a -> Doc
    showtextl = text . map toLower . show

    hashParens :: Doc -> Doc
    hashParens d = text "(# " <> d <> text " #)"

    quoteParens :: Doc -> Doc
    quoteParens d = text "'(" <> d <> text ")"

    -----------------------------
    instance Ppr Loc where
      ppr (Loc { loc_module = md
               , loc_package = pkg
               , loc_start = (start_ln, start_col)
               , loc_end = (end_ln, end_col) })
        = hcat [ text pkg, colon, text md, colon
               , parens $ int start_ln <> comma <> int start_col
               , text "-"
               , parens $ int end_ln <> comma <> int end_col ]

    -- Takes a list of printable things and prints them separated by commas followed
    -- by space.
    commaSep :: Ppr a => [a] -> Doc
    commaSep = commaSepWith ppr

    -- Takes a list of things and prints them with the given pretty-printing
    -- function, separated by commas followed by space.
    commaSepWith :: (a -> Doc) -> [a] -> Doc
    commaSepWith pprFun = sep . punctuate comma . map pprFun

    -- Takes a list of printable things and prints them separated by semicolons
    -- followed by space.
    semiSep :: Ppr a => [a] -> Doc
    semiSep = sep . punctuate semi . map ppr

    -- Prints out the series of vertical bars that wraps an expression or pattern
    -- used in an unboxed sum.
    unboxedSumBars :: Doc -> SumAlt -> SumArity -> Doc
    unboxedSumBars d alt arity = hashParens $
        bars (alt-1) <> d <> bars (arity - alt)
      where
        bars i = hsep (replicate i bar)

    -- Text containing the vertical bar character.
    bar :: Doc
    bar = char '|'