% % (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % HsTypes: Abstract syntax: user-defined types \begin{code}

    {-# LANGUAGE DeriveDataTypeable #-}

    module HsTypes (
    	HsType(..), LHsType,
    	HsTyVarBndr(..), LHsTyVarBndr,
    	HsExplicitFlag(..),
    	HsContext, LHsContext,
    	HsPred(..), LHsPred,
    	HsQuasiQuote(..),

    	LBangType, BangType, HsBang(..),
            getBangType, getBangStrictness,

    	ConDeclField(..), pprConDeclFields,

    	mkExplicitHsForAllTy, mkImplicitHsForAllTy, hsExplicitTvs,
    	hsTyVarName, hsTyVarNames, replaceTyVarName,
    	hsTyVarKind, hsTyVarNameKind,
    	hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
    	splitHsInstDeclTy, splitHsFunType,

    	-- Type place holder
    	PostTcType, placeHolderType, PostTcKind, placeHolderKind,

    	-- Printing
    	pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context,
        ) where

    import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )

    import NameSet( FreeVars )
    import Type
    import HsDoc
    import BasicTypes
    import SrcLoc
    import StaticFlags
    import Outputable
    import FastString

    import Data.Data

\end{code} %************************************************************************ %* * \subsection{Annotating the syntax} %* * %************************************************************************ \begin{code}

    type PostTcKind = Kind
    type PostTcType = Type		-- Used for slots in the abstract syntax
    				-- where we want to keep slot for a type
    				-- to be added by the type checker...but
    				-- before typechecking it's just bogus

    placeHolderType :: PostTcType	-- Used before typechecking
    placeHolderType  = panic "Evaluated the place holder for a PostTcType"

    placeHolderKind :: PostTcKind	-- Used before typechecking
    placeHolderKind  = panic "Evaluated the place holder for a PostTcKind"

\end{code} %************************************************************************ %* * Quasi quotes; used in types and elsewhere %* * %************************************************************************ \begin{code}

    data HsQuasiQuote id = HsQuasiQuote
    		       	   id		-- The quasi-quoter
    		       	   SrcSpan	-- The span of the enclosed string
    		       	   FastString	-- The enclosed string
      deriving (Data, Typeable)

    instance OutputableBndr id => Outputable (HsQuasiQuote id) where
        ppr = ppr_qq

    ppr_qq :: OutputableBndr id => HsQuasiQuote id -> SDoc
    ppr_qq (HsQuasiQuote quoter _ quote) =
        char '[' <> ppr quoter <> ptext (sLit "|") <>
        ppr quote <> ptext (sLit "|]")

\end{code} %************************************************************************ %* * \subsection{Bang annotations} %* * %************************************************************************ \begin{code}

    type LBangType name = Located (BangType name)
    type BangType name  = HsType name	-- Bangs are in the HsType data type

    getBangType :: LHsType a -> LHsType a
    getBangType (L _ (HsBangTy _ ty)) = ty
    getBangType ty                    = ty

    getBangStrictness :: LHsType a -> HsBang
    getBangStrictness (L _ (HsBangTy s _)) = s
    getBangStrictness _                    = HsNoBang

\end{code} %************************************************************************ %* * \subsection{Data types} %* * %************************************************************************ This is the syntax for types as seen in type signatures. \begin{code}

    type LHsContext name = Located (HsContext name)

    type HsContext name = [LHsPred name]

    type LHsPred name = Located (HsPred name)

    data HsPred name = HsClassP name [LHsType name]		 -- class constraint
    		 | HsEqualP (LHsType name) (LHsType name)-- equality constraint
    		 | HsIParam (IPName name) (LHsType name)
    		 deriving (Data, Typeable)

    type LHsType name = Located (HsType name)

    data HsType name
      = HsForAllTy	HsExplicitFlag   	-- Renamer leaves this flag unchanged, to record the way
    					-- the user wrote it originally, so that the printer can
    					-- print it as the user wrote it
    		[LHsTyVarBndr name]	-- With ImplicitForAll, this is the empty list
    					-- until the renamer fills in the variables
    		(LHsContext name)
    		(LHsType name)

      | HsTyVar		name		-- Type variable or type constructor

      | HsAppTy		(LHsType name)
    			(LHsType name)

      | HsFunTy		(LHsType name)   -- function type
    			(LHsType name)

      | HsListTy		(LHsType name)	-- Element type

      | HsPArrTy		(LHsType name)	-- Elem. type of parallel array: [:t:]

      | HsTupleTy		Boxity
    			[LHsType name]	-- Element types (length gives arity)

      | HsOpTy		(LHsType name) (Located name) (LHsType name)

      | HsParTy		(LHsType name)
    	-- Parenthesis preserved for the precedence re-arrangement in RnTypes
    	-- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
    	--
    	-- However, NB that toHsType doesn't add HsParTys (in an effort to keep
    	-- interface files smaller), so when printing a HsType we may need to
    	-- add parens.

      | HsNumTy             Integer		-- Generics only

      | HsPredTy		(HsPred name)	-- Only used in the type of an instance
    					-- declaration, eg.  Eq [a] -> Eq a
    					--			       ^^^^
    					--                            HsPredTy
    					-- Note no need for location info on the
    					-- Enclosed HsPred; the one on the type will do

      | HsKindSig		(LHsType name)	-- (ty :: kind)
    			Kind		-- A type with a kind signature

      | HsQuasiQuoteTy	(HsQuasiQuote name)

      | HsSpliceTy		(HsSplice name)
                            FreeVars  	-- Variables free in the splice (filled in by renamer)
    			PostTcKind

      | HsDocTy             (LHsType name) LHsDocString -- A documented type

      | HsBangTy	HsBang (LHsType name)	-- Bang-style type annotations
      | HsRecTy [ConDeclField name]	        -- Only in data type declarations

      | HsCoreTy Type	-- An escape hatch for tunnelling a *closed*
        	       		-- Core Type through HsSyn.

      deriving (Data, Typeable)

    data HsExplicitFlag = Explicit | Implicit deriving (Data, Typeable)

    data ConDeclField name	-- Record fields have Haddoc docs on them
      = ConDeclField { cd_fld_name :: Located name,
    		   cd_fld_type :: LBangType name,
    		   cd_fld_doc  :: Maybe LHsDocString }
      deriving (Data, Typeable)

    -----------------------
    -- Combine adjacent for-alls.
    -- The following awkward situation can happen otherwise:
    --	f :: forall a. ((Num a) => Int)
    -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
    -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
    -- but the export list abstracts f wrt [a].  Disaster.
    --
    -- A valid type must have one for-all at the top of the type, or of the fn arg types

    mkImplicitHsForAllTy ::                        LHsContext name -> LHsType name -> HsType name
    mkExplicitHsForAllTy :: [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
    mkImplicitHsForAllTy     ctxt ty = mkHsForAllTy Implicit [] ctxt ty
    mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty

    mkHsForAllTy :: HsExplicitFlag -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
    -- Smart constructor for HsForAllTy
    mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
    mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty

    -- mk_forall_ty makes a pure for-all type (no context)
    mk_forall_ty :: HsExplicitFlag -> [LHsTyVarBndr name] -> LHsType name -> HsType name
    mk_forall_ty exp  tvs  (L _ (HsParTy ty))		    = mk_forall_ty exp tvs ty
    mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
    mk_forall_ty exp  tvs  ty			            = HsForAllTy exp tvs (L noSrcSpan []) ty
    	-- Even if tvs is empty, we still make a HsForAll!
    	-- In the Implicit case, this signals the place to do implicit quantification
    	-- In the Explicit case, it prevents implicit quantification
    	--	(see the sigtype production in Parser.y.pp)
    	-- 	so that (forall. ty) isn't implicitly quantified

    plus :: HsExplicitFlag -> HsExplicitFlag -> HsExplicitFlag
    Implicit `plus` Implicit = Implicit
    _        `plus` _        = Explicit

    hsExplicitTvs :: LHsType name -> [name]
    -- The explicitly-given forall'd type variables of a HsType
    hsExplicitTvs (L _ (HsForAllTy Explicit tvs _ _)) = hsLTyVarNames tvs
    hsExplicitTvs _                                   = []

    ---------------------
    type LHsTyVarBndr name = Located (HsTyVarBndr name)

    data HsTyVarBndr name
      = UserTyVar		-- No explicit kinding
             name 		-- See Note [Printing KindedTyVars]
             PostTcKind

      | KindedTyVar
             name
             Kind
          --  *** NOTA BENE *** A "monotype" in a pragma can have
          -- for-alls in it, (mostly to do with dictionaries).  These
          -- must be explicitly Kinded.
      deriving (Data, Typeable)

    hsTyVarName :: HsTyVarBndr name -> name
    hsTyVarName (UserTyVar n _)   = n
    hsTyVarName (KindedTyVar n _) = n

    hsTyVarKind :: HsTyVarBndr name -> Kind
    hsTyVarKind (UserTyVar _ k)   = k
    hsTyVarKind (KindedTyVar _ k) = k

    hsTyVarNameKind :: HsTyVarBndr name -> (name, Kind)
    hsTyVarNameKind (UserTyVar n k)   = (n,k)
    hsTyVarNameKind (KindedTyVar n k) = (n,k)

    hsLTyVarName :: LHsTyVarBndr name -> name
    hsLTyVarName = hsTyVarName . unLoc

    hsTyVarNames :: [HsTyVarBndr name] -> [name]
    hsTyVarNames tvs = map hsTyVarName tvs

    hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
    hsLTyVarNames = map hsLTyVarName

    hsLTyVarLocName :: LHsTyVarBndr name -> Located name
    hsLTyVarLocName = fmap hsTyVarName

    hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
    hsLTyVarLocNames = map hsLTyVarLocName

    replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
    replaceTyVarName (UserTyVar _ k)   n' = UserTyVar n' k
    replaceTyVarName (KindedTyVar _ k) n' = KindedTyVar n' k

\end{code} \begin{code}

    splitHsInstDeclTy
        :: OutputableBndr name
        => HsType name
        -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
    	-- Split up an instance decl type, returning the pieces

    splitHsInstDeclTy inst_ty
      = case inst_ty of
    	HsParTy (L _ ty)	      -> splitHsInstDeclTy ty
    	HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
    	other 			      -> split_tau []  []          other
        -- The type vars should have been computed by now, even if they were implicit
      where
        split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
        split_tau tvs cxt (HsParTy (L _ ty))	    = split_tau tvs cxt ty
        split_tau _ _ _ = pprPanic "splitHsInstDeclTy" (ppr inst_ty)

    -- Splits HsType into the (init, last) parts
    -- Breaks up any parens in the result type:
    --	splitHsFunType (a -> (b -> c)) = ([a,b], c)
    splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
    splitHsFunType (L _ (HsFunTy x y)) = (x:args, res)
      where
      (args, res) = splitHsFunType y
    splitHsFunType (L _ (HsParTy ty))  = splitHsFunType ty
    splitHsFunType other 	   	   = ([], other)

\end{code} %************************************************************************ %* * \subsection{Pretty printing} %* * %************************************************************************ \begin{code}

    instance (OutputableBndr name) => Outputable (HsType name) where
        ppr ty = pprHsType ty

    instance (Outputable name) => Outputable (HsTyVarBndr name) where
        ppr (UserTyVar name _)      = ppr name
        ppr (KindedTyVar name kind) = hsep [ppr name, dcolon, pprParendKind kind]

    instance OutputableBndr name => Outputable (HsPred name) where
        ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprLHsType tys)
        ppr (HsEqualP t1 t2)    = hsep [pprLHsType t1, ptext (sLit "~"),
    				    pprLHsType t2]
        ppr (HsIParam n ty)     = hsep [ppr n, dcolon, ppr ty]

    pprLHsType :: OutputableBndr name => LHsType name -> SDoc
    pprLHsType = pprParendHsType . unLoc

    pprHsForAll :: OutputableBndr name => HsExplicitFlag -> [LHsTyVarBndr name] ->  LHsContext name -> SDoc
    pprHsForAll exp tvs cxt
      | show_forall = forall_part <+> pprHsContext (unLoc cxt)
      | otherwise   = pprHsContext (unLoc cxt)
      where
        show_forall =  opt_PprStyle_Debug
    		|| (not (null tvs) && is_explicit)
        is_explicit = case exp of {Explicit -> True; Implicit -> False}
        forall_part = ptext (sLit "forall") <+> interppSP tvs <> dot

    pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
    pprHsContext []	        = empty
    pprHsContext [L _ pred]
       | noParenHsPred pred = ppr pred <+> darrow
    pprHsContext cxt        = ppr_hs_context cxt <+> darrow

    noParenHsPred :: HsPred name -> Bool
    -- c.f. TypeRep.noParenPred
    noParenHsPred (HsClassP {}) = True
    noParenHsPred (HsEqualP {}) = True
    noParenHsPred (HsIParam {}) = False

    ppr_hs_context :: (OutputableBndr name) => HsContext name -> SDoc
    ppr_hs_context []  = empty
    ppr_hs_context cxt = parens (interpp'SP cxt)

    pprConDeclFields :: OutputableBndr name => [ConDeclField name] -> SDoc
    pprConDeclFields fields = braces (sep (punctuate comma (map ppr_fld fields)))
      where
        ppr_fld (ConDeclField { cd_fld_name = n, cd_fld_type = ty,
    			    cd_fld_doc = doc })
      	= ppr n <+> dcolon <+> ppr ty <+> ppr_mbDoc doc

\end{code} Note [Printing KindedTyVars] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Trac #3830 reminded me that we should really only print the kind signature on a KindedTyVar if the kind signature was put there by the programmer. During kind inference GHC now adds a PostTcKind to UserTyVars, rather than converting to KindedTyVars as before. (As it happens, the message in #3830 comes out a different way now, and the problem doesn't show up; but having the flag on a KindedTyVar seems like the Right Thing anyway.) \begin{code}

    pREC_TOP, pREC_FUN, pREC_OP, pREC_CON :: Int
    pREC_TOP = 0  -- type   in ParseIface.y
    pREC_FUN = 1  -- btype  in ParseIface.y
                  -- Used for LH arg of (->)
    pREC_OP  = 2  -- Used for arg of any infix operator
                  -- (we don't keep their fixities around)
    pREC_CON = 3  -- Used for arg of type applicn:
                  -- always parenthesise unless atomic

    maybeParen :: Int 	-- Precedence of context
    	   -> Int	-- Precedence of top-level operator
    	   -> SDoc -> SDoc	-- Wrap in parens if (ctxt >= op)
    maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
    			       | otherwise	      = p

    -- printing works more-or-less as for Types

    pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc

    pprHsType ty       = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
    pprParendHsType ty = ppr_mono_ty pREC_CON ty

    -- Before printing a type
    -- (a) Remove outermost HsParTy parens
    -- (b) Drop top-level for-all type variables in user style
    --     since they are implicit in Haskell
    prepare :: PprStyle -> HsType name -> HsType name
    prepare sty (HsParTy ty)	  = prepare sty (unLoc ty)
    prepare _   ty                    = ty

    ppr_mono_lty :: (OutputableBndr name) => Int -> LHsType name -> SDoc
    ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)

    ppr_mono_ty :: (OutputableBndr name) => Int -> HsType name -> SDoc
    ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
      = maybeParen ctxt_prec pREC_FUN $
        sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]

    ppr_mono_ty _    (HsBangTy b ty)     = ppr b <> ppr ty
    ppr_mono_ty _    (HsQuasiQuoteTy qq) = ppr qq
    ppr_mono_ty _    (HsRecTy flds)      = pprConDeclFields flds
    ppr_mono_ty _    (HsTyVar name)      = ppr name
    ppr_mono_ty prec (HsFunTy ty1 ty2)   = ppr_fun_ty prec ty1 ty2
    ppr_mono_ty _    (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
    ppr_mono_ty _    (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
    ppr_mono_ty _    (HsListTy ty)	     = brackets (ppr_mono_lty pREC_TOP ty)
    ppr_mono_ty _    (HsPArrTy ty)	     = pabrackets (ppr_mono_lty pREC_TOP ty)
    ppr_mono_ty _    (HsPredTy pred)     = ppr pred
    ppr_mono_ty _    (HsNumTy n)         = integer n  -- generics only
    ppr_mono_ty _    (HsSpliceTy s _ _)  = pprSplice s
    ppr_mono_ty _    (HsCoreTy ty)       = ppr ty

    ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
      = maybeParen ctxt_prec pREC_CON $
        hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]

    ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
      = maybeParen ctxt_prec pREC_OP $
        ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2

    ppr_mono_ty _         (HsParTy ty)
      = parens (ppr_mono_lty pREC_TOP ty)
      -- Put the parens in where the user did
      -- But we still use the precedence stuff to add parens because
      --	toHsType doesn't put in any HsParTys, so we may still need them

    ppr_mono_ty ctxt_prec (HsDocTy ty doc)
      = maybeParen ctxt_prec pREC_OP $
        ppr_mono_lty pREC_OP ty <+> ppr (unLoc doc)
      -- we pretty print Haddock comments on types as if they were
      -- postfix operators

    --------------------------
    ppr_fun_ty :: (OutputableBndr name) => Int -> LHsType name -> LHsType name -> SDoc
    ppr_fun_ty ctxt_prec ty1 ty2
      = let p1 = ppr_mono_lty pREC_FUN ty1
    	p2 = ppr_mono_lty pREC_TOP ty2
        in
        maybeParen ctxt_prec pREC_FUN $
        sep [p1, ptext (sLit "->") <+> p2]

    --------------------------
    pabrackets :: SDoc -> SDoc
    pabrackets p = ptext (sLit "[:") <> p <> ptext (sLit ":]")

\end{code}