%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
%

This module defines interface types and binders

\begin{code}
{-# 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 IfaceType (
	IfExtName, IfLclName, IfIPName,

        IfaceType(..), IfacePredType, IfaceKind, IfaceTyCon(..), IfaceCoCon(..),
	IfaceContext, IfaceBndr(..), IfaceTvBndr, IfaceIdBndr, IfaceCoercion,
	ifaceTyConName,

	-- Conversion from Type -> IfaceType
        toIfaceType, toIfaceKind, toIfaceContext,
	toIfaceBndr, toIfaceIdBndr, toIfaceTvBndrs, 
	toIfaceTyCon, toIfaceTyCon_name,

        -- Conversion from Coercion -> IfaceType
        coToIfaceType,

	-- Printing
	pprIfaceType, pprParendIfaceType, pprIfaceContext,
	pprIfaceIdBndr, pprIfaceTvBndr, pprIfaceTvBndrs, pprIfaceBndrs,
	tOP_PREC, tYCON_PREC, noParens, maybeParen, pprIfaceForAllPart

    ) where

import Coercion
import TypeRep hiding( maybeParen )
import Type (tyConAppTyCon_maybe)
import IParam (ipFastString)
import TyCon
import Id
import Var
import TysWiredIn
import TysPrim
import Name
import BasicTypes
import Outputable
import FastString
\end{code}

%************************************************************************
%*									*
		Local (nested) binders
%*									*
%************************************************************************

\begin{code}
type IfLclName = FastString	-- A local name in iface syntax

type IfExtName = Name	-- An External or WiredIn Name can appear in IfaceSyn
     	       	 	-- (However Internal or System Names never should)

type IfIPName = FastString -- Represent implicit parameters simply as a string

data IfaceBndr 		-- Local (non-top-level) binders
  = IfaceIdBndr {-# UNPACK #-} !IfaceIdBndr
  | IfaceTvBndr {-# UNPACK #-} !IfaceTvBndr

type IfaceIdBndr  = (IfLclName, IfaceType)
type IfaceTvBndr  = (IfLclName, IfaceKind)

-------------------------------
type IfaceKind     = IfaceType
type IfaceCoercion = IfaceType

data IfaceType	   -- A kind of universal type, used for types, kinds, and coercions
  = IfaceTyVar    IfLclName			-- Type/coercion variable only, not tycon
  | IfaceAppTy    IfaceType IfaceType
  | IfaceFunTy    IfaceType IfaceType
  | IfaceForAllTy IfaceTvBndr IfaceType
  | IfaceTyConApp IfaceTyCon [IfaceType]  -- Not necessarily saturated
					  -- Includes newtypes, synonyms, tuples
  | IfaceCoConApp IfaceCoCon [IfaceType]  -- Always saturated

type IfacePredType = IfaceType
type IfaceContext = [IfacePredType]

data IfaceTyCon 	-- Encodes type constructors, kind constructors
     			-- coercion constructors, the lot
  = IfaceTc IfExtName	-- The common case
  | IfaceIntTc | IfaceBoolTc | IfaceCharTc
  | IfaceListTc | IfacePArrTc
  | IfaceTupTc TupleSort Arity 
  | IfaceIPTc IfIPName       -- Used for implicit parameter TyCons

  -- Kind constructors
  | IfaceLiftedTypeKindTc | IfaceOpenTypeKindTc | IfaceUnliftedTypeKindTc
  | IfaceUbxTupleKindTc | IfaceArgTypeKindTc | IfaceConstraintKindTc

  -- SuperKind constructor
  | IfaceSuperKindTc  -- IA0_NOTE: You might want to check if I didn't forget something.

  -- Coercion constructors
data IfaceCoCon
  = IfaceCoAx IfExtName
  | IfaceIPCoAx FastString
  | IfaceReflCo    | IfaceUnsafeCo  | IfaceSymCo
  | IfaceTransCo   | IfaceInstCo
  | IfaceNthCo Int

ifaceTyConName :: IfaceTyCon -> Name
ifaceTyConName IfaceIntTc              = intTyConName
ifaceTyConName IfaceBoolTc 	       = boolTyConName
ifaceTyConName IfaceCharTc 	       = charTyConName
ifaceTyConName IfaceListTc 	       = listTyConName
ifaceTyConName IfacePArrTc 	       = parrTyConName
ifaceTyConName (IfaceTupTc bx ar)      = getName (tupleTyCon bx ar)
ifaceTyConName IfaceLiftedTypeKindTc   = liftedTypeKindTyConName
ifaceTyConName IfaceOpenTypeKindTc     = openTypeKindTyConName
ifaceTyConName IfaceUnliftedTypeKindTc = unliftedTypeKindTyConName
ifaceTyConName IfaceUbxTupleKindTc     = ubxTupleKindTyConName
ifaceTyConName IfaceArgTypeKindTc      = argTypeKindTyConName
ifaceTyConName IfaceConstraintKindTc   = constraintKindTyConName
ifaceTyConName IfaceSuperKindTc        = tySuperKindTyConName
ifaceTyConName (IfaceTc ext)           = ext
ifaceTyConName (IfaceIPTc n)           = pprPanic "ifaceTyConName:IPTc" (ppr n)
	       		    	       	 -- Note [The Name of an IfaceAnyTc]
\end{code}

Note [The Name of an IfaceAnyTc]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
IA0_NOTE: This is an old comment. It needs to be updated with IPTc which
I don't know about.

It isn't easy to get the Name of an IfaceAnyTc in a pure way.  What you
really need to do is to transform it to a TyCon, and get the Name of that.
But doing so needs the monad because there's an IfaceKind inside, and we
need a Kind.

In fact, ifaceTyConName is only used for instances and rules, and we don't
expect to instantiate those at these (internal-ish) Any types, so rather
than solve this potential problem now, I'm going to defer it until it happens!

%************************************************************************
%*									*
		Functions over IFaceTypes
%*									*
%************************************************************************


\begin{code}
splitIfaceSigmaTy :: IfaceType -> ([IfaceTvBndr], [IfacePredType], IfaceType)
-- Mainly for printing purposes
splitIfaceSigmaTy ty
  = (tvs, theta, tau)
  where
    (tvs,   rho)   = split_foralls ty
    (theta, tau)   = split_rho rho

    split_foralls (IfaceForAllTy tv ty) 
	= case split_foralls ty of { (tvs, rho) -> (tv:tvs, rho) }
    split_foralls rho = ([], rho)

    split_rho (IfaceFunTy ty1 ty2)
      | isIfacePredTy ty1 = case split_rho ty2 of { (ps, tau) -> (ty1:ps, tau) }
    split_rho tau = ([], tau)
\end{code}

%************************************************************************
%*									*
		Pretty-printing
%*									*
%************************************************************************

Precedence
~~~~~~~~~~
@ppr_ty@ takes an @Int@ that is the precedence of the context.
The precedence levels are:
\begin{description}
\item[tOP_PREC]   No parens required.
\item[fUN_PREC]   Left hand argument of a function arrow.
\item[tYCON_PREC] Argument of a type constructor.
\end{description}

\begin{code}
tOP_PREC, fUN_PREC, tYCON_PREC :: Int
tOP_PREC    = 0 -- type   in ParseIface.y
fUN_PREC    = 1 -- btype  in ParseIface.y
tYCON_PREC  = 2 -- atype  in ParseIface.y

noParens :: SDoc -> SDoc
noParens pp = pp

maybeParen :: Int -> Int -> SDoc -> SDoc
maybeParen ctxt_prec inner_prec pretty
  | ctxt_prec < inner_prec = pretty
  | otherwise		   = parens pretty
\end{code}


----------------------------- Printing binders ------------------------------------

\begin{code}
instance Outputable IfaceBndr where
    ppr (IfaceIdBndr bndr) = pprIfaceIdBndr bndr
    ppr (IfaceTvBndr bndr) = char '@' <+> pprIfaceTvBndr bndr

pprIfaceBndrs :: [IfaceBndr] -> SDoc
pprIfaceBndrs bs = sep (map ppr bs)

pprIfaceIdBndr :: (IfLclName, IfaceType) -> SDoc
pprIfaceIdBndr (name, ty) = hsep [ppr name, dcolon, ppr ty]

pprIfaceTvBndr :: IfaceTvBndr -> SDoc
pprIfaceTvBndr (tv, IfaceTyConApp IfaceLiftedTypeKindTc [])
  = ppr tv
pprIfaceTvBndr (tv, kind) = parens (ppr tv <> dcolon <> ppr kind)
pprIfaceTvBndrs :: [IfaceTvBndr] -> SDoc
pprIfaceTvBndrs tyvars = hsep (map pprIfaceTvBndr tyvars)
\end{code}

----------------------------- Printing IfaceType ------------------------------------

\begin{code}
---------------------------------
instance Outputable IfaceType where
  ppr ty = pprIfaceType ty

pprIfaceType, pprParendIfaceType ::IfaceType -> SDoc
pprIfaceType       = ppr_ty tOP_PREC
pprParendIfaceType = ppr_ty tYCON_PREC

isIfacePredTy :: IfaceType -> Bool
isIfacePredTy _  = False
-- FIXME: fix this to print iface pred tys correctly
-- isIfacePredTy ty = ifaceTypeKind ty `eqKind` constraintKind

ppr_ty :: Int -> IfaceType -> SDoc
ppr_ty _         (IfaceTyVar tyvar)     = ppr tyvar
ppr_ty ctxt_prec (IfaceTyConApp tc tys) = ppr_tc_app ctxt_prec tc tys

ppr_ty ctxt_prec (IfaceCoConApp tc tys) 
  = maybeParen ctxt_prec tYCON_PREC 
	       (sep [ppr tc, nest 4 (sep (map pprParendIfaceType tys))])

	-- Function types
ppr_ty ctxt_prec (IfaceFunTy ty1 ty2)
  = -- We don't want to lose synonyms, so we mustn't use splitFunTys here.
    maybeParen ctxt_prec fUN_PREC $
    sep (ppr_ty fUN_PREC ty1 : ppr_fun_tail ty2)
  where
    arr | isIfacePredTy ty1 = darrow
        | otherwise         = arrow

    ppr_fun_tail (IfaceFunTy ty1 ty2) 
      = (arr <+> ppr_ty fUN_PREC ty1) : ppr_fun_tail ty2
    ppr_fun_tail other_ty
      = [arr <+> pprIfaceType other_ty]

ppr_ty ctxt_prec (IfaceAppTy ty1 ty2)
  = maybeParen ctxt_prec tYCON_PREC $
    ppr_ty fUN_PREC ty1 <+> pprParendIfaceType ty2

ppr_ty ctxt_prec ty@(IfaceForAllTy _ _)
  = maybeParen ctxt_prec fUN_PREC (pprIfaceForAllPart tvs theta (pprIfaceType tau))
 where		
    (tvs, theta, tau) = splitIfaceSigmaTy ty
     
 -------------------
pprIfaceForAllPart :: [IfaceTvBndr] -> IfaceContext -> SDoc -> SDoc
pprIfaceForAllPart tvs ctxt doc 
  = sep [ppr_tvs, pprIfaceContext ctxt, doc]
  where
    ppr_tvs | null tvs  = empty
            | otherwise = ptext (sLit "forall") <+> pprIfaceTvBndrs tvs <> dot

-------------------
ppr_tc_app :: Int -> IfaceTyCon -> [IfaceType] -> SDoc
ppr_tc_app _         tc          []   = ppr_tc tc

ppr_tc_app _         IfaceListTc [ty] = brackets (pprIfaceType ty)
ppr_tc_app _         IfaceListTc _    = panic "ppr_tc_app IfaceListTc"

ppr_tc_app _         IfacePArrTc [ty] = pabrackets (pprIfaceType ty)
ppr_tc_app _         IfacePArrTc _    = panic "ppr_tc_app IfacePArrTc"

ppr_tc_app _         (IfaceTupTc sort _) tys =
  tupleParens sort (sep (punctuate comma (map pprIfaceType tys)))

ppr_tc_app _         (IfaceIPTc n) [ty] =
  parens (ppr n <> dcolon <> pprIfaceType ty)
ppr_tc_app _         (IfaceIPTc _) _ = panic "ppr_tc_app IfaceIPTc"

ppr_tc_app ctxt_prec tc tys
  = maybeParen ctxt_prec tYCON_PREC 
               (sep [ppr_tc tc, nest 4 (sep (map pprParendIfaceType tys))])

ppr_tc :: IfaceTyCon -> SDoc
-- Wrap infix type constructors in parens
ppr_tc tc@(IfaceTc ext_nm) = parenSymOcc (getOccName ext_nm) (ppr tc)
ppr_tc tc		   = ppr tc

-------------------
instance Outputable IfaceTyCon where
  ppr (IfaceIPTc n)  = ppr (IPName n)
  ppr other_tc       = ppr (ifaceTyConName other_tc)

instance Outputable IfaceCoCon where
  ppr (IfaceCoAx n)    = ppr n
  ppr (IfaceIPCoAx ip) = ppr (IPName ip)
  ppr IfaceReflCo      = ptext (sLit "Refl")
  ppr IfaceUnsafeCo    = ptext (sLit "Unsafe")
  ppr IfaceSymCo       = ptext (sLit "Sym")
  ppr IfaceTransCo     = ptext (sLit "Trans")
  ppr IfaceInstCo      = ptext (sLit "Inst")
  ppr (IfaceNthCo d)   = ptext (sLit "Nth:") <> int d

-------------------
pprIfaceContext :: IfaceContext -> SDoc
-- Prints "(C a, D b) =>", including the arrow
pprIfaceContext []    = empty
pprIfaceContext theta = ppr_preds theta <+> darrow

ppr_preds :: [IfacePredType] -> SDoc
ppr_preds [pred] = ppr pred    -- No parens
ppr_preds preds  = parens (sep (punctuate comma (map ppr preds))) 

-------------------
pabrackets :: SDoc -> SDoc
pabrackets p = ptext (sLit "[:") <> p <> ptext (sLit ":]")
\end{code}

%************************************************************************
%*									*
	Conversion from Type to IfaceType
%*									*
%************************************************************************

\begin{code}
----------------
toIfaceTvBndr :: TyVar -> (IfLclName, IfaceType)
toIfaceTvBndr tyvar   = (occNameFS (getOccName tyvar), toIfaceKind (tyVarKind tyvar))
toIfaceIdBndr :: Id -> (IfLclName, IfaceType)
toIfaceIdBndr id      = (occNameFS (getOccName id),    toIfaceType (idType id))
toIfaceTvBndrs :: [TyVar] -> [(IfLclName, IfaceType)]
toIfaceTvBndrs tyvars = map toIfaceTvBndr tyvars

toIfaceBndr :: Var -> IfaceBndr
toIfaceBndr var
  | isId var  = IfaceIdBndr (toIfaceIdBndr var)
  | otherwise = IfaceTvBndr (toIfaceTvBndr var)

toIfaceKind :: Type -> IfaceType
toIfaceKind = toIfaceType

---------------------
toIfaceType :: Type -> IfaceType
-- Synonyms are retained in the interface type
toIfaceType (TyVarTy tv)      = IfaceTyVar (toIfaceTyVar tv)
toIfaceType (AppTy t1 t2)     = IfaceAppTy (toIfaceType t1) (toIfaceType t2)
toIfaceType (FunTy t1 t2)     = IfaceFunTy (toIfaceType t1) (toIfaceType t2)
toIfaceType (TyConApp tc tys) = IfaceTyConApp (toIfaceTyCon tc) (toIfaceTypes tys)
toIfaceType (ForAllTy tv t)   = IfaceForAllTy (toIfaceTvBndr tv) (toIfaceType t)

toIfaceTyVar :: TyVar -> FastString
toIfaceTyVar = occNameFS . getOccName

toIfaceCoVar :: CoVar -> FastString
toIfaceCoVar = occNameFS . getOccName

----------------
toIfaceTyCon :: TyCon -> IfaceTyCon
toIfaceTyCon tc 
  | isTupleTyCon tc            = IfaceTupTc (tupleTyConSort tc) (tyConArity tc)
  | Just n <- tyConIP_maybe tc = IfaceIPTc (ipFastString n)
  | otherwise	               = toIfaceTyCon_name (tyConName tc)

toIfaceTyCon_name :: Name -> IfaceTyCon
toIfaceTyCon_name nm
  | Just (ATyCon tc) <- wiredInNameTyThing_maybe nm
  = toIfaceWiredInTyCon tc nm
  | otherwise
  = IfaceTc nm

toIfaceWiredInTyCon :: TyCon -> Name -> IfaceTyCon
toIfaceWiredInTyCon tc nm
  | isTupleTyCon tc                 = IfaceTupTc  (tupleTyConSort tc) (tyConArity tc)
  | Just n <- tyConIP_maybe tc      = IfaceIPTc (ipFastString n)
  | nm == intTyConName              = IfaceIntTc
  | nm == boolTyConName             = IfaceBoolTc 
  | nm == charTyConName             = IfaceCharTc 
  | nm == listTyConName             = IfaceListTc 
  | nm == parrTyConName             = IfacePArrTc 
  | nm == liftedTypeKindTyConName   = IfaceLiftedTypeKindTc
  | nm == unliftedTypeKindTyConName = IfaceUnliftedTypeKindTc
  | nm == openTypeKindTyConName     = IfaceOpenTypeKindTc
  | nm == argTypeKindTyConName      = IfaceArgTypeKindTc
  | nm == constraintKindTyConName   = IfaceConstraintKindTc
  | nm == ubxTupleKindTyConName     = IfaceUbxTupleKindTc
  | nm == tySuperKindTyConName      = IfaceSuperKindTc
  | otherwise		            = IfaceTc nm

----------------
toIfaceTypes :: [Type] -> [IfaceType]
toIfaceTypes ts = map toIfaceType ts

----------------
toIfaceContext :: ThetaType -> IfaceContext
toIfaceContext = toIfaceTypes

----------------
coToIfaceType :: Coercion -> IfaceType
coToIfaceType (Refl ty)             = IfaceCoConApp IfaceReflCo [toIfaceType ty]
coToIfaceType (TyConAppCo tc cos)   = IfaceTyConApp (toIfaceTyCon tc) 
                                                    (map coToIfaceType cos)
coToIfaceType (AppCo co1 co2)       = IfaceAppTy    (coToIfaceType co1) 
                                                    (coToIfaceType co2)
coToIfaceType (ForAllCo v co)       = IfaceForAllTy (toIfaceTvBndr v) 
                                                    (coToIfaceType co)
coToIfaceType (CoVarCo cv)          = IfaceTyVar  (toIfaceCoVar cv)
coToIfaceType (AxiomInstCo con cos) = IfaceCoConApp (coAxiomToIfaceType con)
                                                    (map coToIfaceType cos)
coToIfaceType (UnsafeCo ty1 ty2)    = IfaceCoConApp IfaceUnsafeCo 
                                                    [ toIfaceType ty1
                                                    , toIfaceType ty2 ]
coToIfaceType (SymCo co)            = IfaceCoConApp IfaceSymCo 
                                                    [ coToIfaceType co ]
coToIfaceType (TransCo co1 co2)     = IfaceCoConApp IfaceTransCo
                                                    [ coToIfaceType co1
                                                    , coToIfaceType co2 ]
coToIfaceType (NthCo d co)          = IfaceCoConApp (IfaceNthCo d)
                                                    [ coToIfaceType co ]
coToIfaceType (InstCo co ty)        = IfaceCoConApp IfaceInstCo 
                                                    [ coToIfaceType co
                                                    , toIfaceType ty ]

coAxiomToIfaceType :: CoAxiom -> IfaceCoCon
coAxiomToIfaceType con
  | Just tc <- tyConAppTyCon_maybe (co_ax_lhs con)
  , Just ip <- tyConIP_maybe tc
  = IfaceIPCoAx (ipFastString ip)
  | otherwise
  = IfaceCoAx (coAxiomName con)
\end{code}