X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcType.lhs;h=58aac30c12d0763a5a932f703f4e51e41592f930;hb=6c1d2ec4f8f08d77e39de6f79afa4143110901fa;hp=eff458dc8b119b5510bd2a26a9b433bc1ac11fc2;hpb=f7ecf7234c224489be8a5e63fced903b655d92ee;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcType.lhs b/ghc/compiler/typecheck/TcType.lhs index eff458d..58aac30 100644 --- a/ghc/compiler/typecheck/TcType.lhs +++ b/ghc/compiler/typecheck/TcType.lhs @@ -1,394 +1,449 @@ -\begin{code} -#include "HsVersions.h" +% +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +% +\section[TcType]{Types used in the typechecker} +\begin{code} module TcType ( - - SYN_IE(TcTyVar), - newTcTyVar, - newTyVarTy, -- Kind -> NF_TcM s (TcType s) - newTyVarTys, -- Int -> Kind -> NF_TcM s [TcType s] - - - SYN_IE(TcTyVarSet), + + TcTyVar, + TcTyVarSet, + newTyVar, + newTyVarTy, -- Kind -> NF_TcM TcType + newTyVarTys, -- Int -> Kind -> NF_TcM [TcType] ----------------------------------------- - SYN_IE(TcType), TcMaybe(..), - SYN_IE(TcTauType), SYN_IE(TcThetaType), SYN_IE(TcRhoType), + TcType, TcTauType, TcThetaType, TcRhoType, -- Find the type to which a type variable is bound - tcWriteTyVar, -- :: TcTyVar s -> TcType s -> NF_TcM (TcType s) - tcReadTyVar, -- :: TcTyVar s -> NF_TcM (TcMaybe s) + tcPutTyVar, -- :: TcTyVar -> TcType -> NF_TcM TcType + tcGetTyVar, -- :: TcTyVar -> NF_TcM (Maybe TcType) does shorting out + + tcSplitRhoTy, tcInstTyVars, - tcInstSigTyVars, - tcInstType, tcInstSigType, tcInstTcType, tcInstSigTcType, - tcInstTheta, tcInstId, + tcInstSigVar, + tcInstTcType, + + -------------------------------- + TcKind, + newKindVar, newKindVars, newBoxityVar, - zonkTcTyVars, - zonkTcType, - zonkTcTypeToType, - zonkTcTyVar, - zonkTcTyVarToTyVar + -------------------------------- + zonkTcTyVar, zonkTcTyVars, zonkTcSigTyVars, + zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType, + + zonkTcTypeToType, zonkTcTyVarToTyVar, zonkKindEnv ) where +#include "HsVersions.h" -- friends: -import Type ( SYN_IE(Type), SYN_IE(ThetaType), GenType(..), - tyVarsOfTypes, getTyVar_maybe, - splitForAllTy, splitRhoTy, - mkForAllTys, instantiateTy - ) -import TyVar ( SYN_IE(TyVar), GenTyVar(..), SYN_IE(TyVarSet), SYN_IE(GenTyVarSet), - SYN_IE(TyVarEnv), lookupTyVarEnv, addOneToTyVarEnv, - nullTyVarEnv, mkTyVarEnv, - tyVarSetToList - ) +import TypeRep ( Type(..), Kind, TyNote(..) ) -- friend +import Type ( PredType(..), + getTyVar, mkAppTy, + splitPredTy_maybe, splitForAllTys, isNotUsgTy, + isTyVarTy, mkTyVarTy, mkTyVarTys, + openTypeKind, boxedTypeKind, + superKind, superBoxity, + defaultKind, boxedBoxity + ) +import Subst ( Subst, mkTopTyVarSubst, substTy ) +import TyCon ( mkPrimTyCon ) +import PrimRep ( PrimRep(VoidRep) ) +import Var ( TyVar, tyVarKind, tyVarName, isTyVar, isMutTyVar, mkTyVar ) -- others: -import Class ( GenClass ) -import Id ( idType ) -import Kind ( Kind ) -import TcKind ( TcKind ) -import TcMonad hiding ( rnMtoTcM ) -import Usage ( SYN_IE(Usage), GenUsage, SYN_IE(UVar), duffUsage ) - -import TysPrim ( voidTy ) - -IMP_Ubiq() -import Unique ( Unique ) -import UniqFM ( UniqFM ) -import Maybes ( assocMaybe ) -import Util ( zipEqual, nOfThem, panic{-, pprPanic, pprTrace ToDo:rm-} ) - ---import Outputable ( Outputable(..) ) -- Debugging messages ---import PprType ( GenTyVar, GenType ) ---import Pretty -- ditto ---import PprStyle ( PprStyle(..) ) -- ditto +import TcMonad -- TcType, amongst others +import TysWiredIn ( voidTy ) + +import Name ( Name, NamedThing(..), setNameUnique, mkSysLocalName, + mkDerivedName, mkDerivedTyConOcc + ) +import Unique ( Uniquable(..) ) +import Util ( nOfThem ) +import Outputable \end{code} +Utility functions +~~~~~~~~~~~~~~~~~ +These tcSplit functions are like their non-Tc analogues, but they +follow through bound type variables. -Data types -~~~~~~~~~~ +No need for tcSplitForAllTy because a type variable can't be instantiated +to a for-all type. \begin{code} -type TcType s = GenType (TcTyVar s) UVar -- Used during typechecker - -- Invariant on ForAllTy in TcTypes: - -- forall a. T - -- a cannot occur inside a MutTyVar in T; that is, - -- T is "flattened" before quantifying over a - -type TcThetaType s = [(Class, TcType s)] -type TcRhoType s = TcType s -- No ForAllTys -type TcTauType s = TcType s -- No DictTys or ForAllTys - -type Box s = MutableVar s (TcMaybe s) - -data TcMaybe s = UnBound - | BoundTo (TcType s) - | DontBind -- This variant is used for tyvars - -- arising from type signatures, or - -- existentially quantified tyvars; - -- The idea is that we must not unify - -- such tyvars with anything except - -- themselves. - --- Interestingly, you can't use (Maybe (TcType s)) instead of (TcMaybe s), --- because you get a synonym loop if you do! - -type TcTyVar s = GenTyVar (Box s) -type TcTyVarSet s = GenTyVarSet (Box s) +tcSplitRhoTy :: TcType -> NF_TcM (TcThetaType, TcType) +tcSplitRhoTy t + = go t t [] + where + -- A type variable is never instantiated to a dictionary type, + -- so we don't need to do a tcReadVar on the "arg". + go syn_t (FunTy arg res) ts = case splitPredTy_maybe arg of + Just pair -> go res res (pair:ts) + Nothing -> returnNF_Tc (reverse ts, syn_t) + go syn_t (NoteTy _ t) ts = go syn_t t ts + go syn_t (TyVarTy tv) ts = tcGetTyVar tv `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Just ty | not (isTyVarTy ty) -> go syn_t ty ts + other -> returnNF_Tc (reverse ts, syn_t) + go syn_t t ts = returnNF_Tc (reverse ts, syn_t) \end{code} -\begin{code} -tcTyVarToTyVar :: TcTyVar s -> TyVar -tcTyVarToTyVar (TyVar uniq kind name _) = TyVar uniq kind name duffUsage -\end{code} -Type instantiation -~~~~~~~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{New type variables} +%* * +%************************************************************************ \begin{code} -newTcTyVar :: Kind -> NF_TcM s (TcTyVar s) -newTcTyVar kind +newTyVar :: Kind -> NF_TcM TcTyVar +newTyVar kind = tcGetUnique `thenNF_Tc` \ uniq -> - tcNewMutVar UnBound `thenNF_Tc` \ box -> - returnNF_Tc (TyVar uniq kind Nothing box) + tcNewMutTyVar (mkSysLocalName uniq SLIT("t")) kind -newTyVarTy :: Kind -> NF_TcM s (TcType s) +newTyVarTy :: Kind -> NF_TcM TcType newTyVarTy kind - = newTcTyVar kind `thenNF_Tc` \ tc_tyvar -> + = newTyVar kind `thenNF_Tc` \ tc_tyvar -> returnNF_Tc (TyVarTy tc_tyvar) -newTyVarTys :: Int -> Kind -> NF_TcM s [TcType s] +newTyVarTys :: Int -> Kind -> NF_TcM [TcType] newTyVarTys n kind = mapNF_Tc newTyVarTy (nOfThem n kind) +newKindVar :: NF_TcM TcKind +newKindVar + = tcGetUnique `thenNF_Tc` \ uniq -> + tcNewMutTyVar (mkSysLocalName uniq SLIT("k")) superKind `thenNF_Tc` \ kv -> + returnNF_Tc (TyVarTy kv) + +newKindVars :: Int -> NF_TcM [TcKind] +newKindVars n = mapNF_Tc (\ _ -> newKindVar) (nOfThem n ()) + +newBoxityVar :: NF_TcM TcKind +newBoxityVar + = tcGetUnique `thenNF_Tc` \ uniq -> + tcNewMutTyVar (mkSysLocalName uniq SLIT("bx")) superBoxity `thenNF_Tc` \ kv -> + returnNF_Tc (TyVarTy kv) +\end{code} + + +%************************************************************************ +%* * +\subsection{Type instantiation} +%* * +%************************************************************************ --- For signature type variables, mark them as "DontBind" -tcInstTyVars, tcInstSigTyVars - :: [GenTyVar flexi] - -> NF_TcM s ([TcTyVar s], [TcType s], [(GenTyVar flexi, TcType s)]) +Instantiating a bunch of type variables -tcInstTyVars tyvars = inst_tyvars UnBound tyvars -tcInstSigTyVars tyvars = inst_tyvars DontBind tyvars +\begin{code} +tcInstTyVars :: [TyVar] + -> NF_TcM ([TcTyVar], [TcType], Subst) -inst_tyvars initial_cts tyvars - = mapNF_Tc (inst_tyvar initial_cts) tyvars `thenNF_Tc` \ tc_tyvars -> +tcInstTyVars tyvars + = mapNF_Tc tcInstTyVar tyvars `thenNF_Tc` \ tc_tyvars -> let - tys = map TyVarTy tc_tyvars + tys = mkTyVarTys tc_tyvars in - returnNF_Tc (tc_tyvars, tys, zipEqual "inst_tyvars" tyvars tys) + returnNF_Tc (tc_tyvars, tys, mkTopTyVarSubst tyvars tys) + -- Since the tyvars are freshly made, + -- they cannot possibly be captured by + -- any existing for-alls. Hence mkTopTyVarSubst -inst_tyvar initial_cts (TyVar _ kind name _) +tcInstTyVar tyvar = tcGetUnique `thenNF_Tc` \ uniq -> - tcNewMutVar initial_cts `thenNF_Tc` \ box -> - returnNF_Tc (TyVar uniq kind name box) -\end{code} - -@tcInstType@ and @tcInstSigType@ both create a fresh instance of a -type, returning a @TcType@. All inner for-alls are instantiated with -fresh TcTyVars. + let + name = setNameUnique (tyVarName tyvar) uniq + -- Note that we don't change the print-name + -- This won't confuse the type checker but there's a chance + -- that two different tyvars will print the same way + -- in an error message. -dppr-debug will show up the difference + -- Better watch out for this. If worst comes to worst, just + -- use mkSysLocalName. + in + tcNewMutTyVar name (tyVarKind tyvar) -The difference is that tcInstType instantiates all forall'd type -variables (and their bindees) with UnBound type variables, whereas -tcInstSigType instantiates them with DontBind types variables. -@tcInstSigType@ also doesn't take an environment. +tcInstSigVar tyvar -- Very similar to tcInstTyVar + = tcGetUnique `thenNF_Tc` \ uniq -> + let + name = setNameUnique (tyVarName tyvar) uniq + kind = tyVarKind tyvar + in + ASSERT( not (kind == openTypeKind) ) -- Shouldn't happen + tcNewSigTyVar name kind +\end{code} -On the other hand, @tcInstTcType@ instantiates a TcType. It uses -instantiateTy which could take advantage of sharing some day. +@tcInstTcType@ instantiates the outer-level for-alls of a TcType with +fresh type variables, returning them and the instantiated body of the for-all. \begin{code} -tcInstTcType :: TcType s -> NF_TcM s ([TcTyVar s], TcType s) +tcInstTcType :: TcType -> NF_TcM ([TcTyVar], TcType) tcInstTcType ty - = case tyvars of - [] -> returnNF_Tc ([], ty) -- Nothing to do - other -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) -> - returnNF_Tc (tyvars', instantiateTy tenv rho) - where - (tyvars, rho) = splitForAllTy ty - -tcInstSigTcType :: TcType s -> NF_TcM s ([TcTyVar s], TcType s) -tcInstSigTcType ty - = case tyvars of - [] -> returnNF_Tc ([], ty) -- Nothing to do - other -> tcInstSigTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) -> - returnNF_Tc (tyvars', instantiateTy tenv rho) - where - (tyvars, rho) = splitForAllTy ty + = case splitForAllTys ty of + ([], _) -> returnNF_Tc ([], ty) -- Nothing to do + (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) -> + returnNF_Tc (tyvars', substTy tenv rho) +\end{code} -tcInstType :: [(GenTyVar flexi,TcType s)] - -> GenType (GenTyVar flexi) UVar - -> NF_TcM s (TcType s) -tcInstType tenv ty_to_inst - = tcConvert bind_fn occ_fn (mkTyVarEnv tenv) ty_to_inst - where - bind_fn = inst_tyvar UnBound - occ_fn env tyvar = case lookupTyVarEnv env tyvar of - Just ty -> returnNF_Tc ty - Nothing -> panic "tcInstType:1" --(ppAboves [ppr PprDebug ty_to_inst, - -- ppr PprDebug tyvar]) - -tcInstSigType :: GenType (GenTyVar flexi) UVar -> NF_TcM s (TcType s) -tcInstSigType ty_to_inst - = tcConvert bind_fn occ_fn nullTyVarEnv ty_to_inst - where - bind_fn = inst_tyvar DontBind - occ_fn env tyvar = case lookupTyVarEnv env tyvar of - Just ty -> returnNF_Tc ty - Nothing -> panic "tcInstType:2"-- (ppAboves [ppr PprDebug ty_to_inst, - -- ppr PprDebug tyvar]) -zonkTcTyVarToTyVar :: TcTyVar s -> NF_TcM s TyVar -zonkTcTyVarToTyVar tv - = zonkTcTyVar tv `thenNF_Tc` \ tv_ty -> - case tv_ty of -- Should be a tyvar! - TyVarTy tv' -> returnNF_Tc (tcTyVarToTyVar tv') +%************************************************************************ +%* * +\subsection{Putting and getting mutable type variables} +%* * +%************************************************************************ - _ -> --pprTrace "zonkTcTyVarToTyVar:" (ppCat [ppr PprDebug tv, ppr PprDebug tv_ty]) $ - returnNF_Tc (tcTyVarToTyVar tv) +\begin{code} +tcPutTyVar :: TcTyVar -> TcType -> NF_TcM TcType +tcGetTyVar :: TcTyVar -> NF_TcM (Maybe TcType) +\end{code} +Putting is easy: -zonkTcTypeToType :: TyVarEnv Type -> TcType s -> NF_TcM s Type -zonkTcTypeToType env ty - = tcConvert zonkTcTyVarToTyVar occ_fn env ty - where - occ_fn env tyvar - = tcReadTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - BoundTo (TyVarTy tyvar') -> lookup env tyvar' - BoundTo other_ty -> tcConvert zonkTcTyVarToTyVar occ_fn env other_ty - other -> lookup env tyvar +\begin{code} +tcPutTyVar tyvar ty = tcWriteMutTyVar tyvar (Just ty) `thenNF_Tc_` + returnNF_Tc ty +\end{code} - lookup env tyvar = case lookupTyVarEnv env tyvar of - Just ty -> returnNF_Tc ty - Nothing -> returnNF_Tc voidTy -- Unbound type variables go to Void +Getting is more interesting. The easy thing to do is just to read, thus: +\begin{verbatim} +tcGetTyVar tyvar = tcReadMutTyVar tyvar +\end{verbatim} -tcConvert bind_fn occ_fn env ty_to_convert - = doo env ty_to_convert - where - doo env (TyConTy tycon usage) = returnNF_Tc (TyConTy tycon usage) +But it's more fun to short out indirections on the way: If this +version returns a TyVar, then that TyVar is unbound. If it returns +any other type, then there might be bound TyVars embedded inside it. - doo env (SynTy tycon tys ty) = mapNF_Tc (doo env) tys `thenNF_Tc` \ tys' -> - doo env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (SynTy tycon tys' ty') +We return Nothing iff the original box was unbound. - doo env (FunTy arg res usage) = doo env arg `thenNF_Tc` \ arg' -> - doo env res `thenNF_Tc` \ res' -> - returnNF_Tc (FunTy arg' res' usage) +\begin{code} +tcGetTyVar tyvar + = ASSERT2( isMutTyVar tyvar, ppr tyvar ) + tcReadMutTyVar tyvar `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Just ty -> short_out ty `thenNF_Tc` \ ty' -> + tcWriteMutTyVar tyvar (Just ty') `thenNF_Tc_` + returnNF_Tc (Just ty') - doo env (AppTy fun arg) = doo env fun `thenNF_Tc` \ fun' -> - doo env arg `thenNF_Tc` \ arg' -> - returnNF_Tc (AppTy fun' arg') + Nothing -> returnNF_Tc Nothing - doo env (DictTy clas ty usage)= doo env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy clas ty' usage) +short_out :: TcType -> NF_TcM TcType +short_out ty@(TyVarTy tyvar) + | not (isMutTyVar tyvar) + = returnNF_Tc ty - doo env (ForAllUsageTy u us ty) = doo env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllUsageTy u us ty') + | otherwise + = tcReadMutTyVar tyvar `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Just ty' -> short_out ty' `thenNF_Tc` \ ty' -> + tcWriteMutTyVar tyvar (Just ty') `thenNF_Tc_` + returnNF_Tc ty' - -- The two interesting cases! - doo env (TyVarTy tv) = occ_fn env tv + other -> returnNF_Tc ty - doo env (ForAllTy tyvar ty) - = bind_fn tyvar `thenNF_Tc` \ tyvar' -> - let - new_env = addOneToTyVarEnv env tyvar (TyVarTy tyvar') - in - doo new_env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllTy tyvar' ty') +short_out other_ty = returnNF_Tc other_ty +\end{code} -tcInstTheta :: [(TyVar,TcType s)] -> ThetaType -> NF_TcM s (TcThetaType s) -tcInstTheta tenv theta - = mapNF_Tc go theta - where - go (clas,ty) = tcInstType tenv ty `thenNF_Tc` \ tc_ty -> - returnNF_Tc (clas, tc_ty) +%************************************************************************ +%* * +\subsection{Zonking -- the exernal interfaces} +%* * +%************************************************************************ --- A useful function that takes an occurrence of a global thing --- and instantiates its type with fresh type variables -tcInstId :: Id - -> NF_TcM s ([TcTyVar s], -- It's instantiated type - TcThetaType s, -- - TcType s) -- +----------------- Type variables -tcInstId id - = let - (tyvars, rho) = splitForAllTy (idType id) - in - tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', arg_tys, tenv) -> - tcInstType tenv rho `thenNF_Tc` \ rho' -> - let - (theta', tau') = splitRhoTy rho' - in - returnNF_Tc (tyvars', theta', tau') +\begin{code} +zonkTcTyVars :: [TcTyVar] -> NF_TcM [TcType] +zonkTcTyVars tyvars = mapNF_Tc zonkTcTyVar tyvars + +zonkTcTyVar :: TcTyVar -> NF_TcM TcType +zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnNF_Tc (TyVarTy tv)) tyvar + +zonkTcSigTyVars :: [TcTyVar] -> NF_TcM [TcTyVar] +-- This guy is to zonk the tyvars we're about to feed into tcSimplify +-- Usually this job is done by checkSigTyVars, but in a couple of places +-- that is overkill, so we use this simpler chap +zonkTcSigTyVars tyvars + = zonkTcTyVars tyvars `thenNF_Tc` \ tys -> + returnNF_Tc (map (getTyVar "zonkTcSigTyVars") tys) \end{code} -Reading and writing TcTyVars -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +----------------- Types + \begin{code} -tcWriteTyVar :: TcTyVar s -> TcType s -> NF_TcM s () -tcReadTyVar :: TcTyVar s -> NF_TcM s (TcMaybe s) +zonkTcType :: TcType -> NF_TcM TcType +zonkTcType ty = zonkType (\ tv -> returnNF_Tc (TyVarTy tv)) ty + +zonkTcTypes :: [TcType] -> NF_TcM [TcType] +zonkTcTypes tys = mapNF_Tc zonkTcType tys + +zonkTcClassConstraints cts = mapNF_Tc zonk cts + where zonk (clas, tys) + = zonkTcTypes tys `thenNF_Tc` \ new_tys -> + returnNF_Tc (clas, new_tys) + +zonkTcThetaType :: TcThetaType -> NF_TcM TcThetaType +zonkTcThetaType theta = mapNF_Tc zonkTcPredType theta + +zonkTcPredType :: TcPredType -> NF_TcM TcPredType +zonkTcPredType (Class c ts) = + zonkTcTypes ts `thenNF_Tc` \ new_ts -> + returnNF_Tc (Class c new_ts) +zonkTcPredType (IParam n t) = + zonkTcType t `thenNF_Tc` \ new_t -> + returnNF_Tc (IParam n new_t) \end{code} -Writing is easy: +------------------- These ...ToType, ...ToKind versions + are used at the end of type checking \begin{code} -tcWriteTyVar (TyVar uniq kind name box) ty = tcWriteMutVar box (BoundTo ty) -\end{code} +zonkKindEnv :: [(Name, TcKind)] -> NF_TcM [(Name, Kind)] +zonkKindEnv pairs + = mapNF_Tc zonk_it pairs + where + zonk_it (name, tc_kind) = zonkType zonk_unbound_kind_var tc_kind `thenNF_Tc` \ kind -> + returnNF_Tc (name, kind) + + -- When zonking a kind, we want to + -- zonk a *kind* variable to (Type *) + -- zonk a *boxity* variable to * + zonk_unbound_kind_var kv | tyVarKind kv == superKind = tcPutTyVar kv boxedTypeKind + | tyVarKind kv == superBoxity = tcPutTyVar kv boxedBoxity + | otherwise = pprPanic "zonkKindEnv" (ppr kv) + +zonkTcTypeToType :: TcType -> NF_TcM Type +zonkTcTypeToType ty = zonkType zonk_unbound_tyvar ty + where + -- Zonk a mutable but unbound type variable to + -- Void if it has kind Boxed + -- :Void otherwise + zonk_unbound_tyvar tv + | kind == boxedTypeKind + = tcPutTyVar tv voidTy -- Just to avoid creating a new tycon in + -- this vastly common case + | otherwise + = tcPutTyVar tv (TyConApp (mk_void_tycon tv kind) []) + where + kind = tyVarKind tv + + mk_void_tycon tv kind -- Make a new TyCon with the same kind as the + -- type variable tv. Same name too, apart from + -- making it start with a colon (sigh) + = mkPrimTyCon tc_name kind 0 [] VoidRep + where + tc_name = mkDerivedName mkDerivedTyConOcc (getName tv) (getUnique tv) + +-- zonkTcTyVarToTyVar is applied to the *binding* occurrence +-- of a type variable, at the *end* of type checking. It changes +-- the *mutable* type variable into an *immutable* one. +-- +-- It does this by making an immutable version of tv and binds tv to it. +-- Now any bound occurences of the original type variable will get +-- zonked to the immutable version. + +zonkTcTyVarToTyVar :: TcTyVar -> NF_TcM TyVar +zonkTcTyVarToTyVar tv + = let + -- Make an immutable version, defaulting + -- the kind to boxed if necessary + immut_tv = mkTyVar (tyVarName tv) (defaultKind (tyVarKind tv)) + immut_tv_ty = mkTyVarTy immut_tv -Reading is more interesting. The easy thing to do is just to read, thus: -\begin{verbatim} -tcReadTyVar (TyVar uniq kind name box) = tcReadMutVar box -\end{verbatim} + zap tv = tcPutTyVar tv immut_tv_ty + -- Bind the mutable version to the immutable one + in + -- If the type variable is mutable, then bind it to immut_tv_ty + -- so that all other occurrences of the tyvar will get zapped too + zonkTyVar zap tv `thenNF_Tc` \ ty2 -> -But it's more fun to short out indirections on the way: If this -version returns a TyVar, then that TyVar is unbound. If it returns -any other type, then there might be bound TyVars embedded inside it. + WARN( immut_tv_ty /= ty2, ppr tv $$ ppr immut_tv $$ ppr ty2 ) + + returnNF_Tc immut_tv +\end{code} -We return Nothing iff the original box was unbound. + +%************************************************************************ +%* * +\subsection{Zonking -- the main work-horses: zonkType, zonkTyVar} +%* * +%* For internal use only! * +%* * +%************************************************************************ \begin{code} -tcReadTyVar (TyVar uniq kind name box) - = tcReadMutVar box `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - BoundTo ty -> short_out ty `thenNF_Tc` \ ty' -> - tcWriteMutVar box (BoundTo ty') `thenNF_Tc_` - returnNF_Tc (BoundTo ty') +-- zonkType is used for Kinds as well + +-- For unbound, mutable tyvars, zonkType uses the function given to it +-- For tyvars bound at a for-all, zonkType zonks them to an immutable +-- type variable and zonks the kind too + +zonkType :: (TcTyVar -> NF_TcM Type) -- What to do with unbound mutable type variables + -- see zonkTcType, and zonkTcTypeToType + -> TcType + -> NF_TcM Type +zonkType unbound_var_fn ty + = go ty + where + go (TyConApp tycon tys) = mapNF_Tc go tys `thenNF_Tc` \ tys' -> + returnNF_Tc (TyConApp tycon tys') - other -> returnNF_Tc other + go (NoteTy (SynNote ty1) ty2) = go ty1 `thenNF_Tc` \ ty1' -> + go ty2 `thenNF_Tc` \ ty2' -> + returnNF_Tc (NoteTy (SynNote ty1') ty2') -short_out :: TcType s -> NF_TcM s (TcType s) -short_out ty@(TyVarTy (TyVar uniq kind name box)) - = tcReadMutVar box `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - BoundTo ty' -> short_out ty' `thenNF_Tc` \ ty' -> - tcWriteMutVar box (BoundTo ty') `thenNF_Tc_` - returnNF_Tc ty' + go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard free-tyvar annotations - other -> returnNF_Tc ty + go (NoteTy (UsgNote usg) ty2) = go ty2 `thenNF_Tc` \ ty2' -> + returnNF_Tc (NoteTy (UsgNote usg) ty2') -short_out other_ty = returnNF_Tc other_ty -\end{code} + go (NoteTy (UsgForAll uv) ty2)= go ty2 `thenNF_Tc` \ ty2' -> + returnNF_Tc (NoteTy (UsgForAll uv) ty2') + go (PredTy p) = go_pred p `thenNF_Tc` \ p' -> + returnNF_Tc (PredTy p') -Zonking -~~~~~~~ -\begin{code} -zonkTcTyVars :: TcTyVarSet s -> NF_TcM s (TcTyVarSet s) -zonkTcTyVars tyvars - = mapNF_Tc zonkTcTyVar (tyVarSetToList tyvars) `thenNF_Tc` \ tys -> - returnNF_Tc (tyVarsOfTypes tys) - -zonkTcTyVar :: TcTyVar s -> NF_TcM s (TcType s) -zonkTcTyVar tyvar - = tcReadTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - BoundTo ty@(TyVarTy tyvar') -> returnNF_Tc ty - BoundTo other -> zonkTcType other - other -> returnNF_Tc (TyVarTy tyvar) - -zonkTcType :: TcType s -> NF_TcM s (TcType s) - -zonkTcType (TyVarTy tyvar) = zonkTcTyVar tyvar - -zonkTcType (AppTy ty1 ty2) - = zonkTcType ty1 `thenNF_Tc` \ ty1' -> - zonkTcType ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (AppTy ty1' ty2') - -zonkTcType (TyConTy tc u) - = returnNF_Tc (TyConTy tc u) - -zonkTcType (SynTy tc tys ty) - = mapNF_Tc zonkTcType tys `thenNF_Tc` \ tys' -> - zonkTcType ty `thenNF_Tc` \ ty' -> - returnNF_Tc (SynTy tc tys' ty') - -zonkTcType (ForAllTy tv ty) - = zonkTcTyVar tv `thenNF_Tc` \ tv_ty -> - zonkTcType ty `thenNF_Tc` \ ty' -> - case tv_ty of -- Should be a tyvar! - TyVarTy tv' -> - returnNF_Tc (ForAllTy tv' ty') - _ -> --pprTrace "zonkTcType:ForAllTy:" (ppCat [ppr PprDebug tv, ppr PprDebug tv_ty]) $ - - returnNF_Tc (ForAllTy tv{-(tcTyVarToTyVar tv)-} ty') - -zonkTcType (ForAllUsageTy uv uvs ty) - = panic "zonk:ForAllUsageTy" - -zonkTcType (FunTy ty1 ty2 u) - = zonkTcType ty1 `thenNF_Tc` \ ty1' -> - zonkTcType ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (FunTy ty1' ty2' u) - -zonkTcType (DictTy c ty u) - = zonkTcType ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy c ty' u) + go (FunTy arg res) = go arg `thenNF_Tc` \ arg' -> + go res `thenNF_Tc` \ res' -> + returnNF_Tc (FunTy arg' res') + + go (AppTy fun arg) = go fun `thenNF_Tc` \ fun' -> + go arg `thenNF_Tc` \ arg' -> + returnNF_Tc (mkAppTy fun' arg') + + -- The two interesting cases! + go (TyVarTy tyvar) = zonkTyVar unbound_var_fn tyvar + + go (ForAllTy tyvar ty) = zonkTcTyVarToTyVar tyvar `thenNF_Tc` \ tyvar' -> + go ty `thenNF_Tc` \ ty' -> + returnNF_Tc (ForAllTy tyvar' ty') + + go_pred (Class c tys) = mapNF_Tc go tys `thenNF_Tc` \ tys' -> + returnNF_Tc (Class c tys') + go_pred (IParam n ty) = go ty `thenNF_Tc` \ ty' -> + returnNF_Tc (IParam n ty') + +zonkTyVar :: (TcTyVar -> NF_TcM Type) -- What to do for an unbound mutable variable + -> TcTyVar -> NF_TcM TcType +zonkTyVar unbound_var_fn tyvar + | not (isMutTyVar tyvar) -- Not a mutable tyvar. This can happen when + -- zonking a forall type, when the bound type variable + -- needn't be mutable + = ASSERT( isTyVar tyvar ) -- Should not be any immutable kind vars + returnNF_Tc (TyVarTy tyvar) + + | otherwise + = tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Nothing -> unbound_var_fn tyvar -- Mutable and unbound + Just other_ty -> ASSERT( isNotUsgTy other_ty ) + zonkType unbound_var_fn other_ty -- Bound \end{code} +