X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcType.lhs;h=ff0a61e7943f3e17b80f84e91bc5d046f8736844;hb=12b5aeae95e8d2bfa057157c8f02f6c186f4adec;hp=e27dab5442ccb6b9564f650b0a7efa41e65de39c;hpb=9d4c03805bafb6b1e1d47306b6a6c591c998e517;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcType.lhs b/ghc/compiler/typecheck/TcType.lhs index e27dab5..ff0a61e 100644 --- a/ghc/compiler/typecheck/TcType.lhs +++ b/ghc/compiler/typecheck/TcType.lhs @@ -1,394 +1,514 @@ -\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 ( + + TcTyVar, + TcTyVarSet, + newTyVar, + newTyVarTy, -- Kind -> NF_TcM s TcType + newTyVarTys, -- Int -> Kind -> NF_TcM s [TcType] - SYN_IE(TcTyVar), - newTcTyVar, - newTyVarTy, -- Kind -> NF_TcM s (TcType s) - newTyVarTys, -- Int -> Kind -> NF_TcM s [TcType s] - - - SYN_IE(TcTyVarSet), + newTyVarTy_OpenKind, -- NF_TcM s TcType + newOpenTypeKind, -- NF_TcM s TcKind ----------------------------------------- - 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, - zonkTcTyVars, - zonkTcType, - zonkTcTypeToType, - zonkTcTyVar, - zonkTcTyVarToTyVar + typeToTcType, + + tcTypeKind, -- :: TcType -> NF_TcM s TcKind + -------------------------------- + TcKind, + newKindVar, newKindVars, + kindToTcKind, + zonkTcKind, + + -------------------------------- + zonkTcTyVar, zonkTcTyVars, zonkTcTyVarBndr, + zonkTcType, zonkTcTypes, zonkTcThetaType, + + zonkTcTypeToType, zonkTcTyVarToTyVar, + zonkTcKindToKind ) 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 PprType ( pprType ) +import Type ( Type(..), Kind, ThetaType, TyNote(..), + mkAppTy, mkTyConApp, + splitDictTy_maybe, splitForAllTys, + isTyVarTy, mkTyVarTy, mkTyVarTys, + fullSubstTy, substTopTy, + typeCon, openTypeKind, boxedTypeKind, boxedKind, superKind, superBoxity + ) +import TyCon ( tyConKind, mkPrimTyCon ) +import PrimRep ( PrimRep(VoidRep) ) +import VarEnv +import VarSet ( emptyVarSet ) +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 +import TysWiredIn ( voidTy ) + +import Name ( NamedThing(..), setNameUnique, mkSysLocalName, + mkDerivedName, mkDerivedTyConOcc + ) +import Unique ( Unique, Uniquable(..) ) +import Util ( nOfThem ) +import Outputable \end{code} -Data types +Coercions ~~~~~~~~~~ +Type definitions are in TcMonad.lhs \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) +typeToTcType :: Type -> TcType +typeToTcType ty = ty + +kindToTcKind :: Kind -> TcKind +kindToTcKind kind = kind \end{code} +Utility functions +~~~~~~~~~~~~~~~~~ +These tcSplit functions are like their non-Tc analogues, but they +follow through bound type variables. + +No need for tcSplitForAllTy because a type variable can't be instantiated +to a for-all type. + \begin{code} -tcTyVarToTyVar :: TcTyVar s -> TyVar -tcTyVarToTyVar (TyVar uniq kind name _) = TyVar uniq kind name duffUsage +tcSplitRhoTy :: TcType -> NF_TcM s (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 splitDictTy_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} -Type instantiation -~~~~~~~~~~~~~~~~~~ + +%************************************************************************ +%* * +\subsection{New type variables} +%* * +%************************************************************************ \begin{code} -newTcTyVar :: Kind -> NF_TcM s (TcTyVar s) -newTcTyVar kind +newTyVar :: Kind -> NF_TcM s 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 s 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 s [TcType] newTyVarTys n kind = mapNF_Tc newTyVarTy (nOfThem n kind) +newKindVar :: NF_TcM s TcKind +newKindVar + = tcGetUnique `thenNF_Tc` \ uniq -> + tcNewMutTyVar (mkSysLocalName uniq SLIT("k")) superKind `thenNF_Tc` \ kv -> + returnNF_Tc (TyVarTy kv) + +newKindVars :: Int -> NF_TcM s [TcKind] +newKindVars n = mapNF_Tc (\ _ -> newKindVar) (nOfThem n ()) + +-- Returns a type variable of kind (Type bv) where bv is a new boxity var +-- Used when you need a type variable that's definitely a , but you don't know +-- what kind of type (boxed or unboxed). +newTyVarTy_OpenKind :: NF_TcM s TcType +newTyVarTy_OpenKind = newOpenTypeKind `thenNF_Tc` \ kind -> + newTyVarTy kind + +newOpenTypeKind :: NF_TcM s TcKind +newOpenTypeKind = newTyVarTy superBoxity `thenNF_Tc` \ bv -> + returnNF_Tc (mkTyConApp typeCon [bv]) +\end{code} + --- For signature type variables, mark them as "DontBind" -tcInstTyVars, tcInstSigTyVars - :: [GenTyVar flexi] - -> NF_TcM s ([TcTyVar s], [TcType s], [(GenTyVar flexi, TcType s)]) +%************************************************************************ +%* * +\subsection{Type instantiation} +%* * +%************************************************************************ -tcInstTyVars tyvars = inst_tyvars UnBound tyvars -tcInstSigTyVars tyvars = inst_tyvars DontBind tyvars +Instantiating a bunch of type variables -inst_tyvars initial_cts tyvars - = mapNF_Tc (inst_tyvar initial_cts) tyvars `thenNF_Tc` \ tc_tyvars -> +\begin{code} +tcInstTyVars :: [TyVar] + -> NF_TcM s ([TcTyVar], [TcType], TyVarEnv TcType) + +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, zipVarEnv tyvars tys) -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} + 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. + + kind = tyVarKind tyvar + in + + -- Hack alert! Certain system functions (like error) are quantified + -- over type variables with an 'open' kind (a :: ?). When we instantiate + -- these tyvars we want to make a type variable whose kind is (Type bv) + -- where bv is a boxity variable. This makes sure it's a type, but + -- is open about its boxity. We *don't* want to give the thing the + -- kind '?' (= Type AnyBox). + -- + -- This is all a hack to avoid giving error it's "proper" type: + -- error :: forall bv. forall a::Type bv. String -> a -@tcInstType@ and @tcInstSigType@ both create a fresh instance of a -type, returning a @TcType@. All inner for-alls are instantiated with -fresh TcTyVars. + (if kind == openTypeKind then + newOpenTypeKind + else + returnNF_Tc kind) `thenNF_Tc` \ kind' -> -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. + tcNewMutTyVar name kind' -On the other hand, @tcInstTcType@ instantiates a TcType. It uses -instantiateTy which could take advantage of sharing some day. +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} + +@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 s ([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 - -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 -> pprPanic "tcInstType:" (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 -> pprPanic "tcInstType:" (ppAboves [ppr PprDebug ty_to_inst, - ppr PprDebug tyvar]) + = case splitForAllTys ty of + ([], _) -> returnNF_Tc ([], ty) -- Nothing to do + (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) -> + returnNF_Tc (tyvars', fullSubstTy tenv emptyVarSet rho) + -- Since the tyvars are freshly made, + -- they cannot possibly be captured by + -- any existing for-alls. Hence emptyVarSet +\end{code} -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') - _ -> pprTrace "zonkTcTyVarToTyVar:" (ppCat [ppr PprDebug tv, ppr PprDebug tv_ty]) $ - returnNF_Tc (tcTyVarToTyVar tv) +%************************************************************************ +%* * +\subsection{Putting and getting mutable type variables} +%* * +%************************************************************************ +\begin{code} +tcPutTyVar :: TcTyVar -> TcType -> NF_TcM s TcType +tcGetTyVar :: TcTyVar -> NF_TcM s (Maybe TcType) +\end{code} -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 +Putting is easy: - lookup env tyvar = case lookupTyVarEnv env tyvar of - Just ty -> returnNF_Tc ty - Nothing -> returnNF_Tc voidTy -- Unbound type variables go to Void +\begin{code} +tcPutTyVar tyvar ty = tcWriteMutTyVar tyvar (Just ty) `thenNF_Tc_` + returnNF_Tc ty +\end{code} +Getting is more interesting. The easy thing to do is just to read, thus: -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) +\begin{verbatim} +tcGetTyVar tyvar = tcReadMutTyVar tyvar +\end{verbatim} - 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') +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 (FunTy arg res usage) = doo env arg `thenNF_Tc` \ arg' -> - doo env res `thenNF_Tc` \ res' -> - returnNF_Tc (FunTy arg' res' usage) +We return Nothing iff the original box was unbound. - doo env (AppTy fun arg) = doo env fun `thenNF_Tc` \ fun' -> - doo env arg `thenNF_Tc` \ arg' -> - returnNF_Tc (AppTy fun' arg') +\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 (DictTy clas ty usage)= doo env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy clas ty' usage) + Nothing -> returnNF_Tc Nothing - doo env (ForAllUsageTy u us ty) = doo env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllUsageTy u us ty') +short_out :: TcType -> NF_TcM s TcType +short_out ty@(TyVarTy tyvar) + | not (isMutTyVar tyvar) + = returnNF_Tc ty - -- The two interesting cases! - doo env (TyVarTy tv) = occ_fn env tv - - 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') + | 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' + other -> returnNF_Tc ty -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) - --- 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) -- - -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') +short_out other_ty = returnNF_Tc other_ty \end{code} -Reading and writing TcTyVars -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +%************************************************************************ +%* * +\subsection{Zonking -- the exernal interfaces} +%* * +%************************************************************************ + +----------------- Type variables + \begin{code} -tcWriteTyVar :: TcTyVar s -> TcType s -> NF_TcM s () -tcReadTyVar :: TcTyVar s -> NF_TcM s (TcMaybe s) +zonkTcTyVars :: [TcTyVar] -> NF_TcM s [TcType] +zonkTcTyVars tyvars = mapNF_Tc zonkTcTyVar tyvars + +zonkTcTyVarBndr :: TcTyVar -> NF_TcM s TcTyVar +zonkTcTyVarBndr tyvar + = zonkTcTyVar tyvar `thenNF_Tc` \ (TyVarTy tyvar') -> + returnNF_Tc tyvar' + +zonkTcTyVar :: TcTyVar -> NF_TcM s TcType +zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnNF_Tc (TyVarTy tv)) tyvar \end{code} -Writing is easy: +----------------- Types \begin{code} -tcWriteTyVar (TyVar uniq kind name box) ty = tcWriteMutVar box (BoundTo ty) +zonkTcType :: TcType -> NF_TcM s TcType +zonkTcType ty = zonkType (\ tv -> returnNF_Tc (TyVarTy tv)) ty + +zonkTcTypes :: [TcType] -> NF_TcM s [TcType] +zonkTcTypes tys = mapNF_Tc zonkTcType tys + +zonkTcThetaType :: TcThetaType -> NF_TcM s TcThetaType +zonkTcThetaType theta = mapNF_Tc zonk theta + where + zonk (c,ts) = zonkTcTypes ts `thenNF_Tc` \ new_ts -> + returnNF_Tc (c, new_ts) + +zonkTcKind :: TcKind -> NF_TcM s TcKind +zonkTcKind = zonkTcType \end{code} -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} +------------------- These ...ToType, ...ToKind versions + are used at the end of type checking -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. +\begin{code} +zonkTcKindToKind :: TcKind -> NF_TcM s Kind +zonkTcKindToKind kind = zonkType zonk_unbound_kind_var kind + where + -- Zonk a mutable but unbound kind variable to + -- (Type Boxed) if it has kind superKind + -- Boxed if it has kind superBoxity + zonk_unbound_kind_var kv + | super_kind == superKind = tcPutTyVar kv boxedTypeKind + | otherwise = ASSERT( super_kind == superBoxity ) + tcPutTyVar kv boxedKind + where + super_kind = tyVarKind kv + + +zonkTcTypeToType :: TcType -> NF_TcM s Type +zonkTcTypeToType ty = zonkType zonk_unbound_tyvar ty + where + -- Zonk a mutable but unbound type variable to + -- Void if it has kind (Type Boxed) + -- Voidxxx otherwise + zonk_unbound_tyvar tv + = zonkTcKindToKind (tyVarKind tv) `thenNF_Tc` \ kind -> + if kind == boxedTypeKind then + tcPutTyVar tv voidTy -- Just to avoid creating a new tycon in + -- this vastly common case + else + tcPutTyVar tv (TyConApp (mk_void_tycon tv kind) []) + + 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 zonks the type variable, to get a mutable, but unbound, tyvar, tv; +-- zonks its kind, and then makes 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 s TyVar +zonkTcTyVarToTyVar tv + = zonkTcKindToKind (tyVarKind tv) `thenNF_Tc` \ kind -> + let + -- Make an immutable version + immut_tv = mkTyVar (tyVarName tv) kind + immut_tv_ty = mkTyVarTy immut_tv + + 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 -> + ASSERT2( 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 s Type) -- What to do with unbound mutable type variables + -- see zonkTcType, and zonkTcTypeToType + -> TcType + -> NF_TcM s 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 (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') -short_out other_ty = returnNF_Tc other_ty + -- 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') + + +zonkTyVar :: (TcTyVar -> NF_TcM s Type) -- What to do for an unbound mutable variable + -> TcTyVar -> NF_TcM s 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 -> zonkType unbound_var_fn other_ty -- Bound \end{code} +%************************************************************************ +%* * +\subsection{tcTypeKind} +%* * +%************************************************************************ + +Sadly, we need a Tc version of typeKind, that looks though mutable +kind variables. See the notes with Type.typeKind for the typeKindF nonsense + +This is pretty gruesome. -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) +tcTypeKind :: TcType -> NF_TcM s TcKind + +tcTypeKind (TyVarTy tyvar) = returnNF_Tc (tyVarKind tyvar) +tcTypeKind (TyConApp tycon tys) = foldlTc (\k _ -> tcFunResultTy k) (tyConKind tycon) tys +tcTypeKind (NoteTy _ ty) = tcTypeKind ty +tcTypeKind (AppTy fun arg) = tcTypeKind fun `thenNF_Tc` \ fun_kind -> + tcFunResultTy fun_kind +tcTypeKind (FunTy fun arg) = tcTypeKindF arg +tcTypeKind (ForAllTy _ ty) = tcTypeKindF ty + +tcTypeKindF :: TcType -> NF_TcM s TcKind +tcTypeKindF (NoteTy _ ty) = tcTypeKindF ty +tcTypeKindF (FunTy _ ty) = tcTypeKindF ty +tcTypeKindF (ForAllTy _ ty) = tcTypeKindF ty +tcTypeKindF other = tcTypeKind other `thenNF_Tc` \ kind -> + fix_up kind + where + fix_up (TyConApp kc _) | kc == typeCon = returnNF_Tc boxedTypeKind + -- Functions at the type level are always boxed + fix_up (NoteTy _ kind) = fix_up kind + fix_up kind@(TyVarTy tv) = tcGetTyVar tv `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Just kind' -> fix_up kind' + Nothing -> returnNF_Tc kind + fix_up kind = returnNF_Tc kind + +tcFunResultTy (NoteTy _ ty) = tcFunResultTy ty +tcFunResultTy (FunTy arg res) = returnNF_Tc res +tcFunResultTy (TyVarTy tv) = tcGetTyVar tv `thenNF_Tc` \ maybe_ty -> + case maybe_ty of + Just ty' -> tcFunResultTy ty' + -- The Nothing case, and the other cases for tcFunResultTy + -- should never happen... pattern match failure \end{code}