X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcType.lhs;h=ffcf39240730276a2c3d0fa4aa42875aa9eb454a;hb=f714e6b642fd614a9971717045ae47c3d871275e;hp=1008e0cad8bb74316efe01dd30ae0448d76ce2f0;hpb=0596517a9b4b2b32e5d375a986351102ac4540fc;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcType.lhs b/ghc/compiler/typecheck/TcType.lhs index 1008e0c..ffcf392 100644 --- a/ghc/compiler/typecheck/TcType.lhs +++ b/ghc/compiler/typecheck/TcType.lhs @@ -1,322 +1,1181 @@ -\begin{code} -module TcType ( +% +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +% +\section[TcType]{Types used in the typechecker} - TcTyVar(..), - newTcTyVar, - newTyVarTy, -- Kind -> NF_TcM s (TcType s) - newTyVarTys, -- Int -> Kind -> NF_TcM s [TcType s] +This module provides the Type interface for front-end parts of the +compiler. These parts + * treat "source types" as opaque: + newtypes, and predicates are meaningful. + * look through usage types - TcTyVarSet(..), +The "tc" prefix is for "typechechecker", because the type checker +is the principal client. - ----------------------------------------- - TcType(..), TcMaybe(..), - TcTauType(..), TcThetaType(..), TcRhoType(..), +\begin{code} +module TcType ( + -------------------------------- + -- Types + TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType, + TcTyVar, TcTyVarSet, TcKind, + + -------------------------------- + -- TyVarDetails + TyVarDetails(..), isUserTyVar, isSkolemTyVar, + tyVarBindingInfo, + + -------------------------------- + -- Builders + mkPhiTy, mkSigmaTy, + + -------------------------------- + -- Splitters + -- These are important because they do not look through newtypes + tcSplitForAllTys, tcSplitPhiTy, + tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, + tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs, + tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, tcSplitSigmaTy, + tcSplitMethodTy, tcGetTyVar_maybe, tcGetTyVar, + + --------------------------------- + -- Predicates. + -- Again, newtypes are opaque + tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, + isSigmaTy, isOverloadedTy, + isDoubleTy, isFloatTy, isIntTy, + isIntegerTy, isAddrTy, isBoolTy, isUnitTy, + isTauTy, tcIsTyVarTy, tcIsForAllTy, + allDistinctTyVars, + + --------------------------------- + -- Misc type manipulators + deNoteType, classesOfTheta, + tyClsNamesOfType, tyClsNamesOfDFunHead, + getDFunTyKey, + + --------------------------------- + -- Predicate types + getClassPredTys_maybe, getClassPredTys, + isClassPred, isTyVarClassPred, + mkDictTy, tcSplitPredTy_maybe, + isPredTy, isDictTy, tcSplitDFunTy, predTyUnique, + mkClassPred, isInheritablePred, isLinearPred, isIPPred, mkPredName, + + --------------------------------- + -- Foreign import and export + isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool + isFFIImportResultTy, -- :: DynFlags -> Type -> Bool + isFFIExportResultTy, -- :: Type -> Bool + isFFIExternalTy, -- :: Type -> Bool + isFFIDynArgumentTy, -- :: Type -> Bool + isFFIDynResultTy, -- :: Type -> Bool + isFFILabelTy, -- :: Type -> Bool + isFFIDotnetTy, -- :: DynFlags -> Type -> Bool + isFFIDotnetObjTy, -- :: Type -> Bool + + toDNType, -- :: Type -> DNType + + --------------------------------- + -- Unifier and matcher + unifyTysX, unifyTyListsX, unifyExtendTysX, + matchTy, matchTys, match, + + -------------------------------- + -- Rexported from Type + Kind, -- Stuff to do with kinds is insensitive to pre/post Tc + unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds, + isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind, + isSubKind, defaultKind, + isArgTypeKind, isOpenTypeKind, + + Type, PredType(..), ThetaType, + mkForAllTy, mkForAllTys, + mkFunTy, mkFunTys, zipFunTys, + mkTyConApp, mkGenTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys, + mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys, + + isUnLiftedType, -- Source types are always lifted + isUnboxedTupleType, -- Ditto + isPrimitiveType, + + tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes, + tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, + typeKind, + + tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta, + + pprKind, pprParendKind, + pprType, pprParendType, + pprPred, pprTheta, pprThetaArrow, pprClassPred - -- 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) + ) where +#include "HsVersions.h" - tcInstTyVar, -- TyVar -> NF_TcM s (TcTyVar s) - tcInstType, tcInstTcType, tcInstTheta, +-- friends: +import TypeRep ( Type(..), TyNote(..), funTyCon ) -- friend + +import Type ( -- Re-exports + tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, + tyVarsOfTheta, Kind, Type, PredType(..), + ThetaType, unliftedTypeKind, + liftedTypeKind, openTypeKind, mkArrowKind, + isLiftedTypeKind, isUnliftedTypeKind, + isOpenTypeKind, + mkArrowKinds, mkForAllTy, mkForAllTys, + defaultKind, isArgTypeKind, isOpenTypeKind, + mkFunTy, mkFunTys, zipFunTys, + mkTyConApp, mkGenTyConApp, mkAppTy, + mkAppTys, mkSynTy, applyTy, applyTys, + mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, + mkPredTys, isUnLiftedType, + isUnboxedTupleType, isPrimitiveType, + splitTyConApp_maybe, + tidyTopType, tidyType, tidyPred, tidyTypes, + tidyFreeTyVars, tidyOpenType, tidyOpenTypes, + tidyTyVarBndr, tidyOpenTyVar, + tidyOpenTyVars, + isSubKind, + typeKind, repType, + pprKind, pprParendKind, + pprType, pprParendType, + pprPred, pprTheta, pprThetaArrow, pprClassPred + ) +import TyCon ( TyCon, isUnLiftedTyCon, tyConUnique ) +import Class ( Class ) +import Var ( TyVar, tyVarKind, tcTyVarDetails ) +import ForeignCall ( Safety, playSafe, DNType(..) ) +import VarEnv +import VarSet --- zonkTcType, -- TcType s -> NF_TcM s (TcType s) --- zonkTcTheta, -- TcThetaType s -> NF_TcM s (TcThetaType s) +-- others: +import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt ) +import Name ( Name, NamedThing(..), mkInternalName, getSrcLoc ) +import NameSet +import OccName ( OccName, mkDictOcc ) +import PrelNames -- Lots (e.g. in isFFIArgumentTy) +import TysWiredIn ( unitTyCon, charTyCon, listTyCon ) +import BasicTypes ( IPName(..), ipNameName ) +import Unique ( Unique, Uniquable(..) ) +import SrcLoc ( SrcLoc ) +import Util ( cmpList, thenCmp, equalLength, snocView ) +import Maybes ( maybeToBool, expectJust ) +import Outputable +\end{code} - zonkTcTyVars, -- TcTyVarSet s -> NF_TcM s (TcTyVarSet s) - zonkTcType, -- TcType s -> NF_TcM s (TcType s) - zonkTcTypeToType, -- TcType s -> NF_TcM s Type - zonkTcTyVarToTyVar -- TcTyVar s -> NF_TcM s TyVar - ) where +%************************************************************************ +%* * +\subsection{Types} +%* * +%************************************************************************ +The type checker divides the generic Type world into the +following more structured beasts: +sigma ::= forall tyvars. phi + -- A sigma type is a qualified type + -- + -- Note that even if 'tyvars' is empty, theta + -- may not be: e.g. (?x::Int) => Int --- friends: -import Type ( Type(..), ThetaType(..), GenType(..), tyVarsOfTypes, getTyVar_maybe ) -import TyVar ( TyVar(..), GenTyVar(..), TyVarSet(..), GenTyVarSet(..), - tyVarSetToList - ) + -- Note that 'sigma' is in prenex form: + -- all the foralls are at the front. + -- A 'phi' type has no foralls to the right of + -- an arrow --- others: -import Kind ( Kind ) -import Usage ( Usage(..), GenUsage, UVar(..), duffUsage ) -import Class ( GenClass ) -import TcKind ( TcKind ) -import TcMonad - -import Ubiq -import Unique ( Unique ) -import UniqFM ( UniqFM ) -import Name ( getNameShortName ) -import Maybes ( assocMaybe ) -import Util ( panic ) -\end{code} +phi :: theta => rho +rho ::= sigma -> rho + | tau +-- A 'tau' type has no quantification anywhere +-- Note that the args of a type constructor must be taus +tau ::= tyvar + | tycon tau_1 .. tau_n + | tau_1 tau_2 + | tau_1 -> tau_2 -Data types -~~~~~~~~~~ +-- In all cases, a (saturated) type synonym application is legal, +-- provided it expands to the required form. \begin{code} -type TcType s = GenType (TcTyVar s) UVar -- Used during typechecker +type TcType = Type -- A TcType can have mutable type variables -- 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 TcPredType = PredType +type TcThetaType = ThetaType +type TcSigmaType = TcType +type TcRhoType = TcType +type TcTauType = TcType + +type TcKind = Kind +\end{code} -type Box s = MutableVar s (TcMaybe s) -data TcMaybe s = UnBound - | BoundTo (TcType s) +%************************************************************************ +%* * +\subsection{TyVarDetails} +%* * +%************************************************************************ --- Interestingly, you can't use (Maybe (TcType s)) instead of (TcMaybe s), --- because you get a synonym loop if you do! +TyVarDetails gives extra info about type variables, used during type +checking. It's attached to mutable type variables only. +It's knot-tied back to Var.lhs. There is no reason in principle +why Var.lhs shouldn't actually have the definition, but it "belongs" here. -type TcTyVar s = GenTyVar (Box s) -type TcTyVarSet s = GenTyVarSet (Box s) +\begin{code} +type TcTyVar = TyVar -- Used only during type inference + +data TyVarDetails + = SigTv -- Introduced when instantiating a type signature, + -- prior to checking that the defn of a fn does + -- have the expected type. Should not be instantiated. + -- f :: forall a. a -> a + -- f = e + -- When checking e, with expected type (a->a), we + -- should not instantiate a + + | ClsTv -- Scoped type variable introduced by a class decl + -- class C a where ... + + | InstTv -- Ditto, but instance decl + + | PatSigTv -- Scoped type variable, introduced by a pattern + -- type signature \ x::a -> e + + | VanillaTv -- Everything else + +isUserTyVar :: TcTyVar -> Bool -- Avoid unifying these if possible +isUserTyVar tv = case tcTyVarDetails tv of + VanillaTv -> False + other -> True + +isSkolemTyVar :: TcTyVar -> Bool +isSkolemTyVar tv = case tcTyVarDetails tv of + SigTv -> True + ClsTv -> True + InstTv -> True + oteher -> False + +tyVarBindingInfo :: TcTyVar -> SDoc -- Used in checkSigTyVars +tyVarBindingInfo tv + = sep [ptext SLIT("is bound by the") <+> details (tcTyVarDetails tv), + ptext SLIT("at") <+> ppr (getSrcLoc tv)] + where + details SigTv = ptext SLIT("type signature") + details ClsTv = ptext SLIT("class declaration") + details InstTv = ptext SLIT("instance declaration") + details PatSigTv = ptext SLIT("pattern type signature") + details VanillaTv = ptext SLIT("//vanilla//") -- Ditto \end{code} \begin{code} -tcTyVarToTyVar :: TcTyVar s -> TyVar -tcTyVarToTyVar (TyVar uniq kind name _) = TyVar uniq kind name duffUsage +type TcTyVarSet = TyVarSet \end{code} -Type instantiation -~~~~~~~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{Tau, sigma and rho} +%* * +%************************************************************************ \begin{code} -newTcTyVar :: Maybe ShortName -> Kind -> NF_TcM s (TcTyVar s) -newTcTyVar name kind - = tcGetUnique `thenNF_Tc` \ uniq -> - tcNewMutVar UnBound `thenNF_Tc` \ box -> - returnNF_Tc (TyVar uniq kind name box) - -newTyVarTy :: Kind -> NF_TcM s (TcType s) -newTyVarTy kind - = newTcTyVar Nothing kind `thenNF_Tc` \ tc_tyvar -> - returnNF_Tc (TyVarTy tc_tyvar) - -newTyVarTys :: Int -> Kind -> NF_TcM s [TcType s] -newTyVarTys n kind = mapNF_Tc newTyVarTy (take n (repeat kind)) - -tcInstTyVar :: TyVar -> NF_TcM s (TcTyVar s) -tcInstTyVar tyvar@(TyVar uniq kind name _) - = newTcTyVar name kind +mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau) + +mkPhiTy :: [PredType] -> Type -> Type +mkPhiTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta \end{code} -@tcInstType@ and @tcInstTcType@ both create a fresh instance of a -type, returning a @TcType@. All inner for-alls are instantiated with -fresh TcTyVars. +@isTauTy@ tests for nested for-alls. -There are two versions, one for instantiating a @Type@, and one for a @TcType@. -The former must instantiate everything; all tyvars must be bound either -by a forall or by an environment passed in. The latter can do some sharing, -and is happy with free tyvars (which is vital when instantiating the type -of local functions). In the future @tcInstType@ may try to be clever about not -instantiating constant sub-parts. +\begin{code} +isTauTy :: Type -> Bool +isTauTy (TyVarTy v) = True +isTauTy (TyConApp _ tys) = all isTauTy tys +isTauTy (NewTcApp _ tys) = all isTauTy tys +isTauTy (AppTy a b) = isTauTy a && isTauTy b +isTauTy (FunTy a b) = isTauTy a && isTauTy b +isTauTy (PredTy p) = True -- Don't look through source types +isTauTy (NoteTy _ ty) = isTauTy ty +isTauTy other = False +\end{code} \begin{code} -tcInstType :: [(TyVar,TcType s)] -> Type -> NF_TcM s (TcType s) -tcInstType tenv ty_to_inst - = do [(uniq,ty) | (TyVar uniq _ _ _, ty) <- tenv] ty_to_inst +getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to + -- construct a dictionary function name +getDFunTyKey (TyVarTy tv) = getOccName tv +getDFunTyKey (TyConApp tc _) = getOccName tc +getDFunTyKey (NewTcApp tc _) = getOccName tc +getDFunTyKey (AppTy fun _) = getDFunTyKey fun +getDFunTyKey (NoteTy _ t) = getDFunTyKey t +getDFunTyKey (FunTy arg _) = getOccName funTyCon +getDFunTyKey (ForAllTy _ t) = getDFunTyKey t +getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty) +-- PredTy shouldn't happen +\end{code} + + +%************************************************************************ +%* * +\subsection{Expanding and splitting} +%* * +%************************************************************************ + +These tcSplit functions are like their non-Tc analogues, but + a) they do not look through newtypes + b) they do not look through PredTys + c) [future] they ignore usage-type annotations + +However, they are non-monadic and do not follow through mutable type +variables. It's up to you to make sure this doesn't matter. + +\begin{code} +tcSplitForAllTys :: Type -> ([TyVar], Type) +tcSplitForAllTys ty = split ty ty [] + where + split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs) + split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs + split orig_ty t tvs = (reverse tvs, orig_ty) + +tcIsForAllTy (ForAllTy tv ty) = True +tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty +tcIsForAllTy t = False + +tcSplitPhiTy :: Type -> ([PredType], Type) +tcSplitPhiTy ty = split ty ty [] + where + split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of + Just p -> split res res (p:ts) + Nothing -> (reverse ts, orig_ty) + split orig_ty (NoteTy n ty) ts = split orig_ty ty ts + split orig_ty ty ts = (reverse ts, orig_ty) + +tcSplitSigmaTy ty = case tcSplitForAllTys ty of + (tvs, rho) -> case tcSplitPhiTy rho of + (theta, tau) -> (tvs, theta, tau) + +tcTyConAppTyCon :: Type -> TyCon +tcTyConAppTyCon ty = fst (tcSplitTyConApp ty) + +tcTyConAppArgs :: Type -> [Type] +tcTyConAppArgs ty = snd (tcSplitTyConApp ty) + +tcSplitTyConApp :: Type -> (TyCon, [Type]) +tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of + Just stuff -> stuff + Nothing -> pprPanic "tcSplitTyConApp" (pprType ty) + +tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type]) +tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) +tcSplitTyConApp_maybe (NewTcApp tc tys) = Just (tc, tys) +tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res]) +tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty + -- Newtypes are opaque, so they may be split + -- However, predicates are not treated + -- as tycon applications by the type checker +tcSplitTyConApp_maybe other = Nothing + +tcSplitFunTys :: Type -> ([Type], Type) +tcSplitFunTys ty = case tcSplitFunTy_maybe ty of + Nothing -> ([], ty) + Just (arg,res) -> (arg:args, res') + where + (args,res') = tcSplitFunTys res + +tcSplitFunTy_maybe :: Type -> Maybe (Type, Type) +tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res) +tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty +tcSplitFunTy_maybe other = Nothing + +tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg } +tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res } + + +tcSplitAppTy_maybe :: Type -> Maybe (Type, Type) +tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2) +tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2) +tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty +tcSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of + Just (tys', ty') -> Just (TyConApp tc tys', ty') + Nothing -> Nothing +tcSplitAppTy_maybe (NewTcApp tc tys) = case snocView tys of + Just (tys', ty') -> Just (NewTcApp tc tys', ty') + Nothing -> Nothing +tcSplitAppTy_maybe other = Nothing + +tcSplitAppTy ty = case tcSplitAppTy_maybe ty of + Just stuff -> stuff + Nothing -> pprPanic "tcSplitAppTy" (pprType ty) + +tcSplitAppTys :: Type -> (Type, [Type]) +tcSplitAppTys ty + = go ty [] where - do env (TyConTy tycon usage) = returnNF_Tc (TyConTy tycon usage) + go ty args = case tcSplitAppTy_maybe ty of + Just (ty', arg) -> go ty' (arg:args) + Nothing -> (ty,args) - do env (SynTy tycon tys ty) = mapNF_Tc (do env) tys `thenNF_Tc` \ tys' -> - do env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (SynTy tycon tys' ty') +tcGetTyVar_maybe :: Type -> Maybe TyVar +tcGetTyVar_maybe (TyVarTy tv) = Just tv +tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t +tcGetTyVar_maybe other = Nothing - do env (FunTy arg res usage) = do env arg `thenNF_Tc` \ arg' -> - do env res `thenNF_Tc` \ res' -> - returnNF_Tc (FunTy arg' res' usage) +tcGetTyVar :: String -> Type -> TyVar +tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty) - do env (AppTy fun arg) = do env fun `thenNF_Tc` \ fun' -> - do env arg `thenNF_Tc` \ arg' -> - returnNF_Tc (AppTy fun' arg') +tcIsTyVarTy :: Type -> Bool +tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty) +\end{code} - do env (DictTy clas ty usage)= do env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy clas ty' usage) +The type of a method for class C is always of the form: + Forall a1..an. C a1..an => sig_ty +where sig_ty is the type given by the method's signature, and thus in general +is a ForallTy. At the point that splitMethodTy is called, it is expected +that the outer Forall has already been stripped off. splitMethodTy then +returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes stripped off. - do env (TyVarTy (TyVar uniq kind name _)) - = case assocMaybe env uniq of - Just tc_ty -> returnNF_Tc tc_ty - Nothing -> panic "tcInstType" +\begin{code} +tcSplitMethodTy :: Type -> (PredType, Type) +tcSplitMethodTy ty = split ty + where + split (FunTy arg res) = case tcSplitPredTy_maybe arg of + Just p -> (p, res) + Nothing -> panic "splitMethodTy" + split (NoteTy n ty) = split ty + split _ = panic "splitMethodTy" + +tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type]) +-- Split the type of a dictionary function +tcSplitDFunTy ty + = case tcSplitSigmaTy ty of { (tvs, theta, tau) -> + case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) -> + (tvs, theta, clas, tys) }} +\end{code} - do env (ForAllTy (TyVar uniq kind name _) ty) - = newTcTyVar name kind `thenNF_Tc` \ tc_tyvar -> - let - new_env = (uniq, TyVarTy tc_tyvar) : env - in - do new_env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllTy tc_tyvar ty') +(allDistinctTyVars tys tvs) = True + iff +all the types tys are type variables, +distinct from each other and from tvs. - -- ForAllUsage impossible +This is useful when checking that unification hasn't unified signature +type variables. For example, if the type sig is + f :: forall a b. a -> b -> b +we want to check that 'a' and 'b' havn't + (a) been unified with a non-tyvar type + (b) been unified with each other (all distinct) + (c) been unified with a variable free in the environment +\begin{code} +allDistinctTyVars :: [Type] -> TyVarSet -> Bool -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) +allDistinctTyVars [] acc + = True +allDistinctTyVars (ty:tys) acc + = case tcGetTyVar_maybe ty of + Nothing -> False -- (a) + Just tv | tv `elemVarSet` acc -> False -- (b) or (c) + | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv) +\end{code} -tcInstTcType :: [(TcTyVar s,TcType s)] -> TcType s -> NF_TcM s (TcType s) -tcInstTcType tenv ty_to_inst - = do [(uniq,ty) | (TyVar uniq _ _ _, ty) <- tenv] ty_to_inst - where - do env ty@(TyConTy tycon usage) = returnNF_Tc ty - --- Could do clever stuff here to avoid instantiating constant types - do env (SynTy tycon tys ty) = mapNF_Tc (do env) tys `thenNF_Tc` \ tys' -> - do env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (SynTy tycon tys' ty') - - do env (FunTy arg res usage) = do env arg `thenNF_Tc` \ arg' -> - do env res `thenNF_Tc` \ res' -> - returnNF_Tc (FunTy arg' res' usage) - - do env (AppTy fun arg) = do env fun `thenNF_Tc` \ fun' -> - do env arg `thenNF_Tc` \ arg' -> - returnNF_Tc (AppTy fun' arg') - - do env (DictTy clas ty usage)= do env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy clas ty' usage) - - do env ty@(TyVarTy (TyVar uniq kind name _)) - = case assocMaybe env uniq of - Just tc_ty -> returnNF_Tc tc_ty - Nothing -> returnNF_Tc ty - - do env (ForAllTy (TyVar uniq kind name _) ty) - = newTcTyVar name kind `thenNF_Tc` \ tc_tyvar -> - let - new_env = (uniq, TyVarTy tc_tyvar) : env - in - do new_env ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllTy tc_tyvar ty') - - -- ForAllUsage impossible + +%************************************************************************ +%* * +\subsection{Predicate types} +%* * +%************************************************************************ + +\begin{code} +tcSplitPredTy_maybe :: Type -> Maybe PredType + -- Returns Just for predicates only +tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty +tcSplitPredTy_maybe (PredTy p) = Just p +tcSplitPredTy_maybe other = Nothing + +predTyUnique :: PredType -> Unique +predTyUnique (IParam n _) = getUnique (ipNameName n) +predTyUnique (ClassP clas tys) = getUnique clas + +mkPredName :: Unique -> SrcLoc -> PredType -> Name +mkPredName uniq loc (ClassP cls tys) = mkInternalName uniq (mkDictOcc (getOccName cls)) loc +mkPredName uniq loc (IParam ip ty) = mkInternalName uniq (getOccName (ipNameName ip)) loc \end{code} -Reading and writing TcTyVars -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +--------------------- Dictionary types --------------------------------- + \begin{code} -tcWriteTyVar :: TcTyVar s -> TcType s -> NF_TcM s () -tcReadTyVar :: TcTyVar s -> NF_TcM s (TcMaybe s) +mkClassPred clas tys = ClassP clas tys + +isClassPred :: PredType -> Bool +isClassPred (ClassP clas tys) = True +isClassPred other = False + +isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys +isTyVarClassPred other = False + +getClassPredTys_maybe :: PredType -> Maybe (Class, [Type]) +getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys) +getClassPredTys_maybe _ = Nothing + +getClassPredTys :: PredType -> (Class, [Type]) +getClassPredTys (ClassP clas tys) = (clas, tys) + +mkDictTy :: Class -> [Type] -> Type +mkDictTy clas tys = mkPredTy (ClassP clas tys) + +isDictTy :: Type -> Bool +isDictTy (PredTy p) = isClassPred p +isDictTy (NoteTy _ ty) = isDictTy ty +isDictTy other = False +\end{code} + +--------------------- Implicit parameters --------------------------------- + +\begin{code} +isIPPred :: PredType -> Bool +isIPPred (IParam _ _) = True +isIPPred other = False + +isInheritablePred :: PredType -> Bool +-- Can be inherited by a context. For example, consider +-- f x = let g y = (?v, y+x) +-- in (g 3 with ?v = 8, +-- g 4 with ?v = 9) +-- The point is that g's type must be quantifed over ?v: +-- g :: (?v :: a) => a -> a +-- but it doesn't need to be quantified over the Num a dictionary +-- which can be free in g's rhs, and shared by both calls to g +isInheritablePred (ClassP _ _) = True +isInheritablePred other = False + +isLinearPred :: TcPredType -> Bool +isLinearPred (IParam (Linear n) _) = True +isLinearPred other = False +\end{code} + + +%************************************************************************ +%* * +\subsection{Comparison} +%* * +%************************************************************************ + +Comparison, taking note of newtypes, predicates, etc, + +\begin{code} +tcEqType :: Type -> Type -> Bool +tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False } + +tcEqTypes :: [Type] -> [Type] -> Bool +tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False } + +tcEqPred :: PredType -> PredType -> Bool +tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False } + +------------- +tcCmpType :: Type -> Type -> Ordering +tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2 + +tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2 + +tcCmpPred p1 p2 = cmpPredTy emptyVarEnv p1 p2 +------------- +cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2 + +------------- +cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering + -- The "env" maps type variables in ty1 to type variables in ty2 + -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2) + -- we in effect substitute tv2 for tv1 in t1 before continuing + + -- Look through NoteTy +cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2 +cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2 + + -- Deal with equal constructors +cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of + Just tv1a -> tv1a `compare` tv2 + Nothing -> tv1 `compare` tv2 + +cmpTy env (PredTy p1) (PredTy p2) = cmpPredTy env p1 p2 +cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2 +cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2 +cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2) +cmpTy env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2) +cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2 + + -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < NewTcApp < ForAllTy < PredTy +cmpTy env (AppTy _ _) (TyVarTy _) = GT + +cmpTy env (FunTy _ _) (TyVarTy _) = GT +cmpTy env (FunTy _ _) (AppTy _ _) = GT + +cmpTy env (TyConApp _ _) (TyVarTy _) = GT +cmpTy env (TyConApp _ _) (AppTy _ _) = GT +cmpTy env (TyConApp _ _) (FunTy _ _) = GT + +cmpTy env (NewTcApp _ _) (TyVarTy _) = GT +cmpTy env (NewTcApp _ _) (AppTy _ _) = GT +cmpTy env (NewTcApp _ _) (FunTy _ _) = GT +cmpTy env (NewTcApp _ _) (TyConApp _ _) = GT + +cmpTy env (ForAllTy _ _) (TyVarTy _) = GT +cmpTy env (ForAllTy _ _) (AppTy _ _) = GT +cmpTy env (ForAllTy _ _) (FunTy _ _) = GT +cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT +cmpTy env (ForAllTy _ _) (NewTcApp _ _) = GT + +cmpTy env (PredTy _) t2 = GT + +cmpTy env _ _ = LT +\end{code} + +\begin{code} +cmpPredTy :: TyVarEnv TyVar -> PredType -> PredType -> Ordering +cmpPredTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2) + -- Compare types as well as names for implicit parameters + -- This comparison is used exclusively (I think) for the + -- finite map built in TcSimplify +cmpPredTy env (IParam _ _) (ClassP _ _) = LT +cmpPredTy env (ClassP _ _) (IParam _ _) = GT +cmpPredTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2) \end{code} -Writing is easy: +PredTypes are used as a FM key in TcSimplify, +so we take the easy path and make them an instance of Ord + +\begin{code} +instance Eq PredType where { (==) = tcEqPred } +instance Ord PredType where { compare = tcCmpPred } +\end{code} + + +%************************************************************************ +%* * +\subsection{Predicates} +%* * +%************************************************************************ + +isSigmaTy returns true of any qualified type. It doesn't *necessarily* have +any foralls. E.g. + f :: (?x::Int) => Int -> Int \begin{code} -tcWriteTyVar (TyVar uniq kind name box) ty = tcWriteMutVar box (BoundTo ty) +isSigmaTy :: Type -> Bool +isSigmaTy (ForAllTy tyvar ty) = True +isSigmaTy (FunTy a b) = isPredTy a +isSigmaTy (NoteTy n ty) = isSigmaTy ty +isSigmaTy _ = False + +isOverloadedTy :: Type -> Bool +isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty +isOverloadedTy (FunTy a b) = isPredTy a +isOverloadedTy (NoteTy n ty) = isOverloadedTy ty +isOverloadedTy _ = False + +isPredTy :: Type -> Bool -- Belongs in TcType because it does + -- not look through newtypes, or predtypes (of course) +isPredTy (NoteTy _ ty) = isPredTy ty +isPredTy (PredTy sty) = True +isPredTy _ = False \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} +\begin{code} +isFloatTy = is_tc floatTyConKey +isDoubleTy = is_tc doubleTyConKey +isIntegerTy = is_tc integerTyConKey +isIntTy = is_tc intTyConKey +isAddrTy = is_tc addrTyConKey +isBoolTy = is_tc boolTyConKey +isUnitTy = is_tc unitTyConKey + +is_tc :: Unique -> Type -> Bool +-- Newtypes are opaque to this +is_tc uniq ty = case tcSplitTyConApp_maybe ty of + Just (tc, _) -> uniq == getUnique tc + Nothing -> False +\end{code} + + +%************************************************************************ +%* * +\subsection{Misc} +%* * +%************************************************************************ -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} +deNoteType :: Type -> Type + -- Remove synonyms, but not predicate types +deNoteType ty@(TyVarTy tyvar) = ty +deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys) +deNoteType (NewTcApp tycon tys) = NewTcApp tycon (map deNoteType tys) +deNoteType (PredTy p) = PredTy (deNotePredType p) +deNoteType (NoteTy _ ty) = deNoteType ty +deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg) +deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg) +deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty) + +deNotePredType :: PredType -> PredType +deNotePredType (ClassP c tys) = ClassP c (map deNoteType tys) +deNotePredType (IParam n ty) = IParam n (deNoteType ty) +\end{code} -We return Nothing iff the original box was unbound. +Find the free tycons and classes of a type. This is used in the front +end of the compiler. \begin{code} -tcReadTyVar (TyVar uniq kind name box) - = tcReadMutVar box `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - UnBound -> returnNF_Tc UnBound - BoundTo ty -> short_out ty `thenNF_Tc` \ ty' -> - tcWriteMutVar box (BoundTo ty') `thenNF_Tc_` - returnNF_Tc (BoundTo ty') - -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 - UnBound -> returnNF_Tc ty - BoundTo ty' -> short_out ty' `thenNF_Tc` \ ty' -> - tcWriteMutVar box (BoundTo ty') `thenNF_Tc_` - returnNF_Tc ty' - -short_out other_ty = returnNF_Tc other_ty +tyClsNamesOfType :: Type -> NameSet +tyClsNamesOfType (TyVarTy tv) = emptyNameSet +tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys +tyClsNamesOfType (NewTcApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys +tyClsNamesOfType (NoteTy (SynNote ty1) ty2) = tyClsNamesOfType ty1 +tyClsNamesOfType (NoteTy other_note ty2) = tyClsNamesOfType ty2 +tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty +tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys +tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res +tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg +tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty + +tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys + +tyClsNamesOfDFunHead :: Type -> NameSet +-- Find the free type constructors and classes +-- of the head of the dfun instance type +-- The 'dfun_head_type' is because of +-- instance Foo a => Baz T where ... +-- The decl is an orphan if Baz and T are both not locally defined, +-- even if Foo *is* locally defined +tyClsNamesOfDFunHead dfun_ty + = case tcSplitSigmaTy dfun_ty of + (tvs,_,head_ty) -> tyClsNamesOfType head_ty + +classesOfTheta :: ThetaType -> [Class] +-- Looks just for ClassP things; maybe it should check +classesOfTheta preds = [ c | ClassP c _ <- preds ] \end{code} -Zonking -~~~~~~~ -@zonkTcTypeToType@ converts from @TcType@ to @Type@. It follows through all -the substitutions of course. +%************************************************************************ +%* * +\subsection[TysWiredIn-ext-type]{External types} +%* * +%************************************************************************ + +The compiler's foreign function interface supports the passing of a +restricted set of types as arguments and results (the restricting factor +being the ) \begin{code} -zonkTcTypeToType :: TcType s -> NF_TcM s Type -zonkTcTypeToType ty = zonk tcTyVarToTyVar ty +isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool +-- Checks for valid argument type for a 'foreign import' +isFFIArgumentTy dflags safety ty + = checkRepTyCon (legalOutgoingTyCon dflags safety) ty + +isFFIExternalTy :: Type -> Bool +-- Types that are allowed as arguments of a 'foreign export' +isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty + +isFFIImportResultTy :: DynFlags -> Type -> Bool +isFFIImportResultTy dflags ty + = checkRepTyCon (legalFIResultTyCon dflags) ty + +isFFIExportResultTy :: Type -> Bool +isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty + +isFFIDynArgumentTy :: Type -> Bool +-- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr, +-- or a newtype of either. +isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey] + +isFFIDynResultTy :: Type -> Bool +-- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr, +-- or a newtype of either. +isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey] + +isFFILabelTy :: Type -> Bool +-- The type of a foreign label must be Ptr, FunPtr, Addr, +-- or a newtype of either. +isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey] + +isFFIDotnetTy :: DynFlags -> Type -> Bool +isFFIDotnetTy dflags ty + = checkRepTyCon (\ tc -> not (isByteArrayLikeTyCon tc) && + (legalFIResultTyCon dflags tc || + isFFIDotnetObjTy ty || isStringTy ty)) ty + +-- Support String as an argument or result from a .NET FFI call. +isStringTy ty = + case tcSplitTyConApp_maybe (repType ty) of + Just (tc, [arg_ty]) + | tc == listTyCon -> + case tcSplitTyConApp_maybe (repType arg_ty) of + Just (cc,[]) -> cc == charTyCon + _ -> False + _ -> False + +-- Support String as an argument or result from a .NET FFI call. +isFFIDotnetObjTy ty = + let + (_, t_ty) = tcSplitForAllTys ty + in + case tcSplitTyConApp_maybe (repType t_ty) of + Just (tc, [arg_ty]) | getName tc == objectTyConName -> True + _ -> False + +toDNType :: Type -> DNType +toDNType ty + | isStringTy ty = DNString + | isFFIDotnetObjTy ty = DNObject + | Just (tc,argTys) <- tcSplitTyConApp_maybe ty = + case lookup (getUnique tc) dn_assoc of + Just x -> x + Nothing + | tc `hasKey` ioTyConKey -> toDNType (head argTys) + | otherwise -> pprPanic ("toDNType: unsupported .NET type") (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc) + where + dn_assoc :: [ (Unique, DNType) ] + dn_assoc = [ (unitTyConKey, DNUnit) + , (intTyConKey, DNInt) + , (int8TyConKey, DNInt8) + , (int16TyConKey, DNInt16) + , (int32TyConKey, DNInt32) + , (int64TyConKey, DNInt64) + , (wordTyConKey, DNInt) + , (word8TyConKey, DNWord8) + , (word16TyConKey, DNWord16) + , (word32TyConKey, DNWord32) + , (word64TyConKey, DNWord64) + , (floatTyConKey, DNFloat) + , (doubleTyConKey, DNDouble) + , (addrTyConKey, DNPtr) + , (ptrTyConKey, DNPtr) + , (funPtrTyConKey, DNPtr) + , (charTyConKey, DNChar) + , (boolTyConKey, DNBool) + ] + +checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool + -- Look through newtypes + -- Non-recursive ones are transparent to splitTyConApp, + -- but recursive ones aren't +checkRepTyCon check_tc ty + | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc + | otherwise = False + +checkRepTyConKey :: [Unique] -> Type -> Bool +-- Like checkRepTyCon, but just looks at the TyCon key +checkRepTyConKey keys + = checkRepTyCon (\tc -> tyConUnique tc `elem` keys) +\end{code} -zonkTcType :: TcType s -> NF_TcM s (TcType s) -zonkTcType ty = zonk (\tyvar -> tyvar) ty +---------------------------------------------- +These chaps do the work; they are not exported +---------------------------------------------- -zonkTcTyVars :: TcTyVarSet s -> NF_TcM s (TcTyVarSet s) -zonkTcTyVars tyvars - = mapNF_Tc (zonk_tv (\tyvar -> tyvar)) - (tyVarSetToList tyvars) `thenNF_Tc` \ tys -> - returnNF_Tc (tyVarsOfTypes tys) +\begin{code} +legalFEArgTyCon :: TyCon -> Bool +-- It's illegal to return foreign objects and (mutable) +-- bytearrays from a _ccall_ / foreign declaration +-- (or be passed them as arguments in foreign exported functions). +legalFEArgTyCon tc + | isByteArrayLikeTyCon tc + = False + -- It's also illegal to make foreign exports that take unboxed + -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000 + | otherwise + = boxedMarshalableTyCon tc + +legalFIResultTyCon :: DynFlags -> TyCon -> Bool +legalFIResultTyCon dflags tc + | isByteArrayLikeTyCon tc = False + | tc == unitTyCon = True + | otherwise = marshalableTyCon dflags tc + +legalFEResultTyCon :: TyCon -> Bool +legalFEResultTyCon tc + | isByteArrayLikeTyCon tc = False + | tc == unitTyCon = True + | otherwise = boxedMarshalableTyCon tc + +legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool +-- Checks validity of types going from Haskell -> external world +legalOutgoingTyCon dflags safety tc + | playSafe safety && isByteArrayLikeTyCon tc + = False + | otherwise + = marshalableTyCon dflags tc + +marshalableTyCon dflags tc + = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc) + || boxedMarshalableTyCon tc + +boxedMarshalableTyCon tc + = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey + , int32TyConKey, int64TyConKey + , wordTyConKey, word8TyConKey, word16TyConKey + , word32TyConKey, word64TyConKey + , floatTyConKey, doubleTyConKey + , addrTyConKey, ptrTyConKey, funPtrTyConKey + , charTyConKey + , stablePtrTyConKey + , byteArrayTyConKey, mutableByteArrayTyConKey + , boolTyConKey + ] + +isByteArrayLikeTyCon :: TyCon -> Bool +isByteArrayLikeTyCon tc = + getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey] +\end{code} -zonkTcTyVarToTyVar :: TcTyVar s -> NF_TcM s TyVar -zonkTcTyVarToTyVar tyvar - = zonk_tv_to_tv tcTyVarToTyVar tyvar +%************************************************************************ +%* * +\subsection{Unification with an explicit substitution} +%* * +%************************************************************************ -zonk tyvar_fn (TyVarTy tyvar) - = zonk_tv tyvar_fn tyvar +Unify types with an explicit substitution and no monad. +Ignore usage annotations. -zonk tyvar_fn (AppTy ty1 ty2) - = zonk tyvar_fn ty1 `thenNF_Tc` \ ty1' -> - zonk tyvar_fn ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (AppTy ty1' ty2') +\begin{code} +type MySubst + = (TyVarSet, -- Set of template tyvars + TyVarSubstEnv) -- Not necessarily idempotent + +unifyTysX :: TyVarSet -- Template tyvars + -> Type + -> Type + -> Maybe TyVarSubstEnv +unifyTysX tmpl_tyvars ty1 ty2 + = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv) + +unifyExtendTysX :: TyVarSet -- Template tyvars + -> TyVarSubstEnv -- Substitution to start with + -> Type + -> Type + -> Maybe TyVarSubstEnv -- Extended substitution +unifyExtendTysX tmpl_tyvars subst ty1 ty2 + = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst) + +unifyTyListsX :: TyVarSet -> [Type] -> [Type] + -> Maybe TyVarSubstEnv +unifyTyListsX tmpl_tyvars tys1 tys2 + = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv) + + +uTysX :: Type + -> Type + -> (MySubst -> Maybe result) + -> MySubst + -> Maybe result + +uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst +uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst + + -- Variables; go for uVar +uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst + | tyvar1 == tyvar2 + = k subst +uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_) + | tyvar1 `elemVarSet` tmpls + = uVarX tyvar1 ty2 k subst +uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_) + | tyvar2 `elemVarSet` tmpls + = uVarX tyvar2 ty1 k subst + + -- Predicates +uTysX (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) k subst + | n1 == n2 = uTysX t1 t2 k subst +uTysX (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) k subst + | c1 == c2 = uTyListsX tys1 tys2 k subst + + -- Functions; just check the two parts +uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst + = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst + + -- Type constructors must match +uTysX (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) k subst + | tc1 == tc2 = uTyListsX tys1 tys2 k subst +uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst + | (con1 == con2 && equalLength tys1 tys2) + = uTyListsX tys1 tys2 k subst + + -- Applications need a bit of care! + -- They can match FunTy and TyConApp, so use splitAppTy_maybe + -- NB: we've already dealt with type variables and Notes, + -- so if one type is an App the other one jolly well better be too +uTysX (AppTy s1 t1) ty2 k subst + = case tcSplitAppTy_maybe ty2 of + Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst + Nothing -> Nothing -- Fail + +uTysX ty1 (AppTy s2 t2) k subst + = case tcSplitAppTy_maybe ty1 of + Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst + Nothing -> Nothing -- Fail + + -- Not expecting for-alls in unification +#ifdef DEBUG +uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)" +uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)" +#endif + + -- Anything else fails +uTysX ty1 ty2 k subst = Nothing + + +uTyListsX [] [] k subst = k subst +uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst +uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths +\end{code} -zonk tyvar_fn (TyConTy tc u) - = returnNF_Tc (TyConTy tc u) +\begin{code} +-- Invariant: tv1 is a unifiable variable +uVarX tv1 ty2 k subst@(tmpls, env) + = case lookupSubstEnv env tv1 of + Just (DoneTy ty1) -> -- Already bound + uTysX ty1 ty2 k subst + + Nothing -- Not already bound + | typeKind ty2 == tyVarKind tv1 + && occur_check_ok ty2 + -> -- No kind mismatch nor occur check + k (tmpls, extendSubstEnv env tv1 (DoneTy ty2)) + + | otherwise -> Nothing -- Fail if kind mis-match or occur check + where + occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty)) + occur_check_ok_tv tv | tv1 == tv = False + | otherwise = case lookupSubstEnv env tv of + Nothing -> True + Just (DoneTy ty) -> occur_check_ok ty +\end{code} -zonk tyvar_fn (SynTy tc tys ty) - = mapNF_Tc (zonk tyvar_fn) tys `thenNF_Tc` \ tys' -> - zonk tyvar_fn ty `thenNF_Tc` \ ty' -> - returnNF_Tc (SynTy tc tys' ty') -zonk tyvar_fn (ForAllTy tv ty) - = zonk_tv_to_tv tyvar_fn tv `thenNF_Tc` \ tv' -> - zonk tyvar_fn ty `thenNF_Tc` \ ty' -> - returnNF_Tc (ForAllTy tv' ty') -zonk tyvar_fn (ForAllUsageTy uv uvs ty) - = panic "zonk:ForAllUsageTy" +%************************************************************************ +%* * +\subsection{Matching on types} +%* * +%************************************************************************ -zonk tyvar_fn (FunTy ty1 ty2 u) - = zonk tyvar_fn ty1 `thenNF_Tc` \ ty1' -> - zonk tyvar_fn ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (FunTy ty1' ty2' u) +Matching is a {\em unidirectional} process, matching a type against a +template (which is just a type with type variables in it). The +matcher assumes that there are no repeated type variables in the +template, so that it simply returns a mapping of type variables to +types. It also fails on nested foralls. -zonk tyvar_fn (DictTy c ty u) - = zonk tyvar_fn ty `thenNF_Tc` \ ty' -> - returnNF_Tc (DictTy c ty' u) +@matchTys@ matches corresponding elements of a list of templates and +types. It and @matchTy@ both ignore usage annotations, unlike the +main function @match@. +\begin{code} +matchTy :: TyVarSet -- Template tyvars + -> Type -- Template + -> Type -- Proposed instance of template + -> Maybe TyVarSubstEnv -- Matching substitution + + +matchTys :: TyVarSet -- Template tyvars + -> [Type] -- Templates + -> [Type] -- Proposed instance of template + -> Maybe (TyVarSubstEnv, -- Matching substitution + [Type]) -- Left over instance types + +matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv + +matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls + (\ (senv,tys) -> Just (senv,tys)) + emptySubstEnv +\end{code} -zonk_tv tyvar_fn tyvar - = tcReadTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - UnBound -> returnNF_Tc (TyVarTy (tyvar_fn tyvar)) - BoundTo ty -> zonk tyvar_fn ty +@match@ is the main function. It takes a flag indicating whether +usage annotations are to be respected. +\begin{code} +match :: Type -> Type -- Current match pair + -> TyVarSet -- Template vars + -> (TyVarSubstEnv -> Maybe result) -- Continuation + -> TyVarSubstEnv -- Current subst + -> Maybe result + +-- When matching against a type variable, see if the variable +-- has already been bound. If so, check that what it's bound to +-- is the same as ty; if not, bind it and carry on. + +match (TyVarTy v) ty tmpls k senv + | v `elemVarSet` tmpls + = -- v is a template variable + case lookupSubstEnv senv v of + Nothing | typeKind ty == tyVarKind v + -- We do a kind check, just as in the uVarX above + -- The kind check is needed to avoid bogus matches + -- of (a b) with (c d), where the kinds don't match + -- An occur check isn't needed when matching. + -> k (extendSubstEnv senv v (DoneTy ty)) + + | otherwise -> Nothing -- Fails + + Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds + | otherwise -> Nothing -- Fails + + | otherwise + = -- v is not a template variable; ty had better match + -- Can't use (==) because types differ + case tcGetTyVar_maybe ty of + Just v' | v == v' -> k senv -- Success + other -> Nothing -- Failure + -- This tcGetTyVar_maybe is *required* because it must strip Notes. + -- I guess the reason the Note-stripping case is *last* rather than first + -- is to preserve type synonyms etc., so I'm not moving it to the + -- top; but this means that (without the deNotetype) a type + -- variable may not match the pattern (TyVarTy v') as one would + -- expect, due to an intervening Note. KSW 2000-06. + + -- Predicates +match (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) tmpls k senv + | n1 == n2 = match t1 t2 tmpls k senv +match (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) tmpls k senv + | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv + + -- Functions; just check the two parts +match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv + = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv + +match (AppTy fun1 arg1) ty2 tmpls k senv + = case tcSplitAppTy_maybe ty2 of + Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv + Nothing -> Nothing -- Fail + +-- Newtypes are opaque; predicate types should not happen +match (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) tmpls k senv + | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv +match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv + | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv + + -- With type synonyms, we have to be careful for the exact + -- same reasons as in the unifier. Please see the + -- considerable commentary there before changing anything + -- here! (WDP 95/05) +match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv +match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv + +-- Catch-all fails +match _ _ _ _ _ = Nothing + +match_list_exactly tys1 tys2 tmpls k senv + = match_list tys1 tys2 tmpls k' senv + where + k' (senv', tys2') | null tys2' = k senv' -- Succeed + | otherwise = Nothing -- Fail -zonk_tv_to_tv tyvar_fn tyvar - = zonk_tv tyvar_fn tyvar `thenNF_Tc` \ ty -> - case getTyVar_maybe ty of - Nothing -> panic "zonk_tv_to_tv" - Just tyvar -> returnNF_Tc tyvar +match_list [] tys2 tmpls k senv = k (senv, tys2) +match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure +match_list (ty1:tys1) (ty2:tys2) tmpls k senv + = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv \end{code}