X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMonoType.lhs;h=ef3c6709f2c40f308318c620f04b09ad7e92445b;hb=fd3ceb3c17dcb13f1ab1ca05fb026d9954d5b06c;hp=dad3e7baf3db882858bc65e2507e11e13c1e041c;hpb=9dd6e1c216993624a2cd74b62ca0f0569c02c26b;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMonoType.lhs b/ghc/compiler/typecheck/TcMonoType.lhs index dad3e7b..ef3c670 100644 --- a/ghc/compiler/typecheck/TcMonoType.lhs +++ b/ghc/compiler/typecheck/TcMonoType.lhs @@ -1,163 +1,217 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcMonoType]{Typechecking user-specified @MonoTypes@} \begin{code} -module TcMonoType ( tcHsType, tcHsTypeKind, tcContext, tcTyVarScope ) where +module TcMonoType ( tcHsType, tcHsTypeKind, tcHsTopType, tcHsTopBoxedType, + tcContext, tcHsTyVar, kcHsTyVar, + tcExtendTyVarScope, tcExtendTopTyVarScope, + TcSigInfo(..), tcTySig, mkTcSig, noSigs, maybeSig, + checkSigTyVars, sigCtxt, sigPatCtxt + ) where #include "HsVersions.h" -import HsSyn ( HsType(..), HsTyVar(..), pprContext ) -import RnHsSyn ( RenamedHsType(..), RenamedContext(..) ) +import HsSyn ( HsType(..), HsTyVar(..), Sig(..), pprClassAssertion, pprParendHsType ) +import RnHsSyn ( RenamedHsType, RenamedContext, RenamedSig ) +import TcHsSyn ( TcId ) import TcMonad -import TcEnv ( tcLookupTyVar, tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv ) -import TcKind ( TcKind, mkBoxedTypeKind, mkTypeKind, mkArrowKind, - unifyKind, unifyKinds, newKindVar, - kindToTcKind, tcDefaultKind +import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars, + tcGetGlobalTyVars, TcTyThing(..) ) +import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType, + typeToTcType, tcInstTcType, kindToTcKind, + newKindVar, + zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType + ) +import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr ) +import TcUnify ( unifyKind, unifyKinds, unifyTypeKind ) import Type ( Type, ThetaType, - mkTyVarTy, mkFunTy, mkAppTy, mkSynTy, - mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys + mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, zipFunTys, + mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys, splitRhoTy, + boxedTypeKind, unboxedTypeKind, tyVarsOfType, + mkArrowKinds, getTyVar_maybe, getTyVar, + tidyOpenType, tidyOpenTypes, tidyTyVar ) -import TyVar ( TyVar, mkTyVar ) +import Id ( mkUserId, idName, idType, idFreeTyVars ) +import Var ( TyVar, mkTyVar ) +import VarEnv +import VarSet +import Bag ( bagToList ) +import ErrUtils ( Message ) import PrelInfo ( cCallishClassKeys ) import TyCon ( TyCon ) -import Name ( Name, OccName, isTvOcc, getOccName ) -import TysWiredIn ( mkListTy, mkTupleTy ) +import Name ( Name, OccName, isLocallyDefined ) +import TysWiredIn ( mkListTy, mkTupleTy, mkUnboxedTupleTy ) +import SrcLoc ( SrcLoc ) import Unique ( Unique, Uniquable(..) ) -import Util ( zipWithEqual, zipLazy ) +import UniqFM ( eltsUFM ) +import Util ( zipWithEqual, zipLazy, mapAccumL ) import Outputable \end{code} +%************************************************************************ +%* * +\subsection{Checking types} +%* * +%************************************************************************ + tcHsType and tcHsTypeKind ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ tcHsType checks that the type really is of kind Type! \begin{code} -tcHsType :: RenamedHsType -> TcM s Type - +tcHsType :: RenamedHsType -> TcM s TcType tcHsType ty - = tcAddErrCtxt (typeCtxt ty) $ - tc_hs_type ty - -tc_hs_type ty - = tc_hs_type_kind ty `thenTc` \ (kind,ty) -> - -- Check that it really is a type - unifyKind mkTypeKind kind `thenTc_` - returnTc ty + = -- tcAddErrCtxt (typeCtxt ty) $ + tc_type ty + +tcHsTypeKind :: RenamedHsType -> TcM s (TcKind, TcType) +tcHsTypeKind ty + = -- tcAddErrCtxt (typeCtxt ty) $ + tc_type_kind ty + +-- Type-check a type, *and* then lazily zonk it. The important +-- point is that this zonks all the uncommitted *kind* variables +-- in kinds of any any nested for-all tyvars. +-- There won't be any mutable *type* variables at all. +-- +-- NOTE the forkNF_Tc. This makes the zonking lazy, which is +-- absolutely necessary. During the type-checking of a recursive +-- group of tycons/classes (TcTyClsDecls.tcGroup) we use an +-- environment in which we aren't allowed to look at the actual +-- tycons/classes returned from a lookup. Because tc_app does +-- look at the tycon to build the type, we can't look at the type +-- either, until we get out of the loop. The fork delays the +-- zonking till we've completed the loop. Sigh. + +tcHsTopType :: RenamedHsType -> TcM s Type +tcHsTopType ty + = -- tcAddErrCtxt (typeCtxt ty) $ + tc_type ty `thenTc` \ ty' -> + forkNF_Tc (zonkTcTypeToType ty') + +tcHsTopBoxedType :: RenamedHsType -> TcM s Type +tcHsTopBoxedType ty + = -- tcAddErrCtxt (typeCtxt ty) $ + tc_boxed_type ty `thenTc` \ ty' -> + forkNF_Tc (zonkTcTypeToType ty') \end{code} -tcHsTypeKind does the real work. It returns a kind and a type. - -\begin{code} -tcHsTypeKind :: RenamedHsType -> TcM s (TcKind s, Type) - -tcHsTypeKind ty - = tcAddErrCtxt (typeCtxt ty) $ - tc_hs_type_kind ty +The main work horse +~~~~~~~~~~~~~~~~~~~ - -- This equation isn't needed (the next one would handle it fine) - -- but it's rather a common case, so we handle it directly -tc_hs_type_kind (MonoTyVar name) - | isTvOcc (getOccName name) - = tcLookupTyVar name `thenNF_Tc` \ (kind,tyvar) -> - returnTc (kind, mkTyVarTy tyvar) - -tc_hs_type_kind ty@(MonoTyVar name) - = tcFunType ty [] +\begin{code} +tc_boxed_type :: RenamedHsType -> TcM s Type +tc_boxed_type ty + = tc_type_kind ty `thenTc` \ (actual_kind, tc_ty) -> + tcAddErrCtxt (typeKindCtxt ty) + (unifyKind boxedTypeKind actual_kind) `thenTc_` + returnTc tc_ty + +tc_type :: RenamedHsType -> TcM s Type +tc_type ty + -- The type ty must be a *type*, but it can be boxed + -- or unboxed. So we check that is is of form (Type bv) + -- using unifyTypeKind + = tc_type_kind ty `thenTc` \ (actual_kind, tc_ty) -> + tcAddErrCtxt (typeKindCtxt ty) + (unifyTypeKind actual_kind) `thenTc_` + returnTc tc_ty + +tc_type_kind :: RenamedHsType -> TcM s (TcKind, Type) +tc_type_kind ty@(MonoTyVar name) + = tc_app ty [] -tc_hs_type_kind (MonoListTy _ ty) - = tc_hs_type ty `thenTc` \ tau_ty -> - returnTc (mkBoxedTypeKind, mkListTy tau_ty) - -tc_hs_type_kind (MonoTupleTy _ tys) - = mapTc tc_hs_type tys `thenTc` \ tau_tys -> - returnTc (mkBoxedTypeKind, mkTupleTy (length tys) tau_tys) - -tc_hs_type_kind (MonoFunTy ty1 ty2) - = tc_hs_type ty1 `thenTc` \ tau_ty1 -> - tc_hs_type ty2 `thenTc` \ tau_ty2 -> - returnTc (mkBoxedTypeKind, mkFunTy tau_ty1 tau_ty2) - -tc_hs_type_kind (MonoTyApp ty1 ty2) - = tcTyApp ty1 [ty2] - -tc_hs_type_kind (HsForAllTy tv_names context ty) - = tcTyVarScope tv_names $ \ tyvars -> - tcContext context `thenTc` \ theta -> - tc_hs_type ty `thenTc` \ tau -> - -- For-all's are of kind type! - returnTc (mkBoxedTypeKind, mkSigmaTy tyvars theta tau) - --- for unfoldings, and instance decls, only: -tc_hs_type_kind (MonoDictTy class_name tys) - = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) -> - tcLookupClass class_name `thenTc` \ (class_kinds, clas) -> - let - arity = length class_kinds - n_args = length arg_kinds - err = arityErr "Class" class_name arity n_args - in - checkTc (arity == n_args) err `thenTc_` - unifyKinds class_kinds arg_kinds `thenTc_` - returnTc (mkBoxedTypeKind, mkDictTy clas arg_tys) +tc_type_kind (MonoListTy ty) + = tc_boxed_type ty `thenTc` \ tau_ty -> + returnTc (boxedTypeKind, mkListTy tau_ty) + +tc_type_kind (MonoTupleTy tys True {-boxed-}) + = mapTc tc_boxed_type tys `thenTc` \ tau_tys -> + returnTc (boxedTypeKind, mkTupleTy (length tys) tau_tys) + +tc_type_kind (MonoTupleTy tys False {-unboxed-}) + = mapTc tc_type tys `thenTc` \ tau_tys -> + returnTc (unboxedTypeKind, mkUnboxedTupleTy (length tys) tau_tys) + +tc_type_kind (MonoFunTy ty1 ty2) + = tc_type ty1 `thenTc` \ tau_ty1 -> + tc_type ty2 `thenTc` \ tau_ty2 -> + returnTc (boxedTypeKind, mkFunTy tau_ty1 tau_ty2) + +tc_type_kind (MonoTyApp ty1 ty2) + = tc_app ty1 [ty2] + +tc_type_kind (MonoDictTy class_name tys) + = tcClassAssertion (class_name, tys) `thenTc` \ (clas, arg_tys) -> + returnTc (boxedTypeKind, mkDictTy clas arg_tys) + +tc_type_kind (HsForAllTy tv_names context ty) + = tcExtendTyVarScope tv_names $ \ tyvars -> + tcContext context `thenTc` \ theta -> + tc_boxed_type ty `thenTc` \ tau -> + -- Body of a for-all is a boxed type! + returnTc (boxedTypeKind, mkSigmaTy tyvars theta tau) \end{code} Help functions for type applications ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + \begin{code} -tcTyApp (MonoTyApp ty1 ty2) tys - = tcTyApp ty1 (ty2:tys) +tc_app (MonoTyApp ty1 ty2) tys + = tc_app ty1 (ty2:tys) -tcTyApp ty tys +tc_app ty tys | null tys - = tcFunType ty [] + = tc_fun_type ty [] | otherwise - = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) -> - tcFunType ty arg_tys `thenTc` \ (fun_kind, result_ty) -> + = tcAddErrCtxt (appKindCtxt pp_app) $ + mapAndUnzipTc tc_type_kind tys `thenTc` \ (arg_kinds, arg_tys) -> + tc_fun_type ty arg_tys `thenTc` \ (fun_kind, result_ty) -> -- Check argument compatibility - newKindVar `thenNF_Tc` \ result_kind -> - unifyKind fun_kind (foldr mkArrowKind result_kind arg_kinds) + newKindVar `thenNF_Tc` \ result_kind -> + unifyKind fun_kind (mkArrowKinds arg_kinds result_kind) `thenTc_` returnTc (result_kind, result_ty) + where + pp_app = ppr ty <+> sep (map pprParendHsType tys) --- (tcFunType ty arg_tys) returns (kind-of ty, mkAppTys ty arg_tys) +-- (tc_fun_type ty arg_tys) returns (kind-of ty, mkAppTys ty arg_tys) -- But not quite; for synonyms it checks the correct arity, and builds a SynTy -- hence the rather strange functionality. -tcFunType (MonoTyVar name) arg_tys - | isTvOcc (getOccName name) -- Must be a type variable - = tcLookupTyVar name `thenNF_Tc` \ (kind,tyvar) -> - returnTc (kind, mkAppTys (mkTyVarTy tyvar) arg_tys) - - | otherwise -- Must be a type constructor - = tcLookupTyCon name `thenTc` \ (tycon_kind,maybe_arity, tycon) -> - case maybe_arity of - Nothing -> -- Data type or newtype - returnTc (tycon_kind, mkTyConApp tycon arg_tys) - - Just arity -> -- Type synonym - checkTc (arity <= n_args) err_msg `thenTc_` - returnTc (tycon_kind, result_ty) - where - -- It's OK to have an *over-applied* type synonym - -- data Tree a b = ... - -- type Foo a = Tree [a] - -- f :: Foo a b -> ... - result_ty = mkAppTys (mkSynTy tycon (take arity arg_tys)) - (drop arity arg_tys) - err_msg = arityErr "Type synonym constructor" name arity n_args - n_args = length arg_tys - -tcFunType ty arg_tys - = tc_hs_type_kind ty `thenTc` \ (fun_kind, fun_ty) -> +tc_fun_type (MonoTyVar name) arg_tys + = tcLookupTy name `thenTc` \ (tycon_kind, maybe_arity, thing) -> + case thing of + ATyVar tv -> returnTc (tycon_kind, mkAppTys (mkTyVarTy tv) arg_tys) + AClass clas -> failWithTc (classAsTyConErr name) + ATyCon tc -> case maybe_arity of + Nothing -> -- Data or newtype + returnTc (tycon_kind, mkTyConApp tc arg_tys) + + Just arity -> -- Type synonym + checkTc (arity <= n_args) err_msg `thenTc_` + returnTc (tycon_kind, result_ty) + where + -- It's OK to have an *over-applied* type synonym + -- data Tree a b = ... + -- type Foo a = Tree [a] + -- f :: Foo a b -> ... + result_ty = mkAppTys (mkSynTy tc (take arity arg_tys)) + (drop arity arg_tys) + err_msg = arityErr "type synonym" name arity n_args + n_args = length arg_tys + +tc_fun_type ty arg_tys + = tc_type_kind ty `thenTc` \ (fun_kind, fun_ty) -> returnTc (fun_kind, mkAppTys fun_ty arg_tys) \end{code} @@ -167,77 +221,408 @@ Contexts \begin{code} tcContext :: RenamedContext -> TcM s ThetaType -tcContext context = tcAddErrCtxt (thetaCtxt context) $ - mapTc tcClassAssertion context +tcContext context + = --Someone discovered that @CCallable@ and @CReturnable@ + -- could be used in contexts such as: + -- foo :: CCallable a => a -> PrimIO Int + -- Doing this utterly wrecks the whole point of introducing these + -- classes so we specifically check that this isn't being done. + -- + -- We *don't* do this check in tcClassAssertion, because that's + -- called when checking a HsDictTy, and we don't want to reject + -- instance CCallable Int + -- etc. Ugh! + mapTc check_naughty context `thenTc_` + + mapTc tcClassAssertion context + + where + check_naughty (class_name, _) + = checkTc (not (getUnique class_name `elem` cCallishClassKeys)) + (naughtyCCallContextErr class_name) + +tcClassAssertion assn@(class_name, tys) + = tcAddErrCtxt (appKindCtxt (pprClassAssertion assn)) $ + mapAndUnzipTc tc_type_kind tys `thenTc` \ (arg_kinds, arg_tys) -> + tcLookupTy class_name `thenTc` \ (kind, ~(Just arity), thing) -> + case thing of + ATyVar _ -> failWithTc (tyVarAsClassErr class_name) + ATyCon _ -> failWithTc (tyConAsClassErr class_name) + AClass clas -> + -- Check with kind mis-match + checkTc (arity == n_tys) err `thenTc_` + unifyKind kind (mkArrowKinds arg_kinds boxedTypeKind) `thenTc_` + returnTc (clas, arg_tys) + where + n_tys = length tys + err = arityErr "Class" class_name arity n_tys +\end{code} -tcClassAssertion (class_name, tys) - = checkTc (canBeUsedInContext class_name) - (naughtyCCallContextErr class_name) `thenTc_` - tcLookupClass class_name `thenTc` \ (class_kinds, clas) -> - mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (ty_kinds, tc_tys) -> +%************************************************************************ +%* * +\subsection{Type variables, with knot tying!} +%* * +%************************************************************************ + +\begin{code} +tcExtendTopTyVarScope :: TcKind -> [HsTyVar Name] + -> ([TcTyVar] -> TcKind -> TcM s a) + -> TcM s a +tcExtendTopTyVarScope kind tyvar_names thing_inside + = let + (tyvars_w_kinds, result_kind) = zipFunTys tyvar_names kind + tyvars = map mk_tv tyvars_w_kinds + in + tcExtendTyVarEnv tyvars (thing_inside tyvars result_kind) + where + mk_tv (UserTyVar name, kind) = mkTyVar name kind + mk_tv (IfaceTyVar name _, kind) = mkTyVar name kind + -- NB: immutable tyvars, but perhaps with mutable kinds + +tcExtendTyVarScope :: [HsTyVar Name] + -> ([TcTyVar] -> TcM s a) -> TcM s a +tcExtendTyVarScope tv_names thing_inside + = mapNF_Tc tcHsTyVar tv_names `thenNF_Tc` \ tyvars -> + tcExtendTyVarEnv tyvars $ + thing_inside tyvars + +tcHsTyVar :: HsTyVar Name -> NF_TcM s TcTyVar +tcHsTyVar (UserTyVar name) = newKindVar `thenNF_Tc` \ kind -> + tcNewMutTyVar name kind + -- NB: mutable kind => mutable tyvar, so that zonking can bind + -- the tyvar to its immutable form - unifyKinds class_kinds ty_kinds `thenTc_` +tcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (mkTyVar name (kindToTcKind kind)) - returnTc (clas, tc_tys) +kcHsTyVar :: HsTyVar name -> NF_TcM s TcKind +kcHsTyVar (UserTyVar name) = newKindVar +kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (kindToTcKind kind) \end{code} -HACK warning: Someone discovered that @CCallable@ and @CReturnable@ -could be used in contexts such as: -\begin{verbatim} -foo :: CCallable a => a -> PrimIO Int -\end{verbatim} -Doing this utterly wrecks the whole point of introducing these -classes so we specifically check that this isn't being done. +%************************************************************************ +%* * +\subsection{Signatures} +%* * +%************************************************************************ + +@tcSigs@ checks the signatures for validity, and returns a list of +{\em freshly-instantiated} signatures. That is, the types are already +split up, and have fresh type variables installed. All non-type-signature +"RenamedSigs" are ignored. + +The @TcSigInfo@ contains @TcTypes@ because they are unified with +the variable's type, and after that checked to see whether they've +been instantiated. + +\begin{code} +data TcSigInfo + = TySigInfo + Name -- N, the Name in corresponding binding + + TcId -- *Polymorphic* binder for this value... + -- Has name = N + + [TcTyVar] -- tyvars + TcThetaType -- theta + TcTauType -- tau + + TcId -- *Monomorphic* binder for this value + -- Does *not* have name = N + -- Has type tau + + Inst -- Empty if theta is null, or + -- (method mono_id) otherwise + + SrcLoc -- Of the signature + + +maybeSig :: [TcSigInfo] -> Name -> Maybe (TcSigInfo) + -- Search for a particular signature +maybeSig [] name = Nothing +maybeSig (sig@(TySigInfo sig_name _ _ _ _ _ _ _) : sigs) name + | name == sig_name = Just sig + | otherwise = maybeSig sigs name + +-- This little helper is useful to pass to tcPat +noSigs :: Name -> Maybe TcId +noSigs name = Nothing +\end{code} + \begin{code} -canBeUsedInContext :: Name -> Bool -canBeUsedInContext n = not (uniqueOf n `elem` cCallishClassKeys) +tcTySig :: RenamedSig -> TcM s TcSigInfo + +tcTySig (Sig v ty src_loc) + = tcAddSrcLoc src_loc $ + tcHsType ty `thenTc` \ sigma_tc_ty -> + mkTcSig (mkUserId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig -> + returnTc sig + +mkTcSig :: TcId -> SrcLoc -> NF_TcM s TcSigInfo +mkTcSig poly_id src_loc + = -- Instantiate this type + -- It's important to do this even though in the error-free case + -- we could just split the sigma_tc_ty (since the tyvars don't + -- unified with anything). But in the case of an error, when + -- the tyvars *do* get unified with something, we want to carry on + -- typechecking the rest of the program with the function bound + -- to a pristine type, namely sigma_tc_ty + tcInstTcType (idType poly_id) `thenNF_Tc` \ (tyvars, rho) -> + let + (theta, tau) = splitRhoTy rho + -- This splitSigmaTy tries hard to make sure that tau' is a type synonym + -- wherever possible, which can improve interface files. + in + newMethodWithGivenTy SignatureOrigin + poly_id + (mkTyVarTys tyvars) + theta tau `thenNF_Tc` \ inst -> + -- We make a Method even if it's not overloaded; no harm + + returnNF_Tc (TySigInfo name poly_id tyvars theta tau (instToIdBndr inst) inst src_loc) + where + name = idName poly_id \end{code} -Type variables, with knot tying! -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + +%************************************************************************ +%* * +\subsection{Checking signature type variables} +%* * +%************************************************************************ + +@checkSigTyVars@ is used after the type in a type signature has been unified with +the actual type found. It then checks that the type variables of the type signature +are + (a) Still all type variables + eg matching signature [a] against inferred type [(p,q)] + [then a will be unified to a non-type variable] + + (b) Still all distinct + eg matching signature [(a,b)] against inferred type [(p,p)] + [then a and b will be unified together] + + (c) Not mentioned in the environment + eg the signature for f in this: + + g x = ... where + f :: a->[a] + f y = [x,y] + + Here, f is forced to be monorphic by the free occurence of x. + + (d) Not (unified with another type variable that is) in scope. + eg f x :: (r->r) = (\y->y) :: forall a. a->r + when checking the expression type signature, we find that + even though there is nothing in scope whose type mentions r, + nevertheless the type signature for the expression isn't right. + + Another example is in a class or instance declaration: + class C a where + op :: forall b. a -> b + op x = x + Here, b gets unified with a + +Before doing this, the substitution is applied to the signature type variable. + +We used to have the notion of a "DontBind" type variable, which would +only be bound to itself or nothing. Then points (a) and (b) were +self-checking. But it gave rise to bogus consequential error messages. +For example: + + f = (*) -- Monomorphic + + g :: Num a => a -> a + g x = f x x + +Here, we get a complaint when checking the type signature for g, +that g isn't polymorphic enough; but then we get another one when +dealing with the (Num x) context arising from f's definition; +we try to unify x with Int (to default it), but find that x has already +been unified with the DontBind variable "a" from g's signature. +This is really a problem with side-effecting unification; we'd like to +undo g's effects when its type signature fails, but unification is done +by side effect, so we can't (easily). + +So we revert to ordinary type variables for signatures, and try to +give a helpful message in checkSigTyVars. + \begin{code} -tcTyVarScope - :: [HsTyVar Name] -- Names of some type variables - -> ([TyVar] -> TcM s a) -- Thing to type check in their scope - -> TcM s a -- Result +checkSigTyVars :: [TcTyVar] -- The original signature type variables + -> TcM s [TcTyVar] -- Zonked signature type variables + +checkSigTyVars [] = returnTc [] + +checkSigTyVars sig_tyvars + = zonkTcTyVars sig_tyvars `thenNF_Tc` \ sig_tys -> + tcGetGlobalTyVars `thenNF_Tc` \ globals -> -tcTyVarScope tyvar_names thing_inside - = mapAndUnzipNF_Tc tcHsTyVar tyvar_names `thenNF_Tc` \ (names, kinds) -> + checkTcM (all_ok sig_tys globals) + (complain sig_tys globals) `thenTc_` - fixTc (\ ~(rec_tyvars, _) -> - -- Ok to look at names, kinds, but not tyvars! + returnTc (map (getTyVar "checkSigTyVars") sig_tys) - tcExtendTyVarEnv names (kinds `zipLazy` rec_tyvars) - (thing_inside rec_tyvars) `thenTc` \ result -> - - -- Get the tyvar's Kinds from their TcKinds - mapNF_Tc tcDefaultKind kinds `thenNF_Tc` \ kinds' -> + where + all_ok [] acc = True + all_ok (ty:tys) acc = case getTyVar_maybe ty of + Nothing -> False -- Point (a) + Just tv | tv `elemVarSet` acc -> False -- Point (b) or (c) + | otherwise -> all_ok tys (acc `extendVarSet` tv) + - -- Construct the real TyVars + complain sig_tys globals + = -- For the in-scope ones, zonk them and construct a map + -- from the zonked tyvar to the in-scope one + -- If any of the in-scope tyvars zonk to a type, then ignore them; + -- that'll be caught later when we back up to their type sig + tcGetInScopeTyVars `thenNF_Tc` \ in_scope_tvs -> + zonkTcTyVars in_scope_tvs `thenNF_Tc` \ in_scope_tys -> let - tyvars = zipWithEqual "tcTyVarScope" mkTyVar names kinds' + in_scope_assoc = [ (zonked_tv, in_scope_tv) + | (z_ty, in_scope_tv) <- in_scope_tys `zip` in_scope_tvs, + Just zonked_tv <- [getTyVar_maybe z_ty] + ] + in_scope_env = mkVarEnv in_scope_assoc in - returnTc (tyvars, result) - ) `thenTc` \ (_,result) -> - returnTc result - -tcHsTyVar (UserTyVar name) - = newKindVar `thenNF_Tc` \ tc_kind -> - returnNF_Tc (name, tc_kind) -tcHsTyVar (IfaceTyVar name kind) - = returnNF_Tc (name, kindToTcKind kind) + + -- "check" checks each sig tyvar in turn + foldlNF_Tc check + (env2, in_scope_env, []) + (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) -> + + failWithTcM (env3, main_msg $$ nest 4 (vcat msgs)) + where + (env1, tidy_tvs) = mapAccumL tidyTyVar emptyTidyEnv sig_tyvars + (env2, tidy_tys) = tidyOpenTypes env1 sig_tys + + main_msg = ptext SLIT("Inferred type is less polymorphic than expected") + + check (env, acc, msgs) (sig_tyvar,ty) + -- sig_tyvar is from the signature; + -- ty is what you get if you zonk sig_tyvar and then tidy it + -- + -- acc maps a zonked type variable back to a signature type variable + = case getTyVar_maybe ty of { + Nothing -> -- Error (a)! + returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr ty) : msgs) ; + + Just tv -> + + case lookupVarEnv acc tv of { + Just sig_tyvar' -> -- Error (b) or (d)! + returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr sig_tyvar') : msgs) ; + + Nothing -> + + if tv `elemVarSet` globals -- Error (c)! Type variable escapes + -- The least comprehensible, so put it last + then tcGetValueEnv `thenNF_Tc` \ ve -> + find_globals tv env (eltsUFM ve) `thenNF_Tc` \ (env1, globs) -> + returnNF_Tc (env1, acc, escape_msg sig_tyvar tv globs : msgs) + + else -- All OK + returnNF_Tc (env, extendVarEnv acc tv sig_tyvar, msgs) + }} + +-- find_globals looks at the value environment and finds values +-- whose types mention the offending type variable. It has to be +-- careful to zonk the Id's type first, so it has to be in the monad. +-- We must be careful to pass it a zonked type variable, too. +find_globals tv tidy_env ids + | null ids + = returnNF_Tc (tidy_env, []) + +find_globals tv tidy_env (id:ids) + | not (isLocallyDefined id) || + isEmptyVarSet (idFreeTyVars id) + = find_globals tv tidy_env ids + + | otherwise + = zonkTcType (idType id) `thenNF_Tc` \ id_ty -> + if tv `elemVarSet` tyVarsOfType id_ty then + let + (tidy_env', id_ty') = tidyOpenType tidy_env id_ty + in + find_globals tv tidy_env' ids `thenNF_Tc` \ (tidy_env'', globs) -> + returnNF_Tc (tidy_env'', (idName id, id_ty') : globs) + else + find_globals tv tidy_env ids + +escape_msg sig_tv tv globs + = vcat [mk_msg sig_tv <+> ptext SLIT("escapes"), + pp_escape, + ptext SLIT("The following variables in the environment mention") <+> quotes (ppr tv), + nest 4 (vcat_first 10 [ppr name <+> dcolon <+> ppr ty | (name,ty) <- globs]) + ] + where + pp_escape | sig_tv /= tv = ptext SLIT("It unifies with") <+> + quotes (ppr tv) <> comma <+> + ptext SLIT("which is mentioned in the environment") + | otherwise = ptext SLIT("It is mentioned in the environment") + + vcat_first n [] = empty + vcat_first 0 (x:xs) = text "...others omitted..." + vcat_first n (x:xs) = x $$ vcat_first (n-1) xs + +unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> quotes thing +mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv) \end{code} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ +These two context are used with checkSigTyVars + +\begin{code} +sigCtxt :: (Type -> Message) -> Type + -> TidyEnv -> NF_TcM s (TidyEnv, Message) +sigCtxt mk_msg sig_ty tidy_env + = let + (env1, tidy_sig_ty) = tidyOpenType tidy_env sig_ty + in + returnNF_Tc (env1, mk_msg tidy_sig_ty) + +sigPatCtxt bound_tvs bound_ids tidy_env + = returnNF_Tc (env1, + sep [ptext SLIT("When checking a pattern that binds"), + nest 4 (vcat (zipWith ppr_id show_ids tidy_tys))]) + where + show_ids = filter is_interesting bound_ids + is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs + + (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) + ppr_id id ty = ppr id <+> dcolon <+> ppr ty + -- Don't zonk the types so we get the separate, un-unified versions +\end{code} + + +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + \begin{code} naughtyCCallContextErr clas_name - = sep [ptext SLIT("Can't use class"), quotes (ppr clas_name), ptext SLIT("in a context")] + = sep [ptext SLIT("Can't use class") <+> quotes (ppr clas_name), + ptext SLIT("in a context")] typeCtxt ty = ptext SLIT("In the type") <+> quotes (ppr ty) -thetaCtxt theta = ptext SLIT("In the context") <+> quotes (pprContext theta) +typeKindCtxt :: RenamedHsType -> Message +typeKindCtxt ty = sep [ptext SLIT("When checking that"), + nest 2 (quotes (ppr ty)), + ptext SLIT("is a type")] + +appKindCtxt :: SDoc -> Message +appKindCtxt pp = ptext SLIT("When checking kinds in") <+> quotes pp + +classAsTyConErr name + = ptext SLIT("Class used as a type constructor:") <+> ppr name + +tyConAsClassErr name + = ptext SLIT("Type constructor used as a class:") <+> ppr name + +tyVarAsClassErr name + = ptext SLIT("Type variable used as a class:") <+> ppr name \end{code}