X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMonoType.lhs;h=d57b53b6f6ae282b114aaab8c6c9a85621eaf759;hb=17985eb4007ae2415a97335b26fabc82fc38521f;hp=dad3e7baf3db882858bc65e2507e11e13c1e041c;hpb=9dd6e1c216993624a2cd74b62ca0f0569c02c26b;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMonoType.lhs b/ghc/compiler/typecheck/TcMonoType.lhs index dad3e7b..d57b53b 100644 --- a/ghc/compiler/typecheck/TcMonoType.lhs +++ b/ghc/compiler/typecheck/TcMonoType.lhs @@ -1,243 +1,865 @@ % -% (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 ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, + UserTypeCtxt(..), + + -- Kind checking + kcHsTyVar, kcHsTyVars, mkTyClTyVars, + kcHsType, kcHsSigType, kcHsSigTypes, + kcHsLiftedSigType, kcHsContext, + tcScopedTyVars, tcHsTyVars, mkImmutTyVars, + + TcSigInfo(..), tcTySig, mkTcSig, maybeSig, + checkSigTyVars, sigCtxt, sigPatCtxt + ) where #include "HsVersions.h" -import HsSyn ( HsType(..), HsTyVar(..), pprContext ) -import RnHsSyn ( RenamedHsType(..), RenamedContext(..) ) +import HsSyn ( HsType(..), HsTyVarBndr(..), + Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames ) +import RnHsSyn ( RenamedHsType, RenamedHsPred, 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, tcLookup, tcLookupGlobal, + tcGetGlobalTyVars, tcEnvTcIds, tcEnvTyVars, + TyThing(..), TcTyThing(..), tcExtendKindEnv + ) +import TcMType ( newKindVar, tcInstSigVars, + zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar, + unifyKind, unifyOpenTypeKind, + checkValidType, UserTypeCtxt(..), pprUserTypeCtxt ) -import Type ( Type, ThetaType, - mkTyVarTy, mkFunTy, mkAppTy, mkSynTy, - mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys +import TcType ( Type, Kind, SourceType(..), ThetaType, + mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, + tcSplitForAllTys, tcSplitRhoTy, + hoistForAllTys, allDistinctTyVars, + zipFunTys, + mkSigmaTy, mkPredTy, mkTyConApp, + mkAppTys, mkRhoTy, + liftedTypeKind, unliftedTypeKind, mkArrowKind, + mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe, + tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars, + tyVarsOfType, mkForAllTys ) -import TyVar ( TyVar, mkTyVar ) -import PrelInfo ( cCallishClassKeys ) -import TyCon ( TyCon ) -import Name ( Name, OccName, isTvOcc, getOccName ) -import TysWiredIn ( mkListTy, mkTupleTy ) -import Unique ( Unique, Uniquable(..) ) -import Util ( zipWithEqual, zipLazy ) +import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId ) +import PprType ( pprType ) +import Subst ( mkTopTyVarSubst, substTy ) +import CoreFVs ( idFreeTyVars ) +import Id ( mkLocalId, idName, idType ) +import Var ( Id, Var, TyVar, mkTyVar, tyVarKind ) +import VarEnv +import VarSet +import ErrUtils ( Message ) +import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind ) +import Class ( classTyCon ) +import Name ( Name ) +import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon ) +import BasicTypes ( Boxity(..) ) +import SrcLoc ( SrcLoc ) +import Util ( mapAccumL, isSingleton ) import Outputable + \end{code} -tcHsType and tcHsTypeKind -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{Checking types} +%* * +%************************************************************************ -tcHsType checks that the type really is of kind Type! +Generally speaking we now type-check types in three phases -\begin{code} -tcHsType :: RenamedHsType -> TcM s Type + 1. Kind check the HsType [kcHsType] + 2. Convert from HsType to Type, and hoist the foralls [tcHsType] + 3. Check the validity of the resultint type [checkValidType] -tcHsType ty - = tcAddErrCtxt (typeCtxt ty) $ - tc_hs_type ty +Often these steps are done one after the othe (tcHsSigType). +But in mutually recursive groups of type and class decls we do + 1 kind-check the whole group + 2 build TyCons/Classes in a knot-tied wa + 3 check the validity of types in the now-unknotted TyCons/Classes -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 +\begin{code} +tcHsSigType :: UserTypeCtxt -> RenamedHsType -> TcM Type + -- Do kind checking, and hoist for-alls to the top +tcHsSigType ctxt ty = tcAddErrCtxt (checkTypeCtxt ctxt ty) ( + kcTypeType ty `thenTc_` + tcHsType ty + ) `thenTc` \ ty' -> + checkValidType ctxt ty' `thenTc_` + returnTc ty' + +checkTypeCtxt ctxt ty + = vcat [ptext SLIT("In the type:") <+> ppr ty, + ptext SLIT("While checking") <+> pprUserTypeCtxt ctxt ] + +tcHsType :: RenamedHsType -> TcM Type + -- Don't do kind checking, nor validity checking, + -- but do hoist for-alls to the top + -- This is used in type and class decls, where kinding is + -- done in advance, and validity checking is done later + -- [Validity checking done later because of knot-tying issues.] +tcHsType ty = tc_type ty `thenTc` \ ty' -> + returnTc (hoistForAllTys ty') + +tcHsTheta :: RenamedContext -> TcM ThetaType +-- Used when we are expecting a ClassContext (i.e. no implicit params) +-- Does not do validity checking, like tcHsType +tcHsTheta hs_theta = mapTc tc_pred hs_theta + +-- In interface files the type is already kinded, +-- and we definitely don't want to hoist for-alls. +-- Otherwise we'll change +-- dmfail :: forall m:(*->*) Monad m => forall a:* => String -> m a +-- into +-- dmfail :: forall m:(*->*) a:* Monad m => String -> m a +-- which definitely isn't right! +tcIfaceType ty = tc_type ty \end{code} -tcHsTypeKind does the real work. It returns a kind and a type. -\begin{code} -tcHsTypeKind :: RenamedHsType -> TcM s (TcKind s, Type) +%************************************************************************ +%* * +\subsection{Kind checking} +%* * +%************************************************************************ -tcHsTypeKind ty - = tcAddErrCtxt (typeCtxt ty) $ - tc_hs_type_kind ty +Kind checking +~~~~~~~~~~~~~ +When we come across the binding site for some type variables, we +proceed in two stages +1. Figure out what kind each tyvar has - -- 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) +2. Create suitably-kinded tyvars, + extend the envt, + and typecheck the body -tc_hs_type_kind ty@(MonoTyVar name) - = tcFunType 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) -> +To do step 1, we proceed thus: + +1a. Bind each type variable to a kind variable +1b. Apply the kind checker +1c. Zonk the resulting kinds + +The kind checker is passed to tcHsTyVars as an argument. + +For example, when we find + (forall a m. m a -> m a) +we bind a,m to kind varibles and kind-check (m a -> m a). This +makes a get kind *, and m get kind *->*. Now we typecheck (m a -> m a) +in an environment that binds a and m suitably. + +The kind checker passed to tcHsTyVars needs to look at enough to +establish the kind of the tyvar: + * For a group of type and class decls, it's just the group, not + the rest of the program + * For a tyvar bound in a pattern type signature, its the types + mentioned in the other type signatures in that bunch of patterns + * For a tyvar bound in a RULE, it's the type signatures on other + universally quantified variables in the rule + +Note that this may occasionally give surprising results. For example: + + data T a b = MkT (a b) + +Here we deduce a::*->*, b::*. +But equally valid would be + a::(*->*)-> *, b::*->* + +\begin{code} +-- tcHsTyVars is used for type variables in type signatures +-- e.g. forall a. a->a +-- They are immutable, because they scope only over the signature +-- They may or may not be explicitly-kinded +tcHsTyVars :: [HsTyVarBndr Name] + -> TcM a -- The kind checker + -> ([TyVar] -> TcM b) + -> TcM b + +tcHsTyVars [] kind_check thing_inside = thing_inside [] + -- A useful short cut for a common case! + +tcHsTyVars tv_names kind_check thing_inside + = kcHsTyVars tv_names `thenNF_Tc` \ tv_names_w_kinds -> + tcExtendKindEnv tv_names_w_kinds kind_check `thenTc_` + zonkKindEnv tv_names_w_kinds `thenNF_Tc` \ tvs_w_kinds -> let - arity = length class_kinds - n_args = length arg_kinds - err = arityErr "Class" class_name arity n_args + tyvars = mkImmutTyVars tvs_w_kinds in - checkTc (arity == n_args) err `thenTc_` - unifyKinds class_kinds arg_kinds `thenTc_` - returnTc (mkBoxedTypeKind, mkDictTy clas arg_tys) + tcExtendTyVarEnv tyvars (thing_inside tyvars) + +-- tcScopedTyVars is used for scoped type variables +-- e.g. \ (x::a) (y::a) -> x+y +-- They never have explicit kinds (because this is source-code only) +-- They are mutable (because they can get bound to a more specific type) +tcScopedTyVars :: [Name] + -> TcM a -- The kind checker + -> TcM b + -> TcM b +tcScopedTyVars [] kind_check thing_inside = thing_inside + +tcScopedTyVars tv_names kind_check thing_inside + = mapNF_Tc newNamedKindVar tv_names `thenTc` \ kind_env -> + tcExtendKindEnv kind_env kind_check `thenTc_` + zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds -> + listTc [tcNewMutTyVar name kind | (name, kind) <- tvs_w_kinds] `thenNF_Tc` \ tyvars -> + tcExtendTyVarEnv tyvars thing_inside \end{code} + -Help functions for type applications -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} -tcTyApp (MonoTyApp ty1 ty2) tys - = tcTyApp ty1 (ty2:tys) +kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind) +kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)] -tcTyApp ty tys - | null tys - = tcFunType ty [] +kcHsTyVar (UserTyVar name) = newNamedKindVar name +kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (name, kind) + +kcHsTyVars tvs = mapNF_Tc kcHsTyVar tvs + +newNamedKindVar name = newKindVar `thenNF_Tc` \ kind -> + returnNF_Tc (name, kind) + +--------------------------- +kcLiftedType :: RenamedHsType -> TcM () + -- The type ty must be a *lifted* *type* +kcLiftedType ty + = kcHsType ty `thenTc` \ kind -> + tcAddErrCtxt (typeKindCtxt ty) $ + unifyKind liftedTypeKind kind + +--------------------------- +kcTypeType :: RenamedHsType -> TcM () + -- The type ty must be a *type*, but it can be lifted or unlifted. +kcTypeType ty + = kcHsType ty `thenTc` \ kind -> + tcAddErrCtxt (typeKindCtxt ty) $ + unifyOpenTypeKind kind + +--------------------------- +kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM () + -- Used for type signatures +kcHsSigType = kcTypeType +kcHsSigTypes tys = mapTc_ kcHsSigType tys +kcHsLiftedSigType = kcLiftedType + +--------------------------- +kcHsType :: RenamedHsType -> TcM TcKind +kcHsType (HsTyVar name) = kcTyVar name + +kcHsType (HsListTy ty) + = kcLiftedType ty `thenTc` \ tau_ty -> + returnTc liftedTypeKind + +kcHsType (HsTupleTy (HsTupCon _ boxity _) tys) + = mapTc kcTypeType tys `thenTc_` + returnTc (case boxity of + Boxed -> liftedTypeKind + Unboxed -> unliftedTypeKind) + +kcHsType (HsFunTy ty1 ty2) + = kcTypeType ty1 `thenTc_` + kcTypeType ty2 `thenTc_` + returnTc liftedTypeKind + +kcHsType (HsNumTy _) -- The unit type for generics + = returnTc liftedTypeKind + +kcHsType ty@(HsOpTy ty1 op ty2) + = kcTyVar op `thenTc` \ op_kind -> + kcHsType ty1 `thenTc` \ ty1_kind -> + kcHsType ty2 `thenTc` \ ty2_kind -> + tcAddErrCtxt (appKindCtxt (ppr ty)) $ + kcAppKind op_kind ty1_kind `thenTc` \ op_kind' -> + kcAppKind op_kind' ty2_kind + +kcHsType (HsPredTy pred) + = kcHsPred pred `thenTc_` + returnTc liftedTypeKind + +kcHsType ty@(HsAppTy ty1 ty2) + = kcHsType ty1 `thenTc` \ tc_kind -> + kcHsType ty2 `thenTc` \ arg_kind -> + tcAddErrCtxt (appKindCtxt (ppr ty)) $ + kcAppKind tc_kind arg_kind + +kcHsType (HsForAllTy (Just tv_names) context ty) + = kcHsTyVars tv_names `thenNF_Tc` \ kind_env -> + tcExtendKindEnv kind_env $ + kcHsContext context `thenTc_` + kcHsType ty `thenTc_` + returnTc liftedTypeKind + +--------------------------- +kcAppKind fun_kind arg_kind + = case tcSplitFunTy_maybe fun_kind of + Just (arg_kind', res_kind) + -> unifyKind arg_kind arg_kind' `thenTc_` + returnTc res_kind + + Nothing -> newKindVar `thenNF_Tc` \ res_kind -> + unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenTc_` + returnTc res_kind + + +--------------------------- +kcHsContext ctxt = mapTc_ kcHsPred ctxt + +kcHsPred :: RenamedHsPred -> TcM () +kcHsPred pred@(HsIParam name ty) + = tcAddErrCtxt (appKindCtxt (ppr pred)) $ + kcLiftedType ty + +kcHsPred pred@(HsClassP cls tys) + = tcAddErrCtxt (appKindCtxt (ppr pred)) $ + kcClass cls `thenTc` \ kind -> + mapTc kcHsType tys `thenTc` \ arg_kinds -> + unifyKind kind (mkArrowKinds arg_kinds liftedTypeKind) + + --------------------------- +kcTyVar name -- Could be a tyvar or a tycon + = tcLookup name `thenTc` \ thing -> + case thing of + AThing kind -> returnTc kind + ATyVar tv -> returnTc (tyVarKind tv) + AGlobal (ATyCon tc) -> returnTc (tyConKind tc) + other -> failWithTc (wrongThingErr "type" thing name) + +kcClass cls -- Must be a class + = tcLookup cls `thenNF_Tc` \ thing -> + case thing of + AThing kind -> returnTc kind + AGlobal (AClass cls) -> returnTc (tyConKind (classTyCon cls)) + other -> failWithTc (wrongThingErr "class" thing cls) +\end{code} + +%************************************************************************ +%* * +\subsection{tc_type} +%* * +%************************************************************************ + +tc_type, the main work horse +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + ------------------- + *** BIG WARNING *** + ------------------- + +tc_type is used to typecheck the types in the RHS of data +constructors. In the case of recursive data types, that means that +the type constructors themselves are (partly) black holes. e.g. + + data T a = MkT a [T a] + +While typechecking the [T a] on the RHS, T itself is not yet fully +defined. That in turn places restrictions on what you can check in +tcHsType; if you poke on too much you get a black hole. I keep +forgetting this, hence this warning! + +So tc_type does no validity-checking. Instead that's all done +by TcMType.checkValidType + + -------------------------- + *** END OF BIG WARNING *** + -------------------------- - | otherwise - = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) -> - tcFunType 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) - `thenTc_` - returnTc (result_kind, result_ty) +\begin{code} +tc_type :: RenamedHsType -> TcM Type + +tc_type ty@(HsTyVar name) + = tc_app ty [] + +tc_type (HsListTy ty) + = tc_type ty `thenTc` \ tau_ty -> + returnTc (mkListTy tau_ty) + +tc_type (HsTupleTy (HsTupCon _ boxity arity) tys) + = ASSERT( arity == length tys ) + tc_types tys `thenTc` \ tau_tys -> + returnTc (mkTupleTy boxity arity tau_tys) + +tc_type (HsFunTy ty1 ty2) + = tc_type ty1 `thenTc` \ tau_ty1 -> + tc_type ty2 `thenTc` \ tau_ty2 -> + returnTc (mkFunTy tau_ty1 tau_ty2) + +tc_type (HsNumTy n) + = ASSERT(n== 1) + returnTc (mkTyConApp genUnitTyCon []) --- (tcFunType ty arg_tys) returns (kind-of ty, mkAppTys ty arg_tys) +tc_type (HsOpTy ty1 op ty2) + = tc_type ty1 `thenTc` \ tau_ty1 -> + tc_type ty2 `thenTc` \ tau_ty2 -> + tc_fun_type op [tau_ty1,tau_ty2] + +tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2] + +tc_type (HsPredTy pred) + = tc_pred pred `thenTc` \ pred' -> + returnTc (mkPredTy pred') + +tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty) + = let + kind_check = kcHsContext ctxt `thenTc_` kcHsType ty + in + tcHsTyVars tv_names kind_check $ \ tyvars -> + mapTc tc_pred ctxt `thenTc` \ theta -> + tc_type ty `thenTc` \ tau -> + returnTc (mkSigmaTy tyvars theta tau) + +tc_types arg_tys = mapTc tc_type arg_tys +\end{code} + +Help functions for type applications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +\begin{code} +tc_app :: RenamedHsType -> [RenamedHsType] -> TcM Type +tc_app (HsAppTy ty1 ty2) tys + = tc_app ty1 (ty2:tys) + +tc_app ty tys + = tcAddErrCtxt (appKindCtxt pp_app) $ + tc_types tys `thenTc` \ arg_tys -> + case ty of + HsTyVar fun -> tc_fun_type fun arg_tys + other -> tc_type ty `thenTc` \ fun_ty -> + returnNF_Tc (mkAppTys fun_ty arg_tys) + where + pp_app = ppr ty <+> sep (map pprParendHsType tys) + +-- (tc_fun_type ty arg_tys) returns (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) -> - returnTc (fun_kind, mkAppTys fun_ty arg_tys) +tc_fun_type name arg_tys + = tcLookup name `thenTc` \ thing -> + case thing of + ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys) + + AGlobal (ATyCon tc) + | isSynTyCon tc -> returnTc (mkAppTys (mkSynTy tc (take arity arg_tys)) + (drop arity arg_tys)) + | otherwise -> returnTc (mkTyConApp tc arg_tys) + where + arity = tyConArity tc + + + other -> failWithTc (wrongThingErr "type constructor" thing name) \end{code} Contexts ~~~~~~~~ \begin{code} +tc_pred assn@(HsClassP class_name tys) + = tcAddErrCtxt (appKindCtxt (ppr assn)) $ + tc_types tys `thenTc` \ arg_tys -> + tcLookupGlobal class_name `thenTc` \ thing -> + case thing of + AClass clas -> returnTc (ClassP clas arg_tys) + other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name) + +tc_pred assn@(HsIParam name ty) + = tcAddErrCtxt (appKindCtxt (ppr assn)) $ + tc_type ty `thenTc` \ arg_ty -> + returnTc (IParam name arg_ty) +\end{code} -tcContext :: RenamedContext -> TcM s ThetaType -tcContext context = tcAddErrCtxt (thetaCtxt context) $ - mapTc tcClassAssertion context - -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) -> - unifyKinds class_kinds ty_kinds `thenTc_` +%************************************************************************ +%* * +\subsection{Type variables, with knot tying!} +%* * +%************************************************************************ - returnTc (clas, tc_tys) +\begin{code} +mkImmutTyVars :: [(Name,Kind)] -> [TyVar] +mkImmutTyVars pairs = [mkTyVar name kind | (name, kind) <- pairs] + +mkTyClTyVars :: Kind -- Kind of the tycon or class + -> [HsTyVarBndr Name] + -> [TyVar] +mkTyClTyVars kind tyvar_names + = mkImmutTyVars tyvars_w_kinds + where + (tyvars_w_kinds, _) = zipFunTys (hsTyVarNames tyvar_names) 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} -canBeUsedInContext :: Name -> Bool -canBeUsedInContext n = not (uniqueOf n `elem` cCallishClassKeys) +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 + +instance Outputable TcSigInfo where + ppr (TySigInfo nm id tyvars theta tau _ inst loc) = + ppr nm <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau + +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 \end{code} -Type variables, with knot tying! -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + \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 +tcTySig :: RenamedSig -> TcM TcSigInfo + +tcTySig (Sig v ty src_loc) + = tcAddSrcLoc src_loc $ + tcHsSigType (FunSigCtxt v) ty `thenTc` \ sigma_tc_ty -> + mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig -> + returnTc sig + +mkTcSig :: TcId -> SrcLoc -> NF_TcM 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 + let + (tyvars, rho) = tcSplitForAllTys (idType poly_id) + in + tcInstSigVars tyvars `thenNF_Tc` \ tyvars' -> + -- Make *signature* type variables + + let + tyvar_tys' = mkTyVarTys tyvars' + rho' = substTy (mkTopTyVarSubst tyvars tyvar_tys') rho + -- mkTopTyVarSubst because the tyvars' are fresh + + (theta', tau') = tcSplitRhoTy rho' + -- This splitRhoTy tries hard to make sure that tau' is a type synonym + -- wherever possible, which can improve interface files. + in + newMethodWithGivenTy SignatureOrigin + poly_id + tyvar_tys' + 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' (instToId inst) [inst] src_loc) + where + name = idName poly_id +\end{code} + + -tcTyVarScope tyvar_names thing_inside - = mapAndUnzipNF_Tc tcHsTyVar tyvar_names `thenNF_Tc` \ (names, kinds) -> +%************************************************************************ +%* * +\subsection{Checking signature type variables} +%* * +%************************************************************************ - fixTc (\ ~(rec_tyvars, _) -> - -- Ok to look at names, kinds, but not tyvars! +@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] - 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' -> + (b) Still all distinct + eg matching signature [(a,b)] against inferred type [(p,p)] + [then a and b will be unified together] - -- Construct the real TyVars + (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} +checkSigTyVars :: [TcTyVar] -- Universally-quantified type variables in the signature + -> TcTyVarSet -- Tyvars that are free in the type signature + -- Not necessarily zonked + -- These should *already* be in the free-in-env set, + -- and are used here only to improve the error message + -> TcM [TcTyVar] -- Zonked signature type variables + +checkSigTyVars [] free = returnTc [] +checkSigTyVars sig_tyvars free_tyvars + = zonkTcTyVars sig_tyvars `thenNF_Tc` \ sig_tys -> + tcGetGlobalTyVars `thenNF_Tc` \ globals -> + + checkTcM (allDistinctTyVars sig_tys globals) + (complain sig_tys globals) `thenTc_` + + returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys) + + where + 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 + tcGetEnv `thenNF_Tc` \ env -> + let + in_scope_tvs = tcEnvTyVars env + in + 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 <- [tcGetTyVar_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 (tidy_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 tcGetTyVar_maybe ty of { + Nothing -> -- Error (a)! + returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ; + + Just tv -> + + case lookupVarEnv acc tv of { + Just sig_tyvar' -> -- Error (b) or (d)! + returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs) + where + thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar') + + ; Nothing -> + + if tv `elemVarSet` globals -- Error (c)! Type variable escapes + -- The least comprehensible, so put it last + -- Game plan: + -- a) get the local TcIds from the environment, + -- and pass them to find_globals (they might have tv free) + -- b) similarly, find any free_tyvars that mention tv + then tcGetEnv `thenNF_Tc` \ ve -> + find_globals tv tidy_env [] (tcEnvTcIds ve) `thenNF_Tc` \ (tidy_env1, globs) -> + find_frees tv tidy_env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (tidy_env2, frees) -> + returnNF_Tc (tidy_env2, acc, escape_msg sig_tyvar tv globs frees : msgs) + + else -- All OK + returnNF_Tc (tidy_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 :: Var + -> TidyEnv + -> [(Name,Type)] + -> [Id] + -> NF_TcM (TidyEnv,[(Name,Type)]) + +find_globals tv tidy_env acc [] + = returnNF_Tc (tidy_env, acc) + +find_globals tv tidy_env acc (id:ids) + | isEmptyVarSet (idFreeTyVars id) + = find_globals tv tidy_env acc 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 + acc' = (idName id, id_ty') : acc + in + find_globals tv tidy_env' acc' ids + else + find_globals tv tidy_env acc ids + +find_frees tv tidy_env acc [] + = returnNF_Tc (tidy_env, acc) +find_frees tv tidy_env acc (ftv:ftvs) + = zonkTcTyVar ftv `thenNF_Tc` \ ty -> + if tv `elemVarSet` tyVarsOfType ty then + let + (tidy_env', ftv') = tidyTyVar tidy_env ftv + in + find_frees tv tidy_env' (ftv':acc) ftvs + else + find_frees tv tidy_env acc ftvs + + +escape_msg sig_tv tv globs frees + = mk_msg sig_tv <+> ptext SLIT("escapes") $$ + if not (null globs) then + vcat [pp_it <+> ptext SLIT("is mentioned in the environment"), + ptext SLIT("The following variables in the environment mention") <+> quotes (ppr tv), + nest 2 (vcat_first 10 [ppr name <+> dcolon <+> ppr ty | (name,ty) <- globs]) + ] + else if not (null frees) then + vcat [ptext SLIT("It is reachable from the type variable(s)") <+> pprQuotedList frees, + nest 2 (ptext SLIT("which") <+> is_are <+> ptext SLIT("free in the signature")) + ] + else + empty -- Sigh. It's really hard to give a good error message + -- all the time. One bad case is an existential pattern match + where + is_are | isSingleton frees = ptext SLIT("is") + | otherwise = ptext SLIT("are") + pp_it | sig_tv /= tv = ptext SLIT("It unifies with") <+> quotes (ppr tv) <> comma <+> ptext SLIT("which") + | otherwise = ptext SLIT("It") + + vcat_first :: Int -> [SDoc] -> SDoc + 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") <+> 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} -naughtyCCallContextErr clas_name - = sep [ptext SLIT("Can't use class"), quotes (ppr clas_name), ptext SLIT("in a context")] +sigCtxt :: Message -> [TcTyVar] -> TcThetaType -> TcTauType + -> TidyEnv -> NF_TcM (TidyEnv, Message) +sigCtxt when sig_tyvars sig_theta sig_tau tidy_env + = zonkTcType sig_tau `thenNF_Tc` \ actual_tau -> + let + (env1, tidy_sig_tyvars) = tidyTyVars tidy_env sig_tyvars + (env2, tidy_sig_rho) = tidyOpenType env1 (mkRhoTy sig_theta sig_tau) + (env3, tidy_actual_tau) = tidyOpenType env2 actual_tau + msg = vcat [ptext SLIT("Signature type: ") <+> pprType (mkForAllTys tidy_sig_tyvars tidy_sig_rho), + ptext SLIT("Type to generalise:") <+> pprType tidy_actual_tau, + when + ] + in + returnNF_Tc (env3, msg) + +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} -typeCtxt ty = ptext SLIT("In the type") <+> quotes (ppr ty) -thetaCtxt theta = ptext SLIT("In the context") <+> quotes (pprContext theta) +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +\begin{code} +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 + +wrongThingErr expected thing name + = pp_thing thing <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected + where + pp_thing (AGlobal (ATyCon _)) = ptext SLIT("Type constructor") + pp_thing (AGlobal (AClass _)) = ptext SLIT("Class") + pp_thing (AGlobal (AnId _)) = ptext SLIT("Identifier") + pp_thing (ATyVar _) = ptext SLIT("Type variable") + pp_thing (ATcId _) = ptext SLIT("Local identifier") + pp_thing (AThing _) = ptext SLIT("Utterly bogus") \end{code}