X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMonoType.lhs;h=d57b53b6f6ae282b114aaab8c6c9a85621eaf759;hb=2c2509997743edeb63830b86c8ee910db2414c6b;hp=22e2a33cee7a141f0623295ad7806965b12b8ca4;hpb=d133b73a4d4717892ced072d05e039a54ede0ceb;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMonoType.lhs b/ghc/compiler/typecheck/TcMonoType.lhs index 22e2a33..d57b53b 100644 --- a/ghc/compiler/typecheck/TcMonoType.lhs +++ b/ghc/compiler/typecheck/TcMonoType.lhs @@ -4,52 +4,66 @@ \section[TcMonoType]{Typechecking user-specified @MonoTypes@} \begin{code} -module TcMonoType ( tcHsType, tcHsTypeKind, tcHsTopType, tcHsTopBoxedType, - tcContext, tcHsTyVar, kcHsTyVar, - tcExtendTyVarScope, tcExtendTopTyVarScope, - TcSigInfo(..), tcTySig, mkTcSig, noSigs, maybeSig, +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(..), Sig(..), pprClassAssertion, pprParendHsType ) -import RnHsSyn ( RenamedHsType, RenamedContext, RenamedSig ) +import HsSyn ( HsType(..), HsTyVarBndr(..), + Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames ) +import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig ) import TcHsSyn ( TcId ) import TcMonad -import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars, - tcGetGlobalTyVars, TcTyThing(..) +import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal, + tcGetGlobalTyVars, tcEnvTcIds, tcEnvTyVars, + TyThing(..), TcTyThing(..), tcExtendKindEnv ) -import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType, - typeToTcType, kindToTcKind, - newKindVar, tcInstSigVar, - zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType +import TcMType ( newKindVar, tcInstSigVars, + zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar, + unifyKind, unifyOpenTypeKind, + checkValidType, UserTypeCtxt(..), pprUserTypeCtxt ) -import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr ) -import TcUnify ( unifyKind, unifyKinds, unifyTypeKind ) -import Type ( Type, ThetaType, - mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, mkUsgTy, zipFunTys, - mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys, splitForAllTys, splitRhoTy, - boxedTypeKind, unboxedTypeKind, tyVarsOfType, - mkArrowKinds, getTyVar_maybe, getTyVar, - tidyOpenType, tidyOpenTypes, tidyTyVar, fullSubstTy +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 Id ( mkUserId, idName, idType, idFreeTyVars ) -import Var ( TyVar, mkTyVar ) +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 Bag ( bagToList ) import ErrUtils ( Message ) -import PrelInfo ( cCallishClassKeys ) -import TyCon ( TyCon ) -import Name ( Name, OccName, isLocallyDefined ) -import TysWiredIn ( mkListTy, mkTupleTy, mkUnboxedTupleTy ) +import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind ) +import Class ( classTyCon ) +import Name ( Name ) +import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon ) +import BasicTypes ( Boxity(..) ) import SrcLoc ( SrcLoc ) -import Unique ( Unique, Uniquable(..) ) -import UniqFM ( eltsUFM ) -import Util ( zipWithEqual, zipLazy, mapAccumL ) +import Util ( mapAccumL, isSingleton ) import Outputable + \end{code} @@ -59,220 +73,408 @@ import Outputable %* * %************************************************************************ -tcHsType and tcHsTypeKind -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Generally speaking we now type-check types in three phases + + 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 checks that the type really is of kind Type! +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 \begin{code} -tcHsType :: RenamedHsType -> TcM s TcType -tcHsType 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') +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} -The main work horse -~~~~~~~~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{Kind checking} +%* * +%************************************************************************ + +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 + +2. Create suitably-kinded tyvars, + extend the envt, + and typecheck the body + +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} -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 [] +-- 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 + tyvars = mkImmutTyVars tvs_w_kinds + in + 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} -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 (MonoUsgTy usg ty) - = tc_type_kind ty `thenTc` \ (kind, tc_ty) -> - returnTc (kind, mkUsgTy usg tc_ty) - -tc_type_kind (HsForAllTy (Just tv_names) context ty) - = tcExtendTyVarScope tv_names $ \ tyvars -> - tcContext context `thenTc` \ theta -> - case theta of - [] -> -- No context, so propagate body type - tc_type_kind ty `thenTc` \ (kind, tau) -> - returnTc (kind, mkSigmaTy tyvars [] tau) - - other -> -- Context; behave like a function type - -- This matters. Return-unboxed-tuple analysis can - -- give overloaded functions like - -- f :: forall a. Num a => (# a->a, a->a #) - -- And we want these to get through the type checker - - tc_type ty `thenTc` \ tau -> - returnTc (boxedTypeKind, mkSigmaTy tyvars theta tau) + +\begin{code} +kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind) +kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)] + +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 *** + -------------------------- + + +\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 []) + +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 (MonoTyApp ty1 ty2) tys +tc_app :: RenamedHsType -> [RenamedHsType] -> TcM Type +tc_app (HsAppTy ty1 ty2) tys = tc_app ty1 (ty2:tys) tc_app ty tys - | null tys - = tc_fun_type ty [] - - | otherwise = 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 (mkArrowKinds arg_kinds result_kind) - `thenTc_` - returnTc (result_kind, result_ty) + 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 (kind-of ty, mkAppTys ty arg_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. -tc_fun_type (MonoTyVar name) arg_tys - = tcLookupTy name `thenTc` \ (tycon_kind, maybe_arity, thing) -> +tc_fun_type name arg_tys + = tcLookup name `thenTc` \ 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) + 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} - -tcContext :: RenamedContext -> TcM s ThetaType -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) -> +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 - 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 + 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} + %************************************************************************ %* * \subsection{Type variables, with knot tying!} @@ -280,38 +482,16 @@ tcClassAssertion assn@(class_name, tys) %************************************************************************ \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) +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 - 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 - -tcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (mkTyVar name (kindToTcKind kind)) - -kcHsTyVar :: HsTyVar name -> NF_TcM s TcKind -kcHsTyVar (UserTyVar name) = newKindVar -kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (kindToTcKind kind) + (tyvars_w_kinds, _) = zipFunTys (hsTyVarNames tyvar_names) kind \end{code} @@ -346,11 +526,14 @@ data TcSigInfo -- Does *not* have name = N -- Has type tau - Inst -- Empty if theta is null, or + [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 @@ -358,23 +541,19 @@ 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} -tcTySig :: RenamedSig -> TcM s TcSigInfo +tcTySig :: RenamedSig -> TcM 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 -> + = 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 s TcSigInfo +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 @@ -384,15 +563,17 @@ mkTcSig poly_id src_loc -- typechecking the rest of the program with the function bound -- to a pristine type, namely sigma_tc_ty let - (tyvars, rho) = splitForAllTys (idType poly_id) + (tyvars, rho) = tcSplitForAllTys (idType poly_id) in - mapNF_Tc tcInstSigVar tyvars `thenNF_Tc` \ tyvars' -> + tcInstSigVars tyvars `thenNF_Tc` \ tyvars' -> -- Make *signature* type variables let tyvar_tys' = mkTyVarTys tyvars' - rho' = fullSubstTy (zipVarEnv tyvars tyvar_tys') emptyVarSet rho - (theta', tau') = splitRhoTy rho' + 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 @@ -402,7 +583,7 @@ mkTcSig poly_id src_loc 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) + returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc) where name = idName poly_id \end{code} @@ -472,39 +653,38 @@ So we revert to ordinary type variables for signatures, and try to give a helpful message in checkSigTyVars. \begin{code} -checkSigTyVars :: [TcTyVar] -- The original signature type variables - -> TcM s [TcTyVar] -- Zonked signature type variables - -checkSigTyVars [] = returnTc [] - -checkSigTyVars sig_tyvars +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 (all_ok sig_tys globals) + checkTcM (allDistinctTyVars sig_tys globals) (complain sig_tys globals) `thenTc_` - returnTc (map (getTyVar "checkSigTyVars") sig_tys) + returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys) 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) - - 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 -> + tcGetEnv `thenNF_Tc` \ env -> + let + in_scope_tvs = tcEnvTyVars env + in zonkTcTyVars in_scope_tvs `thenNF_Tc` \ in_scope_tys -> let 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] + Just zonked_tv <- [tcGetTyVar_maybe z_ty] ] in_scope_env = mkVarEnv in_scope_assoc in @@ -521,88 +701,128 @@ checkSigTyVars sig_tyvars main_msg = ptext SLIT("Inferred type is less polymorphic than expected") - check (env, acc, msgs) (sig_tyvar,ty) + 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 getTyVar_maybe ty of { + = case tcGetTyVar_maybe ty of { Nothing -> -- Error (a)! - returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr ty) : msgs) ; + 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 (env, acc, unify_msg sig_tyvar (ppr sig_tyvar') : msgs) ; + returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs) + where + thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar') - Nothing -> + ; 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) + -- 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 (env, extendVarEnv acc tv sig_tyvar, msgs) + 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 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 +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' ids `thenNF_Tc` \ (tidy_env'', globs) -> - returnNF_Tc (tidy_env'', (idName id, id_ty') : globs) + 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_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]) - ] + find_frees tv tidy_env acc ftvs + + +escape_msg sig_tv tv globs frees + = mk_msg sig_tv <+> ptext SLIT("escapes") $$ + if not (null globs) then + vcat [pp_it <+> ptext SLIT("is mentioned in the environment"), + ptext SLIT("The following variables in the environment mention") <+> quotes (ppr tv), + nest 2 (vcat_first 10 [ppr name <+> dcolon <+> ppr ty | (name,ty) <- globs]) + ] + else if not (null frees) then + vcat [ptext SLIT("It is reachable from the type variable(s)") <+> pprQuotedList frees, + nest 2 (ptext SLIT("which") <+> is_are <+> ptext SLIT("free in the signature")) + ] + else + empty -- Sigh. It's really hard to give a good error message + -- all the time. One bad case is an existential pattern match where - pp_escape | sig_tv /= tv = ptext SLIT("It unifies with") <+> - quotes (ppr tv) <> comma <+> - ptext SLIT("which is mentioned in the environment") - | otherwise = ptext SLIT("It is mentioned in the environment") + is_are | isSingleton frees = ptext SLIT("is") + | otherwise = ptext SLIT("are") + pp_it | sig_tv /= tv = ptext SLIT("It unifies with") <+> quotes (ppr tv) <> comma <+> ptext SLIT("which") + | otherwise = ptext SLIT("It") vcat_first :: Int -> [SDoc] -> SDoc vcat_first n [] = empty vcat_first 0 (x:xs) = text "...others omitted..." vcat_first n (x:xs) = x $$ vcat_first (n-1) xs -unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> quotes thing +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} 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 +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 (env1, mk_msg tidy_sig_ty) + returnNF_Tc (env3, msg) sigPatCtxt bound_tvs bound_ids tidy_env = returnNF_Tc (env1, @@ -625,12 +845,6 @@ sigPatCtxt bound_tvs bound_ids tidy_env %************************************************************************ \begin{code} -naughtyCCallContextErr clas_name - = 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) - typeKindCtxt :: RenamedHsType -> Message typeKindCtxt ty = sep [ptext SLIT("When checking that"), nest 2 (quotes (ppr ty)), @@ -639,12 +853,13 @@ typeKindCtxt ty = sep [ptext SLIT("When checking that"), 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 +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}