X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMonoType.lhs;h=ef9a43ba3effbb5f91152497b2cbfc65d5f95565;hb=893a774d698f90cd2915cd5305b15bc02e1afb40;hp=e23f7035d379287b444cf1e1c9f9f6aae43ae0e3;hpb=5f8800e201a3ae3262eb68ef0e29906aa309e2ae;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMonoType.lhs b/ghc/compiler/typecheck/TcMonoType.lhs index e23f703..ef9a43b 100644 --- a/ghc/compiler/typecheck/TcMonoType.lhs +++ b/ghc/compiler/typecheck/TcMonoType.lhs @@ -4,66 +4,116 @@ \section[TcMonoType]{Typechecking user-specified @MonoTypes@} \begin{code} -module TcMonoType ( tcHsType, tcHsSigType, tcHsBoxedSigType, - tcContext, tcClassContext, +module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, tcHsPred, + UserTypeCtxt(..), -- Kind checking kcHsTyVar, kcHsTyVars, mkTyClTyVars, - kcHsType, kcHsSigType, kcHsBoxedSigType, kcHsContext, - kcTyVarScope, newSigTyVars, mkImmutTyVars, + kcHsType, kcHsSigType, kcHsSigTypes, + kcHsLiftedSigType, kcHsContext, + tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars, - TcSigInfo(..), tcTySig, mkTcSig, maybeSig, - checkSigTyVars, sigCtxt, sigPatCtxt + TcSigInfo(..), tcTySig, mkTcSig, maybeSig ) where #include "HsVersions.h" -import HsSyn ( HsType(..), HsTyVarBndr(..), HsUsageAnn(..), +import HsSyn ( HsType(..), HsTyVarBndr(..), Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames ) -import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig ) +import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars ) import TcHsSyn ( TcId ) import TcMonad -import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars, - tcExtendUVarEnv, tcLookupUVar, - tcGetGlobalTyVars, valueEnvIds, - TyThing(..), tcExtendKindEnv +import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal, + tcInLocalScope, + TyThing(..), TcTyThing(..), tcExtendKindEnv ) -import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType, - newKindVar, tcInstSigVar, - zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar +import TcMType ( newKindVar, zonkKindEnv, tcInstSigType, + checkValidType, UserTypeCtxt(..), pprUserTypeCtxt ) -import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr, - instFunDeps, instFunDepsOfTheta ) -import FunDeps ( tyVarFunDep, oclose ) import TcUnify ( unifyKind, unifyOpenTypeKind ) -import Type ( Type, Kind, PredType(..), ThetaType, UsageAnn(..), - mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, mkUsgTy, - mkUsForAllTy, zipFunTys, hoistForAllTys, - mkSigmaTy, mkPredTy, mkTyConApp, - mkAppTys, splitForAllTys, splitRhoTy, mkRhoTy, - boxedTypeKind, unboxedTypeKind, mkArrowKind, - mkArrowKinds, getTyVar_maybe, getTyVar, splitFunTy_maybe, - tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars, - tyVarsOfType, tyVarsOfPred, mkForAllTys, - classesOfPreds, isUnboxedTupleType +import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..), + TcTyVar, TcKind, TcThetaType, TcTauType, + mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, + tcSplitForAllTys, tcSplitRhoTy, + hoistForAllTys, zipFunTys, + mkSigmaTy, mkPredTy, mkTyConApp, mkAppTys, + liftedTypeKind, unliftedTypeKind, mkArrowKind, + mkArrowKinds, tcSplitFunTy_maybe ) -import PprType ( pprType, pprPred ) +import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId ) + import Subst ( mkTopTyVarSubst, substTy ) -import Id ( mkVanillaId, idName, idType, idFreeTyVars ) -import Var ( TyVar, mkTyVar, tyVarKind, mkNamedUVar ) -import VarEnv -import VarSet +import Id ( mkLocalId, idName, idType ) +import Var ( TyVar, mkTyVar, tyVarKind ) import ErrUtils ( Message ) -import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind ) -import Class ( ClassContext, classArity, classTyCon ) -import Name ( Name, isLocallyDefined ) -import TysWiredIn ( mkListTy, mkTupleTy ) -import UniqFM ( elemUFM ) +import TyCon ( TyCon, isSynTyCon, tyConKind ) +import Class ( classTyCon ) +import Name ( Name ) +import NameSet +import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon ) import BasicTypes ( Boxity(..) ) import SrcLoc ( SrcLoc ) -import Util ( mapAccumL, isSingleton ) +import Util ( lengthIs ) import Outputable + +\end{code} + + +%************************************************************************ +%* * +\subsection{Checking types} +%* * +%************************************************************************ + +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 resulting type [checkValidType] + +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} +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} @@ -90,7 +140,7 @@ To do step 1, we proceed thus: 1b. Apply the kind checker 1c. Zonk the resulting kinds -The kind checker is passed to kcTyVarScope as an argument. +The kind checker is passed to tcHsTyVars as an argument. For example, when we find (forall a m. m a -> m a) @@ -98,7 +148,7 @@ 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 kcTyVarScope needs to look at enough to +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 @@ -116,308 +166,294 @@ But equally valid would be a::(*->*)-> *, b::*->* \begin{code} -kcTyVarScope :: [HsTyVarBndr Name] - -> TcM s a -- The kind checker - -> TcM s [(Name,Kind)] - -- Do a kind check to find out the kinds of the type variables - -- Then return a bunch of name-kind pairs, from which to - -- construct the type variables. We don't return the tyvars - -- themselves because sometimes we want mutable ones and - -- sometimes we want immutable ones. - -kcTyVarScope [] kind_check = returnTc [] +-- 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! -kcTyVarScope tv_names kind_check +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 + zonkKindEnv tv_names_w_kinds `thenNF_Tc` \ tvs_w_kinds -> + let + tyvars = mkImmutTyVars tvs_w_kinds + in + tcExtendTyVarEnv tyvars (thing_inside tyvars) + + + +tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a +-- tcAddScopedTyVars is used for scoped type variables +-- added by pattern type signatures +-- 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) + +-- Find the not-already-in-scope signature type variables, +-- kind-check them, and bring them into scope +-- +-- We no longer specify that these type variables must be univerally +-- quantified (lots of email on the subject). If you want to put that +-- back in, you need to +-- a) Do a checkSigTyVars after thing_inside +-- b) More insidiously, don't pass in expected_ty, else +-- we unify with it too early and checkSigTyVars barfs +-- Instead you have to pass in a fresh ty var, and unify +-- it with expected_ty afterwards +tcAddScopedTyVars [] thing_inside + = thing_inside -- Quick get-out for the empty case + +tcAddScopedTyVars sig_tys thing_inside + = tcGetEnv `thenNF_Tc` \ env -> + let + all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys + sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs) + not_in_scope tv = not (tcInLocalScope env tv) + in + mapNF_Tc newNamedKindVar sig_tvs `thenTc` \ kind_env -> + tcExtendKindEnv kind_env (kcHsSigTypes sig_tys) `thenTc_` + zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds -> + listTc [ tcNewMutTyVar name kind PatSigTv + | (name, kind) <- tvs_w_kinds] `thenNF_Tc` \ tyvars -> + tcExtendTyVarEnv tyvars thing_inside \end{code} \begin{code} -kcHsTyVar :: HsTyVarBndr name -> NF_TcM s (name, TcKind) -kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM s [(name, TcKind)] +kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind) +kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)] -kcHsTyVar (UserTyVar name) = newKindVar `thenNF_Tc` \ kind -> - returnNF_Tc (name, kind) +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) + --------------------------- -kcBoxedType :: RenamedHsType -> TcM s () - -- The type ty must be a *boxed* *type* -kcBoxedType ty +kcLiftedType :: RenamedHsType -> TcM () + -- The type ty must be a *lifted* *type* +kcLiftedType ty = kcHsType ty `thenTc` \ kind -> tcAddErrCtxt (typeKindCtxt ty) $ - unifyKind boxedTypeKind kind + unifyKind liftedTypeKind kind --------------------------- -kcTypeType :: RenamedHsType -> TcM s () - -- The type ty must be a *type*, but it can be boxed or unboxed. +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, kcHsBoxedSigType :: RenamedHsType -> TcM s () +kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM () -- Used for type signatures -kcHsSigType = kcTypeType -kcHsBoxedSigType = kcBoxedType +kcHsSigType = kcTypeType +kcHsSigTypes tys = mapTc_ kcHsSigType tys +kcHsLiftedSigType = kcLiftedType --------------------------- -kcHsType :: RenamedHsType -> TcM s TcKind -kcHsType (HsTyVar name) - = tcLookupTy name `thenTc` \ thing -> - case thing of - ATyVar tv -> returnTc (tyVarKind tv) - ATyCon tc -> returnTc (tyConKind tc) - AThing k -> returnTc k - other -> failWithTc (wrongThingErr "type" thing name) - -kcHsType (HsUsgTy _ ty) = kcHsType ty -kcHsType (HsUsgForAllTy _ ty) = kcHsType ty +kcHsType :: RenamedHsType -> TcM TcKind +kcHsType (HsTyVar name) = kcTyVar name kcHsType (HsListTy ty) - = kcBoxedType ty `thenTc` \ tau_ty -> - returnTc boxedTypeKind - -kcHsType (HsTupleTy (HsTupCon _ Boxed) tys) - = mapTc kcBoxedType tys `thenTc_` - returnTc boxedTypeKind + = kcLiftedType ty `thenTc` \ tau_ty -> + returnTc liftedTypeKind -kcHsType ty@(HsTupleTy (HsTupCon _ Unboxed) tys) - = failWithTc (unboxedTupleErr ty) - -- Unboxed tuples are illegal everywhere except - -- just after a function arrow (see kcFunResType) +kcHsType (HsTupleTy (HsTupCon _ boxity _) tys) + = mapTc kcTypeType tys `thenTc_` + returnTc (case boxity of + Boxed -> liftedTypeKind + Unboxed -> unliftedTypeKind) kcHsType (HsFunTy ty1 ty2) = kcTypeType ty1 `thenTc_` - kcFunResType ty2 `thenTc_` - returnTc boxedTypeKind + 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 boxedTypeKind + returnTc liftedTypeKind kcHsType ty@(HsAppTy ty1 ty2) - = kcHsType ty1 `thenTc` \ tc_kind -> - kcHsType ty2 `thenTc` \ arg_kind -> - + = kcHsType ty1 `thenTc` \ tc_kind -> + kcHsType ty2 `thenTc` \ arg_kind -> tcAddErrCtxt (appKindCtxt (ppr ty)) $ - case splitFunTy_maybe tc_kind of + 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 tc_kind (mkArrowKind arg_kind res_kind) `thenTc_` + unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenTc_` returnTc res_kind -kcHsType (HsForAllTy (Just tv_names) context ty) - = kcHsTyVars tv_names `thenNF_Tc` \ kind_env -> - tcExtendKindEnv kind_env $ - kcHsContext context `thenTc_` - - -- Context behaves 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 - if null context then - kcHsType ty - else - kcFunResType ty `thenTc_` - returnTc boxedTypeKind - -kcFunResType :: RenamedHsType -> TcM s TcKind --- The only place an unboxed tuple type is allowed --- is at the right hand end of an arrow -kcFunResType (HsTupleTy (HsTupCon _ Unboxed) tys) - = mapTc kcTypeType tys `thenTc_` - returnTc unboxedTypeKind - -kcFunResType ty = kcHsType ty +--------------------------- +kc_pred :: RenamedHsPred -> TcM TcKind -- Does *not* check for a saturated + -- application (reason: used from TcDeriv) +kc_pred pred@(HsIParam name ty) + = kcHsType ty + +kc_pred pred@(HsClassP cls tys) + = kcClass cls `thenTc` \ kind -> + mapTc kcHsType tys `thenTc` \ arg_kinds -> + newKindVar `thenNF_Tc` \ kv -> + unifyKind kind (mkArrowKinds arg_kinds kv) `thenTc_` + returnTc kv --------------------------- kcHsContext ctxt = mapTc_ kcHsPred ctxt -kcHsPred :: RenamedHsPred -> TcM s () -kcHsPred pred@(HsPIParam name ty) +kcHsPred pred -- Checks that the result is of kind liftedType = tcAddErrCtxt (appKindCtxt (ppr pred)) $ - kcBoxedType ty + kc_pred pred `thenTc` \ kind -> + unifyKind liftedTypeKind kind `thenTc_` + returnTc () + -kcHsPred pred@(HsPClass cls tys) - = tcAddErrCtxt (appKindCtxt (ppr pred)) $ - tcLookupTy cls `thenNF_Tc` \ thing -> - (case thing of - AClass cls -> returnTc (tyConKind (classTyCon cls)) - AThing kind -> returnTc kind - other -> failWithTc (wrongThingErr "class" thing cls)) `thenTc` \ kind -> - mapTc kcHsType tys `thenTc` \ arg_kinds -> - unifyKind kind (mkArrowKinds arg_kinds boxedTypeKind) + --------------------------- +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{Checking types} +\subsection{tc_type} %* * %************************************************************************ -tcHsSigType and tcHsBoxedSigType -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +tc_type, the main work horse +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -tcHsSigType and tcHsBoxedSigType are used for type signatures written by the programmer + ------------------- + *** BIG WARNING *** + ------------------- - * We hoist any inner for-alls to the top +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. - * Notice that we kind-check first, because the type-check assumes - that the kinds are already checked. + data T a = MkT a [T a] - * They are only called when there are no kind vars in the environment - so the kind returned is indeed a Kind not a TcKind +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! -\begin{code} -tcHsSigType :: RenamedHsType -> TcM s TcType -tcHsSigType ty - = kcTypeType ty `thenTc_` - tcHsType ty `thenTc` \ ty' -> - returnTc (hoistForAllTys ty') - -tcHsBoxedSigType :: RenamedHsType -> TcM s Type -tcHsBoxedSigType ty - = kcBoxedType ty `thenTc_` - tcHsType ty `thenTc` \ ty' -> - returnTc (hoistForAllTys ty') -\end{code} +So tc_type does no validity-checking. Instead that's all done +by TcMType.checkValidType + -------------------------- + *** END OF BIG WARNING *** + -------------------------- -tcHsType, the main work horse -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} -tcHsType :: RenamedHsType -> TcM s Type -tcHsType ty@(HsTyVar name) +tc_type :: RenamedHsType -> TcM Type + +tc_type ty@(HsTyVar name) = tc_app ty [] -tcHsType (HsListTy ty) - = tcHsType ty `thenTc` \ tau_ty -> +tc_type (HsListTy ty) + = tc_type ty `thenTc` \ tau_ty -> returnTc (mkListTy tau_ty) -tcHsType (HsTupleTy (HsTupCon _ boxity) tys) - = mapTc tcHsType tys `thenTc` \ tau_tys -> - returnTc (mkTupleTy boxity (length tys) tau_tys) +tc_type (HsTupleTy (HsTupCon _ boxity arity) tys) + = ASSERT( tys `lengthIs` arity ) + tc_types tys `thenTc` \ tau_tys -> + returnTc (mkTupleTy boxity arity tau_tys) -tcHsType (HsFunTy ty1 ty2) - = tcHsType ty1 `thenTc` \ tau_ty1 -> - tcHsType ty2 `thenTc` \ tau_ty2 -> +tc_type (HsFunTy ty1 ty2) + = tc_type ty1 `thenTc` \ tau_ty1 -> + tc_type ty2 `thenTc` \ tau_ty2 -> returnTc (mkFunTy tau_ty1 tau_ty2) -tcHsType (HsAppTy ty1 ty2) - = tc_app ty1 [ty2] +tc_type (HsNumTy n) + = ASSERT(n== 1) + returnTc (mkTyConApp genUnitTyCon []) -tcHsType (HsPredTy pred) - = tcClassAssertion True pred `thenTc` \ pred' -> - returnTc (mkPredTy pred') +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] -tcHsType (HsUsgTy usg ty) - = newUsg usg `thenTc` \ usg' -> - tcHsType ty `thenTc` \ tc_ty -> - returnTc (mkUsgTy usg' tc_ty) - where - newUsg usg = case usg of - HsUsOnce -> returnTc UsOnce - HsUsMany -> returnTc UsMany - HsUsVar uv_name -> tcLookupUVar uv_name `thenTc` \ uv -> - returnTc (UsVar uv) +tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2] -tcHsType (HsUsgForAllTy uv_name ty) +tc_type (HsPredTy pred) + = tc_pred pred `thenTc` \ pred' -> + returnTc (mkPredTy pred') + +tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty) = let - uv = mkNamedUVar uv_name + kind_check = kcHsContext ctxt `thenTc_` kcHsType ty in - tcExtendUVarEnv uv_name uv $ - tcHsType ty `thenTc` \ tc_ty -> - returnTc (mkUsForAllTy uv tc_ty) + tcHsTyVars tv_names kind_check $ \ tyvars -> + mapTc tc_pred ctxt `thenTc` \ theta -> + tc_type ty `thenTc` \ tau -> + returnTc (mkSigmaTy tyvars theta tau) -tcHsType full_ty@(HsForAllTy (Just tv_names) ctxt ty) - = kcTyVarScope tv_names - (kcHsContext ctxt `thenTc_` kcFunResType ty) `thenTc` \ tv_kinds -> - let - forall_tyvars = mkImmutTyVars tv_kinds - in - tcExtendTyVarEnv forall_tyvars $ - tcContext ctxt `thenTc` \ theta -> - tcHsType ty `thenTc` \ tau -> - let - -- Check for ambiguity - -- forall V. P => tau - -- is ambiguous if P contains generic variables - -- (i.e. one of the Vs) that are not mentioned in tau - -- - -- However, we need to take account of functional dependencies - -- when we speak of 'mentioned in tau'. Example: - -- class C a b | a -> b where ... - -- Then the type - -- forall x y. (C x y) => x - -- is not ambiguous because x is mentioned and x determines y - -- - -- NOTE: In addition, GHC insists that at least one type variable - -- in each constraint is in V. So we disallow a type like - -- forall a. Eq b => b -> b - -- even in a scope where b is in scope. - -- This is the is_free test below. - - tau_vars = tyVarsOfType tau - fds = instFunDepsOfTheta theta - tvFundep = tyVarFunDep fds - extended_tau_vars = oclose tvFundep tau_vars - is_ambig ct_var = (ct_var `elem` forall_tyvars) && - not (ct_var `elemUFM` extended_tau_vars) - is_free ct_var = not (ct_var `elem` forall_tyvars) - - check_pred pred = checkTc (not any_ambig) (ambigErr pred full_ty) `thenTc_` - checkTc (not all_free) (freeErr pred full_ty) - where - ct_vars = varSetElems (tyVarsOfPred pred) - any_ambig = is_source_polytype && any is_ambig ct_vars - all_free = all is_free ct_vars - - -- Check ambiguity only for source-program types, not - -- for types coming from inteface files. The latter can - -- legitimately have ambiguous types. Example - -- class S a where s :: a -> (Int,Int) - -- instance S Char where s _ = (1,1) - -- f:: S a => [a] -> Int -> (Int,Int) - -- f (_::[a]) x = (a*x,b) - -- where (a,b) = s (undefined::a) - -- Here the worker for f gets the type - -- fw :: forall a. S a => Int -> (# Int, Int #) - -- - -- If the list of tv_names is empty, we have a monotype, - -- and then we don't need to check for ambiguity either, - -- because the test can't fail (see is_ambig). - is_source_polytype = case tv_names of - (UserTyVar _ : _) -> True - other -> False - in - mapTc check_pred theta `thenTc_` - returnTc (mkSigmaTy forall_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) $ - mapTc tcHsType tys `thenTc` \ arg_tys -> - tc_fun_type ty arg_tys + 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) @@ -425,68 +461,42 @@ tc_app ty tys -- But not quite; for synonyms it checks the correct arity, and builds a SynTy -- hence the rather strange functionality. -tc_fun_type (HsTyVar name) arg_tys - = tcLookupTy name `thenTc` \ thing -> +tc_fun_type name arg_tys + = tcLookup name `thenTc` \ thing -> case thing of ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys) - ATyCon tc | isSynTyCon tc -> checkTc arity_ok err_msg `thenTc_` - returnTc (mkAppTys (mkSynTy tc (take arity arg_tys)) - (drop arity arg_tys)) - - | otherwise -> returnTc (mkTyConApp tc arg_tys) - where - - arity_ok = arity <= n_args - arity = tyConArity tc - -- It's OK to have an *over-applied* type synonym - -- data Tree a b = ... - -- type Foo a = Tree [a] - -- f :: Foo a b -> ... - err_msg = arityErr "Type synonym" name arity n_args - n_args = length arg_tys + AGlobal (ATyCon tc) + | isSynTyCon tc -> returnTc (mkSynTy tc arg_tys) + | otherwise -> returnTc (mkTyConApp tc arg_tys) other -> failWithTc (wrongThingErr "type constructor" thing name) - -tc_fun_type ty arg_tys - = tcHsType ty `thenTc` \ fun_ty -> - returnNF_Tc (mkAppTys fun_ty arg_tys) \end{code} Contexts ~~~~~~~~ \begin{code} -tcClassContext :: RenamedContext -> TcM s ClassContext - -- Used when we are expecting a ClassContext (i.e. no implicit params) -tcClassContext context - = tcContext context `thenTc` \ theta -> - returnTc (classesOfPreds theta) - -tcContext :: RenamedContext -> TcM s ThetaType -tcContext context = mapTc (tcClassAssertion False) context +tcHsPred pred = kc_pred pred `thenTc_` tc_pred pred + -- Is happy with a partial application, e.g. (ST s) + -- Used from TcDeriv -tcClassAssertion ccall_ok assn@(HsPClass class_name tys) +tc_pred assn@(HsClassP class_name tys) = tcAddErrCtxt (appKindCtxt (ppr assn)) $ - mapTc tcHsType tys `thenTc` \ arg_tys -> - tcLookupTy class_name `thenTc` \ thing -> + tc_types tys `thenTc` \ arg_tys -> + tcLookupGlobal class_name `thenTc` \ thing -> case thing of - AClass clas -> checkTc (arity == n_tys) err `thenTc_` - returnTc (Class clas arg_tys) - where - arity = classArity clas - 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) - other -> failWithTc (wrongThingErr "class" thing class_name) - -tcClassAssertion ccall_ok assn@(HsPIParam name ty) +tc_pred assn@(HsIParam name ty) = tcAddErrCtxt (appKindCtxt (ppr assn)) $ - tcHsType ty `thenTc` \ arg_ty -> + tc_type ty `thenTc` \ arg_ty -> returnTc (IParam name arg_ty) \end{code} + %************************************************************************ %* * \subsection{Type variables, with knot tying!} @@ -495,10 +505,7 @@ tcClassAssertion ccall_ok assn@(HsPIParam name ty) \begin{code} mkImmutTyVars :: [(Name,Kind)] -> [TyVar] -newSigTyVars :: [(Name,Kind)] -> NF_TcM s [TcTyVar] - mkImmutTyVars pairs = [mkTyVar name kind | (name, kind) <- pairs] -newSigTyVars pairs = listNF_Tc [tcNewSigTyVar name kind | (name,kind) <- pairs] mkTyClTyVars :: Kind -- Kind of the tycon or class -> [HsTyVarBndr Name] @@ -560,16 +567,15 @@ maybeSig (sig@(TySigInfo sig_name _ _ _ _ _ _ _) : sigs) name \begin{code} -tcTySig :: RenamedSig -> TcM s TcSigInfo +tcTySig :: RenamedSig -> TcM TcSigInfo tcTySig (Sig v ty src_loc) = tcAddSrcLoc src_loc $ - tcAddErrCtxt (tcsigCtxt v) $ - tcHsSigType ty `thenTc` \ sigma_tc_ty -> - mkTcSig (mkVanillaId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig -> + 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 @@ -578,272 +584,18 @@ mkTcSig poly_id src_loc -- 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) = splitForAllTys (idType poly_id) - in - mapNF_Tc tcInstSigVar 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') = splitRhoTy rho' - -- This splitRhoTy tries hard to make sure that tau' is a type synonym - -- wherever possible, which can improve interface files. - in + tcInstSigType SigTv (idType poly_id) `thenNF_Tc` \ (tyvars', theta', tau') -> + newMethodWithGivenTy SignatureOrigin - poly_id - tyvar_tys' - theta' tau' `thenNF_Tc` \ inst -> + poly_id + (mkTyVarTys tyvars') + theta' tau' `thenNF_Tc` \ inst -> -- We make a Method even if it's not overloaded; no harm - instFunDeps SignatureOrigin theta' `thenNF_Tc` \ fds -> - returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToIdBndr inst) (inst : fds) src_loc) - where - name = idName poly_id -\end{code} - - - -%************************************************************************ -%* * -\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} -checkSigTyVars :: [TcTyVar] -- Universally-quantified type variables in the signature - -> TcTyVarSet -- Tyvars that are free in the type signature - -- These should *already* be in the global-var set, and are - -- used here only to improve the error message - -> TcM s [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) - (complain sig_tys globals) `thenTc_` - - returnTc (map (getTyVar "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 -> - 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] - ] - in_scope_env = mkVarEnv in_scope_assoc - in - - -- "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 [] (valueEnvIds ve) `thenNF_Tc` \ (env1, globs) -> - find_frees tv env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (env2, frees) -> - returnNF_Tc (env2, acc, escape_msg sig_tyvar tv globs frees : 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 acc [] - = returnNF_Tc (tidy_env, acc) - -find_globals tv tidy_env acc (id:ids) - | not (isLocallyDefined id) || - 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") <+> quotes thing -mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv) + returnNF_Tc (TySigInfo (idName poly_id) poly_id tyvars' theta' tau' + (instToId inst) [inst] src_loc) \end{code} -These two context are used with checkSigTyVars - -\begin{code} -sigCtxt :: Message -> [TcTyVar] -> TcThetaType -> TcTauType - -> TidyEnv -> NF_TcM s (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} %************************************************************************ @@ -853,8 +605,6 @@ sigPatCtxt bound_tvs bound_ids tidy_env %************************************************************************ \begin{code} -tcsigCtxt v = ptext SLIT("In a type signature for") <+> quotes (ppr v) - typeKindCtxt :: RenamedHsType -> Message typeKindCtxt ty = sep [ptext SLIT("When checking that"), nest 2 (quotes (ppr ty)), @@ -863,25 +613,13 @@ typeKindCtxt ty = sep [ptext SLIT("When checking that"), appKindCtxt :: SDoc -> Message appKindCtxt pp = ptext SLIT("When checking kinds in") <+> quotes pp -wrongThingErr expected actual name - = pp_actual actual <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected +wrongThingErr expected thing name + = pp_thing thing <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected where - pp_actual (ATyCon _) = ptext SLIT("Type constructor") - pp_actual (AClass _) = ptext SLIT("Class") - pp_actual (ATyVar _) = ptext SLIT("Type variable") - pp_actual (AThing _) = ptext SLIT("Utterly bogus") - -ambigErr pred ty - = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred), - nest 4 (ptext SLIT("for the type:") <+> ppr ty), - nest 4 (ptext SLIT("Each forall'd type variable mentioned by the constraint must appear after the =>"))] - -freeErr pred ty - = sep [ptext SLIT("The constraint") <+> quotes (pprPred pred) <+> - ptext SLIT("does not mention any of the universally quantified type variables"), - nest 4 (ptext SLIT("in the type") <+> quotes (ppr ty)) - ] - -unboxedTupleErr ty - = sep [ptext (SLIT("Illegal unboxed tuple as a function or contructor argument:")), nest 4 (ppr ty)] + 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}