X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMonoType.lhs;h=c257251ee014a36a85df3df3cdef9410c7928c28;hb=05afb7485eea44d6410139f8a20c94b6f66c46f2;hp=ca4629a164df4070b597ff4b02b4c8975414f182;hpb=6aa013b48b9a85b643672be56f89f0bd0108db1f;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMonoType.lhs b/ghc/compiler/typecheck/TcMonoType.lhs index ca4629a..c257251 100644 --- a/ghc/compiler/typecheck/TcMonoType.lhs +++ b/ghc/compiler/typecheck/TcMonoType.lhs @@ -4,7 +4,7 @@ \section[TcMonoType]{Typechecking user-specified @MonoTypes@} \begin{code} -module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, +module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, tcHsPred, UserTypeCtxt(..), -- Kind checking @@ -13,59 +13,50 @@ module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, kcHsLiftedSigType, kcHsContext, tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars, - TcSigInfo(..), tcTySig, mkTcSig, maybeSig, - checkSigTyVars, sigCtxt, sigPatCtxt + TcSigInfo(..), tcTySig, mkTcSig, maybeSig, tcSigPolyId, tcSigMonoId ) where #include "HsVersions.h" -import HsSyn ( HsType(..), HsTyVarBndr(..), - Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames ) +import HsSyn ( HsType(..), HsTyVarBndr(..), HsTyOp(..), + Sig(..), HsPred(..), HsTupCon(..), hsTyVarNames ) import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars ) import TcHsSyn ( TcId ) -import TcMonad +import TcRnMonad import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal, - tcGetGlobalTyVars, tcLEnvElts, tcInLocalScope, - TyThing(..), TcTyThing(..), tcExtendKindEnv + TyThing(..), TcTyThing(..), tcExtendKindEnv, + getInLocalScope ) -import TcMType ( newKindVar, tcInstSigTyVars, - zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar, - unifyKind, unifyOpenTypeKind, - checkValidType, UserTypeCtxt(..), pprUserTypeCtxt +import TcMType ( newMutTyVar, newKindVar, zonkKindEnv, tcInstType, zonkTcType, + checkValidType, UserTypeCtxt(..), pprUserTypeCtxt, newOpenTypeKind ) +import TcUnify ( unifyKind, unifyFunKind ) import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..), - TcTyVar, TcTyVarSet, TcType, TcKind, TcThetaType, TcTauType, - 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, tidyOpenTyVar, tidyOpenTyVars, - tyVarsOfType, mkForAllTys + TcTyVar, TcKind, TcThetaType, TcTauType, + mkTyVarTy, mkTyVarTys, mkFunTy, isTypeKind, + zipFunTys, mkForAllTys, mkFunTys, tcEqType, isPredTy, + mkSigmaTy, mkPredTy, mkGenTyConApp, mkTyConApp, mkAppTys, + liftedTypeKind, unliftedTypeKind, eqKind, + tcSplitFunTy_maybe, tcSplitForAllTys ) -import qualified Type ( getTyVar_maybe ) +import qualified Type ( splitFunTys ) +import Inst ( Inst, InstOrigin(..), newMethod, instToId ) -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, isMutTyVar, mutTyVarDetails ) -import VarEnv -import VarSet +import Var ( TyVar, mkTyVar, tyVarKind ) import ErrUtils ( Message ) -import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind ) +import TyCon ( TyCon, tyConKind ) import Class ( classTyCon ) -import Name ( Name, getSrcLoc ) +import Name ( Name ) import NameSet -import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon ) +import Subst ( deShadowTy ) +import TysWiredIn ( mkListTy, mkPArrTy, mkTupleTy, genUnitTyCon ) import BasicTypes ( Boxity(..) ) import SrcLoc ( SrcLoc ) -import Util ( isSingleton, lengthIs ) +import Util ( lengthIs ) import Outputable - +import List ( nubBy ) \end{code} @@ -90,12 +81,12 @@ But in mutually recursive groups of type and class decls we do \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_` +tcHsSigType ctxt ty = addErrCtxt (checkTypeCtxt ctxt ty) ( + kcTypeType ty `thenM_` tcHsType ty - ) `thenTc` \ ty' -> - checkValidType ctxt ty' `thenTc_` - returnTc ty' + ) `thenM` \ ty' -> + checkValidType ctxt ty' `thenM_` + returnM ty' checkTypeCtxt ctxt ty = vcat [ptext SLIT("In the type:") <+> ppr ty, @@ -107,13 +98,13 @@ tcHsType :: RenamedHsType -> TcM Type -- 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') +tcHsType ty = tc_type ty `thenM` \ ty' -> + returnM (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 +tcHsTheta hs_theta = mappM tc_pred hs_theta -- In interface files the type is already kinded, -- and we definitely don't want to hoist for-alls. @@ -188,9 +179,9 @@ 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 -> + = kcHsTyVars tv_names `thenM` \ tv_names_w_kinds -> + tcExtendKindEnv tv_names_w_kinds kind_check `thenM_` + zonkKindEnv tv_names_w_kinds `thenM` \ tvs_w_kinds -> let tyvars = mkImmutTyVars tvs_w_kinds in @@ -220,143 +211,220 @@ tcAddScopedTyVars [] thing_inside = thing_inside -- Quick get-out for the empty case tcAddScopedTyVars sig_tys thing_inside - = tcGetEnv `thenNF_Tc` \ env -> + = getInLocalScope `thenM` \ in_scope -> 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) + sig_tvs = filter (not . in_scope) (nameSetToList all_sig_tvs) 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 -> + mappM newNamedKindVar sig_tvs `thenM` \ kind_env -> + tcExtendKindEnv kind_env (kcHsSigTypes sig_tys) `thenM_` + zonkKindEnv kind_env `thenM` \ tvs_w_kinds -> + sequenceM [ newMutTyVar name kind PatSigTv + | (name, kind) <- tvs_w_kinds] `thenM` \ tyvars -> tcExtendTyVarEnv tyvars thing_inside \end{code} \begin{code} -kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind) -kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)] +kcHsTyVar :: HsTyVarBndr name -> TcM (name, TcKind) +kcHsTyVars :: [HsTyVarBndr name] -> TcM [(name, TcKind)] kcHsTyVar (UserTyVar name) = newNamedKindVar name -kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (name, kind) +kcHsTyVar (IfaceTyVar name kind) = returnM (name, kind) -kcHsTyVars tvs = mapNF_Tc kcHsTyVar tvs +kcHsTyVars tvs = mappM kcHsTyVar tvs -newNamedKindVar name = newKindVar `thenNF_Tc` \ kind -> - returnNF_Tc (name, kind) +newNamedKindVar name = newKindVar `thenM` \ kind -> + returnM (name, kind) --------------------------- -kcLiftedType :: RenamedHsType -> TcM () +kcLiftedType :: RenamedHsType -> TcM Kind -- The type ty must be a *lifted* *type* -kcLiftedType ty - = kcHsType ty `thenTc` \ kind -> - tcAddErrCtxt (typeKindCtxt ty) $ - unifyKind liftedTypeKind kind +kcLiftedType ty = kcHsType ty `thenM` \ act_kind -> + checkExpectedKind (ppr ty) act_kind liftedTypeKind --------------------------- 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 + = kcHsType ty `thenM` \ kind -> + if isTypeKind kind then + return () + else + newOpenTypeKind `thenM` \ exp_kind -> + checkExpectedKind (ppr ty) kind exp_kind `thenM_` + returnM () --------------------------- kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM () -- Used for type signatures -kcHsSigType = kcTypeType -kcHsSigTypes tys = mapTc_ kcHsSigType tys -kcHsLiftedSigType = kcLiftedType +kcHsSigType ty = kcTypeType ty +kcHsSigTypes tys = mappM_ kcHsSigType tys +kcHsLiftedSigType ty = kcLiftedType ty `thenM_` returnM () --------------------------- 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 +-- kcHsType *returns* the kind of the type, rather than taking an expected +-- kind as argument as tcExpr does. Reason: the kind of (->) is +-- forall bx1 bx2. Type bx1 -> Type bx2 -> Type Boxed +-- so we'd need to generate huge numbers of bx variables. + +kcHsType (HsTyVar name) = kcTyVar name +kcHsType (HsListTy ty) = kcLiftedType ty +kcHsType (HsPArrTy ty) = kcLiftedType ty +kcHsType (HsParTy ty) = kcHsType ty -- Skip parentheses markers +kcHsType (HsNumTy _) = returnM liftedTypeKind -- The unit type for generics +kcHsType (HsKindSig ty k) = kcHsType ty `thenM` \ act_kind -> + checkExpectedKind (ppr ty) act_kind k + +kcHsType (HsTupleTy (HsTupCon boxity _) tys) + = mappM kcTypeType tys `thenM_` + returnM (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 - + = kcTypeType ty1 `thenM_` + kcTypeType ty2 `thenM_` + returnM liftedTypeKind + +kcHsType (HsOpTy ty1 HsArrow ty2) + = kcTypeType ty1 `thenM_` + kcTypeType ty2 `thenM_` + returnM liftedTypeKind + +kcHsType ty@(HsOpTy ty1 op_ty@(HsTyOp op) ty2) + = addErrCtxt (appKindCtxt (ppr ty)) $ + kcTyVar op `thenM` \ op_kind -> + kcApps (ppr op_ty) op_kind [ty1,ty2] + kcHsType (HsPredTy pred) - = kcHsPred pred `thenTc_` - returnTc liftedTypeKind + = kcHsPred pred `thenM_` + returnM 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 + = addErrCtxt (appKindCtxt (ppr ty)) $ + kc_app ty [] + where + kc_app (HsAppTy f a) as = kc_app f (a:as) + kc_app f as = kcHsType f `thenM` \ fk -> + kcApps (ppr f) fk as kcHsType (HsForAllTy (Just tv_names) context ty) - = kcHsTyVars tv_names `thenNF_Tc` \ kind_env -> + = kcHsTyVars tv_names `thenM` \ kind_env -> tcExtendKindEnv kind_env $ - kcHsContext context `thenTc_` - kcHsType ty `thenTc_` - returnTc liftedTypeKind + kcHsContext context `thenM_` + kcLiftedType ty + -- The body of a forall must be of kind * + -- In principle, I suppose, we could allow unlifted types, + -- but it seems simpler to stick to lifted types for now. --------------------------- -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 +kcApps :: SDoc -- The function + -> TcKind -- Function kind + -> [RenamedHsType] -- Arg types + -> TcM TcKind -- Result kind +kcApps pp_fun fun_kind args + = go fun_kind args + where + go fk [] = returnM fk + go fk (ty:tys) = unifyFunKind fk `thenM` \ mb_fk -> + case mb_fk of { + Nothing -> failWithTc too_few_args ; + Just (ak',fk') -> + kcHsType ty `thenM` \ ak -> + checkExpectedKind (ppr ty) ak ak' `thenM_` + go fk' tys } + + too_few_args = ptext SLIT("Kind error:") <+> quotes pp_fun <+> + ptext SLIT("is applied to too many type arguments") - Nothing -> newKindVar `thenNF_Tc` \ res_kind -> - unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenTc_` - returnTc res_kind +--------------------------- +-- We would like to get a decent error message from +-- (a) Under-applied type constructors +-- f :: (Maybe, Maybe) +-- (b) Over-applied type constructors +-- f :: Int x -> Int x +-- +checkExpectedKind :: SDoc -> TcKind -> TcKind -> TcM TcKind +-- A fancy wrapper for 'unifyKind', which tries to give +-- decent error messages. +-- Returns the same kind that it is passed, exp_kind +checkExpectedKind pp_ty act_kind exp_kind + | act_kind `eqKind` exp_kind -- Short cut for a very common case + = returnM exp_kind + | otherwise + = tryTc (unifyKind exp_kind act_kind) `thenM` \ (errs, mb_r) -> + case mb_r of { + Just _ -> returnM exp_kind ; -- Unification succeeded + Nothing -> + + -- So there's definitely an error + -- Now to find out what sort + zonkTcType exp_kind `thenM` \ exp_kind -> + zonkTcType act_kind `thenM` \ act_kind -> + + let (exp_as, _) = Type.splitFunTys exp_kind + (act_as, _) = Type.splitFunTys act_kind + -- Use the Type versions for kinds + n_exp_as = length exp_as + n_act_as = length act_as + + err | n_exp_as < n_act_as -- E.g. [Maybe] + = quotes pp_ty <+> ptext SLIT("is not applied to enough type arguments") + + -- Now n_exp_as >= n_act_as. In the next two cases, + -- n_exp_as == 0, and hence so is n_act_as + | exp_kind `eqKind` liftedTypeKind && act_kind `eqKind` unliftedTypeKind + = ptext SLIT("Expecting a lifted type, but") <+> quotes pp_ty + <+> ptext SLIT("is unlifted") + + | exp_kind `eqKind` unliftedTypeKind && act_kind `eqKind` liftedTypeKind + = ptext SLIT("Expecting an unlifted type, but") <+> quotes pp_ty + <+> ptext SLIT("is lifted") + + | otherwise -- E.g. Monad [Int] + = sep [ ptext SLIT("Expecting kind") <+> quotes (ppr exp_kind) <> comma, + ptext SLIT("but") <+> quotes pp_ty <+> + ptext SLIT("has kind") <+> quotes (ppr act_kind)] + in + failWithTc (ptext SLIT("Kind error:") <+> err) + } --------------------------- -kcHsContext ctxt = mapTc_ kcHsPred ctxt +kc_pred :: RenamedHsPred -> TcM TcKind -- Does *not* check for a saturated + -- application (reason: used from TcDeriv) +kc_pred pred@(HsIParam name ty) + = kcHsType ty -kcHsPred :: RenamedHsPred -> TcM () -kcHsPred pred@(HsIParam name ty) - = tcAddErrCtxt (appKindCtxt (ppr pred)) $ - kcLiftedType ty +kc_pred pred@(HsClassP cls tys) + = kcClass cls `thenM` \ kind -> + kcApps (ppr cls) kind tys -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) +--------------------------- +kcHsContext ctxt = mappM_ kcHsPred ctxt + +kcHsPred pred -- Checks that the result is of kind liftedType + = addErrCtxt (appKindCtxt (ppr pred)) $ + kc_pred pred `thenM` \ kind -> + checkExpectedKind (ppr pred) kind liftedTypeKind + --------------------------- kcTyVar name -- Could be a tyvar or a tycon - = tcLookup name `thenTc` \ thing -> + = tcLookup name `thenM` \ thing -> case thing of - AThing kind -> returnTc kind - ATyVar tv -> returnTc (tyVarKind tv) - AGlobal (ATyCon tc) -> returnTc (tyConKind tc) + AThing kind -> returnM kind + ATyVar tv -> returnM (tyVarKind tv) + AGlobal (ATyCon tc) -> returnM (tyConKind tc) other -> failWithTc (wrongThingErr "type" thing name) kcClass cls -- Must be a class - = tcLookup cls `thenNF_Tc` \ thing -> + = tcLookup cls `thenM` \ thing -> case thing of - AThing kind -> returnTc kind - AGlobal (AClass cls) -> returnTc (tyConKind (classTyCon cls)) + AThing kind -> returnM kind + AGlobal (AClass cls) -> returnM (tyConKind (classTyCon cls)) other -> failWithTc (wrongThingErr "class" thing cls) \end{code} @@ -398,45 +466,62 @@ tc_type :: RenamedHsType -> TcM Type tc_type ty@(HsTyVar name) = tc_app ty [] +tc_type (HsKindSig ty k) + = tc_type ty -- Kind checking done already + tc_type (HsListTy ty) - = tc_type ty `thenTc` \ tau_ty -> - returnTc (mkListTy tau_ty) + = tc_type ty `thenM` \ tau_ty -> + returnM (mkListTy tau_ty) -tc_type (HsTupleTy (HsTupCon _ boxity arity) tys) +tc_type (HsPArrTy ty) + = tc_type ty `thenM` \ tau_ty -> + returnM (mkPArrTy tau_ty) + +tc_type (HsTupleTy (HsTupCon boxity arity) tys) = ASSERT( tys `lengthIs` arity ) - tc_types tys `thenTc` \ tau_tys -> - returnTc (mkTupleTy boxity arity tau_tys) + tc_types tys `thenM` \ tau_tys -> + returnM (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 ty1 `thenM` \ tau_ty1 -> + tc_type ty2 `thenM` \ tau_ty2 -> + returnM (mkFunTy tau_ty1 tau_ty2) + +tc_type (HsOpTy ty1 HsArrow ty2) + = tc_type ty1 `thenM` \ tau_ty1 -> + tc_type ty2 `thenM` \ tau_ty2 -> + returnM (mkFunTy tau_ty1 tau_ty2) + +tc_type (HsOpTy ty1 (HsTyOp op) ty2) + = tc_type ty1 `thenM` \ tau_ty1 -> + tc_type ty2 `thenM` \ tau_ty2 -> + tc_fun_type op [tau_ty1,tau_ty2] + +tc_type (HsParTy ty) -- Remove the parentheses markers + = tc_type ty 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] + returnM (mkTyConApp genUnitTyCon []) -tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2] +tc_type ty@(HsAppTy ty1 ty2) + = addErrCtxt (appKindCtxt (ppr ty)) $ + tc_app ty1 [ty2] tc_type (HsPredTy pred) - = tc_pred pred `thenTc` \ pred' -> - returnTc (mkPredTy pred') + = tc_pred pred `thenM` \ pred' -> + returnM (mkPredTy pred') tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty) = let - kind_check = kcHsContext ctxt `thenTc_` kcHsType ty + kind_check = kcHsContext ctxt `thenM_` 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) + mappM tc_pred ctxt `thenM` \ theta -> + tc_type ty `thenM` \ tau -> + returnM (mkSigmaTy tyvars theta tau) -tc_types arg_tys = mapTc tc_type arg_tys +tc_types arg_tys = mappM tc_type arg_tys \end{code} Help functions for type applications @@ -448,27 +533,22 @@ 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 -> + = tc_types tys `thenM` \ 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) + other -> tc_type ty `thenM` \ fun_ty -> + returnM (mkAppTys fun_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 name arg_tys - = tcLookup name `thenTc` \ thing -> + = tcLookup name `thenM` \ thing -> case thing of - ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys) + ATyVar tv -> returnM (mkAppTys (mkTyVarTy tv) arg_tys) - AGlobal (ATyCon tc) - | isSynTyCon tc -> returnTc (mkSynTy tc arg_tys) - | otherwise -> returnTc (mkTyConApp tc arg_tys) + AGlobal (ATyCon tc) -> returnM (mkGenTyConApp tc arg_tys) other -> failWithTc (wrongThingErr "type constructor" thing name) \end{code} @@ -477,18 +557,22 @@ tc_fun_type name arg_tys Contexts ~~~~~~~~ \begin{code} +tcHsPred pred = kc_pred pred `thenM_` tc_pred pred + -- Is happy with a partial application, e.g. (ST s) + -- Used from TcDeriv + tc_pred assn@(HsClassP class_name tys) - = tcAddErrCtxt (appKindCtxt (ppr assn)) $ - tc_types tys `thenTc` \ arg_tys -> - tcLookupGlobal class_name `thenTc` \ thing -> + = addErrCtxt (appKindCtxt (ppr assn)) $ + tc_types tys `thenM` \ arg_tys -> + tcLookupGlobal class_name `thenM` \ thing -> case thing of - AClass clas -> returnTc (ClassP clas arg_tys) + AClass clas -> returnM (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) + = addErrCtxt (appKindCtxt (ppr assn)) $ + tc_type ty `thenM` \ arg_ty -> + returnM (IParam name arg_ty) \end{code} @@ -531,8 +615,6 @@ been instantiated. \begin{code} data TcSigInfo = TySigInfo - Name -- N, the Name in corresponding binding - TcId -- *Polymorphic* binder for this value... -- Has name = N @@ -550,15 +632,21 @@ data TcSigInfo 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 + ppr (TySigInfo id tyvars theta tau _ inst loc) = + ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau + +tcSigPolyId :: TcSigInfo -> TcId +tcSigPolyId (TySigInfo id _ _ _ _ _ _) = id + +tcSigMonoId :: TcSigInfo -> TcId +tcSigMonoId (TySigInfo _ _ _ _ id _ _) = id 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 +maybeSig (sig@(TySigInfo sig_id _ _ _ _ _ _) : sigs) name + | name == idName sig_id = Just sig + | otherwise = maybeSig sigs name \end{code} @@ -566,13 +654,13 @@ maybeSig (sig@(TySigInfo sig_name _ _ _ _ _ _ _) : sigs) name 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 + = addSrcLoc src_loc $ + tcHsSigType (FunSigCtxt v) ty `thenM` \ sigma_tc_ty -> + mkTcSig (mkLocalId v sigma_tc_ty) `thenM` \ sig -> + returnM sig -mkTcSig :: TcId -> SrcLoc -> NF_TcM TcSigInfo -mkTcSig poly_id src_loc +mkTcSig :: TcId -> TcM TcSigInfo +mkTcSig poly_id = -- 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 @@ -580,290 +668,79 @@ 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) = tcSplitForAllTys (idType poly_id) - in - tcInstSigTyVars SigTv tyvars `thenNF_Tc` \ tyvars' -> - -- Make *signature* type variables + tcInstType SigTv (idType poly_id) `thenM` \ (tyvars', theta', tau') -> - 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 -> + getInstLoc SignatureOrigin `thenM` \ inst_loc -> + newMethod inst_loc poly_id + (mkTyVarTys tyvars') + theta' tau' `thenM` \ inst -> -- We make a Method even if it's not overloaded; no harm + -- But do not extend the LIE! We're just making an Id. - returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc) - where - name = idName poly_id + getSrcLocM `thenM` \ src_loc -> + returnM (TySigInfo poly_id tyvars' theta' tau' + (instToId inst) [inst] src_loc) \end{code} - %************************************************************************ %* * -\subsection{Checking signature type variables} +\subsection{Errors and contexts} %* * %************************************************************************ -@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 - -- 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 - = -- "check" checks each sig tyvar in turn - foldlNF_Tc check - (env2, emptyVarEnv, []) - (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) -> - - failWithTcM (env3, main_msg $$ vcat msgs) - where - (env1, tidy_tvs) = tidyOpenTyVars 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)! - 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) or (d)! Type variable escapes - -- The least comprehensible, so put it last - -- Game plan: - -- a) get the local TcIds and TyVars 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 (tcLEnvElts 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 - -> [TcTyThing] - -> NF_TcM (TidyEnv, [SDoc]) - -find_globals tv tidy_env things - = go tidy_env [] things - where - go tidy_env acc [] = returnNF_Tc (tidy_env, acc) - go tidy_env acc (thing : things) - = find_thing ignore_it tidy_env thing `thenNF_Tc` \ (tidy_env1, maybe_doc) -> - case maybe_doc of - Just d -> go tidy_env1 (d:acc) things - Nothing -> go tidy_env1 acc things - - ignore_it ty = not (tv `elemVarSet` tyVarsOfType ty) - ------------------------ -find_thing ignore_it tidy_env (ATcId id) - = zonkTcType (idType id) `thenNF_Tc` \ id_ty -> - if ignore_it id_ty then - returnNF_Tc (tidy_env, Nothing) - else let - (tidy_env', tidy_ty) = tidyOpenType tidy_env id_ty - msg = sep [ppr id <+> dcolon <+> ppr tidy_ty, - nest 2 (parens (ptext SLIT("bound at") <+> - ppr (getSrcLoc id)))] - in - returnNF_Tc (tidy_env', Just msg) - -find_thing ignore_it tidy_env (ATyVar tv) - = zonkTcTyVar tv `thenNF_Tc` \ tv_ty -> - if ignore_it tv_ty then - returnNF_Tc (tidy_env, Nothing) - else let - (tidy_env1, tv1) = tidyOpenTyVar tidy_env tv - (tidy_env2, tidy_ty) = tidyOpenType tidy_env1 tv_ty - msg = sep [ptext SLIT("Type variable") <+> quotes (ppr tv1) <+> eq_stuff, nest 2 bound_at] - - eq_stuff | Just tv' <- Type.getTyVar_maybe tv_ty, tv == tv' = empty - | otherwise = equals <+> ppr tv_ty - -- It's ok to use Type.getTyVar_maybe because ty is zonked by now - - bound_at | isMutTyVar tv = mut_info -- The expected case - | otherwise = empty - - mut_info = sep [ptext SLIT("is bound by the") <+> ppr (mutTyVarDetails tv), - ptext SLIT("at") <+> ppr (getSrcLoc tv)] - in - returnNF_Tc (tidy_env2, Just msg) - ------------------------ -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') = tidyOpenTyVar 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:"), - nest 2 (vcat 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} +hoistForAllTys :: Type -> Type +-- Used for user-written type signatures only +-- Move all the foralls and constraints to the top +-- e.g. T -> forall a. a ==> forall a. T -> a +-- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int +-- +-- Also: eliminate duplicate constraints. These can show up +-- when hoisting constraints, notably implicit parameters. +-- +-- We want to 'look through' type synonyms when doing this +-- so it's better done on the Type than the HsType -These two context are used with checkSigTyVars - -\begin{code} -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) = tidyOpenTyVars 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 - ] +hoistForAllTys ty + = let + no_shadow_ty = deShadowTy ty + -- Running over ty with an empty substitution gives it the + -- no-shadowing property. This is important. For example: + -- type Foo r = forall a. a -> r + -- foo :: Foo (Foo ()) + -- Here the hoisting should give + -- foo :: forall a a1. a -> a1 -> () + -- + -- What about type vars that are lexically in scope in the envt? + -- We simply rely on them having a different unique to any + -- binder in 'ty'. Otherwise we'd have to slurp the in-scope-tyvars + -- out of the envt, which is boring and (I think) not necessary. 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))]) + case hoist no_shadow_ty of + (tvs, theta, body) -> mkForAllTys tvs (mkFunTys (nubBy tcEqType theta) body) + -- The 'nubBy' eliminates duplicate constraints, + -- notably implicit parameters 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 + hoist ty + | (tvs1, body_ty) <- tcSplitForAllTys ty, + not (null tvs1) + = case hoist body_ty of + (tvs2,theta,tau) -> (tvs1 ++ tvs2, theta, tau) + + | Just (arg, res) <- tcSplitFunTy_maybe ty + = let + arg' = hoistForAllTys arg -- Don't forget to apply hoist recursively + in -- to the argument type + if (isPredTy arg') then + case hoist res of + (tvs,theta,tau) -> (tvs, arg':theta, tau) + else + case hoist res of + (tvs,theta,tau) -> (tvs, theta, mkFunTy arg' tau) + + | otherwise = ([], [], ty) \end{code} @@ -885,10 +762,11 @@ 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 (AGlobal (ATyCon _)) = ptext SLIT("Type constructor") + pp_thing (AGlobal (AClass _)) = ptext SLIT("Class") + pp_thing (AGlobal (AnId _)) = ptext SLIT("Identifier") + pp_thing (AGlobal (ADataCon _)) = ptext SLIT("Data constructor") pp_thing (ATyVar _) = ptext SLIT("Type variable") - pp_thing (ATcId _) = ptext SLIT("Local identifier") + pp_thing (ATcId _ _ _) = ptext SLIT("Local identifier") pp_thing (AThing _) = ptext SLIT("Utterly bogus") \end{code}