X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=cdd2c7ec28f3d58dd6d49769b6e853c20452e7a7;hb=dd8235367cd61e6811eee42b78c6514e77428c7c;hp=eae1c69d277a5a815e4779ab123267aca08a60b4;hpb=ff755dd9a0a0ad2f106c323852553ea247f16141;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index eae1c69..cdd2c7e 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -4,60 +4,58 @@ \section[TcClassDcl]{Typechecking class declarations} \begin{code} -module TcClassDcl ( kcClassDecl, tcClassDecl1, tcClassDecls2, mkImplicitClassBinds, - tcMethodBind, checkFromThisClass +module TcClassDcl ( tcClassDecl1, checkValidClass, tcClassDecls2, + tcMethodBind, badMethodErr ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), - InPat(..), HsBinds(..), GRHSs(..), - HsExpr(..), HsLit(..), HsType(..), HsPred(..), - mkSimpleMatch, - andMonoBinds, andMonoBindList, getTyVarName, - isClassDecl, isClassOpSig, isPragSig, collectMonoBinders +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + getClassDeclSysNames, placeHolderType ) -import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas, +import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) ) +import RnHsSyn ( RenamedTyClDecl, RenamedClassOpSig, RenamedMonoBinds, - RenamedContext, RenamedHsDecl, RenamedSig + RenamedSig, maybeGenericMatch ) -import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) +import TcHsSyn ( TcMonoBinds ) -import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod ) -import TcEnv ( TcId, ValueEnv, TcTyThing(..), tcAddImportedIdInfo, - tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, - tcExtendLocalValEnv +import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + instToId, newDicts, newMethod ) +import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo, + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv ) import TcBinds ( tcBindWithSigs, tcSpecSigs ) -import TcTyDecls ( mkNewTyConRep ) -import TcMonad -import TcMonoType ( kcHsType, tcHsTopType, tcExtendTopTyVarScope, - tcContext, checkSigTyVars, sigCtxt, mkTcSig +import TcMonoType ( tcHsType, tcHsTheta, checkSigTyVars, sigCtxt, mkTcSig ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcMType ( tcInstSigTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) ) +import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar, + mkSigmaTy, mkTyVarTys, mkPredTys, mkClassPred, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr, tcGetTyVar ) -import TcInstUtil ( classDataCon ) +import TcMonad +import Generics ( mkGenericRhs, validGenericMethodType ) import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) -import Bag ( unionManyBags, bagToList ) -import Class ( mkClass, classBigSig, classSelIds, Class, ClassOpItem ) -import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods ) +import Class ( classTyVars, classBigSig, classTyCon, className, + Class, ClassOpItem, DefMeth (..) ) import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) -import DataCon ( mkDataCon, dataConId, dataConWrapId, notMarkedStrict ) -import Id ( Id, setInlinePragma, idUnfolding, idType, idName ) -import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) ) +import DataCon ( mkDataCon ) +import Id ( Id, idType, idName, setIdLocalExported ) +import Module ( Module ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) import NameSet ( emptyNameSet ) import Outputable -import Type ( Type, ThetaType, ClassContext, - mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, mkDictTys, - mkSigmaTy, mkForAllTys, mkClassPred, classesOfPreds, - boxedTypeKind, mkArrowKind - ) -import Var ( tyVarKind, TyVar ) +import Var ( TyVar ) import VarSet ( mkVarSet, emptyVarSet ) -import TyCon ( AlgTyConFlavour(..), mkClassTyCon ) -import Maybes ( seqMaybe ) -import FiniteMap ( lookupWithDefaultFM ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count, isSingleton, lengthIs, equalLength ) +import Maybes ( seqMaybe, maybeToBool ) \end{code} @@ -97,263 +95,198 @@ Death to "ExpandingDicts". %************************************************************************ %* * -\subsection{Kind checking} -%* * -%************************************************************************ - -\begin{code} -kcClassDecl (ClassDecl context class_name - tyvar_names fundeps class_sigs def_methods pragmas - _ _ _ _ src_loc) - = -- CHECK ARITY 1 FOR HASKELL 1.4 - checkTc (opt_GlasgowExts || length tyvar_names == 1) - (classArityErr class_name) `thenTc_` - - -- Get the (mutable) class kind - tcLookupTy class_name `thenNF_Tc` \ (kind, _) -> - - -- Make suitable tyvars and do kind checking - -- The net effect is to mutate the class kind - tcExtendTopTyVarScope kind tyvar_names $ \ _ _ -> - tcContext context `thenTc_` - mapTc kc_sig the_class_sigs `thenTc_` - - returnTc () - where - the_class_sigs = filter isClassOpSig class_sigs - - kc_sig (ClassOpSig _ _ _ op_ty loc) = tcAddSrcLoc loc (kcHsType op_ty) -\end{code} - - -%************************************************************************ -%* * \subsection{Type checking} %* * %************************************************************************ \begin{code} -tcClassDecl1 rec_env rec_vrcs - (ClassDecl context class_name - tyvar_names fundeps class_sigs def_methods pragmas - tycon_name datacon_name datacon_wkr_name sc_sel_names src_loc) + +tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 rec_env + (ClassDecl {tcdCtxt = context, tcdName = class_name, + tcdTyVars = tyvar_names, tcdFDs = fundeps, + tcdSigs = class_sigs, tcdMeths = def_methods, + tcdSysNames = sys_names, tcdLoc = src_loc}) = -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupTy class_name `thenTc` \ (class_kind, AClass rec_class arity) -> - tcExtendTopTyVarScope class_kind tyvar_names $ \ tyvars _ -> - -- The class kind is by now immutable + tcLookupClass class_name `thenTc` \ clas -> + let + tyvars = classTyVars clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names + in + tcExtendTyVarEnv tyvars $ + + checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env -> -- CHECK THE CONTEXT --- traceTc (text "tcClassCtxt" <+> ppr class_name) `thenTc_` - tcClassContext class_name rec_class tyvars context sc_sel_names - `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) -> --- traceTc (text "tcClassCtxt done" <+> ppr class_name) `thenTc_` - - -- CHECK THE FUNCTIONAL DEPENDENCIES, - tcFundeps fundeps `thenTc` \ fds -> + -- The renamer has already checked that the context mentions + -- only the type variable of the class decl. + -- Context is already kind-checked + ASSERT( equalLength context sc_sel_names ) + tcHsTheta context `thenTc` \ sc_theta -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env rec_class tyvars) - (filter isClassOpSig class_sigs) - `thenTc` \ sig_stuff -> + mapTc (tcClassSig rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff -> - -- MAKE THE CLASS OBJECT ITSELF + -- MAKE THE CLASS DETAILS let (op_tys, op_items) = unzip sig_stuff - clas = mkClass class_name tyvars fds - sc_theta sc_sel_ids op_items - tycon - + sc_tys = mkPredTys sc_theta dict_component_tys = sc_tys ++ op_tys - new_or_data = case dict_component_tys of - [_] -> NewTyCon (mkNewTyConRep tycon) - other -> DataTyCon + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] dict_con = mkDataCon datacon_name - [notMarkedStrict | _ <- dict_component_tys] - [{- No labelled fields -}] - tyvars - [{-No context-}] - [{-No existential tyvars-}] [{-Or context-}] - dict_component_tys - tycon dict_con_id dict_wrap_id + [NotMarkedStrict | _ <- dict_component_tys] + [{- No labelled fields -}] + tyvars + [{-No context-}] + [{-No existential tyvars-}] [{-Or context-}] + dict_component_tys + (classTyCon clas) + dict_con_id dict_wrap_id dict_con_id = mkDataConId datacon_wkr_name dict_con dict_wrap_id = mkDataConWrapId dict_con - - argvrcs = lookupWithDefaultFM rec_vrcs (pprPanic "tcClassDecl1: argvrcs:" $ - ppr tycon_name) - tycon_name - - tycon = mkClassTyCon tycon_name - class_kind - tyvars - argvrcs - dict_con -- Constructors - clas -- Yes! It's a dictionary - new_or_data in - returnTc (class_name, AClass clas arity) -\end{code} - -\begin{code} -tcFundeps = mapTc tc_fundep -tc_fundep (us, vs) = - mapTc tc_fd_tyvar us `thenTc` \ us' -> - mapTc tc_fd_tyvar vs `thenTc` \ vs' -> - returnTc (us', vs') -tc_fd_tyvar v = - tcLookupTy v `thenTc` \(_, ATyVar tv) -> - returnTc tv + returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con) \end{code} \begin{code} -tcClassContext :: Name -> Class -> [TyVar] - -> RenamedContext -- class context - -> [Name] -- Names for superclass selectors - -> TcM s (ClassContext, -- the superclass context - [Type], -- types of the superclass dictionaries - [Id]) -- superclass selector Ids - -tcClassContext class_name rec_class rec_tyvars context sc_sel_names - = -- Check the context. - -- The renamer has already checked that the context mentions - -- only the type variable of the class decl. +checkDefaultBinds :: Class -> [Name] -> Maybe RenamedMonoBinds + -> TcM (Maybe (NameEnv Bool)) + -- The returned environment says + -- x not in env => no default method + -- x -> True => generic default method + -- x -> False => polymorphic default method + + -- Check default bindings + -- a) must be for a class op for this class + -- b) must be all generic or all non-generic + -- and return a mapping from class-op to DefMeth info + + -- But do all this only for source binds + +checkDefaultBinds clas ops Nothing + = returnTc Nothing + +checkDefaultBinds clas ops (Just mbs) + = go mbs `thenTc` \ dm_env -> + returnTc (Just dm_env) + where + go EmptyMonoBinds = returnTc emptyNameEnv - -- For std Haskell check that the context constrains only tyvars - (if opt_GlasgowExts then - returnTc [] - else - mapTc check_constraint context - ) `thenTc_` + go (AndMonoBinds b1 b2) + = go b1 `thenTc` \ dm_info1 -> + go b2 `thenTc` \ dm_info2 -> + returnTc (dm_info1 `plusNameEnv` dm_info2) - tcContext context `thenTc` \ sc_theta -> + go (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ - let - sc_theta' = classesOfPreds sc_theta - sc_tys = mkDictTys sc_theta' - sc_sel_ids = [mkDictSelId sc_name rec_class | sc_name <- sc_sel_names] - in - -- Done - returnTc (sc_theta', sc_tys, sc_sel_ids) + -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_` - where - check_constraint sc@(HsPClass c tys) = checkTc (all is_tyvar tys) - (superClassErr class_name sc) + -- Check that all the defns ar generic, or none are + checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_` - is_tyvar (HsTyVar _) = True - is_tyvar other = False + returnTc (unitNameEnv op all_generic) + where + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic +\end{code} -tcClassSig :: ValueEnv -- Knot tying only! +\begin{code} +tcClassSig :: RecTcEnv -- Knot tying only! -> Class -- ...ditto... -> [TyVar] -- The class type variable, used for error check only + -> Maybe (NameEnv Bool) -- Info about default methods; + -- Nothing => imported class defn with no method binds -> RenamedClassOpSig - -> TcM s (Type, -- Type of the method + -> TcM (Type, -- Type of the method ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding +-- This warrants an explanation: we need to separate generic +-- default methods and default methods later on in the compiler +-- so we distinguish them in checkDefaultBinds, and pass this knowledge in the +-- Class.DefMeth data structure. -tcClassSig rec_env rec_clas rec_clas_tyvars - (ClassOpSig op_name dm_name explicit_dm - op_ty src_loc) +tcClassSig unf_env clas clas_tyvars maybe_dm_env + (ClassOpSig op_name sig_dm op_ty src_loc) = tcAddSrcLoc src_loc $ -- Check the type signature. NB that the envt *already has* -- bindings for the type variables; see comments in TcTyAndClassDcls. + tcHsType op_ty `thenTc` \ local_ty -> - -- NB: Renamer checks that the class type variable is mentioned in local_ty, - -- and that it is not constrained by theta --- traceTc (text "tcClassSig" <+> ppr op_name) `thenTc_` - tcHsTopType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy rec_clas_tyvars - [mkClassPred rec_clas (mkTyVarTys rec_clas_tyvars)] - local_ty + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] -- Build the selector id and default method id - sel_id = mkDictSelId op_name rec_clas - dm_id = mkDefaultMethodId dm_name rec_clas global_ty - final_dm_id = tcAddImportedIdInfo rec_env dm_id - in --- traceTc (text "tcClassSig done" <+> ppr op_name) `thenTc_` - returnTc (local_ty, (sel_id, final_dm_id, explicit_dm)) -\end{code} - - -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ + sel_id = mkDictSelId op_name clas + DefMeth dm_name = sig_dm -The purpose of pass 2 is -\begin{enumerate} -\item -to beat on the explicitly-provided default-method decls (if any), -using them to produce a complete set of default-method decls. -(Omitted ones elicit an error message.) -\item -to produce a definition for the selector function for each method -and superclass dictionary. -\end{enumerate} + dm_info = case maybe_dm_env of + Nothing -> sig_dm + Just dm_env -> mk_src_dm_info dm_env -Pass~2 only applies to locally-defined class declarations. - -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. - -\begin{code} -tcClassDecls2 :: [RenamedHsDecl] - -> NF_TcM s (LIE, TcMonoBinds) - -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, isClassDecl cls_decl] - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_name + in + returnTc (local_ty, (sel_id, dm_info)) \end{code} -@tcClassDecl2@ is the business end of things. +checkValidClass is called once the mutually-recursive knot has been +tied, so we can look at things freely. \begin{code} -tcClassDecl2 :: RenamedTyClDecl -- The class declaration - -> NF_TcM s (LIE, TcMonoBinds) +checkValidClass :: Class -> TcM () +checkValidClass cls + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ gla_exts -> -tcClassDecl2 (ClassDecl context class_name - tyvar_names _ class_sigs default_binds pragmas _ _ _ _ src_loc) + -- Check that the class is unary, unless GlaExs + checkTc (not (null tyvars)) (nullaryClassErr cls) `thenTc_` + checkTc (gla_exts || unary) (classArityErr cls) `thenTc_` - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) + -- Check the super-classes + checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_` - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc src_loc $ - tcLookupTy class_name `thenNF_Tc` \ (_, AClass clas _) -> - tcDefaultMethodBinds clas default_binds class_sigs -\end{code} + -- Check the class operations + mapTc_ check_op op_stuff `thenTc_` -\begin{code} -mkImplicitClassBinds :: [Class] -> NF_TcM s ([Id], TcMonoBinds) -mkImplicitClassBinds classes - = returnNF_Tc (concat cls_ids_s, andMonoBindList binds_s) - -- The selector binds are already in the selector Id's unfoldings - where - (cls_ids_s, binds_s) = unzip (map mk_implicit classes) + -- Check that if the class has generic methods, then the + -- class has only one parameter. We can't do generic + -- multi-parameter type classes! + checkTc (unary || no_generics) (genericMultiParamErr cls) - mk_implicit clas = (all_cls_ids, binds) - where - dict_con = classDataCon clas - all_cls_ids = dataConId dict_con : cls_ids - cls_ids = dataConWrapId dict_con : classSelIds clas - - -- The wrapper and selectors get bindings, the worker does not - binds | isLocallyDefined clas = idsToMonoBinds cls_ids - | otherwise = EmptyMonoBinds + where + (tyvars, theta, _, op_stuff) = classBigSig cls + unary = isSingleton tyvars + no_generics = null [() | (_, GenDefMeth) <- op_stuff] + + check_op (sel_id, dm) + = checkValidTheta SigmaCtxt (tail theta) `thenTc_` + -- The 'tail' removes the initial (C a) from the + -- class itself, leaving just the method type + + checkValidType (FunSigCtxt op_name) tau `thenTc_` + + -- Check that for a generic method, the type of + -- the method is sufficiently simple + checkTc (dm /= GenDefMeth || validGenericMethodType op_ty) + (badGenericMethodType op_name op_ty) + where + op_name = idName sel_id + op_ty = idType sel_id + (_,theta,tau) = tcSplitSigmaTy op_ty \end{code} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -415,97 +348,123 @@ dfun.Foo.List dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -tcDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> [RenamedSig] - -> TcM s (LIE, TcMonoBinds) - -tcDefaultMethodBinds clas default_binds sigs - = -- Check that the default bindings come from this class - checkFromThisClass clas op_items default_binds `thenNF_Tc_` - - -- Do each default method separately - -- For Hugs compatibility we make a default-method for every - -- class op, regardless of whether or not the programmer supplied an - -- explicit default decl for the class. GHC will actually never - -- call the default method for such operations, because it'll whip up - -- a more-informative default method at each instance decl. - mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) -> - - returnTc (plusLIEs const_lies, andMonoBindList defm_binds) +tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id]) + +tcClassDecls2 this_mod decls + = foldr combine + (returnNF_Tc (emptyLIE, EmptyMonoBinds, [])) + [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls] + -- The 'Just' picks out source ClassDecls where - prags = filter isPragSig sigs + combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1, ids1) -> + tc2 `thenNF_Tc` \ (lie2, binds2, ids2) -> + returnNF_Tc (lie1 `plusLIE` lie2, + binds1 `AndMonoBinds` binds2, + ids1 ++ ids2) +\end{code} - (tyvars, _, _, op_items) = classBigSig clas +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) - origin = ClassDeclOrigin +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds, [Id]) - -- We make a separate binding for each default method. - -- At one time I used a single AbsBinds for all of them, thus - -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } - -- But that desugars into - -- ds = \d -> (..., ..., ...) - -- dm1 = \d -> case ds d of (a,b,c) -> a - -- And since ds is big, it doesn't get inlined, so we don't get good - -- default methods. Better to make separate AbsBinds for each - - tc_dm op_item@(_, dm_id, _) - = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) -> - let - theta = [(mkClassPred clas inst_tys)] - in - newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - let - avail_insts = this_dict - in - tcExtendTyVarEnvForMeths tyvars clas_tyvars ( - tcMethodBind clas origin clas_tyvars inst_tys theta - default_binds prags False - op_item - ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) -> +tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs, + tcdMeths = Just default_binds, tcdLoc = src_loc}) + = -- The 'Just' picks out source ClassDecls + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds, [])) $ + tcAddSrcLoc src_loc $ + tcLookupClass class_name `thenNF_Tc` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each + let + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags + in + mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) -> + + returnTc (plusLIEs const_lies, andMonoBindList defm_binds, concat dm_ids_s) - tcAddErrCtxt (defltMethCtxt clas) $ + +tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, []) +tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, []) + -- Generate code for polymorphic default methods only + -- (Generic default methods have turned into instance decls by now.) + -- This is incompatible with Hugs, which expects a polymorphic + -- default method for every class op, regardless of whether or not + -- the programmer supplied an explicit default decl for the class. + -- (If necessary we can fix that, but we don't have a convenient Id to hand.) + +tcDefMeth clas tyvars binds_in prags op_item@(sel_id, DefMeth dm_name) + = tcInstSigTyVars ClsTv tyvars `thenNF_Tc` \ clas_tyvars -> + let + dm_ty = idType sel_id -- Same as dict selector! + -- The default method's type should really come from the + -- iface file, since it could be usage-generalised, but this + -- requires altering the mess of knots in TcModule and I'm + -- too scared to do that. Instead, I have disabled generalisation + -- of types of default methods (and dict funs) by annotating them + -- TyGenNever (in MkId). Ugh! KSW 1999-09. + + inst_tys = mkTyVarTys clas_tyvars + theta = [mkClassPred clas inst_tys] + dm_id = mkDefaultMethodId dm_name dm_ty + local_dm_id = setIdLocalExported dm_id + -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId + in + newDicts origin theta `thenNF_Tc` \ [this_dict] -> + + tcExtendTyVarEnvForMeths tyvars clas_tyvars ( + tcMethodBind clas origin clas_tyvars inst_tys theta + binds_in prags False op_item + ) `thenTc` \ (defm_bind, insts_needed, local_dm_inst) -> - -- tcMethodBind has checked that the class_tyvars havn't - -- been unified with each other or another type, but we must - -- still zonk them before passing them to tcSimplifyAndCheck - mapNF_Tc zonkTcTyVarBndr clas_tyvars `thenNF_Tc` \ clas_tyvars' -> + tcAddErrCtxt (defltMethCtxt clas) $ - -- Check the context - tcSimplifyAndCheck - (ptext SLIT("class") <+> ppr clas) - (mkVarSet clas_tyvars') - avail_insts - insts_needed `thenTc` \ (const_lie, dict_binds) -> + -- Check the context + tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed `thenTc` \ (const_lie, dict_binds) -> + + -- Simplification can do unification + checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' -> - let - full_bind = AbsBinds - clas_tyvars' - [this_dict_id] - [(clas_tyvars', dm_id, local_dm_id)] - emptyNameSet -- No inlines (yet) - (dict_binds `andMonoBinds` defm_bind) - in - returnTc (full_bind, const_lie) -\end{code} - -\begin{code} -checkFromThisClass :: Class -> [ClassOpItem] -> RenamedMonoBinds -> NF_TcM s () -checkFromThisClass clas op_items mono_binds - = mapNF_Tc check_from_this_class bndrs `thenNF_Tc_` - returnNF_Tc () + let + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', local_dm_id, instToId local_dm_inst)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) + in + returnTc (full_bind, const_lie, [dm_id]) where - check_from_this_class (bndr, loc) - | nameOccName bndr `elem` sel_names = returnNF_Tc () - | otherwise = tcAddSrcLoc loc $ - addErrTc (badMethodErr bndr clas) - sel_names = [getOccName sel_id | (sel_id,_,_) <- op_items] - bndrs = bagToList (collectMonoBinders mono_binds) + origin = ClassDeclOrigin \end{code} + +%************************************************************************ +%* * +\subsection{Typechecking a method} +%* * +%************************************************************************ + @tcMethodBind@ is used to type-check both default-method and instance-decl method declarations. We must type-check methods one at a time, because their signatures may have different contexts and @@ -527,124 +486,168 @@ tcMethodBind -> [RenamedSig] -- Pramgas (just for this one) -> Bool -- True <=> This method is from an instance declaration -> ClassOpItem -- The method selector and default-method Id - -> TcM s (TcMonoBinds, LIE, (LIE, TcId)) + -> TcM (TcMonoBinds, LIE, Inst) tcMethodBind clas origin inst_tyvars inst_tys inst_theta - meth_binds prags is_inst_decl - (sel_id, dm_id, explicit_dm) - = tcGetSrcLoc `thenNF_Tc` \ loc -> - - newMethod origin sel_id inst_tys `thenNF_Tc` \ meth@(_, meth_id) -> - mkTcSig meth_id loc `thenNF_Tc` \ sig_info -> - - let - meth_name = idName meth_id - maybe_user_bind = find_bind meth_name meth_binds - - no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False} - - meth_bind = case maybe_user_bind of - Just bind -> bind - Nothing -> mk_default_bind meth_name loc - - meth_prags = find_prags meth_name prags - in - - -- Warn if no method binding, only if -fwarn-missing-methods - warnTc (is_inst_decl && opt_WarnMissingMethods && no_user_bind && not explicit_dm) - (omittedMethodWarn sel_id clas) `thenNF_Tc_` - - -- Check the bindings; first add inst_tyvars to the envt - -- so that we don't quantify over them in nested places - -- The *caller* put the class/inst decl tyvars into the envt - tcExtendGlobalTyVars (mkVarSet inst_tyvars) ( - tcAddErrCtxt (methodCtxt sel_id) $ - tcBindWithSigs NotTopLevel meth_bind - [sig_info] meth_prags NonRecursive - ) `thenTc` \ (binds, insts, _) -> - - - tcExtendLocalValEnv [(meth_name, meth_id)] ( - tcSpecSigs meth_prags - ) `thenTc` \ (prag_binds1, prag_lie) -> - - -- The prag_lie for a SPECIALISE pragma will mention the function - -- itself, so we have to simplify them away right now lest they float - -- outwards! - bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) -> - - - -- Now check that the instance type variables - -- (or, in the case of a class decl, the class tyvars) - -- have not been unified with anything in the environment - tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $ - checkSigTyVars inst_tyvars emptyVarSet `thenTc_` - - returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, - insts `plusLIE` prag_lie', - meth) - where - sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_name - - sel_name = idName sel_id - - -- The renamer just puts the selector ID as the binder in the method binding - -- but we must use the method name; so we substitute it here. Crude but simple. - find_bind meth_name (FunMonoBind op_name fix matches loc) - | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc) - find_bind meth_name (AndMonoBinds b1 b2) - = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2 - find_bind meth_name other = Nothing -- Default case - - - -- Find the prags for this method, and replace the - -- selector name with the method name - find_prags meth_name [] = [] - find_prags meth_name (SpecSig name ty loc : prags) - | name == sel_name = SpecSig meth_name ty loc : find_prags meth_name prags - find_prags meth_name (InlineSig name phase loc : prags) - | name == sel_name = InlineSig meth_name phase loc : find_prags meth_name prags - find_prags meth_name (NoInlineSig name phase loc : prags) - | name == sel_name = NoInlineSig meth_name phase loc : find_prags meth_name prags - find_prags meth_name (prag:prags) = find_prags meth_name prags - - mk_default_bind local_meth_name loc - = FunMonoBind local_meth_name - False -- Not infix decl - [mkSimpleMatch [] (default_expr loc) Nothing loc] - loc - - default_expr loc - | explicit_dm = HsVar (getName dm_id) -- There's a default method - | otherwise = error_expr loc -- No default method - - error_expr loc = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) - (HsLit (HsString (_PK_ (error_msg loc)))) - - error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + meth_binds prags is_inst_decl (sel_id, dm_info) + = tcGetSrcLoc `thenNF_Tc` \ loc -> + newMethod origin sel_id inst_tys `thenNF_Tc` \ meth -> + let + meth_id = instToId meth + meth_name = idName meth_id + sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id + meth_prags = find_prags (idName sel_id) meth_name prags + in + mkTcSig meth_id loc `thenNF_Tc` \ sig_info -> + + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnTc user_bind + Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs -> + returnTc (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs placeHolderType loc] loc) + ) `thenTc` \ meth_bind -> + -- Check the bindings; first add inst_tyvars to the envt + -- so that we don't quantify over them in nested places + -- The *caller* put the class/inst decl tyvars into the envt + tcExtendGlobalTyVars (mkVarSet inst_tyvars) + (tcAddErrCtxt (methodCtxt sel_id) $ + tcBindWithSigs NotTopLevel meth_bind + [sig_info] meth_prags NonRecursive + ) `thenTc` \ (binds, insts, _) -> + + tcExtendLocalValEnv [(meth_name, meth_id)] + (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) -> + + -- The prag_lie for a SPECIALISE pragma will mention the function + -- itself, so we have to simplify them away right now lest they float + -- outwards! + bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) -> + + -- Now check that the instance type variables + -- (or, in the case of a class decl, the class tyvars) + -- have not been unified with anything in the environment + -- + -- We do this for each method independently to localise error messages + -- ...and this is why the call to tcExtendGlobalTyVars must be here + -- rather than in the caller + tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $ + checkSigTyVars inst_tyvars emptyVarSet `thenTc_` + + returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, + insts `plusLIE` prag_lie', + meth) + + -- The user didn't supply a method binding, + -- so we have to make up a default binding + -- The RHS of a default method depends on the default-method info +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc (DefMeth dm_name) + = -- An polymorphic default method + returnTc (HsVar dm_name) + +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth + = -- No default method + -- Warn only if -fwarn-missing-methods + doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn -> + warnTc (is_inst_decl && warn) + (omittedMethodWarn sel_id) `thenNF_Tc_` + returnTc error_rhs + where + error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (HsLit (HsString (_PK_ error_msg))) + error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + + +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth + = -- A generic default method + -- If the method is defined generically, we can only do the job if the + -- instance declaration is for a single-parameter type class with + -- a type constructor applied to type arguments in the instance decl + -- (checkTc, so False provokes the error) + checkTc (not is_inst_decl || simple_inst) + (badGenericInstance sel_id) `thenTc_` + + ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_` + returnTc rhs + where + rhs = mkGenericRhs sel_id clas_tyvar tycon + + stuff = vcat [ppr clas <+> ppr inst_tys, + nest 4 (ppr sel_id <+> equals <+> ppr rhs)] + + -- The tycon is only used in the generic case, and in that + -- case we require that the instance decl is for a single-parameter + -- type class with type variable arguments: + -- instance (...) => C (T a b) + simple_inst = maybeToBool maybe_tycon + clas_tyvar = head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of + [ty] -> case tcSplitTyConApp_maybe ty of + Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon + other -> Nothing + other -> Nothing \end{code} + +\begin{code} +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +find_bind sel_name meth_name (FunMonoBind op_name fix matches loc) + | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc) +find_bind sel_name meth_name (AndMonoBinds b1 b2) + = find_bind sel_name meth_name b1 `seqMaybe` find_bind sel_name meth_name b2 +find_bind sel_name meth_name other = Nothing -- Default case + + -- Find the prags for this method, and replace the + -- selector name with the method name +find_prags sel_name meth_name [] = [] +find_prags sel_name meth_name (SpecSig name ty loc : prags) + | name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (InlineSig sense name phase loc : prags) + | name == sel_name = InlineSig sense meth_name phase loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (prag:prags) = find_prags sel_name meth_name prags +\end{code} + + Contexts and errors ~~~~~~~~~~~~~~~~~~~ \begin{code} -classArityErr class_name - = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) +nullaryClassErr cls + = ptext SLIT("No parameters for class") <+> quotes (ppr cls) -superClassErr class_name sc - = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc) - <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name) +classArityErr cls + = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls), + parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))] -defltMethCtxt class_name - = ptext SLIT("When checking the default methods for class") <+> quotes (ppr class_name) +defltMethCtxt clas + = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas) methodCtxt sel_id = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id) -badMethodErr bndr clas +badMethodErr clas op = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have a method"), quotes (ppr bndr)] + ptext SLIT("does not have a method"), quotes (ppr op)] + +omittedMethodWarn sel_id + = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) + +badGenericMethodType op op_ty + = hang (ptext SLIT("Generic method type is too complex")) + 4 (vcat [ppr op <+> dcolon <+> ppr op_ty, + ptext SLIT("You can only use type variables, arrows, and tuples")]) + +badGenericInstance sel_id + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + ptext SLIT("because the instance declaration is not for a simple type (T a b c)"), + ptext SLIT("(where T is a derivable type constructor)")] + +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) -omittedMethodWarn sel_id clas - = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id), - ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)] +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}