X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=c39d8a068ee9789a3dd2a8927666d498f09cdc34;hb=64ac3c5fc190617c81c8db8c8050c00794ac026d;hp=6b206bb72a821ba51429a279bf5ff232f08ec677;hpb=8dfa24e2d8174289ac5d68f4e4371c1a23d57096;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index 6b206bb..c39d8a0 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -4,54 +4,62 @@ \section[TcClassDcl]{Typechecking class declarations} \begin{code} -module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds, - tcMethodBind, checkFromThisClass +module TcClassDcl ( tcClassDecl1, tcClassDecls2, + MethodSpec, tcMethodBind, mkMethodBind, badMethodErr ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), - InPat(..), HsBinds(..), GRHSs(..), - HsExpr(..), HsLit(..), HsType(..), HsPred(..), - mkSimpleMatch, - andMonoBinds, andMonoBindList, - isClassDecl, isClassOpSig, isPragSig, collectMonoBinders +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), Pat(WildPat), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + placeHolderType ) -import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas, +import BasicTypes ( RecFlag(..), StrictnessMark(..) ) +import RnHsSyn ( RenamedTyClDecl, RenamedSig, RenamedClassOpSig, RenamedMonoBinds, - RenamedContext, RenamedHsDecl, RenamedSig + maybeGenericMatch ) -import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) +import RnEnv ( lookupSysName ) +import TcHsSyn ( TcMonoBinds ) -import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod ) -import TcEnv ( TcId, ValueEnv, TyThing(..), TyThingDetails(..), tcAddImportedIdInfo, - tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, - tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName +import Inst ( Inst, InstOrigin(..), instToId, newDicts, newMethodAtLoc ) +import TcEnv ( TyThingDetails(..), + tcLookupClass, tcExtendTyVarEnv2, + tcExtendTyVarEnv ) -import TcBinds ( tcBindWithSigs, tcSpecSigs ) -import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, sigCtxt, mkTcSig ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcType ( TcType, TcTyVar, tcInstTyVars, tcGetTyVar, zonkTcSigTyVars ) -import TcMonad +import TcBinds ( tcMonoBinds ) +import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig ) +import TcSimplify ( tcSimplifyCheck ) +import TcUnify ( checkSigTyVars, sigCtxt ) +import TcMType ( tcInstTyVars ) +import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar, + mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys, + tcIsTyVarTy, tcSplitTyConApp_maybe + ) +import TcRnMonad +import Generics ( mkGenericRhs ) import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) -import Bag ( unionManyBags, bagToList ) -import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem ) -import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods ) +import Class ( classTyVars, classBigSig, classTyCon, + Class, ClassOpItem, DefMeth (..) ) +import TyCon ( tyConGenInfo ) 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 NameSet ( NameSet, mkNameSet, elemNameSet, emptyNameSet ) +import DataCon ( mkDataCon ) +import Id ( Id, idType, idName, setIdLocalExported, setInlinePragma ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) +import NameSet ( emptyNameSet, unitNameSet ) +import OccName ( mkClassTyConOcc, mkClassDataConOcc, mkWorkerOcc, mkSuperDictSelOcc ) import Outputable -import Type ( Type, ThetaType, ClassContext, - mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, mkDictTys, - mkSigmaTy, mkClassPred, classesOfPreds, - boxedTypeKind, mkArrowKind - ) -import Var ( tyVarKind, TyVar ) -import VarSet ( mkVarSet, emptyVarSet ) +import Var ( TyVar ) +import CmdLineOpts +import UnicodeUtil ( stringToUtf8 ) +import ErrUtils ( dumpIfSet ) +import Util ( count, lengthIs ) import Maybes ( seqMaybe ) +import Maybe ( isJust ) +import FastString \end{code} @@ -96,204 +104,154 @@ Death to "ExpandingDicts". %************************************************************************ \begin{code} -tcClassDecl1 :: ValueEnv -> RenamedTyClDecl -> TcM s (Name, TyThingDetails) -tcClassDecl1 rec_env - (ClassDecl context class_name - tyvar_names fundeps class_sigs def_methods pragmas - tycon_name datacon_name datacon_wkr_name sc_sel_names src_loc) - = -- CHECK ARITY 1 FOR HASKELL 1.4 - checkTc (opt_GlasgowExts || length tyvar_names == 1) - (classArityErr class_name) `thenTc_` - - -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupTy class_name `thenTc` \ (AClass clas) -> + +tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name, + tcdTyVars = tyvar_names, tcdFDs = fundeps, + tcdSigs = class_sigs, tcdMeths = def_methods, + tcdLoc = src_loc}) + = -- LOOK THINGS UP IN THE ENVIRONMENT + tcLookupClass class_name `thenM` \ clas -> let - tyvars = classTyVars clas - dm_bndrs_w_locs = bagToList (collectMonoBinders def_methods) - dm_bndr_set = mkNameSet (map fst dm_bndrs_w_locs) + tyvars = classTyVars clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] in - tcExtendTyVarEnv tyvars $ + tcExtendTyVarEnv tyvars $ + + checkDefaultBinds clas op_names def_methods `thenM` \ mb_dm_env -> -- CHECK THE CONTEXT - tcSuperClasses class_name clas - context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) -> + -- The renamer has already checked that the context mentions + -- only the type variable of the class decl. + -- Context is already kind-checked + tcHsTheta context `thenM` \ sc_theta -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env dm_bndr_set clas tyvars) - (filter isClassOpSig class_sigs) `thenTc` \ sig_stuff -> + mappM (tcClassSig clas tyvars mb_dm_env) op_sigs `thenM` \ sig_stuff -> -- MAKE THE CLASS DETAILS + lookupSysName class_name mkClassDataConOcc `thenM` \ datacon_name -> + lookupSysName datacon_name mkWorkerOcc `thenM` \ datacon_wkr_name -> + mapM (lookupSysName class_name . mkSuperDictSelOcc) + [1..length context] `thenM` \ sc_sel_names -> + -- We number off the superclass selectors, 1, 2, 3 etc so that we + -- can construct names for the selectors. Thus + -- class (C a, C b) => D a b where ... + -- gives superclass selectors + -- D_sc1, D_sc2 + -- (We used to call them D_C, but now we can have two different + -- superclasses both called C!) + lookupSysName class_name mkClassTyConOcc `thenM` \ tycon_name -> let (op_tys, op_items) = unzip sig_stuff - sc_tys = mkDictTys sc_theta + sc_tys = mkPredTys sc_theta dict_component_tys = sc_tys ++ op_tys + 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 - (classTyCon clas) - 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 in - returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con) + returnM (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name) \end{code} \begin{code} -tcSuperClasses :: Name -> Class - -> RenamedContext -- class context - -> [Name] -- Names for superclass selectors - -> TcM s (ClassContext, -- the superclass context - [Id]) -- superclass selector Ids - -tcSuperClasses class_name clas 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 + = returnM Nothing + +checkDefaultBinds clas ops (Just mbs) + = go mbs `thenM` \ dm_env -> + returnM (Just dm_env) + where + go EmptyMonoBinds = returnM 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 `thenM` \ dm_info1 -> + go b2 `thenM` \ dm_info2 -> + returnM (dm_info1 `plusNameEnv` dm_info2) - -- Context is already kind-checked - tcClassContext context `thenTc` \ sc_theta -> - let - sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] - in - -- Done - returnTc (sc_theta, sc_sel_ids) + go (FunMonoBind op _ matches loc) + = addSrcLoc loc $ - where - check_constraint sc@(HsPClass c tys) - = checkTc (all is_tyvar tys) (superClassErr class_name sc) + -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) `thenM_` + + -- Check that all the defns ar generic, or none are + checkTc (all_generic || none_generic) (mixedGenericErr op) `thenM_` - is_tyvar (HsTyVar _) = True - is_tyvar other = False + returnM (unitNameEnv op all_generic) + where + n_generic = count (isJust . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic +\end{code} -tcClassSig :: ValueEnv -- Knot tying only! - -> NameSet -- Names bound in the default-method bindings - -> Class -- ...ditto... +\begin{code} +tcClassSig :: 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 dm_bind_names clas clas_tyvars - (ClassOpSig op_name maybe_dm_stuff op_ty src_loc) - = tcAddSrcLoc src_loc $ +tcClassSig clas clas_tyvars maybe_dm_env + (ClassOpSig op_name sig_dm op_ty src_loc) + = addSrcLoc src_loc $ -- Check the type signature. NB that the envt *already has* -- bindings for the type variables; see comments in TcTyAndClassDcls. + tcHsType op_ty `thenM` \ local_ty -> - -- NB: Renamer checks that the class type variable is mentioned in local_ty, - -- and that it is not constrained by theta - tcHsSigType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy clas_tyvars - [mkClassPred clas (mkTyVarTys clas_tyvars)] - local_ty + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] -- Build the selector id and default method id - sel_id = mkDictSelId op_name clas - in - (case maybe_dm_stuff of - Nothing -> -- Source-file class declaration - newDefaultMethodName op_name src_loc `thenNF_Tc` \ dm_name -> - returnNF_Tc (mkDefaultMethodId dm_name clas global_ty, op_name `elemNameSet` dm_bind_names) - - Just (dm_name, explicit_dm) -> -- Interface-file class decl - let - dm_id = mkDefaultMethodId dm_name clas global_ty - in - returnNF_Tc (tcAddImportedIdInfo rec_env dm_id, explicit_dm) - ) `thenNF_Tc` \ (dm_id, explicit_dm) -> - - returnTc (local_ty, (sel_id, dm_id, explicit_dm)) -\end{code} - + sel_id = mkDictSelId op_name clas + DefMeth dm_name = sig_dm -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ + dm_info = case maybe_dm_env of + Nothing -> sig_dm + Just dm_env -> mk_src_dm_info dm_env -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} - -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) -\end{code} - -@tcClassDecl2@ is the business end of things. - -\begin{code} -tcClassDecl2 :: RenamedTyClDecl -- The class declaration - -> NF_TcM s (LIE, TcMonoBinds) - -tcClassDecl2 (ClassDecl context class_name - tyvar_names _ class_sigs default_binds pragmas _ _ _ _ src_loc) - - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) - - | 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 + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_name + in + returnM (local_ty, (sel_id, dm_info)) \end{code} -\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 - -- We don't return the data constructor etc from the class, - -- because that's done via the class's TyCon - where - (cls_ids_s, binds_s) = unzip (map mk_implicit classes) - - mk_implicit clas = (sel_ids, binds) - where - sel_ids = classSelIds clas - binds | isLocallyDefined clas = idsToMonoBinds sel_ids - | otherwise = EmptyMonoBinds -\end{code} %************************************************************************ %* * @@ -356,238 +314,359 @@ 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 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 :: [RenamedTyClDecl] -> TcM (TcMonoBinds, [Id]) + +tcClassDecls2 decls + = foldr combine + (returnM (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 `thenM` \ (binds1, ids1) -> + tc2 `thenM` \ (binds2, ids2) -> + returnM (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 + -> TcM (TcMonoBinds, [Id]) + +tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs, + tcdMeths = Just default_binds, tcdLoc = src_loc}) + = -- The 'Just' picks out source ClassDecls + recoverM (returnM (EmptyMonoBinds, [])) $ + addSrcLoc src_loc $ + tcLookupClass class_name `thenM` \ 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 + mapAndUnzipM tc_dm op_items `thenM` \ (defm_binds, dm_ids_s) -> - -- 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 + returnM (andMonoBindList defm_binds, concat dm_ids_s) - 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)) -> - - tcAddErrCtxt (defltMethCtxt clas) $ + +tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnM (EmptyMonoBinds, []) +tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnM (EmptyMonoBinds, []) + -- 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) + = tcInstTyVars ClsTv tyvars `thenM` \ (clas_tyvars, inst_tys, _) -> + 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. + + 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 + xtve = tyvars `zip` clas_tyvars + in + newDicts origin theta `thenM` \ [this_dict] -> + + mkMethodBind origin clas inst_tys binds_in op_item `thenM` \ (dm_inst, meth_info) -> + getLIE (tcMethodBind xtve clas_tyvars theta + [this_dict] prags meth_info) `thenM` \ (defm_bind, insts_needed) -> - -- 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 - zonkTcSigTyVars clas_tyvars `thenNF_Tc` \ clas_tyvars' -> + addErrCtxt (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 `thenM` \ dict_binds -> + + -- Simplification can do unification + checkSigTyVars clas_tyvars `thenM` \ 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 -> RenamedMonoBinds -> NF_TcM s () -checkFromThisClass clas mbinds - = mapNF_Tc check_from_this_class bndrs_w_locs `thenNF_Tc_` - returnNF_Tc () + let + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', local_dm_id, instToId dm_inst)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) + in + returnM (full_bind, [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 = map getOccName (classSelIds clas) - bndrs_w_locs = bagToList (collectMonoBinders mbinds) + 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 tyvar sets. \begin{code} +type MethodSpec = (Id, -- Global selector Id + TcSigInfo, -- Signature + RenamedMonoBinds) -- Binding for the method + tcMethodBind - :: Class - -> InstOrigin + :: [(TyVar,TcTyVar)] -- Bindings for type environment -> [TcTyVar] -- Instantiated type variables for the - -- enclosing class/instance decl. - -- They'll be signature tyvars, and we - -- want to check that they don't get bound - -> [TcType] -- Instance types - -> TcThetaType -- Available theta; this could be used to check - -- the method signature, but actually that's done by - -- the caller; here, it's just used for the error message - -> RenamedMonoBinds -- Method binding (pick the right one from in here) - -> [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)) - -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 + -- enclosing class/instance decl. + -- They'll be signature tyvars, and we + -- want to check that they don't get bound + -- Always equal the range of the type envt + -> TcThetaType -- Available theta; it's just used for the error message + -> [Inst] -- Available from context, used to simplify constraints + -- from the method body + -> [RenamedSig] -- Pragmas (e.g. inline pragmas) + -> MethodSpec -- Details of this method + -> TcM TcMonoBinds + +tcMethodBind xtve inst_tyvars inst_theta avail_insts prags + (sel_id, meth_sig, meth_bind) + = -- Check the bindings; first adding 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, _) -> - + tcExtendTyVarEnv2 xtve ( + addErrCtxt (methodCtxt sel_id) $ + getLIE (tcMonoBinds meth_bind [meth_sig] NonRecursive) + ) `thenM` \ ((meth_bind, _, _), meth_lie) -> + + -- Now do context reduction. We simplify wrt both the local tyvars + -- and the ones of the class/instance decl, so that there is + -- no problem with + -- class C a where + -- op :: Eq a => a -> b -> a + -- + -- We do this for each method independently to localise error messages - tcExtendLocalValEnv [(meth_name, meth_id)] ( - tcSpecSigs meth_prags - ) `thenTc` \ (prag_binds1, prag_lie) -> + let + TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig + in + addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ + newDicts SignatureOrigin meth_theta `thenM` \ meth_dicts -> + let + all_tyvars = meth_tvs ++ inst_tyvars + all_insts = avail_insts ++ meth_dicts + in + tcSimplifyCheck + (ptext SLIT("class or instance method") <+> quotes (ppr sel_id)) + all_tyvars all_insts meth_lie `thenM` \ lie_binds -> + + checkSigTyVars all_tyvars `thenM` \ all_tyvars' -> + + let + -- Attach inline pragmas as appropriate + (final_meth_id, inlines) + | (InlineSig inl _ phase _ : _) <- filter is_inline prags + = (meth_id `setInlinePragma` phase, + if inl then unitNameSet (idName meth_id) else emptyNameSet) + | otherwise + = (meth_id, emptyNameSet) + + is_inline (InlineSig _ name _ _) = name == idName sel_id + is_inline other = False + + meth_tvs' = take (length meth_tvs) all_tyvars' + poly_meth_bind = AbsBinds meth_tvs' + (map instToId meth_dicts) + [(meth_tvs', final_meth_id, local_meth_id)] + inlines + (lie_binds `andMonoBinds` meth_bind) + in + returnM poly_meth_bind + + +mkMethodBind :: InstOrigin + -> Class -> [TcType] -- Class and instance types + -> RenamedMonoBinds -- Method binding (pick the right one from in here) + -> ClassOpItem + -> TcM (Inst, -- Method inst + MethodSpec) +-- Find the binding for the specified method, or make +-- up a suitable default method if it isn't there + +mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info) + = getInstLoc origin `thenM` \ inst_loc -> + newMethodAtLoc inst_loc sel_id inst_tys `thenM` \ meth_inst -> + -- Do not dump anything into the LIE + let + meth_id = instToId meth_inst + meth_name = idName meth_id + in + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + getSrcLocM `thenM` \ loc -> + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnM user_bind + Nothing -> mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs -> + returnM (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs placeHolderType loc] loc) + ) `thenM` \ meth_bind -> + + mkTcSig meth_id loc `thenM` \ meth_sig -> + + returnM (meth_inst, (sel_id, meth_sig, meth_bind)) + - -- 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) -> + -- 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 origin clas inst_tys sel_id loc (DefMeth dm_name) + = -- An polymorphic default method + traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_` + returnM (HsVar dm_name) + +mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth + = -- No default method + -- Warn only if -fwarn-missing-methods + doptM Opt_WarnMissingMethods `thenM` \ warn -> + warnTc (isInstDecl origin && warn) + (omittedMethodWarn sel_id) `thenM_` + returnM error_rhs + where + error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc) + simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg)))) + error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + + -- When the type is of form t1 -> t2 -> t3 + -- make a default method like (\ _ _ -> noMethBind "blah") + -- rather than simply (noMethBind "blah") + -- Reason: if t1 or t2 are higher-ranked types we get n + -- silly ambiguity messages. + -- Example: f :: (forall a. Eq a => a -> a) -> Int + -- f = error "urk" + -- Here, tcSub tries to force (error "urk") to have the right type, + -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t) + -- where 't' is fresh ty var. This leads directly to "ambiguous t". + -- + -- NB: technically this changes the meaning of the default-default + -- method slightly, because `seq` can see the lambdas. Oh well. + (_,_,tau1) = tcSplitSigmaTy (idType sel_id) + (_,_,tau2) = tcSplitSigmaTy tau1 + -- Need two splits because the selector can have a type like + -- forall a. Foo a => forall b. Eq b => ... + (arg_tys, _) = tcSplitFunTys tau2 + wild_pats = [WildPat placeHolderType | ty <- arg_tys] + +mkDefMethRhs origin 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) + ASSERT( isInstDecl origin ) -- We never get here from a class decl + + checkTc (isJust maybe_tycon) + (badGenericInstance sel_id (notSimple inst_tys)) `thenM_` + checkTc (isJust (tyConGenInfo tycon)) + (badGenericInstance sel_id (notGeneric tycon)) `thenM_` + + ioToTcRn (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenM_` + returnM 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) + 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 + +isInstDecl InstanceDeclOrigin = True +isInstDecl ClassDeclOrigin = False +\end{code} - -- 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 - 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 ]) +\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) - -superClassErr class_name sc - = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc) - <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name) - -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) + +badGenericInstance sel_id because + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + because] + +notSimple inst_tys + = vcat [ptext SLIT("because the instance type(s)"), + nest 2 (ppr inst_tys), + ptext SLIT("is not a simple type of form (T a b c)")] + +notGeneric tycon + = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+> + ptext SLIT("was not compiled with -fgenerics")] -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)] +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}