X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=fbb450a19913ee51773d7aa29feabadd57dc1022;hb=9d7da331989abcd1844e9d03b8d1e4163796fa85;hp=d4690c68f5939a20fbf7386ec0e6419e30222950;hpb=1bba522f5ec82c43abd2ba4e84127b9c915dd020;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index d4690c6..fbb450a 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -4,48 +4,64 @@ \section[TcClassDcl]{Typechecking class declarations} \begin{code} -module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds, - tcMethodBind, checkFromThisClass +module TcClassDcl ( tcClassSigs, tcClassDecl2, + getGenericInstances, + MethodSpec, tcMethodBind, mkMethodBind, + tcAddDeclCtxt, badMethodErr ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), - HsExpr(..), HsLit(..), HsType(..), HsPred(..), - mkSimpleMatch, andMonoBinds, andMonoBindList, - isClassDecl, isClassOpSig, isPragSig, collectMonoBinders +import HsSyn +import RnHsSyn ( maybeGenericMatch, extractHsTyVars ) +import RnExpr ( rnLExpr ) +import RnEnv ( lookupTopBndrRn, lookupImportedName ) +import Inst ( instToId, newDicts, newDictsAtLoc, newMethod, getOverlapFlag ) +import InstEnv ( mkLocalInstance ) +import TcEnv ( tcLookupLocatedClass, + tcExtendTyVarEnv, + InstInfo(..), pprInstInfoDetails, + simpleInstInfoTyCon, simpleInstInfoTy, + InstBindings(..), newDFunName ) -import BasicTypes ( TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedTyClDecl, - RenamedClassOpSig, RenamedMonoBinds, - RenamedContext, RenamedHsDecl, RenamedSig +import TcBinds ( TcPragFun, tcMonoBinds, tcPrags, mkPragFun ) +import TcHsType ( TcSigInfo(..), tcHsKindedType, tcHsSigType ) +import TcSimplify ( tcSimplifyCheck ) +import TcUnify ( checkSigTyVars, sigCtxt ) +import TcMType ( tcSkolSigTyVars, UserTypeCtxt( GenPatCtxt ), tcSkolType ) +import TcType ( Type, SkolemInfo(ClsSkol, InstSkol, SigSkol), + TcType, TcThetaType, TcTyVar, mkTyVarTys, + mkClassPred, tcSplitSigmaTy, tcSplitFunTys, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy, + getClassPredTys_maybe, mkPhiTy, mkTyVarTy ) -import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) - -import Inst ( InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod ) -import TcEnv ( TcId, ValueEnv, TyThing(..), TyThingDetails(..), tcAddImportedIdInfo, - tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, - tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName - ) -import TcBinds ( tcBindWithSigs, tcSpecSigs ) -import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, sigCtxt, mkTcSig ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcSigTyVars ) -import TcMonad +import TcRnMonad +import Generics ( mkGenericRhs, validGenericInstanceType ) import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) -import Bag ( bagToList ) -import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem ) -import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods ) -import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) -import DataCon ( mkDataCon, notMarkedStrict ) -import Id ( Id, idType, idName ) -import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) ) -import NameSet ( NameSet, mkNameSet, elemNameSet, emptyNameSet ) +import Class ( classTyVars, classBigSig, + Class, ClassOpItem, DefMeth (..) ) +import TyCon ( TyCon, tyConName, tyConHasGenerics ) +import Type ( substTyWith ) +import MkId ( mkDefaultMethodId, mkDictFunId ) +import Id ( Id, idType, idName, mkUserLocal ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, mkNameEnv ) +import NameSet ( nameSetToList ) +import OccName ( reportIfUnused, mkDefaultMethodOcc ) +import RdrName ( RdrName, mkDerivedRdrName ) import Outputable -import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkSigmaTy, mkClassPred ) -import Var ( TyVar ) -import VarSet ( mkVarSet, emptyVarSet ) -import Maybes ( seqMaybe ) +import PrelNames ( genericTyConNames ) +import DynFlags +import ErrUtils ( dumpIfSet_dyn ) +import Util ( count, lengthIs, isSingleton, lengthExceeds ) +import Unique ( Uniquable(..) ) +import ListSetOps ( equivClassesByUniq, minusList ) +import SrcLoc ( Located(..), srcSpanStart, unLoc, noLoc ) +import Maybes ( seqMaybe, isJust, mapCatMaybes ) +import List ( partition ) +import BasicTypes ( RecFlag(..) ) +import Bag +import FastString \end{code} @@ -85,209 +101,65 @@ Death to "ExpandingDicts". %************************************************************************ %* * -\subsection{Type checking} + Type-checking the class op signatures %* * %************************************************************************ \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) -> - let - tyvars = classTyVars clas - dm_bndrs_w_locs = bagToList (collectMonoBinders def_methods) - dm_bndr_set = mkNameSet (map fst dm_bndrs_w_locs) - in - tcExtendTyVarEnv tyvars $ - - -- CHECK THE CONTEXT - tcSuperClasses class_name clas - context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) -> - - -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env dm_bndr_set clas tyvars) - (filter isClassOpSig class_sigs) `thenTc` \ sig_stuff -> - - -- MAKE THE CLASS DETAILS - let - (op_tys, op_items) = unzip sig_stuff - sc_tys = mkDictTys sc_theta - dict_component_tys = sc_tys ++ op_tys - - 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 - - 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) -\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. - - -- For std Haskell check that the context constrains only tyvars - (if opt_GlasgowExts then - returnTc () - else - mapTc_ check_constraint context - ) `thenTc_` - - -- 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) - +tcClassSigs :: Name -- Name of the class + -> [LSig Name] + -> LHsBinds Name + -> TcM [TcMethInfo] + +type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate + -- between tcClassSigs and buildClass +tcClassSigs clas sigs def_methods + = do { dm_env <- checkDefaultBinds clas op_names def_methods + ; mappM (tcClassSig dm_env) op_sigs } where - check_constraint sc@(HsPClass c tys) - = checkTc (all is_tyvar tys) (superClassErr class_name sc) - - is_tyvar (HsTyVar _) = True - is_tyvar other = False - + op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs] + op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs] -tcClassSig :: ValueEnv -- Knot tying only! - -> NameSet -- Names bound in the default-method bindings - -> Class -- ...ditto... - -> [TyVar] -- The class type variable, used for error check only - -> RenamedClassOpSig - -> TcM s (Type, -- Type of the method - ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding +checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool) + -- 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 Bool + -- where True <=> it's a generic default method +checkDefaultBinds clas ops binds + = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds) + return (mkNameEnv dm_infos) -tcClassSig rec_env dm_bind_names clas clas_tyvars - (ClassOpSig op_name maybe_dm_stuff op_ty src_loc) - = tcAddSrcLoc src_loc $ +checkDefaultBind clas ops (FunBind (L _ op) _ (MatchGroup matches _) _) + = do { -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) - -- Check the type signature. NB that the envt *already has* - -- bindings for the type variables; see comments in TcTyAndClassDcls. + -- Check that all the defns ar generic, or none are + ; checkTc (all_generic || none_generic) (mixedGenericErr op) - -- 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 - - -- 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} - - -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ - -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] + ; returnM (op, all_generic) + } 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 + n_generic = count (isJust . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic + + +tcClassSig :: NameEnv Bool -- Info about default methods; + -> LSig Name + -> TcM TcMethInfo + +tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty)) + = setSrcSpan loc $ do + { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope + ; let dm = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just False -> DefMeth + Just True -> GenDefMeth + ; returnM (op_name, dm, op_ty) } \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} %************************************************************************ %* * @@ -350,96 +222,90 @@ dfun.Foo.List dfoo_list \end{verbatim} -\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) - where - prags = filter isPragSig sigs - - (tyvars, _, _, op_items) = classBigSig clas +@tcClassDecls2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) - origin = ClassDeclOrigin - - -- 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)) -> +\begin{code} +tcClassDecl2 :: LTyClDecl Name -- The class declaration + -> TcM (LHsBinds Id, [Id]) + +tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, + tcdMeths = default_binds})) + = recoverM (returnM (emptyLHsBinds, [])) $ + setSrcSpan loc $ + tcLookupLocatedClass 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 + prag_fn = mkPragFun sigs + tc_dm = tcDefMeth clas tyvars default_binds prag_fn + + dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items] + -- 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.) + in + mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) -> + returnM (listToBag defm_binds, concat dm_ids_s) - tcAddErrCtxt (defltMethCtxt clas) $ +tcDefMeth clas tyvars binds_in prag_fn sel_id + = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id) + ; let rigid_info = ClsSkol clas + clas_tyvars = tcSkolSigTyVars rigid_info tyvars + inst_tys = mkTyVarTys clas_tyvars + dm_ty = idType sel_id -- Same as dict selector! + theta = [mkClassPred clas inst_tys] + local_dm_id = mkDefaultMethodId dm_name dm_ty + origin = SigOrigin rigid_info + + ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth) + ; [this_dict] <- newDicts origin theta + ; (defm_bind, insts_needed) <- getLIE (tcMethodBind clas_tyvars theta + [this_dict] prag_fn meth_info) - -- 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) $ do - -- Check the context - tcSimplifyAndCheck - (ptext SLIT("class") <+> ppr clas) - (mkVarSet clas_tyvars') - avail_insts - insts_needed `thenTc` \ (const_lie, dict_binds) -> + -- Check the context + { dict_binds <- tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed + + -- Simplification can do unification + ; checkSigTyVars 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) + ; let + (_,dm_inst_id,_) = meth_info + full_bind = AbsBinds + clas_tyvars + [instToId this_dict] + [(clas_tyvars, local_dm_id, dm_inst_id, [])] + -- No inlines (yet) + (dict_binds `unionBags` defm_bind) + ; returnM (noLoc full_bind, [local_dm_id]) }} + +mkDefMethRdrName :: Id -> RdrName +mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc \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 () - 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) -\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 @@ -447,141 +313,475 @@ time, because their signatures may have different contexts and tyvar sets. \begin{code} +type MethodSpec = (Id, -- Global selector Id + Id, -- Local Id (class tyvars instantiated) + LHsBind Name) -- Binding for the method + tcMethodBind - :: Class - -> InstOrigin - -> [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 + :: [TcTyVar] -- Skolemised type variables for the + -- enclosing class/instance decl. + -- They'll be signature tyvars, and we + -- want to check that they don't get bound + -- Also they are scoped, so we bring them into scope + -- 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 + -> TcPragFun -- Pragmas (e.g. inline pragmas) + -> MethodSpec -- Details of this method + -> TcM (LHsBinds Id) + +tcMethodBind inst_tyvars inst_theta avail_insts prag_fn + (sel_id, meth_id, meth_bind) + = recoverM (returnM emptyLHsBinds) $ + -- If anything fails, recover returning no bindings. + -- This is particularly useful when checking the default-method binding of + -- a class decl. If we don't recover, we don't add the default method to + -- the type enviroment, and we get a tcLookup failure on $dmeth later. + + -- 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, _) -> + + let -- Fake up a TcSigInfo to pass to tcMonoBinds + rigid_info = SigSkol (idName meth_id) + in + tcSkolType rigid_info (idType meth_id) `thenM` \ (tyvars', theta', tau') -> + getInstLoc (SigOrigin rigid_info) `thenM` \ loc -> + let meth_sig = TcSigInfo { sig_id = meth_id, sig_tvs = tyvars', sig_scoped = [], + sig_theta = theta', sig_tau = tau', sig_loc = loc } + lookup_sig name = ASSERT( name == idName meth_id ) + Just meth_sig + in + tcExtendTyVarEnv inst_tyvars ( + addErrCtxt (methodCtxt sel_id) $ + getLIE $ + tcMonoBinds [meth_bind] lookup_sig Recursive + ) `thenM` \ ((meth_bind, mono_bind_infos), 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) -> + addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ + newDictsAtLoc (sig_loc meth_sig) (sig_theta meth_sig) `thenM` \ meth_dicts -> + let + meth_tvs = sig_tvs meth_sig + all_tyvars = meth_tvs ++ inst_tyvars + all_insts = avail_insts ++ meth_dicts + sel_name = idName sel_id + in + tcSimplifyCheck + (ptext SLIT("class or instance method") <+> quotes (ppr sel_id)) + all_tyvars all_insts meth_lie `thenM` \ lie_binds -> - -- 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) -> + checkSigTyVars all_tyvars `thenM_` + tcPrags meth_id (prag_fn sel_name) `thenM` \ prags -> + let + [(_,_,local_meth_id)] = mono_bind_infos + poly_meth_bind = noLoc $ AbsBinds meth_tvs + (map instToId meth_dicts) + [(meth_tvs, meth_id, local_meth_id, prags)] + (lie_binds `unionBags` meth_bind) + in + returnM (unitBag poly_meth_bind) - -- 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 ]) + +mkMethodBind :: InstOrigin + -> Class -> [TcType] -- Class and instance types + -> LHsBinds Name -- Method binding (pick the right one from in here) + -> ClassOpItem + -> TcM (Maybe 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) + = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) -> + let + 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 + getSrcSpanM `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 -> + -- Not infix decl + returnM (noLoc $ FunBind (noLoc meth_name) False + (mkMatchGroup [mkSimpleMatch [] rhs]) + placeHolderNames) + ) `thenM` \ meth_bind -> + + returnM (mb_inst, (sel_id, meth_id, meth_bind)) + +mkMethId :: InstOrigin -> Class + -> Id -> [TcType] -- Selector, and instance types + -> TcM (Maybe Inst, Id) + +-- mkMethId instantiates the selector Id at the specified types +mkMethId origin clas sel_id inst_tys + = let + (tyvars,rho) = tcSplitForAllTys (idType sel_id) + rho_ty = ASSERT( length tyvars == length inst_tys ) + substTyWith tyvars inst_tys rho + (preds,tau) = tcSplitPhiTy rho_ty + first_pred = head preds + in + -- The first predicate should be of form (C a b) + -- where C is the class in question + ASSERT( not (null preds) && + case getClassPredTys_maybe first_pred of + { Just (clas1,tys) -> clas == clas1 ; Nothing -> False } + ) + if isSingleton preds then + -- If it's the only one, make a 'method' + getInstLoc origin `thenM` \ inst_loc -> + newMethod inst_loc sel_id inst_tys preds tau `thenM` \ meth_inst -> + returnM (Just meth_inst, instToId meth_inst) + else + -- If it's not the only one we need to be careful + -- For example, given 'op' defined thus: + -- class Foo a where + -- op :: (?x :: String) => a -> a + -- (mkMethId op T) should return an Inst with type + -- (?x :: String) => T -> T + -- That is, the class-op's context is still there. + -- BUT: it can't be a Method any more, because it breaks + -- INVARIANT 2 of methods. (See the data decl for Inst.) + newUnique `thenM` \ uniq -> + getSrcSpanM `thenM` \ loc -> + let + real_tau = mkPhiTy (tail preds) tau + meth_id = mkUserLocal (getOccName sel_id) uniq real_tau + (srcSpanStart loc) --TODO + in + returnM (Nothing, meth_id) + + -- 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 + = -- An polymorphic default method + lookupImportedName (mkDefMethRdrName sel_id) `thenM` \ dm_name -> + -- Might not be imported, but will be an OrigName + traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_` + returnM (nlHsVar 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 + && reportIfUnused (getOccName sel_id)) + (omittedMethodWarn sel_id) `thenM_` + returnM error_rhs + where + error_rhs = noLoc $ HsLam (mkMatchGroup [mkSimpleMatch wild_pats simple_rhs]) + simple_rhs = nlHsApp (nlHsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (nlHsLit (HsStringPrim (mkFastString 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 = [nlWildPat | 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 + do { checkTc (isJust maybe_tycon) + (badGenericInstance sel_id (notSimple inst_tys)) + ; checkTc (tyConHasGenerics tycon) + (badGenericInstance sel_id (notGeneric tycon)) + + ; dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body" + (vcat [ppr clas <+> ppr inst_tys, + nest 2 (ppr sel_id <+> equals <+> ppr rhs)])) + + -- Rename it before returning it + ; (rn_rhs, _) <- rnLExpr rhs + ; returnM rn_rhs } + where + rhs = mkGenericRhs sel_id clas_tyvar tycon + + -- 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 (SigOrigin (InstSkol _)) = True +isInstDecl (SigOrigin (ClsSkol _)) = False \end{code} -Contexts and errors -~~~~~~~~~~~~~~~~~~~ + \begin{code} -classArityErr class_name - = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) +-- 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 binds + = foldlBag seqMaybe Nothing (mapBag f binds) + where + f (L loc1 (FunBind (L loc2 op_name) fix matches fvs)) | op_name == sel_name + = Just (L loc1 (FunBind (L loc2 meth_name) fix matches fvs)) + f _other = Nothing +\end{code} -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) +%************************************************************************ +%* * +\subsection{Extracting generic instance declaration from class declarations} +%* * +%************************************************************************ + +@getGenericInstances@ extracts the generic instance declarations from a class +declaration. For exmaple + + class C a where + op :: a -> a + + op{ x+y } (Inl v) = ... + op{ x+y } (Inr v) = ... + op{ x*y } (v :*: w) = ... + op{ 1 } Unit = ... + +gives rise to the instance declarations + + instance C (x+y) where + op (Inl v) = ... + op (Inr v) = ... + + instance C (x*y) where + op (v :*: w) = ... + + instance C 1 where + op Unit = ... + + +\begin{code} +getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo] +getGenericInstances class_decls + = do { gen_inst_infos <- mappM (addLocM get_generics) class_decls + ; let { gen_inst_info = concat gen_inst_infos } + + -- Return right away if there is no generic stuff + ; if null gen_inst_info then returnM [] + else do + + -- Otherwise print it out + { dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" + (vcat (map pprInstInfoDetails gen_inst_info))) + ; returnM gen_inst_info }} + +get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods}) + | null generic_binds + = returnM [] -- The comon case: no generic default methods + + | otherwise -- A source class decl with generic default methods + = recoverM (returnM []) $ + tcAddDeclCtxt decl $ + tcLookupLocatedClass class_name `thenM` \ clas -> + + -- Group by type, and + -- make an InstInfo out of each group + let + groups = groupWith listToBag generic_binds + in + mappM (mkGenericInstance clas) groups `thenM` \ inst_infos -> + + -- Check that there is only one InstInfo for each type constructor + -- The main way this can fail is if you write + -- f {| a+b |} ... = ... + -- f {| x+y |} ... = ... + -- Then at this point we'll have an InstInfo for each + let + tc_inst_infos :: [(TyCon, InstInfo)] + tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] + + bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, + group `lengthExceeds` 1] + get_uniq (tc,_) = getUnique tc + in + mappM (addErrTc . dupGenericInsts) bad_groups `thenM_` + + -- Check that there is an InstInfo for each generic type constructor + let + missing = genericTyConNames `minusList` [tyConName tc | (tc,_) <- tc_inst_infos] + in + checkTc (null missing) (missingGenericInstances missing) `thenM_` + + returnM inst_infos + where + generic_binds :: [(HsType Name, LHsBind Name)] + generic_binds = getGenericBinds def_methods + + +--------------------------------- +getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)] + -- Takes a group of method bindings, finds the generic ones, and returns + -- them in finite map indexed by the type parameter in the definition. +getGenericBinds binds = concat (map getGenericBind (bagToList binds)) + +getGenericBind (L loc (FunBind id infixop (MatchGroup matches ty) fvs)) + = groupWith wrap (mapCatMaybes maybeGenericMatch matches) + where + wrap ms = L loc (FunBind id infixop (MatchGroup ms ty) fvs) +getGenericBind _ + = [] + +groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)] +groupWith op [] = [] +groupWith op ((t,v):prs) = (t, op (v:vs)) : groupWith op rest + where + vs = map snd this + (this,rest) = partition same_t prs + same_t (t',v) = t `eqPatType` t' + +eqPatLType :: LHsType Name -> LHsType Name -> Bool +eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2 + +eqPatType :: HsType Name -> HsType Name -> Bool +-- A very simple equality function, only for +-- type patterns in generic function definitions. +eqPatType (HsTyVar v1) (HsTyVar v2) = v1==v2 +eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 +eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 && unLoc op1 == unLoc op2 +eqPatType (HsNumTy n1) (HsNumTy n2) = n1 == n2 +eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2 +eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2 +eqPatType _ _ = False + +--------------------------------- +mkGenericInstance :: Class + -> (HsType Name, LHsBinds Name) + -> TcM InstInfo + +mkGenericInstance clas (hs_ty, binds) + -- Make a generic instance declaration + -- For example: instance (C a, C b) => C (a+b) where { binds } + + = -- Extract the universally quantified type variables + -- and wrap them as forall'd tyvars, so that kind inference + -- works in the standard way + let + sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty))) + hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty) + in + -- Type-check the instance type, and check its form + tcHsSigType GenPatCtxt hs_forall_ty `thenM` \ forall_inst_ty -> + let + (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty + in + checkTc (validGenericInstanceType inst_ty) + (badGenericInstanceType binds) `thenM_` + + -- Make the dictionary function. + getSrcSpanM `thenM` \ span -> + getOverlapFlag `thenM` \ overlap_flag -> + newDFunName clas [inst_ty] (srcSpanStart span) `thenM` \ dfun_name -> + let + inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] + dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty] + ispec = mkLocalInstance dfun_id overlap_flag + in + returnM (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] }) +\end{code} + + +%************************************************************************ +%* * + Error messages +%* * +%************************************************************************ + +\begin{code} +tcAddDeclCtxt decl thing_inside + = addErrCtxt ctxt thing_inside + where + thing = case decl of + ClassDecl {} -> "class" + TySynonym {} -> "type synonym" + TyData {tcdND = NewType} -> "newtype" + TyData {tcdND = DataType} -> "data type" + + ctxt = hsep [ptext SLIT("In the"), text thing, + ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + +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)] - -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)] + 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")] + +badGenericInstanceType binds + = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), + nest 4 (ppr binds)] + +missingGenericInstances missing + = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing + +dupGenericInsts tc_inst_infos + = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"), + nest 4 (vcat (map ppr_inst_ty tc_inst_infos)), + ptext SLIT("All the type patterns for a generic type constructor must be identical") + ] + where + ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst) + +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}