X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=ccfd18a5a3726149e147f0195d5ae7f54085aa1f;hb=9d7da331989abcd1844e9d03b8d1e4163796fa85;hp=e2e65d594a6b3af60086368d1413eeb1daf2efb6;hpb=e72062f5239a13f243d6e98b5124e2fdbab1c940;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index e2e65d5..fbb450a 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,74 +1,67 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcClassDcl]{Typechecking class declarations} \begin{code} +module TcClassDcl ( tcClassSigs, tcClassDecl2, + getGenericInstances, + MethodSpec, tcMethodBind, mkMethodBind, + tcAddDeclCtxt, badMethodErr + ) where + #include "HsVersions.h" -module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind ) where - -IMP_Ubiq() - -import HsSyn ( HsDecl(..), ClassDecl(..), HsBinds(..), MonoBinds(..), - Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..), - DefaultDecl, TyDecl, InstDecl, IfaceSig, Fixity, - HsLit(..), OutPat(..), Sig(..), HsType(..), HsTyVar, InPat(..), - SYN_IE(RecFlag), nonRecursive, andMonoBinds, collectMonoBinders, - Stmt, DoOrListComp, ArithSeqInfo, Fake ) -import HsTypes ( getTyVarName ) -import HsPragmas ( ClassPragmas(..) ) -import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..), - RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds), - RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl) - ) -import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcMonoBinds), SYN_IE(TcExpr), - mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, tcIdType ) - -import Inst ( Inst, InstOrigin(..), SYN_IE(LIE), emptyLIE, plusLIE, newDicts, newMethod ) -import TcEnv ( tcLookupClass, tcLookupTyVar, newLocalIds, tcAddImportedIdInfo, - tcExtendGlobalTyVars ) -import TcBinds ( tcBindWithSigs, TcSigInfo(..) ) -import TcKind ( unifyKind, TcKind ) -import TcMonad -import TcMonoType ( tcHsType, tcContext ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( TcIdOcc(..), SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars, - tcInstSigType, tcInstSigTcType ) -import PragmaInfo ( PragmaInfo(..) ) - -import Bag ( bagToList, unionManyBags ) -import Class ( GenClass, mkClass, classBigSig, - classDefaultMethodId, - classOpTagByOccName, SYN_IE(Class) +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 CmdLineOpts ( opt_PprUserLength ) -import Id ( GenId, mkSuperDictSelId, mkMethodSelId, - mkDefaultMethodId, getIdUnfolding, - idType, SYN_IE(Id) +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 CoreUnfold ( getUnfoldingTemplate ) -import IdInfo -import Name ( Name, isLocallyDefined, moduleString, getSrcLoc, nameOccName, - nameString, NamedThing(..) ) +import TcRnMonad +import Generics ( mkGenericRhs, validGenericInstanceType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +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 Pretty -import PprType ( GenClass, GenType, GenTyVar ) -import SpecEnv ( SpecEnv ) -import SrcLoc ( mkGeneratedSrcLoc ) -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy, - mkForAllTy, mkSigmaTy, splitSigmaTy, SYN_IE(Type) - ) -import TysWiredIn ( stringTy ) -import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) ) -import Unique ( Unique, Uniquable(..) ) -import Util - - --- import TcPragmas ( tcGenPragmas, tcClassOpPragmas ) -tcGenPragmas ty id ps = returnNF_Tc noIdInfo -tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo `addSpecInfo` spec, - noIdInfo) +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} @@ -106,214 +99,68 @@ Now DictTy in Type is just a form of type synomym: Death to "ExpandingDicts". -\begin{code} -tcClassDecl1 rec_env rec_inst_mapper - (ClassDecl context class_name - tyvar_name class_sigs def_methods pragmas src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (classDeclCtxt class_name) $ - - -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupClass class_name `thenTc` \ (class_kind, rec_class) -> - tcLookupTyVar (getTyVarName tyvar_name) `thenNF_Tc` \ (tyvar_kind, rec_tyvar) -> - let - rec_class_inst_env = rec_inst_mapper rec_class - in - - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKind class_kind tyvar_kind `thenTc_` - - -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvar context pragmas - `thenTc` \ (scs, sc_sel_ids) -> - - -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env rec_class rec_tyvar) class_sigs - `thenTc` \ sig_stuff -> - - -- MAKE THE CLASS OBJECT ITSELF - let - (op_sel_ids, defm_ids) = unzip sig_stuff - clas = mkClass (uniqueOf class_name) (getName class_name) rec_tyvar - scs sc_sel_ids op_sel_ids defm_ids - rec_class_inst_env - in - returnTc clas -\end{code} - - - let - clas_ty = mkTyVarTy clas_tyvar - dict_component_tys = classDictArgTys clas_ty - new_or_data = case dict_component_tys of - [_] -> NewType - other -> DataType - - dict_con_id = mkDataCon class_name - [NotMarkedStrict] - [{- No labelled fields -}] - [clas_tyvar] - [{-No context-}] - dict_component_tys - tycon - - tycon = mkDataTyCon class_name - (tyVarKind rec_tyvar `mkArrowKind` mkBoxedTypeKind) - [rec_tyvar] - [{- Empty context -}] - [dict_con_id] - [{- No derived classes -}] - new_or_data - in - - -\begin{code} -tcClassContext :: Class -> TyVar - -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s ([Class], -- the superclasses - [Id]) -- superclass selector Ids - -tcClassContext rec_class rec_tyvar context pragmas - = -- Check the context. - -- The renamer has already checked that the context mentions - -- only the type variable of the class decl. - tcContext context `thenTc` \ theta -> - let - super_classes = [ supers | (supers, _) <- theta ] - in - - -- Make super-class selector ids - mapTc (mk_super_id rec_class) super_classes `thenTc` \ sc_sel_ids -> - - -- Done - returnTc (super_classes, sc_sel_ids) - - where - rec_tyvar_ty = mkTyVarTy rec_tyvar - - mk_super_id rec_class super_class - = tcGetUnique `thenNF_Tc` \ uniq -> - let - ty = mkForAllTy rec_tyvar $ - mkFunTy (mkDictTy rec_class rec_tyvar_ty) - (mkDictTy super_class rec_tyvar_ty) - in - returnTc (mkSuperDictSelId uniq rec_class super_class ty) - - -tcClassSig :: TcEnv s -- Knot tying only! - -> Class -- ...ditto... - -> TyVar -- The class type variable, used for error check only - -> RenamedClassOpSig - -> TcM s (Id, -- selector id - Maybe Id) -- default-method ids - -tcClassSig rec_env rec_clas rec_clas_tyvar - (ClassOpSig op_name maybe_dm_name - 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. - - -- NB: Renamer checks that the class type variable is mentioned in local_ty, - -- and that it is not constrained by theta - tcHsType op_ty `thenTc` \ local_ty -> - let - global_ty = mkSigmaTy [rec_clas_tyvar] - [(rec_clas, mkTyVarTy rec_clas_tyvar)] - local_ty - in - - -- Build the selector id and default method id - let - sel_id = mkMethodSelId op_name rec_clas global_ty - maybe_dm_id = case maybe_dm_name of - Nothing -> Nothing - Just dm_name -> let - dm_id = mkDefaultMethodId dm_name rec_clas global_ty - in - Just (tcAddImportedIdInfo rec_env dm_id) - in - returnTc (sel_id, maybe_dm_id) -\end{code} - - %************************************************************************ %* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} + Type-checking the class op signatures %* * %************************************************************************ -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 s, TcMonoBinds s) - -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - [tcClassDecl2 cls_decl | ClD cls_decl <- decls] +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 - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) -\end{code} + op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs] + op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs] -@tcClassDecl2@ is the business end of things. -\begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcMonoBinds s) +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) -tcClassDecl2 (ClassDecl context class_name - tyvar_name class_sigs default_binds pragmas 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) - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) + -- Check that all the defns ar generic, or none are + ; checkTc (all_generic || none_generic) (mixedGenericErr op) - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc src_loc $ - - -- Get the relevant class - tcLookupClass class_name `thenTc` \ (_, clas) -> - let - (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas - - -- The selector binds are already in the selector Id's unfoldings - sel_binds = [ CoreMonoBind (RealId sel_id) (getUnfoldingTemplate (getIdUnfolding sel_id)) - | sel_id <- sc_sel_ids ++ op_sel_ids, - isLocallyDefined sel_id - ] - - final_sel_binds = andMonoBinds sel_binds - in - -- Generate bindings for the default methods - tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) -> - - returnTc (const_insts, - final_sel_binds `AndMonoBinds` meth_binds) + ; returnM (op, all_generic) + } + where + 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} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -336,23 +183,11 @@ we get the default methods: defm.Foo.op1 :: forall a. Foo a => a -> Bool defm.Foo.op1 = /\a -> \dfoo -> \x -> True -====================== OLD ================== -\begin{verbatim} -defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b -defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z -> - if (op1 a dfoo x) && (< b dord y z) then y else z -\end{verbatim} -Notice that, like all ids, the foralls of defm.Foo.op2 are at the top. -====================== END OF OLD =================== - -NEW: -\begin{verbatim} defm.Foo.op2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b defm.Foo.op2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z -> if (op1 a dfoo x) && (< b dord y z) then y else z \end{verbatim} - When we come across an instance decl, we may need to use the default methods: \begin{verbatim} @@ -387,101 +222,566 @@ dfun.Foo.List dfoo_list \end{verbatim} +@tcClassDecls2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) + \begin{code} -tcDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> TcM s (LIE s, TcMonoBinds s) +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) + +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) + + ; addErrCtxt (defltMethCtxt clas) $ do + + -- 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 + (_,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} -tcDefaultMethodBinds clas default_binds - = -- Construct suitable signatures - tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], [inst_ty], inst_env) -> - -- Typecheck the default bindings - let - clas_tyvar_set = unitTyVarSet clas_tyvar - - tc_dm meth_bind - = let - bndr_name = case meth_bind of - FunMonoBind name _ _ _ -> name - PatMonoBind (VarPatIn name) _ _ -> name - - idx = classOpTagByOccName clas (nameOccName bndr_name) - 1 - sel_id = op_sel_ids !! idx - Just dm_id = defm_ids !! idx - in - tcMethodBind clas origin inst_ty sel_id meth_bind - `thenTc` \ (bind, insts, (_, local_dm_id)) -> - returnTc (bind, insts, ([clas_tyvar], RealId dm_id, local_dm_id)) - in - tcExtendGlobalTyVars clas_tyvar_set ( - mapAndUnzip3Tc tc_dm (flatten default_binds []) - ) `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) -> - - -- Check the context - newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> +%************************************************************************ +%* * +\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 + Id, -- Local Id (class tyvars instantiated) + LHsBind Name) -- Binding for the method + +tcMethodBind + :: [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 + + + 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 + + addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ + newDictsAtLoc (sig_loc meth_sig) (sig_theta meth_sig) `thenM` \ meth_dicts -> let - avail_insts = this_dict + meth_tvs = sig_tvs meth_sig + all_tyvars = meth_tvs ++ inst_tyvars + all_insts = avail_insts ++ meth_dicts + sel_name = idName sel_id in - tcSimplifyAndCheck - clas_tyvar_set - avail_insts - (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) -> + tcSimplifyCheck + (ptext SLIT("class or instance method") <+> quotes (ppr sel_id)) + all_tyvars all_insts meth_lie `thenM` \ lie_binds -> + + checkSigTyVars all_tyvars `thenM_` + tcPrags meth_id (prag_fn sel_name) `thenM` \ prags -> let - full_binds = AbsBinds - [clas_tyvar] - [this_dict_id] - abs_bind_stuff - (dict_binds `AndMonoBinds` andMonoBinds defm_binds) + [(_,_,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 - returnTc (const_lie, full_binds) + returnM (unitBag poly_meth_bind) + + +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 - (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas - origin = ClassDeclOrigin + 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} + - flatten EmptyMonoBinds rest = rest - flatten (AndMonoBinds b1 b2) rest = flatten b1 (flatten b2 rest) - flatten a_bind rest = a_bind : rest +\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 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} -@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. + +%************************************************************************ +%* * +\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} -tcMethodBind - :: Class - -> InstOrigin s - -> TcType s -- Instance type - -> Id -- The method selector - -> RenamedMonoBinds -- Method binding (just one) - -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s)) - -tcMethodBind clas origin inst_ty sel_id meth_bind - = tcAddSrcLoc src_loc $ - newMethod origin (RealId sel_id) [inst_ty] `thenNF_Tc` \ meth@(_, TcId local_meth_id) -> - tcInstSigTcType (idType local_meth_id) `thenNF_Tc` \ (tyvars', rho_ty') -> - let - (theta', tau') = splitRhoTy rho_ty' - sig_info = TySigInfo bndr_name local_meth_id tyvars' theta' tau' src_loc - in - tcBindWithSigs [bndr_name] meth_bind [sig_info] - nonRecursive (\_ -> NoPragmaInfo) `thenTc` \ (binds, insts, _) -> - - returnTc (binds, insts, meth) +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 - (bndr_name, src_loc) = case meth_bind of - FunMonoBind name _ _ loc -> (name, loc) - PatMonoBind (VarPatIn name) _ loc -> (name, loc) + 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} -Contexts -~~~~~~~~ + +%************************************************************************ +%* * + Error messages +%* * +%************************************************************************ + \begin{code} -classDeclCtxt class_name sty - = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name] +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 clas op + = hsep [ptext SLIT("Class"), 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}