X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=3154f84f7281dc48f1b5cdd1c8c19df184c50de4;hb=2ecf1c9f639dc75f1078e88c2e551116923f742a;hp=0b577afd843597310cc2be8796884882e090bbe8;hpb=c3216ad14253e47b4bd332660cb133c5fa753d1e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index 0b577af..3154f84 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,75 +1,61 @@ % -% (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 ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds, + tcMethodBind, badMethodErr + ) where + #include "HsVersions.h" -module TcClassDcl ( tcClassDecl1, tcClassDecls2 ) where - -IMP_Ubiq() - -import HsSyn ( HsDecl(..), ClassDecl(..), HsBinds(..), MonoBinds(..), - Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..), - DefaultDecl, TyDecl, InstDecl, IfaceSig, Fixity, - HsLit(..), OutPat(..), Sig(..), HsType(..), HsTyVar, - SYN_IE(RecFlag), nonRecursive, andMonoBinds, - Stmt, DoOrListComp, ArithSeqInfo, InPat, Fake ) -import HsTypes ( getTyVarName ) -import HsPragmas ( ClassPragmas(..) ) -import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..), - RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds), - RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl) +import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), HsType(..), HsPred(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassDecl, isClassOpSig, isPragSig, + getClassDeclSysNames, tyClDeclName ) -import TcHsSyn ( TcIdOcc(..), 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, tcLookupTyCon, newLocalIds, tcAddImportedIdInfo, - tcExtendGlobalTyVars ) -import TcInstDcls ( tcMethodBind ) -import TcKind ( unifyKind, TcKind ) -import TcMonad -import TcMonoType ( tcHsType, tcContext ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars, tcInstSigType ) -import PragmaInfo ( PragmaInfo(..) ) - -import Bag ( foldBag, unionManyBags ) -import Class ( GenClass, GenClassOp, mkClass, mkClassOp, classBigSig, - classOps, classOpString, classOpLocalType, classDefaultMethodId, - classOpTagByOccName, SYN_IE(ClassOp), SYN_IE(Class) +import BasicTypes ( TopLevelFlag(..), RecFlag(..) ) +import RnHsSyn ( RenamedTyClDecl, + RenamedClassOpSig, RenamedMonoBinds, + RenamedContext, RenamedHsDecl, RenamedSig, + maybeGenericMatch ) -import CmdLineOpts ( opt_PprUserLength ) -import Id ( GenId, mkSuperDictSelId, mkMethodSelId, - mkDefaultMethodId, getIdUnfolding, - idType, SYN_IE(Id) +import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) + +import Inst ( InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + newDicts, newMethod ) +import TcEnv ( TcId, TcEnv, TyThingDetails(..), tcAddImportedIdInfo, + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName ) -import CoreUnfold ( getUnfoldingTemplate ) -import IdInfo -import Name ( Name, isLocallyDefined, moduleString, - nameString, NamedThing(..) ) +import TcBinds ( tcBindWithSigs, tcSpecSigs ) +import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, checkAmbiguity, sigCtxt, mkTcSig ) +import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) +import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcSigTyVars ) +import TcMonad +import Generics ( mkGenericRhs, validGenericMethodType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, classSelIds, classTyCon, classTvsFds, + Class, ClassOpItem, DefMeth (..), FunDep ) +import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) +import DataCon ( mkDataCon, notMarkedStrict ) +import Id ( Id, idType, idName ) +import Name ( Name, isLocallyDefined, NamedThing(..), + NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, + plusNameEnv, nameEnvElts ) +import NameSet ( emptyNameSet ) import Outputable -import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID ) -import Pretty -import PprType ( GenClass, GenType, GenTyVar, GenClassOp ) -import SpecEnv ( SpecEnv ) -import SrcLoc ( mkGeneratedSrcLoc ) -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, - mkForAllTy, mkSigmaTy, splitSigmaTy, SYN_IE(Type) +import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkClassPred, + splitTyConApp_maybe, isTyVarTy ) -import TysWiredIn ( stringTy ) -import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) ) -import Unique ( Unique ) -import UniqFM ( 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 Var ( TyVar ) +import VarSet ( mkVarSet, emptyVarSet ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count ) +import Maybes ( seqMaybe, maybeToBool, orElse ) \end{code} @@ -107,143 +93,196 @@ Now DictTy in Type is just a form of type synomym: Death to "ExpandingDicts". +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ + \begin{code} -tcClassDecl1 rec_inst_mapper +tcClassDecl1 :: TcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 rec_env (ClassDecl context class_name - tyvar_name class_sigs def_methods pragmas src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (classDeclCtxt class_name) $ + tyvar_names fundeps class_sigs def_methods + sys_names src_loc) + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ glaExts -> + checkTc (glaExts || length tyvar_names == 1) + (classArityErr class_name) `thenTc_` -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupClass class_name `thenTc` \ (class_kind, rec_class) -> - tcLookupTyVar (getTyVarName tyvar_name) `thenNF_Tc` \ (tyvar_kind, rec_tyvar) -> + tcLookupClass class_name `thenTc` \ clas -> let - (rec_class_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_class + (tyvars, fds) = classTvsFds clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names in + tcExtendTyVarEnv tyvars $ - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKind class_kind tyvar_kind `thenTc_` - + -- CHECK THAT THE DEFAULT BINDINGS ARE LEGAL + checkDefaultBinds clas op_names def_methods `thenTc` \ dm_info -> + checkGenericClassIsUnary clas dm_info `thenTc_` + -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvar context pragmas - `thenTc` \ (scs, sc_sel_ids) -> + tcSuperClasses clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_class rec_tyvar rec_class_op_inst_fn) class_sigs - `thenTc` \ sig_stuff -> + mapTc (tcClassSig rec_env clas tyvars fds dm_info) + op_sigs `thenTc` \ sig_stuff -> - -- MAKE THE CLASS OBJECT ITSELF + -- MAKE THE CLASS DETAILS let - (ops, op_sel_ids, defm_ids) = unzip3 sig_stuff - clas = mkClass (uniqueOf class_name) (getName class_name) rec_tyvar - scs sc_sel_ids ops op_sel_ids defm_ids - rec_class_inst_env + (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 clas + returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con) \end{code} +\begin{code} +checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds -> TcM (NameEnv (DefMeth Name)) + -- 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 - let - clas_ty = mkTyVarTy clas_tyvar - dict_component_tys = [mkDictTy sc clas_ty | sc <- scs] ++ - [classOpLocalType op | op <- ops]) - 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 +checkDefaultBinds clas ops EmptyMonoBinds = returnTc emptyNameEnv + +checkDefaultBinds clas ops (AndMonoBinds b1 b2) + = checkDefaultBinds clas ops b1 `thenTc` \ dm_info1 -> + checkDefaultBinds clas ops b2 `thenTc` \ dm_info2 -> + returnTc (dm_info1 `plusNameEnv` dm_info2) + +checkDefaultBinds clas ops (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ + + -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_` + + -- Check that all the defns ar generic, or none are + checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_` + + -- Make up the right dm_info + if all_generic then + returnTc (unitNameEnv op GenDefMeth) + else + -- An explicit non-generic default method + newDefaultMethodName op loc `thenNF_Tc` \ dm_name -> + returnTc (unitNameEnv op (DefMeth dm_name)) + + where + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = n_generic == length matches + +checkGenericClassIsUnary clas dm_info + = -- Check that if the class has generic methods, then the + -- class has only one parameter. We can't do generic + -- multi-parameter type classes! + checkTc (unary || no_generics) (genericMultiParamErr clas) + where + unary = length (classTyVars clas) == 1 + no_generics = null [() | GenDefMeth <- nameEnvElts dm_info] +\end{code} \begin{code} -tcClassContext :: Class -> TyVar +tcSuperClasses :: Class -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s ([Class], -- the superclasses - [Id]) -- superclass selector Ids + -> [Name] -- Names for superclass selectors + -> TcM (ClassContext, -- the superclass context + [Id]) -- superclass selector Ids -tcClassContext rec_class rec_tyvar context pragmas +tcSuperClasses 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. - 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 -> + -- For std Haskell check that the context constrains only tyvars + doptsTc Opt_GlasgowExts `thenTc` \ glaExts -> + (if glaExts 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 (super_classes, sc_sel_ids) + returnTc (sc_theta, sc_sel_ids) where - rec_tyvar_ty = mkTyVarTy rec_tyvar + check_constraint sc@(HsPClass c tys) + = checkTc (all is_tyvar tys) (superClassErr clas sc) - 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) + is_tyvar (HsTyVar _) = True + is_tyvar other = False -tcClassSig :: Class -- Knot tying only! - -> TyVar -- The class type variable, used for error check only - -> (ClassOp -> SpecEnv) -- Ditto; the spec info for the class ops +tcClassSig :: TcEnv -- Knot tying only! + -> Class -- ...ditto... + -> [TyVar] -- The class type variable, used for error check only + -> [FunDep TyVar] + -> NameEnv (DefMeth Name) -- Info about default methods -> RenamedClassOpSig - -> TcM s (ClassOp, -- class op - Id, -- selector id - Id) -- default-method ids - -tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn - (ClassOpSig op_name dm_name - op_ty - src_loc) + -> 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 clas clas_tyvars fds dm_info + (ClassOpSig op_name maybe_dm op_ty src_loc) = tcAddSrcLoc src_loc $ - fixTc ( \ ~(_, rec_sel_id, rec_defm_id) -> -- Knot for pragmas -- 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 -> + tcHsSigType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy [rec_clas_tyvar] - [(rec_clas, mkTyVarTy rec_clas_tyvar)] - local_ty - class_op_nm = getOccName op_name - class_op = mkClassOp class_op_nm - (classOpTagByOccName rec_clas{-yeeps!-} class_op_nm) - local_ty + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] in + -- Check for ambiguous class op types + checkAmbiguity True clas_tyvars theta local_ty `thenTc` \ global_ty -> - -- Build the selector id and default method id let - sel_id = mkMethodSelId op_name rec_clas class_op global_ty - defm_id = mkDefaultMethodId dm_name rec_clas class_op False global_ty - -- ToDo: improve the "False" + -- Build the selector id and default method id + sel_id = mkDictSelId op_name clas + + dm_info_name = maybe_dm `orElse` lookupNameEnv dm_info op_name `orElse` NoDefMeth + + dm_info_id = case dm_info_name of + NoDefMeth -> NoDefMeth + GenDefMeth -> GenDefMeth + DefMeth dm_name -> DefMeth (tcAddImportedIdInfo rec_env dm_id) + where + dm_id = mkDefaultMethodId dm_name clas global_ty in - tcAddImportedIdInfo defm_id `thenNF_Tc` \ final_defm_id -> - returnTc (class_op, sel_id, final_defm_id) - ) + -- Check that for a generic method, the type of + -- the method is sufficiently simple + checkTc (dm_info_name /= GenDefMeth || validGenericMethodType local_ty) + (badGenericMethodType op_name op_ty) `thenTc_` + + returnTc (local_ty, (sel_id, dm_info_id)) \end{code} @@ -253,77 +292,27 @@ tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn %* * %************************************************************************ -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 +@mkImplicitClassBinds@ produces a binding 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, TcHsBinds s) - -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyBinds)) - [tcClassDecl2 cls_decl | ClD cls_decl <- decls] +mkImplicitClassBinds :: [Class] -> NF_TcM ([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 - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` binds2) -\end{code} - -@tcClassDecl2@ is the business end of things. - -\begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcHsBinds s) - -tcClassDecl2 (ClassDecl context class_name - tyvar_name class_sigs default_binds pragmas src_loc) - - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyBinds) + (cls_ids_s, binds_s) = unzip (map mk_implicit classes) - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc src_loc $ - - -- Get the relevant class - tcLookupClass class_name `thenTc` \ (_, clas) -> - let - (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids) - = classBigSig clas + mk_implicit clas = (sel_ids, binds) + where + sel_ids = classSelIds clas + binds | isLocallyDefined clas = idsToMonoBinds sel_ids + | otherwise = EmptyMonoBinds +\end{code} - -- 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 = MonoBind (andMonoBinds sel_binds) [] nonRecursive - in - -- Generate bindings for the default methods - tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) -> - mapAndUnzipTc (buildDefaultMethodBind clas clas_tyvar default_binds) - (op_sel_ids `zip` [0..]) - `thenTc` \ (const_insts_s, meth_binds) -> - - returnTc (unionManyBags const_insts_s, - final_sel_binds `ThenBinds` - MonoBind (andMonoBinds meth_binds) [] nonRecursive) -\end{code} %************************************************************************ %* * @@ -347,23 +336,11 @@ 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} @@ -398,56 +375,298 @@ dfun.Foo.List dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -buildDefaultMethodBind - :: Class - -> TcTyVar s - -> RenamedMonoBinds - -> (Id, Int) - -> TcM s (LIE s, TcMonoBinds s) +tcClassDecls2 :: [RenamedHsDecl] -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecls2 decls + = foldr combine + (returnNF_Tc (emptyLIE, EmptyMonoBinds)) + [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, + isClassDecl cls_decl, + isLocallyDefined (tyClDeclName 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} -buildDefaultMethodBind clas clas_tyvar default_binds (sel_id, idx) - = newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) + +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecl2 (ClassDecl context class_name + tyvar_names _ sigs default_binds _ src_loc) + = -- A locally defined class + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ + tcAddSrcLoc src_loc $ + tcLookupClass class_name `thenNF_Tc` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each let - avail_insts = this_dict - defm_id = classDefaultMethodId clas idx - no_prags name = NoPragmaInfo -- No pragmas yet for default methods + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags in - tcExtendGlobalTyVars clas_tyvar_set ( - tcMethodBind noDefmExpr inst_ty no_prags default_binds (sel_id, idx) - ) `thenTc` \ (defm_bind, insts_needed, (_, local_defm_id)) -> - - -- CHECK THE CONTEXT OF THE DEFAULT-METHOD BINDS + mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) -> + + returnTc (plusLIEs const_lies, andMonoBindList defm_binds) + + +tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE) +tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE) + -- Generate code for polymorphic default methods only + -- (Generic default methods have turned into instance decls by now.) + -- This is incompatible with Hugs, which expects a polymorphic + -- default method for every class op, regardless of whether or not + -- the programmer supplied an explicit default decl for the class. + -- (If necessary we can fix that, but we don't have a convenient Id to hand.) + +tcDefMeth clas tyvars binds_in prags op_item@(_, DefMeth 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]) -> + + tcExtendTyVarEnvForMeths tyvars clas_tyvars ( + tcMethodBind clas origin clas_tyvars inst_tys theta + binds_in prags False op_item + ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) -> + + tcAddErrCtxt (defltMethCtxt clas) $ + + -- 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' -> + + -- Check the context tcSimplifyAndCheck - clas_tyvar_set - avail_insts - insts_needed `thenTc` \ (const_lie, dict_binds) -> - + (ptext SLIT("class") <+> ppr clas) + (mkVarSet clas_tyvars') + this_dict + insts_needed `thenTc` \ (const_lie, dict_binds) -> + let - defm_binds = AbsBinds - [clas_tyvar] - [this_dict_id] - [([clas_tyvar], RealId defm_id, local_defm_id)] - (dict_binds `AndMonoBinds` defm_bind) + 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 (const_lie, defm_binds) + returnTc (full_bind, const_lie) + where + 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} +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 (TcMonoBinds, LIE, (LIE, TcId)) + +tcMethodBind clas origin inst_tyvars inst_tys inst_theta + meth_binds prags is_inst_decl (sel_id, dm_info) + = 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 + sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id + meth_prags = find_prags (idName sel_id) meth_name prags + in + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnTc user_bind + Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs -> + returnTc (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs Nothing loc] loc) + ) `thenTc` \ meth_bind -> + -- Check the bindings; first add inst_tyvars to the envt + -- so that we don't quantify over them in nested places + -- The *caller* put the class/inst decl tyvars into the envt + tcExtendGlobalTyVars (mkVarSet inst_tyvars) + (tcAddErrCtxt (methodCtxt sel_id) $ + tcBindWithSigs NotTopLevel meth_bind + [sig_info] meth_prags NonRecursive + ) `thenTc` \ (binds, insts, _) -> + + tcExtendLocalValEnv [(meth_name, meth_id)] + (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) -> + + -- The prag_lie for a SPECIALISE pragma will mention the function + -- itself, so we have to simplify them away right now lest they float + -- outwards! + bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) -> + + -- Now check that the instance type variables + -- (or, in the case of a class decl, the class tyvars) + -- have not been unified with anything in the environment + -- + -- We do this for each method independently to localise error messages + -- ...and this is why the call to tcExtendGlobalTyVars must be here + -- rather than in the caller + tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $ + checkSigTyVars inst_tyvars emptyVarSet `thenTc_` + + returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, + insts `plusLIE` prag_lie', + meth) + + -- The user didn't supply a method binding, + -- so we have to make up a default binding + -- The RHS of a default method depends on the default-method info +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc (DefMeth dm_id) + = -- An polymorphic default method + returnTc (HsVar (idName dm_id)) + +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth + = -- No default method + -- Warn only if -fwarn-missing-methods + doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn -> + warnTc (is_inst_decl && warn) + (omittedMethodWarn sel_id clas) `thenNF_Tc_` + returnTc error_rhs where - clas_tyvar_set = unitTyVarSet clas_tyvar - inst_ty = mkTyVarTy clas_tyvar - origin = ClassDeclOrigin - noDefmExpr _ = HsApp (HsVar (getName nO_DEFAULT_METHOD_ERROR_ID)) - (HsLit (HsString (_PK_ error_msg))) - - error_msg = show (sep [text "Class", ppr (PprForUser opt_PprUserLength) clas, - text "Method", ppr (PprForUser opt_PprUserLength) sel_id]) + error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (HsLit (HsString (_PK_ error_msg))) + error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + + +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth + = -- A generic default method + -- If the method is defined generically, we can only do the job if the + -- instance declaration is for a single-parameter type class with + -- a type constructor applied to type arguments in the instance decl + -- (checkTc, so False provokes the error) + checkTc (not is_inst_decl || simple_inst) + (badGenericInstance sel_id clas) `thenTc_` + + ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_` + returnTc rhs + where + rhs = mkGenericRhs sel_id clas_tyvar tycon + + stuff = vcat [ppr clas <+> ppr inst_tys, + nest 4 (ppr sel_id <+> equals <+> ppr rhs)] + + -- The tycon is only used in the generic case, and in that + -- case we require that the instance decl is for a single-parameter + -- type class with type variable arguments: + -- instance (...) => C (T a b) + simple_inst = maybeToBool maybe_tycon + clas_tyvar = head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of + [ty] -> case splitTyConApp_maybe ty of + Just (tycon, arg_tys) | all isTyVarTy arg_tys -> Just tycon + other -> Nothing + other -> Nothing \end{code} +\begin{code} +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +find_bind sel_name meth_name (FunMonoBind op_name fix matches loc) + | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc) +find_bind sel_name meth_name (AndMonoBinds b1 b2) + = find_bind sel_name meth_name b1 `seqMaybe` find_bind sel_name meth_name b2 +find_bind sel_name meth_name other = Nothing -- Default case + + -- Find the prags for this method, and replace the + -- selector name with the method name +find_prags sel_name meth_name [] = [] +find_prags sel_name meth_name (SpecSig name ty loc : prags) + | name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (InlineSig name phase loc : prags) + | name == sel_name = InlineSig meth_name phase loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (NoInlineSig name phase loc : prags) + | name == sel_name = NoInlineSig 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 -~~~~~~~~ +Contexts and errors +~~~~~~~~~~~~~~~~~~~ \begin{code} -classDeclCtxt class_name sty - = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name] +classArityErr class_name + = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) + +superClassErr clas sc + = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc) + <+> ptext SLIT("in declaration for class") <+> quotes (ppr clas) + +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 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)] + +badGenericMethodType op op_ty + = hang (ptext SLIT("Generic method type is too complex")) + 4 (vcat [ppr op <+> dcolon <+> ppr op_ty, + ptext SLIT("You can only use type variables, arrows, and tuples")]) + +badGenericInstance sel_id clas + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + ptext SLIT("because the instance declaration is not for a simple type (T a b c)"), + ptext SLIT("(where T is a derivable type constructor)"), + 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) + +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}