X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=97e5d5b99e29bb7b43e36bb07a5f392f88072ae2;hb=17985eb4007ae2415a97335b26fabc82fc38521f;hp=e4dec94c52709f8ec6f3daf533b6dca1b7769ad6;hpb=f36fb2ce821caf594c1db5669dd10ca082f66361;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index e4dec94..97e5d5b 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,72 +1,60 @@ % -% (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, tcMethodBind, badMethodErr ) where +module TcClassDcl ( tcClassDecl1, checkValidClass, tcClassDecls2, + tcMethodBind, badMethodErr + ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..), - InPat(..), HsBinds(..), GRHSsAndBinds(..), GRHS(..), - HsExpr(..), HsLit(..), - unguardedRHS, andMonoBinds, getTyVarName +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + getClassDeclSysNames, placeHolderType ) -import HsPragmas ( ClassPragmas(..) ) -import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedClassDecl, RenamedClassPragmas, +import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) ) +import RnHsSyn ( RenamedTyClDecl, RenamedClassOpSig, RenamedMonoBinds, - RenamedContext, RenamedHsDecl, RenamedSig + RenamedSig, maybeGenericMatch ) import TcHsSyn ( TcMonoBinds ) -import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, newDicts, newMethod ) -import TcEnv ( TcIdOcc(..), GlobalValueEnv, tcAddImportedIdInfo, - tcLookupClass, tcLookupTyVar, - tcExtendGlobalTyVars, tcExtendLocalValEnv +import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + instToId, newDicts, newMethod ) +import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo, + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv ) -import TcBinds ( tcBindWithSigs, bindInstsOfLocalFuns, - checkSigTyVars, sigCtxt, tcPragmaSigs, TcSigInfo(..) +import TcBinds ( tcBindWithSigs, tcSpecSigs ) +import TcMonoType ( tcHsType, tcHsTheta, checkSigTyVars, sigCtxt, mkTcSig ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcMType ( tcInstTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) ) +import TcType ( Type, mkSigmaTy, mkTyVarTys, mkPredTys, mkClassPred, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy ) -import TcKind ( unifyKinds, TcKind ) import TcMonad -import TcMonoType ( tcHsType, tcContext ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( TcType, TcTyVar, TcTyVarSet, tcInstSigTyVars, - zonkSigTyVar, tcInstSigTcType - ) -import PrelVals ( nO_METHOD_BINDING_ERROR_ID ) -import FieldLabel ( firstFieldLabelTag ) -import Bag ( unionManyBags ) -import Class ( mkClass, classBigSig, Class ) -import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods ) -import MkId ( mkDataCon, mkSuperDictSelId, - mkMethodSelId, mkDefaultMethodId - ) -import Id ( Id, StrictnessMark(..), - getIdUnfolding, idType, idName - ) -import CoreUnfold ( getUnfoldingTemplate ) -import IdInfo -import Name ( Name, isLocallyDefined, OccName, nameOccName, - NamedThing(..) ) +import Generics ( mkGenericRhs, validGenericMethodType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, classTyCon, className, + Class, ClassOpItem, DefMeth (..) ) +import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) +import DataCon ( mkDataCon ) +import Id ( idType, idName ) +import Module ( Module ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) +import NameSet ( emptyNameSet ) import Outputable -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy, - mkSigmaTy, mkForAllTys, Type, ThetaType - ) -import TyVar ( mkTyVarSet, tyVarKind, TyVar ) -import TyCon ( mkDataTyCon ) -import Kind ( mkBoxedTypeKind, mkArrowKind ) -import Unique ( Unique, Uniquable(..) ) -import Util -import Maybes ( assocMaybe, maybeToBool, seqMaybe ) - - --- import TcPragmas ( tcGenPragmas, tcClassOpPragmas ) -tcGenPragmas ty id ps = returnNF_Tc noIdInfo -tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo, - noIdInfo) +import Var ( TyVar ) +import VarSet ( mkVarSet, emptyVarSet ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count ) +import Maybes ( seqMaybe, maybeToBool ) \end{code} @@ -104,225 +92,212 @@ 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_names class_sigs def_methods pragmas - tycon_name datacon_name src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (classDeclCtxt class_name) $ - - -- CHECK ARITY 1 FOR HASKELL 1.4 - checkTc (opt_GlasgowExts || length tyvar_names == 1) - (classArityErr class_name) `thenTc_` +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ - -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupClass class_name `thenTc` \ (class_kinds, rec_class) -> - mapAndUnzipNF_Tc (tcLookupTyVar . getTyVarName) tyvar_names - `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) -> +\begin{code} - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKinds class_kinds tyvar_kinds `thenTc_` +tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 rec_env + (ClassDecl {tcdCtxt = context, tcdName = class_name, + tcdTyVars = tyvar_names, tcdFDs = fundeps, + tcdSigs = class_sigs, tcdMeths = def_methods, + tcdSysNames = sys_names, tcdLoc = src_loc}) + = -- LOOK THINGS UP IN THE ENVIRONMENT + tcLookupClass class_name `thenTc` \ clas -> + let + tyvars = classTyVars clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names + in + tcExtendTyVarEnv tyvars $ + checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env -> + -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvars context pragmas - `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) -> + -- The renamer has already checked that the context mentions + -- only the type variable of the class decl. + -- Context is already kind-checked + ASSERT( length context == length sc_sel_names ) + tcHsTheta context `thenTc` \ sc_theta -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env rec_class rec_tyvars) class_sigs - `thenTc` \ sig_stuff -> + mapTc (tcClassSig rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff -> - -- MAKE THE CLASS OBJECT ITSELF + -- MAKE THE CLASS DETAILS let - (op_tys, op_sel_ids, defm_ids) = unzip3 sig_stuff - rec_class_inst_env = rec_inst_mapper rec_class - clas = mkClass (getName class_name) rec_tyvars - sc_theta sc_sel_ids op_sel_ids defm_ids - tycon - rec_class_inst_env - + (op_tys, op_items) = unzip sig_stuff + sc_tys = mkPredTys sc_theta dict_component_tys = sc_tys ++ op_tys - new_or_data = case dict_component_tys of - [_] -> NewType - other -> DataType - - dict_con_id = mkDataCon datacon_name - [NotMarkedStrict | _ <- dict_component_tys] - [{- No labelled fields -}] - rec_tyvars - [{-No context-}] - [{-No existential tyvars-}] [{-Or context-}] - dict_component_tys - tycon - - tycon = mkDataTyCon tycon_name - (foldr (mkArrowKind . tyVarKind) mkBoxedTypeKind rec_tyvars) - rec_tyvars - [] -- No context - [dict_con_id] -- Constructors - [] -- No derivings - (Just clas) -- Yes! It's a dictionary - new_or_data - NonRecursive + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] + + dict_con = mkDataCon datacon_name + [NotMarkedStrict | _ <- dict_component_tys] + [{- No labelled fields -}] + tyvars + [{-No context-}] + [{-No existential tyvars-}] [{-Or context-}] + dict_component_tys + (classTyCon clas) + dict_con_id dict_wrap_id + + 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} -tcClassContext :: Class -> [TyVar] - -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s (ThetaType, -- the superclass context - [Type], -- types of the superclass dictionaries - [Id]) -- superclass selector Ids - -tcClassContext rec_class rec_tyvars 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` \ sc_theta -> - let - sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta] - in +checkDefaultBinds :: Class -> [Name] -> Maybe RenamedMonoBinds + -> TcM (Maybe (NameEnv Bool)) + -- The returned environment says + -- x not in env => no default method + -- x -> True => generic default method + -- x -> False => polymorphic default method + + -- Check default bindings + -- a) must be for a class op for this class + -- b) must be all generic or all non-generic + -- and return a mapping from class-op to DefMeth info + + -- But do all this only for source binds + +checkDefaultBinds clas ops Nothing + = returnTc Nothing + +checkDefaultBinds clas ops (Just mbs) + = go mbs `thenTc` \ dm_env -> + returnTc (Just dm_env) + where + go EmptyMonoBinds = returnTc emptyNameEnv - -- Make super-class selector ids - -- We number them off, 1, 2, 3 etc so that we can construct - -- names for the selectors. Thus - -- class (C a, C b) => D a b where ... - -- gives superclass selectors - -- D_sc1, D_sc2 - -- (We used to call them D_C, but now we can have two different - -- superclasses both called C!) - mapTc mk_super_id (sc_theta `zip` [firstFieldLabelTag..]) `thenTc` \ sc_sel_ids -> + go (AndMonoBinds b1 b2) + = go b1 `thenTc` \ dm_info1 -> + go b2 `thenTc` \ dm_info2 -> + returnTc (dm_info1 `plusNameEnv` dm_info2) - -- Done - returnTc (sc_theta, sc_tys, sc_sel_ids) + go (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ - where - rec_tyvar_tys = mkTyVarTys rec_tyvars + -- 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_` - mk_super_id ((super_class, tys), index) - = tcGetUnique `thenNF_Tc` \ uniq -> - let - ty = mkForAllTys rec_tyvars $ - mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys) - in - returnTc (mkSuperDictSelId uniq rec_class index ty) + returnTc (unitNameEnv op all_generic) + where + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = n_generic == length matches +\end{code} -tcClassSig :: GlobalValueEnv -- Knot tying only! +\begin{code} +tcClassSig :: RecTcEnv -- Knot tying only! -> Class -- ...ditto... -> [TyVar] -- The class type variable, used for error check only + -> Maybe (NameEnv Bool) -- Info about default methods -> RenamedClassOpSig - -> TcM s (Type, -- Type of the method - Id, -- selector id - Maybe Id) -- default-method ids - -tcClassSig rec_env rec_clas rec_clas_tyvars - (ClassOpSig op_name maybe_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 unf_env clas clas_tyvars maybe_dm_env + (ClassOpSig op_name sig_dm op_ty src_loc) = tcAddSrcLoc src_loc $ -- Check the type signature. NB that the envt *already has* -- bindings for the type variables; see comments in TcTyAndClassDcls. + tcHsType op_ty `thenTc` \ local_ty -> - -- NB: Renamer checks that the class type variable is mentioned in local_ty, - -- and that it is not constrained by theta - tcHsType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy rec_clas_tyvars - [(rec_clas, mkTyVarTys rec_clas_tyvars)] - local_ty - in + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] + global_ty = mkSigmaTy clas_tyvars theta local_ty + -- The default method's type should really come from the + -- iface file, since it could be usage-generalised, but this + -- requires altering the mess of knots in TcModule and I'm + -- too scared to do that. Instead, I have disabled generalisation + -- of types of default methods (and dict funs) by annotating them + -- TyGenNever (in MkId). Ugh! KSW 1999-09. -- 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) + sel_id = mkDictSelId op_name clas + dm_id = mkDefaultMethodId dm_name global_ty + DefMeth dm_name = sig_dm + + dm_info = case maybe_dm_env of + Nothing -> iface_dm_info + Just dm_env -> mk_src_dm_info dm_env + + iface_dm_info = case sig_dm of + NoDefMeth -> NoDefMeth + GenDefMeth -> GenDefMeth + DefMeth dm_name -> DefMeth (tcAddImportedIdInfo unf_env dm_id) + + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_id in - returnTc (local_ty, sel_id, maybe_dm_id) + returnTc (local_ty, (sel_id, dm_info)) \end{code} +checkValidClass is called once the mutually-recursive knot has been +tied, so we can look at things freely. -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ +\begin{code} +checkValidClass :: Class -> TcM () +checkValidClass cls + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ gla_exts -> -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} + -- Check that the class is unary, unless GlaExs + checkTc (arity > 0) (nullaryClassErr cls) `thenTc_` + checkTc (gla_exts || unary) (classArityErr cls) `thenTc_` -Pass~2 only applies to locally-defined class declarations. + -- Check the super-classes + checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_` -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. + -- Check the class operations + mapTc_ check_op op_stuff `thenTc_` -\begin{code} -tcClassDecls2 :: [RenamedHsDecl] - -> NF_TcM s (LIE s, TcMonoBinds s) + -- Check that if the class has generic methods, then the + -- class has only one parameter. We can't do generic + -- multi-parameter type classes! + checkTc (unary || no_generics) (genericMultiParamErr cls) -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - [tcClassDecl2 cls_decl | ClD cls_decl <- decls] where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) + (tyvars, theta, sel_ids, op_stuff) = classBigSig cls + arity = length tyvars + unary = arity == 1 + no_generics = null [() | (_, GenDefMeth) <- op_stuff] + + check_op (sel_id, dm) + = checkValidTheta SigmaCtxt (tail theta) `thenTc_` + -- The 'tail' removes the initial (C a) from the + -- class itself, leaving just the method type + + checkValidType (FunSigCtxt op_name) tau `thenTc_` + + -- Check that for a generic method, the type of + -- the method is sufficiently simple + checkTc (dm /= GenDefMeth || validGenericMethodType op_ty) + (badGenericMethodType op_name op_ty) + where + op_name = idName sel_id + op_ty = idType sel_id + (_,theta,tau) = tcSplitSigmaTy op_ty \end{code} -@tcClassDecl2@ is the business end of things. - -\begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcMonoBinds s) - -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 $ - - -- Get the relevant class - tcLookupClass class_name `thenTc` \ (_, clas) -> - let - (tyvars, sc_theta, 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) -\end{code} %************************************************************************ %* * @@ -346,23 +321,11 @@ 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} @@ -397,58 +360,110 @@ dfun.Foo.List dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -tcDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> TcM s (LIE s, TcMonoBinds s) +tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds) -tcDefaultMethodBinds clas default_binds - = -- Construct suitable signatures - tcInstSigTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) -> +tcClassDecls2 this_mod decls + = foldr combine + (returnNF_Tc (emptyLIE, EmptyMonoBinds)) + [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls] + -- The 'Just' picks out source ClassDecls + where + combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> + tc2 `thenNF_Tc` \ (lie2, binds2) -> + returnNF_Tc (lie1 `plusLIE` lie2, + binds1 `AndMonoBinds` binds2) +\end{code} + +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) - -- Typecheck the default bindings +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs, + tcdMeths = Just default_binds, tcdLoc = src_loc}) + = -- The 'Just' picks out source ClassDecls + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ + tcAddSrcLoc src_loc $ + tcLookupClass class_name `thenNF_Tc` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each let - tc_dm sel_id_w_dm@(_, Just dm_id) - = tcMethodBind clas origin inst_tys clas_tyvars - default_binds [{-no prags-}] False - sel_id_w_dm `thenTc` \ (bind, insts, (_, local_dm_id)) -> - returnTc (bind, insts, (clas_tyvars, RealId dm_id, local_dm_id)) - in - mapAndUnzip3Tc tc_dm sel_ids_w_dms `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) -> - - -- Check the context - newDicts origin [(clas,inst_tys)] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags + in + 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 - avail_insts = this_dict + theta = [(mkClassPred clas inst_tys)] in - tcAddErrCtxt (classDeclCtxt clas) $ - mapNF_Tc zonkSigTyVar clas_tyvars `thenNF_Tc` \ clas_tyvars' -> - tcSimplifyAndCheck - (ptext SLIT("class") <+> ppr clas) - (mkTyVarSet clas_tyvars') - avail_insts - (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) -> - + newDicts origin theta `thenNF_Tc` \ [this_dict] -> + + tcExtendTyVarEnvForMeths tyvars clas_tyvars ( + tcMethodBind clas origin clas_tyvars inst_tys theta + binds_in prags False op_item + ) `thenTc` \ (defm_bind, insts_needed, local_dm_inst) -> + + tcAddErrCtxt (defltMethCtxt clas) $ + + -- Check the context + tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed `thenTc` \ (const_lie, dict_binds) -> + + -- Simplification can do unification + checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' -> + let - full_binds = AbsBinds - clas_tyvars' - [this_dict_id] - abs_bind_stuff - (dict_binds `AndMonoBinds` andMonoBinds defm_binds) + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', dm_id, instToId local_dm_inst)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) in - returnTc (const_lie, full_binds) - + returnTc (full_bind, const_lie) where - (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas - - sel_ids_w_dms = [pair | pair@(_, Just _) <- op_sel_ids `zip` defm_ids] - -- Just the ones for which there is an explicit - -- user default declaration - 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 @@ -457,140 +472,183 @@ tyvar sets. \begin{code} tcMethodBind :: Class - -> InstOrigin s - -> [TcType s] -- Instance types - -> [TcTyVar s] -- Free variables of those instance types - -- they'll be signature tyvars, and we - -- want to check that they don't bound + -> 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 <=> supply default decl if no explicit decl - -- This is true for instance decls, - -- false for class decls - -> (Id, Maybe Id) -- The method selector and default-method Id - -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s)) - -tcMethodBind clas origin inst_tys inst_tyvars - meth_binds prags supply_default_bind - (sel_id, maybe_dm_id) - | no_user_bind && not supply_default_bind - = pprPanic "tcMethodBind" (ppr clas <+> ppr inst_tys) - - | otherwise - = tcGetSrcLoc `thenNF_Tc` \ loc -> - - -- Warn if no method binding, only if -fwarn-missing-methods - warnTc (opt_WarnMissingMethods && no_user_bind && no_user_default) - (omittedMethodWarn sel_id clas) `thenNF_Tc_` - - newMethod origin (RealId sel_id) inst_tys `thenNF_Tc` \ meth@(_, TcId meth_id) -> - tcInstSigTcType (idType meth_id) `thenNF_Tc` \ (tyvars', rho_ty') -> - let - (theta', tau') = splitRhoTy rho_ty' - - meth_name = idName meth_id - sig_info = TySigInfo meth_name meth_id tyvars' theta' tau' loc - meth_bind = mk_meth_bind meth_name loc - meth_prags = find_prags meth_name prags - in - tcExtendLocalValEnv [meth_name] [meth_id] ( - tcPragmaSigs meth_prags - ) `thenTc` \ (prag_info_fn, prag_binds1, prag_lie) -> - - -- Check that the signatures match - tcExtendGlobalTyVars inst_tyvars ( - tcAddErrCtxt (methodCtxt sel_id) $ - tcBindWithSigs NotTopLevel [meth_name] meth_bind [sig_info] - NonRecursive prag_info_fn - ) `thenTc` \ (binds, insts, _) -> - - -- 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 - tcAddErrCtxt (monoCtxt sel_id) ( - tcAddErrCtxt (sigCtxt sel_id) $ - checkSigTyVars inst_tyvars (idType meth_id) - ) `thenTc_` - - returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, - insts `plusLIE` prag_lie', - meth) - where - sel_name = idName sel_id - - maybe_user_bind = find meth_binds - - no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False} - no_user_default = case maybe_dm_id of {Nothing -> True; other -> False} - - find EmptyMonoBinds = Nothing - find (AndMonoBinds b1 b2) = find b1 `seqMaybe` find b2 - find b@(FunMonoBind op_name _ _ _) = if op_name == sel_name then Just b else Nothing - find b@(PatMonoBind (VarPatIn op_name) _ _) = if op_name == sel_name then Just b else Nothing - find other = panic "Urk! Bad instance method binding" - - -- 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. - mk_meth_bind meth_name loc - = case maybe_user_bind of - Just (FunMonoBind _ fix matches loc) -> FunMonoBind meth_name fix matches loc - Just (PatMonoBind (VarPatIn _) rhs loc) -> PatMonoBind (VarPatIn meth_name) rhs loc - Nothing -> mk_default_bind meth_name loc - - -- 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 spec loc : prags) - | name == sel_name = SpecSig meth_name ty spec loc : find_prags meth_name prags - find_prags meth_name (InlineSig name loc : prags) - | name == sel_name = InlineSig meth_name loc : find_prags meth_name prags - find_prags meth_name (NoInlineSig name loc : prags) - | name == sel_name = NoInlineSig meth_name loc : find_prags meth_name prags - find_prags meth_name (prag:prags) = find_prags meth_name prags - - mk_default_bind local_meth_name loc - = PatMonoBind (VarPatIn local_meth_name) - (GRHSsAndBindsIn (unguardedRHS (default_expr loc) loc) EmptyBinds) - loc - - default_expr loc - = case maybe_dm_id of - Just dm_id -> HsVar (getName dm_id) -- There's a default method - Nothing -> 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 ]) + -> Bool -- True <=> This method is from an instance declaration + -> ClassOpItem -- The method selector and default-method Id + -> TcM (TcMonoBinds, LIE, Inst) + +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 -> + let + meth_id = instToId meth + meth_name = idName meth_id + sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id + meth_prags = find_prags (idName sel_id) meth_name prags + in + mkTcSig meth_id loc `thenNF_Tc` \ sig_info -> + + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnTc user_bind + Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs -> + returnTc (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs placeHolderType loc] loc) + ) `thenTc` \ meth_bind -> + -- Check the bindings; first add inst_tyvars to the envt + -- so that we don't quantify over them in nested places + -- The *caller* put the class/inst decl tyvars into the envt + tcExtendGlobalTyVars (mkVarSet inst_tyvars) + (tcAddErrCtxt (methodCtxt sel_id) $ + tcBindWithSigs NotTopLevel meth_bind + [sig_info] meth_prags NonRecursive + ) `thenTc` \ (binds, insts, _) -> + + tcExtendLocalValEnv [(meth_name, meth_id)] + (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) -> + + -- The prag_lie for a SPECIALISE pragma will mention the function + -- itself, so we have to simplify them away right now lest they float + -- outwards! + bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) -> + + -- Now check that the instance type variables + -- (or, in the case of a class decl, the class tyvars) + -- have not been unified with anything in the environment + -- + -- We do this for each method independently to localise error messages + -- ...and this is why the call to tcExtendGlobalTyVars must be here + -- rather than in the caller + tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $ + checkSigTyVars inst_tyvars emptyVarSet `thenTc_` + + returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, + insts `plusLIE` prag_lie', + meth) + + -- The user didn't supply a method binding, + -- so we have to make up a default binding + -- The RHS of a default method depends on the default-method info +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc (DefMeth dm_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) `thenNF_Tc_` + returnTc error_rhs + where + error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (HsLit (HsString (_PK_ error_msg))) + error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + + +mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth + = -- A generic default method + -- If the method is defined generically, we can only do the job if the + -- instance declaration is for a single-parameter type class with + -- a type constructor applied to type arguments in the instance decl + -- (checkTc, so False provokes the error) + checkTc (not is_inst_decl || simple_inst) + (badGenericInstance sel_id) `thenTc_` + + ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_` + returnTc rhs + where + rhs = mkGenericRhs sel_id clas_tyvar tycon + + stuff = vcat [ppr clas <+> ppr inst_tys, + nest 4 (ppr sel_id <+> equals <+> ppr rhs)] + + -- The tycon is only used in the generic case, and in that + -- case we require that the instance decl is for a single-parameter + -- type class with type variable arguments: + -- instance (...) => C (T a b) + simple_inst = maybeToBool maybe_tycon + clas_tyvar = head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of + [ty] -> case tcSplitTyConApp_maybe ty of + Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon + other -> Nothing + other -> Nothing \end{code} + +\begin{code} +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +find_bind sel_name meth_name (FunMonoBind op_name fix matches loc) + | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc) +find_bind sel_name meth_name (AndMonoBinds b1 b2) + = find_bind sel_name meth_name b1 `seqMaybe` find_bind sel_name meth_name b2 +find_bind sel_name meth_name other = Nothing -- Default case + + -- Find the prags for this method, and replace the + -- selector name with the method name +find_prags sel_name meth_name [] = [] +find_prags sel_name meth_name (SpecSig name ty loc : prags) + | name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (InlineSig 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 and errors ~~~~~~~~~~~~~~~~~~~ \begin{code} -classArityErr class_name - = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) +nullaryClassErr cls + = ptext SLIT("No parameters for class") <+> quotes (ppr cls) -classDeclCtxt class_name - = ptext SLIT("In the class declaration for") <+> quotes (ppr class_name) +classArityErr cls + = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls), + parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))] + +defltMethCtxt 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) -monoCtxt sel_id - = sep [ptext SLIT("Probable cause: the right hand side of") <+> quotes (ppr sel_id), - nest 4 (ptext SLIT("mentions a top-level variable subject to the dreaded monomorphism restriction")) - ] - -badMethodErr bndr clas +badMethodErr clas op = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have a method"), quotes (ppr bndr)] + ptext SLIT("does not have a method"), quotes (ppr op)] + +omittedMethodWarn sel_id + = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) + +badGenericMethodType op op_ty + = hang (ptext SLIT("Generic method type is too complex")) + 4 (vcat [ppr op <+> dcolon <+> ppr op_ty, + ptext SLIT("You can only use type variables, arrows, and tuples")]) + +badGenericInstance sel_id + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + ptext SLIT("because the instance declaration is not for a simple type (T a b c)"), + ptext SLIT("(where T is a derivable type constructor)")] + +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) -omittedMethodWarn sel_id clas - = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id), - ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)] +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}