X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=a89895ad1619a4fd117df7b70becb72342fee19c;hb=979947f545d70c63edb7ca96f6e47008ac90e3bf;hp=66b4d5619e660e07c4eb8ccd2150d03047a6c395;hpb=63d3d2028eebf43770212f55242c938c59d9ba13;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index 66b4d56..a89895a 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,74 +1,62 @@ % -% (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, checkValidClass, tcClassDecls2, + 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, collectMonoBinders, - 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 ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + getClassDeclSysNames, placeHolderType ) -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, tcLookupTyCon, 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 ) -import Class ( GenClass, mkClass, classBigSig, - classDefaultMethodId, - classOpTagByOccName, SYN_IE(Class) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) ) +import RnHsSyn ( RenamedTyClDecl, + RenamedClassOpSig, RenamedMonoBinds, + RenamedSig, maybeGenericMatch ) -import CmdLineOpts ( opt_PprUserLength ) -import Id ( GenId, mkSuperDictSelId, mkMethodSelId, - mkDefaultMethodId, getIdUnfolding, - idType, SYN_IE(Id) +import TcHsSyn ( TcMonoBinds ) + +import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + instToId, newDicts, newMethod ) +import TcEnv ( TyThingDetails(..), + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv ) -import CoreUnfold ( getUnfoldingTemplate ) -import IdInfo -import Name ( Name, isLocallyDefined, moduleString, getSrcLoc, - nameString, NamedThing(..) ) -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 TcBinds ( tcBindWithSigs, tcSpecSigs ) +import TcMonoType ( tcHsType, tcHsTheta, mkTcSig ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcUnify ( checkSigTyVars, sigCtxt ) +import TcMType ( tcInstSigTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) ) +import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar, + mkTyVarTys, mkPredTys, mkClassPred, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy ) -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 TcMonad +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 ( Id, idType, idName, setIdLocalExported ) +import Module ( Module ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) +import NameSet ( emptyNameSet ) +import Outputable +import Var ( TyVar ) +import VarSet ( mkVarSet, emptyVarSet ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count, isSingleton, lengthIs, equalLength ) +import Maybes ( seqMaybe, maybeToBool ) \end{code} @@ -106,214 +94,198 @@ Now DictTy in Type is just a form of type synomym: Death to "ExpandingDicts". +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ + \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) -> + +tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 (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 - rec_class_inst_env = rec_inst_mapper rec_class + 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 $ - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKind class_kind tyvar_kind `thenTc_` - + checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env -> + -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvar context pragmas - `thenTc` \ (scs, 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( equalLength context sc_sel_names ) + tcHsTheta context `thenTc` \ sc_theta -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env rec_class rec_tyvar) class_sigs - `thenTc` \ sig_stuff -> + mapTc (tcClassSig clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff -> - -- MAKE THE CLASS OBJECT ITSELF + -- MAKE THE CLASS DETAILS 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 + (op_tys, op_items) = unzip sig_stuff + sc_tys = mkPredTys sc_theta + dict_component_tys = sc_tys ++ op_tys + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] + + dict_con = mkDataCon datacon_name + [NotMarkedStrict | _ <- dict_component_tys] + [{- No labelled fields -}] + tyvars + [{-No context-}] + [{-No existential tyvars-}] [{-Or context-}] + dict_component_tys + (classTyCon clas) + dict_con_id dict_wrap_id + + 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} - - 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 +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 - mapTc (mk_super_id rec_class) super_classes `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 (super_classes, sc_sel_ids) + go (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ - where - rec_tyvar_ty = mkTyVarTy rec_tyvar + -- 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 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) + returnTc (unitNameEnv op all_generic) + where + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic +\end{code} -tcClassSig :: TcEnv s -- Knot tying only! - -> Class -- ...ditto... - -> TyVar -- The class type variable, used for error check only +\begin{code} +tcClassSig :: Class -- ...ditto... + -> [TyVar] -- The class type variable, used for error check only + -> Maybe (NameEnv Bool) -- Info about default methods; + -- Nothing => imported class defn with no method binds -> RenamedClassOpSig - -> TcM s (Id, -- selector id - Maybe Id) -- default-method ids + -> TcM (Type, -- Type of the method + ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding -tcClassSig rec_env rec_clas rec_clas_tyvar - (ClassOpSig op_name maybe_dm_name - op_ty - src_loc) +-- 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 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_tyvar] - [(rec_clas, mkTyVarTy rec_clas_tyvar)] - local_ty - in + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] -- 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} + sel_id = mkDictSelId op_name clas + DefMeth dm_name = sig_dm + dm_info = case maybe_dm_env of + Nothing -> sig_dm + Just dm_env -> mk_src_dm_info dm_env -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ - -The purpose of pass 2 is -\begin{enumerate} -\item -to beat on the explicitly-provided default-method decls (if any), -using them to produce a complete set of default-method decls. -(Omitted ones elicit an error message.) -\item -to produce a definition for the selector function for each method -and superclass dictionary. -\end{enumerate} - -Pass~2 only applies to locally-defined class declarations. - -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. - -\begin{code} -tcClassDecls2 :: [RenamedHsDecl] - -> NF_TcM s (LIE s, TcMonoBinds s) - -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) + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_name + in + returnTc (local_ty, (sel_id, dm_info)) \end{code} -@tcClassDecl2@ is the business end of things. +checkValidClass is called once the mutually-recursive knot has been +tied, so we can look at things freely. \begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcMonoBinds s) - -tcClassDecl2 (ClassDecl context class_name - tyvar_name class_sigs default_binds pragmas src_loc) - - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) +checkValidClass :: Class -> TcM () +checkValidClass cls + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ gla_exts -> - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc src_loc $ + -- Check that the class is unary, unless GlaExs + checkTc (not (null tyvars)) (nullaryClassErr cls) `thenTc_` + checkTc (gla_exts || unary) (classArityErr cls) `thenTc_` - -- Get the relevant class - tcLookupClass class_name `thenTc` \ (_, clas) -> - let - (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas + -- Check the super-classes + checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_` - -- 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 - ] + -- Check the class operations + mapTc_ check_op op_stuff `thenTc_` - final_sel_binds = andMonoBinds sel_binds - in - -- Generate bindings for the default methods - buildDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) -> + -- 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) - returnTc (const_insts, - final_sel_binds `AndMonoBinds` meth_binds) + where + (tyvars, theta, _, op_stuff) = classBigSig cls + unary = isSingleton tyvars + 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} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -336,23 +308,11 @@ 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} @@ -387,70 +347,307 @@ dfun.Foo.List dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -buildDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> TcM s (LIE s, TcMonoBinds s) +tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id]) + +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, ids1) -> + tc2 `thenNF_Tc` \ (lie2, binds2, ids2) -> + returnNF_Tc (lie1 `plusLIE` lie2, + binds1 `AndMonoBinds` binds2, + ids1 ++ ids2) +\end{code} + +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) -buildDefaultMethodBinds clas default_binds - = -- Construct suitable signatures - tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], [inst_ty], inst_env) -> +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds, [Id]) + +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 - mk_sig (bndr_name, locn) - = let - idx = classOpTagByOccName clas (getOccName bndr_name) - 1 - sel_id = op_sel_ids !! idx - Just dm_id = defm_ids !! idx - in - newMethod origin (RealId sel_id) [inst_ty] `thenNF_Tc` \ meth@(_, TcId local_dm_id) -> - tcInstSigTcType (idType local_dm_id) `thenNF_Tc` \ (tyvars', rho_ty') -> - let - (theta', tau') = splitRhoTy rho_ty' - sig_info = TySigInfo bndr_name local_dm_id tyvars' theta' tau' locn - in - returnNF_Tc (sig_info, ([clas_tyvar], RealId dm_id, TcId local_dm_id)) + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags in - mapAndUnzipNF_Tc mk_sig bndrs `thenNF_Tc` \ (sigs, abs_bind_stuff) -> - - -- Typecheck the default bindings + mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) -> + + returnTc (plusLIEs const_lies, andMonoBindList defm_binds, concat dm_ids_s) + + +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@(sel_id, DefMeth dm_name) + = tcInstSigTyVars ClsTv tyvars `thenNF_Tc` \ clas_tyvars -> let - clas_tyvar_set = unitTyVarSet clas_tyvar + dm_ty = idType sel_id -- Same as dict selector! + -- The default method's type should really come from the + -- iface file, since it could be usage-generalised, but this + -- requires altering the mess of knots in TcModule and I'm + -- too scared to do that. Instead, I have disabled generalisation + -- of types of default methods (and dict funs) by annotating them + -- TyGenNever (in MkId). Ugh! KSW 1999-09. + + inst_tys = mkTyVarTys clas_tyvars + theta = [mkClassPred clas inst_tys] + dm_id = mkDefaultMethodId dm_name dm_ty + local_dm_id = setIdLocalExported dm_id + -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId in - tcExtendGlobalTyVars clas_tyvar_set ( - tcBindWithSigs (map fst bndrs) default_binds sigs nonRecursive (\_ -> NoPragmaInfo) - ) `thenTc` \ (defm_binds, insts_needed, _) -> - - -- Check the context - newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + 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 - avail_insts = this_dict + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', local_dm_id, instToId local_dm_inst)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) in - tcSimplifyAndCheck - clas_tyvar_set - avail_insts - insts_needed `thenTc` \ (const_lie, dict_binds) -> + returnTc (full_bind, const_lie, [dm_id]) + 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, 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 - full_binds = AbsBinds - [clas_tyvar] - [this_dict_id] - abs_bind_stuff - (dict_binds `AndMonoBinds` defm_binds) + meth_id = instToId meth + meth_name = idName meth_id + meth_prags = find_prags (idName sel_id) meth_name prags in - returnTc (const_lie, full_binds) - + 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 + tcAddErrCtxt (ptext SLIT("When checking the type of class method") + <+> quotes (ppr sel_id)) $ + tcAddErrCtxtM (sigCtxt 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_name) + = -- An polymorphic default method + returnTc (HsVar dm_name) + +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 - (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas - origin = ClassDeclOrigin - bndrs = bagToList (collectMonoBinders default_binds) + 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 sense name phase loc : prags) + | name == sel_name = InlineSig sense meth_name phase loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (prag:prags) = find_prags sel_name meth_name prags +\end{code} -Contexts -~~~~~~~~ + +Contexts and errors +~~~~~~~~~~~~~~~~~~~ \begin{code} -classDeclCtxt class_name sty - = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name] +nullaryClassErr cls + = ptext SLIT("No parameters for class") <+> quotes (ppr cls) + +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) + +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) + +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) + +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}