X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=fb29e563bc2d4c893d630a7afa68204ebe0f2abb;hb=115f0fae2f782836550a9419f739fd29c09e4f1b;hp=794eb83876823639510ba37cc153d3edd6e95cc2;hpb=edd06d674dd5ffa05c08b6d75dd3a6b63b016f58;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index 794eb83..fb29e56 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -4,63 +4,65 @@ \section[TcClassDcl]{Typechecking class declarations} \begin{code} -module TcClassDcl ( kcClassDecl, tcClassDecl1, tcClassDecls2, - tcMethodBind, checkFromThisClass +module TcClassDcl ( tcClassDecl1, tcClassDecls2, + MethodSpec, tcMethodBind, mkMethodBind, badMethodErr ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), - InPat(..), HsBinds(..), GRHSs(..), - HsExpr(..), HsLit(..), HsType(..), pprClassAssertion, - unguardedRHS, andMonoBinds, andMonoBindList, getTyVarName, - isClassDecl, isClassOpSig, collectMonoBinders +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), Pat(WildPat), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + placeHolderType ) -import HsPragmas ( ClassPragmas(..) ) -import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas, +import BasicTypes ( RecFlag(..), StrictnessMark(..) ) +import RnHsSyn ( RenamedTyClDecl, RenamedSig, RenamedClassOpSig, RenamedMonoBinds, - RenamedContext, RenamedHsDecl, RenamedSig + maybeGenericMatch ) +import RnEnv ( lookupSysName ) import TcHsSyn ( TcMonoBinds ) -import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod ) -import TcEnv ( TcId, ValueEnv, TcTyThing(..), tcAddImportedIdInfo, - tcLookupClass, tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, - tcExtendLocalValEnv +import Inst ( Inst, InstOrigin(..), instToId, newDicts, newMethod ) +import TcEnv ( TyThingDetails(..), + tcLookupClass, tcExtendTyVarEnv2, + tcExtendTyVarEnv ) -import TcBinds ( tcBindWithSigs, tcSpecSigs ) -import TcUnify ( unifyKinds ) -import TcMonad -import TcMonoType ( tcHsType, tcHsTopType, tcExtendTopTyVarScope, - tcContext, checkSigTyVars, sigCtxt, mkTcSig +import TcBinds ( tcMonoBinds ) +import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig ) +import TcSimplify ( tcSimplifyCheck ) +import TcUnify ( checkSigTyVars, sigCtxt ) +import TcMType ( tcInstTyVars ) +import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar, + mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy, + getClassPredTys_maybe, mkPhiTy ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr, tcGetTyVar ) +import TcRnMonad +import Generics ( mkGenericRhs ) import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) -import FieldLabel ( firstFieldLabelTag ) -import Bag ( unionManyBags, bagToList ) -import Class ( mkClass, classBigSig, Class ) -import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods ) -import MkId ( mkDictSelId, mkDataConId, mkDefaultMethodId ) -import DataCon ( mkDataCon, notMarkedStrict ) -import Id ( Id, setInlinePragma, getIdUnfolding, idType, idName ) -import CoreUnfold ( unfoldingTemplate ) -import IdInfo -import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) ) -import NameSet ( emptyNameSet ) +import Class ( classTyVars, classBigSig, classTyCon, + Class, ClassOpItem, DefMeth (..) ) +import TyCon ( tyConGenInfo ) +import Subst ( substTyWith ) +import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) +import DataCon ( mkDataCon ) +import Id ( Id, idType, idName, mkUserLocal, setIdLocalExported, setInlinePragma ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) +import NameSet ( emptyNameSet, unitNameSet ) +import OccName ( mkClassTyConOcc, mkClassDataConOcc, mkWorkerOcc, + mkSuperDictSelOcc, reportIfUnused ) import Outputable -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, - mkSigmaTy, mkForAllTys, Type, ThetaType, - boxedTypeKind, mkArrowKind - ) -import Var ( tyVarKind, TyVar ) -import VarSet ( mkVarSet ) -import TyCon ( mkAlgTyCon ) -import Unique ( Unique, Uniquable(..) ) -import Util +import Var ( TyVar ) +import CmdLineOpts +import UnicodeUtil ( stringToUtf8 ) +import ErrUtils ( dumpIfSet ) +import Util ( count, lengthIs, isSingleton ) import Maybes ( seqMaybe ) -import FiniteMap ( lookupWithDefaultFM ) +import Maybe ( isJust ) +import FastString \end{code} @@ -100,264 +102,160 @@ Death to "ExpandingDicts". %************************************************************************ %* * -\subsection{Kind checking} -%* * -%************************************************************************ - -\begin{code} -kcClassDecl (ClassDecl context class_name - tyvar_names class_sigs def_methods pragmas - tycon_name datacon_name sc_sel_names src_loc) - = -- CHECK ARITY 1 FOR HASKELL 1.4 - checkTc (opt_GlasgowExts || length tyvar_names == 1) - (classArityErr class_name) `thenTc_` - - -- Get the (mutable) class kind - tcLookupTy class_name `thenNF_Tc` \ (kind, _, _) -> - - -- Make suitable tyvars and do kind checking - -- The net effect is to mutate the class kind - tcExtendTopTyVarScope kind tyvar_names $ \ _ _ -> - tcContext context `thenTc_` - mapTc kc_sig the_class_sigs `thenTc_` - - returnTc () - where - the_class_sigs = filter isClassOpSig class_sigs - - kc_sig (ClassOpSig _ _ op_ty loc) = tcAddSrcLoc loc (tcHsType op_ty) -\end{code} - - -%************************************************************************ -%* * \subsection{Type checking} %* * %************************************************************************ \begin{code} -tcClassDecl1 rec_env rec_inst_mapper rec_vrcs - (ClassDecl context class_name - tyvar_names class_sigs def_methods pragmas - tycon_name datacon_name sc_sel_names src_loc) + +tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name, + tcdTyVars = tyvar_names, tcdFDs = fundeps, + tcdSigs = class_sigs, tcdMeths = def_methods, + tcdLoc = src_loc}) = -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupTy class_name `thenTc` \ (class_kind, _, AClass rec_class) -> - tcExtendTopTyVarScope class_kind tyvar_names $ \ tyvars _ -> - -- The class kind is by now immutable + tcLookupClass class_name `thenM` \ clas -> + let + tyvars = classTyVars clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + in + tcExtendTyVarEnv tyvars $ + + checkDefaultBinds clas op_names def_methods `thenM` \ mb_dm_env -> -- CHECK THE CONTEXT --- traceTc (text "tcClassCtxt" <+> ppr class_name) `thenTc_` - tcClassContext class_name rec_class tyvars context sc_sel_names - `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) -> --- traceTc (text "tcClassCtxt done" <+> ppr class_name) `thenTc_` + -- The renamer has already checked that the context mentions + -- only the type variable of the class decl. + -- Context is already kind-checked + tcHsTheta context `thenM` \ sc_theta -> -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_env rec_class tyvars) - (filter isClassOpSig class_sigs) - `thenTc` \ sig_stuff -> - - -- MAKE THE CLASS OBJECT ITSELF + mappM (tcClassSig clas tyvars mb_dm_env) op_sigs `thenM` \ sig_stuff -> + + -- MAKE THE CLASS DETAILS + lookupSysName class_name mkClassDataConOcc `thenM` \ datacon_name -> + lookupSysName datacon_name mkWorkerOcc `thenM` \ datacon_wkr_name -> + mapM (lookupSysName class_name . mkSuperDictSelOcc) + [1..length context] `thenM` \ sc_sel_names -> + -- We number off the superclass selectors, 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!) + lookupSysName class_name mkClassTyConOcc `thenM` \ tycon_name -> let - (op_tys, op_sel_ids, defm_ids) = unzip3 sig_stuff - rec_class_inst_env = rec_inst_mapper rec_class - clas = mkClass class_name 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 + 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 - tycon dict_con_id - - -- In general, constructors don't have to be inlined, but this one - -- does, because we don't make a top level binding for it. - dict_con_id = mkDataConId dict_con - `setInlinePragma` IMustBeINLINEd - - argvrcs = lookupWithDefaultFM rec_vrcs (pprPanic "tcClassDecl1: argvrcs:" $ - ppr tycon_name) - tycon_name - - tycon = mkAlgTyCon tycon_name - class_kind - tyvars - [] -- No context - argvrcs - [dict_con] -- Constructors - [] -- No derivings - (Just clas) -- Yes! It's a dictionary - new_or_data - NonRecursive + [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 + returnM (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name) \end{code} - \begin{code} -tcClassContext :: Name -> Class -> [TyVar] - -> RenamedContext -- class context - -> [Name] -- Names for superclass selectors - -> TcM s (ThetaType, -- the superclass context - [Type], -- types of the superclass dictionaries - [Id]) -- superclass selector Ids - -tcClassContext class_name rec_class rec_tyvars context sc_sel_names - = -- Check the context. - -- The renamer has already checked that the context mentions - -- only the type variable of the class decl. +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 + = returnM Nothing + +checkDefaultBinds clas ops (Just mbs) + = go mbs `thenM` \ dm_env -> + returnM (Just dm_env) + where + go EmptyMonoBinds = returnM emptyNameEnv - -- For std Haskell check that the context constrains only tyvars - (if opt_GlasgowExts then - returnTc [] - else - mapTc check_constraint context - ) `thenTc_` + go (AndMonoBinds b1 b2) + = go b1 `thenM` \ dm_info1 -> + go b2 `thenM` \ dm_info2 -> + returnM (dm_info1 `plusNameEnv` dm_info2) - tcContext context `thenTc` \ sc_theta -> + go (FunMonoBind op _ matches loc) + = addSrcLoc loc $ - let - sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta] - sc_sel_ids = zipWithEqual "tcClassContext" mk_super_id sc_sel_names sc_tys - in - -- Done - returnTc (sc_theta, sc_tys, sc_sel_ids) + -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) `thenM_` - where - rec_tyvar_tys = mkTyVarTys rec_tyvars + -- Check that all the defns ar generic, or none are + checkTc (all_generic || none_generic) (mixedGenericErr op) `thenM_` - mk_super_id name dict_ty - = mkDictSelId name rec_class ty - where - ty = mkForAllTys rec_tyvars $ - mkFunTy (mkDictTy rec_class rec_tyvar_tys) dict_ty - - check_constraint (c, tys) = checkTc (all is_tyvar tys) - (superClassErr class_name (c, tys)) - - is_tyvar (MonoTyVar _) = True - is_tyvar other = False + returnM (unitNameEnv op all_generic) + where + n_generic = count (isJust . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic +\end{code} -tcClassSig :: ValueEnv -- Knot tying only! - -> Class -- ...ditto... +\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 (Type, -- Type of the method - 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 + +-- 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 rec_clas rec_clas_tyvars - (ClassOpSig op_name maybe_dm_name - op_ty - src_loc) - = tcAddSrcLoc src_loc $ +tcClassSig clas clas_tyvars maybe_dm_env + (ClassOpSig op_name sig_dm op_ty src_loc) + = addSrcLoc src_loc $ -- Check the type signature. NB that the envt *already has* -- bindings for the type variables; see comments in TcTyAndClassDcls. + tcHsType op_ty `thenM` \ local_ty -> - -- NB: Renamer checks that the class type variable is mentioned in local_ty, - -- and that it is not constrained by theta --- traceTc (text "tcClassSig" <+> ppr op_name) `thenTc_` - tcHsTopType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy rec_clas_tyvars - [(rec_clas, mkTyVarTys rec_clas_tyvars)] - local_ty + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] -- Build the selector id and default method id - sel_id = mkDictSelId 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 --- traceTc (text "tcClassSig done" <+> ppr op_name) `thenTc_` - returnTc (local_ty, sel_id, maybe_dm_id) -\end{code} - - -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ - -The purpose of pass 2 is -\begin{enumerate} -\item -to beat on the explicitly-provided default-method decls (if any), -using them to produce a complete set of default-method decls. -(Omitted ones elicit an error message.) -\item -to produce a definition for the selector function for each method -and superclass dictionary. -\end{enumerate} - -Pass~2 only applies to locally-defined class declarations. - -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. - -\begin{code} -tcClassDecls2 :: [RenamedHsDecl] - -> NF_TcM s (LIE, TcMonoBinds) - -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, isClassDecl cls_decl] - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) -\end{code} - -@tcClassDecl2@ is the business end of things. - -\begin{code} -tcClassDecl2 :: RenamedTyClDecl -- The class declaration - -> NF_TcM s (LIE, TcMonoBinds) - -tcClassDecl2 (ClassDecl context class_name - tyvar_names class_sigs default_binds pragmas _ _ _ src_loc) - - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) + sel_id = mkDictSelId op_name clas + DefMeth dm_name = sig_dm - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc src_loc $ + dm_info = case maybe_dm_env of + Nothing -> sig_dm + Just dm_env -> mk_src_dm_info dm_env - -- Get the relevant class - tcLookupClass class_name `thenNF_Tc` \ 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 sel_id (unfoldingTemplate (getIdUnfolding sel_id)) - | sel_id <- sc_sel_ids ++ op_sel_ids - ] + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_name in - -- Generate bindings for the default methods - tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) -> - - returnTc (const_insts, - meth_binds `AndMonoBinds` andMonoBindList sel_binds) + returnM (local_ty, (sel_id, dm_info)) \end{code} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -419,242 +317,399 @@ dfun.Foo.List dfoo_list \end{verbatim} -\begin{code} -tcDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> TcM s (LIE, TcMonoBinds) - -tcDefaultMethodBinds clas default_binds - = -- Check that the default bindings come from this class - checkFromThisClass clas op_sel_ids default_binds `thenNF_Tc_` +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. - -- Do each default method separately - mapAndUnzipTc tc_dm sel_ids_w_dms `thenTc` \ (defm_binds, const_lies) -> +\begin{code} +tcClassDecls2 :: [RenamedTyClDecl] -> TcM (TcMonoBinds, [Id]) - returnTc (plusLIEs const_lies, andMonoBindList defm_binds) +tcClassDecls2 decls + = foldr combine + (returnM (EmptyMonoBinds, [])) + [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls] + -- The 'Just' picks out source ClassDecls where + combine tc1 tc2 = tc1 `thenM` \ (binds1, ids1) -> + tc2 `thenM` \ (binds2, ids2) -> + returnM (binds1 `AndMonoBinds` binds2, + ids1 ++ ids2) +\end{code} - (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 +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) - origin = ClassDeclOrigin +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> TcM (TcMonoBinds, [Id]) + +tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs, + tcdMeths = Just default_binds, tcdLoc = src_loc}) + = -- The 'Just' picks out source ClassDecls + recoverM (returnM (EmptyMonoBinds, [])) $ + addSrcLoc src_loc $ + tcLookupClass class_name `thenM` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each + let + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags + in + mapAndUnzipM tc_dm op_items `thenM` \ (defm_binds, dm_ids_s) -> - -- We make a separate binding for each default method. - -- At one time I used a single AbsBinds for all of them, thus - -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } - -- But that desugars into - -- ds = \d -> (..., ..., ...) - -- dm1 = \d -> case ds d of (a,b,c) -> a - -- And since ds is big, it doesn't get inlined, so we don't get good - -- default methods. Better to make separate AbsBinds for each - - tc_dm sel_id_w_dm@(_, Just dm_id) - = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) -> - let - theta = [(clas,inst_tys)] - in - newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - let - avail_insts = this_dict - in - tcExtendTyVarEnvForMeths tyvars clas_tyvars ( - tcMethodBind clas origin clas_tyvars inst_tys theta - default_binds [{-no prags-}] False - sel_id_w_dm - ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) -> + returnM (andMonoBindList defm_binds, concat dm_ids_s) - tcAddErrCtxt (defltMethCtxt clas) $ + +tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnM (EmptyMonoBinds, []) +tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnM (EmptyMonoBinds, []) + -- 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) + = tcInstTyVars ClsTv tyvars `thenM` \ (clas_tyvars, inst_tys, _) -> + let + 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. + + theta = [mkClassPred clas inst_tys] + local_dm_id = mkDefaultMethodId dm_name dm_ty + xtve = tyvars `zip` clas_tyvars + in + newDicts origin theta `thenM` \ [this_dict] -> + + mkMethodBind origin clas inst_tys binds_in op_item `thenM` \ (_, meth_info) -> + getLIE (tcMethodBind xtve clas_tyvars theta + [this_dict] prags meth_info) `thenM` \ (defm_bind, insts_needed) -> - -- 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 - mapNF_Tc zonkTcTyVarBndr clas_tyvars `thenNF_Tc` \ clas_tyvars' -> + addErrCtxt (defltMethCtxt clas) $ - -- Check the context - tcSimplifyAndCheck - (ptext SLIT("class") <+> ppr clas) - (mkVarSet clas_tyvars') - avail_insts - insts_needed `thenTc` \ (const_lie, dict_binds) -> + -- Check the context + tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed `thenM` \ dict_binds -> + + -- Simplification can do unification + checkSigTyVars clas_tyvars `thenM` \ clas_tyvars' -> - let - full_bind = AbsBinds - clas_tyvars' - [this_dict_id] - [(clas_tyvars', dm_id, local_dm_id)] - emptyNameSet -- No inlines (yet) - (dict_binds `andMonoBinds` defm_bind) - in - returnTc (full_bind, const_lie) -\end{code} - -\begin{code} -checkFromThisClass :: Class -> [Id] -> RenamedMonoBinds -> NF_TcM s () -checkFromThisClass clas op_sel_ids mono_binds - = mapNF_Tc check_from_this_class bndrs `thenNF_Tc_` - returnNF_Tc () + let + (_,dm_inst_id,_) = meth_info + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', local_dm_id, dm_inst_id)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) + in + returnM (full_bind, [local_dm_id]) where - check_from_this_class (bndr, loc) - | nameOccName bndr `elem` sel_names = returnNF_Tc () - | otherwise = tcAddSrcLoc loc $ - addErrTc (badMethodErr bndr clas) - sel_names = map getOccName op_sel_ids - bndrs = bagToList (collectMonoBinders mono_binds) + 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} +type MethodSpec = (Id, -- Global selector Id + Id, -- Local Id (class tyvars instantiated) + RenamedMonoBinds) -- Binding for the method + tcMethodBind - :: Class - -> InstOrigin + :: [(TyVar,TcTyVar)] -- Bindings for type environment -> [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, LIE, (LIE, TcId)) - -tcMethodBind clas origin inst_tyvars inst_tys inst_theta - meth_binds prags supply_default_bind - (sel_id, maybe_dm_id) - = tcGetSrcLoc `thenNF_Tc` \ loc -> - - newMethod origin sel_id inst_tys `thenNF_Tc` \ meth@(_, meth_id) -> - mkTcSig meth_id loc `thenNF_Tc` \ sig_info -> - - let - meth_name = idName meth_id - maybe_user_bind = find_bind meth_name meth_binds - - no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False} - no_user_default = case maybe_dm_id of {Nothing -> True; other -> False} - - meth_bind = case maybe_user_bind of - Just bind -> bind - Nothing -> mk_default_bind meth_name loc - - meth_prags = find_prags meth_name prags - in - - -- Warn if no method binding, only if -fwarn-missing-methods - if no_user_bind && not supply_default_bind then - pprPanic "tcMethodBind" (ppr clas <+> ppr inst_tys) - else - warnTc (opt_WarnMissingMethods && no_user_bind && no_user_default) - (omittedMethodWarn sel_id clas) `thenNF_Tc_` - - -- Check the bindings; first add inst_tyvars to the envt + -- enclosing class/instance decl. + -- They'll be signature tyvars, and we + -- want to check that they don't get bound + -- Always equal the range of the type envt + -> TcThetaType -- Available theta; it's just used for the error message + -> [Inst] -- Available from context, used to simplify constraints + -- from the method body + -> [RenamedSig] -- Pragmas (e.g. inline pragmas) + -> MethodSpec -- Details of this method + -> TcM TcMonoBinds + +tcMethodBind xtve inst_tyvars inst_theta avail_insts prags + (sel_id, meth_id, meth_bind) + = -- Check the bindings; first adding inst_tyvars to the envt -- so that we don't quantify over them in nested places - -- The *caller* put the class/inst decl tyvars into the envt - tcExtendGlobalTyVars (mkVarSet inst_tyvars) ( - tcAddErrCtxt (methodCtxt sel_id) $ - tcBindWithSigs NotTopLevel meth_bind - [sig_info] meth_prags NonRecursive - ) `thenTc` \ (binds, insts, _) -> - - - 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 - tcAddErrCtxtM (sigCtxt sig_msg (mkSigmaTy inst_tyvars inst_theta (idType meth_id))) $ - checkSigTyVars inst_tyvars `thenTc_` - - returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2, - insts `plusLIE` prag_lie', - meth) - where - sig_msg ty = sep [ptext SLIT("When checking the expected type for"), - nest 4 (ppr sel_name <+> dcolon <+> ppr ty)] - - sel_name = idName sel_id - - -- The renamer just puts the selector ID as the binder in the method binding - -- but we must use the method name; so we substitute it here. Crude but simple. - find_bind meth_name (FunMonoBind op_name fix matches loc) - | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc) - find_bind meth_name (PatMonoBind (VarPatIn op_name) grhss loc) - | op_name == sel_name = Just (PatMonoBind (VarPatIn meth_name) grhss loc) - find_bind meth_name (AndMonoBinds b1 b2) - = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2 - find_bind meth_name other = Nothing -- Default case - - - -- Find the prags for this method, and replace the - -- selector name with the method name - find_prags meth_name [] = [] - find_prags meth_name (SpecSig name ty loc : prags) - | name == sel_name = SpecSig meth_name ty loc : find_prags meth_name prags - find_prags meth_name (InlineSig name 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) - (GRHSs (unguardedRHS (default_expr loc) loc) EmptyBinds Nothing) - 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 ]) + mkTcSig meth_id `thenM` \ meth_sig -> + + tcExtendTyVarEnv2 xtve ( + addErrCtxt (methodCtxt sel_id) $ + getLIE (tcMonoBinds meth_bind [meth_sig] NonRecursive) + ) `thenM` \ ((meth_bind, _, _), meth_lie) -> + + -- Now do context reduction. We simplify wrt both the local tyvars + -- and the ones of the class/instance decl, so that there is + -- no problem with + -- class C a where + -- op :: Eq a => a -> b -> a + -- + -- We do this for each method independently to localise error messages + + let + TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig + in + addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ + newDicts SignatureOrigin meth_theta `thenM` \ meth_dicts -> + let + all_tyvars = meth_tvs ++ inst_tyvars + all_insts = avail_insts ++ meth_dicts + in + tcSimplifyCheck + (ptext SLIT("class or instance method") <+> quotes (ppr sel_id)) + all_tyvars all_insts meth_lie `thenM` \ lie_binds -> + + checkSigTyVars all_tyvars `thenM` \ all_tyvars' -> + + let + -- Attach inline pragmas as appropriate + (final_meth_id, inlines) + | (InlineSig inl _ phase _ : _) <- filter is_inline prags + = (meth_id `setInlinePragma` phase, + if inl then unitNameSet (idName meth_id) else emptyNameSet) + | otherwise + = (meth_id, emptyNameSet) + + is_inline (InlineSig _ name _ _) = name == idName sel_id + is_inline other = False + + meth_tvs' = take (length meth_tvs) all_tyvars' + poly_meth_bind = AbsBinds meth_tvs' + (map instToId meth_dicts) + [(meth_tvs', final_meth_id, local_meth_id)] + inlines + (lie_binds `andMonoBinds` meth_bind) + in + returnM poly_meth_bind + + +mkMethodBind :: InstOrigin + -> Class -> [TcType] -- Class and instance types + -> RenamedMonoBinds -- Method binding (pick the right one from in here) + -> ClassOpItem + -> TcM (Maybe Inst, -- Method inst + MethodSpec) +-- Find the binding for the specified method, or make +-- up a suitable default method if it isn't there + +mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info) + = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) -> + let + meth_name = idName meth_id + in + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + getSrcLocM `thenM` \ loc -> + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnM user_bind + Nothing -> mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs -> + returnM (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs placeHolderType loc] loc) + ) `thenM` \ meth_bind -> + + returnM (mb_inst, (sel_id, meth_id, meth_bind)) + +mkMethId :: InstOrigin -> Class + -> Id -> [TcType] -- Selector, and instance types + -> TcM (Maybe Inst, Id) + +-- mkMethId instantiates the selector Id at the specified types +-- THe +mkMethId origin clas sel_id inst_tys + = let + (tyvars,rho) = tcSplitForAllTys (idType sel_id) + rho_ty = ASSERT( length tyvars == length inst_tys ) + substTyWith tyvars inst_tys rho + (preds,tau) = tcSplitPhiTy rho_ty + first_pred = head preds + in + -- The first predicate should be of form (C a b) + -- where C is the class in question + ASSERT( not (null preds) && + case getClassPredTys_maybe first_pred of + { Just (clas1,tys) -> clas == clas1 ; Nothing -> False } + ) + if isSingleton preds then + -- If it's the only one, make a 'method' + getInstLoc origin `thenM` \ inst_loc -> + newMethod inst_loc sel_id inst_tys preds tau `thenM` \ meth_inst -> + returnM (Just meth_inst, instToId meth_inst) + else + -- If it's not the only one we need to be careful + -- For example, given 'op' defined thus: + -- class Foo a where + -- op :: (?x :: String) => a -> a + -- (mkMethId op T) should return an Inst with type + -- (?x :: String) => T -> T + -- That is, the class-op's context is still there. + -- BUT: it can't be a Method any more, because it breaks + -- INVARIANT 2 of methods. (See the data decl for Inst.) + newUnique `thenM` \ uniq -> + getSrcLocM `thenM` \ loc -> + let + real_tau = mkPhiTy (tail preds) tau + meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc + in + returnM (Nothing, meth_id) + + -- The user didn't supply a method binding, + -- so we have to make up a default binding + -- The RHS of a default method depends on the default-method info +mkDefMethRhs origin clas inst_tys sel_id loc (DefMeth dm_name) + = -- An polymorphic default method + traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_` + returnM (HsVar dm_name) + +mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth + = -- No default method + -- Warn only if -fwarn-missing-methods + doptM Opt_WarnMissingMethods `thenM` \ warn -> + warnTc (isInstDecl origin + && warn + && reportIfUnused (getOccName sel_id)) + (omittedMethodWarn sel_id) `thenM_` + returnM error_rhs + where + error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc) + simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg)))) + error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) + + -- When the type is of form t1 -> t2 -> t3 + -- make a default method like (\ _ _ -> noMethBind "blah") + -- rather than simply (noMethBind "blah") + -- Reason: if t1 or t2 are higher-ranked types we get n + -- silly ambiguity messages. + -- Example: f :: (forall a. Eq a => a -> a) -> Int + -- f = error "urk" + -- Here, tcSub tries to force (error "urk") to have the right type, + -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t) + -- where 't' is fresh ty var. This leads directly to "ambiguous t". + -- + -- NB: technically this changes the meaning of the default-default + -- method slightly, because `seq` can see the lambdas. Oh well. + (_,_,tau1) = tcSplitSigmaTy (idType sel_id) + (_,_,tau2) = tcSplitSigmaTy tau1 + -- Need two splits because the selector can have a type like + -- forall a. Foo a => forall b. Eq b => ... + (arg_tys, _) = tcSplitFunTys tau2 + wild_pats = [WildPat placeHolderType | ty <- arg_tys] + +mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth + = -- A generic default method + -- If the method is defined generically, we can only do the job if the + -- instance declaration is for a single-parameter type class with + -- a type constructor applied to type arguments in the instance decl + -- (checkTc, so False provokes the error) + ASSERT( isInstDecl origin ) -- We never get here from a class decl + + checkTc (isJust maybe_tycon) + (badGenericInstance sel_id (notSimple inst_tys)) `thenM_` + checkTc (isJust (tyConGenInfo tycon)) + (badGenericInstance sel_id (notGeneric tycon)) `thenM_` + + ioToTcRn (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenM_` + returnM 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) + clas_tyvar = head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of + [ty] -> case tcSplitTyConApp_maybe ty of + Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon + other -> Nothing + other -> Nothing + +isInstDecl InstanceDeclOrigin = True +isInstDecl ClassDeclOrigin = False \end{code} -Contexts and errors -~~~~~~~~~~~~~~~~~~~ + \begin{code} -classArityErr class_name - = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +find_bind sel_name meth_name (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} -superClassErr class_name sc - = ptext SLIT("Illegal superclass constraint") <+> quotes (pprClassAssertion sc) - <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name) -defltMethCtxt class_name - = ptext SLIT("When checking the default methods for class") <+> quotes (ppr class_name) +Contexts and errors +~~~~~~~~~~~~~~~~~~~ +\begin{code} +defltMethCtxt clas + = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas) methodCtxt sel_id = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id) -badMethodErr bndr clas +badMethodErr clas op = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have a method"), quotes (ppr bndr)] + ptext SLIT("does not have a method"), quotes (ppr op)] + +omittedMethodWarn sel_id + = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) + +badGenericInstance sel_id because + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + because] + +notSimple inst_tys + = vcat [ptext SLIT("because the instance type(s)"), + nest 2 (ppr inst_tys), + ptext SLIT("is not a simple type of form (T a b c)")] + +notGeneric tycon + = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+> + ptext SLIT("was not compiled with -fgenerics")] -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)] +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}