X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=bd07d222aa81a5555d33d61fa8dc7fdb1a3d3f0c;hb=958924a2b338aebbcc8a88ba2cab511517762a19;hp=a48bc1e3c564772691b530260d9be195e882f5da;hpb=7b0181919416d8f04324575b7e17031ca692f5b0;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index a48bc1e..b382af9 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,401 +1,164 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcClassDcl]{Typechecking class declarations} \begin{code} +module TcClassDcl ( tcClassSigs, tcClassDecl2, + getGenericInstances, + MethodSpec, tcMethodBind, mkMethodBind, + tcAddDeclCtxt, badMethodErr + ) where + #include "HsVersions.h" -module TcClassDcl ( - tcClassDecl1, tcClassDecls2 - ) where - -import Ubiq - -import HsSyn ( ClassDecl(..), HsBinds(..), Bind(..), MonoBinds(..), - Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..), - HsLit(..), OutPat(..), Sig(..), PolyType(..), MonoType, - Stmt, Qual, ArithSeqInfo, InPat, Fake ) -import HsPragmas ( ClassPragmas(..) ) -import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..), - RenamedClassOpSig(..), RenamedMonoBinds(..), - RenamedGenPragmas(..), RenamedContext(..), - RnName{-instance Uniquable-} +import HsSyn +import RnHsSyn ( maybeGenericMatch, extractHsTyVars ) +import RnExpr ( rnLExpr ) +import RnEnv ( lookupTopBndrRn, lookupImportedName ) +import Inst ( instToId, newDicts, newDictsAtLoc, newMethod, getOverlapFlag ) +import InstEnv ( mkLocalInstance ) +import TcEnv ( tcLookupLocatedClass, + tcExtendTyVarEnv, + InstInfo(..), pprInstInfoDetails, + simpleInstInfoTyCon, simpleInstInfoTy, + InstBindings(..), newDFunName ) -import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), TcMonoBinds(..), TcExpr(..), - mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, unZonkId ) - -import TcMonad -import Inst ( Inst, InstOrigin(..), LIE(..), emptyLIE, plusLIE, newDicts ) -import TcEnv ( tcLookupClass, tcLookupTyVar, tcLookupTyCon, newLocalIds) -import TcInstDcls ( processInstBinds ) -import TcKind ( unifyKind ) -import TcMonoType ( tcMonoType, tcContext ) -import TcType ( TcType(..), TcTyVar(..), tcInstType, tcInstSigTyVars ) -import TcKind ( TcKind ) - -import Bag ( foldBag ) -import Class ( GenClass, mkClass, mkClassOp, getClassBigSig, - getClassOps, getClassOpString, getClassOpLocalType ) -import CoreUtils ( escErrorMsg ) -import Id ( mkSuperDictSelId, mkMethodSelId, mkDefaultMethodId, - idType ) -import IdInfo ( noIdInfo ) -import Name ( isLocallyDefined, getOrigName, getLocalName ) -import PrelVals ( pAT_ERROR_ID ) -import PprStyle -import Pretty -import PprType ( GenType, GenTyVar, GenClassOp ) -import SpecEnv ( SpecEnv(..) ) -import SrcLoc ( mkGeneratedSrcLoc ) -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, - mkForAllTy, mkSigmaTy, splitSigmaTy) -import TysWiredIn ( stringTy ) -import TyVar ( GenTyVar ) -import Unique ( Unique ) -import Util - --- import TcPragmas ( tcGenPragmas, tcClassOpPragmas ) -tcGenPragmas ty id ps = returnNF_Tc noIdInfo -tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo, noIdInfo) - -\end{code} - -\begin{code} -tcClassDecl1 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 `thenNF_Tc` \ (class_kind, rec_class) -> - tcLookupTyVar tyvar_name `thenNF_Tc` \ (tyvar_kind, rec_tyvar) -> - let - (rec_class_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_class - in - - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKind class_kind tyvar_kind `thenTc_` - - -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvar context pragmas - `thenTc` \ (scs, sc_sel_ids) -> - - -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_class rec_tyvar rec_class_op_inst_fn) class_sigs - `thenTc` \ sig_stuff -> - - -- MAKE THE CLASS OBJECT ITSELF - tcGetUnique `thenNF_Tc` \ uniq -> - let - (ops, op_sel_ids, defm_ids) = unzip3 sig_stuff - clas = mkClass uniq (getName class_name) rec_tyvar - scs sc_sel_ids ops op_sel_ids defm_ids - rec_class_inst_env - in - returnTc clas +import TcBinds ( TcPragFun, tcMonoBinds, tcPrags, mkPragFun ) +import TcHsType ( TcSigInfo(..), tcHsKindedType, tcHsSigType ) +import TcSimplify ( tcSimplifyCheck ) +import TcUnify ( checkSigTyVars, sigCtxt ) +import TcMType ( tcSkolSigTyVars, UserTypeCtxt( GenPatCtxt ), tcSkolType ) +import TcType ( Type, SkolemInfo(ClsSkol, InstSkol, SigSkol), + TcType, TcThetaType, TcTyVar, mkTyVarTys, + mkClassPred, tcSplitSigmaTy, tcSplitFunTys, + tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy, + getClassPredTys_maybe, mkPhiTy, mkTyVarTy + ) +import TcRnMonad +import Generics ( mkGenericRhs, validGenericInstanceType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, + Class, ClassOpItem, DefMeth (..) ) +import TyCon ( TyCon, tyConName, tyConHasGenerics ) +import Type ( substTyWith ) +import MkId ( mkDefaultMethodId, mkDictFunId ) +import Id ( Id, idType, idName, mkUserLocal ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, mkNameEnv ) +import NameSet ( nameSetToList ) +import OccName ( reportIfUnused, mkDefaultMethodOcc ) +import RdrName ( RdrName, mkDerivedRdrName ) +import Outputable +import PrelNames ( genericTyConNames ) +import DynFlags +import UnicodeUtil ( stringToUtf8 ) +import ErrUtils ( dumpIfSet_dyn ) +import Util ( count, lengthIs, isSingleton, lengthExceeds ) +import Unique ( Uniquable(..) ) +import ListSetOps ( equivClassesByUniq, minusList ) +import SrcLoc ( Located(..), srcSpanStart, unLoc, noLoc ) +import Maybes ( seqMaybe, isJust, mapCatMaybes ) +import List ( partition ) +import BasicTypes ( RecFlag(..) ) +import Bag +import FastString \end{code} -\begin{code} -tcClassContext :: Class -> TyVar - -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s ([Class], -- the superclasses - [Id]) -- superclass selector Ids - -tcClassContext rec_class rec_tyvar context pragmas - = -- Check the context. - -- The renamer has already checked that the context mentions - -- only the type variable of the class decl. - tcContext context `thenTc` \ theta -> - let - super_classes = [ supers | (supers, _) <- theta ] - in - - -- Make super-class selector ids - mapTc (mk_super_id rec_class) - (super_classes `zip` maybe_pragmas) `thenTc` \ sc_sel_ids -> - - -- Done - returnTc (super_classes, sc_sel_ids) - - where - mk_super_id rec_class (super_class, maybe_pragma) - = fixTc ( \ rec_super_id -> - tcGetUnique `thenNF_Tc` \ uniq -> - - -- GET THE PRAGMA INFO FOR THE SUPERCLASS - (case maybe_pragma of - Nothing -> returnNF_Tc noIdInfo - Just prag -> tcGenPragmas Nothing{-ty unknown-} rec_super_id prag - ) `thenNF_Tc` \ id_info -> - let - ty = mkForAllTy rec_tyvar ( - mkFunTy (mkDictTy rec_class (mkTyVarTy rec_tyvar)) - (mkDictTy super_class (mkTyVarTy rec_tyvar)) - ) - in - -- BUILD THE SUPERCLASS ID - returnTc (mkSuperDictSelId uniq rec_class super_class ty id_info) - ) - - maybe_pragmas :: [Maybe RenamedGenPragmas] - maybe_pragmas = case pragmas of - NoClassPragmas -> repeat Nothing - SuperDictPragmas prags -> ASSERT(length prags == length context) - map Just prags - -- If there are any pragmas there should - -- be one for each superclass - - - -tcClassSig :: Class -- Knot tying only! - -> TyVar -- The class type variable, used for error check only - -> (ClassOp -> SpecEnv) -- Ditto; the spec info for the class ops - -> RenamedClassOpSig - -> TcM s (ClassOp, -- class op - Id, -- selector id - Id) -- default-method ids - -tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn - (ClassOpSig op_name - (HsForAllTy tyvar_names context monotype) - pragmas src_loc) - = tcAddSrcLoc src_loc $ - fixTc ( \ ~(_, rec_sel_id, rec_defm_id) -> -- Knot for pragmas - - -- Check the type signature. NB that the envt *already has* - -- bindings for the type variables; see comments in TcTyAndClassDcls. - tcContext context `thenTc` \ theta -> - tcMonoType monotype `thenTc` \ tau -> - mapAndUnzipNF_Tc tcLookupTyVar tyvar_names `thenNF_Tc` \ (_,tyvars) -> - let - full_tyvars = rec_clas_tyvar : tyvars - full_theta = (rec_clas, mkTyVarTy rec_clas_tyvar) : theta - global_ty = mkSigmaTy full_tyvars full_theta tau - local_ty = mkSigmaTy tyvars theta tau - class_op = mkClassOp (getLocalName op_name) - (panic "(getTagFromClassOpName op_name)TcClassDecl"{-(getTagFromClassOpName op_name)-}) - local_ty - in - -- Munch the pragmas - tcClassOpPragmas - global_ty - rec_sel_id rec_defm_id - (rec_classop_spec_fn class_op) - pragmas `thenNF_Tc` \ (op_info, defm_info) -> - - -- Build the selector id and default method id - tcGetUnique `thenNF_Tc` \ d_uniq -> - let - op_uniq = uniqueOf op_name - sel_id = mkMethodSelId op_uniq rec_clas class_op global_ty op_info - defm_id = mkDefaultMethodId d_uniq rec_clas class_op False global_ty defm_info - -- ToDo: improve the "False" - in - returnTc (class_op, sel_id, defm_id) - ) -\end{code} +Dictionary handling +~~~~~~~~~~~~~~~~~~~ +Every class implicitly declares a new data type, corresponding to dictionaries +of that class. So, for example: + class (D a) => C a where + op1 :: a -> a + op2 :: forall b. Ord b => a -> b -> b -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ +would implicitly declare -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} + data CDict a = CDict (D a) + (a -> a) + (forall b. Ord b => a -> b -> b) -Pass~2 only applies to locally-defined class declarations. +(We could use a record decl, but that means changing more of the existing apparatus. +One step at at time!) -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. +For classes with just one superclass+method, we use a newtype decl instead: -\begin{code} -tcClassDecls2 :: Bag RenamedClassDecl - -> NF_TcM s (LIE s, TcHsBinds s) - -tcClassDecls2 decls - = foldBag combine - tcClassDecl2 - (returnNF_Tc (emptyLIE, EmptyBinds)) - decls - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` binds2) -\end{code} + class C a where + op :: forallb. a -> b -> b -@tcClassDecl2@ is the business end of things. +generates -\begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcHsBinds s) + newtype CDict a = CDict (forall b. a -> b -> b) -tcClassDecl2 (ClassDecl context class_name - tyvar_name class_sigs default_binds pragmas src_loc) +Now DictTy in Type is just a form of type synomym: + DictTy c t = TyConTy CDict `AppTy` t - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyBinds) +Death to "ExpandingDicts". - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc src_loc $ - - -- Get the relevant class - tcLookupClass class_name `thenNF_Tc` \ (_, clas) -> - let - (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids) - = getClassBigSig clas - in - tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) -> - - -- Generate bindings for the selector functions - buildSelectors clas tyvar clas_tyvar scs sc_sel_ids ops op_sel_ids - `thenNF_Tc` \ sel_binds -> - -- Ditto for the methods - buildDefaultMethodBinds clas clas_tyvar defm_ids default_binds - `thenTc` \ (const_insts, meth_binds) -> - - returnTc (const_insts, sel_binds `ThenBinds` meth_binds) -\end{code} %************************************************************************ %* * -\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses} + Type-checking the class op signatures %* * %************************************************************************ \begin{code} -buildSelectors :: Class -- The class object - -> TyVar -- Class type variable - -> TcTyVar s -- Instantiated class type variable (TyVarTy) - -> [Class] -> [Id] -- Superclasses and selectors - -> [ClassOp] -> [Id] -- Class ops and selectors - -> NF_TcM s (TcHsBinds s) - -buildSelectors clas clas_tyvar clas_tc_tyvar scs sc_sel_ids ops op_sel_ids - = - -- Make new Ids for the components of the dictionary - let - clas_tyvar_ty = mkTyVarTy clas_tc_tyvar - mk_op_ty = tcInstType [(clas_tyvar, clas_tyvar_ty)] . getClassOpLocalType - in - mapNF_Tc mk_op_ty ops `thenNF_Tc` \ op_tys -> - newLocalIds (map getClassOpString ops) op_tys `thenNF_Tc` \ method_ids -> - - newDicts ClassDeclOrigin - [ (super_clas, clas_tyvar_ty) - | super_clas <- scs ] `thenNF_Tc` \ (_,dict_ids) -> - - newDicts ClassDeclOrigin - [ (clas, clas_tyvar_ty) ] `thenNF_Tc` \ (_,[clas_dict]) -> - - -- Make suitable bindings for the selectors - let - mk_sel sel_id method_or_dict - = mkSelBind sel_id clas_tc_tyvar clas_dict dict_ids method_ids method_or_dict - in - listNF_Tc (zipWithEqual mk_sel op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds -> - listNF_Tc (zipWithEqual mk_sel sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds -> - - returnNF_Tc (SingleBind ( - NonRecBind ( - foldr AndMonoBinds - (foldr AndMonoBinds EmptyMonoBinds op_sel_binds) - sc_sel_binds - ))) -\end{code} - -%************************************************************************ -%* * -\subsection[ClassDcl-misc]{Miscellaneous} -%* * -%************************************************************************ +tcClassSigs :: Name -- Name of the class + -> [LSig Name] + -> LHsBinds Name + -> TcM [TcMethInfo] + +type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate + -- between tcClassSigs and buildClass +tcClassSigs clas sigs def_methods + = do { dm_env <- checkDefaultBinds clas op_names def_methods + ; mappM (tcClassSig dm_env) op_sigs } + where + op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs] + op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs] -Make a selector expression for @sel_id@ from a dictionary @clas_dict@ -consisting of @dicts@ and @methods@. -We have to do a bit of jiggery pokery to get the type variables right. -Suppose we have the class decl: -\begin{verbatim} - class Foo a where - op1 :: Ord b => a -> b -> a - op2 :: ... -\end{verbatim} -Then the method selector for \tr{op1} is like this: -\begin{verbatim} - op1_sel = /\a b -> \dFoo dOrd -> case dFoo of - (op1_method,op2_method) -> op1_method b dOrd -\end{verbatim} -Note that the type variable for \tr{b} and the (Ord b) dictionary -are lifted to the top lambda, and -\tr{op1_method} is applied to them. This is preferable to the alternative: -\begin{verbatim} - op1_sel' = /\a -> \dFoo -> case dFoo of - (op1_method,op2_method) -> op1_method -\end{verbatim} -because \tr{op1_sel'} then has the rather strange type -\begin{verbatim} - op1_sel' :: forall a. Foo a -> forall b. Ord b -> a -> b -> a -\end{verbatim} -whereas \tr{op1_sel} (the one we use) has the decent type -\begin{verbatim} - op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a -\end{verbatim} - -NOTE that we return a TcMonoBinds (which is later zonked) even though -there's no real back-substitution to do. It's just simpler this way! +checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool) + -- Check default bindings + -- a) must be for a class op for this class + -- b) must be all generic or all non-generic + -- and return a mapping from class-op to Bool + -- where True <=> it's a generic default method +checkDefaultBinds clas ops binds + = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds) + return (mkNameEnv dm_infos) -NOTE ALSO that the selector has no free type variables, so we -don't bother to instantiate the class-op's local type; instead -we just use the variables inside it. +checkDefaultBind clas ops (FunBind (L _ op) _ (MatchGroup matches _) _) + = do { -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) -\begin{code} -mkSelBind :: Id -- the selector id - -> TcTyVar s -> TcIdOcc s -- class tyvar and dict - -> [TcIdOcc s] -> [TcIdOcc s] -- superclasses and methods in class dict - -> TcIdOcc s -- the superclass/method being slected - -> NF_TcM s (TcMonoBinds s) + -- Check that all the defns ar generic, or none are + ; checkTc (all_generic || none_generic) (mixedGenericErr op) -mkSelBind sel_id clas_tyvar clas_dict dicts methods method_or_dict@(TcId op) - = let - (op_tyvars,op_theta,op_tau) = splitSigmaTy (idType op) - op_tys = mkTyVarTys op_tyvars - in - newDicts ClassDeclOrigin op_theta `thenNF_Tc` \ (_, op_dicts) -> - - -- sel_id = /\ clas_tyvar op_tyvars -> \ clas_dict op_dicts -> - -- case clas_dict of - -- -> method_or_dict op_tyvars op_dicts - - returnNF_Tc (VarMonoBind (RealId sel_id) ( - TyLam (clas_tyvar:op_tyvars) ( - DictLam (clas_dict:op_dicts) ( - HsCase - (HsVar clas_dict) - ([PatMatch (DictPat dicts methods) ( - GRHSMatch (GRHSsAndBindsOut - [OtherwiseGRHS - (mkHsDictApp (mkHsTyApp (HsVar method_or_dict) op_tys) op_dicts) - mkGeneratedSrcLoc] - EmptyBinds - op_tau))]) - mkGeneratedSrcLoc - )))) + ; returnM (op, all_generic) + } + where + n_generic = count (isJust . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = matches `lengthIs` n_generic + + +tcClassSig :: NameEnv Bool -- Info about default methods; + -> LSig Name + -> TcM TcMethInfo + +tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty)) + = setSrcSpan loc $ do + { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope + ; let dm = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just False -> DefMeth + Just True -> GenDefMeth + ; returnM (op_name, dm, op_ty) } \end{code} @@ -421,11 +184,10 @@ we get the default methods: defm.Foo.op1 :: forall a. Foo a => a -> Bool defm.Foo.op1 = /\a -> \dfoo -> \x -> True -defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b -defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z -> +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} -Notice that, like all ids, the foralls of defm.Foo.op2 are at the top. When we come across an instance decl, we may need to use the default methods: @@ -438,14 +200,15 @@ const.Foo.Int.op1 :: Int -> Bool const.Foo.Int.op1 = defm.Foo.op1 Int dfun.Foo.Int const.Foo.Int.op2 :: forall b. Ord b => Int -> b -> b -> b -const.Foo.Int.op2 = /\b -> defm.Foo.op2 Int b dfun.Foo.Int +const.Foo.Int.op2 = defm.Foo.op2 Int dfun.Foo.Int dfun.Foo.Int :: Foo Int dfun.Foo.Int = (const.Foo.Int.op1, const.Foo.Int.op2) \end{verbatim} Notice that, as with method selectors above, we assume that dictionary application is curried, so there's no need to mention the Ord dictionary -in const.Foo.Int.op2 +in const.Foo.Int.op2 (or the type variable). + \begin{verbatim} instance Foo a => Foo [a] where {} @@ -454,74 +217,572 @@ dfun.Foo.List = /\ a -> \ dfoo_a -> let rec op1 = defm.Foo.op1 [a] dfoo_list - op2 = /\b -> \dord -> defm.Foo.op2 [a] b dfoo_list dord + op2 = defm.Foo.op2 [a] dfoo_list dfoo_list = (op1, op2) in dfoo_list \end{verbatim} +@tcClassDecls2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) + \begin{code} -buildDefaultMethodBinds - :: Class - -> TcTyVar s - -> [Id] - -> RenamedMonoBinds - -> TcM s (LIE s, TcHsBinds s) - -buildDefaultMethodBinds clas clas_tyvar - default_method_ids default_binds - = -- Deal with the method declarations themselves - mapNF_Tc unZonkId default_method_ids `thenNF_Tc` \ tc_defm_ids -> - processInstBinds - (makeClassDeclDefaultMethodRhs clas default_method_ids) - [] -- No tyvars in scope for "this inst decl" - emptyLIE -- No insts available - (map TcId tc_defm_ids) - default_binds `thenTc` \ (dicts_needed, default_binds') -> - - returnTc (dicts_needed, SingleBind (NonRecBind default_binds')) +tcClassDecl2 :: LTyClDecl Name -- The class declaration + -> TcM (LHsBinds Id, [Id]) + +tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, + tcdMeths = default_binds})) + = recoverM (returnM (emptyLHsBinds, [])) $ + setSrcSpan loc $ + tcLookupLocatedClass class_name `thenM` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each + let + (tyvars, _, _, op_items) = classBigSig clas + prag_fn = mkPragFun sigs + tc_dm = tcDefMeth clas tyvars default_binds prag_fn + + dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items] + -- Generate code for polymorphic default methods only + -- (Generic default methods have turned into instance decls by now.) + -- This is incompatible with Hugs, which expects a polymorphic + -- default method for every class op, regardless of whether or not + -- the programmer supplied an explicit default decl for the class. + -- (If necessary we can fix that, but we don't have a convenient Id to hand.) + in + mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) -> + returnM (listToBag defm_binds, concat dm_ids_s) + +tcDefMeth clas tyvars binds_in prag_fn sel_id + = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id) + ; let rigid_info = ClsSkol clas + clas_tyvars = tcSkolSigTyVars rigid_info tyvars + inst_tys = mkTyVarTys clas_tyvars + dm_ty = idType sel_id -- Same as dict selector! + theta = [mkClassPred clas inst_tys] + local_dm_id = mkDefaultMethodId dm_name dm_ty + origin = SigOrigin rigid_info + + ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth) + ; [this_dict] <- newDicts origin theta + ; (defm_bind, insts_needed) <- getLIE (tcMethodBind clas_tyvars theta + [this_dict] prag_fn meth_info) + + ; addErrCtxt (defltMethCtxt clas) $ do + + -- Check the context + { dict_binds <- tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed + + -- Simplification can do unification + ; checkSigTyVars clas_tyvars + + ; let + (_,dm_inst_id,_) = meth_info + full_bind = AbsBinds + clas_tyvars + [instToId this_dict] + [(clas_tyvars, local_dm_id, dm_inst_id, [])] + -- No inlines (yet) + (dict_binds `unionBags` defm_bind) + ; returnM (noLoc full_bind, [local_dm_id]) }} + +mkDefMethRdrName :: Id -> RdrName +mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc \end{code} -@makeClassDeclDefaultMethodRhs@ builds the default method for a -class declaration when no explicit default method is given. + +%************************************************************************ +%* * +\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} -makeClassDeclDefaultMethodRhs - :: Class - -> [Id] - -> Int - -> NF_TcM s (TcExpr s) - -makeClassDeclDefaultMethodRhs clas method_ids tag - = tcInstType [] (idType method_id) `thenNF_Tc` \ method_ty -> - let - (tyvars, theta, tau) = splitSigmaTy method_ty - in - newDicts ClassDeclOrigin theta `thenNF_Tc` \ (lie, dict_ids) -> - - returnNF_Tc (mkHsTyLam tyvars ( - mkHsDictLam dict_ids ( - HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [tau]) - (HsLitOut (HsString (_PK_ error_msg)) stringTy)))) +type MethodSpec = (Id, -- Global selector Id + Id, -- Local Id (class tyvars instantiated) + LHsBind Name) -- Binding for the method + +tcMethodBind + :: [TcTyVar] -- Skolemised type variables for the + -- enclosing class/instance decl. + -- They'll be signature tyvars, and we + -- want to check that they don't get bound + -- Also they are scoped, so we bring them into scope + -- Always equal the range of the type envt + -> TcThetaType -- Available theta; it's just used for the error message + -> [Inst] -- Available from context, used to simplify constraints + -- from the method body + -> TcPragFun -- Pragmas (e.g. inline pragmas) + -> MethodSpec -- Details of this method + -> TcM (LHsBinds Id) + +tcMethodBind inst_tyvars inst_theta avail_insts prag_fn + (sel_id, meth_id, meth_bind) + = recoverM (returnM emptyLHsBinds) $ + -- If anything fails, recover returning no bindings. + -- This is particularly useful when checking the default-method binding of + -- a class decl. If we don't recover, we don't add the default method to + -- the type enviroment, and we get a tcLookup failure on $dmeth later. + + -- Check the bindings; first adding inst_tyvars to the envt + -- so that we don't quantify over them in nested places + + + let -- Fake up a TcSigInfo to pass to tcMonoBinds + rigid_info = SigSkol (idName meth_id) + in + tcSkolType rigid_info (idType meth_id) `thenM` \ (tyvars', theta', tau') -> + getInstLoc (SigOrigin rigid_info) `thenM` \ loc -> + let meth_sig = TcSigInfo { sig_id = meth_id, sig_tvs = tyvars', sig_scoped = [], + sig_theta = theta', sig_tau = tau', sig_loc = loc } + lookup_sig name = ASSERT( name == idName meth_id ) + Just meth_sig + in + tcExtendTyVarEnv inst_tyvars ( + addErrCtxt (methodCtxt sel_id) $ + getLIE $ + tcMonoBinds [meth_bind] lookup_sig Recursive + ) `thenM` \ ((meth_bind, mono_bind_infos), meth_lie) -> + + -- Now do context reduction. We simplify wrt both the local tyvars + -- and the ones of the class/instance decl, so that there is + -- no problem with + -- class C a where + -- op :: Eq a => a -> b -> a + -- + -- We do this for each method independently to localise error messages + + addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ + newDictsAtLoc (sig_loc meth_sig) (sig_theta meth_sig) `thenM` \ meth_dicts -> + let + meth_tvs = sig_tvs meth_sig + all_tyvars = meth_tvs ++ inst_tyvars + all_insts = avail_insts ++ meth_dicts + sel_name = idName sel_id + 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_` + + tcPrags meth_id (prag_fn sel_name) `thenM` \ prags -> + let + [(_,_,local_meth_id)] = mono_bind_infos + poly_meth_bind = noLoc $ AbsBinds meth_tvs + (map instToId meth_dicts) + [(meth_tvs, meth_id, local_meth_id, prags)] + (lie_binds `unionBags` meth_bind) + in + returnM (unitBag poly_meth_bind) + + +mkMethodBind :: InstOrigin + -> Class -> [TcType] -- Class and instance types + -> LHsBinds Name -- Method binding (pick the right one from in here) + -> ClassOpItem + -> TcM (Maybe Inst, -- Method inst + MethodSpec) +-- Find the binding for the specified method, or make +-- up a suitable default method if it isn't there + +mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info) + = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) -> + let + meth_name = idName meth_id + in + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + getSrcSpanM `thenM` \ loc -> + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnM user_bind + Nothing -> + mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs -> + -- Not infix decl + returnM (noLoc $ FunBind (noLoc meth_name) False + (mkMatchGroup [mkSimpleMatch [] rhs]) + placeHolderNames) + ) `thenM` \ meth_bind -> + + returnM (mb_inst, (sel_id, meth_id, meth_bind)) + +mkMethId :: InstOrigin -> Class + -> Id -> [TcType] -- Selector, and instance types + -> TcM (Maybe Inst, Id) + +-- mkMethId instantiates the selector Id at the specified types +mkMethId origin clas sel_id inst_tys + = let + (tyvars,rho) = tcSplitForAllTys (idType sel_id) + rho_ty = ASSERT( length tyvars == length inst_tys ) + substTyWith tyvars inst_tys rho + (preds,tau) = tcSplitPhiTy rho_ty + first_pred = head preds + in + -- The first predicate should be of form (C a b) + -- where C is the class in question + ASSERT( not (null preds) && + case getClassPredTys_maybe first_pred of + { Just (clas1,tys) -> clas == clas1 ; Nothing -> False } + ) + if isSingleton preds then + -- If it's the only one, make a 'method' + getInstLoc origin `thenM` \ inst_loc -> + newMethod inst_loc sel_id inst_tys preds tau `thenM` \ meth_inst -> + returnM (Just meth_inst, instToId meth_inst) + else + -- If it's not the only one we need to be careful + -- For example, given 'op' defined thus: + -- class Foo a where + -- op :: (?x :: String) => a -> a + -- (mkMethId op T) should return an Inst with type + -- (?x :: String) => T -> T + -- That is, the class-op's context is still there. + -- BUT: it can't be a Method any more, because it breaks + -- INVARIANT 2 of methods. (See the data decl for Inst.) + newUnique `thenM` \ uniq -> + getSrcSpanM `thenM` \ loc -> + let + real_tau = mkPhiTy (tail preds) tau + meth_id = mkUserLocal (getOccName sel_id) uniq real_tau + (srcSpanStart loc) --TODO + in + returnM (Nothing, meth_id) + + -- The user didn't supply a method binding, + -- so we have to make up a default binding + -- The RHS of a default method depends on the default-method info +mkDefMethRhs origin clas inst_tys sel_id loc DefMeth + = -- An polymorphic default method + lookupImportedName (mkDefMethRdrName sel_id) `thenM` \ dm_name -> + -- Might not be imported, but will be an OrigName + traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_` + returnM (nlHsVar dm_name) + +mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth + = -- No default method + -- Warn only if -fwarn-missing-methods + doptM Opt_WarnMissingMethods `thenM` \ warn -> + warnTc (isInstDecl origin + && warn + && reportIfUnused (getOccName sel_id)) + (omittedMethodWarn sel_id) `thenM_` + returnM error_rhs + where + error_rhs = noLoc $ HsLam (mkMatchGroup [mkSimpleMatch wild_pats simple_rhs]) + simple_rhs = nlHsApp (nlHsVar (getName nO_METHOD_BINDING_ERROR_ID)) + (nlHsLit (HsStringPrim (mkFastString (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 = [nlWildPat | ty <- arg_tys] + +mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth + = -- A generic default method + -- If the method is defined generically, we can only do the job if the + -- instance declaration is for a single-parameter type class with + -- a type constructor applied to type arguments in the instance decl + -- (checkTc, so False provokes the error) + ASSERT( isInstDecl origin ) -- We never get here from a class decl + do { checkTc (isJust maybe_tycon) + (badGenericInstance sel_id (notSimple inst_tys)) + ; checkTc (tyConHasGenerics tycon) + (badGenericInstance sel_id (notGeneric tycon)) + + ; dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body" + (vcat [ppr clas <+> ppr inst_tys, + nest 2 (ppr sel_id <+> equals <+> ppr rhs)])) + + -- Rename it before returning it + ; (rn_rhs, _) <- rnLExpr rhs + ; returnM rn_rhs } where - (clas_mod, clas_name) = getOrigName clas + rhs = mkGenericRhs sel_id clas_tyvar tycon + + -- The tycon is only used in the generic case, and in that + -- case we require that the instance decl is for a single-parameter + -- type class with type variable arguments: + -- instance (...) => C (T a b) + clas_tyvar = head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of + [ty] -> case tcSplitTyConApp_maybe ty of + Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon + other -> Nothing + other -> Nothing + +isInstDecl (SigOrigin (InstSkol _)) = True +isInstDecl (SigOrigin (ClsSkol _)) = False +\end{code} + + +\begin{code} +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +find_bind sel_name meth_name binds + = foldlBag seqMaybe Nothing (mapBag f binds) + where + f (L loc1 (FunBind (L loc2 op_name) fix matches fvs)) | op_name == sel_name + = Just (L loc1 (FunBind (L loc2 meth_name) fix matches fvs)) + f _other = Nothing +\end{code} - method_id = method_ids !! (tag-1) - class_op = (getClassOps clas) !! (tag-1) - error_msg = "%D" -- => No default method for \" - ++ unencoded_part_of_msg +%************************************************************************ +%* * +\subsection{Extracting generic instance declaration from class declarations} +%* * +%************************************************************************ - unencoded_part_of_msg = escErrorMsg ( - _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "." - ++ (ppShow 80 (ppr PprForUser class_op)) - ++ "\"" ) +@getGenericInstances@ extracts the generic instance declarations from a class +declaration. For exmaple + + class C a where + op :: a -> a + + op{ x+y } (Inl v) = ... + op{ x+y } (Inr v) = ... + op{ x*y } (v :*: w) = ... + op{ 1 } Unit = ... + +gives rise to the instance declarations + + instance C (x+y) where + op (Inl v) = ... + op (Inr v) = ... + + instance C (x*y) where + op (v :*: w) = ... + + instance C 1 where + op Unit = ... + + +\begin{code} +getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo] +getGenericInstances class_decls + = do { gen_inst_infos <- mappM (addLocM get_generics) class_decls + ; let { gen_inst_info = concat gen_inst_infos } + + -- Return right away if there is no generic stuff + ; if null gen_inst_info then returnM [] + else do + + -- Otherwise print it out + { dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" + (vcat (map pprInstInfoDetails gen_inst_info))) + ; returnM gen_inst_info }} + +get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods}) + | null generic_binds + = returnM [] -- The comon case: no generic default methods + + | otherwise -- A source class decl with generic default methods + = recoverM (returnM []) $ + tcAddDeclCtxt decl $ + tcLookupLocatedClass class_name `thenM` \ clas -> + + -- Group by type, and + -- make an InstInfo out of each group + let + groups = groupWith listToBag generic_binds + in + mappM (mkGenericInstance clas) groups `thenM` \ inst_infos -> + + -- Check that there is only one InstInfo for each type constructor + -- The main way this can fail is if you write + -- f {| a+b |} ... = ... + -- f {| x+y |} ... = ... + -- Then at this point we'll have an InstInfo for each + let + tc_inst_infos :: [(TyCon, InstInfo)] + tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] + + bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, + group `lengthExceeds` 1] + get_uniq (tc,_) = getUnique tc + in + mappM (addErrTc . dupGenericInsts) bad_groups `thenM_` + + -- Check that there is an InstInfo for each generic type constructor + let + missing = genericTyConNames `minusList` [tyConName tc | (tc,_) <- tc_inst_infos] + in + checkTc (null missing) (missingGenericInstances missing) `thenM_` + + returnM inst_infos + where + generic_binds :: [(HsType Name, LHsBind Name)] + generic_binds = getGenericBinds def_methods + + +--------------------------------- +getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)] + -- Takes a group of method bindings, finds the generic ones, and returns + -- them in finite map indexed by the type parameter in the definition. +getGenericBinds binds = concat (map getGenericBind (bagToList binds)) + +getGenericBind (L loc (FunBind id infixop (MatchGroup matches ty) fvs)) + = groupWith wrap (mapCatMaybes maybeGenericMatch matches) + where + wrap ms = L loc (FunBind id infixop (MatchGroup ms ty) fvs) +getGenericBind _ + = [] + +groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)] +groupWith op [] = [] +groupWith op ((t,v):prs) = (t, op (v:vs)) : groupWith op rest + where + vs = map snd this + (this,rest) = partition same_t prs + same_t (t',v) = t `eqPatType` t' + +eqPatLType :: LHsType Name -> LHsType Name -> Bool +eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2 + +eqPatType :: HsType Name -> HsType Name -> Bool +-- A very simple equality function, only for +-- type patterns in generic function definitions. +eqPatType (HsTyVar v1) (HsTyVar v2) = v1==v2 +eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 +eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 && unLoc op1 == unLoc op2 +eqPatType (HsNumTy n1) (HsNumTy n2) = n1 == n2 +eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2 +eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2 +eqPatType _ _ = False + +--------------------------------- +mkGenericInstance :: Class + -> (HsType Name, LHsBinds Name) + -> TcM InstInfo + +mkGenericInstance clas (hs_ty, binds) + -- Make a generic instance declaration + -- For example: instance (C a, C b) => C (a+b) where { binds } + + = -- Extract the universally quantified type variables + -- and wrap them as forall'd tyvars, so that kind inference + -- works in the standard way + let + sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty))) + hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty) + in + -- Type-check the instance type, and check its form + tcHsSigType GenPatCtxt hs_forall_ty `thenM` \ forall_inst_ty -> + let + (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty + in + checkTc (validGenericInstanceType inst_ty) + (badGenericInstanceType binds) `thenM_` + + -- Make the dictionary function. + getSrcSpanM `thenM` \ span -> + getOverlapFlag `thenM` \ overlap_flag -> + newDFunName clas [inst_ty] (srcSpanStart span) `thenM` \ dfun_name -> + let + inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] + dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty] + ispec = mkLocalInstance dfun_id overlap_flag + in + returnM (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] }) \end{code} -Contexts -~~~~~~~~ +%************************************************************************ +%* * + Error messages +%* * +%************************************************************************ + \begin{code} -classDeclCtxt class_name sty - = ppCat [ppStr "In the class declaration for", ppr sty class_name] +tcAddDeclCtxt decl thing_inside + = addErrCtxt ctxt thing_inside + where + thing = case decl of + ClassDecl {} -> "class" + TySynonym {} -> "type synonym" + TyData {tcdND = NewType} -> "newtype" + TyData {tcdND = DataType} -> "data type" + + ctxt = hsep [ptext SLIT("In the"), text thing, + ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + +defltMethCtxt clas + = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas) + +methodCtxt sel_id + = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id) + +badMethodErr clas op + = hsep [ptext SLIT("Class"), quotes (ppr clas), + ptext SLIT("does not have a method"), quotes (ppr op)] + +omittedMethodWarn sel_id + = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) + +badGenericInstance sel_id because + = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + because] + +notSimple inst_tys + = vcat [ptext SLIT("because the instance type(s)"), + nest 2 (ppr inst_tys), + ptext SLIT("is not a simple type of form (T a b c)")] + +notGeneric tycon + = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+> + ptext SLIT("was not compiled with -fgenerics")] + +badGenericInstanceType binds + = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), + nest 4 (ppr binds)] + +missingGenericInstances missing + = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing + +dupGenericInsts tc_inst_infos + = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"), + nest 4 (vcat (map ppr_inst_ty tc_inst_infos)), + ptext SLIT("All the type patterns for a generic type constructor must be identical") + ] + where + ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst) + +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}