X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=44ea1fc4caa2e69adc898878b2f8ac117f867220;hb=d7b36bbbcd56ee14656223d02e32f5a1f52ea17b;hp=6930b681fe5de702163626e4847dd715dd9e1b61;hpb=0f5e104c36b1dc3d8deeec5fef3d65e7b3a1b5ad;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 6930b68..44ea1fc 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -74,13 +74,16 @@ data DerivSpec = DS { ds_loc :: SrcSpan , ds_theta :: ThetaType , ds_cls :: Class , ds_tys :: [Type] + , ds_tc :: TyCon , ds_newtype :: Bool } -- This spec implies a dfun declaration of the form -- df :: forall tvs. theta => C tys -- The Name is the name for the DFun we'll build -- The tyvars bind all the variables in the theta - -- For family indexes, the tycon is the *family* tycon - -- (not the representation tycon) + -- For family indexes, the tycon in + -- in ds_tys is the *family* tycon + -- in ds_tc is the *representation* tycon + -- For non-family tycons, both are the same -- ds_newtype = True <=> Newtype deriving -- False <=> Vanilla deriving @@ -262,29 +265,29 @@ when the dict is constructed in TcInstDcls.tcInstDecl2 tcDeriving :: [LTyClDecl Name] -- All type constructors -> [LInstDecl Name] -- All instance declarations -> [LDerivDecl Name] -- All stand-alone deriving declarations - -> TcM ([InstInfo], -- The generated "instance decls" + -> TcM ([InstInfo Name], -- The generated "instance decls" HsValBinds Name) -- Extra generated top-level bindings tcDeriving tycl_decls inst_decls deriv_decls = recoverM (return ([], emptyValBindsOut)) $ do { -- Fish the "deriving"-related information out of the TcEnv -- And make the necessary "equations". - ; early_specs <- makeDerivSpecs tycl_decls inst_decls deriv_decls + is_boot <- tcIsHsBoot + ; traceTc (text "tcDeriving" <+> ppr is_boot) + ; early_specs <- makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls ; overlap_flag <- getOverlapFlag ; let (infer_specs, given_specs) = splitEithers early_specs - ; (insts1, aux_binds1) <- mapAndUnzipM (genInst overlap_flag) given_specs + ; insts1 <- mapM (genInst overlap_flag) given_specs - ; final_specs <- extendLocalInstEnv (map iSpec insts1) $ + ; final_specs <- extendLocalInstEnv (map (iSpec . fst) insts1) $ inferInstanceContexts overlap_flag infer_specs - ; (insts2, aux_binds2) <- mapAndUnzipM (genInst overlap_flag) final_specs + ; insts2 <- mapM (genInst overlap_flag) final_specs - ; is_boot <- tcIsHsBoot - ; rn_binds <- makeAuxBinds is_boot tycl_decls - (concat aux_binds1 ++ concat aux_binds2) - - ; let inst_info = insts1 ++ insts2 + -- Generate the generic to/from functions from each type declaration + ; gen_binds <- mkGenericBinds is_boot + ; (inst_info, rn_binds) <- renameDeriv is_boot gen_binds (insts1 ++ insts2) ; dflags <- getDOpts ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" @@ -292,49 +295,77 @@ tcDeriving tycl_decls inst_decls deriv_decls ; return (inst_info, rn_binds) } where - ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc + ddump_deriving :: [InstInfo Name] -> HsValBinds Name -> SDoc ddump_deriving inst_infos extra_binds = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds -makeAuxBinds :: Bool -> [LTyClDecl Name] -> DerivAuxBinds -> TcM (HsValBinds Name) -makeAuxBinds is_boot tycl_decls deriv_aux_binds - | is_boot -- If we are compiling a hs-boot file, - -- don't generate any derived bindings - = return emptyValBindsOut +renameDeriv :: Bool -> LHsBinds RdrName + -> [(InstInfo RdrName, DerivAuxBinds)] + -> TcM ([InstInfo Name], HsValBinds Name) +renameDeriv is_boot gen_binds insts + | is_boot -- If we are compiling a hs-boot file, don't generate any derived bindings + -- The inst-info bindings will all be empty, but it's easier to + -- just use rn_inst_info to change the type appropriately + = do { rn_inst_infos <- mapM rn_inst_info inst_infos + ; return (rn_inst_infos, emptyValBindsOut) } | otherwise - = do { let aux_binds = listToBag (map genAuxBind (rm_dups [] deriv_aux_binds)) - -- Generate any extra not-one-inst-decl-specific binds, + = discardWarnings $ -- Discard warnings about unused bindings etc + do { (rn_gen, dus_gen) <- setOptM Opt_ScopedTypeVariables $ -- Type signatures in patterns + -- are used in the generic binds + rnTopBinds (ValBindsIn gen_binds []) + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to be kept alive + + -- Generate and rename any extra not-one-inst-decl-specific binds, -- notably "con2tag" and/or "tag2con" functions. + -- Bring those names into scope before renaming the instances themselves + ; loc <- getSrcSpanM -- Generic loc for shared bindings + ; let aux_binds = listToBag $ map (genAuxBind loc) $ + rm_dups [] $ concat deriv_aux_binds + ; rn_aux_lhs <- rnTopBindsLHS emptyFsEnv (ValBindsIn aux_binds []) + ; let aux_names = map unLoc (collectHsValBinders rn_aux_lhs) + + ; bindLocalNames aux_names $ + do { (rn_aux, _dus) <- rnTopBindsRHS (mkNameSet aux_names) rn_aux_lhs + ; rn_inst_infos <- mapM rn_inst_info inst_infos + ; return (rn_inst_infos, rn_aux `plusHsValBinds` rn_gen) } } - -- Generate the generic to/from functions from each type declaration - ; gen_binds <- mkGenericBinds tycl_decls - - -- Rename these extra bindings, discarding warnings about unused bindings etc - -- Type signatures in patterns are used in the generic binds - ; discardWarnings $ - setOptM Opt_PatternSignatures $ - do { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn aux_binds []) - ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) - ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to - -- be kept alive - ; return (rn_deriv `plusHsValBinds` rn_gen) } } where + (inst_infos, deriv_aux_binds) = unzip insts + -- Remove duplicate requests for auxilliary bindings rm_dups acc [] = acc rm_dups acc (b:bs) | any (isDupAux b) acc = rm_dups acc bs | otherwise = rm_dups (b:acc) bs + + rn_inst_info (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) + = return (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) + + rn_inst_info (InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs }) + = -- Bring the right type variables into + -- scope (yuk), and rename the method binds + ASSERT( null sigs ) + bindLocalNames (map Var.varName tyvars) $ + do { (rn_binds, _fvs) <- rnMethodBinds clas_nm (\_ -> []) [] binds + ; return (InstInfo { iSpec = inst, iBinds = VanillaInst rn_binds [] }) } + where + (tyvars,_,clas,_) = instanceHead inst + clas_nm = className clas + ----------------------------------------- -mkGenericBinds :: [LTyClDecl Name] -> TcM (LHsBinds RdrName) -mkGenericBinds tycl_decls - = do { tcs <- mapM tcLookupTyCon - [ tc_name | - L _ (TyData { tcdLName = L _ tc_name }) <- tycl_decls] - -- We are only interested in the data type declarations +mkGenericBinds :: Bool -> TcM (LHsBinds RdrName) +mkGenericBinds is_boot + | is_boot + = return emptyBag + | otherwise + = do { gbl_env <- getGblEnv + ; let tcs = typeEnvTyCons (tcg_type_env gbl_env) ; return (unionManyBags [ mkTyConGenericBinds tc | tc <- tcs, tyConHasGenerics tc ]) } - -- And then only in the ones whose 'has-generics' flag is on + -- We are only interested in the data type declarations, + -- and then only in the ones whose 'has-generics' flag is on + -- The predicate tyConHasGenerics finds both of these \end{code} @@ -344,44 +375,45 @@ mkGenericBinds tycl_decls %* * %************************************************************************ -@makeDerivSpecs@ fishes around to find the info about needed derived -instances. Complicating factors: -\begin{itemize} -\item -We can only derive @Enum@ if the data type is an enumeration -type (all nullary data constructors). - -\item -We can only derive @Ix@ if the data type is an enumeration {\em -or} has just one data constructor (e.g., tuples). -\end{itemize} - -[See Appendix~E in the Haskell~1.2 report.] This code here deals w/ -all those. +@makeDerivSpecs@ fishes around to find the info about needed derived instances. \begin{code} -makeDerivSpecs :: [LTyClDecl Name] +makeDerivSpecs :: Bool + -> [LTyClDecl Name] -> [LInstDecl Name] -> [LDerivDecl Name] -> TcM [EarlyDerivSpec] -makeDerivSpecs tycl_decls inst_decls deriv_decls - = do { eqns1 <- mapAndRecoverM deriveTyData $ - extractTyDataPreds tycl_decls ++ - [ pd -- traverse assoc data families - | L _ (InstDecl _ _ _ ats) <- inst_decls - , pd <- extractTyDataPreds ats ] +makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls + | is_boot -- No 'deriving' at all in hs-boot files + = do { mapM_ add_deriv_err deriv_locs + ; return [] } + | otherwise + = do { eqns1 <- mapAndRecoverM deriveTyData all_tydata ; eqns2 <- mapAndRecoverM deriveStandalone deriv_decls - ; return (catMaybes (eqns1 ++ eqns2)) } + ; return (eqns1 ++ eqns2) } where - extractTyDataPreds decls = - [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds] + extractTyDataPreds decls + = [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds] + + all_tydata :: [(LHsType Name, LTyClDecl Name)] + -- Derived predicate paired with its data type declaration + all_tydata = extractTyDataPreds tycl_decls ++ + [ pd -- Traverse assoc data families + | L _ (InstDecl _ _ _ ats) <- inst_decls + , pd <- extractTyDataPreds ats ] + deriv_locs = map (getLoc . snd) all_tydata + ++ map getLoc deriv_decls + + add_deriv_err loc = setSrcSpan loc $ + addErr (hang (ptext (sLit "Deriving not permitted in hs-boot file")) + 2 (ptext (sLit "Use an instance declaration instead"))) ------------------------------------------------------------------ -deriveStandalone :: LDerivDecl Name -> TcM (Maybe EarlyDerivSpec) +deriveStandalone :: LDerivDecl Name -> TcM EarlyDerivSpec -- Standalone deriving declarations --- e.g. deriving instance show a => Show (T a) +-- e.g. deriving instance Show a => Show (T a) -- Rather like tcLocalInstDecl deriveStandalone (L loc (DerivDecl deriv_ty)) = setSrcSpan loc $ @@ -393,9 +425,11 @@ deriveStandalone (L loc (DerivDecl deriv_ty)) <+> text "theta:" <+> ppr theta <+> text "tau:" <+> ppr tau) ; (cls, inst_tys) <- checkValidInstHead tau + ; checkValidInstance tvs theta cls inst_tys + -- C.f. TcInstDcls.tcLocalInstDecl1 + ; let cls_tys = take (length inst_tys - 1) inst_tys inst_ty = last inst_tys - ; traceTc (text "standalone deriving;" <+> text "class:" <+> ppr cls <+> text "class types:" <+> ppr cls_tys @@ -404,23 +438,55 @@ deriveStandalone (L loc (DerivDecl deriv_ty)) (Just theta) } ------------------------------------------------------------------ -deriveTyData :: (LHsType Name, LTyClDecl Name) -> TcM (Maybe EarlyDerivSpec) -deriveTyData (deriv_pred, L loc decl@(TyData { tcdLName = L _ tycon_name, - tcdTyVars = tv_names, - tcdTyPats = ty_pats })) - = setSrcSpan loc $ - tcAddDeclCtxt decl $ - do { let hs_ty_args = ty_pats `orElse` map (nlHsTyVar . hsLTyVarName) tv_names - hs_app = nlHsTyConApp tycon_name hs_ty_args - -- We get kinding info for the tyvars by typechecking (T a b) - -- Hence forming a tycon application and then dis-assembling it - ; (tvs, tc_app) <- tcHsQuantifiedType tv_names hs_app +deriveTyData :: (LHsType Name, LTyClDecl Name) -> TcM EarlyDerivSpec +deriveTyData (L loc deriv_pred, L _ decl@(TyData { tcdLName = L _ tycon_name, + tcdTyVars = tv_names, + tcdTyPats = ty_pats })) + = setSrcSpan loc $ -- Use the location of the 'deriving' item + tcAddDeclCtxt decl $ + do { (tvs, tc, tc_args) <- get_lhs ty_pats ; tcExtendTyVarEnv tvs $ -- Deriving preds may (now) mention -- the type variables for the type constructor + do { (deriv_tvs, cls, cls_tys) <- tcHsDeriv deriv_pred -- The "deriv_pred" is a LHsType to take account of the fact that for -- newtype deriving we allow deriving (forall a. C [a]). - ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys tc_app Nothing } } + + -- Given data T a b c = ... deriving( C d ), + -- we want to drop type variables from T so that (C d (T a)) is well-kinded + ; let cls_tyvars = classTyVars cls + kind = tyVarKind (last cls_tyvars) + (arg_kinds, _) = splitKindFunTys kind + n_args_to_drop = length arg_kinds + n_args_to_keep = tyConArity tc - n_args_to_drop + inst_ty = mkTyConApp tc (take n_args_to_keep tc_args) + inst_ty_kind = typeKind inst_ty + + -- Check that the result really is well-kinded + ; checkTc (n_args_to_keep >= 0 && (inst_ty_kind `eqKind` kind)) + (derivingKindErr tc cls cls_tys kind) + + -- Type families can't be partially applied + -- e.g. newtype instance T Int a = ... deriving( Monad ) + ; checkTc (not (isOpenTyCon tc) || n_args_to_drop == 0) + (typeFamilyPapErr tc cls cls_tys inst_ty) + + ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys inst_ty Nothing } } + where + -- Tiresomely we must figure out the "lhs", which is awkward for type families + -- E.g. data T a b = .. deriving( Eq ) + -- Here, the lhs is (T a b) + -- data instance TF Int b = ... deriving( Eq ) + -- Here, the lhs is (TF Int b) + -- But if we just look up the tycon_name, we get is the *family* + -- tycon, but not pattern types -- they are in the *rep* tycon. + get_lhs Nothing = do { tc <- tcLookupTyCon tycon_name + ; let tvs = tyConTyVars tc + ; return (tvs, tc, mkTyVarTys tvs) } + get_lhs (Just pats) = do { let hs_app = nlHsTyConApp tycon_name pats + ; (tvs, tc_app) <- tcHsQuantifiedType tv_names hs_app + ; let (tc, tc_args) = tcSplitTyConApp tc_app + ; return (tvs, tc, tc_args) } deriveTyData _other = panic "derivTyData" -- Caller ensures that only TyData can happen @@ -429,27 +495,34 @@ deriveTyData _other mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type -> Maybe ThetaType -- Just => context supplied (standalone deriving) -- Nothing => context inferred (deriving on data decl) - -> TcRn (Maybe EarlyDerivSpec) + -> TcRn EarlyDerivSpec +-- Make the EarlyDerivSpec for an instance +-- forall tvs. theta => cls (tys ++ [ty]) +-- where the 'theta' is optional (that's the Maybe part) +-- Assumes that this declaration is well-kinded + mkEqnHelp orig tvs cls cls_tys tc_app mtheta | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app - = do { + , isAlgTyCon tycon -- Check for functions, primitive types etc + = do { (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon tc_args + -- Be careful to test rep_tc here: in the case of families, + -- we want to check the instance tycon, not the family tycon + -- For standalone deriving (mtheta /= Nothing), - -- check that all the data constructors are in scope - -- By this time we know that the thing is algebraic - -- because we've called checkInstHead in derivingStandalone - rdr_env <- getGlobalRdrEnv - ; let hidden_data_cons = filter not_in_scope (tyConDataCons tycon) - not_in_scope dc = null (lookupGRE_Name rdr_env (dataConName dc)) - ; checkTc (isNothing mtheta || null hidden_data_cons) + -- check that all the data constructors are in scope. + -- No need for this when deriving Typeable, becuase we don't need + -- the constructors for that. + ; rdr_env <- getGlobalRdrEnv + ; let hidden_data_cons = isAbstractTyCon rep_tc || any not_in_scope (tyConDataCons rep_tc) + not_in_scope dc = null (lookupGRE_Name rdr_env (dataConName dc)) + ; checkTc (isNothing mtheta || + not hidden_data_cons || + className cls `elem` typeableClassNames) (derivingHiddenErr tycon) ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving - ; (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon tc_args - - -- Be careful to test rep_tc here: in the case of families, we want - -- to check the instance tycon, not the family tycon ; if isDataTyCon rep_tc then mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta @@ -458,11 +531,8 @@ mkEqnHelp orig tvs cls cls_tys tc_app mtheta tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta } | otherwise - = baleOut (derivingThingErr cls cls_tys tc_app - (ptext (sLit "Last argument of the instance must be a type application"))) - -baleOut :: Message -> TcM (Maybe a) -baleOut err = do { addErrTc err; return Nothing } + = failWithTc (derivingThingErr cls cls_tys tc_app + (ptext (sLit "The last argument of the instance must be a data or newtype application"))) \end{code} Note [Looking up family instances for deriving] @@ -504,7 +574,7 @@ tcLookupFamInstExact tycon tys famInstNotFound :: TyCon -> [Type] -> TcM a famInstNotFound tycon tys = failWithTc (ptext (sLit "No family instance for") - <+> quotes (pprTypeApp tycon (ppr tycon) tys)) + <+> quotes (pprTypeApp tycon tys)) \end{code} @@ -517,22 +587,22 @@ famInstNotFound tycon tys \begin{code} mkDataTypeEqn :: InstOrigin -> Bool -> [Var] -> Class -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe ThetaType - -> TcRn (Maybe EarlyDerivSpec) -- Return 'Nothing' if error + -> TcRn EarlyDerivSpec -- Return 'Nothing' if error mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta - | Just err <- checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc + = case checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc of -- NB: pass the *representation* tycon to checkSideConditions - = baleOut (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) err) - - | otherwise - = ASSERT( null cls_tys ) - mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta + CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta + NonDerivableClass -> bale_out (nonStdErr cls) + DerivableClassError msg -> bale_out msg + where + bale_out msg = failWithTc (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) msg) mk_data_eqn, mk_typeable_eqn :: InstOrigin -> [TyVar] -> Class -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe ThetaType - -> TcM (Maybe EarlyDerivSpec) + -> TcM EarlyDerivSpec mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta | getName cls `elem` typeableClassNames = mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta @@ -545,12 +615,14 @@ mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta | data_con <- tyConDataCons rep_tc, arg_ty <- ASSERT( isVanillaDataCon data_con ) dataConInstOrigArgTys data_con rep_tc_args, - not (isUnLiftedType arg_ty) ] -- No constraints for unlifted types? + not (isUnLiftedType arg_ty) ] + -- No constraints for unlifted types + -- Where they are legal we generate specilised function calls -- See Note [Superclasses of derived instance] sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys) (classSCTheta cls) - inst_tys = [mkTyConApp tycon tc_args] + inst_tys = [mkTyConApp tycon tc_args] stupid_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_tc_args stupid_constraints = substTheta stupid_subst (tyConStupidTheta rep_tc) @@ -558,12 +630,12 @@ mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta spec = DS { ds_loc = loc, ds_orig = orig , ds_name = dfun_name, ds_tvs = tvs - , ds_cls = cls, ds_tys = inst_tys + , ds_cls = cls, ds_tys = inst_tys, ds_tc = rep_tc , ds_theta = mtheta `orElse` all_constraints , ds_newtype = False } - ; return (if isJust mtheta then Just (Right spec) -- Specified context - else Just (Left spec)) } -- Infer context + ; return (if isJust mtheta then Right spec -- Specified context + else Left spec) } -- Infer context mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- The Typeable class is special in several ways @@ -587,9 +659,9 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta <> int (tyConArity tycon) <+> ppr tycon <> rparen) ; dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM - ; return (Just $ Right $ + ; return (Right $ DS { ds_loc = loc, ds_orig = orig, ds_name = dfun_name, ds_tvs = [] - , ds_cls = cls, ds_tys = [mkTyConApp tycon []] + , ds_cls = cls, ds_tys = [mkTyConApp tycon []], ds_tc = rep_tc , ds_theta = mtheta `orElse` [], ds_newtype = False }) } ------------------------------------------------------------------ @@ -600,28 +672,36 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- the data constructors - but we need to be careful to fall back to the -- family tycon (with indexes) in error messages. -checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> Maybe SDoc +data DerivStatus = CanDerive + | NonDerivableClass + | DerivableClassError SDoc + +checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> DerivStatus checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc | notNull cls_tys - = Just ty_args_why -- e.g. deriving( Foo s ) + = DerivableClassError ty_args_why -- e.g. deriving( Foo s ) | otherwise = case sideConditions cls of - Just cond -> cond (mayDeriveDataTypeable, rep_tc) - Nothing -> Just non_std_why + Nothing -> NonDerivableClass + Just cond -> case (cond (mayDeriveDataTypeable, rep_tc)) of + Nothing -> CanDerive + Just err -> DerivableClassError err where ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "is not a class") - non_std_why = quotes (ppr cls) <+> ptext (sLit "is not a derivable class") + +nonStdErr :: Class -> SDoc +nonStdErr cls = quotes (ppr cls) <+> ptext (sLit "is not a derivable class") sideConditions :: Class -> Maybe Condition sideConditions cls - | cls_key == eqClassKey = Just cond_std - | cls_key == ordClassKey = Just cond_std - | cls_key == readClassKey = Just cond_std - | cls_key == showClassKey = Just cond_std - | cls_key == enumClassKey = Just (cond_std `andCond` cond_isEnumeration) - | cls_key == ixClassKey = Just (cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)) - | cls_key == boundedClassKey = Just (cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)) - | cls_key == dataClassKey = Just (cond_mayDeriveDataTypeable `andCond` cond_std) + | cls_key == eqClassKey = Just cond_std + | cls_key == ordClassKey = Just cond_std + | cls_key == showClassKey = Just cond_std + | cls_key == readClassKey = Just (cond_std `andCond` cond_noUnliftedArgs) + | cls_key == enumClassKey = Just (cond_std `andCond` cond_isEnumeration) + | cls_key == ixClassKey = Just (cond_std `andCond` cond_enumOrProduct) + | cls_key == boundedClassKey = Just (cond_std `andCond` cond_enumOrProduct) + | cls_key == dataClassKey = Just (cond_mayDeriveDataTypeable `andCond` cond_std `andCond` cond_noUnliftedArgs) | getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK) | otherwise = Nothing where @@ -659,6 +739,22 @@ cond_std (_, rep_tc) existential_why = quotes (pprSourceTyCon rep_tc) <+> ptext (sLit "has non-Haskell-98 constructor(s)") +cond_enumOrProduct :: Condition +cond_enumOrProduct = cond_isEnumeration `orCond` + (cond_isProduct `andCond` cond_noUnliftedArgs) + +cond_noUnliftedArgs :: Condition +-- For some classes (eg Eq, Ord) we allow unlifted arg types +-- by generating specilaised code. For others (eg Data) we don't. +cond_noUnliftedArgs (_, tc) + | null bad_cons = Nothing + | otherwise = Just why + where + bad_cons = [ con | con <- tyConDataCons tc + , any isUnLiftedType (dataConOrigArgTys con) ] + why = ptext (sLit "Constructor") <+> quotes (ppr (head bad_cons)) + <+> ptext (sLit "has arguments of unlifted type") + cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) | isEnumerationTyCon rep_tc = Nothing @@ -710,7 +806,8 @@ std_class_via_iso clas -- These standard classes can be derived for a newtype new_dfun_name :: Class -> TyCon -> TcM Name new_dfun_name clas tycon -- Just a simple wrapper - = newDFunName clas [mkTyConApp tycon []] (getSrcSpan tycon) + = do { loc <- getSrcSpanM -- The location of the instance decl, not of the tycon + ; newDFunName clas [mkTyConApp tycon []] loc } -- The type passed to newDFunName is only used to generate -- a suitable string; hence the empty type arg list \end{code} @@ -750,7 +847,7 @@ a context for the Data instances: mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> [Var] -> Class -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe ThetaType - -> TcRn (Maybe EarlyDerivSpec) + -> TcRn EarlyDerivSpec mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs cls cls_tys tycon tc_args rep_tycon rep_tc_args mtheta | can_derive_via_isomorphism && (newtype_deriving || std_class_via_iso cls) @@ -758,24 +855,27 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs ; dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM ; let spec = DS { ds_loc = loc, ds_orig = orig - , ds_name = dfun_name, ds_tvs = dict_tvs - , ds_cls = cls, ds_tys = inst_tys + , ds_name = dfun_name, ds_tvs = varSetElems dfun_tvs + , ds_cls = cls, ds_tys = inst_tys, ds_tc = rep_tycon , ds_theta = mtheta `orElse` all_preds , ds_newtype = True } - ; return (if isJust mtheta then Just (Right spec) - else Just (Left spec)) } + ; return (if isJust mtheta then Right spec + else Left spec) } - | isNothing mb_std_err -- Use the standard H98 method - = mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta - - -- Otherwise we can't derive - | newtype_deriving = baleOut cant_derive_err -- Too hard - | otherwise = baleOut std_err -- Just complain about being a non-std instance + | otherwise + = case check_conditions of + CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta + -- Use the standard H98 method + DerivableClassError msg -> bale_out msg -- Error with standard class + NonDerivableClass -- Must use newtype deriving + | newtype_deriving -> bale_out cant_derive_err -- Too hard, even with newtype deriving + | otherwise -> bale_out non_std_err -- Try newtype deriving! where - mb_std_err = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon - std_err = derivingThingErr cls cls_tys tc_app $ - vcat [fromJust mb_std_err, - ptext (sLit "Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] + check_conditions = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon + bale_out msg = failWithTc (derivingThingErr cls cls_tys inst_ty msg) + + non_std_err = nonStdErr cls $$ + ptext (sLit "Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension") -- Here is the plan for newtype derivings. We see -- newtype T a1...an = MkT (t ak+1...an) deriving (.., C s1 .. sm, ...) @@ -786,6 +886,8 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- with the last parameter missing -- (T a1 .. ak) matches the kind of C's last argument -- (and hence so does t) + -- The latter kind-check has been done by deriveTyData already, + -- and tc_args are already trimmed -- -- We generate the instance -- instance forall ({a1..ak} u fvs(s1..sm)). @@ -805,15 +907,12 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- We generate the instance -- instance Monad (ST s) => Monad (T s) where - cls_tyvars = classTyVars cls - kind = tyVarKind (last cls_tyvars) - -- Kind of the thing we want to instance - -- e.g. argument kind of Monad, *->* - - (arg_kinds, _) = splitKindFunTys kind - n_args_to_drop = length arg_kinds - -- Want to drop 1 arg from (T s a) and (ST s a) - -- to get instance Monad (ST s) => Monad (T s) + nt_eta_arity = length (fst (newTyConEtadRhs rep_tycon)) + -- For newtype T a b = MkT (S a a b), the TyCon machinery already + -- eta-reduces the represenation type, so we know that + -- T a ~ S a a + -- That's convenient here, because we may have to apply + -- it to fewer than its original complement of arguments -- Note [Newtype representation] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -823,30 +922,21 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- newtype A = MkA B deriving( Num ) -- We want the Num instance of B, *not* the Num instance of Int, -- when making the Num instance of A! - rep_ty = newTyConInstRhs rep_tycon rep_tc_args - (rep_fn, rep_ty_args) = tcSplitAppTys rep_ty - - n_tyargs_to_keep = tyConArity tycon - n_args_to_drop - dropped_tc_args = drop n_tyargs_to_keep tc_args - dropped_tvs = tyVarsOfTypes dropped_tc_args - - n_args_to_keep = length rep_ty_args - n_args_to_drop - args_to_drop = drop n_args_to_keep rep_ty_args - args_to_keep = take n_args_to_keep rep_ty_args - - rep_fn' = mkAppTys rep_fn args_to_keep - rep_tys = cls_tys ++ [rep_fn'] - rep_pred = mkClassPred cls rep_tys + rep_inst_ty = newTyConInstRhs rep_tycon rep_tc_args + rep_tys = cls_tys ++ [rep_inst_ty] + rep_pred = mkClassPred cls rep_tys -- rep_pred is the representation dictionary, from where -- we are gong to get all the methods for the newtype -- dictionary - tc_app = mkTyConApp tycon (take n_tyargs_to_keep tc_args) -- Next we figure out what superclass dictionaries to use -- See Note [Newtype deriving superclasses] above - inst_tys = cls_tys ++ [tc_app] + cls_tyvars = classTyVars cls + dfun_tvs = tyVarsOfTypes tc_args + inst_ty = mkTyConApp tycon tc_args + inst_tys = cls_tys ++ [inst_ty] sc_theta = substTheta (zipOpenTvSubst cls_tyvars inst_tys) (classSCTheta cls) @@ -857,7 +947,6 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- instance C T -- rather than -- instance C Int => C T - dict_tvs = filterOut (`elemVarSet` dropped_tvs) tvs all_preds = rep_pred : sc_theta -- NB: rep_pred comes first ------------------------------------------------------------------- @@ -866,16 +955,13 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs right_arity = length cls_tys + 1 == classArity cls -- Never derive Read,Show,Typeable,Data this way - non_iso_classes = [readClassKey, showClassKey, typeableClassKey, dataClassKey] + non_iso_class cls = className cls `elem` ([readClassName, showClassName, dataClassName] ++ + typeableClassNames) can_derive_via_isomorphism - = not (getUnique cls `elem` non_iso_classes) + = not (non_iso_class cls) && right_arity -- Well kinded; -- eg not: newtype T ... deriving( ST ) -- because ST needs *2* type params - && n_tyargs_to_keep >= 0 -- Type constructor has right kind: - -- eg not: newtype T = T Int deriving( Monad ) - && n_args_to_keep >= 0 -- Rep type has right kind: - -- eg not: newtype T a = T Int deriving( Monad ) && eta_ok -- Eta reduction works && not (isRecursiveTyCon tycon) -- Does not work for recursive tycons: -- newtype A = MkA [A] @@ -891,39 +977,30 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- recursive newtypes too -- Check that eta reduction is OK - eta_ok = (args_to_drop `tcEqTypes` dropped_tc_args) - -- (a) the dropped-off args are identical in the source and rep type + eta_ok = (nt_eta_arity <= length rep_tc_args) + -- (a) the newtype can be eta-reduced to match the number + -- of type argument actually supplied -- newtype T a b = MkT (S [a] b) deriving( Monad ) -- Here the 'b' must be the same in the rep type (S [a] b) + -- And the [a] must not mention 'b'. That's all handled + -- by nt_eta_rity. - && (tyVarsOfType rep_fn' `disjointVarSet` dropped_tvs) - -- (b) the remaining type args do not mention any of the dropped - -- type variables - - && (tyVarsOfTypes cls_tys `disjointVarSet` dropped_tvs) + && (tyVarsOfTypes cls_tys `subVarSet` dfun_tvs) -- (c) the type class args do not mention any of the dropped type -- variables - - && all isTyVarTy dropped_tc_args - -- (d) in case of newtype family instances, the eta-dropped - -- arguments must be type variables (not more complex indexes) - - cant_derive_err = derivingThingErr cls cls_tys tc_app - (vcat [ptext (sLit "even with cunning newtype deriving:"), - if isRecursiveTyCon tycon then - ptext (sLit "the newtype may be recursive") - else empty, - if not right_arity then - quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") - else empty, - if not (n_tyargs_to_keep >= 0) then - ptext (sLit "the type constructor has wrong kind") - else if not (n_args_to_keep >= 0) then - ptext (sLit "the representation type has wrong kind") - else if not eta_ok then - ptext (sLit "the eta-reduction property does not hold") - else empty - ]) + -- newtype T a b = ... deriving( Monad b ) + + cant_derive_err = vcat [ptext (sLit "even with cunning newtype deriving:"), + if isRecursiveTyCon tycon then + ptext (sLit "the newtype may be recursive") + else empty, + if not right_arity then + quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") + else empty, + if not eta_ok then + ptext (sLit "cannot eta-reduce the representation type enough") + else empty + ] \end{code} @@ -1109,50 +1186,40 @@ the renamer. What a great hack! -- Representation tycons differ from the tycon in the instance signature in -- case of instances for indexed families. -- -genInst :: OverlapFlag -> DerivSpec -> TcM (InstInfo, DerivAuxBinds) +genInst :: OverlapFlag -> DerivSpec -> TcM (InstInfo RdrName, DerivAuxBinds) genInst oflag spec | ds_newtype spec - = return (InstInfo { iSpec = mkInstance1 oflag spec + = return (InstInfo { iSpec = mkInstance1 oflag spec , iBinds = NewTypeDerived }, []) | otherwise - = do { fix_env <- getFixityEnv - ; let - inst = mkInstance1 oflag spec - (tyvars,_,clas,[ty]) = instanceHead inst - clas_nm = className clas - (visible_tycon, tyArgs) = tcSplitTyConApp ty + = do { let loc = getSrcSpan (ds_name spec) + inst = mkInstance1 oflag spec + clas = ds_cls spec + rep_tycon = ds_tc spec -- In case of a family instance, we need to use the representation -- tycon (after all, it has the data constructors) - ; (tycon, _) <- tcLookupFamInstExact visible_tycon tyArgs - ; let (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon - - -- Bring the right type variables into - -- scope, and rename the method binds - -- It's a bit yukky that we return *renamed* InstInfo, but - -- *non-renamed* auxiliary bindings - ; (rn_meth_binds, _fvs) <- discardWarnings $ - bindLocalNames (map Var.varName tyvars) $ - rnMethodBinds clas_nm (\_ -> []) [] meth_binds + ; fix_env <- getFixityEnv + ; let (meth_binds, aux_binds) = genDerivBinds loc fix_env clas rep_tycon -- Build the InstInfo ; return (InstInfo { iSpec = inst, - iBinds = VanillaInst rn_meth_binds [] }, + iBinds = VanillaInst meth_binds [] }, aux_binds) } -genDerivBinds :: Class -> FixityEnv -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) -genDerivBinds clas fix_env tycon +genDerivBinds :: SrcSpan -> FixityEnv -> Class -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) +genDerivBinds loc fix_env clas tycon | className clas `elem` typeableClassNames - = (gen_Typeable_binds tycon, []) + = (gen_Typeable_binds loc tycon, []) | otherwise = case assocMaybe gen_list (getUnique clas) of - Just gen_fn -> gen_fn tycon + Just gen_fn -> gen_fn loc tycon Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas) where - gen_list :: [(Unique, TyCon -> (LHsBinds RdrName, DerivAuxBinds))] + gen_list :: [(Unique, SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds))] gen_list = [(eqClassKey, gen_Eq_binds) ,(ordClassKey, gen_Ord_binds) ,(enumClassKey, gen_Enum_binds) @@ -1160,7 +1227,7 @@ genDerivBinds clas fix_env tycon ,(ixClassKey, gen_Ix_binds) ,(showClassKey, gen_Show_binds fix_env) ,(readClassKey, gen_Read_binds fix_env) - ,(dataClassKey, gen_Data_binds fix_env) + ,(dataClassKey, gen_Data_binds) ] \end{code} @@ -1172,6 +1239,18 @@ genDerivBinds clas fix_env tycon %************************************************************************ \begin{code} +derivingKindErr :: TyCon -> Class -> [Type] -> Kind -> Message +derivingKindErr tc cls cls_tys cls_kind + = hang (ptext (sLit "Cannot derive well-kinded instance of form") + <+> quotes (pprClassPred cls cls_tys <+> parens (ppr tc <+> ptext (sLit "...")))) + 2 (ptext (sLit "Class") <+> quotes (ppr cls) + <+> ptext (sLit "expects an argument of kind") <+> quotes (pprKind cls_kind)) + +typeFamilyPapErr :: TyCon -> Class -> [Type] -> Type -> Message +typeFamilyPapErr tc cls cls_tys inst_ty + = hang (ptext (sLit "Derived instance") <+> quotes (pprClassPred cls (cls_tys ++ [inst_ty]))) + 2 (ptext (sLit "requires illegal partial application of data type family") <+> ppr tc) + derivingThingErr :: Class -> [Type] -> Type -> Message -> Message derivingThingErr clas tys ty why = sep [hsep [ptext (sLit "Can't make a derived instance of"),