X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=fab7c61ff07cd2e388a1bf4a0d7141255c112e18;hp=5053a0668e0527078adedf763f4c793d0db60c34;hb=74e1e73af872e63fbbec2bc9442494c3657053c3;hpb=1fab5eeaf45798ee7832497d6518883be451bfca diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 5053a06..fab7c61 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -30,6 +30,7 @@ import HscTypes import Class import Type +import Coercion import ErrUtils import MkId import DataCon @@ -39,15 +40,20 @@ import Name import NameSet import TyCon import TcType +import BuildTyCl +import BasicTypes import Var import VarSet import PrelNames import SrcLoc +import UniqSupply import Util import ListSetOps import Outputable import FastString import Bag + +import Control.Monad \end{code} %************************************************************************ @@ -65,28 +71,47 @@ Overall plan 3. Add the derived bindings, generating InstInfos + \begin{code} -- DerivSpec is purely local to this module data DerivSpec = DS { ds_loc :: SrcSpan - , ds_orig :: InstOrigin + , ds_orig :: CtOrigin , ds_name :: Name , ds_tvs :: [TyVar] , ds_theta :: ThetaType , ds_cls :: Class , ds_tys :: [Type] , ds_tc :: TyCon + , ds_tc_args :: [Type] , 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 in + -- For type families, the tycon in -- in ds_tys is the *family* tycon - -- in ds_tc is the *representation* tycon + -- in ds_tc, ds_tc_args is the *representation* tycon -- For non-family tycons, both are the same -- ds_newtype = True <=> Newtype deriving -- False <=> Vanilla deriving +\end{code} + +Example: + + newtype instance T [a] = MkT (Tree a) deriving( C s ) +==> + axiom T [a] = :RTList a + axiom :RTList a = Tree a + + DS { ds_tvs = [a,s], ds_cls = C, ds_tys = [s, T [a]] + , ds_tc = :RTList, ds_tc_args = [a] + , ds_newtype = True } + +\begin{code} +type DerivContext = Maybe ThetaType + -- Nothing <=> Vanilla deriving; infer the context of the instance decl + -- Just theta <=> Standalone deriving: context supplied by programmer type EarlyDerivSpec = Either DerivSpec DerivSpec -- Left ds => the context for the instance should be inferred @@ -103,6 +128,9 @@ pprDerivSpec (DS { ds_loc = l, ds_name = n, ds_tvs = tvs, ds_cls = c, ds_tys = tys, ds_theta = rhs }) = parens (hsep [ppr l, ppr n, ppr tvs, ppr c, ppr tys] <+> equals <+> ppr rhs) + +instance Outputable DerivSpec where + ppr = pprDerivSpec \end{code} @@ -253,7 +281,12 @@ There may be a coercion needed which we get from the tycon for the newtype when the dict is constructed in TcInstDcls.tcInstDecl2 - +Note [Unused constructors and deriving clauses] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +See Trac #3221. Consider + data T = T1 | T2 deriving( Show ) +Are T1 and T2 unused? Well, no: the deriving clause expands to mention +both of them. So we gather defs/uses from deriving just like anything else. %************************************************************************ %* * @@ -265,49 +298,79 @@ 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 Name], -- The generated "instance decls" - HsValBinds Name) -- Extra generated top-level bindings + -> TcM ([InstInfo Name] -- The generated "instance decls" + ,HsValBinds Name -- Extra generated top-level bindings + ,DefUses + ,[TyCon] -- Extra generated top-level types + ,[TyCon]) -- Extra generated type family instances tcDeriving tycl_decls inst_decls deriv_decls - = recoverM (return ([], emptyValBindsOut)) $ + = recoverM (return ([], emptyValBindsOut, emptyDUs, [], [])) $ do { -- Fish the "deriving"-related information out of the TcEnv -- And make the necessary "equations". is_boot <- tcIsHsBoot - ; traceTc (text "tcDeriving" <+> ppr is_boot) - ; early_specs <- makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls + ; traceTc "tcDeriving" (ppr is_boot) + ; (early_specs, genericsExtras) + <- makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls + ; let (repMetaTys, repTyCons, metaInsts) = unzip3 genericsExtras ; overlap_flag <- getOverlapFlag ; let (infer_specs, given_specs) = splitEithers early_specs - ; insts1 <- mapM (genInst overlap_flag) given_specs + ; insts1 <- mapM (genInst True overlap_flag) given_specs ; final_specs <- extendLocalInstEnv (map (iSpec . fst) insts1) $ inferInstanceContexts overlap_flag infer_specs - ; insts2 <- mapM (genInst overlap_flag) final_specs + ; insts2 <- mapM (genInst False overlap_flag) final_specs - -- 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) + -- We no longer generate the old generic to/from functions + -- from each type declaration, so this is emptyBag + ; gen_binds <- return emptyBag -- mkGenericBinds is_boot tycl_decls + + ; (inst_info, rn_binds, rn_dus) + <- renameDeriv is_boot gen_binds (insts1 ++ insts2 ++ concat metaInsts) ; dflags <- getDOpts ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving inst_info rn_binds)) - - ; return (inst_info, rn_binds) } + (ddump_deriving inst_info rn_binds repMetaTys repTyCons metaInsts)) +{- + ; when (not (null inst_info)) $ + dumpDerivingInfo (ddump_deriving inst_info rn_binds) +-} + ; return ( inst_info, rn_binds, rn_dus + , concat (map metaTyCons2TyCons repMetaTys), repTyCons) } where - ddump_deriving :: [InstInfo Name] -> HsValBinds Name -> SDoc - ddump_deriving inst_infos extra_binds - = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds + ddump_deriving :: [InstInfo Name] -> HsValBinds Name + -> [MetaTyCons] -- ^ Empty data constructors + -> [TyCon] -- ^ Rep type family instances + -> [[(InstInfo RdrName, DerivAuxBinds)]] + -- ^ Instances for the repMetaTys + -> SDoc + ddump_deriving inst_infos extra_binds repMetaTys repTyCons metaInsts + = hang (ptext (sLit "Derived instances")) + 2 (vcat (map (\i -> pprInstInfoDetails i $$ text "") inst_infos) + $$ ppr extra_binds) + $$ hangP "Generic representation" ( + hangP "Generated datatypes for meta-information" + (vcat (map ppr repMetaTys)) + -- The Outputable instance for TyCon unfortunately only prints the name... + $$ hangP "Representation types" + (vcat (map ppr repTyCons)) + $$ hangP "Meta-information instances" + (vcat (map (pprInstInfoDetails . fst) (concat metaInsts)))) + + hangP s x = text "" $$ hang (ptext (sLit s)) 2 x + renameDeriv :: Bool -> LHsBinds RdrName -> [(InstInfo RdrName, DerivAuxBinds)] - -> TcM ([InstInfo Name], HsValBinds Name) + -> TcM ([InstInfo Name], HsValBinds Name, DefUses) 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) } + = do { (rn_inst_infos, fvs) <- mapAndUnzipM rn_inst_info inst_infos + ; return (rn_inst_infos, emptyValBindsOut, usesOnly (plusFVs fvs)) } | otherwise = discardWarnings $ -- Discard warnings about unused bindings etc @@ -320,15 +383,15 @@ renameDeriv is_boot gen_binds insts -- 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) } } + ; let (aux_binds, aux_sigs) = unzip $ map (genAuxBind loc) $ + rm_dups [] $ concat deriv_aux_binds + aux_val_binds = ValBindsIn (listToBag aux_binds) aux_sigs + ; rn_aux_lhs <- rnTopBindsLHS emptyFsEnv aux_val_binds + ; bindLocalNames (collectHsValBinders rn_aux_lhs) $ + do { (rn_aux, dus_aux) <- rnTopBindsRHS rn_aux_lhs + ; (rn_inst_infos, fvs_insts) <- mapAndUnzipM rn_inst_info inst_infos + ; return (rn_inst_infos, rn_aux `plusHsValBinds` rn_gen, + dus_gen `plusDU` dus_aux `plusDU` usesOnly (plusFVs fvs_insts)) } } where (inst_infos, deriv_aux_binds) = unzip insts @@ -339,35 +402,44 @@ renameDeriv is_boot gen_binds insts | otherwise = rm_dups (b:acc) bs - rn_inst_info (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) - = return (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) + rn_inst_info :: InstInfo RdrName -> TcM (InstInfo Name, FreeVars) + rn_inst_info info@(InstInfo { iBinds = NewTypeDerived coi tc }) + = return ( info { iBinds = NewTypeDerived coi tc } + , mkFVs (map dataConName (tyConDataCons tc))) + -- See Note [Newtype deriving and unused constructors] - rn_inst_info (InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs }) + rn_inst_info inst_info@(InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs standalone_deriv }) = -- 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 [] }) } + do { (rn_binds, fvs) <- rnMethodBinds clas_nm (\_ -> []) binds + ; let binds' = VanillaInst rn_binds [] standalone_deriv + ; return (inst_info { iBinds = binds' }, fvs) } where - (tyvars,_,clas,_) = instanceHead inst - clas_nm = className clas - ------------------------------------------ -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 ]) } - -- 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 + (tyvars,_, clas,_) = instanceHead inst + clas_nm = className clas \end{code} +Note [Newtype deriving and unused constructors] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider this (see Trac #1954): + + module Bug(P) where + newtype P a = MkP (IO a) deriving Monad + +If you compile with -fwarn-unused-binds you do not expect the warning +"Defined but not used: data consructor MkP". Yet the newtype deriving +code does not explicitly mention MkP, but it should behave as if you +had written + instance Monad P where + return x = MkP (return x) + ...etc... + +So we want to signal a user of the data constructor 'MkP'. That's +what we do in rn_inst_info, and it's the only reason we have the TyCon +stored in NewTypeDerived. + %************************************************************************ %* * @@ -378,37 +450,93 @@ mkGenericBinds is_boot @makeDerivSpecs@ fishes around to find the info about needed derived instances. \begin{code} +-- Make the "extras" for the generic representation +mkGenDerivExtras :: TyCon + -> TcRn (MetaTyCons, TyCon, [(InstInfo RdrName, DerivAuxBinds)]) +mkGenDerivExtras tc = do + { (metaTyCons, rep0TyInst) <- genGenericRepExtras tc + ; metaInsts <- genDtMeta (tc, metaTyCons) + ; return (metaTyCons, rep0TyInst, metaInsts) } + makeDerivSpecs :: Bool -> [LTyClDecl Name] - -> [LInstDecl Name] + -> [LInstDecl Name] -> [LDerivDecl Name] - -> TcM [EarlyDerivSpec] - + -> TcM ( [EarlyDerivSpec] + , [(MetaTyCons, TyCon, [(InstInfo RdrName, DerivAuxBinds)])]) 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 [] } + | 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 (eqns1 ++ eqns2) } + = do { eqns1 <- mapAndRecoverM deriveTyData all_tydata + ; eqns2 <- mapAndRecoverM deriveStandalone deriv_decls + + -- Generic representation stuff: we might need to add some "extras" + -- to the instances + ; xDerRep <- getDOpts >>= return . xopt Opt_DeriveGeneric + ; generic_extras_deriv <- if not xDerRep + -- No extras if the flag is off + then (return []) + else do { + let allTyNames = [ tcdName d | L _ d <- tycl_decls, isDataDecl d ] + -- Select only those types that derive Generic + ; let sel_tydata = [ tcdName t | (L _ c, L _ t) <- all_tydata + , getClassName c == Just genClassName ] + ; let sel_deriv_decls = catMaybes [ getTypeName t + | L _ (DerivDecl (L _ t)) <- deriv_decls + , getClassName t == Just genClassName ] + ; derTyDecls <- mapM tcLookupTyCon $ + filter (needsExtras xDerRep + (sel_tydata ++ sel_deriv_decls)) allTyNames + -- We need to generate the extras to add to what has + -- already been derived + ; {- pprTrace "sel_tydata" (ppr sel_tydata) $ + pprTrace "sel_deriv_decls" (ppr sel_deriv_decls) $ + pprTrace "derTyDecls" (ppr derTyDecls) $ + pprTrace "deriv_decls" (ppr deriv_decls) $ -} + mapM mkGenDerivExtras derTyDecls } + + -- Merge and return + ; return ( eqns1 ++ eqns2, generic_extras_deriv) } where + -- We need extras if the flag DeriveGeneric is on and this type is + -- deriving Generic + needsExtras xDerRep tydata tc_name = xDerRep && tc_name `elem` tydata + + -- Extracts the name of the class in the deriving + getClassName :: HsType Name -> Maybe Name + getClassName (HsForAllTy _ _ _ (L _ n)) = getClassName n + getClassName (HsPredTy (HsClassP n _)) = Just n + getClassName _ = Nothing + + -- Extracts the name of the type in the deriving + -- This function (and also getClassName above) is not really nice, and I + -- might not have covered all possible cases. I wonder if there is no easier + -- way to extract class and type name from a LDerivDecl... + getTypeName :: HsType Name -> Maybe Name + getTypeName (HsForAllTy _ _ _ (L _ n)) = getTypeName n + getTypeName (HsTyVar n) = Just n + getTypeName (HsOpTy _ (L _ n) _) = Just n + getTypeName (HsPredTy (HsClassP _ [L _ n])) = getTypeName n + getTypeName (HsAppTy (L _ n) _) = getTypeName n + getTypeName (HsParTy (L _ n)) = getTypeName n + getTypeName (HsKindSig (L _ n) _) = getTypeName n + getTypeName _ = Nothing + 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 ] + -- Derived predicate paired with its data type declaration + all_tydata = extractTyDataPreds (instDeclATs inst_decls ++ tycl_decls) deriv_locs = map (getLoc . snd) all_tydata - ++ map getLoc deriv_decls + ++ 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"))) + addErr (hang (ptext (sLit "Deriving not permitted in hs-boot file")) + 2 (ptext (sLit "Use an instance declaration instead"))) ------------------------------------------------------------------ deriveStandalone :: LDerivDecl Name -> TcM EarlyDerivSpec @@ -418,22 +546,22 @@ deriveStandalone :: LDerivDecl Name -> TcM EarlyDerivSpec deriveStandalone (L loc (DerivDecl deriv_ty)) = setSrcSpan loc $ addErrCtxt (standaloneCtxt deriv_ty) $ - do { traceTc (text "standalone deriving decl for" <+> ppr deriv_ty) - ; (tvs, theta, tau) <- tcHsInstHead deriv_ty - ; traceTc (text "standalone deriving;" - <+> text "tvs:" <+> ppr tvs - <+> text "theta:" <+> ppr theta - <+> text "tau:" <+> ppr tau) - ; (cls, inst_tys) <- checkValidInstHead tau - ; checkValidInstance tvs theta cls inst_tys + do { traceTc "Standalone deriving decl for" (ppr deriv_ty) + ; (tvs, theta, cls, inst_tys) <- tcHsInstHead deriv_ty + ; traceTc "Standalone deriving;" $ vcat + [ text "tvs:" <+> ppr tvs + , text "theta:" <+> ppr theta + , text "cls:" <+> ppr cls + , text "tys:" <+> ppr inst_tys ] + ; checkValidInstance deriv_ty 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 - <+> text "type:" <+> ppr inst_ty) + ; traceTc "Standalone deriving:" $ vcat + [ text "class:" <+> ppr cls + , text "class types:" <+> ppr cls_tys + , text "type:" <+> ppr inst_ty ] ; mkEqnHelp StandAloneDerivOrigin tvs cls cls_tys inst_ty (Just theta) } @@ -483,7 +611,7 @@ deriveTyData (L loc deriv_pred, L _ decl@(TyData { tcdLName = L _ tycon_name, -- Type families can't be partially applied -- e.g. newtype instance T Int a = MkT [a] deriving( Monad ) -- Note [Deriving, type families, and partial applications] - ; checkTc (not (isOpenTyCon tc) || n_args_to_drop == 0) + ; checkTc (not (isFamilyTyCon tc) || n_args_to_drop == 0) (typeFamilyPapErr tc cls cls_tys inst_ty) ; mkEqnHelp DerivOrigin (varSetElems univ_tvs) cls cls_tys inst_ty Nothing } } @@ -514,8 +642,8 @@ When there are no type families, it's quite easy: newtype S a = MkS [a] -- :CoS :: S ~ [] -- Eta-reduced - instance Eq [a] => Eq (S a) -- by coercion sym (Eq (coMkS a)) : Eq [a] ~ Eq (S a) - instance Monad [] => Monad S -- by coercion sym (Monad coMkS) : Monad [] ~ Monad S + instance Eq [a] => Eq (S a) -- by coercion sym (Eq (:CoS a)) : Eq [a] ~ Eq (S a) + instance Monad [] => Monad S -- by coercion sym (Monad :CoS) : Monad [] ~ Monad S When type familes are involved it's trickier: @@ -536,8 +664,8 @@ After all, we can write it out ... etc ... \begin{code} -mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type - -> Maybe ThetaType -- Just => context supplied (standalone deriving) +mkEqnHelp :: CtOrigin -> [TyVar] -> Class -> [Type] -> Type + -> DerivContext -- Just => context supplied (standalone deriving) -- Nothing => context inferred (deriving on data decl) -> TcRn EarlyDerivSpec -- Make the EarlyDerivSpec for an instance @@ -548,77 +676,46 @@ mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type mkEqnHelp orig tvs cls cls_tys tc_app mtheta | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app , 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. - -- 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 - - ; if isDataTyCon rep_tc then - mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys - tycon tc_args rep_tc rep_tc_args mtheta - else - mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving - tvs cls cls_tys - tycon tc_args rep_tc rep_tc_args mtheta } + = mk_alg_eqn tycon tc_args | otherwise - = failWithTc (derivingThingErr cls cls_tys tc_app + = failWithTc (derivingThingErr False 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] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -tcLookupFamInstExact is an auxiliary lookup wrapper which requires -that looked-up family instances exist. If called with a vanilla -tycon, the old type application is simply returned. - -If we have - data instance F () = ... deriving Eq - data instance F () = ... deriving Eq -then tcLookupFamInstExact will be confused by the two matches; -but that can't happen because tcInstDecls1 doesn't call tcDeriving -if there are any overlaps. - -There are two other things that might go wrong with the lookup. -First, we might see a standalone deriving clause - deriving Eq (F ()) -when there is no data instance F () in scope. - -Note that it's OK to have - data instance F [a] = ... - deriving Eq (F [(a,b)]) -where the match is not exact; the same holds for ordinary data types -with standalone deriving declrations. + where + bale_out msg = failWithTc (derivingThingErr False cls cls_tys tc_app msg) -\begin{code} -tcLookupFamInstExact :: TyCon -> [Type] -> TcM (TyCon, [Type]) -tcLookupFamInstExact tycon tys - | not (isOpenTyCon tycon) - = return (tycon, tys) - | otherwise - = do { maybeFamInst <- tcLookupFamInst tycon tys - ; case maybeFamInst of - Nothing -> famInstNotFound tycon tys - Just famInst -> return famInst - } - -famInstNotFound :: TyCon -> [Type] -> TcM a -famInstNotFound tycon tys - = failWithTc (ptext (sLit "No family instance for") - <+> quotes (pprTypeApp tycon tys)) + mk_alg_eqn tycon tc_args + | className cls `elem` typeableClassNames + = do { dflags <- getDOpts + ; case checkTypeableConditions (dflags, tycon) of + Just err -> bale_out err + Nothing -> mk_typeable_eqn orig tvs cls tycon tc_args mtheta } + + | isDataFamilyTyCon tycon + , length tc_args /= tyConArity tycon + = bale_out (ptext (sLit "Unsaturated data family application")) + + | otherwise + = do { (rep_tc, rep_tc_args) <- tcLookupDataFamInst 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. + ; 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)) + ; unless (isNothing mtheta || not hidden_data_cons) + (bale_out (derivingHiddenErr tycon)) + + ; dflags <- getDOpts + ; if isDataTyCon rep_tc then + mkDataTypeEqn orig dflags tvs cls cls_tys + tycon tc_args rep_tc rep_tc_args mtheta + else + mkNewTypeEqn orig dflags tvs cls cls_tys + tycon tc_args rep_tc rep_tc_args mtheta } \end{code} @@ -629,59 +726,53 @@ famInstNotFound tycon tys %************************************************************************ \begin{code} -mkDataTypeEqn :: InstOrigin -> Bool -> [Var] -> Class -> [Type] - -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe ThetaType - -> TcRn EarlyDerivSpec -- Return 'Nothing' if error - -mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys +mkDataTypeEqn :: CtOrigin + -> DynFlags + -> [Var] -- Universally quantified type variables in the instance + -> Class -- Class for which we need to derive an instance + -> [Type] -- Other parameters to the class except the last + -> TyCon -- Type constructor for which the instance is requested + -- (last parameter to the type class) + -> [Type] -- Parameters to the type constructor + -> TyCon -- rep of the above (for type families) + -> [Type] -- rep of the above + -> DerivContext -- Context of the instance, for standalone deriving + -> TcRn EarlyDerivSpec -- Return 'Nothing' if error + +mkDataTypeEqn orig dflags tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta - = case checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc of + = case checkSideConditions dflags mtheta cls cls_tys rep_tc of -- NB: pass the *representation* tycon to checkSideConditions - CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta + CanDerive -> go_for_it NonDerivableClass -> bale_out (nonStdErr cls) DerivableClassError msg -> bale_out msg where - bale_out msg = failWithTc (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) msg) + go_for_it = mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta + bale_out msg = failWithTc (derivingThingErr False cls cls_tys (mkTyConApp tycon tc_args) msg) -mk_data_eqn, mk_typeable_eqn - :: InstOrigin -> [TyVar] -> Class - -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe ThetaType - -> TcM EarlyDerivSpec +mk_data_eqn :: CtOrigin -> [TyVar] -> Class + -> TyCon -> [TcType] -> TyCon -> [TcType] -> DerivContext + -> 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 - - | otherwise = do { dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM - ; let ordinary_constraints - = [ mkClassPred cls [arg_ty] - | 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 - -- 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] - - stupid_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_tc_args - stupid_constraints = substTheta stupid_subst (tyConStupidTheta rep_tc) - all_constraints = stupid_constraints ++ sc_constraints ++ ordinary_constraints - + ; let inst_tys = [mkTyConApp tycon tc_args] + inferred_constraints = inferConstraints tvs cls inst_tys rep_tc rep_tc_args spec = DS { ds_loc = loc, ds_orig = orig , ds_name = dfun_name, ds_tvs = tvs - , ds_cls = cls, ds_tys = inst_tys, ds_tc = rep_tc - , ds_theta = mtheta `orElse` all_constraints + , ds_cls = cls, ds_tys = inst_tys + , ds_tc = rep_tc, ds_tc_args = rep_tc_args + , ds_theta = mtheta `orElse` inferred_constraints , ds_newtype = False } ; 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 +---------------------- +mk_typeable_eqn :: CtOrigin -> [TyVar] -> Class + -> TyCon -> [TcType] -> DerivContext + -> TcM EarlyDerivSpec +mk_typeable_eqn orig tvs cls tycon tc_args mtheta -- The Typeable class is special in several ways -- data T a b = ... deriving( Typeable ) -- gives @@ -695,7 +786,7 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta = do { checkTc (cls `hasKey` typeableClassKey) (ptext (sLit "Use deriving( Typeable ) on a data type declaration")) ; real_cls <- tcLookupClass (typeableClassNames !! tyConArity tycon) - ; mk_typeable_eqn orig tvs real_cls tycon [] rep_tc [] (Just []) } + ; mk_typeable_eqn orig tvs real_cls tycon [] (Just []) } | otherwise -- standaone deriving = do { checkTc (null tc_args) @@ -705,9 +796,76 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta ; loc <- getSrcSpanM ; return (Right $ DS { ds_loc = loc, ds_orig = orig, ds_name = dfun_name, ds_tvs = [] - , ds_cls = cls, ds_tys = [mkTyConApp tycon []], ds_tc = rep_tc + , ds_cls = cls, ds_tys = [mkTyConApp tycon []] + , ds_tc = tycon, ds_tc_args = [] , ds_theta = mtheta `orElse` [], ds_newtype = False }) } +---------------------- +inferConstraints :: [TyVar] -> Class -> [TcType] -> TyCon -> [TcType] -> ThetaType +-- Generate a sufficiently large set of constraints that typechecking the +-- generated method definitions should succeed. This set will be simplified +-- before being used in the instance declaration +inferConstraints _ cls inst_tys rep_tc rep_tc_args + -- Generic constraints are easy + | cls `hasKey` genClassKey + = [] + -- The others are a bit more complicated + | otherwise + = ASSERT2( equalLength rep_tc_tvs all_rep_tc_args, ppr cls <+> ppr rep_tc ) + stupid_constraints ++ extra_constraints + ++ sc_constraints ++ con_arg_constraints + where + -- Constraints arising from the arguments of each constructor + con_arg_constraints + = [ mkClassPred cls [arg_ty] + | data_con <- tyConDataCons rep_tc, + arg_ty <- ASSERT( isVanillaDataCon data_con ) + get_constrained_tys $ + dataConInstOrigArgTys data_con all_rep_tc_args, + not (isUnLiftedType arg_ty) ] + -- No constraints for unlifted types + -- Where they are legal we generate specilised function calls + + -- For functor-like classes, two things are different + -- (a) We recurse over argument types to generate constraints + -- See Functor examples in TcGenDeriv + -- (b) The rep_tc_args will be one short + is_functor_like = getUnique cls `elem` functorLikeClassKeys + + get_constrained_tys :: [Type] -> [Type] + get_constrained_tys tys + | is_functor_like = concatMap (deepSubtypesContaining last_tv) tys + | otherwise = tys + + rep_tc_tvs = tyConTyVars rep_tc + last_tv = last rep_tc_tvs + all_rep_tc_args | is_functor_like = rep_tc_args ++ [mkTyVarTy last_tv] + | otherwise = rep_tc_args + + -- Constraints arising from superclasses + -- See Note [Superclasses of derived instance] + sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys) + (classSCTheta cls) + + -- Stupid constraints + stupid_constraints = substTheta subst (tyConStupidTheta rep_tc) + subst = zipTopTvSubst rep_tc_tvs all_rep_tc_args + + -- Extra Data constraints + -- The Data class (only) requires that for + -- instance (...) => Data (T t1 t2) + -- IF t1:*, t2:* + -- THEN (Data t1, Data t2) are among the (...) constraints + -- Reason: when the IF holds, we generate a method + -- dataCast2 f = gcast2 f + -- and we need the Data constraints to typecheck the method + extra_constraints + | cls `hasKey` dataClassKey + , all (isLiftedTypeKind . typeKind) rep_tc_args + = [mkClassPred cls [ty] | ty <- rep_tc_args] + | otherwise + = [] + ------------------------------------------------------------------ -- Check side conditions that dis-allow derivability for particular classes -- This is *apart* from the newtype-deriving mechanism @@ -720,37 +878,52 @@ data DerivStatus = CanDerive | DerivableClassError SDoc -- Standard class, but can't do it | NonDerivableClass -- Non-standard class -checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> DerivStatus -checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc - | Just cond <- sideConditions cls - = case (cond (mayDeriveDataTypeable, rep_tc)) of +checkSideConditions :: DynFlags -> DerivContext -> Class -> [TcType] -> TyCon -> DerivStatus +checkSideConditions dflags mtheta cls cls_tys rep_tc + | Just cond <- sideConditions mtheta cls + = case (cond (dflags, rep_tc)) of Just err -> DerivableClassError err -- Class-specific error - Nothing | null cls_tys -> CanDerive + Nothing | null cls_tys -> CanDerive -- All derivable classes are unary, so + -- cls_tys (the type args other than last) + -- should be null | otherwise -> DerivableClassError ty_args_why -- e.g. deriving( Eq s ) | otherwise = NonDerivableClass -- Not a standard class where ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "is not a class") +checkTypeableConditions :: Condition +checkTypeableConditions = checkFlag Opt_DeriveDataTypeable `andCond` cond_typeableOK + 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 == 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) +sideConditions :: DerivContext -> Class -> Maybe Condition +sideConditions mtheta cls + | 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 (checkFlag Opt_DeriveDataTypeable `andCond` + cond_std `andCond` cond_noUnliftedArgs) + | cls_key == functorClassKey = Just (checkFlag Opt_DeriveFunctor `andCond` + cond_functorOK True) -- NB: no cond_std! + | cls_key == foldableClassKey = Just (checkFlag Opt_DeriveFoldable `andCond` + cond_functorOK False) -- Functor/Fold/Trav works ok for rank-n types + | cls_key == traversableClassKey = Just (checkFlag Opt_DeriveTraversable `andCond` + cond_functorOK False) + | cls_key == genClassKey = Just (cond_RepresentableOk `andCond` + checkFlag Opt_DeriveGeneric) | otherwise = Nothing where cls_key = getUnique cls + cond_std = cond_stdOK mtheta -type Condition = (Bool, TyCon) -> Maybe SDoc - -- Bool is whether or not we are allowed to derive Data and Typeable +type Condition = (DynFlags, TyCon) -> Maybe SDoc + -- first Bool is whether or not we are allowed to derive Data and Typeable + -- second Bool is whether or not we are allowed to derive Functor -- TyCon is the *representation* tycon if the -- data type is an indexed one -- Nothing => OK @@ -758,29 +931,44 @@ type Condition = (Bool, TyCon) -> Maybe SDoc orCond :: Condition -> Condition -> Condition orCond c1 c2 tc = case c1 tc of - Nothing -> Nothing -- c1 succeeds - Just x -> case c2 tc of -- c1 fails + Nothing -> Nothing -- c1 succeeds + Just x -> case c2 tc of -- c1 fails Nothing -> Nothing - Just y -> Just (x $$ ptext (sLit " and") $$ y) - -- Both fail + Just y -> Just (x $$ ptext (sLit " or") $$ y) + -- Both fail andCond :: Condition -> Condition -> Condition andCond c1 c2 tc = case c1 tc of Nothing -> c2 tc -- c1 succeeds Just x -> Just x -- c1 fails -cond_std :: Condition -cond_std (_, rep_tc) - | any (not . isVanillaDataCon) data_cons = Just existential_why - | null data_cons = Just no_cons_why - | otherwise = Nothing +cond_stdOK :: DerivContext -> Condition +cond_stdOK (Just _) _ + = Nothing -- Don't check these conservative conditions for + -- standalone deriving; just generate the code + -- and let the typechecker handle the result +cond_stdOK Nothing (_, rep_tc) + | null data_cons = Just (no_cons_why rep_tc $$ suggestion) + | not (null con_whys) = Just (vcat con_whys $$ suggestion) + | otherwise = Nothing where - data_cons = tyConDataCons rep_tc - no_cons_why = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has no data constructors") - existential_why = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has non-Haskell-98 constructor(s)") + suggestion = ptext (sLit "Possible fix: use a standalone deriving declaration instead") + data_cons = tyConDataCons rep_tc + con_whys = mapCatMaybes check_con data_cons + + check_con :: DataCon -> Maybe SDoc + check_con con + | isVanillaDataCon con + , all isTauTy (dataConOrigArgTys con) = Nothing + | otherwise = Just (badCon con (ptext (sLit "must have a Haskell-98 type"))) +no_cons_why :: TyCon -> SDoc +no_cons_why rep_tc = quotes (pprSourceTyCon rep_tc) <+> + ptext (sLit "must have at least one data constructor") + +cond_RepresentableOk :: Condition +cond_RepresentableOk (_,t) = canDoGenerics t + cond_enumOrProduct :: Condition cond_enumOrProduct = cond_isEnumeration `orCond` (cond_isProduct `andCond` cond_noUnliftedArgs) @@ -794,16 +982,17 @@ cond_noUnliftedArgs (_, tc) 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") + why = badCon (head bad_cons) (ptext (sLit "must have only arguments of lifted type")) cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) - | isEnumerationTyCon rep_tc = Nothing - | otherwise = Just why + | isEnumerationTyCon rep_tc = Nothing + | otherwise = Just why where - why = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has non-nullary constructors") + why = sep [ quotes (pprSourceTyCon rep_tc) <+> + ptext (sLit "must be an enumeration type") + , ptext (sLit "(an enumeration consists of one or more nullary, non-GADT constructors)") ] + -- See Note [Enumeration types] in TyCon cond_isProduct :: Condition cond_isProduct (_, rep_tc) @@ -811,47 +1000,112 @@ cond_isProduct (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has more than one constructor") + ptext (sLit "must have precisely one constructor") cond_typeableOK :: Condition -- OK for Typeable class -- Currently: (a) args all of kind * -- (b) 7 or fewer args -cond_typeableOK (_, rep_tc) - | tyConArity rep_tc > 7 = Just too_many - | not (all (isSubArgTypeKind . tyVarKind) (tyConTyVars rep_tc)) - = Just bad_kind - | isFamInstTyCon rep_tc = Just fam_inst -- no Typable for family insts - | otherwise = Nothing +cond_typeableOK (_, tc) + | tyConArity tc > 7 = Just too_many + | not (all (isSubArgTypeKind . tyVarKind) (tyConTyVars tc)) + = Just bad_kind + | otherwise = Nothing where - too_many = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has too many arguments") - bad_kind = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "has arguments of kind other than `*'") - fam_inst = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "is a type family") - -cond_mayDeriveDataTypeable :: Condition -cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) - | mayDeriveDataTypeable = Nothing - | otherwise = Just why + too_many = quotes (pprSourceTyCon tc) <+> + ptext (sLit "must have 7 or fewer arguments") + bad_kind = quotes (pprSourceTyCon tc) <+> + ptext (sLit "must only have arguments of kind `*'") + +functorLikeClassKeys :: [Unique] +functorLikeClassKeys = [functorClassKey, foldableClassKey, traversableClassKey] + +cond_functorOK :: Bool -> Condition +-- OK for Functor/Foldable/Traversable class +-- Currently: (a) at least one argument +-- (b) don't use argument contravariantly +-- (c) don't use argument in the wrong place, e.g. data T a = T (X a a) +-- (d) optionally: don't use function types +-- (e) no "stupid context" on data type +cond_functorOK allowFunctions (_, rep_tc) + | null tc_tvs + = Just (ptext (sLit "Data type") <+> quotes (ppr rep_tc) + <+> ptext (sLit "must have some type parameters")) + + | not (null bad_stupid_theta) + = Just (ptext (sLit "Data type") <+> quotes (ppr rep_tc) + <+> ptext (sLit "must not have a class context") <+> pprTheta bad_stupid_theta) + + | otherwise + = msum (map check_con data_cons) -- msum picks the first 'Just', if any + where + tc_tvs = tyConTyVars rep_tc + Just (_, last_tv) = snocView tc_tvs + bad_stupid_theta = filter is_bad (tyConStupidTheta rep_tc) + is_bad pred = last_tv `elemVarSet` tyVarsOfPred pred + + data_cons = tyConDataCons rep_tc + check_con con = msum (check_vanilla con : foldDataConArgs (ft_check con) con) + + check_vanilla :: DataCon -> Maybe SDoc + check_vanilla con | isVanillaDataCon con = Nothing + | otherwise = Just (badCon con existential) + + ft_check :: DataCon -> FFoldType (Maybe SDoc) + ft_check con = FT { ft_triv = Nothing, ft_var = Nothing + , ft_co_var = Just (badCon con covariant) + , ft_fun = \x y -> if allowFunctions then x `mplus` y + else Just (badCon con functions) + , ft_tup = \_ xs -> msum xs + , ft_ty_app = \_ x -> x + , ft_bad_app = Just (badCon con wrong_arg) + , ft_forall = \_ x -> x } + + existential = ptext (sLit "must not have existential arguments") + covariant = ptext (sLit "must not use the type variable in a function argument") + functions = ptext (sLit "must not contain function types") + wrong_arg = ptext (sLit "must not use the type variable in an argument other than the last") + +checkFlag :: ExtensionFlag -> Condition +checkFlag flag (dflags, _) + | xopt flag dflags = Nothing + | otherwise = Just why where - why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class") + why = ptext (sLit "You need -X") <> text flag_str + <+> ptext (sLit "to derive an instance for this class") + flag_str = case [ s | (s, f, _) <- xFlags, f==flag ] of + [s] -> s + other -> pprPanic "checkFlag" (ppr other) std_class_via_iso :: Class -> Bool -std_class_via_iso clas -- These standard classes can be derived for a newtype - -- using the isomorphism trick *even if no -fglasgow-exts* - = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey] +-- These standard classes can be derived for a newtype +-- using the isomorphism trick *even if no -XGeneralizedNewtypeDeriving +-- because giving so gives the same results as generating the boilerplate +std_class_via_iso clas + = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey] -- Not Read/Show because they respect the type -- Not Enum, because newtypes are never in Enum +non_iso_class :: Class -> Bool +-- *Never* derive Read, Show, Typeable, Data, Generic by isomorphism, +-- even with -XGeneralizedNewtypeDeriving +non_iso_class cls + = classKey cls `elem` ([ readClassKey, showClassKey, dataClassKey + , genClassKey] ++ typeableClassKeys) + +typeableClassKeys :: [Unique] +typeableClassKeys = map getUnique typeableClassNames + new_dfun_name :: Class -> TyCon -> TcM Name new_dfun_name clas tycon -- Just a simple wrapper = 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 + +badCon :: DataCon -> SDoc -> SDoc +badCon con msg = ptext (sLit "Constructor") <+> quotes (ppr con) <+> msg \end{code} Note [Superclasses of derived instance] @@ -886,39 +1140,43 @@ a context for the Data instances: %************************************************************************ \begin{code} -mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> [Var] -> Class +mkNewTypeEqn :: CtOrigin -> DynFlags -> [Var] -> Class -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] - -> Maybe ThetaType + -> DerivContext -> TcRn EarlyDerivSpec -mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs +mkNewTypeEqn orig dflags tvs cls cls_tys tycon tc_args rep_tycon rep_tc_args mtheta -- Want: instance (...) => cls (cls_tys ++ [tycon tc_args]) where ... | can_derive_via_isomorphism && (newtype_deriving || std_class_via_iso cls) - = do { traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) + = do { traceTc "newtype deriving:" (ppr tycon <+> ppr rep_tys <+> ppr all_preds) ; dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM ; let spec = DS { ds_loc = loc, ds_orig = orig , ds_name = dfun_name, ds_tvs = varSetElems dfun_tvs - , ds_cls = cls, ds_tys = inst_tys, ds_tc = rep_tycon + , ds_cls = cls, ds_tys = inst_tys + , ds_tc = rep_tycon, ds_tc_args = rep_tc_args , ds_theta = mtheta `orElse` all_preds , ds_newtype = True } ; return (if isJust mtheta then Right spec else Left spec) } | 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 + = case checkSideConditions dflags mtheta cls cls_tys rep_tycon of + CanDerive -> go_for_it -- Use the standard H98 method + DerivableClassError msg -- Error with standard class + | can_derive_via_isomorphism -> bale_out (msg $$ suggest_nd) + | otherwise -> bale_out msg 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! + | newtype_deriving -> bale_out cant_derive_err -- Too hard, even with newtype deriving + | can_derive_via_isomorphism -> bale_out (non_std $$ suggest_nd) -- Try newtype deriving! + | otherwise -> bale_out non_std where - check_conditions = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon - bale_out msg = failWithTc (derivingThingErr cls cls_tys inst_ty msg) + newtype_deriving = xopt Opt_GeneralizedNewtypeDeriving dflags + go_for_it = mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta + bale_out msg = failWithTc (derivingThingErr newtype_deriving cls cls_tys inst_ty msg) - non_std_err = nonStdErr cls $$ - ptext (sLit "Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension") + non_std = nonStdErr cls + suggest_nd = 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, ...) @@ -952,7 +1210,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs 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 + -- eta-reduces the representation 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 @@ -995,29 +1253,16 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs ------------------------------------------------------------------- -- Figuring out whether we can only do this newtype-deriving thing - right_arity = length cls_tys + 1 == classArity cls - - -- Never derive Read,Show,Typeable,Data this way - non_iso_class cls = className cls `elem` ([readClassName, showClassName, dataClassName] ++ - typeableClassNames) can_derive_via_isomorphism = not (non_iso_class cls) - && right_arity -- Well kinded; - -- eg not: newtype T ... deriving( ST ) - -- because ST needs *2* type params - && eta_ok -- Eta reduction works - && not (isRecursiveTyCon tycon) -- Does not work for recursive tycons: - -- newtype A = MkA [A] - -- Don't want - -- instance Eq [A] => Eq A !! - -- Here's a recursive newtype that's actually OK - -- newtype S1 = S1 [T1 ()] - -- newtype T1 a = T1 (StateT S1 IO a ) deriving( Monad ) - -- It's currently rejected. Oh well. - -- In fact we generate an instance decl that has method of form - -- meth @ instTy = meth @ repTy - -- (no coerce's). We'd need a coerce if we wanted to handle - -- recursive newtypes too + && arity_ok + && eta_ok + && ats_ok +-- && not (isRecursiveTyCon tycon) -- Note [Recursive newtypes] + + arity_ok = length cls_tys + 1 == classArity cls + -- Well kinded; eg not: newtype T ... deriving( ST ) + -- because ST needs *2* type params -- Check that eta reduction is OK eta_ok = nt_eta_arity <= length rep_tc_args @@ -1028,19 +1273,35 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- And the [a] must not mention 'b'. That's all handled -- by nt_eta_rity. - 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 - ] + ats_ok = null (classATs cls) + -- No associated types for the class, because we don't + -- currently generate type 'instance' decls; and cannot do + -- so for 'data' instance decls + + cant_derive_err + = vcat [ ppUnless arity_ok arity_msg + , ppUnless eta_ok eta_msg + , ppUnless ats_ok ats_msg ] + arity_msg = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") + eta_msg = ptext (sLit "cannot eta-reduce the representation type enough") + ats_msg = ptext (sLit "the class has associated types") \end{code} +Note [Recursive newtypes] +~~~~~~~~~~~~~~~~~~~~~~~~~ +Newtype deriving works fine, even if the newtype is recursive. +e.g. newtype S1 = S1 [T1 ()] + newtype T1 a = T1 (StateT S1 IO a ) deriving( Monad ) +Remember, too, that type families are curretly (conservatively) given +a recursive flag, so this also allows newtype deriving to work +for type famillies. + +We used to exclude recursive types, because we had a rather simple +minded way of generating the instance decl: + newtype A = MkA [A] + instance Eq [A] => Eq A -- Makes typechecker loop! +But now we require a simple context, so it's ok. + %************************************************************************ %* * @@ -1068,7 +1329,7 @@ inferInstanceContexts :: OverlapFlag -> [DerivSpec] -> TcM [DerivSpec] inferInstanceContexts _ [] = return [] inferInstanceContexts oflag infer_specs - = do { traceTc (text "inferInstanceContexts" <+> vcat (map pprDerivSpec infer_specs)) + = do { traceTc "inferInstanceContexts" $ vcat (map pprDerivSpec infer_specs) ; iterate_deriv 1 initial_solutions } where ------------------------------------------------------------------ @@ -1093,7 +1354,7 @@ inferInstanceContexts oflag infer_specs | otherwise = do { -- Extend the inst info from the explicit instance decls -- with the current set of solutions, and simplify each RHS - let inst_specs = zipWithEqual "add_solns" (mkInstance2 oflag) + let inst_specs = zipWithEqual "add_solns" (mkInstance oflag) current_solns infer_specs ; new_solns <- checkNoErrs $ extendLocalInstEnv inst_specs $ @@ -1110,32 +1371,37 @@ inferInstanceContexts oflag infer_specs gen_soln (DS { ds_loc = loc, ds_orig = orig, ds_tvs = tyvars , ds_cls = clas, ds_tys = inst_tys, ds_theta = deriv_rhs }) = setSrcSpan loc $ - addErrCtxt (derivInstCtxt clas inst_tys) $ - do { theta <- tcSimplifyDeriv orig tyvars deriv_rhs - -- checkValidInstance tyvars theta clas inst_tys - -- Not necessary; see Note [Exotic derived instance contexts] - -- in TcSimplify - - -- Check for a bizarre corner case, when the derived instance decl should + addErrCtxt (derivInstCtxt the_pred) $ + do { -- Check for a bizarre corner case, when the derived instance decl should -- have form instance C a b => D (T a) where ... -- Note that 'b' isn't a parameter of T. This gives rise to all sorts -- of problems; in particular, it's hard to compare solutions for - -- equality when finding the fixpoint. So I just rule it out for now. + -- equality when finding the fixpoint. Moreover, simplifyDeriv + -- has an assert failure because it finds a TyVar when it expects + -- only TcTyVars. So I just rule it out for now. I'm not + -- even sure how it can arise. + ; let tv_set = mkVarSet tyvars - weird_preds = [pred | pred <- theta, not (tyVarsOfPred pred `subVarSet` tv_set)] + weird_preds = [pred | pred <- deriv_rhs + , not (tyVarsOfPred pred `subVarSet` tv_set)] ; mapM_ (addErrTc . badDerivedPred) weird_preds + ; theta <- simplifyDeriv orig the_pred tyvars deriv_rhs + -- checkValidInstance tyvars theta clas inst_tys + -- Not necessary; see Note [Exotic derived instance contexts] + -- in TcSimplify + + ; traceTc "TcDeriv" (ppr deriv_rhs $$ ppr theta) -- Claim: the result instance declaration is guaranteed valid -- Hence no need to call: -- checkValidInstance tyvars theta clas inst_tys ; return (sortLe (<=) theta) } -- Canonicalise before returning the solution + where + the_pred = mkClassPred clas inst_tys ------------------------------------------------------------------ -mkInstance1 :: OverlapFlag -> DerivSpec -> Instance -mkInstance1 overlap_flag spec = mkInstance2 overlap_flag (ds_theta spec) spec - -mkInstance2 :: OverlapFlag -> ThetaType -> DerivSpec -> Instance -mkInstance2 overlap_flag theta +mkInstance :: OverlapFlag -> ThetaType -> DerivSpec -> Instance +mkInstance overlap_flag theta (DS { ds_name = dfun_name , ds_tvs = tyvars, ds_cls = clas, ds_tys = tys }) = mkLocalInstance dfun overlap_flag @@ -1224,28 +1490,44 @@ 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 RdrName, DerivAuxBinds) -genInst oflag spec - | ds_newtype spec - = return (InstInfo { iSpec = mkInstance1 oflag spec - , iBinds = NewTypeDerived }, []) +genInst :: Bool -- True <=> standalone deriving + -> OverlapFlag + -> DerivSpec -> TcM (InstInfo RdrName, DerivAuxBinds) +genInst standalone_deriv oflag + spec@(DS { ds_tc = rep_tycon, ds_tc_args = rep_tc_args + , ds_theta = theta, ds_newtype = is_newtype + , ds_name = name, ds_cls = clas }) + | is_newtype + = return (InstInfo { iSpec = inst_spec + , iBinds = NewTypeDerived co rep_tycon }, []) | otherwise - = 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) - ; fix_env <- getFixityEnv - ; let (meth_binds, aux_binds) = genDerivBinds loc fix_env clas rep_tycon - - -- Build the InstInfo - ; return (InstInfo { iSpec = inst, - iBinds = VanillaInst meth_binds [] }, - aux_binds) - } + = do { fix_env <- getFixityEnv + ; let loc = getSrcSpan name + (meth_binds, aux_binds) = genDerivBinds loc fix_env clas rep_tycon + -- In case of a family instance, we need to use the representation + -- tycon (after all, it has the data constructors) + + ; return (InstInfo { iSpec = inst_spec + , iBinds = VanillaInst meth_binds [] standalone_deriv } + , aux_binds) } + where + inst_spec = mkInstance oflag theta spec + co1 = case tyConFamilyCoercion_maybe rep_tycon of + Just co_con -> mkAxInstCo co_con rep_tc_args + Nothing -> id_co + -- Not a family => rep_tycon = main tycon + co2 = mkAxInstCo (newTyConCo rep_tycon) rep_tc_args + co = co1 `mkTransCo` co2 + id_co = mkReflCo (mkTyConApp rep_tycon rep_tc_args) + +-- Example: newtype instance N [a] = N1 (Tree a) +-- deriving instance Eq b => Eq (N [(b,b)]) +-- From the instance, we get an implicit newtype R1:N a = N1 (Tree a) +-- When dealing with the deriving clause +-- co1 : N [(b,b)] ~ R1:N (b,b) +-- co2 : R1:N (b,b) ~ Tree (b,b) +-- co : N [(b,b)] ~ Tree (b,b) genDerivBinds :: SrcSpan -> FixityEnv -> Class -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) genDerivBinds loc fix_env clas tycon @@ -1258,17 +1540,159 @@ genDerivBinds loc fix_env clas tycon Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas) where gen_list :: [(Unique, SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds))] - gen_list = [(eqClassKey, gen_Eq_binds) - ,(ordClassKey, gen_Ord_binds) - ,(enumClassKey, gen_Enum_binds) - ,(boundedClassKey, gen_Bounded_binds) - ,(ixClassKey, gen_Ix_binds) - ,(showClassKey, gen_Show_binds fix_env) - ,(readClassKey, gen_Read_binds fix_env) - ,(dataClassKey, gen_Data_binds) + gen_list = [(eqClassKey, gen_Eq_binds) + ,(ordClassKey, gen_Ord_binds) + ,(enumClassKey, gen_Enum_binds) + ,(boundedClassKey, gen_Bounded_binds) + ,(ixClassKey, gen_Ix_binds) + ,(showClassKey, gen_Show_binds fix_env) + ,(readClassKey, gen_Read_binds fix_env) + ,(dataClassKey, gen_Data_binds) + ,(functorClassKey, gen_Functor_binds) + ,(foldableClassKey, gen_Foldable_binds) + ,(traversableClassKey, gen_Traversable_binds) + ,(genClassKey, genGenericBinds) ] \end{code} +%************************************************************************ +%* * +\subsection[TcDeriv-generic-binds]{Bindings for the new generic deriving mechanism} +%* * +%************************************************************************ + +For the generic representation we need to generate: +\begin{itemize} +\item A Generic instance +\item A Rep type instance +\item Many auxiliary datatypes and instances for them (for the meta-information) +\end{itemize} + +@genGenericBinds@ does (1) +@genGenericRepExtras@ does (2) and (3) +@genGenericAll@ does all of them + +\begin{code} +genGenericBinds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) +genGenericBinds _ tc = (mkBindsRep tc, [ {- No DerivAuxBinds -} ]) + +genGenericRepExtras :: TyCon -> TcM (MetaTyCons, TyCon) +genGenericRepExtras tc = + do uniqS <- newUniqueSupply + let + -- Uniques for everyone + (uniqD:uniqs) = uniqsFromSupply uniqS + (uniqsC,us) = splitAt (length tc_cons) uniqs + uniqsS :: [[Unique]] -- Unique supply for the S datatypes + uniqsS = mkUniqsS tc_arits us + mkUniqsS [] _ = [] + mkUniqsS (n:t) us = case splitAt n us of + (us1,us2) -> us1 : mkUniqsS t us2 + + tc_name = tyConName tc + tc_cons = tyConDataCons tc + tc_arits = map dataConSourceArity tc_cons + + tc_occ = nameOccName tc_name + d_occ = mkGenD tc_occ + c_occ m = mkGenC tc_occ m + s_occ m n = mkGenS tc_occ m n + mod_name = nameModule (tyConName tc) + d_name = mkExternalName uniqD mod_name d_occ wiredInSrcSpan + c_names = [ mkExternalName u mod_name (c_occ m) wiredInSrcSpan + | (u,m) <- zip uniqsC [0..] ] + s_names = [ [ mkExternalName u mod_name (s_occ m n) wiredInSrcSpan + | (u,n) <- zip us [0..] ] | (us,m) <- zip uniqsS [0..] ] + + mkTyCon name = ASSERT( isExternalName name ) + buildAlgTyCon name [] [] mkAbstractTyConRhs + NonRecursive False NoParentTyCon Nothing + + metaDTyCon <- mkTyCon d_name + metaCTyCons <- sequence [ mkTyCon c_name | c_name <- c_names ] + metaSTyCons <- mapM sequence + [ [ mkTyCon s_name + | s_name <- s_namesC ] | s_namesC <- s_names ] + + let metaDts = MetaTyCons metaDTyCon metaCTyCons metaSTyCons + + rep0_tycon <- tc_mkRepTyCon tc metaDts + + -- pprTrace "rep0" (ppr rep0_tycon) $ + return (metaDts, rep0_tycon) +{- +genGenericAll :: TyCon + -> TcM ((InstInfo RdrName, DerivAuxBinds), MetaTyCons, TyCon) +genGenericAll tc = + do (metaDts, rep0_tycon) <- genGenericRepExtras tc + clas <- tcLookupClass genClassName + dfun_name <- new_dfun_name clas tc + let + mkInstRep = (InstInfo { iSpec = inst, iBinds = binds } + , [ {- No DerivAuxBinds -} ]) + inst = mkLocalInstance dfun NoOverlap + binds = VanillaInst (mkBindsRep tc) [] False + + tvs = tyConTyVars tc + tc_ty = mkTyConApp tc (mkTyVarTys tvs) + + dfun = mkDictFunId dfun_name (tyConTyVars tc) [] clas [tc_ty] + return (mkInstRep, metaDts, rep0_tycon) +-} +genDtMeta :: (TyCon, MetaTyCons) -> TcM [(InstInfo RdrName, DerivAuxBinds)] +genDtMeta (tc,metaDts) = + do dClas <- tcLookupClass datatypeClassName + d_dfun_name <- new_dfun_name dClas tc + cClas <- tcLookupClass constructorClassName + c_dfun_names <- sequence [ new_dfun_name cClas tc | _ <- metaC metaDts ] + sClas <- tcLookupClass selectorClassName + s_dfun_names <- sequence (map sequence [ [ new_dfun_name sClas tc + | _ <- x ] + | x <- metaS metaDts ]) + fix_env <- getFixityEnv + + let + (dBinds,cBinds,sBinds) = mkBindsMetaD fix_env tc + + -- Datatype + d_metaTycon = metaD metaDts + d_inst = mkLocalInstance d_dfun NoOverlap + d_binds = VanillaInst dBinds [] False + d_dfun = mkDictFunId d_dfun_name (tyConTyVars tc) [] dClas + [ mkTyConTy d_metaTycon ] + d_mkInst = (InstInfo { iSpec = d_inst, iBinds = d_binds }, []) + + -- Constructor + c_metaTycons = metaC metaDts + c_insts = [ mkLocalInstance (c_dfun c ds) NoOverlap + | (c, ds) <- myZip1 c_metaTycons c_dfun_names ] + c_binds = [ VanillaInst c [] False | c <- cBinds ] + c_dfun c dfun_name = mkDictFunId dfun_name (tyConTyVars tc) [] cClas + [ mkTyConTy c ] + c_mkInst = [ (InstInfo { iSpec = is, iBinds = bs }, []) + | (is,bs) <- myZip1 c_insts c_binds ] + + -- Selector + s_metaTycons = metaS metaDts + s_insts = map (map (\(s,ds) -> mkLocalInstance (s_dfun s ds) NoOverlap)) + (myZip2 s_metaTycons s_dfun_names) + s_binds = [ [ VanillaInst s [] False | s <- ss ] | ss <- sBinds ] + s_dfun s dfun_name = mkDictFunId dfun_name (tyConTyVars tc) [] sClas + [ mkTyConTy s ] + s_mkInst = map (map (\(is,bs) -> (InstInfo {iSpec=is, iBinds=bs}, []))) + (myZip2 s_insts s_binds) + + myZip1 :: [a] -> [b] -> [(a,b)] + myZip1 l1 l2 = ASSERT (length l1 == length l2) zip l1 l2 + + myZip2 :: [[a]] -> [[b]] -> [[(a,b)]] + myZip2 l1 l2 = + ASSERT (and (zipWith (>=) (map length l1) (map length l2))) + [ zip x1 x2 | (x1,x2) <- zip l1 l2 ] + + return (d_mkInst : c_mkInst ++ concat s_mkInst) +\end{code} + %************************************************************************ %* * @@ -1295,12 +1719,15 @@ 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"), - quotes (ppr pred)], - nest 2 (parens why)] +derivingThingErr :: Bool -> Class -> [Type] -> Type -> Message -> Message +derivingThingErr newtype_deriving clas tys ty why + = sep [(hang (ptext (sLit "Can't make a derived instance of")) + 2 (quotes (ppr pred)) + $$ nest 2 extra) <> colon, + nest 2 why] where + extra | newtype_deriving = ptext (sLit "(even with cunning newtype deriving)") + | otherwise = empty pred = mkClassPred clas (tys ++ [ty]) derivingHiddenErr :: TyCon -> SDoc @@ -1312,11 +1739,9 @@ standaloneCtxt :: LHsType Name -> SDoc standaloneCtxt ty = hang (ptext (sLit "In the stand-alone deriving instance for")) 2 (quotes (ppr ty)) -derivInstCtxt :: Class -> [Type] -> Message -derivInstCtxt clas inst_tys - = vcat [ptext (sLit "Alternative fix: use a standalone 'deriving instance' declaration"), - nest 2 (ptext (sLit "instead, so you can specify the instance context yourself")), - ptext (sLit "When deriving the instance for") <+> parens (pprClassPred clas inst_tys)] +derivInstCtxt :: PredType -> Message +derivInstCtxt pred + = ptext (sLit "When deriving the instance for") <+> parens (ppr pred) badDerivedPred :: PredType -> Message badDerivedPred pred