X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=bc1fa9ace4f07264ac4ed36195663b893dcac8be;hb=8254dcf1884fde961c477d5784024ec8ab1d84d2;hp=0f104c60ace19d919b0eeff6cec4f8b7481c7108;hpb=af5a215172aa3b964ece212f229bfee9f7c6b6b2;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index 0f104c6..bc1fa9a 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -15,45 +15,42 @@ import CmdLineOpts ( DynFlag(..) ) import Generics ( mkTyConGenericBinds ) import TcRnMonad -import TcEnv ( newDFunName, +import TcEnv ( newDFunName, pprInstInfoDetails, InstInfo(..), InstBindings(..), - pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv + tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff -import InstEnv ( simpleDFunClassTyCon, extendInstEnv ) -import TcHsType ( tcHsPred ) +import InstEnv ( simpleDFunClassTyCon, extendInstEnvList ) +import TcHsType ( tcHsDeriv ) import TcSimplify ( tcSimplifyDeriv ) import RnBinds ( rnMethodBinds, rnTopBinds ) import RnEnv ( bindLocalNames ) -import TcRnMonad ( thenM, returnM, mapAndUnzipM ) import HscTypes ( DFunId, FixityEnv ) import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) -import Subst ( mkTyVarSubst, substTheta ) +import Type ( zipTvSubst, substTheta ) import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) +import DataCon ( isNullarySrcDataCon, isVanillaDataCon, dataConOrigArgTys ) import Maybes ( catMaybes ) import RdrName ( RdrName ) import Name ( Name, getSrcLoc ) -import NameSet ( NameSet, emptyNameSet, duDefs ) -import Unique ( Unique, getUnique ) +import NameSet ( duDefs ) import Kind ( splitKindFunTys ) import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics, - tyConTheta, isProductTyCon, isDataTyCon, + tyConStupidTheta, isProductTyCon, isDataTyCon, newTyConRhs, isEnumerationTyCon, isRecursiveTyCon, TyCon ) -import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp, - getClassPredTys_maybe, tcTyConAppTyCon, +import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, tcTyConAppTyCon, isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind, tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy ) import Var ( TyVar, tyVarKind, idType, varName ) import VarSet ( mkVarSet, subVarSet ) import PrelNames import SrcLoc ( srcLocSpan, Located(..) ) -import Util ( zipWithEqual, sortLt, notNull ) -import ListSetOps ( removeDups, assoc ) +import Util ( zipWithEqual, sortLe, notNull ) +import ListSetOps ( removeDups, assocMaybe ) import Outputable import Bag \end{code} @@ -183,6 +180,20 @@ pattern matching against a constructor from a data type with a context gives rise to the constraints for that context -- or at least the thinned version. So now all classes are "offending". +[Newtype deriving] +~~~~~~~~~~~~~~~~~~ +Consider this: + class C a b + instance C [a] Char + newtype T = T Char deriving( C [a] ) + +Notice the free 'a' in the deriving. We have to fill this out to + newtype T = T Char deriving( forall a. C [a] ) + +And then translate it to: + instance C [a] Char => C [a] T where ... + + %************************************************************************ @@ -194,11 +205,10 @@ version. So now all classes are "offending". \begin{code} tcDeriving :: [LTyClDecl Name] -- All type constructors -> TcM ([InstInfo], -- The generated "instance decls" - [HsBindGroup Name], -- Extra generated top-level bindings - NameSet) -- Binders to keep alive + [HsBindGroup Name]) -- Extra generated top-level bindings tcDeriving tycl_decls - = recoverM (returnM ([], [], emptyNameSet)) $ + = recoverM (returnM ([], [])) $ do { -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns tycl_decls @@ -216,18 +226,20 @@ tcDeriving tycl_decls -- Rename these extra bindings, discarding warnings about unused bindings etc -- Set -fglasgow exts so that we can have type signatures in patterns, -- which is used in the generic binds - ; (rn_binds, gen_bndrs) + ; rn_binds <- discardWarnings $ setOptM Opt_GlasgowExts $ do { (rn_deriv, _dus1) <- rnTopBinds deriv_binds [] ; (rn_gen, dus_gen) <- rnTopBinds gen_binds [] - ; return (rn_deriv ++ rn_gen, duDefs dus_gen) } + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to + -- be kept alive + ; return (rn_deriv ++ rn_gen) } ; dflags <- getDOpts ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" (ddump_deriving inst_info rn_binds)) - ; returnM (inst_info, rn_binds, gen_bndrs) + ; returnM (inst_info, rn_binds) } where ddump_deriving :: [InstInfo] -> [HsBindGroup Name] -> SDoc @@ -236,7 +248,7 @@ tcDeriving tycl_decls ----------------------------------------- deriveOrdinaryStuff [] -- Short cut - = returnM ([], emptyBag) + = returnM ([], emptyLHsBinds) deriveOrdinaryStuff eqns = do { -- Take the equation list and solve it, to deliver a list of @@ -299,64 +311,40 @@ makeDerivEqns tycl_decls returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ - derive_these :: [(NewOrData, Name, LHsPred Name)] + derive_these :: [(NewOrData, Name, LHsType Name)] -- Find the (nd, TyCon, Pred) pairs that must be `derived' - -- NB: only source-language decls have deriving, no imported ones do derive_these = [ (nd, tycon, pred) | L _ (TyData { tcdND = nd, tcdLName = L _ tycon, - tcdDerivs = Just (L _ preds) }) <- tycl_decls, + tcdDerivs = Just preds }) <- tycl_decls, pred <- preds ] ------------------------------------------------------------------ - mk_eqn :: (NewOrData, Name, LHsPred Name) -> TcM (Maybe DerivEqn, Maybe InstInfo) + mk_eqn :: (NewOrData, Name, LHsType Name) -> TcM (Maybe DerivEqn, Maybe InstInfo) -- We swizzle the tyvars and datacons out of the tycon -- to make the rest of the equation + -- + -- The "deriv_ty" is a LHsType to take account of the fact that for newtype derivign + -- we allow deriving (forall a. C [a]). - mk_eqn (new_or_data, tycon_name, pred) + mk_eqn (new_or_data, tycon_name, hs_deriv_ty) = tcLookupTyCon tycon_name `thenM` \ tycon -> - addSrcSpan (srcLocSpan (getSrcLoc tycon)) $ + setSrcSpan (srcLocSpan (getSrcLoc tycon)) $ addErrCtxt (derivCtxt Nothing tycon) $ tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention -- the type variables for the type constructor - tcHsPred pred `thenM` \ pred' -> - case getClassPredTys_maybe pred' of - Nothing -> bale_out (malformedPredErr tycon pred) - Just (clas, tys) -> doptM Opt_GlasgowExts `thenM` \ gla_exts -> - mk_eqn_help gla_exts new_or_data tycon clas tys + tcHsDeriv hs_deriv_ty `thenM` \ (deriv_tvs, clas, tys) -> + doptM Opt_GlasgowExts `thenM` \ gla_exts -> + mk_eqn_help gla_exts new_or_data tycon deriv_tvs clas tys ------------------------------------------------------------------ - mk_eqn_help gla_exts DataType tycon clas tys - | Just err <- checkSideConditions gla_exts clas tycon tys - = bale_out (derivingThingErr clas tys tycon tyvars err) + mk_eqn_help gla_exts DataType tycon deriv_tvs clas tys + | Just err <- checkSideConditions gla_exts tycon deriv_tvs clas tys + = bale_out (derivingThingErr clas tys tycon (tyConTyVars tycon) err) | otherwise - = new_dfun_name clas tycon `thenM` \ dfun_name -> - returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing) - where - tyvars = tyConTyVars tycon - constraints = extra_constraints ++ ordinary_constraints - -- "extra_constraints": see note [Data decl contexts] above - extra_constraints = tyConTheta tycon - - ordinary_constraints - | clas `hasKey` typeableClassKey -- For the Typeable class, the constraints - -- don't involve the constructor ags, only - -- the tycon tyvars - -- e.g. data T a b = ... - -- we want - -- instance (Typeable a, Typable b) - -- => Typeable (T a b) where - = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] - | otherwise - = [ mkClassPred clas [arg_ty] - | data_con <- tyConDataCons tycon, - arg_ty <- dataConOrigArgTys data_con, - -- Use the same type variables - -- as the type constructor, - -- hence no need to instantiate - not (isUnLiftedType arg_ty) -- No constraints for unlifted types? - ] - - mk_eqn_help gla_exts NewType tycon clas tys + = do { eqn <- mkDataTypeEqn tycon clas + ; returnM (Just eqn, Nothing) } + + mk_eqn_help gla_exts NewType tycon deriv_tvs clas tys | can_derive_via_isomorphism && (gla_exts || std_class_via_iso clas) = -- Go ahead and use the isomorphism traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_` @@ -364,7 +352,7 @@ makeDerivEqns tycl_decls returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name, iBinds = NewTypeDerived rep_tys })) | std_class gla_exts clas - = mk_eqn_help gla_exts DataType tycon clas tys -- Go via bale-out route + = mk_eqn_help gla_exts DataType tycon deriv_tvs clas tys -- Go via bale-out route | otherwise -- Non-standard instance = bale_out (if gla_exts then @@ -374,16 +362,21 @@ makeDerivEqns tycl_decls where -- Here is the plan for newtype derivings. We see -- newtype T a1...an = T (t ak...an) deriving (.., C s1 .. sm, ...) - -- where aj...an do not occur free in t, and the (C s1 ... sm) is a - -- *partial applications* of class C with the last parameter missing + -- where t is a type, + -- ak...an is a suffix of a1..an + -- ak...an do not occur free in t, + -- (C s1 ... sm) is a *partial applications* of class C + -- with the last parameter missing -- -- We generate the instances - -- instance C s1 .. sm (t ak...aj) => C s1 .. sm (T a1...aj) - -- where T a1...aj is the partial application of the LHS of the correct kind + -- instance C s1 .. sm (t ak...ap) => C s1 .. sm (T a1...ap) + -- where T a1...ap is the partial application of the LHS of the correct kind + -- and p >= k -- -- Running example: newtype T s a = MkT (ST s a) deriving( Monad ) -- instance Monad (ST s) => Monad (T s) where -- fail = coerce ... (fail @ ST s) + -- (Actually we don't need the coerce, because non-rec newtypes are transparent clas_tyvars = classTyVars clas kind = tyVarKind (last clas_tyvars) @@ -396,21 +389,19 @@ makeDerivEqns tycl_decls -- to get instance Monad (ST s) => Monad (T s) -- Note [newtype representation] - -- We must not use newTyConRep to get the representation - -- type, because that looks through all intermediate newtypes - -- To get the RHS of *this* newtype, just look at the data - -- constructor. For example + -- Need newTyConRhs *not* newTyConRep to get the representation + -- type, because the latter looks through all intermediate newtypes + -- For example -- newtype B = MkB Int -- 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! - tyvars = tyConTyVars tycon - rep_ty = head (dataConOrigArgTys (head (tyConDataCons tycon))) + (tc_tvs, rep_ty) = newTyConRhs tycon (rep_fn, rep_ty_args) = tcSplitAppTys rep_ty n_tyvars_to_keep = tyConArity tycon - n_args_to_drop - tyvars_to_drop = drop n_tyvars_to_keep tyvars - tyvars_to_keep = take n_tyvars_to_keep tyvars + tyvars_to_drop = drop n_tyvars_to_keep tc_tvs + tyvars_to_keep = take n_tyvars_to_keep tc_tvs n_args_to_keep = length rep_ty_args - n_args_to_drop args_to_drop = drop n_args_to_keep rep_ty_args @@ -441,16 +432,17 @@ makeDerivEqns tycl_decls -- There's no 'corece' needed because after the type checker newtypes -- are transparent. - sc_theta = substTheta (mkTyVarSubst clas_tyvars inst_tys) + sc_theta = substTheta (zipTvSubst clas_tyvars inst_tys) (classSCTheta clas) -- If there are no tyvars, there's no need -- to abstract over the dictionaries we need - dict_args | null tyvars = [] - | otherwise = rep_pred : sc_theta + dict_tvs = deriv_tvs ++ tc_tvs + dict_args | null dict_tvs = [] + | otherwise = rep_pred : sc_theta -- Finally! Here's where we build the dictionary Id - mk_dfun dfun_name = mkDictFunId dfun_name tyvars dict_args clas inst_tys + mk_dfun dfun_name = mkDictFunId dfun_name dict_tvs dict_args clas inst_tys ------------------------------------------------------------------- -- Figuring out whether we can only do this newtype-deriving thing @@ -473,11 +465,14 @@ makeDerivEqns tycl_decls -- 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 -- Check that eta reduction is OK -- (a) the dropped-off args are identical @@ -528,12 +523,46 @@ new_dfun_name clas tycon -- Just a simple wrapper -- a suitable string; hence the empty type arg list ------------------------------------------------------------------ +mkDataTypeEqn :: TyCon -> Class -> TcM DerivEqn +mkDataTypeEqn tycon clas + | clas `hasKey` typeableClassKey + = -- The Typeable class is special in several ways + -- data T a b = ... deriving( Typeable ) + -- gives + -- instance Typeable2 T where ... + -- Notice that: + -- 1. There are no constraints in the instance + -- 2. There are no type variables either + -- 3. The actual class we want to generate isn't necessarily + -- Typeable; it depends on the arity of the type + do { real_clas <- tcLookupClass (typeableClassNames !! tyConArity tycon) + ; dfun_name <- new_dfun_name real_clas tycon + ; return (dfun_name, real_clas, tycon, [], []) } + + | otherwise + = do { dfun_name <- new_dfun_name clas tycon + ; return (dfun_name, clas, tycon, tyvars, constraints) } + where + tyvars = tyConTyVars tycon + constraints = extra_constraints ++ ordinary_constraints + extra_constraints = tyConStupidTheta tycon + -- "extra_constraints": see note [Data decl contexts] above + + ordinary_constraints + = [ mkClassPred clas [arg_ty] + | data_con <- tyConDataCons tycon, + arg_ty <- dataConOrigArgTys data_con, + not (isUnLiftedType arg_ty) -- No constraints for unlifted types? + ] + + +------------------------------------------------------------------ -- Check side conditions that dis-allow derivability for particular classes -- This is *apart* from the newtype-deriving mechanism -checkSideConditions :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc -checkSideConditions gla_exts clas tycon tys - | notNull tys +checkSideConditions :: Bool -> TyCon -> [TyVar] -> Class -> [TcType] -> Maybe SDoc +checkSideConditions gla_exts tycon deriv_tvs clas tys + | notNull deriv_tvs || notNull tys = Just ty_args_why -- e.g. deriving( Foo s ) | otherwise = case [cond | (key,cond) <- sideConditions, key == getUnique clas] of @@ -541,7 +570,7 @@ checkSideConditions gla_exts clas tycon tys [cond] -> cond (gla_exts, tycon) other -> pprPanic "checkSideConditions" (ppr clas) where - ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class") + ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class") non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class") @@ -554,7 +583,7 @@ sideConditions (enumClassKey, cond_std `andCond` cond_isEnumeration), (ixClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), (boundedClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), - (typeableClassKey, cond_glaExts `andCond` cond_allTypeKind), + (typeableClassKey, cond_glaExts `andCond` cond_typeableOK), (dataClassKey, cond_glaExts `andCond` cond_std) ] @@ -575,9 +604,9 @@ andCond c1 c2 tc = case c1 tc of cond_std :: Condition cond_std (gla_exts, tycon) - | any isExistentialDataCon data_cons = Just existential_why - | null data_cons = Just no_cons_why - | otherwise = Nothing + | any (not . isVanillaDataCon) data_cons = Just existential_why + | null data_cons = Just no_cons_why + | otherwise = Nothing where data_cons = tyConDataCons tycon no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors") @@ -597,12 +626,17 @@ cond_isProduct (gla_exts, tycon) where why = quotes (ppr tycon) <+> ptext SLIT("has more than one constructor") -cond_allTypeKind :: Condition -cond_allTypeKind (gla_exts, tycon) - | all (isArgTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing - | otherwise = Just why +cond_typeableOK :: Condition +-- OK for Typeable class +-- Currently: (a) args all of kind * +-- (b) 7 or fewer args +cond_typeableOK (gla_exts, tycon) + | tyConArity tycon > 7 = Just too_many + | not (all (isArgTypeKind . tyVarKind) (tyConTyVars tycon)) = Just bad_kind + | otherwise = Nothing where - why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'") + too_many = quotes (ppr tycon) <+> ptext SLIT("has too many arguments") + bad_kind = quotes (ppr tycon) <+> ptext SLIT("has arguments of kind other than `*'") cond_glaExts :: Condition cond_glaExts (gla_exts, tycon) | gla_exts = Nothing @@ -675,10 +709,10 @@ solveDerivEqns orig_eqns ------------------------------------------------------------------ gen_soln (_, clas, tc,tyvars,deriv_rhs) - = addSrcSpan (srcLocSpan (getSrcLoc tc)) $ + = setSrcSpan (srcLocSpan (getSrcLoc tc)) $ addErrCtxt (derivCtxt (Just clas) tc) $ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> - returnM (sortLt (<) theta) -- Canonicalise before returning the soluction + returnM (sortLe (<=) theta) -- Canonicalise before returning the soluction mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta = mkDictFunId dfun_name tyvars theta @@ -689,7 +723,7 @@ extendLocalInstEnv :: [DFunId] -> TcM a -> TcM a -- for functional dependency errors -- that'll happen in TcInstDcls extendLocalInstEnv dfuns thing_inside = do { env <- getGblEnv - ; let inst_env' = foldl extendInstEnv (tcg_inst_env env) dfuns + ; let inst_env' = extendInstEnvList (tcg_inst_env env) dfuns env' = env { tcg_inst_env = inst_env' } ; setGblEnv env' thing_inside } \end{code} @@ -766,8 +800,7 @@ genInst dfun (tyvars,_,clas,[ty]) = tcSplitDFunTy (idType dfun) clas_nm = className clas tycon = tcTyConAppTyCon ty - (meth_binds, aux_binds) = assoc "gen_bind:bad derived class" - gen_list (getUnique clas) fix_env tycon + (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon in -- Bring the right type variables into -- scope, and rename the method binds @@ -778,22 +811,31 @@ genInst dfun returnM (InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_meth_binds [] }, aux_binds) -gen_list :: [(Unique, FixityEnv -> TyCon -> (LHsBinds RdrName, LHsBinds RdrName))] -gen_list = [(eqClassKey, no_aux_binds (ignore_fix_env gen_Eq_binds)) - ,(ordClassKey, no_aux_binds (ignore_fix_env gen_Ord_binds)) - ,(enumClassKey, no_aux_binds (ignore_fix_env gen_Enum_binds)) - ,(boundedClassKey, no_aux_binds (ignore_fix_env gen_Bounded_binds)) - ,(ixClassKey, no_aux_binds (ignore_fix_env gen_Ix_binds)) - ,(typeableClassKey,no_aux_binds (ignore_fix_env gen_Typeable_binds)) - ,(showClassKey, no_aux_binds gen_Show_binds) - ,(readClassKey, no_aux_binds gen_Read_binds) - ,(dataClassKey, gen_Data_binds) - ] - - -- no_aux_binds is used for generators that don't - -- need to produce any auxiliary bindings -no_aux_binds f fix_env tc = (f fix_env tc, emptyBag) -ignore_fix_env f fix_env tc = f tc +genDerivBinds clas fix_env tycon + | className clas `elem` typeableClassNames + = (gen_Typeable_binds tycon, emptyLHsBinds) + + | otherwise + = case assocMaybe gen_list (getUnique clas) of + Just gen_fn -> gen_fn fix_env tycon + Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas) + where + gen_list :: [(Unique, FixityEnv -> TyCon -> (LHsBinds RdrName, LHsBinds RdrName))] + gen_list = [(eqClassKey, no_aux_binds (ignore_fix_env gen_Eq_binds)) + ,(ordClassKey, no_aux_binds (ignore_fix_env gen_Ord_binds)) + ,(enumClassKey, no_aux_binds (ignore_fix_env gen_Enum_binds)) + ,(boundedClassKey, no_aux_binds (ignore_fix_env gen_Bounded_binds)) + ,(ixClassKey, no_aux_binds (ignore_fix_env gen_Ix_binds)) + ,(typeableClassKey,no_aux_binds (ignore_fix_env gen_Typeable_binds)) + ,(showClassKey, no_aux_binds gen_Show_binds) + ,(readClassKey, no_aux_binds gen_Read_binds) + ,(dataClassKey, gen_Data_binds) + ] + + -- no_aux_binds is used for generators that don't + -- need to produce any auxiliary bindings + no_aux_binds f fix_env tc = (f fix_env tc, emptyLHsBinds) + ignore_fix_env f fix_env tc = f tc \end{code} @@ -843,7 +885,7 @@ genTaggeryBinds dfuns do_con2tag acc_Names tycon | isDataTyCon tycon && ((we_are_deriving eqClassKey tycon - && any isNullaryDataCon (tyConDataCons tycon)) + && any isNullarySrcDataCon (tyConDataCons tycon)) || (we_are_deriving ordClassKey tycon && not (isProductTyCon tycon)) || (we_are_deriving enumClassKey tycon) @@ -881,8 +923,6 @@ derivingThingErr clas tys tycon tyvars why where pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)]) -malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred - derivCtxt :: Maybe Class -> TyCon -> SDoc derivCtxt maybe_cls tycon = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon)