X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=419ec948b24c617343de11af882a12de79ce4375;hb=bb3a29ba8290a6c19602734a56ba0f414f02c289;hp=8fa6feb5d9060d01e0fc42d7470707eaaae53bcc;hpb=da1de991e04dd9a25e9c7253ade7eadf9f399c84;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 8fa6feb..419ec94 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -323,10 +323,10 @@ renameDeriv is_boot gen_binds insts ; 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) + ; let aux_names = map unLoc (collectHsValBinders rn_aux_lhs) ; bindLocalNames aux_names $ - do { (rn_aux, _dus) <- rnTopBindsRHS aux_names rn_aux_lhs + 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) } } @@ -459,19 +459,34 @@ deriveTyData (L loc deriv_pred, L _ decl@(TyData { tcdLName = L _ tycon_name, (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 - + args_to_drop = drop n_args_to_keep tc_args + inst_ty = mkTyConApp tc (take n_args_to_keep tc_args) + inst_ty_kind = typeKind inst_ty + dropped_tvs = mkVarSet (mapCatMaybes getTyVar_maybe args_to_drop) + univ_tvs = (mkVarSet tvs `extendVarSetList` deriv_tvs) + `minusVarSet` dropped_tvs + -- 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) + ; checkTc (sizeVarSet dropped_tvs == n_args_to_drop && -- (a) + tyVarsOfTypes (inst_ty:cls_tys) `subVarSet` univ_tvs) -- (b) + (derivingEtaErr cls cls_tys inst_ty) + -- Check that + -- (a) The data type can be eta-reduced; eg reject: + -- data instance T a a = ... deriving( Monad ) + -- (b) The type class args do not mention any of the dropped type + -- variables + -- newtype T a s = ... deriving( ST s ) + -- Type families can't be partially applied - -- e.g. newtype instance T Int a = ... deriving( Monad ) + -- 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) (typeFamilyPapErr tc cls cls_tys inst_ty) - ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys inst_ty Nothing } } + ; mkEqnHelp DerivOrigin (varSetElems univ_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 ) @@ -490,8 +505,37 @@ deriveTyData (L loc deriv_pred, L _ decl@(TyData { tcdLName = L _ tycon_name, deriveTyData _other = panic "derivTyData" -- Caller ensures that only TyData can happen +\end{code} ------------------------------------------------------------------- +Note [Deriving, type families, and partial applications] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +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 + +When type familes are involved it's trickier: + + data family T a b + newtype instance T Int a = MkT [a] deriving( Eq, Monad ) + -- :RT is the representation type for (T Int a) + -- :CoF:R1T a :: T Int a ~ :RT a -- Not eta reduced + -- :Co:R1T :: :RT ~ [] -- Eta-reduced + + instance Eq [a] => Eq (T Int a) -- easy by coercion + instance Monad [] => Monad (T Int) -- only if we can eta reduce??? + +The "???" bit is that we don't build the :CoF thing in eta-reduced form +Henc the current typeFamilyPapErr, even though the instance makes sense. +After all, we can write it out + instance Monad [] => Monad (T Int) -- only if we can eta reduce??? + return x = MkT [x] + ... etc ... + +\begin{code} mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type -> Maybe ThetaType -- Just => context supplied (standalone deriving) -- Nothing => context inferred (deriving on data decl) @@ -615,7 +659,9 @@ 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) @@ -671,19 +717,17 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- family tycon (with indexes) in error messages. data DerivStatus = CanDerive - | NonDerivableClass - | DerivableClassError SDoc + | 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 - | notNull cls_tys - = DerivableClassError ty_args_why -- e.g. deriving( Foo s ) - | otherwise - = case sideConditions cls of - Nothing -> NonDerivableClass - Just cond -> case (cond (mayDeriveDataTypeable, rep_tc)) of - Nothing -> CanDerive - Just err -> DerivableClassError err + | Just cond <- sideConditions cls + = case (cond (mayDeriveDataTypeable, rep_tc)) of + Just err -> DerivableClassError err -- Class-specific error + Nothing | null cls_tys -> CanDerive + | 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") @@ -692,14 +736,14 @@ 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 @@ -737,6 +781,22 @@ 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 @@ -832,6 +892,7 @@ mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> [Var] -> Class -> TcRn EarlyDerivSpec mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving 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) ; dfun_name <- new_dfun_name cls tycon @@ -916,7 +977,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- See Note [Newtype deriving superclasses] above cls_tyvars = classTyVars cls - dfun_tvs = tyVarsOfTypes tc_args + dfun_tvs = tyVarsOfTypes inst_tys inst_ty = mkTyConApp tycon tc_args inst_tys = cls_tys ++ [inst_ty] sc_theta = substTheta (zipOpenTvSubst cls_tyvars inst_tys) @@ -959,19 +1020,14 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- recursive newtypes too -- Check that eta reduction is OK - eta_ok = (nt_eta_arity <= length rep_tc_args) - -- (a) the newtype can be eta-reduced to match the number + eta_ok = nt_eta_arity <= length rep_tc_args + -- 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. - && (tyVarsOfTypes cls_tys `subVarSet` dfun_tvs) - -- (c) the type class args do not mention any of the dropped type - -- variables - -- 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") @@ -1228,6 +1284,12 @@ derivingKindErr tc cls cls_tys cls_kind 2 (ptext (sLit "Class") <+> quotes (ppr cls) <+> ptext (sLit "expects an argument of kind") <+> quotes (pprKind cls_kind)) +derivingEtaErr :: Class -> [Type] -> Type -> Message +derivingEtaErr cls cls_tys inst_ty + = sep [ptext (sLit "Cannot eta-reduce to an instance of form"), + nest 2 (ptext (sLit "instance (...) =>") + <+> pprClassPred cls (cls_tys ++ [inst_ty]))] + 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])))