X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=54ffe6b2da316d8afc9bbf813fd832aef77b9817;hb=389cca214f33a29646e08d57e3dca862140007b2;hp=1a212408a62dba6273d3f987a5422f5a36e009ed;hpb=79a6f3fa318020567566f92740ba6b9eb542f73f;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 1a21240..54ffe6b 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -49,6 +49,8 @@ import ListSetOps import Outputable import FastString import Bag + +import Control.Monad \end{code} %************************************************************************ @@ -566,15 +568,12 @@ mkEqnHelp orig tvs cls cls_tys tc_app mtheta className cls `elem` typeableClassNames) (derivingHiddenErr tycon) - ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable - ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving - + ; dflags <- getDOpts ; if isDataTyCon rep_tc then - mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys + mkDataTypeEqn orig dflags tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta else - mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving - tvs cls cls_tys + mkNewTypeEqn orig dflags tvs cls cls_tys tycon tc_args rep_tc rep_tc_args mtheta } | otherwise = failWithTc (derivingThingErr cls cls_tys tc_app @@ -631,13 +630,21 @@ 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 :: InstOrigin + -> 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 + -> Maybe ThetaType -- 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 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 NonDerivableClass -> bale_out (nonStdErr cls) @@ -656,29 +663,13 @@ mk_data_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_tc_args = rep_tc_args - , ds_theta = mtheta `orElse` all_constraints + , ds_theta = mtheta `orElse` inferred_constraints , ds_newtype = False } ; return (if isJust mtheta then Right spec -- Specified context @@ -712,6 +703,62 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta , ds_tc = rep_tc, ds_tc_args = rep_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 tvs cls inst_tys rep_tc rep_tc_args + = 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 constraints + -- The Data class (only) requires that for + -- instance (...) => Data (T a b) + -- then (Data a, Data b) are among the (...) constraints + -- Reason: that's what you need to typecheck the method + -- dataCast1 f = gcast1 f + extra_constraints + | cls `hasKey` dataClassKey = [mkClassPred cls [mkTyVarTy tv] | tv <- tvs] + | otherwise = [] + ------------------------------------------------------------------ -- Check side conditions that dis-allow derivability for particular classes -- This is *apart* from the newtype-deriving mechanism @@ -724,10 +771,10 @@ 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 +checkSideConditions :: DynFlags -> Class -> [TcType] -> TyCon -> DerivStatus +checkSideConditions dflags cls cls_tys rep_tc | Just cond <- sideConditions cls - = case (cond (mayDeriveDataTypeable, rep_tc)) of + = case (cond (dflags, 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 ) @@ -740,21 +787,25 @@ 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) + | 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) + | cls_key == functorClassKey = Just (cond_functorOK True) -- NB: no cond_std! + | cls_key == foldableClassKey = Just (cond_functorOK False) -- Functor/Fold/Trav works ok for rank-n types + | cls_key == traversableClassKey = Just (cond_functorOK False) | getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK) | otherwise = Nothing where cls_key = getUnique cls -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 @@ -775,15 +826,21 @@ andCond c1 c2 tc = case c1 tc of cond_std :: Condition cond_std (_, rep_tc) - | any (not . isVanillaDataCon) data_cons = Just existential_why - | null data_cons = Just no_cons_why - | otherwise = Nothing + | null data_cons = Just no_cons_why + | not (null con_whys) = Just (vcat con_whys) + | 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)") + + 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 "does not have a Haskell-98 type"))) cond_enumOrProduct :: Condition cond_enumOrProduct = cond_isEnumeration `orCond` @@ -798,8 +855,7 @@ 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 "has arguments of unlifted type")) cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) @@ -835,9 +891,47 @@ cond_typeableOK (_, rep_tc) fam_inst = quotes (pprSourceTyCon rep_tc) <+> ptext (sLit "is a type family") + +functorLikeClassKeys :: [Unique] +functorLikeClassKeys = [functorClassKey, foldableClassKey, traversableClassKey] + +cond_functorOK :: Bool -> Condition +-- OK for Functor 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 +cond_functorOK allowFunctions (dflags, rep_tc) + | not (dopt Opt_DeriveFunctor dflags) + = Just (ptext (sLit "You need -XDeriveFunctor to derive an instance for this class")) + | otherwise + = msum (map check_con data_cons) -- msum picks the first 'Just', if any + where + 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 "has existential arguments") + covariant = ptext (sLit "uses the type variable in a function argument") + functions = ptext (sLit "contains function types") + wrong_arg = ptext (sLit "uses the type variable in an argument other than the last") + cond_mayDeriveDataTypeable :: Condition -cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) - | mayDeriveDataTypeable = Nothing +cond_mayDeriveDataTypeable (dflags, _) + | dopt Opt_DeriveDataTypeable dflags = Nothing | otherwise = Just why where why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class") @@ -845,7 +939,7 @@ cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) 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] + = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey] -- Not Read/Show because they respect the type -- Not Enum, because newtypes are never in Enum @@ -856,6 +950,9 @@ new_dfun_name clas tycon -- Just a simple wrapper ; 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] @@ -890,11 +987,11 @@ a context for the Data instances: %************************************************************************ \begin{code} -mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> [Var] -> Class +mkNewTypeEqn :: InstOrigin -> DynFlags -> [Var] -> Class -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe ThetaType -> 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) @@ -919,7 +1016,8 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs | newtype_deriving -> bale_out cant_derive_err -- Too hard, even with newtype deriving | otherwise -> bale_out non_std_err -- Try newtype deriving! where - check_conditions = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon + newtype_deriving = dopt Opt_GeneralizedNewtypeDeriving dflags + check_conditions = checkSideConditions dflags cls cls_tys rep_tycon bale_out msg = failWithTc (derivingThingErr cls cls_tys inst_ty msg) non_std_err = nonStdErr cls $$ @@ -1000,19 +1098,21 @@ 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 + && arity_ok + && eta_ok + && ats_ok -- && not (isRecursiveTyCon tycon) -- Note [Recursive newtypes] + -- Never derive Read,Show,Typeable,Data by isomorphism + non_iso_class cls = className cls `elem` ([readClassName, showClassName, dataClassName] ++ + typeableClassNames) + + 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 -- The newtype can be eta-reduced to match the number @@ -1022,17 +1122,19 @@ 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 [ ptext (sLit "even with cunning newtype deriving:") + , if arity_ok then empty else arity_msg + , if eta_ok then empty else eta_msg + , if ats_ok then empty else 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] @@ -1288,6 +1390,9 @@ genDerivBinds loc fix_env clas tycon ,(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) ] \end{code}