X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=e121cc6e2ec7febb9dd566086813f6b8d9e6854a;hb=f61fe72d9bcefdf7f9e04f2d0d94c7d842f7625b;hp=c1025d4eefcc52f0f2462954d721d765765f0922;hpb=22eefb510ad56379cc96b8d14a440579cd55fc81;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index c1025d4..e121cc6 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -257,7 +257,12 @@ 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. %************************************************************************ %* * @@ -270,10 +275,11 @@ 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 + HsValBinds Name, -- Extra generated top-level bindings + DefUses) 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 @@ -291,13 +297,13 @@ tcDeriving tycl_decls inst_decls deriv_decls -- 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) + ; (inst_info, rn_binds, rn_dus) <- renameDeriv is_boot gen_binds (insts1 ++ insts2) ; dflags <- getDOpts ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" (ddump_deriving inst_info rn_binds)) - ; return (inst_info, rn_binds) } + ; return (inst_info, rn_binds, rn_dus) } where ddump_deriving :: [InstInfo Name] -> HsValBinds Name -> SDoc ddump_deriving inst_infos extra_binds @@ -305,13 +311,13 @@ tcDeriving tycl_decls inst_decls deriv_decls 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 @@ -330,9 +336,10 @@ renameDeriv is_boot gen_binds insts ; 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) } } + do { (rn_aux, dus_aux) <- rnTopBindsRHS (mkNameSet aux_names) 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 @@ -344,15 +351,15 @@ renameDeriv is_boot gen_binds insts rn_inst_info (InstInfo { iSpec = inst, iBinds = NewTypeDerived co }) - = return (InstInfo { iSpec = inst, iBinds = NewTypeDerived co }) + = return (InstInfo { iSpec = inst, iBinds = NewTypeDerived co }, emptyFVs) rn_inst_info (InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs }) = -- Bring the right type variables into -- scope (yuk), and rename the method binds ASSERT( null sigs ) bindLocalNames (map Var.varName tyvars) $ - do { (rn_binds, _fvs) <- rnMethodBinds clas_nm (\_ -> []) [] binds - ; return (InstInfo { iSpec = inst, iBinds = VanillaInst rn_binds [] }) } + do { (rn_binds, fvs) <- rnMethodBinds clas_nm (\_ -> []) [] binds + ; return (InstInfo { iSpec = inst, iBinds = VanillaInst rn_binds [] }, fvs) } where (tyvars,_,clas,_) = instanceHead inst clas_nm = className clas @@ -663,52 +670,16 @@ 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 ) - get_constrained_tys $ - substTys subst $ - 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 - - - -- See Note [Superclasses of derived instance] - sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys) - (classSCTheta cls) - inst_tys = [mkTyConApp tycon tc_args] - subst = zipTopTvSubst rep_tc_tvs all_rep_tc_args - stupid_constraints = substTheta 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 } - ; ASSERT2( equalLength rep_tc_tvs all_rep_tc_args, ppr cls <+> ppr tycon ) - return (if isJust mtheta then Right spec -- Specified context + ; return (if isJust mtheta then Right spec -- Specified context else Left spec) } -- Infer context mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta @@ -740,6 +711,61 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta , 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 @@ -775,11 +801,15 @@ sideConditions cls | 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_std `andCond` cond_functorOK True) - | cls_key == foldableClassKey = Just (cond_std `andCond` cond_functorOK False) - | cls_key == traversableClassKey = Just (cond_std `andCond` cond_functorOK False) - | getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK) + | 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) + | getName cls `elem` typeableClassNames = Just (checkFlag Opt_DeriveDataTypeable `andCond` cond_typeableOK) | otherwise = Nothing where cls_key = getUnique cls @@ -807,15 +837,21 @@ 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` @@ -830,8 +866,7 @@ 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) @@ -884,29 +919,37 @@ cond_functorOK allowFunctions (dflags, rep_tc) = msum (map check_con data_cons) -- msum picks the first 'Just', if any where data_cons = tyConDataCons rep_tc - check_con con = msum (foldDataConArgs ft_check con) - - ft_check :: FFoldType (Maybe SDoc) - ft_check = FT { ft_triv = Nothing, ft_var = Nothing, ft_co_var = Just covariant - , ft_fun = \x y -> if allowFunctions then x `mplus` y else Just functions - , ft_tup = \_ xs -> msum xs - , ft_ty_app = \_ x -> x - , ft_bad_app = Just wrong_arg - , ft_forall = \_ x -> x } + 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 } - covariant = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "uses the type variable in a function argument") - functions = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "contains function types") - wrong_arg = quotes (pprSourceTyCon rep_tc) <+> - ptext (sLit "uses the type variable in an argument other than the last") - -cond_mayDeriveDataTypeable :: Condition -cond_mayDeriveDataTypeable (dflags, _) - | dopt Opt_DeriveDataTypeable dflags = Nothing - | otherwise = Just why + 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") + +checkFlag :: DynFlag -> Condition +checkFlag flag (dflags, _) + | dopt 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 @@ -922,6 +965,9 @@ 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]