X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=b1a281994f2d470ae5ea2164eedec6ae46a957ae;hb=1c05d4fbb6ee7ab68470d0aa79d74a3a4f0d8383;hp=445a1f437a80f9e4a93b0ea63d5f9aa907c0ce7e;hpb=f22f248b88346df835b25f03f8d3372c7bb87950;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 445a1f4..b1a2819 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -46,6 +46,7 @@ import SrcLoc import Util import ListSetOps import Outputable +import FastString import Bag \end{code} @@ -265,7 +266,7 @@ tcDeriving :: [LTyClDecl Name] -- All type constructors HsValBinds Name) -- Extra generated top-level bindings tcDeriving tycl_decls inst_decls deriv_decls - = recoverM (returnM ([], emptyValBindsOut)) $ + = recoverM (return ([], emptyValBindsOut)) $ do { -- Fish the "deriving"-related information out of the TcEnv -- And make the necessary "equations". ; early_specs <- makeDerivSpecs tycl_decls inst_decls deriv_decls @@ -286,8 +287,8 @@ tcDeriving tycl_decls inst_decls deriv_decls ; let inst_info = insts1 ++ insts2 ; dflags <- getDOpts - ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving inst_info rn_binds)) + ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info rn_binds)) ; return (inst_info, rn_binds) } where @@ -431,11 +432,22 @@ mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type -> TcRn (Maybe EarlyDerivSpec) mkEqnHelp orig tvs cls cls_tys tc_app mtheta | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app - = do { (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon tc_args + = do { + -- For standalone deriving (mtheta /= Nothing), + -- check that all the data constructors are in scope + -- By this time we know that the thing is algebraic + -- because we've called checkInstHead in derivingStandalone + rdr_env <- getGlobalRdrEnv + ; let hidden_data_cons = filter not_in_scope (tyConDataCons tycon) + not_in_scope dc = null (lookupGRE_Name rdr_env (dataConName dc)) + ; checkTc (isNothing mtheta || null hidden_data_cons) + (derivingHiddenErr tycon) ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving + ; (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 ; if isDataTyCon rep_tc then @@ -447,15 +459,35 @@ mkEqnHelp orig tvs cls cls_tys tc_app mtheta tycon tc_args rep_tc rep_tc_args mtheta } | otherwise = baleOut (derivingThingErr cls cls_tys tc_app - (ptext SLIT("Last argument of the instance must be a type application"))) + (ptext (sLit "Last argument of the instance must be a type application"))) baleOut :: Message -> TcM (Maybe a) baleOut err = do { addErrTc err; return Nothing } \end{code} -Auxiliary lookup wrapper which requires that looked up family instances are -not type instances. If called with a vanilla tycon, the old type application -is simply returned. +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. \begin{code} tcLookupFamInstExact :: TyCon -> [Type] -> TcM (TyCon, [Type]) @@ -465,18 +497,14 @@ tcLookupFamInstExact tycon tys | otherwise = do { maybeFamInst <- tcLookupFamInst tycon tys ; case maybeFamInst of - Nothing -> famInstNotFound tycon tys False - Just famInst@(_, rep_tys) - | not variable_only_subst -> famInstNotFound tycon tys True - | otherwise -> return famInst - where - tvs = map (Type.getTyVar - "TcDeriv.tcLookupFamInstExact") - rep_tys - variable_only_subst = all Type.isTyVarTy rep_tys && - sizeVarSet (mkVarSet tvs) == length tvs - -- renaming may have no repetitions + 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 (ppr tycon) tys)) \end{code} @@ -519,21 +547,24 @@ mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta dataConInstOrigArgTys data_con rep_tc_args, not (isUnLiftedType arg_ty) ] -- No constraints for unlifted types? + -- 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 ++ ordinary_constraints - -- see Note [Data decl contexts] above + all_constraints = stupid_constraints ++ sc_constraints ++ ordinary_constraints spec = DS { ds_loc = loc, ds_orig = orig , ds_name = dfun_name, ds_tvs = tvs - , ds_cls = cls, ds_tys = [mkTyConApp tycon tc_args] + , ds_cls = cls, ds_tys = inst_tys , ds_theta = mtheta `orElse` all_constraints , ds_newtype = False } ; return (if isJust mtheta then Just (Right spec) -- Specified context else Just (Left spec)) } -- Infer context - mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- The Typeable class is special in several ways -- data T a b = ... deriving( Typeable ) @@ -546,13 +577,13 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- Typeable; it depends on the arity of the type | isNothing mtheta -- deriving on a data type decl = do { checkTc (cls `hasKey` typeableClassKey) - (ptext SLIT("Use deriving( Typeable ) on a data type declaration")) + (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 []) } | otherwise -- standaone deriving = do { checkTc (null tc_args) - (ptext SLIT("Derived typeable instance must be of form (Typeable") + (ptext (sLit "Derived typeable instance must be of form (Typeable") <> int (tyConArity tycon) <+> ppr tycon <> rparen) ; dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM @@ -578,8 +609,8 @@ checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc Just cond -> cond (mayDeriveDataTypeable, rep_tc) Nothing -> Just non_std_why where - ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("is not a class") - non_std_why = quotes (ppr cls) <+> ptext SLIT("is not a derivable class") + ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "is not a class") + non_std_why = quotes (ppr cls) <+> ptext (sLit "is not a derivable class") sideConditions :: Class -> Maybe Condition sideConditions cls @@ -608,7 +639,7 @@ orCond c1 c2 tc Nothing -> Nothing -- c1 succeeds Just x -> case c2 tc of -- c1 fails Nothing -> Nothing - Just y -> Just (x $$ ptext SLIT(" and") $$ y) + Just y -> Just (x $$ ptext (sLit " and") $$ y) -- Both fail andCond :: Condition -> Condition -> Condition @@ -624,9 +655,9 @@ cond_std (_, rep_tc) where data_cons = tyConDataCons rep_tc no_cons_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has no data constructors") + ptext (sLit "has no data constructors") existential_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-Haskell-98 constructor(s)") + ptext (sLit "has non-Haskell-98 constructor(s)") cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) @@ -634,7 +665,7 @@ cond_isEnumeration (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-nullary constructors") + ptext (sLit "has non-nullary constructors") cond_isProduct :: Condition cond_isProduct (_, rep_tc) @@ -642,7 +673,7 @@ cond_isProduct (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has more than one constructor") + ptext (sLit "has more than one constructor") cond_typeableOK :: Condition -- OK for Typeable class @@ -656,18 +687,18 @@ cond_typeableOK (_, rep_tc) | otherwise = Nothing where too_many = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has too many arguments") + ptext (sLit "has too many arguments") bad_kind = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has arguments of kind other than `*'") + ptext (sLit "has arguments of kind other than `*'") fam_inst = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("is a type family") + ptext (sLit "is a type family") cond_mayDeriveDataTypeable :: Condition cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) | mayDeriveDataTypeable = Nothing | otherwise = Just why where - why = ptext SLIT("You need -XDeriveDataTypeable to derive an instance for this class") + why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class") std_class_via_iso :: Class -> Bool std_class_via_iso clas -- These standard classes can be derived for a newtype @@ -684,6 +715,30 @@ new_dfun_name clas tycon -- Just a simple wrapper -- a suitable string; hence the empty type arg list \end{code} +Note [Superclasses of derived instance] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In general, a derived instance decl needs the superclasses of the derived +class too. So if we have + data T a = ...deriving( Ord ) +then the initial context for Ord (T a) should include Eq (T a). Often this is +redundant; we'll also generate an Ord constraint for each constructor argument, +and that will probably generate enough constraints to make the Eq (T a) constraint +be satisfied too. But not always; consider: + + data S a = S + instance Eq (S a) + instance Ord (S a) + + data T a = MkT (S a) deriving( Ord ) + instance Num a => Eq (T a) + +The derived instance for (Ord (T a)) must have a (Num a) constraint! +Similarly consider: + data T a = MkT deriving( Data, Typeable ) +Here there *is* no argument field, but we must nevertheless generate +a context for the Data instances: + instance Typable a => Data (T a) where ... + %************************************************************************ %* * @@ -720,7 +775,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs mb_std_err = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon std_err = derivingThingErr cls cls_tys tc_app $ vcat [fromJust mb_std_err, - ptext SLIT("Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] + 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, ...) @@ -760,10 +815,10 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- Want to drop 1 arg from (T s a) and (ST s a) -- to get instance Monad (ST s) => Monad (T s) - -- Note [newtype representation] - -- Need newTyConRhs *not* newTyConRep to get the representation - -- type, because the latter looks through all intermediate newtypes - -- For example + -- Note [Newtype representation] + -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + -- Need newTyConRhs (*not* a recursive representation finder) + -- to get the representation type. 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, @@ -854,19 +909,19 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- arguments must be type variables (not more complex indexes) cant_derive_err = derivingThingErr cls cls_tys tc_app - (vcat [ptext SLIT("even with cunning newtype deriving:"), + (vcat [ptext (sLit "even with cunning newtype deriving:"), if isRecursiveTyCon tycon then - ptext SLIT("the newtype may be recursive") + 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") + quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") else empty, if not (n_tyargs_to_keep >= 0) then - ptext SLIT("the type constructor has wrong kind") + ptext (sLit "the type constructor has wrong kind") else if not (n_args_to_keep >= 0) then - ptext SLIT("the representation type has wrong kind") + ptext (sLit "the representation type has wrong kind") else if not eta_ok then - ptext SLIT("the eta-reduction property does not hold") + ptext (sLit "the eta-reduction property does not hold") else empty ]) \end{code} @@ -1119,31 +1174,28 @@ genDerivBinds clas fix_env tycon \begin{code} derivingThingErr :: Class -> [Type] -> Type -> Message -> Message derivingThingErr clas tys ty why - = sep [hsep [ptext SLIT("Can't make a derived instance of"), + = sep [hsep [ptext (sLit "Can't make a derived instance of"), quotes (ppr pred)], nest 2 (parens why)] where pred = mkClassPred clas (tys ++ [ty]) +derivingHiddenErr :: TyCon -> SDoc +derivingHiddenErr tc + = hang (ptext (sLit "The data constructors of") <+> quotes (ppr tc) <+> ptext (sLit "are not all in scope")) + 2 (ptext (sLit "so you cannot derive an instance for it")) + standaloneCtxt :: LHsType Name -> SDoc -standaloneCtxt ty = hang (ptext SLIT("In the stand-alone deriving instance for")) +standaloneCtxt ty = hang (ptext (sLit "In the stand-alone deriving instance for")) 2 (quotes (ppr ty)) derivInstCtxt :: Class -> [Type] -> Message derivInstCtxt clas inst_tys - = ptext SLIT("When deriving the instance for") <+> parens (pprClassPred clas inst_tys) + = ptext (sLit "When deriving the instance for") <+> parens (pprClassPred clas inst_tys) badDerivedPred :: PredType -> Message badDerivedPred pred - = vcat [ptext SLIT("Can't derive instances where the instance context mentions"), - ptext SLIT("type variables that are not data type parameters"), - nest 2 (ptext SLIT("Offending constraint:") <+> ppr pred)] - -famInstNotFound :: TyCon -> [Type] -> Bool -> TcM a -famInstNotFound tycon tys notExact - = failWithTc (msg <+> quotes (pprTypeApp tycon (ppr tycon) tys)) - where - msg = ptext $ if notExact - then SLIT("No family instance exactly matching") - else SLIT("More than one family instance for") + = vcat [ptext (sLit "Can't derive instances where the instance context mentions"), + ptext (sLit "type variables that are not data type parameters"), + nest 2 (ptext (sLit "Offending constraint:") <+> ppr pred)] \end{code}