X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=e534ebd2030fecf4dc9b42f8cf5b670525ac4e96;hp=58db6185f09ed8de4baaf9cf765350bec1364909;hb=ad94d40948668032189ad22a0ad741ac1f645f50;hpb=7edaba2692e2c3c47e24d5746b5cf16233bca6e5 diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 58db618..e534ebd 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -6,6 +6,13 @@ Handles @deriving@ clauses on @data@ declarations. \begin{code} +{-# OPTIONS -w #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings +-- for details + module TcDeriv ( tcDeriving ) where #include "HsVersions.h" @@ -203,16 +210,18 @@ And then translate it to: %************************************************************************ \begin{code} -tcDeriving :: [LTyClDecl Name] -- All type constructors +tcDeriving :: [LTyClDecl Name] -- All type constructors + -> [LInstDecl Name] -- All instance declarations -> [LDerivDecl Name] -- All stand-alone deriving declarations -> TcM ([InstInfo], -- The generated "instance decls" HsValBinds Name) -- Extra generated top-level bindings -tcDeriving tycl_decls deriv_decls +tcDeriving tycl_decls inst_decls deriv_decls = recoverM (returnM ([], emptyValBindsOut)) $ do { -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". - ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns tycl_decls deriv_decls + ; (ordinary_eqns, newtype_inst_info) + <- makeDerivEqns tycl_decls inst_decls deriv_decls ; (ordinary_inst_info, deriv_binds) <- extendLocalInstEnv (map iSpec newtype_inst_info) $ @@ -234,10 +243,11 @@ tcDeriving tycl_decls deriv_decls ; gen_binds <- mkGenericBinds 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 + -- Type signatures in patterns are used in the generic binds ; rn_binds - <- discardWarnings $ setOptM Opt_GlasgowExts $ do + <- discardWarnings $ + setOptM Opt_PatternSignatures $ + do { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn deriv_binds []) ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to @@ -336,32 +346,49 @@ when the dict is constructed in TcInstDcls.tcInstDecl2 \begin{code} makeDerivEqns :: [LTyClDecl Name] + -> [LInstDecl Name] -> [LDerivDecl Name] -> TcM ([DerivEqn], -- Ordinary derivings [InstInfo]) -- Special newtype derivings -makeDerivEqns tycl_decls deriv_decls +makeDerivEqns tycl_decls inst_decls deriv_decls = do { eqns1 <- mapM deriveTyData $ - [ (p,d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- tycl_decls - , p <- preds ] + extractTyDataPreds tycl_decls ++ + [ pd -- traverse assoc data families + | L _ (InstDecl _ _ _ ats) <- inst_decls + , pd <- extractTyDataPreds ats ] ; eqns2 <- mapM deriveStandalone deriv_decls ; return ([eqn | (Just eqn, _) <- eqns1 ++ eqns2], [inst | (_, Just inst) <- eqns1 ++ eqns2]) } + where + extractTyDataPreds decls = + [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds] + ------------------------------------------------------------------ deriveStandalone :: LDerivDecl Name -> TcM (Maybe DerivEqn, Maybe InstInfo) -- Standalone deriving declarations --- e.g. derive instance Show T +-- e.g. deriving instance show a => Show (T a) -- Rather like tcLocalInstDecl deriveStandalone (L loc (DerivDecl deriv_ty)) = setSrcSpan loc $ addErrCtxt (standaloneCtxt deriv_ty) $ - do { (tvs, theta, tau) <- tcHsInstHead deriv_ty - ; (cls, inst_tys) <- checkValidInstHead tau - ; let cls_tys = take (length inst_tys - 1) inst_tys - inst_ty = last inst_tys - - ; mkEqnHelp StandAloneDerivOrigin tvs cls cls_tys inst_ty } + do { traceTc (text "standalone deriving decl for" <+> ppr deriv_ty) + ; (tvs, theta, tau) <- tcHsInstHead deriv_ty + ; traceTc (text "standalone deriving;" + <+> text "tvs:" <+> ppr tvs + <+> text "theta:" <+> ppr theta + <+> text "tau:" <+> ppr tau) + ; (cls, inst_tys) <- checkValidInstHead tau + ; let cls_tys = take (length inst_tys - 1) inst_tys + inst_ty = last inst_tys + + ; traceTc (text "standalone deriving;" + <+> text "class:" <+> ppr cls + <+> text "class types:" <+> ppr cls_tys + <+> text "type:" <+> ppr inst_ty) + ; mkEqnHelp StandAloneDerivOrigin tvs cls cls_tys inst_ty + (Just theta) } ------------------------------------------------------------------ deriveTyData :: (LHsType Name, LTyClDecl Name) -> TcM (Maybe DerivEqn, Maybe InstInfo) @@ -380,12 +407,15 @@ deriveTyData (deriv_pred, L loc decl@(TyData { tcdLName = L _ tycon_name, do { (deriv_tvs, cls, cls_tys) <- tcHsDeriv deriv_pred -- The "deriv_pred" is a LHsType to take account of the fact that for -- newtype deriving we allow deriving (forall a. C [a]). - ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys tc_app } } + ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys tc_app Nothing } } deriveTyData (deriv_pred, other_decl) = panic "derivTyData" -- Caller ensures that only TyData can happen ------------------------------------------------------------------ -mkEqnHelp orig tvs cls cls_tys tc_app +mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type + -> Maybe DerivRhs + -> TcRn (Maybe DerivEqn, Maybe InstInfo) +mkEqnHelp orig tvs cls cls_tys tc_app mtheta | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app = do { -- Make tc_app saturated, because that's what the -- mkDataTypeEqn things expect @@ -395,16 +425,21 @@ mkEqnHelp orig tvs cls cls_tys tc_app full_tc_args = tc_args ++ mkTyVarTys extra_tvs full_tvs = tvs ++ extra_tvs - ; (rep_tc, rep_tc_args) <- tcLookupFamInst tycon full_tc_args + ; (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon full_tc_args - ; gla_exts <- doptM Opt_GlasgowExts + ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable + ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving ; overlap_flag <- getOverlapFlag - ; if isDataTyCon tycon then - mkDataTypeEqn orig gla_exts full_tvs cls cls_tys - tycon full_tc_args rep_tc rep_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 + mkDataTypeEqn orig mayDeriveDataTypeable full_tvs cls cls_tys + tycon full_tc_args rep_tc rep_tc_args mtheta else - mkNewTypeEqn orig gla_exts overlap_flag full_tvs cls cls_tys - tycon full_tc_args rep_tc rep_tc_args } + mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving overlap_flag + full_tvs cls cls_tys + tycon full_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"))) @@ -412,6 +447,32 @@ mkEqnHelp orig tvs cls cls_tys tc_app baleOut err = addErrTc err >> returnM (Nothing, 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. + +\begin{code} +tcLookupFamInstExact :: TyCon -> [Type] -> TcM (TyCon, [Type]) +tcLookupFamInstExact tycon tys + | not (isOpenTyCon tycon) + = return (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 + } +\end{code} + %************************************************************************ %* * @@ -420,20 +481,26 @@ baleOut err = addErrTc err >> returnM (Nothing, Nothing) %************************************************************************ \begin{code} -mkDataTypeEqn orig gla_exts tvs cls cls_tys tycon tc_args rep_tc rep_tc_args - | Just err <- checkSideConditions gla_exts cls cls_tys rep_tc +mkDataTypeEqn :: InstOrigin -> Bool -> [Var] -> Class -> [Type] + -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe DerivRhs + -> TcRn (Maybe DerivEqn, Maybe InstInfo) +mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys + tycon tc_args rep_tc rep_tc_args mtheta + | Just err <- checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc -- NB: pass the *representation* tycon to checkSideConditions = baleOut (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) err) | otherwise = ASSERT( null cls_tys ) do { loc <- getSrcSpanM - ; eqn <- mk_data_eqn loc orig tvs cls tycon tc_args rep_tc rep_tc_args + ; eqn <- mk_data_eqn loc orig tvs cls tycon tc_args rep_tc + rep_tc_args mtheta ; return (Just eqn, Nothing) } mk_data_eqn :: SrcSpan -> InstOrigin -> [TyVar] -> Class - -> TyCon -> [TcType] -> TyCon -> [TcType] -> TcM DerivEqn -mk_data_eqn loc orig tvs cls tycon tc_args rep_tc rep_tc_args + -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe DerivRhs + -> TcM DerivEqn +mk_data_eqn loc orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta | cls `hasKey` typeableClassKey = -- The Typeable class is special in several ways -- data T a b = ... deriving( Typeable ) @@ -446,22 +513,26 @@ mk_data_eqn loc orig tvs cls tycon tc_args rep_tc rep_tc_args -- 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 (loc, orig, dfun_name, [], real_clas, mkTyConApp tycon [], []) } + ; let theta = fromMaybe [] mtheta + ; return (loc, orig, dfun_name, [], real_clas, mkTyConApp tycon [], theta) + } | otherwise = do { dfun_name <- new_dfun_name cls tycon ; let ordinary_constraints = [ mkClassPred cls [arg_ty] | data_con <- tyConDataCons rep_tc, - arg_ty <- dataConInstOrigArgTys data_con rep_tc_args, + arg_ty <- ASSERT( isVanillaDataCon data_con ) + dataConInstOrigArgTys data_con rep_tc_args, not (isUnLiftedType arg_ty) ] -- No constraints for unlifted types? + theta = fromMaybe ordinary_constraints mtheta tiresome_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_tc_args stupid_constraints = substTheta tiresome_subst (tyConStupidTheta rep_tc) -- see note [Data decl contexts] above ; return (loc, orig, dfun_name, tvs, cls, mkTyConApp tycon tc_args, - stupid_constraints ++ ordinary_constraints) + stupid_constraints ++ theta) } ------------------------------------------------------------------ @@ -473,13 +544,13 @@ mk_data_eqn loc orig tvs cls tycon tc_args rep_tc rep_tc_args -- family tycon (with indexes) in error messages. checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> Maybe SDoc -checkSideConditions gla_exts cls cls_tys rep_tc +checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc | notNull cls_tys = Just ty_args_why -- e.g. deriving( Foo s ) | otherwise = case [cond | (key,cond) <- sideConditions, key == getUnique cls] of [] -> Just (non_std_why cls) - [cond] -> cond (gla_exts, rep_tc) + [cond] -> cond (mayDeriveDataTypeable, rep_tc) other -> pprPanic "checkSideConditions" (ppr cls) where ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("is not a class") @@ -495,12 +566,12 @@ 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_typeableOK), - (dataClassKey, cond_glaExts `andCond` cond_std) + (typeableClassKey, cond_mayDeriveDataTypeable `andCond` cond_typeableOK), + (dataClassKey, cond_mayDeriveDataTypeable `andCond` cond_std) ] type Condition = (Bool, TyCon) -> Maybe SDoc - -- Bool is gla-exts flag + -- Bool is whether or not we are allowed to derive Data and Typeable -- TyCon is the *representation* tycon if the -- data type is an indexed one -- Nothing => OK @@ -519,7 +590,7 @@ andCond c1 c2 tc = case c1 tc of Just x -> Just x -- c1 fails cond_std :: Condition -cond_std (gla_exts, rep_tc) +cond_std (_, rep_tc) | any (not . isVanillaDataCon) data_cons = Just existential_why | null data_cons = Just no_cons_why | otherwise = Nothing @@ -531,7 +602,7 @@ cond_std (gla_exts, rep_tc) ptext SLIT("has non-Haskell-98 constructor(s)") cond_isEnumeration :: Condition -cond_isEnumeration (gla_exts, rep_tc) +cond_isEnumeration (_, rep_tc) | isEnumerationTyCon rep_tc = Nothing | otherwise = Just why where @@ -539,18 +610,18 @@ cond_isEnumeration (gla_exts, rep_tc) ptext SLIT("has non-nullary constructors") cond_isProduct :: Condition -cond_isProduct (gla_exts, rep_tc) +cond_isProduct (_, rep_tc) | isProductTyCon rep_tc = Nothing | otherwise = Just why where - why = (pprSourceTyCon rep_tc) <+> + why = quotes (pprSourceTyCon rep_tc) <+> ptext SLIT("has more than one constructor") cond_typeableOK :: Condition -- OK for Typeable class -- Currently: (a) args all of kind * -- (b) 7 or fewer args -cond_typeableOK (gla_exts, rep_tc) +cond_typeableOK (_, rep_tc) | tyConArity rep_tc > 7 = Just too_many | not (all (isSubArgTypeKind . tyVarKind) (tyConTyVars rep_tc)) = Just bad_kind @@ -564,9 +635,10 @@ cond_typeableOK (gla_exts, rep_tc) fam_inst = quotes (pprSourceTyCon rep_tc) <+> ptext SLIT("is a type family") -cond_glaExts :: Condition -cond_glaExts (gla_exts, _rep_tc) | gla_exts = Nothing - | otherwise = Just why +cond_mayDeriveDataTypeable :: Condition +cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) + | mayDeriveDataTypeable = Nothing + | otherwise = Just why where why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class") @@ -578,7 +650,7 @@ std_class_via_iso clas -- These standard classes can be derived for a newtype new_dfun_name clas tycon -- Just a simple wrapper - = newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon) + = newDFunName clas [mkTyConApp tycon []] (getSrcSpan tycon) -- The type passed to newDFunName is only used to generate -- a suitable string; hence the empty type arg list \end{code} @@ -591,10 +663,13 @@ new_dfun_name clas tycon -- Just a simple wrapper %************************************************************************ \begin{code} -mkNewTypeEqn orig gla_exts overlap_flag tvs cls cls_tys - tycon tc_args - rep_tycon rep_tc_args - | can_derive_via_isomorphism && (gla_exts || std_class_via_iso cls) +mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> OverlapFlag -> [Var] -> Class + -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] + -> Maybe DerivRhs + -> TcRn (Maybe DerivEqn, Maybe InstInfo) +mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving overlap_flag tvs + cls cls_tys tycon tc_args rep_tycon rep_tc_args mtheta + | can_derive_via_isomorphism && (newtype_deriving || std_class_via_iso cls) = do { traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) ; -- Go ahead and use the isomorphism dfun_name <- new_dfun_name cls tycon @@ -603,17 +678,18 @@ mkNewTypeEqn orig gla_exts overlap_flag tvs cls cls_tys | isNothing mb_std_err -- Use the standard H98 method = do { loc <- getSrcSpanM - ; eqn <- mk_data_eqn loc orig tvs cls tycon tc_args rep_tycon rep_tc_args + ; eqn <- mk_data_eqn loc orig tvs cls tycon tc_args rep_tycon + rep_tc_args mtheta ; return (Just eqn, Nothing) } -- Otherwise we can't derive - | gla_exts = baleOut cant_derive_err -- Too hard + | newtype_deriving = baleOut cant_derive_err -- Too hard | otherwise = baleOut std_err -- Just complain about being a non-std instance where - mb_std_err = checkSideConditions gla_exts cls cls_tys rep_tycon + 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 -fglasgow-exts 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, ...) @@ -840,11 +916,11 @@ solveDerivEqns overlap_flag orig_eqns gen_soln :: DerivEqn -> TcM [PredType] gen_soln (loc, orig, _, tyvars, clas, inst_ty, deriv_rhs) = setSrcSpan loc $ + addErrCtxt (derivInstCtxt clas [inst_ty]) $ do { theta <- tcSimplifyDeriv orig tyvars deriv_rhs - ; addErrCtxt (derivInstCtxt theta clas [inst_ty]) $ - do { checkNoErrs (checkValidInstance tyvars theta clas [inst_ty]) - -- See Note [Deriving context] - -- If this fails, don't continue + -- checkValidInstance tyvars theta clas [inst_ty] + -- Not necessary; see Note [Exotic derived instance contexts] + -- in TcSimplify -- Check for a bizarre corner case, when the derived instance decl should -- have form instance C a b => D (T a) where ... @@ -858,7 +934,7 @@ solveDerivEqns overlap_flag orig_eqns -- Claim: the result instance declaration is guaranteed valid -- Hence no need to call: -- checkValidInstance tyvars theta clas inst_tys - ; return (sortLe (<=) theta) } } -- Canonicalise before returning the solution + ; return (sortLe (<=) theta) } -- Canonicalise before returning the solution ------------------------------------------------------------------ mk_inst_spec :: DerivEqn -> DerivSoln -> Instance @@ -877,25 +953,6 @@ extendLocalInstEnv dfuns thing_inside ; setGblEnv env' thing_inside } \end{code} -Note [Deriving context] -~~~~~~~~~~~~~~~~~~~~~~~ -With -fglasgow-exts, we allow things like (C Int a) in the simplified -context for a derived instance declaration, because at a use of this -instance, we might know that a=Bool, and have an instance for (C Int -Bool) - -We nevertheless insist that each predicate meets the termination -conditions. If not, the deriving mechanism generates larger and larger -constraints. Example: - data Succ a = S a - data Seq a = Cons a (Seq (Succ a)) | Nil deriving Show - -Note the lack of a Show instance for Succ. First we'll generate - instance (Show (Succ a), Show a) => Show (Seq a) -and then - instance (Show (Succ (Succ a)), Show (Succ a), Show a) => Show (Seq a) -and so on. Instead we want to complain of no instance for (Show (Succ a)). - %************************************************************************ %* * @@ -977,7 +1034,7 @@ genInst spec -- In case of a family instance, we need to use the representation -- tycon (after all, it has the data constructors) - ; (tycon, _) <- tcLookupFamInst visible_tycon tyArgs + ; (tycon, _) <- tcLookupFamInstExact visible_tycon tyArgs ; let (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon -- Bring the right type variables into @@ -1111,15 +1168,18 @@ derivingThingErr clas tys ty why standaloneCtxt :: LHsType Name -> SDoc standaloneCtxt ty = ptext SLIT("In the stand-alone deriving instance for") <+> quotes (ppr ty) -derivInstCtxt theta clas inst_tys - = hang (ptext SLIT("In the derived instance:")) - 2 (pprThetaArrow theta <+> pprClassPred clas inst_tys) --- Used for the ...Thetas variants; all top level +derivInstCtxt clas inst_tys + = ptext SLIT("When deriving the instance for") <+> parens (pprClassPred clas inst_tys) 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)] -\end{code} - \ No newline at end of file +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") +\end{code}