X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=d414c6f3f3cbddb4442c02f650f2d740263a4669;hp=1a9a8813e5df8c4c005c567a93a43979f7cc700e;hb=08efb089bb9a1a9c77df6caefe15b44d6ab5b2d3;hpb=6777144f7522d8db5935737e12fa451ca3211e6d diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 1a9a881..d414c6f 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -51,10 +51,54 @@ import Bag %************************************************************************ %* * -\subsection[TcDeriv-intro]{Introduction to how we do deriving} + Overview %* * %************************************************************************ +Overall plan +~~~~~~~~~~~~ +1. Convert the decls (i.e. data/newtype deriving clauses, + plus standalone deriving) to [EarlyDerivSpec] + +2. Infer the missing contexts for the Left DerivSpecs + +3. Add the derived bindings, generating InstInfos + +\begin{code} +-- DerivSpec is purely local to this module +data DerivSpec = DS { ds_loc :: SrcSpan + , ds_orig :: InstOrigin + , ds_name :: Name + , ds_tvs :: [TyVar] + , ds_theta :: ThetaType + , ds_cls :: Class + , ds_tys :: [Type] + , ds_newtype :: Bool } + -- This spec implies a dfun declaration of the form + -- df :: forall tvs. theta => C tys + -- The Name is the name for the DFun we'll build + -- The tyvars bind all the variables in the theta + -- For family indexes, the tycon is the *family* tycon + -- (not the representation tycon) + + -- ds_newtype = True <=> Newtype deriving + -- False <=> Vanilla deriving + +type EarlyDerivSpec = Either DerivSpec DerivSpec + -- Left ds => the context for the instance should be inferred + -- (ds_theta is required) + -- Right ds => the context for the instance is supplied by the programmer + +pprDerivSpec :: DerivSpec -> SDoc +pprDerivSpec (DS { ds_loc = l, ds_name = n, ds_tvs = tvs, + ds_cls = c, ds_tys = tys, ds_theta = rhs }) + = parens (hsep [ppr l, ppr n, ppr tvs, ppr c, ppr tys] + <+> equals <+> ppr rhs) +\end{code} + + +Inferring missing contexts +~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data T a b = C1 (Foo a) (Bar b) @@ -133,27 +177,9 @@ this by simplifying the RHS to a form in which So, here are the synonyms for the ``equation'' structures: -\begin{code} -type DerivRhs = ThetaType -type DerivSoln = DerivRhs -type DerivEqn = (SrcSpan, InstOrigin, Name, [TyVar], Class, Type, DerivRhs) - -- (span, orig, df, tvs, C, ty, rhs) - -- implies a dfun declaration of the form - -- df :: forall tvs. rhs => C ty - -- The Name is the name for the DFun we'll build - -- The tyvars bind all the variables in the RHS - -- For family indexes, the tycon is the *family* tycon - -- (not the representation tycon) - -pprDerivEqn :: DerivEqn -> SDoc -pprDerivEqn (l, _, n, tvs, c, ty, rhs) - = parens (hsep [ppr l, ppr n, ppr tvs, ppr c, ppr ty] - <+> equals <+> ppr rhs) -\end{code} - -[Data decl contexts] A note about contexts on data decls -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Note [Data decl contexts] +~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data (RealFloat a) => Complex a = !a :+ !a deriving( Read ) @@ -180,8 +206,8 @@ pattern matching against a constructor from a data type with a context gives rise to the constraints for that context -- or at least the thinned version. So now all classes are "offending". -[Newtype deriving] -~~~~~~~~~~~~~~~~~~ +Note [Newtype deriving] +~~~~~~~~~~~~~~~~~~~~~~~ Consider this: class C a b instance C [a] Char @@ -194,6 +220,27 @@ And then translate it to: instance C [a] Char => C [a] T where ... +Note [Newtype deriving superclasses] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'tys' here come from the partial application in the deriving +clause. The last arg is the new instance type. + +We must pass the superclasses; the newtype might be an instance +of them in a different way than the representation type +E.g. newtype Foo a = Foo a deriving( Show, Num, Eq ) +Then the Show instance is not done via isomorphism; it shows + Foo 3 as "Foo 3" +The Num instance is derived via isomorphism, but the Show superclass +dictionary must the Show instance for Foo, *not* the Show dictionary +gotten from the Num dictionary. So we must build a whole new dictionary +not just use the Num one. The instance we want is something like: + instance (Num a, Show (Foo a), Eq (Foo a)) => Num (Foo a) where + (+) = ((+)@a) + ...etc... +There may be a coercion needed which we get from the tycon for the newtype +when the dict is constructed in TcInstDcls.tcInstDecl2 + + %************************************************************************ @@ -203,84 +250,74 @@ 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_inst_info, deriv_binds) - <- extendLocalInstEnv (map iSpec newtype_inst_info) $ - deriveOrdinaryStuff ordinary_eqns - -- Add the newtype-derived instances to the inst env - -- before tacking the "ordinary" ones + -- And make the necessary "equations". + ; early_specs <- makeDerivSpecs tycl_decls inst_decls deriv_decls - ; let inst_info = newtype_inst_info ++ ordinary_inst_info + ; overlap_flag <- getOverlapFlag + ; let (infer_specs, given_specs) = splitEithers early_specs + ; (insts1, aux_binds1) <- mapAndUnzipM (genInst overlap_flag) given_specs - -- If we are compiling a hs-boot file, - -- don't generate any derived bindings - ; is_boot <- tcIsHsBoot - ; if is_boot then - return (inst_info, emptyValBindsOut) - else do - { + ; final_specs <- extendLocalInstEnv (map iSpec insts1) $ + inferInstanceContexts overlap_flag infer_specs - -- Generate the generic to/from functions from each type declaration - ; gen_binds <- mkGenericBinds tycl_decls + ; (insts2, aux_binds2) <- mapAndUnzipM (genInst overlap_flag) final_specs - -- 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 - ; rn_binds - <- discardWarnings $ setOptM Opt_GlasgowExts $ do - { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn deriv_binds []) - ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) - ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to - -- be kept alive - ; return (rn_deriv `plusHsValBinds` rn_gen) } + ; is_boot <- tcIsHsBoot + ; rn_binds <- makeAuxBinds is_boot tycl_decls + (concat aux_binds1 ++ concat aux_binds2) + ; let inst_info = insts1 ++ insts2 ; dflags <- getDOpts ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" (ddump_deriving inst_info rn_binds)) - ; returnM (inst_info, rn_binds) - }} + ; return (inst_info, rn_binds) } where ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc ddump_deriving inst_infos extra_binds = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds ------------------------------------------ -deriveOrdinaryStuff [] -- Short cut - = returnM ([], emptyLHsBinds) - -deriveOrdinaryStuff eqns - = do { -- Take the equation list and solve it, to deliver a list of - -- solutions, a.k.a. the contexts for the instance decls - -- required for the corresponding equations. - overlap_flag <- getOverlapFlag - ; inst_specs <- solveDerivEqns overlap_flag eqns +makeAuxBinds :: Bool -> [LTyClDecl Name] -> DerivAuxBinds -> TcM (HsValBinds Name) +makeAuxBinds is_boot tycl_decls deriv_aux_binds + | is_boot -- If we are compiling a hs-boot file, + -- don't generate any derived bindings + = return emptyValBindsOut - -- Generate the InstInfo for each dfun, - -- plus any auxiliary bindings it needs - ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst inst_specs + | otherwise + = do { let aux_binds = listToBag (map genAuxBind (rm_dups [] deriv_aux_binds)) + -- Generate any extra not-one-inst-decl-specific binds, + -- notably "con2tag" and/or "tag2con" functions. - -- Generate any extra not-one-inst-decl-specific binds, - -- notably "con2tag" and/or "tag2con" functions. - ; extra_binds <- genTaggeryBinds inst_infos + -- Generate the generic to/from functions from each type declaration + ; gen_binds <- mkGenericBinds tycl_decls - -- Done - ; returnM (map fst inst_infos, - unionManyBags (extra_binds : aux_binds_s)) - } + -- Rename these extra bindings, discarding warnings about unused bindings etc + -- Type signatures in patterns are used in the generic binds + ; discardWarnings $ + setOptM Opt_PatternSignatures $ + do { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn aux_binds []) + ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to + -- be kept alive + ; return (rn_deriv `plusHsValBinds` rn_gen) } } + where + -- Remove duplicate requests for auxilliary bindings + rm_dups acc [] = acc + rm_dups acc (b:bs) | any (isDupAux b) acc = rm_dups acc bs + | otherwise = rm_dups (b:acc) bs ----------------------------------------- +mkGenericBinds :: [LTyClDecl Name] -> TcM (LHsBinds RdrName) mkGenericBinds tycl_decls = do { tcs <- mapM tcLookupTyCon [ tc_name | @@ -294,11 +331,11 @@ mkGenericBinds tycl_decls %************************************************************************ %* * -\subsection[TcDeriv-eqns]{Forming the equations} + From HsSyn to DerivSpec %* * %************************************************************************ -@makeDerivEqns@ fishes around to find the info about needed derived +@makeDerivSpecs@ fishes around to find the info about needed derived instances. Complicating factors: \begin{itemize} \item @@ -313,58 +350,52 @@ or} has just one data constructor (e.g., tuples). [See Appendix~E in the Haskell~1.2 report.] This code here deals w/ all those. -Note [Newtype deriving superclasses] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The 'tys' here come from the partial application in the deriving -clause. The last arg is the new instance type. - -We must pass the superclasses; the newtype might be an instance -of them in a different way than the representation type -E.g. newtype Foo a = Foo a deriving( Show, Num, Eq ) -Then the Show instance is not done via isomorphism; it shows - Foo 3 as "Foo 3" -The Num instance is derived via isomorphism, but the Show superclass -dictionary must the Show instance for Foo, *not* the Show dictionary -gotten from the Num dictionary. So we must build a whole new dictionary -not just use the Num one. The instance we want is something like: - instance (Num a, Show (Foo a), Eq (Foo a)) => Num (Foo a) where - (+) = ((+)@a) - ...etc... -There may be a coercion needed which we get from the tycon for the newtype -when the dict is constructed in TcInstDcls.tcInstDecl2 - - \begin{code} -makeDerivEqns :: [LTyClDecl Name] - -> [LDerivDecl Name] - -> TcM ([DerivEqn], -- Ordinary derivings - [InstInfo]) -- Special newtype derivings +makeDerivSpecs :: [LTyClDecl Name] + -> [LInstDecl Name] + -> [LDerivDecl Name] + -> TcM [EarlyDerivSpec] -makeDerivEqns tycl_decls deriv_decls +makeDerivSpecs 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]) } + ; return (catMaybes (eqns1 ++ eqns2)) } + where + extractTyDataPreds decls = + [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds] + ------------------------------------------------------------------ -deriveStandalone :: LDerivDecl Name -> TcM (Maybe DerivEqn, Maybe InstInfo) +deriveStandalone :: LDerivDecl Name -> TcM (Maybe EarlyDerivSpec) -- 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) +deriveTyData :: (LHsType Name, LTyClDecl Name) -> TcM (Maybe EarlyDerivSpec) deriveTyData (deriv_pred, L loc decl@(TyData { tcdLName = L _ tycon_name, tcdTyVars = tv_names, tcdTyPats = ty_pats })) @@ -380,12 +411,17 @@ 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 } } -deriveTyData (deriv_pred, other_decl) + ; mkEqnHelp DerivOrigin (tvs++deriv_tvs) cls cls_tys tc_app Nothing } } + +deriveTyData _other = panic "derivTyData" -- Caller ensures that only TyData can happen ------------------------------------------------------------------ -mkEqnHelp orig tvs cls cls_tys tc_app +mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type + -> Maybe ThetaType -- Just => context supplied + -- Nothing => context inferred + -> TcRn (Maybe EarlyDerivSpec) +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 @@ -395,24 +431,52 @@ 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 - ; overlap_flag <- getOverlapFlag + ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable + ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving -- 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 gla_exts full_tvs cls cls_tys - tycon full_tc_args rep_tc rep_tc_args + 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 + 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"))) -baleOut err = addErrTc err >> returnM (Nothing, Nothing) +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. + +\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} @@ -423,20 +487,24 @@ 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 ThetaType + -> TcRn (Maybe EarlyDerivSpec) -- Return 'Nothing' if error + +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 - ; return (Just eqn, Nothing) } + mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta -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 +mk_data_eqn :: InstOrigin -> [TyVar] -> Class + -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe ThetaType + -> TcM (Maybe EarlyDerivSpec) +mk_data_eqn 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 ) @@ -449,23 +517,35 @@ 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 [], []) } + ; loc <- getSrcSpanM + ; return (Just $ Right $ + DS { ds_loc = loc, ds_orig = orig, ds_name = dfun_name, ds_tvs = [] + , ds_cls = real_clas, ds_tys = [mkTyConApp tycon []] + , ds_theta = mtheta `orElse` [], ds_newtype = False }) } | 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 <- 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? - tiresome_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_tc_args - stupid_constraints = substTheta tiresome_subst (tyConStupidTheta rep_tc) - -- see note [Data decl contexts] above + 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 - ; return (loc, orig, dfun_name, tvs, cls, mkTyConApp tycon tc_args, - stupid_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_theta = mtheta `orElse` all_constraints + , ds_newtype = False } + + ; return (if isJust mtheta then Just (Right spec) -- Specified context + else Just (Left spec)) } -- Infer context ------------------------------------------------------------------ -- Check side conditions that dis-allow derivability for particular classes @@ -476,17 +556,18 @@ 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) - other -> pprPanic "checkSideConditions" (ppr cls) + [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") +non_std_why :: Class -> SDoc non_std_why cls = quotes (ppr cls) <+> ptext SLIT("is not a derivable class") sideConditions :: [(Unique, Condition)] @@ -498,12 +579,12 @@ 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 @@ -517,12 +598,13 @@ orCond c1 c2 tc Just y -> Just (x $$ ptext SLIT(" and") $$ y) -- Both fail +andCond :: Condition -> Condition -> Condition andCond c1 c2 tc = case c1 tc of Nothing -> c2 tc -- c1 succeeds 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 @@ -534,7 +616,7 @@ 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 @@ -542,7 +624,7 @@ 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 @@ -553,7 +635,7 @@ 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 @@ -567,12 +649,14 @@ 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") + 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 -- using the isomorphism trick *even if no -fglasgow-exts* = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey] @@ -580,6 +664,7 @@ std_class_via_iso clas -- These standard classes can be derived for a newtype -- Not Enum, because newtypes are never in Enum +new_dfun_name :: Class -> TyCon -> TcM Name new_dfun_name clas tycon -- Just a simple wrapper = newDFunName clas [mkTyConApp tycon []] (getSrcSpan tycon) -- The type passed to newDFunName is only used to generate @@ -594,29 +679,35 @@ 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 -> [Var] -> Class + -> [Type] -> TyCon -> [Type] -> TyCon -> [Type] + -> Maybe ThetaType + -> TcRn (Maybe EarlyDerivSpec) +mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving 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 - ; return (Nothing, Just (InstInfo { iSpec = mk_inst_spec dfun_name, - iBinds = NewTypeDerived ntd_info })) } + ; dfun_name <- new_dfun_name cls tycon + ; loc <- getSrcSpanM + ; let spec = DS { ds_loc = loc, ds_orig = orig + , ds_name = dfun_name, ds_tvs = dict_tvs + , ds_cls = cls, ds_tys = inst_tys + , ds_theta = mtheta `orElse` all_preds + , ds_newtype = True } + ; return (if isJust mtheta then Just (Right spec) + else Just (Left spec)) } | 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 - ; return (Just eqn, Nothing) } + = mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta -- Otherwise we can't derive - | gla_exts = baleOut cant_derive_err -- Too hard - | otherwise = baleOut std_err -- Just complain about being a non-std instance + | 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, ...) @@ -700,13 +791,6 @@ mkNewTypeEqn orig gla_exts overlap_flag tvs cls cls_tys -- instance C Int => C T dict_tvs = filterOut (`elemVarSet` dropped_tvs) tvs all_preds = rep_pred : sc_theta -- NB: rep_pred comes first - (dict_args, ntd_info) | null dict_tvs = ([], Just all_preds) - | otherwise = (all_preds, Nothing) - - -- Finally! Here's where we build the dictionary Id - mk_inst_spec dfun_name = mkLocalInstance dfun overlap_flag - where - dfun = mkDictFunId dfun_name dict_tvs dict_args cls inst_tys ------------------------------------------------------------------- -- Figuring out whether we can only do this newtype-deriving thing @@ -796,58 +880,58 @@ ordered by sorting on type varible, tv, (major key) and then class, k, \end{itemize} \begin{code} -solveDerivEqns :: OverlapFlag - -> [DerivEqn] - -> TcM [Instance]-- Solns in same order as eqns. - -- This bunch is Absolutely minimal... - -solveDerivEqns overlap_flag orig_eqns - = do { traceTc (text "solveDerivEqns" <+> vcat (map pprDerivEqn orig_eqns)) - ; iterateDeriv 1 initial_solutions } +inferInstanceContexts :: OverlapFlag -> [DerivSpec] -> TcM [DerivSpec] + +inferInstanceContexts _ [] = return [] + +inferInstanceContexts oflag infer_specs + = do { traceTc (text "inferInstanceContexts" <+> vcat (map pprDerivSpec infer_specs)) + ; iterate_deriv 1 initial_solutions } where + ------------------------------------------------------------------ -- The initial solutions for the equations claim that each -- instance has an empty context; this solution is certainly -- in canonical form. - initial_solutions :: [DerivSoln] - initial_solutions = [ [] | _ <- orig_eqns ] + initial_solutions :: [ThetaType] + initial_solutions = [ [] | _ <- infer_specs ] ------------------------------------------------------------------ - -- iterateDeriv calculates the next batch of solutions, + -- iterate_deriv calculates the next batch of solutions, -- compares it with the current one; finishes if they are the -- same, otherwise recurses with the new solutions. -- It fails if any iteration fails - iterateDeriv :: Int -> [DerivSoln] -> TcM [Instance] - iterateDeriv n current_solns + iterate_deriv :: Int -> [ThetaType] -> TcM [DerivSpec] + iterate_deriv n current_solns | n > 20 -- Looks as if we are in an infinite loop -- This can happen if we have -fallow-undecidable-instances -- (See TcSimplify.tcSimplifyDeriv.) = pprPanic "solveDerivEqns: probable loop" - (vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns) + (vcat (map pprDerivSpec infer_specs) $$ ppr current_solns) | otherwise - = let - inst_specs = zipWithEqual "add_solns" mk_inst_spec - orig_eqns current_solns - in - checkNoErrs ( - -- Extend the inst info from the explicit instance decls + = do { -- Extend the inst info from the explicit instance decls -- with the current set of solutions, and simplify each RHS - extendLocalInstEnv inst_specs $ - mappM gen_soln orig_eqns - ) `thenM` \ new_solns -> - if (current_solns == new_solns) then - returnM inst_specs - else - iterateDeriv (n+1) new_solns + let inst_specs = zipWithEqual "add_solns" (mkInstance2 oflag) + current_solns infer_specs + ; new_solns <- checkNoErrs $ + extendLocalInstEnv inst_specs $ + mapM gen_soln infer_specs + + ; if (current_solns == new_solns) then + return [ spec { ds_theta = soln } + | (spec, soln) <- zip infer_specs current_solns ] + else + iterate_deriv (n+1) new_solns } ------------------------------------------------------------------ - gen_soln :: DerivEqn -> TcM [PredType] - gen_soln (loc, orig, _, tyvars, clas, inst_ty, deriv_rhs) + gen_soln :: DerivSpec -> TcM [PredType] + gen_soln (DS { ds_loc = loc, ds_orig = orig, ds_tvs = tyvars + , ds_cls = clas, ds_tys = inst_tys, ds_theta = deriv_rhs }) = setSrcSpan loc $ + addErrCtxt (derivInstCtxt clas inst_tys) $ 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_tys + -- 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 ... @@ -861,14 +945,20 @@ 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 + +------------------------------------------------------------------ +mkInstance1 :: OverlapFlag -> DerivSpec -> Instance +mkInstance1 overlap_flag spec = mkInstance2 overlap_flag (ds_theta spec) spec + +mkInstance2 :: OverlapFlag -> ThetaType -> DerivSpec -> Instance +mkInstance2 overlap_flag theta + (DS { ds_name = dfun_name + , ds_tvs = tyvars, ds_cls = clas, ds_tys = tys }) + = mkLocalInstance dfun overlap_flag + where + dfun = mkDictFunId dfun_name tyvars theta clas tys - ------------------------------------------------------------------ - mk_inst_spec :: DerivEqn -> DerivSoln -> Instance - mk_inst_spec (loc, orig, dfun_name, tyvars, clas, inst_ty, _) theta - = mkLocalInstance dfun overlap_flag - where - dfun = mkDictFunId dfun_name tyvars theta clas [inst_ty] extendLocalInstEnv :: [Instance] -> TcM a -> TcM a -- Add new locally-defined instances; don't bother to check @@ -880,25 +970,6 @@ 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)). - %************************************************************************ %* * @@ -970,17 +1041,23 @@ the renamer. What a great hack! -- Representation tycons differ from the tycon in the instance signature in -- case of instances for indexed families. -- -genInst :: Instance -> TcM ((InstInfo, TyCon), LHsBinds RdrName) -genInst spec +genInst :: OverlapFlag -> DerivSpec -> TcM (InstInfo, DerivAuxBinds) +genInst oflag spec + | ds_newtype spec + = return (InstInfo { iSpec = mkInstance1 oflag spec + , iBinds = NewTypeDerived }, []) + + | otherwise = do { fix_env <- getFixityEnv ; let - (tyvars,_,clas,[ty]) = instanceHead spec + inst = mkInstance1 oflag spec + (tyvars,_,clas,[ty]) = instanceHead inst clas_nm = className clas (visible_tycon, tyArgs) = tcSplitTyConApp ty -- 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 @@ -989,39 +1066,34 @@ genInst spec -- *non-renamed* auxiliary bindings ; (rn_meth_binds, _fvs) <- discardWarnings $ bindLocalNames (map Var.varName tyvars) $ - rnMethodBinds clas_nm (\n -> []) [] meth_binds + rnMethodBinds clas_nm (\_ -> []) [] meth_binds -- Build the InstInfo - ; return ((InstInfo { iSpec = spec, - iBinds = VanillaInst rn_meth_binds [] }, tycon), + ; return (InstInfo { iSpec = inst, + iBinds = VanillaInst rn_meth_binds [] }, aux_binds) } +genDerivBinds :: Class -> FixityEnv -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) genDerivBinds clas fix_env tycon | className clas `elem` typeableClassNames - = (gen_Typeable_binds tycon, emptyLHsBinds) + = (gen_Typeable_binds tycon, []) | otherwise = case assocMaybe gen_list (getUnique clas) of - Just gen_fn -> gen_fn fix_env tycon + Just gen_fn -> gen_fn tycon Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas) where - gen_list :: [(Unique, FixityEnv -> TyCon -> (LHsBinds RdrName, LHsBinds RdrName))] - gen_list = [(eqClassKey, no_aux_binds (ignore_fix_env gen_Eq_binds)) - ,(ordClassKey, no_aux_binds (ignore_fix_env gen_Ord_binds)) - ,(enumClassKey, no_aux_binds (ignore_fix_env gen_Enum_binds)) - ,(boundedClassKey, no_aux_binds (ignore_fix_env gen_Bounded_binds)) - ,(ixClassKey, no_aux_binds (ignore_fix_env gen_Ix_binds)) - ,(typeableClassKey,no_aux_binds (ignore_fix_env gen_Typeable_binds)) - ,(showClassKey, no_aux_binds gen_Show_binds) - ,(readClassKey, no_aux_binds gen_Read_binds) - ,(dataClassKey, gen_Data_binds) + gen_list :: [(Unique, TyCon -> (LHsBinds RdrName, DerivAuxBinds))] + gen_list = [(eqClassKey, gen_Eq_binds) + ,(ordClassKey, gen_Ord_binds) + ,(enumClassKey, gen_Enum_binds) + ,(boundedClassKey, gen_Bounded_binds) + ,(ixClassKey, gen_Ix_binds) + ,(showClassKey, gen_Show_binds fix_env) + ,(readClassKey, gen_Read_binds fix_env) + ,(dataClassKey, gen_Data_binds fix_env) ] - - -- no_aux_binds is used for generators that don't - -- need to produce any auxiliary bindings - no_aux_binds f fix_env tc = (f fix_env tc, emptyLHsBinds) - ignore_fix_env f fix_env tc = f tc \end{code} @@ -1031,79 +1103,8 @@ genDerivBinds clas fix_env tycon %* * %************************************************************************ - -data Foo ... = ... - -con2tag_Foo :: Foo ... -> Int# -tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int# -maxtag_Foo :: Int -- ditto (NB: not unlifted) - - -We have a @con2tag@ function for a tycon if: -\begin{itemize} -\item -We're deriving @Eq@ and the tycon has nullary data constructors. - -\item -Or: we're deriving @Ord@ (unless single-constructor), @Enum@, @Ix@ -(enum type only????) -\end{itemize} - -We have a @tag2con@ function for a tycon if: -\begin{itemize} -\item -We're deriving @Enum@, or @Ix@ (enum type only???) -\end{itemize} - -If we have a @tag2con@ function, we also generate a @maxtag@ constant. - -\begin{code} -genTaggeryBinds :: [(InstInfo, TyCon)] -> TcM (LHsBinds RdrName) -genTaggeryBinds infos - = do { names_so_far <- foldlM do_con2tag [] tycons_of_interest - ; nm_alist_etc <- foldlM do_tag2con names_so_far tycons_of_interest - ; return (listToBag (map gen_tag_n_con_monobind nm_alist_etc)) } - where - all_CTs = [ (fst (simpleInstInfoClsTy info), tc) - | (info, tc) <- infos] - all_tycons = map snd all_CTs - (tycons_of_interest, _) = removeDups compare all_tycons - - do_con2tag acc_Names tycon - | isDataTyCon tycon && - ((we_are_deriving eqClassKey tycon - && any isNullarySrcDataCon (tyConDataCons tycon)) - || (we_are_deriving ordClassKey tycon - && not (isProductTyCon tycon)) - || (we_are_deriving enumClassKey tycon) - || (we_are_deriving ixClassKey tycon)) - - = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag) - : acc_Names) - | otherwise - = returnM acc_Names - - do_tag2con acc_Names tycon - | isDataTyCon tycon && - (we_are_deriving enumClassKey tycon || - we_are_deriving ixClassKey tycon - && isEnumerationTyCon tycon) - = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con) - : (maxtag_RDR tycon, tycon, GenMaxTag) - : acc_Names) - | otherwise - = returnM acc_Names - - we_are_deriving clas_key tycon - = is_in_eqns clas_key tycon all_CTs - where - is_in_eqns clas_key tycon [] = False - is_in_eqns clas_key tycon ((c,t):cts) - = (clas_key == classKey c && tycon == t) - || is_in_eqns clas_key tycon cts -\end{code} - \begin{code} +derivingThingErr :: Class -> [Type] -> Type -> Message -> Message derivingThingErr clas tys ty why = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr pred)], @@ -1114,15 +1115,21 @@ 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 :: Class -> [Type] -> Message +derivInstCtxt 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)] -\end{code} - +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") +\end{code}