X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=3974bf001500c8df66d0885fea1811aa590e1ff2;hb=04feba252e40d16101b92948cd1e13c7bc1f3062;hp=9c8bf3486c73b9b67636a1c369a673005b4c132a;hpb=6e6f54693cb89f77701583a55dd39cd4d767c61b;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index 9c8bf34..3974bf0 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -10,51 +10,50 @@ module TcDeriv ( tcDeriving ) where #include "HsVersions.h" -import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..), - collectMonoBinders ) -import RdrHsSyn ( RdrNameMonoBinds ) -import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred ) -import CmdLineOpts ( DynFlag(..) ) +import HsSyn +import DynFlags ( DynFlag(..) ) +import Generics ( mkTyConGenericBinds ) import TcRnMonad -import TcEnv ( tcExtendTempInstEnv, newDFunName, - InstInfo(..), pprInstInfo, InstBindings(..), - pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv +import TcEnv ( newDFunName, pprInstInfoDetails, + InstInfo(..), InstBindings(..), simpleInstInfoClsTy, + tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff -import InstEnv ( simpleDFunClassTyCon ) -import TcMonoType ( tcHsPred ) +import InstEnv ( Instance, OverlapFlag, mkLocalInstance, instanceHead, extendInstEnvList ) +import Inst ( getOverlapFlag ) +import TcHsType ( tcHsDeriv ) import TcSimplify ( tcSimplifyDeriv ) -import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( bindLocalsFV, extendTyVarEnvFVRn ) -import TcRnMonad ( thenM, returnM, mapAndUnzipM ) -import HscTypes ( DFunId ) +import RnBinds ( rnMethodBinds, rnTopBinds ) +import RnEnv ( bindLocalNames ) +import HscTypes ( FixityEnv ) -import BasicTypes ( NewOrData(..) ) import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) -import Subst ( mkTyVarSubst, substTheta ) +import Type ( zipOpenTvSubst, substTheta ) import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) -import Maybes ( maybeToBool, catMaybes ) -import Name ( Name, getSrcLoc, nameUnique ) -import NameSet +import DataCon ( isNullarySrcDataCon, isVanillaDataCon, dataConOrigArgTys ) +import Maybes ( catMaybes ) import RdrName ( RdrName ) - -import TyCon ( tyConTyVars, tyConDataCons, tyConArity, - tyConTheta, maybeTyConSingleCon, isDataTyCon, +import Name ( Name, getSrcLoc ) +import NameSet ( duDefs ) +import Kind ( splitKindFunTys ) +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics, + tyConStupidTheta, isProductTyCon, isDataTyCon, newTyConRhs, isEnumerationTyCon, isRecursiveTyCon, TyCon ) -import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe, - isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, isTypeKind, - tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy ) -import Var ( TyVar, tyVarKind, idType, varName ) +import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, tcTyConAppTyCon, + isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind, + tcEqTypes, tcSplitAppTys, mkAppTys ) +import Var ( TyVar, tyVarKind, varName ) import VarSet ( mkVarSet, subVarSet ) import PrelNames -import Util ( zipWithEqual, sortLt, notNull ) -import ListSetOps ( removeDups, assoc ) +import SrcLoc ( srcLocSpan, Located(..) ) +import Util ( zipWithEqual, sortLe, notNull ) +import ListSetOps ( removeDups, assocMaybe ) import Outputable +import Bag \end{code} %************************************************************************ @@ -182,6 +181,20 @@ 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] +~~~~~~~~~~~~~~~~~~ +Consider this: + class C a b + instance C [a] Char + newtype T = T Char deriving( C [a] ) + +Notice the free 'a' in the deriving. We have to fill this out to + newtype T = T Char deriving( forall a. C [a] ) + +And then translate it to: + instance C [a] Char => C [a] T where ... + + %************************************************************************ @@ -191,87 +204,90 @@ version. So now all classes are "offending". %************************************************************************ \begin{code} -tcDeriving :: [RenamedTyClDecl] -- All type constructors - -> TcM ([InstInfo], -- The generated "instance decls". - RenamedHsBinds, -- Extra generated bindings - FreeVars) -- These are free in the generated bindings +tcDeriving :: [LTyClDecl Name] -- All type constructors + -> TcM ([InstInfo], -- The generated "instance decls" + HsValBinds Name) -- Extra generated top-level bindings tcDeriving tycl_decls - = recoverM (returnM ([], EmptyBinds, emptyFVs)) $ - getDOpts `thenM` \ dflags -> - - -- Fish the "deriving"-related information out of the TcEnv - -- and make the necessary "equations". - makeDerivEqns tycl_decls `thenM` \ (ordinary_eqns, newtype_inst_info) -> - tcExtendTempInstEnv (map iDFunId newtype_inst_info) $ - -- Add the newtype-derived instances to the inst env - -- before tacking the "ordinary" ones + = recoverM (returnM ([], emptyValBindsOut)) $ + do { -- Fish the "deriving"-related information out of the TcEnv + -- and make the necessary "equations". + overlap_flag <- getOverlapFlag + ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns overlap_flag tycl_decls + + ; (ordinary_inst_info, deriv_binds) + <- extendLocalInstEnv (map iSpec newtype_inst_info) $ + deriveOrdinaryStuff overlap_flag ordinary_eqns + -- Add the newtype-derived instances to the inst env + -- before tacking the "ordinary" ones + + ; let inst_info = newtype_inst_info ++ ordinary_inst_info + + -- 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 + { + + -- Generate the generic to/from functions from each type declaration + ; 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 + ; 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) } + + + ; dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info rn_binds)) + + ; returnM (inst_info, rn_binds) + }} + where + ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc + ddump_deriving inst_infos extra_binds + = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds - deriveOrdinaryStuff ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) -> - let - inst_info = newtype_inst_info ++ ordinary_inst_info - in +----------------------------------------- +deriveOrdinaryStuff overlap_flag [] -- Short cut + = returnM ([], emptyLHsBinds) - ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving inst_info binds)) `thenM_` +deriveOrdinaryStuff overlap_flag eqns + = do { -- Take the equation list and solve it, to deliver a list of + -- solutions, a.k.a. the contexts for the instance decls + -- required for the corresponding equations. + inst_specs <- solveDerivEqns overlap_flag eqns - returnM (inst_info, binds, fvs) + -- Generate the InstInfo for each dfun, + -- plus any auxiliary bindings it needs + ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst inst_specs - where - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc - ddump_deriving inst_infos extra_binds - = vcat (map ppr_info inst_infos) $$ ppr extra_binds + -- Generate any extra not-one-inst-decl-specific binds, + -- notably "con2tag" and/or "tag2con" functions. + ; extra_binds <- genTaggeryBinds inst_infos - ppr_info inst_info = pprInstInfo inst_info $$ - nest 4 (pprInstInfoDetails inst_info) - -- pprInstInfo doesn't print much: only the type + -- Done + ; returnM (inst_infos, unionManyBags (extra_binds : aux_binds_s)) + } ----------------------------------------- -deriveOrdinaryStuff [] -- Short cut - = returnM ([], EmptyBinds, emptyFVs) - -deriveOrdinaryStuff eqns - = -- 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. - solveDerivEqns eqns `thenM` \ new_dfuns -> - - -- Now augment the InstInfos, adding in the rather boring - -- actual-code-to-do-the-methods binds. We may also need to - -- generate extra not-one-inst-decl-specific binds, notably - -- "con2tag" and/or "tag2con" functions. We do these - -- separately. - gen_taggery_Names new_dfuns `thenM` \ nm_alist_etc -> - - let - extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc - extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list - mbinders = collectMonoBinders extra_mbinds - in - mappM gen_bind new_dfuns `thenM` \ rdr_name_inst_infos -> - - traceTc (text "tcDeriv" <+> vcat (map ppr rdr_name_inst_infos)) `thenM_` - getModule `thenM` \ this_mod -> - initRn (InterfaceMode this_mod) ( - -- Rename to get RenamedBinds. - -- The only tricky bit is that the extra_binds must scope - -- over the method bindings for the instances. - bindLocalsFV (ptext (SLIT("deriving"))) mbinders $ \ _ -> - rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, dus) -> - mapAndUnzipM rn_inst_info rdr_name_inst_infos `thenM` \ (rn_inst_infos, fvs_s) -> - returnM ((rn_inst_infos, rn_extra_binds), - duUses dus `plusFV` plusFVs fvs_s) - ) `thenM` \ ((rn_inst_infos, rn_extra_binds), fvs) -> - returnM (rn_inst_infos, rn_extra_binds, fvs) - - where - rn_inst_info (dfun, binds) - = extendTyVarEnvFVRn (map varName tyvars) $ - -- Bring the right type variables into scope - rnMethodBinds (className cls) [] binds `thenM` \ (rn_binds, fvs) -> - return (InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_binds [] }, fvs) - where - (tyvars, _, cls, _) = tcSplitDFunTy (idType dfun) +mkGenericBinds tycl_decls + = do { tcs <- mapM tcLookupTyCon + [ tc_name | + L _ (TyData { tcdLName = L _ tc_name }) <- tycl_decls] + -- We are only interested in the data type declarations + ; return (unionManyBags [ mkTyConGenericBinds tc | + tc <- tcs, tyConHasGenerics tc ]) } + -- And then only in the ones whose 'has-generics' flag is on \end{code} @@ -297,71 +313,58 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: [RenamedTyClDecl] +makeDerivEqns :: OverlapFlag + -> [LTyClDecl Name] -> TcM ([DerivEqn], -- Ordinary derivings [InstInfo]) -- Special newtype derivings -makeDerivEqns tycl_decls +makeDerivEqns overlap_flag tycl_decls = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) -> returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ - derive_these :: [(NewOrData, Name, RenamedHsPred)] + derive_these :: [(NewOrData, Name, LHsType Name)] -- Find the (nd, TyCon, Pred) pairs that must be `derived' - -- NB: only source-language decls have deriving, no imported ones do derive_these = [ (nd, tycon, pred) - | TyData {tcdND = nd, tcdName = tycon, tcdDerivs = Just preds} <- tycl_decls, + | L _ (TyData { tcdND = nd, tcdLName = L _ tycon, + tcdDerivs = Just preds }) <- tycl_decls, pred <- preds ] ------------------------------------------------------------------ - mk_eqn :: (NewOrData, Name, RenamedHsPred) -> TcM (Maybe DerivEqn, Maybe InstInfo) + mk_eqn :: (NewOrData, Name, LHsType Name) -> TcM (Maybe DerivEqn, Maybe InstInfo) -- We swizzle the tyvars and datacons out of the tycon -- to make the rest of the equation + -- + -- The "deriv_ty" is a LHsType to take account of the fact that for newtype derivign + -- we allow deriving (forall a. C [a]). - mk_eqn (new_or_data, tycon_name, pred) + mk_eqn (new_or_data, tycon_name, hs_deriv_ty) = tcLookupTyCon tycon_name `thenM` \ tycon -> - addSrcLoc (getSrcLoc tycon) $ + setSrcSpan (srcLocSpan (getSrcLoc tycon)) $ addErrCtxt (derivCtxt Nothing tycon) $ tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention -- the type variables for the type constructor - tcHsPred pred `thenM` \ pred' -> - case getClassPredTys_maybe pred' of - Nothing -> bale_out (malformedPredErr tycon pred) - Just (clas, tys) -> doptM Opt_GlasgowExts `thenM` \ gla_exts -> - mk_eqn_help gla_exts new_or_data tycon clas tys + tcHsDeriv hs_deriv_ty `thenM` \ (deriv_tvs, clas, tys) -> + doptM Opt_GlasgowExts `thenM` \ gla_exts -> + mk_eqn_help gla_exts new_or_data tycon deriv_tvs clas tys ------------------------------------------------------------------ - mk_eqn_help gla_exts DataType tycon clas tys - | Just err <- chk_out gla_exts clas tycon tys - = bale_out (derivingThingErr clas tys tycon tyvars err) + mk_eqn_help gla_exts DataType tycon deriv_tvs clas tys + | Just err <- checkSideConditions gla_exts tycon deriv_tvs clas tys + = bale_out (derivingThingErr clas tys tycon (tyConTyVars tycon) err) | otherwise - = new_dfun_name clas tycon `thenM` \ dfun_name -> - returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing) - where - tyvars = tyConTyVars tycon - data_cons = tyConDataCons tycon - constraints = extra_constraints ++ - [ mkClassPred clas [arg_ty] - | data_con <- tyConDataCons tycon, - arg_ty <- dataConOrigArgTys data_con, - -- Use the same type variables - -- as the type constructor, - -- hence no need to instantiate - not (isUnLiftedType arg_ty) -- No constraints for unlifted types? - ] - - -- "extra_constraints": see note [Data decl contexts] above - extra_constraints = tyConTheta tycon + = do { eqn <- mkDataTypeEqn tycon clas + ; returnM (Just eqn, Nothing) } - mk_eqn_help gla_exts NewType tycon clas tys - | can_derive_via_isomorphism && (gla_exts || standard_class gla_exts clas) + mk_eqn_help gla_exts NewType tycon deriv_tvs clas tys + | can_derive_via_isomorphism && (gla_exts || std_class_via_iso clas) = -- Go ahead and use the isomorphism traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_` new_dfun_name clas tycon `thenM` \ dfun_name -> - returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name, + returnM (Nothing, Just (InstInfo { iSpec = mk_inst_spec dfun_name, iBinds = NewTypeDerived rep_tys })) - | standard_class gla_exts clas - = mk_eqn_help gla_exts DataType tycon clas tys -- Go via bale-out route + | std_class gla_exts clas + = mk_eqn_help gla_exts DataType tycon deriv_tvs clas tys -- Go via bale-out route | otherwise -- Non-standard instance = bale_out (if gla_exts then @@ -371,43 +374,46 @@ makeDerivEqns tycl_decls where -- Here is the plan for newtype derivings. We see -- newtype T a1...an = T (t ak...an) deriving (.., C s1 .. sm, ...) - -- where aj...an do not occur free in t, and the (C s1 ... sm) is a - -- *partial applications* of class C with the last parameter missing + -- where t is a type, + -- ak...an is a suffix of a1..an + -- ak...an do not occur free in t, + -- (C s1 ... sm) is a *partial applications* of class C + -- with the last parameter missing -- -- We generate the instances - -- instance C s1 .. sm (t ak...aj) => C s1 .. sm (T a1...aj) - -- where T a1...aj is the partial application of the LHS of the correct kind + -- instance C s1 .. sm (t ak...ap) => C s1 .. sm (T a1...ap) + -- where T a1...ap is the partial application of the LHS of the correct kind + -- and p >= k -- -- Running example: newtype T s a = MkT (ST s a) deriving( Monad ) -- instance Monad (ST s) => Monad (T s) where -- fail = coerce ... (fail @ ST s) + -- (Actually we don't need the coerce, because non-rec newtypes are transparent clas_tyvars = classTyVars clas kind = tyVarKind (last clas_tyvars) -- Kind of the thing we want to instance -- e.g. argument kind of Monad, *->* - (arg_kinds, _) = tcSplitFunTys kind + (arg_kinds, _) = splitKindFunTys kind n_args_to_drop = length arg_kinds -- 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] - -- We must not use newTyConRep to get the representation - -- type, because that looks through all intermediate newtypes - -- To get the RHS of *this* newtype, just look at the data - -- constructor. For example + -- Need newTyConRhs *not* newTyConRep to get the representation + -- type, because the latter looks through all intermediate newtypes + -- 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, -- when making the Num instance of A! - tyvars = tyConTyVars tycon - rep_ty = head (dataConOrigArgTys (head (tyConDataCons tycon))) + (tc_tvs, rep_ty) = newTyConRhs tycon (rep_fn, rep_ty_args) = tcSplitAppTys rep_ty n_tyvars_to_keep = tyConArity tycon - n_args_to_drop - tyvars_to_drop = drop n_tyvars_to_keep tyvars - tyvars_to_keep = take n_tyvars_to_keep tyvars + tyvars_to_drop = drop n_tyvars_to_keep tc_tvs + tyvars_to_keep = take n_tyvars_to_keep tc_tvs n_args_to_keep = length rep_ty_args - n_args_to_drop args_to_drop = drop n_args_to_keep rep_ty_args @@ -438,26 +444,30 @@ makeDerivEqns tycl_decls -- There's no 'corece' needed because after the type checker newtypes -- are transparent. - sc_theta = substTheta (mkTyVarSubst clas_tyvars inst_tys) + sc_theta = substTheta (zipOpenTvSubst clas_tyvars inst_tys) (classSCTheta clas) -- If there are no tyvars, there's no need -- to abstract over the dictionaries we need - dict_args | null tyvars = [] - | otherwise = rep_pred : sc_theta + dict_tvs = deriv_tvs ++ tc_tvs + dict_args | null dict_tvs = [] + | otherwise = rep_pred : sc_theta -- Finally! Here's where we build the dictionary Id - mk_dfun dfun_name = mkDictFunId dfun_name tyvars dict_args clas inst_tys + mk_inst_spec dfun_name + = mkLocalInstance dfun overlap_flag + where + dfun = mkDictFunId dfun_name dict_tvs dict_args clas inst_tys ------------------------------------------------------------------- -- Figuring out whether we can only do this newtype-deriving thing right_arity = length tys + 1 == classArity clas + -- Never derive Read,Show,Typeable,Data this way + non_iso_classes = [readClassKey, showClassKey, typeableClassKey, dataClassKey] can_derive_via_isomorphism - = not (clas `hasKey` readClassKey) -- Never derive Read,Show,Typeable this way - && not (clas `hasKey` showClassKey) - && not (clas `hasKey` typeableClassKey) + = not (getUnique clas `elem` non_iso_classes) && right_arity -- Well kinded; -- eg not: newtype T ... deriving( ST ) -- because ST needs *2* type params @@ -470,6 +480,14 @@ makeDerivEqns tycl_decls -- newtype A = MkA [A] -- Don't want -- instance Eq [A] => Eq A !! + -- Here's a recursive newtype that's actually OK + -- newtype S1 = S1 [T1 ()] + -- newtype T1 a = T1 (StateT S1 IO a ) deriving( Monad ) + -- It's currently rejected. Oh well. + -- In fact we generate an instance decl that has method of form + -- meth @ instTy = meth @ repTy + -- (no coerce's). We'd need a coerce if we wanted to handle + -- recursive newtypes too -- Check that eta reduction is OK -- (a) the dropped-off args are identical @@ -501,44 +519,145 @@ makeDerivEqns tycl_decls bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing) - standard_class gla_exts clas = key `elem` derivableClassKeys - || (gla_exts && (key == typeableClassKey || key == traverseClassKey)) - where - key = classKey clas - ------------------------------------------------------------------ - chk_out :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc - chk_out gla_exts clas tycon tys - | notNull tys = Just ty_args_why - | not (standard_class gla_exts clas) = Just (non_std_why clas) - | clas `hasKey` enumClassKey && not is_enumeration = Just nullary_why - | clas `hasKey` boundedClassKey && not is_enumeration_or_single = Just single_nullary_why - | clas `hasKey` ixClassKey && not is_enumeration_or_single = Just single_nullary_why - | clas `hasKey` typeableClassKey && not all_type_kind = Just not_type_kind_why - | null data_cons = Just no_cons_why - | any isExistentialDataCon data_cons = Just existential_why - | otherwise = Nothing - where - data_cons = tyConDataCons tycon - is_enumeration = isEnumerationTyCon tycon - is_single_con = maybeToBool (maybeTyConSingleCon tycon) - is_enumeration_or_single = is_enumeration || is_single_con - all_type_kind = all (isTypeKind . tyVarKind) (tyConTyVars tycon) - - single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected") - nullary_why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors") - no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors") - ty_args_why = quotes (ppr pred) <+> ptext SLIT("is not a class") - existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)") - not_type_kind_why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'") - - pred = mkClassPred clas tys +std_class gla_exts clas + = key `elem` derivableClassKeys + || (gla_exts && (key == typeableClassKey || key == dataClassKey)) + where + key = classKey clas + +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] + -- Not Read/Show because they respect the type + -- Not Enum, becuase newtypes are never in Enum -non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class") new_dfun_name clas tycon -- Just a simple wrapper = newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon) -- The type passed to newDFunName is only used to generate -- a suitable string; hence the empty type arg list + +------------------------------------------------------------------ +mkDataTypeEqn :: TyCon -> Class -> TcM DerivEqn +mkDataTypeEqn tycon clas + | clas `hasKey` typeableClassKey + = -- The Typeable class is special in several ways + -- data T a b = ... deriving( Typeable ) + -- gives + -- instance Typeable2 T where ... + -- Notice that: + -- 1. There are no constraints in the instance + -- 2. There are no type variables either + -- 3. The actual class we want to generate isn't necessarily + -- 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 (dfun_name, real_clas, tycon, [], []) } + + | otherwise + = do { dfun_name <- new_dfun_name clas tycon + ; return (dfun_name, clas, tycon, tyvars, constraints) } + where + tyvars = tyConTyVars tycon + constraints = extra_constraints ++ ordinary_constraints + extra_constraints = tyConStupidTheta tycon + -- "extra_constraints": see note [Data decl contexts] above + + ordinary_constraints + = [ mkClassPred clas [arg_ty] + | data_con <- tyConDataCons tycon, + arg_ty <- dataConOrigArgTys data_con, + not (isUnLiftedType arg_ty) -- No constraints for unlifted types? + ] + + +------------------------------------------------------------------ +-- Check side conditions that dis-allow derivability for particular classes +-- This is *apart* from the newtype-deriving mechanism + +checkSideConditions :: Bool -> TyCon -> [TyVar] -> Class -> [TcType] -> Maybe SDoc +checkSideConditions gla_exts tycon deriv_tvs clas tys + | notNull deriv_tvs || notNull tys + = Just ty_args_why -- e.g. deriving( Foo s ) + | otherwise + = case [cond | (key,cond) <- sideConditions, key == getUnique clas] of + [] -> Just (non_std_why clas) + [cond] -> cond (gla_exts, tycon) + other -> pprPanic "checkSideConditions" (ppr clas) + where + ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class") + +non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class") + +sideConditions :: [(Unique, Condition)] +sideConditions + = [ (eqClassKey, cond_std), + (ordClassKey, cond_std), + (readClassKey, cond_std), + (showClassKey, cond_std), + (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) + ] + +type Condition = (Bool, TyCon) -> Maybe SDoc -- Nothing => OK + +orCond :: Condition -> Condition -> Condition +orCond c1 c2 tc + = case c1 tc of + Nothing -> Nothing -- c1 succeeds + Just x -> case c2 tc of -- c1 fails + Nothing -> Nothing + Just y -> Just (x $$ ptext SLIT(" and") $$ y) + -- Both fail + +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, tycon) + | any (not . isVanillaDataCon) data_cons = Just existential_why + | null data_cons = Just no_cons_why + | otherwise = Nothing + where + data_cons = tyConDataCons tycon + no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors") + existential_why = quotes (ppr tycon) <+> ptext SLIT("has non-Haskell-98 constructor(s)") + +cond_isEnumeration :: Condition +cond_isEnumeration (gla_exts, tycon) + | isEnumerationTyCon tycon = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors") + +cond_isProduct :: Condition +cond_isProduct (gla_exts, tycon) + | isProductTyCon tycon = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> 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, tycon) + | tyConArity tycon > 7 = Just too_many + | not (all (isArgTypeKind . tyVarKind) (tyConTyVars tycon)) = Just bad_kind + | otherwise = Nothing + where + too_many = quotes (ppr tycon) <+> ptext SLIT("has too many arguments") + bad_kind = quotes (ppr tycon) <+> ptext SLIT("has arguments of kind other than `*'") + +cond_glaExts :: Condition +cond_glaExts (gla_exts, tycon) | gla_exts = Nothing + | otherwise = Just why + where + why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class") \end{code} %************************************************************************ @@ -562,11 +681,12 @@ ordered by sorting on type varible, tv, (major key) and then class, k, \end{itemize} \begin{code} -solveDerivEqns :: [DerivEqn] - -> TcM [DFunId] -- Solns in same order as eqns. +solveDerivEqns :: OverlapFlag + -> [DerivEqn] + -> TcM [Instance]-- Solns in same order as eqns. -- This bunch is Absolutely minimal... -solveDerivEqns orig_eqns +solveDerivEqns overlap_flag orig_eqns = iterateDeriv 1 initial_solutions where -- The initial solutions for the equations claim that each @@ -580,7 +700,7 @@ solveDerivEqns orig_eqns -- 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 [DFunId] + iterateDeriv :: Int -> [DerivSoln] -> TcM [Instance] iterateDeriv n current_solns | n > 20 -- Looks as if we are in an infinite loop -- This can happen if we have -fallow-undecidable-instances @@ -589,30 +709,42 @@ solveDerivEqns orig_eqns (vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns) | otherwise = let - dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns + inst_specs = zipWithEqual "add_solns" mk_inst_spec + orig_eqns current_solns in checkNoErrs ( -- Extend the inst info from the explicit instance decls -- with the current set of solutions, and simplify each RHS - tcExtendTempInstEnv dfuns $ + extendLocalInstEnv inst_specs $ mappM gen_soln orig_eqns ) `thenM` \ new_solns -> if (current_solns == new_solns) then - returnM dfuns + returnM inst_specs else iterateDeriv (n+1) new_solns ------------------------------------------------------------------ - gen_soln (_, clas, tc,tyvars,deriv_rhs) - = addSrcLoc (getSrcLoc tc) $ + = setSrcSpan (srcLocSpan (getSrcLoc tc)) $ addErrCtxt (derivCtxt (Just clas) tc) $ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> - returnM (sortLt (<) theta) -- Canonicalise before returning the soluction + returnM (sortLe (<=) theta) -- Canonicalise before returning the soluction -mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta - = mkDictFunId dfun_name tyvars theta - clas [mkTyConApp tycon (mkTyVarTys tyvars)] + ------------------------------------------------------------------ + mk_inst_spec (dfun_name, clas, tycon, tyvars, _) theta + = mkLocalInstance dfun overlap_flag + where + dfun = mkDictFunId dfun_name tyvars theta clas + [mkTyConApp tycon (mkTyVarTys tyvars)] + +extendLocalInstEnv :: [Instance] -> TcM a -> TcM a +-- Add new locally-defined instances; don't bother to check +-- for functional dependency errors -- that'll happen in TcInstDcls +extendLocalInstEnv dfuns thing_inside + = do { env <- getGblEnv + ; let inst_env' = extendInstEnvList (tcg_inst_env env) dfuns + env' = env { tcg_inst_env = inst_env' } + ; setGblEnv env' thing_inside } \end{code} %************************************************************************ @@ -670,36 +802,64 @@ Much less often (really just for deriving @Ix@), we use a \item We use the renamer!!! Reason: we're supposed to be -producing @RenamedMonoBinds@ for the methods, but that means +producing @LHsBinds Name@ for the methods, but that means producing correctly-uniquified code on the fly. This is entirely possible (the @TcM@ monad has a @UniqueSupply@), but it is painful. -So, instead, we produce @RdrNameMonoBinds@ then heave 'em through +So, instead, we produce @MonoBinds RdrName@ then heave 'em through the renamer. What a great hack! \end{itemize} \begin{code} --- Generate the method bindings for the required instance --- (paired with DFunId, as we need that when renaming --- the method binds) -gen_bind :: DFunId -> TcM (DFunId, RdrNameMonoBinds) -gen_bind dfun - = getFixityEnv `thenM` \ fix_env -> - let - (clas, tycon) = simpleDFunClassTyCon dfun - gen_binds_fn = assoc "gen_bind:bad derived class" - gen_list (getUnique clas) - - 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) - ,(typeableClassKey,gen_Typeable_binds) - ] - in - returnM (dfun, gen_binds_fn tycon) +-- Generate the InstInfo for the required instance, +-- plus any auxiliary bindings required +genInst :: Instance -> TcM (InstInfo, LHsBinds RdrName) +genInst spec + = do { fix_env <- getFixityEnv + ; let + (tyvars,_,clas,[ty]) = instanceHead spec + clas_nm = className clas + tycon = tcTyConAppTyCon ty + (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon + + -- Bring the right type variables into + -- scope, and rename the method binds + -- It's a bit yukky that we return *renamed* InstInfo, but + -- *non-renamed* auxiliary bindings + ; (rn_meth_binds, _fvs) <- discardWarnings $ + bindLocalNames (map varName tyvars) $ + rnMethodBinds clas_nm [] meth_binds + + -- Build the InstInfo + ; return (InstInfo { iSpec = spec, + iBinds = VanillaInst rn_meth_binds [] }, + aux_binds) + } + +genDerivBinds clas fix_env tycon + | className clas `elem` typeableClassNames + = (gen_Typeable_binds tycon, emptyLHsBinds) + + | otherwise + = case assocMaybe gen_list (getUnique clas) of + Just gen_fn -> gen_fn fix_env 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) + ] + + -- 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} @@ -736,25 +896,24 @@ We're deriving @Enum@, or @Ix@ (enum type only???) If we have a @tag2con@ function, we also generate a @maxtag@ constant. \begin{code} -gen_taggery_Names :: [DFunId] - -> TcM [(RdrName, -- for an assoc list - TyCon, -- related tycon - TagThingWanted)] - -gen_taggery_Names dfuns - = foldlM do_con2tag [] tycons_of_interest `thenM` \ names_so_far -> - foldlM do_tag2con names_so_far tycons_of_interest +genTaggeryBinds :: [InstInfo] -> 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 = map simpleDFunClassTyCon dfuns + all_CTs = [ (cls, tcTyConAppTyCon ty) + | info <- infos, + let (cls,ty) = simpleInstInfoClsTy info ] 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 isNullaryDataCon (tyConDataCons tycon)) + && any isNullarySrcDataCon (tyConDataCons tycon)) || (we_are_deriving ordClassKey tycon - && not (maybeToBool (maybeTyConSingleCon tycon))) + && not (isProductTyCon tycon)) || (we_are_deriving enumClassKey tycon) || (we_are_deriving ixClassKey tycon)) @@ -790,8 +949,6 @@ derivingThingErr clas tys tycon tyvars why where pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)]) -malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred - derivCtxt :: Maybe Class -> TyCon -> SDoc derivCtxt maybe_cls tycon = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon)