X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=9ea019053ab2379ff1ff7725ce8fcc328caf1bec;hb=52bd2cc7a9f328e6a7f3f50ac0055a5361f457c1;hp=de7b2b3d2b8408b92881902c9d973c5503257979;hpb=ae969b4759e1914cb44bf126fc56e2e059d050dc;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index de7b2b3..9ea0190 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -10,53 +10,53 @@ module TcDeriv ( tcDeriving ) where #include "HsVersions.h" -import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..), - collectLocatedMonoBinders ) +import HsSyn ( HsBinds(..), TyClDecl(..), MonoBinds(..), + andMonoBindList, collectMonoBinders ) import RdrHsSyn ( RdrNameMonoBinds ) -import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred ) -import CmdLineOpts ( DynFlag(..), DynFlags ) +import RnHsSyn ( RenamedHsBinds, RenamedTyClDecl, RenamedHsPred ) +import CmdLineOpts ( DynFlag(..) ) -import TcMonad -import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo, - tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv +import TcRnMonad +import TcEnv ( tcExtendTempInstEnv, newDFunName, + InstInfo(..), pprInstInfo, InstBindings(..), + pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff -import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv ) +import InstEnv ( simpleDFunClassTyCon ) import TcMonoType ( tcHsPred ) import TcSimplify ( tcSimplifyDeriv ) import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( bindLocatedLocalsRn ) -import RnMonad ( renameDerivedCode, thenRn, mapRn, returnRn ) -import HscTypes ( DFunId, PersistentRenamerState ) - -import BasicTypes ( Fixity, NewOrData(..) ) -import Class ( className, classKey, classTyVars, Class ) -import ErrUtils ( dumpIfSet_dyn, Message ) +import RnEnv ( bindLocalsFV, extendTyVarEnvFVRn ) +import TcRnMonad ( thenM, returnM, mapAndUnzipM ) +import HscTypes ( DFunId ) + +import BasicTypes ( NewOrData(..) ) +import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) +import Subst ( mkTyVarSubst, substTheta ) +import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon ) -import PrelInfo ( needsDataDeclCtxtClassKeys ) +import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) import Maybes ( maybeToBool, catMaybes ) -import Module ( Module ) -import Name ( Name, getSrcLoc, nameUnique ) +import Name ( Name, getSrcLoc ) +import Unique ( Unique, getUnique ) +import NameSet import RdrName ( RdrName ) -import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep, - tyConTheta, maybeTyConSingleCon, isDataTyCon, - isEnumerationTyCon, TyCon +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, + tyConTheta, isProductTyCon, isDataTyCon, + isEnumerationTyCon, isRecursiveTyCon, TyCon ) -import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe, - isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, - tcSplitTyConApp_maybe, tcEqTypes, tyVarsOfTheta ) -import Var ( TyVar, tyVarKind ) +import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp, + getClassPredTys_maybe, + isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, isTypeKind, + tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy ) +import Var ( TyVar, tyVarKind, idType, varName ) import VarSet ( mkVarSet, subVarSet ) import PrelNames -import Util ( zipWithEqual, sortLt, eqListBy ) +import Util ( zipWithEqual, sortLt, notNull ) import ListSetOps ( removeDups, assoc ) import Outputable -import Maybe ( isJust ) -import List ( nub ) -import FastString ( FastString ) \end{code} %************************************************************************ @@ -148,13 +148,16 @@ type DerivEqn = (Name, Class, TyCon, [TyVar], DerivRhs) -- The Name is the name for the DFun we'll build -- The tyvars bind all the variables in the RHS +pprDerivEqn (n,c,tc,tvs,rhs) + = parens (hsep [ppr n, ppr c, ppr tc, ppr tvs] <+> equals <+> ppr rhs) + type DerivRhs = ThetaType type DerivSoln = DerivRhs \end{code} -A note about contexts on data decls -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +[Data decl contexts] A note about contexts on data decls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data (RealFloat a) => Complex a = !a :+ !a deriving( Read ) @@ -176,6 +179,12 @@ context to the instance decl. The "offending classes" are Read, Enum? +FURTHER NOTE ADDED March 2002. In fact, Haskell98 now requires that +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". + + %************************************************************************ %* * @@ -184,91 +193,101 @@ context to the instance decl. The "offending classes" are %************************************************************************ \begin{code} -tcDeriving :: PersistentRenamerState - -> Module -- name of module under scrutiny - -> InstEnv -- What we already know about instances - -> (Name -> Maybe Fixity) -- used in deriving Show and Read - -> [RenamedTyClDecl] -- All type constructors +tcDeriving :: [RenamedTyClDecl] -- All type constructors -> TcM ([InstInfo], -- The generated "instance decls". - RenamedHsBinds) -- Extra generated bindings + RenamedHsBinds, -- Extra generated bindings + FreeVars) -- These are free in the generated bindings -tcDeriving prs mod inst_env get_fixity tycl_decls - = recoverTc (returnTc ([], EmptyBinds)) $ - getDOptsTc `thenNF_Tc` \ dflags -> +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 `thenTc` \ (ordinary_eqns, newtype_inst_info) -> - let + 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 - inst_env1 = extend_inst_env dflags inst_env - (map iDFunId newtype_inst_info) - in - deriveOrdinaryStuff mod prs inst_env1 get_fixity - ordinary_eqns `thenTc` \ (ordinary_inst_info, binds) -> + + deriveOrdinaryStuff ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) -> let inst_info = newtype_inst_info ++ ordinary_inst_info in - ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving inst_info binds)) `thenTc_` + ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info binds)) `thenM_` - returnTc (inst_info, binds) + returnM (inst_info, binds, fvs) where ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc ddump_deriving inst_infos extra_binds - = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds + = vcat (map ppr_info inst_infos) $$ ppr extra_binds + ppr_info inst_info = pprInstInfo inst_info $$ + nest 4 (pprInstInfoDetails inst_info) + -- pprInstInfo doesn't print much: only the type ----------------------------------------- -deriveOrdinaryStuff mod prs inst_env_in get_fixity [] -- Short cut - = returnTc ([], EmptyBinds) +deriveOrdinaryStuff [] -- Short cut + = returnM ([], EmptyBinds, emptyFVs) -deriveOrdinaryStuff mod prs inst_env_in get_fixity eqns +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 inst_env_in eqns `thenTc` \ new_dfuns -> + 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 `thenTc` \ nm_alist_etc -> + gen_taggery_Names new_dfuns `thenM` \ nm_alist_etc -> - tcGetEnv `thenNF_Tc` \ env -> - getDOptsTc `thenNF_Tc` \ dflags -> let extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc - extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list - method_binds_s = map (gen_bind get_fixity) new_dfuns - mbinders = collectLocatedMonoBinders extra_mbinds + extra_mbinds = andMonoBindList 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. - (rn_method_binds_s, rn_extra_binds) - = renameDerivedCode dflags mod prs ( - bindLocatedLocalsRn (ptext (SLIT("deriving"))) mbinders $ \ _ -> - rnTopMonoBinds extra_mbinds [] `thenRn` \ (rn_extra_binds, _) -> - mapRn rn_meths method_binds_s `thenRn` \ rn_method_binds_s -> - returnRn (rn_method_binds_s, rn_extra_binds) - ) - new_inst_infos = zipWith gen_inst_info new_dfuns rn_method_binds_s - in - returnTc (new_inst_infos, rn_extra_binds) + -- 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` \ (pairs, fvs_s) -> + + let + (rn_inst_infos, aux_binds_s) = unzip pairs + all_binds = rn_extra_binds `ThenBinds` foldr ThenBinds EmptyBinds aux_binds_s + in + returnM ((rn_inst_infos, all_binds), + duUses dus `plusFV` plusFVs fvs_s) + ) `thenM` \ ((rn_inst_infos, rn_extra_binds), fvs) -> + returnM (rn_inst_infos, rn_extra_binds, fvs) where - -- Make a Real dfun instead of the dummy one we have so far - gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo - gen_inst_info dfun binds - = InstInfo { iDFunId = dfun, iBinds = binds, iPrags = [] } - - rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) -> - returnRn meths' -- Ignore the free vars returned + rn_inst_info (dfun, (meth_binds, aux_binds)) + = -- Rename the auxiliary bindings + bindLocalsFV (ptext (SLIT("deriving"))) mbinders $ \ _ -> + rnTopMonoBinds aux_binds [] `thenM` \ (rn_aux_binds, dus) -> + + -- Bring the right type variables into scope + extendTyVarEnvFVRn (map varName tyvars) $ + rnMethodBinds (className cls) [] meth_binds `thenM` \ (rn_meth_binds, fvs) -> + + return ((InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_meth_binds [] }, + rn_aux_binds), + duUses dus `plusFV` fvs) + where + mbinders = collectMonoBinders aux_binds + (tyvars, _, cls, _) = tcSplitDFunTy (idType dfun) \end{code} @@ -299,8 +318,8 @@ makeDerivEqns :: [RenamedTyClDecl] [InstInfo]) -- Special newtype derivings makeDerivEqns tycl_decls - = mapAndUnzipTc mk_eqn derive_these `thenTc` \ (maybe_ordinaries, maybe_newtypes) -> - returnTc (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) + = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) -> + returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ derive_these :: [(NewOrData, Name, RenamedHsPred)] @@ -311,73 +330,86 @@ makeDerivEqns tycl_decls pred <- preds ] ------------------------------------------------------------------ - mk_eqn :: (NewOrData, Name, RenamedHsPred) -> NF_TcM (Maybe DerivEqn, Maybe InstInfo) + mk_eqn :: (NewOrData, Name, RenamedHsPred) -> TcM (Maybe DerivEqn, Maybe InstInfo) -- We swizzle the tyvars and datacons out of the tycon -- to make the rest of the equation mk_eqn (new_or_data, tycon_name, pred) - = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> - tcAddSrcLoc (getSrcLoc tycon) $ - tcAddErrCtxt (derivCtxt Nothing tycon) $ + = tcLookupTyCon tycon_name `thenM` \ tycon -> + addSrcLoc (getSrcLoc tycon) $ + addErrCtxt (derivCtxt Nothing tycon) $ tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention -- the type variables for the type constructor - tcHsPred pred `thenTc` \ pred' -> + tcHsPred pred `thenM` \ pred' -> case getClassPredTys_maybe pred' of Nothing -> bale_out (malformedPredErr tycon pred) - Just (clas, tys) -> mk_eqn_help new_or_data tycon clas tys + Just (clas, tys) -> doptM Opt_GlasgowExts `thenM` \ gla_exts -> + mk_eqn_help gla_exts new_or_data tycon clas tys ------------------------------------------------------------------ - mk_eqn_help DataType tycon clas tys - | Just err <- chk_out clas tycon tys + mk_eqn_help gla_exts DataType tycon clas tys + | Just err <- checkSideConditions gla_exts clas tycon tys = bale_out (derivingThingErr clas tys tycon tyvars err) | otherwise - = new_dfun_name clas tycon `thenNF_Tc` \ dfun_name -> - returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing) + = 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 <- dataConRepArgTys 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 notes above about contexts on data decls - extra_constraints | offensive_class = tyConTheta tycon - | otherwise = [] - - offensive_class = classKey clas `elem` needsDataDeclCtxtClassKeys - - - mk_eqn_help NewType tycon clas tys - = doptsTc Opt_GlasgowExts `thenTc` \ gla_exts -> - if can_derive_via_isomorphism && (gla_exts || standard_instance) then - -- Go ahead and use the isomorphism - new_dfun_name clas tycon `thenNF_Tc` \ dfun_name -> - returnTc (Nothing, Just (NewTypeDerived (mk_dfun dfun_name))) - else - if standard_instance then - mk_eqn_help DataType tycon clas [] -- Go via bale-out route - else - bale_out cant_derive_err + constraints = extra_constraints ++ ordinary_constraints + -- "extra_constraints": see note [Data decl contexts] above + extra_constraints = tyConTheta tycon + + ordinary_constraints + | clas `hasKey` typeableClassKey -- For the Typeable class, the constraints + -- don't involve the constructor ags, only + -- the tycon tyvars + -- e.g. data T a b = ... + -- we want + -- instance (Typeable a, Typable b) + -- => Typeable (T a b) where + = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] + | otherwise + = [ 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? + ] + + mk_eqn_help gla_exts NewType tycon clas tys + | can_derive_via_isomorphism && (gla_exts || standard_class gla_exts 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, + iBinds = NewTypeDerived rep_tys })) + | standard_class gla_exts clas + = mk_eqn_help gla_exts DataType tycon clas tys -- Go via bale-out route + + | otherwise -- Non-standard instance + = bale_out (if gla_exts then + cant_derive_err -- Too hard + else + non_std_err) -- Just complain about being a non-std instance where -- Here is the plan for newtype derivings. We see - -- newtype T a1...an = T (t ak...an) deriving (C1...Cm) - -- where aj...an do not occur free in t, and the Ci are *partial applications* of - -- classes with the last parameter missing + -- 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 -- -- We generate the instances - -- instance Ci (t ak...aj) => Ci (T a1...aj) + -- 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 -- -- 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) - kind = tyVarKind (last (classTyVars clas)) + clas_tyvars = classTyVars clas + kind = tyVarKind (last clas_tyvars) -- Kind of the thing we want to instance -- e.g. argument kind of Monad, *->* @@ -386,36 +418,84 @@ makeDerivEqns tycl_decls -- Want to drop 1 arg from (T s a) and (ST s a) -- to get instance Monad (ST s) => Monad (T s) - (tyvars, rep_ty) = newTyConRep tycon - maybe_rep_app = tcSplitTyConApp_maybe rep_ty - Just (rep_tc, rep_ty_args) = maybe_rep_app + -- 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 + -- 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))) + (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 - n_args_to_keep = tyConArity rep_tc - n_args_to_drop + n_args_to_keep = length rep_ty_args - n_args_to_drop args_to_drop = drop n_args_to_keep rep_ty_args args_to_keep = take n_args_to_keep rep_ty_args - ctxt_pred = mkClassPred clas (tys ++ [mkTyConApp rep_tc args_to_keep]) - - mk_dfun dfun_name = mkDictFunId dfun_name clas tyvars - (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)] ) - [ctxt_pred] - - -- We can only do this newtype deriving thing if: - standard_instance = null tys && classKey clas `elem` derivableClassKeys - + rep_tys = tys ++ [mkAppTys rep_fn args_to_keep] + rep_pred = mkClassPred clas rep_tys + -- rep_pred is the representation dictionary, from where + -- we are gong to get all the methods for the newtype dictionary + + inst_tys = (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)]) + -- 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 isomprphism; 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's no 'corece' needed because after the type checker newtypes + -- are transparent. + + sc_theta = substTheta (mkTyVarSubst 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 + + -- Finally! Here's where we build the dictionary Id + mk_dfun dfun_name = mkDictFunId dfun_name tyvars 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 this way - && not (clas `hasKey` showClassKey) - && n_tyvars_to_keep >= 0 -- Well kinded; + = not (getUnique clas `elem` non_iso_classes) + && right_arity -- Well kinded; + -- eg not: newtype T ... deriving( ST ) + -- because ST needs *2* type params + && n_tyvars_to_keep >= 0 -- Type constructor has right kind: -- eg not: newtype T = T Int deriving( Monad ) - && isJust maybe_rep_app -- The rep type is a type constructor app - && n_args_to_keep >= 0 -- Well kinded: + && n_args_to_keep >= 0 -- Rep type has right kind: -- eg not: newtype T a = T Int deriving( Monad ) && eta_ok -- Eta reduction works + && not (isRecursiveTyCon tycon) -- Does not work for recursive tycons: + -- newtype A = MkA [A] + -- Don't want + -- instance Eq [A] => Eq A !! -- Check that eta reduction is OK -- (a) the dropped-off args are identical @@ -425,38 +505,123 @@ makeDerivEqns tycl_decls && (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep) cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep - SLIT("too hard for cunning newtype deriving") - + (vcat [ptext SLIT("even with cunning newtype deriving:"), + if isRecursiveTyCon tycon then + ptext SLIT("the newtype is recursive") + else empty, + if not right_arity then + quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("does not have arity 1") + else empty, + if not (n_tyvars_to_keep >= 0) then + ptext SLIT("the type constructor has wrong kind") + else if not (n_args_to_keep >= 0) then + ptext SLIT("the representation type has wrong kind") + else if not eta_ok then + ptext SLIT("the eta-reduction property does not hold") + else empty + ]) + + non_std_err = derivingThingErr clas tys tycon tyvars_to_keep + (vcat [non_std_why clas, + ptext SLIT("Try -fglasgow-exts for GHC's newtype-deriving extension")]) + + bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing) + standard_class gla_exts clas = key `elem` derivableClassKeys + || (gla_exts && (key == typeableClassKey || key == dataClassKey)) + where + key = classKey clas - bale_out err = addErrTc err `thenNF_Tc_` returnNF_Tc (Nothing, Nothing) - ------------------------------------------------------------------ - chk_out :: Class -> TyCon -> [TcType] -> Maybe FastString - chk_out clas tycon tys - | not (null tys) = Just non_std_why - | not (getUnique clas `elem` derivableClassKeys) = Just non_std_why - | 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 - | 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 - single_nullary_why = SLIT("one constructor data type or type with all nullary constructors expected") - nullary_why = SLIT("data type with all nullary constructors expected") - no_cons_why = SLIT("type has no data constructors") - non_std_why = SLIT("not a derivable class") - existential_why = SLIT("it has existentially-quantified constructor(s)") 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 + + +------------------------------------------------------------------ +-- Check side conditions that dis-allow derivability for particular classes +-- This is *apart* from the newtype-deriving mechanism + +checkSideConditions :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc +checkSideConditions gla_exts clas tycon tys + | 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_allTypeKind), + (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 isExistentialDataCon 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 existentially-quantified 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_allTypeKind :: Condition +cond_allTypeKind (gla_exts, tycon) + | all (isTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over 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} %************************************************************************ @@ -480,13 +645,12 @@ ordered by sorting on type varible, tv, (major key) and then class, k, \end{itemize} \begin{code} -solveDerivEqns :: InstEnv - -> [DerivEqn] +solveDerivEqns :: [DerivEqn] -> TcM [DFunId] -- Solns in same order as eqns. -- This bunch is Absolutely minimal... -solveDerivEqns inst_env_in orig_eqns - = iterateDeriv initial_solutions +solveDerivEqns orig_eqns + = iterateDeriv 1 initial_solutions where -- The initial solutions for the equations claim that each -- instance has an empty context; this solution is certainly @@ -499,46 +663,39 @@ solveDerivEqns inst_env_in 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 :: [DerivSoln] ->TcM [DFunId] - iterateDeriv current_solns - = getDOptsTc `thenNF_Tc` \ dflags -> - let - dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns - inst_env = extend_inst_env dflags inst_env_in dfuns + iterateDeriv :: Int -> [DerivSoln] ->TcM [DFunId] + iterateDeriv 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) + | otherwise + = let + dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns in - checkNoErrsTc ( + checkNoErrs ( -- Extend the inst info from the explicit instance decls -- with the current set of solutions, and simplify each RHS - tcSetInstEnv inst_env $ - mapTc gen_soln orig_eqns - ) `thenTc` \ new_solns -> + tcExtendTempInstEnv dfuns $ + mappM gen_soln orig_eqns + ) `thenM` \ new_solns -> if (current_solns == new_solns) then - returnTc dfuns + returnM dfuns else - iterateDeriv new_solns + iterateDeriv (n+1) new_solns ------------------------------------------------------------------ gen_soln (_, clas, tc,tyvars,deriv_rhs) - = tcAddSrcLoc (getSrcLoc tc) $ - tcAddErrCtxt (derivCtxt (Just clas) tc) $ - tcSimplifyDeriv tyvars deriv_rhs `thenTc` \ theta -> - returnTc (sortLt (<) theta) -- Canonicalise before returning the soluction -\end{code} - -\begin{code} -extend_inst_env dflags inst_env new_dfuns - = new_inst_env - where - (new_inst_env, _errs) = extendInstEnv dflags inst_env new_dfuns - -- Ignore the errors about duplicate instances. - -- We don't want repeated error messages - -- They'll appear later, when we do the top-level extendInstEnvs + = addSrcLoc (getSrcLoc tc) $ + addErrCtxt (derivCtxt (Just clas) tc) $ + tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> + returnM (sortLt (<) theta) -- Canonicalise before returning the soluction mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta - = mkDictFunId dfun_name clas tyvars - [mkTyConApp tycon (mkTyVarTys tyvars)] - theta + = mkDictFunId dfun_name tyvars theta + clas [mkTyConApp tycon (mkTyVarTys tyvars)] \end{code} %************************************************************************ @@ -605,26 +762,32 @@ the renamer. What a great hack! \begin{code} -- Generate the method bindings for the required instance --- (paired with class name, as we need that when renaming +-- (paired with DFunId, as we need that when renaming -- the method binds) -gen_bind :: (Name -> Maybe Fixity) -> DFunId -> (Name, RdrNameMonoBinds) -gen_bind get_fixity dfun - = (cls_nm, binds) - where - cls_nm = className clas - (clas, tycon) = simpleDFunClassTyCon dfun - - binds = assoc "gen_bind:bad derived class" gen_list - (nameUnique cls_nm) tycon - - 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 get_fixity) - ,(readClassKey, gen_Read_binds get_fixity) - ] +gen_bind :: DFunId -> TcM (DFunId, (RdrNameMonoBinds, 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, no_aux_binds gen_Eq_binds) + ,(ordClassKey, no_aux_binds gen_Ord_binds) + ,(enumClassKey, no_aux_binds gen_Enum_binds) + ,(boundedClassKey, no_aux_binds gen_Bounded_binds) + ,(ixClassKey, no_aux_binds gen_Ix_binds) + ,(showClassKey, no_aux_binds (gen_Show_binds fix_env)) + ,(readClassKey, no_aux_binds (gen_Read_binds fix_env)) + ,(typeableClassKey,no_aux_binds gen_Typeable_binds) + ,(dataClassKey, gen_Data_binds fix_env) + ] + + -- Used for generators that don't need to produce + -- any auxiliary bindings + no_aux_binds f tc = (f tc, EmptyMonoBinds) + in + returnM (dfun, gen_binds_fn tycon) \end{code} @@ -667,8 +830,8 @@ gen_taggery_Names :: [DFunId] TagThingWanted)] gen_taggery_Names dfuns - = foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far -> - foldlTc do_tag2con names_so_far tycons_of_interest + = foldlM do_con2tag [] tycons_of_interest `thenM` \ names_so_far -> + foldlM do_tag2con names_so_far tycons_of_interest where all_CTs = map simpleDFunClassTyCon dfuns all_tycons = map snd all_CTs @@ -679,25 +842,25 @@ gen_taggery_Names dfuns ((we_are_deriving eqClassKey tycon && any isNullaryDataCon (tyConDataCons tycon)) || (we_are_deriving ordClassKey tycon - && not (maybeToBool (maybeTyConSingleCon tycon))) + && not (isProductTyCon tycon)) || (we_are_deriving enumClassKey tycon) || (we_are_deriving ixClassKey tycon)) - = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag) + = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag) : acc_Names) | otherwise - = returnTc acc_Names + = returnM acc_Names do_tag2con acc_Names tycon | isDataTyCon tycon && (we_are_deriving enumClassKey tycon || we_are_deriving ixClassKey tycon && isEnumerationTyCon tycon) - = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con) + = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con) : (maxtag_RDR tycon, tycon, GenMaxTag) : acc_Names) | otherwise - = returnTc acc_Names + = returnM acc_Names we_are_deriving clas_key tycon = is_in_eqns clas_key tycon all_CTs @@ -711,7 +874,7 @@ gen_taggery_Names dfuns \begin{code} derivingThingErr clas tys tycon tyvars why = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr pred)], - parens (ptext why)] + parens why] where pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)])