X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=435316bbf10ac0c6c7ef36dee5997c19c818066a;hb=5e34dfe261bf18325fc035ed92f716f3a6249142;hp=ee364ac23783e88280334e6918b51582d94ce092;hpb=61fae1d3fb61c5f53c3fbcb94afe7c548ad31591;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index ee364ac..435316b 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -11,47 +11,50 @@ module TcDeriv ( tcDeriving ) where #include "HsVersions.h" import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..), - collectLocatedMonoBinders ) + collectMonoBinders ) import RdrHsSyn ( RdrNameMonoBinds ) -import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl ) -import CmdLineOpts ( DynFlag(..), DynFlags ) +import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred ) +import CmdLineOpts ( DynFlag(..) ) -import TcMonad -import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo, - tcLookupClass, tcLookupTyCon +import TcRnMonad +import TcEnv ( tcGetInstEnv, tcSetInstEnv, newDFunName, + InstInfo(..), pprInstInfo, InstBindings(..), + pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv ) -import TcSimplify ( tcSimplifyThetas ) +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 ) -import Class ( className, classKey, Class ) -import ErrUtils ( dumpIfSet_dyn, Message ) +import RnEnv ( bindLocalsFVRn ) +import TcRnMonad ( thenM, returnM, mapAndUnzipM ) +import HscTypes ( DFunId ) + +import BasicTypes ( NewOrData(..) ) +import Class ( className, classKey, classTyVars, classSCTheta, Class ) +import Subst ( mkTyVarSubst, substTheta ) +import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon ) -import PrelInfo ( needsDataDeclCtxtClassKeys ) +import DataCon ( dataConRepArgTys, dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) import Maybes ( maybeToBool, catMaybes ) -import Module ( Module ) import Name ( Name, getSrcLoc, nameUnique ) +import NameSet import RdrName ( RdrName ) -import TyCon ( tyConTyVars, tyConDataCons, +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConTheta, maybeTyConSingleCon, isDataTyCon, - isEnumerationTyCon, TyCon + isEnumerationTyCon, isRecursiveTyCon, TyCon ) -import TcType ( ThetaType, mkTyVarTys, mkTyConApp, - isUnLiftedType, mkClassPred ) -import Var ( TyVar ) +import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe, + isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, + tcEqTypes, tcSplitAppTys, mkAppTys ) +import Var ( TyVar, tyVarKind ) +import VarSet ( mkVarSet, subVarSet ) import PrelNames -import Util ( zipWithEqual, sortLt ) +import Util ( zipWithEqual, sortLt, notNull ) import ListSetOps ( removeDups, assoc ) import Outputable -import List ( nub ) \end{code} %************************************************************************ @@ -143,13 +146,16 @@ 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 ) @@ -171,6 +177,12 @@ 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". + + %************************************************************************ %* * @@ -179,76 +191,92 @@ 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_in get_fixity tycl_decls - = recoverTc (returnTc ([], EmptyBinds)) $ +tcDeriving tycl_decls + = recoverM (returnM ([], EmptyBinds, emptyFVs)) $ + getDOpts `thenM` \ dflags -> + tcGetInstEnv `thenM` \ inst_env -> -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". - makeDerivEqns tycl_decls `thenTc` \ eqns -> - if null eqns then - returnTc ([], EmptyBinds) - else + makeDerivEqns tycl_decls `thenM` \ (ordinary_eqns, newtype_inst_info) -> + let + -- 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 inst_env1 ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) -> + let + inst_info = newtype_inst_info ++ ordinary_inst_info + in + + ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info binds)) `thenM_` + + returnM (inst_info, binds, fvs) + + where + ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc + ddump_deriving inst_infos 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 - -- Take the equation list and solve it, to deliver a list of +----------------------------------------- +deriveOrdinaryStuff inst_env_in [] -- Short cut + = returnM ([], EmptyBinds, emptyFVs) + +deriveOrdinaryStuff inst_env_in 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 inst_env_in 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 -> - gen_taggery_Names new_dfuns `thenTc` \ nm_alist_etc -> - - tcGetEnv `thenNF_Tc` \ env -> - getDOptsTc `thenTc` \ 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 + mbinders = collectMonoBinders extra_mbinds + in + mappM gen_bind new_dfuns `thenM` \ method_binds_s -> + traceTc (text "tcDeriv" <+> ppr method_binds_s) `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) - ) - + -- The only tricky bit is that the extra_binds must scope + -- over the method bindings for the instances. + bindLocalsFVRn (ptext (SLIT("deriving"))) mbinders $ \ _ -> + rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, fvs) -> + mapAndUnzipM rn_meths method_binds_s `thenM` \ (rn_method_binds_s, fvs_s) -> + returnM ((rn_method_binds_s, rn_extra_binds), + fvs `plusFV` plusFVs fvs_s) + ) `thenM` \ ((rn_method_binds_s, rn_extra_binds), fvs) -> + let new_inst_infos = zipWith gen_inst_info new_dfuns rn_method_binds_s in + returnM (new_inst_infos, rn_extra_binds, fvs) - ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving new_inst_infos rn_extra_binds)) `thenTc_` - - returnTc (new_inst_infos, rn_extra_binds) where - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc - ddump_deriving inst_infos extra_binds - = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds - 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 = [] } + = InstInfo { iDFunId = dfun, iBinds = VanillaInst binds [] } - rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) -> - returnRn meths' -- Ignore the free vars returned + rn_meths (cls, meths) = rnMethodBinds cls [] meths \end{code} @@ -274,79 +302,217 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: [RenamedTyClDecl] -> TcM [DerivEqn] +makeDerivEqns :: [RenamedTyClDecl] + -> TcM ([DerivEqn], -- Ordinary derivings + [InstInfo]) -- Special newtype derivings makeDerivEqns tycl_decls - = mapTc mk_eqn derive_these `thenTc` \ maybe_eqns -> - returnTc (catMaybes maybe_eqns) + = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) -> + returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ - derive_these :: [(Name, Name)] - -- Find the (Class,TyCon) pairs that must be `derived' + derive_these :: [(NewOrData, Name, RenamedHsPred)] + -- Find the (nd, TyCon, Pred) pairs that must be `derived' -- NB: only source-language decls have deriving, no imported ones do - derive_these = [ (clas,tycon) - | TyData {tcdName = tycon, tcdDerivs = Just classes} <- tycl_decls, - clas <- nub classes ] + derive_these = [ (nd, tycon, pred) + | TyData {tcdND = nd, tcdName = tycon, tcdDerivs = Just preds} <- tycl_decls, + pred <- preds ] ------------------------------------------------------------------ - mk_eqn :: (Name, Name) -> NF_TcM (Maybe DerivEqn) - -- we swizzle the tyvars and datacons out of the tycon + 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 (clas_name, tycon_name) - = tcLookupClass clas_name `thenNF_Tc` \ clas -> - tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> - let - clas_key = classKey clas - tyvars = tyConTyVars tycon - tyvar_tys = mkTyVarTys tyvars - ty = mkTyConApp tycon tyvar_tys - data_cons = tyConDataCons tycon - locn = getSrcLoc tycon - constraints = extra_constraints ++ concat (map mk_constraints data_cons) - - -- "extra_constraints": see notes above about contexts on data decls - extra_constraints - | offensive_class = tyConTheta tycon - | otherwise = [] - - offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys - - mk_constraints data_con - = [ mkClassPred clas [arg_ty] - | arg_ty <- dataConArgTys data_con tyvar_tys, - not (isUnLiftedType arg_ty) -- No constraints for unlifted types? - ] - in - case chk_out clas tycon of - Just err -> tcAddSrcLoc (getSrcLoc tycon) $ - addErrTc err `thenNF_Tc_` - returnNF_Tc Nothing - Nothing -> newDFunName clas [ty] locn `thenNF_Tc` \ dfun_name -> - returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints)) - + mk_eqn (new_or_data, tycon_name, pred) + = 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 `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 + ------------------------------------------------------------------ + mk_eqn_help DataType tycon clas tys + | Just err <- chk_out clas tycon tys + = bale_out (derivingThingErr clas tys tycon tyvars 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 <- dataConRepArgTys data_con, -- dataConOrigArgTys??? + -- 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 + + mk_eqn_help NewType tycon clas tys + = doptM Opt_GlasgowExts `thenM` \ gla_exts -> + if can_derive_via_isomorphism && (gla_exts || standard_instance) then + -- 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 })) + else + if standard_instance then + mk_eqn_help DataType tycon clas [] -- Go via bale-out route + else + bale_out cant_derive_err + 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 + -- + -- 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 + -- + -- 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) + + 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 + 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 + -- 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 = 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 + + 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 + + standard_instance = null tys && classKey clas `elem` derivableClassKeys + + 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; + -- eg not: newtype T = T Int deriving( Monad ) + && n_args_to_keep >= 0 -- Well kinded: + -- 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 + -- (b) the remaining type args mention + -- only the remaining type variables + eta_ok = (args_to_drop `tcEqTypes` mkTyVarTys tyvars_to_drop) + && (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep) + + cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep + (vcat [ptext SLIT("too hard for cunning newtype deriving"), + ppr n_tyvars_to_keep, + ppr n_args_to_keep, + ppr eta_ok, + ppr (isRecursiveTyCon tycon) + ]) + + bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing) ------------------------------------------------------------------ - chk_out :: Class -> TyCon -> Maybe Message - chk_out clas tycon - | clas `hasKey` enumClassKey && not is_enumeration = bog_out nullary_why - | clas `hasKey` boundedClassKey && not is_enumeration_or_single = bog_out single_nullary_why - | clas `hasKey` ixClassKey && not is_enumeration_or_single = bog_out single_nullary_why - | null data_cons = bog_out no_cons_why - | any isExistentialDataCon data_cons = Just (existentialErr clas tycon) - | otherwise = Nothing + chk_out :: Class -> TyCon -> [TcType] -> Maybe SDoc + chk_out clas tycon tys + | notNull 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") + single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected") + nullary_why = ptext SLIT("data type with all nullary constructors expected") + no_cons_why = ptext SLIT("type has no data constructors") + non_std_why = ptext SLIT("not a derivable class") + existential_why = ptext SLIT("it has existentially-quantified constructor(s)") - bog_out why = Just (derivingThingErr clas tycon why) +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 \end{code} %************************************************************************ @@ -376,7 +542,7 @@ solveDerivEqns :: InstEnv -- This bunch is Absolutely minimal... solveDerivEqns inst_env_in orig_eqns - = iterateDeriv initial_solutions + = iterateDeriv 1 initial_solutions where -- The initial solutions for the equations claim that each -- instance has an empty context; this solution is certainly @@ -389,58 +555,51 @@ 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 - = checkNoErrsTc (iterateOnce current_solns) - `thenTc` \ (new_dfuns, new_solns) -> + 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 + = getDOpts `thenM` \ dflags -> + let + dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns + inst_env = extend_inst_env dflags inst_env_in dfuns + in + checkNoErrs ( + -- Extend the inst info from the explicit instance decls + -- with the current set of solutions, and simplify each RHS + tcSetInstEnv inst_env $ + mappM gen_soln orig_eqns + ) `thenM` \ new_solns -> if (current_solns == new_solns) then - returnTc new_dfuns + returnM dfuns else - iterateDeriv new_solns + iterateDeriv (n+1) new_solns ------------------------------------------------------------------ - iterateOnce current_solns - = -- Extend the inst info from the explicit instance decls - -- with the current set of solutions, giving a - getDOptsTc `thenTc` \ dflags -> - let (new_dfuns, inst_env) = - add_solns dflags inst_env_in orig_eqns current_solns - in - -- Simplify each RHS - tcSetInstEnv inst_env ( - listTc [ tcAddSrcLoc (getSrcLoc tc) $ - tcAddErrCtxt (derivCtxt tc) $ - tcSimplifyThetas deriv_rhs - | (_, _,tc,_,deriv_rhs) <- orig_eqns ] - ) `thenTc` \ next_solns -> - - -- Canonicalise the solutions, so they compare nicely - let canonicalised_next_solns = [ sortLt (<) next_soln | next_soln <- next_solns ] - in - returnTc (new_dfuns, canonicalised_next_solns) + + gen_soln (_, clas, tc,tyvars,deriv_rhs) + = addSrcLoc (getSrcLoc tc) $ + addErrCtxt (derivCtxt (Just clas) tc) $ + tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> + returnM (sortLt (<) theta) -- Canonicalise before returning the soluction \end{code} \begin{code} -add_solns :: DynFlags - -> InstEnv -- The global, non-derived ones - -> [DerivEqn] -> [DerivSoln] - -> ([DFunId], InstEnv) - -- the eqns and solns move "in lockstep"; we have the eqns - -- because we need the LHS info for addClassInstance. - -add_solns dflags inst_env_in eqns solns - = (new_dfuns, inst_env) - where - new_dfuns = zipWithEqual "add_solns" mk_deriv_dfun eqns solns - (inst_env, _) = extendInstEnv dflags inst_env_in new_dfuns +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 - mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta - = mkDictFunId dfun_name clas tyvars - [mkTyConApp tycon (mkTyVarTys tyvars)] - theta +mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta + = mkDictFunId dfun_name tyvars theta + clas [mkTyConApp tycon (mkTyVarTys tyvars)] \end{code} %************************************************************************ @@ -509,23 +668,25 @@ the renamer. What a great hack! -- Generate the method bindings for the required instance -- (paired with class name, 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) +gen_bind :: DFunId -> TcM (Name, RdrNameMonoBinds) +gen_bind dfun + = getFixityEnv `thenM` \ fix_env -> + returnM (cls_nm, gen_binds_fn fix_env cls_nm tycon) where cls_nm = className clas (clas, tycon) = simpleDFunClassTyCon dfun - binds = assoc "gen_bind:bad derived class" gen_list - (nameUnique cls_nm) tycon - +gen_binds_fn fix_env cls_nm + = assoc "gen_bind:bad derived class" + gen_list (nameUnique cls_nm) + where 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) + ,(showClassKey, gen_Show_binds fix_env) + ,(readClassKey, gen_Read_binds fix_env) ] \end{code} @@ -569,8 +730,8 @@ 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 @@ -585,21 +746,21 @@ gen_taggery_Names dfuns || (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 @@ -611,17 +772,20 @@ gen_taggery_Names dfuns \end{code} \begin{code} -derivingThingErr :: Class -> TyCon -> FAST_STRING -> Message - -derivingThingErr clas tycon why - = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr clas)], - hsep [ptext SLIT("for the type"), quotes (ppr tycon)], - parens (ptext why)] +derivingThingErr clas tys tycon tyvars why + = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr pred)], + parens why] + where + pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)]) -existentialErr clas tycon - = sep [ptext SLIT("Can't derive any instances for type") <+> quotes (ppr tycon), - ptext SLIT("because it has existentially-quantified constructor(s)")] +malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred -derivCtxt tycon - = ptext SLIT("When deriving classes for") <+> quotes (ppr tycon) +derivCtxt :: Maybe Class -> TyCon -> SDoc +derivCtxt maybe_cls tycon + = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon) + where + cls = case maybe_cls of + Nothing -> ptext SLIT("instances") + Just c -> ptext SLIT("the") <+> quotes (ppr c) <+> ptext SLIT("instance") \end{code} +