X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=a81f8fbfee289f7655e7daf54773fc278a31f69f;hb=5f3bef9e47e5ba78983c5081eacaee00f953279d;hp=ea4828a9ea3fe491e31ff44a9dfdadc15361656b;hpb=7b0181919416d8f04324575b7e17031ca692f5b0;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index ea4828a..a81f8fb 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -1,59 +1,58 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcDeriv]{Deriving} Handles @deriving@ clauses on @data@ declarations. \begin{code} +module TcDeriv ( tcDeriving ) where + #include "HsVersions.h" -module TcDeriv ( - tcDeriving - ) where - -import Ubiq - -import HsSyn ( FixityDecl, Sig, HsBinds(..), Bind(..), MonoBinds(..), - GRHSsAndBinds, Match, HsExpr, HsLit, InPat, - ArithSeqInfo, Fake, MonoType ) -import HsPragmas ( InstancePragmas(..) ) -import RnHsSyn ( RenamedHsBinds(..), RenamedFixityDecl(..) ) -import TcHsSyn ( TcIdOcc ) - -import TcMonad -import Inst ( InstOrigin(..), InstanceMapper(..) ) -import TcEnv ( getEnv_TyCons ) -import TcKind ( TcKind ) ---import TcGenDeriv -- Deriv stuff -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) -import TcSimplify ( tcSimplifyThetas ) - ---import RnMonad4 -import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) ) ---import RnBinds4 ( rnMethodBinds, rnTopBinds ) - -import Bag ( Bag, isEmptyBag, unionBags, listToBag ) -import Class ( GenClass, getClassKey ) -import CmdLineOpts ( opt_CompilingPrelude ) -import ErrUtils ( pprBagOfErrors, addErrLoc, Error(..) ) -import Id ( dataConSig, dataConArity ) -import Maybes ( assocMaybe, maybeToBool, Maybe(..) ) +import HsSyn +import CmdLineOpts ( DynFlag(..) ) + +import Generics ( mkTyConGenericBinds ) +import TcRnMonad +import TcEnv ( newDFunName, pprInstInfoDetails, + InstInfo(..), InstBindings(..), + tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv + ) +import TcGenDeriv -- Deriv stuff +import InstEnv ( simpleDFunClassTyCon, extendInstEnv ) +import TcHsType ( tcHsDeriv ) +import TcSimplify ( tcSimplifyDeriv ) + +import RnBinds ( rnMethodBinds, rnTopBinds ) +import RnEnv ( bindLocalNames ) +import HscTypes ( DFunId, FixityEnv ) + +import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) +import Type ( zipTvSubst, substTheta ) +import ErrUtils ( dumpIfSet_dyn ) +import MkId ( mkDictFunId ) +import DataCon ( isNullarySrcDataCon, isVanillaDataCon, dataConOrigArgTys ) +import Maybes ( catMaybes ) +import RdrName ( RdrName ) +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, tcTyConAppTyCon, + isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind, + tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy ) +import Var ( TyVar, tyVarKind, idType, varName ) +import VarSet ( mkVarSet, subVarSet ) +import PrelNames +import SrcLoc ( srcLocSpan, Located(..) ) +import Util ( zipWithEqual, sortLe, notNull ) +import ListSetOps ( removeDups, assocMaybe ) import Outputable -import PprType ( GenType, GenTyVar, GenClass, TyCon ) -import PprStyle -import Pretty -import SrcLoc ( mkGeneratedSrcLoc, mkUnknownSrcLoc, SrcLoc ) -import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings, - maybeTyConSingleCon, isEnumerationTyCon, TyCon ) -import Type ( GenType(..), TauType(..), mkTyVarTys, applyTyCon, - mkSigmaTy, mkDictTy, isPrimType, instantiateTy, - getAppTyCon, getAppDataTyCon ) -import TyVar ( GenTyVar ) -import UniqFM ( eltsUFM ) -import Unique -- Keys stuff -import Util ( zipWithEqual, zipEqual, sortLt, removeDups, - thenCmp, cmpList, panic, pprPanic, pprPanic# ) +import Bag \end{code} %************************************************************************ @@ -69,6 +68,10 @@ Consider | C3 (T a a) deriving (Eq) +[NOTE: See end of these comments for what to do with + data (C a, D b) => T a b = ... +] + We want to come up with an instance declaration of the form instance (Ping a, Pong b, ...) => Eq (T a b) where @@ -137,91 +140,143 @@ this by simplifying the RHS to a form in which So, here are the synonyms for the ``equation'' structures: \begin{code} -type DerivEqn = (Class, TyCon, [TyVar], DerivRhs) - -- The tyvars bind all the variables in the RHS - -- NEW: it's convenient to re-use InstInfo - -- We'll "panic" out some fields... +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 -type DerivRhs = [(Class, TauType)] -- Same as a ThetaType! +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} -%************************************************************************ -%* * -\subsection[TcDeriv-driver]{Top-level function for \tr{derivings}} -%* * -%************************************************************************ -\begin{code} -tcDeriving :: Module -- name of module under scrutiny - -> GlobalNameMappers -- for "renaming" bits of generated code - -> Bag InstInfo -- What we already know about instances - -> [RenamedFixityDecl] -- Fixity info; used by Read and Show - -> TcM s (Bag InstInfo, -- The generated "instance decls". - RenamedHsBinds, -- Extra generated bindings - PprStyle -> Pretty) -- Printable derived instance decls; - -- for debugging via -ddump-derivings. -tcDeriving = panic "tcDeriving: ToDo LATER" -{- LATER: - -tcDeriving modname renamer_name_funs inst_decl_infos_in fixities - = -- Fish the "deriving"-related information out of the TcEnv - -- and make the necessary "equations". - makeDerivEqns `thenTc` \ 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_decl_infos_in eqns - `thenTc` \ new_inst_infos -> - - -- 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 eqns `thenTc` \ nm_alist_etc -> - let - nm_alist = [ (pn, n) | (pn,n,_,_) <- nm_alist_etc ] +[Data decl contexts] A note about contexts on data decls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider - -- We have the renamer's final "name funs" in our hands - -- (they were passed in). So we can handle ProtoNames - -- that refer to anything "out there". But our generated - -- code may also mention "con2tag" (etc.). So we need - -- to augment to "name funs" to include those. - (rn_val_gnf, rn_tc_gnf) = renamer_name_funs + data (RealFloat a) => Complex a = !a :+ !a deriving( Read ) - deriv_val_gnf pname = case (assoc_maybe nm_alist pname) of - Just xx -> Just xx - Nothing -> rn_val_gnf pname +We will need an instance decl like: - deriver_name_funs = (deriv_val_gnf, rn_tc_gnf) + instance (Read a, RealFloat a) => Read (Complex a) where + ... - assoc_maybe [] _ = Nothing - assoc_maybe ((k,v) : vs) key - = if k `eqProtoName` key then Just v else assoc_maybe vs key - in - gen_tag_n_con_binds deriver_name_funs nm_alist_etc `thenTc` \ extra_binds -> +The RealFloat in the context is because the read method for Complex is bound +to construct a Complex, and doing that requires that the argument type is +in RealFloat. - mapTc (gen_inst_info maybe_mod fixities deriver_name_funs) new_inst_infos - `thenTc` \ really_new_inst_infos -> +But this ain't true for Show, Eq, Ord, etc, since they don't construct +a Complex; they only take them apart. - returnTc (listToBag really_new_inst_infos, - extra_binds, - ddump_deriving really_new_inst_infos extra_binds) - where - maybe_mod = if opt_CompilingPrelude then Nothing else Just mod_name +Our approach: identify the offending classes, and add the data type +context to the instance decl. The "offending classes" are - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> (PprStyle -> Pretty) + Read, Enum? - ddump_deriving inst_infos extra_binds sty - = ppAboves ((map pp_info inst_infos) ++ [ppr sty extra_binds]) - where - pp_info (InstInfo clas tvs ty inst_decl_theta _ _ _ mbinds _ _ _ _) - = ppAbove (ppr sty (mkSigmaTy tvs inst_decl_theta (mkDictTy clas ty))) - (ppr sty mbinds) +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". + +[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 ... + + + + +%************************************************************************ +%* * +\subsection[TcDeriv-driver]{Top-level function for \tr{derivings}} +%* * +%************************************************************************ + +\begin{code} +tcDeriving :: [LTyClDecl Name] -- All type constructors + -> TcM ([InstInfo], -- The generated "instance decls" + [HsBindGroup Name]) -- Extra generated top-level bindings + +tcDeriving tycl_decls + = recoverM (returnM ([], [])) $ + do { -- Fish the "deriving"-related information out of the TcEnv + -- and make the necessary "equations". + ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns tycl_decls + + ; (ordinary_inst_info, deriv_binds) + <- extendLocalInstEnv (map iDFunId newtype_inst_info) $ + deriveOrdinaryStuff ordinary_eqns + -- Add the newtype-derived instances to the inst env + -- before tacking the "ordinary" ones + + -- Generate the generic to/from functions from each type declaration + ; gen_binds <- mkGenericBinds tycl_decls + ; let inst_info = newtype_inst_info ++ ordinary_inst_info + + -- 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 deriv_binds [] + ; (rn_gen, dus_gen) <- rnTopBinds gen_binds [] + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to + -- be kept alive + ; return (rn_deriv ++ 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] -> [HsBindGroup Name] -> SDoc + ddump_deriving inst_infos extra_binds + = vcat (map pprInstInfoDetails inst_infos) $$ vcat (map ppr extra_binds) + +----------------------------------------- +deriveOrdinaryStuff [] -- Short cut + = returnM ([], emptyLHsBinds) + +deriveOrdinaryStuff eqns + = do { -- Take the equation list and solve it, to deliver a list of + -- solutions, a.k.a. the contexts for the instance decls + -- required for the corresponding equations. + ; new_dfuns <- solveDerivEqns eqns + + -- Generate the InstInfo for each dfun, + -- plus any auxiliary bindings it needs + ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst new_dfuns + + -- Generate any extra not-one-inst-decl-specific binds, + -- notably "con2tag" and/or "tag2con" functions. + ; extra_binds <- genTaggeryBinds new_dfuns + + -- Done + ; returnM (inst_infos, unionManyBags (extra_binds : aux_binds_s)) + } + +----------------------------------------- +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} @@ -247,78 +302,347 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: TcM s [DerivEqn] +makeDerivEqns :: [LTyClDecl Name] + -> TcM ([DerivEqn], -- Ordinary derivings + [InstInfo]) -- Special newtype derivings -makeDerivEqns - = tcGetEnv `thenNF_Tc` \ env -> - let - tycons = getEnv_TyCons env - think_about_deriving = need_deriving tycons - in - mapTc (chk_out think_about_deriving) think_about_deriving `thenTc_` - let - (derive_these, _) = removeDups cmp_deriv think_about_deriving - eqns = map mk_eqn derive_these - in - returnTc eqns +makeDerivEqns tycl_decls + = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) -> + returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ - need_deriving :: [TyCon] -> [(Class, TyCon)] - -- find the tycons that have `deriving' clauses - - need_deriving tycons_to_consider - = foldr ( \ tycon acc -> - case (tyConDerivings tycon) of - [] -> acc - cs -> [ (clas,tycon) | clas <- cs ] ++ acc - ) - [] - tycons_to_consider + derive_these :: [(NewOrData, Name, LHsType Name)] + -- Find the (nd, TyCon, Pred) pairs that must be `derived' + derive_these = [ (nd, tycon, pred) + | L _ (TyData { tcdND = nd, tcdLName = L _ tycon, + tcdDerivs = Just preds }) <- tycl_decls, + pred <- preds ] ------------------------------------------------------------------ - chk_out :: [(Class, TyCon)] -> (Class, TyCon) -> TcM s () - chk_out whole_deriving_list this_one@(clas, tycon) - = let - clas_key = getClassKey clas - in - - -- Are things OK for deriving Enum (if appropriate)? - checkTc (clas_key == enumClassKey && not (isEnumerationTyCon tycon)) - (derivingEnumErr tycon) `thenTc_` - - -- Are things OK for deriving Ix (if appropriate)? - checkTc (clas_key == ixClassKey - && not (isEnumerationTyCon tycon - || maybeToBool (maybeTyConSingleCon tycon))) - (derivingIxErr tycon) + 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, hs_deriv_ty) + = tcLookupTyCon tycon_name `thenM` \ tycon -> + setSrcSpan (srcLocSpan (getSrcLoc tycon)) $ + addErrCtxt (derivCtxt Nothing tycon) $ + tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention + -- the type variables for the type constructor + 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 ------------------------------------------------------------------ - cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> TAG_ - cmp_deriv (c1, t1) (c2, t2) - = (c1 `cmp` c2) `thenCmp` (t1 `cmp` t2) + 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 + = do { eqn <- mkDataTypeEqn tycon clas + ; returnM (Just eqn, Nothing) } + + 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, + iBinds = NewTypeDerived rep_tys })) + | 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 + 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 (.., C s1 .. sm, ...) + -- 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...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, _) = 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] + -- 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! + (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 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 + 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 (zipTvSubst clas_tyvars inst_tys) + (classSCTheta clas) + + -- If there are no tyvars, there's no need + -- to abstract over the dictionaries we need + 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 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 (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 ) + && 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 !! + -- 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 + -- (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("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) + +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 + + +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 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") - ------------------------------------------------------------------ - mk_eqn :: (Class, TyCon) -> DerivEqn - -- we swizzle the tyvars and datacons out of the tycon - -- to make the rest of the equation +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 `*'") - mk_eqn (clas, tycon) - = (clas, tycon, tyvars, constraints) - where - tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ??? - tyvar_tys = mkTyVarTys tyvars - data_cons = tyConDataCons tycon - constraints = concat (map mk_constraints data_cons) - - mk_constraints data_con - = [ (clas, instantiateTy inst_env arg_ty) - | arg_ty <- arg_tys, - not (isPrimType arg_ty) -- No constraints for primitive types - ] - where - (con_tyvars, _, arg_tys, _) = dataConSig data_con - inst_env = con_tyvars `zipEqual` tyvar_tys - -- same number of tyvars in data constr and type constr! +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} %************************************************************************ @@ -332,23 +656,22 @@ terms, which is the final correct RHS for the corresponding original equation. \begin{itemize} \item -Each (k,UniTyVarTemplate tv) in a solution constrains only a type +Each (k,TyVarTy tv) in a solution constrains only a type variable, tv. \item -The (k,UniTyVarTemplate tv) pairs in a solution are canonically +The (k,TyVarTy tv) pairs in a solution are canonically ordered by sorting on type varible, tv, (major key) and then class, k, (minor key) \end{itemize} \begin{code} -solveDerivEqns :: Bag InstInfo - -> [DerivEqn] - -> TcM s [InstInfo] -- Solns in same order as eqns. - -- This bunch is Absolutely minimal... +solveDerivEqns :: [DerivEqn] + -> TcM [DFunId] -- Solns in same order as eqns. + -- This bunch is Absolutely minimal... -solveDerivEqns inst_decl_infos_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 @@ -356,90 +679,53 @@ solveDerivEqns inst_decl_infos_in orig_eqns initial_solutions :: [DerivSoln] initial_solutions = [ [] | _ <- orig_eqns ] + ------------------------------------------------------------------ -- iterateDeriv calculates the next batch of solutions, -- compares it with the current one; finishes if they are the -- same, otherwise recurses with the new solutions. - - iterateDeriv :: [DerivSoln] ->TcM s [InstInfo] - - iterateDeriv current_solns - = -- Extend the inst info from the explicit instance decls - -- with the current set of solutions, giving a - - add_solns inst_decl_infos_in orig_eqns current_solns - `thenTc` \ (new_inst_infos, inst_mapper) -> - - -- Simplify each RHS, using a DerivingOrigin containing an - -- inst_mapper reflecting the previous solution - let - mk_deriv_origin clas ty - = DerivingOrigin inst_mapper clas tycon - where - (tycon,_) = getAppTyCon ty - in - listTc [ tcSimplifyThetas mk_deriv_origin rhs - | (_, _, _, rhs) <- orig_eqns - ] `thenTc` \ next_solns -> - - -- Canonicalise the solutions, so they compare nicely - let canonicalised_next_solns - = [ sortLt lt_rhs next_soln | next_soln <- next_solns ] in - - if current_solns `eq_solns` canonicalised_next_solns then - returnTc new_inst_infos + -- It fails if any iteration fails + 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 + checkNoErrs ( + -- Extend the inst info from the explicit instance decls + -- with the current set of solutions, and simplify each RHS + extendLocalInstEnv dfuns $ + mappM gen_soln orig_eqns + ) `thenM` \ new_solns -> + if (current_solns == new_solns) then + returnM dfuns else - iterateDeriv canonicalised_next_solns - - where - ------------------------------------------------------------------ - lt_rhs r1 r2 = case cmp_rhs r1 r2 of { LT_ -> True; _ -> False } - eq_solns s1 s2 = case cmp_solns s1 s2 of { EQ_ -> True; _ -> False } - cmp_solns s1 s2 = cmpList (cmpList cmp_rhs) s1 s2 - cmp_rhs (c1, TyVarTy tv1) (c2, TyVarTy tv2) - = (tv1 `cmp` tv2) `thenCmp` (c1 `cmp` c2) -#ifdef DEBUG - cmp_rhs other_1 other_2 - = pprPanic# "tcDeriv:cmp_rhs:" (ppCat [ppr PprDebug other_1, ppr PprDebug other_2]) -#endif + iterateDeriv (n+1) new_solns -\end{code} + ------------------------------------------------------------------ -\begin{code} -add_solns :: FAST_STRING - -> Bag InstInfo -- The global, non-derived ones - -> [DerivEqn] -> [DerivSoln] - -> TcM s ([InstInfo], -- The new, derived ones - InstanceMapper) - -- the eqns and solns move "in lockstep"; we have the eqns - -- because we need the LHS info for addClassInstance. - -add_solns inst_infos_in eqns solns - = buildInstanceEnvs all_inst_infos `thenTc` \ inst_mapper -> - returnTc (new_inst_infos, inst_mapper) - where - new_inst_infos = zipWithEqual mk_deriv_inst_info eqns solns - - all_inst_infos = inst_infos_in `unionBags` listToBag new_inst_infos - - mk_deriv_inst_info (clas, tycon, tyvars, _) theta - = InstInfo clas tyvars (applyTyCon tycon (mkTyVarTys tyvars)) - theta - theta -- Blarg. This is the dfun_theta slot, - -- which is needed by buildInstanceEnv; - -- This works ok for solving the eqns, and - -- gen_eqns sets it to its final value - -- (incl super class dicts) before we - -- finally return it. -#ifdef DEBUG - (panic "add_soln:dfun_id") (panic "add_soln:const_meth_ids") - (panic "add_soln:binds") (panic "add_soln:from_here") - (panic "add_soln:modname") mkGeneratedSrcLoc - (panic "add_soln:upragmas") -#else - bottom bottom bottom bottom bottom mkGeneratedSrcLoc bottom - where - bottom = panic "add_soln" -#endif + gen_soln (_, clas, tc,tyvars,deriv_rhs) + = setSrcSpan (srcLocSpan (getSrcLoc tc)) $ + addErrCtxt (derivCtxt (Just clas) tc) $ + tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> + 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)] + +extendLocalInstEnv :: [DFunId] -> TcM a -> TcM a +-- Add new locall-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' = foldl extendInstEnv (tcg_inst_env env) dfuns + env' = env { tcg_inst_env = inst_env' } + ; setGblEnv env' thing_inside } \end{code} %************************************************************************ @@ -463,8 +749,7 @@ We want derived instances of @Eq@ and @Ord@ (both v common) to be ``you-couldn't-do-better-by-hand'' efficient. \item -Deriving @Text@---also pretty common, usually just for -@show@---should also be reasonable good code. +Deriving @Show@---also pretty common--- should also be reasonable good code. \item Deriving for the other classes isn't that common or that big a deal. @@ -474,13 +759,13 @@ PRAGMATICS: \begin{itemize} \item -Deriving @Ord@ is done mostly with our non-standard @tagCmp@ method. +Deriving @Ord@ is done mostly with the 1.3 @compare@ method. \item -Deriving @Eq@ also uses @tagCmp@, if we're deriving @Ord@, too. +Deriving @Eq@ also uses @compare@, if we're deriving @Ord@, too. \item -We {\em normally} generated code only for the non-defaulted methods; +We {\em normally} generate code only for the non-defaulted methods; there are some exceptions for @Eq@ and (especially) @Ord@... \item @@ -489,7 +774,6 @@ constructor's numeric (@Int#@) tag. These are generated by @gen_tag_n_con_binds@, and the heuristic for deciding if one of these is around is given by @hasCon2TagFun@. - The examples under the different sections below will make this clearer. @@ -498,112 +782,76 @@ Much less often (really just for deriving @Ix@), we use a @_tag2con_@ function. See the examples. \item -We use Pass~4 of the renamer!!! Reason: we're supposed to be -producing @RenamedMonoBinds@ for the methods, but that means +We use the renamer!!! Reason: we're supposed to be +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 @ProtoNameMonoBinds@ then heave 'em through +So, instead, we produce @MonoBinds RdrName@ then heave 'em through the renamer. What a great hack! \end{itemize} \begin{code} -gen_inst_info :: Maybe Module -- Module name; Nothing => Prelude - -> [RenamedFixityDecl] -- all known fixities; - -- may be needed for Text - -> GlobalNameMappers -- lookup stuff for names we may use - -> InstInfo -- the main stuff to work on - -> TcM s InstInfo -- the gen'd (filled-in) "instance decl" - -gen_inst_info modname fixities deriver_name_funs - info@(InstInfo clas tyvars ty inst_decl_theta _ _ _ _ _ _ locn _) - = - -- Generate the various instance-related Ids - mkInstanceRelatedIds - True {-from_here-} modname - NoInstancePragmas - clas tyvars ty - inst_decl_theta - [{-no user pragmas-}] - `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - -- Generate the bindings for the new instance declaration, - -- rename it, and check for errors - let - (tycon,_,_) = getAppDataTyCon ty - - proto_mbinds - | clas_key == eqClassKey = gen_Eq_binds tycon - | clas_key == showClassKey = gen_Show_binds fixities tycon - | clas_key == ordClassKey = gen_Ord_binds tycon - | clas_key == enumClassKey = gen_Enum_binds tycon - | clas_key == ixClassKey = gen_Ix_binds tycon - | clas_key == readClassKey = gen_Read_binds fixities tycon - | clas_key == binaryClassKey = gen_Binary_binds tycon - | otherwise = panic "gen_inst_info:bad derived class" - in - rn4MtoTcM deriver_name_funs ( - rnMethodBinds clas_Name proto_mbinds - ) `thenNF_Tc` \ (mbinds, errs) -> - - if not (isEmptyBag errs) then - pprPanic "gen_inst_info:renamer errs!\n" - (ppAbove (pprBagOfErrors PprDebug errs) (ppr PprDebug proto_mbinds)) - else - --pprTrace "derived binds:" (ppr PprDebug proto_mbinds) $ - - -- All done +-- Generate the InstInfo for the required instance, +-- plus any auxiliary bindings required +genInst :: DFunId -> TcM (InstInfo, LHsBinds RdrName) +genInst dfun + = getFixityEnv `thenM` \ fix_env -> let - from_here = isLocallyDefined tycon -- If so, then from here + (tyvars,_,clas,[ty]) = tcSplitDFunTy (idType dfun) + clas_nm = className clas + tycon = tcTyConAppTyCon ty + (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon in - returnTc (InstInfo clas tyvars ty inst_decl_theta - dfun_theta dfun_id const_meth_ids - (if from_here then mbinds else EmptyMonoBinds) - from_here modname locn []) + -- Bring the right type variables into + -- scope, and rename the method binds + bindLocalNames (map varName tyvars) $ + rnMethodBinds clas_nm [] meth_binds `thenM` \ (rn_meth_binds, _fvs) -> + + -- Build the InstInfo + returnM (InstInfo { iDFunId = dfun, 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 - clas_key = getClassKey clas - clas_Name - = let (mod, nm) = getOrigName clas in - ClassName clas_key (mkPreludeCoreName mod nm) [] + 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} + %************************************************************************ %* * -\subsection[TcGenDeriv-con2tag-tag2con]{Generating extra binds (@con2tag@ and @tag2con@)} +\subsection[TcDeriv-taggery-Names]{What con2tag/tag2con functions are available?} %* * %************************************************************************ + data Foo ... = ... con2tag_Foo :: Foo ... -> Int# tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int# -maxtag_Foo :: Int -- ditto (NB: not unboxed) - -\begin{code} -gen_tag_n_con_binds :: GlobalNameMappers - -> [(RdrName, RnName, TyCon, TagThingWanted)] - -> TcM s RenamedHsBinds - -gen_tag_n_con_binds deriver_name_funs nm_alist_etc - = let - proto_mbind_list = map gen_tag_n_con_monobind nm_alist_etc - proto_mbinds = foldr AndMonoBinds EmptyMonoBinds proto_mbind_list - in - - rn4MtoTcM deriver_name_funs ( - rnTopBinds (SingleBind (RecBind proto_mbinds)) - ) `thenNF_Tc` \ (binds, errs) -> - - if not (isEmptyBag errs) then - panic "gen_inst_info:renamer errs (2)!" - else - returnTc binds -\end{code} +maxtag_Foo :: Int -- ditto (NB: not unlifted) -%************************************************************************ -%* * -\subsection[TcDeriv-taggery-Names]{What con2tag/tag2con functions are available?} -%* * -%************************************************************************ We have a @con2tag@ function for a tycon if: \begin{itemize} @@ -624,64 +872,63 @@ 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 :: [DerivEqn] - -> TcM s [(RdrName, RnName, -- for an assoc list - TyCon, -- related tycon - TagThingWanted)] - -gen_taggery_Names eqns - = let - all_tycons = [ tc | (_, tc, _, _) <- eqns ] - (tycons_of_interest, _) = removeDups cmp all_tycons - in - foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far -> - foldlTc do_tag2con names_so_far tycons_of_interest +genTaggeryBinds :: [DFunId] -> TcM (LHsBinds RdrName) +genTaggeryBinds dfuns + = 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_tycons = map snd all_CTs + (tycons_of_interest, _) = removeDups compare all_tycons + do_con2tag acc_Names tycon - = if (we_are_deriving eqClassKey tycon - && any ( (== 0).dataConArity ) (tyConDataCons tycon)) - || (we_are_deriving ordClassKey tycon - && not (maybeToBool (maybeTyConSingleCon tycon))) - || (we_are_deriving enumClassKey tycon) - || (we_are_deriving ixClassKey tycon) - then - tcGetUnique `thenNF_Tc` ( \ u -> - returnTc ((con2tag_PN tycon, ValName u (con2tag_FN tycon), tycon, GenCon2Tag) - : acc_Names) ) - else - returnTc acc_Names + | isDataTyCon tycon && + ((we_are_deriving eqClassKey tycon + && any isNullarySrcDataCon (tyConDataCons tycon)) + || (we_are_deriving ordClassKey tycon + && not (isProductTyCon tycon)) + || (we_are_deriving enumClassKey tycon) + || (we_are_deriving ixClassKey tycon)) + + = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag) + : acc_Names) + | otherwise + = returnM acc_Names do_tag2con acc_Names tycon - = if (we_are_deriving enumClassKey tycon) - || (we_are_deriving ixClassKey tycon) - then - tcGetUnique `thenNF_Tc` \ u1 -> - tcGetUnique `thenNF_Tc` \ u2 -> - returnTc ( (tag2con_PN tycon, ValName u1 (tag2con_FN tycon), tycon, GenTag2Con) - : (maxtag_PN tycon, ValName u2 (maxtag_FN tycon), tycon, GenMaxTag) - : acc_Names) - else - returnTc acc_Names + | isDataTyCon tycon && + (we_are_deriving enumClassKey tycon || + we_are_deriving ixClassKey tycon + && isEnumerationTyCon tycon) + = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con) + : (maxtag_RDR tycon, tycon, GenMaxTag) + : acc_Names) + | otherwise + = returnM acc_Names we_are_deriving clas_key tycon - = is_in_eqns clas_key tycon eqns + = is_in_eqns clas_key tycon all_CTs where is_in_eqns clas_key tycon [] = False - is_in_eqns clas_key tycon ((c,t,_,_):eqns) - = (clas_key == getClassKey c && tycon == t) - || is_in_eqns clas_key tycon eqns - + is_in_eqns clas_key tycon ((c,t):cts) + = (clas_key == classKey c && tycon == t) + || is_in_eqns clas_key tycon cts \end{code} \begin{code} -derivingEnumErr :: TyCon -> Error -derivingEnumErr tycon - = addErrLoc (getSrcLoc tycon) "Can't derive an instance of `Enum'" ( \ sty -> - ppBesides [ppStr "type `", ppr sty tycon, ppStr "'"] ) - -derivingIxErr :: TyCon -> Error -derivingIxErr tycon - = addErrLoc (getSrcLoc tycon) "Can't derive an instance of `Ix'" ( \ sty -> - ppBesides [ppStr "type `", ppr sty tycon, ppStr "'"] ) --} +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)]) + +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} +