X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=80dbea987d3ea2c49c3ff510babda96ffc25c1c5;hb=f2123a38b5c050a5ff7bc4ea147eb80950cbe16b;hp=b0791642cb75a024779e4e07b7bdcd6f78a00d4a;hpb=a77abe6a30ea2763cfa1c0ca83cdce9b7200ced2;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index b079164..80dbea9 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -1,59 +1,60 @@ % -% (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} -#include "HsVersions.h" - -module TcDeriv ( - tcDeriving - ) where +module TcDeriv ( tcDeriving ) where -import Ubiq +#include "HsVersions.h" -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 HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..), + collectLocatedMonoBinders ) +import RdrHsSyn ( RdrNameMonoBinds ) +import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred ) +import CmdLineOpts ( DynFlag(..) ) 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 RnMonad -import RnUtils ( RnEnv(..) ) -import RnBinds ( rnMethodBinds, rnTopBinds ) - -import Bag ( emptyBag{-ToDo:rm-}, Bag, isEmptyBag, unionBags, listToBag ) -import Class ( GenClass, classKey ) -import CmdLineOpts ( opt_CompilingPrelude ) -import ErrUtils ( pprBagOfErrors, addErrLoc, Error(..) ) -import Id ( dataConSig, dataConArity ) -import Maybes ( assocMaybe, maybeToBool, Maybe(..) ) +import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo, + tcLookupTyCon, tcExtendTyVarEnv + ) +import TcGenDeriv -- Deriv stuff +import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv ) +import TcMonoType ( tcHsPred ) +import TcSimplify ( tcSimplifyDeriv ) + +import RnBinds ( rnMethodBinds, rnTopMonoBinds ) +import RnEnv ( bindLocatedLocalsRn ) +import RnMonad ( renameDerivedCode, thenRn, mapRn, returnRn ) +import HscTypes ( DFunId, PersistentRenamerState, FixityEnv ) + +import BasicTypes ( NewOrData(..) ) +import Class ( className, classKey, classTyVars, Class ) +import ErrUtils ( dumpIfSet_dyn ) +import MkId ( mkDictFunId ) +import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon ) +import PrelInfo ( needsDataDeclCtxtClassKeys ) +import Maybes ( maybeToBool, catMaybes ) +import Module ( Module ) +import Name ( Name, getSrcLoc, nameUnique ) +import RdrName ( RdrName ) + +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep, + tyConTheta, maybeTyConSingleCon, isDataTyCon, + isEnumerationTyCon, isRecursiveTyCon, TyCon + ) +import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe, + isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, + tcSplitTyConApp_maybe, tcEqTypes ) +import Var ( TyVar, tyVarKind ) +import VarSet ( mkVarSet, subVarSet ) +import PrelNames +import Util ( zipWithEqual, sortLt, notNull ) +import ListSetOps ( removeDups, assoc ) 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 ( emptyUFM ) -import Unique -- Keys stuff -import Util ( zipWithEqual, zipEqual, sortLt, removeDups, - thenCmp, cmpList, panic, pprPanic, pprPanic# ) +import Maybe ( isJust ) \end{code} %************************************************************************ @@ -69,6 +70,10 @@ 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 @@ -137,16 +142,48 @@ 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} + +A note about contexts on data decls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + + data (RealFloat a) => Complex a = !a :+ !a deriving( Read ) + +We will need an instance decl like: + + instance (Read a, RealFloat a) => Read (Complex a) where + ... + +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. + +But this ain't true for Show, Eq, Ord, etc, since they don't construct +a Complex; they only take them apart. + +Our approach: identify the offending classes, and add the data type +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". + + + %************************************************************************ %* * \subsection[TcDeriv-driver]{Top-level function for \tr{derivings}} @@ -154,76 +191,94 @@ type DerivSoln = DerivRhs %************************************************************************ \begin{code} -tcDeriving :: Module -- name of module under scrutiny - -> RnEnv -- 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 modname rn_env inst_decl_infos_in fixities - = returnTc (trace "tcDeriving:ToDo" (emptyBag, EmptyBinds, \ x -> ppNil)) -{- LATER: - -tcDeriving modname rn_env inst_decl_infos_in fixities - = -- Fish the "deriving"-related information out of the TcEnv +tcDeriving :: PersistentRenamerState + -> Module -- name of module under scrutiny + -> InstEnv -- What we already know about instances + -> FixityEnv -- used in deriving Show and Read + -> [RenamedTyClDecl] -- All type constructors + -> TcM ([InstInfo], -- The generated "instance decls". + RenamedHsBinds) -- Extra generated bindings + +tcDeriving prs mod inst_env get_fixity tycl_decls + = recoverTc (returnTc ([], EmptyBinds)) $ + getDOptsTc `thenNF_Tc` \ dflags -> + + -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". - makeDerivEqns `thenTc` \ eqns -> + makeDerivEqns tycl_decls `thenTc` \ (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 mod prs inst_env1 get_fixity + ordinary_eqns `thenTc` \ (ordinary_inst_info, binds) -> + let + inst_info = newtype_inst_info ++ ordinary_inst_info + in - -- Take the equation list and solve it, to deliver a list of + ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info binds)) `thenTc_` + + returnTc (inst_info, binds) + + 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 (ppr (iBinds inst_info)) + -- pprInstInfo doesn't print much: only the type + +----------------------------------------- +deriveOrdinaryStuff mod prs inst_env_in get_fixity [] -- Short cut + = returnTc ([], EmptyBinds) + +deriveOrdinaryStuff mod prs inst_env_in get_fixity 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 -> + solveDerivEqns inst_env_in eqns `thenTc` \ 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 eqns `thenTc` \ nm_alist_etc -> + tcGetEnv `thenNF_Tc` \ env -> + getDOptsTc `thenNF_Tc` \ dflags -> let - nm_alist = [ (pn, n) | (pn,n,_,_) <- nm_alist_etc ] - - -- 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 - - deriv_val_gnf pname = case (assoc_maybe nm_alist pname) of - Just xx -> Just xx - Nothing -> rn_val_gnf pname - - deriver_name_funs = (deriv_val_gnf, rn_tc_gnf) - - assoc_maybe [] _ = Nothing - assoc_maybe ((k,v) : vs) key - = if k `eqProtoName` key then Just v else assoc_maybe vs key + 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 + + -- 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 - gen_tag_n_con_binds deriver_rn_env nm_alist_etc `thenTc` \ extra_binds -> + returnTc (new_inst_infos, rn_extra_binds) - mapTc (gen_inst_info maybe_mod fixities deriver_rn_env) new_inst_infos - `thenTc` \ really_new_inst_infos -> - - 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 - - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> (PprStyle -> Pretty) + -- 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 = [] } - 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) + rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) -> + returnRn meths' -- Ignore the free vars returned \end{code} @@ -249,78 +304,172 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: TcM s [DerivEqn] +makeDerivEqns :: [RenamedTyClDecl] + -> 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 + = mapAndUnzipTc mk_eqn derive_these `thenTc` \ (maybe_ordinaries, maybe_newtypes) -> + returnTc (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, RenamedHsPred)] + -- Find the (nd, TyCon, Pred) pairs that must be `derived' + -- NB: only source-language decls have deriving, no imported ones do + derive_these = [ (nd, tycon, pred) + | TyData {tcdND = nd, tcdName = tycon, tcdDerivs = Just preds} <- tycl_decls, + pred <- preds ] ------------------------------------------------------------------ - chk_out :: [(Class, TyCon)] -> (Class, TyCon) -> TcM s () - chk_out whole_deriving_list this_one@(clas, tycon) - = let - clas_key = classKey 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, RenamedHsPred) -> NF_TcM (Maybe DerivEqn, Maybe InstInfo) + -- We swizzle the tyvars and datacons out of the tycon + -- to make the rest of the equation - ------------------------------------------------------------------ - cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> TAG_ - cmp_deriv (c1, t1) (c2, t2) - = (c1 `cmp` c2) `thenCmp` (t1 `cmp` t2) + mk_eqn (new_or_data, tycon_name, pred) + = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> + tcAddSrcLoc (getSrcLoc tycon) $ + tcAddErrCtxt (derivCtxt Nothing tycon) $ + tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention + -- the type variables for the type constructor + tcHsPred pred `thenTc` \ 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 :: (Class, TyCon) -> DerivEqn - -- we swizzle the tyvars and datacons out of the tycon - -- to make the rest of the equation - - mk_eqn (clas, tycon) - = (clas, tycon, tyvars, constraints) + 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 `thenNF_Tc` \ dfun_name -> + returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing) where - tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ??? - tyvar_tys = mkTyVarTys tyvars + tyvars = tyConTyVars tycon 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! + 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 = tyConTheta tycon + + -- | 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 + 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 + -- + -- We generate the instances + -- instance Ci (t ak...aj) => Ci (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 ) + + kind = tyVarKind (last (classTyVars clas)) + -- 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) + + (tyvars, rep_ty) = newTyConRep tycon + maybe_rep_app = tcSplitTyConApp_maybe rep_ty + Just (rep_tc, rep_ty_args) = maybe_rep_app + + 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 + 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 + + 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 ) + && isJust maybe_rep_app -- The rep type is a type constructor app + && 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 + (ptext SLIT("too hard for cunning newtype deriving")) + + bale_out err = addErrTc err `thenNF_Tc_` returnNF_Tc (Nothing, 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 = 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)") + +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} %************************************************************************ @@ -334,23 +483,23 @@ 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 +solveDerivEqns :: InstEnv -> [DerivEqn] - -> TcM s [InstInfo] -- Solns in same order as eqns. - -- This bunch is Absolutely minimal... + -> TcM [DFunId] -- Solns in same order as eqns. + -- This bunch is Absolutely minimal... -solveDerivEqns inst_decl_infos_in orig_eqns - = iterateDeriv initial_solutions +solveDerivEqns inst_env_in 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 @@ -358,90 +507,57 @@ 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 + = 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 + in + checkNoErrsTc ( + -- 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 -> + if (current_solns == new_solns) then + returnTc dfuns else - iterateDeriv canonicalised_next_solns + iterateDeriv (n+1) new_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 + ------------------------------------------------------------------ + 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} -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) +extend_inst_env dflags inst_env new_dfuns + = new_inst_env 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 + (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 \end{code} %************************************************************************ @@ -465,8 +581,7 @@ 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. @@ -476,13 +591,13 @@ 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 @@ -491,7 +606,6 @@ 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. @@ -500,114 +614,52 @@ 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 +We use the renamer!!! Reason: we're supposed to be producing @RenamedMonoBinds@ 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 @RdrNameMonoBinds@ 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 - -> RnEnv -- 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_rn_env - 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 - rnMtoTcM deriver_rn_env ( - setExtraRn emptyUFM{-no fixities-} $ - 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 - let - from_here = isLocallyDefined tycon -- If so, then from here - 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 []) +-- Generate the method bindings for the required instance +-- (paired with class name, as we need that when renaming +-- the method binds) +gen_bind :: FixityEnv -> DFunId -> (Name, RdrNameMonoBinds) +gen_bind get_fixity dfun + = (cls_nm, binds) where - clas_key = classKey clas - clas_Name - = let (mod, nm) = moduleNamePair clas in - ClassName clas_key (mkPreludeCoreName mod nm) [] + 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) + ] \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 :: RnEnv - -> [(RdrName, RnName, TyCon, TagThingWanted)] - -> TcM s RenamedHsBinds - -gen_tag_n_con_binds deriver_rn_env 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 - - rnMtoTcM deriver_rn_env ( - setExtraRn emptyUFM{-no fixities-} $ - rnTopBinds (SingleBind (RecBind proto_mbinds)) - ) `thenNF_Tc` \ (binds, errs) -> +maxtag_Foo :: Int -- ditto (NB: not unlifted) - if not (isEmptyBag errs) then - panic "gen_inst_info:renamer errs (2)!" - else - returnTc binds -\end{code} - -%************************************************************************ -%* * -\subsection[TcDeriv-taggery-Names]{What con2tag/tag2con functions are available?} -%* * -%************************************************************************ We have a @con2tag@ function for a tycon if: \begin{itemize} @@ -628,64 +680,68 @@ 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 +gen_taggery_Names :: [DFunId] + -> TcM [(RdrName, -- for an assoc list + TyCon, -- related tycon + TagThingWanted)] + +gen_taggery_Names dfuns + = foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far -> + foldlTc do_tag2con names_so_far tycons_of_interest 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 + | isDataTyCon tycon && + ((we_are_deriving eqClassKey tycon + && any isNullaryDataCon (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 + || (we_are_deriving enumClassKey tycon) + || (we_are_deriving ixClassKey tycon)) + + = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag) + : acc_Names) + | otherwise + = returnTc 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) + = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con) + : (maxtag_RDR tycon, tycon, GenMaxTag) + : acc_Names) + | otherwise + = returnTc 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) + is_in_eqns clas_key tycon ((c,t):cts) = (clas_key == classKey c && tycon == t) - || is_in_eqns clas_key tycon eqns - + || 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)]) + +malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred + +derivCtxt :: Maybe Class -> TyCon -> SDoc +derivCtxt maybe_cls tycon + = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon) + where + cls = case maybe_cls of + Nothing -> ptext SLIT("instances") + Just c -> ptext SLIT("the") <+> quotes (ppr c) <+> ptext SLIT("instance") \end{code} +