X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=38567e6aae68f237860090969fd7676328c9dfed;hb=f714e6b642fd614a9971717045ae47c3d871275e;hp=9c15b24ed1fe1390620828bda44243e1c36477b7;hpb=0499865e0ff47ce970030a4d65897a5e2f592605;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index 9c15b24..38567e6 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -10,52 +10,53 @@ module TcDeriv ( tcDeriving ) where #include "HsVersions.h" -import HsSyn ( HsBinds(..), MonoBinds(..), collectLocatedMonoBinders ) -import RdrHsSyn ( RdrNameMonoBinds ) -import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds ) -import CmdLineOpts ( DynFlag(..), DynFlags ) - -import TcMonad -import TcEnv ( TcEnv, tcSetInstEnv, getTcGST, newDFunName ) +import HsSyn +import CmdLineOpts ( DynFlag(..) ) + +import Generics ( mkTyConGenericBinds ) +import TcRnMonad +import TcEnv ( newDFunName, + InstInfo(..), InstBindings(..), + pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv + ) import TcGenDeriv -- Deriv stuff -import InstEnv ( InstInfo(..), InstEnv, - pprInstInfo, simpleDFunClassTyCon, extendInstEnv ) -import TcSimplify ( tcSimplifyThetas ) - -import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( bindLocatedLocalsRn ) -import RnMonad ( --RnNameSupply, - renameSourceCode, thenRn, mapRn, returnRn ) -import HscTypes ( DFunId, GlobalSymbolTable, PersistentRenamerState ) - -import Bag ( Bag, emptyBag, unionBags, listToBag ) -import Class ( classKey, Class ) -import ErrUtils ( dumpIfSet_dyn, Message ) +import InstEnv ( simpleDFunClassTyCon, extendInstEnv ) +import TcHsType ( tcHsPred ) +import TcSimplify ( tcSimplifyDeriv ) + +import RnBinds ( rnMethodBinds, rnTopBinds ) +import RnEnv ( bindLocalNames ) +import TcRnMonad ( thenM, returnM, mapAndUnzipM ) +import HscTypes ( DFunId, FixityEnv ) + +import BasicTypes ( NewOrData(..) ) +import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) +import Subst ( mkTyVarSubst, substTheta ) +import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import Id ( mkVanillaId, idType ) -import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon ) -import PrelInfo ( needsDataDeclCtxtClassKeys ) -import Maybes ( maybeToBool, catMaybes ) -import Module ( Module ) -import Name ( Name, isLocallyDefined, getSrcLoc, NamedThing(..) ) +import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) +import Maybes ( catMaybes ) import RdrName ( RdrName ) ---import RnMonad ( FixityEnv ) - -import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings, - tyConTheta, maybeTyConSingleCon, isDataTyCon, - isEnumerationTyCon, isAlgTyCon, TyCon +import Name ( Name, getSrcLoc ) +import NameSet ( NameSet, emptyNameSet, duDefs ) +import Unique ( Unique, getUnique ) +import Kind ( splitKindFunTys ) +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics, + tyConTheta, isProductTyCon, isDataTyCon, + isEnumerationTyCon, isRecursiveTyCon, TyCon ) -import Type ( TauType, PredType(..), mkTyVarTys, mkTyConApp, - mkSigmaTy, splitSigmaTy, splitDictTy, mkDictTy, - isUnboxedType, splitAlgTyConApp, classesToPreds - ) -import TysWiredIn ( voidTy ) -import Var ( TyVar ) +import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp, + getClassPredTys_maybe, tcTyConAppTyCon, + isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind, + tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy ) +import Var ( TyVar, tyVarKind, idType, varName ) +import VarSet ( mkVarSet, subVarSet ) import PrelNames -import Bag ( bagToList ) -import Util ( zipWithEqual, sortLt, thenCmp ) +import SrcLoc ( srcLocSpan, Located(..) ) +import Util ( zipWithEqual, sortLt, notNull ) import ListSetOps ( removeDups, assoc ) import Outputable +import Bag \end{code} %************************************************************************ @@ -147,15 +148,16 @@ type DerivEqn = (Name, Class, TyCon, [TyVar], DerivRhs) -- The Name is the name for the DFun we'll build -- The tyvars bind all the variables in the RHS -type DerivRhs = [(Class, [TauType])] -- Same as a ThetaType! - --[PredType] -- ... | Class Class [Type==TauType] +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 ) @@ -177,6 +179,12 @@ context to the instance decl. The "offending classes" are Read, Enum? +FURTHER NOTE ADDED March 2002. In fact, Haskell98 now requires that +pattern matching against a constructor from a data type with a context +gives rise to the constraints for that context -- or at least the thinned +version. So now all classes are "offending". + + %************************************************************************ %* * @@ -185,84 +193,79 @@ 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 - -> [TyCon] -- "local_tycons" ??? - -> TcM ([InstInfo], -- The generated "instance decls". - RenamedHsBinds) -- Extra generated bindings - -tcDeriving prs mod inst_env_in get_fixity local_tycons - = recoverTc (returnTc ([], EmptyBinds)) $ - - -- Fish the "deriving"-related information out of the TcEnv - -- and make the necessary "equations". - makeDerivEqns mod local_tycons `thenTc` \ eqns -> - if null eqns then - returnTc ([], EmptyBinds) - else - - -- 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 -> - - -- 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 -> - - 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 - - -- 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) - = renameSourceCode 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 = map gen_inst_info (new_dfuns `zip` rn_method_binds_s) - in - - 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) +tcDeriving :: [LTyClDecl Name] -- All type constructors + -> TcM ([InstInfo], -- The generated "instance decls" + [HsBindGroup Name], -- Extra generated top-level bindings + NameSet) -- Binders to keep alive + +tcDeriving tycl_decls + = recoverM (returnM ([], [], emptyNameSet)) $ + 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, gen_bndrs) + <- discardWarnings $ setOptM Opt_GlasgowExts $ do + { (rn_deriv, _dus1) <- rnTopBinds deriv_binds [] + ; (rn_gen, dus_gen) <- rnTopBinds gen_binds [] + ; return (rn_deriv ++ rn_gen, duDefs dus_gen) } + + + ; dflags <- getDOpts + ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info rn_binds)) + + ; returnM (inst_info, rn_binds, gen_bndrs) + } where - ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc + ddump_deriving :: [InstInfo] -> [HsBindGroup Name] -> SDoc ddump_deriving inst_infos extra_binds - = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds - where - - -- Make a Real dfun instead of the dummy one we have so far - gen_inst_info :: (DFunId, RenamedMonoBinds) -> InstInfo - gen_inst_info (dfun, binds) - = InstInfo { iLocal = True, - iClass = clas, iTyVars = tyvars, - iTys = tys, iTheta = theta, - iDFunId = dfun, - iBinds = binds, - iLoc = getSrcLoc dfun, iPrags = [] } - where - (tyvars, theta, tau) = splitSigmaTy (idType dfun) - (clas, tys) = splitDictTy tau - - rn_meths meths = rnMethodBinds [] meths `thenRn` \ (meths', _) -> returnRn meths' - -- Ignore the free vars returned + = vcat (map pprInstInfoDetails inst_infos) $$ vcat (map ppr extra_binds) + +----------------------------------------- +deriveOrdinaryStuff [] -- Short cut + = returnM ([], emptyBag) + +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} @@ -288,85 +291,325 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: Module -> [TyCon] -> TcM [DerivEqn] +makeDerivEqns :: [LTyClDecl Name] + -> TcM ([DerivEqn], -- Ordinary derivings + [InstInfo]) -- Special newtype derivings -makeDerivEqns this_mod local_tycons - = let - think_about_deriving = need_deriving local_tycons - (derive_these, _) = removeDups cmp_deriv think_about_deriving - in - if null local_tycons then - returnTc [] -- Bale out now - else - mapTc mk_eqn derive_these `thenTc` \ maybe_eqns -> - returnTc (catMaybes maybe_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 -> [(clas,tycon) | clas <- tyConDerivings tycon] ++ acc) - [] - tycons_to_consider - - ------------------------------------------------------------------ - cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> Ordering - cmp_deriv (c1, t1) (c2, t2) - = (c1 `compare` c2) `thenCmp` (t1 `compare` t2) + derive_these :: [(NewOrData, Name, LHsPred Name)] + -- Find the (nd, TyCon, Pred) pairs that must be `derived' + -- NB: only source-language decls have deriving, no imported ones do + derive_these = [ (nd, tycon, pred) + | L _ (TyData { tcdND = nd, tcdLName = L _ tycon, + tcdDerivs = Just (L _ preds) }) <- tycl_decls, + pred <- preds ] ------------------------------------------------------------------ - mk_eqn :: (Class, TyCon) -> NF_TcM (Maybe DerivEqn) - -- we swizzle the tyvars and datacons out of the tycon + mk_eqn :: (NewOrData, Name, LHsPred Name) -> 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, tycon) - = case chk_out clas tycon of - Just err -> addErrTc err `thenNF_Tc_` - returnNF_Tc Nothing - Nothing -> newDFunName this_mod clas tyvar_tys locn `thenNF_Tc` \ dfun_name -> - returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints)) - where - clas_key = classKey clas - tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ??? - tyvar_tys = mkTyVarTys tyvars - 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 = [] - where - offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys - - mk_constraints data_con - = [ (clas, [arg_ty]) - | arg_ty <- instd_arg_tys, - not (isUnboxedType arg_ty) -- No constraints for unboxed types? - ] - where - instd_arg_tys = dataConArgTys data_con tyvar_tys + mk_eqn (new_or_data, tycon_name, pred) + = tcLookupTyCon tycon_name `thenM` \ tycon -> + addSrcSpan (srcLocSpan (getSrcLoc tycon)) $ + addErrCtxt (derivCtxt Nothing tycon) $ + tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention + -- the type variables for the type constructor + tcHsPred pred `thenM` \ pred' -> + case getClassPredTys_maybe pred' of + Nothing -> bale_out (malformedPredErr tycon pred) + Just (clas, tys) -> doptM Opt_GlasgowExts `thenM` \ gla_exts -> + mk_eqn_help gla_exts new_or_data tycon clas tys ------------------------------------------------------------------ - 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 - | any isExistentialDataCon (tyConDataCons tycon) = Just (existentialErr clas tycon) - | otherwise = Nothing - where - 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") - - bog_out why = Just (derivingThingErr clas tycon why) + mk_eqn_help gla_exts DataType tycon clas tys + | Just err <- checkSideConditions gla_exts clas tycon tys + = bale_out (derivingThingErr clas tys tycon tyvars err) + | otherwise + = new_dfun_name clas tycon `thenM` \ dfun_name -> + returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing) + where + tyvars = tyConTyVars tycon + constraints = extra_constraints ++ ordinary_constraints + -- "extra_constraints": see note [Data decl contexts] above + extra_constraints = tyConTheta tycon + + ordinary_constraints + | clas `hasKey` typeableClassKey -- For the Typeable class, the constraints + -- don't involve the constructor ags, only + -- the tycon tyvars + -- e.g. data T a b = ... + -- we want + -- instance (Typeable a, Typable b) + -- => Typeable (T a b) where + = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] + | otherwise + = [ mkClassPred clas [arg_ty] + | data_con <- tyConDataCons tycon, + arg_ty <- dataConOrigArgTys data_con, + -- Use the same type variables + -- as the type constructor, + -- hence no need to instantiate + not (isUnLiftedType arg_ty) -- No constraints for unlifted types? + ] + + mk_eqn_help gla_exts NewType tycon clas tys + | can_derive_via_isomorphism && (gla_exts || 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 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 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, _) = splitKindFunTys kind + n_args_to_drop = length arg_kinds + -- Want to drop 1 arg from (T s a) and (ST s a) + -- to get instance Monad (ST s) => Monad (T s) + + -- Note [newtype representation] + -- We must not use newTyConRep to get the representation + -- type, because that looks through all intermediate newtypes + -- To get the RHS of *this* newtype, just look at the data + -- constructor. For example + -- 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 + + 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. + + -- 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 + +------------------------------------------------------------------ +-- Check side conditions that dis-allow derivability for particular classes +-- This is *apart* from the newtype-deriving mechanism + +checkSideConditions :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc +checkSideConditions gla_exts clas tycon tys + | notNull tys + = Just ty_args_why -- e.g. deriving( Foo s ) + | otherwise + = case [cond | (key,cond) <- sideConditions, key == getUnique clas] of + [] -> Just (non_std_why clas) + [cond] -> cond (gla_exts, tycon) + other -> pprPanic "checkSideConditions" (ppr clas) + where + ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class") + +non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class") + +sideConditions :: [(Unique, Condition)] +sideConditions + = [ (eqClassKey, cond_std), + (ordClassKey, cond_std), + (readClassKey, cond_std), + (showClassKey, cond_std), + (enumClassKey, cond_std `andCond` cond_isEnumeration), + (ixClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), + (boundedClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), + (typeableClassKey, cond_glaExts `andCond` cond_allTypeKind), + (dataClassKey, cond_glaExts `andCond` cond_std) + ] + +type Condition = (Bool, TyCon) -> Maybe SDoc -- Nothing => OK + +orCond :: Condition -> Condition -> Condition +orCond c1 c2 tc + = case c1 tc of + Nothing -> Nothing -- c1 succeeds + Just x -> case c2 tc of -- c1 fails + Nothing -> Nothing + Just y -> Just (x $$ ptext SLIT(" and") $$ y) + -- Both fail + +andCond c1 c2 tc = case c1 tc of + Nothing -> c2 tc -- c1 succeeds + Just x -> Just x -- c1 fails + +cond_std :: Condition +cond_std (gla_exts, tycon) + | any isExistentialDataCon data_cons = Just existential_why + | null data_cons = Just no_cons_why + | otherwise = Nothing + where + data_cons = tyConDataCons tycon + no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors") + existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)") + +cond_isEnumeration :: Condition +cond_isEnumeration (gla_exts, tycon) + | isEnumerationTyCon tycon = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors") + +cond_isProduct :: Condition +cond_isProduct (gla_exts, tycon) + | isProductTyCon tycon = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> ptext SLIT("has more than one constructor") + +cond_allTypeKind :: Condition +cond_allTypeKind (gla_exts, tycon) + | all (isArgTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing + | otherwise = Just why + where + why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'") + +cond_glaExts :: Condition +cond_glaExts (gla_exts, tycon) | gla_exts = Nothing + | otherwise = Just why + where + why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class") \end{code} %************************************************************************ @@ -390,13 +633,12 @@ ordered by sorting on type varible, tv, (major key) and then class, k, \end{itemize} \begin{code} -solveDerivEqns :: InstEnv - -> [DerivEqn] +solveDerivEqns :: [DerivEqn] -> TcM [DFunId] -- Solns in same order as eqns. -- This bunch is Absolutely minimal... -solveDerivEqns inst_env_in orig_eqns - = iterateDeriv initial_solutions +solveDerivEqns orig_eqns + = iterateDeriv 1 initial_solutions where -- The initial solutions for the equations claim that each -- instance has an empty context; this solution is certainly @@ -409,58 +651,48 @@ 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 + = 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 - 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 [ 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) -\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 - -- 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)] - (map pair2PredType theta) - - pair2PredType (clas, tautypes) = Class clas tautypes + gen_soln (_, clas, tc,tyvars,deriv_rhs) + = addSrcSpan (srcLocSpan (getSrcLoc tc)) $ + addErrCtxt (derivCtxt (Just clas) tc) $ + tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> + returnM (sortLt (<) theta) -- Canonicalise before returning the soluction + +mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta + = mkDictFunId dfun_name 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} %************************************************************************ @@ -518,34 +750,51 @@ Much less often (really just for deriving @Ix@), we use a \item We use the renamer!!! Reason: we're supposed to be -producing @RenamedMonoBinds@ for the methods, but that means +producing @LHsBinds Name@ for the methods, but that means producing correctly-uniquified code on the fly. This is entirely possible (the @TcM@ monad has a @UniqueSupply@), but it is painful. -So, instead, we produce @RdrNameMonoBinds@ then heave 'em through +So, instead, we produce @MonoBinds RdrName@ then heave 'em through the renamer. What a great hack! \end{itemize} \begin{code} --- Generate the method bindings for the required instance --- (paired with class name, as we need that when generating dict --- names.) -gen_bind :: (Name -> Maybe Fixity) -> DFunId -> RdrNameMonoBinds -gen_bind get_fixity dfun - | not (isLocallyDefined tycon) = EmptyMonoBinds - | clas `hasKey` showClassKey = gen_Show_binds get_fixity tycon - | clas `hasKey` readClassKey = gen_Read_binds get_fixity tycon - | otherwise - = assoc "gen_bind:bad derived class" - [(eqClassKey, gen_Eq_binds) - ,(ordClassKey, gen_Ord_binds) - ,(enumClassKey, gen_Enum_binds) - ,(boundedClassKey, gen_Bounded_binds) - ,(ixClassKey, gen_Ix_binds) - ] - (classKey clas) - tycon - where - (clas, tycon) = simpleDFunClassTyCon dfun +-- 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 + (tyvars,_,clas,[ty]) = tcSplitDFunTy (idType dfun) + clas_nm = className clas + tycon = tcTyConAppTyCon ty + (meth_binds, aux_binds) = assoc "gen_bind:bad derived class" + gen_list (getUnique clas) fix_env tycon + in + -- 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) + +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, emptyBag) +ignore_fix_env f fix_env tc = f tc \end{code} @@ -560,7 +809,7 @@ data Foo ... = ... con2tag_Foo :: Foo ... -> Int# tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int# -maxtag_Foo :: Int -- ditto (NB: not unboxed) +maxtag_Foo :: Int -- ditto (NB: not unlifted) We have a @con2tag@ function for a tycon if: @@ -582,14 +831,11 @@ We're deriving @Enum@, or @Ix@ (enum type only???) If we have a @tag2con@ function, we also generate a @maxtag@ constant. \begin{code} -gen_taggery_Names :: [DFunId] - -> TcM [(RdrName, -- for an assoc list - TyCon, -- related tycon - TagThingWanted)] - -gen_taggery_Names dfuns - = 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 @@ -600,25 +846,25 @@ gen_taggery_Names dfuns ((we_are_deriving eqClassKey tycon && any isNullaryDataCon (tyConDataCons tycon)) || (we_are_deriving ordClassKey tycon - && not (maybeToBool (maybeTyConSingleCon tycon))) + && not (isProductTyCon tycon)) || (we_are_deriving enumClassKey tycon) || (we_are_deriving ixClassKey tycon)) - = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag) + = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag) : acc_Names) | otherwise - = returnTc acc_Names + = returnM acc_Names do_tag2con acc_Names tycon | isDataTyCon tycon && (we_are_deriving enumClassKey tycon || we_are_deriving ixClassKey tycon && isEnumerationTyCon tycon) - = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con) + = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con) : (maxtag_RDR tycon, tycon, GenMaxTag) : acc_Names) | otherwise - = returnTc acc_Names + = returnM acc_Names we_are_deriving clas_key tycon = is_in_eqns clas_key tycon all_CTs @@ -630,17 +876,20 @@ 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} +