X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=472ce6b94d3942ba706c186acbff3ea569ba2a05;hb=8e512635b618e1daa97022265f268ad4eafda6b4;hp=ee364ac23783e88280334e6918b51582d94ce092;hpb=61fae1d3fb61c5f53c3fbcb94afe7c548ad31591;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index ee364ac..472ce6b 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -10,48 +10,50 @@ module TcDeriv ( tcDeriving ) where #include "HsVersions.h" -import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..), - collectLocatedMonoBinders ) -import RdrHsSyn ( RdrNameMonoBinds ) -import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl ) -import CmdLineOpts ( DynFlag(..), DynFlags ) - -import TcMonad -import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo, - tcLookupClass, tcLookupTyCon +import HsSyn +import DynFlags ( DynFlag(..) ) + +import Generics ( mkTyConGenericBinds ) +import TcRnMonad +import TcEnv ( newDFunName, pprInstInfoDetails, + InstInfo(..), InstBindings(..), simpleInstInfoClsTy, + tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff -import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv ) -import TcSimplify ( tcSimplifyThetas ) - -import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( bindLocatedLocalsRn ) -import RnMonad ( renameDerivedCode, thenRn, mapRn, returnRn ) -import HscTypes ( DFunId, PersistentRenamerState ) - -import BasicTypes ( Fixity ) -import Class ( className, classKey, Class ) -import ErrUtils ( dumpIfSet_dyn, Message ) +import InstEnv ( Instance, OverlapFlag, mkLocalInstance, instanceHead, extendInstEnvList ) +import Inst ( getOverlapFlag ) +import TcHsType ( tcHsDeriv ) +import TcSimplify ( tcSimplifyDeriv ) + +import RnBinds ( rnMethodBinds, rnTopBinds ) +import RnEnv ( bindLocalNames ) +import HscTypes ( FixityEnv ) + +import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) +import Type ( zipOpenTvSubst, substTheta ) +import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon ) -import PrelInfo ( needsDataDeclCtxtClassKeys ) -import Maybes ( maybeToBool, catMaybes ) -import Module ( Module ) -import Name ( Name, getSrcLoc, nameUnique ) +import DataCon ( isNullarySrcDataCon, isVanillaDataCon, dataConOrigArgTys ) +import Maybes ( catMaybes ) import RdrName ( RdrName ) - -import TyCon ( tyConTyVars, tyConDataCons, - tyConTheta, maybeTyConSingleCon, isDataTyCon, - isEnumerationTyCon, TyCon +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 ( ThetaType, mkTyVarTys, mkTyConApp, - isUnLiftedType, mkClassPred ) -import Var ( TyVar ) +import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, tcTyConAppTyCon, + isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind, + tcEqTypes, tcSplitAppTys, mkAppTys ) +import Var ( TyVar, tyVarKind, varName ) +import VarSet ( mkVarSet, subVarSet ) import PrelNames -import Util ( zipWithEqual, sortLt ) -import ListSetOps ( removeDups, assoc ) +import SrcLoc ( srcLocSpan, Located(..) ) +import Util ( zipWithEqual, sortLe, notNull ) +import ListSetOps ( removeDups, assocMaybe ) import Outputable -import List ( nub ) +import Bag \end{code} %************************************************************************ @@ -143,13 +145,16 @@ type DerivEqn = (Name, Class, TyCon, [TyVar], DerivRhs) -- The Name is the name for the DFun we'll build -- The tyvars bind all the variables in the RHS +pprDerivEqn (n,c,tc,tvs,rhs) + = parens (hsep [ppr n, ppr c, ppr tc, ppr tvs] <+> equals <+> ppr rhs) + type DerivRhs = ThetaType type DerivSoln = DerivRhs \end{code} -A note about contexts on data decls -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +[Data decl contexts] A note about contexts on data decls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data (RealFloat a) => Complex a = !a :+ !a deriving( Read ) @@ -171,6 +176,26 @@ 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". + +[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 ... + + + %************************************************************************ %* * @@ -179,76 +204,90 @@ context to the instance decl. The "offending classes" are %************************************************************************ \begin{code} -tcDeriving :: PersistentRenamerState - -> Module -- name of module under scrutiny - -> InstEnv -- What we already know about instances - -> (Name -> Maybe Fixity) -- used in deriving Show and Read - -> [RenamedTyClDecl] -- All type constructors - -> TcM ([InstInfo], -- The generated "instance decls". - RenamedHsBinds) -- Extra generated bindings - -tcDeriving prs mod inst_env_in get_fixity tycl_decls - = recoverTc (returnTc ([], EmptyBinds)) $ - - -- Fish the "deriving"-related information out of the TcEnv - -- and make the necessary "equations". - makeDerivEqns tycl_decls `thenTc` \ eqns -> - if null eqns then - returnTc ([], EmptyBinds) - else - - -- 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) - = 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 - - 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" + HsValBinds Name) -- Extra generated top-level bindings + +tcDeriving tycl_decls + = recoverM (returnM ([], emptyValBindsOut)) $ + do { -- Fish the "deriving"-related information out of the TcEnv + -- and make the necessary "equations". + overlap_flag <- getOverlapFlag + ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns overlap_flag tycl_decls + + ; (ordinary_inst_info, deriv_binds) + <- extendLocalInstEnv (map iSpec newtype_inst_info) $ + deriveOrdinaryStuff overlap_flag ordinary_eqns + -- Add the newtype-derived instances to the inst env + -- before tacking the "ordinary" ones + + ; let inst_info = newtype_inst_info ++ ordinary_inst_info + + -- If we are compiling a hs-boot file, + -- don't generate any derived bindings + ; is_boot <- tcIsHsBoot + ; if is_boot then + return (inst_info, emptyValBindsOut) + else do + { + + -- Generate the generic to/from functions from each type declaration + ; gen_binds <- mkGenericBinds tycl_decls + + -- 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 (ValBindsIn deriv_binds []) + ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to + -- be kept alive + ; return (rn_deriv `plusHsValBinds` 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] -> RenamedHsBinds -> SDoc + ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc ddump_deriving inst_infos extra_binds - = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds - where - - -- Make a Real dfun instead of the dummy one we have so far - gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo - gen_inst_info dfun binds - = InstInfo { iDFunId = dfun, iBinds = binds, iPrags = [] } - - rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) -> - returnRn meths' -- Ignore the free vars returned + = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds + +----------------------------------------- +deriveOrdinaryStuff overlap_flag [] -- Short cut + = returnM ([], emptyLHsBinds) + +deriveOrdinaryStuff overlap_flag 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. + inst_specs <- solveDerivEqns overlap_flag eqns + + -- Generate the InstInfo for each dfun, + -- plus any auxiliary bindings it needs + ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst inst_specs + + -- Generate any extra not-one-inst-decl-specific binds, + -- notably "con2tag" and/or "tag2con" functions. + ; extra_binds <- genTaggeryBinds inst_infos + + -- 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} @@ -274,79 +313,351 @@ or} has just one data constructor (e.g., tuples). all those. \begin{code} -makeDerivEqns :: [RenamedTyClDecl] -> TcM [DerivEqn] - -makeDerivEqns tycl_decls - = mapTc mk_eqn derive_these `thenTc` \ maybe_eqns -> - returnTc (catMaybes maybe_eqns) +makeDerivEqns :: OverlapFlag + -> [LTyClDecl Name] + -> TcM ([DerivEqn], -- Ordinary derivings + [InstInfo]) -- Special newtype derivings + +makeDerivEqns overlap_flag tycl_decls + = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) -> + returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes) where ------------------------------------------------------------------ - derive_these :: [(Name, Name)] - -- Find the (Class,TyCon) pairs that must be `derived' - -- NB: only source-language decls have deriving, no imported ones do - derive_these = [ (clas,tycon) - | TyData {tcdName = tycon, tcdDerivs = Just classes} <- tycl_decls, - clas <- nub classes ] + derive_these :: [(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 ] ------------------------------------------------------------------ - mk_eqn :: (Name, Name) -> NF_TcM (Maybe DerivEqn) - -- we swizzle the tyvars and datacons out of the 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 - - mk_eqn (clas_name, tycon_name) - = tcLookupClass clas_name `thenNF_Tc` \ clas -> - tcLookupTyCon tycon_name `thenNF_Tc` \ tycon -> - let - clas_key = classKey clas - tyvars = tyConTyVars tycon - tyvar_tys = mkTyVarTys tyvars - ty = mkTyConApp tycon tyvar_tys - data_cons = tyConDataCons tycon - locn = getSrcLoc tycon - constraints = extra_constraints ++ concat (map mk_constraints data_cons) - - -- "extra_constraints": see notes above about contexts on data decls - extra_constraints - | offensive_class = tyConTheta tycon - | otherwise = [] - - offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys - - mk_constraints data_con - = [ mkClassPred clas [arg_ty] - | arg_ty <- dataConArgTys data_con tyvar_tys, - not (isUnLiftedType arg_ty) -- No constraints for unlifted types? - ] - in - case chk_out clas tycon of - Just err -> tcAddSrcLoc (getSrcLoc tycon) $ - addErrTc err `thenNF_Tc_` - returnNF_Tc Nothing - Nothing -> newDFunName clas [ty] locn `thenNF_Tc` \ dfun_name -> - returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints)) - - + -- + -- 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 ------------------------------------------------------------------ - chk_out :: Class -> TyCon -> Maybe Message - chk_out clas tycon - | clas `hasKey` enumClassKey && not is_enumeration = bog_out nullary_why - | clas `hasKey` boundedClassKey && not is_enumeration_or_single = bog_out single_nullary_why - | clas `hasKey` ixClassKey && not is_enumeration_or_single = bog_out single_nullary_why - | null data_cons = bog_out no_cons_why - | any isExistentialDataCon data_cons = Just (existentialErr clas tycon) - | otherwise = Nothing - where - data_cons = tyConDataCons tycon - is_enumeration = isEnumerationTyCon tycon - is_single_con = maybeToBool (maybeTyConSingleCon tycon) - is_enumeration_or_single = is_enumeration || is_single_con + 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 { iSpec = mk_inst_spec 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 (zipOpenTvSubst 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_inst_spec dfun_name + = mkLocalInstance dfun overlap_flag + where + dfun = 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 non-Haskell-98 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") - single_nullary_why = SLIT("one constructor data type or type with all nullary constructors expected") - nullary_why = SLIT("data type with all nullary constructors expected") - no_cons_why = SLIT("type has no data constructors") +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 `*'") - bog_out why = Just (derivingThingErr clas tycon why) +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} %************************************************************************ @@ -370,13 +681,13 @@ ordered by sorting on type varible, tv, (major key) and then class, k, \end{itemize} \begin{code} -solveDerivEqns :: InstEnv +solveDerivEqns :: OverlapFlag -> [DerivEqn] - -> TcM [DFunId] -- Solns in same order as eqns. + -> TcM [Instance]-- Solns in same order as eqns. -- This bunch is Absolutely minimal... -solveDerivEqns inst_env_in orig_eqns - = iterateDeriv initial_solutions +solveDerivEqns overlap_flag 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 @@ -389,58 +700,51 @@ solveDerivEqns inst_env_in orig_eqns -- compares it with the current one; finishes if they are the -- same, otherwise recurses with the new solutions. -- It fails if any iteration fails - iterateDeriv :: [DerivSoln] ->TcM [DFunId] - iterateDeriv current_solns - = checkNoErrsTc (iterateOnce current_solns) - `thenTc` \ (new_dfuns, new_solns) -> + iterateDeriv :: Int -> [DerivSoln] -> TcM [Instance] + 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 + inst_specs = zipWithEqual "add_solns" mk_inst_spec + 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 inst_specs $ + mappM gen_soln orig_eqns + ) `thenM` \ new_solns -> if (current_solns == new_solns) then - returnTc new_dfuns + returnM inst_specs else - iterateDeriv new_solns + iterateDeriv (n+1) new_solns ------------------------------------------------------------------ - iterateOnce current_solns - = -- Extend the inst info from the explicit instance decls - -- with the current set of solutions, giving a - getDOptsTc `thenTc` \ dflags -> - let (new_dfuns, inst_env) = - add_solns dflags inst_env_in orig_eqns current_solns - in - -- Simplify each RHS - tcSetInstEnv inst_env ( - listTc [ tcAddSrcLoc (getSrcLoc tc) $ - tcAddErrCtxt (derivCtxt tc) $ - tcSimplifyThetas deriv_rhs - | (_, _,tc,_,deriv_rhs) <- orig_eqns ] - ) `thenTc` \ next_solns -> - - -- Canonicalise the solutions, so they compare nicely - let canonicalised_next_solns = [ sortLt (<) next_soln | next_soln <- next_solns ] - in - returnTc (new_dfuns, canonicalised_next_solns) -\end{code} + gen_soln (_, clas, tc,tyvars,deriv_rhs) + = setSrcSpan (srcLocSpan (getSrcLoc tc)) $ + addErrCtxt (derivCtxt (Just clas) tc) $ + tcSimplifyDeriv tc tyvars deriv_rhs `thenM` \ theta -> + returnM (sortLe (<=) theta) -- Canonicalise before returning the soluction -\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)] - theta + ------------------------------------------------------------------ + mk_inst_spec (dfun_name, clas, tycon, tyvars, _) theta + = mkLocalInstance dfun overlap_flag + where + dfun = mkDictFunId dfun_name tyvars theta clas + [mkTyConApp tycon (mkTyVarTys tyvars)] + +extendLocalInstEnv :: [Instance] -> TcM a -> TcM a +-- Add new locally-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' = extendInstEnvList (tcg_inst_env env) dfuns + env' = env { tcg_inst_env = inst_env' } + ; setGblEnv env' thing_inside } \end{code} %************************************************************************ @@ -498,35 +802,64 @@ 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 renaming --- the method binds) -gen_bind :: (Name -> Maybe Fixity) -> DFunId -> (Name, RdrNameMonoBinds) -gen_bind get_fixity dfun - = (cls_nm, binds) +-- Generate the InstInfo for the required instance, +-- plus any auxiliary bindings required +genInst :: Instance -> TcM (InstInfo, LHsBinds RdrName) +genInst spec + = do { fix_env <- getFixityEnv + ; let + (tyvars,_,clas,[ty]) = instanceHead spec + clas_nm = className clas + tycon = tcTyConAppTyCon ty + (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon + + -- Bring the right type variables into + -- scope, and rename the method binds + -- It's a bit yukky that we return *renamed* InstInfo, but + -- *non-renamed* auxiliary bindings + ; (rn_meth_binds, _fvs) <- discardWarnings $ + bindLocalNames (map varName tyvars) $ + rnMethodBinds clas_nm [] meth_binds + + -- Build the InstInfo + ; return (InstInfo { iSpec = spec, + 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 - cls_nm = className clas - (clas, tycon) = simpleDFunClassTyCon dfun - - binds = assoc "gen_bind:bad derived class" gen_list - (nameUnique cls_nm) tycon - - gen_list = [(eqClassKey, gen_Eq_binds) - ,(ordClassKey, gen_Ord_binds) - ,(enumClassKey, gen_Enum_binds) - ,(boundedClassKey, gen_Bounded_binds) - ,(ixClassKey, gen_Ix_binds) - ,(showClassKey, gen_Show_binds get_fixity) - ,(readClassKey, gen_Read_binds get_fixity) - ] + gen_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} @@ -563,43 +896,42 @@ 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 :: [InstInfo] -> TcM (LHsBinds RdrName) +genTaggeryBinds infos + = 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_CTs = [ (cls, tcTyConAppTyCon ty) + | info <- infos, + let (cls,ty) = simpleInstInfoClsTy info ] all_tycons = map snd all_CTs (tycons_of_interest, _) = removeDups compare all_tycons do_con2tag acc_Names tycon | isDataTyCon tycon && ((we_are_deriving eqClassKey tycon - && any isNullaryDataCon (tyConDataCons tycon)) + && any isNullarySrcDataCon (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 @@ -611,17 +943,18 @@ 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)] - -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)")] +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 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} +