X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDeriv.lhs;h=bd9383fce083a6fb8a734677bb7c949f9d0496e1;hb=8a86866e9e382c1d4d06cad722ddbe965d09997c;hp=0dc41a83f448232dbe5a4897d008176a583bc164;hpb=9af77fa423926fbda946b31e174173d0ec5ebac8;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs index 0dc41a8..bd9383f 100644 --- a/ghc/compiler/typecheck/TcDeriv.lhs +++ b/ghc/compiler/typecheck/TcDeriv.lhs @@ -17,43 +17,44 @@ import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPr import CmdLineOpts ( DynFlag(..) ) import TcRnMonad -import TcEnv ( tcGetInstEnv, tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo, +import TcEnv ( tcExtendTempInstEnv, newDFunName, + InstInfo(..), pprInstInfo, InstBindings(..), pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv ) import TcGenDeriv -- Deriv stuff -import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv ) +import InstEnv ( simpleDFunClassTyCon ) import TcMonoType ( tcHsPred ) import TcSimplify ( tcSimplifyDeriv ) import RnBinds ( rnMethodBinds, rnTopMonoBinds ) -import RnEnv ( bindLocalsFVRn ) -import TcRnMonad ( thenM, returnM, mapAndUnzipM ) +import RnEnv ( bindLocalsFV ) +import TcRnMonad ( thenM, returnM, mapAndUnzipM ) import HscTypes ( DFunId ) import BasicTypes ( NewOrData(..) ) -import Class ( className, classKey, classTyVars, Class ) +import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class ) +import Subst ( mkTyVarSubst, substTheta ) import ErrUtils ( dumpIfSet_dyn ) import MkId ( mkDictFunId ) -import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon ) +import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon ) import Maybes ( maybeToBool, catMaybes ) import Name ( Name, getSrcLoc, nameUnique ) import NameSet import RdrName ( RdrName ) -import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep, +import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConTheta, maybeTyConSingleCon, isDataTyCon, isEnumerationTyCon, isRecursiveTyCon, TyCon ) import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe, isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, - tcSplitTyConApp_maybe, tcEqTypes ) + tcEqTypes, tcSplitAppTys, mkAppTys ) import Var ( TyVar, tyVarKind ) import VarSet ( mkVarSet, subVarSet ) import PrelNames import Util ( zipWithEqual, sortLt, notNull ) import ListSetOps ( removeDups, assoc ) import Outputable -import Maybe ( isJust ) \end{code} %************************************************************************ @@ -153,8 +154,8 @@ 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 ) @@ -198,18 +199,15 @@ tcDeriving :: [RenamedTyClDecl] -- All type constructors tcDeriving tycl_decls = recoverM (returnM ([], EmptyBinds, emptyFVs)) $ getDOpts `thenM` \ dflags -> - tcGetInstEnv `thenM` \ inst_env -> -- Fish the "deriving"-related information out of the TcEnv -- and make the necessary "equations". makeDerivEqns tycl_decls `thenM` \ (ordinary_eqns, newtype_inst_info) -> - let + tcExtendTempInstEnv (map iDFunId newtype_inst_info) $ -- Add the newtype-derived instances to the inst env -- before tacking the "ordinary" ones - inst_env1 = extend_inst_env dflags inst_env - (map iDFunId newtype_inst_info) - in - deriveOrdinaryStuff inst_env1 ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) -> + + deriveOrdinaryStuff ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) -> let inst_info = newtype_inst_info ++ ordinary_inst_info in @@ -229,14 +227,14 @@ tcDeriving tycl_decls -- pprInstInfo doesn't print much: only the type ----------------------------------------- -deriveOrdinaryStuff inst_env_in [] -- Short cut +deriveOrdinaryStuff [] -- Short cut = returnM ([], EmptyBinds, emptyFVs) -deriveOrdinaryStuff inst_env_in eqns +deriveOrdinaryStuff eqns = -- Take the equation list and solve it, to deliver a list of -- solutions, a.k.a. the contexts for the instance decls -- required for the corresponding equations. - solveDerivEqns inst_env_in eqns `thenM` \ new_dfuns -> + solveDerivEqns eqns `thenM` \ new_dfuns -> -- Now augment the InstInfos, adding in the rather boring -- actual-code-to-do-the-methods binds. We may also need to @@ -258,11 +256,11 @@ deriveOrdinaryStuff inst_env_in eqns -- Rename to get RenamedBinds. -- The only tricky bit is that the extra_binds must scope -- over the method bindings for the instances. - bindLocalsFVRn (ptext (SLIT("deriving"))) mbinders $ \ _ -> - rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, fvs) -> + bindLocalsFV (ptext (SLIT("deriving"))) mbinders $ \ _ -> + rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, dus) -> mapAndUnzipM rn_meths method_binds_s `thenM` \ (rn_method_binds_s, fvs_s) -> returnM ((rn_method_binds_s, rn_extra_binds), - fvs `plusFV` plusFVs fvs_s) + duUses dus `plusFV` plusFVs fvs_s) ) `thenM` \ ((rn_method_binds_s, rn_extra_binds), fvs) -> let new_inst_infos = zipWith gen_inst_info new_dfuns rn_method_binds_s @@ -273,7 +271,7 @@ deriveOrdinaryStuff inst_env_in eqns -- Make a Real dfun instead of the dummy one we have so far gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo gen_inst_info dfun binds - = InstInfo { iDFunId = dfun, iBinds = binds, iPrags = [] } + = InstInfo { iDFunId = dfun, iBinds = VanillaInst binds [] } rn_meths (cls, meths) = rnMethodBinds cls [] meths \end{code} @@ -346,45 +344,51 @@ makeDerivEqns tycl_decls constraints = extra_constraints ++ [ mkClassPred clas [arg_ty] | data_con <- tyConDataCons tycon, - arg_ty <- dataConRepArgTys data_con, + 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? ] - -- "extra_constraints": see notes above about contexts on data decls + -- "extra_constraints": see note [Data decl contexts] above extra_constraints = tyConTheta tycon - -- | offensive_class = tyConTheta tycon - -- | otherwise = [] - -- offensive_class = classKey clas `elem` PrelInfo.needsDataDeclCtxtClassKeys - - mk_eqn_help NewType tycon clas tys = doptM Opt_GlasgowExts `thenM` \ gla_exts -> if can_derive_via_isomorphism && (gla_exts || standard_instance) then -- Go ahead and use the isomorphism + traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_` new_dfun_name clas tycon `thenM` \ dfun_name -> - returnM (Nothing, Just (NewTypeDerived (mk_dfun dfun_name))) + returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name, + iBinds = NewTypeDerived rep_tys })) else - if standard_instance then + if standard_instance then mk_eqn_help DataType tycon clas [] -- Go via bale-out route - else + else + -- Non-standard instance + if gla_exts then + -- Too hard bale_out cant_derive_err + else + -- Just complain about being a non-std instance + bale_out non_std_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 + -- 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 Ci (t ak...aj) => Ci (T a1...aj) + -- 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) - kind = tyVarKind (last (classTyVars clas)) + clas_tyvars = classTyVars clas + kind = tyVarKind (last clas_tyvars) -- Kind of the thing we want to instance -- e.g. argument kind of Monad, *->* @@ -393,34 +397,78 @@ makeDerivEqns tycl_decls -- 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 + -- 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 = tyConArity rep_tc - n_args_to_drop + 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 - 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] + 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 - -- We can only do this newtype deriving thing if: standard_instance = null tys && classKey clas `elem` derivableClassKeys + right_arity = length tys + 1 == classArity clas 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; + && 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 ) - && isJust maybe_rep_app -- The rep type is a type constructor app - && n_args_to_keep >= 0 -- Well kinded: + && 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: @@ -436,15 +484,33 @@ makeDerivEqns tycl_decls && (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")) + (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) ------------------------------------------------------------------ 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 + | notNull tys = Just ty_args_why + | not (getUnique clas `elem` derivableClassKeys) = Just (non_std_why clas) | 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 @@ -457,11 +523,15 @@ makeDerivEqns tycl_decls 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)") + single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected") + nullary_why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors") + no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors") + ty_args_why = quotes (ppr pred) <+> ptext SLIT("is not a class") + existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)") + + pred = mkClassPred clas tys + +non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class") new_dfun_name clas tycon -- Just a simple wrapper = newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon) @@ -490,12 +560,11 @@ 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 +solveDerivEqns orig_eqns = iterateDeriv 1 initial_solutions where -- The initial solutions for the equations claim that each @@ -517,15 +586,13 @@ solveDerivEqns inst_env_in orig_eqns = pprPanic "solveDerivEqns: probable loop" (vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns) | otherwise - = getDOpts `thenM` \ dflags -> - let - dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns - inst_env = extend_inst_env dflags inst_env_in dfuns + = 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 - tcSetInstEnv inst_env $ + tcExtendTempInstEnv dfuns $ mappM gen_soln orig_eqns ) `thenM` \ new_solns -> if (current_solns == new_solns) then @@ -540,21 +607,10 @@ solveDerivEqns inst_env_in orig_eqns addErrCtxt (derivCtxt (Just clas) tc) $ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta -> returnM (sortLt (<) theta) -- Canonicalise before returning the soluction -\end{code} - -\begin{code} -extend_inst_env dflags inst_env new_dfuns - = new_inst_env - where - (new_inst_env, _errs) = extendInstEnv dflags inst_env new_dfuns - -- Ignore the errors about duplicate instances. - -- We don't want repeated error messages - -- They'll appear later, when we do the top-level extendInstEnvs mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta - = mkDictFunId dfun_name clas tyvars - [mkTyConApp tycon (mkTyVarTys tyvars)] - theta + = mkDictFunId dfun_name tyvars theta + clas [mkTyConApp tycon (mkTyVarTys tyvars)] \end{code} %************************************************************************