X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcMType.lhs;h=5b660df628bf9e279d2e805acf21cb871a7295a2;hb=19f903bc5210e0cccfafbebdc46ed6e1743991ba;hp=fc620ec3deba193c49a754789048aa8d719334c3;hpb=af97da871e57bfd256f21e3c8bff5ef34b83f7ce;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs index fc620ec..5b660df 100644 --- a/compiler/typecheck/TcMType.lhs +++ b/compiler/typecheck/TcMType.lhs @@ -811,7 +811,7 @@ Consider this: * Now abstract over the 'a', but float out the Num (C d a) constraint because it does not 'really' mention a. (see exactTyVarsOfType) The arg to foo becomes - /\a -> \t -> t+t + \/\a -> \t -> t+t * So we get a dict binding for Num (C d a), which is zonked to give a = () @@ -820,10 +820,10 @@ Consider this: quantification, so the floated dict will still have type (C d a). Which renders this whole note moot; happily!] -* Then the /\a abstraction has a zonked 'a' in it. +* Then the \/\a abstraction has a zonked 'a' in it. All very silly. I think its harmless to ignore the problem. We'll end up with -a /\a in the final result but all the occurrences of a will be zonked to () +a \/\a in the final result but all the occurrences of a will be zonked to () Note [Zonking to Skolem] ~~~~~~~~~~~~~~~~~~~~~~~~ @@ -993,25 +993,25 @@ checkValidType ctxt ty = do rankn <- doptM Opt_RankNTypes polycomp <- doptM Opt_PolymorphicComponents let - rank | rankn = Arbitrary - | rank2 = Rank 2 - | otherwise - = case ctxt of -- Haskell 98 - GenPatCtxt -> Rank 0 - LamPatSigCtxt -> Rank 0 - BindPatSigCtxt -> Rank 0 - DefaultDeclCtxt-> Rank 0 - ResSigCtxt -> Rank 0 - TySynCtxt _ -> Rank 0 - ExprSigCtxt -> Rank 1 - FunSigCtxt _ -> Rank 1 - ConArgCtxt _ -> if polycomp - then Rank 2 + gen_rank n | rankn = ArbitraryRank + | rank2 = Rank 2 + | otherwise = Rank n + rank + = case ctxt of + GenPatCtxt -> MustBeMonoType + DefaultDeclCtxt-> MustBeMonoType + ResSigCtxt -> MustBeMonoType + LamPatSigCtxt -> gen_rank 0 + BindPatSigCtxt -> gen_rank 0 + TySynCtxt _ -> gen_rank 0 + ExprSigCtxt -> gen_rank 1 + FunSigCtxt _ -> gen_rank 1 + ConArgCtxt _ | polycomp -> gen_rank 2 -- We are given the type of the entire -- constructor, hence rank 1 - else Rank 1 - ForSigCtxt _ -> Rank 1 - SpecInstCtxt -> Rank 1 + | otherwise -> gen_rank 1 + ForSigCtxt _ -> gen_rank 1 + SpecInstCtxt -> gen_rank 1 actual_kind = typeKind ty @@ -1037,34 +1037,39 @@ checkValidType ctxt ty = do traceTc (text "checkValidType done" <+> ppr ty) checkValidMonoType :: Type -> TcM () -checkValidMonoType ty = check_mono_type ty +checkValidMonoType ty = check_mono_type MustBeMonoType ty \end{code} \begin{code} -data Rank = Rank Int | Arbitrary +data Rank = ArbitraryRank -- Any rank ok + | MustBeMonoType -- Monotype regardless of flags + | TyConArgMonoType -- Monotype but could be poly if -XImpredicativeTypes + | Rank Int -- Rank n, but could be more with -XRankNTypes -decRank :: Rank -> Rank -decRank Arbitrary = Arbitrary -decRank (Rank n) = Rank (n-1) +decRank :: Rank -> Rank -- Function arguments +decRank (Rank 0) = Rank 0 +decRank (Rank n) = Rank (n-1) +decRank other_rank = other_rank nonZeroRank :: Rank -> Bool -nonZeroRank (Rank 0) = False -nonZeroRank _ = True +nonZeroRank ArbitraryRank = True +nonZeroRank (Rank n) = n>0 +nonZeroRank _ = False ---------------------------------------- data UbxTupFlag = UT_Ok | UT_NotOk -- The "Ok" version means "ok if UnboxedTuples is on" ---------------------------------------- -check_mono_type :: Type -> TcM () -- No foralls anywhere - -- No unlifted types of any kind -check_mono_type ty - = do { check_type (Rank 0) UT_NotOk ty +check_mono_type :: Rank -> Type -> TcM () -- No foralls anywhere + -- No unlifted types of any kind +check_mono_type rank ty + = do { check_type rank UT_NotOk ty ; checkTc (not (isUnLiftedType ty)) (unliftedArgErr ty) } check_type :: Rank -> UbxTupFlag -> Type -> TcM () --- The args say what the *type* context requires, independent +-- The args say what the *type context* requires, independent -- of *flag* settings. You test the flag settings at usage sites. -- -- Rank is allowed rank for function args @@ -1072,7 +1077,7 @@ check_type :: Rank -> UbxTupFlag -> Type -> TcM () check_type rank ubx_tup ty | not (null tvs && null theta) - = do { checkTc (nonZeroRank rank) (forAllTyErr ty) + = do { checkTc (nonZeroRank rank) (forAllTyErr rank ty) -- Reject e.g. (Maybe (?x::Int => Int)), -- with a decent error message ; check_valid_theta SigmaCtxt theta @@ -1113,7 +1118,7 @@ check_type rank ubx_tup ty@(TyConApp tc tys) ; liberal <- doptM Opt_LiberalTypeSynonyms ; if not liberal || isOpenSynTyCon tc then -- For H98 and synonym families, do check the type args - mapM_ check_mono_type tys + mapM_ (check_mono_type TyConArgMonoType) tys else -- In the liberal case (only for closed syns), expand then check case tcView ty of @@ -1126,7 +1131,7 @@ check_type rank ubx_tup ty@(TyConApp tc tys) ; checkTc (ubx_tup_ok ub_tuples_allowed) ubx_tup_msg ; impred <- doptM Opt_ImpredicativeTypes - ; let rank' = if impred then rank else Rank 0 + ; let rank' = if impred then ArbitraryRank else TyConArgMonoType -- c.f. check_arg_type -- However, args are allowed to be unlifted, or -- more unboxed tuples, so can't use check_arg_ty @@ -1170,13 +1175,29 @@ check_arg_type :: Rank -> Type -> TcM () check_arg_type rank ty = do { impred <- doptM Opt_ImpredicativeTypes - ; let rank' = if impred then rank else Rank 0 -- Monotype unless impredicative + ; let rank' = if impred then ArbitraryRank -- Arg of tycon can have arby rank, regardless + else case rank of -- Predictive => must be monotype + MustBeMonoType -> MustBeMonoType + _ -> TyConArgMonoType + -- Make sure that MustBeMonoType is propagated, + -- so that we don't suggest -XImpredicativeTypes in + -- (Ord (forall a.a)) => a -> a + ; check_type rank' UT_NotOk ty ; checkTc (not (isUnLiftedType ty)) (unliftedArgErr ty) } ---------------------------------------- -forAllTyErr, unliftedArgErr, ubxArgTyErr :: Type -> SDoc -forAllTyErr ty = sep [ptext (sLit "Illegal polymorphic or qualified type:"), ppr ty] +forAllTyErr :: Rank -> Type -> SDoc +forAllTyErr rank ty + = vcat [ hang (ptext (sLit "Illegal polymorphic or qualified type:")) 2 (ppr ty) + , suggestion ] + where + suggestion = case rank of + Rank _ -> ptext (sLit "Perhaps you intended to use -XRankNTypes or -XRank2Types") + TyConArgMonoType -> ptext (sLit "Perhaps you intended to use -XImpredicativeTypes") + _ -> empty -- Polytype is always illegal + +unliftedArgErr, ubxArgTyErr :: Type -> SDoc unliftedArgErr ty = sep [ptext (sLit "Illegal unlifted type:"), ppr ty] ubxArgTyErr ty = sep [ptext (sLit "Illegal unboxed tuple type as function argument:"), ppr ty] @@ -1269,7 +1290,7 @@ check_pred_ty dflags ctxt pred@(ClassP cls tys) ; checkTc (arity == n_tys) arity_err -- Check the form of the argument types - ; mapM_ check_mono_type tys + ; mapM_ checkValidMonoType tys ; checkTc (check_class_pred_tys dflags ctxt tys) (predTyVarErr pred $$ how_to_allow) } @@ -1286,11 +1307,11 @@ check_pred_ty dflags _ pred@(EqPred ty1 ty2) ; checkTc (dopt Opt_TypeFamilies dflags) (eqPredTyErr pred) -- Check the form of the argument types - ; check_mono_type ty1 - ; check_mono_type ty2 + ; checkValidMonoType ty1 + ; checkValidMonoType ty2 } -check_pred_ty _ SigmaCtxt (IParam _ ty) = check_mono_type ty +check_pred_ty _ SigmaCtxt (IParam _ ty) = checkValidMonoType ty -- Implicit parameters only allowed in type -- signatures; not in instance decls, superclasses etc -- The reason for not allowing implicit params in instances is a bit @@ -1479,29 +1500,32 @@ checkValidInstHead ty -- Should be a source type Just (clas,tys) -> do dflags <- getDOpts - mapM_ check_mono_type tys check_inst_head dflags clas tys return (clas, tys) }} check_inst_head :: DynFlags -> Class -> [Type] -> TcM () check_inst_head dflags clas tys - -- If GlasgowExts then check at least one isn't a type variable - = do checkTc (dopt Opt_TypeSynonymInstances dflags || - all tcInstHeadTyNotSynonym tys) - (instTypeErr (pprClassPred clas tys) head_type_synonym_msg) - checkTc (dopt Opt_FlexibleInstances dflags || - all tcInstHeadTyAppAllTyVars tys) - (instTypeErr (pprClassPred clas tys) head_type_args_tyvars_msg) - checkTc (dopt Opt_MultiParamTypeClasses dflags || - isSingleton tys) - (instTypeErr (pprClassPred clas tys) head_one_type_msg) - mapM_ check_mono_type tys + = do { -- If GlasgowExts then check at least one isn't a type variable + ; checkTc (dopt Opt_TypeSynonymInstances dflags || + all tcInstHeadTyNotSynonym tys) + (instTypeErr (pprClassPred clas tys) head_type_synonym_msg) + ; checkTc (dopt Opt_FlexibleInstances dflags || + all tcInstHeadTyAppAllTyVars tys) + (instTypeErr (pprClassPred clas tys) head_type_args_tyvars_msg) + ; checkTc (dopt Opt_MultiParamTypeClasses dflags || + isSingleton tys) + (instTypeErr (pprClassPred clas tys) head_one_type_msg) + -- May not contain type family applications + ; mapM_ checkTyFamFreeness tys + + ; mapM_ checkValidMonoType tys -- For now, I only allow tau-types (not polytypes) in -- the head of an instance decl. -- E.g. instance C (forall a. a->a) is rejected -- One could imagine generalising that, but I'm not sure -- what all the consequences might be + } where head_type_synonym_msg = parens ( @@ -1719,7 +1743,7 @@ checkFamInst lhsTys famInsts checkTyFamFreeness :: Type -> TcM () checkTyFamFreeness ty = checkTc (isTyFamFree ty) $ - tyFamInstInIndexErr ty + tyFamInstIllegalErr ty -- Check that a type does not contain any type family applications. -- @@ -1728,9 +1752,9 @@ isTyFamFree = null . tyFamInsts -- Error messages -tyFamInstInIndexErr :: Type -> SDoc -tyFamInstInIndexErr ty - = hang (ptext (sLit "Illegal type family application in type instance") <> +tyFamInstIllegalErr :: Type -> SDoc +tyFamInstIllegalErr ty + = hang (ptext (sLit "Illegal type synonym family application in instance") <> colon) 4 $ ppr ty