X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcUnify.lhs;h=c13cff66fae6e871c7629c506004889d41c1ee5e;hb=5f553f0c0508cb09b75f78e6c2ac1baa4c01b6aa;hp=2cf985ed3a3f2b4998f44e17917bd1c0bcbb4056;hpb=469c3333ae5954cee58cdb1575b41fb1a3c34f06;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcUnify.lhs b/ghc/compiler/typecheck/TcUnify.lhs index 2cf985e..c13cff6 100644 --- a/ghc/compiler/typecheck/TcUnify.lhs +++ b/ghc/compiler/typecheck/TcUnify.lhs @@ -6,18 +6,22 @@ \begin{code} module TcUnify ( -- Full-blown subsumption - tcSub, tcGen, subFunTy, - checkSigTyVars, checkSigTyVarsWrt, sigCtxt, + tcSubOff, tcSubExp, tcGen, + checkSigTyVars, checkSigTyVarsWrt, sigCtxt, findGlobals, -- Various unifications unifyTauTy, unifyTauTyList, unifyTauTyLists, - unifyFunTy, unifyListTy, unifyPArrTy, unifyTupleTy, - unifyKind, unifyKinds, unifyOpenTypeKind, - - -- Coercions - Coercion, ExprCoFn, PatCoFn, - (<$>), (<.>), mkCoercion, - idCoercion, isIdCoercion + unifyKind, unifyKinds, unifyFunKind, + checkExpectedKind, + + -------------------------------- + -- Holes + Expected(..), newHole, readExpectedType, + zapExpectedType, zapExpectedTo, zapExpectedBranches, + subFunTys, unifyFunTy, + zapToListTy, unifyListTy, + zapToPArrTy, unifyPArrTy, + zapToTupleTy, unifyTupleTy ) where @@ -25,76 +29,307 @@ module TcUnify ( import HsSyn ( HsExpr(..) ) -import TcHsSyn ( TypecheckedHsExpr, TcPat, mkHsLet ) -import TypeRep ( Type(..), SourceType(..), TyNote(..), - openKindCon, typeCon ) - -import TcMonad -- TcType, amongst others -import TcType ( TcKind, TcType, TcSigmaType, TcPhiType, TcTyVar, TcTauType, - TcTyVarSet, TcThetaType, - isTauTy, isSigmaTy, +import TcHsSyn ( mkHsLet, mkHsDictLam, + ExprCoFn, idCoercion, isIdCoercion, mkCoercion, (<.>), (<$>) ) +import TypeRep ( Type(..), PredType(..), TyNote(..) ) + +import TcRnMonad -- TcType, amongst others +import TcType ( TcKind, TcType, TcSigmaType, TcRhoType, TcTyVar, TcTauType, + TcTyVarSet, TcThetaType, TyVarDetails(SigTv), + isTauTy, isSigmaTy, mkFunTys, mkTyConApp, tcSplitAppTy_maybe, tcSplitTyConApp_maybe, tcGetTyVar_maybe, tcGetTyVar, - mkTyConApp, mkFunTy, tyVarsOfType, mkRhoTy, + mkFunTy, tyVarsOfType, mkPhiTy, typeKind, tcSplitFunTy_maybe, mkForAllTys, - isHoleTyVar, isSkolemTyVar, isUserTyVar, + isSkolemTyVar, isUserTyVar, tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars, - eqKind, openTypeKind, liftedTypeKind, isTypeKind, - hasMoreBoxityInfo, tyVarBindingInfo, allDistinctTyVars - ) -import qualified Type ( getTyVar_maybe ) -import Inst ( LIE, emptyLIE, plusLIE, - newDicts, instToId, tcInstCall - ) -import TcMType ( getTcTyVar, putTcTyVar, tcInstType, - newTyVarTy, newTyVarTys, newBoxityVar, newHoleTyVarTy, - zonkTcType, zonkTcTyVars, zonkTcTyVarsAndFV, zonkTcTyVar ) + allDistinctTyVars, pprType ) +import Kind ( Kind(..), SimpleKind, KindVar, isArgTypeKind, + openTypeKind, liftedTypeKind, mkArrowKind, + isOpenTypeKind, argTypeKind, isLiftedTypeKind, isUnliftedTypeKind, + isSubKind, pprKind, splitKindFunTys ) +import Inst ( newDicts, instToId, tcInstCall ) +import TcMType ( getTcTyVar, putTcTyVar, tcInstType, newKindVar, + newTyVarTy, newTyVarTys, zonkTcKind, + zonkTcType, zonkTcTyVars, zonkTcTyVarsAndFV, + readKindVar,writeKindVar ) import TcSimplify ( tcSimplifyCheck ) -import TysWiredIn ( listTyCon, parrTyCon, mkListTy, mkPArrTy, mkTupleTy ) -import TcEnv ( TcTyThing(..), tcGetGlobalTyVars, tcLEnvElts ) -import TyCon ( tyConArity, isTupleTyCon, tupleTyConBoxity ) -import PprType ( pprType ) -import Id ( mkSysLocal, idType ) +import TysWiredIn ( listTyCon, parrTyCon, tupleTyCon ) +import TcEnv ( tcGetGlobalTyVars, findGlobals ) +import TyCon ( TyCon, tyConArity, isTupleTyCon, tupleTyConBoxity ) +import Id ( Id, mkSysLocal ) import Var ( Var, varName, tyVarKind ) -import VarSet ( emptyVarSet, unionVarSet, elemVarSet, varSetElems ) +import VarSet ( emptyVarSet, unitVarSet, unionVarSet, elemVarSet, varSetElems ) import VarEnv -import Name ( isSystemName, getSrcLoc ) +import Name ( isSystemName ) import ErrUtils ( Message ) +import SrcLoc ( noLoc ) import BasicTypes ( Boxity, Arity, isBoxed ) -import Util ( equalLength ) -import Maybe ( isNothing ) +import Util ( equalLength, lengthExceeds, notNull ) import Outputable \end{code} +Notes on holes +~~~~~~~~~~~~~~ +* A hole is always filled in with an ordinary type, not another hole. %************************************************************************ %* * -\subsection{Subsumption} +\subsection{'hole' type variables} %* * %************************************************************************ \begin{code} -tcSub :: TcSigmaType -- expected_ty; can be a type scheme; - -- can be a "hole" type variable - -> TcSigmaType -- actual_ty; can be a type scheme - -> TcM (ExprCoFn, LIE) +data Expected ty = Infer (TcRef ty) -- The hole to fill in for type inference + | Check ty -- The type to check during type checking + +newHole :: TcM (TcRef ty) +newHole = newMutVar (error "Empty hole in typechecker") + +readExpectedType :: Expected ty -> TcM ty +readExpectedType (Infer hole) = readMutVar hole +readExpectedType (Check ty) = returnM ty + +zapExpectedType :: Expected TcType -> Kind -> TcM TcTauType +-- In the inference case, ensure we have a monotype +-- (including an unboxed tuple) +zapExpectedType (Infer hole) kind + = do { ty <- newTyVarTy kind ; + writeMutVar hole ty ; + return ty } + +zapExpectedType (Check ty) kind + | typeKind ty `isSubKind` kind = return ty + | otherwise = do { ty1 <- newTyVarTy kind + ; unifyTauTy ty1 ty + ; return ty } + -- The unify is to ensure that 'ty' has the desired kind + -- For example, in (case e of r -> b) we push an OpenTypeKind + -- type variable + +zapExpectedTo :: Expected TcType -> TcTauType -> TcM () +zapExpectedTo (Infer hole) ty2 = writeMutVar hole ty2 +zapExpectedTo (Check ty1) ty2 = unifyTauTy ty1 ty2 + +zapExpectedBranches :: [a] -> Expected TcType -> TcM (Expected TcType) +-- Zap the expected type to a monotype if there is more than one branch +zapExpectedBranches branches exp_ty + | lengthExceeds branches 1 = zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' -> + return (Check exp_ty') + | otherwise = returnM exp_ty + +instance Outputable ty => Outputable (Expected ty) where + ppr (Check ty) = ptext SLIT("Expected type") <+> ppr ty + ppr (Infer hole) = ptext SLIT("Inferring type") +\end{code} + + +%************************************************************************ +%* * +\subsection[Unify-fun]{@unifyFunTy@} +%* * +%************************************************************************ + +@subFunTy@ and @unifyFunTy@ is used to avoid the fruitless +creation of type variables. + +* subFunTy is used when we might be faced with a "hole" type variable, + in which case we should create two new holes. + +* unifyFunTy is used when we expect to encounter only "ordinary" + type variables, so we should create new ordinary type variables + +\begin{code} +subFunTys :: [pat] + -> Expected TcRhoType -- Fail if ty isn't a function type + -> ([(pat, Expected TcRhoType)] -> Expected TcRhoType -> TcM a) + -> TcM a + +subFunTys pats (Infer hole) thing_inside + = -- This is the interesting case + mapM new_pat_hole pats `thenM` \ pats_w_holes -> + newHole `thenM` \ res_hole -> + + -- Do the business + thing_inside pats_w_holes (Infer res_hole) `thenM` \ answer -> + + -- Extract the answers + mapM read_pat_hole pats_w_holes `thenM` \ arg_tys -> + readMutVar res_hole `thenM` \ res_ty -> + + -- Write the answer into the incoming hole + writeMutVar hole (mkFunTys arg_tys res_ty) `thenM_` + + -- And return the answer + returnM answer + where + new_pat_hole pat = newHole `thenM` \ hole -> return (pat, Infer hole) + read_pat_hole (pat, Infer hole) = readMutVar hole + +subFunTys pats (Check ty) thing_inside + = go pats ty `thenM` \ (pats_w_tys, res_ty) -> + thing_inside pats_w_tys res_ty + where + go [] ty = return ([], Check ty) + go (pat:pats) ty = unifyFunTy ty `thenM` \ (arg,res) -> + go pats res `thenM` \ (pats_w_tys, final_res) -> + return ((pat, Check arg) : pats_w_tys, final_res) + +unifyFunTy :: TcRhoType -- Fail if ty isn't a function type + -> TcM (TcType, TcType) -- otherwise return arg and result types + +unifyFunTy ty@(TyVarTy tyvar) + = getTcTyVar tyvar `thenM` \ maybe_ty -> + case maybe_ty of + Just ty' -> unifyFunTy ty' + Nothing -> unify_fun_ty_help ty + +unifyFunTy ty + = case tcSplitFunTy_maybe ty of + Just arg_and_res -> returnM arg_and_res + Nothing -> unify_fun_ty_help ty + +unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification + = newTyVarTy argTypeKind `thenM` \ arg -> + newTyVarTy openTypeKind `thenM` \ res -> + unifyTauTy ty (mkFunTy arg res) `thenM_` + returnM (arg,res) +\end{code} + +\begin{code} +---------------------- +zapToListTy, zapToPArrTy :: Expected TcType -- expected list type + -> TcM TcType -- list element type +unifyListTy, unifyPArrTy :: TcType -> TcM TcType +zapToListTy = zapToXTy listTyCon +unifyListTy = unifyXTy listTyCon +zapToPArrTy = zapToXTy parrTyCon +unifyPArrTy = unifyXTy parrTyCon + +---------------------- +zapToXTy :: TyCon -- T :: *->* + -> Expected TcType -- Expected type (T a) + -> TcM TcType -- Element type, a + +zapToXTy tc (Check ty) = unifyXTy tc ty +zapToXTy tc (Infer hole) = do { elt_ty <- newTyVarTy liftedTypeKind ; + writeMutVar hole (mkTyConApp tc [elt_ty]) ; + return elt_ty } + +---------------------- +unifyXTy :: TyCon -> TcType -> TcM TcType +unifyXTy tc ty@(TyVarTy tyvar) + = getTcTyVar tyvar `thenM` \ maybe_ty -> + case maybe_ty of + Just ty' -> unifyXTy tc ty' + other -> unify_x_ty_help tc ty + +unifyXTy tc ty + = case tcSplitTyConApp_maybe ty of + Just (tycon, [arg_ty]) | tycon == tc -> returnM arg_ty + other -> unify_x_ty_help tc ty + +unify_x_ty_help tc ty -- Revert to ordinary unification + = newTyVarTy liftedTypeKind `thenM` \ elt_ty -> + unifyTauTy ty (mkTyConApp tc [elt_ty]) `thenM_` + returnM elt_ty +\end{code} + +\begin{code} +---------------------- +zapToTupleTy :: Boxity -> Arity -> Expected TcType -> TcM [TcType] +zapToTupleTy boxity arity (Check ty) = unifyTupleTy boxity arity ty +zapToTupleTy boxity arity (Infer hole) = do { (tup_ty, arg_tys) <- new_tuple_ty boxity arity ; + writeMutVar hole tup_ty ; + return arg_tys } + +unifyTupleTy boxity arity ty@(TyVarTy tyvar) + = getTcTyVar tyvar `thenM` \ maybe_ty -> + case maybe_ty of + Just ty' -> unifyTupleTy boxity arity ty' + other -> unify_tuple_ty_help boxity arity ty + +unifyTupleTy boxity arity ty + = case tcSplitTyConApp_maybe ty of + Just (tycon, arg_tys) + | isTupleTyCon tycon + && tyConArity tycon == arity + && tupleTyConBoxity tycon == boxity + -> returnM arg_tys + other -> unify_tuple_ty_help boxity arity ty + +unify_tuple_ty_help boxity arity ty + = new_tuple_ty boxity arity `thenM` \ (tup_ty, arg_tys) -> + unifyTauTy ty tup_ty `thenM_` + returnM arg_tys + +new_tuple_ty boxity arity + = newTyVarTys arity kind `thenM` \ arg_tys -> + return (mkTyConApp tup_tc arg_tys, arg_tys) + where + tup_tc = tupleTyCon boxity arity + kind | isBoxed boxity = liftedTypeKind + | otherwise = argTypeKind -- Components of an unboxed tuple + -- can be unboxed, but not unboxed tuples \end{code} -(tcSub expected_ty actual_ty) checks that - actual_ty <= expected_ty -That is, that a value of type actual_ty is acceptable in + +%************************************************************************ +%* * +\subsection{Subsumption} +%* * +%************************************************************************ + +All the tcSub calls have the form + + tcSub expected_ty offered_ty +which checks + offered_ty <= expected_ty + +That is, that a value of type offered_ty is acceptable in a place expecting a value of type expected_ty. It returns a coercion function - co_fn :: actual_ty -> expected_ty -which takes an HsExpr of type actual_ty into one of type + co_fn :: offered_ty -> expected_ty +which takes an HsExpr of type offered_ty into one of type expected_ty. \begin{code} +tcSubExp :: Expected TcRhoType -> TcRhoType -> TcM ExprCoFn +tcSubOff :: TcSigmaType -> Expected TcSigmaType -> TcM ExprCoFn +\end{code} + +These two check for holes + +\begin{code} +tcSubExp expected_ty offered_ty + = traceTc (text "tcSubExp" <+> (ppr expected_ty $$ ppr offered_ty)) `thenM_` + checkHole expected_ty offered_ty tcSub + +tcSubOff expected_ty offered_ty + = checkHole offered_ty expected_ty (\ off exp -> tcSub exp off) + +-- checkHole looks for a hole in its first arg; +-- If so, and it is uninstantiated, it fills in the hole +-- with its second arg +-- Otherwise it calls thing_inside, passing the two args, looking +-- through any instantiated hole + +checkHole (Infer hole) other_ty thing_inside + = do { writeMutVar hole other_ty; return idCoercion } + +checkHole (Check ty) other_ty thing_inside + = thing_inside ty other_ty +\end{code} + +No holes expected now. Add some error-check context info. + +\begin{code} +tcSub :: TcSigmaType -> TcSigmaType -> TcM ExprCoFn -- Locally used only tcSub expected_ty actual_ty - = traceTc (text "tcSub" <+> details) `thenNF_Tc_` - tcAddErrCtxtM (unifyCtxt "type" expected_ty actual_ty) - (tc_sub expected_ty expected_ty actual_ty actual_ty) + = traceTc (text "tcSub" <+> details) `thenM_` + addErrCtxtM (unifyCtxt "type" expected_ty actual_ty) + (tc_sub expected_ty expected_ty actual_ty actual_ty) where details = vcat [text "Expected:" <+> ppr expected_ty, text "Actual: " <+> ppr actual_ty] @@ -107,7 +342,7 @@ tc_sub :: TcSigmaType -- expected_ty, before expanding synonyms -> TcSigmaType -- ..and after -> TcSigmaType -- actual_ty, before -> TcSigmaType -- ..and after - -> TcM (ExprCoFn, LIE) + -> TcM ExprCoFn ----------------------------------- -- Expand synonyms @@ -115,24 +350,6 @@ tc_sub exp_sty (NoteTy _ exp_ty) act_sty act_ty = tc_sub exp_sty exp_ty act_sty tc_sub exp_sty exp_ty act_sty (NoteTy _ act_ty) = tc_sub exp_sty exp_ty act_sty act_ty ----------------------------------- --- "Hole type variable" case --- Do this case before unwrapping for-alls in the actual_ty - -tc_sub _ (TyVarTy tv) act_sty act_ty - | isHoleTyVar tv - = -- It's a "hole" type variable - getTcTyVar tv `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - - Just ty -> -- Already been assigned - tc_sub ty ty act_sty act_ty ; - - Nothing -> -- Assign it - putTcTyVar tv act_sty `thenNF_Tc_` - returnTc (idCoercion, emptyLIE) - - ------------------------------------ -- Generalisation case -- actual_ty: d:Eq b => b->b -- expected_ty: forall a. Ord a => a->a @@ -149,8 +366,8 @@ tc_sub exp_sty expected_ty act_sty actual_ty -- It's really important to check for escape wrt the free vars of -- both expected_ty *and* actual_ty \ body_exp_ty -> tc_sub body_exp_ty body_exp_ty act_sty actual_ty - ) `thenTc` \ (gen_fn, co_fn, lie) -> - returnTc (gen_fn <.> co_fn, lie) + ) `thenM` \ (gen_fn, co_fn) -> + returnM (gen_fn <.> co_fn) ----------------------------------- -- Specialisation case: @@ -160,9 +377,9 @@ tc_sub exp_sty expected_ty act_sty actual_ty tc_sub exp_sty expected_ty act_sty actual_ty | isSigmaTy actual_ty - = tcInstCall Rank2Origin actual_ty `thenNF_Tc` \ (inst_fn, lie1, body_ty) -> - tc_sub exp_sty expected_ty body_ty body_ty `thenTc` \ (co_fn, lie2) -> - returnTc (co_fn <.> mkCoercion inst_fn, lie1 `plusLIE` lie2) + = tcInstCall Rank2Origin actual_ty `thenM` \ (inst_fn, body_ty) -> + tc_sub exp_sty expected_ty body_ty body_ty `thenM` \ co_fn -> + returnM (co_fn <.> inst_fn) ----------------------------------- -- Function case @@ -182,28 +399,40 @@ tc_sub _ (FunTy exp_arg exp_res) _ (FunTy act_arg act_res) -- when the arg/res is not a tau-type? -- NO! e.g. f :: ((forall a. a->a) -> Int) -> Int -- then x = (f,f) --- is perfectly fine! +-- is perfectly fine, because we can instantiat f's type to a monotype +-- +-- However, we get can get jolly unhelpful error messages. +-- e.g. foo = id runST +-- +-- Inferred type is less polymorphic than expected +-- Quantified type variable `s' escapes +-- Expected type: ST s a -> t +-- Inferred type: (forall s1. ST s1 a) -> a +-- In the first argument of `id', namely `runST' +-- In a right-hand side of function `foo': id runST +-- +-- I'm not quite sure what to do about this! tc_sub exp_sty exp_ty@(FunTy exp_arg exp_res) _ (TyVarTy tv) - = getTcTyVar tv `thenNF_Tc` \ maybe_ty -> + = getTcTyVar tv `thenM` \ maybe_ty -> case maybe_ty of Just ty -> tc_sub exp_sty exp_ty ty ty - Nothing -> imitateFun tv exp_sty `thenNF_Tc` \ (act_arg, act_res) -> + Nothing -> imitateFun tv exp_sty `thenM` \ (act_arg, act_res) -> tcSub_fun exp_arg exp_res act_arg act_res tc_sub _ (TyVarTy tv) act_sty act_ty@(FunTy act_arg act_res) - = getTcTyVar tv `thenNF_Tc` \ maybe_ty -> + = getTcTyVar tv `thenM` \ maybe_ty -> case maybe_ty of Just ty -> tc_sub ty ty act_sty act_ty - Nothing -> imitateFun tv act_sty `thenNF_Tc` \ (exp_arg, exp_res) -> + Nothing -> imitateFun tv act_sty `thenM` \ (exp_arg, exp_res) -> tcSub_fun exp_arg exp_res act_arg act_res ----------------------------------- -- Unification case -- If none of the above match, we revert to the plain unifier tc_sub exp_sty expected_ty act_sty actual_ty - = uTys exp_sty expected_ty act_sty actual_ty `thenTc_` - returnTc (idCoercion, emptyLIE) + = uTys exp_sty expected_ty act_sty actual_ty `thenM_` + returnM idCoercion \end{code} %************************************************************************ @@ -214,43 +443,42 @@ tc_sub exp_sty expected_ty act_sty actual_ty \begin{code} tcSub_fun exp_arg exp_res act_arg act_res - = tcSub act_arg exp_arg `thenTc` \ (co_fn_arg, lie1) -> - tcSub exp_res act_res `thenTc` \ (co_fn_res, lie2) -> - tcGetUnique `thenNF_Tc` \ uniq -> + = tc_sub act_arg act_arg exp_arg exp_arg `thenM` \ co_fn_arg -> + tc_sub exp_res exp_res act_res act_res `thenM` \ co_fn_res -> + newUnique `thenM` \ uniq -> let -- co_fn_arg :: HsExpr exp_arg -> HsExpr act_arg -- co_fn_res :: HsExpr act_res -> HsExpr exp_res -- co_fn :: HsExpr (act_arg -> act_res) -> HsExpr (exp_arg -> exp_res) - arg_id = mkSysLocal SLIT("sub") uniq exp_arg + arg_id = mkSysLocal FSLIT("sub") uniq exp_arg coercion | isIdCoercion co_fn_arg, isIdCoercion co_fn_res = idCoercion | otherwise = mkCoercion co_fn co_fn e = DictLam [arg_id] - (co_fn_res <$> (HsApp e (co_fn_arg <$> (HsVar arg_id)))) + (noLoc (co_fn_res <$> (HsApp (noLoc e) (noLoc (co_fn_arg <$> HsVar arg_id))))) -- Slight hack; using a "DictLam" to get an ordinary simple lambda -- HsVar arg_id :: HsExpr exp_arg -- co_fn_arg $it :: HsExpr act_arg -- HsApp e $it :: HsExpr act_res -- co_fn_res $it :: HsExpr exp_res in - returnTc (coercion, lie1 `plusLIE` lie2) + returnM coercion -imitateFun :: TcTyVar -> TcType -> NF_TcM (TcType, TcType) +imitateFun :: TcTyVar -> TcType -> TcM (TcType, TcType) imitateFun tv ty - = ASSERT( not (isHoleTyVar tv) ) - -- NB: tv is an *ordinary* tyvar and so are the new ones + = -- NB: tv is an *ordinary* tyvar and so are the new ones -- Check that tv isn't a type-signature type variable -- (This would be found later in checkSigTyVars, but -- we get a better error message if we do it here.) - checkTcM (not (isSkolemTyVar tv)) - (failWithTcM (unifyWithSigErr tv ty)) `thenTc_` + checkM (not (isSkolemTyVar tv)) + (failWithTcM (unifyWithSigErr tv ty)) `thenM_` - newTyVarTy openTypeKind `thenNF_Tc` \ arg -> - newTyVarTy openTypeKind `thenNF_Tc` \ res -> - putTcTyVar tv (mkFunTy arg res) `thenNF_Tc_` - returnNF_Tc (arg,res) + newTyVarTy argTypeKind `thenM` \ arg -> + newTyVarTy openTypeKind `thenM` \ res -> + putTcTyVar tv (mkFunTy arg res) `thenM_` + returnM (arg,res) \end{code} @@ -265,16 +493,16 @@ tcGen :: TcSigmaType -- expected_ty -> TcTyVarSet -- Extra tyvars that the universally -- quantified tyvars of expected_ty -- must not be unified - -> (TcPhiType -> TcM (result, LIE)) -- spec_ty - -> TcM (ExprCoFn, result, LIE) + -> (TcRhoType -> TcM result) -- spec_ty + -> TcM (ExprCoFn, result) -- The expression has type: spec_ty -> expected_ty tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall-type -- If not, the call is a no-op - = tcInstType expected_ty `thenNF_Tc` \ (forall_tvs, theta, phi_ty) -> + = tcInstType SigTv expected_ty `thenM` \ (forall_tvs, theta, phi_ty) -> -- Type-check the arg and unify with poly type - thing_inside phi_ty `thenTc` \ (result, lie) -> + getLIE (thing_inside phi_ty) `thenM` \ (result, lie) -> -- Check that the "forall_tvs" havn't been constrained -- The interesting bit here is that we must include the free variables @@ -287,60 +515,39 @@ tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall -- Conclusion: include the free vars of the expected_ty in the -- list of "free vars" for the signature check. - newDicts SignatureOrigin theta `thenNF_Tc` \ dicts -> - tcSimplifyCheck sig_msg forall_tvs dicts lie `thenTc` \ (free_lie, inst_binds) -> - checkSigTyVarsWrt free_tvs forall_tvs `thenTc` \ zonked_tvs -> + newDicts SignatureOrigin theta `thenM` \ dicts -> + tcSimplifyCheck sig_msg forall_tvs dicts lie `thenM` \ inst_binds -> + +#ifdef DEBUG + zonkTcTyVars forall_tvs `thenM` \ forall_tys -> + traceTc (text "tcGen" <+> vcat [text "extra_tvs" <+> ppr extra_tvs, + text "expected_ty" <+> ppr expected_ty, + text "inst ty" <+> ppr forall_tvs <+> ppr theta <+> ppr phi_ty, + text "free_tvs" <+> ppr free_tvs, + text "forall_tys" <+> ppr forall_tys]) `thenM_` +#endif + + checkSigTyVarsWrt free_tvs forall_tvs `thenM` \ zonked_tvs -> + + traceTc (text "tcGen:done") `thenM_` let -- This HsLet binds any Insts which came out of the simplification. -- It's a bit out of place here, but using AbsBind involves inventing -- a couple of new names which seems worse. dict_ids = map instToId dicts - co_fn e = TyLam zonked_tvs (DictLam dict_ids (mkHsLet inst_binds e)) + co_fn e = TyLam zonked_tvs (mkHsDictLam dict_ids (mkHsLet inst_binds (noLoc e))) in - returnTc (mkCoercion co_fn, result, free_lie) + returnM (mkCoercion co_fn, result) where free_tvs = tyVarsOfType expected_ty `unionVarSet` extra_tvs - sig_msg = ptext SLIT("When generalising the type of an expression") + sig_msg = ptext SLIT("expected type of an expression") \end{code} %************************************************************************ %* * -\subsection{Coercion functions} -%* * -%************************************************************************ - -\begin{code} -type Coercion a = Maybe (a -> a) - -- Nothing => identity fn - -type ExprCoFn = Coercion TypecheckedHsExpr -type PatCoFn = Coercion TcPat - -(<.>) :: Coercion a -> Coercion a -> Coercion a -- Composition -Nothing <.> Nothing = Nothing -Nothing <.> Just f = Just f -Just f <.> Nothing = Just f -Just f1 <.> Just f2 = Just (f1 . f2) - -(<$>) :: Coercion a -> a -> a -Just f <$> e = f e -Nothing <$> e = e - -mkCoercion :: (a -> a) -> Coercion a -mkCoercion f = Just f - -idCoercion :: Coercion a -idCoercion = Nothing - -isIdCoercion :: Coercion a -> Bool -isIdCoercion = isNothing -\end{code} - -%************************************************************************ -%* * \subsection[Unify-exported]{Exported unification functions} %* * %************************************************************************ @@ -357,7 +564,7 @@ unifyTauTy ty1 ty2 -- ty1 expected, ty2 inferred -- (no quantification whatsoever) ASSERT2( isTauTy ty1, ppr ty1 ) ASSERT2( isTauTy ty2, ppr ty2 ) - tcAddErrCtxtM (unifyCtxt "type" ty1 ty2) $ + addErrCtxtM (unifyCtxt "type" ty1 ty2) $ uTys ty1 ty1 ty2 ty2 \end{code} @@ -368,8 +575,8 @@ complain if their lengths differ. \begin{code} unifyTauTyLists :: [TcTauType] -> [TcTauType] -> TcM () -unifyTauTyLists [] [] = returnTc () -unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenTc_` +unifyTauTyLists [] [] = returnM () +unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenM_` unifyTauTyLists tys1 tys2 unifyTauTyLists ty1s ty2s = panic "Unify.unifyTauTyLists: mismatched type lists!" \end{code} @@ -380,9 +587,9 @@ lists, when all the elts should be of the same type. \begin{code} unifyTauTyList :: [TcTauType] -> TcM () -unifyTauTyList [] = returnTc () -unifyTauTyList [ty] = returnTc () -unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenTc_` +unifyTauTyList [] = returnM () +unifyTauTyList [ty] = returnM () +unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenM_` unifyTauTyList tys \end{code} @@ -419,42 +626,38 @@ uTys ps_ty1 ty1 ps_ty2 (TyVarTy tyvar2) = uVar True tyvar2 ps_ty1 ty1 -- "True" means args swapped -- Predicates -uTys _ (SourceTy (IParam n1 t1)) _ (SourceTy (IParam n2 t2)) +uTys _ (PredTy (IParam n1 t1)) _ (PredTy (IParam n2 t2)) | n1 == n2 = uTys t1 t1 t2 t2 -uTys _ (SourceTy (ClassP c1 tys1)) _ (SourceTy (ClassP c2 tys2)) +uTys _ (PredTy (ClassP c1 tys1)) _ (PredTy (ClassP c2 tys2)) | c1 == c2 = unifyTauTyLists tys1 tys2 -uTys _ (SourceTy (NType tc1 tys1)) _ (SourceTy (NType tc2 tys2)) - | tc1 == tc2 = unifyTauTyLists tys1 tys2 -- Functions; just check the two parts uTys _ (FunTy fun1 arg1) _ (FunTy fun2 arg2) - = uTys fun1 fun1 fun2 fun2 `thenTc_` uTys arg1 arg1 arg2 arg2 + = uTys fun1 fun1 fun2 fun2 `thenM_` uTys arg1 arg1 arg2 arg2 - -- Type constructors must match + -- NewType constructors must match +uTys _ (NewTcApp tc1 tys1) _ (NewTcApp tc2 tys2) + | tc1 == tc2 = unifyTauTyLists tys1 tys2 + + -- Ordinary type constructors must match uTys ps_ty1 (TyConApp con1 tys1) ps_ty2 (TyConApp con2 tys2) | con1 == con2 && equalLength tys1 tys2 = unifyTauTyLists tys1 tys2 - | con1 == openKindCon - -- When we are doing kind checking, we might match a kind '?' - -- against a kind '*' or '#'. Notably, CCallable :: ? -> *, and - -- (CCallable Int) and (CCallable Int#) are both OK - = unifyOpenTypeKind ps_ty2 - -- Applications need a bit of care! -- They can match FunTy and TyConApp, so use splitAppTy_maybe -- NB: we've already dealt with type variables and Notes, -- so if one type is an App the other one jolly well better be too uTys ps_ty1 (AppTy s1 t1) ps_ty2 ty2 = case tcSplitAppTy_maybe ty2 of - Just (s2,t2) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2 + Just (s2,t2) -> uTys s1 s1 s2 s2 `thenM_` uTys t1 t1 t2 t2 Nothing -> unifyMisMatch ps_ty1 ps_ty2 -- Now the same, but the other way round -- Don't swap the types, because the error messages get worse uTys ps_ty1 ty1 ps_ty2 (AppTy s2 t2) = case tcSplitAppTy_maybe ty1 of - Just (s1,t1) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2 + Just (s1,t1) -> uTys s1 s1 s2 s2 `thenM_` uTys t1 t1 t2 t2 Nothing -> unifyMisMatch ps_ty1 ps_ty2 -- Not expecting for-alls in unification @@ -537,47 +740,51 @@ uVar :: Bool -- False => tyvar is the "expected" -> TcM () uVar swapped tv1 ps_ty2 ty2 - = traceTc (text "uVar" <+> ppr swapped <+> ppr tv1 <+> (ppr ps_ty2 $$ ppr ty2)) `thenNF_Tc_` - getTcTyVar tv1 `thenNF_Tc` \ maybe_ty1 -> + = traceTc (text "uVar" <+> ppr swapped <+> ppr tv1 <+> (ppr ps_ty2 $$ ppr ty2)) `thenM_` + getTcTyVar tv1 `thenM` \ maybe_ty1 -> case maybe_ty1 of Just ty1 | swapped -> uTys ps_ty2 ty2 ty1 ty1 -- Swap back | otherwise -> uTys ty1 ty1 ps_ty2 ty2 -- Same order - other -> uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2 + other -> uUnboundVar swapped tv1 ps_ty2 ty2 -- Expand synonyms; ignore FTVs -uUnboundVar swapped tv1 maybe_ty1 ps_ty2 (NoteTy n2 ty2) - = uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2 +uUnboundVar swapped tv1 ps_ty2 (NoteTy n2 ty2) + = uUnboundVar swapped tv1 ps_ty2 ty2 -- The both-type-variable case -uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2@(TyVarTy tv2) +uUnboundVar swapped tv1 ps_ty2 ty2@(TyVarTy tv2) -- Same type variable => no-op | tv1 == tv2 - = returnTc () + = returnM () -- Distinct type variables - -- ASSERT maybe_ty1 /= Just | otherwise - = getTcTyVar tv2 `thenNF_Tc` \ maybe_ty2 -> + = getTcTyVar tv2 `thenM` \ maybe_ty2 -> case maybe_ty2 of - Just ty2' -> uUnboundVar swapped tv1 maybe_ty1 ty2' ty2' + Just ty2' -> uUnboundVar swapped tv1 ty2' ty2' Nothing | update_tv2 + -- It should always be the case that either k1 <: k2 or k2 <: k1 + -- Reason: a type variable never gets the kinds (#) or # - -> WARN( not (k1 `hasMoreBoxityInfo` k2), (ppr tv1 <+> ppr k1) $$ (ppr tv2 <+> ppr k2) ) - putTcTyVar tv2 (TyVarTy tv1) `thenNF_Tc_` - returnTc () - | otherwise + -> ASSERT2( k1 `isSubKind` k2, (ppr tv1 <+> ppr k1) $$ (ppr tv2 <+> ppr k2) ) + putTcTyVar tv2 (TyVarTy tv1) `thenM_` + returnM () - -> WARN( not (k2 `hasMoreBoxityInfo` k1), (ppr tv2 <+> ppr k2) $$ (ppr tv1 <+> ppr k1) ) - putTcTyVar tv1 ps_ty2 `thenNF_Tc_` - returnTc () + | otherwise + -> ASSERT2( k2 `isSubKind` k1, (ppr tv2 <+> ppr k2) $$ (ppr tv1 <+> ppr k1) ) + putTcTyVar tv1 ps_ty2 `thenM_` + returnM () where k1 = tyVarKind tv1 k2 = tyVarKind tv2 - update_tv2 = (k2 `eqKind` openTypeKind) || (not (k1 `eqKind` openTypeKind) && nicer_to_update_tv2) - -- Try to get rid of open type variables as soon as poss + update_tv2 = k1 `isSubKind` k2 && (k1 /= k2 || nicer_to_update_tv2) + -- Update the variable with least kind info + -- See notes on type inference in Kind.lhs + -- The "nicer to" part only applies if the two kinds are the same, + -- so we can choose which to do. nicer_to_update_tv2 = isUserTyVar tv1 -- Don't unify a signature type variable if poss @@ -585,22 +792,22 @@ uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2@(TyVarTy tv2) -- Try to update sys-y type variables in preference to sig-y ones -- Second one isn't a type variable -uUnboundVar swapped tv1 maybe_ty1 ps_ty2 non_var_ty2 +uUnboundVar swapped tv1 ps_ty2 non_var_ty2 = -- Check that tv1 isn't a type-signature type variable - checkTcM (not (isSkolemTyVar tv1)) - (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenTc_` + checkM (not (isSkolemTyVar tv1)) + (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenM_` -- Do the occurs check, and check that we are not -- unifying a type variable with a polytype -- Returns a zonked type ready for the update - checkValue tv1 ps_ty2 non_var_ty2 `thenTc` \ ty2 -> + checkValue tv1 ps_ty2 non_var_ty2 `thenM` \ ty2 -> -- Check that the kinds match - checkKinds swapped tv1 ty2 `thenTc_` + checkKinds swapped tv1 ty2 `thenM_` -- Perform the update - putTcTyVar tv1 ty2 `thenNF_Tc_` - returnTc () + putTcTyVar tv1 ty2 `thenM_` + returnM () \end{code} \begin{code} @@ -608,15 +815,15 @@ checkKinds swapped tv1 ty2 -- We're about to unify a type variable tv1 with a non-tyvar-type ty2. -- ty2 has been zonked at this stage, which ensures that -- its kind has as much boxity information visible as possible. - | tk2 `hasMoreBoxityInfo` tk1 = returnTc () + | tk2 `isSubKind` tk1 = returnM () | otherwise -- Either the kinds aren't compatible -- (can happen if we unify (a b) with (c d)) -- or we are unifying a lifted type variable with an -- unlifted type: e.g. (id 3#) is illegal - = tcAddErrCtxtM (unifyKindCtxt swapped tv1 ty2) $ - unifyMisMatch k1 k2 + = addErrCtxtM (unifyKindCtxt swapped tv1 ty2) $ + unifyKindMisMatch k1 k2 where (k1,k2) | swapped = (tk2,tk1) @@ -650,16 +857,16 @@ checkValue tv1 ps_ty2 non_var_ty2 -- Rather, we should bind t to () (= non_var_ty2). -- -- That's why we have this two-state occurs-check - = zonkTcType ps_ty2 `thenNF_Tc` \ ps_ty2' -> + = zonkTcType ps_ty2 `thenM` \ ps_ty2' -> case okToUnifyWith tv1 ps_ty2' of { - Nothing -> returnTc ps_ty2' ; -- Success + Nothing -> returnM ps_ty2' ; -- Success other -> - zonkTcType non_var_ty2 `thenNF_Tc` \ non_var_ty2' -> + zonkTcType non_var_ty2 `thenM` \ non_var_ty2' -> case okToUnifyWith tv1 non_var_ty2' of Nothing -> -- This branch rarely succeeds, except in strange cases -- like that in the example above - returnTc non_var_ty2' + returnM non_var_ty2' Just problem -> failWithTcM (unifyCheck problem tv1 ps_ty2') } @@ -680,8 +887,9 @@ okToUnifyWith tv ty ok (AppTy t1 t2) = ok t1 `and` ok t2 ok (FunTy t1 t2) = ok t1 `and` ok t2 ok (TyConApp _ ts) = oks ts + ok (NewTcApp _ ts) = oks ts ok (ForAllTy _ _) = Just NotMonoType - ok (SourceTy st) = ok_st st + ok (PredTy st) = ok_st st ok (NoteTy (FTVNote _) t) = ok t ok (NoteTy (SynNote t1) t2) = ok t1 `and` ok t2 -- Type variables may be free in t1 but not t2 @@ -691,180 +899,140 @@ okToUnifyWith tv ty ok_st (ClassP _ ts) = oks ts ok_st (IParam _ t) = ok t - ok_st (NType _ ts) = oks ts Nothing `and` m = m Just p `and` m = Just p \end{code} -%************************************************************************ -%* * -\subsection[Unify-fun]{@unifyFunTy@} -%* * -%************************************************************************ - -@subFunTy@ and @unifyFunTy@ is used to avoid the fruitless -creation of type variables. - -* subFunTy is used when we might be faced with a "hole" type variable, - in which case we should create two new holes. - -* unifyFunTy is used when we expect to encounter only "ordinary" - type variables, so we should create new ordinary type variables - -\begin{code} -subFunTy :: TcSigmaType -- Fail if ty isn't a function type - -> TcM (TcType, TcType) -- otherwise return arg and result types -subFunTy ty@(TyVarTy tyvar) - - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty -> subFunTy ty - Nothing | isHoleTyVar tyvar - -> newHoleTyVarTy `thenNF_Tc` \ arg -> - newHoleTyVarTy `thenNF_Tc` \ res -> - putTcTyVar tyvar (mkFunTy arg res) `thenNF_Tc_` - returnTc (arg,res) - | otherwise - -> unify_fun_ty_help ty - -subFunTy ty - = case tcSplitFunTy_maybe ty of - Just arg_and_res -> returnTc arg_and_res - Nothing -> unify_fun_ty_help ty - - -unifyFunTy :: TcPhiType -- Fail if ty isn't a function type - -> TcM (TcType, TcType) -- otherwise return arg and result types - -unifyFunTy ty@(TyVarTy tyvar) - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty' -> unifyFunTy ty' - Nothing -> unify_fun_ty_help ty - -unifyFunTy ty - = case tcSplitFunTy_maybe ty of - Just arg_and_res -> returnTc arg_and_res - Nothing -> unify_fun_ty_help ty - -unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification - = newTyVarTy openTypeKind `thenNF_Tc` \ arg -> - newTyVarTy openTypeKind `thenNF_Tc` \ res -> - unifyTauTy ty (mkFunTy arg res) `thenTc_` - returnTc (arg,res) -\end{code} - -\begin{code} -unifyListTy :: TcType -- expected list type - -> TcM TcType -- list element type - -unifyListTy ty@(TyVarTy tyvar) - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty' -> unifyListTy ty' - other -> unify_list_ty_help ty - -unifyListTy ty - = case tcSplitTyConApp_maybe ty of - Just (tycon, [arg_ty]) | tycon == listTyCon -> returnTc arg_ty - other -> unify_list_ty_help ty - -unify_list_ty_help ty -- Revert to ordinary unification - = newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty -> - unifyTauTy ty (mkListTy elt_ty) `thenTc_` - returnTc elt_ty - --- variant for parallel arrays --- -unifyPArrTy :: TcType -- expected list type - -> TcM TcType -- list element type - -unifyPArrTy ty@(TyVarTy tyvar) - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty' -> unifyPArrTy ty' - _ -> unify_parr_ty_help ty -unifyPArrTy ty - = case tcSplitTyConApp_maybe ty of - Just (tycon, [arg_ty]) | tycon == parrTyCon -> returnTc arg_ty - _ -> unify_parr_ty_help ty - -unify_parr_ty_help ty -- Revert to ordinary unification - = newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty -> - unifyTauTy ty (mkPArrTy elt_ty) `thenTc_` - returnTc elt_ty -\end{code} - -\begin{code} -unifyTupleTy :: Boxity -> Arity -> TcType -> TcM [TcType] -unifyTupleTy boxity arity ty@(TyVarTy tyvar) - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty' -> unifyTupleTy boxity arity ty' - other -> unify_tuple_ty_help boxity arity ty - -unifyTupleTy boxity arity ty - = case tcSplitTyConApp_maybe ty of - Just (tycon, arg_tys) - | isTupleTyCon tycon - && tyConArity tycon == arity - && tupleTyConBoxity tycon == boxity - -> returnTc arg_tys - other -> unify_tuple_ty_help boxity arity ty - -unify_tuple_ty_help boxity arity ty - = newTyVarTys arity kind `thenNF_Tc` \ arg_tys -> - unifyTauTy ty (mkTupleTy boxity arity arg_tys) `thenTc_` - returnTc arg_tys - where - kind | isBoxed boxity = liftedTypeKind - | otherwise = openTypeKind -\end{code} - %************************************************************************ %* * -\subsection{Kind unification} + Kind unification %* * %************************************************************************ +Unifying kinds is much, much simpler than unifying types. + \begin{code} unifyKind :: TcKind -- Expected -> TcKind -- Actual -> TcM () -unifyKind k1 k2 - = tcAddErrCtxtM (unifyCtxt "kind" k1 k2) $ - uTys k1 k1 k2 k2 +unifyKind LiftedTypeKind LiftedTypeKind = returnM () +unifyKind UnliftedTypeKind UnliftedTypeKind = returnM () + +unifyKind OpenTypeKind k2 | isOpenTypeKind k2 = returnM () +unifyKind ArgTypeKind k2 | isArgTypeKind k2 = returnM () + -- Respect sub-kinding + +unifyKind (FunKind a1 r1) (FunKind a2 r2) + = do { unifyKind a2 a1; unifyKind r1 r2 } + -- Notice the flip in the argument, + -- so that the sub-kinding works right + +unifyKind (KindVar kv1) k2 = uKVar False kv1 k2 +unifyKind k1 (KindVar kv2) = uKVar True kv2 k1 +unifyKind k1 k2 = unifyKindMisMatch k1 k2 unifyKinds :: [TcKind] -> [TcKind] -> TcM () -unifyKinds [] [] = returnTc () -unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenTc_` +unifyKinds [] [] = returnM () +unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenM_` unifyKinds ks1 ks2 -unifyKinds _ _ = panic "unifyKinds: length mis-match" +unifyKinds _ _ = panic "unifyKinds: length mis-match" + +---------------- +uKVar :: Bool -> KindVar -> TcKind -> TcM () +uKVar swapped kv1 k2 + = do { mb_k1 <- readKindVar kv1 + ; case mb_k1 of + Nothing -> uUnboundKVar swapped kv1 k2 + Just k1 | swapped -> unifyKind k2 k1 + | otherwise -> unifyKind k1 k2 } + +---------------- +uUnboundKVar :: Bool -> KindVar -> TcKind -> TcM () +uUnboundKVar swapped kv1 k2@(KindVar kv2) + | kv1 == kv2 = returnM () + | otherwise -- Distinct kind variables + = do { mb_k2 <- readKindVar kv2 + ; case mb_k2 of + Just k2 -> uUnboundKVar swapped kv1 k2 + Nothing -> writeKindVar kv1 k2 } + +uUnboundKVar swapped kv1 non_var_k2 + = do { k2' <- zonkTcKind non_var_k2 + ; kindOccurCheck kv1 k2' + ; k2'' <- kindSimpleKind swapped k2' + -- KindVars must be bound only to simple kinds + -- Polarities: (kindSimpleKind True ?) succeeds + -- returning *, corresponding to unifying + -- expected: ? + -- actual: kind-ver + ; writeKindVar kv1 k2'' } + +---------------- +kindOccurCheck kv1 k2 -- k2 is zonked + = checkTc (not_in k2) (kindOccurCheckErr kv1 k2) + where + not_in (KindVar kv2) = kv1 /= kv2 + not_in (FunKind a2 r2) = not_in a2 && not_in r2 + not_in other = True + +kindSimpleKind :: Bool -> Kind -> TcM SimpleKind +-- (kindSimpleKind True k) returns a simple kind sk such that sk <: k +-- If the flag is False, it requires k <: sk +-- E.g. kindSimpleKind False ?? = * +-- What about (kv -> *) :=: ?? -> * +kindSimpleKind orig_swapped orig_kind + = go orig_swapped orig_kind + where + go sw (FunKind k1 k2) = do { k1' <- go (not sw) k1 + ; k2' <- go sw k2 + ; return (FunKind k1' k2') } + go True OpenTypeKind = return liftedTypeKind + go True ArgTypeKind = return liftedTypeKind + go sw LiftedTypeKind = return liftedTypeKind + go sw k@(KindVar _) = return k -- KindVars are always simple + go swapped kind = failWithTc (ptext SLIT("Unexpected kind unification failure:") + <+> ppr orig_swapped <+> ppr orig_kind) + -- I think this can't actually happen + +-- T v = MkT v v must be a type +-- T v w = MkT (v -> w) v must not be an umboxed tuple + +---------------- +kindOccurCheckErr tyvar ty + = hang (ptext SLIT("Occurs check: cannot construct the infinite kind:")) + 2 (sep [ppr tyvar, char '=', ppr ty]) + +unifyKindMisMatch ty1 ty2 + = zonkTcKind ty1 `thenM` \ ty1' -> + zonkTcKind ty2 `thenM` \ ty2' -> + let + msg = hang (ptext SLIT("Couldn't match kind")) + 2 (sep [quotes (ppr ty1'), + ptext SLIT("against"), + quotes (ppr ty2')]) + in + failWithTc msg \end{code} \begin{code} -unifyOpenTypeKind :: TcKind -> TcM () --- Ensures that the argument kind is of the form (Type bx) --- for some boxity bx - -unifyOpenTypeKind ty@(TyVarTy tyvar) - = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty -> - case maybe_ty of - Just ty' -> unifyOpenTypeKind ty' - other -> unify_open_kind_help ty - -unifyOpenTypeKind ty - | isTypeKind ty = returnTc () - | otherwise = unify_open_kind_help ty - -unify_open_kind_help ty -- Revert to ordinary unification - = newBoxityVar `thenNF_Tc` \ boxity -> - unifyKind ty (mkTyConApp typeCon [boxity]) +unifyFunKind :: TcKind -> TcM (Maybe (TcKind, TcKind)) +-- Like unifyFunTy, but does not fail; instead just returns Nothing + +unifyFunKind (KindVar kvar) + = readKindVar kvar `thenM` \ maybe_kind -> + case maybe_kind of + Just fun_kind -> unifyFunKind fun_kind + Nothing -> do { arg_kind <- newKindVar + ; res_kind <- newKindVar + ; writeKindVar kvar (mkArrowKind arg_kind res_kind) + ; returnM (Just (arg_kind,res_kind)) } + +unifyFunKind (FunKind arg_kind res_kind) = returnM (Just (arg_kind,res_kind)) +unifyFunKind other = returnM Nothing \end{code} - %************************************************************************ %* * \subsection[Unify-context]{Errors and contexts} @@ -876,12 +1044,12 @@ Errors \begin{code} unifyCtxt s ty1 ty2 tidy_env -- ty1 expected, ty2 inferred - = zonkTcType ty1 `thenNF_Tc` \ ty1' -> - zonkTcType ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (err ty1' ty2') + = zonkTcType ty1 `thenM` \ ty1' -> + zonkTcType ty2 `thenM` \ ty2' -> + returnM (err ty1' ty2') where err ty1 ty2 = (env1, - nest 4 + nest 2 (vcat [ text "Expected" <+> text s <> colon <+> ppr tidy_ty1, text "Inferred" <+> text s <> colon <+> ppr tidy_ty2 @@ -890,42 +1058,42 @@ unifyCtxt s ty1 ty2 tidy_env -- ty1 expected, ty2 inferred (env1, [tidy_ty1,tidy_ty2]) = tidyOpenTypes tidy_env [ty1,ty2] unifyKindCtxt swapped tv1 ty2 tidy_env -- not swapped => tv1 expected, ty2 inferred - -- tv1 is zonked already - = zonkTcType ty2 `thenNF_Tc` \ ty2' -> - returnNF_Tc (err ty2') + -- tv1 and ty2 are zonked already + = returnM msg where - err ty2 = (env2, ptext SLIT("When matching types") <+> - sep [quotes pp_expected, ptext SLIT("and"), quotes pp_actual]) - where - (pp_expected, pp_actual) | swapped = (pp2, pp1) - | otherwise = (pp1, pp2) - (env1, tv1') = tidyOpenTyVar tidy_env tv1 - (env2, ty2') = tidyOpenType env1 ty2 - pp1 = ppr tv1' - pp2 = ppr ty2' + msg = (env2, ptext SLIT("When matching types") <+> + sep [quotes pp_expected <+> ptext SLIT("and"), quotes pp_actual]) + + (pp_expected, pp_actual) | swapped = (pp2, pp1) + | otherwise = (pp1, pp2) + (env1, tv1') = tidyOpenTyVar tidy_env tv1 + (env2, ty2') = tidyOpenType env1 ty2 + pp1 = ppr tv1' <+> dcolon <+> ppr (tyVarKind tv1) + pp2 = ppr ty2' <+> dcolon <+> ppr (typeKind ty2) unifyMisMatch ty1 ty2 - = zonkTcType ty1 `thenNF_Tc` \ ty1' -> - zonkTcType ty2 `thenNF_Tc` \ ty2' -> + = zonkTcType ty1 `thenM` \ ty1' -> + zonkTcType ty2 `thenM` \ ty2' -> let (env, [tidy_ty1, tidy_ty2]) = tidyOpenTypes emptyTidyEnv [ty1',ty2'] msg = hang (ptext SLIT("Couldn't match")) - 4 (sep [quotes (ppr tidy_ty1), + 2 (sep [quotes (ppr tidy_ty1), ptext SLIT("against"), quotes (ppr tidy_ty2)]) in failWithTcM (env, msg) + unifyWithSigErr tyvar ty = (env2, hang (ptext SLIT("Cannot unify the type-signature variable") <+> quotes (ppr tidy_tyvar)) - 4 (ptext SLIT("with the type") <+> quotes (ppr tidy_ty))) + 2 (ptext SLIT("with the type") <+> quotes (ppr tidy_ty))) where (env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar (env2, tidy_ty) = tidyOpenType env1 ty unifyCheck problem tyvar ty = (env2, hang msg - 4 (sep [ppr tidy_tyvar, char '=', ppr tidy_ty])) + 2 (sep [ppr tidy_tyvar, char '=', ppr tidy_ty])) where (env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar (env2, tidy_ty) = tidyOpenType env1 ty @@ -936,6 +1104,64 @@ unifyCheck problem tyvar ty \end{code} +%************************************************************************ +%* * + Checking kinds +%* * +%************************************************************************ + +--------------------------- +-- We would like to get a decent error message from +-- (a) Under-applied type constructors +-- f :: (Maybe, Maybe) +-- (b) Over-applied type constructors +-- f :: Int x -> Int x +-- + +\begin{code} +checkExpectedKind :: Outputable a => a -> TcKind -> TcKind -> TcM () +-- A fancy wrapper for 'unifyKind', which tries +-- to give decent error messages. +checkExpectedKind ty act_kind exp_kind + | act_kind `isSubKind` exp_kind -- Short cut for a very common case + = returnM () + | otherwise + = tryTc (unifyKind exp_kind act_kind) `thenM` \ (errs, mb_r) -> + case mb_r of { + Just _ -> returnM () ; -- Unification succeeded + Nothing -> + + -- So there's definitely an error + -- Now to find out what sort + zonkTcKind exp_kind `thenM` \ exp_kind -> + zonkTcKind act_kind `thenM` \ act_kind -> + + let (exp_as, _) = splitKindFunTys exp_kind + (act_as, _) = splitKindFunTys act_kind + n_exp_as = length exp_as + n_act_as = length act_as + + err | n_exp_as < n_act_as -- E.g. [Maybe] + = quotes (ppr ty) <+> ptext SLIT("is not applied to enough type arguments") + + -- Now n_exp_as >= n_act_as. In the next two cases, + -- n_exp_as == 0, and hence so is n_act_as + | isLiftedTypeKind exp_kind && isUnliftedTypeKind act_kind + = ptext SLIT("Expecting a lifted type, but") <+> quotes (ppr ty) + <+> ptext SLIT("is unlifted") + + | isUnliftedTypeKind exp_kind && isLiftedTypeKind act_kind + = ptext SLIT("Expecting an unlifted type, but") <+> quotes (ppr ty) + <+> ptext SLIT("is lifted") + + | otherwise -- E.g. Monad [Int] + = sep [ ptext SLIT("Expecting kind") <+> quotes (pprKind exp_kind) <> comma, + ptext SLIT("but") <+> quotes (ppr ty) <+> + ptext SLIT("has kind") <+> quotes (pprKind act_kind)] + in + failWithTc (ptext SLIT("Kind error:") <+> err) + } +\end{code} %************************************************************************ %* * @@ -1005,7 +1231,7 @@ checkSigTyVars sig_tvs = check_sig_tyvars emptyVarSet sig_tvs checkSigTyVarsWrt :: TcTyVarSet -> [TcTyVar] -> TcM [TcTyVar] checkSigTyVarsWrt extra_tvs sig_tvs - = zonkTcTyVarsAndFV (varSetElems extra_tvs) `thenNF_Tc` \ extra_tvs' -> + = zonkTcTyVarsAndFV (varSetElems extra_tvs) `thenM` \ extra_tvs' -> check_sig_tyvars extra_tvs' sig_tvs check_sig_tyvars @@ -1017,26 +1243,30 @@ check_sig_tyvars -> TcM [TcTyVar] -- Zonked signature type variables check_sig_tyvars extra_tvs [] - = returnTc [] + = returnM [] check_sig_tyvars extra_tvs sig_tvs - = zonkTcTyVars sig_tvs `thenNF_Tc` \ sig_tys -> - tcGetGlobalTyVars `thenNF_Tc` \ gbl_tvs -> + = zonkTcTyVars sig_tvs `thenM` \ sig_tys -> + tcGetGlobalTyVars `thenM` \ gbl_tvs -> let env_tvs = gbl_tvs `unionVarSet` extra_tvs in - checkTcM (allDistinctTyVars sig_tys env_tvs) - (complain sig_tys env_tvs) `thenTc_` + traceTc (text "check_sig_tyvars" <+> (vcat [text "sig_tys" <+> ppr sig_tys, + text "gbl_tvs" <+> ppr gbl_tvs, + text "extra_tvs" <+> ppr extra_tvs])) `thenM_` - returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys) + checkM (allDistinctTyVars sig_tys env_tvs) + (complain sig_tys env_tvs) `thenM_` + + returnM (map (tcGetTyVar "checkSigTyVars") sig_tys) where complain sig_tys globals = -- "check" checks each sig tyvar in turn - foldlNF_Tc check - (env2, emptyVarEnv, []) - (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) -> + foldlM check + (env2, emptyVarEnv, []) + (tidy_tvs `zip` tidy_tys) `thenM` \ (env3, _, msgs) -> - failWithTcM (env3, main_msg $$ nest 4 (vcat msgs)) + failWithTcM (env3, main_msg $$ nest 2 (vcat msgs)) where (env1, tidy_tvs) = tidyOpenTyVars emptyTidyEnv sig_tvs (env2, tidy_tys) = tidyOpenTypes env1 sig_tys @@ -1050,13 +1280,13 @@ check_sig_tyvars extra_tvs sig_tvs -- acc maps a zonked type variable back to a signature type variable = case tcGetTyVar_maybe ty of { Nothing -> -- Error (a)! - returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ; + returnM (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ; Just tv -> case lookupVarEnv acc tv of { Just sig_tyvar' -> -- Error (b)! - returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs) + returnM (tidy_env, acc, unify_msg sig_tyvar thing : msgs) where thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar') @@ -1067,74 +1297,20 @@ check_sig_tyvars extra_tvs sig_tvs -- Game plan: -- get the local TcIds and TyVars from the environment, -- and pass them to find_globals (they might have tv free) - then tcGetEnv `thenNF_Tc` \ ve -> - find_globals tv tidy_env (tcLEnvElts ve) `thenNF_Tc` \ (tidy_env1, globs) -> - returnNF_Tc (tidy_env1, acc, escape_msg sig_tyvar tv globs : msgs) + then findGlobals (unitVarSet tv) tidy_env `thenM` \ (tidy_env1, globs) -> + returnM (tidy_env1, acc, escape_msg sig_tyvar tv globs : msgs) else -- All OK - returnNF_Tc (tidy_env, extendVarEnv acc tv sig_tyvar, msgs) + returnM (tidy_env, extendVarEnv acc tv sig_tyvar, msgs) }} \end{code} \begin{code} ----------------------- --- find_globals looks at the value environment and finds values --- whose types mention the offending type variable. It has to be --- careful to zonk the Id's type first, so it has to be in the monad. --- We must be careful to pass it a zonked type variable, too. - -find_globals :: Var - -> TidyEnv - -> [TcTyThing] - -> NF_TcM (TidyEnv, [SDoc]) - -find_globals tv tidy_env things - = go tidy_env [] things - where - go tidy_env acc [] = returnNF_Tc (tidy_env, acc) - go tidy_env acc (thing : things) - = find_thing ignore_it tidy_env thing `thenNF_Tc` \ (tidy_env1, maybe_doc) -> - case maybe_doc of - Just d -> go tidy_env1 (d:acc) things - Nothing -> go tidy_env1 acc things - - ignore_it ty = not (tv `elemVarSet` tyVarsOfType ty) - ------------------------ -find_thing ignore_it tidy_env (ATcId id) - = zonkTcType (idType id) `thenNF_Tc` \ id_ty -> - if ignore_it id_ty then - returnNF_Tc (tidy_env, Nothing) - else let - (tidy_env', tidy_ty) = tidyOpenType tidy_env id_ty - msg = sep [ppr id <+> dcolon <+> ppr tidy_ty, - nest 2 (parens (ptext SLIT("bound at") <+> - ppr (getSrcLoc id)))] - in - returnNF_Tc (tidy_env', Just msg) - -find_thing ignore_it tidy_env (ATyVar tv) - = zonkTcTyVar tv `thenNF_Tc` \ tv_ty -> - if ignore_it tv_ty then - returnNF_Tc (tidy_env, Nothing) - else let - (tidy_env1, tv1) = tidyOpenTyVar tidy_env tv - (tidy_env2, tidy_ty) = tidyOpenType tidy_env1 tv_ty - msg = sep [ppr tv1 <+> eq_stuff, nest 2 bound_at] - - eq_stuff | Just tv' <- Type.getTyVar_maybe tv_ty, tv == tv' = empty - | otherwise = equals <+> ppr tv_ty - -- It's ok to use Type.getTyVar_maybe because ty is zonked by now - - bound_at = tyVarBindingInfo tv - in - returnNF_Tc (tidy_env2, Just msg) - ------------------------ escape_msg sig_tv tv globs = mk_msg sig_tv <+> ptext SLIT("escapes") $$ - if not (null globs) then + if notNull globs then vcat [pp_it <+> ptext SLIT("is mentioned in the environment:"), nest 2 (vcat globs)] else @@ -1153,18 +1329,19 @@ mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv) These two context are used with checkSigTyVars \begin{code} -sigCtxt :: [TcTyVar] -> TcThetaType -> TcTauType - -> TidyEnv -> NF_TcM (TidyEnv, Message) -sigCtxt sig_tvs sig_theta sig_tau tidy_env - = zonkTcType sig_tau `thenNF_Tc` \ actual_tau -> +sigCtxt :: Id -> [TcTyVar] -> TcThetaType -> TcTauType + -> TidyEnv -> TcM (TidyEnv, Message) +sigCtxt id sig_tvs sig_theta sig_tau tidy_env + = zonkTcType sig_tau `thenM` \ actual_tau -> let (env1, tidy_sig_tvs) = tidyOpenTyVars tidy_env sig_tvs - (env2, tidy_sig_rho) = tidyOpenType env1 (mkRhoTy sig_theta sig_tau) + (env2, tidy_sig_rho) = tidyOpenType env1 (mkPhiTy sig_theta sig_tau) (env3, tidy_actual_tau) = tidyOpenType env2 actual_tau sub_msg = vcat [ptext SLIT("Signature type: ") <+> pprType (mkForAllTys tidy_sig_tvs tidy_sig_rho), ptext SLIT("Type to generalise:") <+> pprType tidy_actual_tau ] - msg = ptext SLIT("When trying to generalise an inferred type") $$ nest 4 sub_msg + msg = vcat [ptext SLIT("When trying to generalise the type inferred for") <+> quotes (ppr id), + nest 2 sub_msg] in - returnNF_Tc (env3, msg) + returnM (env3, msg) \end{code}