X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcUnify.lhs;h=9f5daeb0bc843eee9969f58dad8c4b5d7b432efb;hb=3f44fb8231db3277a584470cbe7397bec801cd0e;hp=1aa0bf62bb614ebba605b303b7088becc7f8d2cc;hpb=cd6658d04b5451d9b7c5c3b758bff8a0b5a63e7a;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index 1aa0bf6..9f5daeb 100644 --- a/compiler/typecheck/TcUnify.lhs +++ b/compiler/typecheck/TcUnify.lhs @@ -79,7 +79,9 @@ tcInfer tc_infer = withBox openTypeKind tc_infer subFunTys :: SDoc -- Something like "The function f has 3 arguments" -- or "The abstraction (\x.e) takes 1 argument" -> Arity -- Expected # of args - -> BoxyRhoType -- res_ty + -> BoxySigmaType -- res_ty + -> Maybe UserTypeCtxt -- Whether res_ty arises from a user signature + -- Only relevant if we encounter a sigma-type -> ([BoxySigmaType] -> BoxyRhoType -> TcM a) -> TcM (HsWrapper, a) -- Attempt to decompse res_ty to have enough top-level arrows to @@ -108,7 +110,7 @@ subFunTys :: SDoc -- Something like "The function f has 3 arguments" -} -subFunTys error_herald n_pats res_ty thing_inside +subFunTys error_herald n_pats res_ty mb_ctxt thing_inside = loop n_pats [] res_ty where -- In 'loop', the parameter 'arg_tys' accumulates @@ -121,8 +123,8 @@ subFunTys error_herald n_pats res_ty thing_inside | isSigmaTy res_ty -- Do this before checking n==0, because we -- guarantee to return a BoxyRhoType, not a -- BoxySigmaType - = do { (gen_fn, (co_fn, res)) <- tcGen res_ty emptyVarSet $ \ _ res_ty' -> - loop n args_so_far res_ty' + = do { (gen_fn, (co_fn, res)) <- tcGen res_ty emptyVarSet mb_ctxt $ \ _ res_ty -> + loop n args_so_far res_ty ; return (gen_fn <.> co_fn, res) } loop 0 args_so_far res_ty @@ -768,7 +770,7 @@ tc_sub1 orig act_sty act_ty exp_ib exp_sty exp_ty if exp_ib then -- SKOL does not apply if exp_ty is inside a box defer_to_boxy_matching orig act_sty act_ty exp_ib exp_sty exp_ty else do - { (gen_fn, co_fn) <- tcGen exp_ty act_tvs $ \ _ body_exp_ty -> + { (gen_fn, co_fn) <- tcGen exp_ty act_tvs Nothing $ \ _ body_exp_ty -> tc_sub orig act_sty act_ty False body_exp_ty body_exp_ty ; return (gen_fn <.> co_fn) } } @@ -894,26 +896,21 @@ wrapFunResCoercion arg_tys co_fn_res %************************************************************************ \begin{code} -tcGen :: BoxySigmaType -- expected_ty - -> TcTyVarSet -- Extra tyvars that the universally - -- quantified tyvars of expected_ty - -- must not be unified +tcGen :: BoxySigmaType -- expected_ty + -> TcTyVarSet -- Extra tyvars that the universally + -- quantified tyvars of expected_ty + -- must not be unified + -> Maybe UserTypeCtxt -- Just ctxt => this polytype arose directly + -- from a user type sig + -- Nothing => a higher order situation -> ([TcTyVar] -> BoxyRhoType -> TcM result) -> TcM (HsWrapper, 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 +tcGen expected_ty extra_tvs mb_ctxt thing_inside -- We expect expected_ty to be a forall-type + -- If not, the call is a no-op = do { traceTc (text "tcGen") - -- We want the GenSkol info in the skolemised type variables to - -- mention the *instantiated* tyvar names, so that we get a - -- good error message "Rigid variable 'a' is bound by (forall a. a->a)" - -- Hence the tiresome but innocuous fixM - ; ((tvs', theta', rho'), skol_info) <- fixM (\ ~(_, skol_info) -> - do { (forall_tvs, theta, rho_ty) <- tcInstSkolType skol_info expected_ty - -- Get loation from monad, not from expected_ty - ; let skol_info = GenSkol forall_tvs (mkPhiTy theta rho_ty) - ; return ((forall_tvs, theta, rho_ty), skol_info) }) + ; ((tvs', theta', rho'), skol_info) <- instantiate expected_ty ; when debugIsOn $ traceTc (text "tcGen" <+> vcat [ @@ -924,7 +921,8 @@ tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a text "free_tvs" <+> ppr free_tvs]) -- Type-check the arg and unify with poly type - ; (result, lie) <- getLIE (thing_inside tvs' rho') + ; (result, lie) <- getLIE $ + thing_inside tvs' rho' -- Check that the "forall_tvs" havn't been constrained -- The interesting bit here is that we must include the free variables @@ -951,6 +949,23 @@ tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a ; return (co_fn, result) } where free_tvs = tyVarsOfType expected_ty `unionVarSet` extra_tvs + + instantiate :: TcType -> TcM (([TcTyVar],ThetaType,TcRhoType), SkolemInfo) + instantiate expected_ty + | Just ctxt <- mb_ctxt -- This case split is the wohle reason for mb_ctxt + = do { let skol_info = SigSkol ctxt + ; stuff <- tcInstSigType True skol_info expected_ty + ; return (stuff, skol_info) } + + | otherwise -- We want the GenSkol info in the skolemised type variables to + -- mention the *instantiated* tyvar names, so that we get a + -- good error message "Rigid variable 'a' is bound by (forall a. a->a)" + -- Hence the tiresome but innocuous fixM + = fixM $ \ ~(_, skol_info) -> + do { stuff@(forall_tvs, theta, rho_ty) <- tcInstSkolType skol_info expected_ty + -- Get loation from *monad*, not from expected_ty + ; let skol_info = GenSkol forall_tvs (mkPhiTy theta rho_ty) + ; return (stuff, skol_info) } \end{code} @@ -1177,13 +1192,13 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 go outer _ (PredTy p1) _ (PredTy p2) = uPred outer nb1 p1 nb2 p2 - -- Type constructors must match + -- Non-synonym type constructors must match go _ _ (TyConApp con1 tys1) _ (TyConApp con2 tys2) | con1 == con2 && not (isOpenSynTyCon con1) = do { cois <- uTys_s nb1 tys1 nb2 tys2 ; return $ mkTyConAppCoI con1 tys1 cois } - -- See Note [TyCon app] + -- Family synonyms See Note [TyCon app] | con1 == con2 && identicalOpenSynTyConApp = do { cois <- uTys_s nb1 tys1' nb2 tys2' ; return $ mkTyConAppCoI con1 tys1 (replicate n IdCo ++ cois) @@ -1195,6 +1210,29 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 identicalOpenSynTyConApp = idxTys1 `tcEqTypes` idxTys2 -- See Note [OpenSynTyCon app] + -- If we can reduce a family app => proceed with reduct + -- NB: We use isOpenSynTyCon, not isOpenSynTyConApp as we also must + -- defer oversaturated applications! + go outer sty1 ty1@(TyConApp con1 _) sty2 ty2 + | isOpenSynTyCon con1 + = do { (coi1, ty1') <- tcNormaliseFamInst ty1 + ; case coi1 of + IdCo -> defer -- no reduction, see [Deferred Unification] + _ -> liftM (coi1 `mkTransCoI`) $ go outer sty1 ty1' sty2 ty2 + } + + -- If we can reduce a family app => proceed with reduct + -- NB: We use isOpenSynTyCon, not isOpenSynTyConApp as we also must + -- defer oversaturated applications! + go outer sty1 ty1 sty2 ty2@(TyConApp con2 _) + | isOpenSynTyCon con2 + = do { (coi2, ty2') <- tcNormaliseFamInst ty2 + ; case coi2 of + IdCo -> defer -- no reduction, see [Deferred Unification] + _ -> liftM (`mkTransCoI` mkSymCoI coi2) $ + go outer sty1 ty1 sty2 ty2' + } + -- Functions; just check the two parts go _ _ (FunTy fun1 arg1) _ (FunTy fun2 arg2) = do { coi_l <- uTys nb1 fun1 nb2 fun2 @@ -1220,36 +1258,12 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 ; coi_t <- uTys nb1 t1 nb2 t2 ; return $ mkAppTyCoI s1 coi_s t1 coi_t } - -- One or both outermost constructors are type family applications. - -- If we can normalise them away, proceed as usual; otherwise, we - -- need to defer unification by generating a wanted equality constraint. - go outer sty1 ty1 sty2 ty2 - | ty1_is_fun || ty2_is_fun - = do { (coi1, ty1') <- if ty1_is_fun then tcNormaliseFamInst ty1 - else return (IdCo, ty1) - ; (coi2, ty2') <- if ty2_is_fun then tcNormaliseFamInst ty2 - else return (IdCo, ty2) - ; coi <- if isOpenSynTyConApp ty1' || isOpenSynTyConApp ty2' - then do { -- One type family app can't be reduced yet - -- => defer - ; ty1'' <- zonkTcType ty1' - ; ty2'' <- zonkTcType ty2' - ; if tcEqType ty1'' ty2'' - then return IdCo - else -- see [Deferred Unification] - defer_unification outer False orig_ty1 orig_ty2 - } - else -- unification can proceed - go outer sty1 ty1' sty2 ty2' - ; return $ coi1 `mkTransCoI` coi `mkTransCoI` (mkSymCoI coi2) - } - where - ty1_is_fun = isOpenSynTyConApp ty1 - ty2_is_fun = isOpenSynTyConApp ty2 - -- Anything else fails go outer _ _ _ _ = bale_out outer + defer = defer_unification outer False orig_ty1 orig_ty2 + + ---------- uPred :: Outer -> InBox -> PredType -> InBox -> PredType -> TcM CoercionI uPred _ nb1 (IParam n1 t1) nb2 (IParam n2 t2) @@ -1507,7 +1521,7 @@ uMetaVar :: Outer -- tv1 is an un-filled-in meta type variable (maybe boxy, maybe tau) -- ty2 is not a type variable -uMetaVar _ swapped tv1 BoxTv ref1 ps_ty2 _ +uMetaVar outer swapped tv1 BoxTv ref1 ps_ty2 ty2 = -- tv1 is a BoxTv. So we must unbox ty2, to ensure -- that any boxes in ty2 are filled with monotypes -- @@ -1516,15 +1530,21 @@ uMetaVar _ swapped tv1 BoxTv ref1 ps_ty2 _ -- it does, the unbox operation will fill it, and the debug code -- checks for that. do { final_ty <- unBox ps_ty2 - ; when debugIsOn $ do - { meta_details <- readMutVar ref1 - ; case meta_details of - Indirect ty -> WARN( True, ppr tv1 <+> ppr ty ) - return () -- This really should *not* happen - Flexi -> return () - } - ; checkUpdateMeta swapped tv1 ref1 final_ty - ; return IdCo + ; meta_details <- readMutVar ref1 + ; case meta_details of + Indirect _ -> -- This *can* happen due to an occurs check, + -- just as it can in checkTauTvUpdate in the next + -- equation of uMetaVar; see Trac #2414 + -- Note [Occurs check] + -- Go round again. Probably there's an immediate + -- error, but maybe not (a type function might discard + -- its argument). Next time round we'll end up in the + -- TauTv case of uMetaVar. + uVar outer swapped tv1 False ps_ty2 ty2 + -- Setting for nb2::InBox is irrelevant + + Flexi -> do { checkUpdateMeta swapped tv1 ref1 final_ty + ; return IdCo } } uMetaVar outer swapped tv1 _ ref1 ps_ty2 _ @@ -1539,6 +1559,18 @@ uMetaVar outer swapped tv1 _ ref1 ps_ty2 _ } } +{- Note [Occurs check] + ~~~~~~~~~~~~~~~~~~~ +An eager occurs check is made in checkTauTvUpdate, deferring tricky +cases by calling defer_unification (see notes with +checkTauTvUpdate). An occurs check can also (and does) happen in the +BoxTv case, but unBox doesn't check for occurrences, and in any case +doesn't have the type-function-related complexity that +checkTauTvUpdate has. So we content ourselves with spotting the potential +occur check (by the fact that tv1 is now filled), and going round again. +Next time round we'll get the TauTv case of uMetaVar. +-} + ---------------- uUnfilledVars :: Outer -> SwapFlag @@ -1912,7 +1944,7 @@ checkExpectedKind ty act_kind exp_kind | otherwise = do (_errs, mb_r) <- tryTc (unifyKind exp_kind act_kind) case mb_r of - Just _ -> return () ; -- Unification succeeded + Just _ -> return () -- Unification succeeded Nothing -> do -- So there's definitely an error @@ -2006,7 +2038,7 @@ check_sig_tyvars check_sig_tyvars _ [] = return () check_sig_tyvars extra_tvs sig_tvs - = ASSERT( all isSkolemTyVar sig_tvs ) + = ASSERT( all isTcTyVar sig_tvs && all isSkolemTyVar sig_tvs ) do { gbl_tvs <- tcGetGlobalTyVars ; traceTc (text "check_sig_tyvars" <+> (vcat [text "sig_tys" <+> ppr sig_tvs, text "gbl_tvs" <+> ppr gbl_tvs,