X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcUnify.lhs;h=94af19c6eebdaf31668b66efbd06e1a455dcc658;hb=5045af3106f3d1e3cb223c254af2de6a8a265797;hp=2d9ffc169339232c689657a5f2c34ba694abf0ce;hpb=a8cd39e47f464b88a556d026ccadbf70b09e51ed;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index 2d9ffc1..94af19c 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} @@ -1930,7 +1945,7 @@ 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 @@ -2024,7 +2039,7 @@ 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,