X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcPat.lhs;h=defe6fb6aa85607eea1bb08b1a0e5a81ebf412ce;hb=ce9268f652cc4c46af75ae765f859480cf081cda;hp=c2f758de68ff68e1f8eed533a99cba6c96a77bc3;hpb=a003ad80d59f8da861d874f7314b68c20e1afd67;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs index c2f758d..defe6fb 100644 --- a/compiler/typecheck/TcPat.lhs +++ b/compiler/typecheck/TcPat.lhs @@ -447,20 +447,25 @@ tc_pat pstate pat@(TypePat ty) pat_ty thing_inside -- Lists, tuples, arrays tc_pat pstate (ListPat pats _) pat_ty thing_inside = do { (elt_ty, coi) <- boxySplitListTy pat_ty + ; let scoi = mkSymCoI coi ; (pats', pats_tvs, res) <- tcMultiple (\p -> tc_lpat p elt_ty) pats pstate thing_inside - ; return (mkCoPatCoI coi (ListPat pats' elt_ty) pat_ty, pats_tvs, res) } + ; return (mkCoPatCoI scoi (ListPat pats' elt_ty) pat_ty, pats_tvs, res) + } tc_pat pstate (PArrPat pats _) pat_ty thing_inside = do { (elt_ty, coi) <- boxySplitPArrTy pat_ty + ; let scoi = mkSymCoI coi ; (pats', pats_tvs, res) <- tcMultiple (\p -> tc_lpat p elt_ty) pats pstate thing_inside ; ifM (null pats) (zapToMonotype pat_ty) -- c.f. ExplicitPArr in TcExpr - ; return (mkCoPatCoI coi (PArrPat pats' elt_ty) pat_ty, pats_tvs, res) } + ; return (mkCoPatCoI scoi (PArrPat pats' elt_ty) pat_ty, pats_tvs, res) + } tc_pat pstate (TuplePat pats boxity _) pat_ty thing_inside = do { let tc = tupleTyCon boxity (length pats) ; (arg_tys, coi) <- boxySplitTyConApp tc pat_ty + ; let scoi = mkSymCoI coi ; (pats', pats_tvs, res) <- tcMultiple tc_lpat_pr (pats `zip` arg_tys) pstate thing_inside @@ -477,7 +482,7 @@ tc_pat pstate (TuplePat pats boxity _) pat_ty thing_inside | otherwise = unmangled_result ; ASSERT( length arg_tys == length pats ) -- Syntactically enforced - return (mkCoPatCoI coi possibly_mangled_result pat_ty, pats_tvs, res) + return (mkCoPatCoI scoi possibly_mangled_result pat_ty, pats_tvs, res) } ------------------------ @@ -610,18 +615,27 @@ tcConPat :: PatState -> SrcSpan -> DataCon -> TyCon -> HsConPatDetails Name -> (PatState -> TcM a) -> TcM (Pat TcId, [TcTyVar], a) tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside - = do { let (univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _) = dataConFullSig data_con + = do { let (univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _) + = dataConFullSig data_con skol_info = PatSkol data_con origin = SigOrigin skol_info full_theta = eq_theta ++ dict_theta -- Instantiate the constructor type variables [a->ty] - -- This may involve doing a family-instance coercion, and building a wrapper + -- This may involve doing a family-instance coercion, and building a + -- wrapper ; (ctxt_res_tys, coi) <- boxySplitTyConAppWithFamily tycon pat_ty - ; let pat_ty' = mkTyConApp tycon ctxt_res_tys - -- pat_ty /= pat_ty iff coi /= IdCo - wrap_res_pat res_pat - = mkCoPatCoI coi (unwrapFamInstScrutinee tycon ctxt_res_tys res_pat) pat_ty + ; let sym_coi = mkSymCoI coi -- boxy split coercion oriented wrongly + pat_ty' = mkTyConApp tycon ctxt_res_tys + -- pat_ty' /= pat_ty iff coi /= IdCo + + wrap_res_pat res_pat = mkCoPatCoI sym_coi uwScrut pat_ty + where + uwScrut = unwrapFamInstScrutinee tycon ctxt_res_tys res_pat + + ; traceTc $ case sym_coi of + IdCo -> text "sym_coi:IdCo" + ACo co -> text "sym_coi: ACoI" <+> ppr co -- Add the stupid theta ; addDataConStupidTheta data_con ctxt_res_tys @@ -637,17 +651,21 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside then do { -- The common case; no class bindings etc -- (see Note [Arrows and patterns]) (arg_pats', inner_tvs, res) <- tcConArgs data_con arg_tys' - arg_pats pstate thing_inside + arg_pats pstate thing_inside ; let res_pat = ConPatOut { pat_con = L con_span data_con, - pat_tvs = [], pat_dicts = [], pat_binds = emptyLHsBinds, - pat_args = arg_pats', pat_ty = pat_ty' } + pat_tvs = [], pat_dicts = [], + pat_binds = emptyLHsBinds, + pat_args = arg_pats', + pat_ty = pat_ty' } ; return (wrap_res_pat res_pat, inner_tvs, res) } else do -- The general case, with existential, and local equality -- constraints { let eq_preds = [mkEqPred (mkTyVarTy tv, ty) | (tv, ty) <- eq_spec] - theta' = substTheta tenv (full_theta ++ eq_preds) + theta' = substTheta tenv (eq_preds ++ full_theta) + -- order is *important* as we generate the list of + -- dictionary binders from theta' ctxt = pat_ctxt pstate ; checkTc (case ctxt of { ProcPat -> False; other -> True }) (existentialProcPat data_con) @@ -849,11 +867,8 @@ refineAlt con pstate ex_tvs [] pat_ty = return pstate -- Common case: no equational constraints refineAlt con pstate ex_tvs co_vars pat_ty - = do { opt_gadt <- doptM Opt_GADTs -- No type-refinement unless GADTs are on - ; if (not opt_gadt) then return pstate - else do - - { checkTc (isRigidTy pat_ty) (nonRigidMatch con) + = -- See Note [Flags and equational constraints] + do { checkTc (isRigidTy pat_ty) (nonRigidMatch con) -- We are matching against a GADT constructor with non-trivial -- constraints, but pattern type is wobbly. For now we fail. -- We can make sense of this, however: @@ -881,9 +896,20 @@ refineAlt con pstate ex_tvs co_vars pat_ty vcat [ ppr con <+> ppr ex_tvs, ppr [(v, tyVarKind v) | v <- co_vars], ppr reft] - } } } + } } \end{code} +Note [Flags and equational constraints] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If there are equational constraints, we take account of them +regardless of flag settings; -XGADTs etc applies only to the +*definition* of a data type. + +An alternative would be also to reject a program that *used* +constructors with equational constraints. But want we should avoid at +all costs is simply to *ignore* the constraints, since that gives +incomprehensible errors (Trac #2004). + %************************************************************************ %* * @@ -1089,11 +1115,11 @@ lazyPatErr pat tvs nonRigidMatch con = hang (ptext SLIT("GADT pattern match in non-rigid context for") <+> quotes (ppr con)) - 2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context")) + 2 (ptext SLIT("Solution: add a type signature")) nonRigidResult res_ty = hang (ptext SLIT("GADT pattern match with non-rigid result type") <+> quotes (ppr res_ty)) - 2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context")) + 2 (ptext SLIT("Solution: add a type signature")) inaccessibleAlt msg = hang (ptext SLIT("Inaccessible case alternative:")) 2 msg