X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=516c822dbcf959319489e0cf111b7ed7ffec113f;hb=f087e1b53f70e41b7cc91ad1b117967710da2288;hp=66a6816e88cea183071db076e8a6208a7dd6a33a;hpb=cd5abca9d4be624f0c4759d3ef126e4392b81ac7;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 66a6816..516c822 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -10,37 +10,38 @@ module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) +import {-# SOURCE #-} TcExpr( tcMonoExpr ) import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..), pprMatch, getMatchLoc, pprMatchContext, isDoExpr, mkMonoBind, nullMonoBinds, collectSigTysFromPats ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType, - RenamedMatchContext, extractHsTyVars ) +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext ) import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) import TcMonad -import TcMonoType ( kcHsSigTypes, tcScopedTyVars, checkSigTyVars, tcHsSigType, UserTypeCtxt(..), sigPatCtxt ) +import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) -import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars, - tcInLocalScope ) -import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) -import TcMType ( newTyVarTy, unifyFunTy, unifyTauTy ) -import TcType ( tyVarsOfType, isTauTy, mkFunTy, isOverloadedTy, - liftedTypeKind, openTypeKind ) +import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv2 ) +import TcPat ( tcPat, tcMonoPatBndr ) +import TcMType ( newTyVarTy, zonkTcType, zapToType ) +import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType, + mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind ) import TcBinds ( tcBindsAndThen ) +import TcUnify ( subFunTy, checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) import TysWiredIn ( boolTy ) import Id ( idType ) +import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) -import NameSet import VarSet import Var ( Id ) import Bag +import Util ( isSingleton, lengthExceeds, notNull ) import Outputable + import List ( nub ) \end{code} @@ -78,7 +79,7 @@ tcMatchesFun xve fun_name expected_ty matches@(first_match:_) -- because inconsistency between branches -- may show up as something wrong with the (non-existent) type signature - -- No need to zonk expected_ty, because unifyFunTy does that on the fly + -- No need to zonk expected_ty, because subFunTy does that on the fly tcMatches xve (FunRhs fun_name) matches expected_ty \end{code} @@ -109,11 +110,19 @@ tcMatches :: [(Name,Id)] -> TcType -> TcM ([TcMatch], LIE) -tcMatches xve fun_or_case matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> +tcMatches xve ctxt matches expected_ty + = -- If there is more than one branch, and expected_ty is a 'hole', + -- all branches must be types, not type schemes, otherwise the + -- in which we check them would affect the result. + (if lengthExceeds matches 1 then + zapToType expected_ty + else + returnNF_Tc expected_ty) `thenNF_Tc` \ expected_ty' -> + + mapAndUnzipTc (tc_match expected_ty') matches `thenTc` \ (matches, lies) -> returnTc (matches, plusLIEs lies) where - tc_match match = tcMatch xve fun_or_case match expected_ty + tc_match expected_ty match = tcMatch xve ctxt match expected_ty \end{code} @@ -127,51 +136,53 @@ tcMatches xve fun_or_case matches expected_ty tcMatch :: [(Name,Id)] -> RenamedMatchContext -> RenamedMatch - -> TcType -- Expected result-type of the Match. - -- Early unification with this guy gives better error messages + -> TcType -- Expected result-type of the Match. + -- Early unification with this guy gives better error messages + -- We regard the Match as having type + -- (ty1 -> ... -> tyn -> result_ty) + -- where there are n patterns. -> TcM (TcMatch, LIE) -tcMatch xve1 ctxt match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty +tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty = tcAddSrcLoc (getMatchLoc match) $ -- At one stage I removed this; tcAddErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back - - tcMatchPats pats expected_ty tc_grhss `thenTc` \ ((pats', grhss'), lie, ex_binds) -> - returnTc (Match [] pats' Nothing (glue_on Recursive ex_binds grhss'), lie) + tcMatchPats pats expected_ty tc_grhss `thenTc` \ (pats', grhss', lie, ex_binds) -> + returnTc (Match pats' Nothing (glue_on Recursive ex_binds grhss'), lie) where - tc_grhss pats' rhs_ty - = -- Check that the remaining "expected type" is not a rank-2 type - -- If it is it'll mess up the unifier when checking the RHS - checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc` \_ -> + tc_grhss rhs_ty + = tcExtendLocalValEnv2 xve1 $ -- Deal with the result signature - -- It "wraps" the rest of the body typecheck because it may - -- bring into scope the type variables in the signature - tc_result_sig maybe_rhs_sig rhs_ty $ - - -- Typecheck the body - tcExtendLocalValEnv xve1 $ - tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> - returnTc ((pats', grhss'), lie) - - tc_result_sig Nothing rhs_ty thing_inside - = thing_inside - tc_result_sig (Just sig) rhs_ty thing_inside - = tcAddScopedTyVars [sig] $ - tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty -> - - -- Check that the signature isn't a polymorphic one, which - -- we don't permit (at present, anyway) - checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_` - unifyTauTy sig_ty rhs_ty `thenTc_` - thing_inside - - - -- glue_on just avoids stupid dross + case maybe_rhs_sig of + Nothing -> tcGRHSs ctxt grhss rhs_ty + + Just sig -> tcAddScopedTyVars [sig] $ + -- Bring into scope the type variables in the signature + tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty -> + tcGRHSs ctxt grhss sig_ty `thenTc` \ (grhss', lie1) -> + tcSubExp rhs_ty sig_ty `thenTc` \ (co_fn, lie2) -> + returnTc (lift_grhss co_fn rhs_ty grhss', + lie1 `plusLIE` lie2) + +-- lift_grhss pushes the coercion down to the right hand sides, +-- because there is no convenient place to hang it otherwise. +lift_grhss co_fn rhs_ty grhss + | isIdCoercion co_fn = grhss +lift_grhss co_fn rhs_ty (GRHSs grhss binds ty) + = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we + where + lift_grhs (GRHS stmts loc) = GRHS (map lift_stmt stmts) loc + + lift_stmt (ResultStmt e l) = ResultStmt (co_fn <$> e) l + lift_stmt stmt = stmt + +-- glue_on just avoids stupid dross glue_on _ EmptyMonoBinds grhss = grhss -- The common case glue_on is_rec mbinds (GRHSs grhss binds ty) = GRHSs grhss (mkMonoBind mbinds [] is_rec `ThenBinds` binds) ty + tcGRHSs :: RenamedMatchContext -> RenamedGRHSs -> TcType -> TcM (TcGRHSs, LIE) @@ -199,8 +210,8 @@ tcGRHSs ctxt (GRHSs grhss binds _) expected_ty \begin{code} tcMatchPats :: [RenamedPat] -> TcType - -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) - -> TcM (a, LIE, TcDictBinds) + -> (TcType -> TcM (a, LIE)) + -> TcM ([TypecheckedPat], a, LIE, TcDictBinds) -- Typecheck the patterns, extend the environment to bind the variables, -- do the thing inside, use any existentially-bound dictionaries to -- discharge parts of the returning LIE, and deal with pattern type @@ -211,17 +222,10 @@ tcMatchPats pats expected_ty thing_inside tcAddScopedTyVars (collectSigTysFromPats pats) ( -- STEP 2: Typecheck the patterns themselves, gathering all the stuff - tc_match_pats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> - - -- STEP 3: Extend the environment, and do the thing inside - let - xve = bagToList pat_bndrs - pat_ids = map snd xve - in - tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) -> - - returnTc (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) - ) `thenTc` \ (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) -> + -- then do the thing inside + tc_match_pats pats expected_ty thing_inside + + ) `thenTc` \ (pats', lie_req, ex_tvs, ex_ids, ex_lie, result) -> -- STEP 4: Check for existentially bound type variables -- Do this *outside* the scope of the tcAddScopedTyVars, else checkSigTyVars @@ -230,80 +234,77 @@ tcMatchPats pats expected_ty thing_inside -- I'm a bit concerned that lie_req1 from an 'inner' pattern in the list -- might need (via lie_req2) something made available from an 'outer' -- pattern. But it's inconvenient to deal with, and I can't find an example - tcCheckExistentialPat pat_ids ex_tvs lie_avail lie_req2 rhs_ty `thenTc` \ (lie_req2', ex_binds) -> - - returnTc (result, lie_req1 `plusLIE` lie_req2', ex_binds) - -tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a --- Find the not-already-in-scope signature type variables, --- kind-check them, and bring them into scope --- --- We no longer specify that these type variables must be univerally --- quantified (lots of email on the subject). If you want to put that --- back in, you need to --- a) Do a checkSigTyVars after thing_inside --- b) More insidiously, don't pass in expected_ty, else --- we unify with it too early and checkSigTyVars barfs --- Instead you have to pass in a fresh ty var, and unify --- it with expected_ty afterwards -tcAddScopedTyVars sig_tys thing_inside - = tcGetEnv `thenNF_Tc` \ env -> + tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req expected_ty `thenTc` \ (lie_req', ex_binds) -> + -- NB: we *must* pass "expected_ty" not "result_ty" to tcCheckExistentialPat + -- For example, we must reject this program: + -- data C = forall a. C (a -> Int) + -- f (C g) x = g x + -- Here, result_ty will be simply Int, but expected_ty is (a -> Int). + + returnTc (pats', result, lie_req', ex_binds) + +tc_match_pats [] expected_ty thing_inside + = thing_inside expected_ty `thenTc` \ (answer, lie) -> + returnTc ([], lie, emptyBag, [], emptyLIE, answer) + +tc_match_pats (pat:pats) expected_ty thing_inside + = subFunTy expected_ty $ \ arg_ty rest_ty -> + -- This is the unique place we call subFunTy + -- The point is that if expected_y is a "hole", we want + -- to make arg_ty and rest_ty as "holes" too. + tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, ex_tvs, pat_bndrs, ex_lie) -> let - all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys - sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs) - not_in_scope tv = not (tcInLocalScope env tv) - in - tcScopedTyVars sig_tvs (kcHsSigTypes sig_tys) thing_inside - -tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern - -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern + xve = bagToList pat_bndrs + ex_ids = [id | (_, id) <- xve] + -- ex_ids is all the pattern-bound Ids, a superset + -- of the existential Ids used in checkExistentialPat + in + tcExtendLocalValEnv2 xve $ + tc_match_pats pats rest_ty thing_inside `thenTc` \ (pats', lie_reqs, exs_tvs, exs_ids, exs_lie, answer) -> + returnTc ( pat':pats', + lie_req `plusLIE` lie_reqs, + ex_tvs `unionBags` exs_tvs, + ex_ids ++ exs_ids, + ex_lie `plusLIE` exs_lie, + answer + ) + + +tcCheckExistentialPat :: Bag TcTyVar -- Existentially quantified tyvars bound by pattern + -> [TcId] -- Ids bound by this pattern; used + -- (a) by bindsInstsOfLocalFuns + -- (b) to generate helpful error messages -> LIE -- and context -> LIE -- Required context - -> TcType -- and result type; vars in here must not escape + -> TcType -- and type of the Match; vars in here must not escape -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings -tcCheckExistentialPat ids ex_tvs lie_avail lie_req result_ty - | isEmptyBag ex_tvs && all not_overloaded ids +tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_ty + | isEmptyBag ex_tvs && all not_overloaded ex_ids -- Short cut for case when there are no existentials -- and no polymorphic overloaded variables -- e.g. f :: (forall a. Ord a => a -> a) -> Int -> Int -- f op x = .... -- Here we must discharge op Methods - = ASSERT( isEmptyLIE lie_avail ) + = ASSERT( isEmptyLIE ex_lie ) returnTc (lie_req, EmptyMonoBinds) | otherwise - = tcExtendGlobalTyVars (tyVarsOfType result_ty) $ - tcAddErrCtxtM (sigPatCtxt tv_list ids) $ + = tcAddErrCtxtM (sigPatCtxt tv_list ex_ids match_ty) $ -- In case there are any polymorpic, overloaded binders in the pattern -- (which can happen in the case of rank-2 type signatures, or data constructors -- with polymorphic arguments), we must do a bindInstsOfLocalFns here - bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) -> + bindInstsOfLocalFuns lie_req ex_ids `thenTc` \ (lie1, inst_binds) -> -- Deal with overloaded functions bound by the pattern - tcSimplifyCheck doc tv_list (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) -> - checkSigTyVars tv_list emptyVarSet `thenTc_` + tcSimplifyCheck doc tv_list (lieToList ex_lie) lie1 `thenTc` \ (lie2, dict_binds) -> + checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenTc_` returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) where - doc = text ("the existential context of a data constructor") + doc = text ("existential context of a data constructor") tv_list = bagToList ex_tvs not_overloaded id = not (isOverloadedTy (idType id)) - -tc_match_pats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tc_match_pats (pat:pats) expected_ty - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> - tc_match_pats pats rest_ty `thenTc` \ (rhs_ty, pats', lie_reqs, pats_tvs, pats_ids, lie_avails) -> - returnTc ( rhs_ty, - pat':pats', - lie_req `plusLIE` lie_reqs, - pat_tvs `unionBags` pats_tvs, - pat_ids `unionBags` pats_ids, - lie_avail `plusLIE` lie_avails - ) \end{code} @@ -337,7 +338,8 @@ group. But that's fine; there's no shadowing to worry about. \begin{code} tcStmts do_or_lc m_ty stmts - = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) + = ASSERT( notNull stmts ) + tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) tcStmtsAndThen :: (TcStmt -> thing -> thing) -- Combiner @@ -367,13 +369,12 @@ tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) t = tcAddSrcLoc src_loc $ tcAddErrCtxt (stmtCtxt do_or_lc stmt) $ newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> - tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> - tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ [pat'] _ -> - tcPopErrCtxt $ - thing_inside `thenTc` \ (thing, lie) -> - returnTc ((BindStmt pat' exp' src_loc, thing), lie) - ) `thenTc` \ ((stmt', thing), lie, dict_binds) -> - returnTc (combine stmt' (glue_binds combine Recursive dict_binds thing), + tcMonoExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> + tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ -> + tcPopErrCtxt thing_inside + ) `thenTc` \ ([pat'], thing, lie, dict_binds) -> + returnTc (combine (BindStmt pat' exp' src_loc) + (glue_binds combine Recursive dict_binds thing), lie `plusLIE` exp_lie) @@ -404,10 +405,10 @@ tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) t = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( if isDoExpr do_or_lc then newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> - tcExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) -> + tcMonoExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) -> returnTc (ExprStmt exp' any_ty locn, lie) else - tcExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> + tcMonoExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> returnTc (ExprStmt exp' boolTy locn, lie) ) `thenTc` \ (stmt', stmt_lie) -> @@ -420,9 +421,9 @@ tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) t tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( if isDoExpr do_or_lc then - tcExpr exp (m res_elt_ty) + tcMonoExpr exp (m res_elt_ty) else - tcExpr exp res_elt_ty + tcMonoExpr exp res_elt_ty ) `thenTc` \ (exp', stmt_lie) -> thing_inside `thenTc` \ (thing, stmts_lie) -> @@ -449,19 +450,33 @@ number of args are used in each equation. \begin{code} sameNoOfArgs :: [RenamedMatch] -> Bool -sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1 +sameNoOfArgs matches = isSingleton (nub (map args_in_match matches)) where args_in_match :: RenamedMatch -> Int - args_in_match (Match _ pats _ _) = length pats + args_in_match (Match pats _ _) = length pats \end{code} \begin{code} +varyingArgsErr name matches + = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] + matchCtxt ctxt match = hang (pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match) stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt) -varyingArgsErr name matches - = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] +sigPatCtxt bound_tvs bound_ids match_ty tidy_env + = zonkTcType match_ty `thenNF_Tc` \ match_ty' -> + let + (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) + (env2, tidy_mty) = tidyOpenType env1 match_ty' + in + returnNF_Tc (env1, + sep [ptext SLIT("When checking an existential match that binds"), + nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)), + ptext SLIT("and whose type is") <+> ppr tidy_mty]) + where + show_ids = filter is_interesting bound_ids + is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs -lurkingRank2SigErr - = ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type") + ppr_id id ty = ppr id <+> dcolon <+> ppr ty + -- Don't zonk the types so we get the separate, un-unified versions \end{code}