X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=516c822dbcf959319489e0cf111b7ed7ffec113f;hb=f087e1b53f70e41b7cc91ad1b117967710da2288;hp=bd223b46de55025e55a72fcac0d8043c966ca4be;hpb=a170160cc21678c30ca90696d4ae0fc1155f25bf;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index bd223b4..516c822 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -25,11 +25,11 @@ import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv2 ) import TcPat ( tcPat, tcMonoPatBndr ) -import TcMType ( newTyVarTy, zonkTcType ) +import TcMType ( newTyVarTy, zonkTcType, zapToType ) import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType, mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind ) import TcBinds ( tcBindsAndThen ) -import TcUnify ( subFunTy, checkSigTyVarsWrt, tcSub, isIdCoercion, (<$>) ) +import TcUnify ( subFunTy, checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) import TysWiredIn ( boolTy ) @@ -39,7 +39,7 @@ import BasicTypes ( RecFlag(..) ) import VarSet import Var ( Id ) import Bag -import Util ( isSingleton ) +import Util ( isSingleton, lengthExceeds, notNull ) import Outputable import List ( nub ) @@ -111,10 +111,18 @@ tcMatches :: [(Name,Id)] -> TcM ([TcMatch], LIE) tcMatches xve ctxt matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> + = -- 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 ctxt match expected_ty + tc_match expected_ty match = tcMatch xve ctxt match expected_ty \end{code} @@ -138,25 +146,23 @@ tcMatch :: [(Name,Id)] 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) -> + 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 + tc_grhss rhs_ty = tcExtendLocalValEnv2 xve1 $ -- Deal with the result signature case maybe_rhs_sig of - Nothing -> tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> - returnTc ((pats', grhss'), lie) + 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) -> - tcSub rhs_ty sig_ty `thenTc` \ (co_fn, lie2) -> - returnTc ((pats', lift_grhss co_fn rhs_ty grhss'), + 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, @@ -204,8 +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 @@ -216,17 +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 - tcExtendLocalValEnv2 xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) -> - - returnTc (lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) - ) `thenTc` \ (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 @@ -235,66 +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 expected_ty `thenTc` \ (lie_req2', ex_binds) -> + 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 (result, lie_req1 `plusLIE` lie_req2', ex_binds) + 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 + 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 :: [TcId] -- Ids bound by this pattern - -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern +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 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 match_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 - = tcAddErrCtxtM (sigPatCtxt tv_list ids match_ty) $ + = 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) -> - checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `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 - = subFunTy expected_ty `thenTc` \ (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, 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} @@ -328,7 +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 @@ -359,12 +370,11 @@ tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) t tcAddErrCtxt (stmtCtxt do_or_lc stmt) $ newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> tcMonoExpr 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), + 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)