X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=f1048d892b569ebaaa46009b5aa6fde197834338;hb=56b5a8b862d4eaeeaa941dd53e3d1009bdeadc0d;hp=66a6816e88cea183071db076e8a6208a7dd6a33a;hpb=cd5abca9d4be624f0c4759d3ef126e4392b81ac7;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 66a6816..f1048d8 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -5,42 +5,49 @@ \begin{code} module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, - tcStmts, tcStmtsAndThen, tcGRHSs + tcDoStmts, tcStmtsAndThen, tcGRHSs ) where #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 HsSyn ( HsExpr(..), HsBinds(..), Match(..), GRHSs(..), GRHS(..), + MonoBinds(..), Stmt(..), HsMatchContext(..), HsStmtContext(..), + pprMatch, getMatchLoc, isDoExpr, + pprMatchContext, pprStmtContext, pprStmtResultContext, + mkMonoBind, collectSigTysFromPats, andMonoBindList ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType, - RenamedMatchContext, extractHsTyVars ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) - -import TcMonad -import TcMonoType ( kcHsSigTypes, tcScopedTyVars, checkSigTyVars, tcHsSigType, UserTypeCtxt(..), sigPatCtxt ) -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 RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, + RenamedPat, RenamedMatchContext ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds, + TcMonoBinds, TcPat, TcStmt ) + +import TcRnMonad +import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) +import Inst ( tcSyntaxName ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 ) +import TcPat ( tcPat, tcMonoPatBndr ) +import TcMType ( newTyVarTy, newTyVarTys, zonkTcType, zapToType ) +import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType, + mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind, + mkArrowKind, mkAppTy ) import TcBinds ( tcBindsAndThen ) +import TcUnify ( unifyPArrTy,subFunTy, unifyListTy, unifyTauTy, + checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) -import TysWiredIn ( boolTy ) -import Id ( idType ) +import PrelNames ( monadNames, mfixName ) +import TysWiredIn ( boolTy, mkListTy, mkPArrTy ) +import Id ( idType, mkSysLocal, mkLocalId ) +import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) -import NameSet import VarSet import Var ( Id ) import Bag +import Util ( isSingleton, lengthExceeds, notNull, zipEqual ) import Outputable + import List ( nub ) \end{code} @@ -60,7 +67,7 @@ tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group -> Name -> TcType -- Expected type -> [RenamedMatch] - -> TcM ([TcMatch], LIE) + -> TcM [TcMatch] tcMatchesFun xve fun_name expected_ty matches@(first_match:_) = -- Check that they all have the same no of arguments @@ -69,16 +76,16 @@ tcMatchesFun xve fun_name expected_ty matches@(first_match:_) -- sensible location. Note: we have to do this odd -- ann-grabbing, because we don't always have annotations in -- hand when we call tcMatchesFun... - tcAddSrcLoc (getMatchLoc first_match) ( + addSrcLoc (getMatchLoc first_match) ( checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches) - ) `thenTc_` + ) `thenM_` -- ToDo: Don't use "expected" stuff if there ain't a type signature -- 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} @@ -89,15 +96,14 @@ parser guarantees that each equation has exactly one argument. tcMatchesCase :: [RenamedMatch] -- The case alternatives -> TcType -- Type of whole case expressions -> TcM (TcType, -- Inferred type of the scrutinee - [TcMatch], -- Translated alternatives - LIE) + [TcMatch]) -- Translated alternatives tcMatchesCase matches expr_ty - = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty -> - tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenTc` \ (matches', lie) -> - returnTc (scrut_ty, matches', lie) + = newTyVarTy openTypeKind `thenM` \ scrut_ty -> + tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenM` \ matches' -> + returnM (scrut_ty, matches') -tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE) +tcMatchLambda :: RenamedMatch -> TcType -> TcM TcMatch tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty \end{code} @@ -107,13 +113,20 @@ tcMatches :: [(Name,Id)] -> RenamedMatchContext -> [RenamedMatch] -> TcType - -> TcM ([TcMatch], LIE) - -tcMatches xve fun_or_case matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> - returnTc (matches, plusLIEs lies) + -> TcM [TcMatch] + +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 + returnM expected_ty) `thenM` \ expected_ty' -> + + mappM (tc_match expected_ty') matches 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} @@ -127,66 +140,69 @@ 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 - -> TcM (TcMatch, LIE) - -tcMatch xve1 ctxt match@(Match sig_tvs 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) + -> 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 + +tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty + = addSrcLoc (getMatchLoc match) $ -- At one stage I removed this; + addErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back + tcMatchPats pats expected_ty tc_grhss `thenM` \ (pats', grhss', ex_binds) -> + returnM (Match pats' Nothing (glue_on ex_binds grhss')) 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 - + 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 `thenM` \ sig_ty -> + tcGRHSs ctxt grhss sig_ty `thenM` \ grhss' -> + tcSubExp rhs_ty sig_ty `thenM` \ co_fn -> + returnM (lift_grhss co_fn rhs_ty grhss') + +-- 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 EmptyBinds grhss = grhss -- The common case +glue_on binds1 (GRHSs grhss binds2 ty) + = GRHSs grhss (binds1 `ThenBinds` binds2) ty - -- 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) + -> TcM TcGRHSs tcGRHSs ctxt (GRHSs grhss binds _) expected_ty = tcBindsAndThen glue_on binds (tc_grhss grhss) where + m_ty = (\ty -> ty, expected_ty) + tc_grhss grhss - = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> - returnTc (GRHSs grhss' EmptyBinds expected_ty, plusLIEs lies) + = mappM tc_grhs grhss `thenM` \ grhss' -> + returnM (GRHSs grhss' EmptyBinds expected_ty) tc_grhs (GRHS guarded locn) - = tcAddSrcLoc locn $ - tcStmts ctxt (\ty -> ty, expected_ty) guarded `thenTc` \ (guarded', lie) -> - returnTc (GRHS guarded' locn, lie) + = addSrcLoc locn $ + tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' -> + returnM (GRHS guarded' locn) \end{code} @@ -199,8 +215,8 @@ tcGRHSs ctxt (GRHSs grhss binds _) expected_ty \begin{code} tcMatchPats :: [RenamedPat] -> TcType - -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) - -> TcM (a, LIE, TcDictBinds) + -> (TcType -> TcM a) + -> TcM ([TcPat], a, TcHsBinds) -- 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 +227,10 @@ 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 + getLIE (tc_match_pats pats expected_ty thing_inside) + + ) `thenM` \ ((pats', ex_tvs, ex_ids, ex_lie, result), lie_req) -> -- STEP 4: Check for existentially bound type variables -- Do this *outside* the scope of the tcAddScopedTyVars, else checkSigTyVars @@ -230,80 +239,131 @@ 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 `thenM` \ 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). + + returnM (pats', result, mkMonoBind Recursive ex_binds) + +tc_match_pats [] expected_ty thing_inside + = thing_inside expected_ty `thenM` \ answer -> + returnM ([], emptyBag, [], [], 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 `thenM` \ (pat', 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 - -> LIE -- and context - -> LIE -- Required context - -> TcType -- and result type; 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 + 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 `thenM` \ (pats', exs_tvs, exs_ids, exs_lie, answer) -> + returnM ( pat':pats', + ex_tvs `unionBags` exs_tvs, + ex_ids ++ exs_ids, + ex_lie ++ 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 + -> [Inst] -- and context + -> [Inst] -- Required context + -> TcType -- and type of the Match; vars in here must not escape + -> TcM TcDictBinds -- LIE to float out and dict bindings +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 ) - returnTc (lie_req, EmptyMonoBinds) + = ASSERT( null ex_lie ) + extendLIEs lie_req `thenM_` + returnM EmptyMonoBinds | otherwise - = tcExtendGlobalTyVars (tyVarsOfType result_ty) $ - tcAddErrCtxtM (sigPatCtxt tv_list ids) $ + = addErrCtxtM (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) -> + getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) -> -- 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 ex_lie lie `thenM` \ dict_binds -> + checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenM_` - returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) + returnM (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)) +\end{code} -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 - ) + +%************************************************************************ +%* * +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} +%* * +%************************************************************************ + +\begin{code} +tcDoStmts :: HsStmtContext Name -> [RenamedStmt] -> [Name] -> TcType + -> TcM (TcMonoBinds, [TcStmt], [Id]) +tcDoStmts PArrComp stmts method_names res_ty + = unifyPArrTy res_ty `thenM` \elt_ty -> + tcStmts PArrComp (mkPArrTy, elt_ty) stmts `thenM` \ stmts' -> + returnM (EmptyMonoBinds, stmts', [{- unused -}]) + +tcDoStmts ListComp stmts method_names res_ty + = unifyListTy res_ty `thenM` \ elt_ty -> + tcStmts ListComp (mkListTy, elt_ty) stmts `thenM` \ stmts' -> + returnM (EmptyMonoBinds, stmts', [{- unused -}]) + +tcDoStmts do_or_mdo_expr stmts method_names res_ty + = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> + newTyVarTy liftedTypeKind `thenM` \ elt_ty -> + unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_` + + tcStmts do_or_mdo_expr (mkAppTy m_ty, elt_ty) stmts `thenM` \ stmts' -> + + -- Build the then and zero methods in case we need them + -- It's important that "then" and "return" appear just once in the final LIE, + -- not only for typechecker efficiency, but also because otherwise during + -- simplification we end up with silly stuff like + -- then = case d of (t,r) -> t + -- then = then + -- where the second "then" sees that it already exists in the "available" stuff. + -- + mapAndUnzipM (tc_syn_name m_ty) + (zipEqual "tcDoStmts" currentMonadNames method_names) `thenM` \ (binds, ids) -> + returnM (andMonoBindList binds, stmts', ids) + where + currentMonadNames = case do_or_mdo_expr of + DoExpr -> monadNames + MDoExpr -> monadNames ++ [mfixName] + tc_syn_name :: TcType -> (Name,Name) -> TcM (TcMonoBinds, Id) + tc_syn_name m_ty (std_nm, usr_nm) + = tcSyntaxName DoOrigin m_ty std_nm usr_nm `thenM` \ (expr, expr_ty) -> + case expr of + HsVar v -> returnM (EmptyMonoBinds, v) + other -> newUnique `thenM` \ uniq -> + let + id = mkSysLocal FSLIT("syn") uniq expr_ty + in + returnM (VarMonoBind id expr, id) \end{code} @@ -337,16 +397,17 @@ 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 (returnM []) tcStmtsAndThen :: (TcStmt -> thing -> thing) -- Combiner - -> RenamedMatchContext + -> HsStmtContext Name -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs -- elt_ty, where type of the comprehension is (m elt_ty) -> [RenamedStmt] - -> TcM (thing, LIE) - -> TcM (thing, LIE) + -> TcM thing + -> TcM thing -- Base case tcStmtsAndThen combine do_or_lc m_ty [] do_next @@ -364,77 +425,98 @@ tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside thing_inside tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) thing_inside - = 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), - lie `plusLIE` exp_lie) - + = addSrcLoc src_loc $ + addErrCtxt (stmtCtxt do_or_lc stmt) $ + newTyVarTy liftedTypeKind `thenM` \ pat_ty -> + tcMonoExpr exp (m pat_ty) `thenM` \ exp' -> + tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ -> + popErrCtxt thing_inside + ) `thenM` \ ([pat'], thing, dict_binds) -> + returnM (combine (BindStmt pat' exp' src_loc) + (glue_binds combine dict_binds thing)) -- ParStmt tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside - = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) -> - returnTc (combine (ParStmtOut pairs') thing, lie) + = loop bndr_stmts_s `thenM` \ (pairs', thing) -> + returnM (combine (ParStmtOut pairs') thing) where loop [] - = thing_inside `thenTc` \ (thing, stmts_lie) -> - returnTc (([], thing), stmts_lie) + = thing_inside `thenM` \ thing -> + returnM ([], thing) loop ((bndrs,stmts) : pairs) = tcStmtsAndThen - combine_par (DoCtxt ListComp) m_ty stmts + combine_par ListComp m_ty stmts -- Notice we pass on m_ty; the result type is used only -- to get escaping type variables for checkExistentialPat - (tcLookupLocalIds bndrs `thenNF_Tc` \ bndrs' -> - loop pairs `thenTc` \ ((pairs', thing), lie) -> - returnTc (([], (bndrs', pairs', thing)), lie)) `thenTc` \ ((stmts', (bndrs', pairs', thing)), lie) -> + (tcLookupLocalIds bndrs `thenM` \ bndrs' -> + loop pairs `thenM` \ (pairs', thing) -> + returnM ([], (bndrs', pairs', thing))) `thenM` \ (stmts', (bndrs', pairs', thing)) -> - returnTc ( ((bndrs',stmts') : pairs', thing), lie) + returnM ((bndrs',stmts') : pairs', thing) combine_par stmt (stmts, thing) = (stmt:stmts, thing) + -- RecStmt +tcStmtAndThen combine do_or_lc m_ty (RecStmt recNames stmts _) thing_inside + = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> + let + mono_ids = zipWith mkLocalId recNames recTys + in + tcExtendLocalValEnv mono_ids $ + tcStmtsAndThen combine_rec do_or_lc m_ty stmts ( + mappM tc_ret (recNames `zip` recTys) `thenM` \ rets -> + returnM ([], rets) + ) `thenM` \ (stmts', rets) -> + + -- NB: it's the mono_ids that scope over this part + thing_inside `thenM` \ thing -> + + returnM (combine (RecStmt mono_ids stmts' rets) thing) + where + combine_rec stmt (stmts, thing) = (stmt:stmts, thing) + + -- Unify the types of the "final" Ids with those of "knot-tied" Ids + tc_ret (rec_name, mono_ty) + = tcLookupId rec_name `thenM` \ poly_id -> + -- poly_id may have a polymorphic type + -- but mono_ty is just a monomorphic type variable + tcSubExp mono_ty (idType poly_id) `thenM` \ co_fn -> + returnM (co_fn <$> HsVar poly_id) + -- ExprStmt tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + = addErrCtxt (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) -> - returnTc (ExprStmt exp' any_ty locn, lie) + newTyVarTy openTypeKind `thenM` \ any_ty -> + tcMonoExpr exp (m any_ty) `thenM` \ exp' -> + returnM (ExprStmt exp' any_ty locn) else - tcExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> - returnTc (ExprStmt exp' boolTy locn, lie) - ) `thenTc` \ (stmt', stmt_lie) -> + tcMonoExpr exp boolTy `thenM` \ exp' -> + returnM (ExprStmt exp' boolTy locn) + ) `thenM` \ stmt' -> - thing_inside `thenTc` \ (thing, stmts_lie) -> - - returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie) + thing_inside `thenM` \ thing -> + returnM (combine stmt' thing) -- Result statements tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + = addErrCtxt (resCtxt 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 - ) `thenTc` \ (exp', stmt_lie) -> + tcMonoExpr exp res_elt_ty + ) `thenM` \ exp' -> - thing_inside `thenTc` \ (thing, stmts_lie) -> + thing_inside `thenM` \ thing -> - returnTc (combine (ResultStmt exp' locn) thing, - stmt_lie `plusLIE` stmts_lie) + returnM (combine (ResultStmt exp' locn) thing) ------------------------------ -glue_binds combine is_rec binds thing - | nullMonoBinds binds = thing - | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing +glue_binds combine EmptyBinds thing = thing +glue_binds combine other_binds thing = combine (LetStmt other_binds) thing \end{code} @@ -449,19 +531,34 @@ 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} -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)] -lurkingRank2SigErr - = ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type") +matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match) +stmtCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtContext do_or_lc <> colon) 4 (ppr stmt) +resCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtResultContext do_or_lc <> colon) 4 (ppr stmt) + +sigPatCtxt bound_tvs bound_ids match_ty tidy_env + = zonkTcType match_ty `thenM` \ match_ty' -> + let + (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) + (env2, tidy_mty) = tidyOpenType env1 match_ty' + in + returnM (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 + + ppr_id id ty = ppr id <+> dcolon <+> ppr ty + -- Don't zonk the types so we get the separate, un-unified versions \end{code}