X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=f1048d892b569ebaaa46009b5aa6fde197834338;hb=a06f5e7b2158b57e40ebf255eb9d0b74e9625762;hp=87644fad39a82858b5f59bf1f27ac3333e15b71d;hpb=20d387c481324aed48e8469d3fbf0695b3b2e365;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 87644fa..f1048d8 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,40 +4,50 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where +module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, + tcDoStmts, tcStmtsAndThen, tcGRHSs + ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) +import {-# SOURCE #-} TcExpr( tcMonoExpr ) -import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), - MonoBinds(..), StmtCtxt(..), Stmt(..), - pprMatch, getMatchLoc, consLetStmt, - mkMonoBind, 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 ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt ) - -import TcMonad -import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt ) -import Inst ( LIE, plusLIE, emptyLIE, plusLIEs ) -import TcEnv ( TcId, tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars ) -import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig ) -import TcType ( TcType, newTyVarTy ) +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 TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcUnify ( unifyFunTy, unifyTauTy, unifyListTy ) +import TcUnify ( unifyPArrTy,subFunTy, unifyListTy, unifyTauTy, + checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) -import TysWiredIn ( boolTy ) - +import PrelNames ( monadNames, mfixName ) +import TysWiredIn ( boolTy, mkListTy, mkPArrTy ) +import Id ( idType, mkSysLocal, mkLocalId ) +import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) -import Type ( tyVarsOfType, isTauTy, mkArrowKind, mkAppTy, mkFunTy, - liftedTypeKind, openTypeKind ) -import SrcLoc ( SrcLoc ) import VarSet import Var ( Id ) import Bag +import Util ( isSingleton, lengthExceeds, notNull, zipEqual ) import Outputable + import List ( nub ) \end{code} @@ -57,7 +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 @@ -66,17 +76,17 @@ 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 - tcMatches xve matches expected_ty (FunRhs fun_name) + -- No need to zonk expected_ty, because subFunTy does that on the fly + tcMatches xve (FunRhs fun_name) matches expected_ty \end{code} @tcMatchesCase@ doesn't do the argument-count check because the @@ -86,31 +96,37 @@ 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 [] matches (mkFunTy scrut_ty expr_ty) CaseAlt `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 match res_ty = tcMatch [] match res_ty LambdaBody +tcMatchLambda :: RenamedMatch -> TcType -> TcM TcMatch +tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty \end{code} \begin{code} tcMatches :: [(Name,Id)] + -> RenamedMatchContext -> [RenamedMatch] -> TcType - -> StmtCtxt - -> TcM ([TcMatch], LIE) - -tcMatches xve matches expected_ty fun_or_case - = 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 match expected_ty fun_or_case + tc_match expected_ty match = tcMatch xve ctxt match expected_ty \end{code} @@ -122,141 +138,232 @@ tcMatches xve matches expected_ty fun_or_case \begin{code} tcMatch :: [(Name,Id)] + -> RenamedMatchContext -> RenamedMatch - -> TcType -- Expected result-type of the Match. - -- Early unification with this guy gives better error messages - -> StmtCtxt - -> TcM (TcMatch, 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')) -tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt - = tcAddSrcLoc (getMatchLoc match) $ - tcAddErrCtxt (matchCtxt ctxt match) $ + where + tc_grhss rhs_ty + = tcExtendLocalValEnv2 xve1 $ + + -- Deal with the result signature + 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 - if null sig_tvs then -- The common case - tc_match expected_ty `thenTc` \ (_, match_and_lie) -> - returnTc match_and_lie - else - -- If there are sig tvs we must be careful *not* to use - -- expected_ty right away, else we'll unify with tyvars free - -- in the envt. So invent a fresh tyvar and use that instead - newTyVarTy openTypeKind `thenNF_Tc` \ tyvar_ty -> +tcGRHSs :: RenamedMatchContext -> RenamedGRHSs + -> TcType + -> TcM TcGRHSs - -- Extend the tyvar env and check the match itself - tcTyVars sig_tvs (mapTc_ kcHsSigType sig_tys) `thenTc` \ sig_tyvars -> - tcExtendTyVarEnv sig_tyvars (tc_match tyvar_ty) `thenTc` \ (pat_ids, match_and_lie) -> +tcGRHSs ctxt (GRHSs grhss binds _) expected_ty + = tcBindsAndThen glue_on binds (tc_grhss grhss) + where + m_ty = (\ty -> ty, expected_ty) - -- Check that the scoped type variables from the patterns - -- have not been constrained - tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) ( - checkSigTyVars sig_tyvars emptyVarSet - ) `thenTc_` + tc_grhss grhss + = mappM tc_grhs grhss `thenM` \ grhss' -> + returnM (GRHSs grhss' EmptyBinds expected_ty) - -- *Now* we're free to unify with expected_ty - unifyTauTy expected_ty tyvar_ty `thenTc_` + tc_grhs (GRHS guarded locn) + = addSrcLoc locn $ + tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' -> + returnM (GRHS guarded' locn) +\end{code} - returnTc match_and_lie - where - sig_tys = case maybe_rhs_sig of { Just t -> [t]; Nothing -> [] } - ++ collectSigTysFromPats pats - - tc_match expected_ty -- Any sig tyvars are in scope by now - = -- STEP 1: Typecheck the patterns - tcMatchPats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> - let - xve2 = bagToList pat_bndrs - pat_ids = map snd xve2 - ex_tv_list = bagToList ex_tvs - in - - -- STEP 2: 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_` - - -- STEP 3: Unify with the rhs type signature if any - (case maybe_rhs_sig of - Nothing -> returnTc () - Just sig -> tcHsSigType 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 rhs_ty sig_ty - ) `thenTc_` - - -- STEP 4: Typecheck the guarded RHSs and the associated where clause - tcExtendLocalValEnv xve1 (tcExtendLocalValEnv xve2 ( - tcGRHSs grhss rhs_ty ctxt - )) `thenTc` \ (grhss', lie_req2) -> - - -- STEP 5: Check for existentially bound type variables - tcExtendGlobalTyVars (tyVarsOfType rhs_ty) ( - tcAddErrCtxtM (sigPatCtxt ex_tv_list pat_ids) $ - checkSigTyVars ex_tv_list emptyVarSet `thenTc` \ zonked_ex_tvs -> - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_ex_tvs) - lie_avail (lie_req1 `plusLIE` lie_req2) - ) `thenTc` \ (lie_req', ex_binds) -> - - -- STEP 6 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' pat_ids `thenTc` \ (lie_req'', inst_binds) -> +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ - -- Phew! All done. - let - grhss'' = glue_on Recursive ex_binds $ - glue_on Recursive inst_binds grhss' - in - returnTc (pat_ids, (Match [] pats' Nothing grhss'', lie_req'')) +\begin{code} +tcMatchPats + :: [RenamedPat] -> TcType + -> (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 +-- signatures + +tcMatchPats pats expected_ty thing_inside + = -- STEP 1: Bring pattern-signature type variables into scope + tcAddScopedTyVars (collectSigTysFromPats pats) ( + + -- STEP 2: Typecheck the patterns themselves, gathering all the stuff + -- 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 + -- complains that 'a' is captured by the inscope 'a'! (Test (d) in checkSigTyVars.) + -- + -- 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 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 + 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 + ) - -- 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 :: RenamedGRHSs - -> TcType -> StmtCtxt - -> TcM (TcGRHSs, LIE) +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( null ex_lie ) + extendLIEs lie_req `thenM_` + returnM EmptyMonoBinds + + | otherwise + = 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 + getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) -> -tcGRHSs (GRHSs grhss binds _) expected_ty ctxt - = tcBindsAndThen glue_on binds (tc_grhss grhss) - where - tc_grhss grhss - = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> - returnTc (GRHSs grhss' EmptyBinds (Just expected_ty), plusLIEs lies) + -- Deal with overloaded functions bound by the pattern + tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds -> + checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenM_` - tc_grhs (GRHS guarded locn) - = tcAddSrcLoc locn $ - tcStmts ctxt (\ty -> ty) expected_ty locn guarded - `thenTc` \ ((guarded', _), lie) -> - returnTc (GRHS guarded' locn, lie) + returnM (dict_binds `AndMonoBinds` inst_binds) + where + doc = text ("existential context of a data constructor") + tv_list = bagToList ex_tvs + not_overloaded id = not (isOverloadedTy (idType id)) \end{code} %************************************************************************ %* * -\subsection{tcMatchPats} +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} %* * %************************************************************************ \begin{code} -tcMatchPats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tcMatchPats (pat:pats) expected_ty - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - tcPat tcPatBndr_NoSigs pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> - tcMatchPats 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 - ) +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} @@ -266,126 +373,150 @@ tcMatchPats (pat:pats) expected_ty %* * %************************************************************************ +Typechecking statements is rendered a bit tricky by parallel list comprehensions: -\begin{code} -tcParStep src_loc stmts - = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenTc` \ m -> - newTyVarTy liftedTypeKind `thenTc` \ elt_ty -> - unifyListTy (mkAppTy m elt_ty) `thenTc_` - - tcStmts ListComp (mkAppTy m) elt_ty src_loc stmts `thenTc` \ ((stmts', val_env), stmts_lie) -> - returnTc (stmts', val_env, stmts_lie) - -tcStmts :: StmtCtxt - -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs - -> TcType -- elt_ty, where type of the comprehension is (m elt_ty) - -> SrcLoc - -> [RenamedStmt] - -> TcM (([TcStmt], [(Name, TcId)]), LIE) - -tcStmts do_or_lc m elt_ty loc (ParStmtOut bndrstmtss : stmts) - = let stmtss = map snd bndrstmtss in - mapAndUnzip3Tc (tcParStep loc) stmtss `thenTc` \ (stmtss', val_envs, lies) -> - let outstmts = zip (map (map snd) val_envs) stmtss' - lie = plusLIEs lies - new_val_env = concat val_envs - in - tcExtendLocalValEnv new_val_env ( - tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), stmts_lie) -> - returnTc ((ParStmtOut outstmts : stmts', rest_val_env ++ new_val_env), lie `plusLIE` stmts_lie) - -tcStmts do_or_lc m elt_ty loc (stmt@(ReturnStmt exp) : stmts) - = ASSERT( null stmts ) - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) -> - returnTc (([ReturnStmt exp'], []), exp_lie) - - -- ExprStmt at the end -tcStmts do_or_lc m elt_ty loc [stmt@(ExprStmt exp src_loc)] - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExpr exp (m elt_ty) `thenTc` \ (exp', exp_lie) -> - returnTc (([ExprStmt exp' src_loc], []), exp_lie) - - -- ExprStmt not at the end -tcStmts do_or_lc m elt_ty loc (stmt@(ExprStmt exp src_loc) : stmts) - = ASSERT( isDoStmt do_or_lc ) - tcAddSrcLoc src_loc ( - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - -- exp has type (m tau) for some tau (doesn't matter what) - newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> - tcExpr exp (m any_ty) - ) `thenTc` \ (exp', exp_lie) -> - tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) -> - returnTc ((ExprStmt exp' src_loc : stmts', rest_val_env), - exp_lie `plusLIE` stmts_lie) - -tcStmts do_or_lc m elt_ty loc (stmt@(GuardStmt exp src_loc) : stmts) - = ASSERT( not (isDoStmt do_or_lc) ) - tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - tcAddSrcLoc src_loc $ - tcExpr exp boolTy - ) `thenTc` \ (exp', exp_lie) -> - tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) -> - -- ZZ is this right? - returnTc ((GuardStmt exp' src_loc : stmts', rest_val_env), - exp_lie `plusLIE` stmts_lie) - -tcStmts do_or_lc m elt_ty loc (stmt@(BindStmt pat exp src_loc) : stmts) - = tcAddSrcLoc src_loc ( - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> - tcPat tcPatBndr_NoSigs pat pat_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail) -> - tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> - returnTc (pat', exp', - pat_lie `plusLIE` exp_lie, - pat_tvs, pat_ids, avail) - ) `thenTc` \ (pat', exp', lie_req, pat_tvs, pat_bndrs, lie_avail) -> - let - new_val_env = bagToList pat_bndrs - pat_ids = map snd new_val_env - pat_tv_list = bagToList pat_tvs - in + [ (g x, h x) | ... ; let g v = ... + | ... ; let h v = ... ] - -- Do the rest; we don't need to add the pat_tvs to the envt - -- because they all appear in the pat_ids's types - tcExtendLocalValEnv new_val_env ( - tcStmts do_or_lc m elt_ty loc stmts - ) `thenTc` \ ((stmts', rest_val_env), stmts_lie) -> +It's possible that g,h are overloaded, so we need to feed the LIE from the +(g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns). +Similarly if we had an existential pattern match: + data T = forall a. Show a => C a - -- Reinstate context for existential checks - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $ - tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $ + [ (show x, show y) | ... ; C x <- ... + | ... ; C y <- ... ] - checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs -> +Then we need the LIE from (show x, show y) to be simplified against +the bindings for x and y. - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_pat_tvs) - lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) -> +It's difficult to do this in parallel, so we rely on the renamer to +ensure that g,h and x,y don't duplicate, and simply grow the environment. +So the binders of the first parallel group will be in scope in the second +group. But that's fine; there's no shadowing to worry about. - -- ZZ we have to be sure that concating the val_env lists preserves - -- shadowing properly... - returnTc ((BindStmt pat' exp' src_loc : - consLetStmt (mkMonoBind dict_binds [] Recursive) stmts', - rest_val_env ++ new_val_env), - lie_req `plusLIE` final_lie) +\begin{code} +tcStmts do_or_lc m_ty stmts + = ASSERT( notNull stmts ) + tcStmtsAndThen (:) do_or_lc m_ty stmts (returnM []) + +tcStmtsAndThen + :: (TcStmt -> thing -> thing) -- Combiner + -> 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 + -> TcM thing -tcStmts do_or_lc m elt_ty loc (LetStmt binds : stmts) - = tcBindsAndThen -- No error context, but a binding group is - combine -- rather a large thing for an error context anyway - binds - (tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), lie) -> - -- ZZ fix val_env - returnTc ((stmts', rest_val_env), lie) - where - combine is_rec binds' (stmts', val_env) = (consLetStmt (mkMonoBind binds' [] is_rec) stmts', undefined) + -- Base case +tcStmtsAndThen combine do_or_lc m_ty [] do_next + = do_next -tcStmts do_or_lc m elt_ty loc [] = returnTc (([], []), emptyLIE) +tcStmtsAndThen combine do_or_lc m_ty (stmt:stmts) do_next + = tcStmtAndThen combine do_or_lc m_ty stmt + (tcStmtsAndThen combine do_or_lc m_ty stmts do_next) -isDoStmt DoStmt = True -isDoStmt other = False + -- LetStmt +tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside + = tcBindsAndThen -- No error context, but a binding group is + (glue_binds combine) -- rather a large thing for an error context anyway + binds + thing_inside + +tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) thing_inside + = 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 `thenM` \ (pairs', thing) -> + returnM (combine (ParStmtOut pairs') thing) + where + loop [] + = thing_inside `thenM` \ thing -> + returnM ([], thing) + + loop ((bndrs,stmts) : pairs) + = tcStmtsAndThen + 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 `thenM` \ bndrs' -> + loop pairs `thenM` \ (pairs', thing) -> + returnM ([], (bndrs', pairs', thing))) `thenM` \ (stmts', (bndrs', pairs', thing)) -> + + 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 + = addErrCtxt (stmtCtxt do_or_lc stmt) ( + if isDoExpr do_or_lc then + newTyVarTy openTypeKind `thenM` \ any_ty -> + tcMonoExpr exp (m any_ty) `thenM` \ exp' -> + returnM (ExprStmt exp' any_ty locn) + else + tcMonoExpr exp boolTy `thenM` \ exp' -> + returnM (ExprStmt exp' boolTy locn) + ) `thenM` \ stmt' -> + + 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 + = addErrCtxt (resCtxt do_or_lc stmt) ( + if isDoExpr do_or_lc then + tcMonoExpr exp (m res_elt_ty) + else + tcMonoExpr exp res_elt_ty + ) `thenM` \ exp' -> + + thing_inside `thenM` \ thing -> + + returnM (combine (ResultStmt exp' locn) thing) + + +------------------------------ +glue_binds combine EmptyBinds thing = thing +glue_binds combine other_binds thing = combine (LetStmt other_binds) thing \end{code} @@ -400,46 +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 CaseAlt match - = hang (ptext SLIT("In a case alternative:")) - 4 (pprMatch (True,empty) {-is_case-} match) - -matchCtxt (FunRhs fun) match - = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr_fun), char ':']) - 4 (pprMatch (False, ppr_fun) {-not case-} match) - where - ppr_fun = ppr fun - -matchCtxt LambdaBody match - = hang (ptext SLIT("In the lambda expression")) - 4 (pprMatch (True, empty) match) - 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) -stmtCtxt do_or_lc stmt - = hang (ptext SLIT("In") <+> what <> 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 - what = case do_or_lc of - ListComp -> ptext SLIT("a list-comprehension qualifier") - DoStmt -> ptext SLIT("a do statement") - PatBindRhs -> thing <+> ptext SLIT("a pattern binding") - FunRhs f -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f) - CaseAlt -> thing <+> ptext SLIT("a case alternative") - LambdaBody -> thing <+> ptext SLIT("a lambda abstraction") - thing = case stmt of - BindStmt _ _ _ -> ptext SLIT("a pattern guard for") - GuardStmt _ _ -> ptext SLIT("a guard for") - ExprStmt _ _ -> ptext SLIT("the right-hand side of") + 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}