X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=21c74dcce4ca3162ed6b2740d31d13929049a31c;hb=7e7c11b2b285fd00758baac1be3784322a2aff62;hp=317e33542f21e90678bf01140d5690fe60f5f388;hpb=203a687fbdb9bf54592f907302d8e47e174bb549;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 317e335..21c74dc 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,48 +4,53 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, - tcDoStmts, tcStmtsAndThen, tcGRHSs +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + matchCtxt, + tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig, + tcMatchPats, + TcStmtCtxt(..), TcMatchCtxt(..) ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcMonoExpr ) +import {-# SOURCE #-} TcExpr( tcCheckRho, tcMonoExpr ) import HsSyn ( HsExpr(..), HsBinds(..), Match(..), GRHSs(..), GRHS(..), MonoBinds(..), Stmt(..), HsMatchContext(..), HsStmtContext(..), + ReboundNames, pprMatch, getMatchLoc, isDoExpr, pprMatchContext, pprStmtContext, pprStmtResultContext, - mkMonoBind, nullMonoBinds, collectSigTysFromPats, andMonoBindList + mkMonoBind, collectSigTysFromPats, glueBindsOnGRHSs ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedHsExpr, RenamedPat, RenamedMatchContext ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds, - TcMonoBinds, TcPat, TcStmt ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds, TcExpr, + TcPat, TcStmt, ExprCoFn, + isIdCoercion, (<$>), (<.>) ) import TcRnMonad -import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) -import Inst ( tcSyntaxName ) +import TcHsType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) +import Inst ( tcSyntaxName, tcInstCall ) import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 ) import TcPat ( tcPat, tcMonoPatBndr ) -import TcMType ( newTyVarTy, newTyVarTys, zonkTcType, zapToType ) -import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType, +import TcMType ( newTyVarTy, newTyVarTys, zonkTcType ) +import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, + tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy ) import TcBinds ( tcBindsAndThen ) -import TcUnify ( unifyPArrTy,subFunTy, unifyListTy, unifyTauTy, - checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) +import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType, + unifyTauTy, subFunTys, unifyPArrTy, unifyListTy, unifyFunTy, + checkSigTyVarsWrt, tcSubExp, tcGen ) import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) -import PrelNames ( monadNames, mfixName ) import TysWiredIn ( boolTy, mkListTy, mkPArrTy ) -import Id ( idType, mkSysLocal, mkLocalId ) +import Id ( idType, mkLocalId ) import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) import VarSet -import Var ( Id ) import Bag -import Util ( isSingleton, lengthExceeds, notNull, zipEqual ) +import Util ( isSingleton, notNull ) import Outputable import List ( nub ) @@ -63,13 +68,12 @@ is used in error messages. It checks that all the equations have the same number of arguments before using @tcMatches@ to do the work. \begin{code} -tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group - -> Name - -> TcType -- Expected type +tcMatchesFun :: Name -> [RenamedMatch] + -> Expected TcRhoType -- Expected type -> TcM [TcMatch] -tcMatchesFun xve fun_name expected_ty matches@(first_match:_) +tcMatchesFun fun_name matches@(first_match:_) expected_ty = -- Check that they all have the same no of arguments -- Set the location to that of the first equation, so that -- any inter-equation error messages get some vaguely @@ -85,48 +89,80 @@ 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 subFunTy does that on the fly - tcMatches xve (FunRhs fun_name) matches expected_ty + -- No need to zonk expected_ty, because subFunTys does that on the fly + tcMatches match_ctxt matches expected_ty + where + match_ctxt = MC { mc_what = FunRhs fun_name, + mc_body = tcMonoExpr } \end{code} @tcMatchesCase@ doesn't do the argument-count check because the parser guarantees that each equation has exactly one argument. \begin{code} -tcMatchesCase :: [RenamedMatch] -- The case alternatives - -> TcType -- Type of whole case expressions - -> TcM (TcType, -- Inferred type of the scrutinee - [TcMatch]) -- Translated alternatives - -tcMatchesCase matches expr_ty - = newTyVarTy openTypeKind `thenM` \ scrut_ty -> - tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenM` \ matches' -> +tcMatchesCase :: TcMatchCtxt -- Case context + -> [RenamedMatch] -- The case alternatives + -> Expected TcRhoType -- Type of whole case expressions + -> TcM (TcRhoType, -- Inferred type of the scrutinee + [TcMatch]) -- Translated alternatives + +tcMatchesCase ctxt matches (Check expr_ty) + = -- This case is a bit yukky, because it prevents the + -- scrutinee being higher-ranked, which might just possible + -- matter if we were seq'ing on it. But it's awkward to fix. + newTyVarTy openTypeKind `thenM` \ scrut_ty -> + tcMatches ctxt matches (Check (mkFunTy scrut_ty expr_ty)) `thenM` \ matches' -> + returnM (scrut_ty, matches') + +tcMatchesCase ctxt matches (Infer hole) + = newHole `thenM` \ fun_hole -> + tcMatches ctxt matches (Infer fun_hole) `thenM` \ matches' -> + readMutVar fun_hole `thenM` \ fun_ty -> + -- The result of tcMatches is bound to be a function type + unifyFunTy fun_ty `thenM` \ (scrut_ty, res_ty) -> + writeMutVar hole res_ty `thenM_` returnM (scrut_ty, matches') + -tcMatchLambda :: RenamedMatch -> TcType -> TcM TcMatch -tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty +tcMatchLambda :: RenamedMatch -> Expected TcRhoType -> TcM TcMatch +tcMatchLambda match res_ty = tcMatch match_ctxt match res_ty + where + match_ctxt = MC { mc_what = LambdaExpr, + mc_body = tcMonoExpr } \end{code} +@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. + +\begin{code} +tcGRHSsPat :: RenamedGRHSs + -> Expected TcRhoType + -> TcM TcGRHSs +tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty + where + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcMonoExpr } +\end{code} \begin{code} -tcMatches :: [(Name,Id)] - -> RenamedMatchContext +data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module + = MC { mc_what :: RenamedMatchContext, -- What kind of thing this is + mc_body :: RenamedHsExpr -- Type checker for a body of an alternative + -> Expected TcRhoType + -> TcM TcExpr } + +tcMatches :: TcMatchCtxt -> [RenamedMatch] - -> TcType + -> Expected TcRhoType -> TcM [TcMatch] -tcMatches xve ctxt matches expected_ty - = -- If there is more than one branch, and expected_ty is a 'hole', +tcMatches ctxt matches exp_ty + = -- If there is more than one branch, and exp_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 + -- order in which we check them would affect the result. + zapExpectedBranches matches exp_ty `thenM` \ exp_ty' -> + mappM (tc_match exp_ty') matches where - tc_match expected_ty match = tcMatch xve ctxt match expected_ty + tc_match exp_ty match = tcMatch ctxt match exp_ty \end{code} @@ -137,72 +173,112 @@ tcMatches xve ctxt matches expected_ty %************************************************************************ \begin{code} -tcMatch :: [(Name,Id)] - -> RenamedMatchContext +tcMatch :: TcMatchCtxt -> RenamedMatch - -> TcType -- Expected result-type of the Match. + -> Expected TcRhoType -- 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 +tcMatch 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')) + addErrCtxt (matchCtxt (mc_what ctxt) match) $ -- I'm not sure why, so I put it back + subFunTys pats expected_ty $ \ pats_w_tys rhs_ty -> + -- This is the unique place we call subFunTys + -- The point is that if expected_y is a "hole", we want + -- to make arg_ty and rest_ty as "holes" too. + tcMatchPats pats_w_tys rhs_ty (tc_grhss rhs_ty) `thenM` \ (pats', grhss', ex_binds) -> + returnM (Match pats' Nothing (glueBindsOnGRHSs ex_binds grhss')) where tc_grhss rhs_ty - = tcExtendLocalValEnv2 xve1 $ - - -- Deal with the result signature - case maybe_rhs_sig of - Nothing -> tcGRHSs ctxt grhss rhs_ty + = case maybe_rhs_sig of -- Deal with the result signature + 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 + tcHsSigType ResSigCtxt sig `thenM` \ sig_ty -> + tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty `thenM` \ (co_fn, grhss') -> + + -- Pushes the coercion down to the right hand sides, + -- because there is no convenient place to hang it otherwise. + if isIdCoercion co_fn then + returnM grhss' + else + readExpectedType rhs_ty `thenM` \ rhs_ty' -> + returnM (lift_grhss co_fn rhs_ty' grhss') + lift_grhss co_fn rhs_ty (GRHSs grhss binds ty) - = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we + = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since the coercion does 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 - -tcGRHSs :: RenamedMatchContext -> RenamedGRHSs - -> TcType +tcGRHSs :: TcMatchCtxt -> RenamedGRHSs + -> Expected TcRhoType -> TcM TcGRHSs -tcGRHSs ctxt (GRHSs grhss binds _) expected_ty - = tcBindsAndThen glue_on binds (tc_grhss grhss) - where - m_ty = (\ty -> ty, expected_ty) + -- Special case when there is just one equation with a degenerate + -- guard; then we pass in the full Expected type, so that we get + -- good inference from simple things like + -- f = \(x::forall a.a->a) -> + -- This is a consequence of the fact that tcStmts takes a TcType, + -- not a Expected TcType, a decision we could revisit if necessary +tcGRHSs ctxt (GRHSs [GRHS [ResultStmt rhs loc1] loc2] binds _) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + mc_body ctxt rhs exp_ty `thenM` \ rhs' -> + readExpectedType exp_ty `thenM` \ exp_ty' -> + returnM (GRHSs [GRHS [ResultStmt rhs' loc1] loc2] EmptyBinds exp_ty') + +tcGRHSs ctxt (GRHSs grhss binds _) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + zapExpectedType exp_ty `thenM` \ exp_ty' -> + -- Even if there is only one guard, we zap the RHS type to + -- a monotype. Reason: it makes tcStmts much easier, + -- and even a one-armed guard has a notional second arm + let + stmt_ctxt = SC { sc_what = PatGuard (mc_what ctxt), + sc_rhs = tcCheckRho, + sc_body = sc_body, + sc_ty = exp_ty' } + sc_body body = mc_body ctxt body (Check exp_ty') + + tc_grhs (GRHS guarded locn) + = addSrcLoc locn $ + tcStmts stmt_ctxt guarded `thenM` \ guarded' -> + returnM (GRHS guarded' locn) + in + mappM tc_grhs grhss `thenM` \ grhss' -> + returnM (GRHSs grhss' EmptyBinds exp_ty') +\end{code} - tc_grhss grhss - = mappM tc_grhs grhss `thenM` \ grhss' -> - returnM (GRHSs grhss' EmptyBinds expected_ty) - tc_grhs (GRHS guarded locn) - = addSrcLoc locn $ - tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' -> - returnM (GRHS guarded' locn) +\begin{code} +tcThingWithSig :: TcSigmaType -- Type signature + -> (TcRhoType -> TcM r) -- How to type check the thing inside + -> Expected TcRhoType -- Overall expected result type + -> TcM (ExprCoFn, r) +-- Used for expressions with a type signature, and for result type signatures + +tcThingWithSig sig_ty thing_inside res_ty + | not (isSigmaTy sig_ty) + = thing_inside sig_ty `thenM` \ result -> + tcSubExp res_ty sig_ty `thenM` \ co_fn -> + returnM (co_fn, result) + + | otherwise -- The signature has some outer foralls + = -- Must instantiate the outer for-alls of sig_tc_ty + -- else we risk instantiating a ? res_ty to a forall-type + -- which breaks the invariant that tcMonoExpr only returns phi-types + tcGen sig_ty emptyVarSet thing_inside `thenM` \ (gen_fn, result) -> + tcInstCall SignatureOrigin sig_ty `thenM` \ (inst_fn, inst_sig_ty) -> + tcSubExp res_ty inst_sig_ty `thenM` \ co_fn -> + returnM (co_fn <.> inst_fn <.> gen_fn, result) + -- Note that we generalise, then instantiate. Ah well. \end{code} @@ -214,21 +290,22 @@ tcGRHSs ctxt (GRHSs grhss binds _) expected_ty \begin{code} tcMatchPats - :: [RenamedPat] -> TcType - -> (TcType -> TcM a) + :: [(RenamedPat, Expected TcRhoType)] + -> Expected TcRhoType + -> 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 +tcMatchPats pats_w_tys body_ty thing_inside = -- STEP 1: Bring pattern-signature type variables into scope - tcAddScopedTyVars (collectSigTysFromPats pats) ( + tcAddScopedTyVars (collectSigTysFromPats (map fst pats_w_tys)) ( -- STEP 2: Typecheck the patterns themselves, gathering all the stuff -- then do the thing inside - getLIE (tc_match_pats pats expected_ty thing_inside) + getLIE (tc_match_pats pats_w_tys thing_inside) ) `thenM` \ ((pats', ex_tvs, ex_ids, ex_lie, result), lie_req) -> @@ -239,25 +316,22 @@ 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 ex_tvs ex_ids ex_lie lie_req expected_ty `thenM` \ ex_binds -> - -- NB: we *must* pass "expected_ty" not "result_ty" to tcCheckExistentialPat + tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req + pats_w_tys body_ty `thenM` \ ex_binds -> + -- NB: we *must* pass "pats_w_tys" not just "body_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). + -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int). returnM (pats', result, mkMonoBind Recursive ex_binds) -tc_match_pats [] expected_ty thing_inside - = thing_inside expected_ty `thenM` \ answer -> +tc_match_pats [] thing_inside + = thing_inside `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) -> +tc_match_pats ((pat,pat_ty):pats) thing_inside + = tcPat tcMonoPatBndr pat pat_ty `thenM` \ (pat', ex_tvs, pat_bndrs, ex_lie) -> let xve = bagToList pat_bndrs ex_ids = [id | (_, id) <- xve] @@ -265,7 +339,7 @@ tc_match_pats (pat:pats) expected_ty thing_inside -- 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) -> + tc_match_pats pats thing_inside `thenM` \ (pats', exs_tvs, exs_ids, exs_lie, answer) -> returnM ( pat':pats', ex_tvs `unionBags` exs_tvs, ex_ids ++ exs_ids, @@ -280,9 +354,11 @@ tcCheckExistentialPat :: Bag TcTyVar -- Existentially quantified tyvars bound by -- (b) to generate helpful error messages -> [Inst] -- and context -> [Inst] -- Required context - -> TcType -- and type of the Match; vars in here must not escape + -> [(pat,Expected TcRhoType)] -- Types of the patterns + -> Expected TcRhoType -- Type of the body of the match + -- Tyvars in either of these must not escape -> TcM TcDictBinds -- LIE to float out and dict bindings -tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_ty +tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req pats_w_tys body_ty | isEmptyBag ex_tvs && all not_overloaded ex_ids -- Short cut for case when there are no existentials -- and no polymorphic overloaded variables @@ -294,7 +370,9 @@ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_ty returnM EmptyMonoBinds | otherwise - = addErrCtxtM (sigPatCtxt tv_list ex_ids match_ty) $ + = -- Read the by-now-filled-in expected types + mapM readExpectedType (body_ty : map snd pats_w_tys) `thenM` \ tys -> + addErrCtxtM (sigPatCtxt tv_list ex_ids tys) $ -- 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 @@ -303,7 +381,9 @@ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_ty -- 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_` + + -- Check for type variable escape + checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_` returnM (dict_binds `AndMonoBinds` inst_binds) where @@ -320,24 +400,31 @@ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_ty %************************************************************************ \begin{code} -tcDoStmts :: HsStmtContext Name -> [RenamedStmt] -> [Name] -> TcType - -> TcM (TcMonoBinds, [TcStmt], [Id]) +tcDoStmts :: HsStmtContext Name + -> [RenamedStmt] -> ReboundNames Name + -> TcRhoType -- To keep it simple, we don't have an "expected" type here + -> TcM ([TcStmt], ReboundNames TcId) 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 -}]) + = unifyPArrTy res_ty `thenM` \elt_ty -> + tcComprehension PArrComp mkPArrTy elt_ty stmts `thenM` \ stmts' -> + returnM (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 -}]) + = unifyListTy res_ty ` thenM` \ elt_ty -> + tcComprehension ListComp mkListTy elt_ty stmts `thenM` \ stmts' -> + returnM (stmts', [{- unused -}]) -tcDoStmts do_or_mdo_expr stmts method_names res_ty +tcDoStmts do_or_mdo 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' -> + let + ctxt = SC { sc_what = do_or_mdo, + sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mkAppTy m_ty rhs_elt_ty), + sc_body = \ body -> tcCheckRho body res_ty, + sc_ty = res_ty } + in + tcStmts ctxt 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, @@ -346,24 +433,17 @@ tcDoStmts do_or_mdo_expr stmts method_names res_ty -- 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) + mapM (tcSyntaxName DoOrigin m_ty) method_names `thenM` \ methods -> + + returnM (stmts', methods) + +tcComprehension do_or_lc mk_mty elt_ty stmts + = tcStmts ctxt stmts 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) + ctxt = SC { sc_what = do_or_lc, + sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mk_mty rhs_elt_ty), + sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no mk_mty! + sc_ty = mk_mty elt_ty } \end{code} @@ -396,121 +476,121 @@ 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. \begin{code} -tcStmts do_or_lc m_ty stmts +tcStmts ctxt stmts = ASSERT( notNull stmts ) - tcStmtsAndThen (:) do_or_lc m_ty stmts (returnM []) - + tcStmtsAndThen (:) ctxt stmts (returnM []) + +data TcStmtCtxt + = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is + sc_rhs :: RenamedHsExpr -> TcType -> TcM TcExpr, -- Type checker for RHS computations + sc_body :: RenamedHsExpr -> TcM TcExpr, -- Type checker for return computation + sc_ty :: TcType } -- Return type; used *only* to check + -- for escape in existential patterns 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) + -> TcStmtCtxt -> [RenamedStmt] -> TcM thing -> TcM thing -- Base case -tcStmtsAndThen combine do_or_lc m_ty [] do_next - = do_next +tcStmtsAndThen combine ctxt [] thing_inside + = thing_inside -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) +tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside + = tcStmtAndThen combine ctxt stmt $ + tcStmtsAndThen combine ctxt stmts $ + thing_inside -- LetStmt -tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside +tcStmtAndThen combine ctxt (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 + -- BindStmt +tcStmtAndThen combine ctxt stmt@(BindStmt pat exp src_loc) thing_inside = addSrcLoc src_loc $ - addErrCtxt (stmtCtxt do_or_lc stmt) $ + addErrCtxt (stmtCtxt ctxt stmt) $ newTyVarTy liftedTypeKind `thenM` \ pat_ty -> - tcMonoExpr exp (m pat_ty) `thenM` \ exp' -> - tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ -> + sc_rhs ctxt exp pat_ty `thenM` \ exp' -> + tcMatchPats [(pat, Check pat_ty)] (Check (sc_ty ctxt)) ( popErrCtxt thing_inside ) `thenM` \ ([pat'], thing, dict_binds) -> returnM (combine (BindStmt pat' exp' src_loc) (glue_binds combine dict_binds thing)) + -- ExprStmt +tcStmtAndThen combine ctxt stmt@(ExprStmt exp _ src_loc) thing_inside + = addSrcLoc src_loc ( + addErrCtxt (stmtCtxt ctxt stmt) $ + if isDoExpr (sc_what ctxt) + then -- do or mdo; the expression is a computation + newTyVarTy openTypeKind `thenM` \ any_ty -> + sc_rhs ctxt exp any_ty `thenM` \ exp' -> + returnM (ExprStmt exp' any_ty src_loc) + else -- List comprehensions, pattern guards; expression is a boolean + tcCheckRho exp boolTy `thenM` \ exp' -> + returnM (ExprStmt exp' boolTy src_loc) + ) `thenM` \ stmt' -> + + thing_inside `thenM` \ thing -> + returnM (combine stmt' thing) + + -- ParStmt -tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside +tcStmtAndThen combine ctxt (ParStmt bndr_stmts_s) thing_inside = loop bndr_stmts_s `thenM` \ (pairs', thing) -> - returnM (combine (ParStmtOut pairs') thing) + returnM (combine (ParStmt 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)) -> + loop [] = thing_inside `thenM` \ thing -> + returnM ([], thing) - returnM ((bndrs',stmts') : pairs', thing) + loop ((stmts, bndrs) : pairs) + = tcStmtsAndThen combine_par ctxt stmts $ + -- Notice we pass on ctxt; 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) - combine_par stmt (stmts, thing) = (stmt:stmts, thing) + combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing) -- RecStmt -tcStmtAndThen combine do_or_lc m_ty (RecStmt recNames stmts _) thing_inside +tcStmtAndThen combine ctxt (RecStmt stmts laterNames recNames _) thing_inside = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> let - mono_ids = zipWith mkLocalId recNames recTys + rec_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 + tcExtendLocalValEnv rec_ids $ + tcStmtsAndThen combine_rec ctxt stmts ( + mappM tc_ret (recNames `zip` recTys) `thenM` \ rec_rets -> + tcLookupLocalIds laterNames `thenM` \ later_ids -> + returnM ([], (later_ids, rec_rets)) + ) `thenM` \ (stmts', (later_ids, rec_rets)) -> + + tcExtendLocalValEnv later_ids $ + -- NB: The rec_ids for the recursive things + -- already scope over this part thing_inside `thenM` \ thing -> - returnM (combine (RecStmt mono_ids stmts' rets) thing) + returnM (combine (RecStmt stmts' later_ids rec_ids rec_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 -> + = 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 -> + tcSubExp (Check 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 -> - +tcStmtAndThen combine ctxt stmt@(ResultStmt exp locn) thing_inside + = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' -> + thing_inside `thenM` \ thing -> returnM (combine (ResultStmt exp' locn) thing) @@ -541,24 +621,32 @@ sameNoOfArgs matches = isSingleton (nub (map args_in_match matches)) varyingArgsErr name matches = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] -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' -> +matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) + 4 (pprMatch ctxt match) + +stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) 4 (ppr stmt) + where + pp_ctxt = case stmt of + ResultStmt _ _ -> pprStmtResultContext + other -> pprStmtContext + +sigPatCtxt bound_tvs bound_ids tys tidy_env + = -- tys is (body_ty : pat_tys) + mapM zonkTcType tys `thenM` \ tys' -> let - (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) - (env2, tidy_mty) = tidyOpenType env1 match_ty' + (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) + (_env2, tidy_body_ty : tidy_pat_tys) = tidyOpenTypes env1 tys' 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]) + ptext SLIT("The pattern(s) have type(s):") <+> vcat (map ppr tidy_pat_tys), + ptext SLIT("The body has type:") <+> ppr tidy_body_ty + ]) 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 + ppr_id id ty = ppr id <+> dcolon <+> ppr ty -- Don't zonk the types so we get the separate, un-unified versions \end{code}