X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=6f7c6956d8d5834c3b8c1b750a511827ec5530bb;hb=ff845ab59d1d465d874d3908fd0cdd61b8594da2;hp=05797f5426e333c8a3e9371c9f6628bc125834e4;hpb=f714e6b642fd614a9971717045ae47c3d871275e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 05797f5..6f7c695 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -13,40 +13,38 @@ module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcCheckRho, tcMonoExpr ) +import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho, tcMonoExpr ) -import HsSyn ( HsExpr(..), LHsExpr, HsBindGroup(..), +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), Match(..), LMatch, GRHSs(..), GRHS(..), Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), ReboundNames, LPat, pprMatch, isDoExpr, pprMatchContext, pprStmtContext, pprStmtResultContext, - collectSigTysFromPats, glueBindsOnGRHSs + collectPatsBinders, glueBindsOnGRHSs ) -import TcHsSyn ( ExprCoFn, TcDictBinds, isIdCoercion, (<$>), (<.>) ) +import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) ) import TcRnMonad -import TcHsType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) +import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) ) import Inst ( tcSyntaxName, tcInstCall ) -import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 ) -import TcPat ( tcPat, tcMonoPatBndr ) -import TcMType ( newTyVarTy, newTyVarTys, zonkTcType ) -import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, - tyVarsOfTypes, tidyOpenTypes, isSigmaTy, typeKind, - mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind, - mkArrowKind, mkAppTy ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv ) +import TcPat ( PatCtxt(..), tcPats ) +import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType, isRigidType ) +import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys, + tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkTyConApp, + liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy ) import TcBinds ( tcBindsAndThen ) -import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType, - unifyTauTy, subFunTys, unifyPArrTy, unifyListTy, unifyFunTy, - checkSigTyVarsWrt, tcSubExp, tcGen ) -import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcUnify ( Expected(..), zapExpectedType, readExpectedType, + unifyTauTy, subFunTys, unifyListTy, unifyTyConApp, + checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen, + unifyAppTy ) import Name ( Name ) -import TysWiredIn ( boolTy, mkListTy, mkPArrTy ) +import TysWiredIn ( boolTy, parrTyCon, listTyCon ) import Id ( idType, mkLocalId ) import CoreFVs ( idFreeTyVars ) -import BasicTypes ( RecFlag(..) ) import VarSet -import Bag import Util ( isSingleton, notNull ) import Outputable import SrcLoc ( Located(..), noLoc ) @@ -67,26 +65,30 @@ same number of arguments before using @tcMatches@ to do the work. \begin{code} tcMatchesFun :: Name - -> [LMatch Name] - -> Expected TcRhoType -- Expected type - -> TcM [LMatch TcId] - -tcMatchesFun fun_name matches@(first_match:_) expected_ty - = -- Check that they all have the same no of arguments - -- Location is in the monad, set the caller so that - -- any inter-equation error messages get some vaguely - -- sensible location. Note: we have to do this odd - -- ann-grabbing, because we don't always have annotations in - -- hand when we call tcMatchesFun... - checkTc (sameNoOfArgs matches) - (varyingArgsErr fun_name matches) `thenM_` + -> MatchGroup Name + -> Expected TcRhoType -- Expected type of function + -> TcM (MatchGroup TcId) -- Returns type of body + +tcMatchesFun fun_name matches exp_ty + = do { -- Check that they all have the same no of arguments + -- Location is in the monad, set the caller so that + -- any inter-equation error messages get some vaguely + -- sensible location. Note: we have to do this odd + -- ann-grabbing, because we don't always have annotations in + -- hand when we call tcMatchesFun... + checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches) -- 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 subFunTys does that on the fly - tcMatches match_ctxt matches expected_ty + -- This is one of two places places we call subFunTys + -- The point is that if expected_y is a "hole", we want + -- to make pat_tys and rhs_ty as "holes" too. + ; exp_ty' <- zapExpectedBranches matches exp_ty + ; subFunTys matches exp_ty' $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty matches + } where match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcMonoExpr } @@ -97,29 +99,19 @@ parser guarantees that each equation has exactly one argument. \begin{code} tcMatchesCase :: TcMatchCtxt -- Case context - -> [LMatch Name] -- The case alternatives + -> TcRhoType -- Type of scrutinee + -> MatchGroup Name -- The case alternatives -> Expected TcRhoType -- Type of whole case expressions - -> TcM (TcRhoType, -- Inferred type of the scrutinee - [LMatch TcId]) -- Translated alternatives - -tcMatchesCase ctxt matches (Check expr_ty) - = newTyVarTy openTypeKind `thenM` \ scrut_ty -> - -- openTypeKind because the scrutinee can be an unboxed type - 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 :: LMatch Name -> Expected TcRhoType -> TcM (LMatch TcId) -tcMatchLambda match res_ty = tcMatch match_ctxt res_ty match + -> TcM (MatchGroup TcId) -- Translated alternatives + +tcMatchesCase ctxt scrut_ty matches exp_ty + = do { exp_ty' <- zapExpectedBranches matches exp_ty + ; tcMatches ctxt [Check scrut_ty] exp_ty' matches } + +tcMatchLambda :: MatchGroup Name -> Expected TcRhoType -> TcM (MatchGroup TcId) +tcMatchLambda match exp_ty -- One branch so no unifyBranches needed + = subFunTys match exp_ty $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty match where match_ctxt = MC { mc_what = LambdaExpr, mc_body = tcMonoExpr } @@ -137,26 +129,6 @@ tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty mc_body = tcMonoExpr } \end{code} -\begin{code} -data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module - = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is - mc_body :: LHsExpr Name -- Type checker for a body of an alternative - -> Expected TcRhoType - -> TcM (LHsExpr TcId) } - -tcMatches :: TcMatchCtxt - -> [LMatch Name] - -> Expected TcRhoType - -> TcM [LMatch TcId] - -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 - -- order in which we check them would affect the result. - zapExpectedBranches matches exp_ty `thenM` \ exp_ty' -> - mappM (tcMatch ctxt exp_ty') matches -\end{code} - %************************************************************************ %* * @@ -165,52 +137,68 @@ tcMatches ctxt matches exp_ty %************************************************************************ \begin{code} +tcMatches :: TcMatchCtxt + -> [Expected TcRhoType] -- Expected pattern types + -> Expected TcRhoType -- Expected result-type of the Match. + -> MatchGroup Name + -> TcM (MatchGroup TcId) + +data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module + = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is + mc_body :: LHsExpr Name -- Type checker for a body of an alternative + -> Expected TcRhoType + -> TcM (LHsExpr TcId) } + +tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) + = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches + ; pat_tys' <- mapM readExpectedType pat_tys + ; rhs_ty' <- readExpectedType rhs_ty + ; return (MatchGroup matches' (mkFunTys pat_tys' rhs_ty')) } + +------------- tcMatch :: TcMatchCtxt - -> 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. + -> [Expected TcRhoType] -- Expected pattern types + -> Expected TcRhoType -- Expected result-type of the Match. -> LMatch Name -> TcM (LMatch TcId) -tcMatch ctxt exp_ty match = wrapLocM (tc_match ctxt exp_ty) match +tcMatch ctxt pat_tys rhs_ty match + = wrapLocM (tc_match ctxt pat_tys rhs_ty) match -tc_match ctxt expected_ty match@(Match pats maybe_rhs_sig 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')) +tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss) + = addErrCtxt (matchCtxt (mc_what ctxt) match) $ + do { (pats', grhss') <- tcMatchPats pats pat_tys rhs_ty $ + tc_grhss ctxt maybe_rhs_sig grhss rhs_ty + ; returnM (Match pats' Nothing grhss') } - where - tc_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 -> - 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 (fmap lift_grhs) grhss) binds rhs_ty -- Change the type, since the coercion does + +------------- +tc_grhss ctxt Nothing grhss rhs_ty + = tcGRHSs ctxt grhss rhs_ty -- No result signature + +tc_grhss ctxt (Just res_sig) grhss rhs_ty + = do { (sig_tvs, sig_ty) <- tcHsPatSigType ResSigCtxt res_sig + ; traceTc (text "tc_grhss" <+> ppr sig_tvs) + ; (co_fn, grhss') <- tcExtendTyVarEnv sig_tvs $ + tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty + + -- Push the coercion down to the right hand sides, + -- because there is no convenient place to hang it otherwise. + ; if isIdCoercion co_fn then + return grhss' + else + return (lift_grhss co_fn grhss') } + +------------- +lift_grhss co_fn (GRHSs grhss binds) + = GRHSs (map (fmap lift_grhs) grhss) binds where lift_grhs (GRHS stmts) = GRHS (map lift_stmt stmts) lift_stmt (L loc (ResultStmt e)) = L loc (ResultStmt (fmap (co_fn <$>) e)) lift_stmt stmt = stmt +------------- tcGRHSs :: TcMatchCtxt -> GRHSs Name -> Expected TcRhoType -> TcM (GRHSs TcId) @@ -221,13 +209,12 @@ tcGRHSs :: TcMatchCtxt -> GRHSs Name -- 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 [L loc1 (GRHS [L loc2 (ResultStmt rhs)])] binds _) exp_ty +tcGRHSs ctxt (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs)])] binds) exp_ty = tcBindsAndThen glueBindsOnGRHSs binds $ mc_body ctxt rhs exp_ty `thenM` \ rhs' -> - readExpectedType exp_ty `thenM` \ exp_ty' -> - returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] [] exp_ty') + returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] []) -tcGRHSs ctxt (GRHSs grhss binds _) exp_ty +tcGRHSs ctxt (GRHSs grhss binds) exp_ty = tcBindsAndThen glueBindsOnGRHSs binds $ zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' -> -- Even if there is only one guard, we zap the RHS type to @@ -235,7 +222,7 @@ tcGRHSs ctxt (GRHSs grhss binds _) exp_ty -- 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_rhs = tcInferRho, sc_body = sc_body, sc_ty = exp_ty' } sc_body body = mc_body ctxt body (Check exp_ty') @@ -245,7 +232,7 @@ tcGRHSs ctxt (GRHSs grhss binds _) exp_ty returnM (GRHS guarded') in mappM (wrapLocM tc_grhs) grhss `thenM` \ grhss' -> - returnM (GRHSs grhss' [] exp_ty') + returnM (GRHSs grhss' []) \end{code} @@ -267,7 +254,7 @@ tcThingWithSig sig_ty thing_inside res_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) -> + tcInstCall InstSigOrigin 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. @@ -281,109 +268,48 @@ tcThingWithSig sig_ty thing_inside res_ty %************************************************************************ \begin{code} -tcMatchPats - :: [(LPat Name, Expected TcRhoType)] - -> Expected TcRhoType - -> TcM a - -> TcM ([LPat TcId], a, HsBindGroup TcId) +tcMatchPats :: [LPat Name] + -> [Expected TcSigmaType] -- Pattern types + -> Expected TcRhoType -- Result type; + -- used only to check existential escape + -> TcM a + -> TcM ([LPat TcId], a) -- 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_w_tys body_ty thing_inside - = -- STEP 1: Bring pattern-signature type variables into scope - 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_w_tys 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 - pats_w_tys body_ty `thenM` \ ex_binds -> - -- NB: we *must* pass "pats_w_tys" not just "body_ty" to tcCheckExistentialPat +tcMatchPats pats tys body_ty thing_inside + = do { do_refinement <- can_refine body_ty + ; (pats', ex_tvs, res) <- tcPats (LamPat do_refinement) pats tys thing_inside + ; tcCheckExistentialPat pats' ex_tvs tys body_ty + ; returnM (pats', res) } + where + -- Do GADT refinement if we are doing checking (not inference) + -- and the body_ty is completely rigid + -- ToDo: explain why + can_refine (Infer _) = return False + can_refine (Check ty) = isRigidType ty + +tcCheckExistentialPat :: [LPat TcId] -- Patterns (just for error message) + -> [TcTyVar] -- Existentially quantified tyvars bound by pattern + -> [Expected TcSigmaType] -- Types of the patterns + -> Expected TcRhoType -- Type of the body of the match + -- Tyvars in either of these must not escape + -> TcM () + -- NB: we *must* pass "pats_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 (C -> a -> Int). - returnM (pats', result, HsBindGroup ex_binds [] Recursive) - -tc_match_pats [] thing_inside - = thing_inside `thenM` \ answer -> - returnM ([], emptyBag, [], [], answer) +tcCheckExistentialPat pats [] pat_tys body_ty + = return () -- Short cut for case when there are no existentials -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] - -- ex_ids is all the pattern-bound Ids, a superset - -- of the existential Ids used in checkExistentialPat - in - tcExtendLocalValEnv2 xve $ - traceTc (text "tc_match_pats" <+> (ppr xve $$ ppr (map (idType . snd) xve) $$ - ppr (map (typeKind . idType . snd) xve))) `thenM_` - 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, - 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 - -> [(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 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 - -- 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 emptyBag - - | otherwise - = -- 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 - -- with polymorphic arguments), we must do a bindInstsOfLocalFns here - getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) -> - - -- Deal with overloaded functions bound by the pattern - tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds -> - - -- Check for type variable escape - checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_` - - returnM (dict_binds `unionBags` inst_binds) - where - doc = text ("existential context of a data constructor") - tv_list = bagToList ex_tvs - not_overloaded id = not (isOverloadedTy (idType id)) +tcCheckExistentialPat pats ex_tvs pat_tys body_ty + = do { tys <- mapM readExpectedType (body_ty : pat_tys) + ; addErrCtxtM (sigPatCtxt (collectPatsBinders pats) ex_tvs tys) $ + checkSigTyVarsWrt (tyVarsOfTypes tys) ex_tvs } \end{code} @@ -399,22 +325,24 @@ tcDoStmts :: HsStmtContext Name -> TcRhoType -- To keep it simple, we don't have an "expected" type here -> TcM ([LStmt TcId], ReboundNames TcId) tcDoStmts PArrComp stmts method_names res_ty - = unifyPArrTy res_ty `thenM` \elt_ty -> - tcComprehension PArrComp mkPArrTy elt_ty stmts `thenM` \ stmts' -> - returnM (stmts', [{- unused -}]) + = do { [elt_ty] <- unifyTyConApp parrTyCon res_ty + ; stmts' <- tcComprehension PArrComp parrTyCon elt_ty stmts + ; return (stmts', [{- unused -}]) } tcDoStmts ListComp stmts method_names res_ty = unifyListTy res_ty ` thenM` \ elt_ty -> - tcComprehension ListComp mkListTy elt_ty stmts `thenM` \ stmts' -> + tcComprehension ListComp listTyCon elt_ty stmts `thenM` \ stmts' -> returnM (stmts', [{- unused -}]) tcDoStmts do_or_mdo stmts method_names res_ty - = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> - newTyVarTy liftedTypeKind `thenM` \ elt_ty -> + = newTyFlexiVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> + newTyFlexiVarTy liftedTypeKind `thenM` \ elt_ty -> unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_` let ctxt = SC { sc_what = do_or_mdo, - sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mkAppTy m_ty rhs_elt_ty), + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; rhs_elt_ty <- unifyAppTy m_ty rhs_ty + ; return (rhs', rhs_elt_ty) }, sc_body = \ body -> tcCheckRho body res_ty, sc_ty = res_ty } in @@ -431,13 +359,15 @@ tcDoStmts do_or_mdo stmts method_names res_ty returnM (stmts', methods) -tcComprehension do_or_lc mk_mty elt_ty stmts +tcComprehension do_or_lc m_tycon elt_ty stmts = tcStmts ctxt stmts where 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 } + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; [rhs_elt_ty] <- unifyTyConApp m_tycon rhs_ty + ; return (rhs', rhs_elt_ty) }, + sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no m_tycon here! + sc_ty = mkTyConApp m_tycon [elt_ty] } \end{code} @@ -476,10 +406,17 @@ tcStmts ctxt stmts data TcStmtCtxt = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is - sc_rhs :: LHsExpr Name -> TcType -> TcM (LHsExpr TcId), -- Type checker for RHS computations + sc_rhs :: LHsExpr Name -> TcM (LHsExpr TcId, TcType), -- Type inference for RHS computations sc_body :: LHsExpr Name -> TcM (LHsExpr TcId), -- Type checker for return computation sc_ty :: TcType } -- Return type; used *only* to check -- for escape in existential patterns + -- We use type *inference* for the RHS computations, becuase of GADTs. + -- do { pat <- rhs; } + -- is rather like + -- case rhs of { pat -> } + -- We do inference on rhs, so that information about its type can be refined + -- when type-checking the pattern. + tcStmtsAndThen :: (LStmt TcId -> thing -> thing) -- Combiner -> TcStmtCtxt @@ -505,25 +442,21 @@ tcStmtAndThen combine ctxt (L _ (LetStmt binds)) thing_inside -- BindStmt tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside - = addSrcSpan src_loc $ + = setSrcSpan src_loc $ addErrCtxt (stmtCtxt ctxt stmt) $ - newTyVarTy liftedTypeKind `thenM` \ pat_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 (L src_loc (BindStmt pat' exp')) - (glue_binds combine dict_binds thing)) + do { (exp', pat_ty) <- sc_rhs ctxt exp + ; ([pat'], thing) <- tcMatchPats [pat] [Check pat_ty] (Check (sc_ty ctxt)) $ + popErrCtxt thing_inside + ; return (combine (L src_loc (BindStmt pat' exp')) thing) } -- ExprStmt tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside - = addSrcSpan src_loc ( + = setSrcSpan src_loc ( addErrCtxt (stmtCtxt ctxt stmt) $ if isDoExpr (sc_what ctxt) then -- do or mdo; the expression is a computation - newTyVarTy liftedTypeKind `thenM` \ any_ty -> - sc_rhs ctxt exp any_ty `thenM` \ exp' -> - returnM (L src_loc (ExprStmt exp' any_ty)) + sc_rhs ctxt exp `thenM` \ (exp', exp_ty) -> + returnM (L src_loc (ExprStmt exp' exp_ty)) else -- List comprehensions, pattern guards; expression is a boolean tcCheckRho exp boolTy `thenM` \ exp' -> returnM (L src_loc (ExprStmt exp' boolTy)) @@ -553,18 +486,19 @@ tcStmtAndThen combine ctxt (L src_loc (ParStmt bndr_stmts_s)) thing_inside -- RecStmt tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thing_inside - = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> +-- gaw 2004 + = newTyFlexiVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> let rec_ids = zipWith mkLocalId recNames recTys in - tcExtendLocalValEnv rec_ids $ + tcExtendIdEnv rec_ids $ tcStmtsAndThen combine_rec ctxt stmts ( - mappM tc_ret (recNames `zip` recTys) `thenM` \ rec_rets -> + zipWithM tc_ret recNames recTys `thenM` \ rec_rets -> tcLookupLocalIds laterNames `thenM` \ later_ids -> returnM ([], (later_ids, rec_rets)) ) `thenM` \ (stmts', (later_ids, rec_rets)) -> - tcExtendLocalValEnv later_ids $ + tcExtendIdEnv later_ids $ -- NB: The rec_ids for the recursive things -- already scope over this part thing_inside `thenM` \ thing -> @@ -574,7 +508,7 @@ tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thi 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) + 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 @@ -604,8 +538,9 @@ glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing number of args are used in each equation. \begin{code} -sameNoOfArgs :: [LMatch Name] -> Bool -sameNoOfArgs matches = isSingleton (nub (map args_in_match matches)) +sameNoOfArgs :: MatchGroup Name -> Bool +sameNoOfArgs (MatchGroup matches _) + = isSingleton (nub (map args_in_match matches)) where args_in_match :: LMatch Name -> Int args_in_match (L _ (Match pats _ _)) = length pats @@ -624,7 +559,7 @@ stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) ResultStmt _ -> pprStmtResultContext other -> pprStmtContext -sigPatCtxt bound_tvs bound_ids tys tidy_env +sigPatCtxt bound_ids bound_tvs tys tidy_env = -- tys is (body_ty : pat_tys) mapM zonkTcType tys `thenM` \ tys' -> let