X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcMatches.lhs;h=a73b1d3a91de9f8fd41dfff2ecbd62090919e790;hp=37fbd190f811bc8b6a43d20eb20c89bb4876d875;hb=b10d7d079ec9c3fc22d4700fe484dd297bddb805;hpb=27de38efce6d73d2a0209f803cfa98c82773e773 diff --git a/compiler/typecheck/TcMatches.lhs b/compiler/typecheck/TcMatches.lhs index 37fbd19..a73b1d3 100644 --- a/compiler/typecheck/TcMatches.lhs +++ b/compiler/typecheck/TcMatches.lhs @@ -12,7 +12,8 @@ module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, tcDoStmt, tcMDoStmt, tcGuardStmt ) where -import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr ) +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRhoNC, tcCheckId, + tcMonoExpr, tcMonoExprNC, tcPolyExpr ) import HsSyn import TcRnMonad @@ -23,14 +24,15 @@ import TcMType import TcType import TcBinds import TcUnify -import TcSimplify import Name import TysWiredIn import PrelNames import Id import TyCon import TysPrim +import Coercion ( mkSymCoI ) import Outputable +import BasicTypes ( Arity ) import Util import SrcLoc import FastString @@ -51,12 +53,17 @@ import Control.Monad is used in error messages. It checks that all the equations have the same number of arguments before using @tcMatches@ to do the work. +Note [Polymorphic expected type for tcMatchesFun] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +tcMatchesFun may be given a *sigma* (polymorphic) type +so it must be prepared to use tcGen to skolemise it. +See Note [sig_tau may be polymorphic] in TcPat. + \begin{code} tcMatchesFun :: Name -> Bool -> MatchGroup Name - -> BoxyRhoType -- Expected type of function - -> TcM (HsWrapper, MatchGroup TcId) -- Returns type of body - + -> TcSigmaType -- Expected type of function + -> TcM (HsWrapper, MatchGroup TcId) -- Returns type of body tcMatchesFun fun_name inf matches exp_ty = do { -- Check that they all have the same no of arguments -- Location is in the monad, set the caller so that @@ -64,22 +71,19 @@ tcMatchesFun fun_name inf matches exp_ty -- sensible location. Note: we have to do this odd -- ann-grabbing, because we don't always have annotations in -- hand when we call tcMatchesFun... - checkArgs 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 - - -- 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. - ; subFunTys doc n_pats exp_ty $ \ pat_tys rhs_ty -> - tcMatches match_ctxt pat_tys rhs_ty matches - } + traceTc "tcMatchesFun" (ppr fun_name $$ ppr exp_ty) + ; checkArgs fun_name matches + + ; (wrap_gen, (wrap_fun, group)) + <- tcGen (SigSkol (FunSigCtxt fun_name)) exp_ty $ \ _ exp_rho -> + -- Note [Polymorphic expected type for tcMatchesFun] + matchFunTys herald arity exp_rho $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty matches + ; return (wrap_gen <.> wrap_fun, group) } where - doc = ptext (sLit "The equation(s) for") <+> quotes (ppr fun_name) - <+> ptext (sLit "have") <+> speakNOf n_pats (ptext (sLit "argument")) - n_pats = matchGroupArity matches + arity = matchGroupArity matches + herald = ptext (sLit "The equation(s) for") + <+> quotes (ppr fun_name) <+> ptext (sLit "have") match_ctxt = MC { mc_what = FunRhs fun_name inf, mc_body = tcBody } \end{code} @@ -90,27 +94,25 @@ parser guarantees that each equation has exactly one argument. tcMatchesCase :: TcMatchCtxt -- Case context -> TcRhoType -- Type of scrutinee -> MatchGroup Name -- The case alternatives - -> BoxyRhoType -- Type of whole case expressions + -> TcRhoType -- Type of whole case expressions -> TcM (MatchGroup TcId) -- Translated alternatives tcMatchesCase ctxt scrut_ty matches res_ty - | isEmptyMatchGroup matches - = -- Allow empty case expressions - do { -- Make sure we follow the invariant that res_ty is filled in - res_ty' <- refineBoxToTau res_ty - ; return (MatchGroup [] (mkFunTys [scrut_ty] res_ty')) } + | isEmptyMatchGroup matches -- Allow empty case expressions + = return (MatchGroup [] (mkFunTys [scrut_ty] res_ty)) | otherwise = tcMatches ctxt [scrut_ty] res_ty matches -tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (HsWrapper, MatchGroup TcId) +tcMatchLambda :: MatchGroup Name -> TcRhoType -> TcM (HsWrapper, MatchGroup TcId) tcMatchLambda match res_ty - = subFunTys doc n_pats res_ty $ \ pat_tys rhs_ty -> + = matchFunTys doc n_pats res_ty $ \ pat_tys rhs_ty -> tcMatches match_ctxt pat_tys rhs_ty match where n_pats = matchGroupArity match doc = sep [ ptext (sLit "The lambda expression") - <+> quotes (pprSetDepth 1 $ pprMatches (LambdaExpr :: HsMatchContext Name) match), + <+> quotes (pprSetDepth (PartWay 1) $ + pprMatches (LambdaExpr :: HsMatchContext Name) match), -- The pprSetDepth makes the abstraction print briefly ptext (sLit "has") <+> speakNOf n_pats (ptext (sLit "argument"))] match_ctxt = MC { mc_what = LambdaExpr, @@ -120,7 +122,7 @@ tcMatchLambda match res_ty @tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId) +tcGRHSsPat :: GRHSs Name -> TcRhoType -> TcM (GRHSs TcId) -- Used for pattern bindings tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty where @@ -129,6 +131,23 @@ tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty \end{code} +\begin{code} +matchFunTys + :: SDoc -- See Note [Herald for matchExpecteFunTys] in TcUnify + -> Arity + -> TcRhoType + -> ([TcSigmaType] -> TcRhoType -> TcM a) + -> TcM (HsWrapper, a) + +-- Written in CPS style for historical reasons; +-- could probably be un-CPSd, like matchExpectedTyConApp + +matchFunTys herald arity res_ty thing_inside + = do { (coi, pat_tys, res_ty) <- matchExpectedFunTys herald arity res_ty + ; res <- thing_inside pat_tys res_ty + ; return (coiToHsWrapper (mkSymCoI coi), res) } +\end{code} + %************************************************************************ %* * \subsection{tcMatch} @@ -137,8 +156,8 @@ tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty \begin{code} tcMatches :: TcMatchCtxt - -> [BoxySigmaType] -- Expected pattern types - -> BoxyRhoType -- Expected result-type of the Match. + -> [TcSigmaType] -- Expected pattern types + -> TcRhoType -- Expected result-type of the Match. -> MatchGroup Name -> TcM (MatchGroup TcId) @@ -146,7 +165,7 @@ 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 - -> BoxyRhoType + -> TcRhoType -> TcM (LHsExpr TcId) } tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) @@ -156,8 +175,8 @@ tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) ------------- tcMatch :: TcMatchCtxt - -> [BoxySigmaType] -- Expected pattern types - -> BoxyRhoType -- Expected result-type of the Match. + -> [TcSigmaType] -- Expected pattern types + -> TcRhoType -- Expected result-type of the Match. -> LMatch Name -> TcM (LMatch TcId) @@ -166,8 +185,8 @@ tcMatch ctxt pat_tys rhs_ty match where tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss) = add_match_ctxt match $ - do { (pats', grhss') <- tcLamPats pats pat_tys rhs_ty $ - tc_grhss ctxt maybe_rhs_sig grhss + do { (pats', grhss') <- tcPats (mc_what ctxt) pats pat_tys $ + tc_grhss ctxt maybe_rhs_sig grhss rhs_ty ; return (Match pats' Nothing grhss') } tc_grhss ctxt Nothing grhss rhs_ty @@ -185,7 +204,7 @@ tcMatch ctxt pat_tys rhs_ty match m_ctxt -> addErrCtxt (pprMatchInCtxt m_ctxt match) thing_inside ------------- -tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType +tcGRHSs :: TcMatchCtxt -> GRHSs Name -> TcRhoType -> TcM (GRHSs TcId) -- Notice that we pass in the full res_ty, so that we get @@ -201,7 +220,7 @@ tcGRHSs ctxt (GRHSs grhss binds) res_ty ; return (GRHSs grhss' binds') } ------------- -tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId) +tcGRHS :: TcMatchCtxt -> TcRhoType -> GRHS Name -> TcM (GRHS TcId) tcGRHS ctxt res_ty (GRHS guards rhs) = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $ @@ -222,10 +241,10 @@ tcGRHS ctxt res_ty (GRHS guards rhs) tcDoStmts :: HsStmtContext Name -> [LStmt Name] -> LHsExpr Name - -> BoxyRhoType + -> TcRhoType -> TcM (HsExpr TcId) -- Returns a HsDo tcDoStmts ListComp stmts body res_ty - = do { (elt_ty, coi) <- boxySplitListTy res_ty + = do { (coi, elt_ty) <- matchExpectedListTy res_ty ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $ tcBody body @@ -233,7 +252,7 @@ tcDoStmts ListComp stmts body res_ty (HsDo ListComp stmts' body' (mkListTy elt_ty)) } tcDoStmts PArrComp stmts body res_ty - = do { (elt_ty, coi) <- boxySplitPArrTy res_ty + = do { (coi, elt_ty) <- matchExpectedPArrTy res_ty ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $ tcBody body @@ -241,33 +260,30 @@ tcDoStmts PArrComp stmts body res_ty (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) } tcDoStmts DoExpr stmts body res_ty - = do { (stmts', body') <- tcStmts DoExpr tcDoStmt stmts - res_ty $ + = do { (stmts', body') <- tcStmts DoExpr tcDoStmt stmts res_ty $ tcBody body ; return (HsDo DoExpr stmts' body' res_ty) } tcDoStmts ctxt@(MDoExpr _) stmts body res_ty - = do { ((m_ty, elt_ty), coi) <- boxySplitAppTy res_ty - ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty - tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty -> + = do { (coi, (m_ty, elt_ty)) <- matchExpectedAppTy res_ty + ; let res_ty' = mkAppTy m_ty elt_ty -- The matchExpected consumes res_ty + tc_rhs rhs = tcInfer $ \ pat_ty -> tcMonoExpr rhs (mkAppTy m_ty pat_ty) - ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts - res_ty' $ + ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $ tcBody body ; let names = [mfixName, bindMName, thenMName, returnMName, failMName] - ; insts <- mapM (newMethodFromName DoOrigin m_ty) names - ; return $ - mkHsWrapCoI coi - (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') } + ; insts <- mapM (\name -> newMethodFromName DoOrigin name m_ty) names + ; return $ mkHsWrapCoI coi $ + HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty' } tcDoStmts ctxt _ _ _ = pprPanic "tcDoStmts" (pprStmtContext ctxt) -tcBody :: LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId) +tcBody :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId) tcBody body res_ty - = do { traceTc (text "tcBody" <+> ppr res_ty) - ; body' <- tcPolyExpr body res_ty + = do { traceTc "tcBody" (ppr res_ty) + ; body' <- tcMonoExpr body res_ty ; return body' } \end{code} @@ -283,15 +299,15 @@ tcBody body res_ty type TcStmtChecker = forall thing. HsStmtContext Name -> Stmt Name - -> BoxyRhoType -- Result type for comprehension - -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt + -> TcRhoType -- Result type for comprehension + -> (TcRhoType -> TcM thing) -- Checker for what follows the stmt -> TcM (Stmt TcId, thing) tcStmts :: HsStmtContext Name -> TcStmtChecker -- NB: higher-rank type -> [LStmt Name] - -> BoxyRhoType - -> (BoxyRhoType -> TcM thing) + -> TcRhoType + -> (TcRhoType -> TcM thing) -> TcM ([LStmt TcId], thing) -- Note the higher-rank type. stmt_chk is applied at different @@ -326,9 +342,10 @@ tcGuardStmt _ (ExprStmt guard _ _) res_ty thing_inside ; thing <- thing_inside res_ty ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) } -tcGuardStmt _ (BindStmt pat rhs _ _) res_ty thing_inside - = do { (rhs', rhs_ty) <- tcInferRho rhs - ; (pat', thing) <- tcLamPat pat rhs_ty res_ty thing_inside +tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { (rhs', rhs_ty) <- tcInferRhoNC rhs -- Stmt has a context already + ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat rhs_ty $ + thing_inside res_ty ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } tcGuardStmt _ stmt _ _ @@ -342,10 +359,11 @@ tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray) -> TcStmtChecker -- A generator, pat <- rhs -tcLcStmt m_tc _ (BindStmt pat rhs _ _) res_ty thing_inside - = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty -> - tcMonoExpr rhs (mkTyConApp m_tc [ty]) - ; (pat', thing) <- tcLamPat pat pat_ty res_ty thing_inside +tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { pat_ty <- newFlexiTyVarTy liftedTypeKind + ; rhs' <- tcMonoExpr rhs (mkTyConApp m_tc [pat_ty]) + ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $ + thing_inside res_ty ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } -- A boolean guard @@ -359,7 +377,7 @@ tcLcStmt _ _ (ExprStmt rhs _ _) res_ty thing_inside -- | ... ; let h v = ... ] -- -- 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). +-- (g x, h x) up through both lots of bindings (so we get the bindLocalMethods). -- Similarly if we had an existential pattern match: -- -- data T = forall a. Show a => C a @@ -391,7 +409,7 @@ tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s) elt_ty thing_inside ; return (ids, pairs', thing) } ; return ( (stmts', ids) : pairs', thing ) } -tcLcStmt m_tc ctxt (TransformStmt (stmts, binders) usingExpr maybeByExpr) elt_ty thing_inside = do +tcLcStmt m_tc ctxt (TransformStmt stmts binders usingExpr maybeByExpr) elt_ty thing_inside = do (stmts', (binders', usingExpr', maybeByExpr', thing)) <- tcStmts (TransformStmtCtxt ctxt) (tcLcStmt m_tc) stmts elt_ty $ \elt_ty' -> do let alphaListTy = mkTyConApp m_tc [alphaTy] @@ -400,12 +418,17 @@ tcLcStmt m_tc ctxt (TransformStmt (stmts, binders) usingExpr maybeByExpr) elt_ty case maybeByExpr of Nothing -> do -- We must validate that usingExpr :: forall a. [a] -> [a] - usingExpr' <- tcPolyExpr usingExpr (mkForAllTy alphaTyVar (alphaListTy `mkFunTy` alphaListTy)) + let using_ty = mkForAllTy alphaTyVar (alphaListTy `mkFunTy` alphaListTy) + usingExpr' <- tcPolyExpr usingExpr using_ty return (usingExpr', Nothing) Just byExpr -> do - -- We must infer a type such that e :: t and then check that usingExpr :: forall a. (a -> t) -> [a] -> [a] - (byExpr', tTy) <- tcInferRho byExpr - usingExpr' <- tcPolyExpr usingExpr (mkForAllTy alphaTyVar ((alphaTy `mkFunTy` tTy) `mkFunTy` (alphaListTy `mkFunTy` alphaListTy))) + -- We must infer a type such that e :: t and then check that + -- usingExpr :: forall a. (a -> t) -> [a] -> [a] + (byExpr', tTy) <- tcInferRhoNC byExpr + let using_ty = mkForAllTy alphaTyVar $ + (alphaTy `mkFunTy` tTy) + `mkFunTy` alphaListTy `mkFunTy` alphaListTy + usingExpr' <- tcPolyExpr usingExpr using_ty return (usingExpr', Just byExpr') binders' <- tcLookupLocalIds binders @@ -413,46 +436,52 @@ tcLcStmt m_tc ctxt (TransformStmt (stmts, binders) usingExpr maybeByExpr) elt_ty return (binders', usingExpr', maybeByExpr', thing) - return (TransformStmt (stmts', binders') usingExpr' maybeByExpr', thing) + return (TransformStmt stmts' binders' usingExpr' maybeByExpr', thing) -tcLcStmt m_tc ctxt (GroupStmt (stmts, bindersMap) groupByClause) elt_ty thing_inside = do - (stmts', (bindersMap', groupByClause', thing)) <- +tcLcStmt m_tc ctxt (GroupStmt stmts bindersMap by using) elt_ty thing_inside + = do { let (bndr_names, list_bndr_names) = unzip bindersMap + + ; (stmts', (bndr_ids, by', using_ty, elt_ty')) <- tcStmts (TransformStmtCtxt ctxt) (tcLcStmt m_tc) stmts elt_ty $ \elt_ty' -> do - let alphaListTy = mkTyConApp m_tc [alphaTy] - alphaListListTy = mkTyConApp m_tc [alphaListTy] - - groupByClause' <- - case groupByClause of - GroupByNothing usingExpr -> - -- We must validate that usingExpr :: forall a. [a] -> [[a]] - tcPolyExpr usingExpr (mkForAllTy alphaTyVar (alphaListTy `mkFunTy` alphaListListTy)) >>= (return . GroupByNothing) - GroupBySomething eitherUsingExpr byExpr -> do - -- We must infer a type such that byExpr :: t - (byExpr', tTy) <- tcInferRho byExpr - - -- If it exists, we then check that usingExpr :: forall a. (a -> t) -> [a] -> [[a]] - let expectedUsingType = mkForAllTy alphaTyVar ((alphaTy `mkFunTy` tTy) `mkFunTy` (alphaListTy `mkFunTy` alphaListListTy)) - eitherUsingExpr' <- - case eitherUsingExpr of - Left usingExpr -> (tcPolyExpr usingExpr expectedUsingType) >>= (return . Left) - Right usingExpr -> (tcPolyExpr (noLoc usingExpr) expectedUsingType) >>= (return . Right . unLoc) - return $ GroupBySomething eitherUsingExpr' byExpr' - - -- Find the IDs and types of all old binders - let (oldBinders, newBinders) = unzip bindersMap - oldBinders' <- tcLookupLocalIds oldBinders + (by', using_ty) <- + case by of + Nothing -> -- check that using :: forall a. [a] -> [[a]] + return (Nothing, mkForAllTy alphaTyVar $ + alphaListTy `mkFunTy` alphaListListTy) + + Just by_e -> -- check that using :: forall a. (a -> t) -> [a] -> [[a]] + -- where by :: t + do { (by_e', t_ty) <- tcInferRhoNC by_e + ; return (Just by_e', mkForAllTy alphaTyVar $ + (alphaTy `mkFunTy` t_ty) + `mkFunTy` alphaListTy + `mkFunTy` alphaListListTy) } + -- Find the Ids (and hence types) of all old binders + bndr_ids <- tcLookupLocalIds bndr_names - -- Ensure that every old binder of type b is linked up with its new binder which should have type [b] - let newBinders' = zipWith associateNewBinder oldBinders' newBinders - - -- Type check the thing in the environment with these new binders and return the result - thing <- tcExtendIdEnv newBinders' (thing_inside elt_ty') - return (zipEqual "tcLcStmt: Old and new binder lists were not of the same length" oldBinders' newBinders', groupByClause', thing) + return (bndr_ids, by', using_ty, elt_ty') - return (GroupStmt (stmts', bindersMap') groupByClause', thing) - where - associateNewBinder :: TcId -> Name -> TcId - associateNewBinder oldBinder newBinder = mkLocalId newBinder (mkTyConApp m_tc [idType oldBinder]) + -- Ensure that every old binder of type b is linked up with + -- its new binder which should have type [b] + ; let list_bndr_ids = zipWith mk_list_bndr list_bndr_names bndr_ids + bindersMap' = bndr_ids `zip` list_bndr_ids + -- See Note [GroupStmt binder map] in HsExpr + + ; using' <- case using of + Left e -> do { e' <- tcPolyExpr e using_ty; return (Left e') } + Right e -> do { e' <- tcPolyExpr (noLoc e) using_ty; return (Right (unLoc e')) } + + -- Type check the thing in the environment with + -- these new binders and return the result + ; thing <- tcExtendIdEnv list_bndr_ids (thing_inside elt_ty') + ; return (GroupStmt stmts' bindersMap' by' using', thing) } + where + alphaListTy = mkTyConApp m_tc [alphaTy] + alphaListListTy = mkTyConApp m_tc [alphaListTy] + + mk_list_bndr :: Name -> TcId -> TcId + mk_list_bndr list_bndr_name bndr_id + = mkLocalId list_bndr_name (mkTyConApp m_tc [idType bndr_id]) tcLcStmt _ _ stmt _ _ = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt) @@ -463,25 +492,21 @@ tcLcStmt _ _ stmt _ _ tcDoStmt :: TcStmtChecker -tcDoStmt _ (BindStmt pat rhs bind_op fail_op) res_ty thing_inside - = do { (rhs', rhs_ty) <- tcInferRho rhs - -- We should 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. - - -- Deal with rebindable syntax: - -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty - -- This level of generality is needed for using do-notation - -- in full generality; see Trac #1537 - ; ((bind_op', new_res_ty), pat_ty) <- - withBox liftedTypeKind $ \ pat_ty -> - withBox liftedTypeKind $ \ new_res_ty -> - tcSyntaxOp DoOrigin bind_op - (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty) +tcDoStmt ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside + = do { -- Deal with rebindable syntax: + -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty + -- This level of generality is needed for using do-notation + -- in full generality; see Trac #1537 + + -- I'd like to put this *after* the tcSyntaxOp + -- (see Note [Treat rebindable syntax first], but that breaks + -- the rigidity info for GADTs. When we move to the new story + -- for GADTs, we can move this after tcSyntaxOp + rhs_ty <- newFlexiTyVarTy liftedTypeKind + ; pat_ty <- newFlexiTyVarTy liftedTypeKind + ; new_res_ty <- newFlexiTyVarTy liftedTypeKind + ; bind_op' <- tcSyntaxOp DoOrigin bind_op + (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty) -- If (but only if) the pattern can fail, -- typecheck the 'fail' operator @@ -489,31 +514,81 @@ tcDoStmt _ (BindStmt pat rhs bind_op fail_op) res_ty thing_inside then return noSyntaxExpr else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy new_res_ty) - ; (pat', thing) <- tcLamPat pat pat_ty new_res_ty thing_inside + ; rhs' <- tcMonoExprNC rhs rhs_ty + ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $ + thing_inside new_res_ty ; return (BindStmt pat' rhs' bind_op' fail_op', thing) } tcDoStmt _ (ExprStmt rhs then_op _) res_ty thing_inside - = do { (rhs', rhs_ty) <- tcInferRho rhs - - -- Deal with rebindable syntax; (>>) :: rhs_ty -> new_res_ty -> res_ty - ; (then_op', new_res_ty) <- - withBox liftedTypeKind $ \ new_res_ty -> - tcSyntaxOp DoOrigin then_op + = do { -- Deal with rebindable syntax; + -- (>>) :: rhs_ty -> new_res_ty -> res_ty + -- See also Note [Treat rebindable syntax first] + rhs_ty <- newFlexiTyVarTy liftedTypeKind + ; new_res_ty <- newFlexiTyVarTy liftedTypeKind + ; then_op' <- tcSyntaxOp DoOrigin then_op (mkFunTys [rhs_ty, new_res_ty] res_ty) + ; rhs' <- tcMonoExprNC rhs rhs_ty ; thing <- thing_inside new_res_ty ; return (ExprStmt rhs' then_op' rhs_ty, thing) } -tcDoStmt ctxt (RecStmt {}) _ _ - = failWithTc (ptext (sLit "Illegal 'rec' stmt in") <+> pprStmtContext ctxt) - -- This case can't be caught in the renamer - -- see RnExpr.checkRecStmt +tcDoStmt ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = later_names + , recS_rec_ids = rec_names, recS_ret_fn = ret_op + , recS_mfix_fn = mfix_op, recS_bind_fn = bind_op }) + res_ty thing_inside + = do { let tup_names = rec_names ++ filterOut (`elem` rec_names) later_names + ; tup_elt_tys <- newFlexiTyVarTys (length tup_names) liftedTypeKind + ; let tup_ids = zipWith mkLocalId tup_names tup_elt_tys + tup_ty = mkBoxedTupleTy tup_elt_tys + + ; tcExtendIdEnv tup_ids $ do + { stmts_ty <- newFlexiTyVarTy liftedTypeKind + ; (stmts', (ret_op', tup_rets)) + <- tcStmts ctxt tcDoStmt stmts stmts_ty $ \ inner_res_ty -> + do { tup_rets <- zipWithM tcCheckId tup_names tup_elt_tys + -- Unify the types of the "final" Ids (which may + -- be polymorphic) with those of "knot-tied" Ids + ; ret_op' <- tcSyntaxOp DoOrigin ret_op (mkFunTy tup_ty inner_res_ty) + ; return (ret_op', tup_rets) } + + ; mfix_res_ty <- newFlexiTyVarTy liftedTypeKind + ; mfix_op' <- tcSyntaxOp DoOrigin mfix_op + (mkFunTy (mkFunTy tup_ty stmts_ty) mfix_res_ty) + + ; new_res_ty <- newFlexiTyVarTy liftedTypeKind + ; bind_op' <- tcSyntaxOp DoOrigin bind_op + (mkFunTys [mfix_res_ty, mkFunTy tup_ty new_res_ty] res_ty) + + ; thing <- thing_inside new_res_ty +-- ; lie_binds <- bindLocalMethods lie tup_ids + + ; let rec_ids = takeList rec_names tup_ids + ; later_ids <- tcLookupLocalIds later_names + ; traceTc "tcdo" $ vcat [ppr rec_ids <+> ppr (map idType rec_ids), + ppr later_ids <+> ppr (map idType later_ids)] + ; return (RecStmt { recS_stmts = stmts', recS_later_ids = later_ids + , recS_rec_ids = rec_ids, recS_ret_fn = ret_op' + , recS_mfix_fn = mfix_op', recS_bind_fn = bind_op' + , recS_rec_rets = tup_rets, recS_dicts = emptyTcEvBinds }, thing) + }} tcDoStmt _ stmt _ _ = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt) +\end{code} +Note [Treat rebindable syntax first] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When typechecking + do { bar; ... } :: IO () +we want to typecheck 'bar' in the knowledge that it should be an IO thing, +pushing info from the context into the RHS. To do this, we check the +rebindable syntax first, and push that information into (tcMonoExprNC rhs). +Otherwise the error shows up when cheking the rebindable syntax, and +the expected/inferred stuff is back to front (see Trac #3613). + +\begin{code} -------------------------------- -- Mdo-notation -- The distinctive features here are @@ -522,9 +597,10 @@ tcDoStmt _ stmt _ _ tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference -> TcStmtChecker -tcMDoStmt tc_rhs _ (BindStmt pat rhs _ _) res_ty thing_inside +tcMDoStmt tc_rhs ctxt (BindStmt pat rhs _ _) res_ty thing_inside = do { (rhs', pat_ty) <- tc_rhs rhs - ; (pat', thing) <- tcLamPat pat pat_ty res_ty thing_inside + ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $ + thing_inside res_ty ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } tcMDoStmt tc_rhs _ (ExprStmt rhs _ _) res_ty thing_inside @@ -532,38 +608,32 @@ tcMDoStmt tc_rhs _ (ExprStmt rhs _ _) res_ty thing_inside ; thing <- thing_inside res_ty ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) } -tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) res_ty thing_inside +tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _ _ _ _) res_ty thing_inside = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind ; let rec_ids = zipWith mkLocalId recNames rec_tys ; tcExtendIdEnv rec_ids $ do { (stmts', (later_ids, rec_rets)) <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ _res_ty' -> -- ToDo: res_ty not really right - do { rec_rets <- zipWithM tc_ret recNames rec_tys + do { rec_rets <- zipWithM tcCheckId recNames rec_tys ; later_ids <- tcLookupLocalIds laterNames ; return (later_ids, rec_rets) } - ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE (thing_inside res_ty)) + ; thing <- tcExtendIdEnv later_ids (thing_inside res_ty) -- NB: The rec_ids for the recursive things -- already scope over this part. This binding may shadow -- some of them with polymorphic things with the same Name -- (see note [RecStmt] in HsExpr) - ; lie_binds <- bindInstsOfLocalFuns lie later_ids + +-- Need the bindLocalMethods if we re-add Method constraints +-- ; lie_binds <- bindLocalMethods lie later_ids + ; let lie_binds = emptyTcEvBinds - ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing) + ; return (RecStmt stmts' later_ids rec_ids noSyntaxExpr noSyntaxExpr noSyntaxExpr rec_rets lie_binds, thing) }} - where - -- Unify the types of the "final" Ids with those of "knot-tied" Ids - tc_ret rec_name mono_ty - = do { poly_id <- tcLookupId rec_name - -- poly_id may have a polymorphic type - -- but mono_ty is just a monomorphic type variable - ; co_fn <- tcSubExp DoOrigin (idType poly_id) mono_ty - ; return (mkHsWrap co_fn (HsVar poly_id)) } tcMDoStmt _ _ stmt _ _ = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt) - \end{code} @@ -591,6 +661,6 @@ checkArgs fun (MatchGroup (match1:matches) _) args_in_match :: LMatch Name -> Int args_in_match (L _ (Match pats _ _)) = length pats -checkArgs _ _ = panic "TcPat.checkArgs" -- Matches always non-empty +checkArgs fun _ = pprPanic "TcPat.checkArgs" (ppr fun) -- Matches always non-empty \end{code}