X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=5aeb1dd1b229c518ee5b52c8ac54709c8c85cbcc;hb=1159c0c06db593588cfae24e47a80e71c51c6129;hp=cdd417fdfcf576d90782c544a70b922f86602413;hpb=61bfd5dd3b9d70404d6f93c030a9bb1c402b9d31;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index cdd417f..5aeb1dd 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,44 +4,52 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, - tcStmts, tcStmtsAndThen, tcGRHSs +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + tcMatchPats, matchCtxt, TcMatchCtxt(..), + tcStmts, tcDoStmts, + tcDoStmt, tcMDoStmt, tcGuardStmt, + tcThingWithSig ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcCheckRho, tcInferRho, tcMonoExpr, tcCheckSigma ) -import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), - MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..), - pprMatch, getMatchLoc, pprMatchContext, isDoExpr, - mkMonoBind, nullMonoBinds, collectSigTysFromPats +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + LPat, pprMatch, isIrrefutableHsPat, + pprMatchContext, pprStmtContext, pprMatchRhsContext, + collectPatsBinders, glueBindsOnGRHSs, noSyntaxExpr ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType, - RenamedMatchContext, extractHsTyVars ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) - -import TcMonad -import TcMonoType ( kcHsSigTypes, tcAddScopedTyVars, checkSigTyVars, tcHsSigType, UserTypeCtxt(..), sigPatCtxt ) -import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) -import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars, - tcInLocalScope ) -import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) -import TcMType ( newTyVarTy, unifyFunTy, unifyTauTy ) -import TcType ( TcType, TcTyVar, tyVarsOfType, isTauTy, - mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind ) +import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) ) + +import TcRnMonad +import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) ) +import Inst ( tcInstCall, newMethodFromName ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv ) +import TcPat ( PatCtxt(..), tcPats ) +import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType ) +import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys, + tyVarsOfTypes, tidyOpenTypes, isSigmaTy, + liftedTypeKind, openTypeKind, mkFunTy, mkAppTy ) import TcBinds ( tcBindsAndThen ) -import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcUnify ( Expected(..), zapExpectedType, readExpectedType, + unifyTauTy, subFunTys, unifyTyConApp, + checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen, + unifyAppTy, zapToListTy, zapToTyConApp ) +import TcSimplify ( bindInstsOfLocalFuns ) import Name ( Name ) -import TysWiredIn ( boolTy ) -import Id ( idType ) -import BasicTypes ( RecFlag(..) ) -import NameSet +import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy ) +import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName ) +import Id ( idType, mkLocalId ) +import TyCon ( TyCon ) +import CoreFVs ( idFreeTyVars ) import VarSet -import Var ( Id ) -import Bag import Util ( isSingleton ) import Outputable +import SrcLoc ( Located(..) ) import List ( nub ) \end{code} @@ -58,64 +66,69 @@ 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 - -> [RenamedMatch] - -> TcM ([TcMatch], LIE) - -tcMatchesFun xve fun_name expected_ty matches@(first_match:_) - = -- 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 - -- 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) ( - checkTc (sameNoOfArgs matches) - (varyingArgsErr fun_name matches) - ) `thenTc_` +tcMatchesFun :: Name + -> 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 unifyFunTy does that on the fly - tcMatches xve (FunRhs fun_name) 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 } \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 - LIE) - -tcMatchesCase matches expr_ty - = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty -> - tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenTc` \ (matches', lie) -> - returnTc (scrut_ty, matches', lie) - -tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE) -tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty +tcMatchesCase :: TcMatchCtxt -- Case context + -> TcRhoType -- Type of scrutinee + -> MatchGroup Name -- The case alternatives + -> Expected TcRhoType -- Type of whole case expressions + -> 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 } \end{code} +@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -tcMatches :: [(Name,Id)] - -> RenamedMatchContext - -> [RenamedMatch] - -> TcType - -> TcM ([TcMatch], LIE) - -tcMatches xve fun_or_case matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> - returnTc (matches, plusLIEs lies) +tcGRHSsPat :: GRHSs Name + -> Expected TcRhoType + -> TcM (GRHSs TcId) +tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty where - tc_match match = tcMatch xve fun_or_case match expected_ty + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcMonoExpr } \end{code} @@ -126,72 +139,123 @@ tcMatches xve fun_or_case matches expected_ty %************************************************************************ \begin{code} -tcMatch :: [(Name,Id)] - -> RenamedMatchContext - -> RenamedMatch - -> 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, LIE) - -tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty - = tcAddSrcLoc (getMatchLoc match) $ -- At one stage I removed this; - tcAddErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back - - tcMatchPats pats expected_ty tc_grhss `thenTc` \ ((pats', grhss'), lie, ex_binds) -> - returnTc (Match pats' Nothing (glue_on Recursive ex_binds grhss'), lie) - - where - tc_grhss pats' rhs_ty - = -- Check that the remaining "expected type" is not a rank-2 type - -- If it is it'll mess up the unifier when checking the RHS - checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc` \_ -> - - -- Deal with the result signature - -- It "wraps" the rest of the body typecheck because it may - -- bring into scope the type variables in the signature - tc_result_sig maybe_rhs_sig rhs_ty $ - - -- Typecheck the body - tcExtendLocalValEnv xve1 $ - tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> - returnTc ((pats', grhss'), lie) - - tc_result_sig Nothing rhs_ty thing_inside - = thing_inside - tc_result_sig (Just sig) rhs_ty thing_inside - = tcAddScopedTyVars [sig] $ - tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty -> - - -- Check that the signature isn't a polymorphic one, which - -- we don't permit (at present, anyway) - checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_` - unifyTauTy sig_ty rhs_ty `thenTc_` - thing_inside - - - -- glue_on just avoids stupid dross -glue_on _ EmptyMonoBinds grhss = grhss -- The common case -glue_on is_rec mbinds (GRHSs grhss binds ty) - = GRHSs grhss (mkMonoBind mbinds [] is_rec `ThenBinds` binds) ty - -tcGRHSs :: RenamedMatchContext -> RenamedGRHSs - -> TcType - -> TcM (TcGRHSs, LIE) - -tcGRHSs ctxt (GRHSs grhss binds _) expected_ty - = tcBindsAndThen glue_on binds (tc_grhss grhss) +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 pattern types + -> Expected TcRhoType -- Expected result-type of the Match. + -> LMatch Name + -> TcM (LMatch TcId) + +tcMatch ctxt pat_tys rhs_ty match + = wrapLocM (tc_match ctxt pat_tys rhs_ty) match + +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') } + + +------------- +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 - tc_grhss grhss - = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> - returnTc (GRHSs grhss' EmptyBinds expected_ty, plusLIEs lies) - - tc_grhs (GRHS guarded locn) - = tcAddSrcLoc locn $ - tcStmts ctxt (\ty -> ty, expected_ty) guarded `thenTc` \ (guarded', lie) -> - returnTc (GRHS guarded' locn, lie) + lift_grhs (GRHS stmts rhs) = GRHS stmts (fmap (co_fn <$>) rhs) + +------------- +tcGRHSs :: TcMatchCtxt -> GRHSs Name + -> Expected TcRhoType + -> TcM (GRHSs TcId) + + -- 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 [L loc1 (GRHS [] rhs)] binds) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + mc_body ctxt rhs exp_ty `thenM` \ rhs' -> + returnM (GRHSs [L loc1 (GRHS [] rhs')] []) + +tcGRHSs ctxt (GRHSs grhss binds) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + do { exp_ty' <- zapExpectedType exp_ty openTypeKind + -- 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 match_ctxt = mc_what ctxt + stmt_ctxt = PatGuard match_ctxt + tc_grhs (GRHS guards rhs) + = do { (guards', rhs') + <- tcStmts stmt_ctxt (tcGuardStmt exp_ty') guards $ + addErrCtxt (grhsCtxt match_ctxt rhs) $ + tcCheckRho rhs exp_ty' + ; return (GRHS guards' rhs') } + + ; grhss' <- mappM (wrapLocM tc_grhs) grhss + ; returnM (GRHSs grhss' []) } +\end{code} + + +\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 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. \end{code} @@ -202,228 +266,329 @@ tcGRHSs ctxt (GRHSs grhss binds _) expected_ty %************************************************************************ \begin{code} -tcMatchPats - :: [RenamedPat] -> TcType - -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) - -> TcM (a, LIE, TcDictBinds) +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 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 - tc_match_pats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> - - -- STEP 3: Extend the environment, and do the thing inside - let - xve = bagToList pat_bndrs - pat_ids = map snd xve - in - tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) -> - - returnTc (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) - ) `thenTc` \ (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) -> - - -- 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 pat_ids ex_tvs lie_avail lie_req2 expected_ty `thenTc` \ (lie_req2', ex_binds) -> - -- NB: we *must* pass "expected_ty" not "result_ty" to tcCheckExistentialPat +tcMatchPats pats tys body_ty thing_inside + = do { (pats', ex_tvs, res) <- tcPats LamPat pats tys thing_inside + ; tcCheckExistentialPat pats' ex_tvs tys body_ty + ; returnM (pats', res) } + +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 (a -> Int). - - returnTc (result, lie_req1 `plusLIE` lie_req2', ex_binds) - -tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern - -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern - -> LIE -- and context - -> LIE -- Required context - -> TcType -- and type of the Match; vars in here must not escape - -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings -tcCheckExistentialPat ids ex_tvs lie_avail lie_req match_ty - | isEmptyBag ex_tvs && all not_overloaded ids - -- Short cut for case when there are no existentials - -- and no polymorphic overloaded variables - -- e.g. f :: (forall a. Ord a => a -> a) -> Int -> Int - -- f op x = .... - -- Here we must discharge op Methods - = ASSERT( isEmptyLIE lie_avail ) - returnTc (lie_req, EmptyMonoBinds) - - | otherwise - = tcExtendGlobalTyVars (tyVarsOfType match_ty) $ - tcAddErrCtxtM (sigPatCtxt tv_list ids) $ - - -- In case there are any polymorpic, overloaded binders in the pattern - -- (which can happen in the case of rank-2 type signatures, or data constructors - -- with polymorphic arguments), we must do a bindInstsOfLocalFns here - bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) -> - - -- Deal with overloaded functions bound by the pattern - tcSimplifyCheck doc tv_list (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) -> - checkSigTyVars tv_list emptyVarSet `thenTc_` - - returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) - where - doc = text ("the existential context of a data constructor") - tv_list = bagToList ex_tvs - not_overloaded id = not (isOverloadedTy (idType id)) - -tc_match_pats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tc_match_pats (pat:pats) expected_ty - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> - tc_match_pats pats rest_ty `thenTc` \ (rhs_ty, pats', lie_reqs, pats_tvs, pats_ids, lie_avails) -> - returnTc ( rhs_ty, - pat':pats', - lie_req `plusLIE` lie_reqs, - pat_tvs `unionBags` pats_tvs, - pat_ids `unionBags` pats_ids, - lie_avail `plusLIE` lie_avails - ) + -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int). + +tcCheckExistentialPat pats [] pat_tys body_ty + = return () -- Short cut for case when there are no existentials + +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} %************************************************************************ %* * -\subsection{tcStmts} +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} %* * %************************************************************************ -Typechecking statements is rendered a bit tricky by parallel list comprehensions: - - [ (g x, h x) | ... ; let g v = ... - | ... ; 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). -Similarly if we had an existential pattern match: - - data T = forall a. Show a => C a - - [ (show x, show y) | ... ; C x <- ... - | ... ; C y <- ... ] +\begin{code} +tcDoStmts :: HsStmtContext Name + -> [LStmt Name] + -> LHsExpr Name + -> Expected TcRhoType + -> TcM (HsExpr TcId) -- Returns a HsDo +tcDoStmts ListComp stmts body res_ty + = do { elt_ty <- zapToListTy res_ty + ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon elt_ty) stmts $ + addErrCtxt (doBodyCtxt ListComp body) $ + tcCheckRho body elt_ty + ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) } + +tcDoStmts PArrComp stmts body res_ty + = do { [elt_ty] <- zapToTyConApp parrTyCon res_ty + ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon elt_ty) stmts $ + addErrCtxt (doBodyCtxt PArrComp body) $ + tcCheckRho body elt_ty + ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) } + +tcDoStmts DoExpr stmts body res_ty + = do { res_ty' <- zapExpectedType res_ty liftedTypeKind + ; (m_ty, _) <- unifyAppTy res_ty' + ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty res_ty') stmts $ + addErrCtxt (doBodyCtxt DoExpr body) $ + tcCheckRho body res_ty' + ; return (HsDo DoExpr stmts' body' res_ty') } + +tcDoStmts cxt@(MDoExpr _) stmts body res_ty + = do { res_ty' <- zapExpectedType res_ty liftedTypeKind + ; (m_ty, _) <- unifyAppTy res_ty' + ; let tc_rhs rhs = do { (rhs', rhs_ty) <- tcInferRho rhs + ; (n_ty, pat_ty) <- unifyAppTy rhs_ty + ; unifyTauTy m_ty n_ty + ; return (rhs', pat_ty) } + + ; (stmts', body') <- tcStmts cxt (tcMDoStmt res_ty' tc_rhs) stmts $ + addErrCtxt (doBodyCtxt cxt body) $ + tcCheckRho body res_ty' + + ; let names = [mfixName, bindMName, thenMName, returnMName, failMName] + ; insts <- mapM (newMethodFromName DoOrigin m_ty) names + ; return (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') } + +tcDoStmts ctxt stmts body res_ty = pprPanic "tcDoStmts" (pprStmtContext ctxt) +\end{code} -Then we need the LIE from (show x, show y) to be simplified against -the bindings for x and y. -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. +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ \begin{code} -tcStmts do_or_lc m_ty stmts - = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) - -tcStmtsAndThen - :: (TcStmt -> thing -> thing) -- Combiner - -> RenamedMatchContext - -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs - -- elt_ty, where type of the comprehension is (m elt_ty) - -> [RenamedStmt] - -> TcM (thing, LIE) - -> TcM (thing, LIE) - - -- Base case -tcStmtsAndThen combine do_or_lc m_ty [] do_next - = do_next - -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) - - -- 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 +type TcStmtChecker + = forall thing. HsStmtContext Name + -> Stmt Name + -> TcM thing + -> TcM (Stmt TcId, thing) + +tcStmts :: HsStmtContext Name + -> TcStmtChecker -- NB: higher-rank type + -> [LStmt Name] + -> TcM thing + -> TcM ([LStmt TcId], thing) + +-- Note the higher-rank type. stmt_chk is applied at different +-- types in the equations for tcStmts + +tcStmts ctxt stmt_chk [] thing_inside + = do { thing <- thing_inside + ; return ([], thing) } + +-- LetStmts are handled uniformly, regardless of context +tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) thing_inside + = tcBindsAndThen -- No error context, but a binding group is + glue_binds -- 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 - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (stmtCtxt do_or_lc stmt) $ - newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> - tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> - tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ [pat'] _ -> - tcPopErrCtxt $ - thing_inside `thenTc` \ (thing, lie) -> - returnTc ((BindStmt pat' exp' src_loc, thing), lie) - ) `thenTc` \ ((stmt', thing), lie, dict_binds) -> - returnTc (combine stmt' (glue_binds combine Recursive dict_binds thing), - lie `plusLIE` exp_lie) - - - -- ParStmt -tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside - = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) -> - returnTc (combine (ParStmtOut pairs') thing, lie) + (tcStmts ctxt stmt_chk stmts thing_inside) + where + glue_binds binds (stmts, thing) = (L loc (LetStmt [binds]) : stmts, thing) + + +-- For the vanilla case, handle the location-setting part +tcStmts ctxt stmt_chk (L loc stmt : stmts) thing_inside + = do { (stmt', (stmts', thing)) <- + setSrcSpan loc $ + addErrCtxt (stmtCtxt ctxt stmt) $ + stmt_chk ctxt stmt $ + popErrCtxt $ + tcStmts ctxt stmt_chk stmts $ + thing_inside + ; return (L loc stmt' : stmts', thing) } + +-------------------------------- +-- Pattern guards +tcGuardStmt :: TcType -> TcStmtChecker +tcGuardStmt res_ty ctxt (ExprStmt guard _ _) thing_inside + = do { guard' <- tcCheckRho guard boolTy + ; thing <- thing_inside + ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) } + +tcGuardStmt res_ty ctxt (BindStmt pat rhs _ _) thing_inside + = do { (rhs', rhs_ty) <- tcInferRho rhs + ; (pat', thing) <- tcBindPat pat rhs_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcGuardStmt res_ty ctxt stmt thing_inside + = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt) + + +-------------------------------- +-- List comprehensions and PArrays + +tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray) + -> TcType -- The element type of the list or PArray + -> TcStmtChecker + +-- A generator, pat <- rhs +tcLcStmt m_tc elt_ty ctxt (BindStmt pat rhs _ _) thing_inside + = do { (rhs', rhs_ty) <- tcInferRho rhs + ; [pat_ty] <- unifyTyConApp m_tc rhs_ty + ; (pat', thing) <- tcBindPat pat pat_ty elt_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +-- A boolean guard +tcLcStmt m_tc elt_ty ctxt (ExprStmt rhs _ _) thing_inside + = do { rhs' <- tcCheckRho rhs boolTy + ; thing <- thing_inside + ; return (ExprStmt rhs' noSyntaxExpr boolTy, thing) } + +-- A parallel set of comprehensions +-- [ (g x, h x) | ... ; let g v = ... +-- | ... ; 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). +-- Similarly if we had an existential pattern match: +-- +-- data T = forall a. Show a => C a +-- +-- [ (show x, show y) | ... ; C x <- ... +-- | ... ; C y <- ... ] +-- +-- Then we need the LIE from (show x, show y) to be simplified against +-- the bindings for x and y. +-- +-- 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. + +tcLcStmt m_tc elt_ty ctxt (ParStmt bndr_stmts_s) thing_inside + = do { (pairs', thing) <- loop bndr_stmts_s + ; return (ParStmt pairs', thing) } where - loop [] - = thing_inside `thenTc` \ (thing, stmts_lie) -> - returnTc (([], thing), stmts_lie) - - loop ((bndrs,stmts) : pairs) - = tcStmtsAndThen - combine_par (DoCtxt ListComp) m_ty stmts - -- Notice we pass on m_ty; the result type is used only - -- to get escaping type variables for checkExistentialPat - (tcLookupLocalIds bndrs `thenNF_Tc` \ bndrs' -> - loop pairs `thenTc` \ ((pairs', thing), lie) -> - returnTc (([], (bndrs', pairs', thing)), lie)) `thenTc` \ ((stmts', (bndrs', pairs', thing)), lie) -> - - returnTc ( ((bndrs',stmts') : pairs', thing), lie) - - combine_par stmt (stmts, thing) = (stmt:stmts, thing) - - -- ExprStmt -tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - if isDoExpr do_or_lc then - newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> - tcExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) -> - returnTc (ExprStmt exp' any_ty locn, lie) - else - tcExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> - returnTc (ExprStmt exp' boolTy locn, lie) - ) `thenTc` \ (stmt', stmt_lie) -> - - thing_inside `thenTc` \ (thing, stmts_lie) -> - - returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie) - - - -- Result statements -tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - if isDoExpr do_or_lc then - tcExpr exp (m res_elt_ty) - else - tcExpr exp res_elt_ty - ) `thenTc` \ (exp', stmt_lie) -> - - thing_inside `thenTc` \ (thing, stmts_lie) -> - - returnTc (combine (ResultStmt exp' locn) thing, - stmt_lie `plusLIE` stmts_lie) - - ------------------------------- -glue_binds combine is_rec binds thing - | nullMonoBinds binds = thing - | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing + -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing) + loop [] = do { thing <- thing_inside + ; return ([], thing) } + + loop ((stmts, names) : pairs) + = do { (stmts', (ids, pairs', thing)) + <- tcStmts ctxt (tcLcStmt m_tc elt_ty) stmts $ + do { ids <- tcLookupLocalIds names + ; (pairs', thing) <- loop pairs + ; return (ids, pairs', thing) } + ; return ( (stmts', ids) : pairs', thing ) } + +tcLcStmt m_tc elt_ty ctxt stmt thing_inside + = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Do-notation +-- The main excitement here is dealing with rebindable syntax + +tcDoStmt :: TcType -- Monad type, m + -> TcType -- Result type, m b + -> TcStmtChecker + -- BindStmt +tcDoStmt m_ty res_ty ctxt (BindStmt pat rhs bind_op fail_op) thing_inside + = do { -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b + ; (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. + + ; (n_ty, pat_ty) <- unifyAppTy rhs_ty + ; unifyTauTy m_ty n_ty + ; let bind_ty = mkFunTys [rhs_ty, mkFunTy pat_ty res_ty] res_ty + + ; (pat', thing) <- tcBindPat pat pat_ty res_ty thing_inside + + -- Rebindable syntax stuff + ; bind_op' <- tcSyntaxOp DoOrigin bind_op bind_ty + -- If (but only if) the pattern can fail, + -- typecheck the 'fail' operator + ; fail_op' <- if isIrrefutableHsPat pat' + then return noSyntaxExpr + else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy res_ty) + ; return (BindStmt pat' rhs' bind_op' fail_op', thing) } + + +tcDoStmt m_ty res_ty ctxt (ExprStmt rhs then_op _) thing_inside + = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b + a_ty <- newTyFlexiVarTy liftedTypeKind + ; let rhs_ty = mkAppTy m_ty a_ty + then_ty = mkFunTys [rhs_ty, res_ty] res_ty + ; then_op' <- tcSyntaxOp DoOrigin then_op then_ty + ; rhs' <- tcCheckSigma rhs rhs_ty + ; thing <- thing_inside + ; return (ExprStmt rhs' then_op' rhs_ty, thing) } + +tcDoStmt m_ty res_ty ctxt stmt thing_inside + = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Mdo-notation +-- The distinctive features here are +-- (a) RecStmts, and +-- (b) no rebindable syntax + +tcMDoStmt :: TcType -- Result type, m b + -> (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference + -> TcStmtChecker +tcMDoStmt res_ty tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) thing_inside + = do { (rhs', pat_ty) <- tc_rhs rhs + ; (pat', thing) <- tcBindPat pat pat_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcMDoStmt res_ty tc_rhs ctxt (ExprStmt rhs then_op _) thing_inside + = do { (rhs', elt_ty) <- tc_rhs rhs + ; thing <- thing_inside + ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) } + +tcMDoStmt res_ty tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) thing_inside + = do { rec_tys <- newTyFlexiVarTys (length recNames) liftedTypeKind + ; let rec_ids = zipWith mkLocalId recNames rec_tys + ; tcExtendIdEnv rec_ids $ do + { (stmts', (later_ids, rec_rets)) + <- tcStmts ctxt (tcMDoStmt res_ty tc_rhs) stmts $ + -- ToDo: res_ty not really right + do { rec_rets <- zipWithM tc_ret recNames rec_tys + ; later_ids <- tcLookupLocalIds laterNames + ; return (later_ids, rec_rets) } + + ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE thing_inside) + -- 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 + + ; return (RecStmt stmts' later_ids rec_ids 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 + = tcLookupId rec_name `thenM` \ poly_id -> + -- poly_id may have a polymorphic type + -- but mono_ty is just a monomorphic type variable + tcSubExp (Check mono_ty) (idType poly_id) `thenM` \ co_fn -> + returnM (co_fn <$> HsVar poly_id) + +tcMDoStmt res_ty tc_rhs ctxt stmt thing_inside + = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt) + +----------------- +tcBindPat :: LPat Name -> TcType + -> TcType -- Result type; used only to check existential escape + -> TcM a + -> TcM (LPat TcId, a) +tcBindPat pat pat_ty res_ty thing_inside + = do { ([pat'],thing) <- tcMatchPats [pat] [Check pat_ty] + (Check res_ty) thing_inside + ; return (pat', thing) } \end{code} @@ -437,20 +602,48 @@ glue_binds combine is_rec binds thing number of args are used in each equation. \begin{code} -sameNoOfArgs :: [RenamedMatch] -> 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 :: RenamedMatch -> Int - args_in_match (Match pats _ _) = length pats + args_in_match :: LMatch Name -> Int + args_in_match (L _ (Match pats _ _)) = length pats \end{code} \begin{code} -matchCtxt ctxt match = hang (pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match) -stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt) - varyingArgsErr name matches = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] -lurkingRank2SigErr - = ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type") +matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) + 4 (pprMatch ctxt match) + +grhsCtxt ctxt rhs = hang (ptext SLIT("In") <+> pprMatchRhsContext ctxt <> colon) + 4 (ppr rhs) + +doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc +doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon) + 4 (ppr body) + +stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon) + 4 (ppr stmt) + +sigPatCtxt bound_ids bound_tvs 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_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("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 + -- Don't zonk the types so we get the separate, un-unified versions \end{code}