X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=5aeb1dd1b229c518ee5b52c8ac54709c8c85cbcc;hb=91944423d83620441d6d3b120654a10fb41cfb3c;hp=3cd3df53910c700a2c0dfde88fad64591a4c1096;hpb=26741ec416bae2c502ef00a2ba0e79050a32cb67;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 3cd3df5..5aeb1dd 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -1,223 +1,649 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcMatches]{Typecheck some @Matches@} \begin{code} +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + tcMatchPats, matchCtxt, TcMatchCtxt(..), + tcStmts, tcDoStmts, + tcDoStmt, tcMDoStmt, tcGuardStmt, + tcThingWithSig + ) where + #include "HsVersions.h" -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where - -IMP_Ubiq() - -import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat, - HsExpr, HsBinds, OutPat, Fake, - collectPatBinders, pprMatch ) -import RnHsSyn ( RenamedMatch(..) ) -import TcHsSyn ( TcIdOcc(..), TcMatch(..) ) - -import TcMonad hiding ( rnMtoTcM ) -import Inst ( Inst, LIE(..), plusLIE ) -import TcEnv ( newMonoIds ) -IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds ) -import TcPat ( tcPat ) -import TcType ( TcType(..), TcMaybe, zonkTcType ) -import Unify ( unifyTauTy, unifyTauTyList ) - -import Kind ( Kind, mkTypeKind ) -import Pretty -import RnHsSyn ( RnName{-instance Outputable-} ) -import Type ( isTyVarTy, mkFunTy, getFunTy_maybe ) -import Util +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcCheckRho, tcInferRho, tcMonoExpr, tcCheckSigma ) + +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + LPat, pprMatch, isIrrefutableHsPat, + pprMatchContext, pprStmtContext, pprMatchRhsContext, + collectPatsBinders, glueBindsOnGRHSs, noSyntaxExpr + ) +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 TcUnify ( Expected(..), zapExpectedType, readExpectedType, + unifyTauTy, subFunTys, unifyTyConApp, + checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen, + unifyAppTy, zapToListTy, zapToTyConApp ) +import TcSimplify ( bindInstsOfLocalFuns ) +import Name ( Name ) +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 Util ( isSingleton ) +import Outputable +import SrcLoc ( Located(..) ) + +import List ( nub ) \end{code} +%************************************************************************ +%* * +\subsection{tcMatchesFun, tcMatchesCase} +%* * +%************************************************************************ + @tcMatchesFun@ typechecks a @[Match]@ list which occurs in a @FunMonoBind@. The second argument is the name of the function, which 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 :: RnName - -> TcType s -- Expected type - -> [RenamedMatch] - -> TcM s ([TcMatch s], LIE s) - -tcMatchesFun fun_name expected_ty matches@(first_match:_) - = -- 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 (get_Match_loc first_match) ( - - -- Check that they all have the same no of arguments - checkTc (all_same (noOfArgs 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 - -- We need to substitute so that we can see as much about the type as possible - zonkTcType expected_ty `thenNF_Tc` \ expected_ty' -> - tcMatchesExpected expected_ty' (MFun fun_name) matches - - ) + -- 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 - all_same :: [Int] -> Bool - all_same [] = True -- Should never happen (ToDo: panic?) - all_same [x] = True - all_same (x:xs) = all ((==) x) xs + 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 :: TcType s -> [RenamedMatch] -> TcM s ([TcMatch s], LIE s) -tcMatchesCase expected_ty matches = tcMatchesExpected expected_ty MCase matches +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} -data FunOrCase = MCase | MFun RnName -- Records whether doing fun or case rhss; - -- used to produced better error messages - -tcMatchesExpected :: TcType s - -> FunOrCase - -> [RenamedMatch] - -> TcM s ([TcMatch s], LIE s) - -tcMatchesExpected expected_ty fun_or_case [match] - = tcAddSrcLoc (get_Match_loc match) $ - tcAddErrCtxt (matchCtxt fun_or_case match) $ - tcMatchExpected expected_ty match `thenTc` \ (match', lie) -> - returnTc ([match'], lie) - -tcMatchesExpected expected_ty fun_or_case (match1 : matches) - = tcAddSrcLoc (get_Match_loc match1) ( - tcAddErrCtxt (matchCtxt fun_or_case match1) $ - tcMatchExpected expected_ty match1 - ) `thenTc` \ (match1', lie1) -> - tcMatchesExpected expected_ty fun_or_case matches `thenTc` \ (matches', lie2) -> - returnTc (match1' : matches', plusLIE lie1 lie2) - -tcMatches :: [RenamedMatch] -> TcM s ([TcMatch s], LIE s, [TcType s]) - -tcMatches [match] - = tcAddSrcLoc (get_Match_loc match) $ - tcMatch match `thenTc` \ (match', lie, ty) -> - returnTc ([match'], lie, [ty]) - -tcMatches (match1 : matches) - = tcAddSrcLoc (get_Match_loc match1) ( - tcMatch match1 - ) `thenTc` \ (match1', lie1, match1_ty) -> - tcMatches matches `thenTc` \ (matches', lie2, matches_ty) -> - returnTc (match1' : matches', plusLIE lie1 lie2, match1_ty : matches_ty) +tcGRHSsPat :: GRHSs Name + -> Expected TcRhoType + -> TcM (GRHSs TcId) +tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty + where + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcMonoExpr } \end{code} + +%************************************************************************ +%* * +\subsection{tcMatch} +%* * +%************************************************************************ + \begin{code} -tcMatchExpected - :: TcType s -- This gives the expected - -- result-type of the Match. Early unification - -- with this guy gives better error messages - -> RenamedMatch - -> TcM s (TcMatch s,LIE s) -- NB No type returned, because it was passed - -- in instead! - -tcMatchExpected expected_ty the_match@(PatMatch pat match) - = case getFunTy_maybe expected_ty of - - Nothing -> -- Not a function type (eg type variable) - -- So use tcMatch instead - tcMatch the_match `thenTc` \ (match', lie_match, match_ty) -> - unifyTauTy match_ty expected_ty `thenTc_` - returnTc (match', lie_match) - - Just (arg_ty,rest_ty) -> -- It's a function type! - let binders = collectPatBinders pat - in - newMonoIds binders mkTypeKind (\ _ -> - tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) -> - unifyTauTy arg_ty pat_ty `thenTc_` - tcMatchExpected rest_ty match `thenTc` \ (match', lie_match) -> - returnTc (PatMatch pat' match', - plusLIE lie_pat lie_match) - ) - -tcMatchExpected expected_ty (GRHSMatch grhss_and_binds) - = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) -> - unifyTauTy grhss_ty expected_ty `thenTc_` - returnTc (GRHSMatch grhss_and_binds', lie) - -tcMatch :: RenamedMatch -> TcM s (TcMatch s, LIE s, TcType s) - -tcMatch (PatMatch pat match) - = let binders = collectPatBinders pat - in - newMonoIds binders mkTypeKind (\ _ -> - -- NB TypeKind; lambda-bound variables are allowed - -- to unify with unboxed types. - - tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) -> - tcMatch match `thenTc` \ (match', lie_match, match_ty) -> - returnTc (PatMatch pat' match', - plusLIE lie_pat lie_match, - mkFunTy pat_ty match_ty) - ) - -tcMatch (GRHSMatch grhss_and_binds) - = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) -> - returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty) +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 + 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} -@noOfArgs@ takes a @[RenamedMatch]@ and returns a list telling how -many arguments were used in each of the equations. This is used to -report a sensible error message when different equations have -different numbers of arguments. - \begin{code} -noOfArgs :: [RenamedMatch] -> [Int] +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} -noOfArgs ms = map args_in_match ms - where - args_in_match :: RenamedMatch -> Int - args_in_match (GRHSMatch _) = 0 - args_in_match (PatMatch _ match) = 1 + args_in_match match + +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ + +\begin{code} +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 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 (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} -@get_Match_loc@ takes a @RenamedMatch@ and returns the -source-location gotten from the GRHS inside. -THis is something of a nuisance, but no more. + +%************************************************************************ +%* * +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} +%* * +%************************************************************************ \begin{code} -get_Match_loc :: RenamedMatch -> SrcLoc - -get_Match_loc (PatMatch _ m) = get_Match_loc m -get_Match_loc (GRHSMatch (GRHSsAndBindsIn (g:_) _)) - = get_GRHS_loc g - where - get_GRHS_loc (OtherwiseGRHS _ locn) = locn - get_GRHS_loc (GRHS _ _ locn) = locn +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} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ -\begin{code} -matchCtxt MCase match sty - = ppHang (ppStr "In a \"case\" branch:") - 4 (pprMatch sty True{-is_case-} match) -matchCtxt (MFun fun) match sty - = ppHang (ppBesides [ppStr "In an equation for function ", ppr sty fun, ppChar ':']) - 4 (ppBesides [ppr sty fun, ppSP, pprMatch sty False{-not case-} match]) +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ + +\begin{code} +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 + (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 :: [([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} +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same +number of args are used in each equation. + \begin{code} -varyingArgsErr name matches sty - = ppSep [ppStr "Varying number of arguments for function", ppr sty name] +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 +\end{code} + +\begin{code} +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) + +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}