X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=07a1094d58de98b08937c346db5965a070bac90f;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=31a31501a0fb872b99216cbf3c991a621c1f3e6c;hpb=6c381e873e222417d9a67aeec77b9555eca7b7a8;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 31a3150..07a1094 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -1,36 +1,58 @@ % -% (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} -#include "HsVersions.h" - -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where - -import Ubiq - -import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat, - HsExpr, HsBinds, OutPat, Fake, - collectPatBinders, pprMatch ) -import RnHsSyn ( RenamedMatch(..) ) -import TcHsSyn ( TcIdOcc(..), TcMatch(..) ) +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + matchCtxt, TcMatchCtxt(..), + tcStmts, tcDoStmts, + tcDoStmt, tcMDoStmt, tcGuardStmt + ) where -import TcMonad -import Inst ( Inst, LIE(..), plusLIE ) -import TcEnv ( newMonoIds ) -import TcLoop ( tcGRHSsAndBinds ) -import TcPat ( tcPat ) -import TcType ( TcType(..), TcMaybe, zonkTcType ) -import Unify ( unifyTauTy, unifyTauTyList ) +#include "HsVersions.h" -import Kind ( Kind, mkTypeKind ) +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr ) + +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + pprMatch, isIrrefutableHsPat, mkHsCoerce, + pprMatchContext, pprStmtContext, + noSyntaxExpr, matchGroupArity, pprMatches, + ExprCoFn ) + +import TcRnMonad +import TcHsType ( tcPatSig, UserTypeCtxt(..) ) +import Inst ( newMethodFromName ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv2 ) +import TcPat ( PatCtxt(..), tcPats, tcPat ) +import TcMType ( newFlexiTyVarTy, newFlexiTyVarTys ) +import TcType ( TcType, TcRhoType, + BoxySigmaType, BoxyRhoType, + mkFunTys, mkFunTy, mkAppTy, mkTyConApp, + liftedTypeKind ) +import TcBinds ( tcLocalBinds ) +import TcUnify ( boxySplitAppTy, boxySplitTyConApp, boxySplitListTy, + subFunTys, tcSubExp, withBox ) +import TcSimplify ( bindInstsOfLocalFuns ) import Name ( Name ) -import Pretty -import Type ( isTyVarTy, mkFunTy, getFunTy_maybe ) -import Util +import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy ) +import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName ) +import Id ( idType, mkLocalId ) +import TyCon ( TyCon ) +import Outputable +import SrcLoc ( Located(..), getLoc ) +import ErrUtils ( Message ) \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 @@ -38,183 +60,456 @@ same number of arguments before using @tcMatches@ to do the work. \begin{code} tcMatchesFun :: Name - -> 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_` + -> MatchGroup Name + -> BoxyRhoType -- Expected type of function + -> TcM (ExprCoFn, 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... + 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 - -- 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. + ; subFunTys doc n_pats 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 + doc = ptext SLIT("The equation(s) for") <+> quotes (ppr fun_name) + <+> ptext SLIT("have") <+> speakNOf n_pats (ptext SLIT("argument")) + n_pats = matchGroupArity matches + match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcPolyExpr } \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 + -> BoxyRhoType -- Type of whole case expressions + -> TcM (MatchGroup TcId) -- Translated alternatives + +tcMatchesCase ctxt scrut_ty matches res_ty + = tcMatches ctxt [scrut_ty] res_ty matches + +tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (ExprCoFn, MatchGroup TcId) +tcMatchLambda match res_ty + = subFunTys 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 match), + -- The pprSetDepth makes the abstraction print briefly + ptext SLIT("has") <+> speakNOf n_pats (ptext SLIT("argument"))] + match_ctxt = MC { mc_what = LambdaExpr, + mc_body = tcPolyExpr } \end{code} +@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -data FunOrCase = MCase | MFun Name -- 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 -> BoxyRhoType -> TcM (GRHSs TcId) +tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty + where + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcPolyExpr } \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 (\ _ -> - 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 + -> [BoxySigmaType] -- Expected pattern types + -> BoxyRhoType -- 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 + -> BoxyRhoType + -> TcM (LHsExpr TcId) } + +tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) + = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches + ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) } + +------------- +tcMatch :: TcMatchCtxt + -> [BoxySigmaType] -- Expected pattern types + -> BoxyRhoType -- 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 + where + tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss) + = addErrCtxt (matchCtxt (mc_what ctxt) match) $ + do { (pats', grhss') <- tcPats LamPat pats pat_tys rhs_ty $ + tc_grhss ctxt maybe_rhs_sig grhss + ; 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 { (inner_ty, sig_tvs) <- tcPatSig ResSigCtxt res_sig rhs_ty + ; tcExtendTyVarEnv2 sig_tvs $ + tcGRHSs ctxt grhss inner_ty } + +------------- +tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId) + +-- Notice that we pass in the full res_ty, so that we get +-- good inference from simple things like +-- f = \(x::forall a.a->a) -> +-- We used to force it to be a monotype when there was more than one guard +-- but we don't need to do that any more + +tcGRHSs ctxt (GRHSs grhss binds) res_ty + = do { (binds', grhss') <- tcLocalBinds binds $ + mappM (wrapLocM (tcGRHS ctxt res_ty)) grhss + + ; returnM (GRHSs grhss' binds') } + +------------- +tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId) + +tcGRHS ctxt res_ty (GRHS guards rhs) + = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $ + mc_body ctxt rhs + ; return (GRHS guards' rhs') } + where + stmt_ctxt = PatGuard (mc_what ctxt) \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. +%************************************************************************ +%* * +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} +%* * +%************************************************************************ \begin{code} -noOfArgs :: [RenamedMatch] -> [Int] - -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 +tcDoStmts :: HsStmtContext Name + -> [LStmt Name] + -> LHsExpr Name + -> BoxyRhoType + -> TcM (HsExpr TcId) -- Returns a HsDo +tcDoStmts ListComp stmts body res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $ + tcBody (doBodyCtxt ListComp body) body + ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) } + +tcDoStmts PArrComp stmts body res_ty + = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty + ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $ + tcBody (doBodyCtxt PArrComp body) body + ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) } + +tcDoStmts DoExpr stmts body res_ty + = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty + ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty + ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty) stmts res_ty' $ + tcBody (doBodyCtxt DoExpr body) body + ; return (HsDo DoExpr stmts' body' res_ty') } + +tcDoStmts ctxt@(MDoExpr _) stmts body res_ty + = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty + ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty + tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty -> + tcMonoExpr rhs (mkAppTy m_ty pat_ty) + + ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $ + tcBody (doBodyCtxt ctxt body) body + + ; 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) + +tcBody :: Message -> LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId) +tcBody ctxt body res_ty + = -- addErrCtxt ctxt $ -- This context adds little that is useful + tcPolyExpr body res_ty \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{tcStmts} +%* * +%************************************************************************ \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 +type TcStmtChecker + = forall thing. HsStmtContext Name + -> Stmt Name + -> BoxyRhoType -- Result type for comprehension + -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt + -> TcM (Stmt TcId, thing) + + -- The incoming BoxyRhoType may be refined by type refinements + -- before being passed to the thing_inside + +tcStmts :: HsStmtContext Name + -> TcStmtChecker -- NB: higher-rank type + -> [LStmt Name] + -> BoxyRhoType + -> (BoxyRhoType -> 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 [] res_ty thing_inside + = do { thing <- thing_inside res_ty + ; return ([], thing) } + +-- LetStmts are handled uniformly, regardless of context +tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside + = do { (binds', (stmts',thing)) <- tcLocalBinds binds $ + tcStmts ctxt stmt_chk stmts res_ty thing_inside + ; return (L loc (LetStmt binds') : stmts', thing) } + +-- For the vanilla case, handle the location-setting part +tcStmts ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside + = do { (stmt', (stmts', thing)) <- + setSrcSpan loc $ + addErrCtxt (stmtCtxt ctxt stmt) $ + stmt_chk ctxt stmt res_ty $ \ res_ty' -> + popErrCtxt $ + tcStmts ctxt stmt_chk stmts res_ty' $ + thing_inside + ; return (L loc stmt' : stmts', thing) } + +-------------------------------- +-- Pattern guards +tcGuardStmt :: TcStmtChecker +tcGuardStmt ctxt (ExprStmt guard _ _) res_ty thing_inside + = do { guard' <- tcMonoExpr guard boolTy + ; thing <- thing_inside res_ty + ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) } + +tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { (rhs', rhs_ty) <- tcInferRho rhs + ; (pat', thing) <- tcPat LamPat pat rhs_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcGuardStmt ctxt stmt res_ty thing_inside + = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt) + + +-------------------------------- +-- List comprehensions and PArrays + +tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray) + -> TcStmtChecker + +-- A generator, pat <- rhs +tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty -> + tcMonoExpr rhs (mkTyConApp m_tc [ty]) + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +-- A boolean guard +tcLcStmt m_tc ctxt (ExprStmt rhs _ _) res_ty thing_inside + = do { rhs' <- tcMonoExpr rhs boolTy + ; thing <- thing_inside res_ty + ; 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 ctxt (ParStmt bndr_stmts_s) elt_ty 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 elt_ty -- No refinement from pattern + ; return ([], thing) } -- matching in the branches + + loop ((stmts, names) : pairs) + = do { (stmts', (ids, pairs', thing)) + <- tcStmts ctxt (tcLcStmt m_tc) stmts elt_ty $ \ elt_ty' -> + do { ids <- tcLookupLocalIds names + ; (pairs', thing) <- loop pairs + ; return (ids, pairs', thing) } + ; return ( (stmts', ids) : pairs', thing ) } + +tcLcStmt m_tc ctxt stmt elt_ty thing_inside + = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Do-notation +-- The main excitement here is dealing with rebindable syntax + +tcDoStmt :: TcType -- Monad type, m + -> TcStmtChecker + +tcDoStmt m_ty ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside + = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ pat_ty -> + tcMonoExpr rhs (mkAppTy m_ty pat_ty) + -- 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. + + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + + -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b + ; let bind_ty = mkFunTys [mkAppTy m_ty pat_ty, + mkFunTy pat_ty res_ty] res_ty + ; 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 ctxt (ExprStmt rhs then_op _) res_ty thing_inside + = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b + a_ty <- newFlexiTyVarTy 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' <- tcPolyExpr rhs rhs_ty + ; thing <- thing_inside res_ty + ; return (ExprStmt rhs' then_op' rhs_ty, thing) } + +tcDoStmt m_ty ctxt stmt res_ty thing_inside + = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Mdo-notation +-- The distinctive features here are +-- (a) RecStmts, and +-- (b) no rebindable syntax + +tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference + -> TcStmtChecker +tcMDoStmt tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside + = do { (rhs', pat_ty) <- tc_rhs rhs + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcMDoStmt tc_rhs ctxt (ExprStmt rhs then_op _) res_ty thing_inside + = do { (rhs', elt_ty) <- tc_rhs rhs + ; thing <- thing_inside res_ty + ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) } + +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 + ; later_ids <- tcLookupLocalIds laterNames + ; return (later_ids, rec_rets) } + + ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE (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 + + ; 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 + = 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 (idType poly_id) mono_ty + ; return (mkHsCoerce co_fn (HsVar poly_id)) } + +tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside + = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt) + \end{code} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ + +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same +number of args are used in each equation. + \begin{code} -matchCtxt MCase match sty - = ppHang (ppStr "In a \"case\" branch:") - 4 (pprMatch sty True{-is_case-} match) +checkArgs :: Name -> MatchGroup Name -> TcM () +checkArgs fun (MatchGroup (match1:matches) _) + | null bad_matches = return () + | otherwise + = failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+> + ptext SLIT("have different numbers of arguments"), + nest 2 (ppr (getLoc match1)), + nest 2 (ppr (getLoc (head bad_matches)))]) + where + n_args1 = args_in_match match1 + bad_matches = [m | m <- matches, args_in_match m /= n_args1] -matchCtxt (MFun fun) match sty - = ppHang (ppBesides [ppStr "In an equation for function ", ppr sty fun, ppChar ':']) - 4 (ppBesides [ppr sty fun, pprMatch sty False{-not case-} match]) + args_in_match :: LMatch Name -> Int + args_in_match (L _ (Match pats _ _)) = length pats \end{code} - \begin{code} -varyingArgsErr name matches sty - = ppSep [ppStr "Varying number of arguments for function", ppr sty name] +matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) + 4 (pprMatch ctxt match) + +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) \end{code}