X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=6f7c6956d8d5834c3b8c1b750a511827ec5530bb;hb=6a4854eaa266d994ebd0d471614a52b43dd329d9;hp=1eba8210bd3af8c0a977b3f466f6b073c3a380a4;hpb=12899612693163154531da3285ec99c1c8ca2226;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 1eba821..6f7c695 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -1,222 +1,581 @@ % -% (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 - -IMP_Ubiq() +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + matchCtxt, + tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig, + tcMatchPats, + TcStmtCtxt(..), TcMatchCtxt(..) + ) where -import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat, - HsExpr, HsBinds, OutPat, Fake, - collectPatBinders, pprMatch ) -import RnHsSyn ( SYN_IE(RenamedMatch), RnName{-instance Outputable-} ) -import TcHsSyn ( TcIdOcc(..), SYN_IE(TcMatch) ) - -import TcMonad hiding ( rnMtoTcM ) -import Inst ( Inst, SYN_IE(LIE), plusLIE ) -import TcEnv ( newMonoIds ) -IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds ) -import TcPat ( tcPat ) -import TcType ( SYN_IE(TcType), TcMaybe, zonkTcType ) -import Unify ( unifyTauTy, unifyTauTyList ) +#include "HsVersions.h" -import Kind ( Kind, mkTypeKind ) -import Pretty -import Type ( isTyVarTy, mkFunTy, getFunTy_maybe ) -import Util +import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho, tcMonoExpr ) + +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + ReboundNames, LPat, + pprMatch, isDoExpr, + pprMatchContext, pprStmtContext, pprStmtResultContext, + collectPatsBinders, glueBindsOnGRHSs + ) +import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) ) + +import TcRnMonad +import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) ) +import Inst ( tcSyntaxName, tcInstCall ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv ) +import TcPat ( PatCtxt(..), tcPats ) +import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType, isRigidType ) +import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys, + tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkTyConApp, + liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy ) +import TcBinds ( tcBindsAndThen ) +import TcUnify ( Expected(..), zapExpectedType, readExpectedType, + unifyTauTy, subFunTys, unifyListTy, unifyTyConApp, + checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen, + unifyAppTy ) +import Name ( Name ) +import TysWiredIn ( boolTy, parrTyCon, listTyCon ) +import Id ( idType, mkLocalId ) +import CoreFVs ( idFreeTyVars ) +import VarSet +import Util ( isSingleton, notNull ) +import Outputable +import SrcLoc ( Located(..), noLoc ) + +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 expected_ty match_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 pat_ty arg_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 expected_ty grhss_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 +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) = GRHS (map lift_stmt stmts) + + lift_stmt (L loc (ResultStmt e)) = L loc (ResultStmt (fmap (co_fn <$>) e)) + lift_stmt stmt = stmt + +------------- +tcGRHSs :: TcMatchCtxt -> GRHSs Name + -> Expected TcRhoType + -> TcM (GRHSs TcId) + + -- 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 [L loc2 (ResultStmt rhs)])] binds) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + mc_body ctxt rhs exp_ty `thenM` \ rhs' -> + returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] []) + +tcGRHSs ctxt (GRHSs grhss binds) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' -> + -- Even if there is only one guard, we zap the RHS type to + -- a monotype. Reason: it makes tcStmts much easier, + -- and even a one-armed guard has a notional second arm + let + stmt_ctxt = SC { sc_what = PatGuard (mc_what ctxt), + sc_rhs = tcInferRho, + sc_body = sc_body, + sc_ty = exp_ty' } + sc_body body = mc_body ctxt body (Check exp_ty') + + tc_grhs (GRHS guarded) + = tcStmts stmt_ctxt guarded `thenM` \ guarded' -> + returnM (GRHS guarded') 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) + mappM (wrapLocM tc_grhs) grhss `thenM` \ 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 +%************************************************************************ +%* * +\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 { do_refinement <- can_refine body_ty + ; (pats', ex_tvs, res) <- tcPats (LamPat do_refinement) pats tys thing_inside + ; tcCheckExistentialPat pats' ex_tvs tys body_ty + ; returnM (pats', res) } where - args_in_match :: RenamedMatch -> Int - args_in_match (GRHSMatch _) = 0 - args_in_match (PatMatch _ match) = 1 + args_in_match match + -- Do GADT refinement if we are doing checking (not inference) + -- and the body_ty is completely rigid + -- ToDo: explain why + can_refine (Infer _) = return False + can_refine (Check ty) = isRigidType ty + +tcCheckExistentialPat :: [LPat TcId] -- Patterns (just for error message) + -> [TcTyVar] -- Existentially quantified tyvars bound by pattern + -> [Expected TcSigmaType] -- Types of the patterns + -> Expected TcRhoType -- Type of the body of the match + -- Tyvars in either of these must not escape + -> TcM () + -- NB: we *must* pass "pats_tys" not just "body_ty" to tcCheckExistentialPat + -- For example, we must reject this program: + -- data C = forall a. C (a -> Int) + -- f (C g) x = g x + -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int). + +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] -> ReboundNames Name + -> TcRhoType -- To keep it simple, we don't have an "expected" type here + -> TcM ([LStmt TcId], ReboundNames TcId) +tcDoStmts PArrComp stmts method_names res_ty + = do { [elt_ty] <- unifyTyConApp parrTyCon res_ty + ; stmts' <- tcComprehension PArrComp parrTyCon elt_ty stmts + ; return (stmts', [{- unused -}]) } + +tcDoStmts ListComp stmts method_names res_ty + = unifyListTy res_ty ` thenM` \ elt_ty -> + tcComprehension ListComp listTyCon elt_ty stmts `thenM` \ stmts' -> + returnM (stmts', [{- unused -}]) + +tcDoStmts do_or_mdo stmts method_names res_ty + = newTyFlexiVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> + newTyFlexiVarTy liftedTypeKind `thenM` \ elt_ty -> + unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_` + let + ctxt = SC { sc_what = do_or_mdo, + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; rhs_elt_ty <- unifyAppTy m_ty rhs_ty + ; return (rhs', rhs_elt_ty) }, + sc_body = \ body -> tcCheckRho body res_ty, + sc_ty = res_ty } + in + tcStmts ctxt stmts `thenM` \ stmts' -> + + -- Build the then and zero methods in case we need them + -- It's important that "then" and "return" appear just once in the final LIE, + -- not only for typechecker efficiency, but also because otherwise during + -- simplification we end up with silly stuff like + -- then = case d of (t,r) -> t + -- then = then + -- where the second "then" sees that it already exists in the "available" stuff. + mapM (tcSyntaxName DoOrigin m_ty) method_names `thenM` \ methods -> + + returnM (stmts', methods) + +tcComprehension do_or_lc m_tycon elt_ty stmts + = tcStmts ctxt stmts + where + ctxt = SC { sc_what = do_or_lc, + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; [rhs_elt_ty] <- unifyTyConApp m_tycon rhs_ty + ; return (rhs', rhs_elt_ty) }, + sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no m_tycon here! + sc_ty = mkTyConApp m_tycon [elt_ty] } \end{code} -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} +%* * +%************************************************************************ + +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 <- ... ] + +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. + +\begin{code} +tcStmts ctxt stmts + = ASSERT( notNull stmts ) + tcStmtsAndThen (:) ctxt stmts (returnM []) + +data TcStmtCtxt + = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is + sc_rhs :: LHsExpr Name -> TcM (LHsExpr TcId, TcType), -- Type inference for RHS computations + sc_body :: LHsExpr Name -> TcM (LHsExpr TcId), -- Type checker for return computation + sc_ty :: TcType } -- Return type; used *only* to check + -- for escape in existential patterns + -- We use type *inference* for the RHS computations, becuase of GADTs. + -- do { pat <- rhs; } + -- is rather like + -- case rhs of { pat -> } + -- We do inference on rhs, so that information about its type can be refined + -- when type-checking the pattern. + +tcStmtsAndThen + :: (LStmt TcId -> thing -> thing) -- Combiner + -> TcStmtCtxt + -> [LStmt Name] + -> TcM thing + -> TcM thing + + -- Base case +tcStmtsAndThen combine ctxt [] thing_inside + = thing_inside + +tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside + = tcStmtAndThen combine ctxt stmt $ + tcStmtsAndThen combine ctxt stmts $ + thing_inside + + -- LetStmt +tcStmtAndThen combine ctxt (L _ (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 + binds + thing_inside + + -- BindStmt +tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside + = setSrcSpan src_loc $ + addErrCtxt (stmtCtxt ctxt stmt) $ + do { (exp', pat_ty) <- sc_rhs ctxt exp + ; ([pat'], thing) <- tcMatchPats [pat] [Check pat_ty] (Check (sc_ty ctxt)) $ + popErrCtxt thing_inside + ; return (combine (L src_loc (BindStmt pat' exp')) thing) } + + -- ExprStmt +tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside + = setSrcSpan src_loc ( + addErrCtxt (stmtCtxt ctxt stmt) $ + if isDoExpr (sc_what ctxt) + then -- do or mdo; the expression is a computation + sc_rhs ctxt exp `thenM` \ (exp', exp_ty) -> + returnM (L src_loc (ExprStmt exp' exp_ty)) + else -- List comprehensions, pattern guards; expression is a boolean + tcCheckRho exp boolTy `thenM` \ exp' -> + returnM (L src_loc (ExprStmt exp' boolTy)) + ) `thenM` \ stmt' -> + + thing_inside `thenM` \ thing -> + returnM (combine stmt' thing) + + + -- ParStmt +tcStmtAndThen combine ctxt (L src_loc (ParStmt bndr_stmts_s)) thing_inside + = loop bndr_stmts_s `thenM` \ (pairs', thing) -> + returnM (combine (L src_loc (ParStmt pairs')) thing) + where + loop [] = thing_inside `thenM` \ thing -> + returnM ([], thing) + + loop ((stmts, bndrs) : pairs) + = tcStmtsAndThen combine_par ctxt stmts $ + -- Notice we pass on ctxt; the result type is used only + -- to get escaping type variables for checkExistentialPat + tcLookupLocalIds bndrs `thenM` \ bndrs' -> + loop pairs `thenM` \ (pairs', thing) -> + returnM (([], bndrs') : pairs', thing) + + combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing) + + -- RecStmt +tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thing_inside +-- gaw 2004 + = newTyFlexiVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> + let + rec_ids = zipWith mkLocalId recNames recTys + in + tcExtendIdEnv rec_ids $ + tcStmtsAndThen combine_rec ctxt stmts ( + zipWithM tc_ret recNames recTys `thenM` \ rec_rets -> + tcLookupLocalIds laterNames `thenM` \ later_ids -> + returnM ([], (later_ids, rec_rets)) + ) `thenM` \ (stmts', (later_ids, rec_rets)) -> + + tcExtendIdEnv later_ids $ + -- NB: The rec_ids for the recursive things + -- already scope over this part + thing_inside `thenM` \ thing -> + + returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) thing) + where + combine_rec stmt (stmts, thing) = (stmt:stmts, thing) + + -- Unify the types of the "final" Ids with those of "knot-tied" Ids + tc_ret rec_name mono_ty + = 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 (L src_loc (co_fn <$> HsVar poly_id)) + + -- Result statements +tcStmtAndThen combine ctxt (L src_loc stmt@(ResultStmt exp)) thing_inside + = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' -> + thing_inside `thenM` \ thing -> + returnM (combine (L src_loc (ResultStmt exp')) thing) + + +------------------------------ +glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing + -- ToDo: fix the noLoc \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} +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 sty - = ppSep [ppStr "Varying number of arguments for function", ppr sty name] +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) + +stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) 4 (ppr stmt) + where + pp_ctxt = case stmt of + ResultStmt _ -> pprStmtResultContext + other -> pprStmtContext + +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}