X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=51723ec0d2f88a3fec78b4383acf53f737913397;hb=05446f0f1e826cd95c8bbcc355015a02ec8595ca;hp=6be207626fcb4df302c8000dd652144088af1a0e;hpb=438596897ebbe25a07e1c82085cfbc5bdb00f09e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 6be2076..51723ec 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,214 +4,412 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchExpected ) where +module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where #include "HsVersions.h" -import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds ) +import {-# SOURCE #-} TcExpr( tcExpr ) -import HsSyn ( HsBinds(..), Match(..), GRHSsAndBinds(..), - MonoBinds(..), StmtCtxt(..), - pprMatch, getMatchLoc +import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), + MonoBinds(..), StmtCtxt(..), Stmt(..), + pprMatch, getMatchLoc, consLetStmt, + mkMonoBind, collectSigTysFromPats ) -import RnHsSyn ( RenamedMatch ) -import TcHsSyn ( TcMatch ) +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt ) import TcMonad -import TcMonoType ( checkSigTyVars, noSigs, existentialPatCtxt ) -import Inst ( Inst, LIE, plusLIE, emptyLIE ) -import TcEnv ( tcExtendEnvWithPat, tcExtendGlobalTyVars ) -import TcPat ( tcPat ) +import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt ) +import Inst ( LIE, plusLIE, emptyLIE, plusLIEs ) +import TcEnv ( tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars ) +import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig ) import TcType ( TcType, newTyVarTy ) +import TcBinds ( tcBindsAndThen ) import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcUnify ( unifyFunTy ) +import TcUnify ( unifyFunTy, unifyTauTy ) import Name ( Name ) +import TysWiredIn ( boolTy ) import BasicTypes ( RecFlag(..) ) -import Type ( Kind, tyVarsOfType, isTauTy, mkFunTy, openTypeKind ) +import Type ( tyVarsOfType, isTauTy, mkFunTy, boxedTypeKind, openTypeKind ) import VarSet -import Util +import Var ( Id ) import Bag import Outputable -import SrcLoc (SrcLoc) +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 :: Name - -> TcType s -- Expected type +tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group + -> Name + -> TcType -- Expected type -> [RenamedMatch] - -> TcM s ([TcMatch s], LIE s) + -> TcM ([TcMatch], LIE) -tcMatchesFun fun_name expected_ty matches@(first_match:_) - = -- Set the location to that of the first equation, so that +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) ( - - -- Check that they all have the same no of arguments - checkTc (all_same (noOfArgs matches)) - (varyingArgsErr fun_name matches) `thenTc_` + checkTc (sameNoOfArgs matches) + (varyingArgsErr fun_name matches) + ) `thenTc_` -- 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 - tcMatchesExpected matches expected_ty (FunRhs fun_name) - - ) - where - all_same :: [Int] -> Bool - all_same [] = True -- Should never happen (ToDo: panic?) - all_same [x] = True - all_same (x:xs) = all ((==) x) xs + tcMatches xve matches expected_ty (FunRhs fun_name) \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 -- Type of whole case expressions - -> [RenamedMatch] -- The case alternatives - -> TcM s (TcType s, -- Inferred type of the scrutinee - [TcMatch s], -- Translated alternatives - LIE s) +tcMatchesCase :: [RenamedMatch] -- The case alternatives + -> TcType -- Type of whole case expressions + -> TcM (TcType, -- Inferred type of the scrutinee + [TcMatch], -- Translated alternatives + LIE) -tcMatchesCase expr_ty matches +tcMatchesCase matches expr_ty = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty -> - tcMatchesExpected matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) -> + tcMatches [] matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) -> returnTc (scrut_ty, matches', lie) + +tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE) +tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody \end{code} \begin{code} -tcMatchesExpected :: [RenamedMatch] - -> TcType s - -> StmtCtxt - -> TcM s ([TcMatch s], LIE s) - -tcMatchesExpected [match] expected_ty fun_or_case - = tcAddSrcLoc (getMatchLoc match) $ - tcAddErrCtxt (matchCtxt fun_or_case match) $ - tcMatchExpected match expected_ty fun_or_case `thenTc` \ (match', lie) -> - returnTc ([match'], lie) - -tcMatchesExpected (match1 : matches) expected_ty fun_or_case - = tcAddSrcLoc (getMatchLoc match1) ( - tcAddErrCtxt (matchCtxt fun_or_case match1) $ - tcMatchExpected match1 expected_ty fun_or_case - ) `thenTc` \ (match1', lie1) -> - tcMatchesExpected matches expected_ty fun_or_case `thenTc` \ (matches', lie2) -> - returnTc (match1' : matches', plusLIE lie1 lie2) +tcMatches :: [(Name,Id)] + -> [RenamedMatch] + -> TcType + -> StmtCtxt + -> TcM ([TcMatch], LIE) + +tcMatches xve matches expected_ty fun_or_case + = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> + returnTc (matches, plusLIEs lies) + where + tc_match match = tcMatch xve match expected_ty fun_or_case \end{code} + +%************************************************************************ +%* * +\subsection{tcMatch} +%* * +%************************************************************************ + \begin{code} -tcMatchExpected - :: RenamedMatch - -> TcType s -- Expected result-type of the Match. +tcMatch :: [(Name,Id)] + -> RenamedMatch + -> TcType -- Expected result-type of the Match. -- Early unification with this guy gives better error messages -> StmtCtxt - -> TcM s (TcMatch s,LIE s) + -> TcM (TcMatch, LIE) -tcMatchExpected match expected_ty ctxt - = tcMatchExpected_help emptyBag emptyBag emptyLIE match expected_ty ctxt +tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt + = tcAddSrcLoc (getMatchLoc match) $ + tcAddErrCtxt (matchCtxt ctxt match) $ + if null sig_tvs then -- The common case + tc_match expected_ty `thenTc` \ (_, match_and_lie) -> + returnTc match_and_lie -tcMatchExpected_help bound_tvs bound_ids bound_lie - the_match@(PatMatch pat match) expected_ty ctxt - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> + else + -- If there are sig tvs we must be careful *not* to use + -- expected_ty right away, else we'll unify with tyvars free + -- in the envt. So invent a fresh tyvar and use that instead + newTyVarTy openTypeKind `thenNF_Tc` \ tyvar_ty -> - tcPat noSigs pat arg_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail_lie) -> + -- Extend the tyvar env and check the match itself + tcTyVars sig_tvs (mapTc_ kcHsSigType sig_tys) `thenTc` \ sig_tyvars -> + tcExtendTyVarEnv sig_tyvars (tc_match tyvar_ty) `thenTc` \ (pat_ids, match_and_lie) -> - tcMatchExpected_help - (bound_tvs `unionBags` pat_tvs) - (bound_ids `unionBags` pat_ids) - (bound_lie `plusLIE` avail_lie) - match rest_ty ctxt `thenTc` \ (match', lie_match) -> + -- Check that the scoped type variables from the patterns + -- have not been constrained + tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) ( + checkSigTyVars sig_tyvars emptyVarSet + ) `thenTc_` - returnTc (PatMatch pat' match', pat_lie `plusLIE` lie_match) + -- *Now* we're free to unify with expected_ty + unifyTauTy expected_ty tyvar_ty `thenTc_` + returnTc match_and_lie -tcMatchExpected_help bound_tvs bound_ids bound_lie - (GRHSMatch grhss_and_binds) expected_ty ctxt - = -- Check that the remaining "expected type" is not a rank-2 type + where + sig_tys = case maybe_rhs_sig of { Just t -> [t]; Nothing -> [] } + ++ collectSigTysFromPats pats + + tc_match expected_ty -- Any sig tyvars are in scope by now + = -- STEP 1: Typecheck the patterns + tcMatchPats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> + let + xve2 = bagToList pat_bndrs + pat_ids = map snd xve2 + ex_tv_list = bagToList ex_tvs + in + + -- STEP 2: 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 expected_ty) - lurkingRank2SigErr `thenTc_` + checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc_` + + -- STEP 3: Unify with the rhs type signature if any + (case maybe_rhs_sig of + Nothing -> returnTc () + Just sig -> tcHsSigType 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 rhs_ty sig_ty + ) `thenTc_` + + -- STEP 4: Typecheck the guarded RHSs and the associated where clause + tcExtendLocalValEnv xve1 (tcExtendLocalValEnv xve2 ( + tcGRHSs grhss rhs_ty ctxt + )) `thenTc` \ (grhss', lie_req2) -> + + -- STEP 5: Check for existentially bound type variables + tcExtendGlobalTyVars (tyVarsOfType rhs_ty) ( + tcAddErrCtxtM (sigPatCtxt ex_tv_list pat_ids) $ + checkSigTyVars ex_tv_list emptyVarSet `thenTc` \ zonked_ex_tvs -> + tcSimplifyAndCheck + (text ("the existential context of a data constructor")) + (mkVarSet zonked_ex_tvs) + lie_avail (lie_req1 `plusLIE` lie_req2) + ) `thenTc` \ (lie_req', ex_binds) -> + + -- STEP 6 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' pat_ids `thenTc` \ (lie_req'', inst_binds) -> - tcExtendEnvWithPat bound_ids ( - tcGRHSsAndBinds grhss_and_binds expected_ty ctxt - ) `thenTc` \ (GRHSsAndBindsOut grhss binds ty, lie) -> + -- Phew! All done. + let + grhss'' = glue_on Recursive ex_binds $ + glue_on Recursive inst_binds grhss' + in + returnTc (pat_ids, (Match [] pats' Nothing grhss'', lie_req'')) + -- 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 - -- Check for existentially bound type variables - tcExtendGlobalTyVars (tyVarsOfType expected_ty) ( - tcAddErrCtxtM (existentialPatCtxt bound_tvs bound_ids) $ - checkSigTyVars (bagToList bound_tvs) `thenTc` \ zonked_pat_tvs -> - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_pat_tvs) - bound_lie lie - ) `thenTc` \ (ex_lie, ex_binds) -> +tcGRHSs :: RenamedGRHSs + -> TcType -> StmtCtxt + -> TcM (TcGRHSs, LIE) + +tcGRHSs (GRHSs grhss binds _) expected_ty ctxt + = tcBindsAndThen glue_on binds (tc_grhss grhss) + where + tc_grhss grhss + = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> + returnTc (GRHSs grhss' EmptyBinds (Just expected_ty), plusLIEs lies) + + tc_grhs (GRHS guarded locn) + = tcAddSrcLoc locn $ + tcStmts ctxt (\ty -> ty) guarded expected_ty `thenTc` \ (guarded', lie) -> + returnTc (GRHS guarded' locn, lie) +\end{code} + + +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ + +\begin{code} +tcMatchPats [] expected_ty + = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) + +tcMatchPats (pat:pats) expected_ty + = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> + tcPat tcPatBndr_NoSigs pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> + tcMatchPats 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 + ) +\end{code} - -- 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 ex_lie bound_id_list `thenTc` \ (inst_lie, inst_binds) -> +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ + + +\begin{code} +tcStmts :: StmtCtxt + -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs + -> [RenamedStmt] + -> TcType -- elt_ty, where type of the comprehension is (m elt_ty) + -> TcM ([TcStmt], LIE) + +tcStmts do_or_lc m (stmt@(ReturnStmt exp) : stmts) elt_ty + = ASSERT( null stmts ) + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) -> + returnTc ([ReturnStmt exp'], exp_lie) + + -- ExprStmt at the end +tcStmts do_or_lc m [stmt@(ExprStmt exp src_loc)] elt_ty + = tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + tcExpr exp (m elt_ty) `thenTc` \ (exp', exp_lie) -> + returnTc ([ExprStmt exp' src_loc], exp_lie) + + -- ExprStmt not at the end +tcStmts do_or_lc m (stmt@(ExprStmt exp src_loc) : stmts) elt_ty + = ASSERT( isDoStmt do_or_lc ) + tcAddSrcLoc src_loc ( + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + -- exp has type (m tau) for some tau (doesn't matter what) + newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> + tcExpr exp (m any_ty) + ) `thenTc` \ (exp', exp_lie) -> + tcStmts do_or_lc m stmts elt_ty `thenTc` \ (stmts', stmts_lie) -> + returnTc (ExprStmt exp' src_loc : stmts', + exp_lie `plusLIE` stmts_lie) + +tcStmts do_or_lc m (stmt@(GuardStmt exp src_loc) : stmts) elt_ty + = ASSERT( not (isDoStmt do_or_lc) ) + tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + tcAddSrcLoc src_loc $ + tcExpr exp boolTy + ) `thenTc` \ (exp', exp_lie) -> + tcStmts do_or_lc m stmts elt_ty `thenTc` \ (stmts', stmts_lie) -> + returnTc (GuardStmt exp' src_loc : stmts', + exp_lie `plusLIE` stmts_lie) + +tcStmts do_or_lc m (stmt@(BindStmt pat exp src_loc) : stmts) elt_ty + = tcAddSrcLoc src_loc ( + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + newTyVarTy boxedTypeKind `thenNF_Tc` \ pat_ty -> + tcPat tcPatBndr_NoSigs pat pat_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail) -> + tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> + returnTc (pat', exp', + pat_lie `plusLIE` exp_lie, + pat_tvs, pat_ids, avail) + ) `thenTc` \ (pat', exp', lie_req, pat_tvs, pat_bndrs, lie_avail) -> let - binds' = ex_binds `glue_on` (inst_binds `glue_on` binds) + new_val_env = bagToList pat_bndrs + pat_ids = map snd new_val_env + pat_tv_list = bagToList pat_tvs in - returnTc (GRHSMatch (GRHSsAndBindsOut grhss binds' ty), inst_lie) - where - bound_id_list = map snd (bagToList bound_ids) - -- glue_on just avoids stupid dross - glue_on EmptyMonoBinds binds = binds -- The common case - glue_on mbinds binds = MonoBind mbinds [] Recursive `ThenBinds` binds + -- Do the rest; we don't need to add the pat_tvs to the envt + -- because they all appear in the pat_ids's types + tcExtendLocalValEnv new_val_env ( + tcStmts do_or_lc m stmts elt_ty + ) `thenTc` \ (stmts', stmts_lie) -> + + + -- Reinstate context for existential checks + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $ + tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $ + + checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs -> + + tcSimplifyAndCheck + (text ("the existential context of a data constructor")) + (mkVarSet zonked_pat_tvs) + lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) -> + + returnTc (BindStmt pat' exp' src_loc : + consLetStmt (mkMonoBind dict_binds [] Recursive) stmts', + lie_req `plusLIE` final_lie) + +tcStmts do_or_lc m (LetStmt binds : stmts) elt_ty + = tcBindsAndThen -- No error context, but a binding group is + combine -- rather a large thing for an error context anyway + binds + (tcStmts do_or_lc m stmts elt_ty) + where + combine is_rec binds' stmts' = consLetStmt (mkMonoBind binds' [] is_rec) stmts' + + +isDoStmt DoStmt = True +isDoStmt other = False \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{Errors and contexts} +%* * +%************************************************************************ -\begin{code} -noOfArgs :: [RenamedMatch] -> [Int] +@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same +number of args are used in each equation. -noOfArgs ms = map args_in_match ms +\begin{code} +sameNoOfArgs :: [RenamedMatch] -> Bool +sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1 where args_in_match :: RenamedMatch -> Int - args_in_match (GRHSMatch _) = 0 - args_in_match (PatMatch _ match) = 1 + args_in_match match + args_in_match (Match _ pats _ _) = length pats \end{code} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ \begin{code} matchCtxt CaseAlt match - = hang (ptext SLIT("In a \"case\" branch:")) - 4 (pprMatch True{-is_case-} match) + = hang (ptext SLIT("In a case alternative:")) + 4 (pprMatch (True,empty) {-is_case-} match) matchCtxt (FunRhs fun) match - = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr fun), char ':']) - 4 (hcat [ppr fun, space, pprMatch False{-not case-} match]) -\end{code} + = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr_fun), char ':']) + 4 (pprMatch (False, ppr_fun) {-not case-} match) + where + ppr_fun = ppr fun +matchCtxt LambdaBody match + = hang (ptext SLIT("In the lambda expression")) + 4 (pprMatch (True, empty) match) -\begin{code} 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") + +stmtCtxt do_or_lc stmt + = hang (ptext SLIT("In") <+> what <> colon) + 4 (ppr stmt) + where + what = case do_or_lc of + ListComp -> ptext SLIT("a list-comprehension qualifier") + DoStmt -> ptext SLIT("a do statement") + PatBindRhs -> thing <+> ptext SLIT("a pattern binding") + FunRhs f -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f) + CaseAlt -> thing <+> ptext SLIT("a case alternative") + LambdaBody -> thing <+> ptext SLIT("a lambda abstraction") + thing = case stmt of + BindStmt _ _ _ -> ptext SLIT("a pattern guard for") + GuardStmt _ _ -> ptext SLIT("a guard for") + ExprStmt _ _ -> ptext SLIT("the right-hand side of") \end{code}