X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsExpr.lhs;h=11fddf57af96ab769a95d37faad8e6243e42f94b;hp=6126b6302e2de99ab7412413674b40147e19536e;hb=fb6d198f498d4e325a540f28aaa6e1d1530839c3;hpb=6f547477aba779646caa7043d65825c59f10256b diff --git a/compiler/deSugar/DsExpr.lhs b/compiler/deSugar/DsExpr.lhs index 6126b63..11fddf5 100644 --- a/compiler/deSugar/DsExpr.lhs +++ b/compiler/deSugar/DsExpr.lhs @@ -29,7 +29,6 @@ import Name import NameEnv #ifdef GHCI -import PrelNames -- Template Haskell stuff iff bootstrapped import DsMeta #endif @@ -44,12 +43,15 @@ import Type import Coercion import CoreSyn import CoreUtils +import CoreFVs import MkCore import DynFlags import StaticFlags import CostCentre import Id +import Var +import VarSet import PrelInfo import DataCon import TysWiredIn @@ -61,6 +63,8 @@ import Util import Bag import Outputable import FastString + +import Control.Monad \end{code} @@ -207,7 +211,9 @@ dsExpr (HsVar var) = return (Var var) dsExpr (HsIPVar ip) = return (Var (ipNameName ip)) dsExpr (HsLit lit) = dsLit lit dsExpr (HsOverLit lit) = dsOverLit lit -dsExpr (HsWrap co_fn e) = dsCoercion co_fn (dsExpr e) +dsExpr (HsWrap co_fn e) = do { co_fn' <- dsCoercion co_fn + ; e' <- dsExpr e + ; return (co_fn' e') } dsExpr (NegApp expr neg_expr) = App <$> dsExpr neg_expr <*> dsLExpr expr @@ -216,7 +222,7 @@ dsExpr (HsLam a_Match) = uncurry mkLams <$> matchWrapper LambdaExpr a_Match dsExpr (HsApp fun arg) - = mkCoreApp <$> dsLExpr fun <*> dsLExpr arg + = mkCoreAppDs <$> dsLExpr fun <*> dsLExpr arg \end{code} Operator sections. At first it looks as if we can convert @@ -243,10 +249,10 @@ will sort it out. \begin{code} dsExpr (OpApp e1 op _ e2) = -- for the type of y, we need the type of op's 2nd argument - mkCoreApps <$> dsLExpr op <*> mapM dsLExpr [e1, e2] + mkCoreAppsDs <$> dsLExpr op <*> mapM dsLExpr [e1, e2] dsExpr (SectionL expr op) -- Desugar (e !) to ((!) e) - = mkCoreApp <$> dsLExpr op <*> dsLExpr expr + = mkCoreAppDs <$> dsLExpr op <*> dsLExpr expr -- dsLExpr (SectionR op expr) -- \ x -> op x expr dsExpr (SectionR op expr) = do @@ -258,7 +264,26 @@ dsExpr (SectionR op expr) = do x_id <- newSysLocalDs x_ty y_id <- newSysLocalDs y_ty return (bindNonRec y_id y_core $ - Lam x_id (mkCoreApps core_op [Var x_id, Var y_id])) + Lam x_id (mkCoreAppsDs core_op [Var x_id, Var y_id])) + +dsExpr (ExplicitTuple tup_args boxity) + = do { let go (lam_vars, args) (Missing ty) + -- For every missing expression, we need + -- another lambda in the desugaring. + = do { lam_var <- newSysLocalDs ty + ; return (lam_var : lam_vars, Var lam_var : args) } + go (lam_vars, args) (Present expr) + -- Expressions that are present don't generate + -- lambdas, just arguments. + = do { core_expr <- dsLExpr expr + ; return (lam_vars, core_expr : args) } + + ; (lam_vars, args) <- foldM go ([], []) (reverse tup_args) + -- The reverse is because foldM goes left-to-right + + ; return $ mkCoreLams lam_vars $ + mkConApp (tupleCon boxity (length tup_args)) + (map (Type . exprType) args ++ args) } dsExpr (HsSCC cc expr) = do mod_name <- getModuleDs @@ -273,7 +298,7 @@ dsExpr (HsCoreAnn fs expr) dsExpr (HsCase discrim matches@(MatchGroup _ rhs_ty)) | isEmptyMatchGroup matches -- A Core 'case' is always non-empty = -- So desugar empty HsCase to error call - mkErrorAppDs pAT_ERROR_ID (funResultTy rhs_ty) "case" + mkErrorAppDs pAT_ERROR_ID (funResultTy rhs_ty) (ptext (sLit "case")) | otherwise = do { core_discrim <- dsLExpr discrim @@ -334,11 +359,6 @@ dsExpr (ExplicitPArr ty xs) = do unary fn x = mkApps (Var fn) [Type ty, x] binary fn x y = mkApps (Var fn) [Type ty, x, y] -dsExpr (ExplicitTuple expr_list boxity) = do - core_exprs <- mapM dsLExpr expr_list - return (mkConApp (tupleCon boxity (length expr_list)) - (map (Type . exprType) core_exprs ++ core_exprs)) - dsExpr (ArithSeq expr (From from)) = App <$> dsExpr expr <*> dsLExpr from @@ -396,8 +416,8 @@ dsExpr (RecordCon (L _ data_con_id) con_expr rbinds) = do = case findField (rec_flds rbinds) lbl of (rhs:rhss) -> ASSERT( null rhss ) dsLExpr rhs - [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showSDoc (ppr lbl)) - unlabelled_bottom arg_ty = mkErrorAppDs rEC_CON_ERROR_ID arg_ty "" + [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (ppr lbl) + unlabelled_bottom arg_ty = mkErrorAppDs rEC_CON_ERROR_ID arg_ty empty labels = dataConFieldLabels (idDataCon data_con_id) -- The data_con_id is guaranteed to be the wrapper id of the constructor @@ -628,23 +648,30 @@ makes all list literals be generated via the simple route. \begin{code} - dsExplicitList :: PostTcType -> [LHsExpr Id] -> DsM CoreExpr -- See Note [Desugaring explicit lists] -dsExplicitList elt_ty xs = do - dflags <- getDOptsDs - xs' <- mapM dsLExpr xs - if opt_SimpleListLiterals || not (dopt Opt_EnableRewriteRules dflags) - then return $ mkListExpr elt_ty xs' - else mkBuildExpr elt_ty (mkSplitExplicitList (thisPackage dflags) xs') +dsExplicitList elt_ty xs + = do { dflags <- getDOptsDs + ; xs' <- mapM dsLExpr xs + ; let (dynamic_prefix, static_suffix) = spanTail is_static xs' + ; if opt_SimpleListLiterals -- -fsimple-list-literals + || not (dopt Opt_EnableRewriteRules dflags) -- Rewrite rules off + || null dynamic_prefix -- Avoid build (\c n. foldr c n xs)! + then return $ mkListExpr elt_ty xs' + else mkBuildExpr elt_ty (mkSplitExplicitList dynamic_prefix static_suffix) } where - mkSplitExplicitList this_package xs' (c, _) (n, n_ty) = do - let (dynamic_prefix, static_suffix) = spanTail (rhsIsStatic this_package) xs' - static_suffix' = mkListExpr elt_ty static_suffix - - folded_static_suffix <- mkFoldrExpr elt_ty n_ty (Var c) (Var n) static_suffix' - let build_body = foldr (App . App (Var c)) folded_static_suffix dynamic_prefix - return build_body + is_static :: CoreExpr -> Bool + is_static e = all is_static_var (varSetElems (exprFreeVars e)) + + is_static_var :: Var -> Bool + is_static_var v + | isId v = isExternalName (idName v) -- Top-level things are given external names + | otherwise = False -- Type variables + + mkSplitExplicitList prefix suffix (c, _) (n, n_ty) + = do { let suffix' = mkListExpr elt_ty suffix + ; folded_suffix <- mkFoldrExpr elt_ty n_ty (Var c) (Var n) suffix' + ; return (foldr (App . App (Var c)) folded_suffix prefix) } spanTail :: (a -> Bool) -> [a] -> ([a], [a]) spanTail f xs = (reverse rejected, reverse satisfying) @@ -661,34 +688,69 @@ dsDo :: [LStmt Id] -> Type -- Type of the whole expression -> DsM CoreExpr -dsDo stmts body _result_ty - = go (map unLoc stmts) +dsDo stmts body result_ty + = goL stmts where - go [] = dsLExpr body - - go (ExprStmt rhs then_expr _ : stmts) + -- result_ty must be of the form (m b) + (m_ty, _b_ty) = tcSplitAppTy result_ty + + goL [] = dsLExpr body + goL ((L loc stmt):lstmts) = putSrcSpanDs loc (go loc stmt lstmts) + + go _ (ExprStmt rhs then_expr _) stmts = do { rhs2 <- dsLExpr rhs - ; then_expr2 <- dsExpr then_expr - ; rest <- go stmts + ; case tcSplitAppTy_maybe (exprType rhs2) of + Just (container_ty, returning_ty) -> warnDiscardedDoBindings rhs container_ty returning_ty + _ -> return () + ; then_expr2 <- dsExpr then_expr + ; rest <- goL stmts ; return (mkApps then_expr2 [rhs2, rest]) } - go (LetStmt binds : stmts) - = do { rest <- go stmts + go _ (LetStmt binds) stmts + = do { rest <- goL stmts ; dsLocalBinds binds rest } - go (BindStmt pat rhs bind_op fail_op : stmts) - = - do { body <- go stmts - ; rhs' <- dsLExpr rhs - ; bind_op' <- dsExpr bind_op - ; var <- selectSimpleMatchVarL pat - ; let bind_ty = exprType bind_op' -- rhs -> (pat -> res1) -> res2 - res1_ty = funResultTy (funArgTy (funResultTy bind_ty)) - ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat - res1_ty (cantFailMatchResult body) - ; match_code <- handle_failure pat match fail_op - ; return (mkApps bind_op' [rhs', Lam var match_code]) } + go _ (BindStmt pat rhs bind_op fail_op) stmts + = do { body <- goL stmts + ; rhs' <- dsLExpr rhs + ; bind_op' <- dsExpr bind_op + ; var <- selectSimpleMatchVarL pat + ; let bind_ty = exprType bind_op' -- rhs -> (pat -> res1) -> res2 + res1_ty = funResultTy (funArgTy (funResultTy bind_ty)) + ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat + res1_ty (cantFailMatchResult body) + ; match_code <- handle_failure pat match fail_op + ; return (mkApps bind_op' [rhs', Lam var match_code]) } + go loc (RecStmt { recS_stmts = rec_stmts, recS_later_ids = later_ids + , recS_rec_ids = rec_ids, recS_ret_fn = return_op + , recS_mfix_fn = mfix_op, recS_bind_fn = bind_op + , recS_rec_rets = rec_rets, recS_dicts = binds }) stmts + = ASSERT( length rec_ids > 0 ) + goL (new_bind_stmt : let_stmt : stmts) + where + -- returnE <- dsExpr return_id + -- mfixE <- dsExpr mfix_id + new_bind_stmt = L loc $ BindStmt (mkLHsPatTup later_pats) mfix_app + bind_op + noSyntaxExpr -- Tuple cannot fail + + let_stmt = L loc $ LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] [])) + + tup_ids = rec_ids ++ filterOut (`elem` rec_ids) later_ids + rec_tup_pats = map nlVarPat tup_ids + later_pats = rec_tup_pats + rets = map noLoc rec_rets + + mfix_app = nlHsApp (noLoc mfix_op) mfix_arg + mfix_arg = noLoc $ HsLam (MatchGroup [mkSimpleMatch [mfix_pat] body] + (mkFunTy tup_ty body_ty)) + mfix_pat = noLoc $ LazyPat $ mkLHsPatTup rec_tup_pats + body = noLoc $ HsDo DoExpr rec_stmts return_app body_ty + return_app = nlHsApp (noLoc return_op) (mkLHsTupleExpr rets) + body_ty = mkAppTy m_ty tup_ty + tup_ty = mkBoxedTupleTy (map idType tup_ids) -- Deals with singleton case + -- In a do expression, pattern-match failure just calls -- the monadic 'fail' rather than throwing an exception handle_failure pat match fail_op @@ -719,8 +781,11 @@ dsMDo :: PostTcTable -> DsM CoreExpr dsMDo tbl stmts body result_ty - = go (map unLoc stmts) + = goL stmts where + goL [] = dsLExpr body + goL ((L loc stmt):lstmts) = putSrcSpanDs loc (go loc stmt lstmts) + (m_ty, b_ty) = tcSplitAppTy result_ty -- result_ty must be of the form (m b) mfix_id = lookupEvidence tbl mfixName return_id = lookupEvidence tbl returnMName @@ -729,19 +794,18 @@ dsMDo tbl stmts body result_ty fail_id = lookupEvidence tbl failMName ctxt = MDoExpr tbl - go [] = dsLExpr body - - go (LetStmt binds : stmts) - = do { rest <- go stmts + go _ (LetStmt binds) stmts + = do { rest <- goL stmts ; dsLocalBinds binds rest } - go (ExprStmt rhs _ rhs_ty : stmts) + go _ (ExprStmt rhs _ rhs_ty) stmts = do { rhs2 <- dsLExpr rhs - ; rest <- go stmts + ; warnDiscardedDoBindings rhs m_ty rhs_ty + ; rest <- goL stmts ; return (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) } - go (BindStmt pat rhs _ _ : stmts) - = do { body <- go stmts + go _ (BindStmt pat rhs _ _) stmts + = do { body <- goL stmts ; var <- selectSimpleMatchVarL pat ; match <- matchSinglePat (Var var) (StmtCtxt ctxt) pat result_ty (cantFailMatchResult body) @@ -753,13 +817,14 @@ dsMDo tbl stmts body result_ty ; return (mkApps (Var bind_id) [Type (hsLPatType pat), Type b_ty, rhs', Lam var match_code]) } - go (RecStmt rec_stmts later_ids rec_ids rec_rets binds : stmts) + go loc (RecStmt rec_stmts later_ids rec_ids _ _ _ rec_rets binds) stmts = ASSERT( length rec_ids > 0 ) ASSERT( length rec_ids == length rec_rets ) - go (new_bind_stmt : let_stmt : stmts) + pprTrace "dsMDo" (ppr later_ids) $ + goL (new_bind_stmt : let_stmt : stmts) where - new_bind_stmt = mkBindStmt (mk_tup_pat later_pats) mfix_app - let_stmt = LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] [])) + new_bind_stmt = L loc $ mkBindStmt (mk_tup_pat later_pats) mfix_app + let_stmt = L loc $ LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] [])) -- Remove the later_ids that appear (without fancy coercions) @@ -782,11 +847,10 @@ dsMDo tbl stmts body result_ty mfix_pat = noLoc $ LazyPat $ mk_tup_pat rec_tup_pats body = noLoc $ HsDo ctxt rec_stmts return_app body_ty body_ty = mkAppTy m_ty tup_ty - tup_ty = mkCoreTupTy (map idType (later_ids' ++ rec_ids)) - -- mkCoreTupTy deals with singleton case + tup_ty = mkBoxedTupleTy (map idType (later_ids' ++ rec_ids)) -- Deals with singleton case return_app = nlHsApp (nlHsTyApp return_id [tup_ty]) - (mk_ret_tup rets) + (mkLHsTupleExpr rets) mk_wild_pat :: Id -> LPat Id mk_wild_pat v = noLoc $ WildPat $ idType v @@ -798,8 +862,41 @@ dsMDo tbl stmts body result_ty mk_tup_pat :: [LPat Id] -> LPat Id mk_tup_pat [p] = p mk_tup_pat ps = noLoc $ mkVanillaTuplePat ps Boxed +\end{code} + - mk_ret_tup :: [LHsExpr Id] -> LHsExpr Id - mk_ret_tup [r] = r - mk_ret_tup rs = noLoc $ ExplicitTuple rs Boxed +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +\begin{code} +-- Warn about certain types of values discarded in monadic bindings (#3263) +warnDiscardedDoBindings :: LHsExpr Id -> Type -> Type -> DsM () +warnDiscardedDoBindings rhs container_ty returning_ty = do { + -- Warn about discarding non-() things in 'monadic' binding + ; warn_unused <- doptDs Opt_WarnUnusedDoBind + ; if warn_unused && not (returning_ty `tcEqType` unitTy) + then warnDs (unusedMonadBind rhs returning_ty) + else do { + -- Warn about discarding m a things in 'monadic' binding of the same type, + -- but only if we didn't already warn due to Opt_WarnUnusedDoBind + ; warn_wrong <- doptDs Opt_WarnWrongDoBind + ; case tcSplitAppTy_maybe returning_ty of + Just (returning_container_ty, _) -> when (warn_wrong && container_ty `tcEqType` returning_container_ty) $ + warnDs (wrongMonadBind rhs returning_ty) + _ -> return () } } + +unusedMonadBind :: LHsExpr Id -> Type -> SDoc +unusedMonadBind rhs returning_ty + = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr returning_ty <> dot $$ + ptext (sLit "Suppress this warning by saying \"_ <- ") <> ppr rhs <> ptext (sLit "\",") $$ + ptext (sLit "or by using the flag -fno-warn-unused-do-bind") + +wrongMonadBind :: LHsExpr Id -> Type -> SDoc +wrongMonadBind rhs returning_ty + = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr returning_ty <> dot $$ + ptext (sLit "Suppress this warning by saying \"_ <- ") <> ppr rhs <> ptext (sLit "\",") $$ + ptext (sLit "or by using the flag -fno-warn-wrong-do-bind") \end{code}