X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FdeSugar%2FDsExpr.lhs;h=820bd9ac3e6ba051a7f7cf93ec2e578c95c4fe93;hb=86db518e34d94c2c3ecc35d0695fec10a8067464;hp=509cce23b6e710c4a25a7f0bbf401394d3cf7da1;hpb=79b22beb4d2eca1877d99d55838ba6ce69658405;p=ghc-hetmet.git diff --git a/compiler/deSugar/DsExpr.lhs b/compiler/deSugar/DsExpr.lhs index 509cce2..820bd9a 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 @@ -61,6 +60,8 @@ import Util import Bag import Outputable import FastString + +import Control.Monad \end{code} @@ -216,7 +217,7 @@ dsExpr (HsLam a_Match) = uncurry mkLams <$> matchWrapper LambdaExpr a_Match dsExpr (HsApp fun arg) - = mkCoreApp <$> dsLExpr fun <*> dsLExpr arg + = mkCoreAppDs <$> dsLExpr fun <*> dsLExpr arg \end{code} Operator sections. At first it looks as if we can convert @@ -243,10 +244,10 @@ will sort it out. \begin{code} dsExpr (OpApp e1 op _ e2) = -- for the type of y, we need the type of op's 2nd argument - mkCoreApps <$> 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 +259,26 @@ 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 @@ -334,11 +354,6 @@ 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 @@ -662,23 +677,27 @@ dsDo :: [LStmt Id] -> DsM CoreExpr dsDo stmts body _result_ty - = go (map unLoc stmts) + = goL stmts where - go [] = dsLExpr body - - go (ExprStmt rhs then_expr _ : stmts) + goL [] = dsLExpr body + goL ((L loc stmt):lstmts) = putSrcSpanDs loc (go 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) + go (BindStmt pat rhs bind_op fail_op) stmts = - do { body <- go stmts + do { body <- goL stmts ; rhs' <- dsLExpr rhs ; bind_op' <- dsExpr bind_op ; var <- selectSimpleMatchVarL pat @@ -719,8 +738,11 @@ 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 +751,18 @@ 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 +774,13 @@ 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) + 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) @@ -786,7 +807,7 @@ dsMDo tbl stmts body result_ty -- mkCoreTupTy 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 +819,41 @@ 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}