X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsListComp.lhs;h=166bfc244c54ec31ab5f0fa9fd7d444cf773c04d;hp=f4ab7b3d9ce37e373c5e83181afc882333e14efc;hb=7fc01c4671980ea3c66d549c0ece4d82fd3f5ade;hpb=67cb409159fa9136dff942b8baaec25909416022 diff --git a/compiler/deSugar/DsListComp.lhs b/compiler/deSugar/DsListComp.lhs index f4ab7b3..166bfc2 100644 --- a/compiler/deSugar/DsListComp.lhs +++ b/compiler/deSugar/DsListComp.lhs @@ -6,7 +6,7 @@ Desugaring list comprehensions and array comprehensions \begin{code} -{-# OPTIONS -w #-} +{-# OPTIONS -fno-warn-incomplete-patterns #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and fix -- any warnings in the module. See @@ -19,28 +19,24 @@ module DsListComp ( dsListComp, dsPArrComp ) where import {-# SOURCE #-} DsExpr ( dsLExpr, dsLocalBinds ) -import BasicTypes import HsSyn import TcHsSyn import CoreSyn +import MkCore import DsMonad -- the monadery used in the desugarer import DsUtils import DynFlags import CoreUtils -import Var +import Id import Type -import TysPrim import TysWiredIn import Match import PrelNames -import PrelInfo import SrcLoc -import Panic import Outputable - -import Control.Monad ( liftM2 ) +import FastString \end{code} List comprehensions may be desugared in one of two ways: ``ordinary'' @@ -58,24 +54,16 @@ dsListComp lquals body elt_ty = do dflags <- getDOptsDs let quals = map unLoc lquals - if not (dopt Opt_RewriteRules dflags) || dopt Opt_IgnoreInterfacePragmas dflags + if not (dopt Opt_EnableRewriteRules dflags) || dopt Opt_IgnoreInterfacePragmas dflags -- Either rules are switched off, or we are ignoring what there are; -- Either way foldr/build won't happen, so use the more efficient -- Wadler-style desugaring || isParallelComp quals -- Foldr-style desugaring can't handle parallel list comprehensions then deListComp quals body (mkNilExpr elt_ty) - else do -- Foldr/build should be enabled, so desugar - -- into foldrs and builds - [n_tyvar] <- newTyVarsDs [alphaTyVar] - - let n_ty = mkTyVarTy n_tyvar - c_ty = mkFunTys [elt_ty, n_ty] n_ty - [c, n] <- newSysLocalsDs [c_ty, n_ty] - - result <- dfListComp c n quals body - build_id <- dsLookupGlobalId buildName - returnDs (Var build_id `App` Type elt_ty `App` mkLams [n_tyvar, c, n] result) + else mkBuildExpr elt_ty (\(c, _) (n, _) -> dfListComp c n quals body) + -- Foldr/build should be enabled, so desugar + -- into foldrs and builds where -- We must test for ParStmt anywhere, not just at the head, because an extension @@ -104,7 +92,7 @@ dsInnerListComp (stmts, bndrs) = do -- Given such a statement it gives you back an expression representing how to compute the transformed -- list and the tuple that you need to bind from that list in order to proceed with your desugaring dsTransformStmt :: Stmt Id -> DsM (CoreExpr, LPat Id) -dsTransformStmt (TransformStmt (stmts, binders) usingExpr maybeByExpr) = do +dsTransformStmt (TransformStmt stmts binders usingExpr maybeByExpr) = do (expr, binders_tuple_type) <- dsInnerListComp (stmts, binders) usingExpr' <- dsLExpr usingExpr @@ -129,7 +117,7 @@ dsTransformStmt (TransformStmt (stmts, binders) usingExpr maybeByExpr) = do -- Given such a statement it gives you back an expression representing how to compute the transformed -- list and the tuple that you need to bind from that list in order to proceed with your desugaring dsGroupStmt :: Stmt Id -> DsM (CoreExpr, LPat Id) -dsGroupStmt (GroupStmt (stmts, binderMap) groupByClause) = do +dsGroupStmt (GroupStmt stmts binderMap by using) = do let (fromBinders, toBinders) = unzip binderMap fromBindersTypes = map idType fromBinders @@ -138,23 +126,19 @@ dsGroupStmt (GroupStmt (stmts, binderMap) groupByClause) = do toBindersTupleType = mkBigCoreTupTy toBindersTypes -- Desugar an inner comprehension which outputs a list of tuples of the "from" binders - (expr, fromBindersTupleType) <- dsInnerListComp (stmts, fromBinders) + (expr, from_tup_ty) <- dsInnerListComp (stmts, fromBinders) -- Work out what arguments should be supplied to that expression: i.e. is an extraction -- function required? If so, create that desugared function and add to arguments - (usingExpr', usingArgs) <- - case groupByClause of - GroupByNothing usingExpr -> liftM2 (,) (dsLExpr usingExpr) (return [expr]) - GroupBySomething usingExpr byExpr -> do - usingExpr' <- dsLExpr (either id noLoc usingExpr) - - byExpr' <- dsLExpr byExpr - - us <- newUniqueSupply - [fromBindersTuple] <- newSysLocalsDs [fromBindersTupleType] - let byExprWrapper = mkTupleCase us fromBinders byExpr' fromBindersTuple (Var fromBindersTuple) - - return (usingExpr', [Lam fromBindersTuple byExprWrapper, expr]) + usingExpr' <- dsLExpr (either id noLoc using) + usingArgs <- case by of + Nothing -> return [expr] + Just by_e -> do { by_e' <- dsLExpr by_e + ; us <- newUniqueSupply + ; [from_tup_id] <- newSysLocalsDs [from_tup_ty] + ; let by_wrap = mkTupleCase us fromBinders by_e' + from_tup_id (Var from_tup_id) + ; return [Lam from_tup_id by_wrap, expr] } -- Create an unzip function for the appropriate arity and element types and find "map" (unzip_fn, unzip_rhs) <- mkUnzipBind fromBindersTypes @@ -162,12 +146,12 @@ dsGroupStmt (GroupStmt (stmts, binderMap) groupByClause) = do -- Generate the expressions to build the grouped list let -- First we apply the grouping function to the inner list - inner_list_expr = mkApps usingExpr' ((Type fromBindersTupleType) : usingArgs) + inner_list_expr = mkApps usingExpr' ((Type from_tup_ty) : usingArgs) -- Then we map our "unzip" across it to turn the lists of tuples into tuples of lists -- We make sure we instantiate the type variable "a" to be a list of "from" tuples and -- the "b" to be a tuple of "to" lists! unzipped_inner_list_expr = mkApps (Var map_id) - [Type (mkListTy fromBindersTupleType), Type toBindersTupleType, Var unzip_fn, inner_list_expr] + [Type (mkListTy from_tup_ty), Type toBindersTupleType, Var unzip_fn, inner_list_expr] -- Then finally we bind the unzip function around that expression bound_unzipped_inner_list_expr = Let (Rec [(unzip_fn, unzip_rhs)]) unzipped_inner_list_expr @@ -247,7 +231,7 @@ deListComp :: [Stmt Id] -> LHsExpr Id -> CoreExpr -> DsM CoreExpr deListComp (ParStmt stmtss_w_bndrs : quals) body list = do - exps_and_qual_tys <- mappM dsInnerListComp stmtss_w_bndrs + exps_and_qual_tys <- mapM dsInnerListComp stmtss_w_bndrs let (exps, qual_tys) = unzip exps_and_qual_tys (zip_fn, zip_rhs) <- mkZipBind qual_tys @@ -260,40 +244,46 @@ deListComp (ParStmt stmtss_w_bndrs : quals) body list bndrs_s = map snd stmtss_w_bndrs -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above - pat = mkBigLHsPatTup pats + pat = mkBigLHsPatTup pats pats = map mkBigLHsVarPatTup bndrs_s -- Last: the one to return -deListComp [] body list -- Figure 7.4, SLPJ, p 135, rule C above - = dsLExpr body `thenDs` \ core_body -> - returnDs (mkConsExpr (exprType core_body) core_body list) +deListComp [] body list = do -- Figure 7.4, SLPJ, p 135, rule C above + core_body <- dsLExpr body + return (mkConsExpr (exprType core_body) core_body list) -- Non-last: must be a guard -deListComp (ExprStmt guard _ _ : quals) body list -- rule B above - = dsLExpr guard `thenDs` \ core_guard -> - deListComp quals body list `thenDs` \ core_rest -> - returnDs (mkIfThenElse core_guard core_rest list) +deListComp (ExprStmt guard _ _ : quals) body list = do -- rule B above + core_guard <- dsLExpr guard + core_rest <- deListComp quals body list + return (mkIfThenElse core_guard core_rest list) -- [e | let B, qs] = let B in [e | qs] -deListComp (LetStmt binds : quals) body list - = deListComp quals body list `thenDs` \ core_rest -> +deListComp (LetStmt binds : quals) body list = do + core_rest <- deListComp quals body list dsLocalBinds binds core_rest -deListComp (stmt@(TransformStmt _ _ _) : quals) body list = do +deListComp (stmt@(TransformStmt {}) : quals) body list = do (inner_list_expr, pat) <- dsTransformStmt stmt deBindComp pat inner_list_expr quals body list -deListComp (stmt@(GroupStmt _ _) : quals) body list = do +deListComp (stmt@(GroupStmt {}) : quals) body list = do (inner_list_expr, pat) <- dsGroupStmt stmt deBindComp pat inner_list_expr quals body list -deListComp (BindStmt pat list1 _ _ : quals) body core_list2 -- rule A' above - = dsLExpr list1 `thenDs` \ core_list1 -> +deListComp (BindStmt pat list1 _ _ : quals) body core_list2 = do -- rule A' above + core_list1 <- dsLExpr list1 deBindComp pat core_list1 quals body core_list2 \end{code} \begin{code} +deBindComp :: OutPat Id + -> CoreExpr + -> [Stmt Id] + -> LHsExpr Id + -> CoreExpr + -> DsM (Expr Id) deBindComp pat core_list1 quals body core_list2 = do let u3_ty@u1_ty = exprType core_list1 -- two names, same thing @@ -350,27 +340,27 @@ dfListComp :: Id -> Id -- 'c' and 'n' -> DsM CoreExpr -- Last: the one to return -dfListComp c_id n_id [] body - = dsLExpr body `thenDs` \ core_body -> - returnDs (mkApps (Var c_id) [core_body, Var n_id]) +dfListComp c_id n_id [] body = do + core_body <- dsLExpr body + return (mkApps (Var c_id) [core_body, Var n_id]) -- Non-last: must be a guard -dfListComp c_id n_id (ExprStmt guard _ _ : quals) body - = dsLExpr guard `thenDs` \ core_guard -> - dfListComp c_id n_id quals body `thenDs` \ core_rest -> - returnDs (mkIfThenElse core_guard core_rest (Var n_id)) - -dfListComp c_id n_id (LetStmt binds : quals) body - -- new in 1.3, local bindings - = dfListComp c_id n_id quals body `thenDs` \ core_rest -> +dfListComp c_id n_id (ExprStmt guard _ _ : quals) body = do + core_guard <- dsLExpr guard + core_rest <- dfListComp c_id n_id quals body + return (mkIfThenElse core_guard core_rest (Var n_id)) + +dfListComp c_id n_id (LetStmt binds : quals) body = do + -- new in 1.3, local bindings + core_rest <- dfListComp c_id n_id quals body dsLocalBinds binds core_rest -dfListComp c_id n_id (stmt@(TransformStmt _ _ _) : quals) body = do +dfListComp c_id n_id (stmt@(TransformStmt {}) : quals) body = do (inner_list_expr, pat) <- dsTransformStmt stmt -- Anyway, we bind the newly transformed list via the generic binding function dfBindComp c_id n_id (pat, inner_list_expr) quals body -dfListComp c_id n_id (stmt@(GroupStmt _ _) : quals) body = do +dfListComp c_id n_id (stmt@(GroupStmt {}) : quals) body = do (inner_list_expr, pat) <- dsGroupStmt stmt -- Anyway, we bind the newly grouped list via the generic binding function dfBindComp c_id n_id (pat, inner_list_expr) quals body @@ -403,13 +393,7 @@ dfBindComp c_id n_id (pat, core_list1) quals body = do pat core_rest (Var b) -- now build the outermost foldr, and return - foldr_id <- dsLookupGlobalId foldrName - return (Var foldr_id `App` Type x_ty - `App` Type b_ty - `App` mkLams [x, b] core_expr - `App` Var n_id - `App` core_list1) - + mkFoldrExpr x_ty b_ty (mkLams [x, b] core_expr) (Var n_id) core_list1 \end{code} %************************************************************************ @@ -430,9 +414,9 @@ mkZipBind :: [Type] -> DsM (Id, CoreExpr) -- (a2:as'2) -> (a1, a2) : zip as'1 as'2)] mkZipBind elt_tys = do - ass <- mappM newSysLocalDs elt_list_tys - as' <- mappM newSysLocalDs elt_tys - as's <- mappM newSysLocalDs elt_list_tys + ass <- mapM newSysLocalDs elt_list_tys + as' <- mapM newSysLocalDs elt_tys + as's <- mapM newSysLocalDs elt_list_tys zip_fn <- newSysLocalDs zip_fn_ty @@ -470,12 +454,11 @@ mkUnzipBind elt_tys = do ax <- newSysLocalDs elt_tuple_ty axs <- newSysLocalDs elt_list_tuple_ty ys <- newSysLocalDs elt_tuple_list_ty - xs <- mappM newSysLocalDs elt_tys - xss <- mappM newSysLocalDs elt_list_tys + xs <- mapM newSysLocalDs elt_tys + xss <- mapM newSysLocalDs elt_list_tys unzip_fn <- newSysLocalDs unzip_fn_ty - foldr_id <- dsLookupGlobalId foldrName [us1, us2] <- sequence [newUniqueSupply, newUniqueSupply] let nil_tuple = mkBigCoreTup (map mkNilExpr elt_tys) @@ -487,10 +470,8 @@ mkUnzipBind elt_tys = do folder_body_outer_case = mkTupleCase us2 xs folder_body_inner_case ax (Var ax) folder_body = mkLams [ax, axs] folder_body_outer_case - unzip_body = mkApps (Var foldr_id) [Type elt_tuple_ty, Type elt_list_tuple_ty, folder_body, nil_tuple, Var ys] - unzip_body_saturated = mkLams [ys] unzip_body - - return (unzip_fn, unzip_body_saturated) + unzip_body <- mkFoldrExpr elt_tuple_ty elt_list_tuple_ty folder_body nil_tuple (Var ys) + return (unzip_fn, mkLams [ys] unzip_body) where elt_tuple_ty = mkBigCoreTupTy elt_tys elt_tuple_list_ty = mkListTy elt_tuple_ty @@ -523,12 +504,32 @@ dsPArrComp :: [Stmt Id] -> DsM CoreExpr dsPArrComp [ParStmt qss] body _ = -- parallel comprehension dePArrParComp qss body -dsPArrComp qs body _ = -- no ParStmt in `qs' - dsLookupGlobalId singletonPName `thenDs` \sglP -> - let unitArray = mkApps (Var sglP) [Type unitTy, - mkCoreTup []] - in - dePArrComp qs body (mkLHsPatTup []) unitArray + +-- Special case for simple generators: +-- +-- <<[:e' | p <- e, qs:]>> = <<[: e' | qs :]>> p e +-- +-- if matching again p cannot fail, or else +-- +-- <<[:e' | p <- e, qs:]>> = +-- <<[:e' | qs:]>> p (filterP (\x -> case x of {p -> True; _ -> False}) e) +-- +dsPArrComp (BindStmt p e _ _ : qs) body _ = do + filterP <- dsLookupGlobalId filterPName + ce <- dsLExpr e + let ety'ce = parrElemType ce + false = Var falseDataConId + true = Var trueDataConId + v <- newSysLocalDs ety'ce + pred <- matchSimply (Var v) (StmtCtxt PArrComp) p true false + let gen | isIrrefutableHsPat p = ce + | otherwise = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] + dePArrComp qs body p gen + +dsPArrComp qs body _ = do -- no ParStmt in `qs' + sglP <- dsLookupGlobalId singletonPName + let unitArray = mkApps (Var sglP) [Type unitTy, mkCoreTup []] + dePArrComp qs body (noLoc $ WildPat unitTy) unitArray @@ -542,22 +543,19 @@ dePArrComp :: [Stmt Id] -- -- <<[:e' | :]>> pa ea = mapP (\pa -> e') ea -- -dePArrComp [] e' pa cea = - dsLookupGlobalId mapPName `thenDs` \mapP -> - let ty = parrElemType cea - in - deLambda ty pa e' `thenDs` \(clam, - ty'e') -> - returnDs $ mkApps (Var mapP) [Type ty, Type ty'e', clam, cea] +dePArrComp [] e' pa cea = do + mapP <- dsLookupGlobalId mapPName + let ty = parrElemType cea + (clam, ty'e') <- deLambda ty pa e' + return $ mkApps (Var mapP) [Type ty, Type ty'e', clam, cea] -- -- <<[:e' | b, qs:]>> pa ea = <<[:e' | qs:]>> pa (filterP (\pa -> b) ea) -- -dePArrComp (ExprStmt b _ _ : qs) body pa cea = - dsLookupGlobalId filterPName `thenDs` \filterP -> - let ty = parrElemType cea - in - deLambda ty pa b `thenDs` \(clam,_) -> - dePArrComp qs body pa (mkApps (Var filterP) [Type ty, clam, cea]) +dePArrComp (ExprStmt b _ _ : qs) body pa cea = do + filterP <- dsLookupGlobalId filterPName + let ty = parrElemType cea + (clam,_) <- deLambda ty pa b + dePArrComp qs body pa (mkApps (Var filterP) [Type ty, clam, cea]) -- -- <<[:e' | p <- e, qs:]>> pa ea = @@ -572,27 +570,24 @@ dePArrComp (ExprStmt b _ _ : qs) body pa cea = -- in -- <<[:e' | qs:]>> (pa, p) (crossMapP ea ef) -- -dePArrComp (BindStmt p e _ _ : qs) body pa cea = - dsLookupGlobalId filterPName `thenDs` \filterP -> - dsLookupGlobalId crossMapPName `thenDs` \crossMapP -> - dsLExpr e `thenDs` \ce -> - let ety'cea = parrElemType cea - ety'ce = parrElemType ce - false = Var falseDataConId - true = Var trueDataConId - in - newSysLocalDs ety'ce `thenDs` \v -> - matchSimply (Var v) (StmtCtxt PArrComp) p true false `thenDs` \pred -> - let cef | isIrrefutableHsPat p = ce - | otherwise = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] - in - mkLambda ety'cea pa cef `thenDs` \(clam, - _ ) -> - let ety'cef = ety'ce -- filter doesn't change the element type - pa' = mkLHsPatTup [pa, p] - in - dePArrComp qs body pa' (mkApps (Var crossMapP) - [Type ety'cea, Type ety'cef, cea, clam]) +dePArrComp (BindStmt p e _ _ : qs) body pa cea = do + filterP <- dsLookupGlobalId filterPName + crossMapP <- dsLookupGlobalId crossMapPName + ce <- dsLExpr e + let ety'cea = parrElemType cea + ety'ce = parrElemType ce + false = Var falseDataConId + true = Var trueDataConId + v <- newSysLocalDs ety'ce + pred <- matchSimply (Var v) (StmtCtxt PArrComp) p true false + let cef | isIrrefutableHsPat p = ce + | otherwise = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] + (clam, _) <- mkLambda ety'cea pa cef + let ety'cef = ety'ce -- filter doesn't change the element type + pa' = mkLHsPatTup [pa, p] + + dePArrComp qs body pa' (mkApps (Var crossMapP) + [Type ety'cea, Type ety'cef, cea, clam]) -- -- <<[:e' | let ds, qs:]>> pa ea = -- <<[:e' | qs:]>> (pa, (x_1, ..., x_n)) @@ -600,26 +595,23 @@ dePArrComp (BindStmt p e _ _ : qs) body pa cea = -- where -- {x_1, ..., x_n} = DV (ds) -- Defined Variables -- -dePArrComp (LetStmt ds : qs) body pa cea = - dsLookupGlobalId mapPName `thenDs` \mapP -> - let xs = map unLoc (collectLocalBinders ds) - ty'cea = parrElemType cea - in - newSysLocalDs ty'cea `thenDs` \v -> - dsLocalBinds ds (mkCoreTup (map Var xs)) `thenDs` \clet -> - newSysLocalDs (exprType clet) `thenDs` \let'v -> - let projBody = mkDsLet (NonRec let'v clet) $ - mkCoreTup [Var v, Var let'v] - errTy = exprType projBody - errMsg = "DsListComp.dePArrComp: internal error!" - in - mkErrorAppDs pAT_ERROR_ID errTy errMsg `thenDs` \cerr -> - matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr`thenDs` \ccase -> - let pa' = mkLHsPatTup [pa, mkLHsPatTup (map nlVarPat xs)] - proj = mkLams [v] ccase - in - dePArrComp qs body pa' (mkApps (Var mapP) - [Type ty'cea, Type errTy, proj, cea]) +dePArrComp (LetStmt ds : qs) body pa cea = do + mapP <- dsLookupGlobalId mapPName + let xs = collectLocalBinders ds + ty'cea = parrElemType cea + v <- newSysLocalDs ty'cea + clet <- dsLocalBinds ds (mkCoreTup (map Var xs)) + let'v <- newSysLocalDs (exprType clet) + let projBody = mkCoreLet (NonRec let'v clet) $ + mkCoreTup [Var v, Var let'v] + errTy = exprType projBody + errMsg = ptext (sLit "DsListComp.dePArrComp: internal error!") + cerr <- mkErrorAppDs pAT_ERROR_ID errTy errMsg + ccase <- matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr + let pa' = mkLHsPatTup [pa, mkLHsPatTup (map nlVarPat xs)] + proj = mkLams [v] ccase + dePArrComp qs body pa' (mkApps (Var mapP) + [Type ty'cea, Type errTy, proj, cea]) -- -- The parser guarantees that parallel comprehensions can only appear as -- singeltons qualifier lists, which we already special case in the caller. @@ -634,31 +626,28 @@ dePArrComp (ParStmt _ : _) _ _ _ = -- where -- {x_1, ..., x_n} = DV (qs) -- -dePArrParComp qss body = - deParStmt qss `thenDs` \(pQss, - ceQss) -> - dePArrComp [] body pQss ceQss +dePArrParComp :: [([LStmt Id], [Id])] -> LHsExpr Id -> DsM CoreExpr +dePArrParComp qss body = do + (pQss, ceQss) <- deParStmt qss + dePArrComp [] body pQss ceQss where deParStmt [] = -- empty parallel statement lists have no source representation panic "DsListComp.dePArrComp: Empty parallel list comprehension" - deParStmt ((qs, xs):qss) = -- first statement - let res_expr = mkLHsVarTup xs - in - dsPArrComp (map unLoc qs) res_expr undefined `thenDs` \cqs -> + deParStmt ((qs, xs):qss) = do -- first statement + let res_expr = mkLHsVarTuple xs + cqs <- dsPArrComp (map unLoc qs) res_expr undefined parStmts qss (mkLHsVarPatTup xs) cqs --- parStmts [] pa cea = return (pa, cea) - parStmts ((qs, xs):qss) pa cea = -- subsequent statements (zip'ed) - dsLookupGlobalId zipPName `thenDs` \zipP -> + parStmts ((qs, xs):qss) pa cea = do -- subsequent statements (zip'ed) + zipP <- dsLookupGlobalId zipPName let pa' = mkLHsPatTup [pa, mkLHsVarPatTup xs] - ty'cea = parrElemType cea - res_expr = mkLHsVarTup xs - in - dsPArrComp (map unLoc qs) res_expr undefined `thenDs` \cqs -> + ty'cea = parrElemType cea + res_expr = mkLHsVarTuple xs + cqs <- dsPArrComp (map unLoc qs) res_expr undefined let ty'cqs = parrElemType cqs - cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs] - in + cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs] parStmts qss pa' cea' -- generate Core corresponding to `\p -> e' @@ -668,8 +657,7 @@ deLambda :: Type -- type of the argument -> LHsExpr Id -- body -> DsM (CoreExpr, Type) deLambda ty p e = - dsLExpr e `thenDs` \ce -> - mkLambda ty p ce + mkLambda ty p =<< dsLExpr e -- generate Core for a lambda pattern match, where the body is already in Core -- @@ -677,14 +665,13 @@ mkLambda :: Type -- type of the argument -> LPat Id -- argument pattern -> CoreExpr -- desugared body -> DsM (CoreExpr, Type) -mkLambda ty p ce = - newSysLocalDs ty `thenDs` \v -> - let errMsg = "DsListComp.deLambda: internal error!" - ce'ty = exprType ce - in - mkErrorAppDs pAT_ERROR_ID ce'ty errMsg `thenDs` \cerr -> - matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr `thenDs` \res -> - returnDs (mkLams [v] res, ce'ty) +mkLambda ty p ce = do + v <- newSysLocalDs ty + let errMsg = ptext (sLit "DsListComp.deLambda: internal error!") + ce'ty = exprType ce + cerr <- mkErrorAppDs pAT_ERROR_ID ce'ty errMsg + res <- matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr + return (mkLams [v] res, ce'ty) -- obtain the element type of the parallel array produced by the given Core -- expression