Desugaring exporessions.
\begin{code}
+{-# OPTIONS -w #-}
+-- 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
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module DsExpr ( dsExpr, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where
#include "HsVersions.h"
-#if defined(GHCI) && defined(BREAKPOINT)
-import Foreign.StablePtr
-import GHC.Exts
-import IOEnv
-import PrelNames
-import TysWiredIn
-import TypeRep
-import TyCon
-#endif
+
import Match
import MatchLit
import DsUtils
import DsArrows
import DsMonad
+import Name
#ifdef GHCI
+import PrelNames
-- Template Haskell stuff iff bootstrapped
import DsMeta
#endif
import Id
import PrelInfo
import DataCon
-import TyCon
import TysWiredIn
import BasicTypes
import PrelNames
-------------------------
dsValBinds :: HsValBinds Id -> CoreExpr -> DsM CoreExpr
-dsValBinds (ValBindsOut binds _) body = foldrDs ds_val_bind body binds
+dsValBinds (ValBindsOut binds _) body = foldrM ds_val_bind body binds
-------------------------
dsIPBinds (IPBinds ip_binds dict_binds) body
; let inner = Let (Rec prs) body
-- The dict bindings may not be in
-- dependency order; hence Rec
- ; foldrDs ds_ip_bind inner ip_binds }
+ ; foldrM ds_ip_bind inner ip_binds }
where
ds_ip_bind (L _ (IPBind n e)) body
- = dsLExpr e `thenDs` \ e' ->
- returnDs (Let (NonRec (ipNameName n) e') body)
+ = do e' <- dsLExpr e
+ return (Let (NonRec (ipNameName n) e') body)
-------------------------
ds_val_bind :: (RecFlag, LHsBinds Id) -> CoreExpr -> DsM CoreExpr
-- below. Then pattern-match would fail. Urk.)
putSrcSpanDs loc $
case bind of
- FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn, fun_tick = tick }
- -> matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) ->
- ASSERT( null args ) -- Functions aren't lifted
- ASSERT( isIdHsWrapper co_fn )
- mkOptTickBox tick rhs `thenDs` \ rhs' ->
- returnDs (bindNonRec fun rhs' body_w_exports)
+ FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn,
+ fun_tick = tick, fun_infix = inf }
+ -> do (args, rhs) <- matchWrapper (FunRhs (idName fun ) inf) matches
+ MASSERT( null args ) -- Functions aren't lifted
+ MASSERT( isIdHsWrapper co_fn )
+ rhs' <- mkOptTickBox tick rhs
+ return (bindNonRec fun rhs' body_w_exports)
PatBind {pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }
-> -- let C x# y# = rhs in body
-- ==> case rhs of C x# y# -> body
putSrcSpanDs loc $
- do { rhs <- dsGuarded grhss ty
- ; let upat = unLoc pat
- eqn = EqnInfo { eqn_pats = [upat],
- eqn_rhs = cantFailMatchResult body_w_exports }
- ; var <- selectMatchVar upat
- ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body)
- ; return (scrungleMatch var rhs result) }
+ do { rhs <- dsGuarded grhss ty
+ ; let upat = unLoc pat
+ eqn = EqnInfo { eqn_pats = [upat],
+ eqn_rhs = cantFailMatchResult body_w_exports }
+ ; var <- selectMatchVar upat
+ ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body)
+ ; return (scrungleMatch var rhs result) }
other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body)
| x == var = Case scrut bndr ty alts
scrungle (Let binds body) = Let binds (scrungle body)
scrungle other = panic ("scrungleMatch: tuple pattern:\n" ++ showSDoc (ppr other))
-\end{code}
+
+\end{code}
%************************************************************************
%* *
\begin{code}
dsLExpr :: LHsExpr Id -> DsM CoreExpr
+
dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e
dsExpr :: HsExpr Id -> DsM CoreExpr
-
dsExpr (HsPar e) = dsLExpr e
dsExpr (ExprWithTySigOut e _) = dsLExpr e
-dsExpr (HsVar var) = returnDs (Var var)
-dsExpr (HsIPVar ip) = returnDs (Var (ipNameName ip))
+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) = dsCoercion co_fn (dsExpr e)
dsExpr (NegApp expr neg_expr)
- = do { core_expr <- dsLExpr expr
- ; core_neg <- dsExpr neg_expr
- ; return (core_neg `App` core_expr) }
+ = App <$> dsExpr neg_expr <*> dsLExpr expr
dsExpr expr@(HsLam a_Match)
- = matchWrapper LambdaExpr a_Match `thenDs` \ (binders, matching_code) ->
- returnDs (mkLams binders matching_code)
-
-#if defined(GHCI) && defined(BREAKPOINT)
-dsExpr (HsApp (L _ (HsApp realFun@(L _ (HsWrap _ fun)) (L loc arg))) _)
- | HsVar funId <- fun
- , idName funId `elem` [breakpointJumpName, breakpointCondJumpName]
- , ids <- filter (isValidType . idType) (extractIds arg)
- = do warnDs (text "Extracted ids:" <+> ppr ids <+> ppr (map idType ids))
- stablePtr <- ioToIOEnv $ newStablePtr ids
- -- Yes, I know... I'm gonna burn in hell.
- let Ptr addr# = castStablePtrToPtr stablePtr
- funCore <- dsLExpr realFun
- argCore <- dsLExpr (L loc (HsLit (HsInt (fromIntegral (I# (addr2Int# addr#))))))
- hvalCore <- dsLExpr (L loc (extractHVals ids))
- return ((funCore `App` argCore) `App` hvalCore)
- where extractIds :: HsExpr Id -> [Id]
- extractIds (HsApp fn arg)
- | HsVar argId <- unLoc arg
- = argId:extractIds (unLoc fn)
- | HsWrap co_fn arg' <- unLoc arg
- , HsVar argId <- arg' -- SLPJ: not sure what is going on here
- = error (showSDoc (ppr co_fn)) -- argId:extractIds (unLoc fn)
- extractIds x = []
- extractHVals ids = ExplicitList unitTy (map (L loc . HsVar) ids)
- -- checks for tyvars and unlifted kinds.
- isValidType (TyVarTy _) = False
- isValidType (FunTy a b) = isValidType a && isValidType b
- isValidType (NoteTy _ t) = isValidType t
- isValidType (AppTy a b) = isValidType a && isValidType b
- isValidType (TyConApp con ts) = not (isUnLiftedTyCon con) && all isValidType ts
- isValidType _ = True
-#endif
+ = uncurry mkLams <$> matchWrapper LambdaExpr a_Match
dsExpr expr@(HsApp fun arg)
- = dsLExpr fun `thenDs` \ core_fun ->
- dsLExpr arg `thenDs` \ core_arg ->
- returnDs (core_fun `App` core_arg)
+ = mkDsApp <$> dsLExpr fun <*> dsLExpr arg
\end{code}
Operator sections. At first it looks as if we can convert
\begin{code}
dsExpr (OpApp e1 op _ e2)
- = dsLExpr op `thenDs` \ core_op ->
- -- for the type of y, we need the type of op's 2nd argument
- dsLExpr e1 `thenDs` \ x_core ->
- dsLExpr e2 `thenDs` \ y_core ->
- returnDs (mkApps core_op [x_core, y_core])
+ = -- for the type of y, we need the type of op's 2nd argument
+ mkDsApps <$> dsLExpr op <*> mapM dsLExpr [e1, e2]
dsExpr (SectionL expr op) -- Desugar (e !) to ((!) e)
- = dsLExpr op `thenDs` \ core_op ->
- dsLExpr expr `thenDs` \ x_core ->
- returnDs (App core_op x_core)
+ = mkDsApp <$> dsLExpr op <*> dsLExpr expr
-- dsLExpr (SectionR op expr) -- \ x -> op x expr
-dsExpr (SectionR op expr)
- = dsLExpr op `thenDs` \ core_op ->
+dsExpr (SectionR op expr) = do
+ core_op <- dsLExpr op
-- for the type of x, we need the type of op's 2nd argument
- let
- (x_ty:y_ty:_, _) = splitFunTys (exprType core_op)
- -- See comment with SectionL
- in
- dsLExpr expr `thenDs` \ y_core ->
- newSysLocalDs x_ty `thenDs` \ x_id ->
- newSysLocalDs y_ty `thenDs` \ y_id ->
+ let (x_ty:y_ty:_, _) = splitFunTys (exprType core_op)
+ -- See comment with SectionL
+ y_core <- dsLExpr expr
+ x_id <- newSysLocalDs x_ty
+ y_id <- newSysLocalDs y_ty
+ return (bindNonRec y_id y_core $
+ Lam x_id (mkDsApps core_op [Var x_id, Var y_id]))
- returnDs (bindNonRec y_id y_core $
- Lam x_id (mkApps core_op [Var x_id, Var y_id]))
-
-dsExpr (HsSCC cc expr)
- = dsLExpr expr `thenDs` \ core_expr ->
- getModuleDs `thenDs` \ mod_name ->
- returnDs (Note (SCC (mkUserCC cc mod_name)) core_expr)
+dsExpr (HsSCC cc expr) = do
+ mod_name <- getModuleDs
+ Note (SCC (mkUserCC cc mod_name)) <$> dsLExpr expr
-- hdaume: core annotation
dsExpr (HsCoreAnn fs expr)
- = dsLExpr expr `thenDs` \ core_expr ->
- returnDs (Note (CoreNote $ unpackFS fs) core_expr)
+ = Note (CoreNote $ unpackFS fs) <$> dsLExpr expr
-dsExpr (HsCase discrim matches)
- = dsLExpr discrim `thenDs` \ core_discrim ->
- matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) ->
- returnDs (scrungleMatch discrim_var core_discrim matching_code)
+dsExpr (HsCase discrim matches) = do
+ core_discrim <- dsLExpr discrim
+ ([discrim_var], matching_code) <- matchWrapper CaseAlt matches
+ return (scrungleMatch discrim_var core_discrim matching_code)
-dsExpr (HsLet binds body)
- = dsLExpr body `thenDs` \ body' ->
+-- Pepe: The binds are in scope in the body but NOT in the binding group
+-- This is to avoid silliness in breakpoints
+dsExpr (HsLet binds body) = do
+ body' <- dsLExpr body
dsLocalBinds binds body'
-- We need the `ListComp' form to use `deListComp' (rather than the "do" form)
[elt_ty] = tcTyConAppArgs result_ty
dsExpr (HsIf guard_expr then_expr else_expr)
- = dsLExpr guard_expr `thenDs` \ core_guard ->
- dsLExpr then_expr `thenDs` \ core_then ->
- dsLExpr else_expr `thenDs` \ core_else ->
- returnDs (mkIfThenElse core_guard core_then core_else)
+ = mkIfThenElse <$> dsLExpr guard_expr <*> dsLExpr then_expr <*> dsLExpr else_expr
\end{code}
dsExpr (ExplicitList ty xs)
= go xs
where
- go [] = returnDs (mkNilExpr ty)
- go (x:xs) = dsLExpr x `thenDs` \ core_x ->
- go xs `thenDs` \ core_xs ->
- returnDs (mkConsExpr ty core_x core_xs)
+ go [] = return (mkNilExpr ty)
+ go (x:xs) = mkConsExpr ty <$> dsLExpr x <*> go xs
-- we create a list from the array elements and convert them into a list using
-- `PrelPArr.toP'
-- that we can exploit the fact that we already know the length of the array
-- here at compile time
--
-dsExpr (ExplicitPArr ty xs)
- = dsLookupGlobalId toPName `thenDs` \toP ->
- dsExpr (ExplicitList ty xs) `thenDs` \coreList ->
- returnDs (mkApps (Var toP) [Type ty, coreList])
+dsExpr (ExplicitPArr ty xs) = do
+ toP <- dsLookupGlobalId toPName
+ coreList <- dsExpr (ExplicitList ty xs)
+ return (mkApps (Var toP) [Type ty, coreList])
-dsExpr (ExplicitTuple expr_list boxity)
- = mappM dsLExpr expr_list `thenDs` \ core_exprs ->
- returnDs (mkConApp (tupleCon boxity (length expr_list))
- (map (Type . exprType) core_exprs ++ core_exprs))
+dsExpr (ExplicitTuple expr_list boxity) = do
+ core_exprs <- mapM dsLExpr expr_list
+ return (mkConApp (tupleCon boxity (length expr_list))
+ (map (Type . exprType) core_exprs ++ core_exprs))
dsExpr (ArithSeq expr (From from))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- returnDs (App expr2 from2)
+ = App <$> dsExpr expr <*> dsLExpr from
-dsExpr (ArithSeq expr (FromTo from two))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr two `thenDs` \ two2 ->
- returnDs (mkApps expr2 [from2, two2])
+dsExpr (ArithSeq expr (FromTo from to))
+ = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, to]
dsExpr (ArithSeq expr (FromThen from thn))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr thn `thenDs` \ thn2 ->
- returnDs (mkApps expr2 [from2, thn2])
-
-dsExpr (ArithSeq expr (FromThenTo from thn two))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr thn `thenDs` \ thn2 ->
- dsLExpr two `thenDs` \ two2 ->
- returnDs (mkApps expr2 [from2, thn2, two2])
-
-dsExpr (PArrSeq expr (FromTo from two))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr two `thenDs` \ two2 ->
- returnDs (mkApps expr2 [from2, two2])
-
-dsExpr (PArrSeq expr (FromThenTo from thn two))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr thn `thenDs` \ thn2 ->
- dsLExpr two `thenDs` \ two2 ->
- returnDs (mkApps expr2 [from2, thn2, two2])
+ = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn]
+
+dsExpr (ArithSeq expr (FromThenTo from thn to))
+ = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn, to]
+
+dsExpr (PArrSeq expr (FromTo from to))
+ = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, to]
+
+dsExpr (PArrSeq expr (FromThenTo from thn to))
+ = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn, to]
dsExpr (PArrSeq expr _)
= panic "DsExpr.dsExpr: Infinite parallel array!"
constructor @C@, setting all of @C@'s fields to bottom.
\begin{code}
-dsExpr (RecordCon (L _ data_con_id) con_expr rbinds)
- = dsExpr con_expr `thenDs` \ con_expr' ->
+dsExpr (RecordCon (L _ data_con_id) con_expr rbinds) = do
+ con_expr' <- dsExpr con_expr
let
- (arg_tys, _) = tcSplitFunTys (exprType con_expr')
- -- A newtype in the corner should be opaque;
- -- hence TcType.tcSplitFunTys
-
- mk_arg (arg_ty, lbl) -- Selector id has the field label as its name
- = case [rhs | (L _ sel_id, rhs) <- rbinds, lbl == idName sel_id] 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 ""
-
- labels = dataConFieldLabels (idDataCon data_con_id)
- -- The data_con_id is guaranteed to be the wrapper id of the constructor
- in
-
- (if null labels
- then mappM unlabelled_bottom arg_tys
- else mappM mk_arg (zipEqual "dsExpr:RecordCon" arg_tys labels))
- `thenDs` \ con_args ->
-
- returnDs (mkApps con_expr' con_args)
+ (arg_tys, _) = tcSplitFunTys (exprType con_expr')
+ -- A newtype in the corner should be opaque;
+ -- hence TcType.tcSplitFunTys
+
+ mk_arg (arg_ty, lbl) -- Selector id has the field label as its name
+ = 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 ""
+
+ labels = dataConFieldLabels (idDataCon data_con_id)
+ -- The data_con_id is guaranteed to be the wrapper id of the constructor
+
+ con_args <- if null labels
+ then mapM unlabelled_bottom arg_tys
+ else mapM mk_arg (zipEqual "dsExpr:RecordCon" arg_tys labels)
+
+ return (mkApps con_expr' con_args)
\end{code}
Record update is a little harder. Suppose we have the decl:
dictionaries.
\begin{code}
-dsExpr (RecordUpd record_expr [] record_in_ty record_out_ty)
+dsExpr expr@(RecordUpd record_expr (HsRecFields { rec_flds = fields })
+ cons_to_upd in_inst_tys out_inst_tys)
+ | null fields
= dsLExpr record_expr
-
-dsExpr expr@(RecordUpd record_expr rbinds record_in_ty record_out_ty)
- = dsLExpr record_expr `thenDs` \ record_expr' ->
-
- -- Desugar the rbinds, and generate let-bindings if
- -- necessary so that we don't lose sharing
-
- let
- in_inst_tys = tcTyConAppArgs record_in_ty -- Newtype opaque
- out_inst_tys = tcTyConAppArgs record_out_ty -- Newtype opaque
- in_out_ty = mkFunTy record_in_ty record_out_ty
-
- mk_val_arg field old_arg_id
- = case [rhs | (L _ sel_id, rhs) <- rbinds, field == idName sel_id] of
- (rhs:rest) -> ASSERT(null rest) rhs
- [] -> nlHsVar old_arg_id
-
- mk_alt con
- = ASSERT( isVanillaDataCon con )
- newSysLocalsDs (dataConInstOrigArgTys con in_inst_tys) `thenDs` \ arg_ids ->
- -- This call to dataConInstOrigArgTys won't work for existentials
- -- but existentials don't have record types anyway
- let
- val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
- (dataConFieldLabels con) arg_ids
- rhs = foldl (\a b -> nlHsApp a b)
- (nlHsTyApp (dataConWrapId con) out_inst_tys)
- val_args
- in
- returnDs (mkSimpleMatch [mkPrefixConPat con (map nlVarPat arg_ids) record_in_ty] rhs)
- in
- -- Record stuff doesn't work for existentials
+ | otherwise
+ = -- Record stuff doesn't work for existentials
-- The type checker checks for this, but we need
-- worry only about the constructors that are to be updated
- ASSERT2( all isVanillaDataCon cons_to_upd, ppr expr )
+ ASSERT2( notNull cons_to_upd && all isVanillaDataCon cons_to_upd, ppr expr )
+
+ do { record_expr' <- dsLExpr record_expr
+ ; let -- Awkwardly, for families, the match goes
+ -- from instance type to family type
+ tycon = dataConTyCon (head cons_to_upd)
+ in_ty = mkTyConApp tycon in_inst_tys
+ in_out_ty = mkFunTy in_ty
+ (mkFamilyTyConApp tycon out_inst_tys)
+
+ mk_val_arg field old_arg_id
+ = case findField fields field of
+ (rhs:rest) -> ASSERT(null rest) rhs
+ [] -> nlHsVar old_arg_id
+
+ mk_alt con
+ = ASSERT( isVanillaDataCon con )
+ do { arg_ids <- newSysLocalsDs (dataConInstOrigArgTys con in_inst_tys)
+ -- This call to dataConInstOrigArgTys won't work for existentials
+ -- but existentials don't have record types anyway
+ ; let val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
+ (dataConFieldLabels con) arg_ids
+ rhs = foldl (\a b -> nlHsApp a b)
+ (nlHsTyApp (dataConWrapId con) out_inst_tys)
+ val_args
+ pat = mkPrefixConPat con (map nlVarPat arg_ids) in_ty
+
+ ; return (mkSimpleMatch [pat] rhs) }
-- It's important to generate the match with matchWrapper,
-- and the right hand sides with applications of the wrapper Id
-- so that everything works when we are doing fancy unboxing on the
-- constructor aguments.
- mappM mk_alt cons_to_upd `thenDs` \ alts ->
- matchWrapper RecUpd (MatchGroup alts in_out_ty) `thenDs` \ ([discrim_var], matching_code) ->
-
- returnDs (bindNonRec discrim_var record_expr' matching_code)
+ ; alts <- mapM mk_alt cons_to_upd
+ ; ([discrim_var], matching_code) <- matchWrapper RecUpd (MatchGroup alts in_out_ty)
- where
- updated_fields :: [FieldLabel]
- updated_fields = [ idName sel_id | (L _ sel_id,_) <- rbinds]
-
- -- Get the type constructor from the record_in_ty
- -- so that we are sure it'll have all its DataCons
- -- (In GHCI, it's possible that some TyCons may not have all
- -- their constructors, in a module-loop situation.)
- tycon = tcTyConAppTyCon record_in_ty
- data_cons = tyConDataCons tycon
- cons_to_upd = filter has_all_fields data_cons
-
- has_all_fields :: DataCon -> Bool
- has_all_fields con_id
- = all (`elem` con_fields) updated_fields
- where
- con_fields = dataConFieldLabels con_id
+ ; return (bindNonRec discrim_var record_expr' matching_code) }
\end{code}
Here is where we desugar the Template Haskell brackets and escapes
Hpc Support
\begin{code}
-dsExpr (HsTick ix e) = do
+dsExpr (HsTick ix vars e) = do
e' <- dsLExpr e
- mkTickBox ix e'
+ mkTickBox ix vars e'
-- There is a problem here. The then and else branches
-- have no free variables, so they are open to lifting.
dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig"
#endif
+
+findField :: [HsRecField Id arg] -> Name -> [arg]
+findField rbinds lbl
+ = [rhs | HsRecField { hsRecFieldId = id, hsRecFieldArg = rhs } <- rbinds
+ , lbl == idName (unLoc id) ]
\end{code}
%--------------------------------------------------------------------
= do { rhs2 <- dsLExpr rhs
; then_expr2 <- dsExpr then_expr
; rest <- go stmts
- ; returnDs (mkApps then_expr2 [rhs2, rest]) }
+ ; return (mkApps then_expr2 [rhs2, rest]) }
go (LetStmt binds : stmts)
= do { rest <- go stmts
; dsLocalBinds binds rest }
-
+
go (BindStmt pat rhs bind_op fail_op : stmts)
- = do { body <- go stmts
+ =
+ do { body <- go stmts
; var <- selectSimpleMatchVarL pat
; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat
result_ty (cantFailMatchResult body)
; match_code <- handle_failure pat match fail_op
- ; rhs' <- dsLExpr rhs
+ ; rhs' <- dsLExpr rhs
; bind_op' <- dsExpr bind_op
- ; returnDs (mkApps bind_op' [rhs', Lam var match_code]) }
+ ; return (mkApps bind_op' [rhs', Lam var match_code]) }
-- In a do expression, pattern-match failure just calls
-- the monadic 'fail' rather than throwing an exception
go (ExprStmt rhs _ rhs_ty : stmts)
= do { rhs2 <- dsLExpr rhs
; rest <- go stmts
- ; returnDs (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) }
+ ; return (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) }
go (BindStmt pat rhs _ _ : stmts)
= do { body <- go stmts
; match_code <- extractMatchResult match fail_expr
; rhs' <- dsLExpr rhs
- ; returnDs (mkApps (Var bind_id) [Type (hsLPatType pat), Type b_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)