X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FdeSugar%2FDsExpr.lhs;h=406d7934400b139cbf6b5b38accaf6900647e184;hb=3c245de9199f522f75ace92219256badbd928bd6;hp=3969f3fa6bc852604f082c54a78da2d315f3259c;hpb=9614b62b9ebc29cc4d59e499ad462af264ea0e52;p=ghc-hetmet.git diff --git a/ghc/compiler/deSugar/DsExpr.lhs b/ghc/compiler/deSugar/DsExpr.lhs index 3969f3f..406d793 100644 --- a/ghc/compiler/deSugar/DsExpr.lhs +++ b/ghc/compiler/deSugar/DsExpr.lhs @@ -1,203 +1,213 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[DsExpr]{Matching expressions (Exprs)} \begin{code} +module DsExpr ( dsExpr, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where + #include "HsVersions.h" -module DsExpr ( dsExpr ) where +import Match ( matchWrapper, matchSinglePat, matchEquations ) +import MatchLit ( dsLit, dsOverLit ) +import DsBinds ( dsLHsBinds, dsCoercion ) +import DsGRHSs ( dsGuarded ) +import DsListComp ( dsListComp, dsPArrComp ) +import DsUtils ( mkErrorAppDs, mkStringExpr, mkConsExpr, mkNilExpr, + extractMatchResult, cantFailMatchResult, matchCanFail, + mkCoreTupTy, selectSimpleMatchVarL, lookupEvidence, selectMatchVar ) +import DsArrows ( dsProcExpr ) +import DsMonad -IMP_Ubiq() -#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201 -IMPORT_DELOOPER(DsLoop) -- partly to get dsBinds, partly to chk dsExpr -#else -import {-# SOURCE #-} DsBinds (dsBinds ) +#ifdef GHCI + -- Template Haskell stuff iff bootstrapped +import DsMeta ( dsBracket ) #endif -import HsSyn ( failureFreePat, - HsExpr(..), OutPat(..), HsLit(..), ArithSeqInfo(..), - Stmt(..), DoOrListComp(..), Match(..), HsBinds, HsType, Fixity, - GRHSsAndBinds - ) -import TcHsSyn ( SYN_IE(TypecheckedHsExpr), SYN_IE(TypecheckedHsBinds), - SYN_IE(TypecheckedRecordBinds), SYN_IE(TypecheckedPat), - SYN_IE(TypecheckedStmt) - ) +import HsSyn +import TcHsSyn ( hsPatType, mkVanillaTuplePat ) + +-- NB: The desugarer, which straddles the source and Core worlds, sometimes +-- needs to see source types (newtypes etc), and sometimes not +-- So WATCH OUT; check each use of split*Ty functions. +-- Sigh. This is a pain. + +import TcType ( tcSplitAppTy, tcSplitFunTys, tcTyConAppTyCon, + tcTyConAppArgs, isUnLiftedType, Type, mkAppTy ) +import Type ( funArgTy, splitFunTys, isUnboxedTupleType, mkFunTy ) import CoreSyn +import CoreUtils ( exprType, mkIfThenElse, bindNonRec ) -import DsMonad -import DsCCall ( dsCCall ) -import DsHsSyn ( outPatType ) -import DsListComp ( dsListComp ) -import DsUtils ( mkAppDs, mkConDs, mkPrimDs, dsExprToAtomGivenTy, mkTupleExpr, - mkErrorAppDs, showForErr, EquationInfo, - MatchResult, SYN_IE(DsCoreArg) - ) -import Match ( matchWrapper ) - -import CoreUtils ( coreExprType, substCoreExpr, argToExpr, - mkCoreIfThenElse, unTagBinders ) import CostCentre ( mkUserCC ) -import FieldLabel ( fieldLabelType, FieldLabel ) -import Id ( idType, nullIdEnv, addOneToIdEnv, - dataConArgTys, dataConFieldLabels, - recordSelectorFieldLabel, SYN_IE(Id) - ) -import Literal ( mkMachInt, Literal(..) ) -import Name ( Name{--O only-} ) -import Outputable ( PprStyle(..), Outputable(..) ) -import PprType ( GenType ) -import PrelVals ( rEC_CON_ERROR_ID, rEC_UPD_ERROR_ID, voidId ) -import Pretty ( Doc, hcat, ptext, text ) -import Type ( splitSigmaTy, splitFunTy, typePrimRep, - getAppDataTyConExpandingDicts, maybeAppTyCon, getAppTyCon, applyTy, - maybeBoxedPrimType, splitAppTy, SYN_IE(Type) - ) -import TysPrim ( voidTy ) -import TysWiredIn ( mkTupleTy, tupleCon, nilDataCon, consDataCon, listTyCon, mkListTy, - charDataCon, charTy - ) -import TyVar ( nullTyVarEnv, addOneToTyVarEnv, GenTyVar{-instance Eq-} ) -import Usage ( SYN_IE(UVar) ) -import Maybes ( maybeToBool ) -import Util ( zipEqual, pprError, panic, assertPanic ) - -mk_nil_con ty = mkCon nilDataCon [] [ty] [] -- micro utility... +import Id ( Id, idType, idName, idDataCon ) +import PrelInfo ( rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID ) +import DataCon ( DataCon, dataConWrapId, dataConFieldLabels, dataConInstOrigArgTys ) +import DataCon ( isVanillaDataCon ) +import TyCon ( FieldLabel, tyConDataCons ) +import TysWiredIn ( tupleCon ) +import BasicTypes ( RecFlag(..), Boxity(..), ipNameName ) +import PrelNames ( toPName, + returnMName, bindMName, thenMName, failMName, + mfixName ) +import SrcLoc ( Located(..), unLoc, getLoc, noLoc ) +import Util ( zipEqual, zipWithEqual ) +import Bag ( bagToList ) +import Outputable +import FastString \end{code} -The funny business to do with variables is that we look them up in the -Id-to-Id and Id-to-Id maps that the monadery is carrying -around; if we get hits, we use the value accordingly. %************************************************************************ %* * -\subsection[DsExpr-vars-and-cons]{Variables and constructors} + dsLocalBinds, dsValBinds %* * %************************************************************************ \begin{code} -dsExpr :: TypecheckedHsExpr -> DsM CoreExpr - -dsExpr e@(HsVar var) = dsId var -\end{code} +dsLocalBinds :: HsLocalBinds Id -> CoreExpr -> DsM CoreExpr +dsLocalBinds EmptyLocalBinds body = return body +dsLocalBinds (HsValBinds binds) body = dsValBinds binds body +dsLocalBinds (HsIPBinds binds) body = dsIPBinds binds body + +------------------------- +dsValBinds :: HsValBinds Id -> CoreExpr -> DsM CoreExpr +dsValBinds (ValBindsOut binds _) body = foldrDs ds_val_bind body binds + +------------------------- +dsIPBinds (IPBinds ip_binds dict_binds) body + = do { prs <- dsLHsBinds dict_binds + ; let inner = foldr (\(x,r) e -> Let (NonRec x r) e) body prs + ; foldrDs 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) + +------------------------- +ds_val_bind :: (RecFlag, LHsBinds Id) -> CoreExpr -> DsM CoreExpr +-- Special case for bindings which bind unlifted variables +-- We need to do a case right away, rather than building +-- a tuple and doing selections. +-- Silently ignore INLINE and SPECIALISE pragmas... +ds_val_bind (NonRecursive, hsbinds) body + | [L _ (AbsBinds [] [] exports binds)] <- bagToList hsbinds, + (L loc bind : null_binds) <- bagToList binds, + isBangHsBind bind + || isUnboxedTupleBind bind + || or [isUnLiftedType (idType g) | (_, g, _, _) <- exports] + = let + body_w_exports = foldr bind_export body exports + bind_export (tvs, g, l, _) body = ASSERT( null tvs ) + bindNonRec g (Var l) body + in + ASSERT (null null_binds) + -- Non-recursive, non-overloaded bindings only come in ones + -- ToDo: in some bizarre case it's conceivable that there + -- could be dict binds in the 'binds'. (See the notes + -- 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 } + -> matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) -> + ASSERT( null args ) -- Functions aren't lifted + ASSERT( isIdCoercion co_fn ) + returnDs (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_wrap = idWrapper, eqn_pats = [upat], + eqn_rhs = cantFailMatchResult body_w_exports } + ; var <- selectMatchVar upat ty + ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body) + ; return (scrungleMatch var rhs result) } + + other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body) + + +-- Ordinary case for bindings; none should be unlifted +ds_val_bind (is_rec, binds) body + = do { prs <- dsLHsBinds binds + ; ASSERT( not (any (isUnLiftedType . idType . fst) prs) ) + case prs of + [] -> return body + other -> return (Let (Rec prs) body) } + -- Use a Rec regardless of is_rec. + -- Why? Because it allows the binds to be all + -- mixed up, which is what happens in one rare case + -- Namely, for an AbsBind with no tyvars and no dicts, + -- but which does have dictionary bindings. + -- See notes with TcSimplify.inferLoop [NO TYVARS] + -- It turned out that wrapping a Rec here was the easiest solution + -- + -- NB The previous case dealt with unlifted bindings, so we + -- only have to deal with lifted ones now; so Rec is ok + +isUnboxedTupleBind :: HsBind Id -> Bool +isUnboxedTupleBind (PatBind { pat_rhs_ty = ty }) = isUnboxedTupleType ty +isUnboxedTupleBind other = False + +scrungleMatch :: Id -> CoreExpr -> CoreExpr -> CoreExpr +-- Returns something like (let var = scrut in body) +-- but if var is an unboxed-tuple type, it inlines it in a fragile way +-- Special case to handle unboxed tuple patterns; they can't appear nested +-- The idea is that +-- case e of (# p1, p2 #) -> rhs +-- should desugar to +-- case e of (# x1, x2 #) -> ... match p1, p2 ... +-- NOT +-- let x = e in case x of .... +-- +-- But there may be a big +-- let fail = ... in case e of ... +-- wrapping the whole case, which complicates matters slightly +-- It all seems a bit fragile. Test is dsrun013. + +scrungleMatch var scrut body + | isUnboxedTupleType (idType var) = scrungle body + | otherwise = bindNonRec var scrut body + where + scrungle (Case (Var x) bndr ty alts) + | 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} %************************************************************************ %* * -\subsection[DsExpr-literals]{Literals} +\subsection[DsExpr-vars-and-cons]{Variables, constructors, literals} %* * %************************************************************************ -We give int/float literals type Integer and Rational, respectively. -The typechecker will (presumably) have put \tr{from{Integer,Rational}s} -around them. - -ToDo: put in range checks for when converting "i" -(or should that be in the typechecker?) - -For numeric literals, we try to detect there use at a standard type -(Int, Float, etc.) are directly put in the right constructor. -[NB: down with the @App@ conversion.] -Otherwise, we punt, putting in a "NoRep" Core literal (where the -representation decisions are delayed)... - -See also below where we look for @DictApps@ for \tr{plusInt}, etc. - \begin{code} -dsExpr (HsLitOut (HsString s) _) - | _NULL_ s - = returnDs (mk_nil_con charTy) - - | _LENGTH_ s == 1 - = let - the_char = mkCon charDataCon [] [] [LitArg (MachChar (_HEAD_ s))] - the_nil = mk_nil_con charTy - in - mkConDs consDataCon [TyArg charTy, VarArg the_char, VarArg the_nil] - --- "_" => build (\ c n -> c 'c' n) -- LATER - --- "str" ==> build (\ c n -> foldr charTy T c n "str") - -{- LATER: -dsExpr (HsLitOut (HsString str) _) - = newTyVarsDs [alphaTyVar] `thenDs` \ [new_tyvar] -> - let - new_ty = mkTyVarTy new_tyvar - in - newSysLocalsDs [ - charTy `mkFunTy` (new_ty `mkFunTy` new_ty), - new_ty, - mkForallTy [alphaTyVar] - ((charTy `mkFunTy` (alphaTy `mkFunTy` alphaTy)) - `mkFunTy` (alphaTy `mkFunTy` alphaTy)) - ] `thenDs` \ [c,n,g] -> - returnDs (mkBuild charTy new_tyvar c n g ( - foldl App - (CoTyApp (CoTyApp (Var foldrId) charTy) new_ty) *** ensure non-prim type *** - [VarArg c,VarArg n,LitArg (NoRepStr str)])) --} - --- otherwise, leave it as a NoRepStr; --- the Core-to-STG pass will wrap it in an application of "unpackCStringId". - -dsExpr (HsLitOut (HsString str) _) - = returnDs (Lit (NoRepStr str)) - -dsExpr (HsLitOut (HsLitLit s) ty) - = returnDs ( mkCon data_con [] [] [LitArg (MachLitLit s kind)] ) - where - (data_con, kind) - = case (maybeBoxedPrimType ty) of - Just (boxing_data_con, prim_ty) - -> (boxing_data_con, typePrimRep prim_ty) - Nothing - -> pprError "ERROR: ``literal-literal'' not a single-constructor type: " - (hcat [ptext s, text "; type: ", ppr PprDebug ty]) - -dsExpr (HsLitOut (HsInt i) ty) - = returnDs (Lit (NoRepInteger i ty)) - -dsExpr (HsLitOut (HsFrac r) ty) - = returnDs (Lit (NoRepRational r ty)) - --- others where we know what to do: - -dsExpr (HsLitOut (HsIntPrim i) _) - = if (i >= toInteger minInt && i <= toInteger maxInt) then - returnDs (Lit (mkMachInt i)) - else - error ("ERROR: Int constant " ++ show i ++ out_of_range_msg) +dsLExpr :: LHsExpr Id -> DsM CoreExpr +dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e -dsExpr (HsLitOut (HsFloatPrim f) _) - = returnDs (Lit (MachFloat f)) - -- ToDo: range checking needed! +dsExpr :: HsExpr Id -> DsM CoreExpr -dsExpr (HsLitOut (HsDoublePrim d) _) - = returnDs (Lit (MachDouble d)) - -- ToDo: range checking needed! +dsExpr (HsPar e) = dsLExpr e +dsExpr (ExprWithTySigOut e _) = dsLExpr e +dsExpr (HsVar var) = returnDs (Var var) +dsExpr (HsIPVar ip) = returnDs (Var (ipNameName ip)) +dsExpr (HsLit lit) = dsLit lit +dsExpr (HsOverLit lit) = dsOverLit lit -dsExpr (HsLitOut (HsChar c) _) - = returnDs ( mkCon charDataCon [] [] [LitArg (MachChar c)] ) - -dsExpr (HsLitOut (HsCharPrim c) _) - = returnDs (Lit (MachChar c)) - -dsExpr (HsLitOut (HsStringPrim s) _) - = returnDs (Lit (MachStr s)) - --- end of literals magic. -- +dsExpr (NegApp expr neg_expr) + = do { core_expr <- dsLExpr expr + ; core_neg <- dsExpr neg_expr + ; return (core_neg `App` core_expr) } dsExpr expr@(HsLam a_Match) - = matchWrapper LambdaMatch [a_Match] "lambda" `thenDs` \ (binders, matching_code) -> - returnDs ( mkValLam binders matching_code ) + = matchWrapper LambdaExpr a_Match `thenDs` \ (binders, matching_code) -> + returnDs (mkLams binders matching_code) dsExpr expr@(HsApp fun arg) - = dsExpr fun `thenDs` \ core_fun -> - dsExpr arg `thenDs` \ core_arg -> - dsExprToAtomGivenTy core_arg (coreExprType core_arg) $ \ atom_arg -> - returnDs (core_fun `App` atom_arg) - + = dsLExpr fun `thenDs` \ core_fun -> + dsLExpr arg `thenDs` \ core_arg -> + returnDs (core_fun `App` core_arg) \end{code} Operator sections. At first it looks as if we can convert @@ -223,203 +233,237 @@ will sort it out. \begin{code} dsExpr (OpApp e1 op _ e2) - = dsExpr op `thenDs` \ core_op -> + = dsLExpr op `thenDs` \ core_op -> -- for the type of y, we need the type of op's 2nd argument - let - (x_ty:y_ty:_, _) = splitFunTy (coreExprType core_op) - in - dsExpr e1 `thenDs` \ x_core -> - dsExpr e2 `thenDs` \ y_core -> - dsExprToAtomGivenTy x_core x_ty $ \ x_atom -> - dsExprToAtomGivenTy y_core y_ty $ \ y_atom -> - returnDs (core_op `App` x_atom `App` y_atom) + dsLExpr e1 `thenDs` \ x_core -> + dsLExpr e2 `thenDs` \ y_core -> + returnDs (mkApps core_op [x_core, y_core]) dsExpr (SectionL expr op) - = dsExpr op `thenDs` \ core_op -> + = dsLExpr op `thenDs` \ core_op -> -- for the type of y, we need the type of op's 2nd argument let - (x_ty:y_ty:_, _) = splitFunTy (coreExprType core_op) + (x_ty:y_ty:_, _) = splitFunTys (exprType core_op) + -- Must look through an implicit-parameter type; + -- newtype impossible; hence Type.splitFunTys in - dsExpr expr `thenDs` \ x_core -> - dsExprToAtomGivenTy x_core x_ty $ \ x_atom -> - + dsLExpr expr `thenDs` \ x_core -> + newSysLocalDs x_ty `thenDs` \ x_id -> newSysLocalDs y_ty `thenDs` \ y_id -> - returnDs (mkValLam [y_id] (core_op `App` x_atom `App` VarArg y_id)) --- dsExpr (SectionR op expr) -- \ x -> op x expr + returnDs (bindNonRec x_id x_core $ + Lam y_id (mkApps core_op [Var x_id, Var y_id])) + +-- dsLExpr (SectionR op expr) -- \ x -> op x expr dsExpr (SectionR op expr) - = dsExpr op `thenDs` \ core_op -> + = dsLExpr op `thenDs` \ core_op -> -- for the type of x, we need the type of op's 2nd argument let - (x_ty:y_ty:_, _) = splitFunTy (coreExprType core_op) + (x_ty:y_ty:_, _) = splitFunTys (exprType core_op) + -- See comment with SectionL in - dsExpr expr `thenDs` \ y_expr -> - dsExprToAtomGivenTy y_expr y_ty $ \ y_atom -> - + dsLExpr expr `thenDs` \ y_core -> newSysLocalDs x_ty `thenDs` \ x_id -> - returnDs (mkValLam [x_id] (core_op `App` VarArg x_id `App` y_atom)) + newSysLocalDs y_ty `thenDs` \ y_id -> -dsExpr (CCall label args may_gc is_asm result_ty) - = mapDs dsExpr args `thenDs` \ core_args -> - dsCCall label core_args may_gc is_asm result_ty - -- dsCCall does all the unboxification, etc. + returnDs (bindNonRec y_id y_core $ + Lam x_id (mkApps core_op [Var x_id, Var y_id])) dsExpr (HsSCC cc expr) - = dsExpr expr `thenDs` \ core_expr -> - getModuleAndGroupDs `thenDs` \ (mod_name, group_name) -> - returnDs ( SCC (mkUserCC cc mod_name group_name) core_expr) - -dsExpr expr@(HsCase discrim matches src_loc) - = putSrcLocDs src_loc $ - dsExpr discrim `thenDs` \ core_discrim -> - matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) -> - returnDs ( mkCoLetAny (NonRec discrim_var core_discrim) matching_code ) - -dsExpr (HsLet binds expr) - = dsBinds False binds `thenDs` \ core_binds -> - dsExpr expr `thenDs` \ core_expr -> - returnDs ( mkCoLetsAny core_binds core_expr ) - -dsExpr (HsDoOut do_or_lc stmts return_id then_id zero_id result_ty src_loc) - | maybeToBool maybe_list_comp + = dsLExpr expr `thenDs` \ core_expr -> + getModuleDs `thenDs` \ mod_name -> + returnDs (Note (SCC (mkUserCC cc mod_name)) core_expr) + + +-- hdaume: core annotation + +dsExpr (HsCoreAnn fs expr) + = dsLExpr expr `thenDs` \ core_expr -> + returnDs (Note (CoreNote $ unpackFS fs) core_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 (HsLet binds body) + = dsLExpr body `thenDs` \ body' -> + dsLocalBinds binds body' + +-- We need the `ListComp' form to use `deListComp' (rather than the "do" form) +-- because the interpretation of `stmts' depends on what sort of thing it is. +-- +dsExpr (HsDo ListComp stmts body result_ty) = -- Special case for list comprehensions - putSrcLocDs src_loc $ - dsListComp stmts elt_ty + dsListComp stmts body elt_ty + where + [elt_ty] = tcTyConAppArgs result_ty - | otherwise - = putSrcLocDs src_loc $ - dsDo do_or_lc stmts return_id then_id zero_id result_ty +dsExpr (HsDo DoExpr stmts body result_ty) + = dsDo stmts body result_ty + +dsExpr (HsDo (MDoExpr tbl) stmts body result_ty) + = dsMDo tbl stmts body result_ty + +dsExpr (HsDo PArrComp stmts body result_ty) + = -- Special case for array comprehensions + dsPArrComp (map unLoc stmts) body elt_ty where - maybe_list_comp - = case (do_or_lc, maybeAppTyCon result_ty) of - (ListComp, Just (tycon, [elt_ty])) - | tycon == listTyCon - -> Just elt_ty - other -> Nothing - -- We need the ListComp form to use deListComp (rather than the "do" form) - -- because the "return" in a do block is a call to "PrelBase.return", and - -- not a ReturnStmt. Only the ListComp form has ReturnStmts - - Just elt_ty = maybe_list_comp - -dsExpr (HsIf guard_expr then_expr else_expr src_loc) - = putSrcLocDs src_loc $ - dsExpr guard_expr `thenDs` \ core_guard -> - dsExpr then_expr `thenDs` \ core_then -> - dsExpr else_expr `thenDs` \ core_else -> - returnDs (mkCoreIfThenElse core_guard core_then core_else) + [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) \end{code} -Type lambda and application -~~~~~~~~~~~~~~~~~~~~~~~~~~~ +\noindent +\underline{\bf Type lambda and application} +% ~~~~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} dsExpr (TyLam tyvars expr) - = dsExpr expr `thenDs` \ core_expr -> - returnDs (mkTyLam tyvars core_expr) + = dsLExpr expr `thenDs` \ core_expr -> + returnDs (mkLams tyvars core_expr) dsExpr (TyApp expr tys) - = dsExpr expr `thenDs` \ core_expr -> - returnDs (mkTyApp core_expr tys) + = dsLExpr expr `thenDs` \ core_expr -> + returnDs (mkTyApps core_expr tys) \end{code} -Various data construction things -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +\noindent +\underline{\bf Various data construction things} +% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} -dsExpr (ExplicitListOut ty xs) +dsExpr (ExplicitList ty xs) = go xs where - list_ty = mkListTy ty - - -- xs can ocasaionlly be huge, so don't try to take - -- coreExprType of core_xs, as dsArgToAtom does - -- (that gives a quadratic algorithm) - go [] = returnDs (mk_nil_con ty) - go (x:xs) = dsExpr x `thenDs` \ core_x -> - dsExprToAtomGivenTy core_x ty $ \ arg_x -> + go [] = returnDs (mkNilExpr ty) + go (x:xs) = dsLExpr x `thenDs` \ core_x -> go xs `thenDs` \ core_xs -> - dsExprToAtomGivenTy core_xs list_ty $ \ arg_xs -> - returnDs (Con consDataCon [TyArg ty, arg_x, arg_xs]) + returnDs (mkConsExpr ty core_x core_xs) -dsExpr (ExplicitTuple expr_list) - = mapDs dsExpr expr_list `thenDs` \ core_exprs -> - mkConDs (tupleCon (length expr_list)) - (map (TyArg . coreExprType) core_exprs ++ map VarArg core_exprs) +-- we create a list from the array elements and convert them into a list using +-- `PrelPArr.toP' +-- +-- * the main disadvantage to this scheme is that `toP' traverses the list +-- twice: once to determine the length and a second time to put to elements +-- into the array; this inefficiency could be avoided by exposing some of +-- the innards of `PrelPArr' to the compiler (ie, have a `PrelPArrBase') so +-- 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 (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 (ArithSeq expr (From from)) + = dsExpr expr `thenDs` \ expr2 -> + dsLExpr from `thenDs` \ from2 -> + returnDs (App expr2 from2) -dsExpr (ArithSeqOut expr (From from)) +dsExpr (ArithSeq expr (FromTo from two)) = dsExpr expr `thenDs` \ expr2 -> - dsExpr from `thenDs` \ from2 -> - mkAppDs expr2 [VarArg from2] + dsLExpr from `thenDs` \ from2 -> + dsLExpr two `thenDs` \ two2 -> + returnDs (mkApps expr2 [from2, two2]) -dsExpr (ArithSeqOut expr (FromTo from two)) +dsExpr (ArithSeq expr (FromThen from thn)) = dsExpr expr `thenDs` \ expr2 -> - dsExpr from `thenDs` \ from2 -> - dsExpr two `thenDs` \ two2 -> - mkAppDs expr2 [VarArg from2, VarArg two2] + dsLExpr from `thenDs` \ from2 -> + dsLExpr thn `thenDs` \ thn2 -> + returnDs (mkApps expr2 [from2, thn2]) -dsExpr (ArithSeqOut expr (FromThen from thn)) +dsExpr (ArithSeq expr (FromThenTo from thn two)) = dsExpr expr `thenDs` \ expr2 -> - dsExpr from `thenDs` \ from2 -> - dsExpr thn `thenDs` \ thn2 -> - mkAppDs expr2 [VarArg from2, VarArg thn2] + dsLExpr from `thenDs` \ from2 -> + dsLExpr thn `thenDs` \ thn2 -> + dsLExpr two `thenDs` \ two2 -> + returnDs (mkApps expr2 [from2, thn2, two2]) -dsExpr (ArithSeqOut expr (FromThenTo from thn two)) +dsExpr (PArrSeq expr (FromTo from two)) = dsExpr expr `thenDs` \ expr2 -> - dsExpr from `thenDs` \ from2 -> - dsExpr thn `thenDs` \ thn2 -> - dsExpr two `thenDs` \ two2 -> - mkAppDs expr2 [VarArg from2, VarArg thn2, VarArg two2] + 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]) + +dsExpr (PArrSeq expr _) + = panic "DsExpr.dsExpr: Infinite parallel array!" + -- the parser shouldn't have generated it and the renamer and typechecker + -- shouldn't have let it through \end{code} -Record construction and update -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +\noindent +\underline{\bf Record construction and update} +% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For record construction we do this (assuming T has three arguments) - +\begin{verbatim} T { op2 = e } ==> let err = /\a -> recConErr a T (recConErr t1 "M.lhs/230/op1") e (recConErr t1 "M.lhs/230/op3") - -recConErr then converts its arugment string into a proper message +\end{verbatim} +@recConErr@ then converts its arugment string into a proper message before printing it as - +\begin{verbatim} M.lhs, line 230: missing field op1 was evaluated +\end{verbatim} +We also handle @C{}@ as valid construction syntax for an unlabelled +constructor @C@, setting all of @C@'s fields to bottom. \begin{code} -dsExpr (RecordCon con_expr rbinds) +dsExpr (RecordCon (L _ data_con_id) con_expr rbinds) = dsExpr con_expr `thenDs` \ con_expr' -> let - con_id = get_con con_expr' - (arg_tys, _) = splitFunTy (coreExprType con_expr') + (arg_tys, _) = tcSplitFunTys (exprType con_expr') + -- A newtype in the corner should be opaque; + -- hence TcType.tcSplitFunTys - mk_arg (arg_ty, lbl) - = case [rhs | (sel_id,rhs,_) <- rbinds, - lbl == recordSelectorFieldLabel sel_id] of + 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 ) - dsExpr rhs - [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showForErr lbl) + 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 - mapDs mk_arg (zipEqual "dsExpr:RecordCon" arg_tys (dataConFieldLabels con_id)) `thenDs` \ con_args -> - mkAppDs con_expr' (map VarArg con_args) - where - -- "con_expr'" is simply an application of the constructor Id - -- to types and (perhaps) dictionaries. This gets the constructor... - get_con (Var con) = con - get_con (App fun _) = get_con fun + + (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) \end{code} Record update is a little harder. Suppose we have the decl: - +\begin{verbatim} data T = T1 {op1, op2, op3 :: Int} | T2 {op4, op2 :: Int} | T3 - +\end{verbatim} Then we translate as follows: - +\begin{verbatim} r { op2 = e } ===> let op2 = e in @@ -427,248 +471,273 @@ Then we translate as follows: T1 op1 _ op3 -> T1 op1 op2 op3 T2 op4 _ -> T2 op4 op2 other -> recUpdError "M.lhs/230" - -It's important that we use the constructor Ids for T1, T2 etc on the -RHSs, and do not generate a Core Con directly, because the constructor +\end{verbatim} +It's important that we use the constructor Ids for @T1@, @T2@ etc on the +RHSs, and do not generate a Core constructor application directly, because the constructor might do some argument-evaluation first; and may have to throw away some dictionaries. \begin{code} -dsExpr (RecordUpdOut record_expr record_out_ty dicts rbinds) - = dsExpr record_expr `thenDs` \ record_expr' -> +dsExpr (RecordUpd record_expr [] record_in_ty record_out_ty) + = 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 - dsRbinds rbinds $ \ rbinds' -> + let - record_in_ty = coreExprType record_expr' - (tycon, in_inst_tys, cons) = getAppDataTyConExpandingDicts record_in_ty - (_, out_inst_tys, _) = getAppDataTyConExpandingDicts record_out_ty - cons_to_upd = filter has_all_fields cons - - -- initial_args are passed to every constructor - initial_args = map TyArg out_inst_tys ++ map VarArg dicts - - mk_val_arg (field, arg_id) - = case [arg | (f, arg) <- rbinds', - field == recordSelectorFieldLabel f] of - (arg:args) -> ASSERT(null args) - arg - [] -> VarArg arg_id + 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 - = newSysLocalsDs (dataConArgTys con in_inst_tys) `thenDs` \ arg_ids -> + = 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 = map mk_val_arg (zipEqual "dsExpr:RecordUpd" (dataConFieldLabels con) arg_ids) + val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg + (dataConFieldLabels con) arg_ids + rhs = foldl (\a b -> nlHsApp a b) + (noLoc $ TyApp (nlHsVar (dataConWrapId con)) + out_inst_tys) + val_args in - returnDs (con, arg_ids, mkGenApp (mkGenApp (Var con) initial_args) val_args) - - mk_default - | length cons_to_upd == length cons - = returnDs NoDefault - | otherwise - = newSysLocalDs record_in_ty `thenDs` \ deflt_id -> - mkErrorAppDs rEC_UPD_ERROR_ID record_out_ty "" `thenDs` \ err -> - returnDs (BindDefault deflt_id err) + returnDs (mkSimpleMatch [noLoc $ ConPatOut (noLoc con) [] [] emptyLHsBinds + (PrefixCon (map nlVarPat arg_ids)) record_in_ty] + rhs) in - mapDs mk_alt cons_to_upd `thenDs` \ alts -> - mk_default `thenDs` \ deflt -> + -- 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 ) - returnDs (Case record_expr' (AlgAlts alts deflt)) + -- 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) where - has_all_fields :: Id -> Bool + 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 ok rbinds + = all (`elem` con_fields) updated_fields where - con_fields = dataConFieldLabels con_id - ok (sel_id, _, _) = recordSelectorFieldLabel sel_id `elem` con_fields + con_fields = dataConFieldLabels con_id \end{code} -Dictionary lambda and application -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +\noindent +\underline{\bf Dictionary lambda and application} +% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @DictLam@ and @DictApp@ turn into the regular old things. (OLD:) @DictFunApp@ also becomes a curried application, albeit slightly more complicated; reminiscent of fully-applied constructors. \begin{code} dsExpr (DictLam dictvars expr) - = dsExpr expr `thenDs` \ core_expr -> - returnDs (mkValLam dictvars core_expr) + = dsLExpr expr `thenDs` \ core_expr -> + returnDs (mkLams dictvars core_expr) ------------------ dsExpr (DictApp expr dicts) -- becomes a curried application - = mapDs lookupEnvDs dicts `thenDs` \ core_dicts -> - dsExpr expr `thenDs` \ core_expr -> - returnDs (foldl (\f d -> f `App` (VarArg d)) core_expr core_dicts) + = dsLExpr expr `thenDs` \ core_expr -> + returnDs (foldl (\f d -> f `App` (Var d)) core_expr dicts) + +dsExpr (HsCoerce co_fn e) = dsCoercion co_fn (dsExpr e) \end{code} -@SingleDicts@ become @Locals@; @Dicts@ turn into tuples, unless -of length 0 or 1. -@ClassDictLam dictvars methods expr@ is ``the opposite'': -\begin{verbatim} -\ x -> case x of ( dictvars-and-methods-tuple ) -> expr -\end{verbatim} +Here is where we desugar the Template Haskell brackets and escapes + +\begin{code} +-- Template Haskell stuff + +#ifdef GHCI /* Only if bootstrapping */ +dsExpr (HsBracketOut x ps) = dsBracket x ps +dsExpr (HsSpliceE s) = pprPanic "dsExpr:splice" (ppr s) +#endif + +-- Arrow notation extension +dsExpr (HsProc pat cmd) = dsProcExpr pat cmd +\end{code} + + \begin{code} -dsExpr (SingleDict dict) -- just a local - = lookupEnvDs dict `thenDs` \ dict' -> - returnDs (Var dict') - -dsExpr (Dictionary [] []) -- Empty dictionary represented by void, - = returnDs (Var voidId) -- (not, as would happen if we took the next case, by ()) - -dsExpr (Dictionary dicts methods) - = mapDs lookupEnvDs (dicts ++ methods) `thenDs` \ d_and_ms' -> - returnDs (mkTupleExpr d_and_ms') - -dsExpr (ClassDictLam dicts methods expr) - = dsExpr expr `thenDs` \ core_expr -> - case num_of_d_and_ms of - 0 -> newSysLocalDs voidTy `thenDs` \ new_x -> - returnDs (mkValLam [new_x] core_expr) - - 1 -> -- no untupling - returnDs (mkValLam dicts_and_methods core_expr) - - _ -> -- untuple it - newSysLocalDs tuple_ty `thenDs` \ new_x -> - returnDs ( - Lam (ValBinder new_x) - (Case (Var new_x) - (AlgAlts - [(tuple_con, dicts_and_methods, core_expr)] - NoDefault))) - where - num_of_d_and_ms = length dicts + length methods - dicts_and_methods = dicts ++ methods - tuple_ty = mkTupleTy num_of_d_and_ms (map idType dicts_and_methods) - tuple_con = tupleCon num_of_d_and_ms #ifdef DEBUG -- HsSyn constructs that just shouldn't be here: -dsExpr (HsDo _ _ _) = panic "dsExpr:HsDo" -dsExpr (ExplicitList _) = panic "dsExpr:ExplicitList" dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig" -dsExpr (ArithSeqIn _) = panic "dsExpr:ArithSeqIn" #endif -out_of_range_msg -- ditto - = " out of range: [" ++ show minInt ++ ", " ++ show maxInt ++ "]\n" \end{code} - %-------------------------------------------------------------------- -\begin{code} -dsId v - = lookupEnvDs v `thenDs` \ v' -> - returnDs (Var v') -\end{code} +Desugar 'do' and 'mdo' expressions (NOT list comprehensions, they're +handled in DsListComp). Basically does the translation given in the +Haskell 98 report: \begin{code} -dsRbinds :: TypecheckedRecordBinds -- The field bindings supplied - -> ([(Id, CoreArg)] -> DsM CoreExpr) -- A continuation taking the field - -- bindings with atomic rhss - -> DsM CoreExpr -- The result of the continuation, - -- wrapped in suitable Lets - -dsRbinds [] continue_with - = continue_with [] - -dsRbinds ((sel_id, rhs, pun_flag) : rbinds) continue_with - = dsExpr rhs `thenDs` \ rhs' -> - dsExprToAtomGivenTy rhs' (coreExprType rhs') $ \ rhs_atom -> - dsRbinds rbinds $ \ rbinds' -> - continue_with ((sel_id, rhs_atom) : rbinds') -\end{code} +dsDo :: [LStmt Id] + -> LHsExpr Id + -> Type -- Type of the whole expression + -> DsM CoreExpr -\begin{code} --- do_unfold ty_env val_env (Lam (TyBinder tyvar) body) (TyArg ty : args) --- = do_unfold (addOneToTyVarEnv ty_env tyvar ty) val_env body args --- --- do_unfold ty_env val_env (Lam (ValBinder binder) body) (arg@(VarArg expr) : args) --- = dsExprToAtom arg $ \ arg_atom -> --- do_unfold ty_env --- (addOneToIdEnv val_env binder (argToExpr arg_atom)) --- body args --- --- do_unfold ty_env val_env body args --- = -- Clone the remaining part of the template --- uniqSMtoDsM (substCoreExpr val_env ty_env body) `thenDs` \ body' -> --- --- -- Apply result to remaining arguments --- mkAppDs body' args +dsDo stmts body result_ty + = go (map unLoc stmts) + where + go [] = dsLExpr body + + go (ExprStmt rhs then_expr _ : stmts) + = do { rhs2 <- dsLExpr rhs + ; then_expr2 <- dsExpr then_expr + ; rest <- go stmts + ; returnDs (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 + ; 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 + ; bind_op' <- dsExpr bind_op + ; returnDs (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 + handle_failure pat match fail_op + | matchCanFail match + = do { fail_op' <- dsExpr fail_op + ; fail_msg <- mkStringExpr (mk_fail_msg pat) + ; extractMatchResult match (App fail_op' fail_msg) } + | otherwise + = extractMatchResult match (error "It can't fail") + +mk_fail_msg pat = "Pattern match failure in do expression at " ++ + showSDoc (ppr (getLoc pat)) \end{code} -Basically does the translation given in the Haskell~1.3 report: +Translation for RecStmt's: +----------------------------- +We turn (RecStmt [v1,..vn] stmts) into: + + (v1,..,vn) <- mfix (\~(v1,..vn). do stmts + return (v1,..vn)) + \begin{code} -dsDo :: DoOrListComp - -> [TypecheckedStmt] - -> Id -- id for: return m - -> Id -- id for: (>>=) m - -> Id -- id for: zero m - -> Type -- Element type; the whole expression has type (m t) +dsMDo :: PostTcTable + -> [LStmt Id] + -> LHsExpr Id + -> Type -- Type of the whole expression -> DsM CoreExpr -dsDo do_or_lc stmts return_id then_id zero_id result_ty - = dsId return_id `thenDs` \ return_ds -> - dsId then_id `thenDs` \ then_ds -> - dsId zero_id `thenDs` \ zero_ds -> - let - (_, b_ty) = splitAppTy result_ty -- result_ty must be of the form (m b) - - go [ReturnStmt expr] - = dsExpr expr `thenDs` \ expr2 -> - mkAppDs return_ds [TyArg b_ty, VarArg expr2] - - go (GuardStmt expr locn : stmts) - = do_expr expr locn `thenDs` \ expr2 -> - go stmts `thenDs` \ rest -> - mkAppDs zero_ds [TyArg b_ty] `thenDs` \ zero_expr -> - returnDs (mkCoreIfThenElse expr2 rest zero_expr) +dsMDo tbl stmts body result_ty + = go (map unLoc stmts) + where + (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 + bind_id = lookupEvidence tbl bindMName + then_id = lookupEvidence tbl thenMName + fail_id = lookupEvidence tbl failMName + ctxt = MDoExpr tbl + + go [] = dsLExpr body - go (ExprStmt expr locn : stmts) - = do_expr expr locn `thenDs` \ expr2 -> - let - (_, a_ty) = splitAppTy (coreExprType expr2) -- Must be of form (m a) - in - if null stmts then - returnDs expr2 - else - go stmts `thenDs` \ rest -> - newSysLocalDs a_ty `thenDs` \ ignored_result_id -> - mkAppDs then_ds [TyArg a_ty, TyArg b_ty, VarArg expr2, - VarArg (mkValLam [ignored_result_id] rest)] + go (LetStmt binds : stmts) + = do { rest <- go stmts + ; dsLocalBinds binds rest } + + 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]) } - go (LetStmt binds : stmts ) - = dsBinds False binds `thenDs` \ binds2 -> - go stmts `thenDs` \ rest -> - returnDs (mkCoLetsAny binds2 rest) + go (BindStmt pat rhs _ _ : stmts) + = do { body <- go stmts + ; var <- selectSimpleMatchVarL pat + ; match <- matchSinglePat (Var var) (StmtCtxt ctxt) pat + result_ty (cantFailMatchResult body) + ; fail_msg <- mkStringExpr (mk_fail_msg pat) + ; let fail_expr = mkApps (Var fail_id) [Type b_ty, fail_msg] + ; match_code <- extractMatchResult match fail_expr + + ; rhs' <- dsLExpr rhs + ; returnDs (mkApps (Var bind_id) [Type (hsPatType pat), Type b_ty, + rhs', Lam var match_code]) } - go (BindStmt pat expr locn : stmts) - = putSrcLocDs locn $ - dsExpr expr `thenDs` \ expr2 -> - let - (_, a_ty) = splitAppTy (coreExprType expr2) -- Must be of form (m a) - zero_expr = TyApp (HsVar zero_id) [b_ty] - main_match = PatMatch pat (SimpleMatch ( - HsDoOut do_or_lc stmts return_id then_id zero_id result_ty locn)) - the_matches - = if failureFreePat pat - then [main_match] - else [main_match, PatMatch (WildPat a_ty) (SimpleMatch zero_expr)] - in - matchWrapper DoBindMatch the_matches match_msg - `thenDs` \ (binders, matching_code) -> - mkAppDs then_ds [TyArg a_ty, TyArg b_ty, - VarArg expr2, VarArg (mkValLam binders matching_code)] - in - go stmts - - where - do_expr expr locn = putSrcLocDs locn (dsExpr expr) + go (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) + where + new_bind_stmt = mkBindStmt (mk_tup_pat later_pats) mfix_app + let_stmt = LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] [])) - match_msg = case do_or_lc of - DoStmt -> "`do' statement" - ListComp -> "comprehension" + + -- Remove the later_ids that appear (without fancy coercions) + -- in rec_rets, because there's no need to knot-tie them separately + -- See Note [RecStmt] in HsExpr + later_ids' = filter (`notElem` mono_rec_ids) later_ids + mono_rec_ids = [ id | HsVar id <- rec_rets ] + + mfix_app = nlHsApp (noLoc $ TyApp (nlHsVar mfix_id) [tup_ty]) mfix_arg + mfix_arg = noLoc $ HsLam (MatchGroup [mkSimpleMatch [mfix_pat] body] + (mkFunTy tup_ty body_ty)) + + -- The rec_tup_pat must bind the rec_ids only; remember that the + -- trimmed_laters may share the same Names + -- Meanwhile, the later_pats must bind the later_vars + rec_tup_pats = map mk_wild_pat later_ids' ++ map nlVarPat rec_ids + later_pats = map nlVarPat later_ids' ++ map mk_later_pat rec_ids + rets = map nlHsVar later_ids' ++ map noLoc rec_rets + + 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 + + return_app = nlHsApp (noLoc $ TyApp (nlHsVar return_id) [tup_ty]) + (mk_ret_tup rets) + + mk_wild_pat :: Id -> LPat Id + mk_wild_pat v = noLoc $ WildPat $ idType v + + mk_later_pat :: Id -> LPat Id + mk_later_pat v | v `elem` later_ids' = mk_wild_pat v + | otherwise = nlVarPat v + + mk_tup_pat :: [LPat Id] -> LPat Id + mk_tup_pat [p] = p + mk_tup_pat ps = noLoc $ mkVanillaTuplePat ps Boxed + + mk_ret_tup :: [LHsExpr Id] -> LHsExpr Id + mk_ret_tup [r] = r + mk_ret_tup rs = noLoc $ ExplicitTuple rs Boxed \end{code}