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Diffstat (limited to 'ghc/compiler/deSugar/DsExpr.lhs')
| -rw-r--r-- | ghc/compiler/deSugar/DsExpr.lhs | 781 |
1 files changed, 0 insertions, 781 deletions
diff --git a/ghc/compiler/deSugar/DsExpr.lhs b/ghc/compiler/deSugar/DsExpr.lhs deleted file mode 100644 index e8e9e7b370..0000000000 --- a/ghc/compiler/deSugar/DsExpr.lhs +++ /dev/null @@ -1,781 +0,0 @@ -% -% (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" -#if defined(GHCI) && defined(BREAKPOINT) -import Foreign.StablePtr ( newStablePtr, castStablePtrToPtr ) -import GHC.Exts ( Ptr(..), Int(..), addr2Int# ) -import IOEnv ( ioToIOEnv ) -import PrelNames ( breakpointJumpName ) -import TysWiredIn ( unitTy ) -import TypeRep ( Type(..) ) -#endif - -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 - -#ifdef GHCI - -- Template Haskell stuff iff bootstrapped -import DsMeta ( dsBracket ) -#endif - -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 CostCentre ( mkUserCC ) -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} - - -%************************************************************************ -%* * - dsLocalBinds, dsValBinds -%* * -%************************************************************************ - -\begin{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-vars-and-cons]{Variables, constructors, literals} -%* * -%************************************************************************ - -\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 (HsLit lit) = dsLit lit -dsExpr (HsOverLit lit) = dsOverLit lit - -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 LambdaExpr a_Match `thenDs` \ (binders, matching_code) -> - returnDs (mkLams binders matching_code) - -#if defined(GHCI) && defined(BREAKPOINT) -dsExpr (HsApp (L _ (HsApp realFun@(L _ (HsCoerce _ fun)) (L loc arg))) _) - | HsVar funId <- fun - , idName funId == breakpointJumpName - , ids <- filter (not.hasTyVar.idType) (extractIds arg) - = do dsWarn (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) - | TyApp arg' ts <- unLoc arg - , HsVar argId <- unLoc arg' - = error (showSDoc (ppr ts)) -- argId:extractIds (unLoc fn) - extractIds x = [] - extractHVals ids = ExplicitList unitTy (map (L loc . HsVar) ids) - hasTyVar (TyVarTy _) = True - hasTyVar (FunTy a b) = hasTyVar a || hasTyVar b - hasTyVar (NoteTy _ t) = hasTyVar t - hasTyVar (AppTy a b) = hasTyVar a || hasTyVar b - hasTyVar (TyConApp _ ts) = any hasTyVar ts - hasTyVar _ = False -#endif - -dsExpr expr@(HsApp fun 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 -\begin{verbatim} - (expr op) -\end{verbatim} -to -\begin{verbatim} - \x -> op expr x -\end{verbatim} - -But no! expr might be a redex, and we can lose laziness badly this -way. Consider -\begin{verbatim} - map (expr op) xs -\end{verbatim} -for example. So we convert instead to -\begin{verbatim} - let y = expr in \x -> op y x -\end{verbatim} -If \tr{expr} is actually just a variable, say, then the simplifier -will sort it out. - -\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]) - -dsExpr (SectionL expr 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:_, _) = splitFunTys (exprType core_op) - -- Must look through an implicit-parameter type; - -- newtype impossible; hence Type.splitFunTys - in - dsLExpr expr `thenDs` \ x_core -> - newSysLocalDs x_ty `thenDs` \ x_id -> - newSysLocalDs y_ty `thenDs` \ y_id -> - - 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) - = dsLExpr op `thenDs` \ core_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 -> - - 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) - - --- 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 - dsListComp stmts body elt_ty - where - [elt_ty] = tcTyConAppArgs 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 - [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} - - -\noindent -\underline{\bf Type lambda and application} -% ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -\begin{code} -dsExpr (TyLam tyvars expr) - = dsLExpr expr `thenDs` \ core_expr -> - returnDs (mkLams tyvars core_expr) - -dsExpr (TyApp expr tys) - = dsLExpr expr `thenDs` \ core_expr -> - returnDs (mkTyApps core_expr tys) -\end{code} - - -\noindent -\underline{\bf Various data construction things} -% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -\begin{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) - --- 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 (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 (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]) - -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} - -\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") -\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 (L _ data_con_id) con_expr rbinds) - = dsExpr con_expr `thenDs` \ 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) -\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 - case r of - T1 op1 _ op3 -> T1 op1 op2 op3 - T2 op4 _ -> T2 op4 op2 - other -> recUpdError "M.lhs/230" -\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 (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 - - 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 - = 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) - (noLoc $ TyApp (nlHsVar (dataConWrapId con)) - out_inst_tys) - val_args - in - returnDs (mkSimpleMatch [noLoc $ ConPatOut (noLoc con) [] [] emptyLHsBinds - (PrefixCon (map nlVarPat arg_ids)) record_in_ty] - rhs) - in - -- 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 ) - - -- 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 - 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 -\end{code} - - -\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) - = dsLExpr expr `thenDs` \ core_expr -> - returnDs (mkLams dictvars core_expr) - ------------------- - -dsExpr (DictApp expr dicts) -- becomes a curried application - = 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} - -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} - -#ifdef DEBUG --- HsSyn constructs that just shouldn't be here: -dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig" -#endif - -\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} -dsDo :: [LStmt Id] - -> LHsExpr Id - -> Type -- Type of the whole expression - -> DsM CoreExpr - -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} - -Translation for RecStmt's: ------------------------------ -We turn (RecStmt [v1,..vn] stmts) into: - - (v1,..,vn) <- mfix (\~(v1,..vn). do stmts - return (v1,..vn)) - -\begin{code} -dsMDo :: PostTcTable - -> [LStmt Id] - -> LHsExpr Id - -> Type -- Type of the whole expression - -> DsM CoreExpr - -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 (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 (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 (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)] [])) - - - -- 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} |