X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FdeSugar%2FDsExpr.lhs;h=406d7934400b139cbf6b5b38accaf6900647e184;hb=3c245de9199f522f75ace92219256badbd928bd6;hp=4bcc2c98020b851861f9f48b181484af34510036;hpb=550421384b8364cdaf3135f7859c9f7d7ee1fff1;p=ghc-hetmet.git diff --git a/ghc/compiler/deSugar/DsExpr.lhs b/ghc/compiler/deSugar/DsExpr.lhs index 4bcc2c9..406d793 100644 --- a/ghc/compiler/deSugar/DsExpr.lhs +++ b/ghc/compiler/deSugar/DsExpr.lhs @@ -4,19 +4,18 @@ \section[DsExpr]{Matching expressions (Exprs)} \begin{code} -module DsExpr ( dsExpr, dsLExpr, dsLet, dsLit ) where +module DsExpr ( dsExpr, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where #include "HsVersions.h" - -import Match ( matchWrapper, matchSimply ) -import MatchLit ( dsLit ) -import DsBinds ( dsHsBinds, AutoScc(..) ) +import Match ( matchWrapper, matchSinglePat, matchEquations ) +import MatchLit ( dsLit, dsOverLit ) +import DsBinds ( dsLHsBinds, dsCoercion ) import DsGRHSs ( dsGuarded ) import DsListComp ( dsListComp, dsPArrComp ) -import DsUtils ( mkErrorAppDs, mkStringLit, mkConsExpr, mkNilExpr, - mkCoreTupTy, selectMatchVarL, - dsReboundNames, lookupReboundName ) +import DsUtils ( mkErrorAppDs, mkStringExpr, mkConsExpr, mkNilExpr, + extractMatchResult, cantFailMatchResult, matchCanFail, + mkCoreTupTy, selectSimpleMatchVarL, lookupEvidence, selectMatchVar ) import DsArrows ( dsProcExpr ) import DsMonad @@ -26,28 +25,25 @@ import DsMeta ( dsBracket ) #endif import HsSyn -import TcHsSyn ( hsPatType ) +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, tcTyConAppArgs, - tcSplitTyConApp, isUnLiftedType, Type, - mkAppTy ) -import Type ( splitFunTys ) +import TcType ( tcSplitAppTy, tcSplitFunTys, tcTyConAppTyCon, + tcTyConAppArgs, isUnLiftedType, Type, mkAppTy ) +import Type ( funArgTy, splitFunTys, isUnboxedTupleType, mkFunTy ) import CoreSyn import CoreUtils ( exprType, mkIfThenElse, bindNonRec ) -import FieldLabel ( FieldLabel, fieldLabelTyCon ) import CostCentre ( mkUserCC ) -import Id ( Id, idType, idName, recordSelectorFieldLabel ) +import Id ( Id, idType, idName, idDataCon ) import PrelInfo ( rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID ) import DataCon ( DataCon, dataConWrapId, dataConFieldLabels, dataConInstOrigArgTys ) -import DataCon ( isExistentialDataCon ) -import Name ( Name ) -import TyCon ( tyConDataCons ) +import DataCon ( isVanillaDataCon ) +import TyCon ( FieldLabel, tyConDataCons ) import TysWiredIn ( tupleCon ) import BasicTypes ( RecFlag(..), Boxity(..), ipNameName ) import PrelNames ( toPName, @@ -63,75 +59,82 @@ import FastString %************************************************************************ %* * -\subsection{dsLet} + dsLocalBinds, dsValBinds %* * %************************************************************************ -@dsLet@ is a match-result transformer, taking the @MatchResult@ for the body -and transforming it into one for the let-bindings enclosing the body. - -This may seem a bit odd, but (source) let bindings can contain unboxed -binds like -\begin{verbatim} - C x# = e -\end{verbatim} -This must be transformed to a case expression and, if the type has -more than one constructor, may fail. - \begin{code} -dsLet :: [HsBindGroup Id] -> CoreExpr -> DsM CoreExpr -dsLet groups body = foldlDs dsBindGroup body (reverse groups) - -dsBindGroup :: CoreExpr -> HsBindGroup Id -> DsM CoreExpr -dsBindGroup body (HsIPBinds binds) - = foldlDs dsIPBind body binds +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 - dsIPBind body (L _ (IPBind n e)) - = dsLExpr e `thenDs` \ e' -> - returnDs (Let (NonRec (ipNameName n) e') body) + 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 pragmas... -dsBindGroup body bind@(HsBindGroup hsbinds sigs is_rec) - | [L _ (AbsBinds [] [] exports inlines binds)] <- bagToList hsbinds, - or [isUnLiftedType (idType g) | (_, g, l) <- exports] - = ASSERT (case is_rec of {NonRecursive -> True; other -> False}) - -- Unlifted bindings are always non-recursive - -- and are always a Fun or Pat monobind - -- +-- 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.) - let - body_w_exports = foldr bind_export body exports - bind_export (tvs, g, l) body = ASSERT( null tvs ) - bindNonRec g (Var l) body - - mk_error_app pat = mkErrorAppDs iRREFUT_PAT_ERROR_ID - (exprType body) - (showSDoc (ppr pat)) - in - case bagToList binds of - [L loc (FunBind (L _ fun) _ matches)] - -> putSrcSpanDs loc $ - matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) -> + 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) - [L loc (PatBind pat grhss)] - -> putSrcSpanDs loc $ - dsGuarded grhss `thenDs` \ rhs -> - mk_error_app pat `thenDs` \ error_expr -> - matchSimply rhs PatBindRhs pat body_w_exports error_expr - - other -> pprPanic "dsLet: unlifted" (ppr bind $$ ppr body) - --- Ordinary case for bindings -dsBindGroup body (HsBindGroup binds sigs is_rec) - = dsHsBinds NoSccs binds [] `thenDs` \ prs -> - returnDs (Let (Rec prs) body) + PatBind {pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty } + -> -- let C x# y# = rhs in body + -- ==> case rhs of C x# y# -> body + putSrcSpanDs loc $ + do { rhs <- dsGuarded grhss ty + ; let upat = unLoc pat + eqn = EqnInfo { eqn_wrap = idWrapper, eqn_pats = [upat], + eqn_rhs = cantFailMatchResult body_w_exports } + ; var <- selectMatchVar upat ty + ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body) + ; return (scrungleMatch var rhs result) } + + other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ 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 @@ -142,6 +145,35 @@ dsBindGroup body (HsBindGroup binds sigs is_rec) -- -- 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} %************************************************************************ @@ -156,14 +188,20 @@ dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e dsExpr :: HsExpr Id -> DsM CoreExpr -dsExpr (HsPar x) = dsLExpr x -dsExpr (HsVar var) = returnDs (Var var) -dsExpr (HsIPVar ip) = returnDs (Var (ipNameName ip)) -dsExpr (HsLit lit) = dsLit lit --- HsOverLit has been gotten rid of by the type checker +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) -> + = matchWrapper LambdaExpr a_Match `thenDs` \ (binders, matching_code) -> returnDs (mkLams binders matching_code) dsExpr expr@(HsApp fun arg) @@ -243,47 +281,35 @@ dsExpr (HsCoreAnn fs expr) = dsLExpr expr `thenDs` \ core_expr -> returnDs (Note (CoreNote $ unpackFS fs) core_expr) --- special case to handle unboxed tuple patterns. - -dsExpr (HsCase discrim matches) - | all ubx_tuple_match matches - = dsLExpr discrim `thenDs` \ core_discrim -> - matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) -> - case matching_code of - Case (Var x) bndr alts | x == discrim_var -> - returnDs (Case core_discrim bndr alts) - _ -> panic ("dsLExpr: tuple pattern:\n" ++ showSDoc (ppr matching_code)) - where - ubx_tuple_match (L _ (Match [L _ (TuplePat _ Unboxed)] _ _)) = True - ubx_tuple_match _ = False - dsExpr (HsCase discrim matches) = dsLExpr discrim `thenDs` \ core_discrim -> - matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) -> - returnDs (bindNonRec discrim_var core_discrim matching_code) + matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) -> + returnDs (scrungleMatch discrim_var core_discrim matching_code) dsExpr (HsLet binds body) = dsLExpr body `thenDs` \ body' -> - dsLet binds 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 _ result_ty) +dsExpr (HsDo ListComp stmts body result_ty) = -- Special case for list comprehensions - dsListComp stmts elt_ty + dsListComp stmts body elt_ty where - (_, [elt_ty]) = tcSplitTyConApp result_ty + [elt_ty] = tcTyConAppArgs result_ty + +dsExpr (HsDo DoExpr stmts body result_ty) + = dsDo stmts body result_ty -dsExpr (HsDo do_or_lc stmts ids result_ty) - | isDoExpr do_or_lc - = dsDo do_or_lc stmts ids result_ty +dsExpr (HsDo (MDoExpr tbl) stmts body result_ty) + = dsMDo tbl stmts body result_ty -dsExpr (HsDo PArrComp stmts _ result_ty) +dsExpr (HsDo PArrComp stmts body result_ty) = -- Special case for array comprehensions - dsPArrComp (map unLoc stmts) elt_ty + dsPArrComp (map unLoc stmts) body elt_ty where - (_, [elt_ty]) = tcSplitTyConApp result_ty + [elt_ty] = tcTyConAppArgs result_ty dsExpr (HsIf guard_expr then_expr else_expr) = dsLExpr guard_expr `thenDs` \ core_guard -> @@ -322,7 +348,7 @@ dsExpr (ExplicitList ty 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 +-- * 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 @@ -339,44 +365,44 @@ dsExpr (ExplicitTuple expr_list boxity) returnDs (mkConApp (tupleCon boxity (length expr_list)) (map (Type . exprType) core_exprs ++ core_exprs)) -dsExpr (ArithSeqOut expr (From from)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> +dsExpr (ArithSeq expr (From from)) + = dsExpr expr `thenDs` \ expr2 -> + dsLExpr from `thenDs` \ from2 -> returnDs (App expr2 from2) -dsExpr (ArithSeqOut expr (FromTo from two)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ 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 (ArithSeqOut expr (FromThen from thn)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> +dsExpr (ArithSeq expr (FromThen from thn)) + = dsExpr expr `thenDs` \ expr2 -> + dsLExpr from `thenDs` \ from2 -> dsLExpr thn `thenDs` \ thn2 -> returnDs (mkApps expr2 [from2, thn2]) -dsExpr (ArithSeqOut expr (FromThenTo from thn two)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> +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 (PArrSeqOut expr (FromTo from two)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> +dsExpr (PArrSeq expr (FromTo from two)) + = dsExpr expr `thenDs` \ expr2 -> + dsLExpr from `thenDs` \ from2 -> dsLExpr two `thenDs` \ two2 -> returnDs (mkApps expr2 [from2, two2]) -dsExpr (PArrSeqOut expr (FromThenTo from thn two)) - = dsLExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> +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 (PArrSeqOut expr _) +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 @@ -404,22 +430,22 @@ We also handle @C{}@ as valid construction syntax for an unlabelled constructor @C@, setting all of @C@'s fields to bottom. \begin{code} -dsExpr (RecordConOut data_con con_expr rbinds) - = dsLExpr con_expr `thenDs` \ con_expr' -> +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) - = case [rhs | (L _ 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 ) 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 data_con + labels = dataConFieldLabels (idDataCon data_con_id) + -- The data_con_id is guaranteed to be the wrapper id of the constructor in (if null labels @@ -452,10 +478,10 @@ might do some argument-evaluation first; and may have to throw away some dictionaries. \begin{code} -dsExpr (RecordUpdOut record_expr record_in_ty record_out_ty []) +dsExpr (RecordUpd record_expr [] record_in_ty record_out_ty) = dsLExpr record_expr -dsExpr expr@(RecordUpdOut record_expr record_in_ty record_out_ty rbinds) +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 @@ -464,16 +490,17 @@ dsExpr expr@(RecordUpdOut record_expr record_in_ty record_out_ty rbinds) 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 == recordSelectorFieldLabel sel_id] of + = 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 dataConArgTys won't work for existentials + -- 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 @@ -482,34 +509,33 @@ dsExpr expr@(RecordUpdOut record_expr record_in_ty record_out_ty rbinds) out_inst_tys) val_args in - returnDs (mkSimpleMatch [noLoc $ ConPatOut con (PrefixCon (map nlVarPat arg_ids)) record_in_ty [] []] - rhs - record_out_ty) + 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 (not . isExistentialDataCon) cons_to_upd, ppr expr ) + 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 alts `thenDs` \ ([discrim_var], matching_code) -> + 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 = [ recordSelectorFieldLabel sel_id - | (L _ sel_id,_) <- rbinds] + updated_fields = [ idName sel_id | (L _ sel_id,_) <- rbinds] - -- Get the type constructor from the first field label, + -- 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 = fieldLabelTyCon (head updated_fields) + tycon = tcTyConAppTyCon record_in_ty data_cons = tyConDataCons tycon cons_to_upd = filter has_all_fields data_cons @@ -537,6 +563,8 @@ dsExpr (DictLam dictvars 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 @@ -546,7 +574,7 @@ Here is where we desugar the Template Haskell brackets and escapes #ifdef GHCI /* Only if bootstrapping */ dsExpr (HsBracketOut x ps) = dsBracket x ps -dsExpr (HsSplice n e) = pprPanic "dsExpr:splice" (ppr e) +dsExpr (HsSpliceE s) = pprPanic "dsExpr:splice" (ppr s) #endif -- Arrow notation extension @@ -559,8 +587,6 @@ dsExpr (HsProc pat cmd) = dsProcExpr pat cmd #ifdef DEBUG -- HsSyn constructs that just shouldn't be here: dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig" -dsExpr (ArithSeqIn _) = panic "dsExpr:ArithSeqIn" -dsExpr (PArrSeqIn _) = panic "dsExpr:PArrSeqIn" #endif \end{code} @@ -572,65 +598,48 @@ handled in DsListComp). Basically does the translation given in the Haskell 98 report: \begin{code} -dsDo :: HsStmtContext Name - -> [LStmt Id] - -> ReboundNames Id -- id for: [return,fail,>>=,>>] and possibly mfixName - -> Type -- Element type; the whole expression has type (m t) +dsDo :: [LStmt Id] + -> LHsExpr Id + -> Type -- Type of the whole expression -> DsM CoreExpr -dsDo do_or_lc stmts ids result_ty - = dsReboundNames ids `thenDs` \ (meth_binds, ds_meths) -> - let - return_id = lookupReboundName ds_meths returnMName - fail_id = lookupReboundName ds_meths failMName - bind_id = lookupReboundName ds_meths bindMName - then_id = lookupReboundName ds_meths thenMName - - (m_ty, b_ty) = tcSplitAppTy result_ty -- result_ty must be of the form (m b) - - -- For ExprStmt, see the comments near HsExpr.Stmt about - -- exactly what ExprStmts mean! - -- - -- In dsDo we can only see DoStmt and ListComp (no guards) - - go [ResultStmt expr] = dsLExpr expr - - - go (ExprStmt expr a_ty : stmts) - = dsLExpr expr `thenDs` \ expr2 -> - go stmts `thenDs` \ rest -> - returnDs (mkApps then_id [Type a_ty, Type b_ty, expr2, rest]) - - go (LetStmt binds : stmts) - = go stmts `thenDs` \ rest -> - dsLet binds rest - - go (BindStmt pat expr : stmts) - = go stmts `thenDs` \ body -> - dsLExpr expr `thenDs` \ rhs -> - mkStringLit (mk_msg (getLoc pat)) `thenDs` \ core_msg -> - let - -- In a do expression, pattern-match failure just calls - -- the monadic 'fail' rather than throwing an exception - fail_expr = mkApps fail_id [Type b_ty, core_msg] - a_ty = hsPatType pat - in - selectMatchVarL pat `thenDs` \ var -> - matchSimply (Var var) (StmtCtxt do_or_lc) pat - body fail_expr `thenDs` \ match_code -> - returnDs (mkApps bind_id [Type a_ty, Type b_ty, rhs, Lam var match_code]) - - go (RecStmt rec_stmts later_vars rec_vars rec_rets : stmts) - = go (bind_stmt : stmts) - where - bind_stmt = dsRecStmt m_ty ds_meths rec_stmts later_vars rec_vars rec_rets - - in - go (map unLoc stmts) `thenDs` \ stmts_code -> - returnDs (foldr Let stmts_code meth_binds) - +dsDo stmts body result_ty + = go (map unLoc stmts) where - mk_msg locn = "Pattern match failure in do expression at " ++ showSDoc (ppr locn) + 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: @@ -641,36 +650,94 @@ We turn (RecStmt [v1,..vn] stmts) into: return (v1,..vn)) \begin{code} -dsRecStmt :: Type -- Monad type constructor :: * -> * - -> [(Name,Id)] -- Rebound Ids - -> [LStmt Id] - -> [Id] -> [Id] -> [LHsExpr Id] - -> Stmt Id -dsRecStmt m_ty ds_meths stmts later_vars rec_vars rec_rets - = ASSERT( length vars == length rets ) - BindStmt tup_pat mfix_app - where - vars@(var1:rest) = later_vars ++ rec_vars -- Always at least one - rets@(ret1:_) = map nlHsVar later_vars ++ rec_rets - one_var = null rest - - mfix_app = nlHsApp (noLoc $ TyApp (nlHsVar mfix_id) [tup_ty]) mfix_arg - mfix_arg = noLoc $ HsLam (mkSimpleMatch [tup_pat] body tup_ty) - - tup_expr | one_var = ret1 - | otherwise = noLoc $ ExplicitTuple rets Boxed - tup_ty = mkCoreTupTy (map idType vars) - -- Deals with singleton case - tup_pat | one_var = nlVarPat var1 - | otherwise = noLoc $ LazyPat (noLoc $ TuplePat (map nlVarPat vars) Boxed) - - body = noLoc $ HsDo DoExpr (stmts ++ [return_stmt]) - [(n, nlHsVar id) | (n,id) <- ds_meths] -- A bit of a hack - (mkAppTy m_ty tup_ty) +dsMDo :: PostTcTable + -> [LStmt Id] + -> LHsExpr Id + -> Type -- Type of the whole expression + -> DsM CoreExpr - Var return_id = lookupReboundName ds_meths returnMName - Var mfix_id = lookupReboundName ds_meths mfixName +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)] [])) - return_stmt = noLoc $ ResultStmt return_app - return_app = nlHsApp (noLoc $ TyApp (nlHsVar return_id) [tup_ty]) tup_expr + + -- 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}