% % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[RnExpr]{Renaming of expressions} Basically dependency analysis. Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes. In general, all of these functions return a renamed thing, and a set of free variables. \begin{code} module RnExpr ( rnLExpr, rnExpr, rnStmts ) where #include "HsVersions.h" #ifdef GHCI import {-# SOURCE #-} TcSplice( runQuasiQuoteExpr ) #endif /* GHCI */ import RnSource ( rnSrcDecls, rnSplice, checkTH ) import RnBinds ( rnLocalBindsAndThen, rnValBindsLHS, rnValBindsRHS, rnMatchGroup, makeMiniFixityEnv) import HsSyn import TcRnMonad import RnEnv import RnTypes ( rnHsTypeFVs, mkOpFormRn, mkOpAppRn, mkNegAppRn, checkSectionPrec) import RnPat import DynFlags ( DynFlag(..) ) import BasicTypes ( FixityDirection(..) ) import PrelNames ( thFAKE, hasKey, assertIdKey, assertErrorName, loopAName, choiceAName, appAName, arrAName, composeAName, firstAName, negateName, thenMName, bindMName, failMName, groupWithName ) import Name import NameSet import RdrName import LoadIface ( loadInterfaceForName ) import UniqSet import List ( nub ) import Util ( isSingleton ) import ListSetOps ( removeDups ) import Maybes ( expectJust ) import Outputable import SrcLoc import FastString import List ( unzip4 ) import Control.Monad \end{code} \begin{code} -- XXX thenM :: Monad a => a b -> (b -> a c) -> a c thenM = (>>=) thenM_ :: Monad a => a b -> a c -> a c thenM_ = (>>) returnM :: Monad m => a -> m a returnM = return mappM :: (Monad m) => (a -> m b) -> [a] -> m [b] mappM = mapM checkM :: Monad m => Bool -> m () -> m () checkM = unless \end{code} %************************************************************************ %* * \subsubsection{Expressions} %* * %************************************************************************ \begin{code} rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars) rnExprs ls = rnExprs' ls emptyUniqSet where rnExprs' [] acc = returnM ([], acc) rnExprs' (expr:exprs) acc = rnLExpr expr `thenM` \ (expr', fvExpr) -> -- Now we do a "seq" on the free vars because typically it's small -- or empty, especially in very long lists of constants let acc' = acc `plusFV` fvExpr in acc' `seq` rnExprs' exprs acc' `thenM` \ (exprs', fvExprs) -> returnM (expr':exprs', fvExprs) \end{code} Variables. We look up the variable and return the resulting name. \begin{code} rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars) rnLExpr = wrapLocFstM rnExpr rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars) rnExpr (HsVar v) = do name <- lookupOccRn v ignore_asserts <- doptM Opt_IgnoreAsserts finish_var ignore_asserts name where finish_var ignore_asserts name | ignore_asserts || not (name `hasKey` assertIdKey) = return (HsVar name, unitFV name) | otherwise = do { (e, fvs) <- mkAssertErrorExpr ; return (e, fvs `addOneFV` name) } rnExpr (HsIPVar v) = newIPNameRn v `thenM` \ name -> returnM (HsIPVar name, emptyFVs) rnExpr (HsLit lit@(HsString s)) = do { opt_OverloadedStrings <- doptM Opt_OverloadedStrings ; if opt_OverloadedStrings then rnExpr (HsOverLit (mkHsIsString s placeHolderType)) else -- Same as below rnLit lit `thenM_` returnM (HsLit lit, emptyFVs) } rnExpr (HsLit lit) = rnLit lit `thenM_` returnM (HsLit lit, emptyFVs) rnExpr (HsOverLit lit) = rnOverLit lit `thenM` \ (lit', fvs) -> returnM (HsOverLit lit', fvs) rnExpr (HsApp fun arg) = rnLExpr fun `thenM` \ (fun',fvFun) -> rnLExpr arg `thenM` \ (arg',fvArg) -> returnM (HsApp fun' arg', fvFun `plusFV` fvArg) rnExpr (OpApp e1 op _ e2) = rnLExpr e1 `thenM` \ (e1', fv_e1) -> rnLExpr e2 `thenM` \ (e2', fv_e2) -> rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) -> -- Deal with fixity -- When renaming code synthesised from "deriving" declarations -- we used to avoid fixity stuff, but we can't easily tell any -- more, so I've removed the test. Adding HsPars in TcGenDeriv -- should prevent bad things happening. lookupFixityRn op_name `thenM` \ fixity -> mkOpAppRn e1' op' fixity e2' `thenM` \ final_e -> returnM (final_e, fv_e1 `plusFV` fv_op `plusFV` fv_e2) rnExpr (NegApp e _) = rnLExpr e `thenM` \ (e', fv_e) -> lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) -> mkNegAppRn e' neg_name `thenM` \ final_e -> returnM (final_e, fv_e `plusFV` fv_neg) rnExpr (HsPar e) = rnLExpr e `thenM` \ (e', fvs_e) -> returnM (HsPar e', fvs_e) -- Template Haskell extensions -- Don't ifdef-GHCI them because we want to fail gracefully -- (not with an rnExpr crash) in a stage-1 compiler. rnExpr e@(HsBracket br_body) = checkTH e "bracket" `thenM_` rnBracket br_body `thenM` \ (body', fvs_e) -> returnM (HsBracket body', fvs_e) rnExpr (HsSpliceE splice) = rnSplice splice `thenM` \ (splice', fvs) -> returnM (HsSpliceE splice', fvs) #ifndef GHCI rnExpr e@(HsQuasiQuoteE _) = pprPanic "Cant do quasiquotation without GHCi" (ppr e) #else rnExpr (HsQuasiQuoteE qq) = rnQuasiQuote qq `thenM` \ (qq', fvs_qq) -> runQuasiQuoteExpr qq' `thenM` \ (L _ expr') -> rnExpr expr' `thenM` \ (expr'', fvs_expr) -> returnM (expr'', fvs_qq `plusFV` fvs_expr) #endif /* GHCI */ rnExpr section@(SectionL expr op) = rnLExpr expr `thenM` \ (expr', fvs_expr) -> rnLExpr op `thenM` \ (op', fvs_op) -> checkSectionPrec InfixL section op' expr' `thenM_` returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr) rnExpr section@(SectionR op expr) = rnLExpr op `thenM` \ (op', fvs_op) -> rnLExpr expr `thenM` \ (expr', fvs_expr) -> checkSectionPrec InfixR section op' expr' `thenM_` returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr) rnExpr (HsCoreAnn ann expr) = rnLExpr expr `thenM` \ (expr', fvs_expr) -> returnM (HsCoreAnn ann expr', fvs_expr) rnExpr (HsSCC lbl expr) = rnLExpr expr `thenM` \ (expr', fvs_expr) -> returnM (HsSCC lbl expr', fvs_expr) rnExpr (HsTickPragma info expr) = rnLExpr expr `thenM` \ (expr', fvs_expr) -> returnM (HsTickPragma info expr', fvs_expr) rnExpr (HsLam matches) = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) -> returnM (HsLam matches', fvMatch) rnExpr (HsCase expr matches) = rnLExpr expr `thenM` \ (new_expr, e_fvs) -> rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) -> returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs) rnExpr (HsLet binds expr) = rnLocalBindsAndThen binds $ \ binds' -> rnLExpr expr `thenM` \ (expr',fvExpr) -> returnM (HsLet binds' expr', fvExpr) rnExpr (HsDo do_or_lc stmts body _) = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $ rnLExpr body ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) } rnExpr (ExplicitList _ exps) = rnExprs exps `thenM` \ (exps', fvs) -> returnM (ExplicitList placeHolderType exps', fvs) rnExpr (ExplicitPArr _ exps) = rnExprs exps `thenM` \ (exps', fvs) -> returnM (ExplicitPArr placeHolderType exps', fvs) rnExpr (ExplicitTuple exps boxity) = checkTupSize (length exps) `thenM_` rnExprs exps `thenM` \ (exps', fvs) -> returnM (ExplicitTuple exps' boxity, fvs) rnExpr (RecordCon con_id _ rbinds) = do { conname <- lookupLocatedOccRn con_id ; (rbinds', fvRbinds) <- rnHsRecFields_Con conname rnLExpr rbinds ; return (RecordCon conname noPostTcExpr rbinds', fvRbinds `addOneFV` unLoc conname) } rnExpr (RecordUpd expr rbinds _ _ _) = do { (expr', fvExpr) <- rnLExpr expr ; (rbinds', fvRbinds) <- rnHsRecFields_Update rnLExpr rbinds ; return (RecordUpd expr' rbinds' [] [] [], fvExpr `plusFV` fvRbinds) } rnExpr (ExprWithTySig expr pty) = do { (pty', fvTy) <- rnHsTypeFVs doc pty ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $ rnLExpr expr ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) } where doc = text "In an expression type signature" rnExpr (HsIf p b1 b2) = rnLExpr p `thenM` \ (p', fvP) -> rnLExpr b1 `thenM` \ (b1', fvB1) -> rnLExpr b2 `thenM` \ (b2', fvB2) -> returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2]) rnExpr (HsType a) = rnHsTypeFVs doc a `thenM` \ (t, fvT) -> returnM (HsType t, fvT) where doc = text "In a type argument" rnExpr (ArithSeq _ seq) = rnArithSeq seq `thenM` \ (new_seq, fvs) -> returnM (ArithSeq noPostTcExpr new_seq, fvs) rnExpr (PArrSeq _ seq) = rnArithSeq seq `thenM` \ (new_seq, fvs) -> returnM (PArrSeq noPostTcExpr new_seq, fvs) \end{code} These three are pattern syntax appearing in expressions. Since all the symbols are reservedops we can simply reject them. We return a (bogus) EWildPat in each case. \begin{code} rnExpr e@EWildPat = patSynErr e rnExpr e@(EAsPat {}) = patSynErr e rnExpr e@(EViewPat {}) = patSynErr e rnExpr e@(ELazyPat {}) = patSynErr e \end{code} %************************************************************************ %* * Arrow notation %* * %************************************************************************ \begin{code} rnExpr (HsProc pat body) = newArrowScope $ rnPatsAndThen_LocalRightwards ProcExpr [pat] $ \ [pat'] -> rnCmdTop body `thenM` \ (body',fvBody) -> returnM (HsProc pat' body', fvBody) rnExpr (HsArrApp arrow arg _ ho rtl) = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) -> rnLExpr arg `thenM` \ (arg',fvArg) -> returnM (HsArrApp arrow' arg' placeHolderType ho rtl, fvArrow `plusFV` fvArg) where select_arrow_scope tc = case ho of HsHigherOrderApp -> tc HsFirstOrderApp -> escapeArrowScope tc -- infix form rnExpr (HsArrForm op (Just _) [arg1, arg2]) = escapeArrowScope (rnLExpr op) `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) -> rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) -> rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) -> -- Deal with fixity lookupFixityRn op_name `thenM` \ fixity -> mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e -> returnM (final_e, fv_arg1 `plusFV` fv_op `plusFV` fv_arg2) rnExpr (HsArrForm op fixity cmds) = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) -> rnCmdArgs cmds `thenM` \ (cmds',fvCmds) -> returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds) rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other) -- HsWrap \end{code} %************************************************************************ %* * Arrow commands %* * %************************************************************************ \begin{code} rnCmdArgs :: [LHsCmdTop RdrName] -> RnM ([LHsCmdTop Name], FreeVars) rnCmdArgs [] = returnM ([], emptyFVs) rnCmdArgs (arg:args) = rnCmdTop arg `thenM` \ (arg',fvArg) -> rnCmdArgs args `thenM` \ (args',fvArgs) -> returnM (arg':args', fvArg `plusFV` fvArgs) rnCmdTop :: LHsCmdTop RdrName -> RnM (LHsCmdTop Name, FreeVars) rnCmdTop = wrapLocFstM rnCmdTop' where rnCmdTop' (HsCmdTop cmd _ _ _) = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) -> let cmd_names = [arrAName, composeAName, firstAName] ++ nameSetToList (methodNamesCmd (unLoc cmd')) in -- Generate the rebindable syntax for the monad lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) -> returnM (HsCmdTop cmd' [] placeHolderType cmd_names', fvCmd `plusFV` cmd_fvs) --------------------------------------------------- -- convert OpApp's in a command context to HsArrForm's convertOpFormsLCmd :: LHsCmd id -> LHsCmd id convertOpFormsLCmd = fmap convertOpFormsCmd convertOpFormsCmd :: HsCmd id -> HsCmd id convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match) convertOpFormsCmd (OpApp c1 op fixity c2) = let arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType [] arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType [] in HsArrForm op (Just fixity) [arg1, arg2] convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c) convertOpFormsCmd (HsCase exp matches) = HsCase exp (convertOpFormsMatch matches) convertOpFormsCmd (HsIf exp c1 c2) = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2) convertOpFormsCmd (HsLet binds cmd) = HsLet binds (convertOpFormsLCmd cmd) convertOpFormsCmd (HsDo ctxt stmts body ty) = HsDo ctxt (map (fmap convertOpFormsStmt) stmts) (convertOpFormsLCmd body) ty -- Anything else is unchanged. This includes HsArrForm (already done), -- things with no sub-commands, and illegal commands (which will be -- caught by the type checker) convertOpFormsCmd c = c convertOpFormsStmt :: StmtLR id id -> StmtLR id id convertOpFormsStmt (BindStmt pat cmd _ _) = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr convertOpFormsStmt (ExprStmt cmd _ _) = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType convertOpFormsStmt (RecStmt stmts lvs rvs es binds) = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds convertOpFormsStmt stmt = stmt convertOpFormsMatch :: MatchGroup id -> MatchGroup id convertOpFormsMatch (MatchGroup ms ty) = MatchGroup (map (fmap convert) ms) ty where convert (Match pat mty grhss) = Match pat mty (convertOpFormsGRHSs grhss) convertOpFormsGRHSs :: GRHSs id -> GRHSs id convertOpFormsGRHSs (GRHSs grhss binds) = GRHSs (map convertOpFormsGRHS grhss) binds convertOpFormsGRHS :: Located (GRHS id) -> Located (GRHS id) convertOpFormsGRHS = fmap convert where convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd) --------------------------------------------------- type CmdNeeds = FreeVars -- Only inhabitants are -- appAName, choiceAName, loopAName -- find what methods the Cmd needs (loop, choice, apply) methodNamesLCmd :: LHsCmd Name -> CmdNeeds methodNamesLCmd = methodNamesCmd . unLoc methodNamesCmd :: HsCmd Name -> CmdNeeds methodNamesCmd (HsArrApp _arrow _arg _ HsFirstOrderApp _rtl) = emptyFVs methodNamesCmd (HsArrApp _arrow _arg _ HsHigherOrderApp _rtl) = unitFV appAName methodNamesCmd (HsArrForm {}) = emptyFVs methodNamesCmd (HsPar c) = methodNamesLCmd c methodNamesCmd (HsIf _ c1 c2) = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName methodNamesCmd (HsLet _ c) = methodNamesLCmd c methodNamesCmd (HsDo _ stmts body _) = methodNamesStmts stmts `plusFV` methodNamesLCmd body methodNamesCmd (HsApp c _) = methodNamesLCmd c methodNamesCmd (HsLam match) = methodNamesMatch match methodNamesCmd (HsCase _ matches) = methodNamesMatch matches `addOneFV` choiceAName methodNamesCmd _ = emptyFVs -- Other forms can't occur in commands, but it's not convenient -- to error here so we just do what's convenient. -- The type checker will complain later --------------------------------------------------- methodNamesMatch :: MatchGroup Name -> FreeVars methodNamesMatch (MatchGroup ms _) = plusFVs (map do_one ms) where do_one (L _ (Match _ _ grhss)) = methodNamesGRHSs grhss ------------------------------------------------- -- gaw 2004 methodNamesGRHSs :: GRHSs Name -> FreeVars methodNamesGRHSs (GRHSs grhss _) = plusFVs (map methodNamesGRHS grhss) ------------------------------------------------- methodNamesGRHS :: Located (GRHS Name) -> CmdNeeds methodNamesGRHS (L _ (GRHS _ rhs)) = methodNamesLCmd rhs --------------------------------------------------- methodNamesStmts :: [Located (StmtLR Name Name)] -> FreeVars methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts) --------------------------------------------------- methodNamesLStmt :: Located (StmtLR Name Name) -> FreeVars methodNamesLStmt = methodNamesStmt . unLoc methodNamesStmt :: StmtLR Name Name -> FreeVars methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd methodNamesStmt (BindStmt _ cmd _ _) = methodNamesLCmd cmd methodNamesStmt (RecStmt stmts _ _ _ _) = methodNamesStmts stmts `addOneFV` loopAName methodNamesStmt (LetStmt _) = emptyFVs methodNamesStmt (ParStmt _) = emptyFVs methodNamesStmt (TransformStmt _ _ _) = emptyFVs methodNamesStmt (GroupStmt _ _) = emptyFVs -- ParStmt, TransformStmt and GroupStmt can't occur in commands, but it's not convenient to error -- here so we just do what's convenient \end{code} %************************************************************************ %* * Arithmetic sequences %* * %************************************************************************ \begin{code} rnArithSeq :: ArithSeqInfo RdrName -> RnM (ArithSeqInfo Name, FreeVars) rnArithSeq (From expr) = rnLExpr expr `thenM` \ (expr', fvExpr) -> returnM (From expr', fvExpr) rnArithSeq (FromThen expr1 expr2) = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) -> rnLExpr expr2 `thenM` \ (expr2', fvExpr2) -> returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2) rnArithSeq (FromTo expr1 expr2) = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) -> rnLExpr expr2 `thenM` \ (expr2', fvExpr2) -> returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2) rnArithSeq (FromThenTo expr1 expr2 expr3) = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) -> rnLExpr expr2 `thenM` \ (expr2', fvExpr2) -> rnLExpr expr3 `thenM` \ (expr3', fvExpr3) -> returnM (FromThenTo expr1' expr2' expr3', plusFVs [fvExpr1, fvExpr2, fvExpr3]) \end{code} %************************************************************************ %* * Template Haskell brackets %* * %************************************************************************ \begin{code} rnBracket :: HsBracket RdrName -> RnM (HsBracket Name, FreeVars) rnBracket (VarBr n) = do { name <- lookupOccRn n ; this_mod <- getModule ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the do { loadInterfaceForName msg name -- home interface is loaded, and this is the ; return () } -- only way that is going to happen ; returnM (VarBr name, unitFV name) } where msg = ptext (sLit "Need interface for Template Haskell quoted Name") rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e ; return (ExpBr e', fvs) } rnBracket (PatBr _) = do { addErr (ptext (sLit "Tempate Haskell pattern brackets are not supported yet")); failM } rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t ; return (TypBr t', fvs) } where doc = ptext (sLit "In a Template-Haskell quoted type") rnBracket (DecBr group) = do { gbl_env <- getGblEnv ; let new_gbl_env = gbl_env { -- Set the module to thFAKE. The top-level names from the bracketed -- declarations will go into the name cache, and we don't want them to -- confuse the Names for the current module. -- By using a pretend module, thFAKE, we keep them safely out of the way. tcg_mod = thFAKE, -- The emptyDUs is so that we just collect uses for this group alone -- in the call to rnSrcDecls below tcg_dus = emptyDUs } ; setGblEnv new_gbl_env $ do { -- In this situation we want to *shadow* top-level bindings. -- foo = 1 -- bar = [d| foo = 1 |] -- If we don't shadow, we'll get an ambiguity complaint when we do -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo' -- -- Furthermore, arguably if the splice does define foo, that should hide -- any foo's further out -- -- The shadowing is acheived by calling rnSrcDecls with True as the shadowing flag ; (tcg_env, group') <- rnSrcDecls True group -- Discard the tcg_env; it contains only extra info about fixity ; return (DecBr group', allUses (tcg_dus tcg_env)) } } \end{code} %************************************************************************ %* * \subsubsection{@Stmt@s: in @do@ expressions} %* * %************************************************************************ \begin{code} rnStmts :: HsStmtContext Name -> [LStmt RdrName] -> RnM (thing, FreeVars) -> RnM (([LStmt Name], thing), FreeVars) rnStmts (MDoExpr _) = rnMDoStmts rnStmts ctxt = rnNormalStmts ctxt rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName] -> RnM (thing, FreeVars) -> RnM (([LStmt Name], thing), FreeVars) -- Used for cases *other* than recursive mdo -- Implements nested scopes rnNormalStmts _ [] thing_inside = do { (thing, fvs) <- thing_inside ; return (([],thing), fvs) } rnNormalStmts ctxt (L loc stmt : stmts) thing_inside = do { ((stmt', (stmts', thing)), fvs) <- rnStmt ctxt stmt $ rnNormalStmts ctxt stmts thing_inside ; return (((L loc stmt' : stmts'), thing), fvs) } rnStmt :: HsStmtContext Name -> Stmt RdrName -> RnM (thing, FreeVars) -> RnM ((Stmt Name, thing), FreeVars) rnStmt _ (ExprStmt expr _ _) thing_inside = do { (expr', fv_expr) <- rnLExpr expr ; (then_op, fvs1) <- lookupSyntaxName thenMName ; (thing, fvs2) <- thing_inside ; return ((ExprStmt expr' then_op placeHolderType, thing), fv_expr `plusFV` fvs1 `plusFV` fvs2) } rnStmt ctxt (BindStmt pat expr _ _) thing_inside = do { (expr', fv_expr) <- rnLExpr expr -- The binders do not scope over the expression ; (bind_op, fvs1) <- lookupSyntaxName bindMName ; (fail_op, fvs2) <- lookupSyntaxName failMName ; rnPatsAndThen_LocalRightwards (StmtCtxt ctxt) [pat] $ \ [pat'] -> do { (thing, fvs3) <- thing_inside ; return ((BindStmt pat' expr' bind_op fail_op, thing), fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }} -- fv_expr shouldn't really be filtered by the rnPatsAndThen -- but it does not matter because the names are unique rnStmt ctxt (LetStmt binds) thing_inside = do { checkLetStmt ctxt binds ; rnLocalBindsAndThen binds $ \binds' -> do { (thing, fvs) <- thing_inside ; return ((LetStmt binds', thing), fvs) } } rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside = do { checkRecStmt ctxt ; rn_rec_stmts_and_then rec_stmts $ \ segs -> do { (thing, fvs) <- thing_inside ; let segs_w_fwd_refs = addFwdRefs segs (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs) fwd_vars = nameSetToList (plusFVs fs) uses = plusFVs us rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds ; return ((rec_stmt, thing), uses `plusFV` fvs) } } rnStmt ctxt (ParStmt segs) thing_inside = do { checkParStmt ctxt ; ((segs', thing), fvs) <- rnParallelStmts (ParStmtCtxt ctxt) segs thing_inside ; return ((ParStmt segs', thing), fvs) } rnStmt ctxt (TransformStmt (stmts, _) usingExpr maybeByExpr) thing_inside = do checkTransformStmt ctxt (usingExpr', fv_usingExpr) <- rnLExpr usingExpr ((stmts', binders, (maybeByExpr', thing)), fvs) <- rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \_unshadowed_bndrs -> do (maybeByExpr', fv_maybeByExpr) <- rnMaybeLExpr maybeByExpr (thing, fv_thing) <- thing_inside return ((maybeByExpr', thing), fv_maybeByExpr `plusFV` fv_thing) return ((TransformStmt (stmts', binders) usingExpr' maybeByExpr', thing), fv_usingExpr `plusFV` fvs) where rnMaybeLExpr Nothing = return (Nothing, emptyFVs) rnMaybeLExpr (Just expr) = do (expr', fv_expr) <- rnLExpr expr return (Just expr', fv_expr) rnStmt ctxt (GroupStmt (stmts, _) groupByClause) thing_inside = do checkTransformStmt ctxt -- We must rename the using expression in the context before the transform is begun groupByClauseAction <- case groupByClause of GroupByNothing usingExpr -> do (usingExpr', fv_usingExpr) <- rnLExpr usingExpr (return . return) (GroupByNothing usingExpr', fv_usingExpr) GroupBySomething eitherUsingExpr byExpr -> do (eitherUsingExpr', fv_eitherUsingExpr) <- case eitherUsingExpr of Right _ -> return (Right $ HsVar groupWithName, unitNameSet groupWithName) Left usingExpr -> do (usingExpr', fv_usingExpr) <- rnLExpr usingExpr return (Left usingExpr', fv_usingExpr) return $ do (byExpr', fv_byExpr) <- rnLExpr byExpr return (GroupBySomething eitherUsingExpr' byExpr', fv_eitherUsingExpr `plusFV` fv_byExpr) -- We only use rnNormalStmtsAndFindUsedBinders to get unshadowed_bndrs, so -- perhaps we could refactor this to use rnNormalStmts directly? ((stmts', _, (groupByClause', usedBinderMap, thing)), fvs) <- rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do (groupByClause', fv_groupByClause) <- groupByClauseAction unshadowed_bndrs' <- mapM newLocalName unshadowed_bndrs let binderMap = zip unshadowed_bndrs unshadowed_bndrs' -- Bind the "thing" inside a context where we have REBOUND everything -- bound by the statements before the group. This is necessary since after -- the grouping the same identifiers actually have different meanings -- i.e. they refer to lists not singletons! (thing, fv_thing) <- bindLocalNames unshadowed_bndrs' thing_inside -- We remove entries from the binder map that are not used in the thing_inside. -- We can then use that usage information to ensure that the free variables do -- not contain the things we just bound, but do contain the things we need to -- make those bindings (i.e. the corresponding non-listy variables) -- Note that we also retain those entries which have an old binder in our -- own free variables (the using or by expression). This is because this map -- is reused in the desugarer to create the type to bind from the statements -- that occur before this one. If the binders we need are not in the map, they -- will never get bound into our desugared expression and hence the simplifier -- crashes as we refer to variables that don't exist! let usedBinderMap = filter (\(old_binder, new_binder) -> (new_binder `elemNameSet` fv_thing) || (old_binder `elemNameSet` fv_groupByClause)) binderMap (usedOldBinders, usedNewBinders) = unzip usedBinderMap real_fv_thing = (delListFromNameSet fv_thing usedNewBinders) `plusFV` (mkNameSet usedOldBinders) return ((groupByClause', usedBinderMap, thing), fv_groupByClause `plusFV` real_fv_thing) traceRn (text "rnStmt: implicitly rebound these used binders:" <+> ppr usedBinderMap) return ((GroupStmt (stmts', usedBinderMap) groupByClause', thing), fvs) rnNormalStmtsAndFindUsedBinders :: HsStmtContext Name -> [LStmt RdrName] -> ([Name] -> RnM (thing, FreeVars)) -> RnM (([LStmt Name], [Name], thing), FreeVars) rnNormalStmtsAndFindUsedBinders ctxt stmts thing_inside = do ((stmts', (used_bndrs, inner_thing)), fvs) <- rnNormalStmts ctxt stmts $ do -- Find the Names that are bound by stmts that -- by assumption we have just renamed local_env <- getLocalRdrEnv let stmts_binders = collectLStmtsBinders stmts bndrs = map (expectJust "rnStmt" . lookupLocalRdrEnv local_env . unLoc) stmts_binders -- If shadow, we'll look up (Unqual x) twice, getting -- the second binding both times, which is the -- one we want unshadowed_bndrs = nub bndrs -- Typecheck the thing inside, passing on all -- the Names bound before it for its information (thing, fvs) <- thing_inside unshadowed_bndrs -- Figure out which of the bound names are used -- after the statements we renamed let used_bndrs = filter (`elemNameSet` fvs) bndrs return ((used_bndrs, thing), fvs) -- Flatten the tuple returned by the above call a bit! return ((stmts', used_bndrs, inner_thing), fvs) rnParallelStmts :: HsStmtContext Name -> [([LStmt RdrName], [RdrName])] -> RnM (thing, FreeVars) -> RnM (([([LStmt Name], [Name])], thing), FreeVars) rnParallelStmts ctxt segs thing_inside = do orig_lcl_env <- getLocalRdrEnv go orig_lcl_env [] segs where go orig_lcl_env bndrs [] = do let (bndrs', dups) = removeDups cmpByOcc bndrs inner_env = extendLocalRdrEnv orig_lcl_env bndrs' mappM dupErr dups (thing, fvs) <- setLocalRdrEnv inner_env thing_inside return (([], thing), fvs) go orig_lcl_env bndrs_so_far ((stmts, _) : segs) = do ((stmts', bndrs, (segs', thing)), fvs) <- rnNormalStmtsAndFindUsedBinders ctxt stmts $ \new_bndrs -> do -- Typecheck the thing inside, passing on all -- the Names bound, but separately; revert the envt setLocalRdrEnv orig_lcl_env $ do go orig_lcl_env (new_bndrs ++ bndrs_so_far) segs let seg' = (stmts', bndrs) return (((seg':segs'), thing), delListFromNameSet fvs bndrs) cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2 dupErr vs = addErr (ptext (sLit "Duplicate binding in parallel list comprehension for:") <+> quotes (ppr (head vs))) \end{code} %************************************************************************ %* * \subsubsection{mdo expressions} %* * %************************************************************************ \begin{code} type FwdRefs = NameSet type Segment stmts = (Defs, Uses, -- May include defs FwdRefs, -- A subset of uses that are -- (a) used before they are bound in this segment, or -- (b) used here, and bound in subsequent segments stmts) -- Either Stmt or [Stmt] ---------------------------------------------------- rnMDoStmts :: [LStmt RdrName] -> RnM (thing, FreeVars) -> RnM (([LStmt Name], thing), FreeVars) rnMDoStmts stmts thing_inside = -- Step1: Bring all the binders of the mdo into scope -- (Remember that this also removes the binders from the -- finally-returned free-vars.) -- And rename each individual stmt, making a -- singleton segment. At this stage the FwdRefs field -- isn't finished: it's empty for all except a BindStmt -- for which it's the fwd refs within the bind itself -- (This set may not be empty, because we're in a recursive -- context.) rn_rec_stmts_and_then stmts $ \ segs -> do { ; (thing, fvs_later) <- thing_inside ; let -- Step 2: Fill in the fwd refs. -- The segments are all singletons, but their fwd-ref -- field mentions all the things used by the segment -- that are bound after their use segs_w_fwd_refs = addFwdRefs segs -- Step 3: Group together the segments to make bigger segments -- Invariant: in the result, no segment uses a variable -- bound in a later segment grouped_segs = glomSegments segs_w_fwd_refs -- Step 4: Turn the segments into Stmts -- Use RecStmt when and only when there are fwd refs -- Also gather up the uses from the end towards the -- start, so we can tell the RecStmt which things are -- used 'after' the RecStmt (stmts', fvs) = segsToStmts grouped_segs fvs_later ; return ((stmts', thing), fvs) } --------------------------------------------- -- wrapper that does both the left- and right-hand sides rn_rec_stmts_and_then :: [LStmt RdrName] -- assumes that the FreeVars returned includes -- the FreeVars of the Segments -> ([Segment (LStmt Name)] -> RnM (a, FreeVars)) -> RnM (a, FreeVars) rn_rec_stmts_and_then s cont = do { -- (A) Make the mini fixity env for all of the stmts fix_env <- makeMiniFixityEnv (collectRecStmtsFixities s) -- (B) Do the LHSes ; new_lhs_and_fv <- rn_rec_stmts_lhs fix_env s -- ...bring them and their fixities into scope ; let bound_names = map unLoc $ collectLStmtsBinders (map fst new_lhs_and_fv) ; bindLocalNamesFV_WithFixities bound_names fix_env $ do -- (C) do the right-hand-sides and thing-inside { segs <- rn_rec_stmts bound_names new_lhs_and_fv ; (res, fvs) <- cont segs ; warnUnusedLocalBinds bound_names fvs ; return (res, fvs) }} -- get all the fixity decls in any Let stmt collectRecStmtsFixities :: [LStmtLR RdrName RdrName] -> [LFixitySig RdrName] collectRecStmtsFixities l = foldr (\ s -> \acc -> case s of (L _ (LetStmt (HsValBinds (ValBindsIn _ sigs)))) -> foldr (\ sig -> \ acc -> case sig of (L loc (FixSig s)) -> (L loc s) : acc _ -> acc) acc sigs _ -> acc) [] l -- left-hand sides rn_rec_stmt_lhs :: MiniFixityEnv -> LStmt RdrName -- rename LHS, and return its FVs -- Warning: we will only need the FreeVars below in the case of a BindStmt, -- so we don't bother to compute it accurately in the other cases -> RnM [(LStmtLR Name RdrName, FreeVars)] rn_rec_stmt_lhs _ (L loc (ExprStmt expr a b)) = return [(L loc (ExprStmt expr a b), -- this is actually correct emptyFVs)] rn_rec_stmt_lhs fix_env (L loc (BindStmt pat expr a b)) = do -- should the ctxt be MDo instead? (pat', fv_pat) <- rnBindPat (localRecNameMaker fix_env) pat return [(L loc (BindStmt pat' expr a b), fv_pat)] rn_rec_stmt_lhs _ (L _ (LetStmt binds@(HsIPBinds _))) = do { addErr (badIpBinds (ptext (sLit "an mdo expression")) binds) ; failM } rn_rec_stmt_lhs fix_env (L loc (LetStmt (HsValBinds binds))) = do binds' <- rnValBindsLHS fix_env binds return [(L loc (LetStmt (HsValBinds binds')), -- Warning: this is bogus; see function invariant emptyFVs )] rn_rec_stmt_lhs fix_env (L _ (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec = rn_rec_stmts_lhs fix_env stmts rn_rec_stmt_lhs _ stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt" (ppr stmt) rn_rec_stmt_lhs _ stmt@(L _ (TransformStmt _ _ _)) -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt" (ppr stmt) rn_rec_stmt_lhs _ stmt@(L _ (GroupStmt _ _)) -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt" (ppr stmt) rn_rec_stmt_lhs _ (L _ (LetStmt EmptyLocalBinds)) = panic "rn_rec_stmt LetStmt EmptyLocalBinds" rn_rec_stmts_lhs :: MiniFixityEnv -> [LStmt RdrName] -> RnM [(LStmtLR Name RdrName, FreeVars)] rn_rec_stmts_lhs fix_env stmts = let boundNames = collectLStmtsBinders stmts doc = text "In a recursive mdo-expression" in do -- First do error checking: we need to check for dups here because we -- don't bind all of the variables from the Stmt at once -- with bindLocatedLocals. checkDupRdrNames doc boundNames mappM (rn_rec_stmt_lhs fix_env) stmts `thenM` \ ls -> returnM (concat ls) -- right-hand-sides rn_rec_stmt :: [Name] -> LStmtLR Name RdrName -> FreeVars -> RnM [Segment (LStmt Name)] -- Rename a Stmt that is inside a RecStmt (or mdo) -- Assumes all binders are already in scope -- Turns each stmt into a singleton Stmt rn_rec_stmt _ (L loc (ExprStmt expr _ _)) _ = rnLExpr expr `thenM` \ (expr', fvs) -> lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) -> returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet, L loc (ExprStmt expr' then_op placeHolderType))] rn_rec_stmt _ (L loc (BindStmt pat' expr _ _)) fv_pat = rnLExpr expr `thenM` \ (expr', fv_expr) -> lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) -> lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) -> let bndrs = mkNameSet (collectPatBinders pat') fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2 in returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs, L loc (BindStmt pat' expr' bind_op fail_op))] rn_rec_stmt _ (L _ (LetStmt binds@(HsIPBinds _))) _ = do { addErr (badIpBinds (ptext (sLit "an mdo expression")) binds) ; failM } rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds'))) _ = do (binds', du_binds) <- -- fixities and unused are handled above in rn_rec_stmts_and_then rnValBindsRHS all_bndrs binds' returnM [(duDefs du_binds, duUses du_binds, emptyNameSet, L loc (LetStmt (HsValBinds binds')))] -- no RecStmt case becuase they get flattened above when doing the LHSes rn_rec_stmt _ stmt@(L _ (RecStmt _ _ _ _ _)) _ = pprPanic "rn_rec_stmt: RecStmt" (ppr stmt) rn_rec_stmt _ stmt@(L _ (ParStmt _)) _ -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt: ParStmt" (ppr stmt) rn_rec_stmt _ stmt@(L _ (TransformStmt _ _ _)) _ -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt: TransformStmt" (ppr stmt) rn_rec_stmt _ stmt@(L _ (GroupStmt _ _)) _ -- Syntactically illegal in mdo = pprPanic "rn_rec_stmt: GroupStmt" (ppr stmt) rn_rec_stmt _ (L _ (LetStmt EmptyLocalBinds)) _ = panic "rn_rec_stmt: LetStmt EmptyLocalBinds" rn_rec_stmts :: [Name] -> [(LStmtLR Name RdrName, FreeVars)] -> RnM [Segment (LStmt Name)] rn_rec_stmts bndrs stmts = mappM (uncurry (rn_rec_stmt bndrs)) stmts `thenM` \ segs_s -> returnM (concat segs_s) --------------------------------------------- addFwdRefs :: [Segment a] -> [Segment a] -- So far the segments only have forward refs *within* the Stmt -- (which happens for bind: x <- ...x...) -- This function adds the cross-seg fwd ref info addFwdRefs pairs = fst (foldr mk_seg ([], emptyNameSet) pairs) where mk_seg (defs, uses, fwds, stmts) (segs, later_defs) = (new_seg : segs, all_defs) where new_seg = (defs, uses, new_fwds, stmts) all_defs = later_defs `unionNameSets` defs new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs) -- Add the downstream fwd refs here ---------------------------------------------------- -- Glomming the singleton segments of an mdo into -- minimal recursive groups. -- -- At first I thought this was just strongly connected components, but -- there's an important constraint: the order of the stmts must not change. -- -- Consider -- mdo { x <- ...y... -- p <- z -- y <- ...x... -- q <- x -- z <- y -- r <- x } -- -- Here, the first stmt mention 'y', which is bound in the third. -- But that means that the innocent second stmt (p <- z) gets caught -- up in the recursion. And that in turn means that the binding for -- 'z' has to be included... and so on. -- -- Start at the tail { r <- x } -- Now add the next one { z <- y ; r <- x } -- Now add one more { q <- x ; z <- y ; r <- x } -- Now one more... but this time we have to group a bunch into rec -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x } -- Now one more, which we can add on without a rec -- { p <- z ; -- rec { y <- ...x... ; q <- x ; z <- y } ; -- r <- x } -- Finally we add the last one; since it mentions y we have to -- glom it togeher with the first two groups -- { rec { x <- ...y...; p <- z ; y <- ...x... ; -- q <- x ; z <- y } ; -- r <- x } glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]] glomSegments [] = [] glomSegments ((defs,uses,fwds,stmt) : segs) -- Actually stmts will always be a singleton = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others where segs' = glomSegments segs (extras, others) = grab uses segs' (ds, us, fs, ss) = unzip4 extras seg_defs = plusFVs ds `plusFV` defs seg_uses = plusFVs us `plusFV` uses seg_fwds = plusFVs fs `plusFV` fwds seg_stmts = stmt : concat ss grab :: NameSet -- The client -> [Segment a] -> ([Segment a], -- Needed by the 'client' [Segment a]) -- Not needed by the client -- The result is simply a split of the input grab uses dus = (reverse yeses, reverse noes) where (noes, yeses) = span not_needed (reverse dus) not_needed (defs,_,_,_) = not (intersectsNameSet defs uses) ---------------------------------------------------- segsToStmts :: [Segment [LStmt Name]] -> FreeVars -- Free vars used 'later' -> ([LStmt Name], FreeVars) segsToStmts [] fvs_later = ([], fvs_later) segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later = ASSERT( not (null ss) ) (new_stmt : later_stmts, later_uses `plusFV` uses) where (later_stmts, later_uses) = segsToStmts segs fvs_later new_stmt | non_rec = head ss | otherwise = L (getLoc (head ss)) $ RecStmt ss (nameSetToList used_later) (nameSetToList fwds) [] emptyLHsBinds where non_rec = isSingleton ss && isEmptyNameSet fwds used_later = defs `intersectNameSet` later_uses -- The ones needed after the RecStmt \end{code} %************************************************************************ %* * \subsubsection{Assertion utils} %* * %************************************************************************ \begin{code} srcSpanPrimLit :: SrcSpan -> HsExpr Name srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span)))) mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars) -- Return an expression for (assertError "Foo.hs:27") mkAssertErrorExpr = getSrcSpanM `thenM` \ sloc -> let expr = HsApp (L sloc (HsVar assertErrorName)) (L sloc (srcSpanPrimLit sloc)) in returnM (expr, emptyFVs) \end{code} %************************************************************************ %* * \subsubsection{Errors} %* * %************************************************************************ \begin{code} ---------------------- -- Checking when a particular Stmt is ok checkLetStmt :: HsStmtContext Name -> HsLocalBinds RdrName -> RnM () checkLetStmt (ParStmtCtxt _) (HsIPBinds binds) = addErr (badIpBinds (ptext (sLit "a parallel list comprehension:")) binds) checkLetStmt _ctxt _binds = return () -- We do not allow implicit-parameter bindings in a parallel -- list comprehension. I'm not sure what it might mean. --------- checkRecStmt :: HsStmtContext Name -> RnM () checkRecStmt (MDoExpr {}) = return () -- Recursive stmt ok in 'mdo' checkRecStmt (DoExpr {}) = return () -- ..and in 'do' but only because of arrows: -- proc x -> do { ...rec... } -- We don't have enough context to distinguish this situation here -- so we leave it to the type checker checkRecStmt ctxt = addErr msg where msg = ptext (sLit "Illegal 'rec' stmt in") <+> pprStmtContext ctxt --------- checkParStmt :: HsStmtContext Name -> RnM () checkParStmt _ = do { parallel_list_comp <- doptM Opt_ParallelListComp ; checkErr parallel_list_comp msg } where msg = ptext (sLit "Illegal parallel list comprehension: use -XParallelListComp") --------- checkTransformStmt :: HsStmtContext Name -> RnM () checkTransformStmt ListComp -- Ensure we are really within a list comprehension because otherwise the -- desugarer will break when we come to operate on a parallel array = do { transform_list_comp <- doptM Opt_TransformListComp ; checkErr transform_list_comp msg } where msg = ptext (sLit "Illegal transform or grouping list comprehension: use -XTransformListComp") checkTransformStmt (ParStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension checkTransformStmt (TransformStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension checkTransformStmt ctxt = addErr msg where msg = ptext (sLit "Illegal transform or grouping in") <+> pprStmtContext ctxt --------- patSynErr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars) patSynErr e = do { addErr (sep [ptext (sLit "Pattern syntax in expression context:"), nest 4 (ppr e)]) ; return (EWildPat, emptyFVs) } badIpBinds :: Outputable a => SDoc -> a -> SDoc badIpBinds what binds = hang (ptext (sLit "Implicit-parameter bindings illegal in") <+> what) 2 (ppr binds) \end{code}