2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[RnExpr]{Renaming of expressions}
6 Basically dependency analysis.
8 Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes. In
9 general, all of these functions return a renamed thing, and a set of
14 rnLExpr, rnExpr, rnStmts
17 #include "HsVersions.h"
19 import RnSource ( rnSrcDecls, rnSplice, checkTH )
20 import RnBinds ( rnLocalBindsAndThen, rnValBinds,
21 rnMatchGroup, trimWith )
26 import OccName ( plusOccEnv )
27 import RnNames ( getLocalDeclBinders, extendRdrEnvRn )
28 import RnTypes ( rnHsTypeFVs, rnLPat, rnOverLit, rnPatsAndThen, rnLit,
29 mkOpFormRn, mkOpAppRn, mkNegAppRn, checkSectionPrec,
30 dupFieldErr, checkTupSize )
31 import DynFlags ( DynFlag(..) )
32 import BasicTypes ( FixityDirection(..) )
33 import PrelNames ( hasKey, assertIdKey, assertErrorName,
34 loopAName, choiceAName, appAName, arrAName, composeAName, firstAName,
35 negateName, thenMName, bindMName, failMName )
36 import Name ( Name, nameOccName )
38 import RdrName ( RdrName, emptyGlobalRdrEnv, extendLocalRdrEnv, lookupLocalRdrEnv )
39 import LoadIface ( loadHomeInterface )
40 import UnicodeUtil ( stringToUtf8 )
41 import UniqFM ( isNullUFM )
42 import UniqSet ( emptyUniqSet )
44 import Util ( isSingleton )
45 import ListSetOps ( removeDups )
46 import Maybes ( fromJust )
48 import SrcLoc ( Located(..), unLoc, getLoc, cmpLocated )
51 import List ( unzip4 )
55 %************************************************************************
57 \subsubsection{Expressions}
59 %************************************************************************
62 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
63 rnExprs ls = rnExprs' ls emptyUniqSet
65 rnExprs' [] acc = returnM ([], acc)
66 rnExprs' (expr:exprs) acc
67 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
69 -- Now we do a "seq" on the free vars because typically it's small
70 -- or empty, especially in very long lists of constants
72 acc' = acc `plusFV` fvExpr
74 (grubby_seqNameSet acc' rnExprs') exprs acc' `thenM` \ (exprs', fvExprs) ->
75 returnM (expr':exprs', fvExprs)
77 -- Grubby little function to do "seq" on namesets; replace by proper seq when GHC can do seq
78 grubby_seqNameSet ns result | isNullUFM ns = result
82 Variables. We look up the variable and return the resulting name.
85 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
86 rnLExpr = wrapLocFstM rnExpr
88 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
91 = lookupOccRn v `thenM` \ name ->
92 doptM Opt_IgnoreAsserts `thenM` \ ignore_asserts ->
93 if name `hasKey` assertIdKey && not ignore_asserts then
94 -- We expand it to (GHC.Err.assertError location_string)
95 mkAssertErrorExpr `thenM` \ (e, fvs) ->
96 returnM (e, fvs `addOneFV` name)
97 -- Keep 'assert' as a free var, to ensure it's not reported as unused!
99 -- The normal case. Even if the Id was 'assert', if we are
100 -- ignoring assertions we leave it as GHC.Base.assert;
101 -- this function just ignores its first arg.
102 returnM (HsVar name, unitFV name)
105 = newIPNameRn v `thenM` \ name ->
106 returnM (HsIPVar name, emptyFVs)
110 returnM (HsLit lit, emptyFVs)
112 rnExpr (HsOverLit lit)
113 = rnOverLit lit `thenM` \ (lit', fvs) ->
114 returnM (HsOverLit lit', fvs)
116 rnExpr (HsApp fun arg)
117 = rnLExpr fun `thenM` \ (fun',fvFun) ->
118 rnLExpr arg `thenM` \ (arg',fvArg) ->
119 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
121 rnExpr (OpApp e1 op _ e2)
122 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
123 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
124 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
127 -- When renaming code synthesised from "deriving" declarations
128 -- we used to avoid fixity stuff, but we can't easily tell any
129 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
130 -- should prevent bad things happening.
131 lookupFixityRn op_name `thenM` \ fixity ->
132 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
135 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
138 = rnLExpr e `thenM` \ (e', fv_e) ->
139 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
140 mkNegAppRn e' neg_name `thenM` \ final_e ->
141 returnM (final_e, fv_e `plusFV` fv_neg)
144 = rnLExpr e `thenM` \ (e', fvs_e) ->
145 returnM (HsPar e', fvs_e)
147 -- Template Haskell extensions
148 -- Don't ifdef-GHCI them because we want to fail gracefully
149 -- (not with an rnExpr crash) in a stage-1 compiler.
150 rnExpr e@(HsBracket br_body)
151 = checkTH e "bracket" `thenM_`
152 rnBracket br_body `thenM` \ (body', fvs_e) ->
153 returnM (HsBracket body', fvs_e)
155 rnExpr e@(HsSpliceE splice)
156 = rnSplice splice `thenM` \ (splice', fvs) ->
157 returnM (HsSpliceE splice', fvs)
159 rnExpr section@(SectionL expr op)
160 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
161 rnLExpr op `thenM` \ (op', fvs_op) ->
162 checkSectionPrec InfixL section op' expr' `thenM_`
163 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
165 rnExpr section@(SectionR op expr)
166 = rnLExpr op `thenM` \ (op', fvs_op) ->
167 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
168 checkSectionPrec InfixR section op' expr' `thenM_`
169 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
171 rnExpr (HsCoreAnn ann expr)
172 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
173 returnM (HsCoreAnn ann expr', fvs_expr)
175 rnExpr (HsSCC lbl expr)
176 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
177 returnM (HsSCC lbl expr', fvs_expr)
179 rnExpr (HsLam matches)
180 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
181 returnM (HsLam matches', fvMatch)
183 rnExpr (HsCase expr matches)
184 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
185 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
186 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
188 rnExpr (HsLet binds expr)
189 = rnLocalBindsAndThen binds $ \ binds' ->
190 rnLExpr expr `thenM` \ (expr',fvExpr) ->
191 returnM (HsLet binds' expr', fvExpr)
193 rnExpr e@(HsDo do_or_lc stmts body _)
194 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
196 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
198 rnExpr (ExplicitList _ exps)
199 = rnExprs exps `thenM` \ (exps', fvs) ->
200 returnM (ExplicitList placeHolderType exps', fvs `addOneFV` listTyCon_name)
202 rnExpr (ExplicitPArr _ exps)
203 = rnExprs exps `thenM` \ (exps', fvs) ->
204 returnM (ExplicitPArr placeHolderType exps', fvs)
206 rnExpr e@(ExplicitTuple exps boxity)
207 = checkTupSize tup_size `thenM_`
208 rnExprs exps `thenM` \ (exps', fvs) ->
209 returnM (ExplicitTuple exps' boxity, fvs `addOneFV` tycon_name)
211 tup_size = length exps
212 tycon_name = tupleTyCon_name boxity tup_size
214 rnExpr (RecordCon con_id _ rbinds)
215 = lookupLocatedOccRn con_id `thenM` \ conname ->
216 rnRbinds "construction" rbinds `thenM` \ (rbinds', fvRbinds) ->
217 returnM (RecordCon conname noPostTcExpr rbinds',
218 fvRbinds `addOneFV` unLoc conname)
220 rnExpr (RecordUpd expr rbinds _ _)
221 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
222 rnRbinds "update" rbinds `thenM` \ (rbinds', fvRbinds) ->
223 returnM (RecordUpd expr' rbinds' placeHolderType placeHolderType,
224 fvExpr `plusFV` fvRbinds)
226 rnExpr (ExprWithTySig expr pty)
227 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
228 rnHsTypeFVs doc pty `thenM` \ (pty', fvTy) ->
229 returnM (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy)
231 doc = text "In an expression type signature"
233 rnExpr (HsIf p b1 b2)
234 = rnLExpr p `thenM` \ (p', fvP) ->
235 rnLExpr b1 `thenM` \ (b1', fvB1) ->
236 rnLExpr b2 `thenM` \ (b2', fvB2) ->
237 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
240 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
241 returnM (HsType t, fvT)
243 doc = text "In a type argument"
245 rnExpr (ArithSeq _ seq)
246 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
247 returnM (ArithSeq noPostTcExpr new_seq, fvs)
249 rnExpr (PArrSeq _ seq)
250 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
251 returnM (PArrSeq noPostTcExpr new_seq, fvs)
254 These three are pattern syntax appearing in expressions.
255 Since all the symbols are reservedops we can simply reject them.
256 We return a (bogus) EWildPat in each case.
259 rnExpr e@EWildPat = addErr (patSynErr e) `thenM_`
260 returnM (EWildPat, emptyFVs)
262 rnExpr e@(EAsPat _ _) = addErr (patSynErr e) `thenM_`
263 returnM (EWildPat, emptyFVs)
265 rnExpr e@(ELazyPat _) = addErr (patSynErr e) `thenM_`
266 returnM (EWildPat, emptyFVs)
269 %************************************************************************
273 %************************************************************************
276 rnExpr (HsProc pat body)
278 rnPatsAndThen ProcExpr [pat] $ \ [pat'] ->
279 rnCmdTop body `thenM` \ (body',fvBody) ->
280 returnM (HsProc pat' body', fvBody)
282 rnExpr (HsArrApp arrow arg _ ho rtl)
283 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
284 rnLExpr arg `thenM` \ (arg',fvArg) ->
285 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
286 fvArrow `plusFV` fvArg)
288 select_arrow_scope tc = case ho of
289 HsHigherOrderApp -> tc
290 HsFirstOrderApp -> escapeArrowScope tc
293 rnExpr (HsArrForm op (Just _) [arg1, arg2])
294 = escapeArrowScope (rnLExpr op)
295 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
296 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
297 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
301 lookupFixityRn op_name `thenM` \ fixity ->
302 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
305 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
307 rnExpr (HsArrForm op fixity cmds)
308 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
309 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
310 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
312 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
313 -- DictApp, DictLam, TyApp, TyLam
317 %************************************************************************
321 %************************************************************************
324 rnCmdArgs [] = returnM ([], emptyFVs)
326 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
327 rnCmdArgs args `thenM` \ (args',fvArgs) ->
328 returnM (arg':args', fvArg `plusFV` fvArgs)
331 rnCmdTop = wrapLocFstM rnCmdTop'
333 rnCmdTop' (HsCmdTop cmd _ _ _)
334 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
336 cmd_names = [arrAName, composeAName, firstAName] ++
337 nameSetToList (methodNamesCmd (unLoc cmd'))
339 -- Generate the rebindable syntax for the monad
340 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
342 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
343 fvCmd `plusFV` cmd_fvs)
345 ---------------------------------------------------
346 -- convert OpApp's in a command context to HsArrForm's
348 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
349 convertOpFormsLCmd = fmap convertOpFormsCmd
351 convertOpFormsCmd :: HsCmd id -> HsCmd id
353 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
354 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
355 convertOpFormsCmd (OpApp c1 op fixity c2)
357 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
358 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
360 HsArrForm op (Just fixity) [arg1, arg2]
362 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
365 convertOpFormsCmd (HsCase exp matches)
366 = HsCase exp (convertOpFormsMatch matches)
368 convertOpFormsCmd (HsIf exp c1 c2)
369 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
371 convertOpFormsCmd (HsLet binds cmd)
372 = HsLet binds (convertOpFormsLCmd cmd)
374 convertOpFormsCmd (HsDo ctxt stmts body ty)
375 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
376 (convertOpFormsLCmd body) ty
378 -- Anything else is unchanged. This includes HsArrForm (already done),
379 -- things with no sub-commands, and illegal commands (which will be
380 -- caught by the type checker)
381 convertOpFormsCmd c = c
383 convertOpFormsStmt (BindStmt pat cmd _ _)
384 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
385 convertOpFormsStmt (ExprStmt cmd _ _)
386 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
387 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
388 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
389 convertOpFormsStmt stmt = stmt
391 convertOpFormsMatch (MatchGroup ms ty)
392 = MatchGroup (map (fmap convert) ms) ty
393 where convert (Match pat mty grhss)
394 = Match pat mty (convertOpFormsGRHSs grhss)
396 convertOpFormsGRHSs (GRHSs grhss binds)
397 = GRHSs (map convertOpFormsGRHS grhss) binds
399 convertOpFormsGRHS = fmap convert
401 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
403 ---------------------------------------------------
404 type CmdNeeds = FreeVars -- Only inhabitants are
405 -- appAName, choiceAName, loopAName
407 -- find what methods the Cmd needs (loop, choice, apply)
408 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
409 methodNamesLCmd = methodNamesCmd . unLoc
411 methodNamesCmd :: HsCmd Name -> CmdNeeds
413 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
415 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
417 methodNamesCmd cmd@(HsArrForm {}) = emptyFVs
419 methodNamesCmd (HsPar c) = methodNamesLCmd c
421 methodNamesCmd (HsIf p c1 c2)
422 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
424 methodNamesCmd (HsLet b c) = methodNamesLCmd c
426 methodNamesCmd (HsDo sc stmts body ty)
427 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
429 methodNamesCmd (HsApp c e) = methodNamesLCmd c
431 methodNamesCmd (HsLam match) = methodNamesMatch match
433 methodNamesCmd (HsCase scrut matches)
434 = methodNamesMatch matches `addOneFV` choiceAName
436 methodNamesCmd other = emptyFVs
437 -- Other forms can't occur in commands, but it's not convenient
438 -- to error here so we just do what's convenient.
439 -- The type checker will complain later
441 ---------------------------------------------------
442 methodNamesMatch (MatchGroup ms ty)
443 = plusFVs (map do_one ms)
445 do_one (L _ (Match pats sig_ty grhss)) = methodNamesGRHSs grhss
447 -------------------------------------------------
449 methodNamesGRHSs (GRHSs grhss binds) = plusFVs (map methodNamesGRHS grhss)
451 -------------------------------------------------
452 methodNamesGRHS (L _ (GRHS stmts rhs)) = methodNamesLCmd rhs
454 ---------------------------------------------------
455 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
457 ---------------------------------------------------
458 methodNamesLStmt = methodNamesStmt . unLoc
460 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
461 methodNamesStmt (BindStmt pat cmd _ _) = methodNamesLCmd cmd
462 methodNamesStmt (RecStmt stmts _ _ _ _)
463 = methodNamesStmts stmts `addOneFV` loopAName
464 methodNamesStmt (LetStmt b) = emptyFVs
465 methodNamesStmt (ParStmt ss) = emptyFVs
466 -- ParStmt can't occur in commands, but it's not convenient to error
467 -- here so we just do what's convenient
471 %************************************************************************
475 %************************************************************************
478 rnArithSeq (From expr)
479 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
480 returnM (From expr', fvExpr)
482 rnArithSeq (FromThen expr1 expr2)
483 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
484 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
485 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
487 rnArithSeq (FromTo expr1 expr2)
488 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
489 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
490 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
492 rnArithSeq (FromThenTo expr1 expr2 expr3)
493 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
494 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
495 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
496 returnM (FromThenTo expr1' expr2' expr3',
497 plusFVs [fvExpr1, fvExpr2, fvExpr3])
501 %************************************************************************
503 \subsubsection{@Rbinds@s and @Rpats@s: in record expressions}
505 %************************************************************************
509 = mappM_ field_dup_err dup_fields `thenM_`
510 mapFvRn rn_rbind rbinds `thenM` \ (rbinds', fvRbind) ->
511 returnM (rbinds', fvRbind)
513 (_, dup_fields) = removeDups cmpLocated [ f | (f,_) <- rbinds ]
515 field_dup_err dups = mappM_ (\f -> addLocErr f (dupFieldErr str)) dups
517 rn_rbind (field, expr)
518 = lookupLocatedGlobalOccRn field `thenM` \ fieldname ->
519 rnLExpr expr `thenM` \ (expr', fvExpr) ->
520 returnM ((fieldname, expr'), fvExpr `addOneFV` unLoc fieldname)
523 %************************************************************************
525 Template Haskell brackets
527 %************************************************************************
530 rnBracket (VarBr n) = do { name <- lookupOccRn n
531 ; loadHomeInterface msg name -- Reason: deprecation checking asumes the
532 -- home interface is loaded, and this is the
533 -- only way that is going to happen
534 ; returnM (VarBr name, unitFV name) }
536 msg = ptext SLIT("Need interface for Template Haskell quoted Name")
538 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
539 ; return (ExpBr e', fvs) }
540 rnBracket (PatBr p) = do { (p', fvs) <- rnLPat p
541 ; return (PatBr p', fvs) }
542 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
543 ; return (TypBr t', fvs) }
545 doc = ptext SLIT("In a Template-Haskell quoted type")
546 rnBracket (DecBr group)
547 = do { gbl_env <- getGblEnv
548 ; names <- getLocalDeclBinders gbl_env group
549 ; rdr_env' <- extendRdrEnvRn (tcg_mod gbl_env) emptyGlobalRdrEnv names
551 ; setGblEnv (gbl_env { tcg_rdr_env = tcg_rdr_env gbl_env `plusOccEnv` rdr_env',
552 tcg_dus = emptyDUs }) $ do
553 -- Notice plusOccEnv, not plusGlobalRdrEnv. In this situation we want
554 -- to *shadow* top-level bindings. E.g.
556 -- bar = [d| foo = 1|]
557 -- So we drop down to plusOccEnv. (Perhaps there should be a fn in RdrName.)
559 -- The emptyDUs is so that we just collect uses for this group alone
561 { (tcg_env, group') <- rnSrcDecls group
562 -- Discard the tcg_env; it contains only extra info about fixity
563 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
566 %************************************************************************
568 \subsubsection{@Stmt@s: in @do@ expressions}
570 %************************************************************************
573 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
574 -> RnM (thing, FreeVars)
575 -> RnM (([LStmt Name], thing), FreeVars)
577 rnStmts (MDoExpr _) = rnMDoStmts
578 rnStmts ctxt = rnNormalStmts ctxt
580 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
581 -> RnM (thing, FreeVars)
582 -> RnM (([LStmt Name], thing), FreeVars)
583 -- Used for cases *other* than recursive mdo
584 -- Implements nested scopes
586 rnNormalStmts ctxt [] thing_inside
587 = do { (thing, fvs) <- thing_inside
588 ; return (([],thing), fvs) }
590 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
591 = do { ((stmt', (stmts', thing)), fvs)
592 <- rnStmt ctxt stmt $
593 rnNormalStmts ctxt stmts thing_inside
594 ; return (((L loc stmt' : stmts'), thing), fvs) }
596 rnStmt :: HsStmtContext Name -> Stmt RdrName
597 -> RnM (thing, FreeVars)
598 -> RnM ((Stmt Name, thing), FreeVars)
600 rnStmt ctxt (ExprStmt expr _ _) thing_inside
601 = do { (expr', fv_expr) <- rnLExpr expr
602 ; (then_op, fvs1) <- lookupSyntaxName thenMName
603 ; (thing, fvs2) <- thing_inside
604 ; return ((ExprStmt expr' then_op placeHolderType, thing),
605 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
607 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
608 = do { (expr', fv_expr) <- rnLExpr expr
609 -- The binders do not scope over the expression
610 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
611 ; (fail_op, fvs2) <- lookupSyntaxName failMName
612 ; rnPatsAndThen (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
613 { (thing, fvs3) <- thing_inside
614 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
615 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
616 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
617 -- but it does not matter because the names are unique
619 rnStmt ctxt (LetStmt binds) thing_inside
620 = do { checkErr (ok ctxt binds)
621 (badIpBinds (ptext SLIT("a parallel list comprehension:")) binds)
622 ; rnLocalBindsAndThen binds $ \ binds' -> do
623 { (thing, fvs) <- thing_inside
624 ; return ((LetStmt binds', thing), fvs) }}
626 -- We do not allow implicit-parameter bindings in a parallel
627 -- list comprehension. I'm not sure what it might mean.
628 ok (ParStmtCtxt _) (HsIPBinds _) = False
631 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
632 = bindLocatedLocalsRn doc (collectLStmtsBinders rec_stmts) $ \ bndrs ->
633 rn_rec_stmts bndrs rec_stmts `thenM` \ segs ->
634 thing_inside `thenM` \ (thing, fvs) ->
636 segs_w_fwd_refs = addFwdRefs segs
637 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
638 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
639 fwd_vars = nameSetToList (plusFVs fs)
641 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
643 returnM ((rec_stmt, thing), uses `plusFV` fvs)
645 doc = text "In a recursive do statement"
647 rnStmt ctxt (ParStmt segs) thing_inside
648 = do { opt_GlasgowExts <- doptM Opt_GlasgowExts
649 ; checkM opt_GlasgowExts parStmtErr
650 ; orig_lcl_env <- getLocalRdrEnv
651 ; ((segs',thing), fvs) <- go orig_lcl_env [] segs
652 ; return ((ParStmt segs', thing), fvs) }
654 -- type ParSeg id = [([LStmt id], [id])]
655 -- go :: NameSet -> [ParSeg RdrName]
656 -- -> RnM (([ParSeg Name], thing), FreeVars)
658 go orig_lcl_env bndrs []
659 = do { let { (bndrs', dups) = removeDups cmpByOcc bndrs
660 ; inner_env = extendLocalRdrEnv orig_lcl_env bndrs' }
662 ; (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
663 ; return (([], thing), fvs) }
665 go orig_lcl_env bndrs_so_far ((stmts, _) : segs)
666 = do { ((stmts', (bndrs, segs', thing)), fvs)
667 <- rnNormalStmts par_ctxt stmts $ do
668 { -- Find the Names that are bound by stmts
669 lcl_env <- getLocalRdrEnv
670 ; let { rdr_bndrs = collectLStmtsBinders stmts
671 ; bndrs = map ( fromJust
672 . lookupLocalRdrEnv lcl_env
674 ; new_bndrs = nub bndrs ++ bndrs_so_far
675 -- The nub is because there might be shadowing
677 -- So we'll look up (Unqual x) twice, getting
678 -- the second binding both times, which is the
681 -- Typecheck the thing inside, passing on all
682 -- the Names bound, but separately; revert the envt
683 ; ((segs', thing), fvs) <- setLocalRdrEnv orig_lcl_env $
684 go orig_lcl_env new_bndrs segs
686 -- Figure out which of the bound names are used
687 ; let used_bndrs = filter (`elemNameSet` fvs) bndrs
688 ; return ((used_bndrs, segs', thing), fvs) }
690 ; let seg' = (stmts', bndrs)
691 ; return (((seg':segs'), thing),
692 delListFromNameSet fvs bndrs) }
694 par_ctxt = ParStmtCtxt ctxt
696 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
697 dupErr vs = addErr (ptext SLIT("Duplicate binding in parallel list comprehension for:")
698 <+> quotes (ppr (head vs)))
702 %************************************************************************
704 \subsubsection{mdo expressions}
706 %************************************************************************
709 type FwdRefs = NameSet
710 type Segment stmts = (Defs,
711 Uses, -- May include defs
712 FwdRefs, -- A subset of uses that are
713 -- (a) used before they are bound in this segment, or
714 -- (b) used here, and bound in subsequent segments
715 stmts) -- Either Stmt or [Stmt]
718 ----------------------------------------------------
719 rnMDoStmts :: [LStmt RdrName]
720 -> RnM (thing, FreeVars)
721 -> RnM (([LStmt Name], thing), FreeVars)
722 rnMDoStmts stmts thing_inside
723 = -- Step1: bring all the binders of the mdo into scope
724 -- Remember that this also removes the binders from the
725 -- finally-returned free-vars
726 bindLocatedLocalsRn doc (collectLStmtsBinders stmts) $ \ bndrs ->
728 -- Step 2: Rename each individual stmt, making a
729 -- singleton segment. At this stage the FwdRefs field
730 -- isn't finished: it's empty for all except a BindStmt
731 -- for which it's the fwd refs within the bind itself
732 -- (This set may not be empty, because we're in a recursive
734 segs <- rn_rec_stmts bndrs stmts
736 ; (thing, fvs_later) <- thing_inside
739 -- Step 3: Fill in the fwd refs.
740 -- The segments are all singletons, but their fwd-ref
741 -- field mentions all the things used by the segment
742 -- that are bound after their use
743 segs_w_fwd_refs = addFwdRefs segs
745 -- Step 4: Group together the segments to make bigger segments
746 -- Invariant: in the result, no segment uses a variable
747 -- bound in a later segment
748 grouped_segs = glomSegments segs_w_fwd_refs
750 -- Step 5: Turn the segments into Stmts
751 -- Use RecStmt when and only when there are fwd refs
752 -- Also gather up the uses from the end towards the
753 -- start, so we can tell the RecStmt which things are
754 -- used 'after' the RecStmt
755 (stmts', fvs) = segsToStmts grouped_segs fvs_later
757 ; return ((stmts', thing), fvs) }
759 doc = text "In a recursive mdo-expression"
761 ---------------------------------------------
762 rn_rec_stmts :: [Name] -> [LStmt RdrName] -> RnM [Segment (LStmt Name)]
763 rn_rec_stmts bndrs stmts = mappM (rn_rec_stmt bndrs) stmts `thenM` \ segs_s ->
764 returnM (concat segs_s)
766 ----------------------------------------------------
767 rn_rec_stmt :: [Name] -> LStmt RdrName -> RnM [Segment (LStmt Name)]
768 -- Rename a Stmt that is inside a RecStmt (or mdo)
769 -- Assumes all binders are already in scope
770 -- Turns each stmt into a singleton Stmt
772 rn_rec_stmt all_bndrs (L loc (ExprStmt expr _ _))
773 = rnLExpr expr `thenM` \ (expr', fvs) ->
774 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
775 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
776 L loc (ExprStmt expr' then_op placeHolderType))]
778 rn_rec_stmt all_bndrs (L loc (BindStmt pat expr _ _))
779 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
780 rnLPat pat `thenM` \ (pat', fv_pat) ->
781 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
782 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
784 bndrs = mkNameSet (collectPatBinders pat')
785 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
787 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
788 L loc (BindStmt pat' expr' bind_op fail_op))]
790 rn_rec_stmt all_bndrs (L loc (LetStmt binds@(HsIPBinds _)))
791 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
794 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds)))
795 = rnValBinds (trimWith all_bndrs) binds `thenM` \ (binds', du_binds) ->
796 returnM [(duDefs du_binds, duUses du_binds,
797 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
799 rn_rec_stmt all_bndrs (L loc (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
800 = rn_rec_stmts all_bndrs stmts
802 rn_rec_stmt all_bndrs stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
803 = pprPanic "rn_rec_stmt" (ppr stmt)
805 ---------------------------------------------
806 addFwdRefs :: [Segment a] -> [Segment a]
807 -- So far the segments only have forward refs *within* the Stmt
808 -- (which happens for bind: x <- ...x...)
809 -- This function adds the cross-seg fwd ref info
812 = fst (foldr mk_seg ([], emptyNameSet) pairs)
814 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
815 = (new_seg : segs, all_defs)
817 new_seg = (defs, uses, new_fwds, stmts)
818 all_defs = later_defs `unionNameSets` defs
819 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
820 -- Add the downstream fwd refs here
822 ----------------------------------------------------
823 -- Glomming the singleton segments of an mdo into
824 -- minimal recursive groups.
826 -- At first I thought this was just strongly connected components, but
827 -- there's an important constraint: the order of the stmts must not change.
830 -- mdo { x <- ...y...
837 -- Here, the first stmt mention 'y', which is bound in the third.
838 -- But that means that the innocent second stmt (p <- z) gets caught
839 -- up in the recursion. And that in turn means that the binding for
840 -- 'z' has to be included... and so on.
842 -- Start at the tail { r <- x }
843 -- Now add the next one { z <- y ; r <- x }
844 -- Now add one more { q <- x ; z <- y ; r <- x }
845 -- Now one more... but this time we have to group a bunch into rec
846 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
847 -- Now one more, which we can add on without a rec
849 -- rec { y <- ...x... ; q <- x ; z <- y } ;
851 -- Finally we add the last one; since it mentions y we have to
852 -- glom it togeher with the first two groups
853 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
854 -- q <- x ; z <- y } ;
857 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
860 glomSegments ((defs,uses,fwds,stmt) : segs)
861 -- Actually stmts will always be a singleton
862 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
864 segs' = glomSegments segs
865 (extras, others) = grab uses segs'
866 (ds, us, fs, ss) = unzip4 extras
868 seg_defs = plusFVs ds `plusFV` defs
869 seg_uses = plusFVs us `plusFV` uses
870 seg_fwds = plusFVs fs `plusFV` fwds
871 seg_stmts = stmt : concat ss
873 grab :: NameSet -- The client
875 -> ([Segment a], -- Needed by the 'client'
876 [Segment a]) -- Not needed by the client
877 -- The result is simply a split of the input
879 = (reverse yeses, reverse noes)
881 (noes, yeses) = span not_needed (reverse dus)
882 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
885 ----------------------------------------------------
886 segsToStmts :: [Segment [LStmt Name]]
887 -> FreeVars -- Free vars used 'later'
888 -> ([LStmt Name], FreeVars)
890 segsToStmts [] fvs_later = ([], fvs_later)
891 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
892 = ASSERT( not (null ss) )
893 (new_stmt : later_stmts, later_uses `plusFV` uses)
895 (later_stmts, later_uses) = segsToStmts segs fvs_later
896 new_stmt | non_rec = head ss
897 | otherwise = L (getLoc (head ss)) $
898 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
901 non_rec = isSingleton ss && isEmptyNameSet fwds
902 used_later = defs `intersectNameSet` later_uses
903 -- The ones needed after the RecStmt
906 %************************************************************************
908 \subsubsection{Assertion utils}
910 %************************************************************************
913 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
914 -- Return an expression for (assertError "Foo.hs:27")
916 = getSrcSpanM `thenM` \ sloc ->
918 expr = HsApp (L sloc (HsVar assertErrorName)) (L sloc (HsLit msg))
919 msg = HsStringPrim (mkFastString (stringToUtf8 (showSDoc (ppr sloc))))
921 returnM (expr, emptyFVs)
924 %************************************************************************
926 \subsubsection{Errors}
928 %************************************************************************
932 = sep [ptext SLIT("Pattern syntax in expression context:"),
935 parStmtErr = addErr (ptext SLIT("Illegal parallel list comprehension: use -fglasgow-exts"))
937 badIpBinds what binds
938 = hang (ptext SLIT("Implicit-parameter bindings illegal in") <+> what)