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 HscTypes ( availNames )
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 SrcLoc ( SrcSpan )
34 import PrelNames ( thFAKE, hasKey, assertIdKey, assertErrorName,
35 loopAName, choiceAName, appAName, arrAName, composeAName, firstAName,
36 negateName, thenMName, bindMName, failMName )
38 import Name ( Name, nameOccName, nameIsLocalOrFrom )
40 import RdrName ( RdrName, extendLocalRdrEnv, lookupLocalRdrEnv, hideSomeUnquals )
41 import LoadIface ( loadInterfaceForName )
42 import UniqFM ( isNullUFM )
43 import UniqSet ( emptyUniqSet )
45 import Util ( isSingleton )
46 import ListSetOps ( removeDups )
47 import Maybes ( expectJust )
49 import SrcLoc ( Located(..), unLoc, getLoc, cmpLocated )
52 import List ( unzip4 )
56 %************************************************************************
58 \subsubsection{Expressions}
60 %************************************************************************
63 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
64 rnExprs ls = rnExprs' ls emptyUniqSet
66 rnExprs' [] acc = returnM ([], acc)
67 rnExprs' (expr:exprs) acc
68 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
70 -- Now we do a "seq" on the free vars because typically it's small
71 -- or empty, especially in very long lists of constants
73 acc' = acc `plusFV` fvExpr
75 (grubby_seqNameSet acc' rnExprs') exprs acc' `thenM` \ (exprs', fvExprs) ->
76 returnM (expr':exprs', fvExprs)
78 -- Grubby little function to do "seq" on namesets; replace by proper seq when GHC can do seq
79 grubby_seqNameSet ns result | isNullUFM ns = result
83 Variables. We look up the variable and return the resulting name.
86 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
87 rnLExpr = wrapLocFstM rnExpr
89 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
92 = do name <- lookupOccRn v
93 ignore_asserts <- doptM Opt_IgnoreAsserts
94 finish_var ignore_asserts name
96 finish_var ignore_asserts name
97 | ignore_asserts || not (name `hasKey` assertIdKey)
98 = return (HsVar name, unitFV name)
100 = do { (e, fvs) <- mkAssertErrorExpr
101 ; return (e, fvs `addOneFV` name) }
104 = newIPNameRn v `thenM` \ name ->
105 returnM (HsIPVar name, emptyFVs)
107 rnExpr (HsLit lit@(HsString s))
109 opt_OverloadedStrings <- doptM Opt_OverloadedStrings
110 ; if opt_OverloadedStrings then
111 rnExpr (HsOverLit (mkHsIsString s))
112 else -- Same as below
114 returnM (HsLit lit, emptyFVs)
119 returnM (HsLit lit, emptyFVs)
121 rnExpr (HsOverLit lit)
122 = rnOverLit lit `thenM` \ (lit', fvs) ->
123 returnM (HsOverLit lit', fvs)
125 rnExpr (HsApp fun arg)
126 = rnLExpr fun `thenM` \ (fun',fvFun) ->
127 rnLExpr arg `thenM` \ (arg',fvArg) ->
128 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
130 rnExpr (OpApp e1 op _ e2)
131 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
132 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
133 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
136 -- When renaming code synthesised from "deriving" declarations
137 -- we used to avoid fixity stuff, but we can't easily tell any
138 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
139 -- should prevent bad things happening.
140 lookupFixityRn op_name `thenM` \ fixity ->
141 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
144 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
147 = rnLExpr e `thenM` \ (e', fv_e) ->
148 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
149 mkNegAppRn e' neg_name `thenM` \ final_e ->
150 returnM (final_e, fv_e `plusFV` fv_neg)
153 = rnLExpr e `thenM` \ (e', fvs_e) ->
154 returnM (HsPar e', fvs_e)
156 -- Template Haskell extensions
157 -- Don't ifdef-GHCI them because we want to fail gracefully
158 -- (not with an rnExpr crash) in a stage-1 compiler.
159 rnExpr e@(HsBracket br_body)
160 = checkTH e "bracket" `thenM_`
161 rnBracket br_body `thenM` \ (body', fvs_e) ->
162 returnM (HsBracket body', fvs_e)
164 rnExpr e@(HsSpliceE splice)
165 = rnSplice splice `thenM` \ (splice', fvs) ->
166 returnM (HsSpliceE splice', fvs)
168 rnExpr section@(SectionL expr op)
169 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
170 rnLExpr op `thenM` \ (op', fvs_op) ->
171 checkSectionPrec InfixL section op' expr' `thenM_`
172 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
174 rnExpr section@(SectionR op expr)
175 = rnLExpr op `thenM` \ (op', fvs_op) ->
176 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
177 checkSectionPrec InfixR section op' expr' `thenM_`
178 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
180 rnExpr (HsCoreAnn ann expr)
181 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
182 returnM (HsCoreAnn ann expr', fvs_expr)
184 rnExpr (HsSCC lbl expr)
185 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
186 returnM (HsSCC lbl expr', fvs_expr)
187 rnExpr (HsTickPragma info expr)
188 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
189 returnM (HsTickPragma info expr', fvs_expr)
191 rnExpr (HsLam matches)
192 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
193 returnM (HsLam matches', fvMatch)
195 rnExpr (HsCase expr matches)
196 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
197 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
198 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
200 rnExpr (HsLet binds expr)
201 = rnLocalBindsAndThen binds $ \ binds' ->
202 rnLExpr expr `thenM` \ (expr',fvExpr) ->
203 returnM (HsLet binds' expr', fvExpr)
205 rnExpr e@(HsDo do_or_lc stmts body _)
206 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
208 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
210 rnExpr (ExplicitList _ exps)
211 = rnExprs exps `thenM` \ (exps', fvs) ->
212 returnM (ExplicitList placeHolderType exps', fvs `addOneFV` listTyCon_name)
214 rnExpr (ExplicitPArr _ exps)
215 = rnExprs exps `thenM` \ (exps', fvs) ->
216 returnM (ExplicitPArr placeHolderType exps', fvs)
218 rnExpr e@(ExplicitTuple exps boxity)
219 = checkTupSize tup_size `thenM_`
220 rnExprs exps `thenM` \ (exps', fvs) ->
221 returnM (ExplicitTuple exps' boxity, fvs `addOneFV` tycon_name)
223 tup_size = length exps
224 tycon_name = tupleTyCon_name boxity tup_size
226 rnExpr (RecordCon con_id _ (HsRecordBinds rbinds))
227 = lookupLocatedOccRn con_id `thenM` \ conname ->
228 rnRbinds "construction" rbinds `thenM` \ (rbinds', fvRbinds) ->
229 returnM (RecordCon conname noPostTcExpr (HsRecordBinds rbinds'),
230 fvRbinds `addOneFV` unLoc conname)
232 rnExpr (RecordUpd expr (HsRecordBinds rbinds) _ _)
233 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
234 rnRbinds "update" rbinds `thenM` \ (rbinds', fvRbinds) ->
235 returnM (RecordUpd expr' (HsRecordBinds rbinds') placeHolderType placeHolderType,
236 fvExpr `plusFV` fvRbinds)
238 rnExpr (ExprWithTySig expr pty)
239 = do { (pty', fvTy) <- rnHsTypeFVs doc pty
240 ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $
242 ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) }
244 doc = text "In an expression type signature"
246 rnExpr (HsIf p b1 b2)
247 = rnLExpr p `thenM` \ (p', fvP) ->
248 rnLExpr b1 `thenM` \ (b1', fvB1) ->
249 rnLExpr b2 `thenM` \ (b2', fvB2) ->
250 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
253 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
254 returnM (HsType t, fvT)
256 doc = text "In a type argument"
258 rnExpr (ArithSeq _ seq)
259 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
260 returnM (ArithSeq noPostTcExpr new_seq, fvs)
262 rnExpr (PArrSeq _ seq)
263 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
264 returnM (PArrSeq noPostTcExpr new_seq, fvs)
267 These three are pattern syntax appearing in expressions.
268 Since all the symbols are reservedops we can simply reject them.
269 We return a (bogus) EWildPat in each case.
272 rnExpr e@EWildPat = patSynErr e
273 rnExpr e@(EAsPat {}) = patSynErr e
274 rnExpr e@(ELazyPat {}) = patSynErr e
277 %************************************************************************
281 %************************************************************************
284 rnExpr (HsProc pat body)
286 rnPatsAndThen ProcExpr [pat] $ \ [pat'] ->
287 rnCmdTop body `thenM` \ (body',fvBody) ->
288 returnM (HsProc pat' body', fvBody)
290 rnExpr (HsArrApp arrow arg _ ho rtl)
291 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
292 rnLExpr arg `thenM` \ (arg',fvArg) ->
293 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
294 fvArrow `plusFV` fvArg)
296 select_arrow_scope tc = case ho of
297 HsHigherOrderApp -> tc
298 HsFirstOrderApp -> escapeArrowScope tc
301 rnExpr (HsArrForm op (Just _) [arg1, arg2])
302 = escapeArrowScope (rnLExpr op)
303 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
304 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
305 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
309 lookupFixityRn op_name `thenM` \ fixity ->
310 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
313 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
315 rnExpr (HsArrForm op fixity cmds)
316 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
317 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
318 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
320 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
325 %************************************************************************
329 %************************************************************************
332 rnCmdArgs [] = returnM ([], emptyFVs)
334 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
335 rnCmdArgs args `thenM` \ (args',fvArgs) ->
336 returnM (arg':args', fvArg `plusFV` fvArgs)
339 rnCmdTop = wrapLocFstM rnCmdTop'
341 rnCmdTop' (HsCmdTop cmd _ _ _)
342 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
344 cmd_names = [arrAName, composeAName, firstAName] ++
345 nameSetToList (methodNamesCmd (unLoc cmd'))
347 -- Generate the rebindable syntax for the monad
348 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
350 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
351 fvCmd `plusFV` cmd_fvs)
353 ---------------------------------------------------
354 -- convert OpApp's in a command context to HsArrForm's
356 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
357 convertOpFormsLCmd = fmap convertOpFormsCmd
359 convertOpFormsCmd :: HsCmd id -> HsCmd id
361 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
362 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
363 convertOpFormsCmd (OpApp c1 op fixity c2)
365 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
366 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
368 HsArrForm op (Just fixity) [arg1, arg2]
370 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
373 convertOpFormsCmd (HsCase exp matches)
374 = HsCase exp (convertOpFormsMatch matches)
376 convertOpFormsCmd (HsIf exp c1 c2)
377 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
379 convertOpFormsCmd (HsLet binds cmd)
380 = HsLet binds (convertOpFormsLCmd cmd)
382 convertOpFormsCmd (HsDo ctxt stmts body ty)
383 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
384 (convertOpFormsLCmd body) ty
386 -- Anything else is unchanged. This includes HsArrForm (already done),
387 -- things with no sub-commands, and illegal commands (which will be
388 -- caught by the type checker)
389 convertOpFormsCmd c = c
391 convertOpFormsStmt (BindStmt pat cmd _ _)
392 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
393 convertOpFormsStmt (ExprStmt cmd _ _)
394 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
395 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
396 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
397 convertOpFormsStmt stmt = stmt
399 convertOpFormsMatch (MatchGroup ms ty)
400 = MatchGroup (map (fmap convert) ms) ty
401 where convert (Match pat mty grhss)
402 = Match pat mty (convertOpFormsGRHSs grhss)
404 convertOpFormsGRHSs (GRHSs grhss binds)
405 = GRHSs (map convertOpFormsGRHS grhss) binds
407 convertOpFormsGRHS = fmap convert
409 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
411 ---------------------------------------------------
412 type CmdNeeds = FreeVars -- Only inhabitants are
413 -- appAName, choiceAName, loopAName
415 -- find what methods the Cmd needs (loop, choice, apply)
416 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
417 methodNamesLCmd = methodNamesCmd . unLoc
419 methodNamesCmd :: HsCmd Name -> CmdNeeds
421 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
423 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
425 methodNamesCmd cmd@(HsArrForm {}) = emptyFVs
427 methodNamesCmd (HsPar c) = methodNamesLCmd c
429 methodNamesCmd (HsIf p c1 c2)
430 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
432 methodNamesCmd (HsLet b c) = methodNamesLCmd c
434 methodNamesCmd (HsDo sc stmts body ty)
435 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
437 methodNamesCmd (HsApp c e) = methodNamesLCmd c
439 methodNamesCmd (HsLam match) = methodNamesMatch match
441 methodNamesCmd (HsCase scrut matches)
442 = methodNamesMatch matches `addOneFV` choiceAName
444 methodNamesCmd other = emptyFVs
445 -- Other forms can't occur in commands, but it's not convenient
446 -- to error here so we just do what's convenient.
447 -- The type checker will complain later
449 ---------------------------------------------------
450 methodNamesMatch (MatchGroup ms _)
451 = plusFVs (map do_one ms)
453 do_one (L _ (Match pats sig_ty grhss)) = methodNamesGRHSs grhss
455 -------------------------------------------------
457 methodNamesGRHSs (GRHSs grhss binds) = plusFVs (map methodNamesGRHS grhss)
459 -------------------------------------------------
460 methodNamesGRHS (L _ (GRHS stmts rhs)) = methodNamesLCmd rhs
462 ---------------------------------------------------
463 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
465 ---------------------------------------------------
466 methodNamesLStmt = methodNamesStmt . unLoc
468 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
469 methodNamesStmt (BindStmt pat cmd _ _) = methodNamesLCmd cmd
470 methodNamesStmt (RecStmt stmts _ _ _ _)
471 = methodNamesStmts stmts `addOneFV` loopAName
472 methodNamesStmt (LetStmt b) = emptyFVs
473 methodNamesStmt (ParStmt ss) = emptyFVs
474 -- ParStmt can't occur in commands, but it's not convenient to error
475 -- here so we just do what's convenient
479 %************************************************************************
483 %************************************************************************
486 rnArithSeq (From expr)
487 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
488 returnM (From expr', fvExpr)
490 rnArithSeq (FromThen expr1 expr2)
491 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
492 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
493 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
495 rnArithSeq (FromTo expr1 expr2)
496 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
497 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
498 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
500 rnArithSeq (FromThenTo expr1 expr2 expr3)
501 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
502 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
503 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
504 returnM (FromThenTo expr1' expr2' expr3',
505 plusFVs [fvExpr1, fvExpr2, fvExpr3])
509 %************************************************************************
511 \subsubsection{@Rbinds@s and @Rpats@s: in record expressions}
513 %************************************************************************
517 = mappM_ field_dup_err dup_fields `thenM_`
518 mapFvRn rn_rbind rbinds `thenM` \ (rbinds', fvRbind) ->
519 returnM (rbinds', fvRbind)
521 (_, dup_fields) = removeDups cmpLocated [ f | (f,_) <- rbinds ]
523 field_dup_err dups = mappM_ (\f -> addLocErr f (dupFieldErr str)) dups
525 rn_rbind (field, expr)
526 = lookupLocatedGlobalOccRn field `thenM` \ fieldname ->
527 rnLExpr expr `thenM` \ (expr', fvExpr) ->
528 returnM ((fieldname, expr'), fvExpr `addOneFV` unLoc fieldname)
531 %************************************************************************
533 Template Haskell brackets
535 %************************************************************************
538 rnBracket (VarBr n) = do { name <- lookupOccRn n
539 ; this_mod <- getModule
540 ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the
541 do { loadInterfaceForName msg name -- home interface is loaded, and this is the
542 ; return () } -- only way that is going to happen
543 ; returnM (VarBr name, unitFV name) }
545 msg = ptext SLIT("Need interface for Template Haskell quoted Name")
547 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
548 ; return (ExpBr e', fvs) }
549 rnBracket (PatBr p) = do { (p', fvs) <- rnLPat p
550 ; return (PatBr p', fvs) }
551 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
552 ; return (TypBr t', fvs) }
554 doc = ptext SLIT("In a Template-Haskell quoted type")
555 rnBracket (DecBr group)
556 = do { gbl_env <- getGblEnv
558 ; let gbl_env1 = gbl_env { tcg_mod = thFAKE }
559 -- Note the thFAKE. The top-level names from the bracketed
560 -- declarations will go into the name cache, and we don't want them to
561 -- confuse the Names for the current module.
562 -- By using a pretend module, thFAKE, we keep them safely out of the way.
564 ; avails <- getLocalDeclBinders gbl_env1 group
565 ; let names = concatMap availNames avails
567 ; let new_occs = map nameOccName names
568 trimmed_rdr_env = hideSomeUnquals (tcg_rdr_env gbl_env) new_occs
570 ; rdr_env' <- extendRdrEnvRn trimmed_rdr_env avails
571 -- In this situation we want to *shadow* top-level bindings.
573 -- bar = [d| foo = 1|]
574 -- If we don't shadow, we'll get an ambiguity complaint when we do
575 -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo'
577 -- Furthermore, arguably if the splice does define foo, that should hide
578 -- any foo's further out
580 -- The shadowing is acheived by the call to hideSomeUnquals, which removes
581 -- the unqualified bindings of things defined by the bracket
583 ; setGblEnv (gbl_env { tcg_rdr_env = rdr_env',
584 tcg_dus = emptyDUs }) $ do
585 -- The emptyDUs is so that we just collect uses for this group alone
587 { (tcg_env, group') <- rnSrcDecls group
588 -- Discard the tcg_env; it contains only extra info about fixity
589 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
592 %************************************************************************
594 \subsubsection{@Stmt@s: in @do@ expressions}
596 %************************************************************************
599 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
600 -> RnM (thing, FreeVars)
601 -> RnM (([LStmt Name], thing), FreeVars)
603 rnStmts (MDoExpr _) = rnMDoStmts
604 rnStmts ctxt = rnNormalStmts ctxt
606 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
607 -> RnM (thing, FreeVars)
608 -> RnM (([LStmt Name], thing), FreeVars)
609 -- Used for cases *other* than recursive mdo
610 -- Implements nested scopes
612 rnNormalStmts ctxt [] thing_inside
613 = do { (thing, fvs) <- thing_inside
614 ; return (([],thing), fvs) }
616 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
617 = do { ((stmt', (stmts', thing)), fvs)
618 <- rnStmt ctxt stmt $
619 rnNormalStmts ctxt stmts thing_inside
620 ; return (((L loc stmt' : stmts'), thing), fvs) }
622 rnStmt :: HsStmtContext Name -> Stmt RdrName
623 -> RnM (thing, FreeVars)
624 -> RnM ((Stmt Name, thing), FreeVars)
626 rnStmt ctxt (ExprStmt expr _ _) thing_inside
627 = do { (expr', fv_expr) <- rnLExpr expr
628 ; (then_op, fvs1) <- lookupSyntaxName thenMName
629 ; (thing, fvs2) <- thing_inside
630 ; return ((ExprStmt expr' then_op placeHolderType, thing),
631 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
633 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
634 = do { (expr', fv_expr) <- rnLExpr expr
635 -- The binders do not scope over the expression
636 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
637 ; (fail_op, fvs2) <- lookupSyntaxName failMName
638 ; rnPatsAndThen (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
639 { (thing, fvs3) <- thing_inside
640 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
641 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
642 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
643 -- but it does not matter because the names are unique
645 rnStmt ctxt (LetStmt binds) thing_inside
646 = do { checkErr (ok ctxt binds)
647 (badIpBinds (ptext SLIT("a parallel list comprehension:")) binds)
648 ; rnLocalBindsAndThen binds $ \ binds' -> do
649 { (thing, fvs) <- thing_inside
650 ; return ((LetStmt binds', thing), fvs) }}
652 -- We do not allow implicit-parameter bindings in a parallel
653 -- list comprehension. I'm not sure what it might mean.
654 ok (ParStmtCtxt _) (HsIPBinds _) = False
657 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
658 = bindLocatedLocalsRn doc (collectLStmtsBinders rec_stmts) $ \ bndrs ->
659 rn_rec_stmts bndrs rec_stmts `thenM` \ segs ->
660 thing_inside `thenM` \ (thing, fvs) ->
662 segs_w_fwd_refs = addFwdRefs segs
663 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
664 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
665 fwd_vars = nameSetToList (plusFVs fs)
667 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
669 returnM ((rec_stmt, thing), uses `plusFV` fvs)
671 doc = text "In a recursive do statement"
673 rnStmt ctxt (ParStmt segs) thing_inside
674 = do { opt_GlasgowExts <- doptM Opt_GlasgowExts
675 ; checkM opt_GlasgowExts parStmtErr
676 ; orig_lcl_env <- getLocalRdrEnv
677 ; ((segs',thing), fvs) <- go orig_lcl_env [] segs
678 ; return ((ParStmt segs', thing), fvs) }
680 -- type ParSeg id = [([LStmt id], [id])]
681 -- go :: NameSet -> [ParSeg RdrName]
682 -- -> RnM (([ParSeg Name], thing), FreeVars)
684 go orig_lcl_env bndrs []
685 = do { let { (bndrs', dups) = removeDups cmpByOcc bndrs
686 ; inner_env = extendLocalRdrEnv orig_lcl_env bndrs' }
688 ; (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
689 ; return (([], thing), fvs) }
691 go orig_lcl_env bndrs_so_far ((stmts, _) : segs)
692 = do { ((stmts', (bndrs, segs', thing)), fvs)
693 <- rnNormalStmts par_ctxt stmts $ do
694 { -- Find the Names that are bound by stmts
695 lcl_env <- getLocalRdrEnv
696 ; let { rdr_bndrs = collectLStmtsBinders stmts
697 ; bndrs = map ( expectJust "rnStmt"
698 . lookupLocalRdrEnv lcl_env
700 ; new_bndrs = nub bndrs ++ bndrs_so_far
701 -- The nub is because there might be shadowing
703 -- So we'll look up (Unqual x) twice, getting
704 -- the second binding both times, which is the
707 -- Typecheck the thing inside, passing on all
708 -- the Names bound, but separately; revert the envt
709 ; ((segs', thing), fvs) <- setLocalRdrEnv orig_lcl_env $
710 go orig_lcl_env new_bndrs segs
712 -- Figure out which of the bound names are used
713 ; let used_bndrs = filter (`elemNameSet` fvs) bndrs
714 ; return ((used_bndrs, segs', thing), fvs) }
716 ; let seg' = (stmts', bndrs)
717 ; return (((seg':segs'), thing),
718 delListFromNameSet fvs bndrs) }
720 par_ctxt = ParStmtCtxt ctxt
722 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
723 dupErr vs = addErr (ptext SLIT("Duplicate binding in parallel list comprehension for:")
724 <+> quotes (ppr (head vs)))
728 %************************************************************************
730 \subsubsection{mdo expressions}
732 %************************************************************************
735 type FwdRefs = NameSet
736 type Segment stmts = (Defs,
737 Uses, -- May include defs
738 FwdRefs, -- A subset of uses that are
739 -- (a) used before they are bound in this segment, or
740 -- (b) used here, and bound in subsequent segments
741 stmts) -- Either Stmt or [Stmt]
744 ----------------------------------------------------
745 rnMDoStmts :: [LStmt RdrName]
746 -> RnM (thing, FreeVars)
747 -> RnM (([LStmt Name], thing), FreeVars)
748 rnMDoStmts stmts thing_inside
749 = -- Step1: bring all the binders of the mdo into scope
750 -- Remember that this also removes the binders from the
751 -- finally-returned free-vars
752 bindLocatedLocalsRn doc (collectLStmtsBinders stmts) $ \ bndrs ->
754 -- Step 2: Rename each individual stmt, making a
755 -- singleton segment. At this stage the FwdRefs field
756 -- isn't finished: it's empty for all except a BindStmt
757 -- for which it's the fwd refs within the bind itself
758 -- (This set may not be empty, because we're in a recursive
760 segs <- rn_rec_stmts bndrs stmts
762 ; (thing, fvs_later) <- thing_inside
765 -- Step 3: Fill in the fwd refs.
766 -- The segments are all singletons, but their fwd-ref
767 -- field mentions all the things used by the segment
768 -- that are bound after their use
769 segs_w_fwd_refs = addFwdRefs segs
771 -- Step 4: Group together the segments to make bigger segments
772 -- Invariant: in the result, no segment uses a variable
773 -- bound in a later segment
774 grouped_segs = glomSegments segs_w_fwd_refs
776 -- Step 5: Turn the segments into Stmts
777 -- Use RecStmt when and only when there are fwd refs
778 -- Also gather up the uses from the end towards the
779 -- start, so we can tell the RecStmt which things are
780 -- used 'after' the RecStmt
781 (stmts', fvs) = segsToStmts grouped_segs fvs_later
783 ; return ((stmts', thing), fvs) }
785 doc = text "In a recursive mdo-expression"
787 ---------------------------------------------
788 rn_rec_stmts :: [Name] -> [LStmt RdrName] -> RnM [Segment (LStmt Name)]
789 rn_rec_stmts bndrs stmts = mappM (rn_rec_stmt bndrs) stmts `thenM` \ segs_s ->
790 returnM (concat segs_s)
792 ----------------------------------------------------
793 rn_rec_stmt :: [Name] -> LStmt RdrName -> RnM [Segment (LStmt Name)]
794 -- Rename a Stmt that is inside a RecStmt (or mdo)
795 -- Assumes all binders are already in scope
796 -- Turns each stmt into a singleton Stmt
798 rn_rec_stmt all_bndrs (L loc (ExprStmt expr _ _))
799 = rnLExpr expr `thenM` \ (expr', fvs) ->
800 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
801 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
802 L loc (ExprStmt expr' then_op placeHolderType))]
804 rn_rec_stmt all_bndrs (L loc (BindStmt pat expr _ _))
805 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
806 rnLPat pat `thenM` \ (pat', fv_pat) ->
807 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
808 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
810 bndrs = mkNameSet (collectPatBinders pat')
811 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
813 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
814 L loc (BindStmt pat' expr' bind_op fail_op))]
816 rn_rec_stmt all_bndrs (L loc (LetStmt binds@(HsIPBinds _)))
817 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
820 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds)))
821 = rnValBinds (trimWith all_bndrs) binds `thenM` \ (binds', du_binds) ->
822 returnM [(duDefs du_binds, duUses du_binds,
823 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
825 rn_rec_stmt all_bndrs (L loc (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
826 = rn_rec_stmts all_bndrs stmts
828 rn_rec_stmt all_bndrs stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
829 = pprPanic "rn_rec_stmt" (ppr stmt)
831 ---------------------------------------------
832 addFwdRefs :: [Segment a] -> [Segment a]
833 -- So far the segments only have forward refs *within* the Stmt
834 -- (which happens for bind: x <- ...x...)
835 -- This function adds the cross-seg fwd ref info
838 = fst (foldr mk_seg ([], emptyNameSet) pairs)
840 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
841 = (new_seg : segs, all_defs)
843 new_seg = (defs, uses, new_fwds, stmts)
844 all_defs = later_defs `unionNameSets` defs
845 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
846 -- Add the downstream fwd refs here
848 ----------------------------------------------------
849 -- Glomming the singleton segments of an mdo into
850 -- minimal recursive groups.
852 -- At first I thought this was just strongly connected components, but
853 -- there's an important constraint: the order of the stmts must not change.
856 -- mdo { x <- ...y...
863 -- Here, the first stmt mention 'y', which is bound in the third.
864 -- But that means that the innocent second stmt (p <- z) gets caught
865 -- up in the recursion. And that in turn means that the binding for
866 -- 'z' has to be included... and so on.
868 -- Start at the tail { r <- x }
869 -- Now add the next one { z <- y ; r <- x }
870 -- Now add one more { q <- x ; z <- y ; r <- x }
871 -- Now one more... but this time we have to group a bunch into rec
872 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
873 -- Now one more, which we can add on without a rec
875 -- rec { y <- ...x... ; q <- x ; z <- y } ;
877 -- Finally we add the last one; since it mentions y we have to
878 -- glom it togeher with the first two groups
879 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
880 -- q <- x ; z <- y } ;
883 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
886 glomSegments ((defs,uses,fwds,stmt) : segs)
887 -- Actually stmts will always be a singleton
888 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
890 segs' = glomSegments segs
891 (extras, others) = grab uses segs'
892 (ds, us, fs, ss) = unzip4 extras
894 seg_defs = plusFVs ds `plusFV` defs
895 seg_uses = plusFVs us `plusFV` uses
896 seg_fwds = plusFVs fs `plusFV` fwds
897 seg_stmts = stmt : concat ss
899 grab :: NameSet -- The client
901 -> ([Segment a], -- Needed by the 'client'
902 [Segment a]) -- Not needed by the client
903 -- The result is simply a split of the input
905 = (reverse yeses, reverse noes)
907 (noes, yeses) = span not_needed (reverse dus)
908 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
911 ----------------------------------------------------
912 segsToStmts :: [Segment [LStmt Name]]
913 -> FreeVars -- Free vars used 'later'
914 -> ([LStmt Name], FreeVars)
916 segsToStmts [] fvs_later = ([], fvs_later)
917 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
918 = ASSERT( not (null ss) )
919 (new_stmt : later_stmts, later_uses `plusFV` uses)
921 (later_stmts, later_uses) = segsToStmts segs fvs_later
922 new_stmt | non_rec = head ss
923 | otherwise = L (getLoc (head ss)) $
924 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
927 non_rec = isSingleton ss && isEmptyNameSet fwds
928 used_later = defs `intersectNameSet` later_uses
929 -- The ones needed after the RecStmt
932 %************************************************************************
934 \subsubsection{Assertion utils}
936 %************************************************************************
939 srcSpanPrimLit :: SrcSpan -> HsExpr Name
940 srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span))))
942 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
943 -- Return an expression for (assertError "Foo.hs:27")
945 = getSrcSpanM `thenM` \ sloc ->
947 expr = HsApp (L sloc (HsVar assertErrorName))
948 (L sloc (srcSpanPrimLit sloc))
950 returnM (expr, emptyFVs)
953 %************************************************************************
955 \subsubsection{Errors}
957 %************************************************************************
960 patSynErr e = do { addErr (sep [ptext SLIT("Pattern syntax in expression context:"),
962 ; return (EWildPat, emptyFVs) }
964 parStmtErr = addErr (ptext SLIT("Illegal parallel list comprehension: use -fglasgow-exts"))
966 badIpBinds what binds
967 = hang (ptext SLIT("Implicit-parameter bindings illegal in") <+> what)