2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[RnPat]{Renaming of patterns}
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
13 module RnPat (-- main entry points
14 rnPat, rnPats, rnBindPat,
16 NameMaker, applyNameMaker, -- a utility for making names:
17 localRecNameMaker, topRecNameMaker, -- sometimes we want to make local names,
18 -- sometimes we want to make top (qualified) names.
20 rnHsRecFields1, HsRecFieldContext(..),
25 -- Pattern Error messages that are also used elsewhere
26 checkTupSize, patSigErr
29 -- ENH: thin imports to only what is necessary for patterns
31 import {-# SOURCE #-} RnExpr ( rnLExpr )
33 import {-# SOURCE #-} TcSplice ( runQuasiQuotePat )
36 #include "HsVersions.h"
40 import TcHsSyn ( hsOverLitName )
43 import DynFlags ( DynFlag(..) )
45 import Constants ( mAX_TUPLE_SIZE )
50 import ListSetOps ( removeDups, minusList )
54 import Literal ( inCharRange )
55 import Control.Monad ( when )
59 %*********************************************************
63 %*********************************************************
67 The CpsRn monad uses continuation-passing style to support this
74 where rs::[RdrName], ns::[Name]
76 The idea is that '...blah...'
77 a) sees the bindings of ns
78 b) returns the free variables it mentions
79 so that bindNames can report unused ones
82 mapM rnPatAndThen [p1, p2, p3]
83 has a *left-to-right* scoping: it makes the binders in
87 newtype CpsRn b = CpsRn { unCpsRn :: forall r. (b -> RnM (r, FreeVars))
88 -> RnM (r, FreeVars) }
89 -- See Note [CpsRn monad]
91 instance Monad CpsRn where
92 return x = CpsRn (\k -> k x)
93 (CpsRn m) >>= mk = CpsRn (\k -> m (\v -> unCpsRn (mk v) k))
95 runCps :: CpsRn a -> RnM (a, FreeVars)
96 runCps (CpsRn m) = m (\r -> return (r, emptyFVs))
98 liftCps :: RnM a -> CpsRn a
99 liftCps rn_thing = CpsRn (\k -> rn_thing >>= k)
101 liftCpsFV :: RnM (a, FreeVars) -> CpsRn a
102 liftCpsFV rn_thing = CpsRn (\k -> do { (v,fvs1) <- rn_thing
104 ; return (r, fvs1 `plusFV` fvs2) })
106 wrapSrcSpanCps :: (a -> CpsRn b) -> Located a -> CpsRn (Located b)
107 -- Set the location, and also wrap it around the value returned
108 wrapSrcSpanCps fn (L loc a)
109 = CpsRn (\k -> setSrcSpan loc $
110 unCpsRn (fn a) $ \v ->
113 lookupConCps :: Located RdrName -> CpsRn (Located Name)
115 = CpsRn (\k -> do { con_name <- lookupLocatedOccRn con_rdr
116 ; (r, fvs) <- k con_name
117 ; return (r, fvs `plusFV` unitFV (unLoc con_name)) })
120 %*********************************************************
124 %*********************************************************
126 Externally abstract type of name makers,
127 which is how you go from a RdrName to a Name
132 Bool -- True <=> report unused bindings
133 -- (even if True, the warning only comes out
134 -- if -fwarn-unused-matches is on)
136 | LetMk -- Let bindings, incl top level
137 -- Do *not* check for unused bindings
138 (Maybe Module) -- Just m => top level of module m
139 -- Nothing => not top level
142 topRecNameMaker :: Module -> MiniFixityEnv -> NameMaker
143 topRecNameMaker mod fix_env = LetMk (Just mod) fix_env
145 localRecNameMaker :: MiniFixityEnv -> NameMaker
146 localRecNameMaker fix_env = LetMk Nothing fix_env
148 matchNameMaker :: HsMatchContext a -> NameMaker
149 matchNameMaker ctxt = LamMk report_unused
151 -- Do not report unused names in interactive contexts
152 -- i.e. when you type 'x <- e' at the GHCi prompt
153 report_unused = case ctxt of
154 StmtCtxt GhciStmt -> False
157 newName :: NameMaker -> Located RdrName -> CpsRn Name
158 newName (LamMk report_unused) rdr_name
159 = CpsRn (\ thing_inside ->
160 do { name <- newLocalBndrRn rdr_name
161 ; (res, fvs) <- bindLocalName name (thing_inside name)
162 ; when report_unused $ warnUnusedMatches [name] fvs
163 ; return (res, name `delFV` fvs) })
165 newName (LetMk mb_top fix_env) rdr_name
166 = CpsRn (\ thing_inside ->
167 do { name <- case mb_top of
168 Nothing -> newLocalBndrRn rdr_name
169 Just mod -> newTopSrcBinder mod rdr_name
170 ; bindLocalNamesFV_WithFixities [name] fix_env $
173 -- Note: the bindLocalNamesFV_WithFixities is somewhat suspicious
174 -- because it binds a top-level name as a local name.
175 -- however, this binding seems to work, and it only exists for
176 -- the duration of the patterns and the continuation;
177 -- then the top-level name is added to the global env
178 -- before going on to the RHSes (see RnSource.lhs).
182 %*********************************************************
184 External entry points
186 %*********************************************************
188 There are various entry points to renaming patterns, depending on
189 (1) whether the names created should be top-level names or local names
190 (2) whether the scope of the names is entirely given in a continuation
191 (e.g., in a case or lambda, but not in a let or at the top-level,
192 because of the way mutually recursive bindings are handled)
193 (3) whether the a type signature in the pattern can bind
194 lexically-scoped type variables (for unpacking existential
195 type vars in data constructors)
196 (4) whether we do duplicate and unused variable checking
197 (5) whether there are fixity declarations associated with the names
198 bound by the patterns that need to be brought into scope with them.
200 Rather than burdening the clients of this module with all of these choices,
201 we export the three points in this design space that we actually need:
204 -- ----------- Entry point 1: rnPats -------------------
205 -- Binds local names; the scope of the bindings is entirely in the thing_inside
206 -- * allows type sigs to bind type vars
208 -- * unused and duplicate checking
210 rnPats :: HsMatchContext Name -- for error messages
212 -> ([LPat Name] -> RnM (a, FreeVars))
214 rnPats ctxt pats thing_inside
215 = do { envs_before <- getRdrEnvs
217 -- (0) bring into scope all of the type variables bound by the patterns
218 -- (1) rename the patterns, bringing into scope all of the term variables
219 -- (2) then do the thing inside.
220 ; bindPatSigTyVarsFV (collectSigTysFromPats pats) $
221 unCpsRn (rnLPatsAndThen (matchNameMaker ctxt) pats) $ \ pats' -> do
222 { -- Check for duplicated and shadowed names
223 -- Because we don't bind the vars all at once, we can't
224 -- check incrementally for duplicates;
225 -- Nor can we check incrementally for shadowing, else we'll
226 -- complain *twice* about duplicates e.g. f (x,x) = ...
227 ; let names = collectPatsBinders pats'
228 ; addErrCtxt doc_pat $ checkDupAndShadowedNames envs_before names
229 ; thing_inside pats' } }
231 doc_pat = ptext (sLit "In") <+> pprMatchContext ctxt
233 rnPat :: HsMatchContext Name -- for error messages
235 -> (LPat Name -> RnM (a, FreeVars))
236 -> RnM (a, FreeVars) -- Variables bound by pattern do not
237 -- appear in the result FreeVars
238 rnPat ctxt pat thing_inside
239 = rnPats ctxt [pat] (\[pat'] -> thing_inside pat')
241 applyNameMaker :: NameMaker -> Located RdrName -> RnM Name
242 applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newName mk rdr); return n }
244 -- ----------- Entry point 2: rnBindPat -------------------
245 -- Binds local names; in a recursive scope that involves other bound vars
246 -- e.g let { (x, Just y) = e1; ... } in ...
247 -- * does NOT allows type sig to bind type vars
249 -- * no unused and duplicate checking
250 -- * fixities might be coming in
251 rnBindPat :: NameMaker
253 -> RnM (LPat Name, FreeVars)
254 -- Returned FreeVars are the free variables of the pattern,
255 -- of course excluding variables bound by this pattern
257 rnBindPat name_maker pat = runCps (rnLPatAndThen name_maker pat)
261 %*********************************************************
265 %*********************************************************
268 -- ----------- Entry point 3: rnLPatAndThen -------------------
269 -- General version: parametrized by how you make new names
271 rnLPatsAndThen :: NameMaker -> [LPat RdrName] -> CpsRn [LPat Name]
272 rnLPatsAndThen mk = mapM (rnLPatAndThen mk)
273 -- Despite the map, the monad ensures that each pattern binds
274 -- variables that may be mentioned in subsequent patterns in the list
278 rnLPatAndThen :: NameMaker -> LPat RdrName -> CpsRn (LPat Name)
279 rnLPatAndThen nm lpat = wrapSrcSpanCps (rnPatAndThen nm) lpat
281 rnPatAndThen :: NameMaker -> Pat RdrName -> CpsRn (Pat Name)
282 rnPatAndThen _ (WildPat _) = return (WildPat placeHolderType)
283 rnPatAndThen mk (ParPat pat) = do { pat' <- rnLPatAndThen mk pat; return (ParPat pat') }
284 rnPatAndThen mk (LazyPat pat) = do { pat' <- rnLPatAndThen mk pat; return (LazyPat pat') }
285 rnPatAndThen mk (BangPat pat) = do { pat' <- rnLPatAndThen mk pat; return (BangPat pat') }
286 rnPatAndThen mk (VarPat rdr) = do { loc <- liftCps getSrcSpanM
287 ; name <- newName mk (L loc rdr)
288 ; return (VarPat name) }
289 -- we need to bind pattern variables for view pattern expressions
290 -- (e.g. in the pattern (x, x -> y) x needs to be bound in the rhs of the tuple)
292 rnPatAndThen mk (SigPatIn pat ty)
293 = do { patsigs <- liftCps (doptM Opt_ScopedTypeVariables)
295 then do { pat' <- rnLPatAndThen mk pat
296 ; ty' <- liftCpsFV (rnHsTypeFVs tvdoc ty)
297 ; return (SigPatIn pat' ty') }
298 else do { liftCps (addErr (patSigErr ty))
299 ; rnPatAndThen mk (unLoc pat) } }
301 tvdoc = text "In a pattern type-signature"
303 rnPatAndThen mk (LitPat lit)
305 = do { ovlStr <- liftCps (doptM Opt_OverloadedStrings)
307 then rnPatAndThen mk (mkNPat (mkHsIsString s placeHolderType) Nothing)
309 | otherwise = normal_lit
311 normal_lit = do { liftCps (rnLit lit); return (LitPat lit) }
313 rnPatAndThen _ (NPat lit mb_neg _eq)
314 = do { lit' <- liftCpsFV $ rnOverLit lit
315 ; mb_neg' <- liftCpsFV $ case mb_neg of
316 Nothing -> return (Nothing, emptyFVs)
317 Just _ -> do { (neg, fvs) <- lookupSyntaxName negateName
318 ; return (Just neg, fvs) }
319 ; eq' <- liftCpsFV $ lookupSyntaxName eqName
320 ; return (NPat lit' mb_neg' eq') }
322 rnPatAndThen mk (NPlusKPat rdr lit _ _)
323 = do { new_name <- newName mk rdr
324 ; lit' <- liftCpsFV $ rnOverLit lit
325 ; minus <- liftCpsFV $ lookupSyntaxName minusName
326 ; ge <- liftCpsFV $ lookupSyntaxName geName
327 ; return (NPlusKPat (L (nameSrcSpan new_name) new_name) lit' ge minus) }
328 -- The Report says that n+k patterns must be in Integral
330 rnPatAndThen mk (AsPat rdr pat)
331 = do { new_name <- newName mk rdr
332 ; pat' <- rnLPatAndThen mk pat
333 ; return (AsPat (L (nameSrcSpan new_name) new_name) pat') }
335 rnPatAndThen mk p@(ViewPat expr pat ty)
336 = do { liftCps $ do { vp_flag <- doptM Opt_ViewPatterns
337 ; checkErr vp_flag (badViewPat p) }
338 -- Because of the way we're arranging the recursive calls,
339 -- this will be in the right context
340 ; expr' <- liftCpsFV $ rnLExpr expr
341 ; pat' <- rnLPatAndThen mk pat
342 ; return (ViewPat expr' pat' ty) }
344 rnPatAndThen mk (ConPatIn con stuff)
345 -- rnConPatAndThen takes care of reconstructing the pattern
346 = rnConPatAndThen mk con stuff
348 rnPatAndThen mk (ListPat pats _)
349 = do { pats' <- rnLPatsAndThen mk pats
350 ; return (ListPat pats' placeHolderType) }
352 rnPatAndThen mk (PArrPat pats _)
353 = do { pats' <- rnLPatsAndThen mk pats
354 ; return (PArrPat pats' placeHolderType) }
356 rnPatAndThen mk (TuplePat pats boxed _)
357 = do { liftCps $ checkTupSize (length pats)
358 ; pats' <- rnLPatsAndThen mk pats
359 ; return (TuplePat pats' boxed placeHolderType) }
361 rnPatAndThen _ (TypePat ty)
362 = do { ty' <- liftCpsFV $ rnHsTypeFVs (text "In a type pattern") ty
363 ; return (TypePat ty') }
366 rnPatAndThen _ p@(QuasiQuotePat {})
367 = pprPanic "Can't do QuasiQuotePat without GHCi" (ppr p)
369 rnPatAndThen mk (QuasiQuotePat qq)
370 = do { pat <- liftCps $ runQuasiQuotePat qq
371 ; L _ pat' <- rnLPatAndThen mk pat
375 rnPatAndThen _ pat = pprPanic "rnLPatAndThen" (ppr pat)
379 rnConPatAndThen :: NameMaker
380 -> Located RdrName -- the constructor
381 -> HsConPatDetails RdrName
384 rnConPatAndThen mk con (PrefixCon pats)
385 = do { con' <- lookupConCps con
386 ; pats' <- rnLPatsAndThen mk pats
387 ; return (ConPatIn con' (PrefixCon pats')) }
389 rnConPatAndThen mk con (InfixCon pat1 pat2)
390 = do { con' <- lookupConCps con
391 ; pat1' <- rnLPatAndThen mk pat1
392 ; pat2' <- rnLPatAndThen mk pat2
393 ; fixity <- liftCps $ lookupFixityRn (unLoc con')
394 ; liftCps $ mkConOpPatRn con' fixity pat1' pat2' }
396 rnConPatAndThen mk con (RecCon rpats)
397 = do { con' <- lookupConCps con
398 ; rpats' <- rnHsRecPatsAndThen mk con' rpats
399 ; return (ConPatIn con' (RecCon rpats')) }
402 rnHsRecPatsAndThen :: NameMaker
403 -> Located Name -- Constructor
404 -> HsRecFields RdrName (LPat RdrName)
405 -> CpsRn (HsRecFields Name (LPat Name))
406 rnHsRecPatsAndThen mk (L _ con) hs_rec_fields@(HsRecFields { rec_dotdot = dd })
407 = do { flds <- liftCpsFV $ rnHsRecFields1 (HsRecFieldPat con) VarPat hs_rec_fields
408 ; flds' <- mapM rn_field (flds `zip` [1..])
409 ; return (HsRecFields { rec_flds = flds', rec_dotdot = dd }) }
411 rn_field (fld, n') = do { arg' <- rnLPatAndThen (nested_mk dd mk n')
413 ; return (fld { hsRecFieldArg = arg' }) }
415 -- Suppress unused-match reporting for fields introduced by ".."
416 nested_mk Nothing mk _ = mk
417 nested_mk (Just _) mk@(LetMk {}) _ = mk
418 nested_mk (Just n) (LamMk report_unused) n' = LamMk (report_unused && (n' <= n))
422 %************************************************************************
426 %************************************************************************
429 data HsRecFieldContext
436 -> (RdrName -> arg) -- When punning, use this to build a new field
437 -> HsRecFields RdrName (Located arg)
438 -> RnM ([HsRecField Name (Located arg)], FreeVars)
440 -- This supprisingly complicated pass
441 -- a) looks up the field name (possibly using disambiguation)
442 -- b) fills in puns and dot-dot stuff
443 -- When we we've finished, we've renamed the LHS, but not the RHS,
444 -- of each x=e binding
446 rnHsRecFields1 ctxt mk_arg (HsRecFields { rec_flds = flds, rec_dotdot = dotdot })
447 = do { pun_ok <- doptM Opt_RecordPuns
448 ; disambig_ok <- doptM Opt_DisambiguateRecordFields
449 ; parent <- check_disambiguation disambig_ok mb_con
450 ; flds1 <- mapM (rn_fld pun_ok parent) flds
451 ; mapM_ (addErr . dupFieldErr ctxt) dup_flds
452 ; flds2 <- rn_dotdot dotdot mb_con flds1
453 ; return (flds2, mkFVs (getFieldIds flds2)) }
455 mb_con = case ctxt of
456 HsRecFieldUpd -> Nothing
457 HsRecFieldCon con -> Just con
458 HsRecFieldPat con -> Just con
460 Nothing -> ptext (sLit "constructor field name")
461 Just con -> ptext (sLit "field of constructor") <+> quotes (ppr con)
463 name_to_arg (L loc n) = L loc (mk_arg (mkRdrUnqual (nameOccName n)))
465 rn_fld pun_ok parent (HsRecField { hsRecFieldId = fld
466 , hsRecFieldArg = arg
468 = do { fld' <- wrapLocM (lookupSubBndr parent doc) fld
470 then do { checkErr pun_ok (badPun fld)
471 ; return (name_to_arg fld') }
473 ; return (HsRecField { hsRecFieldId = fld'
474 , hsRecFieldArg = arg'
475 , hsRecPun = pun }) }
477 rn_dotdot Nothing _mb_con flds -- No ".." at all
479 rn_dotdot (Just {}) Nothing flds -- ".." on record update
480 = do { addErr (badDotDot ctxt); return flds }
481 rn_dotdot (Just n) (Just con) flds -- ".." on record con/pat
482 = ASSERT( n == length flds )
483 do { loc <- getSrcSpanM -- Rather approximate
484 ; dd_flag <- doptM Opt_RecordWildCards
485 ; checkErr dd_flag (needFlagDotDot ctxt)
487 ; con_fields <- lookupConstructorFields con
488 ; let present_flds = getFieldIds flds
489 absent_flds = con_fields `minusList` present_flds
490 extras = [ HsRecField
491 { hsRecFieldId = L loc f
492 , hsRecFieldArg = name_to_arg (L loc f)
496 ; return (flds ++ extras) }
498 check_disambiguation :: Bool -> Maybe Name -> RnM Parent
499 -- When disambiguation is on, return the parent *type constructor*
500 -- That is, the parent of the data constructor. That's the parent
501 -- to use for looking up record fields.
502 check_disambiguation disambig_ok mb_con
503 | disambig_ok, Just con <- mb_con
504 = do { env <- getGlobalRdrEnv
505 ; return (case lookupGRE_Name env con of
507 gres -> WARN( True, ppr con <+> ppr gres ) NoParent) }
508 | otherwise = return NoParent
510 dup_flds :: [[RdrName]]
511 -- Each list represents a RdrName that occurred more than once
512 -- (the list contains all occurrences)
513 -- Each list in dup_fields is non-empty
514 (_, dup_flds) = removeDups compare (getFieldIds flds)
516 getFieldIds :: [HsRecField id arg] -> [id]
517 getFieldIds flds = map (unLoc . hsRecFieldId) flds
519 needFlagDotDot :: HsRecFieldContext -> SDoc
520 needFlagDotDot ctxt = vcat [ptext (sLit "Illegal `..' in record") <+> pprRFC ctxt,
521 ptext (sLit "Use -XRecordWildCards to permit this")]
523 badDotDot :: HsRecFieldContext -> SDoc
524 badDotDot ctxt = ptext (sLit "You cannot use `..' in a record") <+> pprRFC ctxt
526 badPun :: Located RdrName -> SDoc
527 badPun fld = vcat [ptext (sLit "Illegal use of punning for field") <+> quotes (ppr fld),
528 ptext (sLit "Use -XNamedFieldPuns to permit this")]
530 dupFieldErr :: HsRecFieldContext -> [RdrName] -> SDoc
531 dupFieldErr ctxt dups
532 = hsep [ptext (sLit "duplicate field name"),
533 quotes (ppr (head dups)),
534 ptext (sLit "in record"), pprRFC ctxt]
536 pprRFC :: HsRecFieldContext -> SDoc
537 pprRFC (HsRecFieldCon {}) = ptext (sLit "construction")
538 pprRFC (HsRecFieldPat {}) = ptext (sLit "pattern")
539 pprRFC (HsRecFieldUpd {}) = ptext (sLit "update")
543 %************************************************************************
545 \subsubsection{Literals}
547 %************************************************************************
549 When literals occur we have to make sure
550 that the types and classes they involve
554 rnLit :: HsLit -> RnM ()
555 rnLit (HsChar c) = checkErr (inCharRange c) (bogusCharError c)
558 rnOverLit :: HsOverLit t -> RnM (HsOverLit Name, FreeVars)
559 rnOverLit lit@(OverLit {ol_val=val})
560 = do { let std_name = hsOverLitName val
561 ; (from_thing_name, fvs) <- lookupSyntaxName std_name
562 ; let rebindable = case from_thing_name of
563 HsVar v -> v /= std_name
564 _ -> panic "rnOverLit"
565 ; return (lit { ol_witness = from_thing_name
566 , ol_rebindable = rebindable }, fvs) }
569 %************************************************************************
571 \subsubsection{Errors}
573 %************************************************************************
576 checkTupSize :: Int -> RnM ()
577 checkTupSize tup_size
578 | tup_size <= mAX_TUPLE_SIZE
581 = addErr (sep [ptext (sLit "A") <+> int tup_size <> ptext (sLit "-tuple is too large for GHC"),
582 nest 2 (parens (ptext (sLit "max size is") <+> int mAX_TUPLE_SIZE)),
583 nest 2 (ptext (sLit "Workaround: use nested tuples or define a data type"))])
585 patSigErr :: Outputable a => a -> SDoc
587 = (ptext (sLit "Illegal signature in pattern:") <+> ppr ty)
588 $$ nest 4 (ptext (sLit "Use -XScopedTypeVariables to permit it"))
590 bogusCharError :: Char -> SDoc
592 = ptext (sLit "character literal out of range: '\\") <> char c <> char '\''
594 badViewPat :: Pat RdrName -> SDoc
595 badViewPat pat = vcat [ptext (sLit "Illegal view pattern: ") <+> ppr pat,
596 ptext (sLit "Use -XViewPatterns to enable view patterns")]