2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[RnBinds]{Renaming and dependency analysis of bindings}
6 This module does renaming and dependency analysis on value bindings in
7 the abstract syntax. It does {\em not} do cycle-checks on class or
8 type-synonym declarations; those cannot be done at this stage because
9 they may be affected by renaming (which isn't fully worked out yet).
12 module RnBinds (rnTopBinds, rnTopBindsLHS, rnTopBindsRHS, -- use these for top-level bindings
13 rnLocalBindsAndThen, rnValBindsLHS, rnValBindsRHS, -- or these for local bindings
14 rnMethodBinds, renameSigs, mkSigTvFn,
15 rnMatchGroup, rnGRHSs,
16 makeMiniFixityEnv, MiniFixityEnv
19 import {-# SOURCE #-} RnExpr( rnLExpr, rnStmts )
25 import RnTypes ( rnHsSigType, rnLHsType, checkPrecMatch)
26 import RnPat (rnPats, rnBindPat,
27 NameMaker, localRecNameMaker, topRecNameMaker, applyNameMaker
31 import DynFlags ( DynFlag(..) )
35 import RdrName ( RdrName, rdrNameOcc )
37 import ListSetOps ( findDupsEq )
38 import BasicTypes ( RecFlag(..) )
39 import Digraph ( SCC(..), stronglyConnCompFromEdgedVertices )
43 import Data.List ( partition )
44 import Maybes ( orElse )
48 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
49 -- place and can be used when complaining.
51 The code tree received by the function @rnBinds@ contains definitions
52 in where-clauses which are all apparently mutually recursive, but which may
53 not really depend upon each other. For example, in the top level program
58 the definitions of @a@ and @y@ do not depend on each other at all.
59 Unfortunately, the typechecker cannot always check such definitions.
60 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
61 definitions. In Proceedings of the International Symposium on Programming,
62 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
63 However, the typechecker usually can check definitions in which only the
64 strongly connected components have been collected into recursive bindings.
65 This is precisely what the function @rnBinds@ does.
67 ToDo: deal with case where a single monobinds binds the same variable
70 The vertag tag is a unique @Int@; the tags only need to be unique
71 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
72 (heavy monad machinery not needed).
75 %************************************************************************
77 %* naming conventions *
79 %************************************************************************
81 \subsection[name-conventions]{Name conventions}
83 The basic algorithm involves walking over the tree and returning a tuple
84 containing the new tree plus its free variables. Some functions, such
85 as those walking polymorphic bindings (HsBinds) and qualifier lists in
86 list comprehensions (@Quals@), return the variables bound in local
87 environments. These are then used to calculate the free variables of the
88 expression evaluated in these environments.
90 Conventions for variable names are as follows:
93 new code is given a prime to distinguish it from the old.
96 a set of variables defined in @Exp@ is written @dvExp@
99 a set of variables free in @Exp@ is written @fvExp@
102 %************************************************************************
104 %* analysing polymorphic bindings (HsBindGroup, HsBind)
106 %************************************************************************
108 \subsubsection[dep-HsBinds]{Polymorphic bindings}
110 Non-recursive expressions are reconstructed without any changes at top
111 level, although their component expressions may have to be altered.
112 However, non-recursive expressions are currently not expected as
113 \Haskell{} programs, and this code should not be executed.
115 Monomorphic bindings contain information that is returned in a tuple
116 (a @FlatMonoBinds@) containing:
120 a unique @Int@ that serves as the ``vertex tag'' for this binding.
123 the name of a function or the names in a pattern. These are a set
124 referred to as @dvLhs@, the defined variables of the left hand side.
127 the free variables of the body. These are referred to as @fvBody@.
130 the definition's actual code. This is referred to as just @code@.
133 The function @nonRecDvFv@ returns two sets of variables. The first is
134 the set of variables defined in the set of monomorphic bindings, while the
135 second is the set of free variables in those bindings.
137 The set of variables defined in a non-recursive binding is just the
138 union of all of them, as @union@ removes duplicates. However, the
139 free variables in each successive set of cumulative bindings is the
140 union of those in the previous set plus those of the newest binding after
141 the defined variables of the previous set have been removed.
143 @rnMethodBinds@ deals only with the declarations in class and
144 instance declarations. It expects only to see @FunMonoBind@s, and
145 it expects the global environment to contain bindings for the binders
146 (which are all class operations).
148 %************************************************************************
150 \subsubsection{ Top-level bindings}
152 %************************************************************************
155 -- for top-level bindings, we need to make top-level names,
156 -- so we have a different entry point than for local bindings
157 rnTopBindsLHS :: MiniFixityEnv
158 -> HsValBinds RdrName
159 -> RnM (HsValBindsLR Name RdrName)
160 rnTopBindsLHS fix_env binds
161 = rnValBindsLHSFromDoc (topRecNameMaker fix_env) binds
163 rnTopBindsRHS :: NameSet -- Names bound by these binds
164 -> HsValBindsLR Name RdrName
165 -> RnM (HsValBinds Name, DefUses)
166 rnTopBindsRHS bound_names binds =
167 do { is_boot <- tcIsHsBoot
169 then rnTopBindsBoot binds
170 else rnValBindsRHSGen (\x -> x) -- don't trim free vars
173 -- Wrapper if we don't need to do anything in between the left and right,
174 -- or anything else in the scope of the left
176 -- Never used when there are fixity declarations
177 rnTopBinds :: HsValBinds RdrName
178 -> RnM (HsValBinds Name, DefUses)
180 do nl <- rnTopBindsLHS emptyFsEnv b
181 let bound_names = collectHsValBinders nl
182 bindLocalNames bound_names $ rnTopBindsRHS (mkNameSet bound_names) nl
185 rnTopBindsBoot :: HsValBindsLR Name RdrName -> RnM (HsValBinds Name, DefUses)
186 -- A hs-boot file has no bindings.
187 -- Return a single HsBindGroup with empty binds and renamed signatures
188 rnTopBindsBoot (ValBindsIn mbinds sigs)
189 = do { checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
190 ; sigs' <- renameSigs Nothing okHsBootSig sigs
191 ; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
192 rnTopBindsBoot b = pprPanic "rnTopBindsBoot" (ppr b)
197 %*********************************************************
201 %*********************************************************
204 rnLocalBindsAndThen :: HsLocalBinds RdrName
205 -> (HsLocalBinds Name -> RnM (result, FreeVars))
206 -> RnM (result, FreeVars)
207 -- This version (a) assumes that the binding vars are *not* already in scope
208 -- (b) removes the binders from the free vars of the thing inside
209 -- The parser doesn't produce ThenBinds
210 rnLocalBindsAndThen EmptyLocalBinds thing_inside
211 = thing_inside EmptyLocalBinds
213 rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
214 = rnValBindsAndThen val_binds $ \ val_binds' ->
215 thing_inside (HsValBinds val_binds')
217 rnLocalBindsAndThen (HsIPBinds binds) thing_inside = do
218 (binds',fv_binds) <- rnIPBinds binds
219 (thing, fvs_thing) <- thing_inside (HsIPBinds binds')
220 return (thing, fvs_thing `plusFV` fv_binds)
222 rnIPBinds :: HsIPBinds RdrName -> RnM (HsIPBinds Name, FreeVars)
223 rnIPBinds (IPBinds ip_binds _no_dict_binds) = do
224 (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
225 return (IPBinds ip_binds' emptyLHsBinds, plusFVs fvs_s)
227 rnIPBind :: IPBind RdrName -> RnM (IPBind Name, FreeVars)
228 rnIPBind (IPBind n expr) = do
229 name <- newIPNameRn n
230 (expr',fvExpr) <- rnLExpr expr
231 return (IPBind name expr', fvExpr)
235 %************************************************************************
239 %************************************************************************
242 -- Renaming local binding gropus
243 -- Does duplicate/shadow check
244 rnValBindsLHS :: MiniFixityEnv
245 -> HsValBinds RdrName
246 -> RnM ([Name], HsValBindsLR Name RdrName)
247 rnValBindsLHS fix_env binds
248 = do { -- Do error checking: we need to check for dups here because we
249 -- don't don't bind all of the variables from the ValBinds at once
250 -- with bindLocatedLocals any more.
252 -- Note that we don't want to do this at the top level, since
253 -- sorting out duplicates and shadowing there happens elsewhere.
254 -- The behavior is even different. For example,
257 -- should not produce a shadowing warning (but it will produce
258 -- an ambiguity warning if you use f), but
260 -- g = let f = ... in f
262 ; binds' <- rnValBindsLHSFromDoc (localRecNameMaker fix_env) binds
263 ; let bound_names = collectHsValBinders binds'
265 ; checkDupAndShadowedNames envs bound_names
266 ; return (bound_names, binds') }
268 -- renames the left-hand sides
269 -- generic version used both at the top level and for local binds
270 -- does some error checking, but not what gets done elsewhere at the top level
271 rnValBindsLHSFromDoc :: NameMaker
272 -> HsValBinds RdrName
273 -> RnM (HsValBindsLR Name RdrName)
274 rnValBindsLHSFromDoc topP (ValBindsIn mbinds sigs)
275 = do { mbinds' <- mapBagM (rnBindLHS topP doc) mbinds
276 ; return $ ValBindsIn mbinds' sigs }
278 bndrs = collectHsBindsBinders mbinds
279 doc = text "In the binding group for:" <+> pprWithCommas ppr bndrs
281 rnValBindsLHSFromDoc _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
283 -- General version used both from the top-level and for local things
284 -- Assumes the LHS vars are in scope
286 -- Does not bind the local fixity declarations
287 rnValBindsRHSGen :: (FreeVars -> FreeVars) -- for trimming free var sets
288 -- The trimming function trims the free vars we attach to a
289 -- binding so that it stays reasonably small
290 -> NameSet -- Names bound by the LHSes
291 -> HsValBindsLR Name RdrName
292 -> RnM (HsValBinds Name, DefUses)
294 rnValBindsRHSGen trim bound_names (ValBindsIn mbinds sigs)
295 = do { -- rename the sigs
296 sigs' <- renameSigs (Just bound_names) okBindSig sigs
298 ; binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs') trim) mbinds
299 ; case depAnalBinds binds_w_dus of
300 (anal_binds, anal_dus) -> do
301 { let valbind' = ValBindsOut anal_binds sigs'
302 valbind'_dus = usesOnly (hsSigsFVs sigs') `plusDU` anal_dus
303 ; return (valbind', valbind'_dus) }}
305 rnValBindsRHSGen _ _ b = pprPanic "rnValBindsRHSGen" (ppr b)
307 -- Wrapper for local binds
309 -- The *client* of this function is responsible for checking for unused binders;
310 -- it doesn't (and can't: we don't have the thing inside the binds) happen here
312 -- The client is also responsible for bringing the fixities into scope
313 rnValBindsRHS :: NameSet -- names bound by the LHSes
314 -> HsValBindsLR Name RdrName
315 -> RnM (HsValBinds Name, DefUses)
316 rnValBindsRHS bound_names binds
317 = rnValBindsRHSGen trim bound_names binds
319 trim fvs = intersectNameSet bound_names fvs
320 -- Only keep the names the names from this group
323 -- wrapper that does both the left- and right-hand sides
325 -- here there are no local fixity decls passed in;
326 -- the local fixity decls come from the ValBinds sigs
327 rnValBindsAndThen :: HsValBinds RdrName
328 -> (HsValBinds Name -> RnM (result, FreeVars))
329 -> RnM (result, FreeVars)
330 rnValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
331 = do { -- (A) Create the local fixity environment
332 new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
334 -- (B) Rename the LHSes
335 ; (bound_names, new_lhs) <- rnValBindsLHS new_fixities binds
337 -- ...and bring them (and their fixities) into scope
338 ; bindLocalNamesFV bound_names $
339 addLocalFixities new_fixities bound_names $ do
341 { -- (C) Do the RHS and thing inside
342 (binds', dus) <- rnValBindsRHS (mkNameSet bound_names) new_lhs
343 ; (result, result_fvs) <- thing_inside binds'
345 -- Report unused bindings based on the (accurate)
348 -- should report 'x' unused
349 ; let real_uses = findUses dus result_fvs
350 ; warnUnusedLocalBinds bound_names real_uses
353 -- The variables "used" in the val binds are:
354 -- (1) the uses of the binds (allUses)
355 -- (2) the FVs of the thing-inside
356 all_uses = allUses dus `plusFV` result_fvs
357 -- Note [Unused binding hack]
358 -- ~~~~~~~~~~~~~~~~~~~~~~~~~~
359 -- Note that *in contrast* to the above reporting of
360 -- unused bindings, (1) above uses duUses to return *all*
361 -- the uses, even if the binding is unused. Otherwise consider:
363 -- y = let p = x in 'x' -- NB: p not used
364 -- If we don't "see" the dependency of 'y' on 'x', we may put the
365 -- bindings in the wrong order, and the type checker will complain
366 -- that x isn't in scope
368 -- But note that this means we won't report 'x' as unused,
369 -- whereas we would if we had { x = 3; p = x; y = 'x' }
371 ; return (result, all_uses) }}
372 -- The bound names are pruned out of all_uses
373 -- by the bindLocalNamesFV call above
375 rnValBindsAndThen bs _ = pprPanic "rnValBindsAndThen" (ppr bs)
378 -- Process the fixity declarations, making a FastString -> (Located Fixity) map
379 -- (We keep the location around for reporting duplicate fixity declarations.)
381 -- Checks for duplicates, but not that only locally defined things are fixed.
382 -- Note: for local fixity declarations, duplicates would also be checked in
383 -- check_sigs below. But we also use this function at the top level.
385 makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv
387 makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
389 add_one env (L loc (FixitySig (L name_loc name) fixity)) = do
390 { -- this fixity decl is a duplicate iff
391 -- the ReaderName's OccName's FastString is already in the env
392 -- (we only need to check the local fix_env because
393 -- definitions of non-local will be caught elsewhere)
394 let { fs = occNameFS (rdrNameOcc name)
395 ; fix_item = L loc fixity };
397 case lookupFsEnv env fs of
398 Nothing -> return $ extendFsEnv env fs fix_item
399 Just (L loc' _) -> do
401 addErrAt name_loc (dupFixityDecl loc' name)
405 dupFixityDecl :: SrcSpan -> RdrName -> SDoc
406 dupFixityDecl loc rdr_name
407 = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
408 ptext (sLit "also at ") <+> ppr loc]
410 ---------------------
412 -- renaming a single bind
414 rnBindLHS :: NameMaker
417 -- returns the renamed left-hand side,
418 -- and the FreeVars *of the LHS*
419 -- (i.e., any free variables of the pattern)
420 -> RnM (LHsBindLR Name RdrName)
422 rnBindLHS name_maker _ (L loc (PatBind { pat_lhs = pat,
424 pat_rhs_ty=pat_rhs_ty
426 = setSrcSpan loc $ do
427 -- we don't actually use the FV processing of rnPatsAndThen here
428 (pat',pat'_fvs) <- rnBindPat name_maker pat
429 return (L loc (PatBind { pat_lhs = pat',
431 -- we temporarily store the pat's FVs here;
432 -- gets updated to the FVs of the whole bind
433 -- when doing the RHS below
435 -- these will get ignored in the next pass,
436 -- when we rename the RHS
437 pat_rhs_ty = pat_rhs_ty }))
439 rnBindLHS name_maker _ (L loc (FunBind { fun_id = name@(L nameLoc _),
441 fun_matches = matches,
442 fun_co_fn = fun_co_fn,
446 do { newname <- applyNameMaker name_maker name
447 ; return (L loc (FunBind { fun_id = L nameLoc newname,
449 fun_matches = matches,
450 -- we temporatily store the LHS's FVs (empty in this case) here
451 -- gets updated when doing the RHS below
453 -- everything else will get ignored in the next pass
454 fun_co_fn = fun_co_fn,
458 rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)
460 -- assumes the left-hands-side vars are in scope
461 rnBind :: (Name -> [Name]) -- Signature tyvar function
462 -> (FreeVars -> FreeVars) -- Trimming function for rhs free vars
463 -> LHsBindLR Name RdrName
464 -> RnM (LHsBind Name, [Name], Uses)
465 rnBind _ trim (L loc (PatBind { pat_lhs = pat,
467 -- pat fvs were stored here while
468 -- after processing the LHS
469 bind_fvs = pat_fvs }))
471 do {let bndrs = collectPatBinders pat
473 ; (grhss', fvs) <- rnGRHSs PatBindRhs grhss
474 -- No scoped type variables for pattern bindings
475 ; let all_fvs = pat_fvs `plusFV` fvs
478 ; fvs' `seq` -- See Note [Free-variable space leak]
479 return (L loc (PatBind { pat_lhs = pat,
481 pat_rhs_ty = placeHolderType,
487 (L loc (FunBind { fun_id = name,
488 fun_infix = is_infix,
489 fun_matches = matches,
493 -- invariant: no free vars here when it's a FunBind
495 do { let plain_name = unLoc name
497 ; (matches', fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
498 -- bindSigTyVars tests for Opt_ScopedTyVars
499 rnMatchGroup (FunRhs plain_name is_infix) matches
500 ; let fvs' = trim fvs
502 ; when is_infix $ checkPrecMatch plain_name matches'
504 ; fvs' `seq` -- See Note [Free-variable space leak]
506 return (L loc (FunBind { fun_id = name,
507 fun_infix = is_infix,
508 fun_matches = matches',
510 fun_co_fn = idHsWrapper,
511 fun_tick = Nothing }),
515 rnBind _ _ b = pprPanic "rnBind" (ppr b)
518 Note [Free-variable space leak]
519 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
522 and we seq fvs' before turning it as part of a record.
524 The reason is that trim is sometimes something like
525 \xs -> intersectNameSet (mkNameSet bound_names) xs
526 and we don't want to retain the list bound_names. This showed up in
530 ---------------------
531 depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
532 -> ([(RecFlag, LHsBinds Name)], DefUses)
533 -- Dependency analysis; this is important so that
534 -- unused-binding reporting is accurate
535 depAnalBinds binds_w_dus
536 = (map get_binds sccs, map get_du sccs)
538 sccs = stronglyConnCompFromEdgedVertices edges
540 keyd_nodes = bagToList binds_w_dus `zip` [0::Int ..]
542 edges = [ (node, key, [key | n <- nameSetToList uses,
543 Just key <- [lookupNameEnv key_map n] ])
544 | (node@(_,_,uses), key) <- keyd_nodes ]
546 key_map :: NameEnv Int -- Which binding it comes from
547 key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
550 get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
551 get_binds (CyclicSCC binds_w_dus) = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
553 get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
554 get_du (CyclicSCC binds_w_dus) = (Just defs, uses)
556 defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
557 uses = unionManyNameSets [u | (_,_,u) <- binds_w_dus]
560 ---------------------
561 -- Bind the top-level forall'd type variables in the sigs.
564 -- The 'a' scopes over the rhs
566 -- NB: there'll usually be just one (for a function binding)
567 -- but if there are many, one may shadow the rest; too bad!
568 -- e.g x :: [a] -> [a]
571 -- In e, 'a' will be in scope, and it'll be the one from 'y'!
573 mkSigTvFn :: [LSig Name] -> (Name -> [Name])
574 -- Return a lookup function that maps an Id Name to the names
575 -- of the type variables that should scope over its body..
577 = \n -> lookupNameEnv env n `orElse` []
579 env :: NameEnv [Name]
580 env = mkNameEnv [ (name, map hsLTyVarName ltvs)
581 | L _ (TypeSig (L _ name)
582 (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs]
583 -- Note the pattern-match on "Explicit"; we only bind
584 -- type variables from signatures with an explicit top-level for-all
588 @rnMethodBinds@ is used for the method bindings of a class and an instance
589 declaration. Like @rnBinds@ but without dependency analysis.
591 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
592 That's crucial when dealing with an instance decl:
594 instance Foo (T a) where
597 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
598 and unless @op@ occurs we won't treat the type signature of @op@ in the class
599 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
600 in many ways the @op@ in an instance decl is just like an occurrence, not
604 rnMethodBinds :: Name -- Class name
605 -> (Name -> [Name]) -- Signature tyvar function
606 -> [Name] -- Names for generic type variables
608 -> RnM (LHsBinds Name, FreeVars)
610 rnMethodBinds cls sig_fn gen_tyvars binds
611 = foldlM do_one (emptyBag,emptyFVs) (bagToList binds)
613 do_one (binds,fvs) bind
614 = do { (bind', fvs_bind) <- rnMethodBind cls sig_fn gen_tyvars bind
615 ; return (binds `unionBags` bind', fvs_bind `plusFV` fvs) }
620 -> LHsBindLR RdrName RdrName
621 -> RnM (Bag (LHsBindLR Name Name), FreeVars)
622 rnMethodBind cls sig_fn gen_tyvars (L loc (FunBind { fun_id = name, fun_infix = is_infix,
623 fun_matches = MatchGroup matches _ }))
624 = setSrcSpan loc $ do
625 sel_name <- wrapLocM (lookupInstDeclBndr cls) name
626 let plain_name = unLoc sel_name
627 -- We use the selector name as the binder
629 (new_matches, fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
630 mapFvRn (rn_match (FunRhs plain_name is_infix)) matches
631 let new_group = MatchGroup new_matches placeHolderType
633 when is_infix $ checkPrecMatch plain_name new_group
634 return (unitBag (L loc (FunBind {
635 fun_id = sel_name, fun_infix = is_infix,
636 fun_matches = new_group,
637 bind_fvs = fvs, fun_co_fn = idHsWrapper,
638 fun_tick = Nothing })),
639 fvs `addOneFV` plain_name)
640 -- The 'fvs' field isn't used for method binds
642 -- Truly gruesome; bring into scope the correct members of the generic
643 -- type variables. See comments in RnSource.rnSourceDecl(ClassDecl)
644 rn_match info match@(L _ (Match (L _ (TypePat ty) : _) _ _))
645 = extendTyVarEnvFVRn gen_tvs $
648 tvs = map (rdrNameOcc.unLoc) (extractHsTyRdrTyVars ty)
649 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
651 rn_match info match = rnMatch info match
653 -- Can't handle method pattern-bindings which bind multiple methods.
654 rnMethodBind _ _ _ (L loc bind@(PatBind {})) = do
655 addErrAt loc (methodBindErr bind)
656 return (emptyBag, emptyFVs)
658 rnMethodBind _ _ _ b = pprPanic "rnMethodBind" (ppr b)
663 %************************************************************************
665 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
667 %************************************************************************
669 @renameSigs@ checks for:
671 \item more than one sig for one thing;
672 \item signatures given for things not bound here;
675 At the moment we don't gather free-var info from the types in
676 signatures. We'd only need this if we wanted to report unused tyvars.
679 renameSigs :: Maybe NameSet -- If (Just ns) complain if the sig isn't for one of ns
680 -> (Sig RdrName -> Bool) -- Complain about the wrong kind of signature if this is False
683 -- Renames the signatures and performs error checks
684 renameSigs mb_names ok_sig sigs
685 = do { let (good_sigs, bad_sigs) = partition (ok_sig . unLoc) sigs
686 ; mapM_ unknownSigErr bad_sigs -- Misplaced
687 ; mapM_ dupSigDeclErr (findDupsEq eqHsSig sigs) -- Duplicate
688 ; sigs' <- mapM (wrapLocM (renameSig mb_names)) good_sigs
691 ----------------------
692 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
693 -- because this won't work for:
694 -- instance Foo T where
697 -- We'll just rename the INLINE prag to refer to whatever other 'op'
698 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
699 -- Doesn't seem worth much trouble to sort this.
701 renameSig :: Maybe NameSet -> Sig RdrName -> RnM (Sig Name)
702 -- FixitySig is renamed elsewhere.
703 renameSig _ (IdSig x)
704 = return (IdSig x) -- Actually this never occurs
705 renameSig mb_names sig@(TypeSig v ty)
706 = do { new_v <- lookupSigOccRn mb_names sig v
707 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
708 ; return (TypeSig new_v new_ty) }
710 renameSig _ (SpecInstSig ty)
711 = do { new_ty <- rnLHsType (text "A SPECIALISE instance pragma") ty
712 ; return (SpecInstSig new_ty) }
714 renameSig mb_names sig@(SpecSig v ty inl)
715 = do { new_v <- lookupSigOccRn mb_names sig v
716 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
717 ; return (SpecSig new_v new_ty inl) }
719 renameSig mb_names sig@(InlineSig v s)
720 = do { new_v <- lookupSigOccRn mb_names sig v
721 ; return (InlineSig new_v s) }
723 renameSig mb_names sig@(FixSig (FixitySig v f))
724 = do { new_v <- lookupSigOccRn mb_names sig v
725 ; return (FixSig (FixitySig new_v f)) }
729 %************************************************************************
733 %************************************************************************
736 rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
737 rnMatchGroup ctxt (MatchGroup ms _)
738 = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
739 ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
741 rnMatch :: HsMatchContext Name -> LMatch RdrName -> RnM (LMatch Name, FreeVars)
742 rnMatch ctxt = wrapLocFstM (rnMatch' ctxt)
744 rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
745 rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
746 = do { -- Result type signatures are no longer supported
747 case maybe_rhs_sig of
749 Just (L loc ty) -> addErrAt loc (resSigErr ctxt match ty)
751 -- Now the main event
752 -- note that there are no local ficity decls for matches
753 ; rnPats ctxt pats $ \ pats' -> do
754 { (grhss', grhss_fvs) <- rnGRHSs ctxt grhss
756 ; return (Match pats' Nothing grhss', grhss_fvs) }}
757 -- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
759 resSigErr :: HsMatchContext Name -> Match RdrName -> HsType RdrName -> SDoc
760 resSigErr ctxt match ty
761 = vcat [ ptext (sLit "Illegal result type signature") <+> quotes (ppr ty)
762 , nest 2 $ ptext (sLit "Result signatures are no longer supported in pattern matches")
763 , pprMatchInCtxt ctxt match ]
767 %************************************************************************
769 \subsubsection{Guarded right-hand sides (GRHSs)}
771 %************************************************************************
774 rnGRHSs :: HsMatchContext Name -> GRHSs RdrName -> RnM (GRHSs Name, FreeVars)
776 rnGRHSs ctxt (GRHSs grhss binds)
777 = rnLocalBindsAndThen binds $ \ binds' -> do
778 (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
779 return (GRHSs grhss' binds', fvGRHSs)
781 rnGRHS :: HsMatchContext Name -> LGRHS RdrName -> RnM (LGRHS Name, FreeVars)
782 rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)
784 rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
785 rnGRHS' ctxt (GRHS guards rhs)
786 = do { pattern_guards_allowed <- doptM Opt_PatternGuards
787 ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $
790 ; unless (pattern_guards_allowed || is_standard_guard guards')
791 (addWarn (nonStdGuardErr guards'))
793 ; return (GRHS guards' rhs', fvs) }
795 -- Standard Haskell 1.4 guards are just a single boolean
796 -- expression, rather than a list of qualifiers as in the
798 is_standard_guard [] = True
799 is_standard_guard [L _ (ExprStmt _ _ _)] = True
800 is_standard_guard _ = False
803 %************************************************************************
805 \subsection{Error messages}
807 %************************************************************************
810 dupSigDeclErr :: [LSig RdrName] -> RnM ()
811 dupSigDeclErr sigs@(L loc sig : _)
813 vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
814 nest 2 (vcat (map ppr_sig sigs))]
816 what_it_is = hsSigDoc sig
817 ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
818 dupSigDeclErr [] = panic "dupSigDeclErr"
820 unknownSigErr :: LSig RdrName -> RnM ()
821 unknownSigErr (L loc sig)
823 sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
825 methodBindErr :: HsBindLR RdrName RdrName -> SDoc
827 = hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
830 bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
831 bindsInHsBootFile mbinds
832 = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
835 nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
836 nonStdGuardErr guards
837 = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
838 4 (interpp'SP guards)