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 (rnPatsAndThen_LocalRightwards, rnBindPat,
27 NameMaker, localRecNameMaker, topRecNameMaker, applyNameMaker
31 import PrelNames ( mkUnboundName )
32 import DynFlags ( DynFlag(..) )
36 import RdrName ( RdrName, rdrNameOcc )
38 import ListSetOps ( findDupsEq )
39 import BasicTypes ( RecFlag(..) )
40 import Digraph ( SCC(..), stronglyConnCompFromEdgedVertices )
44 import Data.List ( partition )
45 import Maybes ( orElse )
46 import Monad ( foldM, unless )
49 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
50 -- place and can be used when complaining.
52 The code tree received by the function @rnBinds@ contains definitions
53 in where-clauses which are all apparently mutually recursive, but which may
54 not really depend upon each other. For example, in the top level program
59 the definitions of @a@ and @y@ do not depend on each other at all.
60 Unfortunately, the typechecker cannot always check such definitions.
61 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
62 definitions. In Proceedings of the International Symposium on Programming,
63 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
64 However, the typechecker usually can check definitions in which only the
65 strongly connected components have been collected into recursive bindings.
66 This is precisely what the function @rnBinds@ does.
68 ToDo: deal with case where a single monobinds binds the same variable
71 The vertag tag is a unique @Int@; the tags only need to be unique
72 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
73 (heavy monad machinery not needed).
76 %************************************************************************
78 %* naming conventions *
80 %************************************************************************
82 \subsection[name-conventions]{Name conventions}
84 The basic algorithm involves walking over the tree and returning a tuple
85 containing the new tree plus its free variables. Some functions, such
86 as those walking polymorphic bindings (HsBinds) and qualifier lists in
87 list comprehensions (@Quals@), return the variables bound in local
88 environments. These are then used to calculate the free variables of the
89 expression evaluated in these environments.
91 Conventions for variable names are as follows:
94 new code is given a prime to distinguish it from the old.
97 a set of variables defined in @Exp@ is written @dvExp@
100 a set of variables free in @Exp@ is written @fvExp@
103 %************************************************************************
105 %* analysing polymorphic bindings (HsBindGroup, HsBind)
107 %************************************************************************
109 \subsubsection[dep-HsBinds]{Polymorphic bindings}
111 Non-recursive expressions are reconstructed without any changes at top
112 level, although their component expressions may have to be altered.
113 However, non-recursive expressions are currently not expected as
114 \Haskell{} programs, and this code should not be executed.
116 Monomorphic bindings contain information that is returned in a tuple
117 (a @FlatMonoBinds@) containing:
121 a unique @Int@ that serves as the ``vertex tag'' for this binding.
124 the name of a function or the names in a pattern. These are a set
125 referred to as @dvLhs@, the defined variables of the left hand side.
128 the free variables of the body. These are referred to as @fvBody@.
131 the definition's actual code. This is referred to as just @code@.
134 The function @nonRecDvFv@ returns two sets of variables. The first is
135 the set of variables defined in the set of monomorphic bindings, while the
136 second is the set of free variables in those bindings.
138 The set of variables defined in a non-recursive binding is just the
139 union of all of them, as @union@ removes duplicates. However, the
140 free variables in each successive set of cumulative bindings is the
141 union of those in the previous set plus those of the newest binding after
142 the defined variables of the previous set have been removed.
144 @rnMethodBinds@ deals only with the declarations in class and
145 instance declarations. It expects only to see @FunMonoBind@s, and
146 it expects the global environment to contain bindings for the binders
147 (which are all class operations).
149 %************************************************************************
151 \subsubsection{ Top-level bindings}
153 %************************************************************************
156 -- for top-level bindings, we need to make top-level names,
157 -- so we have a different entry point than for local bindings
158 rnTopBindsLHS :: MiniFixityEnv
159 -> HsValBinds RdrName
160 -> RnM (HsValBindsLR Name RdrName)
161 rnTopBindsLHS fix_env binds =
162 (uncurry $ rnValBindsLHSFromDoc (topRecNameMaker fix_env)) (bindersAndDoc binds) binds
164 rnTopBindsRHS :: [Name] -- the names bound by these binds
165 -> HsValBindsLR Name RdrName
166 -> RnM (HsValBinds Name, DefUses)
167 rnTopBindsRHS bound_names binds =
168 do { is_boot <- tcIsHsBoot
170 then rnTopBindsBoot binds
171 else rnValBindsRHSGen (\x -> x) -- don't trim free vars
175 -- wrapper if we don't need to do anything in between the left and right,
176 -- or anything else in the scope of the left
178 -- never used when there are fixity declarations
179 rnTopBinds :: HsValBinds RdrName
180 -> RnM (HsValBinds Name, DefUses)
182 do nl <- rnTopBindsLHS emptyFsEnv b
183 let bound_names = map unLoc (collectHsValBinders nl)
184 bindLocalNames bound_names $ rnTopBindsRHS bound_names nl
187 rnTopBindsBoot :: HsValBindsLR Name RdrName -> RnM (HsValBinds Name, DefUses)
188 -- A hs-boot file has no bindings.
189 -- Return a single HsBindGroup with empty binds and renamed signatures
190 rnTopBindsBoot (ValBindsIn mbinds sigs)
191 = do { checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
192 ; sigs' <- renameSigs Nothing okHsBootSig sigs
193 ; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
194 rnTopBindsBoot b = pprPanic "rnTopBindsBoot" (ppr b)
199 %*********************************************************
203 %*********************************************************
206 rnLocalBindsAndThen :: HsLocalBinds RdrName
207 -> (HsLocalBinds Name -> RnM (result, FreeVars))
208 -> RnM (result, FreeVars)
209 -- This version (a) assumes that the binding vars are *not* already in scope
210 -- (b) removes the binders from the free vars of the thing inside
211 -- The parser doesn't produce ThenBinds
212 rnLocalBindsAndThen EmptyLocalBinds thing_inside
213 = thing_inside EmptyLocalBinds
215 rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
216 = rnValBindsAndThen val_binds $ \ val_binds' ->
217 thing_inside (HsValBinds val_binds')
219 rnLocalBindsAndThen (HsIPBinds binds) thing_inside = do
220 (binds',fv_binds) <- rnIPBinds binds
221 (thing, fvs_thing) <- thing_inside (HsIPBinds binds')
222 return (thing, fvs_thing `plusFV` fv_binds)
224 rnIPBinds :: HsIPBinds RdrName -> RnM (HsIPBinds Name, FreeVars)
225 rnIPBinds (IPBinds ip_binds _no_dict_binds) = do
226 (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
227 return (IPBinds ip_binds' emptyLHsBinds, plusFVs fvs_s)
229 rnIPBind :: IPBind RdrName -> RnM (IPBind Name, FreeVars)
230 rnIPBind (IPBind n expr) = do
231 name <- newIPNameRn n
232 (expr',fvExpr) <- rnLExpr expr
233 return (IPBind name expr', fvExpr)
237 %************************************************************************
241 %************************************************************************
244 -- wrapper for local binds
245 -- creates the documentation info and calls the helper below
246 rnValBindsLHS :: MiniFixityEnv
247 -> HsValBinds RdrName
248 -> RnM (HsValBindsLR Name RdrName)
249 rnValBindsLHS fix_env binds =
250 let (boundNames,doc) = bindersAndDoc binds
251 in rnValBindsLHSFromDoc_Local boundNames doc fix_env binds
253 -- a helper used for local binds that does the duplicates check,
254 -- just so we don't forget to do it somewhere
255 rnValBindsLHSFromDoc_Local :: [Located RdrName] -- RdrNames of the LHS (so we don't have to gather them twice)
256 -> SDoc -- doc string for dup names and shadowing
258 -> HsValBinds RdrName
259 -> RnM (HsValBindsLR Name RdrName)
261 rnValBindsLHSFromDoc_Local boundNames doc fix_env binds = do
262 -- Do error checking: we need to check for dups here because we
263 -- don't don't bind all of the variables from the ValBinds at once
264 -- with bindLocatedLocals any more.
265 checkDupAndShadowedRdrNames doc boundNames
267 -- (Note that we don't want to do this at the top level, since
268 -- sorting out duplicates and shadowing there happens elsewhere.
269 -- The behavior is even different. For example,
272 -- should not produce a shadowing warning (but it will produce
273 -- an ambiguity warning if you use f), but
275 -- g = let f = ... in f
277 rnValBindsLHSFromDoc (localRecNameMaker fix_env) boundNames doc binds
279 bindersAndDoc :: HsValBinds RdrName -> ([Located RdrName], SDoc)
280 bindersAndDoc binds =
282 -- the unrenamed bndrs for error checking and reporting
283 orig = collectHsValBinders binds
284 doc = text "In the binding group for:" <+> pprWithCommas ppr (map unLoc orig)
288 -- renames the left-hand sides
289 -- generic version used both at the top level and for local binds
290 -- does some error checking, but not what gets done elsewhere at the top level
291 rnValBindsLHSFromDoc :: NameMaker
292 -> [Located RdrName] -- RdrNames of the LHS (so we don't have to gather them twice)
293 -> SDoc -- doc string for dup names and shadowing
294 -> HsValBinds RdrName
295 -> RnM (HsValBindsLR Name RdrName)
296 rnValBindsLHSFromDoc topP _original_bndrs doc (ValBindsIn mbinds sigs) = do
298 mbinds' <- mapBagM (rnBindLHS topP doc) mbinds
299 return $ ValBindsIn mbinds' sigs
300 rnValBindsLHSFromDoc _ _ _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
302 -- General version used both from the top-level and for local things
303 -- Assumes the LHS vars are in scope
305 -- Does not bind the local fixity declarations
306 rnValBindsRHSGen :: (FreeVars -> FreeVars) -- for trimming free var sets
307 -- The trimming function trims the free vars we attach to a
308 -- binding so that it stays reasonably small
309 -> [Name] -- names bound by the LHSes
310 -> HsValBindsLR Name RdrName
311 -> RnM (HsValBinds Name, DefUses)
313 rnValBindsRHSGen trim bound_names (ValBindsIn mbinds sigs) = do
315 sigs' <- renameSigs (Just (mkNameSet bound_names)) okBindSig sigs
317 binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs') trim) mbinds
318 case depAnalBinds binds_w_dus of
319 (anal_binds, anal_dus) ->
320 do let valbind' = ValBindsOut anal_binds sigs'
321 valbind'_dus = usesOnly (hsSigsFVs sigs') `plusDU` anal_dus
322 return (valbind', valbind'_dus)
324 rnValBindsRHSGen _ _ b = pprPanic "rnValBindsRHSGen" (ppr b)
326 -- Wrapper for local binds
328 -- The *client* of this function is responsible for checking for unused binders;
329 -- it doesn't (and can't: we don't have the thing inside the binds) happen here
331 -- The client is also responsible for bringing the fixities into scope
332 rnValBindsRHS :: [Name] -- names bound by the LHSes
333 -> HsValBindsLR Name RdrName
334 -> RnM (HsValBinds Name, DefUses)
335 rnValBindsRHS bound_names binds =
336 rnValBindsRHSGen (\ fvs -> -- only keep the names the names from this group
337 intersectNameSet (mkNameSet bound_names) fvs) bound_names binds
341 -- wrapper that does both the left- and right-hand sides
343 -- here there are no local fixity decls passed in;
344 -- the local fixity decls come from the ValBinds sigs
345 rnValBindsAndThen :: HsValBinds RdrName
346 -> (HsValBinds Name -> RnM (result, FreeVars))
347 -> RnM (result, FreeVars)
348 rnValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
349 = do { let (original_bndrs, doc) = bindersAndDoc binds
351 -- (A) Create the local fixity environment
352 ; new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
354 -- (B) Rename the LHSes
355 ; new_lhs <- rnValBindsLHSFromDoc_Local original_bndrs doc new_fixities binds
356 ; let bound_names = map unLoc $ collectHsValBinders new_lhs
358 -- ...and bring them (and their fixities) into scope
359 ; bindLocalNamesFV_WithFixities bound_names new_fixities $ do
361 { -- (C) Do the RHS and thing inside
362 (binds', dus) <- rnValBindsRHS bound_names new_lhs
363 ; (result, result_fvs) <- thing_inside binds'
365 -- Report unused bindings based on the (accurate)
368 -- should report 'x' unused
369 ; let real_uses = findUses dus result_fvs
370 ; warnUnusedLocalBinds bound_names real_uses
373 -- The variables "used" in the val binds are:
374 -- (1) the uses of the binds (duUses)
375 -- (2) the FVs of the thing-inside
376 all_uses = duUses dus `plusFV` result_fvs
377 -- Note [Unused binding hack]
378 -- ~~~~~~~~~~~~~~~~~~~~~~~~~~
379 -- Note that *in contrast* to the above reporting of
380 -- unused bindings, (1) above uses duUses to return *all*
381 -- the uses, even if the binding is unused. Otherwise consider:
383 -- y = let p = x in 'x' -- NB: p not used
384 -- If we don't "see" the dependency of 'y' on 'x', we may put the
385 -- bindings in the wrong order, and the type checker will complain
386 -- that x isn't in scope
388 -- But note that this means we won't report 'x' as unused,
389 -- whereas we would if we had { x = 3; p = x; y = 'x' }
391 ; return (result, all_uses) }}
392 -- The bound names are pruned out of all_uses
393 -- by the bindLocalNamesFV call above
395 rnValBindsAndThen bs _ = pprPanic "rnValBindsAndThen" (ppr bs)
398 -- Process the fixity declarations, making a FastString -> (Located Fixity) map
399 -- (We keep the location around for reporting duplicate fixity declarations.)
401 -- Checks for duplicates, but not that only locally defined things are fixed.
402 -- Note: for local fixity declarations, duplicates would also be checked in
403 -- check_sigs below. But we also use this function at the top level.
405 makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv
407 makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
409 add_one env (L loc (FixitySig (L name_loc name) fixity)) = do
410 { -- this fixity decl is a duplicate iff
411 -- the ReaderName's OccName's FastString is already in the env
412 -- (we only need to check the local fix_env because
413 -- definitions of non-local will be caught elsewhere)
414 let { fs = occNameFS (rdrNameOcc name)
415 ; fix_item = L loc fixity };
417 case lookupFsEnv env fs of
418 Nothing -> return $ extendFsEnv env fs fix_item
419 Just (L loc' _) -> do
421 addLocErr (L name_loc name) (dupFixityDecl loc')
425 dupFixityDecl :: SrcSpan -> RdrName -> SDoc
426 dupFixityDecl loc rdr_name
427 = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
428 ptext (sLit "also at ") <+> ppr loc]
430 ---------------------
432 -- renaming a single bind
434 rnBindLHS :: NameMaker
437 -- returns the renamed left-hand side,
438 -- and the FreeVars *of the LHS*
439 -- (i.e., any free variables of the pattern)
440 -> RnM (LHsBindLR Name RdrName)
442 rnBindLHS name_maker _ (L loc (PatBind { pat_lhs = pat,
444 pat_rhs_ty=pat_rhs_ty
446 = setSrcSpan loc $ do
447 -- we don't actually use the FV processing of rnPatsAndThen here
448 (pat',pat'_fvs) <- rnBindPat name_maker pat
449 return (L loc (PatBind { pat_lhs = pat',
451 -- we temporarily store the pat's FVs here;
452 -- gets updated to the FVs of the whole bind
453 -- when doing the RHS below
455 -- these will get ignored in the next pass,
456 -- when we rename the RHS
457 pat_rhs_ty = pat_rhs_ty }))
459 rnBindLHS name_maker _ (L loc (FunBind { fun_id = name@(L nameLoc _),
461 fun_matches = matches,
462 fun_co_fn = fun_co_fn,
466 do { (newname, _fvs) <- applyNameMaker name_maker name $ \ newname ->
467 return (newname, emptyFVs)
468 ; return (L loc (FunBind { fun_id = L nameLoc newname,
470 fun_matches = matches,
471 -- we temporatily store the LHS's FVs (empty in this case) here
472 -- gets updated when doing the RHS below
474 -- everything else will get ignored in the next pass
475 fun_co_fn = fun_co_fn,
479 rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)
481 -- assumes the left-hands-side vars are in scope
482 rnBind :: (Name -> [Name]) -- Signature tyvar function
483 -> (FreeVars -> FreeVars) -- Trimming function for rhs free vars
484 -> LHsBindLR Name RdrName
485 -> RnM (LHsBind Name, [Name], Uses)
486 rnBind _ trim (L loc (PatBind { pat_lhs = pat,
488 -- pat fvs were stored here while
489 -- processing the LHS
492 do {let bndrs = collectPatBinders pat
494 ; (grhss', fvs) <- rnGRHSs PatBindRhs grhss
495 -- No scoped type variables for pattern bindings
496 ; let fvs' = trim fvs
498 ; fvs' `seq` -- See Note [Free-variable space leak]
499 return (L loc (PatBind { pat_lhs = pat,
501 pat_rhs_ty = placeHolderType,
503 bndrs, pat_fvs `plusFV` fvs) }
507 (L loc (FunBind { fun_id = name,
509 fun_matches = matches,
513 -- invariant: no free vars here when it's a FunBind
515 do { let plain_name = unLoc name
517 ; (matches', fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
518 -- bindSigTyVars tests for Opt_ScopedTyVars
519 rnMatchGroup (FunRhs plain_name inf) matches
520 ; let fvs' = trim fvs
522 ; checkPrecMatch inf plain_name matches'
524 ; fvs' `seq` -- See Note [Free-variable space leak]
525 return (L loc (FunBind { fun_id = name,
527 fun_matches = matches',
529 fun_co_fn = idHsWrapper,
530 fun_tick = Nothing }),
534 rnBind _ _ b = pprPanic "rnBind" (ppr b)
537 Note [Free-variable space leak]
538 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
541 and we seq fvs' before turning it as part of a record.
543 The reason is that trim is sometimes something like
544 \xs -> intersectNameSet (mkNameSet bound_names) xs
545 and we don't want to retain the list bound_names. This showed up in
549 ---------------------
550 depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
551 -> ([(RecFlag, LHsBinds Name)], DefUses)
552 -- Dependency analysis; this is important so that
553 -- unused-binding reporting is accurate
554 depAnalBinds binds_w_dus
555 = (map get_binds sccs, map get_du sccs)
557 sccs = stronglyConnCompFromEdgedVertices edges
559 keyd_nodes = bagToList binds_w_dus `zip` [0::Int ..]
561 edges = [ (node, key, [key | n <- nameSetToList uses,
562 Just key <- [lookupNameEnv key_map n] ])
563 | (node@(_,_,uses), key) <- keyd_nodes ]
565 key_map :: NameEnv Int -- Which binding it comes from
566 key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
569 get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
570 get_binds (CyclicSCC binds_w_dus) = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
572 get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
573 get_du (CyclicSCC binds_w_dus) = (Just defs, uses)
575 defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
576 uses = unionManyNameSets [u | (_,_,u) <- binds_w_dus]
579 ---------------------
580 -- Bind the top-level forall'd type variables in the sigs.
583 -- The 'a' scopes over the rhs
585 -- NB: there'll usually be just one (for a function binding)
586 -- but if there are many, one may shadow the rest; too bad!
587 -- e.g x :: [a] -> [a]
590 -- In e, 'a' will be in scope, and it'll be the one from 'y'!
592 mkSigTvFn :: [LSig Name] -> (Name -> [Name])
593 -- Return a lookup function that maps an Id Name to the names
594 -- of the type variables that should scope over its body..
596 = \n -> lookupNameEnv env n `orElse` []
598 env :: NameEnv [Name]
599 env = mkNameEnv [ (name, map hsLTyVarName ltvs)
600 | L _ (TypeSig (L _ name)
601 (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs]
602 -- Note the pattern-match on "Explicit"; we only bind
603 -- type variables from signatures with an explicit top-level for-all
607 @rnMethodBinds@ is used for the method bindings of a class and an instance
608 declaration. Like @rnBinds@ but without dependency analysis.
610 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
611 That's crucial when dealing with an instance decl:
613 instance Foo (T a) where
616 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
617 and unless @op@ occurs we won't treat the type signature of @op@ in the class
618 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
619 in many ways the @op@ in an instance decl is just like an occurrence, not
623 rnMethodBinds :: Name -- Class name
624 -> (Name -> [Name]) -- Signature tyvar function
625 -> [Name] -- Names for generic type variables
627 -> RnM (LHsBinds Name, FreeVars)
629 rnMethodBinds cls sig_fn gen_tyvars binds
630 = foldM do_one (emptyBag,emptyFVs) (bagToList binds)
631 where do_one (binds,fvs) bind = do
632 (bind', fvs_bind) <- rnMethodBind cls sig_fn gen_tyvars bind
633 return (bind' `unionBags` binds, fvs_bind `plusFV` fvs)
638 -> LHsBindLR RdrName RdrName
639 -> RnM (Bag (LHsBindLR Name Name), FreeVars)
640 rnMethodBind cls sig_fn gen_tyvars (L loc (FunBind { fun_id = name, fun_infix = inf,
641 fun_matches = MatchGroup matches _ }))
642 = setSrcSpan loc $ do
643 sel_name <- lookupInstDeclBndr cls name
644 let plain_name = unLoc sel_name
645 -- We use the selector name as the binder
647 bindSigTyVarsFV (sig_fn plain_name) $ do
648 (new_matches, fvs) <- mapFvRn (rn_match plain_name) matches
650 new_group = MatchGroup new_matches placeHolderType
652 checkPrecMatch inf plain_name new_group
653 return (unitBag (L loc (FunBind {
654 fun_id = sel_name, fun_infix = inf,
655 fun_matches = new_group,
656 bind_fvs = fvs, fun_co_fn = idHsWrapper,
657 fun_tick = Nothing })),
658 fvs `addOneFV` plain_name)
659 -- The 'fvs' field isn't used for method binds
661 -- Truly gruesome; bring into scope the correct members of the generic
662 -- type variables. See comments in RnSource.rnSourceDecl(ClassDecl)
663 rn_match sel_name match@(L _ (Match (L _ (TypePat ty) : _) _ _))
664 = extendTyVarEnvFVRn gen_tvs $
665 rnMatch (FunRhs sel_name inf) match
667 tvs = map (rdrNameOcc.unLoc) (extractHsTyRdrTyVars ty)
668 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
670 rn_match sel_name match = rnMatch (FunRhs sel_name inf) match
673 -- Can't handle method pattern-bindings which bind multiple methods.
674 rnMethodBind _ _ _ mbind@(L _ (PatBind _ _ _ _)) = do
675 addLocErr mbind methodBindErr
676 return (emptyBag, emptyFVs)
678 rnMethodBind _ _ _ b = pprPanic "rnMethodBind" (ppr b)
683 %************************************************************************
685 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
687 %************************************************************************
689 @renameSigs@ checks for:
691 \item more than one sig for one thing;
692 \item signatures given for things not bound here;
695 At the moment we don't gather free-var info from the types in
696 signatures. We'd only need this if we wanted to report unused tyvars.
699 renameSigs :: Maybe NameSet -- If (Just ns) complain if the sig isn't for one of ns
700 -> (Sig RdrName -> Bool) -- Complain about the wrong kind of signature if this is False
703 -- Renames the signatures and performs error checks
704 renameSigs mb_names ok_sig sigs
705 = do { let (good_sigs, bad_sigs) = partition (ok_sig . unLoc) sigs
706 ; mapM_ unknownSigErr bad_sigs -- Misplaced
707 ; mapM_ dupSigDeclErr (findDupsEq eqHsSig sigs) -- Duplicate
708 ; sigs' <- mapM (wrapLocM (renameSig mb_names)) good_sigs
711 ----------------------
712 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
713 -- because this won't work for:
714 -- instance Foo T where
717 -- We'll just rename the INLINE prag to refer to whatever other 'op'
718 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
719 -- Doesn't seem worth much trouble to sort this.
721 renameSig :: Maybe NameSet -> Sig RdrName -> RnM (Sig Name)
722 -- FixitySig is renamed elsewhere.
723 renameSig mb_names sig@(TypeSig v ty)
724 = do { new_v <- lookupSigLocOccRn mb_names sig v
725 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
726 ; return (TypeSig new_v new_ty) }
728 renameSig _ (SpecInstSig ty)
729 = do { new_ty <- rnLHsType (text "A SPECIALISE instance pragma") ty
730 ; return (SpecInstSig new_ty) }
732 renameSig mb_names sig@(SpecSig v ty inl)
733 = do { new_v <- lookupSigLocOccRn mb_names sig v
734 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
735 ; return (SpecSig new_v new_ty inl) }
737 renameSig mb_names sig@(InlineSig v s)
738 = do { new_v <- lookupSigLocOccRn mb_names sig v
739 ; return (InlineSig new_v s) }
741 renameSig mb_names sig@(FixSig (FixitySig v f))
742 = do { new_v <- lookupSigLocOccRn mb_names sig v
743 ; return (FixSig (FixitySig new_v f)) }
745 -- lookupSigOccRn is used for type signatures and pragmas
751 -- It's clear that the 'f' in the signature must refer to A.f
752 -- The Haskell98 report does not stipulate this, but it will!
753 -- So we must treat the 'f' in the signature in the same way
754 -- as the binding occurrence of 'f', using lookupBndrRn
756 -- However, consider this case:
760 -- We don't want to say 'f' is out of scope; instead, we want to
761 -- return the imported 'f', so that later on the reanamer will
762 -- correctly report "misplaced type sig".
764 lookupSigLocOccRn :: Maybe NameSet -> Sig RdrName -> Located RdrName -> RnM (Located Name)
765 lookupSigLocOccRn mb_names sig = wrapLocM (lookupSigOccRn mb_names sig)
767 lookupSigOccRn :: Maybe NameSet -> Sig RdrName -> RdrName -> RnM Name
768 lookupSigOccRn mb_names sig v
769 = do { mb_n <- lookupBndrRn_maybe v
771 Just n -> case mb_names of {
772 Nothing -> return n ;
773 Just ns | n `elemNameSet` ns -> return n
774 | otherwise -> bale_out_with local_msg } ;
777 { mb_n <- lookupGreRn_maybe v
779 Just _ -> bale_out_with import_msg
780 Nothing -> bale_out_with empty
784 = do { addErr (sep [ ptext (sLit "The") <+> hsSigDoc sig
785 <+> ptext (sLit "for") <+> quotes (ppr v)
786 , nest 2 $ ptext (sLit "lacks an accompanying binding")]
788 ; return (mkUnboundName v) }
790 local_msg = parens $ ptext (sLit "The") <+> hsSigDoc sig <+> ptext (sLit "must be given where")
791 <+> quotes (ppr v) <+> ptext (sLit "is declared")
793 import_msg = parens $ ptext (sLit "You cannot give a") <+> hsSigDoc sig
794 <+> ptext (sLit "an imported value")
798 %************************************************************************
802 %************************************************************************
805 rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
806 rnMatchGroup ctxt (MatchGroup ms _)
807 = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
808 ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
810 rnMatch :: HsMatchContext Name -> LMatch RdrName -> RnM (LMatch Name, FreeVars)
811 rnMatch ctxt = wrapLocFstM (rnMatch' ctxt)
813 rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
814 rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
815 = do { -- Result type signatures are no longer supported
816 case maybe_rhs_sig of
818 Just ty -> addLocErr ty (resSigErr ctxt match)
821 -- Now the main event
822 -- note that there are no local ficity decls for matches
823 ; rnPatsAndThen_LocalRightwards ctxt pats $ \ pats' -> do
824 { (grhss', grhss_fvs) <- rnGRHSs ctxt grhss
826 ; return (Match pats' Nothing grhss', grhss_fvs) }}
827 -- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
830 resSigErr :: HsMatchContext Name -> Match RdrName -> HsType RdrName -> SDoc
831 resSigErr ctxt match ty
832 = vcat [ ptext (sLit "Illegal result type signature") <+> quotes (ppr ty)
833 , nest 2 $ ptext (sLit "Result signatures are no longer supported in pattern matches")
834 , pprMatchInCtxt ctxt match ]
838 %************************************************************************
840 \subsubsection{Guarded right-hand sides (GRHSs)}
842 %************************************************************************
845 rnGRHSs :: HsMatchContext Name -> GRHSs RdrName -> RnM (GRHSs Name, FreeVars)
847 rnGRHSs ctxt (GRHSs grhss binds)
848 = rnLocalBindsAndThen binds $ \ binds' -> do
849 (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
850 return (GRHSs grhss' binds', fvGRHSs)
852 rnGRHS :: HsMatchContext Name -> LGRHS RdrName -> RnM (LGRHS Name, FreeVars)
853 rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)
855 rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
856 rnGRHS' ctxt (GRHS guards rhs)
857 = do { pattern_guards_allowed <- doptM Opt_PatternGuards
858 ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $
861 ; unless (pattern_guards_allowed || is_standard_guard guards')
862 (addWarn (nonStdGuardErr guards'))
864 ; return (GRHS guards' rhs', fvs) }
866 -- Standard Haskell 1.4 guards are just a single boolean
867 -- expression, rather than a list of qualifiers as in the
869 is_standard_guard [] = True
870 is_standard_guard [L _ (ExprStmt _ _ _)] = True
871 is_standard_guard _ = False
874 %************************************************************************
876 \subsection{Error messages}
878 %************************************************************************
881 dupSigDeclErr :: [LSig RdrName] -> RnM ()
882 dupSigDeclErr sigs@(L loc sig : _)
884 vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
885 nest 2 (vcat (map ppr_sig sigs))]
887 what_it_is = hsSigDoc sig
888 ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
889 dupSigDeclErr [] = panic "dupSigDeclErr"
891 unknownSigErr :: LSig RdrName -> RnM ()
892 unknownSigErr (L loc sig)
894 sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
896 methodBindErr :: HsBindLR RdrName RdrName -> SDoc
898 = hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
901 bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
902 bindsInHsBootFile mbinds
903 = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
906 nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
907 nonStdGuardErr guards
908 = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
909 4 (interpp'SP guards)