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
316 sigs' <- renameSigs (Just (mkNameSet bound_names)) okBindSig sigs
318 binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs') trim) mbinds
319 case depAnalBinds binds_w_dus of
320 (anal_binds, anal_dus) ->
321 do let valbind' = ValBindsOut anal_binds sigs'
322 valbind'_dus = usesOnly (hsSigsFVs sigs') `plusDU` anal_dus
323 return (valbind', valbind'_dus)
325 rnValBindsRHSGen _ _ b = pprPanic "rnValBindsRHSGen" (ppr b)
327 -- Wrapper for local binds
329 -- The *client* of this function is responsible for checking for unused binders;
330 -- it doesn't (and can't: we don't have the thing inside the binds) happen here
332 -- The client is also responsible for bringing the fixities into scope
333 rnValBindsRHS :: [Name] -- names bound by the LHSes
334 -> HsValBindsLR Name RdrName
335 -> RnM (HsValBinds Name, DefUses)
336 rnValBindsRHS bound_names binds =
337 rnValBindsRHSGen (\ fvs -> -- only keep the names the names from this group
338 intersectNameSet (mkNameSet bound_names) fvs) bound_names binds
342 -- wrapper that does both the left- and right-hand sides
344 -- here there are no local fixity decls passed in;
345 -- the local fixity decls come from the ValBinds sigs
346 rnValBindsAndThen :: HsValBinds RdrName
347 -> (HsValBinds Name -> RnM (result, FreeVars))
348 -> RnM (result, FreeVars)
349 rnValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
350 = do { let (original_bndrs, doc) = bindersAndDoc binds
352 -- (A) Create the local fixity environment
353 ; new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
355 -- (B) Rename the LHSes
356 ; new_lhs <- rnValBindsLHSFromDoc_Local original_bndrs doc new_fixities binds
357 ; let bound_names = map unLoc $ collectHsValBinders new_lhs
359 -- ...and bring them (and their fixities) into scope
360 ; bindLocalNamesFV_WithFixities bound_names new_fixities $ do
362 { -- (C) Do the RHS and thing inside
363 (binds', dus) <- rnValBindsRHS bound_names new_lhs
364 ; (result, result_fvs) <- thing_inside binds'
366 -- Report unused bindings based on the (accurate)
369 -- should report 'x' unused
370 ; let real_uses = findUses dus result_fvs
371 ; warnUnusedLocalBinds bound_names real_uses
374 -- The variables "used" in the val binds are:
375 -- (1) the uses of the binds (duUses)
376 -- (2) the FVs of the thing-inside
377 all_uses = duUses dus `plusFV` result_fvs
378 -- Note [Unused binding hack]
379 -- ~~~~~~~~~~~~~~~~~~~~~~~~~~
380 -- Note that *in contrast* to the above reporting of
381 -- unused bindings, (1) above uses duUses to return *all*
382 -- the uses, even if the binding is unused. Otherwise consider:
384 -- y = let p = x in 'x' -- NB: p not used
385 -- If we don't "see" the dependency of 'y' on 'x', we may put the
386 -- bindings in the wrong order, and the type checker will complain
387 -- that x isn't in scope
389 -- But note that this means we won't report 'x' as unused,
390 -- whereas we would if we had { x = 3; p = x; y = 'x' }
392 ; return (result, all_uses) }}
393 -- The bound names are pruned out of all_uses
394 -- by the bindLocalNamesFV call above
396 rnValBindsAndThen bs _ = pprPanic "rnValBindsAndThen" (ppr bs)
399 -- Process the fixity declarations, making a FastString -> (Located Fixity) map
400 -- (We keep the location around for reporting duplicate fixity declarations.)
402 -- Checks for duplicates, but not that only locally defined things are fixed.
403 -- Note: for local fixity declarations, duplicates would also be checked in
404 -- check_sigs below. But we also use this function at the top level.
406 makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv
408 makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
410 add_one env (L loc (FixitySig (L name_loc name) fixity)) = do
411 { -- this fixity decl is a duplicate iff
412 -- the ReaderName's OccName's FastString is already in the env
413 -- (we only need to check the local fix_env because
414 -- definitions of non-local will be caught elsewhere)
415 let { fs = occNameFS (rdrNameOcc name)
416 ; fix_item = L loc fixity };
418 case lookupFsEnv env fs of
419 Nothing -> return $ extendFsEnv env fs fix_item
420 Just (L loc' _) -> do
422 addLocErr (L name_loc name) (dupFixityDecl loc')
426 dupFixityDecl :: SrcSpan -> RdrName -> SDoc
427 dupFixityDecl loc rdr_name
428 = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
429 ptext (sLit "also at ") <+> ppr loc]
431 ---------------------
433 -- renaming a single bind
435 rnBindLHS :: NameMaker
438 -- returns the renamed left-hand side,
439 -- and the FreeVars *of the LHS*
440 -- (i.e., any free variables of the pattern)
441 -> RnM (LHsBindLR Name RdrName)
443 rnBindLHS name_maker _ (L loc (PatBind { pat_lhs = pat,
445 pat_rhs_ty=pat_rhs_ty
447 = setSrcSpan loc $ do
448 -- we don't actually use the FV processing of rnPatsAndThen here
449 (pat',pat'_fvs) <- rnBindPat name_maker pat
450 return (L loc (PatBind { pat_lhs = pat',
452 -- we temporarily store the pat's FVs here;
453 -- gets updated to the FVs of the whole bind
454 -- when doing the RHS below
456 -- these will get ignored in the next pass,
457 -- when we rename the RHS
458 pat_rhs_ty = pat_rhs_ty }))
460 rnBindLHS name_maker _ (L loc (FunBind { fun_id = name@(L nameLoc _),
462 fun_matches = matches,
463 fun_co_fn = fun_co_fn,
467 do { (newname, _fvs) <- applyNameMaker name_maker name $ \ newname ->
468 return (newname, emptyFVs)
469 ; return (L loc (FunBind { fun_id = L nameLoc newname,
471 fun_matches = matches,
472 -- we temporatily store the LHS's FVs (empty in this case) here
473 -- gets updated when doing the RHS below
475 -- everything else will get ignored in the next pass
476 fun_co_fn = fun_co_fn,
480 rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)
482 -- assumes the left-hands-side vars are in scope
483 rnBind :: (Name -> [Name]) -- Signature tyvar function
484 -> (FreeVars -> FreeVars) -- Trimming function for rhs free vars
485 -> LHsBindLR Name RdrName
486 -> RnM (LHsBind Name, [Name], Uses)
487 rnBind _ trim (L loc (PatBind { pat_lhs = pat,
489 -- pat fvs were stored here while
490 -- processing the LHS
493 do {let bndrs = collectPatBinders pat
495 ; (grhss', fvs) <- rnGRHSs PatBindRhs grhss
496 -- No scoped type variables for pattern bindings
497 ; let fvs' = trim fvs
499 ; fvs' `seq` -- See Note [Free-variable space leak]
500 return (L loc (PatBind { pat_lhs = pat,
502 pat_rhs_ty = placeHolderType,
504 bndrs, pat_fvs `plusFV` fvs) }
508 (L loc (FunBind { fun_id = name,
510 fun_matches = matches,
514 -- invariant: no free vars here when it's a FunBind
516 do { let plain_name = unLoc name
518 ; (matches', fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
519 -- bindSigTyVars tests for Opt_ScopedTyVars
520 rnMatchGroup (FunRhs plain_name inf) matches
521 ; let fvs' = trim fvs
523 ; checkPrecMatch inf plain_name matches'
525 ; fvs' `seq` -- See Note [Free-variable space leak]
526 return (L loc (FunBind { fun_id = name,
528 fun_matches = matches',
530 fun_co_fn = idHsWrapper,
531 fun_tick = Nothing }),
535 rnBind _ _ b = pprPanic "rnBind" (ppr b)
538 Note [Free-variable space leak]
539 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
542 and we seq fvs' before turning it as part of a record.
544 The reason is that trim is sometimes something like
545 \xs -> intersectNameSet (mkNameSet bound_names) xs
546 and we don't want to retain the list bound_names. This showed up in
550 ---------------------
551 depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
552 -> ([(RecFlag, LHsBinds Name)], DefUses)
553 -- Dependency analysis; this is important so that
554 -- unused-binding reporting is accurate
555 depAnalBinds binds_w_dus
556 = (map get_binds sccs, map get_du sccs)
558 sccs = stronglyConnCompFromEdgedVertices edges
560 keyd_nodes = bagToList binds_w_dus `zip` [0::Int ..]
562 edges = [ (node, key, [key | n <- nameSetToList uses,
563 Just key <- [lookupNameEnv key_map n] ])
564 | (node@(_,_,uses), key) <- keyd_nodes ]
566 key_map :: NameEnv Int -- Which binding it comes from
567 key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
570 get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
571 get_binds (CyclicSCC binds_w_dus) = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
573 get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
574 get_du (CyclicSCC binds_w_dus) = (Just defs, uses)
576 defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
577 uses = unionManyNameSets [u | (_,_,u) <- binds_w_dus]
580 ---------------------
581 -- Bind the top-level forall'd type variables in the sigs.
584 -- The 'a' scopes over the rhs
586 -- NB: there'll usually be just one (for a function binding)
587 -- but if there are many, one may shadow the rest; too bad!
588 -- e.g x :: [a] -> [a]
591 -- In e, 'a' will be in scope, and it'll be the one from 'y'!
593 mkSigTvFn :: [LSig Name] -> (Name -> [Name])
594 -- Return a lookup function that maps an Id Name to the names
595 -- of the type variables that should scope over its body..
597 = \n -> lookupNameEnv env n `orElse` []
599 env :: NameEnv [Name]
600 env = mkNameEnv [ (name, map hsLTyVarName ltvs)
601 | L _ (TypeSig (L _ name)
602 (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs]
603 -- Note the pattern-match on "Explicit"; we only bind
604 -- type variables from signatures with an explicit top-level for-all
608 @rnMethodBinds@ is used for the method bindings of a class and an instance
609 declaration. Like @rnBinds@ but without dependency analysis.
611 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
612 That's crucial when dealing with an instance decl:
614 instance Foo (T a) where
617 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
618 and unless @op@ occurs we won't treat the type signature of @op@ in the class
619 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
620 in many ways the @op@ in an instance decl is just like an occurrence, not
624 rnMethodBinds :: Name -- Class name
625 -> (Name -> [Name]) -- Signature tyvar function
626 -> [Name] -- Names for generic type variables
628 -> RnM (LHsBinds Name, FreeVars)
630 rnMethodBinds cls sig_fn gen_tyvars binds
631 = foldM do_one (emptyBag,emptyFVs) (bagToList binds)
632 where do_one (binds,fvs) bind = do
633 (bind', fvs_bind) <- rnMethodBind cls sig_fn gen_tyvars bind
634 return (bind' `unionBags` binds, fvs_bind `plusFV` fvs)
639 -> LHsBindLR RdrName RdrName
640 -> RnM (Bag (LHsBindLR Name Name), FreeVars)
641 rnMethodBind cls sig_fn gen_tyvars (L loc (FunBind { fun_id = name, fun_infix = inf,
642 fun_matches = MatchGroup matches _ }))
643 = setSrcSpan loc $ do
644 sel_name <- lookupInstDeclBndr cls name
645 let plain_name = unLoc sel_name
646 -- We use the selector name as the binder
648 bindSigTyVarsFV (sig_fn plain_name) $ do
649 (new_matches, fvs) <- mapFvRn (rn_match plain_name) matches
651 new_group = MatchGroup new_matches placeHolderType
653 checkPrecMatch inf plain_name new_group
654 return (unitBag (L loc (FunBind {
655 fun_id = sel_name, fun_infix = inf,
656 fun_matches = new_group,
657 bind_fvs = fvs, fun_co_fn = idHsWrapper,
658 fun_tick = Nothing })),
659 fvs `addOneFV` plain_name)
660 -- The 'fvs' field isn't used for method binds
662 -- Truly gruesome; bring into scope the correct members of the generic
663 -- type variables. See comments in RnSource.rnSourceDecl(ClassDecl)
664 rn_match sel_name match@(L _ (Match (L _ (TypePat ty) : _) _ _))
665 = extendTyVarEnvFVRn gen_tvs $
666 rnMatch (FunRhs sel_name inf) match
668 tvs = map (rdrNameOcc.unLoc) (extractHsTyRdrTyVars ty)
669 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
671 rn_match sel_name match = rnMatch (FunRhs sel_name inf) match
674 -- Can't handle method pattern-bindings which bind multiple methods.
675 rnMethodBind _ _ _ mbind@(L _ (PatBind _ _ _ _)) = do
676 addLocErr mbind methodBindErr
677 return (emptyBag, emptyFVs)
679 rnMethodBind _ _ _ b = pprPanic "rnMethodBind" (ppr b)
684 %************************************************************************
686 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
688 %************************************************************************
690 @renameSigs@ checks for:
692 \item more than one sig for one thing;
693 \item signatures given for things not bound here;
696 At the moment we don't gather free-var info from the types in
697 signatures. We'd only need this if we wanted to report unused tyvars.
700 renameSigs :: Maybe NameSet -- If (Just ns) complain if the sig isn't for one of ns
701 -> (Sig RdrName -> Bool) -- Complain about the wrong kind of signature if this is False
704 -- Renames the signatures and performs error checks
705 renameSigs mb_names ok_sig sigs
706 = do { let (good_sigs, bad_sigs) = partition (ok_sig . unLoc) sigs
707 ; mapM_ unknownSigErr bad_sigs -- Misplaced
708 ; mapM_ dupSigDeclErr (findDupsEq eqHsSig sigs) -- Duplicate
709 ; sigs' <- mapM (wrapLocM (renameSig mb_names)) good_sigs
712 ----------------------
713 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
714 -- because this won't work for:
715 -- instance Foo T where
718 -- We'll just rename the INLINE prag to refer to whatever other 'op'
719 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
720 -- Doesn't seem worth much trouble to sort this.
722 renameSig :: Maybe NameSet -> Sig RdrName -> RnM (Sig Name)
723 -- FixitySig is renamed elsewhere.
724 renameSig mb_names sig@(TypeSig v ty)
725 = do { new_v <- lookupSigLocOccRn mb_names sig v
726 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
727 ; return (TypeSig new_v new_ty) }
729 renameSig _ (SpecInstSig ty)
730 = do { new_ty <- rnLHsType (text "A SPECIALISE instance pragma") ty
731 ; return (SpecInstSig new_ty) }
733 renameSig mb_names sig@(SpecSig v ty inl)
734 = do { new_v <- lookupSigLocOccRn mb_names sig v
735 ; new_ty <- rnHsSigType (quotes (ppr v)) ty
736 ; return (SpecSig new_v new_ty inl) }
738 renameSig mb_names sig@(InlineSig v s)
739 = do { new_v <- lookupSigLocOccRn mb_names sig v
740 ; return (InlineSig new_v s) }
742 renameSig mb_names sig@(FixSig (FixitySig v f))
743 = do { new_v <- lookupSigLocOccRn mb_names sig v
744 ; return (FixSig (FixitySig new_v f)) }
746 -- lookupSigOccRn is used for type signatures and pragmas
752 -- It's clear that the 'f' in the signature must refer to A.f
753 -- The Haskell98 report does not stipulate this, but it will!
754 -- So we must treat the 'f' in the signature in the same way
755 -- as the binding occurrence of 'f', using lookupBndrRn
757 -- However, consider this case:
761 -- We don't want to say 'f' is out of scope; instead, we want to
762 -- return the imported 'f', so that later on the reanamer will
763 -- correctly report "misplaced type sig".
765 lookupSigLocOccRn :: Maybe NameSet -> Sig RdrName -> Located RdrName -> RnM (Located Name)
766 lookupSigLocOccRn mb_names sig = wrapLocM (lookupSigOccRn mb_names sig)
768 lookupSigOccRn :: Maybe NameSet -> Sig RdrName -> RdrName -> RnM Name
769 lookupSigOccRn mb_names sig v
770 = do { mb_n <- lookupBndrRn_maybe v
772 Just n -> case mb_names of {
773 Nothing -> return n ;
774 Just ns | n `elemNameSet` ns -> return n
775 | otherwise -> bale_out_with local_msg } ;
778 { mb_n <- lookupGreRn_maybe v
780 Just _ -> bale_out_with import_msg
781 Nothing -> bale_out_with empty
785 = do { addErr (sep [ ptext (sLit "The") <+> hsSigDoc sig
786 <+> ptext (sLit "for") <+> quotes (ppr v)
787 , nest 2 $ ptext (sLit "lacks an accompanying binding")]
789 ; return (mkUnboundName v) }
791 local_msg = parens $ ptext (sLit "The") <+> hsSigDoc sig <+> ptext (sLit "must be given where")
792 <+> quotes (ppr v) <+> ptext (sLit "is declared")
794 import_msg = parens $ ptext (sLit "You cannot give a") <+> hsSigDoc sig
795 <+> ptext (sLit "an imported value")
799 %************************************************************************
803 %************************************************************************
806 rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
807 rnMatchGroup ctxt (MatchGroup ms _)
808 = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
809 ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
811 rnMatch :: HsMatchContext Name -> LMatch RdrName -> RnM (LMatch Name, FreeVars)
812 rnMatch ctxt = wrapLocFstM (rnMatch' ctxt)
814 rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
815 rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
816 = do { -- Result type signatures are no longer supported
817 case maybe_rhs_sig of
819 Just ty -> addLocErr ty (resSigErr ctxt match)
822 -- Now the main event
823 -- note that there are no local ficity decls for matches
824 ; rnPatsAndThen_LocalRightwards ctxt pats $ \ pats' -> do
825 { (grhss', grhss_fvs) <- rnGRHSs ctxt grhss
827 ; return (Match pats' Nothing grhss', grhss_fvs) }}
828 -- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
831 resSigErr :: HsMatchContext Name -> Match RdrName -> HsType RdrName -> SDoc
832 resSigErr ctxt match ty
833 = vcat [ ptext (sLit "Illegal result type signature") <+> quotes (ppr ty)
834 , nest 2 $ ptext (sLit "Result signatures are no longer supported in pattern matches")
835 , pprMatchInCtxt ctxt match ]
839 %************************************************************************
841 \subsubsection{Guarded right-hand sides (GRHSs)}
843 %************************************************************************
846 rnGRHSs :: HsMatchContext Name -> GRHSs RdrName -> RnM (GRHSs Name, FreeVars)
848 rnGRHSs ctxt (GRHSs grhss binds)
849 = rnLocalBindsAndThen binds $ \ binds' -> do
850 (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
851 return (GRHSs grhss' binds', fvGRHSs)
853 rnGRHS :: HsMatchContext Name -> LGRHS RdrName -> RnM (LGRHS Name, FreeVars)
854 rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)
856 rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
857 rnGRHS' ctxt (GRHS guards rhs)
858 = do { pattern_guards_allowed <- doptM Opt_PatternGuards
859 ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $
862 ; unless (pattern_guards_allowed || is_standard_guard guards')
863 (addWarn (nonStdGuardErr guards'))
865 ; return (GRHS guards' rhs', fvs) }
867 -- Standard Haskell 1.4 guards are just a single boolean
868 -- expression, rather than a list of qualifiers as in the
870 is_standard_guard [] = True
871 is_standard_guard [L _ (ExprStmt _ _ _)] = True
872 is_standard_guard _ = False
875 %************************************************************************
877 \subsection{Error messages}
879 %************************************************************************
882 dupSigDeclErr :: [LSig RdrName] -> RnM ()
883 dupSigDeclErr sigs@(L loc sig : _)
885 vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
886 nest 2 (vcat (map ppr_sig sigs))]
888 what_it_is = hsSigDoc sig
889 ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
890 dupSigDeclErr [] = panic "dupSigDeclErr"
892 unknownSigErr :: LSig RdrName -> RnM ()
893 unknownSigErr (L loc sig)
895 sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
897 methodBindErr :: HsBindLR RdrName RdrName -> SDoc
899 = hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
902 bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
903 bindsInHsBootFile mbinds
904 = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
907 nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
908 nonStdGuardErr guards
909 = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
910 4 (interpp'SP guards)