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).
13 rnTopBinds, rnTopMonoBinds,
14 rnMethodBinds, renameSigs,
19 #include "HsVersions.h"
21 import {-# SOURCE #-} RnSource ( rnHsSigType )
24 import HsBinds ( eqHsSig, sigName, hsSigDoc )
28 import RnExpr ( rnMatch, rnGRHSs, rnPat, checkPrecMatch )
29 import RnEnv ( bindLocatedLocalsRn, lookupBndrRn,
30 lookupGlobalOccRn, lookupSigOccRn,
31 warnUnusedLocalBinds, mapFvRn, extendTyVarEnvFVRn,
32 FreeVars, emptyFVs, plusFV, plusFVs, unitFV, addOneFV
34 import CmdLineOpts ( DynFlag(..) )
35 import Digraph ( stronglyConnComp, SCC(..) )
36 import Name ( OccName, Name, nameOccName )
38 import RdrName ( RdrName, rdrNameOcc )
39 import BasicTypes ( RecFlag(..) )
40 import List ( partition )
42 import PrelNames ( isUnboundName )
45 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
46 -- place and can be used when complaining.
48 The code tree received by the function @rnBinds@ contains definitions
49 in where-clauses which are all apparently mutually recursive, but which may
50 not really depend upon each other. For example, in the top level program
55 the definitions of @a@ and @y@ do not depend on each other at all.
56 Unfortunately, the typechecker cannot always check such definitions.
57 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
58 definitions. In Proceedings of the International Symposium on Programming,
59 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
60 However, the typechecker usually can check definitions in which only the
61 strongly connected components have been collected into recursive bindings.
62 This is precisely what the function @rnBinds@ does.
64 ToDo: deal with case where a single monobinds binds the same variable
67 The vertag tag is a unique @Int@; the tags only need to be unique
68 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
69 (heavy monad machinery not needed).
73 type Cycle = [VertexTag]
74 type Edge = (VertexTag, VertexTag)
77 %************************************************************************
79 %* naming conventions *
81 %************************************************************************
83 \subsection[name-conventions]{Name conventions}
85 The basic algorithm involves walking over the tree and returning a tuple
86 containing the new tree plus its free variables. Some functions, such
87 as those walking polymorphic bindings (HsBinds) and qualifier lists in
88 list comprehensions (@Quals@), return the variables bound in local
89 environments. These are then used to calculate the free variables of the
90 expression evaluated in these environments.
92 Conventions for variable names are as follows:
95 new code is given a prime to distinguish it from the old.
98 a set of variables defined in @Exp@ is written @dvExp@
101 a set of variables free in @Exp@ is written @fvExp@
104 %************************************************************************
106 %* analysing polymorphic bindings (HsBinds, Bind, MonoBinds) *
108 %************************************************************************
110 \subsubsection[dep-HsBinds]{Polymorphic bindings}
112 Non-recursive expressions are reconstructed without any changes at top
113 level, although their component expressions may have to be altered.
114 However, non-recursive expressions are currently not expected as
115 \Haskell{} programs, and this code should not be executed.
117 Monomorphic bindings contain information that is returned in a tuple
118 (a @FlatMonoBindsInfo@) containing:
122 a unique @Int@ that serves as the ``vertex tag'' for this binding.
125 the name of a function or the names in a pattern. These are a set
126 referred to as @dvLhs@, the defined variables of the left hand side.
129 the free variables of the body. These are referred to as @fvBody@.
132 the definition's actual code. This is referred to as just @code@.
135 The function @nonRecDvFv@ returns two sets of variables. The first is
136 the set of variables defined in the set of monomorphic bindings, while the
137 second is the set of free variables in those bindings.
139 The set of variables defined in a non-recursive binding is just the
140 union of all of them, as @union@ removes duplicates. However, the
141 free variables in each successive set of cumulative bindings is the
142 union of those in the previous set plus those of the newest binding after
143 the defined variables of the previous set have been removed.
145 @rnMethodBinds@ deals only with the declarations in class and
146 instance declarations. It expects only to see @FunMonoBind@s, and
147 it expects the global environment to contain bindings for the binders
148 (which are all class operations).
150 %************************************************************************
152 \subsubsection{ Top-level bindings}
154 %************************************************************************
156 @rnTopBinds@ assumes that the environment already
157 contains bindings for the binders of this particular binding.
160 rnTopBinds :: RdrNameHsBinds -> RnMS (RenamedHsBinds, FreeVars)
162 rnTopBinds EmptyBinds = returnRn (EmptyBinds, emptyFVs)
163 rnTopBinds (MonoBind bind sigs _) = rnTopMonoBinds bind sigs
164 -- The parser doesn't produce other forms
167 rnTopMonoBinds mbinds sigs
168 = mapRn lookupBndrRn binder_rdr_names `thenRn` \ binder_names ->
170 bndr_name_set = mkNameSet binder_names
172 renameSigs (okBindSig bndr_name_set) sigs `thenRn` \ (siglist, sig_fvs) ->
173 doptRn Opt_WarnMissingSigs `thenRn` \ warnMissing ->
175 type_sig_vars = [n | Sig n _ _ <- siglist]
176 un_sigd_binders | warnMissing = nameSetToList (delListFromNameSet
177 bndr_name_set type_sig_vars)
180 mapRn_ (addWarnRn.missingSigWarn) un_sigd_binders `thenRn_`
182 rn_mono_binds siglist mbinds `thenRn` \ (final_binds, bind_fvs) ->
183 returnRn (final_binds, bind_fvs `plusFV` sig_fvs)
185 binder_rdr_names = collectMonoBinders mbinds
188 %************************************************************************
192 %************************************************************************
194 \subsubsection{Nested binds}
198 \item collects up the binders for this declaration group,
199 \item checks that they form a set
200 \item extends the environment to bind them to new local names
201 \item calls @rnMonoBinds@ to do the real work
205 rnBinds :: RdrNameHsBinds
206 -> (RenamedHsBinds -> RnMS (result, FreeVars))
207 -> RnMS (result, FreeVars)
209 rnBinds EmptyBinds thing_inside = thing_inside EmptyBinds
210 rnBinds (MonoBind bind sigs _) thing_inside = rnMonoBinds bind sigs thing_inside
211 -- the parser doesn't produce other forms
214 rnMonoBinds :: RdrNameMonoBinds
216 -> (RenamedHsBinds -> RnMS (result, FreeVars))
217 -> RnMS (result, FreeVars)
219 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
220 = -- Extract all the binders in this group,
221 -- and extend current scope, inventing new names for the new binders
222 -- This also checks that the names form a set
223 bindLocatedLocalsRn (text "a binding group")
224 mbinders_w_srclocs $ \ new_mbinders ->
226 binder_set = mkNameSet new_mbinders
228 -- Rename the signatures
229 renameSigs (okBindSig binder_set) sigs `thenRn` \ (siglist, sig_fvs) ->
231 -- Report the fixity declarations in this group that
232 -- don't refer to any of the group's binders.
233 -- Then install the fixity declarations that do apply here
234 -- Notice that they scope over thing_inside too
236 fixity_sigs = [(name,sig) | FixSig sig@(FixitySig name _ _) <- siglist ]
238 extendFixityEnv fixity_sigs $
240 rn_mono_binds siglist mbinds `thenRn` \ (binds, bind_fvs) ->
242 -- Now do the "thing inside", and deal with the free-variable calculations
243 thing_inside binds `thenRn` \ (result,result_fvs) ->
245 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
246 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
248 warnUnusedLocalBinds unused_binders `thenRn_`
249 returnRn (result, delListFromNameSet all_fvs new_mbinders)
251 mbinders_w_srclocs = collectLocatedMonoBinders mbinds
255 %************************************************************************
257 \subsubsection{ MonoBinds -- the main work is done here}
259 %************************************************************************
261 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
262 It assumes that all variables bound in this group are already in scope.
263 This is done {\em either} by pass 3 (for the top-level bindings),
264 {\em or} by @rnMonoBinds@ (for the nested ones).
267 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
269 -> RnMS (RenamedHsBinds, --
270 FreeVars) -- Free variables
272 rn_mono_binds siglist mbinds
274 -- Rename the bindings, returning a MonoBindsInfo
275 -- which is a list of indivisible vertices so far as
276 -- the strongly-connected-components (SCC) analysis is concerned
277 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
279 -- Do the SCC analysis
281 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
282 scc_result = stronglyConnComp edges
283 final_binds = foldr (ThenBinds . reconstructCycle) EmptyBinds scc_result
285 -- Deal with bound and free-var calculation
286 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
288 returnRn (final_binds, rhs_fvs)
291 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
292 unique ``vertex tags'' on its output; minor plumbing required.
294 Sigh --- need to pass along the signatures for the group of bindings,
295 in case any of them \fbox{\ ???\ }
298 flattenMonoBinds :: [RenamedSig] -- Signatures
300 -> RnMS [FlatMonoBindsInfo]
302 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
304 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
305 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
306 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
307 returnRn (flat1 ++ flat2)
309 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
310 = pushSrcLocRn locn $
311 rnPat pat `thenRn` \ (pat', pat_fvs) ->
313 -- Find which things are bound in this group
315 names_bound_here = mkNameSet (collectPatBinders pat')
317 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
318 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
321 fvs `plusFV` pat_fvs,
322 PatMonoBind pat' grhss' locn,
326 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
327 = pushSrcLocRn locn $
328 lookupBndrRn name `thenRn` \ new_name ->
330 names_bound_here = unitNameSet new_name
332 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
333 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
334 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
336 [(unitNameSet new_name,
338 FunMonoBind new_name inf new_matches locn,
343 sigsForMe names_bound_here sigs
344 = foldlRn check [] (filter (sigForThisGroup names_bound_here) sigs)
346 check sigs sig = case filter (eqHsSig sig) sigs of
347 [] -> returnRn (sig:sigs)
348 other -> dupSigDeclErr sig `thenRn_`
353 @rnMethodBinds@ is used for the method bindings of a class and an instance
354 declaration. Like @rnMonoBinds@ but without dependency analysis.
356 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
357 That's crucial when dealing with an instance decl:
359 instance Foo (T a) where
362 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
363 and unless @op@ occurs we won't treat the type signature of @op@ in the class
364 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
365 in many ways the @op@ in an instance decl is just like an occurrence, not
369 rnMethodBinds :: [Name] -- Names for generic type variables
371 -> RnMS (RenamedMonoBinds, FreeVars)
373 rnMethodBinds gen_tyvars EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
375 rnMethodBinds gen_tyvars (AndMonoBinds mb1 mb2)
376 = rnMethodBinds gen_tyvars mb1 `thenRn` \ (mb1', fvs1) ->
377 rnMethodBinds gen_tyvars mb2 `thenRn` \ (mb2', fvs2) ->
378 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
380 rnMethodBinds gen_tyvars (FunMonoBind name inf matches locn)
381 = pushSrcLocRn locn $
383 lookupGlobalOccRn name `thenRn` \ sel_name ->
384 -- We use the selector name as the binder
386 mapFvRn rn_match matches `thenRn` \ (new_matches, fvs) ->
387 mapRn_ (checkPrecMatch inf sel_name) new_matches `thenRn_`
388 returnRn (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
390 -- Gruesome; bring into scope the correct members of the generic type variables
391 -- See comments in RnSource.rnDecl(ClassDecl)
392 rn_match match@(Match _ (TypePatIn ty : _) _ _)
393 = extendTyVarEnvFVRn gen_tvs (rnMatch match)
395 tvs = map rdrNameOcc (extractHsTyRdrNames ty)
396 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
398 rn_match match = rnMatch match
401 -- Can't handle method pattern-bindings which bind multiple methods.
402 rnMethodBinds gen_tyvars mbind@(PatMonoBind other_pat _ locn)
403 = pushSrcLocRn locn $
404 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
408 %************************************************************************
410 \subsection[reconstruct-deps]{Reconstructing dependencies}
412 %************************************************************************
414 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
415 as the two cases are similar.
418 reconstructCycle :: SCC FlatMonoBindsInfo
421 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
422 = MonoBind binds sigs NonRecursive
424 reconstructCycle (CyclicSCC cycle)
425 = MonoBind this_gp_binds this_gp_sigs Recursive
427 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
428 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
431 %************************************************************************
433 \subsubsection{ Manipulating FlatMonoBindInfo}
435 %************************************************************************
437 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
438 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
439 a function binding, and has itself been dependency-analysed and
443 type FlatMonoBindsInfo
444 = (NameSet, -- Set of names defined in this vertex
445 NameSet, -- Set of names used in this vertex
447 [RenamedSig]) -- Signatures, if any, for this vertex
449 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
452 = [ (info, tag, dest_vertices (nameSetToList names_used))
453 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
456 -- An edge (v,v') indicates that v depends on v'
457 dest_vertices src_mentions = [ target_vertex
458 | ((names_defined, _, _, _), target_vertex) <- flat_info,
459 mentioned_name <- src_mentions,
460 mentioned_name `elemNameSet` names_defined
465 %************************************************************************
467 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
469 %************************************************************************
471 @renameSigs@ checks for:
473 \item more than one sig for one thing;
474 \item signatures given for things not bound here;
475 \item with suitably flaggery, that all top-level things have type signatures.
478 At the moment we don't gather free-var info from the types in
479 signatures. We'd only need this if we wanted to report unused tyvars.
482 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
484 -> RnMS ([RenamedSig], FreeVars)
486 renameSigs ok_sig [] = returnRn ([], emptyFVs) -- Common shortcut
488 renameSigs ok_sig sigs
489 = -- Rename the signatures
490 mapFvRn renameSig sigs `thenRn` \ (sigs', fvs) ->
492 -- Check for (a) duplicate signatures
493 -- (b) signatures for things not in this group
495 in_scope = filter is_in_scope sigs'
496 is_in_scope sig = case sigName sig of
497 Just n -> not (isUnboundName n)
499 (goods, bads) = partition ok_sig in_scope
501 mapRn_ unknownSigErr bads `thenRn_`
502 returnRn (goods, fvs)
504 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
505 -- because this won't work for:
506 -- instance Foo T where
509 -- We'll just rename the INLINE prag to refer to whatever other 'op'
510 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
511 -- Doesn't seem worth much trouble to sort this.
513 renameSig :: Sig RdrName -> RnMS (Sig Name, FreeVars)
514 -- ClassOpSig is renamed elsewhere.
515 renameSig (Sig v ty src_loc)
516 = pushSrcLocRn src_loc $
517 lookupSigOccRn v `thenRn` \ new_v ->
518 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
519 returnRn (Sig new_v new_ty src_loc, fvs `addOneFV` new_v)
521 renameSig (SpecInstSig ty src_loc)
522 = pushSrcLocRn src_loc $
523 rnHsSigType (text "A SPECIALISE instance pragma") ty `thenRn` \ (new_ty, fvs) ->
524 returnRn (SpecInstSig new_ty src_loc, fvs)
526 renameSig (SpecSig v ty src_loc)
527 = pushSrcLocRn src_loc $
528 lookupSigOccRn v `thenRn` \ new_v ->
529 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
530 returnRn (SpecSig new_v new_ty src_loc, fvs `addOneFV` new_v)
532 renameSig (FixSig (FixitySig v fix src_loc))
533 = pushSrcLocRn src_loc $
534 lookupSigOccRn v `thenRn` \ new_v ->
535 returnRn (FixSig (FixitySig new_v fix src_loc), unitFV new_v)
537 renameSig (InlineSig v p src_loc)
538 = pushSrcLocRn src_loc $
539 lookupSigOccRn v `thenRn` \ new_v ->
540 returnRn (InlineSig new_v p src_loc, unitFV new_v)
542 renameSig (NoInlineSig v p src_loc)
543 = pushSrcLocRn src_loc $
544 lookupSigOccRn v `thenRn` \ new_v ->
545 returnRn (NoInlineSig new_v p src_loc, unitFV new_v)
549 renameIE :: (RdrName -> RnMS Name) -> IE RdrName -> RnMS (IE Name, FreeVars)
550 renameIE lookup_occ_nm (IEVar v)
551 = lookup_occ_nm v `thenRn` \ new_v ->
552 returnRn (IEVar new_v, unitFV new_v)
554 renameIE lookup_occ_nm (IEThingAbs v)
555 = lookup_occ_nm v `thenRn` \ new_v ->
556 returnRn (IEThingAbs new_v, unitFV new_v)
558 renameIE lookup_occ_nm (IEThingAll v)
559 = lookup_occ_nm v `thenRn` \ new_v ->
560 returnRn (IEThingAll new_v, unitFV new_v)
562 renameIE lookup_occ_nm (IEThingWith v vs)
563 = lookup_occ_nm v `thenRn` \ new_v ->
564 mapRn lookup_occ_nm vs `thenRn` \ new_vs ->
565 returnRn (IEThingWith new_v new_vs, plusFVs [ unitFV x | x <- new_v:new_vs ])
567 renameIE lookup_occ_nm (IEModuleContents m)
568 = returnRn (IEModuleContents m, emptyFVs)
572 %************************************************************************
574 \subsection{Error messages}
576 %************************************************************************
581 addErrRn (sep [ptext SLIT("Duplicate") <+> ptext what_it_is <> colon,
584 (what_it_is, loc) = hsSigDoc sig
588 addErrRn (sep [ptext SLIT("Misplaced") <+> ptext what_it_is <> colon,
591 (what_it_is, loc) = hsSigDoc sig
594 = sep [ptext SLIT("definition but no type signature for"), quotes (ppr var)]
597 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))