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, renameSigsFVs,
19 #include "HsVersions.h"
23 import HsBinds ( eqHsSig, sigName, hsSigDoc )
27 import RnTypes ( rnHsSigType, rnHsType )
28 import RnExpr ( rnMatch, rnGRHSs, rnPat, checkPrecMatch )
29 import RnEnv ( bindLocatedLocalsRn, lookupBndrRn, lookupInstDeclBndr,
30 lookupSigOccRn, bindPatSigTyVars,
31 warnUnusedLocalBinds, mapFvRn, extendTyVarEnvFVRn,
33 import CmdLineOpts ( DynFlag(..) )
34 import Digraph ( stronglyConnComp, SCC(..) )
35 import Name ( Name, nameOccName, nameSrcLoc )
37 import RdrName ( RdrName, rdrNameOcc )
38 import BasicTypes ( RecFlag(..) )
39 import List ( partition )
41 import PrelNames ( isUnboundName )
44 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
45 -- place and can be used when complaining.
47 The code tree received by the function @rnBinds@ contains definitions
48 in where-clauses which are all apparently mutually recursive, but which may
49 not really depend upon each other. For example, in the top level program
54 the definitions of @a@ and @y@ do not depend on each other at all.
55 Unfortunately, the typechecker cannot always check such definitions.
56 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
57 definitions. In Proceedings of the International Symposium on Programming,
58 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
59 However, the typechecker usually can check definitions in which only the
60 strongly connected components have been collected into recursive bindings.
61 This is precisely what the function @rnBinds@ does.
63 ToDo: deal with case where a single monobinds binds the same variable
66 The vertag tag is a unique @Int@; the tags only need to be unique
67 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
68 (heavy monad machinery not needed).
74 %************************************************************************
76 %* naming conventions *
78 %************************************************************************
80 \subsection[name-conventions]{Name conventions}
82 The basic algorithm involves walking over the tree and returning a tuple
83 containing the new tree plus its free variables. Some functions, such
84 as those walking polymorphic bindings (HsBinds) and qualifier lists in
85 list comprehensions (@Quals@), return the variables bound in local
86 environments. These are then used to calculate the free variables of the
87 expression evaluated in these environments.
89 Conventions for variable names are as follows:
92 new code is given a prime to distinguish it from the old.
95 a set of variables defined in @Exp@ is written @dvExp@
98 a set of variables free in @Exp@ is written @fvExp@
101 %************************************************************************
103 %* analysing polymorphic bindings (HsBinds, Bind, MonoBinds) *
105 %************************************************************************
107 \subsubsection[dep-HsBinds]{Polymorphic bindings}
109 Non-recursive expressions are reconstructed without any changes at top
110 level, although their component expressions may have to be altered.
111 However, non-recursive expressions are currently not expected as
112 \Haskell{} programs, and this code should not be executed.
114 Monomorphic bindings contain information that is returned in a tuple
115 (a @FlatMonoBindsInfo@) containing:
119 a unique @Int@ that serves as the ``vertex tag'' for this binding.
122 the name of a function or the names in a pattern. These are a set
123 referred to as @dvLhs@, the defined variables of the left hand side.
126 the free variables of the body. These are referred to as @fvBody@.
129 the definition's actual code. This is referred to as just @code@.
132 The function @nonRecDvFv@ returns two sets of variables. The first is
133 the set of variables defined in the set of monomorphic bindings, while the
134 second is the set of free variables in those bindings.
136 The set of variables defined in a non-recursive binding is just the
137 union of all of them, as @union@ removes duplicates. However, the
138 free variables in each successive set of cumulative bindings is the
139 union of those in the previous set plus those of the newest binding after
140 the defined variables of the previous set have been removed.
142 @rnMethodBinds@ deals only with the declarations in class and
143 instance declarations. It expects only to see @FunMonoBind@s, and
144 it expects the global environment to contain bindings for the binders
145 (which are all class operations).
147 %************************************************************************
149 \subsubsection{ Top-level bindings}
151 %************************************************************************
153 @rnTopBinds@ assumes that the environment already
154 contains bindings for the binders of this particular binding.
157 rnTopBinds :: RdrNameHsBinds -> RnMS (RenamedHsBinds, FreeVars)
159 rnTopBinds EmptyBinds = returnRn (EmptyBinds, emptyFVs)
160 rnTopBinds (MonoBind bind sigs _) = rnTopMonoBinds bind sigs
161 -- The parser doesn't produce other forms
164 rnTopMonoBinds mbinds sigs
165 = mapRn lookupBndrRn binder_rdr_names `thenRn` \ binder_names ->
166 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
168 bndr_name_set = mkNameSet binder_names
170 renameSigsFVs (okBindSig bndr_name_set) sigs `thenRn` \ (siglist, sig_fvs) ->
172 ifOptRn Opt_WarnMissingSigs (
174 type_sig_vars = [n | Sig n _ _ <- siglist]
175 un_sigd_binders = nameSetToList (delListFromNameSet bndr_name_set type_sig_vars)
177 mapRn_ missingSigWarn un_sigd_binders
180 rn_mono_binds siglist mbinds `thenRn` \ (final_binds, bind_fvs) ->
181 returnRn (final_binds, bind_fvs `plusFV` sig_fvs)
183 binder_rdr_names = collectMonoBinders mbinds
186 %************************************************************************
190 %************************************************************************
192 \subsubsection{Nested binds}
196 \item collects up the binders for this declaration group,
197 \item checks that they form a set
198 \item extends the environment to bind them to new local names
199 \item calls @rnMonoBinds@ to do the real work
203 rnBinds :: RdrNameHsBinds
204 -> (RenamedHsBinds -> RnMS (result, FreeVars))
205 -> RnMS (result, FreeVars)
207 rnBinds EmptyBinds thing_inside = thing_inside EmptyBinds
208 rnBinds (MonoBind bind sigs _) thing_inside = rnMonoBinds bind sigs thing_inside
209 -- the parser doesn't produce other forms
212 rnMonoBinds :: RdrNameMonoBinds
214 -> (RenamedHsBinds -> RnMS (result, FreeVars))
215 -> RnMS (result, FreeVars)
217 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
218 = -- Extract all the binders in this group,
219 -- and extend current scope, inventing new names for the new binders
220 -- This also checks that the names form a set
221 bindLocatedLocalsRn doc mbinders_w_srclocs $ \ new_mbinders ->
222 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
224 binder_set = mkNameSet new_mbinders
226 -- Rename the signatures
227 renameSigsFVs (okBindSig binder_set) sigs `thenRn` \ (siglist, sig_fvs) ->
229 -- Report the fixity declarations in this group that
230 -- don't refer to any of the group's binders.
231 -- Then install the fixity declarations that do apply here
232 -- Notice that they scope over thing_inside too
234 fixity_sigs = [(name,sig) | FixSig sig@(FixitySig name _ _) <- siglist ]
236 extendFixityEnv fixity_sigs $
238 rn_mono_binds siglist mbinds `thenRn` \ (binds, bind_fvs) ->
240 -- Now do the "thing inside", and deal with the free-variable calculations
241 thing_inside binds `thenRn` \ (result,result_fvs) ->
243 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
244 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
246 warnUnusedLocalBinds unused_binders `thenRn_`
247 returnRn (result, delListFromNameSet all_fvs new_mbinders)
249 mbinders_w_srclocs = collectLocatedMonoBinders mbinds
250 doc = text "In the binding group for" <+> pp_bndrs mbinders_w_srclocs
251 pp_bndrs [(b,_)] = quotes (ppr b)
252 pp_bndrs bs = fsep (punctuate comma [ppr b | (b,_) <- bs])
256 %************************************************************************
258 \subsubsection{ MonoBinds -- the main work is done here}
260 %************************************************************************
262 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
263 It assumes that all variables bound in this group are already in scope.
264 This is done {\em either} by pass 3 (for the top-level bindings),
265 {\em or} by @rnMonoBinds@ (for the nested ones).
268 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
270 -> RnMS (RenamedHsBinds, -- Dependency analysed
271 FreeVars) -- Free variables
273 rn_mono_binds siglist mbinds
275 -- Rename the bindings, returning a MonoBindsInfo
276 -- which is a list of indivisible vertices so far as
277 -- the strongly-connected-components (SCC) analysis is concerned
278 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
280 -- Do the SCC analysis
282 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
283 scc_result = stronglyConnComp edges
284 final_binds = foldr (ThenBinds . reconstructCycle) EmptyBinds scc_result
286 -- Deal with bound and free-var calculation
287 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
289 returnRn (final_binds, rhs_fvs)
292 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
293 unique ``vertex tags'' on its output; minor plumbing required.
295 Sigh --- need to pass along the signatures for the group of bindings,
296 in case any of them \fbox{\ ???\ }
299 flattenMonoBinds :: [RenamedSig] -- Signatures
301 -> RnMS [FlatMonoBindsInfo]
303 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
305 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
306 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
307 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
308 returnRn (flat1 ++ flat2)
310 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
311 = pushSrcLocRn locn $
312 rnPat pat `thenRn` \ (pat', pat_fvs) ->
314 -- Find which things are bound in this group
316 names_bound_here = mkNameSet (collectPatBinders pat')
318 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
319 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
322 fvs `plusFV` pat_fvs,
323 PatMonoBind pat' grhss' locn,
327 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
328 = pushSrcLocRn locn $
329 lookupBndrRn name `thenRn` \ new_name ->
331 names_bound_here = unitNameSet new_name
333 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
334 mapFvRn (rnMatch (FunRhs name)) matches `thenRn` \ (new_matches, fvs) ->
335 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
337 [(unitNameSet new_name,
339 FunMonoBind new_name inf new_matches locn,
344 sigsForMe names_bound_here sigs
345 = foldlRn check [] (filter (sigForThisGroup names_bound_here) sigs)
347 check sigs sig = case filter (eqHsSig sig) sigs of
348 [] -> returnRn (sig:sigs)
349 other -> dupSigDeclErr sig `thenRn_`
354 @rnMethodBinds@ is used for the method bindings of a class and an instance
355 declaration. Like @rnMonoBinds@ but without dependency analysis.
357 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
358 That's crucial when dealing with an instance decl:
360 instance Foo (T a) where
363 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
364 and unless @op@ occurs we won't treat the type signature of @op@ in the class
365 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
366 in many ways the @op@ in an instance decl is just like an occurrence, not
370 rnMethodBinds :: Name -- Class name
371 -> [Name] -- Names for generic type variables
373 -> RnMS (RenamedMonoBinds, FreeVars)
375 rnMethodBinds cls gen_tyvars EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
377 rnMethodBinds cls gen_tyvars (AndMonoBinds mb1 mb2)
378 = rnMethodBinds cls gen_tyvars mb1 `thenRn` \ (mb1', fvs1) ->
379 rnMethodBinds cls gen_tyvars mb2 `thenRn` \ (mb2', fvs2) ->
380 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
382 rnMethodBinds cls gen_tyvars (FunMonoBind name inf matches locn)
383 = pushSrcLocRn locn $
385 lookupInstDeclBndr cls name `thenRn` \ sel_name ->
386 -- We use the selector name as the binder
388 mapFvRn rn_match matches `thenRn` \ (new_matches, fvs) ->
389 mapRn_ (checkPrecMatch inf sel_name) new_matches `thenRn_`
390 returnRn (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
392 -- Gruesome; bring into scope the correct members of the generic type variables
393 -- See comments in RnSource.rnSourceDecl(ClassDecl)
394 rn_match match@(Match (TypePatIn ty : _) _ _)
395 = extendTyVarEnvFVRn gen_tvs (rnMatch (FunRhs name) match)
397 tvs = map rdrNameOcc (extractHsTyRdrNames ty)
398 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
400 rn_match match = rnMatch (FunRhs name) match
403 -- Can't handle method pattern-bindings which bind multiple methods.
404 rnMethodBinds cls gen_tyvars mbind@(PatMonoBind other_pat _ locn)
405 = pushSrcLocRn locn $
406 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
410 %************************************************************************
412 \subsection[reconstruct-deps]{Reconstructing dependencies}
414 %************************************************************************
416 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
417 as the two cases are similar.
420 reconstructCycle :: SCC FlatMonoBindsInfo
423 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
424 = MonoBind binds sigs NonRecursive
426 reconstructCycle (CyclicSCC cycle)
427 = MonoBind this_gp_binds this_gp_sigs Recursive
429 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
430 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
433 %************************************************************************
435 \subsubsection{ Manipulating FlatMonoBindInfo}
437 %************************************************************************
439 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
440 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
441 a function binding, and has itself been dependency-analysed and
445 type FlatMonoBindsInfo
446 = (NameSet, -- Set of names defined in this vertex
447 NameSet, -- Set of names used in this vertex
449 [RenamedSig]) -- Signatures, if any, for this vertex
451 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
454 = [ (info, tag, dest_vertices (nameSetToList names_used))
455 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
458 -- An edge (v,v') indicates that v depends on v'
459 dest_vertices src_mentions = [ target_vertex
460 | ((names_defined, _, _, _), target_vertex) <- flat_info,
461 mentioned_name <- src_mentions,
462 mentioned_name `elemNameSet` names_defined
467 %************************************************************************
469 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
471 %************************************************************************
473 @renameSigs@ checks for:
475 \item more than one sig for one thing;
476 \item signatures given for things not bound here;
477 \item with suitably flaggery, that all top-level things have type signatures.
480 At the moment we don't gather free-var info from the types in
481 signatures. We'd only need this if we wanted to report unused tyvars.
484 renameSigsFVs ok_sig sigs
485 = renameSigs ok_sig sigs `thenRn` \ sigs' ->
486 returnRn (sigs', hsSigsFVs sigs')
488 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
492 renameSigs ok_sig [] = returnRn []
494 renameSigs ok_sig sigs
495 = -- Rename the signatures
496 mapRn renameSig sigs `thenRn` \ sigs' ->
498 -- Check for (a) duplicate signatures
499 -- (b) signatures for things not in this group
501 in_scope = filter is_in_scope sigs'
502 is_in_scope sig = case sigName sig of
503 Just n -> not (isUnboundName n)
505 (goods, bads) = partition ok_sig in_scope
507 mapRn_ unknownSigErr bads `thenRn_`
510 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
511 -- because this won't work for:
512 -- instance Foo T where
515 -- We'll just rename the INLINE prag to refer to whatever other 'op'
516 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
517 -- Doesn't seem worth much trouble to sort this.
519 renameSig :: Sig RdrName -> RnMS (Sig Name)
520 -- ClassOpSig is renamed elsewhere.
521 renameSig (Sig v ty src_loc)
522 = pushSrcLocRn src_loc $
523 lookupSigOccRn v `thenRn` \ new_v ->
524 rnHsSigType (quotes (ppr v)) ty `thenRn` \ new_ty ->
525 returnRn (Sig new_v new_ty src_loc)
527 renameSig (SpecInstSig ty src_loc)
528 = pushSrcLocRn src_loc $
529 rnHsType (text "A SPECIALISE instance pragma") ty `thenRn` \ new_ty ->
530 returnRn (SpecInstSig new_ty src_loc)
532 renameSig (SpecSig v ty src_loc)
533 = pushSrcLocRn src_loc $
534 lookupSigOccRn v `thenRn` \ new_v ->
535 rnHsSigType (quotes (ppr v)) ty `thenRn` \ new_ty ->
536 returnRn (SpecSig new_v new_ty src_loc)
538 renameSig (FixSig (FixitySig v fix src_loc))
539 = pushSrcLocRn src_loc $
540 lookupSigOccRn v `thenRn` \ new_v ->
541 returnRn (FixSig (FixitySig new_v fix src_loc))
543 renameSig (InlineSig b v p src_loc)
544 = pushSrcLocRn src_loc $
545 lookupSigOccRn v `thenRn` \ new_v ->
546 returnRn (InlineSig b new_v p src_loc)
550 %************************************************************************
552 \subsection{Error messages}
554 %************************************************************************
559 addErrRn (sep [ptext SLIT("Duplicate") <+> what_it_is <> colon,
562 (what_it_is, loc) = hsSigDoc sig
566 addErrRn (sep [ptext SLIT("Misplaced") <+> what_it_is <> colon,
569 (what_it_is, loc) = hsSigDoc sig
572 = pushSrcLocRn (nameSrcLoc var) $
573 addWarnRn (sep [ptext SLIT("Definition but no type signature for"), quotes (ppr var)])
576 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))