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 rnTopMonoBinds, rnMonoBinds, rnMethodBinds,
14 renameSigs, renameSigsFVs, unknownSigErr
17 #include "HsVersions.h"
21 import HsBinds ( eqHsSig, sigName, hsSigDoc )
25 import RnTypes ( rnHsSigType, rnHsType )
26 import RnExpr ( rnMatch, rnGRHSs, rnPat, checkPrecMatch )
27 import RnEnv ( bindLocatedLocalsRn, lookupBndrRn, lookupInstDeclBndr,
28 lookupSigOccRn, bindPatSigTyVars, bindLocalFixities,
29 warnUnusedLocalBinds, mapFvRn, extendTyVarEnvFVRn,
31 import CmdLineOpts ( DynFlag(..) )
32 import Digraph ( stronglyConnComp, SCC(..) )
33 import Name ( Name, nameOccName, nameSrcLoc )
35 import RdrName ( RdrName, rdrNameOcc )
36 import BasicTypes ( RecFlag(..), FixitySig(..) )
37 import List ( partition )
39 import PrelNames ( isUnboundName )
42 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
43 -- place and can be used when complaining.
45 The code tree received by the function @rnBinds@ contains definitions
46 in where-clauses which are all apparently mutually recursive, but which may
47 not really depend upon each other. For example, in the top level program
52 the definitions of @a@ and @y@ do not depend on each other at all.
53 Unfortunately, the typechecker cannot always check such definitions.
54 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
55 definitions. In Proceedings of the International Symposium on Programming,
56 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
57 However, the typechecker usually can check definitions in which only the
58 strongly connected components have been collected into recursive bindings.
59 This is precisely what the function @rnBinds@ does.
61 ToDo: deal with case where a single monobinds binds the same variable
64 The vertag tag is a unique @Int@; the tags only need to be unique
65 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
66 (heavy monad machinery not needed).
72 %************************************************************************
74 %* naming conventions *
76 %************************************************************************
78 \subsection[name-conventions]{Name conventions}
80 The basic algorithm involves walking over the tree and returning a tuple
81 containing the new tree plus its free variables. Some functions, such
82 as those walking polymorphic bindings (HsBinds) and qualifier lists in
83 list comprehensions (@Quals@), return the variables bound in local
84 environments. These are then used to calculate the free variables of the
85 expression evaluated in these environments.
87 Conventions for variable names are as follows:
90 new code is given a prime to distinguish it from the old.
93 a set of variables defined in @Exp@ is written @dvExp@
96 a set of variables free in @Exp@ is written @fvExp@
99 %************************************************************************
101 %* analysing polymorphic bindings (HsBinds, Bind, MonoBinds) *
103 %************************************************************************
105 \subsubsection[dep-HsBinds]{Polymorphic bindings}
107 Non-recursive expressions are reconstructed without any changes at top
108 level, although their component expressions may have to be altered.
109 However, non-recursive expressions are currently not expected as
110 \Haskell{} programs, and this code should not be executed.
112 Monomorphic bindings contain information that is returned in a tuple
113 (a @FlatMonoBindsInfo@) containing:
117 a unique @Int@ that serves as the ``vertex tag'' for this binding.
120 the name of a function or the names in a pattern. These are a set
121 referred to as @dvLhs@, the defined variables of the left hand side.
124 the free variables of the body. These are referred to as @fvBody@.
127 the definition's actual code. This is referred to as just @code@.
130 The function @nonRecDvFv@ returns two sets of variables. The first is
131 the set of variables defined in the set of monomorphic bindings, while the
132 second is the set of free variables in those bindings.
134 The set of variables defined in a non-recursive binding is just the
135 union of all of them, as @union@ removes duplicates. However, the
136 free variables in each successive set of cumulative bindings is the
137 union of those in the previous set plus those of the newest binding after
138 the defined variables of the previous set have been removed.
140 @rnMethodBinds@ deals only with the declarations in class and
141 instance declarations. It expects only to see @FunMonoBind@s, and
142 it expects the global environment to contain bindings for the binders
143 (which are all class operations).
145 %************************************************************************
147 \subsubsection{ Top-level bindings}
149 %************************************************************************
151 @rnTopMonoBinds@ assumes that the environment already
152 contains bindings for the binders of this particular binding.
155 rnTopMonoBinds mbinds sigs
156 = mappM lookupBndrRn binder_rdr_names `thenM` \ binder_names ->
157 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
159 bndr_name_set = mkNameSet binder_names
161 renameSigsFVs (okBindSig bndr_name_set) sigs `thenM` \ (siglist, sig_fvs) ->
163 -- Warn about missing signatures, but not in interface mode
164 -- (This is important when renaming bindings from 'deriving' clauses.)
165 getModeRn `thenM` \ mode ->
166 doptM Opt_WarnMissingSigs `thenM` \ warn_missing_sigs ->
167 (if not (isInterfaceMode mode && warn_missing_sigs) then
169 type_sig_vars = [n | Sig n _ _ <- siglist]
170 un_sigd_binders = nameSetToList (delListFromNameSet bndr_name_set type_sig_vars)
172 mappM_ missingSigWarn un_sigd_binders
177 rn_mono_binds siglist mbinds `thenM` \ (final_binds, bind_fvs) ->
178 returnM (final_binds, bind_fvs `plusFV` sig_fvs)
180 binder_rdr_names = collectMonoBinders mbinds
183 %************************************************************************
187 %************************************************************************
189 \subsubsection{Nested binds}
193 \item collects up the binders for this declaration group,
194 \item checks that they form a set
195 \item extends the environment to bind them to new local names
196 \item calls @rnMonoBinds@ to do the real work
200 rnMonoBinds :: RdrNameMonoBinds
202 -> (RenamedHsBinds -> RnM (result, FreeVars))
203 -> RnM (result, FreeVars)
205 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
206 = -- Extract all the binders in this group,
207 -- and extend current scope, inventing new names for the new binders
208 -- This also checks that the names form a set
209 bindLocatedLocalsRn doc mbinders_w_srclocs $ \ new_mbinders ->
210 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
212 binder_set = mkNameSet new_mbinders
214 -- Rename the signatures
215 renameSigsFVs (okBindSig binder_set) sigs `thenM` \ (siglist, sig_fvs) ->
217 -- Report the fixity declarations in this group that
218 -- don't refer to any of the group's binders.
219 -- Then install the fixity declarations that do apply here
220 -- Notice that they scope over thing_inside too
221 bindLocalFixities [sig | FixSig sig <- siglist ] $
223 rn_mono_binds siglist mbinds `thenM` \ (binds, bind_fvs) ->
225 -- Now do the "thing inside", and deal with the free-variable calculations
226 thing_inside binds `thenM` \ (result,result_fvs) ->
228 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
229 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
231 warnUnusedLocalBinds unused_binders `thenM_`
232 returnM (result, delListFromNameSet all_fvs new_mbinders)
234 mbinders_w_srclocs = collectLocatedMonoBinders mbinds
235 doc = text "In the binding group for" <+> pp_bndrs mbinders_w_srclocs
236 pp_bndrs [(b,_)] = quotes (ppr b)
237 pp_bndrs bs = fsep (punctuate comma [ppr b | (b,_) <- bs])
241 %************************************************************************
243 \subsubsection{ MonoBinds -- the main work is done here}
245 %************************************************************************
247 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
248 It assumes that all variables bound in this group are already in scope.
249 This is done {\em either} by pass 3 (for the top-level bindings),
250 {\em or} by @rnMonoBinds@ (for the nested ones).
253 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
255 -> RnM (RenamedHsBinds, -- Dependency analysed
256 FreeVars) -- Free variables
258 rn_mono_binds siglist mbinds
260 -- Rename the bindings, returning a MonoBindsInfo
261 -- which is a list of indivisible vertices so far as
262 -- the strongly-connected-components (SCC) analysis is concerned
263 flattenMonoBinds siglist mbinds `thenM` \ mbinds_info ->
265 -- Do the SCC analysis
267 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
268 scc_result = stronglyConnComp edges
269 final_binds = foldr (ThenBinds . reconstructCycle) EmptyBinds scc_result
271 -- Deal with bound and free-var calculation
272 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
274 returnM (final_binds, rhs_fvs)
277 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
278 unique ``vertex tags'' on its output; minor plumbing required.
280 Sigh --- need to pass along the signatures for the group of bindings,
281 in case any of them \fbox{\ ???\ }
284 flattenMonoBinds :: [RenamedSig] -- Signatures
286 -> RnM [FlatMonoBindsInfo]
288 flattenMonoBinds sigs EmptyMonoBinds = returnM []
290 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
291 = flattenMonoBinds sigs bs1 `thenM` \ flat1 ->
292 flattenMonoBinds sigs bs2 `thenM` \ flat2 ->
293 returnM (flat1 ++ flat2)
295 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
297 rnPat pat `thenM` \ (pat', pat_fvs) ->
299 -- Find which things are bound in this group
301 names_bound_here = mkNameSet (collectPatBinders pat')
303 sigsForMe names_bound_here sigs `thenM` \ sigs_for_me ->
304 rnGRHSs grhss `thenM` \ (grhss', fvs) ->
307 fvs `plusFV` pat_fvs,
308 PatMonoBind pat' grhss' locn,
312 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
314 lookupBndrRn name `thenM` \ new_name ->
316 names_bound_here = unitNameSet new_name
318 sigsForMe names_bound_here sigs `thenM` \ sigs_for_me ->
319 mapFvRn (rnMatch (FunRhs name)) matches `thenM` \ (new_matches, fvs) ->
320 mappM_ (checkPrecMatch inf new_name) new_matches `thenM_`
322 [(unitNameSet new_name,
324 FunMonoBind new_name inf new_matches locn,
329 sigsForMe names_bound_here sigs
330 = foldlM check [] (filter (sigForThisGroup names_bound_here) sigs)
332 check sigs sig = case filter (eqHsSig sig) sigs of
333 [] -> returnM (sig:sigs)
334 other -> dupSigDeclErr sig `thenM_`
339 @rnMethodBinds@ is used for the method bindings of a class and an instance
340 declaration. Like @rnMonoBinds@ but without dependency analysis.
342 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
343 That's crucial when dealing with an instance decl:
345 instance Foo (T a) where
348 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
349 and unless @op@ occurs we won't treat the type signature of @op@ in the class
350 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
351 in many ways the @op@ in an instance decl is just like an occurrence, not
355 rnMethodBinds :: Name -- Class name
356 -> [Name] -- Names for generic type variables
358 -> RnM (RenamedMonoBinds, FreeVars)
360 rnMethodBinds cls gen_tyvars EmptyMonoBinds = returnM (EmptyMonoBinds, emptyFVs)
362 rnMethodBinds cls gen_tyvars (AndMonoBinds mb1 mb2)
363 = rnMethodBinds cls gen_tyvars mb1 `thenM` \ (mb1', fvs1) ->
364 rnMethodBinds cls gen_tyvars mb2 `thenM` \ (mb2', fvs2) ->
365 returnM (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
367 rnMethodBinds cls gen_tyvars (FunMonoBind name inf matches locn)
370 lookupInstDeclBndr cls name `thenM` \ sel_name ->
371 -- We use the selector name as the binder
373 mapFvRn rn_match matches `thenM` \ (new_matches, fvs) ->
374 mappM_ (checkPrecMatch inf sel_name) new_matches `thenM_`
375 returnM (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
377 -- Gruesome; bring into scope the correct members of the generic type variables
378 -- See comments in RnSource.rnSourceDecl(ClassDecl)
379 rn_match match@(Match (TypePat ty : _) _ _)
380 = extendTyVarEnvFVRn gen_tvs (rnMatch (FunRhs name) match)
382 tvs = map rdrNameOcc (extractHsTyRdrNames ty)
383 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
385 rn_match match = rnMatch (FunRhs name) match
388 -- Can't handle method pattern-bindings which bind multiple methods.
389 rnMethodBinds cls gen_tyvars mbind@(PatMonoBind other_pat _ locn)
390 = addSrcLoc locn (addErr (methodBindErr mbind)) `thenM_`
391 returnM (EmptyMonoBinds, emptyFVs)
395 %************************************************************************
397 \subsection[reconstruct-deps]{Reconstructing dependencies}
399 %************************************************************************
401 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
402 as the two cases are similar.
405 reconstructCycle :: SCC FlatMonoBindsInfo
408 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
409 = MonoBind binds sigs NonRecursive
411 reconstructCycle (CyclicSCC cycle)
412 = MonoBind this_gp_binds this_gp_sigs Recursive
414 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
415 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
418 %************************************************************************
420 \subsubsection{ Manipulating FlatMonoBindInfo}
422 %************************************************************************
424 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
425 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
426 a function binding, and has itself been dependency-analysed and
430 type FlatMonoBindsInfo
431 = (NameSet, -- Set of names defined in this vertex
432 NameSet, -- Set of names used in this vertex
434 [RenamedSig]) -- Signatures, if any, for this vertex
436 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
439 = [ (info, tag, dest_vertices (nameSetToList names_used))
440 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
443 -- An edge (v,v') indicates that v depends on v'
444 dest_vertices src_mentions = [ target_vertex
445 | ((names_defined, _, _, _), target_vertex) <- flat_info,
446 mentioned_name <- src_mentions,
447 mentioned_name `elemNameSet` names_defined
452 %************************************************************************
454 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
456 %************************************************************************
458 @renameSigs@ checks for:
460 \item more than one sig for one thing;
461 \item signatures given for things not bound here;
462 \item with suitably flaggery, that all top-level things have type signatures.
465 At the moment we don't gather free-var info from the types in
466 signatures. We'd only need this if we wanted to report unused tyvars.
469 renameSigsFVs ok_sig sigs
470 = renameSigs ok_sig sigs `thenM` \ sigs' ->
471 returnM (sigs', hsSigsFVs sigs')
473 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
477 renameSigs ok_sig [] = returnM []
479 renameSigs ok_sig sigs
480 = -- Rename the signatures
481 mappM renameSig sigs `thenM` \ sigs' ->
483 -- Check for (a) duplicate signatures
484 -- (b) signatures for things not in this group
486 in_scope = filter is_in_scope sigs'
487 is_in_scope sig = case sigName sig of
488 Just n -> not (isUnboundName n)
490 (goods, bads) = partition ok_sig in_scope
492 mappM_ unknownSigErr bads `thenM_`
495 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
496 -- because this won't work for:
497 -- instance Foo T where
500 -- We'll just rename the INLINE prag to refer to whatever other 'op'
501 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
502 -- Doesn't seem worth much trouble to sort this.
504 renameSig :: Sig RdrName -> RnM (Sig Name)
505 -- ClassOpSig is renamed elsewhere.
506 renameSig (Sig v ty src_loc)
507 = addSrcLoc src_loc $
508 lookupSigOccRn v `thenM` \ new_v ->
509 rnHsSigType (quotes (ppr v)) ty `thenM` \ new_ty ->
510 returnM (Sig new_v new_ty src_loc)
512 renameSig (SpecInstSig ty src_loc)
513 = addSrcLoc src_loc $
514 rnHsType (text "A SPECIALISE instance pragma") ty `thenM` \ new_ty ->
515 returnM (SpecInstSig new_ty src_loc)
517 renameSig (SpecSig v ty src_loc)
518 = addSrcLoc src_loc $
519 lookupSigOccRn v `thenM` \ new_v ->
520 rnHsSigType (quotes (ppr v)) ty `thenM` \ new_ty ->
521 returnM (SpecSig new_v new_ty src_loc)
523 renameSig (FixSig (FixitySig v fix src_loc))
524 = addSrcLoc src_loc $
525 lookupSigOccRn v `thenM` \ new_v ->
526 returnM (FixSig (FixitySig new_v fix src_loc))
528 renameSig (InlineSig b v p src_loc)
529 = addSrcLoc src_loc $
530 lookupSigOccRn v `thenM` \ new_v ->
531 returnM (InlineSig b new_v p src_loc)
535 %************************************************************************
537 \subsection{Error messages}
539 %************************************************************************
544 addErr (sep [ptext SLIT("Duplicate") <+> what_it_is <> colon,
547 (what_it_is, loc) = hsSigDoc sig
551 addErr (sep [ptext SLIT("Misplaced") <+> what_it_is <> colon,
554 (what_it_is, loc) = hsSigDoc sig
557 = addSrcLoc (nameSrcLoc var) $
558 addWarn (sep [ptext SLIT("Definition but no type signature for"), quotes (ppr var)])
561 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))