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 -- No need to extend the environment; that has been done already
159 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
160 -- Hmm; by analogy with Ids, this doesn't look right
162 bndr_name_set = mkNameSet binder_names
164 renameSigsFVs (okBindSig bndr_name_set) sigs `thenM` \ (siglist, sig_fvs) ->
166 -- Warn about missing signatures, but not in interface mode
167 -- (This is important when renaming bindings from 'deriving' clauses.)
168 getModeRn `thenM` \ mode ->
169 doptM Opt_WarnMissingSigs `thenM` \ warn_missing_sigs ->
170 (if warn_missing_sigs && not (isInterfaceMode mode) then
172 type_sig_vars = [n | Sig n _ _ <- siglist]
173 un_sigd_binders = nameSetToList (delListFromNameSet bndr_name_set type_sig_vars)
175 mappM_ missingSigWarn un_sigd_binders
180 rn_mono_binds siglist mbinds `thenM` \ (final_binds, bind_fvs) ->
181 returnM (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 rnMonoBinds :: RdrNameMonoBinds
205 -> (RenamedHsBinds -> RnM (result, FreeVars))
206 -> RnM (result, FreeVars)
208 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
209 = -- Extract all the binders in this group,
210 -- and extend current scope, inventing new names for the new binders
211 -- This also checks that the names form a set
212 bindLocatedLocalsRn doc mbinders_w_srclocs $ \ new_mbinders ->
213 bindPatSigTyVars (collectSigTysFromMonoBinds mbinds) $
215 binder_set = mkNameSet new_mbinders
217 -- Rename the signatures
218 renameSigsFVs (okBindSig binder_set) sigs `thenM` \ (siglist, sig_fvs) ->
220 -- Report the fixity declarations in this group that
221 -- don't refer to any of the group's binders.
222 -- Then install the fixity declarations that do apply here
223 -- Notice that they scope over thing_inside too
224 bindLocalFixities [sig | FixSig sig <- siglist ] $
226 rn_mono_binds siglist mbinds `thenM` \ (binds, bind_fvs) ->
228 -- Now do the "thing inside", and deal with the free-variable calculations
229 thing_inside binds `thenM` \ (result,result_fvs) ->
231 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
232 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
234 warnUnusedLocalBinds unused_binders `thenM_`
235 returnM (result, delListFromNameSet all_fvs new_mbinders)
237 mbinders_w_srclocs = collectLocatedMonoBinders mbinds
238 doc = text "In the binding group for" <+> pp_bndrs mbinders_w_srclocs
239 pp_bndrs [(b,_)] = quotes (ppr b)
240 pp_bndrs bs = fsep (punctuate comma [ppr b | (b,_) <- bs])
244 %************************************************************************
246 \subsubsection{ MonoBinds -- the main work is done here}
248 %************************************************************************
250 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
251 It assumes that all variables bound in this group are already in scope.
252 This is done {\em either} by pass 3 (for the top-level bindings),
253 {\em or} by @rnMonoBinds@ (for the nested ones).
256 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
258 -> RnM (RenamedHsBinds, -- Dependency analysed
259 FreeVars) -- Free variables
261 rn_mono_binds siglist mbinds
263 -- Rename the bindings, returning a MonoBindsInfo
264 -- which is a list of indivisible vertices so far as
265 -- the strongly-connected-components (SCC) analysis is concerned
266 flattenMonoBinds siglist mbinds `thenM` \ mbinds_info ->
268 -- Do the SCC analysis
270 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
271 scc_result = stronglyConnComp edges
272 final_binds = foldr (ThenBinds . reconstructCycle) EmptyBinds scc_result
274 -- Deal with bound and free-var calculation
275 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
277 returnM (final_binds, rhs_fvs)
280 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
281 unique ``vertex tags'' on its output; minor plumbing required.
283 Sigh --- need to pass along the signatures for the group of bindings,
284 in case any of them \fbox{\ ???\ }
287 flattenMonoBinds :: [RenamedSig] -- Signatures
289 -> RnM [FlatMonoBindsInfo]
291 flattenMonoBinds sigs EmptyMonoBinds = returnM []
293 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
294 = flattenMonoBinds sigs bs1 `thenM` \ flat1 ->
295 flattenMonoBinds sigs bs2 `thenM` \ flat2 ->
296 returnM (flat1 ++ flat2)
298 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
300 rnPat pat `thenM` \ (pat', pat_fvs) ->
302 -- Find which things are bound in this group
304 names_bound_here = mkNameSet (collectPatBinders pat')
306 sigsForMe names_bound_here sigs `thenM` \ sigs_for_me ->
307 rnGRHSs grhss `thenM` \ (grhss', fvs) ->
310 fvs `plusFV` pat_fvs,
311 PatMonoBind pat' grhss' locn,
315 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
317 lookupBndrRn name `thenM` \ new_name ->
319 names_bound_here = unitNameSet new_name
321 sigsForMe names_bound_here sigs `thenM` \ sigs_for_me ->
322 mapFvRn (rnMatch (FunRhs name)) matches `thenM` \ (new_matches, fvs) ->
323 mappM_ (checkPrecMatch inf new_name) new_matches `thenM_`
325 [(unitNameSet new_name,
327 FunMonoBind new_name inf new_matches locn,
332 sigsForMe names_bound_here sigs
333 = foldlM check [] (filter (sigForThisGroup names_bound_here) sigs)
335 check sigs sig = case filter (eqHsSig sig) sigs of
336 [] -> returnM (sig:sigs)
337 other -> dupSigDeclErr sig `thenM_`
342 @rnMethodBinds@ is used for the method bindings of a class and an instance
343 declaration. Like @rnMonoBinds@ but without dependency analysis.
345 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
346 That's crucial when dealing with an instance decl:
348 instance Foo (T a) where
351 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
352 and unless @op@ occurs we won't treat the type signature of @op@ in the class
353 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
354 in many ways the @op@ in an instance decl is just like an occurrence, not
358 rnMethodBinds :: Name -- Class name
359 -> [Name] -- Names for generic type variables
361 -> RnM (RenamedMonoBinds, FreeVars)
363 rnMethodBinds cls gen_tyvars EmptyMonoBinds = returnM (EmptyMonoBinds, emptyFVs)
365 rnMethodBinds cls gen_tyvars (AndMonoBinds mb1 mb2)
366 = rnMethodBinds cls gen_tyvars mb1 `thenM` \ (mb1', fvs1) ->
367 rnMethodBinds cls gen_tyvars mb2 `thenM` \ (mb2', fvs2) ->
368 returnM (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
370 rnMethodBinds cls gen_tyvars (FunMonoBind name inf matches locn)
373 lookupInstDeclBndr cls name `thenM` \ sel_name ->
374 -- We use the selector name as the binder
376 mapFvRn rn_match matches `thenM` \ (new_matches, fvs) ->
377 mappM_ (checkPrecMatch inf sel_name) new_matches `thenM_`
378 returnM (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
380 -- Gruesome; bring into scope the correct members of the generic type variables
381 -- See comments in RnSource.rnSourceDecl(ClassDecl)
382 rn_match match@(Match (TypePat ty : _) _ _)
383 = extendTyVarEnvFVRn gen_tvs (rnMatch (FunRhs name) match)
385 tvs = map rdrNameOcc (extractHsTyRdrNames ty)
386 gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs]
388 rn_match match = rnMatch (FunRhs name) match
391 -- Can't handle method pattern-bindings which bind multiple methods.
392 rnMethodBinds cls gen_tyvars mbind@(PatMonoBind other_pat _ locn)
393 = addSrcLoc locn (addErr (methodBindErr mbind)) `thenM_`
394 returnM (EmptyMonoBinds, emptyFVs)
398 %************************************************************************
400 \subsection[reconstruct-deps]{Reconstructing dependencies}
402 %************************************************************************
404 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
405 as the two cases are similar.
408 reconstructCycle :: SCC FlatMonoBindsInfo
411 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
412 = MonoBind binds sigs NonRecursive
414 reconstructCycle (CyclicSCC cycle)
415 = MonoBind this_gp_binds this_gp_sigs Recursive
417 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
418 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
421 %************************************************************************
423 \subsubsection{ Manipulating FlatMonoBindInfo}
425 %************************************************************************
427 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
428 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
429 a function binding, and has itself been dependency-analysed and
433 type FlatMonoBindsInfo
434 = (NameSet, -- Set of names defined in this vertex
435 NameSet, -- Set of names used in this vertex
437 [RenamedSig]) -- Signatures, if any, for this vertex
439 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
442 = [ (info, tag, dest_vertices (nameSetToList names_used))
443 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
446 -- An edge (v,v') indicates that v depends on v'
447 dest_vertices src_mentions = [ target_vertex
448 | ((names_defined, _, _, _), target_vertex) <- flat_info,
449 mentioned_name <- src_mentions,
450 mentioned_name `elemNameSet` names_defined
455 %************************************************************************
457 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
459 %************************************************************************
461 @renameSigs@ checks for:
463 \item more than one sig for one thing;
464 \item signatures given for things not bound here;
465 \item with suitably flaggery, that all top-level things have type signatures.
468 At the moment we don't gather free-var info from the types in
469 signatures. We'd only need this if we wanted to report unused tyvars.
472 renameSigsFVs ok_sig sigs
473 = renameSigs ok_sig sigs `thenM` \ sigs' ->
474 returnM (sigs', hsSigsFVs sigs')
476 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
480 renameSigs ok_sig [] = returnM []
482 renameSigs ok_sig sigs
483 = -- Rename the signatures
484 mappM renameSig sigs `thenM` \ sigs' ->
486 -- Check for (a) duplicate signatures
487 -- (b) signatures for things not in this group
489 in_scope = filter is_in_scope sigs'
490 is_in_scope sig = case sigName sig of
491 Just n -> not (isUnboundName n)
493 (goods, bads) = partition ok_sig in_scope
495 mappM_ unknownSigErr bads `thenM_`
498 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
499 -- because this won't work for:
500 -- instance Foo T where
503 -- We'll just rename the INLINE prag to refer to whatever other 'op'
504 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
505 -- Doesn't seem worth much trouble to sort this.
507 renameSig :: Sig RdrName -> RnM (Sig Name)
508 -- ClassOpSig is renamed elsewhere.
509 renameSig (Sig v ty src_loc)
510 = addSrcLoc src_loc $
511 lookupSigOccRn v `thenM` \ new_v ->
512 rnHsSigType (quotes (ppr v)) ty `thenM` \ new_ty ->
513 returnM (Sig new_v new_ty src_loc)
515 renameSig (SpecInstSig ty src_loc)
516 = addSrcLoc src_loc $
517 rnHsType (text "A SPECIALISE instance pragma") ty `thenM` \ new_ty ->
518 returnM (SpecInstSig new_ty src_loc)
520 renameSig (SpecSig v ty src_loc)
521 = addSrcLoc src_loc $
522 lookupSigOccRn v `thenM` \ new_v ->
523 rnHsSigType (quotes (ppr v)) ty `thenM` \ new_ty ->
524 returnM (SpecSig new_v new_ty src_loc)
526 renameSig (FixSig (FixitySig v fix src_loc))
527 = addSrcLoc src_loc $
528 lookupSigOccRn v `thenM` \ new_v ->
529 returnM (FixSig (FixitySig new_v fix src_loc))
531 renameSig (InlineSig b v p src_loc)
532 = addSrcLoc src_loc $
533 lookupSigOccRn v `thenM` \ new_v ->
534 returnM (InlineSig b new_v p src_loc)
538 %************************************************************************
540 \subsection{Error messages}
542 %************************************************************************
547 addErr (sep [ptext SLIT("Duplicate") <+> what_it_is <> colon,
550 (what_it_is, loc) = hsSigDoc sig
554 addErr (sep [ptext SLIT("Misplaced") <+> what_it_is <> colon,
557 (what_it_is, loc) = hsSigDoc sig
560 = addSrcLoc (nameSrcLoc var) $
561 addWarn (sep [ptext SLIT("Definition but no type signature for"), quotes (ppr var)])
564 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))