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,
32 FreeVars, emptyFVs, plusFV, plusFVs, unitFV, addOneFV
34 import CmdLineOpts ( opt_WarnMissingSigs )
35 import Digraph ( stronglyConnComp, SCC(..) )
36 import Name ( OccName, Name, nameOccName, mkUnboundName, isUnboundName )
38 import RdrName ( RdrName, rdrNameOcc )
39 import BasicTypes ( RecFlag(..) )
40 import List ( partition )
41 import Bag ( bagToList )
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) ->
174 type_sig_vars = [n | Sig n _ _ <- siglist]
175 un_sigd_binders | opt_WarnMissingSigs = nameSetToList (delListFromNameSet bndr_name_set type_sig_vars)
178 mapRn_ (addWarnRn.missingSigWarn) un_sigd_binders `thenRn_`
180 rn_mono_binds siglist mbinds `thenRn` \ (final_binds, bind_fvs) ->
181 returnRn (final_binds, bind_fvs `plusFV` sig_fvs)
183 binder_rdr_names = map fst (bagToList (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 (text "a binding group")
222 mbinders_w_srclocs $ \ new_mbinders ->
224 binder_set = mkNameSet new_mbinders
226 -- Rename the signatures
227 renameSigs (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 = bagToList (collectMonoBinders mbinds)
253 %************************************************************************
255 \subsubsection{ MonoBinds -- the main work is done here}
257 %************************************************************************
259 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
260 It assumes that all variables bound in this group are already in scope.
261 This is done {\em either} by pass 3 (for the top-level bindings),
262 {\em or} by @rnMonoBinds@ (for the nested ones).
265 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
267 -> RnMS (RenamedHsBinds, --
268 FreeVars) -- Free variables
270 rn_mono_binds siglist mbinds
272 -- Rename the bindings, returning a MonoBindsInfo
273 -- which is a list of indivisible vertices so far as
274 -- the strongly-connected-components (SCC) analysis is concerned
275 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
277 -- Do the SCC analysis
279 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
280 scc_result = stronglyConnComp edges
281 final_binds = foldr (ThenBinds . reconstructCycle) EmptyBinds scc_result
283 -- Deal with bound and free-var calculation
284 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
286 returnRn (final_binds, rhs_fvs)
289 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
290 unique ``vertex tags'' on its output; minor plumbing required.
292 Sigh --- need to pass along the signatures for the group of bindings,
293 in case any of them \fbox{\ ???\ }
296 flattenMonoBinds :: [RenamedSig] -- Signatures
298 -> RnMS [FlatMonoBindsInfo]
300 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
302 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
303 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
304 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
305 returnRn (flat1 ++ flat2)
307 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
308 = pushSrcLocRn locn $
309 rnPat pat `thenRn` \ (pat', pat_fvs) ->
311 -- Find which things are bound in this group
313 names_bound_here = mkNameSet (collectPatBinders pat')
315 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
316 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
319 fvs `plusFV` pat_fvs,
320 PatMonoBind pat' grhss' locn,
324 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
325 = pushSrcLocRn locn $
326 lookupBndrRn name `thenRn` \ new_name ->
328 names_bound_here = unitNameSet new_name
330 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
331 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
332 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
334 [(unitNameSet new_name,
336 FunMonoBind new_name inf new_matches locn,
341 sigsForMe names_bound_here sigs
342 = foldlRn check [] (filter (sigForThisGroup names_bound_here) sigs)
344 check sigs sig = case filter (eqHsSig sig) sigs of
345 [] -> returnRn (sig:sigs)
346 other -> dupSigDeclErr sig `thenRn_`
351 @rnMethodBinds@ is used for the method bindings of a class and an instance
352 declaration. Like @rnMonoBinds@ but without dependency analysis.
354 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
355 That's crucial when dealing with an instance decl:
357 instance Foo (T a) where
360 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
361 and unless @op@ occurs we won't treat the type signature of @op@ in the class
362 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
363 in many ways the @op@ in an instance decl is just like an occurrence, not
367 rnMethodBinds :: RdrNameMonoBinds -> RnMS (RenamedMonoBinds, FreeVars)
369 rnMethodBinds EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
371 rnMethodBinds (AndMonoBinds mb1 mb2)
372 = rnMethodBinds mb1 `thenRn` \ (mb1', fvs1) ->
373 rnMethodBinds mb2 `thenRn` \ (mb2', fvs2) ->
374 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
376 rnMethodBinds (FunMonoBind name inf matches locn)
377 = pushSrcLocRn locn $
379 lookupGlobalOccRn name `thenRn` \ sel_name ->
380 -- We use the selector name as the binder
382 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
383 mapRn_ (checkPrecMatch inf sel_name) new_matches `thenRn_`
384 returnRn (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
386 -- Can't handle method pattern-bindings which bind multiple methods.
387 rnMethodBinds mbind@(PatMonoBind other_pat _ locn)
388 = pushSrcLocRn locn $
389 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
393 %************************************************************************
395 \subsection[reconstruct-deps]{Reconstructing dependencies}
397 %************************************************************************
399 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
400 as the two cases are similar.
403 reconstructCycle :: SCC FlatMonoBindsInfo
406 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
407 = MonoBind binds sigs NonRecursive
409 reconstructCycle (CyclicSCC cycle)
410 = MonoBind this_gp_binds this_gp_sigs Recursive
412 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
413 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
416 %************************************************************************
418 \subsubsection{ Manipulating FlatMonoBindInfo}
420 %************************************************************************
422 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
423 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
424 a function binding, and has itself been dependency-analysed and
428 type FlatMonoBindsInfo
429 = (NameSet, -- Set of names defined in this vertex
430 NameSet, -- Set of names used in this vertex
432 [RenamedSig]) -- Signatures, if any, for this vertex
434 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
437 = [ (info, tag, dest_vertices (nameSetToList names_used))
438 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
441 -- An edge (v,v') indicates that v depends on v'
442 dest_vertices src_mentions = [ target_vertex
443 | ((names_defined, _, _, _), target_vertex) <- flat_info,
444 mentioned_name <- src_mentions,
445 mentioned_name `elemNameSet` names_defined
450 %************************************************************************
452 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
454 %************************************************************************
456 @renameSigs@ checks for:
458 \item more than one sig for one thing;
459 \item signatures given for things not bound here;
460 \item with suitably flaggery, that all top-level things have type signatures.
463 At the moment we don't gather free-var info from the types in
464 signatures. We'd only need this if we wanted to report unused tyvars.
467 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
469 -> RnMS ([RenamedSig], FreeVars)
471 renameSigs ok_sig [] = returnRn ([], emptyFVs) -- Common shortcut
473 renameSigs ok_sig sigs
474 = -- Rename the signatures
475 mapFvRn renameSig sigs `thenRn` \ (sigs', fvs) ->
477 -- Check for (a) duplicate signatures
478 -- (b) signatures for things not in this group
480 in_scope = filter is_in_scope sigs'
481 is_in_scope sig = case sigName sig of
482 Just n -> not (isUnboundName n)
484 (goods, bads) = partition ok_sig in_scope
486 mapRn_ unknownSigErr bads `thenRn_`
487 returnRn (goods, fvs)
489 -- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
490 -- because this won't work for:
491 -- instance Foo T where
494 -- We'll just rename the INLINE prag to refer to whatever other 'op'
495 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
496 -- Doesn't seem worth much trouble to sort this.
498 renameSig :: Sig RdrName -> RnMS (Sig Name, FreeVars)
500 renameSig (Sig v ty src_loc)
501 = pushSrcLocRn src_loc $
502 lookupSigOccRn v `thenRn` \ new_v ->
503 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
504 returnRn (Sig new_v new_ty src_loc, fvs `addOneFV` new_v)
506 renameSig (SpecInstSig ty src_loc)
507 = pushSrcLocRn src_loc $
508 rnHsSigType (text "A SPECIALISE instance pragma") ty `thenRn` \ (new_ty, fvs) ->
509 returnRn (SpecInstSig new_ty src_loc, fvs)
511 renameSig (SpecSig v ty src_loc)
512 = pushSrcLocRn src_loc $
513 lookupSigOccRn v `thenRn` \ new_v ->
514 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
515 returnRn (SpecSig new_v new_ty src_loc, fvs `addOneFV` new_v)
517 renameSig (FixSig (FixitySig v fix src_loc))
518 = pushSrcLocRn src_loc $
519 lookupSigOccRn v `thenRn` \ new_v ->
520 returnRn (FixSig (FixitySig new_v fix src_loc), unitFV new_v)
522 renameSig (InlineSig v p src_loc)
523 = pushSrcLocRn src_loc $
524 lookupSigOccRn v `thenRn` \ new_v ->
525 returnRn (InlineSig new_v p src_loc, unitFV new_v)
527 renameSig (NoInlineSig v p src_loc)
528 = pushSrcLocRn src_loc $
529 lookupSigOccRn v `thenRn` \ new_v ->
530 returnRn (NoInlineSig new_v p src_loc, unitFV new_v)
534 renameIE :: (RdrName -> RnMS Name) -> IE RdrName -> RnMS (IE Name, FreeVars)
535 renameIE lookup_occ_nm (IEVar v)
536 = lookup_occ_nm v `thenRn` \ new_v ->
537 returnRn (IEVar new_v, unitFV new_v)
539 renameIE lookup_occ_nm (IEThingAbs v)
540 = lookup_occ_nm v `thenRn` \ new_v ->
541 returnRn (IEThingAbs new_v, unitFV new_v)
543 renameIE lookup_occ_nm (IEThingAll v)
544 = lookup_occ_nm v `thenRn` \ new_v ->
545 returnRn (IEThingAll new_v, unitFV new_v)
547 renameIE lookup_occ_nm (IEThingWith v vs)
548 = lookup_occ_nm v `thenRn` \ new_v ->
549 mapRn lookup_occ_nm vs `thenRn` \ new_vs ->
550 returnRn (IEThingWith new_v new_vs, plusFVs [ unitFV x | x <- new_v:new_vs ])
552 renameIE lookup_occ_nm (IEModuleContents m)
553 = returnRn (IEModuleContents m, emptyFVs)
557 %************************************************************************
559 \subsection{Error messages}
561 %************************************************************************
566 addErrRn (sep [ptext SLIT("Duplicate") <+> ptext what_it_is <> colon,
569 (what_it_is, loc) = hsSigDoc sig
573 addErrRn (sep [ptext SLIT("Misplaced") <+> ptext what_it_is <> colon,
576 (what_it_is, loc) = hsSigDoc sig
579 = sep [ptext SLIT("definition but no type signature for"), quotes (ppr var)]
582 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))