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, lookupOccRn, lookupSigOccRn,
31 warnUnusedLocalBinds, mapFvRn,
32 FreeVars, emptyFVs, plusFV, plusFVs, unitFV, addOneFV,
35 import CmdLineOpts ( opt_WarnMissingSigs )
36 import Digraph ( stronglyConnComp, SCC(..) )
37 import Name ( OccName, Name, nameOccName, mkUnboundName, isUnboundName )
39 import RdrName ( RdrName, rdrNameOcc )
40 import BasicTypes ( RecFlag(..), TopLevelFlag(..) )
41 import List ( partition )
42 import Bag ( bagToList )
46 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
47 -- place and can be used when complaining.
49 The code tree received by the function @rnBinds@ contains definitions
50 in where-clauses which are all apparently mutually recursive, but which may
51 not really depend upon each other. For example, in the top level program
56 the definitions of @a@ and @y@ do not depend on each other at all.
57 Unfortunately, the typechecker cannot always check such definitions.
58 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
59 definitions. In Proceedings of the International Symposium on Programming,
60 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
61 However, the typechecker usually can check definitions in which only the
62 strongly connected components have been collected into recursive bindings.
63 This is precisely what the function @rnBinds@ does.
65 ToDo: deal with case where a single monobinds binds the same variable
68 The vertag tag is a unique @Int@; the tags only need to be unique
69 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
70 (heavy monad machinery not needed).
74 type Cycle = [VertexTag]
75 type Edge = (VertexTag, VertexTag)
78 %************************************************************************
80 %* naming conventions *
82 %************************************************************************
84 \subsection[name-conventions]{Name conventions}
86 The basic algorithm involves walking over the tree and returning a tuple
87 containing the new tree plus its free variables. Some functions, such
88 as those walking polymorphic bindings (HsBinds) and qualifier lists in
89 list comprehensions (@Quals@), return the variables bound in local
90 environments. These are then used to calculate the free variables of the
91 expression evaluated in these environments.
93 Conventions for variable names are as follows:
96 new code is given a prime to distinguish it from the old.
99 a set of variables defined in @Exp@ is written @dvExp@
102 a set of variables free in @Exp@ is written @fvExp@
105 %************************************************************************
107 %* analysing polymorphic bindings (HsBinds, Bind, MonoBinds) *
109 %************************************************************************
111 \subsubsection[dep-HsBinds]{Polymorphic bindings}
113 Non-recursive expressions are reconstructed without any changes at top
114 level, although their component expressions may have to be altered.
115 However, non-recursive expressions are currently not expected as
116 \Haskell{} programs, and this code should not be executed.
118 Monomorphic bindings contain information that is returned in a tuple
119 (a @FlatMonoBindsInfo@) containing:
123 a unique @Int@ that serves as the ``vertex tag'' for this binding.
126 the name of a function or the names in a pattern. These are a set
127 referred to as @dvLhs@, the defined variables of the left hand side.
130 the free variables of the body. These are referred to as @fvBody@.
133 the definition's actual code. This is referred to as just @code@.
136 The function @nonRecDvFv@ returns two sets of variables. The first is
137 the set of variables defined in the set of monomorphic bindings, while the
138 second is the set of free variables in those bindings.
140 The set of variables defined in a non-recursive binding is just the
141 union of all of them, as @union@ removes duplicates. However, the
142 free variables in each successive set of cumulative bindings is the
143 union of those in the previous set plus those of the newest binding after
144 the defined variables of the previous set have been removed.
146 @rnMethodBinds@ deals only with the declarations in class and
147 instance declarations. It expects only to see @FunMonoBind@s, and
148 it expects the global environment to contain bindings for the binders
149 (which are all class operations).
151 %************************************************************************
153 \subsubsection{ Top-level bindings}
155 %************************************************************************
157 @rnTopBinds@ assumes that the environment already
158 contains bindings for the binders of this particular binding.
161 rnTopBinds :: RdrNameHsBinds -> RnMS (RenamedHsBinds, FreeVars)
163 rnTopBinds EmptyBinds = returnRn (EmptyBinds, emptyFVs)
164 rnTopBinds (MonoBind bind sigs _) = rnTopMonoBinds bind sigs
165 -- The parser doesn't produce other forms
168 rnTopMonoBinds EmptyMonoBinds sigs
169 = returnRn (EmptyBinds, emptyFVs)
171 rnTopMonoBinds mbinds sigs
172 = mapRn lookupBndrRn binder_rdr_names `thenRn` \ binder_names ->
174 bndr_name_set = mkNameSet binder_names
176 renameSigs (okBindSig bndr_name_set) sigs `thenRn` \ (siglist, sig_fvs) ->
178 type_sig_vars = [n | Sig n _ _ <- siglist]
179 un_sigd_binders | opt_WarnMissingSigs = nameSetToList (delListFromNameSet bndr_name_set type_sig_vars)
182 mapRn_ (addWarnRn.missingSigWarn) un_sigd_binders `thenRn_`
184 rn_mono_binds siglist mbinds `thenRn` \ (final_binds, bind_fvs) ->
185 returnRn (final_binds, bind_fvs `plusFV` sig_fvs)
187 binder_rdr_names = map fst (bagToList (collectMonoBinders mbinds))
190 %************************************************************************
194 %************************************************************************
196 \subsubsection{Nested binds}
200 \item collects up the binders for this declaration group,
201 \item checks that they form a set
202 \item extends the environment to bind them to new local names
203 \item calls @rnMonoBinds@ to do the real work
207 rnBinds :: RdrNameHsBinds
208 -> (RenamedHsBinds -> RnMS (result, FreeVars))
209 -> RnMS (result, FreeVars)
211 rnBinds EmptyBinds thing_inside = thing_inside EmptyBinds
212 rnBinds (MonoBind bind sigs _) thing_inside = rnMonoBinds bind sigs thing_inside
213 -- the parser doesn't produce other forms
216 rnMonoBinds :: RdrNameMonoBinds
218 -> (RenamedHsBinds -> RnMS (result, FreeVars))
219 -> RnMS (result, FreeVars)
221 rnMonoBinds EmptyMonoBinds sigs thing_inside = thing_inside EmptyBinds
223 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
224 = -- Extract all the binders in this group,
225 -- and extend current scope, inventing new names for the new binders
226 -- This also checks that the names form a set
227 bindLocatedLocalsRn (text "a binding group")
228 mbinders_w_srclocs $ \ new_mbinders ->
230 binder_set = mkNameSet new_mbinders
232 -- Rename the signatures
233 renameSigs (okBindSig binder_set) sigs `thenRn` \ (siglist, sig_fvs) ->
235 -- Report the fixity declarations in this group that
236 -- don't refer to any of the group's binders.
237 -- Then install the fixity declarations that do apply here
238 -- Notice that they scope over thing_inside too
240 fixity_sigs = [(name,sig) | FixSig sig@(FixitySig name _ _) <- siglist ]
242 extendFixityEnv fixity_sigs $
244 rn_mono_binds siglist mbinds `thenRn` \ (binds, bind_fvs) ->
246 -- Now do the "thing inside", and deal with the free-variable calculations
247 thing_inside binds `thenRn` \ (result,result_fvs) ->
249 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
250 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
252 warnUnusedLocalBinds unused_binders `thenRn_`
253 returnRn (result, delListFromNameSet all_fvs new_mbinders)
255 mbinders_w_srclocs = bagToList (collectMonoBinders mbinds)
259 %************************************************************************
261 \subsubsection{ MonoBinds -- the main work is done here}
263 %************************************************************************
265 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
266 It assumes that all variables bound in this group are already in scope.
267 This is done {\em either} by pass 3 (for the top-level bindings),
268 {\em or} by @rnMonoBinds@ (for the nested ones).
271 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
273 -> RnMS (RenamedHsBinds, --
274 FreeVars) -- Free variables
276 rn_mono_binds siglist mbinds
278 -- Rename the bindings, returning a MonoBindsInfo
279 -- which is a list of indivisible vertices so far as
280 -- the strongly-connected-components (SCC) analysis is concerned
281 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
283 -- Do the SCC analysis
285 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
286 scc_result = stronglyConnComp edges
287 final_binds = foldr1 ThenBinds (map reconstructCycle scc_result)
289 -- Deal with bound and free-var calculation
290 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
292 returnRn (final_binds, rhs_fvs)
295 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
296 unique ``vertex tags'' on its output; minor plumbing required.
298 Sigh --- need to pass along the signatures for the group of bindings,
299 in case any of them \fbox{\ ???\ }
302 flattenMonoBinds :: [RenamedSig] -- Signatures
304 -> RnMS [FlatMonoBindsInfo]
306 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
308 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
309 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
310 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
311 returnRn (flat1 ++ flat2)
313 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
314 = pushSrcLocRn locn $
315 rnPat pat `thenRn` \ (pat', pat_fvs) ->
317 -- Find which things are bound in this group
319 names_bound_here = mkNameSet (collectPatBinders pat')
321 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
322 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
325 fvs `plusFV` pat_fvs,
326 PatMonoBind pat' grhss' locn,
330 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
331 = pushSrcLocRn locn $
332 lookupBndrRn name `thenRn` \ new_name ->
334 names_bound_here = unitNameSet new_name
336 sigsForMe names_bound_here sigs `thenRn` \ sigs_for_me ->
337 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
338 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
340 [(unitNameSet new_name,
342 FunMonoBind new_name inf new_matches locn,
347 sigsForMe names_bound_here sigs
348 = foldlRn check [] (filter (sigForThisGroup names_bound_here) sigs)
350 check sigs sig = case filter (eqHsSig sig) sigs of
351 [] -> returnRn (sig:sigs)
352 other -> dupSigDeclErr sig `thenRn_`
357 @rnMethodBinds@ is used for the method bindings of a class and an instance
358 declaration. Like @rnMonoBinds@ but without dependency analysis.
360 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
361 That's crucial when dealing with an instance decl:
363 instance Foo (T a) where
366 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
367 and unless @op@ occurs we won't treat the type signature of @op@ in the class
368 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
369 in many ways the @op@ in an instance decl is just like an occurrence, not
373 rnMethodBinds :: RdrNameMonoBinds -> RnMS (RenamedMonoBinds, FreeVars)
375 rnMethodBinds EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
377 rnMethodBinds (AndMonoBinds mb1 mb2)
378 = rnMethodBinds mb1 `thenRn` \ (mb1', fvs1) ->
379 rnMethodBinds mb2 `thenRn` \ (mb2', fvs2) ->
380 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
382 rnMethodBinds (FunMonoBind name inf matches locn)
383 = pushSrcLocRn locn $
385 lookupGlobalOccRn name `thenRn` \ sel_name ->
386 -- We use the selector name as the binder
388 mapFvRn rnMatch 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 -- Can't handle method pattern-bindings which bind multiple methods.
393 rnMethodBinds mbind@(PatMonoBind other_pat _ locn)
394 = pushSrcLocRn locn $
395 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
399 %************************************************************************
401 \subsection[reconstruct-deps]{Reconstructing dependencies}
403 %************************************************************************
405 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
406 as the two cases are similar.
409 reconstructCycle :: SCC FlatMonoBindsInfo
412 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
413 = MonoBind binds sigs NonRecursive
415 reconstructCycle (CyclicSCC cycle)
416 = MonoBind this_gp_binds this_gp_sigs Recursive
418 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
419 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
422 %************************************************************************
424 \subsubsection{ Manipulating FlatMonoBindInfo}
426 %************************************************************************
428 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
429 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
430 a function binding, and has itself been dependency-analysed and
434 type FlatMonoBindsInfo
435 = (NameSet, -- Set of names defined in this vertex
436 NameSet, -- Set of names used in this vertex
438 [RenamedSig]) -- Signatures, if any, for this vertex
440 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
443 = [ (info, tag, dest_vertices (nameSetToList names_used))
444 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
447 -- An edge (v,v') indicates that v depends on v'
448 dest_vertices src_mentions = [ target_vertex
449 | ((names_defined, _, _, _), target_vertex) <- flat_info,
450 mentioned_name <- src_mentions,
451 mentioned_name `elemNameSet` names_defined
456 %************************************************************************
458 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
460 %************************************************************************
462 @renameSigs@ checks for:
464 \item more than one sig for one thing;
465 \item signatures given for things not bound here;
466 \item with suitably flaggery, that all top-level things have type signatures.
469 At the moment we don't gather free-var info from the types in
470 signatures. We'd only need this if we wanted to report unused tyvars.
473 renameSigs :: (RenamedSig -> Bool) -- OK-sig predicate
475 -> RnMS ([RenamedSig], FreeVars)
477 renameSigs ok_sig [] = returnRn ([], emptyFVs) -- Common shortcut
479 renameSigs ok_sig sigs
480 = -- Rename the signatures
481 mapFvRn renameSig sigs `thenRn` \ (sigs', fvs) ->
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 mapRn_ unknownSigErr bads `thenRn_`
493 returnRn (goods, fvs)
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 -> RnMS (Sig Name, FreeVars)
506 renameSig (Sig v ty src_loc)
507 = pushSrcLocRn src_loc $
508 lookupSigOccRn v `thenRn` \ new_v ->
509 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
510 returnRn (Sig new_v new_ty src_loc, fvs `addOneFV` new_v)
512 renameSig (SpecInstSig ty src_loc)
513 = pushSrcLocRn src_loc $
514 rnHsSigType (text "A SPECIALISE instance pragma") ty `thenRn` \ (new_ty, fvs) ->
515 returnRn (SpecInstSig new_ty src_loc, fvs)
517 renameSig (SpecSig v ty src_loc)
518 = pushSrcLocRn src_loc $
519 lookupSigOccRn v `thenRn` \ new_v ->
520 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
521 returnRn (SpecSig new_v new_ty src_loc, fvs `addOneFV` new_v)
523 renameSig (FixSig (FixitySig v fix src_loc))
524 = pushSrcLocRn src_loc $
525 lookupSigOccRn v `thenRn` \ new_v ->
526 returnRn (FixSig (FixitySig new_v fix src_loc), unitFV new_v)
528 renameSig (InlineSig v p src_loc)
529 = pushSrcLocRn src_loc $
530 lookupSigOccRn v `thenRn` \ new_v ->
531 returnRn (InlineSig new_v p src_loc, unitFV new_v)
533 renameSig (NoInlineSig v p src_loc)
534 = pushSrcLocRn src_loc $
535 lookupSigOccRn v `thenRn` \ new_v ->
536 returnRn (NoInlineSig new_v p src_loc, unitFV new_v)
540 renameIE :: (RdrName -> RnMS Name) -> IE RdrName -> RnMS (IE Name, FreeVars)
541 renameIE lookup_occ_nm (IEVar v)
542 = lookup_occ_nm v `thenRn` \ new_v ->
543 returnRn (IEVar new_v, unitFV new_v)
545 renameIE lookup_occ_nm (IEThingAbs v)
546 = lookup_occ_nm v `thenRn` \ new_v ->
547 returnRn (IEThingAbs new_v, unitFV new_v)
549 renameIE lookup_occ_nm (IEThingAll v)
550 = lookup_occ_nm v `thenRn` \ new_v ->
551 returnRn (IEThingAll new_v, unitFV new_v)
553 renameIE lookup_occ_nm (IEThingWith v vs)
554 = lookup_occ_nm v `thenRn` \ new_v ->
555 mapRn lookup_occ_nm vs `thenRn` \ new_vs ->
556 returnRn (IEThingWith new_v new_vs, plusFVs [ unitFV x | x <- new_v:new_vs ])
558 renameIE lookup_occ_nm (IEModuleContents m)
559 = returnRn (IEModuleContents m, emptyFVs)
563 %************************************************************************
565 \subsection{Error messages}
567 %************************************************************************
572 addErrRn (sep [ptext SLIT("Duplicate") <+> ptext what_it_is <> colon,
575 (what_it_is, loc) = hsSigDoc sig
579 addErrRn (sep [ptext SLIT("Misplaced") <+> ptext what_it_is <> colon,
582 (what_it_is, loc) = hsSigDoc sig
585 = sep [ptext SLIT("definition but no type signature for"), quotes (ppr var)]
588 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))