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 ( sigsForMe )
28 import RnExpr ( rnMatch, rnGRHSs, rnPat, checkPrecMatch )
29 import RnEnv ( bindLocatedLocalsRn, lookupBndrRn, lookupGlobalOccRn,
30 warnUnusedLocalBinds, mapFvRn,
31 FreeVars, emptyFVs, plusFV, plusFVs, unitFV, addOneFV,
34 import CmdLineOpts ( opt_WarnMissingSigs )
35 import Digraph ( stronglyConnComp, SCC(..) )
36 import Name ( OccName, Name, nameOccName )
38 import RdrName ( RdrName, rdrNameOcc )
39 import BasicTypes ( RecFlag(..), TopLevelFlag(..) )
40 import Util ( thenCmp, removeDups )
41 import List ( partition )
42 import ListSetOps ( minusList )
43 import Bag ( bagToList )
44 import FiniteMap ( lookupFM, listToFM )
45 import Maybe ( isJust )
49 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
50 -- place and can be used when complaining.
52 The code tree received by the function @rnBinds@ contains definitions
53 in where-clauses which are all apparently mutually recursive, but which may
54 not really depend upon each other. For example, in the top level program
59 the definitions of @a@ and @y@ do not depend on each other at all.
60 Unfortunately, the typechecker cannot always check such definitions.
61 \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
62 definitions. In Proceedings of the International Symposium on Programming,
63 Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
64 However, the typechecker usually can check definitions in which only the
65 strongly connected components have been collected into recursive bindings.
66 This is precisely what the function @rnBinds@ does.
68 ToDo: deal with case where a single monobinds binds the same variable
71 The vertag tag is a unique @Int@; the tags only need to be unique
72 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
73 (heavy monad machinery not needed).
77 type Cycle = [VertexTag]
78 type Edge = (VertexTag, VertexTag)
81 %************************************************************************
83 %* naming conventions *
85 %************************************************************************
87 \subsection[name-conventions]{Name conventions}
89 The basic algorithm involves walking over the tree and returning a tuple
90 containing the new tree plus its free variables. Some functions, such
91 as those walking polymorphic bindings (HsBinds) and qualifier lists in
92 list comprehensions (@Quals@), return the variables bound in local
93 environments. These are then used to calculate the free variables of the
94 expression evaluated in these environments.
96 Conventions for variable names are as follows:
99 new code is given a prime to distinguish it from the old.
102 a set of variables defined in @Exp@ is written @dvExp@
105 a set of variables free in @Exp@ is written @fvExp@
108 %************************************************************************
110 %* analysing polymorphic bindings (HsBinds, Bind, MonoBinds) *
112 %************************************************************************
114 \subsubsection[dep-HsBinds]{Polymorphic bindings}
116 Non-recursive expressions are reconstructed without any changes at top
117 level, although their component expressions may have to be altered.
118 However, non-recursive expressions are currently not expected as
119 \Haskell{} programs, and this code should not be executed.
121 Monomorphic bindings contain information that is returned in a tuple
122 (a @FlatMonoBindsInfo@) containing:
126 a unique @Int@ that serves as the ``vertex tag'' for this binding.
129 the name of a function or the names in a pattern. These are a set
130 referred to as @dvLhs@, the defined variables of the left hand side.
133 the free variables of the body. These are referred to as @fvBody@.
136 the definition's actual code. This is referred to as just @code@.
139 The function @nonRecDvFv@ returns two sets of variables. The first is
140 the set of variables defined in the set of monomorphic bindings, while the
141 second is the set of free variables in those bindings.
143 The set of variables defined in a non-recursive binding is just the
144 union of all of them, as @union@ removes duplicates. However, the
145 free variables in each successive set of cumulative bindings is the
146 union of those in the previous set plus those of the newest binding after
147 the defined variables of the previous set have been removed.
149 @rnMethodBinds@ deals only with the declarations in class and
150 instance declarations. It expects only to see @FunMonoBind@s, and
151 it expects the global environment to contain bindings for the binders
152 (which are all class operations).
154 %************************************************************************
156 \subsubsection{ Top-level bindings}
158 %************************************************************************
160 @rnTopBinds@ assumes that the environment already
161 contains bindings for the binders of this particular binding.
164 rnTopBinds :: RdrNameHsBinds -> RnMS (RenamedHsBinds, FreeVars)
166 rnTopBinds EmptyBinds = returnRn (EmptyBinds, emptyFVs)
167 rnTopBinds (MonoBind bind sigs _) = rnTopMonoBinds bind sigs
168 -- The parser doesn't produce other forms
171 rnTopMonoBinds EmptyMonoBinds sigs
172 = returnRn (EmptyBinds, emptyFVs)
174 rnTopMonoBinds mbinds sigs
175 = mapRn lookupBndrRn binder_rdr_names `thenRn` \ binder_names ->
177 binder_set = mkNameSet binder_names
178 binder_occ_fm = listToFM [(nameOccName x,x) | x <- binder_names]
180 renameSigs opt_WarnMissingSigs binder_set
181 (lookupSigOccRn binder_occ_fm) sigs `thenRn` \ (siglist, sig_fvs) ->
182 rn_mono_binds siglist mbinds `thenRn` \ (final_binds, bind_fvs) ->
183 returnRn (final_binds, bind_fvs `plusFV` sig_fvs)
185 binder_rdr_names = map fst (bagToList (collectMonoBinders mbinds))
187 -- the names appearing in the sigs have to be bound by
188 -- this group's binders.
189 lookupSigOccRn binder_occ_fm rdr_name
190 = case lookupFM binder_occ_fm (rdrNameOcc rdr_name) of
191 Nothing -> failWithRn (mkUnboundName rdr_name)
192 (unknownNameErr rdr_name)
196 %************************************************************************
200 %************************************************************************
202 \subsubsection{Nested binds}
206 \item collects up the binders for this declaration group,
207 \item checks that they form a set
208 \item extends the environment to bind them to new local names
209 \item calls @rnMonoBinds@ to do the real work
213 rnBinds :: RdrNameHsBinds
214 -> (RenamedHsBinds -> RnMS (result, FreeVars))
215 -> RnMS (result, FreeVars)
217 rnBinds EmptyBinds thing_inside = thing_inside EmptyBinds
218 rnBinds (MonoBind bind sigs _) thing_inside = rnMonoBinds bind sigs thing_inside
219 -- the parser doesn't produce other forms
222 rnMonoBinds :: RdrNameMonoBinds
224 -> (RenamedHsBinds -> RnMS (result, FreeVars))
225 -> RnMS (result, FreeVars)
227 rnMonoBinds EmptyMonoBinds sigs thing_inside = thing_inside EmptyBinds
229 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
230 = -- Extract all the binders in this group,
231 -- and extend current scope, inventing new names for the new binders
232 -- This also checks that the names form a set
233 bindLocatedLocalsRn (text "a binding group") mbinders_w_srclocs
236 binder_set = mkNameSet new_mbinders
238 -- Weed out the fixity declarations that do not
239 -- apply to any of the binders in this group.
240 (sigs_for_me, fixes_not_for_me) = partition forLocalBind sigs
242 forLocalBind (FixSig sig@(FixitySig name _ _ )) =
243 isJust (lookupFM binder_occ_fm (rdrNameOcc name))
244 forLocalBind _ = True
246 binder_occ_fm = listToFM [(nameOccName x,x) | x <- new_mbinders]
249 -- Report the fixity declarations in this group that
250 -- don't refer to any of the group's binders.
252 mapRn_ (unknownSigErr) fixes_not_for_me `thenRn_`
253 renameSigs False binder_set
254 (lookupSigOccRn binder_occ_fm) sigs_for_me `thenRn` \ (siglist, sig_fvs) ->
256 fixity_sigs = [(name,sig) | FixSig sig@(FixitySig name _ _) <- siglist ]
258 -- Install the fixity declarations that do apply here and go.
259 extendFixityEnv fixity_sigs (
260 rn_mono_binds siglist mbinds
261 ) `thenRn` \ (binds, bind_fvs) ->
263 -- Now do the "thing inside", and deal with the free-variable calculations
264 thing_inside binds `thenRn` \ (result,result_fvs) ->
266 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
267 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
269 warnUnusedLocalBinds unused_binders `thenRn_`
270 returnRn (result, delListFromNameSet all_fvs new_mbinders)
272 mbinders_w_srclocs = bagToList (collectMonoBinders mbinds)
276 %************************************************************************
278 \subsubsection{ MonoBinds -- the main work is done here}
280 %************************************************************************
282 @rn_mono_binds@ is used by {\em both} top-level and nested bindings.
283 It assumes that all variables bound in this group are already in scope.
284 This is done {\em either} by pass 3 (for the top-level bindings),
285 {\em or} by @rnMonoBinds@ (for the nested ones).
288 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
290 -> RnMS (RenamedHsBinds, --
291 FreeVars) -- Free variables
293 rn_mono_binds siglist mbinds
295 -- Rename the bindings, returning a MonoBindsInfo
296 -- which is a list of indivisible vertices so far as
297 -- the strongly-connected-components (SCC) analysis is concerned
298 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
300 -- Do the SCC analysis
302 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
303 scc_result = stronglyConnComp edges
304 final_binds = foldr1 ThenBinds (map reconstructCycle scc_result)
306 -- Deal with bound and free-var calculation
307 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
309 returnRn (final_binds, rhs_fvs)
312 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
313 unique ``vertex tags'' on its output; minor plumbing required.
315 Sigh --- need to pass along the signatures for the group of bindings,
316 in case any of them \fbox{\ ???\ }
319 flattenMonoBinds :: [RenamedSig] -- Signatures
321 -> RnMS [FlatMonoBindsInfo]
323 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
325 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
326 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
327 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
328 returnRn (flat1 ++ flat2)
330 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
331 = pushSrcLocRn locn $
332 rnPat pat `thenRn` \ (pat', pat_fvs) ->
334 -- Find which things are bound in this group
336 names_bound_here = mkNameSet (collectPatBinders pat')
337 sigs_for_me = sigsForMe (`elemNameSet` names_bound_here) sigs
339 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
342 fvs `plusFV` pat_fvs,
343 PatMonoBind pat' grhss' locn,
347 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
348 = pushSrcLocRn locn $
349 lookupBndrRn name `thenRn` \ new_name ->
351 sigs_for_me = sigsForMe (new_name ==) sigs
353 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
354 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
356 [(unitNameSet new_name,
358 FunMonoBind new_name inf new_matches locn,
364 @rnMethodBinds@ is used for the method bindings of a class and an instance
365 declaration. Like @rnMonoBinds@ but without dependency analysis.
367 NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
368 That's crucial when dealing with an instance decl:
370 instance Foo (T a) where
373 This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
374 and unless @op@ occurs we won't treat the type signature of @op@ in the class
375 decl for @Foo@ as a source of instance-decl gates. But we should! Indeed,
376 in many ways the @op@ in an instance decl is just like an occurrence, not
380 rnMethodBinds :: RdrNameMonoBinds -> RnMS (RenamedMonoBinds, FreeVars)
382 rnMethodBinds EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
384 rnMethodBinds (AndMonoBinds mb1 mb2)
385 = rnMethodBinds mb1 `thenRn` \ (mb1', fvs1) ->
386 rnMethodBinds mb2 `thenRn` \ (mb2', fvs2) ->
387 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
389 rnMethodBinds (FunMonoBind name inf matches locn)
390 = pushSrcLocRn locn $
392 lookupGlobalOccRn name `thenRn` \ sel_name ->
393 -- We use the selector name as the binder
395 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
396 mapRn_ (checkPrecMatch inf sel_name) new_matches `thenRn_`
397 returnRn (FunMonoBind sel_name inf new_matches locn, fvs `addOneFV` sel_name)
399 rnMethodBinds (PatMonoBind (VarPatIn name) grhss locn)
400 = pushSrcLocRn locn $
401 lookupGlobalOccRn name `thenRn` \ sel_name ->
402 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
403 returnRn (PatMonoBind (VarPatIn sel_name) grhss' locn, fvs `addOneFV` sel_name)
405 -- Can't handle method pattern-bindings which bind multiple methods.
406 rnMethodBinds mbind@(PatMonoBind other_pat _ locn)
407 = pushSrcLocRn locn $
408 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
412 %************************************************************************
414 \subsection[reconstruct-deps]{Reconstructing dependencies}
416 %************************************************************************
418 This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
419 as the two cases are similar.
422 reconstructCycle :: SCC FlatMonoBindsInfo
425 reconstructCycle (AcyclicSCC (_, _, binds, sigs))
426 = MonoBind binds sigs NonRecursive
428 reconstructCycle (CyclicSCC cycle)
429 = MonoBind this_gp_binds this_gp_sigs Recursive
431 this_gp_binds = foldr1 AndMonoBinds [binds | (_, _, binds, _) <- cycle]
432 this_gp_sigs = foldr1 (++) [sigs | (_, _, _, sigs) <- cycle]
435 %************************************************************************
437 \subsubsection{ Manipulating FlatMonoBindInfo}
439 %************************************************************************
441 During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
442 The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
443 a function binding, and has itself been dependency-analysed and
447 type FlatMonoBindsInfo
448 = (NameSet, -- Set of names defined in this vertex
449 NameSet, -- Set of names used in this vertex
451 [RenamedSig]) -- Signatures, if any, for this vertex
453 mkEdges :: [(FlatMonoBindsInfo, VertexTag)] -> [(FlatMonoBindsInfo, VertexTag, [VertexTag])]
456 = [ (info, tag, dest_vertices (nameSetToList names_used))
457 | (info@(names_defined, names_used, mbind, sigs), tag) <- flat_info
460 -- An edge (v,v') indicates that v depends on v'
461 dest_vertices src_mentions = [ target_vertex
462 | ((names_defined, _, _, _), target_vertex) <- flat_info,
463 mentioned_name <- src_mentions,
464 mentioned_name `elemNameSet` names_defined
469 %************************************************************************
471 \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
473 %************************************************************************
475 @renameSigs@ checks for:
477 \item more than one sig for one thing;
478 \item signatures given for things not bound here;
479 \item with suitably flaggery, that all top-level things have type signatures.
482 At the moment we don't gather free-var info from the types in
483 signatures. We'd only need this if we wanted to report unused tyvars.
486 renameSigs :: Bool -- True => warn if (required) type signatures are missing.
487 -> NameSet -- Set of names bound in this group
488 -> (RdrName -> RnMS Name)
490 -> RnMS ([RenamedSig], FreeVars) -- List of Sig constructors
492 renameSigs sigs_required binders lookup_occ_nm sigs
493 = -- Rename the signatures
494 mapFvRn (renameSig lookup_occ_nm) sigs `thenRn` \ (sigs', fvs) ->
496 -- Check for (a) duplicate signatures
497 -- (b) signatures for things not in this group
498 -- (c) optionally, bindings with no signature
500 (goodies, dups) = removeDups cmp_sig (sigsForMe (not . isUnboundName) sigs')
501 not_this_group = sigsForMe (not . (`elemNameSet` binders)) goodies
502 type_sig_vars = [n | Sig n _ _ <- goodies]
503 un_sigd_binders | sigs_required = nameSetToList binders `minusList` type_sig_vars
506 mapRn_ dupSigDeclErr dups `thenRn_`
507 mapRn_ unknownSigErr not_this_group `thenRn_`
508 mapRn_ (addWarnRn.missingSigWarn) un_sigd_binders `thenRn_`
509 returnRn (sigs', fvs)
511 -- we need bindings of *some* sort for every name
513 -- We use lookupOccRn in the signatures, which is a little bit unsatisfactory
514 -- because this won't work for:
515 -- instance Foo T where
518 -- We'll just rename the INLINE prag to refer to whatever other 'op'
519 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
520 -- Doesn't seem worth much trouble to sort this.
522 renameSig lookup_occ_nm (Sig v ty src_loc)
523 = pushSrcLocRn src_loc $
524 lookup_occ_nm v `thenRn` \ new_v ->
525 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
526 returnRn (Sig new_v new_ty src_loc, fvs `addOneFV` new_v)
528 renameSig _ (SpecInstSig ty src_loc)
529 = pushSrcLocRn src_loc $
530 rnHsSigType (text "A SPECIALISE instance pragma") ty `thenRn` \ (new_ty, fvs) ->
531 returnRn (SpecInstSig new_ty src_loc, fvs)
533 renameSig lookup_occ_nm (SpecSig v ty src_loc)
534 = pushSrcLocRn src_loc $
535 lookup_occ_nm v `thenRn` \ new_v ->
536 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
537 returnRn (SpecSig new_v new_ty src_loc, fvs `addOneFV` new_v)
539 renameSig lookup_occ_nm (FixSig (FixitySig v fix src_loc))
540 = pushSrcLocRn src_loc $
541 lookup_occ_nm v `thenRn` \ new_v ->
542 returnRn (FixSig (FixitySig new_v fix src_loc), unitFV new_v)
544 renameSig lookup_occ_nm (InlineSig v p src_loc)
545 = pushSrcLocRn src_loc $
546 lookup_occ_nm v `thenRn` \ new_v ->
547 returnRn (InlineSig new_v p src_loc, unitFV new_v)
549 renameSig lookup_occ_nm (NoInlineSig v p src_loc)
550 = pushSrcLocRn src_loc $
551 lookup_occ_nm v `thenRn` \ new_v ->
552 returnRn (NoInlineSig new_v p src_loc, unitFV new_v)
555 Checking for distinct signatures; oh, so boring
558 cmp_sig :: RenamedSig -> RenamedSig -> Ordering
559 cmp_sig (Sig n1 _ _) (Sig n2 _ _) = n1 `compare` n2
560 cmp_sig (InlineSig n1 _ _) (InlineSig n2 _ _) = n1 `compare` n2
561 cmp_sig (NoInlineSig n1 _ _) (NoInlineSig n2 _ _) = n1 `compare` n2
562 cmp_sig (SpecInstSig ty1 _) (SpecInstSig ty2 _) = cmpHsType compare ty1 ty2
563 cmp_sig (SpecSig n1 ty1 _) (SpecSig n2 ty2 _)
564 = -- may have many specialisations for one value;
565 -- but not ones that are exactly the same...
566 thenCmp (n1 `compare` n2) (cmpHsType compare ty1 ty2)
568 cmp_sig other_1 other_2 -- Tags *must* be different
569 | (sig_tag other_1) _LT_ (sig_tag other_2) = LT
572 sig_tag (Sig n1 _ _) = (ILIT(1) :: FAST_INT)
573 sig_tag (SpecSig n1 _ _) = ILIT(2)
574 sig_tag (InlineSig n1 _ _) = ILIT(3)
575 sig_tag (NoInlineSig n1 _ _) = ILIT(4)
576 sig_tag (SpecInstSig _ _) = ILIT(5)
577 sig_tag (FixSig _) = ILIT(6)
578 sig_tag _ = panic# "tag(RnBinds)"
581 %************************************************************************
583 \subsection{Error messages}
585 %************************************************************************
588 dupSigDeclErr (sig:sigs)
590 addErrRn (sep [ptext SLIT("Duplicate") <+> ptext what_it_is <> colon,
593 (what_it_is, loc) = sig_doc sig
597 addErrRn (sep [ptext SLIT("Misplaced"),
598 ptext what_it_is <> colon,
601 (what_it_is, loc) = sig_doc sig
603 sig_doc (Sig _ _ loc) = (SLIT("type signature"),loc)
604 sig_doc (ClassOpSig _ _ _ _ loc) = (SLIT("class-method type signature"), loc)
605 sig_doc (SpecSig _ _ loc) = (SLIT("SPECIALISE pragma"),loc)
606 sig_doc (InlineSig _ _ loc) = (SLIT("INLINE pragma"),loc)
607 sig_doc (NoInlineSig _ _ loc) = (SLIT("NOINLINE pragma"),loc)
608 sig_doc (SpecInstSig _ loc) = (SLIT("SPECIALISE instance pragma"),loc)
609 sig_doc (FixSig (FixitySig _ _ loc)) = (SLIT("fixity declaration"), loc)
612 = sep [ptext SLIT("definition but no type signature for"), quotes (ppr var)]
615 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))