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 %* 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 %************************************************************************
203 - collects up the binders for this declaration group,
204 - checks that they form a set
205 - extends the environment to bind them to new local names
206 - calls @rnMonoBinds@ to do the real work
209 rnBinds :: RdrNameHsBinds
210 -> (RenamedHsBinds -> RnMS (result, FreeVars))
211 -> RnMS (result, FreeVars)
213 rnBinds EmptyBinds thing_inside = thing_inside EmptyBinds
214 rnBinds (MonoBind bind sigs _) thing_inside = rnMonoBinds bind sigs thing_inside
215 -- the parser doesn't produce other forms
218 rnMonoBinds :: RdrNameMonoBinds
220 -> (RenamedHsBinds -> RnMS (result, FreeVars))
221 -> RnMS (result, FreeVars)
223 rnMonoBinds EmptyMonoBinds sigs thing_inside = thing_inside EmptyBinds
225 rnMonoBinds mbinds sigs thing_inside -- Non-empty monobinds
226 = -- Extract all the binders in this group,
227 -- and extend current scope, inventing new names for the new binders
228 -- This also checks that the names form a set
229 bindLocatedLocalsRn (text "a binding group") mbinders_w_srclocs $ \ new_mbinders ->
231 binder_set = mkNameSet new_mbinders
233 -- Weed out the fixity declarations that do not
234 -- apply to any of the binders in this group.
235 (sigs_for_me, fixes_not_for_me) = partition forLocalBind sigs
237 forLocalBind (FixSig sig@(FixitySig name _ _ )) =
238 isJust (lookupFM binder_occ_fm (rdrNameOcc name))
239 forLocalBind _ = True
241 binder_occ_fm = listToFM [(nameOccName x,x) | x <- new_mbinders]
244 -- Report the fixity declarations in this group that
245 -- don't refer to any of the group's binders.
247 mapRn_ (unknownSigErr) fixes_not_for_me `thenRn_`
248 renameSigs False binder_set
249 (lookupSigOccRn binder_occ_fm) sigs_for_me `thenRn` \ (siglist, sig_fvs) ->
251 fixity_sigs = [(name,sig) | FixSig sig@(FixitySig name _ _) <- siglist ]
253 -- Install the fixity declarations that do apply here and go.
254 extendFixityEnv fixity_sigs (
255 rn_mono_binds siglist mbinds
256 ) `thenRn` \ (binds, bind_fvs) ->
258 -- Now do the "thing inside", and deal with the free-variable calculations
259 thing_inside binds `thenRn` \ (result,result_fvs) ->
261 all_fvs = result_fvs `plusFV` bind_fvs `plusFV` sig_fvs
262 unused_binders = nameSetToList (binder_set `minusNameSet` all_fvs)
264 warnUnusedLocalBinds unused_binders `thenRn_`
265 returnRn (result, delListFromNameSet all_fvs new_mbinders)
267 mbinders_w_srclocs = bagToList (collectMonoBinders mbinds)
271 %************************************************************************
273 %* MonoBinds -- the main work is done here
275 %************************************************************************
277 @rn_mono_binds@ is used by *both* top-level and nested bindings. It
278 assumes that all variables bound in this group are already in scope.
279 This is done *either* by pass 3 (for the top-level bindings), *or* by
280 @rnMonoBinds@ (for the nested ones).
283 rn_mono_binds :: [RenamedSig] -- Signatures attached to this group
285 -> RnMS (RenamedHsBinds, --
286 FreeVars) -- Free variables
288 rn_mono_binds siglist mbinds
290 -- Rename the bindings, returning a MonoBindsInfo
291 -- which is a list of indivisible vertices so far as
292 -- the strongly-connected-components (SCC) analysis is concerned
293 flattenMonoBinds siglist mbinds `thenRn` \ mbinds_info ->
295 -- Do the SCC analysis
297 edges = mkEdges (mbinds_info `zip` [(0::Int)..])
298 scc_result = stronglyConnComp edges
299 final_binds = foldr1 ThenBinds (map reconstructCycle scc_result)
301 -- Deal with bound and free-var calculation
302 rhs_fvs = plusFVs [fvs | (_,fvs,_,_) <- mbinds_info]
304 returnRn (final_binds, rhs_fvs)
307 @flattenMonoBinds@ is ever-so-slightly magical in that it sticks
308 unique ``vertex tags'' on its output; minor plumbing required.
310 Sigh - need to pass along the signatures for the group of bindings,
314 flattenMonoBinds :: [RenamedSig] -- Signatures
316 -> RnMS [FlatMonoBindsInfo]
318 flattenMonoBinds sigs EmptyMonoBinds = returnRn []
320 flattenMonoBinds sigs (AndMonoBinds bs1 bs2)
321 = flattenMonoBinds sigs bs1 `thenRn` \ flat1 ->
322 flattenMonoBinds sigs bs2 `thenRn` \ flat2 ->
323 returnRn (flat1 ++ flat2)
325 flattenMonoBinds sigs (PatMonoBind pat grhss locn)
326 = pushSrcLocRn locn $
327 rnPat pat `thenRn` \ (pat', pat_fvs) ->
329 -- Find which things are bound in this group
331 names_bound_here = mkNameSet (collectPatBinders pat')
332 sigs_for_me = sigsForMe (`elemNameSet` names_bound_here) sigs
334 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
337 fvs `plusFV` pat_fvs,
338 PatMonoBind pat' grhss' locn,
342 flattenMonoBinds sigs (FunMonoBind name inf matches locn)
343 = pushSrcLocRn locn $
344 lookupBndrRn name `thenRn` \ new_name ->
346 sigs_for_me = sigsForMe (new_name ==) sigs
348 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
349 mapRn_ (checkPrecMatch inf new_name) new_matches `thenRn_`
351 [(unitNameSet new_name,
353 FunMonoBind new_name inf new_matches locn,
359 @rnMethodBinds@ is used for the method bindings of a class and an instance
360 declaration. like @rnMonoBinds@ but without dependency analysis.
363 rnMethodBinds :: RdrNameMonoBinds -> RnMS (RenamedMonoBinds, FreeVars)
365 rnMethodBinds EmptyMonoBinds = returnRn (EmptyMonoBinds, emptyFVs)
367 rnMethodBinds (AndMonoBinds mb1 mb2)
368 = rnMethodBinds mb1 `thenRn` \ (mb1', fvs1) ->
369 rnMethodBinds mb2 `thenRn` \ (mb2', fvs2) ->
370 returnRn (mb1' `AndMonoBinds` mb2', fvs1 `plusFV` fvs2)
372 rnMethodBinds (FunMonoBind name inf matches locn)
373 = pushSrcLocRn locn $
375 lookupGlobalOccRn name `thenRn` \ sel_name ->
376 -- We use the selector name as the binder
378 mapFvRn rnMatch matches `thenRn` \ (new_matches, fvs) ->
379 mapRn_ (checkPrecMatch inf sel_name) new_matches `thenRn_`
380 returnRn (FunMonoBind sel_name inf new_matches locn, fvs)
382 rnMethodBinds (PatMonoBind (VarPatIn name) grhss locn)
383 = pushSrcLocRn locn $
384 lookupGlobalOccRn name `thenRn` \ sel_name ->
385 rnGRHSs grhss `thenRn` \ (grhss', fvs) ->
386 returnRn (PatMonoBind (VarPatIn sel_name) grhss' locn, fvs)
388 -- Can't handle method pattern-bindings which bind multiple methods.
389 rnMethodBinds mbind@(PatMonoBind other_pat _ locn)
390 = pushSrcLocRn locn $
391 failWithRn (EmptyMonoBinds, emptyFVs) (methodBindErr mbind)
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 %* 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: (a)~more than one sig for one thing;
459 (b)~signatures given for things not bound here; (c)~with suitably
460 flaggery, that all top-level things have type signatures.
462 At the moment we don't gather free-var info from the types in
463 signatures. We'd only need this if we wanted to report unused tyvars.
466 renameSigs :: Bool -- True => warn if (required) type signatures are missing.
467 -> NameSet -- Set of names bound in this group
468 -> (RdrName -> RnMS Name)
470 -> RnMS ([RenamedSig], FreeVars) -- List of Sig constructors
472 renameSigs sigs_required binders lookup_occ_nm sigs
473 = -- Rename the signatures
474 mapFvRn (renameSig lookup_occ_nm) sigs `thenRn` \ (sigs', fvs) ->
476 -- Check for (a) duplicate signatures
477 -- (b) signatures for things not in this group
478 -- (c) optionally, bindings with no signature
480 (goodies, dups) = removeDups cmp_sig (sigsForMe (not . isUnboundName) sigs')
481 not_this_group = sigsForMe (not . (`elemNameSet` binders)) goodies
482 type_sig_vars = [n | Sig n _ _ <- goodies]
483 un_sigd_binders | sigs_required = nameSetToList binders `minusList` type_sig_vars
486 mapRn_ dupSigDeclErr dups `thenRn_`
487 mapRn_ unknownSigErr not_this_group `thenRn_`
488 mapRn_ (addWarnRn.missingSigWarn) un_sigd_binders `thenRn_`
489 returnRn (sigs', fvs)
491 -- we need bindings of *some* sort for every name
493 -- We use lookupOccRn in the signatures, which is a little bit unsatisfactory
494 -- because this won't work for:
495 -- instance Foo T where
498 -- We'll just rename the INLINE prag to refer to whatever other 'op'
499 -- is in scope. (I'm assuming that Baz.op isn't in scope unqualified.)
500 -- Doesn't seem worth much trouble to sort this.
502 renameSig lookup_occ_nm (Sig v ty src_loc)
503 = pushSrcLocRn src_loc $
504 lookup_occ_nm v `thenRn` \ new_v ->
505 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
506 returnRn (Sig new_v new_ty src_loc, fvs `addOneFV` new_v)
508 renameSig _ (SpecInstSig ty src_loc)
509 = pushSrcLocRn src_loc $
510 rnHsSigType (text "A SPECIALISE instance pragma") ty `thenRn` \ (new_ty, fvs) ->
511 returnRn (SpecInstSig new_ty src_loc, fvs)
513 renameSig lookup_occ_nm (SpecSig v ty src_loc)
514 = pushSrcLocRn src_loc $
515 lookup_occ_nm v `thenRn` \ new_v ->
516 rnHsSigType (quotes (ppr v)) ty `thenRn` \ (new_ty,fvs) ->
517 returnRn (SpecSig new_v new_ty src_loc, fvs `addOneFV` new_v)
519 renameSig lookup_occ_nm (InlineSig v src_loc)
520 = pushSrcLocRn src_loc $
521 lookup_occ_nm v `thenRn` \ new_v ->
522 returnRn (InlineSig new_v src_loc, unitFV new_v)
524 renameSig lookup_occ_nm (FixSig (FixitySig v fix src_loc))
525 = pushSrcLocRn src_loc $
526 lookup_occ_nm v `thenRn` \ new_v ->
527 returnRn (FixSig (FixitySig new_v fix src_loc), unitFV new_v)
529 renameSig lookup_occ_nm (NoInlineSig v src_loc)
530 = pushSrcLocRn src_loc $
531 lookup_occ_nm v `thenRn` \ new_v ->
532 returnRn (NoInlineSig new_v src_loc, unitFV new_v)
535 Checking for distinct signatures; oh, so boring
538 cmp_sig :: RenamedSig -> RenamedSig -> Ordering
539 cmp_sig (Sig n1 _ _) (Sig n2 _ _) = n1 `compare` n2
540 cmp_sig (InlineSig n1 _) (InlineSig n2 _) = n1 `compare` n2
541 cmp_sig (NoInlineSig n1 _) (NoInlineSig n2 _) = n1 `compare` n2
542 cmp_sig (SpecInstSig ty1 _) (SpecInstSig ty2 _) = cmpHsType compare ty1 ty2
543 cmp_sig (SpecSig n1 ty1 _) (SpecSig n2 ty2 _)
544 = -- may have many specialisations for one value;
545 -- but not ones that are exactly the same...
546 thenCmp (n1 `compare` n2) (cmpHsType compare ty1 ty2)
548 cmp_sig other_1 other_2 -- Tags *must* be different
549 | (sig_tag other_1) _LT_ (sig_tag other_2) = LT
552 sig_tag (Sig n1 _ _) = (ILIT(1) :: FAST_INT)
553 sig_tag (SpecSig n1 _ _) = ILIT(2)
554 sig_tag (InlineSig n1 _) = ILIT(3)
555 sig_tag (NoInlineSig n1 _) = ILIT(4)
556 sig_tag (SpecInstSig _ _) = ILIT(5)
557 sig_tag (FixSig _) = ILIT(6)
558 sig_tag _ = panic# "tag(RnBinds)"
561 %************************************************************************
563 \subsection{Error messages}
565 %************************************************************************
568 dupSigDeclErr (sig:sigs)
570 addErrRn (sep [ptext SLIT("Duplicate") <+> ptext what_it_is <> colon,
573 (what_it_is, loc) = sig_doc sig
577 addErrRn (sep [ptext SLIT("Misplaced"),
578 ptext what_it_is <> colon,
581 (what_it_is, loc) = sig_doc sig
583 sig_doc (Sig _ _ loc) = (SLIT("type signature"),loc)
584 sig_doc (ClassOpSig _ _ _ loc) = (SLIT("class-method type signature"), loc)
585 sig_doc (SpecSig _ _ loc) = (SLIT("SPECIALISE pragma"),loc)
586 sig_doc (InlineSig _ loc) = (SLIT("INLINE pragma"),loc)
587 sig_doc (NoInlineSig _ loc) = (SLIT("NOINLINE pragma"),loc)
588 sig_doc (SpecInstSig _ loc) = (SLIT("SPECIALISE instance pragma"),loc)
589 sig_doc (FixSig (FixitySig _ _ loc)) = (SLIT("fixity declaration"), loc)
592 = sep [ptext SLIT("definition but no type signature for"), quotes (ppr var)]
595 = hang (ptext SLIT("Can't handle multiple methods defined by one pattern binding"))