2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 The Desugarer: turning HsSyn into Core.
9 module Desugar ( deSugar, deSugarExpr ) where
21 import CoqPass ( coqPassCoreToString, coqPassCoreToCore )
27 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
28 -- depends on DsExpr.hi-boot.
34 import CoreMonad ( endPass, CoreToDo(..) )
48 %************************************************************************
50 %* The main function: deSugar
52 %************************************************************************
55 -- | Main entry point to the desugarer.
56 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
57 -- Can modify PCS by faulting in more declarations
61 tcg_env@(TcGblEnv { tcg_mod = mod,
63 tcg_type_env = type_env,
64 tcg_imports = imports,
65 tcg_exports = exports,
67 tcg_rdr_env = rdr_env,
68 tcg_fix_env = fix_env,
69 tcg_inst_env = inst_env,
70 tcg_fam_inst_env = fam_inst_env,
74 tcg_imp_specs = imp_specs,
75 tcg_ev_binds = ev_binds,
80 tcg_fam_insts = fam_insts,
81 tcg_hpc = other_hpc_info })
83 = do { let dflags = hsc_dflags hsc_env
84 ; showPass dflags "Desugar"
86 -- Desugar the program
87 ; let export_set = availsToNameSet exports
88 ; let auto_scc = mkAutoScc dflags mod export_set
89 ; let target = hscTarget dflags
90 ; let hpcInfo = emptyHpcInfo other_hpc_info
94 return (emptyMessages,
95 Just ([], nilOL, [], [], NoStubs, hpcInfo, emptyModBreaks, undefined, undefined
116 (binds_cvr,ds_hpc_info, modBreaks)
118 || target == HscInterpreted)
119 && (not (isHsBoot hsc_src))
120 then addCoverageTicksToBinds dflags mod mod_loc
121 (typeEnvTyCons type_env) binds
122 else return (binds, hpcInfo, emptyModBreaks)
123 initDs hsc_env mod rdr_env type_env $ do
124 do { ds_ev_binds <- dsEvBinds ev_binds
125 ; core_prs <- dsTopLHsBinds auto_scc binds_cvr
126 ; (spec_prs, spec_rules) <- dsImpSpecs imp_specs
127 ; (ds_fords, foreign_prs) <- dsForeigns fords
128 ; ds_rules <- mapMaybeM dsRule rules
129 ; ds_vects <- mapM dsVect vects
130 ; hetmet_brak <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_brak_name else return undefined
131 ; hetmet_esc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_esc_name else return undefined
132 ; hetmet_PGArrow <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_name else return undefined
133 ; hetmet_pga_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_id_name else return undefined
134 ; hetmet_pga_comp <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_comp_name else return undefined
135 ; hetmet_pga_first <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_first_name else return undefined
136 ; hetmet_pga_second <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_second_name else return undefined
137 ; hetmet_pga_cancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancell_name else return undefined
138 ; hetmet_pga_cancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancelr_name else return undefined
139 ; hetmet_pga_uncancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancell_name else return undefined
140 ; hetmet_pga_uncancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancelr_name else return undefined
141 ; hetmet_pga_assoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_assoc_name else return undefined
142 ; hetmet_pga_unassoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_unassoc_name else return undefined
143 ; hetmet_pga_copy <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_copy_name else return undefined
144 ; hetmet_pga_drop <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_drop_name else return undefined
145 ; hetmet_pga_swap <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_swap_name else return undefined
146 ; hetmet_pga_applyl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyl_name else return undefined
147 ; hetmet_pga_applyr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyr_name else return undefined
148 ; hetmet_pga_curryl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryl_name else return undefined
149 ; hetmet_pga_curryr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryr_name else return undefined
151 | opt_Hpc = hpcInitCode mod ds_hpc_info
153 ; return ( ds_ev_binds
154 , foreign_prs `appOL` core_prs `appOL` spec_prs
155 , spec_rules ++ ds_rules, ds_vects
156 , ds_fords `appendStubC` hpc_init
157 , ds_hpc_info, modBreaks, hetmet_brak, hetmet_esc
165 , hetmet_pga_uncancell
166 , hetmet_pga_uncancelr
179 Nothing -> return (msgs, Nothing) ;
180 Just (ds_ev_binds, all_prs, all_rules, ds_vects, ds_fords,ds_hpc_info, modBreaks, hetmet_brak, hetmet_esc
188 , hetmet_pga_uncancell
189 , hetmet_pga_uncancelr
198 , hetmet_pga_curryr) -> do
200 { -- Add export flags to bindings
201 keep_alive <- readIORef keep_var
202 ; let (rules_for_locals, rules_for_imps)
203 = partition isLocalRule all_rules
204 final_prs = addExportFlagsAndRules target
205 export_set keep_alive rules_for_locals (fromOL all_prs)
207 final_pgm = combineEvBinds ds_ev_binds final_prs
208 -- Notice that we put the whole lot in a big Rec, even the foreign binds
209 -- When compiling PrelFloat, which defines data Float = F# Float#
210 -- we want F# to be in scope in the foreign marshalling code!
211 -- You might think it doesn't matter, but the simplifier brings all top-level
212 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
214 -- Lint result if necessary, and print
215 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared, before opt" $
216 (vcat [ pprCoreBindings final_pgm
217 , pprRules rules_for_imps ])
219 ; (ds_binds, ds_rules_for_imps) <- simpleOptPgm dflags final_pgm rules_for_imps
220 -- The simpleOptPgm gets rid of type
221 -- bindings plus any stupid dead code
223 ; ds_binds' <- if dopt Opt_F_coqpass dflags
224 then do { us <- mkSplitUniqSupply '~'
225 ; return (coqPassCoreToCore
251 ; dumpIfSet_dyn dflags Opt_D_coqpass "Coq Pass Output" $ text $ coqPassCoreToString ds_binds'
253 ; dumpIfSet_dyn dflags Opt_D_dump_coqpass "After Coq Pass" (text $ showSDoc $ pprCoreBindings ds_binds')
255 ; endPass dflags CoreDesugar ds_binds' ds_rules_for_imps
257 ; let used_names = mkUsedNames tcg_env
258 ; deps <- mkDependencies tcg_env
260 ; let mod_guts = ModGuts {
262 mg_boot = isHsBoot hsc_src,
263 mg_exports = exports,
265 mg_used_names = used_names,
266 mg_dir_imps = imp_mods imports,
267 mg_rdr_env = rdr_env,
268 mg_fix_env = fix_env,
273 mg_fam_insts = fam_insts,
274 mg_inst_env = inst_env,
275 mg_fam_inst_env = fam_inst_env,
276 mg_rules = ds_rules_for_imps,
277 mg_binds = ds_binds',
278 mg_foreign = ds_fords,
279 mg_hpc_info = ds_hpc_info,
280 mg_modBreaks = modBreaks,
281 mg_vect_decls = ds_vects,
282 mg_vect_info = noVectInfo
284 ; return (msgs, Just mod_guts)
287 dsImpSpecs :: [LTcSpecPrag] -> DsM (OrdList (Id,CoreExpr), [CoreRule])
289 = do { spec_prs <- mapMaybeM (dsSpec Nothing) imp_specs
290 ; let (spec_binds, spec_rules) = unzip spec_prs
291 ; return (concatOL spec_binds, spec_rules) }
293 combineEvBinds :: [DsEvBind] -> [(Id,CoreExpr)] -> [CoreBind]
294 -- Top-level bindings can include coercion bindings, but not via superclasses
295 -- See Note [Top-level evidence]
296 combineEvBinds [] val_prs
298 combineEvBinds (LetEvBind (NonRec b r) : bs) val_prs
299 | isId b = combineEvBinds bs ((b,r):val_prs)
300 | otherwise = NonRec b r : combineEvBinds bs val_prs
301 combineEvBinds (LetEvBind (Rec prs) : bs) val_prs
302 = combineEvBinds bs (prs ++ val_prs)
303 combineEvBinds (CaseEvBind x _ _ : _) _
304 = pprPanic "topEvBindPairs" (ppr x)
307 Note [Top-level evidence]
308 ~~~~~~~~~~~~~~~~~~~~~~~~~
309 Top-level evidence bindings may be mutually recursive with the top-level value
310 bindings, so we must put those in a Rec. But we can't put them *all* in a Rec
311 because the occurrence analyser doesn't teke account of type/coercion variables
312 when computing dependencies.
314 So we pull out the type/coercion variables (which are in dependency order),
319 mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
320 mkAutoScc dflags mod exports
321 | not opt_SccProfilingOn -- No profiling
323 -- Add auto-scc on all top-level things
324 | dopt Opt_AutoSccsOnAllToplevs dflags
325 = AddSccs mod (\id -> not $ isDerivedOccName $ getOccName id)
326 -- See #1641. This is pretty yucky, but I can't see a better way
327 -- to identify compiler-generated Ids, and at least this should
329 -- Only on exported things
330 | dopt Opt_AutoSccsOnExportedToplevs dflags
331 = AddSccs mod (\id -> idName id `elemNameSet` exports)
335 deSugarExpr :: HscEnv
336 -> Module -> GlobalRdrEnv -> TypeEnv
338 -> IO (Messages, Maybe CoreExpr)
339 -- Prints its own errors; returns Nothing if error occurred
341 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
342 let dflags = hsc_dflags hsc_env
343 showPass dflags "Desugar"
346 (msgs, mb_core_expr) <- initDs hsc_env this_mod rdr_env type_env $
350 Nothing -> return (msgs, Nothing)
354 dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
356 return (msgs, Just expr)
359 %************************************************************************
361 %* Add rules and export flags to binders
363 %************************************************************************
366 addExportFlagsAndRules
367 :: HscTarget -> NameSet -> NameSet -> [CoreRule]
368 -> [(Id, t)] -> [(Id, t)]
369 addExportFlagsAndRules target exports keep_alive rules prs
372 add_one bndr = add_rules name (add_export name bndr)
376 ---------- Rules --------
377 -- See Note [Attach rules to local ids]
378 -- NB: the binder might have some existing rules,
379 -- arising from specialisation pragmas
381 | Just rules <- lookupNameEnv rule_base name
382 = bndr `addIdSpecialisations` rules
385 rule_base = extendRuleBaseList emptyRuleBase rules
387 ---------- Export flag --------
388 -- See Note [Adding export flags]
390 | dont_discard name = setIdExported bndr
393 dont_discard :: Name -> Bool
394 dont_discard name = is_exported name
395 || name `elemNameSet` keep_alive
397 -- In interactive mode, we don't want to discard any top-level
398 -- entities at all (eg. do not inline them away during
399 -- simplification), and retain them all in the TypeEnv so they are
400 -- available from the command line.
402 -- isExternalName separates the user-defined top-level names from those
403 -- introduced by the type checker.
404 is_exported :: Name -> Bool
405 is_exported | target == HscInterpreted = isExternalName
406 | otherwise = (`elemNameSet` exports)
410 Note [Adding export flags]
411 ~~~~~~~~~~~~~~~~~~~~~~~~~~
412 Set the no-discard flag if either
413 a) the Id is exported
414 b) it's mentioned in the RHS of an orphan rule
415 c) it's in the keep-alive set
417 It means that the binding won't be discarded EVEN if the binding
418 ends up being trivial (v = w) -- the simplifier would usually just
419 substitute w for v throughout, but we don't apply the substitution to
420 the rules (maybe we should?), so this substitution would make the rule
423 You might wonder why exported Ids aren't already marked as such;
424 it's just because the type checker is rather busy already and
425 I didn't want to pass in yet another mapping.
427 Note [Attach rules to local ids]
428 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
429 Find the rules for locally-defined Ids; then we can attach them
430 to the binders in the top-level bindings
433 - It makes the rules easier to look up
434 - It means that transformation rules and specialisations for
435 locally defined Ids are handled uniformly
436 - It keeps alive things that are referred to only from a rule
437 (the occurrence analyser knows about rules attached to Ids)
438 - It makes sure that, when we apply a rule, the free vars
439 of the RHS are more likely to be in scope
440 - The imported rules are carried in the in-scope set
441 which is extended on each iteration by the new wave of
442 local binders; any rules which aren't on the binding will
446 %************************************************************************
448 %* Desugaring transformation rules
450 %************************************************************************
453 dsRule :: LRuleDecl Id -> DsM (Maybe CoreRule)
454 dsRule (L loc (HsRule name act vars lhs _tv_lhs rhs _fv_rhs))
456 do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
458 ; lhs' <- unsetOptM Opt_EnableRewriteRules $
459 unsetOptM Opt_WarnIdentities $
460 dsLExpr lhs -- Note [Desugaring RULE left hand sides]
462 ; rhs' <- dsLExpr rhs
464 -- Substitute the dict bindings eagerly,
465 -- and take the body apart into a (f args) form
466 ; case decomposeRuleLhs bndrs' lhs' of {
467 Left msg -> do { warnDs msg; return Nothing } ;
468 Right (final_bndrs, fn_id, args) -> do
470 { let is_local = isLocalId fn_id
471 -- NB: isLocalId is False of implicit Ids. This is good becuase
472 -- we don't want to attach rules to the bindings of implicit Ids,
473 -- because they don't show up in the bindings until just before code gen
474 fn_name = idName fn_id
475 final_rhs = simpleOptExpr rhs' -- De-crap it
476 rule = mkRule False {- Not auto -} is_local
477 name act fn_name final_bndrs args final_rhs
482 Note [Desugaring RULE left hand sides]
483 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
484 For the LHS of a RULE we do *not* want to desugar
485 [x] to build (\cn. x `c` n)
486 We want to leave explicit lists simply as chains
487 of cons's. We can achieve that slightly indirectly by
488 switching off EnableRewriteRules. See DsExpr.dsExplicitList.
490 That keeps the desugaring of list comprehensions simple too.
492 Nor do we want to warn of conversion identities on the LHS;
493 the rule is precisly to optimise them:
494 {-# RULES "fromRational/id" fromRational = id :: Rational -> Rational #-}
497 %************************************************************************
499 %* Desugaring vectorisation declarations
501 %************************************************************************
504 dsVect :: LVectDecl Id -> DsM CoreVect
505 dsVect (L loc (HsVect v rhs))
507 do { rhs' <- fmapMaybeM dsLExpr rhs
508 ; return $ Vect (unLoc v) rhs'
510 -- dsVect (L loc (HsVect v Nothing))
511 -- = return $ Vect v Nothing
512 -- dsVect (L loc (HsVect v (Just rhs)))
513 -- = putSrcSpanDs loc $
514 -- do { rhs' <- dsLExpr rhs
515 -- ; return $ Vect v (Just rhs')