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
11 #include "HsVersions.h"
28 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
29 -- depends on DsExpr.hi-boot.
51 %************************************************************************
53 %* The main function: deSugar
55 %************************************************************************
58 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Maybe ModGuts)
59 -- Can modify PCS by faulting in more declarations
63 tcg_env@(TcGblEnv { tcg_mod = mod,
65 tcg_type_env = type_env,
66 tcg_imports = imports,
67 tcg_exports = exports,
69 tcg_inst_uses = dfun_uses_var,
72 tcg_rdr_env = rdr_env,
73 tcg_fix_env = fix_env,
74 tcg_inst_env = inst_env,
75 tcg_fam_inst_env = fam_inst_env,
76 tcg_deprecs = deprecs,
81 tcg_fam_insts = fam_insts })
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 mod export_set
89 ; let target = hscTarget dflags
90 ; mb_res <- case target of
91 HscNothing -> return (Just ([], [], NoStubs, noHpcInfo, emptyModBreaks))
92 _ -> do (binds_cvr,ds_hpc_info, modBreaks)
93 <- if opt_Hpc || target == HscInterpreted
94 then addCoverageTicksToBinds dflags mod mod_loc (typeEnvTyCons type_env) binds
95 else return (binds, noHpcInfo, emptyModBreaks)
96 initDs hsc_env mod rdr_env type_env $ do
97 { core_prs <- dsTopLHsBinds auto_scc binds_cvr
98 ; (ds_fords, foreign_prs) <- dsForeigns fords
99 ; let all_prs = foreign_prs ++ core_prs
100 local_bndrs = mkVarSet (map fst all_prs)
101 ; ds_rules <- mappM (dsRule mod local_bndrs) rules
102 ; return (all_prs, catMaybes ds_rules, ds_fords, ds_hpc_info, modBreaks)
105 Nothing -> return Nothing ;
106 Just (all_prs, ds_rules, ds_fords,ds_hpc_info, modBreaks) -> do
108 { -- Add export flags to bindings
109 keep_alive <- readIORef keep_var
110 ; let final_prs = addExportFlags target export_set
111 keep_alive all_prs ds_rules
112 ds_binds = [Rec final_prs]
113 -- Notice that we put the whole lot in a big Rec, even the foreign binds
114 -- When compiling PrelFloat, which defines data Float = F# Float#
115 -- we want F# to be in scope in the foreign marshalling code!
116 -- You might think it doesn't matter, but the simplifier brings all top-level
117 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
119 -- Lint result if necessary
120 ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds
123 ; doIfSet (dopt Opt_D_dump_ds dflags)
124 (printDump (ppr_ds_rules ds_rules))
126 ; dfun_uses <- readIORef dfun_uses_var -- What dfuns are used
127 ; th_used <- readIORef th_var -- Whether TH is used
128 ; let used_names = allUses dus `unionNameSets` dfun_uses
129 pkgs | th_used = insertList thPackageId (imp_dep_pkgs imports)
130 | otherwise = imp_dep_pkgs imports
132 dep_mods = eltsUFM (delFromUFM (imp_dep_mods imports) (moduleName mod))
133 -- M.hi-boot can be in the imp_dep_mods, but we must remove
134 -- it before recording the modules on which this one depends!
135 -- (We want to retain M.hi-boot in imp_dep_mods so that
136 -- loadHiBootInterface can see if M's direct imports depend
137 -- on M.hi-boot, and hence that we should do the hi-boot consistency
140 dir_imp_mods = imp_mods imports
142 ; usages <- mkUsageInfo hsc_env dir_imp_mods dep_mods used_names
145 -- Modules don't compare lexicographically usually,
146 -- but we want them to do so here.
147 le_mod :: Module -> Module -> Bool
148 le_mod m1 m2 = moduleNameFS (moduleName m1)
149 <= moduleNameFS (moduleName m2)
150 le_dep_mod :: (ModuleName, IsBootInterface) -> (ModuleName, IsBootInterface) -> Bool
151 le_dep_mod (m1,_) (m2,_) = moduleNameFS m1 <= moduleNameFS m2
153 deps = Deps { dep_mods = sortLe le_dep_mod dep_mods,
154 dep_pkgs = sortLe (<=) pkgs,
155 dep_orphs = sortLe le_mod (imp_orphs imports),
156 dep_finsts = sortLe le_mod (imp_finsts imports) }
157 -- sort to get into canonical order
161 mg_boot = isHsBoot hsc_src,
162 mg_exports = exports,
165 mg_dir_imps = [m | (m,_,_) <- moduleEnvElts dir_imp_mods],
166 mg_rdr_env = rdr_env,
167 mg_fix_env = fix_env,
168 mg_deprecs = deprecs,
171 mg_fam_insts = fam_insts,
172 mg_inst_env = inst_env,
173 mg_fam_inst_env = fam_inst_env,
176 mg_foreign = ds_fords,
177 mg_hpc_info = ds_hpc_info,
178 mg_modBreaks = modBreaks,
179 mg_vect_info = noVectInfo
181 ; return (Just mod_guts)
184 mkAutoScc :: Module -> NameSet -> AutoScc
185 mkAutoScc mod exports
186 | not opt_SccProfilingOn -- No profiling
188 | opt_AutoSccsOnAllToplevs -- Add auto-scc on all top-level things
189 = AddSccs mod (\id -> True)
190 | opt_AutoSccsOnExportedToplevs -- Only on exported things
191 = AddSccs mod (\id -> idName id `elemNameSet` exports)
196 deSugarExpr :: HscEnv
197 -> Module -> GlobalRdrEnv -> TypeEnv
199 -> IO (Maybe CoreExpr)
200 -- Prints its own errors; returns Nothing if error occurred
202 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
203 = do { let dflags = hsc_dflags hsc_env
204 ; showPass dflags "Desugar"
207 ; mb_core_expr <- initDs hsc_env this_mod rdr_env type_env $
210 ; case mb_core_expr of {
211 Nothing -> return Nothing ;
215 dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
217 ; return (Just expr) } } }
220 -- Set the no-discard flag if either
221 -- a) the Id is exported
222 -- b) it's mentioned in the RHS of an orphan rule
223 -- c) it's in the keep-alive set
225 -- It means that the binding won't be discarded EVEN if the binding
226 -- ends up being trivial (v = w) -- the simplifier would usually just
227 -- substitute w for v throughout, but we don't apply the substitution to
228 -- the rules (maybe we should?), so this substitution would make the rule
231 -- You might wonder why exported Ids aren't already marked as such;
232 -- it's just because the type checker is rather busy already and
233 -- I didn't want to pass in yet another mapping.
235 addExportFlags target exports keep_alive prs rules
236 = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
239 | dont_discard bndr = setIdExported bndr
242 orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
244 not (isLocalRule rule) ]
245 -- A non-local rule keeps alive the free vars of its right-hand side.
246 -- (A "non-local" is one whose head function is not locally defined.)
247 -- Local rules are (later, after gentle simplification)
248 -- attached to the Id, and that keeps the rhs free vars alive.
250 dont_discard bndr = is_exported name
251 || name `elemNameSet` keep_alive
252 || bndr `elemVarSet` orph_rhs_fvs
256 -- In interactive mode, we don't want to discard any top-level
257 -- entities at all (eg. do not inline them away during
258 -- simplification), and retain them all in the TypeEnv so they are
259 -- available from the command line.
261 -- isExternalName separates the user-defined top-level names from those
262 -- introduced by the type checker.
263 is_exported :: Name -> Bool
264 is_exported | target == HscInterpreted = isExternalName
265 | otherwise = (`elemNameSet` exports)
267 ppr_ds_rules [] = empty
269 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
275 %************************************************************************
277 %* Desugaring transformation rules
279 %************************************************************************
282 dsRule :: Module -> IdSet -> LRuleDecl Id -> DsM (Maybe CoreRule)
283 dsRule mod in_scope (L loc (HsRule name act vars lhs tv_lhs rhs fv_rhs))
285 do { let bndrs = [var | RuleBndr (L _ var) <- vars]
286 ; lhs' <- dsLExpr lhs
287 ; rhs' <- dsLExpr rhs
289 ; case decomposeRuleLhs (occurAnalyseExpr lhs') of {
290 Nothing -> do { warnDs msg; return Nothing } ;
291 Just (fn_id, args) -> do
293 -- Substitute the dict bindings eagerly,
294 -- and take the body apart into a (f args) form
295 { let local_rule = isLocalId fn_id
296 -- NB: isLocalId is False of implicit Ids. This is good becuase
297 -- we don't want to attach rules to the bindings of implicit Ids,
298 -- because they don't show up in the bindings until just before code gen
299 fn_name = idName fn_id
301 rule = Rule { ru_name = name, ru_fn = fn_name, ru_act = act,
302 ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs',
303 ru_rough = roughTopNames args,
304 ru_local = local_rule }
308 msg = hang (ptext SLIT("RULE left-hand side too complicated to desugar; ignored"))