2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Desugar]{@deSugar@: the main function}
7 module Desugar ( deSugar, deSugarExpr ) where
9 #include "HsVersions.h"
11 import CmdLineOpts ( DynFlag(..), dopt, opt_SccProfilingOn )
12 import HscTypes ( ModGuts(..), ModGuts, HscEnv(..), GhciMode(..),
13 Dependencies(..), TypeEnv,
14 unQualInScope, availsToNameSet )
15 import HsSyn ( RuleDecl(..), RuleBndr(..), HsExpr(..), LHsExpr,
16 HsBindGroup(..), LRuleDecl, HsBind(..) )
17 import TcRnTypes ( TcGblEnv(..), ImportAvails(..) )
18 import MkIface ( mkUsageInfo )
19 import Id ( Id, setIdLocalExported, idName )
20 import Name ( Name, isExternalName )
22 import PprCore ( pprIdRules, pprCoreExpr )
23 import Subst ( substExpr, mkSubst, mkInScopeSet )
25 import DsExpr ( dsLExpr )
26 import DsBinds ( dsHsBinds, AutoScc(..) )
27 import DsForeign ( dsForeigns )
28 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
29 -- depends on DsExpr.hi-boot.
30 import Module ( Module, moduleEnvElts, emptyModuleEnv )
32 import RdrName ( GlobalRdrEnv )
36 import Bag ( isEmptyBag, mapBag, emptyBag, bagToList )
37 import CoreLint ( showPass, endPass )
38 import CoreFVs ( ruleRhsFreeVars )
39 import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings,
40 mkWarnMsg, errorsFound, WarnMsg )
42 import qualified Pretty
43 import UniqSupply ( mkSplitUniqSupply )
44 import SrcLoc ( Located(..), SrcSpan, unLoc )
45 import DATA_IOREF ( readIORef )
49 %************************************************************************
51 %* The main function: deSugar
53 %************************************************************************
56 deSugar :: HscEnv -> TcGblEnv -> IO (Maybe ModGuts)
57 -- Can modify PCS by faulting in more declarations
60 tcg_env@(TcGblEnv { tcg_mod = mod,
61 tcg_type_env = type_env,
62 tcg_imports = imports,
63 tcg_exports = exports,
65 tcg_inst_uses = dfun_uses_var,
66 tcg_rdr_env = rdr_env,
67 tcg_fix_env = fix_env,
68 tcg_deprecs = deprecs,
70 = do { showPass dflags "Desugar"
73 ; let { is_boot = imp_dep_mods imports }
74 ; (results, warnings) <- initDs hsc_env mod type_env is_boot $
75 dsProgram ghci_mode tcg_env
77 ; let { (ds_binds, ds_rules, ds_fords) = results
78 ; warns = mapBag mk_warn warnings
79 ; warn_doc = pprBagOfWarnings warns }
81 -- Display any warnings
82 ; doIfSet (not (isEmptyBag warnings))
85 -- If warnings are considered errors, leave.
86 ; if errorsFound dflags (warns, emptyBag)
90 -- Lint result if necessary
91 { endPass dflags "Desugar" Opt_D_dump_ds ds_binds
94 ; doIfSet (dopt Opt_D_dump_ds dflags)
95 (printDump (ppr_ds_rules ds_rules))
97 ; dfun_uses <- readIORef dfun_uses_var -- What dfuns are used
98 ; let used_names = allUses dus `unionNameSets` dfun_uses
99 ; usages <- mkUsageInfo hsc_env imports used_names
101 deps = Deps { dep_mods = moduleEnvElts (imp_dep_mods imports),
102 dep_pkgs = imp_dep_pkgs imports,
103 dep_orphs = imp_orphs imports }
106 mg_exports = exports,
109 mg_dir_imps = [m | (m,_) <- moduleEnvElts (imp_mods imports)],
110 mg_rdr_env = rdr_env,
111 mg_fix_env = fix_env,
112 mg_deprecs = deprecs,
117 mg_foreign = ds_fords }
119 ; return (Just mod_guts)
123 dflags = hsc_dflags hsc_env
124 ghci_mode = hsc_mode hsc_env
125 print_unqual = unQualInScope rdr_env
127 -- Desugarer warnings are SDocs; here we
128 -- add the info about whether or not to print unqualified
129 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
130 mk_warn (loc, sdoc) = mkWarnMsg loc print_unqual sdoc
133 deSugarExpr :: HscEnv
134 -> Module -> GlobalRdrEnv -> TypeEnv
137 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
138 = do { showPass dflags "Desugar"
139 ; us <- mkSplitUniqSupply 'd'
142 ; let { is_boot = emptyModuleEnv } -- Assume no hi-boot files when
143 -- doing stuff from the command line
144 ; (core_expr, ds_warns) <- initDs hsc_env this_mod type_env is_boot $
147 -- Display any warnings
148 -- Note: if -Werror is used, we don't signal an error here.
149 ; doIfSet (not (isEmptyBag ds_warns))
150 (printErrs (pprBagOfWarnings (mapBag mk_warn ds_warns)))
153 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
158 dflags = hsc_dflags hsc_env
159 print_unqual = unQualInScope rdr_env
161 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
162 mk_warn (loc,sdoc) = mkWarnMsg loc print_unqual sdoc
165 dsProgram ghci_mode (TcGblEnv { tcg_exports = exports,
166 tcg_keep = keep_alive,
170 = dsHsBinds auto_scc binds [] `thenDs` \ core_prs ->
171 dsForeigns fords `thenDs` \ (ds_fords, foreign_prs) ->
173 all_prs = foreign_prs ++ core_prs
174 local_bndrs = mkVarSet (map fst all_prs)
176 mappM (dsRule local_bndrs) rules `thenDs` \ ds_rules ->
178 final_prs = addExportFlags ghci_mode exports keep_alive
179 local_bndrs all_prs ds_rules
180 ds_binds = [Rec final_prs]
181 -- Notice that we put the whole lot in a big Rec, even the foreign binds
182 -- When compiling PrelFloat, which defines data Float = F# Float#
183 -- we want F# to be in scope in the foreign marshalling code!
184 -- You might think it doesn't matter, but the simplifier brings all top-level
185 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
187 returnDs (ds_binds, ds_rules, ds_fords)
189 auto_scc | opt_SccProfilingOn = TopLevel
193 -- Set the no-discard flag if either
194 -- a) the Id is exported
195 -- b) it's mentioned in the RHS of an orphan rule
196 -- c) it's in the keep-alive set
198 -- It means that the binding won't be discarded EVEN if the binding
199 -- ends up being trivial (v = w) -- the simplifier would usually just
200 -- substitute w for v throughout, but we don't apply the substitution to
201 -- the rules (maybe we should?), so this substitution would make the rule
204 -- You might wonder why exported Ids aren't already marked as such;
205 -- it's just because the type checker is rather busy already and
206 -- I didn't want to pass in yet another mapping.
208 addExportFlags ghci_mode exports keep_alive bndrs prs rules
209 = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
211 add_export bndr | dont_discard bndr = setIdLocalExported bndr
214 orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
215 | (id, rule) <- rules,
216 not (id `elemVarSet` bndrs) ]
217 -- An orphan rule must keep alive the free vars
218 -- of its right-hand side.
219 -- Non-orphan rules are attached to the Id (bndr_with_rules above)
220 -- and that keeps the rhs free vars alive
222 dont_discard bndr = is_exported name
223 || name `elemNameSet` keep_alive
224 || bndr `elemVarSet` orph_rhs_fvs
228 -- In interactive mode, we don't want to discard any top-level
229 -- entities at all (eg. do not inline them away during
230 -- simplification), and retain them all in the TypeEnv so they are
231 -- available from the command line.
233 -- isExternalName separates the user-defined top-level names from those
234 -- introduced by the type checker.
235 is_exported :: Name -> Bool
236 is_exported | ghci_mode == Interactive = isExternalName
237 | otherwise = (`elemNameSet` export_fvs)
239 export_fvs = availsToNameSet exports
241 ppr_ds_rules [] = empty
243 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
249 %************************************************************************
251 %* Desugaring transformation rules
253 %************************************************************************
256 dsRule :: IdSet -> LRuleDecl Id -> DsM (Id, CoreRule)
257 dsRule in_scope (L loc (HsRule name act vars lhs rhs))
259 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
260 dsLExpr rhs `thenDs` \ core_rhs ->
261 returnDs (fn, Rule name act tpl_vars args core_rhs)
263 tpl_vars = [var | RuleBndr (L _ var) <- vars]
264 all_vars = mkInScopeSet (extendVarSetList in_scope tpl_vars)
270 (HsLet [HsBindGroup dict_binds _ _] body) -> (dict_binds, body)
271 other -> (emptyBag, lhs)
273 mappM ds_dict_bind (bagToList dict_binds) `thenDs` \ dict_binds' ->
274 dsLExpr body `thenDs` \ body' ->
276 -- Substitute the dict bindings eagerly,
277 -- and take the body apart into a (f args) form
279 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
280 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
281 -- Note recursion here... substitution won't terminate
282 -- if there is genuine recursion... which there isn't
284 subst = mkSubst all_vars subst_env
285 body'' = substExpr subst body'
288 -- Now unpack the resulting body
290 pair = case collectArgs body'' of
291 (Var fn, args) -> (fn, args)
292 other -> pprPanic "dsRule" (ppr lhs)
296 ds_dict_bind (L _ (VarBind id rhs)) =
297 dsLExpr rhs `thenDs` \ rhs' ->