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 UniqSupply ( mkSplitUniqSupply )
43 import SrcLoc ( Located(..), SrcSpan, unLoc )
44 import DATA_IOREF ( readIORef )
48 %************************************************************************
50 %* The main function: deSugar
52 %************************************************************************
55 deSugar :: HscEnv -> TcGblEnv -> IO (Maybe ModGuts)
56 -- Can modify PCS by faulting in more declarations
59 tcg_env@(TcGblEnv { tcg_mod = mod,
60 tcg_type_env = type_env,
61 tcg_imports = imports,
62 tcg_exports = exports,
64 tcg_inst_uses = dfun_uses_var,
65 tcg_rdr_env = rdr_env,
66 tcg_fix_env = fix_env,
67 tcg_deprecs = deprecs,
69 = do { showPass dflags "Desugar"
72 ; let { is_boot = imp_dep_mods imports }
73 ; (results, warnings) <- initDs hsc_env mod type_env is_boot $
74 dsProgram ghci_mode tcg_env
76 ; let { (ds_binds, ds_rules, ds_fords) = results
77 ; warns = mapBag mk_warn warnings
78 ; warn_doc = pprBagOfWarnings warns }
80 -- Display any warnings
81 ; doIfSet (not (isEmptyBag warnings))
84 -- If warnings are considered errors, leave.
85 ; if errorsFound dflags (warns, emptyBag)
89 -- Lint result if necessary
90 { endPass dflags "Desugar" Opt_D_dump_ds ds_binds
93 ; doIfSet (dopt Opt_D_dump_ds dflags)
94 (printDump (ppr_ds_rules ds_rules))
96 ; dfun_uses <- readIORef dfun_uses_var -- What dfuns are used
97 ; let used_names = allUses dus `unionNameSets` dfun_uses
98 ; usages <- mkUsageInfo hsc_env imports used_names
100 deps = Deps { dep_mods = moduleEnvElts (imp_dep_mods imports),
101 dep_pkgs = imp_dep_pkgs imports,
102 dep_orphs = imp_orphs imports }
105 mg_exports = exports,
108 mg_dir_imps = [m | (m,_) <- moduleEnvElts (imp_mods imports)],
109 mg_rdr_env = rdr_env,
110 mg_fix_env = fix_env,
111 mg_deprecs = deprecs,
116 mg_foreign = ds_fords }
118 ; return (Just mod_guts)
122 dflags = hsc_dflags hsc_env
123 ghci_mode = hsc_mode hsc_env
124 print_unqual = unQualInScope rdr_env
126 -- Desugarer warnings are SDocs; here we
127 -- add the info about whether or not to print unqualified
128 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
129 mk_warn (loc, sdoc) = mkWarnMsg loc print_unqual sdoc
132 deSugarExpr :: HscEnv
133 -> Module -> GlobalRdrEnv -> TypeEnv
136 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
137 = do { showPass dflags "Desugar"
138 ; us <- mkSplitUniqSupply 'd'
141 ; let { is_boot = emptyModuleEnv } -- Assume no hi-boot files when
142 -- doing stuff from the command line
143 ; (core_expr, ds_warns) <- initDs hsc_env this_mod type_env is_boot $
146 -- Display any warnings
147 -- Note: if -Werror is used, we don't signal an error here.
148 ; doIfSet (not (isEmptyBag ds_warns))
149 (printErrs (pprBagOfWarnings (mapBag mk_warn ds_warns)))
152 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
157 dflags = hsc_dflags hsc_env
158 print_unqual = unQualInScope rdr_env
160 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
161 mk_warn (loc,sdoc) = mkWarnMsg loc print_unqual sdoc
164 dsProgram ghci_mode (TcGblEnv { tcg_exports = exports,
165 tcg_keep = keep_alive,
169 = dsHsBinds auto_scc binds [] `thenDs` \ core_prs ->
170 dsForeigns fords `thenDs` \ (ds_fords, foreign_prs) ->
172 all_prs = foreign_prs ++ core_prs
173 local_bndrs = mkVarSet (map fst all_prs)
175 mappM (dsRule local_bndrs) rules `thenDs` \ ds_rules ->
177 final_prs = addExportFlags ghci_mode exports keep_alive
178 local_bndrs all_prs ds_rules
179 ds_binds = [Rec final_prs]
180 -- Notice that we put the whole lot in a big Rec, even the foreign binds
181 -- When compiling PrelFloat, which defines data Float = F# Float#
182 -- we want F# to be in scope in the foreign marshalling code!
183 -- You might think it doesn't matter, but the simplifier brings all top-level
184 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
186 returnDs (ds_binds, ds_rules, ds_fords)
188 auto_scc | opt_SccProfilingOn = TopLevel
192 -- Set the no-discard flag if either
193 -- a) the Id is exported
194 -- b) it's mentioned in the RHS of an orphan rule
195 -- c) it's in the keep-alive set
197 -- It means that the binding won't be discarded EVEN if the binding
198 -- ends up being trivial (v = w) -- the simplifier would usually just
199 -- substitute w for v throughout, but we don't apply the substitution to
200 -- the rules (maybe we should?), so this substitution would make the rule
203 -- You might wonder why exported Ids aren't already marked as such;
204 -- it's just because the type checker is rather busy already and
205 -- I didn't want to pass in yet another mapping.
207 addExportFlags ghci_mode exports keep_alive bndrs prs rules
208 = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
210 add_export bndr | dont_discard bndr = setIdLocalExported bndr
213 orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
214 | (id, rule) <- rules,
215 not (id `elemVarSet` bndrs) ]
216 -- An orphan rule must keep alive the free vars
217 -- of its right-hand side.
218 -- Non-orphan rules are attached to the Id (bndr_with_rules above)
219 -- and that keeps the rhs free vars alive
221 dont_discard bndr = is_exported name
222 || name `elemNameSet` keep_alive
223 || bndr `elemVarSet` orph_rhs_fvs
227 -- In interactive mode, we don't want to discard any top-level
228 -- entities at all (eg. do not inline them away during
229 -- simplification), and retain them all in the TypeEnv so they are
230 -- available from the command line.
232 -- isExternalName separates the user-defined top-level names from those
233 -- introduced by the type checker.
234 is_exported :: Name -> Bool
235 is_exported | ghci_mode == Interactive = isExternalName
236 | otherwise = (`elemNameSet` exports)
238 ppr_ds_rules [] = empty
240 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
246 %************************************************************************
248 %* Desugaring transformation rules
250 %************************************************************************
253 dsRule :: IdSet -> LRuleDecl Id -> DsM (Id, CoreRule)
254 dsRule in_scope (L loc (HsRule name act vars lhs rhs))
256 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
257 dsLExpr rhs `thenDs` \ core_rhs ->
258 returnDs (fn, Rule name act tpl_vars args core_rhs)
260 tpl_vars = [var | RuleBndr (L _ var) <- vars]
261 all_vars = mkInScopeSet (extendVarSetList in_scope tpl_vars)
267 (HsLet [HsBindGroup dict_binds _ _] body) -> (dict_binds, body)
268 other -> (emptyBag, lhs)
270 mappM ds_dict_bind (bagToList dict_binds) `thenDs` \ dict_binds' ->
271 dsLExpr body `thenDs` \ body' ->
273 -- Substitute the dict bindings eagerly,
274 -- and take the body apart into a (f args) form
276 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
277 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
278 -- Note recursion here... substitution won't terminate
279 -- if there is genuine recursion... which there isn't
281 subst = mkSubst all_vars subst_env
282 body'' = substExpr subst body'
285 -- Now unpack the resulting body
287 pair = case collectArgs body'' of
288 (Var fn, args) -> (fn, args)
289 other -> pprPanic "dsRule" (ppr lhs)
293 ds_dict_bind (L _ (VarBind id rhs)) =
294 dsLExpr rhs `thenDs` \ rhs' ->