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 ( Bag, isEmptyBag, mapBag, emptyBag, bagToList )
37 import CoreLint ( showPass, endPass )
38 import CoreFVs ( ruleRhsFreeVars )
39 import Packages ( thPackage )
40 import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings,
41 mkWarnMsg, errorsFound, WarnMsg )
42 import ListSetOps ( insertList )
44 import UniqSupply ( mkSplitUniqSupply )
45 import SrcLoc ( Located(..), SrcSpan, unLoc )
46 import DATA_IOREF ( readIORef )
48 import Data.List ( sort )
51 %************************************************************************
53 %* The main function: deSugar
55 %************************************************************************
58 deSugar :: HscEnv -> TcGblEnv -> IO (Bag WarnMsg, Maybe ModGuts)
59 -- Can modify PCS by faulting in more declarations
62 tcg_env@(TcGblEnv { tcg_mod = mod,
63 tcg_type_env = type_env,
64 tcg_imports = imports,
65 tcg_exports = exports,
67 tcg_inst_uses = dfun_uses_var,
69 tcg_rdr_env = rdr_env,
70 tcg_fix_env = fix_env,
71 tcg_deprecs = deprecs,
73 = do { showPass dflags "Desugar"
76 ; (results, warnings) <- initDs hsc_env mod type_env $
77 dsProgram ghci_mode tcg_env
79 ; let { (ds_binds, ds_rules, ds_fords) = results
80 ; warns = mapBag mk_warn warnings
83 -- If warnings are considered errors, leave.
84 ; if errorsFound dflags (warns, emptyBag)
85 then return (warns, Nothing)
88 -- Lint result if necessary
89 { endPass dflags "Desugar" Opt_D_dump_ds ds_binds
92 ; doIfSet (dopt Opt_D_dump_ds dflags)
93 (printDump (ppr_ds_rules ds_rules))
95 ; dfun_uses <- readIORef dfun_uses_var -- What dfuns are used
96 ; let used_names = allUses dus `unionNameSets` dfun_uses
97 ; usages <- mkUsageInfo hsc_env imports used_names
99 ; th_used <- readIORef th_var
101 pkgs | th_used = insertList thPackage (imp_dep_pkgs imports)
102 | otherwise = imp_dep_pkgs imports
104 deps = Deps { dep_mods = moduleEnvElts (imp_dep_mods imports),
105 dep_pkgs = sort pkgs,
106 dep_orphs = sort (imp_orphs imports) }
107 -- sort to get into canonical order
111 mg_exports = exports,
114 mg_dir_imps = [m | (m,_,_) <- moduleEnvElts (imp_mods imports)],
115 mg_rdr_env = rdr_env,
116 mg_fix_env = fix_env,
117 mg_deprecs = deprecs,
122 mg_foreign = ds_fords }
124 ; return (warns, Just mod_guts)
128 dflags = hsc_dflags hsc_env
129 ghci_mode = hsc_mode hsc_env
130 print_unqual = unQualInScope rdr_env
132 -- Desugarer warnings are SDocs; here we
133 -- add the info about whether or not to print unqualified
134 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
135 mk_warn (loc, sdoc) = mkWarnMsg loc print_unqual sdoc
138 deSugarExpr :: HscEnv
139 -> Module -> GlobalRdrEnv -> TypeEnv
142 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
143 = do { showPass dflags "Desugar"
144 ; us <- mkSplitUniqSupply 'd'
147 ; (core_expr, ds_warns) <- initDs hsc_env this_mod type_env $
150 -- Display any warnings
151 -- Note: if -Werror is used, we don't signal an error here.
152 ; doIfSet (not (isEmptyBag ds_warns))
153 (printErrs (pprBagOfWarnings (mapBag mk_warn ds_warns)))
156 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
161 dflags = hsc_dflags hsc_env
162 print_unqual = unQualInScope rdr_env
164 mk_warn :: (SrcSpan,SDoc) -> WarnMsg
165 mk_warn (loc,sdoc) = mkWarnMsg loc print_unqual sdoc
168 dsProgram ghci_mode (TcGblEnv { tcg_exports = exports,
169 tcg_keep = keep_alive,
173 = dsHsBinds auto_scc binds [] `thenDs` \ core_prs ->
174 dsForeigns fords `thenDs` \ (ds_fords, foreign_prs) ->
176 all_prs = foreign_prs ++ core_prs
177 local_bndrs = mkVarSet (map fst all_prs)
179 mappM (dsRule local_bndrs) rules `thenDs` \ ds_rules ->
181 final_prs = addExportFlags ghci_mode exports keep_alive
182 local_bndrs all_prs ds_rules
183 ds_binds = [Rec final_prs]
184 -- Notice that we put the whole lot in a big Rec, even the foreign binds
185 -- When compiling PrelFloat, which defines data Float = F# Float#
186 -- we want F# to be in scope in the foreign marshalling code!
187 -- You might think it doesn't matter, but the simplifier brings all top-level
188 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
190 returnDs (ds_binds, ds_rules, ds_fords)
192 auto_scc | opt_SccProfilingOn = TopLevel
196 -- Set the no-discard flag if either
197 -- a) the Id is exported
198 -- b) it's mentioned in the RHS of an orphan rule
199 -- c) it's in the keep-alive set
201 -- It means that the binding won't be discarded EVEN if the binding
202 -- ends up being trivial (v = w) -- the simplifier would usually just
203 -- substitute w for v throughout, but we don't apply the substitution to
204 -- the rules (maybe we should?), so this substitution would make the rule
207 -- You might wonder why exported Ids aren't already marked as such;
208 -- it's just because the type checker is rather busy already and
209 -- I didn't want to pass in yet another mapping.
211 addExportFlags ghci_mode exports keep_alive bndrs prs rules
212 = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
214 add_export bndr | dont_discard bndr = setIdLocalExported bndr
217 orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
218 | (id, rule) <- rules,
219 not (id `elemVarSet` bndrs) ]
220 -- An orphan rule must keep alive the free vars
221 -- of its right-hand side.
222 -- Non-orphan rules are attached to the Id (bndr_with_rules above)
223 -- and that keeps the rhs free vars alive
225 dont_discard bndr = is_exported name
226 || name `elemNameSet` keep_alive
227 || bndr `elemVarSet` orph_rhs_fvs
231 -- In interactive mode, we don't want to discard any top-level
232 -- entities at all (eg. do not inline them away during
233 -- simplification), and retain them all in the TypeEnv so they are
234 -- available from the command line.
236 -- isExternalName separates the user-defined top-level names from those
237 -- introduced by the type checker.
238 is_exported :: Name -> Bool
239 is_exported | ghci_mode == Interactive = isExternalName
240 | otherwise = (`elemNameSet` exports)
242 ppr_ds_rules [] = empty
244 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
250 %************************************************************************
252 %* Desugaring transformation rules
254 %************************************************************************
257 dsRule :: IdSet -> LRuleDecl Id -> DsM (Id, CoreRule)
258 dsRule in_scope (L loc (HsRule name act vars lhs rhs))
260 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
261 dsLExpr rhs `thenDs` \ core_rhs ->
262 returnDs (fn, Rule name act tpl_vars args core_rhs)
264 tpl_vars = [var | RuleBndr (L _ var) <- vars]
265 all_vars = mkInScopeSet (extendVarSetList in_scope tpl_vars)
271 (HsLet [HsBindGroup dict_binds _ _] body) -> (dict_binds, body)
272 other -> (emptyBag, lhs)
274 mappM ds_dict_bind (bagToList dict_binds) `thenDs` \ dict_binds' ->
275 dsLExpr body `thenDs` \ body' ->
277 -- Substitute the dict bindings eagerly,
278 -- and take the body apart into a (f args) form
280 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
281 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
282 -- Note recursion here... substitution won't terminate
283 -- if there is genuine recursion... which there isn't
285 subst = mkSubst all_vars subst_env
286 body'' = substExpr subst body'
289 -- Now unpack the resulting body
291 pair = case collectArgs body'' of
292 (Var fn, args) -> (fn, args)
293 other -> pprPanic "dsRule" (ppr lhs)
297 ds_dict_bind (L _ (VarBind id rhs)) =
298 dsLExpr rhs `thenDs` \ rhs' ->