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(..), ExternalPackageState(..),
13 PersistentCompilerState(..), Dependencies(..), TypeEnv, GlobalRdrEnv,
14 lookupType, unQualInScope )
15 import HsSyn ( MonoBinds, RuleDecl(..), RuleBndr(..),
16 HsExpr(..), HsBinds(..), MonoBinds(..) )
17 import TcHsSyn ( TypecheckedRuleDecl, TypecheckedHsExpr )
18 import TcRnTypes ( TcGblEnv(..), ImportAvails(..) )
19 import MkIface ( mkUsageInfo )
22 import PprCore ( pprIdRules, pprCoreExpr )
23 import Subst ( substExpr, mkSubst, mkInScopeSet )
25 import DsExpr ( dsExpr )
26 import DsBinds ( dsMonoBinds, 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 )
32 import NameEnv ( lookupNameEnv )
35 import Bag ( isEmptyBag, mapBag, emptyBag )
36 import CoreLint ( showPass, endPass )
37 import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings,
38 addShortWarnLocLine, errorsFound )
40 import qualified Pretty
41 import UniqSupply ( mkSplitUniqSupply )
42 import Maybes ( orElse )
43 import SrcLoc ( SrcLoc )
45 import DATA_IOREF ( readIORef )
48 %************************************************************************
50 %* The main function: deSugar
52 %************************************************************************
55 deSugar :: HscEnv -> PersistentCompilerState
56 -> TcGblEnv -> IO (Maybe ModGuts)
59 (TcGblEnv { tcg_mod = mod,
60 tcg_type_env = type_env,
61 tcg_usages = usage_var,
62 tcg_imports = imports,
63 tcg_exports = exports,
64 tcg_rdr_env = rdr_env,
65 tcg_fix_env = fix_env,
66 tcg_deprecs = deprecs,
71 = do { showPass dflags "Desugar"
72 ; us <- mkSplitUniqSupply 'd'
73 ; usages <- readIORef usage_var
76 ; let ((ds_binds, ds_rules, ds_fords), ds_warns)
77 = initDs dflags us lookup mod
78 (dsProgram binds rules fords)
80 warns = mapBag mk_warn ds_warns
81 warn_doc = pprBagOfWarnings warns
83 -- Display any warnings
84 ; doIfSet (not (isEmptyBag ds_warns))
87 -- if warnings are considered errors, leave.
88 ; if errorsFound dflags (warns, emptyBag)
92 -- Lint result if necessary
93 endPass dflags "Desugar" Opt_D_dump_ds ds_binds
96 ; doIfSet (dopt Opt_D_dump_ds dflags)
97 (printDump (ppr_ds_rules ds_rules))
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,
107 mg_usages = mkUsageInfo hsc_env eps imports usages,
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 print_unqual = unQualInScope rdr_env
125 -- Desugarer warnings are SDocs; here we
126 -- add the info about whether or not to print unqualified
127 mk_warn :: (SrcLoc,SDoc) -> (SrcLoc, Pretty.Doc)
128 mk_warn (loc, sdoc) = addShortWarnLocLine loc print_unqual sdoc
130 -- The lookup function passed to initDs is used for well-known Ids,
131 -- such as fold, build, cons etc, so the chances are
132 -- it'll be found in the package symbol table. That's
133 -- why we don't merge all these tables
136 hpt = hsc_HPT hsc_env
137 lookup n = case lookupType hpt pte n of {
140 case lookupNameEnv type_env n of
142 other -> pprPanic "Desugar: lookup:" (ppr n)
145 deSugarExpr :: HscEnv
146 -> PersistentCompilerState
147 -> Module -> GlobalRdrEnv -> TypeEnv
150 deSugarExpr hsc_env pcs this_mod rdr_env type_env tc_expr
151 = do { showPass dflags "Desugar"
152 ; us <- mkSplitUniqSupply 'd'
155 ; let (core_expr, ds_warns) = initDs dflags us lookup this_mod (dsExpr tc_expr)
156 warn_doc = pprBagOfWarnings (mapBag mk_warn ds_warns)
158 -- Display any warnings
159 -- Note: if -Werror is used, we don't signal an error here.
160 ; doIfSet (not (isEmptyBag ds_warns))
164 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
169 dflags = hsc_dflags hsc_env
170 hpt = hsc_HPT hsc_env
171 pte = eps_PTE (pcs_EPS pcs)
172 lookup n = lookupNameEnv type_env n `orElse` -- Look in the type env of the
173 -- current module first
174 lookupType hpt pte n `orElse` -- Then other modules
175 pprPanic "Desugar: lookup:" (ppr n)
177 mk_warn :: (SrcLoc,SDoc) -> (SrcLoc, Pretty.Doc)
178 mk_warn (loc,sdoc) = addShortWarnLocLine loc print_unqual sdoc
180 print_unqual = unQualInScope rdr_env
182 dsProgram all_binds rules fo_decls
183 = dsMonoBinds auto_scc all_binds [] `thenDs` \ core_prs ->
184 dsForeigns fo_decls `thenDs` \ (ds_fords, foreign_binds) ->
186 ds_binds = [Rec (foreign_binds ++ core_prs)]
187 -- Notice that we put the whole lot in a big Rec, even the foreign binds
188 -- When compiling PrelFloat, which defines data Float = F# Float#
189 -- we want F# to be in scope in the foreign marshalling code!
190 -- You might think it doesn't matter, but the simplifier brings all top-level
191 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
193 local_binders = mkVarSet (bindersOfBinds ds_binds)
195 mapDs (dsRule local_binders) rules `thenDs` \ ds_rules ->
196 returnDs (ds_binds, ds_rules, ds_fords)
198 auto_scc | opt_SccProfilingOn = TopLevel
201 ppr_ds_rules [] = empty
203 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
209 %************************************************************************
211 %* Desugaring transformation rules
213 %************************************************************************
216 dsRule :: IdSet -> TypecheckedRuleDecl -> DsM (Id, CoreRule)
217 dsRule in_scope (IfaceRuleOut fun rule) -- Built-in rules come this way
218 = returnDs (fun, rule)
220 dsRule in_scope (HsRule name act vars lhs rhs loc)
222 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
223 dsExpr rhs `thenDs` \ core_rhs ->
224 returnDs (fn, Rule name act tpl_vars args core_rhs)
226 tpl_vars = [var | RuleBndr var <- vars]
227 all_vars = mkInScopeSet (in_scope `unionVarSet` mkVarSet tpl_vars)
231 (dict_binds, body) = case lhs of
232 (HsLet (MonoBind dict_binds _ _) body) -> (dict_binds, body)
233 other -> (EmptyMonoBinds, lhs)
235 ds_dict_binds dict_binds `thenDs` \ dict_binds' ->
236 dsExpr body `thenDs` \ body' ->
238 -- Substitute the dict bindings eagerly,
239 -- and take the body apart into a (f args) form
241 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
242 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
243 -- Note recursion here... substitution won't terminate
244 -- if there is genuine recursion... which there isn't
246 subst = mkSubst all_vars subst_env
247 body'' = substExpr subst body'
250 -- Now unpack the resulting body
252 pair = case collectArgs body'' of
253 (Var fn, args) -> (fn, args)
254 other -> pprPanic "dsRule" (ppr lhs)
258 ds_dict_binds EmptyMonoBinds = returnDs []
259 ds_dict_binds (AndMonoBinds b1 b2) = ds_dict_binds b1 `thenDs` \ env1 ->
260 ds_dict_binds b2 `thenDs` \ env2 ->
261 returnDs (env1 ++ env2)
262 ds_dict_binds (VarMonoBind id rhs) = dsExpr rhs `thenDs` \ rhs' ->