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 )
36 import CoreLint ( showPass, endPass )
37 import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings, addShortWarnLocLine )
39 import qualified Pretty
40 import UniqSupply ( mkSplitUniqSupply )
41 import Maybes ( orElse )
42 import SrcLoc ( SrcLoc )
44 import DATA_IOREF ( readIORef )
47 %************************************************************************
49 %* The main function: deSugar
51 %************************************************************************
54 deSugar :: HscEnv -> PersistentCompilerState
55 -> TcGblEnv -> IO ModGuts
58 (TcGblEnv { tcg_mod = mod,
59 tcg_type_env = type_env,
60 tcg_usages = usage_var,
61 tcg_imports = imports,
62 tcg_exports = exports,
63 tcg_rdr_env = rdr_env,
64 tcg_fix_env = fix_env,
65 tcg_deprecs = deprecs,
70 = do { showPass dflags "Desugar"
71 ; us <- mkSplitUniqSupply 'd'
72 ; usages <- readIORef usage_var
75 ; let ((ds_binds, ds_rules, ds_fords), ds_warns)
76 = initDs dflags us lookup mod
77 (dsProgram binds rules fords)
79 warn_doc = pprBagOfWarnings (mapBag mk_warn ds_warns)
81 -- Display any warnings
82 ; doIfSet (not (isEmptyBag ds_warns))
85 -- Lint result if necessary
86 ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds
89 ; doIfSet (dopt Opt_D_dump_ds dflags)
90 (printDump (ppr_ds_rules ds_rules))
93 deps = Deps { dep_mods = moduleEnvElts (imp_dep_mods imports),
94 dep_pkgs = imp_dep_pkgs imports,
95 dep_orphs = imp_orphs imports }
100 mg_usages = mkUsageInfo hsc_env eps imports usages,
101 mg_dir_imps = [m | (m,_) <- moduleEnvElts (imp_mods imports)],
102 mg_rdr_env = rdr_env,
103 mg_fix_env = fix_env,
104 mg_deprecs = deprecs,
109 mg_foreign = ds_fords }
115 dflags = hsc_dflags hsc_env
116 print_unqual = unQualInScope rdr_env
118 -- Desugarer warnings are SDocs; here we
119 -- add the info about whether or not to print unqualified
120 mk_warn :: (SrcLoc,SDoc) -> (SrcLoc, Pretty.Doc)
121 mk_warn (loc, sdoc) = addShortWarnLocLine loc print_unqual sdoc
123 -- The lookup function passed to initDs is used for well-known Ids,
124 -- such as fold, build, cons etc, so the chances are
125 -- it'll be found in the package symbol table. That's
126 -- why we don't merge all these tables
129 hpt = hsc_HPT hsc_env
130 lookup n = case lookupType hpt pte n of {
133 case lookupNameEnv type_env n of
135 other -> pprPanic "Desugar: lookup:" (ppr n)
138 deSugarExpr :: HscEnv
139 -> PersistentCompilerState
140 -> Module -> GlobalRdrEnv -> TypeEnv
143 deSugarExpr hsc_env pcs this_mod rdr_env type_env tc_expr
144 = do { showPass dflags "Desugar"
145 ; us <- mkSplitUniqSupply 'd'
148 ; let (core_expr, ds_warns) = initDs dflags us lookup this_mod (dsExpr tc_expr)
149 warn_doc = pprBagOfWarnings (mapBag mk_warn ds_warns)
151 -- Display any warnings
152 ; doIfSet (not (isEmptyBag ds_warns))
156 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
161 dflags = hsc_dflags hsc_env
162 hpt = hsc_HPT hsc_env
163 pte = eps_PTE (pcs_EPS pcs)
164 lookup n = lookupNameEnv type_env n `orElse` -- Look in the type env of the
165 -- current module first
166 lookupType hpt pte n `orElse` -- Then other modules
167 pprPanic "Desugar: lookup:" (ppr n)
169 mk_warn :: (SrcLoc,SDoc) -> (SrcLoc, Pretty.Doc)
170 mk_warn (loc,sdoc) = addShortWarnLocLine loc print_unqual sdoc
172 print_unqual = unQualInScope rdr_env
174 dsProgram all_binds rules fo_decls
175 = dsMonoBinds auto_scc all_binds [] `thenDs` \ core_prs ->
176 dsForeigns fo_decls `thenDs` \ (ds_fords, foreign_binds) ->
178 ds_binds = [Rec (foreign_binds ++ core_prs)]
179 -- Notice that we put the whole lot in a big Rec, even the foreign binds
180 -- When compiling PrelFloat, which defines data Float = F# Float#
181 -- we want F# to be in scope in the foreign marshalling code!
182 -- You might think it doesn't matter, but the simplifier brings all top-level
183 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
185 local_binders = mkVarSet (bindersOfBinds ds_binds)
187 mapDs (dsRule local_binders) rules `thenDs` \ ds_rules ->
188 returnDs (ds_binds, ds_rules, ds_fords)
190 auto_scc | opt_SccProfilingOn = TopLevel
193 ppr_ds_rules [] = empty
195 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
201 %************************************************************************
203 %* Desugaring transformation rules
205 %************************************************************************
208 dsRule :: IdSet -> TypecheckedRuleDecl -> DsM (Id, CoreRule)
209 dsRule in_scope (IfaceRuleOut fun rule) -- Built-in rules come this way
210 = returnDs (fun, rule)
212 dsRule in_scope (HsRule name act vars lhs rhs loc)
214 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
215 dsExpr rhs `thenDs` \ core_rhs ->
216 returnDs (fn, Rule name act tpl_vars args core_rhs)
218 tpl_vars = [var | RuleBndr var <- vars]
219 all_vars = mkInScopeSet (in_scope `unionVarSet` mkVarSet tpl_vars)
223 (dict_binds, body) = case lhs of
224 (HsLet (MonoBind dict_binds _ _) body) -> (dict_binds, body)
225 other -> (EmptyMonoBinds, lhs)
227 ds_dict_binds dict_binds `thenDs` \ dict_binds' ->
228 dsExpr body `thenDs` \ body' ->
230 -- Substitute the dict bindings eagerly,
231 -- and take the body apart into a (f args) form
233 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
234 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
235 -- Note recursion here... substitution won't terminate
236 -- if there is genuine recursion... which there isn't
238 subst = mkSubst all_vars subst_env
239 body'' = substExpr subst body'
242 -- Now unpack the resulting body
244 pair = case collectArgs body'' of
245 (Var fn, args) -> (fn, args)
246 other -> pprPanic "dsRule" (ppr lhs)
250 ds_dict_binds EmptyMonoBinds = returnDs []
251 ds_dict_binds (AndMonoBinds b1 b2) = ds_dict_binds b1 `thenDs` \ env1 ->
252 ds_dict_binds b2 `thenDs` \ env2 ->
253 returnDs (env1 ++ env2)
254 ds_dict_binds (VarMonoBind id rhs) = dsExpr rhs `thenDs` \ rhs' ->