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 ( DynFlags, DynFlag(..), dopt, opt_SccProfilingOn )
12 import HsSyn ( MonoBinds, RuleDecl(..), RuleBndr(..),
13 HsExpr(..), HsBinds(..), MonoBinds(..) )
14 import TcHsSyn ( TypecheckedRuleDecl, TypecheckedHsExpr )
15 import TcModule ( TcResults(..) )
18 import PprCore ( pprIdCoreRule, pprCoreExpr )
19 import Subst ( substExpr, mkSubst, mkInScopeSet )
21 import DsExpr ( dsExpr )
22 import DsBinds ( dsMonoBinds, AutoScc(..) )
23 import DsForeign ( dsForeigns )
24 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
25 -- depends on DsExpr.hi-boot.
26 import Module ( Module )
28 import Name ( lookupNameEnv )
31 import Bag ( isEmptyBag )
32 import CoreLint ( showPass, endPass )
33 import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings )
35 import UniqSupply ( mkSplitUniqSupply )
36 import HscTypes ( HomeSymbolTable, PersistentCompilerState(..), TyThing(..), lookupType, )
39 %************************************************************************
41 %* The main function: deSugar
43 %************************************************************************
45 The only trick here is to get the @DsMonad@ stuff off to a good
50 -> PersistentCompilerState -> HomeSymbolTable
51 -> Module -> PrintUnqualified
53 -> IO ([CoreBind], [(Id,CoreRule)], (SDoc, SDoc, [CoreBndr]))
55 deSugar dflags pcs hst mod_name unqual
56 (TcResults {tc_env = local_type_env,
60 = do { showPass dflags "Desugar"
61 ; us <- mkSplitUniqSupply 'd'
64 ; let (result, ds_warns) = initDs dflags us lookup mod_name
65 (dsProgram mod_name all_binds rules fo_decls)
66 (ds_binds, ds_rules, _) = result
68 -- Display any warnings
69 ; doIfSet (not (isEmptyBag ds_warns))
70 (printErrs unqual (pprBagOfWarnings ds_warns))
72 -- Lint result if necessary
73 ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds
76 ; doIfSet (dopt Opt_D_dump_ds dflags)
77 (printDump (ppr_ds_rules ds_rules))
83 -- The lookup function passed to initDs is used for well-known Ids,
84 -- such as fold, build, cons etc, so the chances are
85 -- it'll be found in the package symbol table. That's
86 -- why we don't merge all these tables
88 lookup n = case lookupType hst pte n of {
91 case lookupNameEnv local_type_env n of
93 other -> pprPanic "Desugar: lookup:" (ppr n)
96 deSugarExpr :: DynFlags
97 -> PersistentCompilerState -> HomeSymbolTable
98 -> Module -> PrintUnqualified
101 deSugarExpr dflags pcs hst mod_name unqual tc_expr
102 = do { showPass dflags "Desugar"
103 ; us <- mkSplitUniqSupply 'd'
106 ; let (core_expr, ds_warns) = initDs dflags us lookup mod_name (dsExpr tc_expr)
108 -- Display any warnings
109 ; doIfSet (not (isEmptyBag ds_warns))
110 (printErrs unqual (pprBagOfWarnings ds_warns))
113 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
119 lookup n = case lookupType hst pte n of
121 other -> pprPanic "Desugar: lookup:" (ppr n)
123 dsProgram mod_name all_binds rules fo_decls
124 = dsMonoBinds auto_scc all_binds [] `thenDs` \ core_prs ->
125 dsForeigns mod_name fo_decls `thenDs` \ (fe_binders, foreign_binds, h_code, c_code) ->
127 ds_binds = [Rec (foreign_binds ++ core_prs)]
128 -- Notice that we put the whole lot in a big Rec, even the foreign binds
129 -- When compiling PrelFloat, which defines data Float = F# Float#
130 -- we want F# to be in scope in the foreign marshalling code!
131 -- You might think it doesn't matter, but the simplifier brings all top-level
132 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
134 local_binders = mkVarSet (bindersOfBinds ds_binds)
136 mapDs (dsRule local_binders) rules `thenDs` \ rules' ->
137 returnDs (ds_binds, rules', (h_code, c_code, fe_binders))
139 auto_scc | opt_SccProfilingOn = TopLevel
142 ppr_ds_rules [] = empty
144 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
145 vcat (map pprIdCoreRule rules)
149 %************************************************************************
151 %* Desugaring transformation rules
153 %************************************************************************
156 dsRule :: IdSet -> TypecheckedRuleDecl -> DsM (Id, CoreRule)
157 dsRule in_scope (HsRule name sig_tvs vars lhs rhs loc)
159 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
160 dsExpr rhs `thenDs` \ core_rhs ->
161 returnDs (fn, Rule name tpl_vars args core_rhs)
163 tpl_vars = sig_tvs ++ [var | RuleBndr var <- vars]
164 all_vars = mkInScopeSet (in_scope `unionVarSet` mkVarSet tpl_vars)
168 (dict_binds, body) = case lhs of
169 (HsLet (MonoBind dict_binds _ _) body) -> (dict_binds, body)
170 other -> (EmptyMonoBinds, lhs)
172 ds_dict_binds dict_binds `thenDs` \ dict_binds' ->
173 dsExpr body `thenDs` \ body' ->
175 -- Substitute the dict bindings eagerly,
176 -- and take the body apart into a (f args) form
178 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
179 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
180 -- Note recursion here... substitution won't terminate
181 -- if there is genuine recursion... which there isn't
183 subst = mkSubst all_vars subst_env
184 body'' = substExpr subst body'
187 -- Now unpack the resulting body
189 pair = case collectArgs body'' of
190 (Var fn, args) -> (fn, args)
191 other -> pprPanic "dsRule" (ppr lhs)
195 ds_dict_binds EmptyMonoBinds = returnDs []
196 ds_dict_binds (AndMonoBinds b1 b2) = ds_dict_binds b1 `thenDs` \ env1 ->
197 ds_dict_binds b2 `thenDs` \ env2 ->
198 returnDs (env1 ++ env2)
199 ds_dict_binds (VarMonoBind id rhs) = dsExpr rhs `thenDs` \ rhs' ->