2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Desugar]{@deSugar@: the main function}
7 module Desugar ( deSugar ) 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 )
15 import TcModule ( TcResults(..) )
17 import Rules ( ProtoCoreRule(..), pprProtoCoreRule )
18 import Subst ( substExpr, mkSubst, mkInScopeSet )
20 import DsExpr ( dsExpr )
21 import DsBinds ( dsMonoBinds, AutoScc(..) )
22 import DsForeign ( dsForeigns )
23 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
24 -- depends on DsExpr.hi-boot.
25 import Module ( Module )
28 import Bag ( isEmptyBag )
29 import CoreLint ( beginPass, endPass )
30 import ErrUtils ( doIfSet, pprBagOfWarnings )
32 import UniqSupply ( UniqSupply )
33 import HscTypes ( HomeSymbolTable )
36 %************************************************************************
38 %* The main function: deSugar
40 %************************************************************************
42 The only trick here is to get the @DsMonad@ stuff off to a good
51 -> IO ([CoreBind], [ProtoCoreRule], SDoc, SDoc, [CoreBndr])
53 deSugar dflags mod_name us hst
54 (TcResults {tc_env = global_val_env,
60 beginPass dflags "Desugar"
62 let (result, ds_warns) =
63 initDs dflags us (hst,pcs,global_val_env) mod_name
64 (dsProgram mod_name all_binds rules fo_decls)
65 (ds_binds, ds_rules, _, _, _) = result
67 -- Display any warnings
68 doIfSet (not (isEmptyBag ds_warns))
69 (printErrs (pprBagOfWarnings ds_warns))
71 -- Lint result if necessary
72 let do_dump_ds = dopt Opt_D_dump_ds dflags
73 endPass dflags "Desugar" do_dump_ds ds_binds
75 doIfSet do_dump_ds (printDump (ppr_ds_rules ds_rules))
79 dsProgram mod_name all_binds rules fo_decls
80 = dsMonoBinds auto_scc all_binds [] `thenDs` \ core_prs ->
81 dsForeigns mod_name fo_decls `thenDs` \ (fe_binders, foreign_binds, h_code, c_code) ->
83 ds_binds = [Rec (foreign_binds ++ core_prs)]
84 -- Notice that we put the whole lot in a big Rec, even the foreign binds
85 -- When compiling PrelFloat, which defines data Float = F# Float#
86 -- we want F# to be in scope in the foreign marshalling code!
87 -- You might think it doesn't matter, but the simplifier brings all top-level
88 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
90 local_binders = mkVarSet (bindersOfBinds ds_binds)
92 mapDs (dsRule local_binders) rules `thenDs` \ rules' ->
93 returnDs (ds_binds, rules', h_code, c_code, fe_binders)
95 auto_scc | opt_SccProfilingOn = TopLevel
98 ppr_ds_rules [] = empty
100 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
101 vcat (map pprProtoCoreRule rules)
105 %************************************************************************
107 %* Desugaring transformation rules
109 %************************************************************************
112 dsRule :: IdSet -> TypecheckedRuleDecl -> DsM ProtoCoreRule
113 dsRule in_scope (IfaceRuleOut fn rule)
114 = returnDs (ProtoCoreRule False {- non-local -} fn rule)
116 dsRule in_scope (HsRule name sig_tvs vars lhs rhs loc)
118 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
119 dsExpr rhs `thenDs` \ core_rhs ->
120 returnDs (ProtoCoreRule True {- local -} fn
121 (Rule name tpl_vars args core_rhs))
123 tpl_vars = sig_tvs ++ [var | RuleBndr var <- vars]
124 all_vars = mkInScopeSet (in_scope `unionVarSet` mkVarSet tpl_vars)
128 (dict_binds, body) = case lhs of
129 (HsLet (MonoBind dict_binds _ _) body) -> (dict_binds, body)
130 other -> (EmptyMonoBinds, lhs)
132 ds_dict_binds dict_binds `thenDs` \ dict_binds' ->
133 dsExpr body `thenDs` \ body' ->
135 -- Substitute the dict bindings eagerly,
136 -- and take the body apart into a (f args) form
138 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
139 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
140 -- Note recursion here... substitution won't terminate
141 -- if there is genuine recursion... which there isn't
143 subst = mkSubst all_vars subst_env
144 body'' = substExpr subst body'
147 -- Now unpack the resulting body
149 pair = case collectArgs body'' of
150 (Var fn, args) -> (fn, args)
151 other -> pprPanic "dsRule" (ppr lhs)
155 ds_dict_binds EmptyMonoBinds = returnDs []
156 ds_dict_binds (AndMonoBinds b1 b2) = ds_dict_binds b1 `thenDs` \ env1 ->
157 ds_dict_binds b2 `thenDs` \ env2 ->
158 returnDs (env1 ++ env2)
159 ds_dict_binds (VarMonoBind id rhs) = dsExpr rhs `thenDs` \ rhs' ->