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(..) )
18 import PprCore ( pprIdCoreRule )
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 )
30 import Bag ( isEmptyBag )
31 import CoreLint ( beginPass, endPass )
32 import ErrUtils ( doIfSet, pprBagOfWarnings )
34 import UniqSupply ( UniqSupply )
35 import HscTypes ( HomeSymbolTable )
38 %************************************************************************
40 %* The main function: deSugar
42 %************************************************************************
44 The only trick here is to get the @DsMonad@ stuff off to a good
53 -> IO ([CoreBind], [(Id,CoreRule)], SDoc, SDoc, [CoreBndr])
55 deSugar dflags mod_name us hst
56 (TcResults {tc_env = global_val_env,
62 beginPass dflags "Desugar"
64 let (result, ds_warns) =
65 initDs dflags us (hst,pcs,global_val_env) mod_name
66 (dsProgram mod_name all_binds rules fo_decls)
67 (ds_binds, ds_rules, _, _, _) = result
69 -- Display any warnings
70 doIfSet (not (isEmptyBag ds_warns))
71 (printErrs (pprBagOfWarnings ds_warns))
73 -- Lint result if necessary
74 let do_dump_ds = dopt Opt_D_dump_ds dflags
75 endPass dflags "Desugar" do_dump_ds ds_binds
77 doIfSet do_dump_ds (printDump (ppr_ds_rules ds_rules))
81 dsProgram mod_name all_binds rules fo_decls
82 = dsMonoBinds auto_scc all_binds [] `thenDs` \ core_prs ->
83 dsForeigns mod_name fo_decls `thenDs` \ (fe_binders, foreign_binds, h_code, c_code) ->
85 ds_binds = [Rec (foreign_binds ++ core_prs)]
86 -- Notice that we put the whole lot in a big Rec, even the foreign binds
87 -- When compiling PrelFloat, which defines data Float = F# Float#
88 -- we want F# to be in scope in the foreign marshalling code!
89 -- You might think it doesn't matter, but the simplifier brings all top-level
90 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
92 local_binders = mkVarSet (bindersOfBinds ds_binds)
94 mapDs (dsRule local_binders) rules `thenDs` \ rules' ->
95 returnDs (ds_binds, rules', h_code, c_code, fe_binders)
97 auto_scc | opt_SccProfilingOn = TopLevel
100 ppr_ds_rules [] = empty
102 = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
103 vcat (map pprIdCoreRule rules)
107 %************************************************************************
109 %* Desugaring transformation rules
111 %************************************************************************
114 dsRule :: IdSet -> TypecheckedRuleDecl -> DsM (Id, CoreRule)
115 dsRule in_scope (HsRule name sig_tvs vars lhs rhs loc)
117 ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
118 dsExpr rhs `thenDs` \ core_rhs ->
119 returnDs (fn, Rule name tpl_vars args core_rhs)
121 tpl_vars = sig_tvs ++ [var | RuleBndr var <- vars]
122 all_vars = mkInScopeSet (in_scope `unionVarSet` mkVarSet tpl_vars)
126 (dict_binds, body) = case lhs of
127 (HsLet (MonoBind dict_binds _ _) body) -> (dict_binds, body)
128 other -> (EmptyMonoBinds, lhs)
130 ds_dict_binds dict_binds `thenDs` \ dict_binds' ->
131 dsExpr body `thenDs` \ body' ->
133 -- Substitute the dict bindings eagerly,
134 -- and take the body apart into a (f args) form
136 subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
137 [ContEx subst_env rhs | (id,rhs) <- dict_binds']
138 -- Note recursion here... substitution won't terminate
139 -- if there is genuine recursion... which there isn't
141 subst = mkSubst all_vars subst_env
142 body'' = substExpr subst body'
145 -- Now unpack the resulting body
147 pair = case collectArgs body'' of
148 (Var fn, args) -> (fn, args)
149 other -> pprPanic "dsRule" (ppr lhs)
153 ds_dict_binds EmptyMonoBinds = returnDs []
154 ds_dict_binds (AndMonoBinds b1 b2) = ds_dict_binds b1 `thenDs` \ env1 ->
155 ds_dict_binds b2 `thenDs` \ env2 ->
156 returnDs (env1 ++ env2)
157 ds_dict_binds (VarMonoBind id rhs) = dsExpr rhs `thenDs` \ rhs' ->