[es6] Re-implement rest parameters via desugaring.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index effa562e2bc9d25862bd37e8d57ac6ae9f87ee57..130b68b4e6a1964dec0e0a0c3d5975f39b42a73b 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -980,6 +980,7 @@ class Parser : public ParserBase<ParserTraits> {
     Scope* hoist_scope;
     VariableMode mode;
     bool is_const;
+    bool is_rest;
     bool needs_init;
     int declaration_pos;
     int initialization_pos;
@@ -998,6 +999,8 @@ class Parser : public ParserBase<ParserTraits> {
       Expression* pattern;
       int initializer_position;
       Expression* initializer;
+      bool is_rest = false;

[adamk, 2015/08/28 23:26:37]

Does this compile? I think this and the below should be initialized in the
constructor.

[caitp (gmail), 2015/08/28 23:58:01]

Compiles with clang version 3.8.0 (trunk 242792), but will do. This pattern is
used in a few other structs in the tree though

[adamk, 2015/08/29 01:01:07]

Huh, I may just be out of date. Feel free to leave this as-is if we're already
doing this elsewhere.

[caitp (gmail), 2015/08/29 15:51:59]

It turns out these members were unused anyways, so there isn't any reason to
keep them regardless. They're gone

+      int rest_literal_index = 0;
     };
 
     DeclarationParsingResult()
@@ -1338,10 +1341,8 @@ void ParserTraits::DeclareFormalParameter(
     ExpressionClassifier* classifier) {
   bool is_duplicate = false;
   bool is_simple = classifier->is_simple_parameter_list();
-  // TODO(caitp): Remove special handling for rest once desugaring is in.
-  auto name = is_simple || parameter.is_rest
-      ? parameter.name : parser_->ast_value_factory()->empty_string();
-  auto mode = is_simple || parameter.is_rest ? VAR : TEMPORARY;
+  auto name = parameter.name;
+  auto mode = is_simple ? VAR : TEMPORARY;
   if (!is_simple) scope->SetHasNonSimpleParameters();
   bool is_optional = parameter.initializer != nullptr;
   Variable* var = scope->DeclareParameter(