[es6] Re-implement rest parameters via desugaring.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 7eb73d9023547f9587a95aec5d64d6153c8b2fdb..6eb4f16f3a6d0fd24492f3847311237805060eac 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -89,7 +89,8 @@ namespace internal {
   V(SuperPropertyReference)     \
   V(SuperCallReference)         \
   V(CaseClause)                 \
-  V(EmptyParentheses)
+  V(EmptyParentheses)           \
+  V(RestParameter)
 
 #define AST_NODE_LIST(V)                        \
   DECLARATION_NODE_LIST(V)                      \
@@ -1730,6 +1731,29 @@ class VariableProxy final : public Expression {
 };
 
 
+class RestParameter final : public Expression {
+ public:
+  DECLARE_NODE_TYPE(RestParameter)
+
+  VariableProxy* parameter() const { return parameter_; }
+  int literal_index() const { return literal_index_; }
+
+  int end_position() const { return parameter_->end_position(); }
+
+ protected:
+  RestParameter(Zone* zone, VariableProxy* parameter, int literal_index,
+                int position)
+      : Expression(zone, position),
+        parameter_(parameter),
+        literal_index_(literal_index) {}
+
+  VariableProxy* parameter_;
+  int literal_index_;
+
+  friend class AstLiteralReindexer;
+};
+
+
 // Left-hand side can only be a property, a global or a (parameter or local)
 // slot.
 enum LhsKind {
@@ -3499,6 +3523,15 @@ class AstNodeFactory final BASE_EMBEDDED {
         VariableProxy(zone_, name, variable_kind, start_position, end_position);
   }
 
+  RestParameter* NewRestParameter(VariableProxy* parameter, int literal_index,
+                                  int position) {
+    DCHECK_NOT_NULL(parameter);
+    DCHECK(literal_index >= 0);
+    DCHECK(position >= 0);
+
+    return new (zone_) RestParameter(zone_, parameter, literal_index, position);
+  }
+
   Property* NewProperty(Expression* obj, Expression* key, int pos) {
     return new (zone_) Property(zone_, obj, key, pos);
   }