[es6] support rest parameters in arrow functions (alternative)

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 8a13e21b1ef9929954f6a5301681bd5eaa21cbbc..3de1eeb266f9a62da0d49aa3a71daf4f1a257fe3 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -75,6 +75,7 @@ namespace internal {
   V(FunctionLiteral)            \
   V(ClassLiteral)               \
   V(NativeFunctionLiteral)      \
+  V(Spread)                     \
   V(Conditional)                \
   V(VariableProxy)              \
   V(Literal)                    \
@@ -2224,6 +2225,27 @@ class CompareOperation FINAL : public Expression {
 };
 
 
+class Spread FINAL : public Expression {
+ public:
+  DECLARE_NODE_TYPE(Spread)
+
+  Expression* expression() const { return expression_; }
+
+  static int num_ids() { return parent_num_ids(); }
+
+ protected:
+  Spread(Zone* zone, Expression* expression, int position)
+      : Expression(zone, position),
+        expression_(expression) {}
+  static int parent_num_ids() { return Expression::num_ids(); }
+
+ private:
+  int local_id(int n) const { return base_id() + parent_num_ids() + n; }
+
+  Expression* expression_;
+};
+
+
 class Conditional FINAL : public Expression {
  public:
   DECLARE_NODE_TYPE(Conditional)
@@ -3432,6 +3454,10 @@ class AstNodeFactory FINAL BASE_EMBEDDED {
     return new (zone_) CompareOperation(zone_, op, left, right, pos);
   }
 
+  Spread* NewSpread(Expression* expression, int position) {
+    return new (zone_) Spread(zone_, expression, position);
+  }
+
   Conditional* NewConditional(Expression* condition,
                               Expression* then_expression,
                               Expression* else_expression,