From 0c1e1e757cd7703d53adaf2587eac80eabcbd9bc Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Wed, 11 Feb 2015 00:02:51 +1100
Subject: [PATCH] default optional builder keys to `false`

---
 .../transformation/transformers/es6/tail-call.js     |  7 +++----
 lib/6to5/types/index.js                              | 12 +++++++++---
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/lib/6to5/transformation/transformers/es6/tail-call.js b/lib/6to5/transformation/transformers/es6/tail-call.js
index fb0325d7aa..3fa4de1efa 100644
--- a/lib/6to5/transformation/transformers/es6/tail-call.js
+++ b/lib/6to5/transformation/transformers/es6/tail-call.js
@@ -197,11 +197,10 @@ TailCallTransformer.prototype.subTransformSequenceExpression = function (node) {
 };
 
 TailCallTransformer.prototype.subTransformCallExpression = function (node) {
-  var callee = node.callee, prop, thisBinding, args;
+  var callee = node.callee, thisBinding, args;
 
-  if (t.isMemberExpression(callee, { computed: false }) &&
-      t.isIdentifier(prop = callee.property)) {
-    switch (prop.name) {
+  if (t.isMemberExpression(callee, { computed: false }) && t.isIdentifier(callee.property)) {
+    switch (callee.property.name) {
       case "call":
         args = t.arrayExpression(node.arguments.slice(1));
         break;
diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index 012bb267e6..0b90c56175 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -105,9 +105,15 @@ each(t.BUILDER_KEYS, function (keys, type) {
     var node = new Node;
     node.start = null;
     node.type = type;
-    each(keys, function (key, i) {
-      node[key] = args[i];
-    });
+
+    for (var i = 0; i < keys.length; i++) {
+      var arg = args[i];
+      if (arg === undefined) arg = false;
+
+      var key = keys[i];
+      node[key] = arg;
+    }
+
     return node;
   };
 });