From b9b1a44c285b50c79220a751b555ed44285db7b4 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 22 Jan 2015 10:53:05 +1100
Subject: [PATCH] support async await inside of let scoping closure wrapper -
 fixes #565

---
 lib/6to5/transformation/transformers/es6/block-scoping.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/6to5/transformation/transformers/es6/block-scoping.js b/lib/6to5/transformation/transformers/es6/block-scoping.js
index 023120b268..7778f36db9 100644
--- a/lib/6to5/transformation/transformers/es6/block-scoping.js
+++ b/lib/6to5/transformation/transformers/es6/block-scoping.js
@@ -211,12 +211,20 @@ LetScoping.prototype.needsClosure = function () {
   var call = t.callExpression(fn, params);
   var ret  = this.scope.generateUidIdentifier("ret");
 
+  // handle generators
   var hasYield = traverse.hasType(fn.body, this.scope, "YieldExpression", t.FUNCTION_TYPES);
   if (hasYield) {
     fn.generator = true;
     call = t.yieldExpression(call, true);
   }
 
+  // handlers async functions
+  var hasAsync = traverse.hasType(fn.body, this.scope, "AwaitExpression", t.FUNCTION_TYPES);
+  if (hasAsync) {
+    fn.async = true;
+    call = t.awaitExpression(call, true);
+  }
+
   this.build(ret, call);
 };