3.3.1: If `promise` and `x` refer to the same object, reject `promise`

with a `TypeError' as the reason.

lib/rsvp/promise.js

@@ -138,6 +138,10 @@ function handleThenable(promise, value) {
   resolved;
 
   try {
+    if (promise === value) {
+      throw new TypeError("A promises callback cannot return that same promise.");
+    }
+
     if (objectOrFunction(value)) {
       then = value.then;