use simple loops always in array comprehensions, support yield inside of array comprehensions - closes #325, fixes #252

test/fixtures/transformation/es7-array-comprehension/array-expression-single/expected.js

@@ -1,5 +1,12 @@
 "use strict";
 
-var arr = [1, 2, 3].map(function (i) {
-  return i * i;
-});
+var arr = (function () {
+  var _arr = [];
+
+  for (var _iterator = [1, 2, 3][Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+    var i = _step.value;
+    _arr.push(i * i);
+  }
+
+  return _arr;
+})();