dry up array comprehension and arrow functions by introducing an alias-functions transformer

lib/6to5/transformers/array-comprehension.js

@@ -9,12 +9,14 @@ var single = function (node) {
   var templateName = "array-comprehension-map";
   if (node.filter) templateName = "array-comprehension-filter";
 
-  return util.template(templateName, {
+  var result = util.template(templateName, {
     STATEMENT: node.body,
     FILTER:    node.filter,
     ARRAY:     block.right,
     KEY:       block.left
   });
+  result._aliasFunction = true;
+  return result;
 };
 
 var multiple = function (node, file) {
@@ -23,6 +25,7 @@ var multiple = function (node, file) {
   var container = util.template("array-comprehension-container", {
     KEY: uid
   });
+  container._aliasFunction = true;
 
   var block = container.callee.body;
   var body  = block.body;
@@ -47,7 +50,10 @@ var multiple = function (node, file) {
         var filter = util.template("if", {
           STATEMENT: node.filter
         });
+
+        // set if body
         filter.consequent.body = [child];
+
         child = filter;
       }
     }
@@ -56,7 +62,10 @@ var multiple = function (node, file) {
       ARRAY: self.right,
       KEY:   self.left
     }, true);
+
+    // set function body
     container2.expression.arguments[0].body.body = [child];
+
     return container2;
   };