add Scope::getFunctionParent method

lib/6to5/traverse/scope.js

@@ -299,11 +299,21 @@ Scope.prototype.push = function (opts) {
  */
 
 Scope.prototype.add = function (node) {
+  var scope = this.getFunctionParent();
+  scope._add(node, scope.references);
+};
+
+/**
+ * Walk up the scope tree until we hit either a Function or reach the
+ * very top at hit Program.
+ */
+
+Scope.prototype.getFunctionParent = function () {
   var scope = this;
   while (scope.parent && !t.isFunction(scope.block)) {
     scope = scope.parent;
   }
-  scope._add(node, scope.references);
+  return scope;
 };
 
 /**