--- groovy-core-GROOVY_1_8_9/src/main/org/codehaus/groovy/runtime/SwingGroovyMethods.java	2013-02-15 09:42:29.000000000 +0100
+++ groovy-core-GROOVY_1_8_9/src/main/org/codehaus/groovy/runtime/SwingGroovyMethods.java	2018-12-18 11:28:02.474773520 +0100
@@ -673,7 +673,7 @@
      */
     @SuppressWarnings("unchecked")
     public static Iterator<TreeNode> iterator(TreeNode self) {
-        return DefaultGroovyMethods.iterator(self.children());
+        return (Iterator<TreeNode>) DefaultGroovyMethods.iterator(self.children());
     }
 
     /**