private static Class<?> enableAsserts(Class<?> cls) {
            try {
                ClassLoader loader = cls.getClassLoader();
                if (loader != null)
                    loader.setPackageAssertionStatus("com.sun.tools.javac", true);
                else
                    trace(FINE, "loader == null");
            } catch (SecurityException ex) {
                trace(FINE, ex);
            }
            return cls;
        }