h as "<tt>IValidatable</tt>" and then have the template call the virtual function <tt>IValidatable::Validate(...)</tt>.
                This has the disadvantage of adding an indirect call, reducing the ability to inline, and other CPU perf characteristics - but for code that's not particularly hot may be
                the simplest way. In this case in Chromium this was not acceptable for security reasons.</li>
            <li>Have each <tt>T::Validate</tt> be foldable, as then each "call" in the template