Beware that &quot;%identity&quot; is an unsafe feature that breaks all safety guarantees if used badly.<br><br>If you were, for example, to change your definition of &quot;foo&quot; (in a way not always representable as integers, such as adding a constructor with parameters), int_of_foo would become incorrect. The compiler wouldn&#39;t warn you, and you could get pretty bad failures (segfaults). You&#39;re on your own.<br>

<br>