When adding a JSF phase listener to faces-config.xml

<lifecycle>
   <phase-listener>com.demo.web.jsf.JsfCdiPhaseListener</phase-listener>
</lifecycle>

You are presented a warning that phase-listener references to "com.demo.web.jsf.JsfCdiPhaseListener" that does not extend javax.faces.event.PhaseListener

In reality you cannot extend javax.faces.event.PhaseListener you must implement it. So this check should be looking for implements rather than extends. See http://balusc.omnifaces.org/2006/09/debug-jsf-lifecycle.html

In java 8 at least you get a compiler error if you try and extend avax.faces.event.PhaseListener.

The type PhaseListener cannot be the superclass of JsfCdiPhaseListener; a superclass must be a class