The jaxrs 2.1 spec section 3.2 require resource method parameters be checked at deployment time of errors handling @DefaultValue annotations. This must be added in wfly because
resteasy is not called until the first client request.

Testing
Build and deploy attached app to wildfly.
Before code fix deployment should be successful.
Running app with cmd: curl "http://localhost:8080/jaxrs-wf/a?param=2"
should fail.
After code fix deployment should fail with detailed msg.