@Inject @OSGiServiceIntfA a;
I actually don't like this approach or I don't see why it's needed, even though non-existing annotations are mostly harmless.
I would simply stay -- code wise -- on the plain CDI,
where configuration wise one could -- due to potential over-kill --- flag the deployment as OSGi aware,
meaning it would also try to resolve injections against registered OSGi services; wrt type matching.