I ran the metamodel test suite against 9EA, 9.0.1, and 9.0.4 and it passes. After I reviewed your repository code, I see why your code fails and I couldn't reproduce it with the test suite. Your code uses a different annotation pattern than what was reported by this issue, hence why it was not resolved. More specifically, this the example here used an annotation on an array type but your use case is where you annotate the element type of a collection container, e.g.

List<@NotNull String> values;

I'll add a follow-up task and address the issue. Are you able to identify any other use cases where this is problematic?