Tighten requirements for auto-closeable beans #968

The spec currently does not require the auto-closeable beans to implement the AutoCloseable interface, i.e. an auto-closeable bean is not required to define AutoCloseable in its set of bean types.

So a user can annotate any bean with @AutoClose but it's a NOOP unless it implements AutoCloseable.

Since @AutoClose makes no sense without AutoCloseable, it might be worth tightening the requirements and treat @AutoClose without AutoCloseable as a definition error. This could help users understand the purpose of the annotation.

I know that one argument against this requirement is more flexibility in producer methods:

@Produces
@AutoClose
public FooBar produce() {
    // FooBar is not AutoClosable -> NOOP is expected
    return someCondition ? new FooBar() : new CloseableFooBar();
}

But I'm not sure this flexibility is worth it. And it definitely makes no sense for class-based beans.