This bug is covered under:
The problem is essentially that groovy classes coming in from binary are not yet recognized as groovy classes and so the Java parser/resolver tries to resolve references in them and (as you would expect) fails miserably.
I have done a little bit of work in this area (primarily to remove synthetic members from appearing in the outline view and elsewhere), but much more work needs to be done.
Until now, there haven't been many people screaming for this support, so I haven't spent much time on it. But, if you do want to see this happen, then make some noise.