Project: datamanagement
Issue DM-5609: Investigate clang issues regarding friendship and protected members 
In DM-5590, we worked around a problem in which clang 3.8 refused to access protected members of a cousin class given a friend declaration in the base. To our best understanding at time of writing, the code is valid: it seems possible that this is a bug in clang. Investigate what went wrong, produce a minimal test case, and (if appropriate) report this as an upstream bug.
Story points: 3