During the addition of an injected class type to a record it may happen
that a CXXRecordDecl in the redecl chain does not have a described
template set and this caused an assert in LLDB.
I don't believe it is directly related to modules but that it just triggers the issue because it may be bringing in more. You can find a description here https://clang.llvm.org/docs/CommandGuide/clang.html#cmdoption-g and @aprantl pointed me to this talk if you want to even more http://llvm.org/devmtg/2015-10/#talk19
@martong have you had a chance to look at this some more? We ran into another problem that this fixes partially.
I didn't have time to deal with this yet (these days we are preparing an internal release and that took away my time).
Can I help in any way?
I think the only thing missing is to have a test. You mentioned previously that you could help with that and I would appreciate all your help. I think a test with clang-import-test would be just great.