I have been discussing quite a bit with Paul and Tobias on how to
proceed. It's a bit of a nasty situation, since we do have *some* OOP
in 4.5, but for sure it won't be perfect. [One of the most tricky
aspects is that there are situations where compilation goes through
fine, but stuff fails at runtime (cf. PR41829). These issues are the
same on the trunk and fortran-dev.]
My proposal would be to merge the current state of fortran-dev to the
trunk now, and leave the advanced TBP stuff that Paul is working on
for 4.6. As I said, the features on the branch can be considered to be
rather stable (the more experimental stuff has not been committed
yet), and most of it is rather low-risk wrt regressions, since it is
hidden behind BT_CLASS guards.