Hi Ben,
Sorry for not asking this sooner, but I'd like to merge some form of
https://phabricator.haskell.org/D2961 in time for 8.2 if possible. Sadly, doing it "the right way" (according to Simon) is proving to be extremely challenging. A previous iteration of D2961 does work (albeit the code is not as pretty as it ought to be).
Are you still planning to cut the 8.2 release tomorrow? If so, I think I'll revert back to the working version of D2961 and merge that, and leave doing it the right way as future work.