Matthew, Ben, David I've just submitted MR 426. It's a batch of four patcheshttps://gitlab.haskell.org/ghc/ghc/merge_requests/426/commits, one of which makes the GHC tree validate again. Might you keep an eye on it. David/anyone: one of them "Stop inferring polymorphic kinds" makes a small change to HsSyn (removing a field). I don't know whether that'll require changing Haddock - or how to do so. Might you check? Gotta run Thanks! Simon