The most recent Clojure alpha (1.9.0-alpha12) contained a patch closing CLJ-1224. This had the unfortunate side effect of breaking some existing software, notably datascript. I've filed an issue upstream as well: https://github.com/tonsky/datascript/issues/176
It's not clear to me what the best resolution is; IIUC the behavior datascript was trying to accomplish is what records now do automagically, although I might have misunderstood. Ideally, datascript wouldn't have the serious performance regression on >=1.8.0, but it definitely should compile on 1.9.0, regardless of how that's resolved.