Currently, while nonsensical, it is technically possible to recur to a ^:once fn** point.
The current patch make attempting to do so a compile time error.
This is useful so that code like (future (recur)) doesn't compile, giving users the impression that it's supposed to work (see comments at https://dev.clojure.org/jira/browse/ASYNC-185 for an example)
Patch: 0001-CLJ-2317-disallow-recur-to-once-fn.patch
