When we do `pr-str` and then `read-string` on a priority map, the reading fails. I think this is because the priority-map reader is registered as a string, not a symbol.  To reproduce: ```clj (cljs.reader/read-string (pr-str (pm/priority-map :a 1))) ``` To fix: ```clj (cljs.reader/register-tag-parser! 'tailrecursion.priority-map pm/read-priority-map) ```