If you have #queue  in your code, the code generated is
when it could, for the empty vector case generate
I updated the attached patch.
Those tests don't actually get run when you do 'lein test', looks like Travis does a build and runs them using jsc. I replicated locally, not sure if there are commands to make that easier.
With the patch #queue  is free.
Benchmarking: (simple-benchmark [f (fn  #queue )] (f) 1e8)
CLJS-2916.patch of 19/Sep/18 6:12 PM LGTM.
It passes all tests, including Canary tests. Perf looks good given the previous comment.
CLJS-2916.patch added to Patch Tender