On the latest versions of clojurescript (1.10.741) and clojure/test.check (1.0.0) a compilation warning is emitted when compiling the clojure.test.check.generators
namespace:
WARNING: cljs.core/<=, all arguments must be numbers, got [#{nil js/Number} number] instead at line 1193 ~/.cljs/.aot_cache/1.10.741/26FED25/clojure/test/check/generators.cljc
I put a minimal reproduction case on Github starting with the CLJS getting started guide: https://github.com/AdamFrey/cljs-test-check-warning-example.
Googling that warning message returns stacktraces including that line from 2 or so years ago posted by people, so this doesn't appear to be a new regression.
I asked about this issue on #test-check channel in the Clojurians Slack and a test.check contributor said that it was likely a false positive warning, based on the source code where the warning came from.