cljs.core.specs.alpha: Check early if let binding vector is even

Question

When CLJ-2376 is applied, port it to ClojureScript.

This line can be updated to match the revision in the patch in CLJ-2376:
https://github.com/clojure/clojurescript/blob/17b71461ee6304e3696e397add1f4780525553fc/src/main/cljs/cljs/core/specs/alpha.cljc#L59

Answer 1

Reference: https://clojure.atlassian.net/browse/CLJS-2828 (reported by mfikes)