In Clojure:
user=> (conj {:a 1} '([:b 2] [:c 3]))
Execution error (ClassCastException) at user/eval3 (REPL:1).
clojure.lang.PersistentVector cannot be cast to java.util.Map$Entry
But in ClojureScript:
cljs.user=> (conj {:a 1} '([:b 2] [:c 3]))
{:a 1, :b 2, :c 3}
There is a check that the entries satisfy {{vector?}}, but we could instead require that they satisfy {{map-entry?}}. In fact, the error message given when {{vector?}} isn't satisfied is: "conj on a map takes _map entries_ or seqables of _map entries_."
Rationale: Even though this change would reject some programs, those programs are incorrect (only accidentally work), and, if ported to Clojure would fail there. Additionally, leveraging the fact that they are map entries would allow access to their keys and values, which can lead to faster code. (See leveraging map entries in CLJS-3116)
