Is there a specific guideline for when the js/ is needed/preferred for externs inference and when it is not? No specifics in the https://clojurescript.org/guides/externs. Two different examples from https://gist.github.com/swannodette/4fc9ccc13f62c66456daf19c47692799.

(defn foo [^String x]
  (.indexOf x "bar"))

(defn foo [^js/React.Component c]
  (.render c))