Let-aliasing breaks flow inference for results of `class`

Question

The following code complains a NPE is possible from .isArray,
but clearly the assertion prevents that. This issue is related
to let-aliasing, probably related to core.typed not knowing how
to update the type of `c` with the information that it's class
is non-nil.


(fn [a :- t/Any]
  (let [c (class a)
        _ (assert c)]
    (.isArray c)))

Answer 1

Reference: https://clojure.atlassian.net/browse/CTYP-326 (reported by ambrosebs)