* undefined is a ref cycle, special case

Author: swannodette

src/main/clojure/cljs/analyzer.cljc

@@ -1067,10 +1067,10 @@
                        (assoc :info nil)))))
 
              (or
-               ;; If the tag isn't Function, try to resolve it
-               ;; similar to the super case above
+               ;; If the tag isn't Function or undefined,
+               ;; try to resolve it similar to the super case above
                (let [tag (:tag info')]
-                 (when (and tag (not= 'Function tag))
+                 (when (and tag (not (contains? '#{Function undefined} tag)))
                    (resolve-extern (into [tag] (next pre)) externs top
                      (-> ret
                        (assoc :resolved [])

src/test/clojure/cljs/externs_infer_tests.clj

@@ -53,7 +53,9 @@
     (is (= '[Console]
             (-> (ana/resolve-extern '[console] externs) :resolved)))
     (is (= '[Console prototype log]
-            (-> (ana/resolve-extern '[console log] externs) :resolved)))))
+            (-> (ana/resolve-extern '[console log] externs) :resolved)))
+    (is (= '[undefined]
+            (-> (ana/resolve-extern '[undefined] externs) :resolved)))))
 
 (comment
   (clojure.test/test-vars [#'test-resolve-extern])
@@ -62,6 +64,7 @@
   ;; succeeds
   (ana/resolve-extern '[console] externs)
   (ana/resolve-extern '[console log] externs)
+  (ana/resolve-extern '[undefined] externs)
 
   )