CLJS-3408: Handle @extends in externs (#218)

* externs: parse @extends into :super
* add test case
* check base type when checking externs
* add CLJS-3408 test, verifying reported issue is resolved

Author: swannodette

src/main/clojure/cljs/analyzer.cljc

@@ -1048,7 +1048,10 @@
                xmeta (meta x')]
            (if (and (= 'Function (:tag xmeta)) (:ctor xmeta))
              (or (has-extern?* (into '[prototype] (next pre)) externs' top)
-                 (has-extern?* (next pre) externs' top))
+                 (has-extern?* (next pre) externs' top)
+                 ;; check base type if it exists
+                 (when-let [super (:super xmeta)]
+                   (has-extern?* (into [super] (next pre)) externs top)))
              (recur (next pre) externs' top))))))))
 
 (defn has-extern?

src/main/clojure/cljs/externs.clj

@@ -73,7 +73,9 @@
             {:tag (get-tag ty)}
             (if (or (.isConstructor info) (.isInterface info))
               (let [qname (symbol (.. node getFirstChild getQualifiedName))]
-                (cond-> {:tag 'Function}
+                (cond-> (merge {:tag 'Function}
+                          (when (.hasBaseType info)
+                            {:super (get-tag (.getBaseType info))}))
                   (.isConstructor info) (merge {:ctor qname})
                   (.isInterface info) (merge {:iface qname})))
               (if (or (.hasReturnType info)

src/test/clojure/cljs/externs_infer_tests.clj

@@ -475,6 +475,17 @@
                ["Object.renderInline;"])
             res)))))
 
+(deftest test-cljs-3408
+  (testing "inheritance of JS Types is inferred"
+    (let [ws  (atom [])
+          res (infer-test-helper
+                {:forms '[(ns foo.core)
+                          (.querySelectorAll js/document "div")]
+                 :warnings ws
+                 :warn true
+                 :with-core? true})]
+      (is (empty? @ws)))))
+
 (comment
   (binding [ana/*cljs-ns* ana/*cljs-ns*]
     (ana/no-warn

src/test/clojure/cljs/externs_parsing_tests.clj

@@ -10,7 +10,8 @@
   (:require [cljs.closure :as closure]
             [cljs.externs :as externs]
             [clojure.java.io :as io]
-            [clojure.test :as test :refer [deftest is]]))
+            [clojure.test :as test :refer [deftest is]])
+  (:import [com.google.javascript.jscomp CommandLineRunner]))
 
 (deftest cljs-3121
   (let [externs (externs/parse-externs
@@ -34,6 +35,16 @@
     (is (= 'any (get-in ns [:defs 'get :ret-tag])))
     (is (= 'array (get-in ns [:defs 'getKeys :ret-tag])))))
 
+(deftest test-parse-super
+  (let [info (->
+               (filter
+                 (fn [s]
+                   (= "externs.zip//w3c_dom2.js" (.getName s)))
+                 (CommandLineRunner/getDefaultExterns))
+               first externs/parse-externs externs/index-externs
+               (find 'HTMLDocument) first meta)]
+    (is (= 'Document (:super info)))))
+
 (comment
 
   (externs/parse-externs