data_readers.clj should contain a legal Clojure map, not an ad hoc da…

…ta structure

src/clj/clojure/core.clj

@@ -6613,13 +6613,6 @@
    (.. Thread currentThread getContextClassLoader
        (getResources "data_readers.clj"))))
 
-(defn- assert-symbol [^clojure.lang.LineNumberingPushbackReader reader x]
-  (when-not (symbol? x)
-    (throw (ex-info "non-symbol in data-reader file"
-                    {:file *file*
-                     :line (.getLineNumber reader)
-                     :value x}))))
-
 (defn- data-reader-var [sym]
   (intern (create-ns (symbol (namespace sym)))
           (symbol (name sym))))
@@ -6629,23 +6622,33 @@
                    (java.io.InputStreamReader.
                     (.openStream url) "UTF-8"))]
     (binding [*file* (.getFile url)]
-     (loop [mappings mappings]
-       (if-let [tag (read rdr false nil)]
-         (do (assert-symbol rdr tag)
-             (when (contains? mappings tag)
-               (throw (ex-info "Conflicting data-reader mapping"
-                               {:file *file*
-                                :line (.getLineNumber rdr)
-                                :symbol tag})))
-             (let [target (read rdr true nil)]
-               (assert-symbol rdr target)
-               (recur (assoc mappings tag (data-reader-var target)))))
-         mappings)))))
+      (let [new-mappings (read rdr false nil)]
+        (when (not (map? new-mappings))
+          (throw (ex-info (str "Not a valid data-reader map")
+                          {:url url})))
+        (reduce
+         (fn [m [k v]]
+           (when (not (symbol? k))
+             (throw (ex-info (str "Invalid form in data-reader file")
+                             {:url url
+                              :form k})))
+           (when (contains? mappings k)
+             (throw (ex-info "Conflicting data-reader mapping"
+                             {:url url
+                              :conflict k
+                              :mappings m})))
+           (assoc m k (data-reader-var v)))
+         mappings
+         new-mappings)))))
 
 (defn- load-data-readers []
   (alter-var-root #'*data-readers*
                   (fn [mappings]
                     (reduce load-data-reader-file
                             mappings (data-reader-urls)))))
 
-(load-data-readers)
+(try
+ (load-data-readers)
+ (catch Throwable t
+   (.printStackTrace t)
+   (throw t)))