Hey everyone. I was playing around with the protocols/deftype stuff
and ran into a weird NullPointerException when calling the satisfies?
function. Seems to only happen with a java.lang.Object instance.
Clojure 1.2.0-master-SNAPSHOT
user=> (defprotocol Greeter (greet [this]))
Greeter
user=> (satisfies? Greeter nil)
false
user=> (satisfies? Greeter "")
false
user=> (satisfies? Greeter (Object.))
java.lang.NullPointerException (NO_SOURCE_FILE:0)
Narrowed it down to this function:
;; core_deftype.clj
(defn find-protocol-impl [protocol x]
(if (instance? (:on-interface protocol) x)
x
(let [c (class x)
impl #(get (:impls protocol) %)]
(or (impl c)
(and c (or (first (remove nil? (map impl (butlast (super-chain c)))))
(when-let [t (reduce pref (filter impl (disj
(supers c) Object)))]
(impl t))
(impl Object)))))))
More specifically, here:
(disj (supers c) Object)
Since in this case, `c` is java.lang.Object, supers returns nil which
disj doesn't seem to like. Shouldn't disj handle nil gracefully?
Thanks,
Allen
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