CLJ-2094 - Eagerly evaluated protocols should refer to latest versions

By referencing the `:var` on protocols when passed to protocol functions, any
protocols that are eagerly evaluated (in functions such as `partial`) will
properly use the most up-to-date set of `:impls` on the protocol instead of
those that exist at partial-application time.

src/clj/clojure/core_deftype.clj

@@ -533,10 +533,16 @@
   ([^Class a ^Class b]
      (if (.isAssignableFrom a b) b a)))
 
+(defn- latest-p
+  "Get the latest version of the protocol before use."
+  [protocol]
+  (deref (:var protocol)))
+
 (defn find-protocol-impl [protocol x]
   (if (instance? (:on-interface protocol) x)
     x
     (let [c (class x)
+          protocol (latest-p protocol)
           impl #(get (:impls protocol) %)]
       (or (impl c)
           (and c (or (first (remove nil? (map impl (butlast (super-chain c)))))
@@ -559,13 +565,13 @@
   {:added "1.2"}
   [protocol atype]
   (boolean (or (implements? protocol atype) 
-               (get (:impls protocol) atype))))
+               (get (:impls (latest-p protocol)) atype))))
 
 (defn extenders 
   "Returns a collection of the types explicitly extending protocol"
   {:added "1.2"}
   [protocol]
-  (keys (:impls protocol)))
+  (keys (:impls (latest-p protocol))))
 
 (defn satisfies? 
   "Returns true if x satisfies the protocol"

test/clojure/test_clojure/protocols.clj

@@ -691,6 +691,33 @@
           (reify LongsHintedProto
             (longs-hinted [_] (long-array [1])))))))
 
+;; CLJ-2094 - Eagerly evaluated protocols should refer to latest versions
+
+(require '[clojure.spec.alpha :as s])
+
+(defprotocol CLJ-2094
+  (execute [_]))
+
+(def partial-extends-clj-2094 (partial extends? CLJ-2094))
+(def partial-extenders-clj-2094 (partial extenders CLJ-2094))
+(def partial-find-protocol-method-clj-204
+  (partial find-protocol-method CLJ-2094 :execute))
+(def partial-satisfies-clj-2094 (partial satisfies? CLJ-2094))
+(s/def ::clj-2094 (partial satisfies? CLJ-2094))
+
+(defrecord Foo-2094 [])
+
+(extend-type Foo-2094
+  CLJ-2094
+  (execute [_]))
+
+(deftest test-satisfies-uses-latest
+  (is (partial-extends-clj-2094 Foo-2094))
+  (is (= [Foo-2094] (partial-extenders-clj-2094)))
+  (is (partial-find-protocol-method-clj-204 (->Foo-2094)))
+  (is (partial-satisfies-clj-2094 (->Foo-2094)))
+  (is (s/valid? ::clj-2094 (->Foo-2094))))
+
 ;; CLJ-1180 - resolve type hints in protocol methods
 
 (import 'clojure.lang.ISeq)