use more recent idiom for creating symbol from var

Author: puredanger

src/main/clojure/clojure/spec/alpha.clj

@@ -306,9 +306,7 @@
   "Returns a symbol from a symbol or var"
   [x]
   (if (var? x)
-    (let [^clojure.lang.Var v x]
-      (symbol (str (.name (.ns v)))
-              (str (.sym v))))
+    (symbol x)
     x))
 
 (defn- unfn [expr]