CLJS-3382: Fix regression in .apply after CLJS-3024 (#182)

Co-authored-by: Nikita Prokopov <niki@tonsky.me>

Author: swannodette

src/main/clojure/cljs/core.cljc

@@ -1507,12 +1507,13 @@
           ~(with-meta
              `(fn ~[this-sym argsym]
                 (this-as ~this-sym
-                  (.apply (.-call ~this-sym) ~this-sym
-                    (.concat (array ~this-sym)
-                      (if (> (.-length ~argsym) ~max-ifn-arity)
-                        (doto (.slice ~argsym 0 ~max-ifn-arity)
-                          (.push (.slice ~argsym ~max-ifn-arity)))
-                        ~argsym)))))
+                  (let [args# (cljs.core/aclone ~argsym)]
+                    (.apply (.-call ~this-sym) ~this-sym
+                      (.concat (array ~this-sym)
+                        (if (> (.-length args#) ~max-ifn-arity)
+                          (doto (.slice args# 0 ~max-ifn-arity)
+                            (.push (.slice args# ~max-ifn-arity)))
+                          args#))))))
              (meta form)))]
       (ifn-invoke-methods type type-sym form))))
 

src/test/cljs/cljs/apply_test.cljs

@@ -47,7 +47,10 @@
   (is (= (range 22) (apply meta-f (range 22)))
         "Should properly call the last IFn arity with 20 args with last being a seq")
   (is (= (range 22) (.apply meta-f nil (to-array (range 22))))
-        ".apply should also handle >20 arguments"))
+        ".apply should also handle >20 arguments")
+  (let [ctor #(.apply meta-f nil (js-arguments))] ; CLJS-3382
+    (is (= '(1 2 3) (.apply ctor nil #js [1 2 3])))
+    (is (= (range 30) (.apply ctor nil (to-array (range 30)))))))
 
 (deftest multi-arity-test
   (is (= 2 (apply (fn ([a] a) ([a b] b)) 1 [2])))