CLJS-2741: Function invoke errors report arity off by 1

Author: mfikes

src/main/clojure/cljs/compiler.cljc

@@ -906,7 +906,10 @@
                 (emitln "return " n ".call(this" (if (zero? pcnt) nil
                                                      (list "," (comma-sep (take pcnt maxparams)))) ");"))))
           (emitln "}")
-          (emitln "throw(new Error('Invalid arity: ' + (arguments.length - 1)));")
+          (let [arg-count-js (if (= 'self__ (-> ms first val :params first :name))
+                               "(arguments.length - 1)"
+                               "arguments.length")]
+            (emitln "throw(new Error('Invalid arity: ' + " arg-count-js "));"))
           (emitln "};")
           (when variadic
             (emitln mname ".cljs$lang$maxFixedArity = " max-fixed-arity ";")

src/test/cljs/cljs/core_test.cljs

@@ -1537,6 +1537,17 @@
   ;; Make sure we didn't delete the alpha? fn
   (is (some? alpha-2585?)))
 
+(defn fn-2741* ([x]) ([x y]))
+(def fn-2741 fn-2741*)
+
+(deftest test-cljs-2741
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 0" ((fn ([x]) ([x y])))))
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 3" ((fn ([x]) ([x y])) 1 2 3)))
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 0" (fn-2741)))
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 3" (fn-2741 1 2 3)))
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 0" ({})))
+  (is (thrown-with-msg? js/Error #".*Invalid arity: 3" ({} 1 2 3))))
+
 (comment
   ;; ObjMap
   ;; (let [ks (map (partial str "foo") (range 500))