Only last parameter between parentheses can have spread

test/mocha/arrow.js

@@ -0,0 +1,25 @@
+var assert = require("assert");
+var uglify = require("../../");
+
+describe("Arrow functions", function() {
+    it("Should not accept spread tokens on non-last parameters or without arguments parentheses", function() {
+        var tests = [
+            "var a = ...a => {return a.join()}",
+            "var b = (a, ...b, c) => { return a + b.join() + c}",
+            "var c = (...a, b) => a.join()"
+        ];
+        var test = function(code) {
+            return function() {
+                uglify.parse(code, {fromString: true});
+            }
+        }
+        var error = function(e) {
+            return e instanceof uglify.JS_Parse_Error &&
+                e.message === "Unexpected token: expand (...)";
+        }
+
+        for (var i = 0; i < tests.length; i++) {
+            assert.throws(test(tests[i]), error);
+        }
+    });
+});