Only last parameter between parentheses can have spread

test/mocha/function.js

@@ -0,0 +1,30 @@
+var assert = require("assert");
+var uglify = require("../../");
+
+describe("Function", function() {
+    it("Should not accept spread on non-last parameters", function() {
+        var tests = [
+            "var a = function(...a, b) { return a.join(b) }",
+            "var b = function(a, b, ...c, d) { return c.join(a + b) + d }",
+            "function foo(...a, b) { return a.join(b) }",
+            "function bar(a, b, ...c, d) { return c.join(a + b) + d }",
+            "var a = function*(...a, b) { return a.join(b) }",
+            "var b = function*(a, b, ...c, d) { return c.join(a + b) + d }",
+            "function* foo(...a, b) { return a.join(b) }",
+            "function* bar(a, b, ...c, d) { return c.join(a + b) + d }"
+        ];
+        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);
+        }
+    });
+});