[parser] disallow language mode directive in body of function with non-simple parameters

test/mjsunit/harmony/arrow-rest-params.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --harmony-rest-parameters --harmony-arrow-functions
 
 (function testRestIndex() {
   assertEquals(5, ((...args) => args.length)(1,2,3,4,5));
   assertEquals(4, ((a, ...args) => args.length)(1,2,3,4,5));
   assertEquals(3, ((a, b, ...args) => args.length)(1,2,3,4,5));
   assertEquals(2, ((a, b, c, ...args) => args.length)(1,2,3,4,5));
   assertEquals(1, ((a, b, c, d, ...args) => args.length)(1,2,3,4,5));
   assertEquals(0, ((a, b, c, d, e, ...args) => args.length)(1,2,3,4,5));
 })();
 
 // strictTest and sloppyTest should be called with descending natural
 // numbers, as in:
 //
 //   strictTest(6,5,4,3,2,1)
 //
-var strictTest = (a, b, ...c) => {
+var strictTest = (() => {
   "use strict";
-  assertEquals(Array, c.constructor);
-  assertTrue(Array.isArray(c));
+  return (a, b, ...c) => {
+    assertEquals(Array, c.constructor);
+    assertTrue(Array.isArray(c));
 
-  var expectedLength = (a === undefined) ? 0 : a - 2;
-  assertEquals(expectedLength, c.length);
+    var expectedLength = (a === undefined) ? 0 : a - 2;
+    assertEquals(expectedLength, c.length);
 
-  for (var i = 2; i < a; ++i) {
-    assertEquals(c[i - 2], a - i);
-  }
-}
+    for (var i = 2; i < a; ++i) {
+      assertEquals(c[i - 2], a - i);
+    }
+  };
+})();
 
 var sloppyTest = (a, b, ...c) => {
   assertEquals(Array, c.constructor);
   assertTrue(Array.isArray(c));
 
   var expectedLength = (a === undefined) ? 0 : a - 2;
   assertEquals(expectedLength, c.length);
 
   for (var i = 2; i < a; ++i) {
     assertEquals(c[i - 2], a - i);
@@ skipping 90 matching lines @@
 })();
 
 
 (function testUnmappedArguments() {
   // Normal functions make their arguments object unmapped, but arrow
   // functions don't have an arguments object anyway.  Check that the
   // right thing happens for arguments in arrow functions with rest
   // parameters.
   assertSame(arguments, ((...rest) => arguments)());
 })();