[strong] Implement static restrictions on binding 'undefined' in arrow functions

test/mjsunit/strong/undefined.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: --strong-mode --harmony-sloppy --harmony-arrow-functions
 
 // Repurposing the strict mode 'eval' and 'arguments' tests to test for correct
 // behaviour of 'undefined' as an identifier in strong mode.
 "use strict";
 
@@ skipping 89 matching lines @@
              SyntaxError);
 
 //Object literal method
 CheckStrongMode("({ foo(a, b, undefined, c, d) {} });");
 assertThrows("({ foo(a, b, undefined, c, d) {'use strong';} });", SyntaxError);
 
 //Object literal generator method
 CheckStrongMode("({ *foo(a, b, undefined, c, d) {} });");
 assertThrows("({ *foo(a, b, undefined, c, d) {'use strong';} });", SyntaxError);
 
-// Arrow function expression with 'undefined' param
-// TODO(conradw): Checking arrow function heads is hard to modify just now
-// CheckStrongMode("(undefined => {})");
-// assertThrows("(undefined => {'use strong';})");
-
 // Class declaration named 'undefined'
 CheckStrongMode("class undefined {}");
 assertThrows("class undefined {'use strong'}", SyntaxError);
 
 // Class expression named 'undefined'
 CheckStrongMode("(class undefined {});");
 assertThrows("(class undefined {'use strong'});", SyntaxError);
 
 // Binding/assigning to 'undefined' in for
 CheckStrongMode("for(undefined = 0;false;);");
@@ skipping 58 matching lines @@
 CheckStrongMode("print(--undefined);");
 CheckStrongMode("let x = --undefined;");
 
 // Function constructor: 'undefined' parameter name
 assertDoesNotThrow(function() {
   Function("undefined", "");
 });
 assertThrows(function() {
   Function("undefined", "'use strong';");
 }, SyntaxError);
+
+// Arrow functions with undefined parameters
+CheckStrongMode("(undefined => {return});");
+assertThrows("(undefined => {'use strong';});");
+
+CheckStrongMode("((undefined, b, c) => {return});");
+assertThrows("((undefined, b, c) => {'use strong';});");
+
+CheckStrongMode("((a, undefined, c) => {return});");
+assertThrows("((a, undefined, c) => {'use strong';});");
+
+CheckStrongMode("((a, b, undefined) => {return});");
+assertThrows("((a, b, undefined) => {'use strong';});");