153441 2016-01-25 13:18:54 -0800 Global lexical declarations should shadow configurable global properties 2016-06-23 11:30:12 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED DUPLICATE 148763 P2 Normal --- 1 esprehn rniwa adamk ggaren keith_miller rniwa saam ysuzuki oldest_to_newest 1158468 0 esprehn 2016-01-25 13:18:54 -0800 ex. class Node { } SyntaxError: Can't create duplicate variable that shadows a global property: 'Node' but you can write var Node = class Node { } this works fine in Chrome and Firefox 45. 1204866 1 esprehn 2016-06-23 11:13:10 -0700 This is still broken, I think something is wrong in your lexical scoping. 1204868 2 esprehn 2016-06-23 11:14:58 -0700 I just checked today's nightly: r202375 and it still happens. 1204871 3 adamk 2016-06-23 11:22:11 -0700 In general, it seems that JSC refuses to create lexical bindings that shadow configurable properties on the global object, contra the spec (see https://tc39.github.io/ecma262/#sec-hasrestrictedglobalproperty). Here's a DOM-less repro: >>> let Array = 5 Exception: SyntaxError: Can't create duplicate variable that shadows a global property: 'Array' or one with a self-created property: >>> Object.defineProperty(this, 'foo', {value: 5, configurable: true, writable: true}) [object global] >>> let foo = 10 Exception: SyntaxError: Can't create duplicate variable that shadows a global property: 'Foo' 1204876 4 saam 2016-06-23 11:30:12 -0700 *** This bug has been marked as a duplicate of bug 148763 ***