XS incorrectly rejects `undefined` bindings

[gibson042]

Environment: XS 15.5.1, slot 32 bytes, ID 4 bytes

Description
There are details at tc39/test262#4332 , but the summary is that XS incorrectly fails to create scoped bindings and function parameters named undefined.

Steps to Reproduce

{
  const undefined = 1;
  print(undefined === 1 ? 'PASS' : 'FAIL');
}
(function(undefined) { print(undefined === 1 ? 'PASS' : 'FAIL'); })(1);
(function({ undefined }) { print(undefined === 1 ? 'PASS' : 'FAIL'); })({ undefined: 1 });

Actual behavior

FAIL
FAIL
FAIL

Expected behavior

PASS
PASS
PASS

[phoddie]

Thank you for the report. This is caused by a bug in the parser. The fix is to remove a few lines of code. We'll have that in the next release.