Selected value breaks for radios with numbers and strings as keys

Reproducing is very simple if you have Views:

(No, it's not a Views bug!)

1. Create a new view of Content
2. Add filter for Published
3. Expose it
4. Unrequire it
5. Make its default - Any -
6. Save it, and the edit it

The selected default value is now No, which is wrong, because the actual value is "All". If you view the HTML source, you'll see both - Any- and No are checked.

This is Drupal's fault, because of:

  if (isset($element['#return_value']) && $element['#value'] !== FALSE && $element['#value'] == $element['#return_value']) {
    $element['#attributes']['checked'] = 'checked';
  }

in theme_radio() in form.inc. (It's really PHP's fault for comparing strings and numbers like a crazy person, but we all know that.)

The default value is 0, a potential value is "All", and that of course is equal in PHP!

The fix is pretty simple too, assuming radio values (#options's keys) and #default_value are always scalar:

Instead of

$element['#value'] == $element['#return_value']

check

(string) $element['#value'] === (string) $element['#return_value']

because "0" and "All" aren't identical.