Date field not obeying widget alters for #required

Coming from the Required by Role contrib module:
#2017555-4: Does not work on date fields

Basically, the Required by Role module works by using hook_widget_form_alter() to alter the #required property for widgets for Fields.

This works for most fields, but not fields from the Date module.

I tracked down the problem, and the reason it is not working with Date fields is that when the Date module takes the widget information and constructs the editing form, it is going back to instance settings to check #required, instead of using the altered widget settings. This patch fixes it... I'm not sure if it has other implications, but maybe you would know? It seems to work correctly both for Date fields using Required by Role, and Date fields that are not using Required by Role.