detect anonymous union at compile time

[cal]

On Thursday, 28 March 2013 at 20:18:45 UTC, Andrej Mitrovic wrote:
> On Thursday, 28 March 2013 at 20:02:18 UTC, cal wrote:
> .offsetof will also require access rights to the fields.

Just realized that format.d is able to figure it out, since it 
prints #{overlap...} for unions. I can use that code, which works 
regardless of protection. Thanks