What's the correct opEquals signature for structs?

[Johannes Pfau]

My std.uuid module doesn't compile with the latest dmd. I guess it's
because of a wrong opEquals signature, this is what I have now:

----------
@safe pure nothrow bool opEquals(ref const UUID s) const
{
    return s.data == this.data;
}
----------

and

----------
assert(UUID("00000000-0000-0000-0000-000000000000") == nilUUID);
----------
The complete code is here:
https://github.com/jpf91/phobos/blob/std.uuid/std/uuid.d

What's the best way to solve this issue?