Why is my structure template does not compile?

[Weed]

>>> ref Element opIndexAssign( in Element a, in uint n )
>>> {
>>> data[n] += a;
>>> return data[n];
>>> }
>>
>> I'm guessing as I don't use 2.0 but I think that this is a bug. DMD is 
>> trying to say that the above returns are trying to return something 
>> that can't be referenced (like a math expression result).
>>
> 
> It is a bug, indeed. The struct 'invariant' prevents proper template 
> instantiation somehow... Removing it makes code work as intended.
> I'll submit a bug report.

Thank you!

Give a link to the bugreport later?