Unary operators for Variants

[Jeff via Digitalmars-d-learn]

So, I can't seem to get unary operators to work with variants. 
For example:

Variant x = 10;
writeln(-x); // Error: x is not of arithmetic type, it is a 
VariantN!32LU

Obviously binary operators like + work fine. Is there a reason 
opUnary wasn't implemented as well? Is there a work-around for me 
to implement it myself outside of the VariantN class?

Thanks!