opCmp and unittest as a nested function

[bearophile]

Alexandr Druzhinin:

> http://dpaste.dzfl.pl/f7364d416cb2
> Error appeared when I defined opCmp and now I can't understand 
> what's the reason of the error. Why does tween need access to 
> unittest?

Try to use "static struct" instead of a "struct".

Bye,
bearophile