Perfect forwarding

[Adam D. Ruppe]

On Sunday, 26 July 2020 at 01:29:21 UTC, Andrei Alexandrescu 
wrote:
> So the challenge is implementing forward() to do this.

I know the trick to do this, but I won't post the answer yet 
because I don't want to ruin it for others who want to try.

However I'm going to point out that my trick doesn't work if you 
are trying to forward a template, since template params cannot be 
introspected. As far as I know, there is no solution to that.

My impl also does a bonus: forwarding UDAs as well. That requires 
very new dmd though because until very recently that would hit a 
compiler bug! But it is possible.


Note: part of the challenge is making sure it works with 
user-defined types too. Your first thought of an implementation 
might not, so test that with a struct from an import when there's 
a local struct with the same name....