`in` parameters made useful

[Adam D. Ruppe]

On Friday, 31 July 2020 at 21:49:25 UTC, Mathias LANG wrote:
> B) It makes `in` take the effect of `ref` when it makes sense.

i like it

> D) It allows to pass rvalues to `in`. Because we know it's 
> `scope`, so it cannot be escaped (allegedly), and it's `const`, 
> so it cannot be modified, it's only logical that you can give 
> it rvalues.

i like this too


I've argued before the compiler should be allowed to optimize 
this in `in` case anyway so yeah you have my support here.