`in` parameters made useful

[Kagamin]

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. 
> It always pass something by `ref` if the type has elaborate 
> construction / destruction (postblit, copy constructor, 
> destructors). If the type doesn't have any of those it is only 
> passed by `ref` if it cannot be passed in register.

You mean if it fits in two registers, it's still passed by 
reference? 16 bytes is the size of uuid and is better passed by 
value.