-preview=in might break code

[IGotD-]

On Monday, 5 October 2020 at 07:55:57 UTC, Walter Bright wrote:
>
> The problem is not dmd compiled code calling gdc/ldc compiled 
> code. The problem is code that works with one compiler fails 
> with another, because the "to ref or not to ref" decision is 
> *implementation defined*.

Ouch, so this mean that how 'in' works must be a defined standard 
that all D compilers adhere to. Also this standard must be 
defined for each CPU architecture.