What's happening with the `in` storage class

[SonicFreak94]

On Saturday, 9 June 2018 at 02:17:18 UTC, Adam D. Ruppe wrote:
> On Saturday, 9 June 2018 at 02:13:00 UTC, Walter Bright wrote:
>> But it was never enforced, meaning that suddenly enforcing it 
>> is just going to break code left and right.
>
>
> It isn't going to break anything. It is going to *correctly 
> diagnose already broken code*.
>
> That's a significant difference. Real world D users don't like 
> broken code, but they DO like the compiler catching new bugs 
> that slipped by before.

I agree. I would rather my potentially broken code be pointed out 
to me rather than removing the much more concise `in` from my 
code. In any case, I feel as though the concept of both `in` and 
`out` should be fairly intuitive. `in` would be a read-only 
reference (C# has received this recently), and `out` is a 
reference with the intention to write.