What's happening with the `in` storage class

[Adam D. Ruppe]

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.