dip1000 and preview in combine to cause extra safety errors

[Dukc]

On Wednesday, 8 June 2022 at 14:52:53 UTC, Steven Schveighoffer 
wrote:
> ```d
> string foo(in string s)
> {
>     return s;
> }
>
> void main()
> {
>     import std.stdio;
>     string[] result;
>     foreach(c; "hello")
>     {
>         result ~= foo([c]);
>     }
>     writeln(result);
> }
> ```
>
> With no previews, preview=dip1000, or preview=in, this outputs: 
> `["h", "e", "l", "l", "o"]`
>
> With both preview=dip1000 and preview=in, this outputs: `["o", 
> "o", "o", "o", "o"]`
>
> What is happening is the compiler is somehow convinced that it 
> can allocate the array literal on the stack (and overwrites 
> that literal each loop).
>
> I know this isn't `@safe` code, but `@system` code shouldn't be 
> made less safe by the preview switches!
>
> I know people write `in` instead of `const` all the time 
> *simply because it's shorter*.
>
> Thoughts?
>
> -Steve

Sorry to wake up an old thread, but I have a request. May I use 
this as an example of what can go wrong in `@system` code for the 
"Memory safety in modern systems programming language" series in 
the D blog? And if, is a direct link here okay?