Why use a DFA instead of DIP1000?

[Dennis]

On Saturday, 13 September 2025 at 02:39:40 UTC, Richard (Rikki) 
Andrew Cattermole wrote:
> Paraphrased, why should we use a DFA engine instead of DIP1000?
>
> (...)
>
> Afterwards, I came up with an example, where DIP1000 will error:

Thanks for providing the example, it's a great discussion starter.

Like I said yesterday, it's not that I don't "know what data flow 
analysis is all about" - when you have a solution, you can come 
up with problems it solves, sure.

I was mostly curious what real world code made you believe that 
more advanced DFA is necessary for useful scope pointer analysis. 
There's many problems with DIP1000, but no issue was ever opened 
requesting scope checks to be disabled in dead code. As far as 
I'm aware, [users expect dead code to be type checked by the 
frontend as 
usual](https://forum.dlang.org/post/hullwyrnmgcaoghaqbux@forum.dlang.org).