Why use a DFA instead of DIP1000?

[kdevel]

On Saturday, 13 September 2025 at 11:08:29 UTC, IchorDev wrote:
> [...]
>> What about "release" mode? And what about that code:
>>
>> ```d
>> void main ()
>> {
>>    assert (0);
>>
>>    string s = "x";
>>    s [0] = 'y';
>> }
>> ```
>
> The program has entered an invalid state and the behaviour of 
> the continuing execution of the program is undefined.

Please note that the program is not run but just compiled.

> [...]
>> Is "Error: cannot modify `immutable` expression `s[0]`" a 
>> false positive, too?
>
> It's not a 'false positive' because it's not related to 
> DIP1000's stack escape rules at all.

I thought that the intent of the original code

```d
int* ptr;

void func(bool b, scope int* p) @safe {
   assert(!b);

   if (b) {
     ptr = p; // Error: scope variable `p` assigned to global 
variable `ptr`
   }
}
```

was to show that there is some code-block

```d
     ptr = p; // Error: scope variable `p` assigned to global 
variable `ptr`
```

which is never executed regardless of the value of `b`.