Why use a DFA instead of DIP1000?

[Richard (Rikki) Andrew Cattermole]

On 14/09/2025 1:06 AM, kdevel wrote:
> 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`.

Half right.

There is a code block that will never be executed, it is because of 
variable b's state is known to prevent that code block from execution.