Why do immutable variables need reference counting?

[wjoe]

On Tuesday, 12 April 2022 at 22:23:18 UTC, ag0aep6g wrote:
> On Tuesday, 12 April 2022 at 19:54:13 UTC, wjoe wrote:
>> Especially since it's only a promise and the compiler accepts 
>> this:
>>
>> void foo (const(char)[] arr)
>> {
>>   cast(char[])arr[0..3] = "baz";
>> }
>> string bar = "123";
>> foo(bar);
>> assert(bar=="baz");
>>
>> But I could cast away const and modify the string bar.
>
> No, you could not. You're relying on undefined behavior there. 
> Just because the compiler accepts something, doesn't mean it's 
> ok.
>
> If you want to be guarded against wandering into undefined 
> territory, that's what @safe does. With @safe, the cast doesn't 
> compile.

Undefined behavior yes, but regardless the example proves it can 
be done in @system code.
A few versions ago, possibly due to a bug or regression, the 
compiler didn't complain in @safe code either.

Of course you are correct academically. However, since it's 
possible, I'd wager my last hat that code like this is out in the 
wild.