Why dtor are not executed when removing a struct from associative arrays?

[jfondren]

On Monday, 20 September 2021 at 12:23:00 UTC, Learner wrote:
> I was expecting something like going out of scope for that
>
> ```(D)
> import std.stdio;
>
> struct S
> {
>     ~this()
>     {
>         writeln("S is being destructed");
>     }
> }
>
> void main()
> {
> 	S[int] aa;
>     aa[1] = S();
>     aa.remove(1);
>     writeln("Why no dtor call on remove?");
> }
>
> I was expecting S instance dtor called
> S is being destructed
> ```

This looks to me like a bug, as

```d
import core.memory : GC;
GC.collect;
```

immediately after the `.remove` will call the struct's destructor.

I only see https://issues.dlang.org/show_bug.cgi?id=20379 as 
related, though.

Here's another workaround:

```d
alias purge = (kv, k) { kv[k] = typeof(kv[k]).init; kv.remove(k); 
};
```

with the same caveat of the `.init` structs also getting 
destructed later, you can use that in place of `.remove`.