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

[Ali Çehreli]

On 9/20/21 5:23 AM, Learner wrote:

> I was expecting S instance dtor called
> S is being destructed

If you are sure the element can be destroyed, you can call destroy():

import std.stdio;

enum someSpecialInitValue = 777;

struct S
{
   int i = someSpecialInitValue;

   this(int i)
   {
     this.i = i;
   }

   ~this()
   {
     writeln("S with ", i, " is being destructed");
   }
}

void destroyAndRemove(AA, Key)(AA aa, Key key) {
   auto found = key in aa;
   if (found) {
     destroy(*found);
     aa.remove(key);
   }
}

void main()
{
   S[int] aa;
   aa[1] = S(1);
   aa.destroyAndRemove(1);
   writeln("Actually, 2 dtor calls! :)");
}

destroy() puts the object to its initial state, which means, it gets 
destroyed again. That's why there are two destructor calls below for the 
same object. I used a special value to demonstrate the second destructor 
is called on the init state:

S with 1 is being destructed
Actually, 2 dtor calls! :)
S with 777 is being destructed

Ali