BlockThingsIterator + voodoo dolls + game save = CTD?

This is a really weird one, so I'm not sure of my example is perfectly minimal, but here's what I managed to compile.

In Beautiful Doom I have Explosive Barrel that fires a BlockThingsIterator every second and searches for other Explosive Barrels nearby, which it then puts in an array (originally this was done to fine-tune the amount of certain visual effects when multiple barrels are close to each other; that part isn't present in the attached example, only the iterator). This resulted in Very Fatal Error when attempting to save the game in Eviternity maps with death exits, so I can only assume it was related to voodoo dolls. As soon as I disabled the iterator, crashes stopped.

Steps to reproduce:

• Run the attached example (bti_crash.pk3) on a map with a death exit (e.g. Eviternity map 05)

• Save the game

• Result: crash to desktop

I was able to trigger this in 4.5.0 as well as a few later dev builds.

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It has nothing to do with voodoo dolls, the provided code should not compile at all. It's a bug in compiler's type checking. Variable of actor type must not be pushed to array of class types.

Code:

Class CTDExplosiveBarrel : ExplosiveBarrel replaces ExplosiveBarrel {
   private array < Class<CTDExplosiveBarrel> > barrels;  // <-- class type
   const ddist = 14;
   override void Tick() {
      super.Tick();
      if (GetAge() % 35 == 0) {
         BlockThingsIterator itr = BlockThingsIterator.Create(self,ddist);
         while (itr.next()) {
            let obj = itr.thing;
            if (obj == self)
               continue;
            if (!(obj is "CTDExplosiveBarrel"))
               continue;
            if (barrels.Find(obj) != barrels.Size())
               continue;
            if (distance3D(obj) > ddist)
               continue;
            barrels.Push(obj);  // <-- actor type
         }
         console.printf("other barrels nearby: %d",barrels.Size());
      }
   }
}

It has nothing to do with voodoo dolls, the provided code should not compile at all. It's a bug in compiler's type checking. Variable of actor type must not be pushed to array of class types.

...Yes, you're actually right

However, not only this code compiles, it actually works (the printf) gives out the correct results. So, there's still a bug there at least.

Yes, there's an elusive type checking bug in the array code. Since the actors get pushed onto the array, the count will be correct, though.

The thing is, I started with private array < CTDExplosiveBarrel > barrels, and barrels.Push(obj) gave me a "return type mismatch". That's when I got confused and changed the array type. Apparently I simply had to cast obj.