[Dlang-internal] Strange behavior when appending pointers of structs to arrays

[Jonathan M. Wilbur]

Given the following code:

import std.stdio : writeln;

---
struct Foo
{
     Foo*[] children;
     void value()
     {
         Foo bar = Foo();
         version (bad1)
         {
             this.children ~= &bar;
         }
         version (bad2)
         {
             this.children.length += 1u;
             this.children[$-1] = &bar;
         }
     }
     void bark()
     {
         writeln("children: ", this.children.length);
         writeln("grandchildren: ", 
this.children[0].children.length);
     }
}

void main ()
{
     Foo foo = Foo();
     version (good)
     {
         Foo bar = Foo();
         foo.children ~= &bar;
     }
     else
     {
         foo.value();
     }
     foo.bark();
}
---

The resulting executable returns the following outputs:

C:\Users\Jonathan\Desktop\bug>dmd .\bug.d -version=bad1

C:\Users\Jonathan\Desktop\bug>bug.exe
children: 1
grandchildren: 4203068

C:\Users\Jonathan\Desktop\bug>dmd .\bug.d -version=bad2

C:\Users\Jonathan\Desktop\bug>bug.exe
children: 1
grandchildren: 1

C:\Users\Jonathan\Desktop\bug>dmd .\bug.d -version=good

C:\Users\Jonathan\Desktop\bug>bug.exe
children: 1
grandchildren: 0


Why?