Nested classes question?

[Dave Akers via Digitalmars-d-learn]

When a program exits and D's memory management is cleaning up 
calling all of the ~this's is there a reason it calls the outer 
class's ~this before the inner class's ~this?

I was recently exploring the possibility of using 
https://github.com/bheads/d-leveldb and the example in the readme 
seg faulted, when digging into it i found out that the outer 
class was being destroyed before the inner causing the database 
to be closed before an iterator for the database was destroyed.