The issue is that you're thinking as you would in Java.
I guess the rule in D for immutable is this: Immutable data won't change as long as it exists.
The last part of that sentence would be a stupid thing to say in Java because things don't just cease to exist while you're still doing something with them. That is not the case in D.
That being said it's very unlikely that you will ever run into this situation. You have to end the lifetime of the object manually to run into these issues. And in that case it'll be very easy to figure out what's wrong.
