Garbage collector collects live objects

[Ruslan Mullakhmetov via Digitalmars-d-learn]

On Wednesday, 10 December 2014 at 08:46:12 UTC, Ruslan 
Mullakhmetov wrote:
> yes. that was the mistake. also after fixing bug in Blk 
> Attributes printing i got more reasonable attrs
>
> for object blk: FINALIZE
> for array of objects blk: NO_SCAN APPENDABLE
>
> this is sound good except for NO_SCAN.
>
> ...
> the other question why this happens... try to debug more.

I've done more dubugging.

what i've found:

initially array blk has only attrs APPENDABLE, but after some 
time this blk is shrinked and reallocated (moved) and then 
NO_SCAN attr appears.


here the output of my extended logs:

--------
before tag: 1 len: 2 ptr: 103DD9058 root: 103DD8000:8192 attr: 
APPENDABLE
after tag: 1 len: 3 ptr: 103A21DD0 root: 103A21DC0:64 attr: 
NO_SCAN APPENDABLE
--------

this is produced by the following code

http://dpaste.dzfl.pl/0c6dc16270a1

so in a nutshell after appending to array via ~= operator blk 
attrs changed from APPENDABLE to NO_SCAN APPENDABLE which cause 
the problem.

why and how this happens? can anybody explain it to me?