What is going on in this code?

[Daniel Kozak via Digitalmars-d]

On Thursday, 14 April 2016 at 13:08:56 UTC, Carlin wrote:
> On Thursday, 14 April 2016 at 10:29:43 UTC, ag0aep6g wrote:
>> [...]
>
> Thanks, that works perfectly! I couldn't figure it out and I 
> knew I had to be missing something really basic. I still don't 
> understand though why it works in release but not in debug.

because with release build dub will enable inlining. So I guess 
there is a stack frame elimination