opIndexUnary post in-/decrement how to ?

[wjoe]

On Wednesday, 14 July 2021 at 11:31:36 UTC, Tejas wrote:
>
> ``` {auto a = i[1] , ++i[1] , a} //note the , not the ;```
>
> Sorry I can't provide something even more concrete.

Yes I saw that, and I suppose it would work just fine if it were 
rewritten to just  ```++i[1]```.
What I'm struggling to understand is the ```{auto a = i[1], ... 
,a}``` part. I can't parse that. What's up with the assignment 
and the comma stuff ?