opIndexUnary post in-/decrement how to ?

[Tejas]

On Wednesday, 14 July 2021 at 20:55:32 UTC, wjoe wrote:
> On Wednesday, 14 July 2021 at 16:13:35 UTC, Tejas wrote:
>> [...]
>
> Congratulations:) Unfortunately I haven't got anything I could 
> return by ref so I can't take advantage of a low hanging fruit.
> In my book overloading operators is no fun - at all - and 
> always a last resort because it requires so much time and 
> testing and causes so many headaches.
>
> Workarounds exist like ```i[n] += 1``` or direct call via 
> ```i.opIndexUnary!"++"(n)``` or simply ```++i[n]```.
> But that's beside the point. There's nothing in the spec that 
> says something about something needs to be returned by ref.
> Rewriting manually compiles and works as intended. So clearly 
> something else is going on which makes the compiler select 
> ```opIndex``` over ```opIndexUnary``` rewriting it post to pre.
> In my particular case the compiler can rule out ```opIndex``` 
> so why does it abort instead of trying ```opIndexUnary``` ? Or 
> was it trying and it didn't work ? If that's the case I'd like 
> to know the reason why it discarded ```opIndexUnary```.
>
> Anyways all the answers so far are much appreciated!

I'm so sorry all this was basically useless for you.

I can't spend more time on this, so as a last resort I leave you 
this:

https://dlang.org/phobos/std_bitmanip.html

This is the official bit manipulation standard library, maybe it 
will help you in some way; the ```bitfield``` struct looked 
mighty familiar to your ```part_int``` struct, but maybe that's 
my cognitive bias,  you should verify it.

Best of luck!