study: use checkedint as a drop-in replacement of native long

[mw]

On Monday, 17 August 2020 at 17:15:59 UTC, H. S. Teoh wrote:
> On Mon, Aug 17, 2020 at 05:10:01PM +0000, mw via Digitalmars-d 
> wrote:
>> 
>> https://issues.dlang.org/show_bug.cgi?id=21169
>
> You might want to consider splitting up that bug into multiple 
> smaller, more self-contained bugs.  Less intimidating that way 
> for potential contributors to fix. ;-)

Was hesitating between splitting or not, then thought user may 
want to take the full picture into consideration the best 
approach to fix the issue, e.g. in case 
one-stone-that-can-kill-multiple-birds.

(People can always submit separate a PR to fix one particular 
issue).


> Chain assignment fix: https://github.com/dlang/phobos/pull/7599

Thanks for the PR, I just added comments: does this fix also work 
for mixed native & checked chain assignment? i.e. add to unittest:

```
   long la, lb;
   Checked!long ca, cb;

   la = ca = lb = cb;  // mixed chain assign
   ca = la = cb = lb;
```