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

[Gregor Mückl]

On Wednesday, 24 March 2021 at 17:38:14 UTC, H. S. Teoh wrote:
> Since there is only one sensible meaning of `a = b = c`...

If I'm reading the spec on expressions right, the compiler is 
actually free to interpret that as (a = b) = c if it feels 
particularly adventurous. The evaluation order of assignment 
operations is explicitly undefined...

I think the intent was to not force an order of execution of 
subexpressions on either side of a single assignment (e.g. a[i] = 
a[j] with an opIndex implementation), but this seems to leave too 
much leeway for assignment chains.

Side note: having an undefined order of execution of the sides of 
an assignment can be a great source of fun (read: surprising) 
bugs in C++. Just going from GCC to clang switches the order 
around.