Range violation instead of empty slice on a[3 .. 2]

[SimonN via Digitalmars-d-learn]

On Sunday, 22 November 2015 at 00:24:43 UTC, Jonathan M Davis 
wrote:
>> this is only an error if bounds checking is not turned on.
> It's a logic error regardless.

> you're going to have to create a wrapper.

Right, I am using a wrapper, and I'm not relying on any behavior 
of a[3..2] during -boundscheck=off.

> How does the runtime know that you're not just
> providing it garbage values?

The runtime flags an empty slice as an error here, seemingly 
without reason, because the slice can't access any element 
outside of bounds.

However, considering (2U - 3U) > 0, I understand that there is no 
way to catch this problem without comparing the two bounds. And 
the comparison is designed to be skippable for speed. Therefore, 
3..2 is reasonably flagged as an error.

So, thanks for pointing it it out again!

-- Simon