Equality of empty OffsetArrays changes in Julia 1.5

[mbauman]

Previously, empty arrays with different offsets compared as different because their axes compared as different.

In Julia master (JuliaLang/julia#32348), empty ranges are now equal, making OffsetArray([],-1) == OffsetArray([], -2).

I'm not sure what the right semantic is here; I believe this was untested in the entire ecosystem.

[StefanKarpinski]

Would be great to get feedback on this now while we can still revert the change before 1.5 if it turns out to be a Bad Thing.

[timholy]

As I commented there, I don't know the answer.

But here's a way of thinking about it: an OffsetArray is really just an optimized representation of an ordered dict, with index=>value pairs. When the container is empty, there are no pairs, so of course two such dicts are the same.