Begin-less range with step not returning the correct class

[ccocchi]

Hello,

While working on Array#slice with Enumerator::ArithmeticSequence (for 3.0 support), I found a discrepancy between Cruby 3.0.1 and truffleruby 22.0 :

# ruby 3.0.1p64
irb(main):018:0> (..0).step(1).class
=> Enumerator::ArithmeticSequence

vs

# truffleruby 22.0.0-dev-59020ff8, like ruby 3.0.2, Interpreted JVM [x86_64-darwin]
irb(main):002:0> (..0).step(1).class
=> Enumerator

The problem seems to only occur when dealing with begin-less range, the method #step returns a Enumerator::ArithmeticSequence for other type of ranges.

[eregon]

Thank you for the report, it looks like it works for endless ranges but not beginless ranges.

If you'd like to fix this yourself with a PR then please go ahead, I think it is fairly straightforward (in Range#step_internal).
If not please reply here and we'll try to take care of it.

[ccocchi]

Made a PR for it 🙂