The proposal is that Range#=== optimize by reducing method calls.
$ cat t.rb i = 0 while i < 1_000_000 case i when 1..1000 end i += 1 end
$ time ./miniruby -e 1 ./miniruby -e 1 0.01s user 0.00s system 85% cpu 0.013 total
$ time ./miniruby t.rb ./miniruby t.rb 0.60s user 0.00s system 99% cpu 0.605 total
$ time ./miniruby t.rb ./miniruby t.rb 0.41s user 0.00s system 99% cpu 0.420 total
Break compatibility in this case.
I don't know how to fix this issue.
But I think, This is a key sentence maybe.