Restrict gem to < Ruby 3.0

[jahfer]

Until #87 is closed, this gem produces unreliable results under Ruby 3.

Make sure these are checked before submitting your PR — thank you!

• bin/fmt was successfully run

[dylanahsmith]

We are already using rotoscope on ruby 3. The main concern would be with caller_singleton_method? (at least in combination with caller_method_name and call.caller_class_name), but that isn't being used by that use of rotoscope.

[jahfer]

but that isn't being used by that use of rotoscope

Not sure I follow. The script you shared in #87 (comment) suggests to me that the gem currently produces incorrect instance/class attribution when the caller is a C method. #caller_singleton_method? is part of the public API.

[dylanahsmith]

Yes, it is a part of rotoscope's API, but it is only a problem for apps that actually use that method. I mean we are using rotoscope on ruby 3 at Shopify, but without using that method. Adding a ruby version constraint would just block that dependency on rotoscope from being updated.