The custom-set exercism is based around the deprecated Set module and removed Set behaviour

[lpil]

Hello!

The Set module was deprecated in 1.2, and the behaviour has since been removed. It's not possible to directly port the changes to the MapSet replacement as it's a single data structure implementation rather than a behaviour with a default implementation.

This exercise needs to be removed, or entirely re-written. :(

I notice there are other open issues for this exercise. #198 #180 #121

[devonestes]

Yeah, at this point we just need to totally re-write the test suite for that exercise, so that's going to happen eventually. I'm confident that we can keep the exercise as it is, though, and just replace the test suite.

[lpil]

When we do so it would be good to add a note saying that in the real world we should use MapSet instead of inventing our own set :)