The kata is broken again. Everything seems ok locally, but here I can't neither test nor attempt my solution because of the following error:

<no location info>: error:
    Simplifier ticks exhausted
  When trying UnfoldingDone $w$cprettify
  To increase the limit, use -fsimpl-tick-factor=N (default 100).
   
  In addition try adjusting -funfolding-case-threshold=N and
  -funfolding-case-scaling=N for the module in question.
  Using threshold=1 and scaling=5 should break most inlining loops.
   
  If you need to increase the tick factor substantially, while also
  adjusting unfolding parameters please file a bug report and
  indicate the factor you needed.
   
  If GHC was unable to complete compilation even with a very large factor
  (a thousand or more), please consult the "Known bugs or infelicities"
  section in the Users Guide before filing a report. There are a
  few situations unlikely to occur in practical programs for which
  simplifier non-termination has been judged acceptable.
   
  To see detailed counts use -ddump-simpl-stats
  Total ticks: 58523

Fixed.

I added a translation of this Kata over to Idris, adapting the structure of the code as close as possible (except moving (:<:) from a typeclass (interface in Idris) to a data type that covers all 3 instances similar to the Elem datatype in the Idris standard library.

Idris is a functional language like Haskell, but with a Dependent type system instead. It also, unlike Haskell, uses Strict instead of lazy evaluation.

https://www.codewars.com/kumite/63f93ea7cbfbb30047dcece3?sel=63f93ea7cbfbb30047dcece3

I'd appreciate any help or suggestions!

Description should be language-agnostic

The link to Data Types a la Carte in the description is dead

I completely and fully agree with you - this kata is 6kyu at best. I personally feel somewhat at odds with myself now that I pretty much got free points off this kata - I was really hoping for an exciting headscratcher in OCaml.

A lot of the difficulty for me in this one was trying to understand exactly what the task was. Once, I finally figured that out, the actual Kata is actually pretty good, but I don't think it's super clear from the description or the provided test cases as to what the actual task is.

W is a Monoid

please post as a 'suggestion', not an 'issue', and add a link to the translation

I feel that this kata is free elo. It is way too easy for 2nd kyu kata. In every other language You have to sweat a lot to find/write solution for 2nd kyu kata (personal opinion). I was just starting in OCaml (8 kyu) and while looking for suitable kata for me i found this. Firstly i thought that there is going to be a trap somewhere and I will spend a lot of time solving it, but i got a little bit upset when i didn't find any. It feels more like 5th/6th kyu katas (easier ones from them) than 2nd kyu…

I've pushed a cpp version translation which is completed by user @SPA004, and I've got his authorization.

I've solved the kata!
:D

why this kata is recommended for me who's a 5kyu beginner ... :|

I am in the same situation now. Do you have any tip on what to look out for?

Edit: After posting the spoilers from moonberry where revealed. It was indeed related to limit and suppress

Finally fixed in 2022.