I don't know why this error occurred: uncaught exception: IOException of type UserError user error (Could not parse solution correctly)

Ouch. Right. I forgot that.

Why is this best practice? Isn't it a bit verbose and slow?

hint : you will have to write a custom type, with a custom Monoid instance

This hint should be removed since you actually don't have to do that.

hint : there is a suitable Monoid in Data.Monoid

IMO, this one could be removed too, although it could be left as is considering it's an actual hint and not a plain false statement.

Everything seems to work fine now.

Poetry, wow. Thanks for this gem.

I also thought they would be stricter.

I liked that they weren't, which meant I had to create extra type families and thus I learnt a lot more about the pattern, buuuuuut... if this were marked in the description somehow, I'd have scored a victory on first pass, which is always nice (and the amount of times you do this is tallied in your profile!)

So... more information, pwetty please? :3

I'm getting an error when submitting my solution (but not when testing them)

FoldMapSpec.hs:5:8:
  Could not find module `Test.Hspec.Codewars'
  Perhaps you meant
    Test.Hspec.Compat
    Test.Hspec.Core (from hspec-2.2.4@hspec_GEAgkH1Gbr9BY0qzvd784f)
    Test.Hspec.Core.Tree
  Use -v to see a list of the files searched for.

Fixed ;-)

I hope you mean 'semantically correct' ...

Well, I did told you to reuse the combinators to prevent expanding into SK hell ;-)