src/Course/List.hs:662:10: error:
    • Illegal equational constraint a ~ Char
      (Use GADTs or TypeFamilies to permit this)
    • In the instance declaration for ‘IsString (List a)’
    |
662 | instance (a ~ Char) => IsString (List a) where
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Failed, four modules loaded.

<no location info>: error:
    Could not find module ‘Test.Loader’
    It is not a module in the current program, or in any known package.
Loaded GHCi configuration from /home/fernando/Coding/Haskell/fp-course/.ghci
Loaded GHCi configuration from /tmp/haskell-stack-ghci/2a3bbd58/ghci-script