Error found:
in module Main
at tests/purs/failing/TooFewClassInstanceArgs.purs:8:1 - 8:33 (line 8, column 1 - line 8, column 33)

  The type class Main.Foo expects 2 arguments.
  But the instance fooString only provided 1.

in type class instance
                 
  Main.Foo String
                 

See https://github.com/purescript/documentation/blob/master/errors/ClassInstanceArityMismatch.md for more information,
or to contribute content related to this error.