Error found:
in module Main
at tests/purs/failing/Superclasses5.purs:17:1 - 18:18 (line 17, column 1 - line 18, column 18)

  A case expression could not be determined to cover all inputs.
  The following additional cases are required to cover all inputs:

    _

  Alternatively, add a Partial constraint to the type of the enclosing value.

while checking that expression case $0 of       
                                 [ x ] -> [ su x
                                          ]     
  has type t0
in value declaration suArray

where t0 is an unknown type

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