Error found:
in module Main
at tests/purs/failing/TypeClasses2.purs:7:8 - 7:22 (line 7, column 8 - line 7, column 22)

  No type class instance was found for
                    
    Main.Show String
                    

while applying a function show
  of type Show t0 => t0 -> String
  to argument "testing"
while inferring the type of show "testing"
in value declaration test

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.