Error found:
in module Main
at tests/purs/failing/2379.purs:6:8 - 6:19 (line 6, column 8 - line 6, column 19)

  No type class instance was found for class
         
    Lib.Y
         
  because the class was not in scope. Perhaps it was not exported.

while solving type class constraint
           
  Lib.Y Int
           
while applying a function x
  of type X t0 => t0 -> String
  to argument [ 1
              , 2
              , 3
              ]  
while inferring the type of x [ 1
                              , 2
                              , 3
                              ]  
in value declaration test

where t0 is an unknown type

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