Error found:
in module Main
at tests/purs/failing/881.purs:10:1 - 13:12 (line 10, column 1 - line 13, column 12)

  Multiple value declarations exist for foo.

in type class instance
            
  Main.Foo X
            

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