Error found:
in module Main
at tests/purs/failing/RowInInstanceNotDetermined1.purs:8:1 - 8:29 (line 8, column 1 - line 8, column 29)

  Type class instance head is invalid due to use of type
      
    ()
      
  All types appearing in instance declarations must be of the form T a_1 .. a_n, where each type a_i is of the same form, unless the type is fully determined by other type class arguments via functional dependencies.

in type class instance
                    
  Main.C Unit       
         Unit       
         (Record ())
                    

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