Error: An error occurred in the renaming clause of a formal generic.
What to do:
  In the case of a multi-constraint generic (like in  'G -> {A,B}')
  one has to ensure that for every used feature there are no ambiguities.
  In order to achieve that goal you can use a renaming clause.
  For example: G -> {A rename f as g end, B}
Hint: The renaming for formal generics is analogous to the
  renaming occuring during inheritance.