VCFG, chapter 4 (Classes), page 52

     A Formal_generics  part  of  a  Class_declaration  is
     valid  if  and  only if every Formal_generic_name `G'
     appearing  in it  satisfies  the   following   three
     conditions:

        1 `G' is different from the name of any  class  in
          the surrounding universe.

        2 `G'    is     different     from    any    other
          Formal_generic_name   appearing   in   the  same
          Formal_generics_part.

        3 The  only  types  involved in the Constraint, if
          any,  are  classes  or formal generic parameters
          other than `G'.
