VTUG, chapter 12 (Types), page 201

     Unconstrained Genericity rule

     Let  `CT'   be   a   Class_type  having  a  non-empty
     Actual_generics part,  whose base  class `C' is not a
     constrained generic class.  `CT' is valid if and only
     if `C' satisfies the following two conditions:

        1 `C' is a generic class.

        2  The  number  of  Type  components   in   `CT''s
          Actual_generics  list  is the same as the number
          of    Formal_generic    parameters    in     the
          Formal_generic_list of `C''s declaration.