VTGC, ECMA Eiffel, chapter 8.12.9

    Generic Constraint rule

    A Constraint part appearing in the Formal_generics  part
    of a class C is  valid if and only if it  satisfies  the
    following conditions for every Single_constraint listing
    a type T in its Constraining_types:

        1 `T' involves no anchored type.

        2 If a  Renaming  clause `rename rename_list end' is
          present, a class  definition of the form class NEW
          inherit  BT rename  rename_list  end  (preceded by
          deferred if the base classof T is deferred), where
          BT is the base class of T, would be valid.

        3 Every  name listed  in the  Constraint_creators is
          the generically  constrained name of a procedure p
          of one of the corresponding constraining types.