VNCC, chapter 13 (Conformance), page 219


     Let `T' and `V' be two types.  `V' conforms to `T' if
     and only if one of the following holds:

        1 `V' and `T' are identical.

        2 `V' conforms directly to `T'.

        3 `V' is `NONE' and `T' is a reference type.

        4 `V' is B [`Y1, ... Yn'] for some  generic  class
          `B',  `T'  is B [`X1, ... Xn'], and every one of
          the   `Yi'   conforms   (recursively)   to   the
          corresponding `Xi'.

        5 `T' is a reference type and, for some type  `U',
          `V'   conforms   to   `U'   and   `U'   conforms
          (recursively) to `T'.
