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'.