Derivation type constraints: specification terminology
Chapter 3: Parameterized typing with generics: 3.3.1
Last updated: 1/28/2008
One part of the C# 3 language spec (10.1.5) talks about derivation type constraints being fulfilled by the type argument "deriving from" the constraint - and I've quoted that in the book. However, this is a fairly crude way of expressing it, and is likely to change in future versions. The actual meaning won't (unless it's expanded to be less restrictive somehow) but the terminology well be improved.