// CS0315: The type `int' cannot be used as type parameter `U' in the generic type or method `A<int?>.Test<U>()'. There is no boxing conversion from `int' to `int?' // Line: 19 class A<T> { public static void Test<U> () where U : T { } } class B : A<int?> { } class Program { public static void Main () { B.Test<int> (); } }