// CS1503: Argument `#2' cannot convert `IFoo<object>' expression to type `IFoo<int>' // Line: 18 interface IFoo<in T> { } class C { public static void Foo<T> (IFoo<T> e1, IFoo<T> e2) { } public static void Main () { IFoo<int> a = null; IFoo<object> b = null; Foo (a, b); } }