class A : B<int>
{
    static void Main()
    {
        new A().Foo(1); // error CS0121: The call is ambiguous between the following methods or properties: 'B<S>.Foo<T>(T, params S[])' and 'B<S>.Foo<T>(T, params T[])'
    }

    public override void Foo<T>(T x, int[] y) { }
    public override void Foo<T>(T x, params T[] y) { }
}

class B<S>
{
    public virtual void Foo<T>(T x, params S[] y) { }
    public virtual void Foo<T>(T x, params T[] y) { }
}