RSRP-286975: error CS1061: 'object' does not contain a definition for 'Length' and no extension method 'Length' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?)

abstract class B<S>
{
    public abstract void Foo<T>(T x) where T : S;
}

class C : B<string[]>
{
    public override void Foo<T>(T x)
    {
        foreach (var y in x)
        {
            var z = y.Length;
        }
    }
}