MemoryPackSerializationException in complex polymorphism

[Darkar25]

Looks like MemoryPack does not support chained polymorhism.
This example would produce MemoryPackSerializationException upon calling the Serialize method.

internal class Program
{
    static void Main(string[] args)
    {
        _ = MemoryPackSerializer.Serialize<IA>(new B());
    }
}
[MemoryPackable]
[MemoryPackUnion(0, typeof(A))]
public partial interface IA { }
[MemoryPackable]
[MemoryPackUnion(0, typeof(B))]
public abstract partial class A : IA { }
[MemoryPackable]
public partial class B : A { }

As if the unions weren't confusing enough already, they require the concrete(non-abstract) implementations rather than just the classes that inherit from the specified interface/abstract class.
However, this code would work:

[MemoryPackable]
[MemoryPackUnion(0, typeof(B))]
public partial interface IA { }
[MemoryPackable]
[MemoryPackUnion(0, typeof(B))]
public abstract partial class A : IA { }
[MemoryPackable]
public partial class B : A { }