✅ Invalid cast between interface types

IMarked<Arr<Option<Unit>>, CountOfField>

public interface FieldUnits : IMarked<Arr<Option<Unit>>, CountOfField> {}

System.InvalidCastException: 'Unable to cast object of type 'Marked`2[LanguageExt.Arr`1[LanguageExt.Option`1[Unit]],CountOfField]' to type 'FieldUnits'.'

var units = (FieldUnits)Enumerable.Repeat(Option<Unit>.None, CountOfField.Count).ToArr().mark(default(CountOfField));