C# でのユニット型実装

Unit.cs

using System;
using System.Diagnostics.CodeAnalysis;

[Serializable]
public struct Unit : IEquatable<Unit>, IComparable, IComparable<Unit>
{
    public override bool Equals([NotNullWhen(true)] object? obj)
    {
        return obj is Unit;
    }

    public bool Equals(Unit other)
    {
        return true;
    }

    int IComparable.CompareTo(object? other)
    {
        if (other is null)
        {
            return 1;
        }
        else if (other is not Unit)
        {
            throw new ArgumentException(null, nameof(other));
        }
        else
        {
            return 0;
        }
    }

    public int CompareTo(Unit other)
    {
        return 0;
    }

    public override int GetHashCode()
    {
        return 0;
    }

    public override string ToString()
    {
        return "()";
    }

    public static bool operator ==(Unit left, Unit right)
    {
        return true;
    }

    public static bool operator !=(Unit left, Unit right)
    {
        return false;
    }
}