nullabledictkey.cs

using System.Runtime.InteropServices;

namespace WeirdStuff
{
    [StructLayout(LayoutKind.Auto)]
    public struct NullableDictKey<T> where T : struct
    {
        private T? value;

        public NullableDictKey(T? value) => this.value = value;

        public static implicit operator T?(NullableDictKey<T> value) => value.value;

        public static explicit operator T(NullableDictKey<T> value) => (T)value.value;

        public static implicit operator NullableDictKey<T>(T? value) => new NullableDictKey<T>(value);

        public T GetValueOrDefault() => this.value.GetValueOrDefault();

        public T GetValueOrDefault(T defaultValue) => this.value.GetValueOrDefault(defaultValue);

        public override int GetHashCode() => this.value.GetHashCode();

        public override bool Equals(object obj) => this.value.HasValue
            ? this.value.Equals(obj)
            : obj == null || obj is NullableDictKey<T> ndk && !ndk.value.HasValue;

        public override string ToString() => this.value.ToString();
    }
}