NullableEqualityComparer.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
 
namespace System.Collections.Generic;
 
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public sealed class NullableEqualityComparer<T> : EqualityComparer<T?> where T : struct, IEquatable<T>
{
    internal override int IndexOf(T?[] array, T? value, int startIndex, int count)
    {
        int num = startIndex + count;
        if (!value.HasValue)
        {
            for (int i = startIndex; i < num; i++)
            {
                if (!array[i].HasValue)
                {
                    return i;
                }
            }
        }
        else
        {
            for (int j = startIndex; j < num; j++)
            {
                if (array[j].HasValue && array[j].value.Equals(value.value))
                {
                    return j;
                }
            }
        }
        return -1;
    }
 
    internal override int LastIndexOf(T?[] array, T? value, int startIndex, int count)
    {
        int num = startIndex - count + 1;
        if (!value.HasValue)
        {
            for (int num2 = startIndex; num2 >= num; num2--)
            {
                if (!array[num2].HasValue)
                {
                    return num2;
                }
            }
        }
        else
        {
            for (int num3 = startIndex; num3 >= num; num3--)
            {
                if (array[num3].HasValue && array[num3].value.Equals(value.value))
                {
                    return num3;
                }
            }
        }
        return -1;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override bool Equals(T? x, T? y)
    {
        if (x.HasValue)
        {
            if (y.HasValue)
            {
                return x.value.Equals(y.value);
            }
            return false;
        }
        if (y.HasValue)
        {
            return false;
        }
        return true;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override int GetHashCode(T? obj)
    {
        return obj.GetHashCode();
    }
 
    public override bool Equals([NotNullWhen(true)] object? obj)
    {
        if (obj != null)
        {
            return GetType() == obj.GetType();
        }
        return false;
    }
 
    public override int GetHashCode()
    {
        return GetType().GetHashCode();
    }
}