mono/netcore/System.Private.CoreLib/shared/System/ByReference.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Runtime.CompilerServices;
using System.Runtime.Versioning;

namespace System
{
    // ByReference<T> is meant to be used to represent "ref T" fields. It is working
    // around lack of first class support for byref fields in C# and IL. The JIT and
    // type loader has special handling for it that turns it into a thin wrapper around ref T.
    [NonVersionable]
    internal readonly ref struct ByReference<T>
    {
#pragma warning disable CA1823, 169 // private field '{blah}' is never used
        private readonly IntPtr _value;
#pragma warning restore CA1823, 169

        [Intrinsic]
        public ByReference(ref T value)
        {
            // Implemented as a JIT intrinsic - This default implementation is for
            // completeness and to provide a concrete error if called via reflection
            // or if intrinsic is missed.
            throw new PlatformNotSupportedException();
        }

        public ref T Value
        {
            // Implemented as a JIT intrinsic - This default implementation is for
            // completeness and to provide a concrete error if called via reflection
            // or if the intrinsic is missed.
            [Intrinsic]
            get => throw new PlatformNotSupportedException();
        }
    }
}