// 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;
 
namespace Roslyn.Utilities;
 
/// <summary>
/// A covariant interface form of <see cref="ReferenceCountedDisposable{T}"/> that lets you re-cast an <see cref="ReferenceCountedDisposable{T}"/>
/// to a more base type. This can include types that do not implement <see cref="IDisposable"/> if you want to prevent a caller from accidentally
/// disposing <see cref="Target"/> directly.
/// </summary>
/// <typeparam name="T"></typeparam>
internal interface IReferenceCountedDisposable<out T> : IDisposable, IAsyncDisposable
    where T : class
{
    /// <summary>
    /// Gets the target object.
    /// </summary>
    /// <remarks>
    /// <para>This call is not valid after <see cref="IDisposable.Dispose"/> is called. If this property or the target
    /// object is used concurrently with a call to <see cref="IDisposable.Dispose"/>, it is possible for the code to be
    /// using a disposed object. After the current instance is disposed, this property throws
    /// <see cref="ObjectDisposedException"/>. However, the exact time when this property starts throwing after
    /// <see cref="IDisposable.Dispose"/> is called is unspecified; code is expected to not use this property or the object
    /// it returns after any code invokes <see cref="IDisposable.Dispose"/>.</para>
    /// </remarks>
    /// <value>The target object.</value>
    T Target { get; }
 
    /// <summary>
    /// Increments the reference count for the disposable object, and returns a new disposable reference to it.
    /// </summary>
    /// <remarks>
    /// <para>The returned object is an independent reference to the same underlying object. Disposing of the
    /// returned value multiple times will only cause the reference count to be decreased once.</para>
    /// </remarks>
    /// <returns>A new <see cref="ReferenceCountedDisposable{T}"/> pointing to the same underlying object, if it
    /// has not yet been disposed; otherwise, <see langword="null"/> if this reference to the underlying object
    /// has already been disposed.</returns>
    IReferenceCountedDisposable<T>? TryAddReference();
}