using System;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;

#if NET40
[assembly: TypeForwardedTo(typeof(AggregateException))]
[assembly: TypeForwardedTo(typeof(OperationCanceledException))]
[assembly: TypeForwardedTo(typeof(CancellationToken))]
[assembly: TypeForwardedTo(typeof(CancellationTokenRegistration))]
[assembly: TypeForwardedTo(typeof(CancellationTokenSource))]
[assembly: TypeForwardedTo(typeof(Task))]
[assembly: TypeForwardedTo(typeof(Task<>))]
[assembly: TypeForwardedTo(typeof(TaskCanceledException))]
[assembly: TypeForwardedTo(typeof(TaskCompletionSource<>))]
[assembly: TypeForwardedTo(typeof(TaskContinuationOptions))]
[assembly: TypeForwardedTo(typeof(TaskCreationOptions))]
[assembly: TypeForwardedTo(typeof(TaskExtensions))]
[assembly: TypeForwardedTo(typeof(TaskFactory))]
[assembly: TypeForwardedTo(typeof(TaskFactory<>))]
[assembly: TypeForwardedTo(typeof(TaskScheduler))]
[assembly: TypeForwardedTo(typeof(TaskSchedulerException))]
[assembly: TypeForwardedTo(typeof(TaskStatus))]
[assembly: TypeForwardedTo(typeof(UnobservedTaskExceptionEventArgs))]

namespace System.Runtime.CompilerServices
{
    internal static class AsyncServices
    {
        internal static void ThrowAsync(Exception exception, SynchronizationContext targetContext)
        {
            if (targetContext != null)
            {
                try
                {
                    targetContext.Post(state => throw PrepareExceptionForRethrow((Exception)state), exception);
                    return;
                }
                catch (Exception ex)
                {
                    exception = new AggregateException(new Exception[]
                    {
                        exception,
                        ex
                    });
                }
            }
            ThreadPool.QueueUserWorkItem(state => throw PrepareExceptionForRethrow((Exception)state), exception);
        }

        internal static Exception PrepareExceptionForRethrow(Exception exc) => exc;
    }
}
#endif