[2.7.0] Asynchronous tasks swallow exceptions

[JechoJekov]

When an async task awaits on another async task and the latter fails with an exception it is not propagated to the initial caller.

public static class Application
{
    public static void Main()
    {
        Console.WriteLine("Application started.");

        Run();
    }

    static async void Run()
    {
        var t = new TestAsync();
        var value = await t.AsyncError1();
        Console.WriteLine(value.ToString());
    }
}

class TestAsync
{
    public async Task<long> AsyncError1()
    {
        var value = await AsyncError2();

        Console.WriteLine(value.ToString());
        Console.WriteLine("Raising an error 1.");

        throw new Exception("This is an error 1.");
    }

    Task<long> AsyncError2()
    {
        Console.WriteLine("Raising an error 2.");

        throw new Exception("This is an error 2.");
    }
}

The code above prints the following on the console:

Application started.
Raising an error 2.

In .NET such exceptions gets raised on a thread-pool thread and crashes the application. However, Saltarelle ignores them.

In the following code:

public static class Application
{
    public static void Main()
    {
        Console.WriteLine("Application started.");

        Run();
    }

    static async void Run()
    {
        try
        {
            var t = new TestAsync();
            var value = await t.AsyncError1();
            Console.WriteLine(value.ToString());
        }
        catch (Exception exc)
        {
            Console.WriteLine("An error occurred during the exception of the first async method: " + exc.Message);
        }
    }
}

class TestAsync
{
    public async Task<long> AsyncError1()
    {
        var value = await AsyncError2();

        Console.WriteLine(value.ToString());
        Console.WriteLine("Raising an error 1.");

        throw new Exception("This is an error 1.");
    }

    Task<long> AsyncError2()
    {
        Console.WriteLine("Raising an error 2.");

        throw new Exception("This is an error 2.");
    }
}

the exception is caught by the "Run" method and displayed on the console:

Application started.
Raising an error 2.
An error occurred during the exception of the first async method: This is an error 2.

The reason is that the "AsyncError1()" method call is awaited inside a try-catch block.

Swallowing the exception may cause parts of the application to fail silently and makes it difficult to track the reason.

IMO if a task fails and there is no continuation callback (as in the case when a task is awaited inside a try-catch block) the exception should still be raised. This will cause it to be displayed on the console and to fire the "window.onerror" event.