Incorrect value while debugging in Visual Studio 2015

Assume we have sample code (VS2015, WinForms, .Net 4.6.1):

List<int> items = new List<int>();
private async Task test(int id)
{
    id = 1;
    int id_real = id;

    int index = items.FindIndex(x => x == id);
}

private async void button1_Click(object sender, EventArgs e)
{
    await test(0);
}

Now "the feature":

How is that possible? The interesting part - it is only Visual Studio watcher problem, runtime result remains correct.

For now I know it is only happens in VS2015, and cause of this behaviour - the last string in test method.