VSTHRD003 should flag awaiting Task from fields

[AArnott]

The following does not produce a diagnostic from VSTHRD003:

class Program
{
    static Task t;
    static JoinableTaskFactory jtf;

    static void Main(string[] args)
    {
        jtf.Run(async delegate
        {
            await t;
        });
    }
}

It seems VSTHRD003 only triggers when the Task is a local variable.