This is code from the Twisted library: https://github.com/twisted/twisted/blob/trunk/src/twisted/internet/defer.py#... It "unwinds" a generator to yield a result before others. I don't have hard evidence, but my experience is that that kind of manipulation leaks resources, specially if exceptions escape from the final callback. Is there a bug in exception handling in the generator logic, or is unwinding just inherently wrong? How could the needs tried to solved with unwinding be handled with async? -- Juancarlo *Añez*