I was making an analogy between how the “raise” statement works, and how the throw() method could work. In this example, there are three exception objects (MainError, SubError, and ValueError). I was suggesting that it is okay for the context to be set to the MainError instance, because that is how the analogous version using a “raise” statement works.

def main():
    try:
        raise MainError("Context inside generator")
    except MainError:
        yield  # __context__ could be changed to MainError

coro = main()
coro.send(None)
try:
    try: raise ValueError("Context outside of generator")
    except ValueError: raise SubError()
except SubError as ex:
    coro.throw(ex)  # __context__ is ValueError

# raise analogy:

try:
    try: raise ValueError("Context outside of generator")
    except ValueError as ex: raise SubError()
except SubError as ex:
    saved = ex  # __context__ is ValueError

try:
    raise MainError("Context inside generator")
except MainError:
    raise saved  # Changes __context__ to MainError

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Sorry I’m not really familiar with the code to quickly propose a patch or review your change though.