bpo-46202: Remove opcode POP_EXCEPT_AND_RERAISE

[iritkatriel]

Following the reduction of exc_info to just one stack item, POP_EXCEPT_AND_RERAISE can be replaced by an equivalent sequence of other opcodes.

One of the except* usages can be simplified further because it doesn't need to restore lasti. (this was moved to another pr).

https://bugs.python.org/issue46202

[brandtbucher]

Nice! Looks good to me, except for one weird bug I stumbled upon while reviewing it.

It's not directly related to these changes, but it still probably deserves to be fixed:

[bedevere-bot]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[iritkatriel]

I think the bot wants this in a new comment:

I have made the requested changes; please review again.

[bedevere-bot]

Thanks for making the requested changes!

@brandtbucher: please review the changes made to this pull request.

[ericsnowcurrently]

This strictly relates to re-raising an exception, right?

try:
    ...
except Exception:
    ...
    raise  # re-raise

and not raising an exception while handing another:

try:
    ...
except Exception as exc:
    ...
    raise exc
    # or raise Exception
    # or raise exc from exc2

[iritkatriel]

This strictly relates to re-raising an exception, right?

try:
    ...
except Exception:
    ...
    raise  # re-raise

and not raising an exception while handing another:

try:
    ...
except Exception as exc:
    ...
    raise exc
    # or raise Exception
    # or raise exc from exc2

It's for both - it's when you are about the exit a finally block, and you have a previous "handled exception" on the stack (because this finally is from a try-except or a with-statement which is nested in an except clause), and above it you have the lasti and an exception that you need to raise. So you need to pop the TOS and the lasti below it and raise, but first you need to take the THIRD item and use it to restore exc_info.

[ericsnowcurrently]

LGTM

(assuming you address any other review comments, of course)

[iritkatriel]

I think this PR lost focus a bit. I want to split the except* changes into a separate PR and just do a straightforward opcode removal in this one.

[iritkatriel]

I committed the except* changes separately so this PR now just removes POP_EXCEPT_AND_RERAISE.

[ericsnowcurrently]

LGTM