• Investigate current failures and relevant code paths for except* and starred indexing
• Implement minimal runtime/support changes for except* handling
• Implement support for starred expressions in subscripts and related runtime behavior
• Add/adjust targeted tests validating new behaviors
• Run targeted checks/tests to verify changes
• Final review and cleanup

---

This section details on the original issue you should resolve

<issue_title>Two CPython 3.11 syntax changes involving * operator are unsupported</issue_title>
<issue_description>## Feature

In Python 3.11, the except* was added for working with ExceptionGroups. The availability of ExceptionGroup itself will depend on #4247, but in the meantime, the following snippet is valid CPython 3.11 that currently throws a SyntaxError in RustPython:

try:
    print("yay")
except* Exception as e:
    print("oh no")

I discovered this while digging into some code that ruff cannot handle, which on the surface looks like a slightly different issue. The following snippet is valid CPython 3.11 but also throws a SyntaxError in RustPython:

my_dict = {}
my_dict[*"ab"] = 1

The expected behaviour is that the string should be unpacked and the value of the dict with key ('a','b') set to 1. In case that feels a little contrived, here's what I was doing at the time:

import typing
values = ["dog", "cat"]
Pets = typing.Literal[*values]

Python Documentation

The first incompatibility issue is clearly documented here, and called out under New syntax features in What’s New In Python 3.11.

However the second incompatibility is not documented in the changelog, and I did confirm that this was new in CPython 3.11, as the snippet throws a syntax error in 3.10.

I wonder if this was a (nice?) side-effect of the changes that were introduced to make except* work. There is a seemingly related precedent for this, where using * to unpack without parentheses in for statements was enabled via the PEG parser in CPython 3.9, but was not noticed then and only documented in 3.11.

</issue_description>

<agent_instructions>Start from: SyntaxError: rustPython does not implement this feature yet

</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@DimitrisJim Unpacking in indexes was introduced with PEP 646 (specifically, see [here](https://peps.python.org/pep-0646/#change-1-star-expressions-in-indexes)). I guess it isn't documented in that section because it isn't new syntax per se, more of a change in where `*` is allowed (it probably should be in the [Other Language Changes](https://peps.python.org/pep-0646/#change-1-star-expressions-in-indexes) though, which also mentions another small syntax change). @charliermarsh Fixed :) @youknowone resolved by @charliermarsh , thanks! @youknowone I am sorry, the parser part is done but runtime is not. @charliermarsh Ah correct! @fanninpm cc @qingshi163 for inclusion in #4423 @DimitrisJim let's break this up in two issues? they touch on different subjects and the unpacking might be a good issue for someone to tackle. (plus, the title doesn't make it obvious that the parsing part of this is solved but the runtime isn't)

• Fixes Two CPython 3.11 syntax changes involving * operator are unsupported #4479

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