FrameLocalsProxy `|=` and `update()` mishandle errors raised while merging mappings

Bug report

Bug description:

Bug description

FrameLocalsProxy does not correctly propagate exceptions raised while merging a dict subclass or another supported mapping-like object.

There are two related problems in Objects/frameobject.c:

1. framelocalsproxy_inplace_or() returns Py_NotImplemented when framelocalsproxy_merge() fails. If the merge failed because Python code raised an exception, the slot returns a normal object while an exception is still set. In a pydebug build this triggers a fatal _Py_CheckSlotResult error.
2. framelocalsproxy_update() replaces any failure from framelocalsproxy_merge() with a generic TypeError, masking the original exception.

This is a sub-issue of https://github.com/python/cpython/issues/146102 with gist details
A minimal reproducer is below.

import operator
import sys

class BadDict(dict):
    def keys(self):
        raise RuntimeError("keys() failed!")

def repro_update():
    locs = sys._getframe().f_locals
    print(type(locs))

    try:
        locs.update(BadDict())
    except TypeError as exc:
        print("BUG: update() masked RuntimeError as TypeError:", exc)
    except RuntimeError as exc:
        print("OK: update() propagated RuntimeError:", exc)

def repro_inplace_or():
    locs = sys._getframe().f_locals
    print(type(locs))

    try:
        operator.ior(locs, BadDict())
    except RuntimeError as exc:
        print("OK: |= propagated RuntimeError:", exc)
    except BaseException as exc:
        print("BUG: |= raised wrong exception:", type(exc).__name__, exc)
    else:
        print("BUG: |= swallowed RuntimeError")

repro_update()
repro_inplace_or()

operator.ior(locs, BadDict()) is used to exercise the same nb_inplace_or slot as locs |= BadDict().

Actual behavior

For .update(), the original RuntimeError from BadDict.keys() is replaced with a generic TypeError:

<class 'FrameLocalsProxy'>
BUG: update() masked RuntimeError as TypeError: update() argument must be dict or another FrameLocalsProxy

For |= on a pydebug build, the interpreter aborts because the slot reports success while an exception remains set:

<class 'FrameLocalsProxy'>
Fatal Python error: _Py_CheckSlotResult: Slot |= of type FrameLocalsProxy succeeded with an exception set
Python runtime state: initialized
Traceback (most recent call last):
  File "/tmp/repro_ior.py", line 6, in keys
    raise RuntimeError("keys() failed!")
RuntimeError: keys() failed!
Aborted (core dumped)

Expected behavior

Both FrameLocalsProxy.update() and FrameLocalsProxy.__ior__() should propagate the original exception raised while merging:

<class 'FrameLocalsProxy'>
OK: update() propagated RuntimeError: keys() failed!
<class 'FrameLocalsProxy'>
OK: |= propagated RuntimeError: keys() failed!

I will submit a PR to fix this

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-153421

Objects/frameobject.c の framelocalsproxy_inplace_or() と framelocalsproxy_update() から始め、次に BadDict.keys() が RuntimeError を発生させる最小再現プログラムを実行します。完了条件は、両方の操作が debug-build での slot failure なしに元の例外を伝播し、報告された挙動に対するリグレッションカバレッジがあることです。