`_PyPegen_add_type_comment_to_arg` can fail in` _PyPegen_name_default_pair`

[StanFromIreland]

Crash report

What happened?

>>> import _testcapi
>>> _testcapi.Py_CompileStringExFlags(b"def a(f=8,#type: \x80\n\x80", "<test>", 256, 0x0800 | 0x1000)
python: Objects/typeobject.c:2440: type_call: Assertion `!_PyErr_Occurred(tstate)' failed.
Aborted                    (core dumped) ./python

In _PyPegen_name_default_pair, we call:

cpython/Parser/action_helpers.c

Line 437 in a95ee3a

a->arg = _PyPegen_add_type_comment_to_arg(p, arg, tc);

but don't check if it failed (and returned NULL).

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Output from running 'python -VV' on the command line:

No response

Linked PRs

• gh-148157: Check for _PyPegen_add_type_comment_to_arg fail in _PyPegen_name_default_pair #148158
• [3.14] gh-148157: Check for _PyPegen_add_type_comment_to_arg fail in _PyPegen_name_default_pair (GH-148158) #148162
• [3.13] gh-148157: Check for _PyPegen_add_type_comment_to_arg fail in _PyPegen_name_default_pair (GH-148158) #148163