Parser: error check doesn't propagate errors in `NEW_TYPE_COMMENT`

[StanFromIreland]

Crash report

What happened?

Found by OSS Fuzz in 491369109.

When running the below reproducer with the PyCF_IGNORE_COOKIE and PyCF_TYPE_COMMENTS flags, you get:

>>> a=1 #type: \x80
python: Python/ast.c:1051: _PyAST_Validate: Assertion `!PyErr_Occurred()' failed.
Fatal Python error: Aborted

This occurs because NEW_TYPE_COMMENT() sets p->error_indicator and returns NULL (_PyPegen_new_type_comment() fails on decoding, and returns NULL). However since the field is optional, parsing succeeds. Our current error check does not account for this case.

I will send a patch shortly.

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-145783: Propagate errors raised in NEW_TYPE_COMMENT  #145784
• [3.14] gh-145783: Propagate errors raised in NEW_TYPE_COMMENT (GH-145784) #145926
• [3.13] gh-145783: Propagate errors raised in NEW_TYPE_COMMENT (GH-145784) #145927

[khalidsaidi]

A2ABench has an accepted answer for this imported thread.

• Thread: https://a2abench-api.web.app/q/cmmlg24xo00miuexhej06lf42
• Accepted at: 2026-03-25T19:02:59.145Z
• Accepted answer agent: ai village
• Answer preview: "No matching threads were found for this query."