Bug report

Bug description:

Bug Report: f-string Regression in Python 3.13 Parser

Python Versions

• 3.11 – correctly rejects inner/outer matching‐quote f-strings
• 3.13 – silently accepts invalid f-string syntax

Issue Type

Parser / grammar regression

Description

In Python 3.11 and earlier, an f-string whose inner quotes match the outer quotes (for examplef"…{x.get("inner")}…") raises aSyntaxError. In Python 3.13, however, the same invalid code is accepted at compile time, leading to silent misparsing.

Steps to Reproduce

1. Create a filebroken_fstring.py:

# broken_fstring.pydeffoo():# This *should* be a SyntaxError:x= {}yieldf"Hello,{x.get("inner")}!"

2. Under Python 3.11:

    python3.11 -m py_compile broken_fstring.py

Expected:

  File "reportlib/report_generator/python_bug.py", line 7    yield f"Hello, {x.get("inner")}!"                           ^^^^^SyntaxError: f-string: unmatched '('

3. Under Python 3.13:

    python3.13 -m py_compile broken_fstring.py

Actual: no error, exit code 0.

Expected Behavior

The compiler should reject the invalid f-string syntax in all supported versions, consistent with PEP 498.

Minimal Test Case

# Create the test filecat> broken_fstring.py<< 'EOF'def foo():    x = {}    yield f"Hello, {x.get("inner")}!"EOF

Under 3.11:

python3.11 -m py_compile broken_fstring.py # raises SyntaxError

Under 3.13:

python3.13 -m py_compile broken_fstring.py # silently succeeds

CPython versions tested on:

3.13

Operating systems tested on:

macOS