Port, board and/or hardware

unix VARIANT=coverage

MicroPython version

MicroPython v1.26.0-preview.387.g67acac257f.dirty on 2025-07-19; linux [GCC 12.2.0] version

Reproduction

Run the following code:

def f(a, b): pass          
f(None, x=b"", y:=True)                                                 

Expected behaviour

Code is rejected at byte-compile time similar to Python:

  File "/tmp/qstrcrash.py", line 2
    f(None, x=b"", y:=True)
                          ^
SyntaxError: positional argument follows keyword argument

Observed behaviour

The file byte-compiles but an assertion error occurs when executing the call to f:

micropython: ../../py/qstr.c:198: find_qstr: Assertion `*q < pool->len' failed.

Additional Information

This is a minimized test case based on a crash found by fuzzing micropython

Code of Conduct

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