Opaque type for io.TextIOWrapper seek and tell?

The following prints 18446744073709551620 (as I discovered in https://github.com/python/cpython/issues/93077):

import io
stream = io.TextIOWrapper(io.BytesIO(b'"")\r\nx\r\n'))
stream.read(1)
stream.read(1)
stream.read(1)
print('-----> tell:', stream.tell())

This is not a bug. The documentation says that .tell() returns "an opaque number" that "does not usually represent a number of bytes in the underlying binary storage".

In fact, calling .seek() with anything else than 0 or a return value of .tell() "produces undefined behaviour". I just relied on that today, without knowing it. I wrote this code:

def _upgrade_high_scores_file(file: IO[str], old_version: int) -> None:
    ...
    file.seek(len(b"catris high scores file v"))
    ...

This shouldn't pass the type check IMO.

Commencez par examiner les annotations de io.TextIOWrapper seek() et tell() dans typeshed, ainsi que la documentation Python citée dans l’issue. Une modification complète représenterait les résultats de tell() comme des valeurs opaques et empêcherait seek() d’accepter des offsets arbitraires, tout en continuant à autoriser 0 et une valeur renvoyée par tell().