The typing module has subtle changes that are not even documented: Typing types now have a __name__ attribute. That confused the parser of the pyi generator because suddenly stingizing Callable[..., Optional[str]] resulted in Callable[..., Optional] because of special rules that return the generic name of a typing type, which was very unexpected. Finding this bug took a lot of debugging of the recursive `_resolve_type` function. We finally move the debugging_aid string as a function into lib/tool.py, because this was very helpful. [ChangeLog][shiboken6] The parser for .pyi files needed an update because of undocumented changes in typing.py for Python 3.10 . Task-number: PYSIDE-1436 Change-Id: I3b8f2c1aa52a23014a8a915a0c677af96dfc536f Reviewed-by: Christian Tismer <tismer@stackless.com>