Things to check first
Typeguard version
4.4.4
Python version
3.11.13, 3.13.7, 3.14.0
What happened?
Here is an example use of @typechecked:
from typeguard import typechecked
@typechecked
def demo(arg: str | None = None) -> None:
if arg is None:
(arg,) = ("abc",)
print(f"{type(arg)=}, {arg=}")
return None
demo()Failure:
Traceback (most recent call last):
File "/tmp/t.py", line 14, in <module>
demo()
~~~~^^
File "/tmp/t.py", line 9, in demo
(arg,) = ("abc",)
File "typeguard/_functions.py", line 283, in check_variable_assignment
check_type_internal(val, annotation, memo)
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
File "typeguard/_checkers.py", line 960, in check_type_internal
checker(value, origin_type, args, memo)
~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "typeguard/_checkers.py", line 454, in check_uniontype
raise TypeCheckError(f"did not match any element in the union:\n{formatted_errors}")
typeguard.TypeCheckError: value assigned to arg (tuple) did not match any element in the union:
str: is not an instance of str
NoneType: is not an instance of NoneType
If we remove the decorator, it outputs type(arg)=<class 'str'>, arg='abc'.
I think typeguard is confused by the tuple unpacking (arg,) = ("abc",) and thinks arg is a tuple while it should be str.
How can we reproduce the bug?
Run the above example
Things to check first
I have searched the existing issues and didn't find my bug already reported there
I have checked that my bug is still present in the latest release
Typeguard version
4.4.4
Python version
3.11.13, 3.13.7, 3.14.0
What happened?
Here is an example use of
@typechecked:Failure:
If we remove the decorator, it outputs
type(arg)=<class 'str'>, arg='abc'.I think typeguard is confused by the tuple unpacking
(arg,) = ("abc",)and thinksargis a tuple while it should bestr.How can we reproduce the bug?
Run the above example