typing.Literal can not be correctly checked against if it was imported via wildcard import

[xiaosiyu0603]

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

4.3.0

Python version

3.11.5

What happened?

My code:

from typing import *
from typeguard import typechecked


@typechecked
def test(string: Literal["hi"] | Literal['hello']):
    return string


print(test("hi"))

Exception raised when running in python:

D:\Home\Desktop>python tgt.py
Traceback (most recent call last):
  File "D:\Home\Desktop\tgt.py", line 11, in <module>
    print(test("hi"))
          ^^^^^^^^^^
  File "D:\Home\Desktop\tgt.py", line 7, in test     
    def test(string: Literal["hi"] | Literal['hello']):
                             ^^^^
NameError: name 'hi' is not defined

How can we reproduce the bug?

Maybe run the code?

[agronholm]

This is caused by the wildcard import, the use of which is bad practice. If instead you do:

from typing import Literal

This works fine. The underlying problem is that the AST transformer looks for typing.Literal and special cases it, but as it can't see where Literal comes from, it doesn't special case Literal, and ends up removing the quotes.

[xiaosiyu0603]

It works well, thanks a lot! 😀🙏

(It's a little hard for python programmers who lack professional background to discover such mistake.😂 Adding some warnings to the documentation might be helpful.)

[agronholm]

I'll think about that. This is a shortcoming of the library though, and it could some day be fixed. It wll involve nontrivial amounts of work though.