Boolean literals not recognized as Literals

[jolaf]

The following code:

from typing import Literal, Tuple, Union

x: bool = False

def f() -> Union[Tuple[Literal[True], int], Tuple[Literal[False], str]]:
    if x:
        return (True, 5)
    else:
        return (False, 'oops')

print(f())

produces the following ouput:

$ python3 test.py
(False, 'oops')

$ mypy test.py
test.py: note: In function "f":
test.py:7:16: error: Incompatible return value type (got "Tuple[bool, int]", expected "Union[Tuple[Literal[True], int], Tuple[Literal[False], str]]")  [return-value]
            return (True, 5)
                   ^
test.py:9:16: error: Incompatible return value type (got "Tuple[bool, str]", expected "Union[Tuple[Literal[True], int], Tuple[Literal[False], str]]")  [return-value]
            return (False, 'oops')
                   ^
Found 2 errors in 1 file (checked 1 source file)

$ mypy --version
mypy 0.910

$ python3 --version
Python 3.8.10

$ cat /etc/issue
Ubuntu 20.04.3 LTS \n \l

$ uname -a
Linux ubuntu 5.4.0-88-generic #99-Ubuntu SMP Thu Sep 23 17:29:00 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

From my point of view, the code looks correct, and mypy should not object.

[jolaf]

Thanks, @sobolevn, @JukkaL!