[advanced-typeguard] Unexpectedly pass

[F-park]

The below code can pass the challenge.

from typing import Any, TypeGuard


def is_string(value: Any) -> TypeGuard[str]:
    ...

However, If we replace ... with pass, it fail

from typing import Any, TypeGuard


def is_string(value: Any) -> TypeGuard[str]:
    pass

Shall we modify it?

[laike9m]

This is the expected behavior. pyright (and probably other type checkers) treat ... differently than pass. Normally ... will not trigger type error like you observed.

[laike9m]

Reference

microsoft/pyright#5985 (comment)

[F-park]

However, the solution of advanced-typeguard is as below.

def is_string(value: Any) -> TypeGuard[str]:
    return isinstance(value, str)

Just use ... to pass the challenge is confusing.

[laike9m]

I see your point. Adding return isinstance(value, str) to the question file seems to be the best fix, which also makes the intent more clear. wdyt?

[F-park]

return isinstance(value, str) is already in the question file, I am not sure we can replace ... with """Write your code here""" to avoid this bug？

[laike9m]

I mean, we can put the following in the question file

def is_string(value: Any):
    return isinstance(value, str)

Without annotating the return value with TypeGuard[str], it will also fail, which is what we want

[F-park]

Looks good to me

[laike9m]

ok I'll change it this way.

[laike9m]

Fixed in 0fa2d80