Type of conditional expression is object

[cjolowicz]

The type of the following conditional expression is object:

s: str = "key=value"
a, b = s.split("=", 1) if "=" in s else ("key", "default")
# main.py:2: error: 'builtins.object' object is not iterable

It should be a union type instead, such as Union[List[str], Tuple[str, str]].

(Note that str.split returns List[str] while the else branch has the type Tuple[str, str].)

• Gist
• Playground

This is a follow-up to #3487.

[JukkaL]

Alternatively, inferring Sequence[str] for the conditional expression would help in this case.

Inferring a union type would break backward compatibility. If the fallout is not too bad, it may still make sense.

[ilevkivskyi]

Note that a good fix for #4975 may automatically lead to inferring Sequence here.

[cjolowicz]

Here is a simpler reproduction:

a, b = [1, 2] if bool() else (1, 2)

[intgr]

This issue is addressed in PR #8335.

[emmatyping]

Closing as this was fixed by #8335. Thanks @intgr !