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].)

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This is a follow-up to #3487.