(🎁) Infer local partial type when using `extend` with generator

[KotlinIsland]

a = []  # main.py:1: error: Need type annotation for "a" (hint: "a: List[<type>] = ...")
a.extend(a for a in [1])
reveal_type(a)  # main.py:3: note: Revealed type is "builtins.list[Any]"

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