```py from typing import TypeVar T1 = TypeVar("T1") T2 = TypeVar("T2") def f(t1: T1, t2: T2) -> T1 | T2: return t1 a: int = f(1, None) or 1 # error: Argument 2 to "f" has incompatible type "None"; expected "int" [arg-type] def f1(t1: T1, t2: T1) -> T1: return t1 b: int = f1(1, None) or 1 # no error ```