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@xuwei-k
Created August 22, 2021 10:24
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object Main {
def head[A](list: List[A]): A = list.head
def x1: List[Int] | List[String] = List(3)
// この変換は可能。逆の変換は無理
def x2: List[Int | String] = x1
def x3 = head(x1)
def x4 = head(x2)
x3 : (Int | String) // Matchableになってしまってコンパイルエラー
x4 : (Int | String) // これは成功
}
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