scala - 无法复制具有重复参数的案例类

Question

为什么不能使用带有重复参数的case类的copy方法？

例如，为什么这段代码的最后一行给了我错误？

case class A(i: Int)
case class B(i: Int*)

val a = A(1).copy(i = 2)
val b1 = B(i = Seq(4, 5): _*)
val b2 = B(2, 3).copy(i = Seq(4, 5): _*)

value copy is not a member of B

Answer 1

根据斯卡拉 specs copy编译器不会为具有重复参数的案例类生成方法。

A method named copy is implicitly added to every case class unless the class already has a member (directly defined or inherited) with that name, or the class has a repeated parameter.