scala - Binding.scala 中的 BindingSeq 和常量？

Question

• Binding属于. val_Var
• BindingSeq也应该是val的Vars。

但是，要构造Binding的序列，BindingSeq不能从序列构造。有什么不对？

import com.thoughtworks.binding.Binding
import com.thoughtworks.binding.Binding.{BindingSeq, Var, Vars}

val x1: Var[Int] = Var{1}
val x2: Binding[Int] = Binding{1}
val x3: Vars[Int] = Vars{Seq(1,2,3): _*}
val x4: BindingSeq[Int] = BindingSeq{Seq(1,2,3): _*}
ScalaFiddle.scala:18: error: .this.com.thoughtworks.binding.Binding.BindingSeq.type does not take parameters
  val x4: BindingSeq[Int] = BindingSeq{Seq(1,2,3): _*}