ductyping.scala

  class C {
    def call(num:Int):Unit = {

    }
  }
  class X {
    type Hoge = { def call(num:Int):Unit;}
    def exe(hoge:Hoge, num:Int) = {
      hoge.call(num)
    }
  }
  var x = new X();
  x.exe(new C(