Scala：如何让编译器从Seq[T]类型的函数参数推断类型？

我正在生成一个泛型函数，它对以下类的不同子类进行排序：

class SortableByGeographicPoint(val geographicPoint: Int)

其子类如下所示：

case class A(id: Int, override val geographicPoint: Int) extends SortableByGeographicPoint(geographicPoint)

我的职能是：

def sortByGeoPoint[T <: SortableByGeographicPoint](sequence: Seq[SortableByGeographicPoint]): Seq[T] = {
   sequence.sortBy(_.geographicPoint) map(_.asInstanceOf[T])
}

---

def sortByGeoPoint[TOops，我只需要这样做：

  def sortByGeoPoint2[T <: SortableByGeographicPoint](sequence: Seq[SortableByGeographicPoint]): Seq[T] = {
      sequence.sortBy(_.geographicPoint) map(_.asInstanceOf[T])
  }

不需要安装
asInstanceOf
，这是不安全的：

def sortByGeoPoint3[T <: SortableByGeographicPoint](sequence: Seq[T]): Seq[T] = 
  sequence.sortBy(_.geographicPoint)

def sortByGeoPoint3[T为什么不在
Seq
类型参数中使用
T

def sortByGeoPoint[T <: SortableByGeographicPoint](sequence: Seq[T]): Seq[T] =
  sequence.sortBy(_.geographicPoint)

def sortByGeoPoint[T
def sortByGeoPoint3[T <: SortableByGeographicPoint](sequence: Seq[T]): Seq[T] = 
  sequence.sortBy(_.geographicPoint)

def sortByGeoPoint[T <: SortableByGeographicPoint](sequence: Seq[T]): Seq[T] =
  sequence.sortBy(_.geographicPoint)