在scala中，为什么不能从同一范围推断出这个隐式参数？

Question

我正在编写一个简单的Apache Spark实用程序，它根据提供的初始值自动创建一个AccumulatorV2：

  import java.lang

  type Acc[T] = AccumulatorV2[T, T]

  implicit val long1: Long => Acc[lang.Long] = _ => new LongAccumulator()LongAccumulator()

  implicit def double1: Double => Acc[lang.Double] = _ => new DoubleAccumulator()

  def accumulator[T1, T2](
                           initialValue: T1,
                           name: String
                         )(implicit
                           canBuildFrom: T1 => Acc[T2],
                           converter: T1 => T2,
                           sc: SparkContext = SparkContext.getOrCreate()
                         ): Acc[T2] = {

    val acc: Acc[T2] = canBuildFrom(initialValue)
    acc.reset()
    acc.add(initialValue)

    sc.register(acc, name)

    acc
  }

2个隐含参数：canBuildFrom和converter应该分别由隐式函数和编译器预定义的类型转换提供。但是，当我试着打电话时：

Metrics.accumulator(0L, "webDriverDispatched")

我收到以下错误信息：

Error:(102, 84) No implicit view available from Long => com.tribbloids.spookystuff.Metrics.Acc[T2].
                          webDriverDispatched: Acc[lang.Long] = Metrics.accumulator(0L, "webDriverDispatched"),
Error:(102, 84) not enough arguments for method accumulator: (implicit canBuildFrom: Long => com.tribbloids.spookystuff.Metrics.Acc[T2], implicit converter: Long => T2, implicit sc: org.apache.spark.SparkContext)com.tribbloids.spookystuff.Metrics.Acc[T2].
Unspecified value parameters canBuildFrom, converter.
                          webDriverDispatched: Acc[lang.Long] = Metrics.accumulator(0L, "webDriverDispatched"),

为什么scala编译器找不到合适的隐式值？我应该怎么做才能解决它？