它似乎适用于 WeakTypeTag 而不是 TypeTag(也改变 typeTag 到 weakTypeTag).我真的不知道为什么；找不到任何关于此的具体文档.

Ok so the real reason I ran into this is that my ScalaTests failed to compile, because I defined some of the classes inside of the test scope that call another class file expecting to work with TypeTags. Notice that because class B is within my "test" (pretend this is a scala test call) , typetag no longer becomes viable. I suspect maybe I shouldn't be attempting this on an anonymous class inside of a local scope, but could someone help me understand please? Thanks

import scala.reflect.runtime.universe._
import scala.Symbol


class TypeTagger[T:TypeTag] {
  val tt = typeTag[T]
}

object TypeTagger {
  def apply[T]()(implicit  tt:TypeTag[T]) = new TypeTagger[T]
}

object TestRunTypeTagger extends App {
  class A

  val test = new TypeTagger[A]

  {
    class B
    val test2 = TypeTagger[B]()    //fails
  }
}

Error: No TypeTag available for B val test2 = TypeTaggerB

                       ^ not enough arguments for method apply: (implicit tt:

reflect.runtime.universe.TypeTag[B])chorle.scala.testarea.TypeTagger[B] in object TypeTagger. Unspecified value parameter tt. val test2 = TypeTaggerB

                         ^

It seems to work with a WeakTypeTag instead of a TypeTag (also change typeTag to weakTypeTag). I have no idea why really; couldn't find any documentation about this specifically.