Type erasure and solutions to avoid it - work in progress / published by https://github.com/dacr/code-examples-manager #b88b5c9e-7aed-476a-8b44-8ff30015cfd1/630224776ca57356d8b878c030bb35685076918f

scala-erasures.sc

// summary : Type erasure and solutions to avoid it - work in progress
// keywords : scala, erasure, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : b88b5c9e-7aed-476a-8b44-8ff30015cfd1
// created-on : 2022-07-04T09:29:07+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala  "3.2.2"
//> using dep "dev.zio::izumi-reflect:2.1.3"
// ---------------------

// See - https://medium.com/@sinisalouc/overcoming-type-erasure-in-scala-8f2422070d20

// ----------------------- default - everything is erased type information is lost
{
  object Extractor {
    def extract[T](list: List[Any]) = list.flatMap {
      case element: T => Some(element)
      case _          => None
    }
  }

  val list   = List(1, "string1", List(), "string2")
  val result = Extractor.extract[String](list)
  println(result) // List(1, string1, List(), string2)
}

// ----------------------- ClassTag
{
  import scala.reflect.ClassTag
  object Extractor {
    //def extract[T : ClassTag](list: List[Any])  // Alternative context
    def extract[T](list: List[Any])(implicit tag: ClassTag[T]) =
      list.flatMap {
        case element: T => Some(element)
        case _          => None
      }
  }
  val list: List[Any] = List(1, "string1", List(), "string2")
  val result = Extractor.extract[String](list)
  println(result) // List(string1, string2)
}


// ----------------------- TypeTag (work in progress required for scala3)
{
  import izumi.reflect.*
  object Recognizer {
    def recognize[T](x: T)(implicit tag: Tag[T]): String =
      val ref = tag.tag.ref
      List(ref.repr,ref.longName, ref.shortName, ref.typeArgs).mkString("\n")
//      match {
//        case TypeRef(utype, usymbol, args) =>
//          List(utype, usymbol, args).mkString("\n")
//      }
  }

  val list: List[Int] = List(1, 2)
  val result = Recognizer.recognize(list)
  println(result)
  // prints:
  //   scala.type
  //   type List
  //   List(Int)
}