Is it possible to convert a TypeTag to a Manifest?

Question

Our library uses TypeTags, but now we need to interact with another library which requires Manifests. Is there any simple way to create a Manifest from a TypeTag?

Answer 1

gourlaysama's anwer uses Class[_], thus type arguments are being erased. I've come up with an implementation that preserves the type arguments here: How to maintain type parameter during TypeTag to Manifest conversion?

Here's the code:

  def toManifest[T:TypeTag]: Manifest[T] = {
    val t = typeTag[T]
    val mirror = t.mirror
    def toManifestRec(t: Type): Manifest[_] = {
      val clazz = ClassTag[T](mirror.runtimeClass(t)).runtimeClass
      if (t.typeArgs.length == 1) {
        val arg = toManifestRec(t.typeArgs.head)
        ManifestFactory.classType(clazz, arg)
      } else if (t.typeArgs.length > 1) {
        val args = t.typeArgs.map(x => toManifestRec(x))
        ManifestFactory.classType(clazz, args.head, args.tail: _*)
      } else {
        ManifestFactory.classType(clazz)
      }
    }
    toManifestRec(t.tpe).asInstanceOf[Manifest[T]]
  }