specialized member of value class: crash

object Bippy {

  implicit final class C(val x: Int) extends AnyVal {

    def +++[@specialized T](y: T) = ()

  }

  def f = 1 +++ 2

}

$plus$plus$plus$mIc$sp not found in class C's decls: Scope{

  val x: Int;

  private[this] val x: Int;

  def <init>(x: Int): Bippy.C;

  def +++[T](y: T): Unit;

  override def hashCode(): Int;

  override def equals(x$1: Any): Boolean

}

	at scala.Predef$.assert(Predef.scala:182)

	at scala.tools.nsc.Global.assert(Global.scala:213)

	at scala.tools.nsc.transform.ExtensionMethods.scala$tools$nsc$transform$ExtensionMethods$$extensionNames(ExtensionMethods.scala:65)

	at scala.tools.nsc.transform.ExtensionMethods$$anonfun$extensionMethod$1.apply(ExtensionMethods.scala:74)

	at scala.tools.nsc.transform.ExtensionMethods$$anonfun$extensionMethod$1.apply(ExtensionMethods.scala:72)

	at scala.reflect.internal.SymbolTable.atPhase(SymbolTable.scala:185)