chaining throwable matchers invokes sut multiple times about specs2 HOT 2 CLOSED

import org.specs2.matcher._
import scala.reflect.ClassTag

class MySpec extends mutable.Specification {
  def throwIt(): Unit = {
    println("OH NO")
    throw new IllegalArgumentException("foo")
  }

  "not double-invoke throwable" >> {
    throwIt() must throwAnException[IllegalArgumentException];
  }

  def throwAnException[E <: Throwable](implicit c: ClassTag[E]): Matcher[Any] =
    new Matcher[Any] {
      def apply[S <: Any](s: Expectable[S]) = {
        // catch the exception if necessary
        val exception: Option[Throwable] = try { s.evaluate; None } catch { case e: Throwable => Some (e) };
        
        // re-throw the exception locally and use normal matchers
        // in this case the exception is thrown twice but it's not a big deal
        lazy val e = exception.foreach(e => throw e)
        val result: MatchResult[Unit] = e must (throwA[Throwable] and throwAn[E](c))

        // a bit of massaging is necessary to return a typed result
        result.asInstanceOf[MatchResult[Nothing]].setExpectable(s)
      }
    }

}