Typeclass for Scala map that allows to get values and ensure their type

typefull_map.scala

import scala.collection.Map
import scala.reflect.ClassTag

final case class TypefullMapOps[K, V, M <: Map[_, _]](m: M)(implicit ev: M <:< Map[K, V]) {
  def getT[A <: V : ClassTag](k: K): Option[A] = m.get(k) match {
    case Some(x) => x match {
      case v: A => Some(v)
      case _ => throw new RuntimeException
    }
    case _ => None
  }

  def getOrElseT[A <: V : ClassTag](k: K, d: A): A = m.get(k) match {
    case Some(x) => x match {
      case v: A => v
      case _ => throw new RuntimeException
    }
    case _ => d
  }
}

implicit def toTypefullMapOps[K, V, M <: Map[_, _]](m: M)(implicit ev: M <:< Map[K, V]): TypefullMapOps[K, V, M] =
  TypefullMapOps(m)

val m = Map("foo" -> 5.2, "bar" -> true, "baz" -> "go")

m.getT[Boolean]("bar")
m.getOrElseT[Double]("foo", 10.0)