scalameta-tut-macro-caller.scala

// the signature is slightly different, as our macro need to access `get` and `put` method, but not `getOrElse`
// you can implement both signature though
trait SyncCache[K, V] {
  def get(k: K): Option[V]
  def put(k: K, v: V): Unit
}

val cacheBackend = new SyncCache[Int, Int]

@cache(cacheBackend)
def fib(i: Int): Int = i match {
  case 0 => 0
  case 1 => 1
  case n => fib(n - 2) + fib(n - 1)
}