I am building a aggregation framework with some code which looks like this

trait Aggregate[T <: Aggregate[T, K], K] { self: T => def plus(another: T): T def show: K }

I have couple of aggregations like this,

case class Count(value: Long = 1) extends Aggregate[Count, Long] { def plus(another: Count) = Count(value + another.value) def show = value }

Once i define a aggregation which is like this,

case class By[T <: Aggregate[T, K], K, G](values: HashMap[G, T]) extends Aggregate[By[T, K, G], Map[G, K]] { override def plus(another: By[T, K, G]): By[T, K, G] = By(values.merged(another.values){case ((k1,v1), (k2,v2)) => (k1, v1 plus v2)}) override def show: Map[G, K] = values.map{case (k,v) => k -> v.show} } object By { def apply[T <: Aggregate[T,K], K, G](key:G, value:T):By[T, K, G] = By(HashMap(key -> value)) }

I cannot write something like this

By("key1", Count(100))

Instead i had to write this

By[Count, Long, String]("key1", Count(100))