Cannot resolve Writes[T] at runtime in Play Json

I am trying to make a generic Writer to get me the String representation of a json with Play Json. What I've got till now is

import com.twitter.finatra.http.Controller
import play.api.libs.json.{Json, Writes}

trait MyController extends Controller {
  def handle(request: AnyRef) =
    response
     .ok
     .json(createJsonResponse(manage(request)))
     .toFuture

   def manage[T : Writes](request: AnyRef): T

  // There should be an implicit Writes[T] in scope
   def createJsonResponse[T : Writes](data: T) = Json.stringify(Json.toJson[T](data))
}

I have case class TotalsForResponse(issuer: String, total: Int) defined and

  object JsonFormatters {
   implicit val totalsForResponseWrites = Json.format[TotalsForResponse]
  }

This should provide me at RunTime with an implicit Writes[T] in scope. IN one of my controllers I have

def manage[T : Writes](request: AnyRef) = request match {

case TotalInvestorsForRequest(issuer) =>
  TotalsForResponse(issuer,
    TitleSectionDBHandler.totalInvestorsFor(issuer))
  .asInstanceOf[T]
}

which results in diverging implicit expansion for type play.api.libs.json.Writes[Nothing] at runtime. This was taken from this example which I couldn't get it to work. Any ideas?