def combine[T](cc: CaseClass[Typeclass, T])(implicit no: SwaggerContentNotCombineable) = no.absurd

@implicitNotFound("SwagerContent could be derived only for sealed traits")
final abstract class SwaggerContentNotCombineable {
  def absurd: Nothing
}

service TestService {
  get /get/1
  get() 

  get /get/2/{d.f1}/{d.f2}?f3={d.f3}&f4={d.f4}
  get(d: D)

  get /get/3?f1={...d.f1}
  get3(d: D2)

  // D2 fields will be transferred into body spec
  post  /post/1/{d.f1}/{d.f2}?f3={d.f3}&f4={d.f4} 
  post1(d: D1, body d2: D2)

  get /get/4?f1={...d.f1}&f2={d.f2} 
  get4(d: D3)

  get /get/5/{a}
  get5(a: i32)

  get /get/6?++={d}
  get6(d: D3)

  get /get/7?++={d}
  get7(d: D4)
}