if r != rZero {
				pool.Put(r)
			}
		}
}

// NewSingleHandler creates a typed handler that can provide Marshal/Unmarshal.
// Use Register to register a server handler.
// Use Call to initiate a clientside call.
func NewSingleHandler[Req, Resp RoundTripper](h HandlerID, newReq func() Req, newResp func() Resp) *SingleHandler[Req, Resp] {
	s := SingleHandler[Req, Resp]{id: h}
	s.newReq, s.recycleReq = recycleFunc[Req](newReq)