CombinerBase.scala

def ~>[Out](junction: UniformFanInShape[T, Out])(implicit b: Builder[_]): PortOps[Out, Unit] = {
        def bind(n: Int): Unit = {
          if (n == junction.inSeq.length)
            throw new IllegalArgumentException(s"no more inlets free on $junction")
          else if (b.module.upstreams.contains(junction.in(n))) bind(n + 1) // it's already part of the graph
          else b.addEdge(importAndGetPort(b), junction.in(n)) // b.add(), add it to the graph
        }
        bind(0)
        junction.out
      }

      def ~>[Out](junction: UniformFanOutShape[T, Out])(implicit b: Builder[_]): PortOps[Out, Unit] = {
        // b.add(), add it to the graph
        b.addEdge(importAndGetPort(b), junction.in)
        try findOut(b, junction, 0)
        catch {
          case e: IllegalArgumentException ⇒ new DisabledPortOps(e.getMessage)
        }
      }