gistfile1.scala

scala> :paste
// Entering paste mode (ctrl-D to finish)

trait Context

object Helper {
  def stuff(implicit c: Context) = 3
  def stuff_=(i: Int)(implicit c: Context) = ()

  // woot
  type C[_] = Context
  def stuff2[T: C] = 3
  def stuff2_=[T: C](i: Int) = ()
}
object Test {
  implicit val c: Context = ???
  val s1 = Helper.stuff
           Helper.stuff = 3
  val s2 = Helper.stuff2
           Helper.stuff2 = 3
}

// Exiting paste mode, now interpreting.

<console>:23: error: reassignment to val
                  Helper.stuff2 = 3
                                ^