Doing something useful with bare singleton types and no macros ...

blah.scala

scala> trait Label[T] { val value: Boolean }
defined trait Label

scala> def mkInstance(s: String, v: Boolean): Label[s.type] = new Label[s.type] { val value = v }
mkInstance: (s: String, v: Boolean)Label[s.type]

scala> implicit def lTrue = mkInstance("True", true)
lTrue: Label[String("True")]

scala> implicit def lFalse = mkInstance("False", false)
lFalse: Label[String("False")]

scala> def label(s: String)(implicit ls: Label[s.type]): Boolean = ls.value
label: (s: String)(implicit ls: Label[s.type])Boolean

scala> label("True")
res0: Boolean = true

scala> label("False")
res1: Boolean = false