No Nothings

gistfile1.scala

def unexpected : Nothing = sys.error("Unexpected invocation")

// Encoding for "A is not a subtype of B"
trait <:!<[A, B]

// Uses ambiguity to rule out the cases we're trying to exclude
implicit def nsub[A, B] : A <:!< B = null
implicit def nsubAmbig1[A, B >: A] : A <:!< B = unexpected
implicit def nsubAmbig2[A, B >: A] : A <:!< B = unexpected

// Type alias for context bound
type |¬|[T] = {
  type λ[U] = U <:!< T
}

def something[T: |¬|[Nothing]#λ](t : T) = t

val smth1 = something(23)                // OK
val smth2 = something("foo")             // OK
val smth3 = something(error("Boom!"))    // Does not compile

implicit def nsubAmbig1[A, B >: A] : A <:!< B = unexpected
implicit def nsubAmbig2[A, B >: A] : A <:!< B = unexpected

why this duplication?

@epiphyllum because otherwise, this trick doesn't work 😄