trait Exp[+T]
case class Const[T](t: T) extends Exp[T]
implicit def pure[T](t: T): Exp[T] = Const(t)
case class LiftTuple2[A1, A2](t1: Exp[A1], t2: Exp[A2]) extends Exp[(A1, A2)]
implicit def tuple2ToTuple2ExpPrime[ArgFOO1, A2, E1 <% Exp[ArgFOO1], E2 <% Exp[A2]](tuple: (E1, E2)): LiftTuple2[ArgFOO1, A2] = LiftTuple2[ArgFOO1, A2](tuple._1, tuple._2)

val a = pure(1)
val b = pure("")
val c = pure(2)
def asExp[T](t: Exp[T]) = t //an evaluation context triggering implicit conversions
tuple2ToTuple2ExpPrime(((a, b), c))
asExp(tuple2ToTuple2ExpPrime( ((a, b), c) ))
asExp(((a, b), c)) //does not compile

scala> asExp(((a, b), c)) //does not compile
<console>:19: error: No implicit view available from (Exp[Int], Exp[java.lang.String]) => Exp[ArgFOO1].
              asExp(((a, b), c)) //does not compile
                    ^

case class LiftTuple3[A1, A2, A3](t1: Exp[A1], t2: Exp[A2], t3: Exp[A3]) extends Exp[(A1, A2, A3)]
implicit def tuple3ToTuple3Exp[A1, A2, A3](tuple: (Exp[A1], Exp[A2], Exp[A3])): LiftTuple3[A1, A2, A3] = LiftTuple3[A1, A2, A3](tuple._1, tuple._2, tuple._3)
val d = pure(2.0)
asExp(tuple2ToTuple2ExpPrime((a, b, c), d))
asExp(((a, b, c), d)) //does not compile

scala> asExp(((a, b, c), d)) //does not compile
<console>:23: error: No implicit view available from (Exp[Int], Exp[java.lang.String], Exp[Int]) => Exp[ArgFOO1].
              asExp(((a, b, c), d)) //does not compile
                    ^

scala> asExp( (asExp( (a, b) ), c) )
<console>:19: error: No implicit view available from Exp[Int] => Exp[ArgFOO1].
              asExp( (asExp( (a, b) ), c) )
                             ^
scala> implicit def identity2[A](x: A): A         = x
identity2: [A](x: A)A

scala> asExp( (asExp( (a, b) ), c) )
<console>:21: error: No implicit view available from Exp[Int] => Exp[ArgFOO1].
              asExp( (asExp( (a, b) ), c) )