trait Generic[T] { type Repr } object Generic { type Aux[T, Repr0] = Generic[T] { type Repr = Repr0 } import scala.language.experimental.macros implicit def materializeGeneric[T, Repr]: Generic.Aux[T, Repr] = macro Macros.impl[T] } object Test extends App { case class C(x: Int, y: Int) // this doesn't work because of SI-7470 // well, in fact SI-7470 has been fixed: https://github.com/scala/scala/pull/2499 // it's just that the fix hasn't been backported to 2.10.x // if you've made this compile, consider taking a look at the aforementioned pull request def reprify[T, Repr](x: T)(implicit generic: Generic.Aux[T, Repr]) = ??? reprify(C(40, 2)) // this is a compilation error at the moment as explained in SI-8104 // because matchesPt in implicit search says that depoly() isn't a subtype of Generic.Aux[C, (Int, Int)] // which is rightfully so, because depoly only replaces type parameters, not type members with wildcard types // however in the future we might want to relax the matchesPt check, so this might start compiling // therefore, if you've broken this test, then you should be happy, because most likely you've just enabled an interesting use case! implicitly[Generic.Aux[C, (Int, Int)]] }