Type error for staged tuple operations

[odersky]

The following code typechecks OK, but gives a type error when inlining. I believe that should not happen, since the error is in library code.

object Test {

  val unit = ()

  def f[T <: Tuple, X](xs: T, x: X) =
    xs ++ x *: unit
}

The error I get is:

5 |sealed trait Tuple extends Any {
  |          ^^^^^^^^^^^^^^^
  |          found:    Tuple.Concat[T(xs)(Tuple_this), (T$27 *: T$28)(that)]
  |          required: Tuple.Concat[T(xs), (X *: Unit(Test.unit))(?1)]
  |          
  |          where:    ?1 is an unknown value of type X *: Unit(Test.unit)
  | This location is in code that was inlined at matchtypes.scala:6

Also, it seems the position is wrong for the error.

[Jasper-M]

I sincerely hope this kind of type error is not something that an end user is expected to receive?