Question

In Scala 2.10, this works:

implicit class T1[A](val self: Iterator[A]) {
  def :+[B >: A](elem: B): Iterator[B] =
    self ++ Iterator(elem)
}

But when I try to make it a value class:

implicit class T2[A](val self: Iterator[A]) extends AnyVal {
  def :+[B >: A](elem: B): Iterator[B] =
    self ++ Iterator(elem)  
}

I get the error:

type arguments [B] do not conform to method ++'s type parameter bounds [B >: A]

Why?

Answer 1

It is a bug and it is already fixed in the current nightly.

See this ticket for more information.