TypeParamVsAnnotationWeirdness.scala

object Common {
  trait I[A, B] {
    def apply(a: A): B
  }

  def i[A, B](f: A => B): I[A, B] = new I[A,B] {
    def apply(a: A) = f(a)
  }

  case class Z(boz: String)
}

import Common._

object WorkingCase {

  val bozy: I[String, Z] = i(newBoz => Z(boz = newBoz))

  val boz = bozy("zob")
}

object BuggyCase {

  val bozy = i[String, Z](newBoz => Z(boz = newBoz))

  val boz = bozy("zob")  // fails?!
}

Correct. Seems to be something to do with a named parameter clashing with the assignment variable name in this particular case. Strange.