Incorrect "never used" for trait referenced by classOf

[scabug]

In the example:

package test
object Test {
  def main(args: Array[String]): Unit = {
    println(classOf[IsInFactUsed])
  }

  private trait IsInFactUsed
}

Compiling with -Ywarn-unused gives an incorrect warning

$ scalac -Ywarn-unused test.scala 
test.scala:8: warning: private trait IsInFactUsed in object Test is never used
  private trait IsInFactUsed
                ^
one warning found

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9058?orig=1
Reporter: Emiliano Clariá (eclaria)
Affected Versions: 2.11.4

[lrytz]

scala/scala#6190