lucmac:sandbox luc$ cat Test.scala 
package o
package a {
  class C {
    def hihi = List(1,2).map(_ * 2)
  }
}
package object a {
  def f = 1
}
lucmac:sandbox luc$ scalac -Ybackend:GenBCode -Ydelambdafy:method Test.scala 
Test.scala:4: warning: Class o.a.C$lambda$$hihi$1 differs only in case from o.a.C$lambda$$hihi$1. Such classes will overwrite one another on case-insensitive filesystems.
    def hihi = List(1,2).map(_ * 2)
                               ^
one warning found