% scalac29 -d /tmp a.scala 
a.scala:2: error: Bippy is not a member of scala.collection.mutable
  import scala.collection.mutable.{
         ^
one error found

% m1scalac -d /tmp a.scala 
a.scala:2: error: object Bippy is not a member of package scala.collection.mutable
  import scala.collection.mutable.{
         ^
a.scala:7: error: not found: type ArrayBuffer
  val ab1 = new ArrayBuffer[String]
                ^
a.scala:9: error: not found: value ArrayBuilder
  val abu1 = ArrayBuilder.make[Long]
             ^
a.scala:10: error: not found: value ArrayBuilder
  val abu2 = ArrayBuilder.make[Float]
             ^
a.scala:12: error: not found: value ArraySeq
  val aq1 = ArraySeq(1, 2, 3)
            ^
a.scala:14: error: not found: type ArrayStack
  val as1 = new ArrayStack[Int]
                ^
a.scala:16: error: not found: type BitSet
  val bs1 = new BitSet()
                ^
a.scala:18: error: not found: type DoubleLinkedList
  val dl1 = new DoubleLinkedList[Int](2, null)
                ^
a.scala:20: error: not found: type HashMap
  val hm1 = new HashMap[String, Int]
                ^
a.scala:22: error: not found: type HashSet
  val hs1 = new HashSet[String]
                ^
a.scala:23: error: not found: type History
  val h1 = new History[String, Int]
               ^
a.scala:25: error: not found: type ListBuffer
  val lb1 = new ListBuffer[String]
                ^
a.scala:27: error: not found: type Queue
  val q1 = new Queue[Int]
               ^
a.scala:29: error: not found: type Stack
  val s1 = new Stack[Int]
               ^
a.scala:33: error: not found: value WrappedArray
  val wa1 = WrappedArray.make(Array(1, 2, 3))
            ^
15 errors found