SI-6710 / PR 5072 follow-up: fix Unit.box / Unit.unbox

The backend replaces .box / .unbox methods by corresponding invocations
to BoxesRunTime, but not for Unit.

This commit restores the body of `Unit.box` and `Unit.unbox`.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/library/scala/Unit.scala b/src/library/scala/Unit.scala
index 397d7b823b..eb6d1d0ddf 100644
--- a/src/library/scala/Unit.scala
+++ b/src/library/scala/Unit.scala
@@ -30,7 +30,7 @@ object Unit extends AnyValCompanion {
    *  @param  x   the Unit to be boxed
    *  @return     a scala.runtime.BoxedUnit offering `x` as its underlying value.
    */
-  def box(x: Unit): scala.runtime.BoxedUnit = ???
+  def box(x: Unit): scala.runtime.BoxedUnit = scala.runtime.BoxedUnit.UNIT
 
   /** Transform a boxed type into a value type.  Note that this
    *  method is not typesafe: it accepts any Object, but will throw
@@ -40,7 +40,7 @@ object Unit extends AnyValCompanion {
    *  @throws     ClassCastException  if the argument is not a scala.runtime.BoxedUnit
    *  @return     the Unit value ()
    */
-  def unbox(x: java.lang.Object): Unit = ???
+  def unbox(x: java.lang.Object): Unit = x.asInstanceOf[scala.runtime.BoxedUnit]
 
   /** The String representation of the scala.Unit companion object. */
   override def toString = "object scala.Unit"