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`.

2 files changed, 6 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
index 6d3d458324..cea264c57a 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
@@ -658,16 +658,16 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
           genInvokeDynamicLambda(attachment.target, attachment.arity, attachment.functionalInterface, attachment.sam)
           generatedType = methodBTypeFromSymbol(fun.symbol).returnType
 
-        case Apply(fun @ _, List(expr)) if currentRun.runDefinitions.isBox(fun.symbol) =>
+        case Apply(fun, List(expr)) if currentRun.runDefinitions.isBox(fun.symbol) =>
           val nativeKind = tpeTK(expr)
           genLoad(expr, nativeKind)
           val MethodNameAndType(mname, methodType) = srBoxesRuntimeBoxToMethods(nativeKind)
           bc.invokestatic(srBoxesRunTimeRef.internalName, mname, methodType.descriptor, app.pos)
-          generatedType = boxResultType(fun.symbol) // was typeToBType(fun.symbol.tpe.resultType)
+          generatedType = boxResultType(fun.symbol)
 
-        case Apply(fun @ _, List(expr)) if currentRun.runDefinitions.isUnbox(fun.symbol) =>
+        case Apply(fun, List(expr)) if currentRun.runDefinitions.isUnbox(fun.symbol) =>
           genLoad(expr)
-          val boxType = unboxResultType(fun.symbol) // was typeToBType(fun.symbol.owner.linkedClassOfClass.tpe)
+          val boxType = unboxResultType(fun.symbol)
           generatedType = boxType
           val MethodNameAndType(mname, methodType) = srBoxesRuntimeUnboxToMethods(boxType)
           bc.invokestatic(srBoxesRunTimeRef.internalName, mname, methodType.descriptor, app.pos)
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"