Fix erasure for classOf[Unit], don't erase to classOf[BoxedUnit]

2 files changed, 15 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/transform/Erasure.scala b/src/reflect/scala/reflect/internal/transform/Erasure.scala
index c069e2c198..412c49f571 100644
--- a/src/reflect/scala/reflect/internal/transform/Erasure.scala
+++ b/src/reflect/scala/reflect/internal/transform/Erasure.scala
@@ -113,7 +113,8 @@ trait Erasure {
 
     def apply(tp: Type): Type = tp match {
       case ConstantType(ct) =>
-        if (ct.tag == ClazzTag) ConstantType(Constant(apply(ct.typeValue)))
+        // erase classOf[List[_]] to classOf[List]. special case for classOf[Unit], avoid erasing to classOf[BoxedUnit].
+        if (ct.tag == ClazzTag && ct.typeValue.typeSymbol != UnitClass) ConstantType(Constant(apply(ct.typeValue)))
         else tp
       case st: ThisType if st.sym.isPackageClass =>
         tp
@@ -165,7 +166,7 @@ trait Erasure {
 
   /**   The erasure |T| of a type T. This is:
    *
-   *   - For a constant type, itself.
+   *   - For a constant type classOf[T], classOf[|T|], unless T is Unit. For any other constant type, itself.
    *   - For a type-bounds structure, the erasure of its upper bound.
    *   - For every other singleton type, the erasure of its supertype.
    *   - For a typeref scala.Array+[T] where T is an abstract type, AnyRef.
diff --git a/test/junit/scala/issues/RunTest.scala b/test/junit/scala/issues/RunTest.scala
index 781f2ef343..0605947e63 100644
--- a/test/junit/scala/issues/RunTest.scala
+++ b/test/junit/scala/issues/RunTest.scala
@@ -147,4 +147,16 @@ class RunTest extends ClearAfterClass {
     assertEquals(run[String](definitions("Object") + runCode), "hi" * 9)
     assertEquals(run[String](definitions("String") + runCode), "hi" * 9) // bridge method for clone generated
   }
+
+  @Test
+  def classOfUnitConstant(): Unit = {
+    val code =
+      """abstract class A { def f: Class[_] }
+        |class C extends A { final val f = classOf[Unit] }
+        |val c = new C
+        |(c.f, (c: A).f)
+      """.stripMargin
+    val u = Void.TYPE
+    assertEquals(run[(Class[_], Class[_])](code), (u, u))
+  }
 }