Merge pull request scala#4490 from retronym/ticket/9298

SI-9298 Fix erasure of value classes in Java

Author: lrytz

src/reflect/scala/reflect/internal/transform/Erasure.scala

@@ -254,6 +254,8 @@ trait Erasure {
     def mergeParents(parents: List[Type]): Type =
       if (parents.isEmpty) ObjectTpe
       else parents.head
+
+    override protected def eraseDerivedValueClassRef(tref: TypeRef): Type = eraseNormalClassRef(tref)
   }
 
   object scalaErasure extends ScalaErasureMap

test/files/run/t9298/Test.java

@@ -0,0 +1,7 @@
+public class Test {
+	public void consume(VC vc) {}
+
+	public static void main(String[] args) {
+		new Client().test();
+	}
+}

test/files/run/t9298/VC.scala

@@ -0,0 +1,5 @@
+class VC(val s: String) extends AnyVal
+
+class Client {
+  def test = new Test().consume(new VC(""))
+}

test/files/run/t9298b/Test.java

@@ -0,0 +1,7 @@
+public class Test {
+	public VC identity(VC vc) { return vc; }
+
+	public static void main(String[] args) {
+		new Client().test();
+	}
+}

test/files/run/t9298b/VC.scala

@@ -0,0 +1,8 @@
+class VC(val s: Int) extends AnyVal
+
+class Client {
+  def test = {
+    val vc: VC = new Test().identity(new VC(42))
+    assert(vc.s == 42)
+  }
+}