Fix compatibility of Java with value classes

This avoids getting a runtime error when calling a Java-defined method
whose signature contains value classes. It happened because we erased
the value classes in this signature even though it comes from a
classfile.

Amusingly, this problem also exists in scalac:
<https://issues.scala-lang.org/browse/SI-9298>

3 files changed, 19 insertions, 0 deletions

diff --git a/tests/pos/valueclasses/t9298/JUse.java b/tests/pos/valueclasses/t9298/JUse.java
new file mode 100644
index 000000000..a872c895a
--- /dev/null
+++ b/tests/pos/valueclasses/t9298/JUse.java
@@ -0,0 +1,7 @@
+package t9298;
+
+class JUse {
+  public static Meter jm() {
+    return new Meter(2);
+  }
+}
diff --git a/tests/pos/valueclasses/t9298/Meter.scala b/tests/pos/valueclasses/t9298/Meter.scala
new file mode 100644
index 000000000..290b28509
--- /dev/null
+++ b/tests/pos/valueclasses/t9298/Meter.scala
@@ -0,0 +1,3 @@
+package t9298
+
+class Meter(val x: Int) extends AnyVal
diff --git a/tests/pos/valueclasses/t9298/Use.scala b/tests/pos/valueclasses/t9298/Use.scala
new file mode 100644
index 000000000..41f1fb035
--- /dev/null
+++ b/tests/pos/valueclasses/t9298/Use.scala
@@ -0,0 +1,9 @@
+// TODO: this should be a run test once we have run tests
+
+package t9298
+
+object Use {
+  def main(args: Array[String]): Unit = {
+    val x: Meter = JUse.jm
+  }
+}