Compiling and running the following program results in an error:
 java.lang.InternalError: must be primitive type: X

$ cat X.java
public value class X {
    public static void main(String[] args) {
        Object o = new X();
        o.toString();
    }
}

$ ~/gitreps/valhalla/build/linux-x86_64-server-release/images/jdk/bin/javac -g X.java
$ ~/gitreps/valhalla/build/linux-x86_64-server-release/images/jdk/bin/java X
Exception in thread "main" java.lang.InternalError: must be primitive type: X
at java.base/java.lang.runtime.PrimitiveObjectMethods.primitiveObjectHashCode(PrimitiveObjectMethods.java:439)
at java.base/java.lang.Object.hashCode(Native Method)
at java.base/java.lang.Object.toString(Object.java:269)
at X.main(X.java:4)