--- old/src/java.base/share/classes/java/lang/ref/PhantomReference.java	2019-05-23 15:39:18.441433248 -0400
+++ new/src/java.base/share/classes/java/lang/ref/PhantomReference.java	2019-05-23 15:39:18.045431284 -0400
@@ -30,6 +30,9 @@
  * Phantom reference objects, which are enqueued after the collector
  * determines that their referents may otherwise be reclaimed.  Phantom
  * references are most often used to schedule post-mortem cleanup actions.
+ * <p>
+ * The referent must not be an instance of an inline class; such a value
+ * can never have another reference to it and cannot be held in a reference type.
  *
  * <p> Suppose the garbage collector determines at a certain point in time
  * that an object is <a href="package-summary.html#reachability">
@@ -72,6 +75,8 @@
      * @param referent the object the new phantom reference will refer to
      * @param q the queue with which the reference is to be registered,
      *          or {@code null} if registration is not required
+     * @throws IllegalArgumentException if the referent is an instance of an
+     *         {@link Class#isInlineClass() inlineClass}
      */
     public PhantomReference(T referent, ReferenceQueue<? super T> q) {
         super(referent, q);