src/java.base/share/classes/java/time/chrono/ChronoLocalDateImpl.java

@@ -140,11 +140,12 @@
   * Subclasses should be Serializable wherever possible.
   *
   * @param <D> the ChronoLocalDate of this date-time
   * @since 1.8
   */
- abstract class ChronoLocalDateImpl<D extends ChronoLocalDate>
+ // See doc/value-class-preview.md for an overview of value class generation
+ abstract /*value*/ class ChronoLocalDateImpl<D extends ChronoLocalDate>
          implements ChronoLocalDate, Temporal, TemporalAdjuster, Serializable {
  
      /**
       * Serialization version.
       */