private CHM copy_slot_and_check( int idx, Object should_help ) {
      // We're only here because the caller saw a Prime, which implies a
      // table-copy is in progress.
      assert _newchm != null;
      if( copy_slot(idx) )      // Copy the desired slot
        copy_check_and_promote(1); // Record the slot copied
      // Generically help along any copy (except if called recursively from a helper)
      if( should_help != null ) _nbhml.help_copy();
      return _newchm;
    }
Auto-boxing version of {@link #replace}.
jctools-core/src/main/java/org/jctools/maps/NonBlockingHashMapLong.java