code: public int lastBufferIndexOf(KType e1) {
      final int bufLen = buffer.length;
      final int last = oneLeft(head, bufLen);
      for (int i = oneLeft(tail, bufLen); i != last; i = oneLeft(i, bufLen)) {
        if (Intrinsics.equals(this, e1, buffer[i]))
          return i;
      }
  
      return -1;
    }
docs: Return the index of the last (counting from tail) element equal to
  <code>e1</code>. The index points to the {@link #buffer} array.
  
  @param e1
  The element to look for.
  @return Returns the index of the first element equal to <code>e1</code> or
  <code>-1</code> if not found.