public abstract class AbstractChannelHandlerContext implements ChannelHandlerContext {
  ...
  @Override
  public ChannelPromise bind(SocketAddress localAddress, ChannelPromise promise) {
    ObjectUtil.checkNotNull(localAddress, "localAddress");
    if (isNotValidPromise(promise)) {
      // canceled
      return promise;
    }

    final AbstractChannelHandlerContext next = findContextOutbound();
    final EventLoop eventLoop = next.eventLoop();
    if (eventLoop.inEventLoop()) {
      next.invokeBind(localAddress, promise);
    } else {
      safeExecute(eventLoop, () -> next.invokeBind(localAddress, promise), promise);
    }
    return promise;
  }

  private void invokeBind(SocketAddress localAddress, ChannelPromise promise) {
    try {
      ((ChannelOutboundHandler) handler()).bind(this, localAddress, promise);
    } catch (Throwable t) {
      promise.setFailure(t);
    }
  }
}