Closing the concurrent channel does not cancel outstanding async operations. Cancelling produces wrong error code

[dragon-dreamer]

Here is an example code which demonstrates the issue (boost 1.87, VS2022, Win10):

#include <boost/asio/thread_pool.hpp>
#include <boost/asio/awaitable.hpp>
#include <boost/asio/use_awaitable.hpp>
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/this_coro.hpp>
#include <boost/asio/as_tuple.hpp>
#include <boost/asio/experimental/awaitable_operators.hpp>
#include <boost/asio/experimental/concurrent_channel.hpp>

#include <syncstream>
#include <iostream>

boost::asio::awaitable<void> send_to_channel(
	boost::asio::experimental::concurrent_channel<void()>& ch)
{
	co_await boost::asio::this_coro::throw_if_cancelled(false);

	std::osyncstream(std::cerr) << "Sending to channel...\n";
	auto [ec] = co_await ch.async_send(boost::asio::as_tuple(boost::asio::use_awaitable));
	std::osyncstream(std::cerr) << "Error " << ec << "\n";
}

int main()
{
	boost::asio::thread_pool ctx{ 20 };

	boost::asio::experimental::concurrent_channel<void()> ch(ctx);

	using namespace boost::asio::experimental::awaitable_operators;
	for (int i = 0; i < 50; ++i)
	{
		boost::asio::co_spawn(ctx, send_to_channel(ch),
			boost::asio::detached);
	}

	std::this_thread::sleep_for(std::chrono::seconds(1));
	std::cerr << "Closing channel!\n";

        // I would expect this call to cancel all outstanding async
        // operations, but this does not happen.
	ch.close();

	ctx.join();
}

The program just hangs, and the last line in the output I see is "Closing channel!".

If I call ch.cancel() after close(), this does cancel the pending operations, however, the error code I get is 0 (no error), which is also unexpected. According to the manual, it should be boost::asio::experimental::error::channel_cancelled instead.