stream.async_connect() ambiguous overload with asio::as_tuple(asio::use_awaitable) about beast

[ashtum]

The issue arises from using an executor with a default completion token in this line:

auto stream = asio::use_awaitable.as_default_on(beast::tcp_stream(co_await asio::this_coro::executor));

This adds a default value for the last parameter (the completion token), resulting in ambiguous calls because the first parameters like EndpointSequence and ConnectCondition aren't constrained. If you change stream to:

auto stream = beast::tcp_stream(co_await asio::this_coro::executor);

the issue goes away. I'll investigate if there's a way to constrain these template parameters and fix the problem.

[Rhidian12]

Aha, that explains a lot, I was following one of the examples, which made them like this.
Thanks a lot for the quick help! You can close this issue then if you want :)

[ashtum]

Unfortunately, there is no type trait for constraining ConnectCondition in Asio. Indeed, the issue also exists in Asio: https://godbolt.org/z/aqxns58n5.

I've raised the issue in the Asio repository: chriskohlhoff/asio#1476.