[asio-users] boost-1.74 regression in handler type

[Arvid N. <arv...@gm...>]

It appears that boost-1.74 does not accept a std::bind() expression as a
valid handler. It used to, in previous versions.

The error is (what appears to be) a SFINAE failure because whatever bind
object is returned by std::bind() is not considered a valid receiver.

It seems likely this was introduced in the work to conform with P0443.

I had to make the following changes to make my code build with boost-1.74

https://github.com/arvidn/libtorrent/pull/5057/files#diff-8775d2d9460d9b7a42d64f06511742d7L2743

-- 
Arvid Norberg