I am attempting to using a custom match function as part of a boost::asio composed operation. VS2017 cannot deduce the parameters with the custom match condition when passing in a std::move(*this) as the handler for an async operation.
The composed operation is a class that has a void operator()(boost::beast::error_code ec, std::size_t bytes_transferred) overload. eg:
class match_char { public: explicit match_char(char c) : c_(c) {} template <typename Iterator> std::pair<Iterator, bool> operator()( Iterator begin, Iterator end) const { Iterator i = begin; while (i != end) if (c_ == *i++) return std::make_pair(i, true); return std::make_pair(i, false); } private: char c_; }; namespace asio { template <> struct is_match_condition<match_char> : public boost::true_type {}; } // namespace asio template<class AsyncStream, class DynamicBuffer, class Handler> class composed_op { public: int state = 0; // --- boilerplate code void operator()(boost::beast::error_code ec, std::size_t bytes_transferred) { switch(state) { case x: return boost::asio::async_read_until(stream, buffer, match_char('a'), std::move(*this)); } } } When using a straight void handler(boost::system::error_code ec, std::size_t bytes); instead of std::move(*this) is compiles fine. The follow is the output from MSVC 2017. Any help in being able to tell the compiler which overload to use would be greatly appreciated.
1>C:\Users\xxxx\builds\dev\src\comm/read_msg.hpp(310): error C2665: 'boost::asio::read_until': none of the 5 overloads could convert all the argument types 1>C:\Users\xxxx\builds\boost_1_64_0\boost/asio/impl/read_until.hpp(265): note: could be 'size_t boost::asio::read_until<AsyncStream,std::allocator<char>,comm::detail::match_char>(SyncReadStream &,boost::asio::basic_streambuf<std::allocator<char>> &,MatchCondition,boost::system::error_code &,void *)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> SyncReadStream=boost::beast::test::string_iostream, 1> MatchCondition=comm::detail::match_char 1> ] 1>C:\Users\xxxx\builds\boost_1_64_0\boost/asio/impl/read_until.hpp(317): note: or 'size_t boost::asio::read_until<AsyncStream,std::allocator<char>,comm::detail::match_char>(SyncReadStream &,boost::asio::basic_streambuf<std::allocator<char>> &,MatchCondition,void *)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> SyncReadStream=boost::beast::test::string_iostream, 1> MatchCondition=comm::detail::match_char 1> ] 1>C:\Users\xxxx\builds\boost_1_64_0\boost/asio/impl/read_until.hpp(206): note: or 'size_t boost::asio::read_until<AsyncStream,std::allocator<char>>(SyncReadStream &,boost::asio::basic_streambuf<std::allocator<char>> &,const boost::regex &,boost::system::error_code &)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> SyncReadStream=boost::beast::test::string_iostream 1> ] 1>C:\Users\xxxx\builds\boost_1_64_0\boost/asio/impl/read_until.hpp(139): note: or 'size_t boost::asio::read_until<AsyncStream,std::allocator<char>>(SyncReadStream &,boost::asio::basic_streambuf<std::allocator<char>> &,const std::string &,boost::system::error_code &)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> SyncReadStream=boost::beast::test::string_iostream 1> ] 1>C:\Users\xxxx\builds\boost_1_64_0\boost/asio/impl/read_until.hpp(48): note: or 'size_t boost::asio::read_until<AsyncStream,std::allocator<char>>(SyncReadStream &,boost::asio::basic_streambuf<std::allocator<char>> &,char,boost::system::error_code &)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> SyncReadStream=boost::beast::test::string_iostream 1> ] 1>C:\Users\xxxx\builds\dev\src\comm/read_msg.hpp(310): note: while trying to match the argument list '(boost::beast::test::string_iostream, boost::asio::streambuf, comm::detail::match_char, comm::read_msg_op<AsyncStream,DynamicBuffer,____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e>>)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> DynamicBuffer=comm::wire_msg 1> ] 1>C:\Users\xxxx\builds\dev\src\comm/read_msg.hpp(286): note: while compiling class template member function 'void comm::read_msg_op<AsyncStream,DynamicBuffer,____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e>>::operator ()(boost::beast::error_code,::size_t)' 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> DynamicBuffer=comm::wire_msg 1> ] 1>C:\Users\xxxx\builds\dev\src\comm/read_msg.hpp(483): note: see reference to function template instantiation 'void comm::read_msg_op<AsyncStream,DynamicBuffer,____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e>>::operator ()(boost::beast::error_code,::size_t)' being compiled 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> DynamicBuffer=comm::wire_msg 1> ] 1>C:\Users\xxxx\builds\dev\src\comm/read_msg.hpp(483): note: see reference to class template instantiation 'comm::read_msg_op<AsyncStream,DynamicBuffer,____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e>>' being compiled 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> DynamicBuffer=comm::wire_msg 1> ] 1>C:\Users\xxxx\builds\dev\src\comm\test\read_msg_test.cpp(55): note: see reference to function template instantiation 'void comm::read_msg<boost::beast::test::string_iostream,comm::wire_msg,____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e>&>(AsyncStream &,DynamicBuffer &,CompletionToken)' being compiled 1> with 1> [ 1> AsyncStream=boost::beast::test::string_iostream, 1> DynamicBuffer=comm::wire_msg, 1> CompletionToken=____C_A_T_C_H____T_E_S_T____74::<lambda_881e0622dc11cafb22751f624439b95e> & 1> ] 
