id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
7988	[Coroutine] Support for C++11 range-for is missing	ld	olli	"Using a snapshot of the upcoming GCC 4.8 release and Boost 1.53, the following does not compile:

{{{#!cpp
#include <boost/coroutine/all.hpp>

int main()
{
    using coro = boost::coroutines::coroutine<int()>;
    for(int i: coro { [](coro::caller_type& yield) { yield(42); } }) {
        // unused
        static_cast<void>(i);
    }
}
}}}

As far as I can tell, this is because while Boost.Coroutine does provide functionality for e.g. boost::begin(c) and boost::end(c), it does not provide for the similar, ADL-enabled uses like begin(c) and end(c), where begin and end are in scope.

As it so happens, boost::begin and boost::end do ADL on behalf of the users -- their Standard counterparts do not, and a range-for statement is specified to make use of unqualified calls to begin and end.

To substantiate my hypothesis, adding begin and end function templates in e.g. namespace boost::coroutines does appear to make the previous snippet compile, and more involved examples behave as expected.

{{{#!cpp
// Try adding this:
namespace boost { namespace coroutines {

template<typename Sig> auto begin(coroutine<Sig>& c)
-> decltype(boost::begin(c))
{ return boost::begin(c); }

template<typename Sig> auto end(coroutine<Sig>& c)
-> decltype(boost::end(c))
{ return boost::end(c); }

} }
}}}"	Bugs	closed	To Be Determined	coroutine	Boost 1.53.0	Problem	fixed