On 12/20/2010 9:21 AM, Christopher Schmidt wrote: [...]
Unfortunately this still leaves us with ADL ambiguity in some cases:
https://svn.boost.org/trac/boost/ticket/4028#comment:6
-Christopher
That boost::fusion::begin/end could be found via ADL in range-based for loops is a bit worrying, and, as mentioned in the ticket, SFINAE'ing out boost::fusion::begin/end for only Boost.Fusion sequences is only a partial solution, as it doesn't help for structures having both range and Boost.Fusion interfaces. I don't know if I fully understand the problem, and I don't know if the following is a viable solution or what all the implications are (yes, that's a lot of qualifications), but maybe we could put the Boost.Fusion data structures (and anything else that would cause boost::fusion to be included in the set of "associated namespaces" when using ADL for unqualified begin/end) into another namespace, and bring them into the boost::fusion namespace with using declarations. Then maybe boost::fusion::begin/end wouldn't be found via ADL, but one would still refer to them as boost::fusion::vector, etc. E.g., the following compiles on MSVC9: namespace fusion_data_structures { struct X { }; } // namespace fusion_data_structures namespace fusion { template< class T > void f(T) { } using fusion_data_structures::X; } // namespace fusion template< class T > void f(T) { } int main(int argc, char* argv[]) { fusion::X x; f(x); return 0; } The fusion_data_structures namespace would be an implementation-detail, never to be referred to outside of the Boost.Fusion library. Just a thought, - Jeff