http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/n4357.html

http://open-std.org/JTC1/SC22/WG21/docs/papers/2014/n4226.pdf

Discussed in Urbana. EWG was supportive of the idea, CWG pointed out various issues related to multiple translation units. Authors are encouraged to revise.