http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60448
--- Comment #14 from Alisdair Meredith <public at alisdairm dot net> --- Among other things, it lets fools like me write code relying on a behavior, not realizing that the code is not portable. As a user I swing between the convenience of having that utility, vs. the inconvenience of it being an extension rather than mandated. Other issues are whether rampant use of SFINAE tricks has an impact on resource usage during compilation, and more confusing error messages along the lines of "I could not find this function that you have clearly supplied". With Concepts Lite coming, there should be a cleaner way in the language to get the same effects, so as a single user data point, I would prefer to defer any non-standard-mandated changes along these lines until after Concepts lands - in whatever form that turns out to be. More research demonstrating the cost is really not significant in medium-large scale software might soften my view.
