Does C++11 change the behavior of explicitly calling std::swap to ensure ADL-located swap's are found, like boost::swap?

Question

Background

Consider for this question the following code:

#include 

namespace ns
{
    struct foo
    {
        foo() : i(0) {}
              


        

Answer 1

I would have had to vote against your proof-of-concept implementation had it been proposed. I fear it would break the following code, which I'm pretty sure I've seen in the wild at least once or twice over the past dozen years.

namespace oops
{

    struct foo
    {
        foo() : i(0) {}
        int i;

        void swap(foo& x) {std::swap(*this, x);}
    };

    void swap(foo& lhs, foo& rhs)
    {
        lhs.swap(rhs);
    }

}

Whether you think the above is good code or bad, it works as the author intends in C++98/03 and so the bar for silently breaking it is pretty high. Telling users that in C++11 they would no longer have to write using std::swap; isn't a sufficiently high benefit to outweigh the disadvantage of silently turning the above code into infinite recursion.

Another way to get out of writing using std::swap; is to use std::iter_swap instead:

template 
void do_swap(T& lhs, T& rhs)
{
    std::iter_swap(&lhs, &rhs); // internally does what do_swap did above
}