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

In C++20, this is finally standardized:

std::swap(a, b);

This uses ADL to call the correct overload and imposes the correct requirements to use in SFINAE. The magic is specified in [namespace.std]/7:

Other than in namespace std or in a namespace within namespace std, a program may provide an overload for any library function template designated as a customization point, provided that (a) the overload's declaration depends on at least one user-defined type and (b) the overload meets the standard library requirements for the customization point.¹⁷⁴ [ Note: This permits a (qualified or unqualified) call to the customization point to invoke the most appropriate overload for the given arguments. — end note ]

^{174) Any library customization point must be prepared to work adequately with any user-defined overload that meets the minimum requirements of this document. Therefore an implementation may elect, under the as-if rule ([intro.execution]), to provide any customization point in the form of an instantiated function object ([function.objects]) even though the customization point's specification is in the form of a function template. The template parameters of each such function object and the function parameters and return type of the object's operator() must match those of the corresponding customization point's specification.}

^{(emphasis mine)}

And swap is designated as a customization point in [utility.swap]:

template
  constexpr void swap(T& a, T& b) noexcept(see below);

Remarks: This function is a designated customization point ([namespace.std]) and shall not participate in overload resolution unless is_­move_­constructible_­v is true and is_­move_­assignable_­v is true. The expression inside noexcept is equivalent to:

is_nothrow_move_constructible_v && is_nothrow_move_assignable_v

Requires: Type T shall be Cpp17MoveConstructible (Table 26) and Cpp17MoveAssignable (Table 28).

Effects: Exchanges values stored in two locations.

^{(emphasis mine)}