Approaches to function SFINAE in C++

Question

I am using function SFINAE heavily in a project and am not sure if there are any differences between the following two approaches (other than style):

#include &l         


        

Answer 1

In addition to max66's answer, another reason to prefer method 2 is that with method 1, you can (accidentally) pass an explicit type parameter as the second template argument and defeat the SFINAE mechanism completely. This could happen as a typo, copy/paste error, or as an oversight in a larger template mechanism.

#include 
#include 
#include 

// NOTE: foo should only accept T=int
template >>
void foo(){
    std::cout << "method 1" << std::endl;
}

int main(){

    // works fine
    foo();

    // ERROR: subsitution failure, as expected
    // foo();

    // Oops! also works, even though T != int :(
    foo();

    return 0;
}

Live demo here