How does the compiler determine between a function using SFINAE and a standard function if both are viable?

Question

Consider the following code:

#include 
#include 

template 
class A
{
public:
    // Allow func to be ca         


        

Answer 1

The rule is that if a non function template and a function template specialization have the same signature, then the non function template is chosen over the template specialization. This can be found in [over.match.best]/2

Given these definitions, a viable function F1 is defined to be a better function than another viable function F2 if for all arguments i, ICSi(F1) is not a worse conversion sequence than ICSi(F2), and then

[...]

• F1 is not a function template specialization and F2 is a function template specialization [...]

Answer 2

You can read about overload resolution here. In particular

If any candidate is a function template, its specializations are generated using template argument deduction, and such specializations are treated just like non-template functions except where specified otherwise in the tie-breaker rules.

And then

Best viable function

For each pair of viable function F1 and F2, the implicit conversion sequences from the i-th argument to i-th parameter are ranked to determine which one is better [...]

F1 is determined to be a better function than F2 if implicit conversions for all arguments of F1 are not worse than the implicit conversions for all arguments of F2, and [...]

4) [...] F1 is a non-template function while F2 is a template specialization

Basically the same rules apply in this simpler example:

#include<iostream>

template <typename T> 
void foo(T i) { std::cout << "template" ; }

void foo(int i) { std::cout << "non template"; }

int main() {
    foo(1);   // non template
}