Member function call in decltype

Question

The following code:

struct A
{
    int f(int);
    auto g(int x) -> decltype(f(x));
};

Fails to compile with the error:

erro         


        

Answer 1

After some tests, neither decltype(declval().f(x)) nor decltype(((A*)0)->f(x)) will work.

However, it seems that using boost::bind will work (and it's "under-the-hood" version):

struct A
{
    int f(int);
    auto g(int x) -> decltype(boost::bind(&A::f,0,x)());
    auto h(int x) -> decltype((((A*)0)->*(&A::f))(x)); //similarly (what Boost.Bind does under-the-hood.
};

Of course, this is not pretty. I guess you can look into how boost::bind does it to maybe find a nicer solution.

EDIT

As MSN suggested, you can also make your own function template to resolve this:

template< typename R, typename C, typename... Args > R member_func(R (C::*)(Args...)); 

struct A
{
    int f(int);
    auto g(int x) -> decltype(member_func(&A::f));
};