[Bug c++/96204] gcc complains about private member access in SFINAE context

redi at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Wed Jul 15 10:03:58 GMT 2020


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96204

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-07-15
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |rejects-valid

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Klaus Rudolph from comment #0)
> Full code example:

The example is incomplete, and you didn't say how you're compiling it.

This is the complete example, and requires -std=c++17

#include <type_traits>
#include <iostream>
using std::void_t;
using std::cout;
using std::endl;

template <typename, typename = void_t<>>
struct has_set_attr_method {
    static constexpr bool value = false;
};
template <typename T>
struct has_set_attr_method<T, void_t<decltype(std::declval<T>().setAttr(1))>> {
    static constexpr bool value = true;
};

struct Parent
{
    public:
        template<typename T>
            static void create()    {   
                auto obj = T::create();
                if constexpr(has_set_attr_method<T>::value) {
                    cout << "has setAttr" << endl;
                } else {
                    cout << "no setAttr" << endl;
                }
            }
};

struct Child : public Parent {
    public:
        friend class Parent;
        static auto create() {
            return Child();
        }

    private:
        void setAttr(int) {
        }
};

int main() {
    Parent::create<Child>();
}



#include <type_traits>
#include <iostream>
using std::void_t;
using std::cout;
using std::endl;


(In reply to Klaus Rudolph from comment #1)
> Maybe related to: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64335

I don't think so, that is "accepts-invalid" not "rejects-valid" and it was
fixed years ago.


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