Question

When using the new function declarator syntax and decltype, how does one access members? It appears that this is not accessible:

template <typename Func>
struct context_binder
{
public:
    context_binder(const Func& func) :
            func(func)
    { }

    template <typename... TArgs>
    auto operator ()(TArgs&&... args) const
            -> decltype(this->func(std::forward<TArgs>(args)...))
    {
        return func(std::forward<TArgs>(args)...);
    }
private:
    Func func;
};

This yields the compiler error:

scratch.cpp:34:25: error: invalid use of ‘this’ at top level

My compiler is g++ 4.6.2.

---

My workaround is to declare a static member called self with the same type as the class, which has two problems:

1. It will not pick up the CV-qualifiers automatically, like this would.
2. I have to move the member declarations above the decltype usage or it can’t see the member (although that seems more like a compiler bug).

Answer 1

Upgrade to GCC 4.7. Version 4.6 doesn’t support this where you’re trying to use it.

Another question covers some workarounds you might be able to use.