async does not work for member function pointers when called on types with self-defined unary operator*

[eschnett]

In the code below, the function g uses the STL, while the function h uses HPX. g compiles fine, but h does not. This is with Clang 3.4.2, using GCC 4.9.0's STL, and using Boost 1.55, running on OS X.

#include <future>
#include <hpx/hpx.hpp>

struct s {
  int f() const;
};

struct p {
  s *x;
  s &operator*() const { return *x; }
};

std::future<int> g(p x) { return std::async(&s::f, x); }

hpx::future<int> h(p x) { return hpx::async(&s::f, x); }

The relevant part of the error message is

async.cc:15:34: error: no matching function for call to 'async'
hpx::future<int> h(p x) { return hpx::async(&s::f, x); }

/Users/eschnett/SIMFACTORY/hpx-master/install/include/hpx/preprocessed/async_5.hpp:148:5: note: 
      candidate template ignored: substitution failure [with F = int (s::*)()
      const, A0 = p &]: no type named 'type' in 'boost::lazy_enable_if_c<false,
      hpx::detail::create_future<int (s::*(p &))() const, int> >'
    async(F && f, A0 && a0)
    ^

The respective async declaration in HPX is:

    template <typename F, typename A0>
    typename boost::lazy_enable_if_c<
        traits::detail::is_callable_not_action<
            typename util::decay<F>::type(
                typename util::decay<A0>::type)>::value
     && !traits::is_bound_action<typename util::decay<F>::type>::value
      , detail::create_future<F(A0)>
    >::type
    async(F && f, A0 && a0)

It appears that traits::detail::is_callable_not_action is returning false, which is wrong.

[K-ballo]

Fixed by cd3a2e2