1// DR 339
2//
3// Test of the use of the function call operator with SFINAE
4typedef char yes_type;
5struct no_type { char data[2]; };
6
7template<typename T> T create_a();
8
9template<typename T> struct type { };
10
11template<bool, typename T = void> struct enable_if { typedef T type; };
12template<typename T> struct enable_if<false, T> { };
13
14template<typename F, typename T1, typename T2>
15  typename enable_if<sizeof(create_a<F>()(create_a<T1>(), create_a<T2>()), 1),
16		     yes_type>::type
17  check_is_callable2(type<F>, type<T1>, type<T2>);
18
19no_type check_is_callable2(...);
20
21template<typename F, typename T1, typename T2 = T1>
22struct is_callable2
23{
24  static const bool value =
25    (sizeof(check_is_callable2(type<F>(), type<T1>(), type<T2>()))
26     == sizeof(yes_type));
27};
28
29#define JOIN( X, Y ) DO_JOIN( X, Y )
30#define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
31#define DO_JOIN2( X, Y ) X##Y
32
33#ifdef __GXX_EXPERIMENTAL_CXX0X__
34#  define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
35#else
36#  define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
37#endif
38
39
40struct A;
41struct B;
42
43struct A {
44  A(B);
45};
46
47struct B {
48  B(A);
49};
50
51struct F {
52  void operator()(A, A);
53
54private:
55  void operator()(B, B);
56};
57
58STATIC_ASSERT((!is_callable2<F, B, B>::value));
59