1// DR 339
2//
3// Test of the use of the comma operator with SFINAE
4
5// Boilerplate helpers
6typedef char yes_type;
7struct no_type { char data[2]; };
8
9template<typename T> T create_a();
10template<typename T> struct type { };
11
12template<bool, typename T = void> struct enable_if { typedef T type; };
13template<typename T> struct enable_if<false, T> { };
14
15#define JOIN( X, Y ) DO_JOIN( X, Y )
16#define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
17#define DO_JOIN2( X, Y ) X##Y
18
19template<typename T, typename U>
20  typename enable_if<(sizeof(create_a<T>(), create_a<U>()) > 0),
21		     yes_type>::type
22  check_comma(int);
23
24template<typename T, typename U> no_type check_comma(...);
25
26template<typename T, typename U>
27struct has_comma
28{
29  static const bool value =
30    (sizeof(check_comma<T, U>(0)) == sizeof(yes_type));
31};
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
39struct X { };
40struct Y { };
41struct Z { };
42
43bool operator,(X&, Y);
44bool operator,(X, Z);
45void operator,(const Y&, const Z&);
46
47STATIC_ASSERT((has_comma<int, float>::value));
48STATIC_ASSERT((has_comma<int, X>::value));
49STATIC_ASSERT((has_comma<X, X>::value));
50STATIC_ASSERT((has_comma<X, Y>::value));
51STATIC_ASSERT((has_comma<X&, Y>::value));
52STATIC_ASSERT((has_comma<X, Z>::value));
53STATIC_ASSERT((!has_comma<Y, Z>::value));
54