Viewing file:  sfinae13.C (3.26 KB) -rw-r--r--
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// DR 339
//
// Test of the use of casts with SFINAE
// Boilerplate helpers
typedef char yes_type;
struct no_type { char data[2]; };
template<typename T> T create_a();
template<typename T> struct type { };
template<bool, typename T = void> struct enable_if { typedef T type; };
template<typename T> struct enable_if<false, T> { };
#define JOIN( X, Y ) DO_JOIN( X, Y )
#define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
#define DO_JOIN2( X, Y ) X##Y
#define CHECK_CAST(CastKind) \
template<typename T, typename U> \
typename enable_if<(sizeof((JOIN(CastKind,_cast)<U>(create_a<T>())), 0) > 0), \
yes_type>::type \
JOIN(check_,JOIN(CastKind,_cast))(int); \
\
template<typename T, typename U> \
no_type JOIN(check_,JOIN(CastKind,_cast))(...); \
\
template<typename T, typename U> \
struct JOIN(has_,JOIN(CastKind,_cast)) \
{ \
static const bool value = \
(sizeof(JOIN(check_,JOIN(CastKind,_cast))<T, U>(0)) == sizeof(yes_type)); \
}
template<typename T, typename U>
typename enable_if<(sizeof(((U)create_a<T>()), 0) > 0), yes_type>::type
check_c_cast(int);
template<typename T, typename U> no_type check_c_cast(...);
template<typename T, typename U>
struct has_c_cast
{
static const bool value =
(sizeof(check_c_cast<T, U>(0)) == sizeof(yes_type));
};
#ifdef __GXX_EXPERIMENTAL_CXX0X__
# define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
#else
# define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
#endif
CHECK_CAST(static);
CHECK_CAST(dynamic);
CHECK_CAST(const);
CHECK_CAST(reinterpret);
struct X { virtual void f(); };
struct Y { operator bool(); };
struct Z : public X { };
STATIC_ASSERT((has_static_cast<int, float>::value));
STATIC_ASSERT((!has_static_cast<X, Y>::value));
STATIC_ASSERT((has_static_cast<Z, X>::value));
STATIC_ASSERT(!(has_dynamic_cast<int, float>::value));
STATIC_ASSERT(!(has_dynamic_cast<X, Y>::value));
STATIC_ASSERT(!(has_dynamic_cast<X, Z>::value));
STATIC_ASSERT(!(has_dynamic_cast<Y, Z>::value));
STATIC_ASSERT((has_dynamic_cast<X*, Z*>::value));
STATIC_ASSERT((has_dynamic_cast<X*, Y*>::value));
STATIC_ASSERT(!(has_dynamic_cast<Y*, Z*>::value));
STATIC_ASSERT(!(has_const_cast<int, float>::value));
STATIC_ASSERT((has_const_cast<const int*, int*>::value));
STATIC_ASSERT((has_const_cast<int*, const int*>::value));
STATIC_ASSERT(!(has_const_cast<const int*, float*>::value));
STATIC_ASSERT((has_reinterpret_cast<int*, float*>::value));
STATIC_ASSERT(!(has_reinterpret_cast<void*, char>::value));
STATIC_ASSERT(!(has_reinterpret_cast<const X, X>::value));
STATIC_ASSERT((has_c_cast<int, float>::value));
STATIC_ASSERT(!(has_c_cast<X, Y>::value));
STATIC_ASSERT(!(has_c_cast<void*, char>::value));
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