gcc/testsuite/g++.dg/template/sfinae13.C

   1 // DR 339
   2 //
   3 // Test of the use of casts with SFINAE
   4
   5 // Boilerplate helpers
   6 typedef char yes_type;
   7 struct no_type { char data[2]; };
   8
   9 template<typename T> T create_a();
  10 template<typename T> struct type { };
  11
  12 template<bool, typename T = void> struct enable_if { typedef T type; };
  13 template<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
  19 #define CHECK_CAST(CastKind)                                            \
  20 template<typename T, typename U>                                        \
  21  typename enable_if<(sizeof((JOIN(CastKind,_cast)<U>(create_a<T>())), 0) > 0), \
  22                    yes_type>::type                                      \
  23   JOIN(check_,JOIN(CastKind,_cast))(int);                               \
  24                                                                         \
  25 template<typename T, typename U>                                        \
  26   no_type JOIN(check_,JOIN(CastKind,_cast))(...);                       \
  27                                                                         \
  28 template<typename T, typename U>                                        \
  29 struct JOIN(has_,JOIN(CastKind,_cast))                                  \
  30 {                                                                       \
  31   static const bool value =                                             \
  32     (sizeof(JOIN(check_,JOIN(CastKind,_cast))<T, U>(0)) == sizeof(yes_type)); \
  33 }
  34
  35 template<typename T, typename U>
  36 typename enable_if<(sizeof(((U)create_a<T>()), 0) > 0), yes_type>::type
  37   check_c_cast(int);
  38
  39 template<typename T, typename U> no_type check_c_cast(...);
  40
  41 template<typename T, typename U>
  42 struct has_c_cast
  43 {
  44   static const bool value =
  45     (sizeof(check_c_cast<T, U>(0)) == sizeof(yes_type));
  46 };
  47
  48 #ifdef __GXX_EXPERIMENTAL_CXX0X__
  49 #  define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
  50 #else
  51 #  define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
  52 #endif
  53
  54 CHECK_CAST(static);
  55 CHECK_CAST(dynamic);
  56 CHECK_CAST(const);
  57 CHECK_CAST(reinterpret);
  58
  59 struct X { virtual void f(); };
  60 struct Y { operator bool(); };
  61 struct Z : public X { };
  62
  63 STATIC_ASSERT((has_static_cast<int, float>::value));
  64 STATIC_ASSERT((!has_static_cast<X, Y>::value));
  65 STATIC_ASSERT((has_static_cast<Z, X>::value));
  66
  67 STATIC_ASSERT(!(has_dynamic_cast<int, float>::value));
  68 STATIC_ASSERT(!(has_dynamic_cast<X, Y>::value));
  69 STATIC_ASSERT(!(has_dynamic_cast<X, Z>::value));
  70 STATIC_ASSERT(!(has_dynamic_cast<Y, Z>::value));
  71 STATIC_ASSERT((has_dynamic_cast<X*, Z*>::value));
  72 STATIC_ASSERT((has_dynamic_cast<X*, Y*>::value));
  73 STATIC_ASSERT(!(has_dynamic_cast<Y*, Z*>::value));
  74
  75 STATIC_ASSERT(!(has_const_cast<int, float>::value));
  76 STATIC_ASSERT((has_const_cast<const int*, int*>::value));
  77 STATIC_ASSERT((has_const_cast<int*, const int*>::value));
  78 STATIC_ASSERT(!(has_const_cast<const int*, float*>::value));
  79
  80 STATIC_ASSERT((has_reinterpret_cast<int*, float*>::value));
  81 STATIC_ASSERT(!(has_reinterpret_cast<void*, char>::value));
  82 STATIC_ASSERT(!(has_reinterpret_cast<const X, X>::value));
  83
  84 STATIC_ASSERT((has_c_cast<int, float>::value));
  85 STATIC_ASSERT(!(has_c_cast<X, Y>::value));
  86 STATIC_ASSERT(!(has_c_cast<void*, char>::value));