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111
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1 // DR 339
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2 //
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3 // Test of the use of casts with SFINAE
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4
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5 // Boilerplate helpers
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6 typedef char yes_type;
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7 struct no_type { char data[2]; };
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8
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9 template<typename T> T create_a();
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10 template<typename T> struct type { };
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11
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12 template<bool, typename T = void> struct enable_if { typedef T type; };
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13 template<typename T> struct enable_if<false, T> { };
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14
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15 #define JOIN( X, Y ) DO_JOIN( X, Y )
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16 #define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
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17 #define DO_JOIN2( X, Y ) X##Y
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18
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19 #define CHECK_CAST(CastKind) \
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20 template<typename T, typename U> \
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21 typename enable_if<(sizeof((JOIN(CastKind,_cast)<U>(create_a<T>())), 0) > 0), \
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22 yes_type>::type \
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23 JOIN(check_,JOIN(CastKind,_cast))(int); \
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24 \
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25 template<typename T, typename U> \
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26 no_type JOIN(check_,JOIN(CastKind,_cast))(...); \
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27 \
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28 template<typename T, typename U> \
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29 struct JOIN(has_,JOIN(CastKind,_cast)) \
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30 { \
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31 static const bool value = \
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32 (sizeof(JOIN(check_,JOIN(CastKind,_cast))<T, U>(0)) == sizeof(yes_type)); \
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33 }
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34
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35 template<typename T, typename U>
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36 typename enable_if<(sizeof(((U)create_a<T>()), 0) > 0), yes_type>::type
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37 check_c_cast(int);
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38
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39 template<typename T, typename U> no_type check_c_cast(...);
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40
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41 template<typename T, typename U>
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42 struct has_c_cast
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43 {
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44 static const bool value =
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45 (sizeof(check_c_cast<T, U>(0)) == sizeof(yes_type));
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46 };
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47
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48 #ifdef __GXX_EXPERIMENTAL_CXX0X__
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49 # define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
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50 #else
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51 # define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
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52 #endif
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53
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54 CHECK_CAST(static);
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55 CHECK_CAST(dynamic);
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56 CHECK_CAST(const);
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57 CHECK_CAST(reinterpret);
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58
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59 struct X { virtual void f(); };
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60 struct Y { operator bool(); };
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61 struct Z : public X { };
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62
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63 STATIC_ASSERT((has_static_cast<int, float>::value));
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64 STATIC_ASSERT((!has_static_cast<X, Y>::value));
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65 STATIC_ASSERT((has_static_cast<Z, X>::value));
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66
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67 STATIC_ASSERT(!(has_dynamic_cast<int, float>::value));
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68 STATIC_ASSERT(!(has_dynamic_cast<X, Y>::value));
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69 STATIC_ASSERT(!(has_dynamic_cast<X, Z>::value));
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70 STATIC_ASSERT(!(has_dynamic_cast<Y, Z>::value));
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71 STATIC_ASSERT((has_dynamic_cast<X*, Z*>::value));
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72 STATIC_ASSERT((has_dynamic_cast<X*, Y*>::value));
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73 STATIC_ASSERT(!(has_dynamic_cast<Y*, Z*>::value));
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74
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75 STATIC_ASSERT(!(has_const_cast<int, float>::value));
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76 STATIC_ASSERT((has_const_cast<const int*, int*>::value));
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77 STATIC_ASSERT((has_const_cast<int*, const int*>::value));
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78 STATIC_ASSERT(!(has_const_cast<const int*, float*>::value));
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79
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80 STATIC_ASSERT((has_reinterpret_cast<int*, float*>::value));
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81 STATIC_ASSERT(!(has_reinterpret_cast<void*, char>::value));
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82 STATIC_ASSERT(!(has_reinterpret_cast<const X, X>::value));
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83
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84 STATIC_ASSERT((has_c_cast<int, float>::value));
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85 STATIC_ASSERT(!(has_c_cast<X, Y>::value));
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86 STATIC_ASSERT(!(has_c_cast<void*, char>::value));
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