1 // RUN: %check_clang_tidy %s bugprone-forwarding-reference-overload %t 2 3 namespace std { 4 template <bool B, class T = void> struct enable_if { typedef T type; }; 5 6 template <class T> struct enable_if<true, T> { typedef T type; }; 7 8 template <bool B, class T = void> 9 using enable_if_t = typename enable_if<B, T>::type; 10 11 template <class T> struct enable_if_nice { typedef T type; }; 12 } // namespace std 13 14 namespace foo { 15 template <class T> struct enable_if { typedef T type; }; 16 } // namespace foo 17 18 template <typename T> constexpr bool just_true = true; 19 20 class Test1 { 21 public: 22 template <typename T> Test1(T &&n); 23 // CHECK-NOTES: [[@LINE-1]]:25: warning: constructor accepting a forwarding reference can hide the copy and move constructors [bugprone-forwarding-reference-overload] 24 // CHECK-NOTES: 48:3: note: copy constructor declared here 25 // CHECK-NOTES: 49:3: note: copy constructor declared here 26 // CHECK-NOTES: 50:3: note: move constructor declared here 27 28 template <typename T> Test1(T &&n, int i = 5, ...); 29 // CHECK-NOTES: :[[@LINE-1]]:25: warning: constructor accepting a forwarding reference can hide the copy and move constructors 30 // CHECK-NOTES: 48:3: note: copy constructor declared here 31 // CHECK-NOTES: 49:3: note: copy constructor declared here 32 // CHECK-NOTES: 50:3: note: move constructor declared here 33 34 template <typename T, typename U = typename std::enable_if_nice<T>::type> 35 Test1(T &&n); 36 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors 37 // CHECK-NOTES: 48:3: note: copy constructor declared here 38 // CHECK-NOTES: 49:3: note: copy constructor declared here 39 // CHECK-NOTES: 50:3: note: move constructor declared here 40 41 template <typename T> 42 Test1(T &&n, typename foo::enable_if<long>::type i = 5, ...); 43 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors 44 // CHECK-NOTES: 48:3: note: copy constructor declared here 45 // CHECK-NOTES: 49:3: note: copy constructor declared here 46 // CHECK-NOTES: 50:3: note: move constructor declared here 47 Test1(const Test1 & other)48 Test1(const Test1 &other) {} Test1(Test1 & other)49 Test1(Test1 &other) {} Test1(Test1 && other)50 Test1(Test1 &&other) {} 51 }; 52 53 template <typename U> class Test2 { 54 public: 55 // Two parameters without default value, can't act as copy / move constructor. 56 template <typename T, class V> Test2(T &&n, V &&m, int i = 5, ...); 57 58 // Guarded with enable_if. 59 template <typename T> 60 Test2(T &&n, int i = 5, 61 std::enable_if_t<sizeof(int) < sizeof(long), int> a = 5, ...); 62 63 // Guarded with enable_if. 64 template <typename T, typename X = typename std::enable_if< 65 sizeof(int) < sizeof(long), double>::type &> 66 Test2(T &&n); 67 68 // Guarded with enable_if. 69 template <typename T> 70 Test2(T &&n, typename std::enable_if<just_true<T>>::type **a = nullptr); 71 72 // Guarded with enable_if. 73 template <typename T, typename X = std::enable_if_t<just_true<T>> *&&> 74 Test2(T &&n, double d = 0.0); 75 76 // Not a forwarding reference parameter. 77 template <typename T> Test2(const T &&n); 78 79 // Not a forwarding reference parameter. 80 Test2(int &&x); 81 82 // Two parameters without default value, can't act as copy / move constructor. 83 template <typename T> Test2(T &&n, int x); 84 85 // Not a forwarding reference parameter. 86 template <typename T> Test2(U &&n); 87 }; 88 89 // The copy and move constructors are both disabled. 90 class Test3 { 91 public: 92 template <typename T> Test3(T &&n); 93 94 template <typename T> Test3(T &&n, int I = 5, ...); 95 96 Test3(const Test3 &rhs) = delete; 97 98 private: 99 Test3(Test3 &&rhs); 100 }; 101 102 // Both the copy and the (compiler generated) move constructors can be hidden. 103 class Test4 { 104 public: 105 template <typename T> Test4(T &&n); 106 // CHECK-NOTES: :[[@LINE-1]]:25: warning: constructor accepting a forwarding reference can hide the copy and move constructors 107 108 Test4(const Test4 &rhs); 109 // CHECK-NOTES: :[[@LINE-1]]:3: note: copy constructor declared here 110 }; 111 112 // Nothing can be hidden, the copy constructor is implicitly deleted. 113 class Test5 { 114 public: 115 template <typename T> Test5(T &&n); 116 117 Test5(Test5 &&rhs) = delete; 118 }; 119 120 // Only the move constructor can be hidden. 121 class Test6 { 122 public: 123 template <typename T> Test6(T &&n); 124 // CHECK-NOTES: :[[@LINE-1]]:25: warning: constructor accepting a forwarding reference can hide the move constructor 125 126 Test6(Test6 &&rhs); 127 // CHECK-NOTES: :[[@LINE-1]]:3: note: move constructor declared here 128 private: 129 Test6(const Test6 &rhs); 130 }; 131 132 // Do not dereference a null BaseType. 133 template <class _Callable> class result_of; 134 template <class _Fp, class ..._Args> class result_of<_Fp(_Args...)> { }; 135 template <class _Tp> using result_of_t = typename result_of<_Tp>::type; 136 137 template <class... _Types> struct __overload; 138 template <class _Tp, class... _Types> 139 struct __overload<_Tp, _Types...> : __overload<_Types...> { 140 using __overload<_Types...>::operator(); 141 }; 142 143 template <class _Tp, class... _Types> 144 using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type; 145 146 template <class... _Types> 147 class variant { 148 public: 149 template <class _Arg, class _Tp = __best_match_t<_Arg, _Types...> > variant(_Arg && __arg)150 constexpr variant(_Arg&& __arg) {} 151 // CHECK-NOTES: :[[@LINE-1]]:13: warning: constructor accepting a forwarding reference can hide the copy and move constructors 152 }; 153