1// RUN: %check_clang_tidy %s bugprone-forwarding-reference-overload %t
2
3namespace std {
4template <bool B, class T = void> struct enable_if { typedef T type; };
5
6template <class T> struct enable_if<true, T> { typedef T type; };
7
8template <bool B, class T = void>
9using enable_if_t = typename enable_if<B, T>::type;
10
11template <class T> struct enable_if_nice { typedef T type; };
12} // namespace std
13
14namespace foo {
15template <class T> struct enable_if { typedef T type; };
16} // namespace foo
17
18template <typename T> constexpr bool just_true = true;
19
20class Test1 {
21public:
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
48 Test1(const Test1 &other) {}
49 Test1(Test1 &other) {}
50 Test1(Test1 &&other) {}
51};
52
53template <typename U> class Test2 {
54public:
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.
90class Test3 {
91public:
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
98private:
99 Test3(Test3 &&rhs);
100};
101
102// Both the copy and the (compiler generated) move constructors can be hidden.
103class Test4 {
104public:
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.
113class Test5 {
114public:
115 template <typename T> Test5(T &&n);
116
117 Test5(Test5 &&rhs) = delete;
118};
119
120// Only the move constructor can be hidden.
121class Test6 {
122public:
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
128private:
129 Test6(const Test6 &rhs);
130};
131
132// Do not dereference a null BaseType.
133template <class _Callable> class result_of;
134template <class _Fp, class ..._Args> class result_of<_Fp(_Args...)> { };
135template <class _Tp> using result_of_t = typename result_of<_Tp>::type;
136
137template <class... _Types> struct __overload;
138template <class _Tp, class... _Types>
139struct __overload<_Tp, _Types...> : __overload<_Types...> {
140 using __overload<_Types...>::operator();
141};
142
143template <class _Tp, class... _Types>
144using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type;
145
146template <class... _Types>
147class variant {
148public:
149 template <class _Arg, class _Tp = __best_match_t<_Arg, _Types...> >
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
154namespace std {
155template <class T, class U> struct is_same { static constexpr bool value = false; };
156template <class T> struct is_same<T, T> { static constexpr bool value = true; };
157template <class T, class U> constexpr bool is_same_v = is_same<T, U>::value;
158template <class T> struct remove_reference { using type = T; };
159template <class T> struct remove_reference<T&> { using type = T; };
160template <class T> struct remove_reference<T&&> { using type = T; };
161template <class T> using remove_reference_t = typename remove_reference<T>::type;
162template <class T> struct remove_cv { using type = T; };
163template <class T> struct remove_cv<const T> { using type = T; };
164template <class T> struct remove_cv<volatile T> { using type = T; };
165template <class T> struct remove_cv<const volatile T> { using type = T; };
166template <class T> using remove_cv_t = typename remove_cv<T>::type;
167template <class T> struct remove_cvref { using type = remove_cv_t<remove_reference_t<T>>; };
168template <class T> using remove_cvref_t = typename remove_cvref<T>::type;
169} // namespace std
170
171// Handle enable_if when used as a non-type template parameter.
172class Test7 {
173public:
174 // Guarded with enable_if.
175 template <class T,
176 typename std::enable_if_t<std::is_same_v<std::remove_cvref_t<T>, int>, int>::type = 0>
177 Test7(T &&t);
178
179 // Guarded with enable_if.
180 template <class T,
181 std::enable_if_t<
182 !std::is_same_v<std::remove_cvref_t<T>, Test7>
183 && !std::is_same_v<std::remove_cvref_t<T>, bool>, int> = true>
184 Test7(T &&t);
185
186 Test7(const Test7 &other) = default;
187 Test7(Test7 &&other) = default;
188};
189
190// Handle enable_if when used as a non-type template parameter following
191// a variadic template parameter pack.
192class Test8 {
193public:
194 // Guarded with enable_if.
195 template <class T, class... A,
196 std::enable_if_t<
197 !std::is_same_v<std::remove_cvref_t<T>, Test8>
198 || (sizeof...(A) > 0)>* = nullptr>
199 Test8(T &&t, A &&... a);
200
201 Test8(const Test8 &other) = default;
202 Test8(Test8 &&other) = default;
203};
204
205// Non-type template parameter failure cases.
206class Test9 {
207public:
208 // Requires a default argument (such as a literal, implicit cast expression, etc.)
209 template <class T,
210 std::enable_if_t<std::is_same_v<std::remove_cvref_t<T>, bool>, int>>
211 Test9(T &&t);
212 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors
213 // CHECK-NOTES: 240:3: note: copy constructor declared here
214 // CHECK-NOTES: 241:3: note: move constructor declared here
215
216 // Requires a default argument (such as a literal, implicit cast expression, etc.)
217 template <class T,
218 std::enable_if_t<std::is_same_v<std::remove_cvref_t<T>, long>>*>
219 Test9(T &&t);
220 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors
221 // CHECK-NOTES: 240:3: note: copy constructor declared here
222 // CHECK-NOTES: 241:3: note: move constructor declared here
223
224 // Only std::enable_if or std::enable_if_t are supported
225 template <class T,
226 typename std::enable_if_nice<T>::type* = nullptr>
227 Test9(T &&t);
228 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors
229 // CHECK-NOTES: 240:3: note: copy constructor declared here
230 // CHECK-NOTES: 241:3: note: move constructor declared here
231
232 // Only std::enable_if or std::enable_if_t are supported
233 template <class T,
234 typename foo::enable_if<T>::type = 0>
235 Test9(T &&t);
236 // CHECK-NOTES: :[[@LINE-1]]:3: warning: constructor accepting a forwarding reference can hide the copy and move constructors
237 // CHECK-NOTES: 240:3: note: copy constructor declared here
238 // CHECK-NOTES: 241:3: note: move constructor declared here
239
240 Test9(const Test9 &other) = default;
241 Test9(Test9 &&other) = default;
242};
243
244
245template <typename T>
246class Test10 {
247public:
248 enum E {};
249 E e;
250
251 Test10(T &&Item, E e)
252 : e(e){}
253};
254
255// A deleted ctor cannot hide anything
256class Test11 {
257public:
258 template <typename T>
259 Test11(T&&) = delete;
260
261 Test11(const Test11 &) = default;
262 Test11(Test11 &&) = default;
263};
264

source code of clang-tools-extra/test/clang-tidy/checkers/bugprone/forwarding-reference-overload.cpp