1 // RUN: %clang_cc1 -std=c++2a -x c++ -verify %s
2
3 template<typename T>
4 constexpr bool is_ptr_v = false;
5
6 template<typename T>
7 constexpr bool is_ptr_v<T*> = true;
8
9 template<typename T, typename U>
10 constexpr bool is_same_v = false;
11
12 template<typename T>
13 constexpr bool is_same_v<T, T> = true;
14
15 template<typename T> requires is_ptr_v<T> // expected-note {{because 'is_ptr_v<int>' evaluated to false}}
16 // expected-note@-1{{because 'is_ptr_v<char>' evaluated to false}}
dereference(T t)17 auto dereference(T t) { // expected-note {{candidate template ignored: constraints not satisfied [with T = int]}}
18 // expected-note@-1{{candidate template ignored: constraints not satisfied [with T = char]}}
19 return *t;
20 }
21
22 static_assert(is_same_v<decltype(dereference<int*>(nullptr)), int>);
23 static_assert(is_same_v<decltype(dereference(2)), int>); // expected-error {{no matching function for call to 'dereference'}}
24 static_assert(is_same_v<decltype(dereference<char>('a')), char>); // expected-error {{no matching function for call to 'dereference'}}
25
26 template<typename T> requires (T{} + T{}) // expected-note {{because substituted constraint expression is ill-formed: invalid operands to binary expression ('A' and 'A')}}
foo(T t)27 auto foo(T t) { // expected-note {{candidate template ignored: constraints not satisfied [with T = A]}}
28 return t + t;
29 }
30
31
32 template<typename T> requires (!((T{} - T{}) && (T{} + T{})) || false)
33 // expected-note@-1{{because substituted constraint expression is ill-formed: invalid operands to binary expression ('A' and 'A')}}
34 // expected-note@-2{{and 'false' evaluated to false}}
bar(T t)35 auto bar(T t) { // expected-note {{candidate template ignored: constraints not satisfied [with T = A]}}
36 return t + t;
37 }
38
39 struct A { };
40
41 static_assert(foo(A{})); // expected-error {{no matching function for call to 'foo'}}
42 static_assert(bar(A{})); // expected-error {{no matching function for call to 'bar'}}