1 // RUN: %clang_cc1 -std=c++2a -x c++ -verify %s
2 
3 template<typename T> requires (sizeof(T) >= 2) // expected-note{{because 'sizeof(char) >= 2' (1 >= 2) evaluated to false}}
4 struct A {
5   static constexpr int value = sizeof(T);
6 };
7 
8 static_assert(A<int>::value == 4);
9 static_assert(A<char>::value == 1); // expected-error{{constraints not satisfied for class template 'A' [with T = char]}}
10 
11 template<typename T, typename U>
12   requires (sizeof(T) != sizeof(U) // expected-note{{because 'sizeof(int) != sizeof(char [4])' (4 != 4) evaluated to false}}
13             && sizeof(T) >= 4) // expected-note{{because 'sizeof(char) >= 4' (1 >= 4) evaluated to false}}
14 constexpr int SizeDiff = sizeof(T) > sizeof(U) ? sizeof(T) - sizeof(U) : sizeof(U) - sizeof(T);
15 
16 static_assert(SizeDiff<int, char> == 3);
17 static_assert(SizeDiff<int, char[4]> == 0); // expected-error{{constraints not satisfied for variable template 'SizeDiff' [with T = int, U = char [4]]}}
18 static_assert(SizeDiff<char, int> == 3); // expected-error{{constraints not satisfied for variable template 'SizeDiff' [with T = char, U = int]}}
19 
20 template<typename... Ts>
21   requires ((sizeof(Ts) == 4) || ...) // expected-note{{because 'sizeof(char) == 4' (1 == 4) evaluated to false}} expected-note{{'sizeof(long long) == 4' (8 == 4) evaluated to false}} expected-note{{'sizeof(int [20]) == 4' (80 == 4) evaluated to false}}
22 constexpr auto SumSizes = (sizeof(Ts) + ...);
23 
24 static_assert(SumSizes<char, long long, int> == 13);
25 static_assert(SumSizes<char, long long, int[20]> == 89); // expected-error{{constraints not satisfied for variable template 'SumSizes' [with Ts = <char, long long, int [20]>]}}
26 
27 template<typename T>
28 concept IsBig = sizeof(T) > 100; // expected-note{{because 'sizeof(int) > 100' (4 > 100) evaluated to false}}
29 
30 template<typename T>
31   requires IsBig<T> // expected-note{{'int' does not satisfy 'IsBig'}}
32 using BigPtr = T*;
33 
34 static_assert(sizeof(BigPtr<int>)); // expected-error{{constraints not satisfied for alias template 'BigPtr' [with T = int]}}}}
35 
36 template<typename T> requires T::value // expected-note{{because substituted constraint expression is ill-formed: type 'int' cannot be used prior to '::' because it has no members}}
37 struct S { static constexpr bool value = true; };
38 
39 struct S2 { static constexpr bool value = true; };
40 
41 static_assert(S<int>::value); // expected-error{{constraints not satisfied for class template 'S' [with T = int]}}
42 static_assert(S<S2>::value);
43 
44 template<typename T>
45 struct AA
46 {
47     template<typename U> requires (sizeof(U) == sizeof(T)) // expected-note{{because 'sizeof(int [2]) == sizeof(int)' (8 == 4) evaluated to false}}
48     struct B
49     {
50         static constexpr int a = 0;
51     };
52 
53     template<typename U> requires (sizeof(U) == sizeof(T)) // expected-note{{because 'sizeof(int [2]) == sizeof(int)' (8 == 4) evaluated to false}}
54     static constexpr int b = 1;
55 
56     template<typename U> requires (sizeof(U) == sizeof(T)) // expected-note{{because 'sizeof(int [2]) == sizeof(int)' (8 == 4) evaluated to false}}
getBAA57     static constexpr int getB() { // expected-note{{candidate template ignored: constraints not satisfied [with U = int [2]]}}
58         return 2;
59     }
60 
fooAA61     static auto foo()
62     {
63         return B<T[2]>::a; // expected-error{{constraints not satisfied for class template 'B' [with U = int [2]]}}
64     }
65 
foo1AA66     static auto foo1()
67     {
68         return b<T[2]>; // expected-error{{constraints not satisfied for variable template 'b' [with U = int [2]]}}
69     }
70 
foo2AA71     static auto foo2()
72     {
73         return AA<T>::getB<T[2]>(); // expected-error{{no matching function for call to 'getB'}}
74     }
75 };
76 
77 constexpr auto x = AA<int>::foo(); // expected-note{{in instantiation of member function 'AA<int>::foo' requested here}}
78 constexpr auto x1 = AA<int>::foo1(); // expected-note{{in instantiation of member function 'AA<int>::foo1' requested here}}
79 constexpr auto x2 = AA<int>::foo2(); // expected-note{{in instantiation of member function 'AA<int>::foo2' requested here}}
80 
81 template<typename T>
82 struct B { using type = typename T::type; }; // expected-error{{type 'int' cannot be used prior to '::' because it has no members}}
83 
84 template<typename T> requires B<T>::type // expected-note{{in instantiation of template class 'B<int>' requested here}}
85                                          // expected-note@-1{{while substituting template arguments into constraint expression here}}
86 struct C { };
87 
88 template<typename T> requires (T{}) // expected-error{{atomic constraint must be of type 'bool' (found 'int')}}
89 struct D { };
90 
91 static_assert(C<int>{}); // expected-note{{while checking constraint satisfaction for template 'C<int>' required here}}
92 static_assert(D<int>{}); // expected-note{{while checking constraint satisfaction for template 'D<int>' required here}}
93