clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp

   1 // RUN: %clang_cc1 -std=c++2a -x c++ %s -verify
   2
   3 using A = int;
   4
   5 template<typename T, typename U>
   6 constexpr bool is_same_v = false;
   7
   8 template<typename T>
   9 constexpr bool is_same_v<T, T> = true;
  10
  11 template<typename T, typename U>
  12 concept same_as = is_same_v<T, U>;
  13
  14 static_assert(requires { requires true; 0; typename A;
  15                          { 0 } -> same_as<int>; });
  16 static_assert(is_same_v<bool, decltype(requires { requires false; })>);
  17
  18 // Check that requires expr is an unevaluated context.
  19 struct Y {
  20   int i;
  21   static constexpr bool r = requires { i; };
  22 };
  23
  24 template<typename T> requires requires (T t) {
  25   requires false; // expected-note{{because 'false' evaluated to false}}
  26   requires false;
  27   requires requires {
  28     requires false;
  29   };
  30 }
  31 struct r1 { };
  32
  33 using r1i = r1<int>;
  34 // expected-error@-1 {{constraints not satisfied for class template 'r1' [with T = int]}}
  35
  36 template<typename T> requires requires (T t) {
  37   requires requires {
  38     requires false; // expected-note{{because 'false' evaluated to false}}
  39   };
  40 }
  41 struct r2 { };
  42
  43 using r2i = r2<int>;
  44 // expected-error@-1 {{constraints not satisfied for class template 'r2' [with T = int]}}
  45
  46 template<typename T> requires requires (T t) {
  47   requires requires {
  48     requires true;
  49   };
  50   requires true;
  51   requires requires {
  52     requires false; // expected-note{{because 'false' evaluated to false}}
  53   };
  54 }
  55 struct r3 { };
  56
  57 using r3i = r3<int>;
  58 // expected-error@-1 {{constraints not satisfied for class template 'r3' [with T = int]}}
  59
  60 template<typename T>
  61 struct S { static const int s = T::value; };
  62
  63 template<typename T> requires requires { T::value; S<T>::s; }
  64 // expected-note@-1 {{because 'T::value' would be invalid: type 'int' cannot be used prior to '::' because it has no members}}
  65 struct r4 { };
  66
  67 using r4i = r4<int>;
  68 // expected-error@-1 {{constraints not satisfied for class template 'r4' [with T = int]}}