clang/test/CXX/temp/temp.constr/temp.constr.constr/partial-specializations.cpp

   1 // RUN: %clang_cc1 -std=c++2a -x c++ -verify %s
   2
   3 namespace class_templates
   4 {
   5   template<typename T, typename U> requires (sizeof(T) >= 4) // expected-note {{because 'sizeof(char) >= 4' (1 >= 4) evaluated to false}}
   6   struct is_same { static constexpr bool value = false; };
   7
   8   template<typename T> requires (sizeof(T*) >= 4 && sizeof(T) >= 4)
   9   struct is_same<T*, T*> { static constexpr bool value = true; };
  10
  11   static_assert(!is_same<char*, char*>::value);
  12   static_assert(!is_same<short*, short*>::value);
  13   static_assert(is_same<int*, int*>::value);
  14   static_assert(is_same<char, char>::value); // expected-error {{constraints not satisfied for class template 'is_same' [with T = char, U = char]}}
  15
  16   template<typename T>
  17   struct A { using type = typename T::type; }; // expected-error{{type 'int *' cannot be used prior to '::' because it has no members}}
  18
  19   template<typename T>
  20   struct B {};
  21
  22   template<typename T> requires A<T>::type // expected-note{{in instantiation of template class 'class_templates::A<int *>' requested here}}
  23                                            // expected-note@-1{{while substituting template arguments into constraint expression here}}
  24   struct B<T*> {};
  25
  26   template<typename T> requires (T{}) // expected-error{{atomic constraint must be of type 'bool' (found 'int')}}
  27   struct B<T**> {};
  28
  29   static_assert(((void)B<int**>{}, true)); // expected-note{{while checking constraint satisfaction for class template partial specialization 'B<int *>' required here}}
  30   // expected-note@-1{{while checking constraint satisfaction for class template partial specialization 'B<int>' required here}}
  31   // expected-note@-2{{during template argument deduction for class template partial specialization 'B<T *>' [with T = int *]}}
  32   // expected-note@-3{{during template argument deduction for class template partial specialization 'B<T **>' [with T = int]}}
  33   // expected-note@-4 2{{in instantiation of template class 'class_templates::B<int **>' requested here}}
  34
  35   template<typename T, typename U = double>
  36   concept same_as = is_same<T, U>::value;
  37
  38   template<same_as<bool> T> requires A<T>::type
  39   struct B<T*> {};
  40   // expected-note@-1{{previous}}
  41
  42   template<same_as<bool> T> requires A<T>::type
  43   struct B<T*> {};
  44   // expected-error@-1{{redefinition}}
  45
  46   template<same_as T> requires A<T>::type
  47   struct B<T*> {};
  48
  49   template<same_as<int> T> requires A<T>::type
  50   struct B<T*> {};
  51 }
  52
  53 namespace variable_templates
  54 {
  55   template<typename T, typename U> requires (sizeof(T) >= 4)
  56   constexpr bool is_same_v = false;
  57
  58   template<typename T> requires (sizeof(T*) >= 4 && sizeof(T) >= 4)
  59   constexpr bool is_same_v<T*, T*> = true;
  60
  61   static_assert(!is_same_v<char*, char*>);
  62   static_assert(!is_same_v<short*, short*>);
  63   static_assert(is_same_v<int*, int*>);
  64
  65   template<typename T>
  66   struct A { using type = typename T::type; }; // expected-error{{type 'int *' cannot be used prior to '::' because it has no members}}
  67
  68   template<typename T>
  69   constexpr bool v1 = false;
  70
  71   template<typename T> requires A<T>::type // expected-note{{in instantiation of template class 'variable_templates::A<int *>' requested here}}
  72                                            // expected-note@-1{{while substituting template arguments into constraint expression here}}
  73   constexpr bool v1<T*> = true;
  74
  75   template<typename T> requires (T{}) // expected-error{{atomic constraint must be of type 'bool' (found 'int')}}
  76   constexpr bool v1<T**> = true;
  77
  78   static_assert(v1<int**>); // expected-note{{while checking constraint satisfaction for variable template partial specialization 'v1<int *>' required here}}
  79   // expected-note@-1{{while checking constraint satisfaction for variable template partial specialization 'v1<int>' required here}}
  80   // expected-note@-2{{during template argument deduction for variable template partial specialization 'v1<T *>' [with T = int *]}}
  81   // expected-note@-3{{during template argument deduction for variable template partial specialization 'v1<T **>' [with T = int]}}
  82   // expected-error@-4{{static assertion failed due to requirement 'v1<int **>'}}
  83
  84 }