clang/test/SemaTemplate/instantiate-requires-clause.cpp

   1 // RUN: %clang_cc1 -std=c++2a -x c++ %s -Wno-unused-value -verify
   2
   3 template <typename... Args> requires ((sizeof(Args) == 1), ...)
   4 // expected-note@-1 {{because '(sizeof(int) == 1) , (sizeof(char) == 1) , (sizeof(int) == 1)' evaluated to false}}
   5 void f1(Args&&... args) { }
   6 // expected-note@-1 {{candidate template ignored: constraints not satisfied [with Args = <int, char, int>]}}
   7
   8 using f11 = decltype(f1('a'));
   9 using f12 = decltype(f1(1, 'b'));
  10 using f13 = decltype(f1(1, 'b', 2));
  11 // expected-error@-1 {{no matching function for call to 'f1'}}
  12
  13 template <typename... Args>
  14 void f2(Args&&... args) requires ((sizeof(args) == 1), ...) { }
  15 // expected-note@-1 {{candidate template ignored: constraints not satisfied [with Args = <int, char, int>]}}
  16 // expected-note@-2 {{because '(sizeof (args) == 1) , (sizeof (args) == 1) , (sizeof (args) == 1)' evaluated to false}}
  17
  18 using f21 = decltype(f2('a'));
  19 using f22 = decltype(f2(1, 'b'));
  20 using f23 = decltype(f2(1, 'b', 2));
  21 // expected-error@-1 {{no matching function for call to 'f2'}}
  22
  23 template <typename... Args> requires ((sizeof(Args) == 1), ...)
  24 // expected-note@-1 {{because '(sizeof(int) == 1) , (sizeof(char) == 1) , (sizeof(int) == 1)' evaluated to false}}
  25 void f3(Args&&... args) requires ((sizeof(args) == 1), ...) { }
  26 // expected-note@-1 {{candidate template ignored: constraints not satisfied [with Args = <int, char, int>]}}
  27
  28 using f31 = decltype(f3('a'));
  29 using f32 = decltype(f3(1, 'b'));
  30 using f33 = decltype(f3(1, 'b', 2));
  31 // expected-error@-1 {{no matching function for call to 'f3'}}
  32
  33 template<typename T>
  34 struct S {
  35         template<typename U>
  36         static constexpr auto f(U const index) requires(index, true) {
  37                 return true;
  38         }
  39 };
  40
  41 static_assert(S<void>::f(1));
  42
  43 // Similar to the 'S' test, but tries to use 'U' in the requires clause.
  44 template <typename T2>
  45 struct S1 {
  46   // expected-note@+3 {{candidate template ignored: constraints not satisfied [with U = int]}}
  47   // expected-note@+3 {{because substituted constraint expression is ill-formed: type 'int' cannot be used prior to '::' because it has no members}}
  48   template <typename U>
  49   static constexpr auto f(U const index)
  50     requires(U::foo)
  51   { return true; }
  52 };
  53
  54 // expected-error@+1 {{no matching function for call to 'f'}}
  55 static_assert(S1<void>::f(1));
  56
  57 constexpr auto value = 0;
  58
  59 template<typename T>
  60 struct S2 {
  61   template<typename = void> requires(value, true)
  62   static constexpr auto f() requires(value, true) {
  63   }
  64 };
  65
  66 static_assert((S2<int>::f(), true));
  67
  68 template<typename T>
  69 struct S3 {
  70         template<typename... Args> requires true
  71         static constexpr void f(Args...) { }
  72 };
  73
  74 static_assert((S3<int>::f(), true));
  75
  76 template<typename T>
  77 struct S4 {
  78     template<typename>
  79     constexpr void foo() requires (decltype(this)(), true) { }
  80     constexpr void goo() requires (decltype(this)(), true) { }
  81 };
  82
  83 static_assert((S4<int>{}.foo<int>(), S4<int>{}.goo(), true));