clang/test/Parser/cxx2a-placeholder-type-constraint.cpp

   1 // RUN: %clang_cc1 -std=c++2a -x c++ %s -verify
   2
   3 template<typename T, typename U=void>
   4 concept C = true;
   5
   6 namespace ns {
   7   template<typename T, typename U=void>
   8   concept D = true;
   9 }
  10
  11 int foo() {
  12   int I;
  13   {ns::D auto a = 1;}
  14   {C auto a = 1;}
  15   {C<> auto a = 1;}
  16   {C<int> auto a = 1;}
  17   {ns::D<int> auto a = 1;}
  18   {const ns::D auto &a = 1;}
  19   {const C auto &a = 1;}
  20   {const C<> auto &a = 1;}
  21   {const C<int> auto &a = 1;}
  22   {const ns::D<int> auto &a = 1;}
  23   {C decltype(auto) a = 1;}
  24   {C<> decltype(auto) a = 1;}
  25   {C<int> decltype(auto) a = 1;}
  26   {const C<> decltype(auto) &a = 1;} // expected-error{{'decltype(auto)' cannot be combined with other type specifiers}}
  27   // expected-error@-1{{cannot form reference to 'decltype(auto)'}}
  28   {const C<int> decltype(auto) &a = 1;} // expected-error{{'decltype(auto)' cannot be combined with other type specifiers}}
  29   // expected-error@-1{{cannot form reference to 'decltype(auto)'}}
  30   {C a = 1;}
  31   // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  32   {C const a2 = 1;}
  33   // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  34   {C &a3 = I;}
  35   // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  36   {C &&a4 = 1;}
  37   // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  38   {C decltype a19 = 1;}
  39   // expected-error@-1{{expected '('}}
  40   {C decltype(1) a20 = 1;}
  41   // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  42 }
  43
  44 void foo1(C auto &a){}
  45 void foo2(C const &a){}
  46 // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  47 void foo3(C auto const &a){}
  48 void foo4(const C &a){}
  49 // expected-error@-1{{expected 'auto' or 'decltype(auto)' after concept name}}
  50
  51 namespace non_type {
  52   template<int v>
  53   concept C1 = true;
  54
  55   auto f() -> C1 auto {} // expected-error{{concept named in type constraint is not a type concept}}
  56   auto g(C1 auto); // expected-error{{concept named in type constraint is not a type concept}}
  57   C1 auto a = 0; // expected-error{{concept named in type constraint is not a type concept}}
  58   C1 decltype(auto) b = 0; // expected-error{{concept named in type constraint is not a type concept}}
  59 }
  60
  61 namespace arity {
  62   template<typename v, typename>
  63   concept C1 = true;
  64
  65   auto f() -> C1 auto {} // expected-error{{'C1' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}}
  66   auto g(C1 auto); // expected-error{{'C1' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}}
  67   C1 auto a = 0; // expected-error{{'C1' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}}
  68   C1 decltype(auto) b = 0; // expected-error{{'C1' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}}
  69 }