clang/test/SemaTemplate/instantiate-template-argument.cpp

   1 // RUN: %clang_cc1 -std=c++2a -x c++ %s -verify
   2
   3 template<auto T, decltype(T) U>
   4 concept C1 = sizeof(U) >= 4;
   5 // sizeof(U) >= 4 [U = U (decltype(T))]
   6
   7 template<typename Y, char V>
   8 concept C2 = C1<Y{}, V>;
   9 // sizeof(U) >= 4 [U = V (decltype(Y{}))]
  10
  11 template<char W>
  12 constexpr int foo() requires C2<int, W> { return 1; }
  13 // sizeof(U) >= 4 [U = W (decltype(int{}))]
  14
  15 template<char X>
  16 // expected-note@+1{{candidate function}}
  17 constexpr int foo() requires C1<1, X> && true { return 2; }
  18 // sizeof(U) >= 4 [U = X (decltype(1))]
  19
  20 static_assert(foo<'a'>() == 2);
  21
  22 template<char Z>
  23 // expected-note@+1{{candidate function}}
  24 constexpr int foo() requires C2<long long, Z> && true { return 3; }
  25 // sizeof(U) >= 4 [U = Z (decltype(long long{}))]
  26
  27 static_assert(foo<'a'>() == 3);
  28 // expected-error@-1{{call to 'foo' is ambiguous}}