1 // This file contains references to sections of the Coroutines TS, which can be 2 // found at http://wg21.link/coroutines. 3 4 // RUN: %clang_cc1 -std=c++20 -verify %s -fcxx-exceptions -fexceptions -Wunused-result 5 6 namespace std { 7 8 template<typename ...T> 9 struct coroutine_traits { 10 struct promise_type {}; 11 }; 12 13 template <> struct coroutine_traits<void>; // expected-note {{forward declaration of 'std::coroutine_traits<void>'}} 14 } // namespace std 15 uses_forward_declaration()16void uses_forward_declaration() { 17 co_return; // expected-error {{this function cannot be a coroutine: missing definition of specialization 'coroutine_traits<void>'}} 18 } 19