text: //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // UNSUPPORTED: libcpp-has-no-threads
  // UNSUPPORTED: c++98, c++03, c++11
  
  // <shared_mutex>
  
  // template <class Mutex> class shared_lock;
  
  // explicit operator bool() const noexcept;
  
  #include <shared_mutex>
  #include <cassert>
  
  std::shared_timed_mutex m;
  
  int main(int, char**)
  {
      std::shared_lock<std::shared_timed_mutex> lk0;
      assert(static_cast<bool>(lk0) == false);
      std::shared_lock<std::shared_timed_mutex> lk1(m);
      assert(static_cast<bool>(lk1) == true);
      lk1.unlock();
      assert(static_cast<bool>(lk1) == false);
      static_assert(noexcept(static_cast<bool>(lk0)), "explicit operator bool() must be noexcept");
  
    return 0;
  }
  