test/libcxx/thread/thread.lock/thread.lock.guard/nodiscard.fail.cpp

//===----------------------------------------------------------------------===//
//
// 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

// [[nodiscard]] on constructors isn't supported by all compilers
// UNSUPPORTED: clang-6, clang-6, clang-8, clang-9
// UNSUPPORTED: apple-clang-9, apple-clang-10, apple-clang-11

// <mutex>

// template <class Mutex> class lock_guard;

// [[nodiscard]] explicit lock_guard(mutex_type& m);
// [[nodiscard]] lock_guard(mutex_type& m, adopt_lock_t);

// Test that we properly apply [[nodiscard]] to lock_guard's constructors,
// which is a libc++ extension.

// MODULES_DEFINES: _LIBCPP_ENABLE_NODISCARD
#define _LIBCPP_ENABLE_NODISCARD
#include <mutex>

int main(int, char**) {
    std::mutex m;
    std::lock_guard<std::mutex>{m}; // expected-error{{ignoring temporary created by a constructor declared with 'nodiscard' attribute}}
    std::lock_guard<std::mutex>{m, std::adopt_lock}; // expected-error{{ignoring temporary created by a constructor declared with 'nodiscard' attribute}}
    return 0;
}