Method invoke

test/concurrent/test_execution_queue.cpp:72–79

TEST(concurrent_execution_queue, execute_fail_when_launch_consumer_error) {
  struct E : public Executor {
    virtual int invoke(
        MoveOnlyFunction<void(void)>&& function) noexcept override {
      if (times++ == 0) {
        return -1;
      }
      function();
      return 0;
    }
    size_t times = 0;
  } executor;
  ConcurrentExecutionQueue<::std::string> queue;