std::experimental::ranges::Semiregular
From cppreference.com
                    
                                        
                    < cpp | experimental | ranges
                    
                                                            
                    |   Defined in header  <experimental/ranges/concepts>
  | 
||
|   template< class T > concept bool Semiregular = Copyable<T> && DefaultConstructible<T>;  | 
(ranges TS) | |
The Semiregular concept specifies that a type is both copyable and default constructible. It is satisfied by types that behave similarly to built-in types like int, except that they need not support comparison with ==.