std::DefaultConstructible
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <concepts> | ||
| template < class T > concept DefaultConstructible = std::Constructible<T>; | (since C++20) | |
The DefaultConstructible concept provides a shorthand for the common case when the question is whether a type can be constructed with no arguments.
See also
| (C++20) | specifies that a variable of the type can be constructed from or bound to a set of argument types (concept) | 
| checks if a type has a default constructor (class template) |