std::reference_converts_from_temporary(3)

NAME
std::reference_converts_from_temporary - std::reference_converts_from_temporary

Synopsis
   Defined in header <type_traits>
   template< class T, class U > (since C++23)
   struct reference_converts_from_temporary;
   Let V be std::remove_cv_t<U> if U is a scalar type or cv void, or U otherwise. If T
   is a reference type, and given a hypothetic expression e such that decltype(e) is V,
   the variable definition T ref = e; is well-formed and binds a temporary object to
   ref, then provides the member constant value equal to true. Otherwise, value is
   false.
   If T is an lvalue reference type to a const- but not volatile-qualified object type
   or an rvalue reference type, both std::remove_reference_t<T> and
   std::remove_reference_t<U> shall be complete types, cv void, or an arrays of unknown
   bound; otherwise the behavior is undefined.
   If an instantiation of a template above depends, directly or indirectly, on an
   incomplete type, and that instantiation could yield a different result if that type
   were hypothetically completed, the behavior is undefined.
   If the program adds specializations for std::reference_converts_from_temporary or
   std::reference_converts_from_temporary_v, the behavior is undefined.

Member constants
            true if T is a reference type, a U value can be bound to T in
   value copy-initialization, and a temporary object would be bound to the
   [static] reference, false otherwise
            (public static member constant)

Member functions
   operator bool converts the object to bool, returns value
                 (public member function)
   operator() returns value
   (C++14) (public member function)

Member types
   Type Definition
   value_type bool
   type std::integral_constant<bool, value>

Notes
   std::reference_converts_from_temporary can be used for rejecting some cases that
   always produce dangling references.

Example
// Run this code
 #include <type_traits>
 int main() {}
 static_assert(std::reference_converts_from_temporary_v<int&&, int> == true);
 static_assert(std::reference_converts_from_temporary_v<const int&, int> == true);
 static_assert(std::reference_converts_from_temporary_v<int&&, int&&> == false);
 static_assert(std::reference_converts_from_temporary_v<const int&, int&&> == false);
 static_assert(std::reference_converts_from_temporary_v<int&&, long&&> == true);
 static_assert(std::reference_converts_from_temporary_v<int&&, long> == true);

See also
   is_convertible
   is_nothrow_convertible checks if a type can be converted to the other type
   (C++11) (class template)
   (C++20)
   invoke invokes any Callable object with given arguments
   invoke_r and possibility to specify return type
   (C++17) (since C++23)
   (C++23) (function template)
   bind binds one or more arguments to a function object
   (C++11) (function template)
   visit calls the provided functor with the arguments held by one or
   (C++17) more variants
                        (function template)
   constructor constructs a new std::function instance
                        (public member function of std::function<R(Args...)>)
   constructor constructs a new std::move_only_function object
   (C++23) (public member function of std::move_only_function)
                        constructs the task object
   constructor (public member function of std::packaged_task<R(Args...)>)