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std::refere...m_temporary(3)   C++ Standard Libary  std::refere...m_temporary(3)

NAME
     std::reference_constructs_from_temporary	     -	     std::reference_con-
     structs_from_temporary

Synopsis
	Defined in header <type_traits>
	template< class T, class U >		     (since C++23)
	struct reference_constructs_from_temporary;

	Let V be std::remove_cv_t<U> if U is a scalar type or cv void, or U oth-
     erwise. If T
	is a reference type, and given a hypothetic expression e such  that  de-
     cltype(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  ar-
     rays 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_con-
     structs_from_temporary or
	std::reference_constructs_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	 direct-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_constructs_from_temporary  can be used for rejecting some
     cases that
	always produce dangling references.

	It is also possible to use member initializer list to reject  binding  a
     temporary
	object to a reference if the compiler has implemented CWG1696.

Example
     // Run this code

      #include <type_traits>

      static_assert(std::reference_constructs_from_temporary_v<int&&,	int>  ==
     true);
      static_assert(std::reference_constructs_from_temporary_v<const int&,  int>
     == true);
      static_assert(std::reference_constructs_from_temporary_v<int&&,  int&&> ==
     false);
      static_assert(std::reference_constructs_from_temporary_v<const	   int&,
     int&&> == false);
      static_assert(std::reference_constructs_from_temporary_v<int&&, long&&> ==
     true);
      static_assert(std::reference_constructs_from_temporary_v<int&&,  long>  ==
     true);

      int main() {}

See also
	is_constructible
	is_trivially_constructible
	is_nothrow_constructible   checks if a type has a constructor  for  spe-
     cific arguments
	(C++11) 		   (class template)
	(C++11)
	(C++11)
	constructor		   constructs a new tuple
				   (public    member	function   of	std::tu-
     ple<Types...>)
	constructor		   constructs new pair
				   (public member function of std::pair<T1,T2>)
	make_from_tuple 	   construct an object with a tuple of arguments
	(C++17) 		   (function template)

http://cppreference.com 	   2024.06.10	    std::refere...m_temporary(3)
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