std::reference_converts_from_temporary
| Defined in header <type_traits>
|
||
| template< class T, class U > struct reference_converts_from_temporary; |
(since C++23) | |
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 hypothetical 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.
Helper variable template
| template< class T, class U > inline constexpr bool reference_converts_from_temporary_v = |
(since C++23) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is a reference type, a U value can be bound to T in copy-initialization, and a temporary object would be bound to the reference, false otherwise (public static member constant) |
Member functions
| operator bool |
converts the object to bool, returns value (public member function) |
| operator() (C++14) |
returns value (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
#include <type_traits> int main() {} static_assert( std::reference_converts_from_temporary_v<int&&, int> == true && std::reference_converts_from_temporary_v<const int&, int> == true && std::reference_converts_from_temporary_v<int&&, int&&> == false && std::reference_converts_from_temporary_v<const int&, int&&> == false && std::reference_converts_from_temporary_v<int&&, long&&> == true && std::reference_converts_from_temporary_v<int&&, long> == true);
See also
| (C++11)(C++20) |
checks if a type can be converted to the other type (class template) |
| (C++17)(C++23) |
invokes any Callable object with given arguments and possibility to specify return type(since C++23) (function template) |
| (C++11) |
binds one or more arguments to a function object (function template) |
| (C++17) |
calls the provided functor with the arguments held by one or more variants (function template) |
constructs a new std::function instance (public member function of std::function<R(Args...)>) | |
constructs a new std::move_only_function object (public member function of std::move_only_function) | |
| constructs the task object (public member function of std::packaged_task<R(Args...)>) |