std::reference_converts_from_temporary
Defined in header <type_traits> |
||
|---|---|---|
|
(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 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.
The behavior of a program that adds specializations for std::reference_converts_from_temporary or std::reference_converts_from_temporary_v is undefined.
Helper variable template
|
(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);
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
|
(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...)>) |
|
|
(C++23)
|
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...)>) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/types/reference_converts_from_temporary