NAME¶

std::is_literal_type - std::is_literal_type

Synopsis¶

Defined in header <type_traits>
template< class T > (since C++11)
struct is_literal_type; (deprecated in C++17)
(removed in C++20)

std::is_literal_type is a UnaryTypeTrait.

(This type trait has been deprecated^[1] and removed^[2] as offering negligible
value to generic code.)

If T satisfies all requirements of LiteralType, provides the member constant value
equal to true. For any other type, value is false.

If std::remove_all_extents_t<T> is an incomplete type and not (possibly
cv-qualified) void, the behavior is undefined.

If the program adds specializations for std::is_literal_type or
std::is_literal_type_v, the behavior is undefined.

Template parameters¶

T - a type to check

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_literal_type_v = (deprecated)
is_literal_type<T>::value; (removed in C++20)

Inherited from std::integral_constant

Member constants¶

value true if T is a literal type, false otherwise
[static] (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¶

Only literal types may be used as parameters to or returned from constexpr
functions. Only literal classes may have constexpr member functions.

Example¶

// Run this code

#include <type_traits>

struct A { int m; };
static_assert(std::is_literal_type_v<A> == true);

struct B { virtual ~B(); };
static_assert(std::is_literal_type_v<B> == false);

int main() {}

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2015 C++11 T could be an array of incomplete the behavior is
class type with unknown bound undefined in this case

External links¶

1. ↑ Alisdair Meredith. "Deprecate the is_literal Trait". Deprecating Vestigial
Library Parts in C++17. "The is_literal type trait offers negligible value to
generic code, as what is really needed is the ability to know that a specific
construction would produce constant initialization."
2. ↑ Alisdair Meredith, Stephan T. Lavavej, Tomasz Kamiński. "Deprecated type
traits". Reviewing Deprecated Facilities of C++17 for C++20. "Strong
recommendation: Remove the traits that can live on as zombies. [...] Toronto
Review: Accept strong recommendation, strike from C++20."