# std::is_literal_type

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Defined in header `<type_traits>` |  |
template< class T > struct is_literal_type; |  | (since C++11) (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 > constexpr bool is_literal_type_v = is_literal_type<T>::value; |  | (since C++17) (deprecated) (removed in C++20)

## Inherited from std::integral_constant

### Member constants

value [static] | true if `T` is a literal type, 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

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 class type with unknown bound | the behavior is 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."

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