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Showing content from https://cplusplus.com/reference/type_traits/is_literal_type/ below:

class template

<type_traits>

std::is_literal_type

template <class T> struct is_literal_type;

Is literal type

Trait class that identifies whether T is a literal type.

A literal type is a type that can qualify as constexpr. This is true for scalar types, references, certain classes, and arrays of any such types.

A class that is a literal type is a class (defined with class, struct or union) that:

has a trivial destructor,
every constructor call and any non-static data member that has brace- or equal- initializers is a constant expression,
is an aggregate type, or has at least one constexpr constructor or constructor template that is not a copy or move constructor, and
has all non-static data members and base classes of literal types

is_literal_type inherits from integral_constant as being either true_type or false_type, depending on whether T is a trivial type.

Template parameters

T: A complete type, or void (possible cv-qualified), or an array of unknown bound of a complete element type.

Member types Inherited from integral_constant:

Member constants Inherited from integral_constant:
member constant definition value either true or false
Member functions Inherited from integral_constant:

operator bool: Returns value (public member function)

Example

// is_literal_type example
#include <iostream>
#include <type_traits>

struct A { };
struct B { ~B(){} };

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_literal_type:" << std::endl;
  std::cout << "int: " << std::is_literal_type<int>::value << std::endl;
  std::cout << "int&: " << std::is_literal_type<int&>::value << std::endl;
  std::cout << "int*: " << std::is_literal_type<int*>::value << std::endl;
  std::cout << "A: " << std::is_literal_type<A>::value << std::endl;
  std::cout << "B: " << std::is_literal_type<B>::value << std::endl;
  return 0;
}

Output:

is_literal_type:
int: true
int&: true
int*: true
A: true
B: false