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Standard library header <meta> (C++26)

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Standard library headers
 

Includes

(C++20)
Three-way comparison operator support[edit]
std::initializer_list class template[edit]

Concepts

Defined in namespace std::meta
specifies a range of reflection values
(concept) [edit]

Types

Defined in namespace std::meta
(C++26)
the type of reflection values
(typedef) [edit]
exception thrown by reflection functions
(class) [edit]
a context for access checking
(class) [edit]
data member options including name, alignment, and bit width
(class) [edit]
the offset of a member or base class relative to its enclosing class
(class) [edit]
(C++26)
constants that identify overloadable operators
(enum) [edit]

Functions

Defined in namespace std::meta
Promoting compile-time storage into static storage
promotes a compile-time string to static storage, returning a reflection representing the static string
(function template) [edit]
promotes compile-time array into static storage, returning a reflection representing the static array
(function template) [edit]
promotes compile-time string to static storage, returning a pointer to the first character of the static string
(function template) [edit]
promotes compile-time array into static storage, returning a span of the static array
(function template) [edit]
promotes compile-time value into static storage, returning a pointer to the static object
(function template) [edit]
Operator representations
identifies the operator represented by the reflection
(function) [edit]
(C++26)(C++26)
converts a meta::operators enumerator to its symbolic name
(function) [edit]
Reflection names and locations
checks if reflection represents an entity that has an identifier
(function) [edit]
if the reflected entity has an identifier, obtains its name
(function) [edit]
obtains a string suitable for identifying the reflected entity
(function) [edit]
obtains the source location of the reflected entity
(function) [edit]
Reflection queries
(C++26)
determines the type of the reflected entity
(function) [edit]
(C++26)
obtains a reflection of the object of the reflected variable
(function) [edit]
obtains a reflection of the constant value of the reflected entity
(function) [edit]
checks if reflection represents a public, protected, or private member or base class
(function) [edit]
checks if reflection represents a virtual member function or virtual base class
(function) [edit]
checks if reflection represents a pure virtual member function
(function) [edit]
checks if reflection represents a member function that overrides another member function
(function) [edit]
(C++26)
checks if reflection represents a final class or final member function
(function) [edit]
checks if reflection represents a deleted function
(function) [edit]
checks if reflection represents a defaulted function
(function) [edit]
checks if reflection represents a user-provided function
(function) [edit]
checks if reflection represents a user-declared function
(function) [edit]
checks if reflection represents a member function that is declared explicit
(function) [edit]
checks if reflection represents a noexcept function or function type
(function) [edit]
checks if reflection represents a bit-field or a data member description of bit-field
(function) [edit]
checks if reflection represents an enumerator
(function) [edit]
checks if reflection represents an annotation
(function) [edit]
(C++26)
checks if reflection represents a const type or a function type with const qualifier
(function) [edit]
checks if reflection represents a volatile type or a function type with volatile qualifier
(function) [edit]
checks if reflection represents a mutable non-static data member
(function) [edit]
checks if the reflected entity is a ref qualified member function
(function) [edit]
checks if the reflected entity has a storage duration
(function) [edit]
checks if the reflected entity has a linkage
(function) [edit]
checks if the reflected entity has "C" language linkage (extern "C")
(function) [edit]
checks if reflection represents a complete type
(function) [edit]
checks if the reflected type has its list of members completely defined
(function) [edit]
checks if reflection represents a variable
(function) [edit]
(C++26)
checks if reflection represents a type
(function) [edit]
checks if reflection represents a namespace
(function) [edit]
checks if reflection represents a type alias
(function) [edit]
checks if reflection represents a namespace alias
(function) [edit]
checks if reflection represents a function
(function) [edit]
checks if reflection represents a conversion function
(function) [edit]
checks if reflection represents an operator overload
(function) [edit]
checks if reflection represents a user-defined literal operator
(function) [edit]
checks if reflection represents a special member function
(function) [edit]
checks if the reflected entity is a constructor of this kind
(function) [edit]
checks if the reflected entity is an assignment operator of this kind
(function) [edit]
checks if the reflected entity is a destructor
(function) [edit]
checks if reflection represents a function parameter
(function) [edit]
checks if reflection represents an explicit object parameter
(function) [edit]
checks if reflected function parameter has a default argument
(function) [edit]
checks if reflection represents a function or function type with an ellipsis parameter
(function) [edit]
checks if reflected entity is a template
(function) [edit]
checks if reflected entity is a function template
(function) [edit]
checks if reflected entity is a variable template
(function) [edit]
checks if reflected entity is a class template
(function) [edit]
checks if reflected entity is a alias template
(function) [edit]
checks if reflected entity is a conversion function template
(function) [edit]
checks if reflected entity is an operator function template
(function) [edit]
checks if reflected entity is a literal operator template
(function) [edit]
checks if reflected entity is a constructor template
(function) [edit]
checks if reflection represents a concept
(function) [edit]
(C++26)
checks if reflection represents a (scalar) value
(function) [edit]
(C++26)
checks if reflection represents a static object
(function) [edit]
checks if reflection represents a structured binding
(function) [edit]
checks if reflection represents a class member
(function) [edit]
checks if reflection represents a namespace member
(function) [edit]
checks if reflection represents a non-static data member
(function) [edit]
checks if reflection represents a static class member
(function) [edit]
(C++26)
checks if reflection represents a direct base class relationship
(function) [edit]
checks if reflected non-static data member has a default member initializer
(function) [edit]
checks if the reflected entity is contained in a scope
(function) [edit]
(C++26)
obtains the scope that contains the reflected entity
(function) [edit]
(C++26)
determines the underlying entity of the reflected type/namespace alias
(function) [edit]
checks if reflected entity is produced by substituting template arguments into a template
(function) [edit]
determines the template used to instantiate the reflected entity
(function) [edit]
obtains the template arguments of the reflected entity
(function) [edit]
obtains the parameters of the reflected function
(function) [edit]
obtains the variable of the reflected function parameter in the function definition
(function) [edit]
obtains the return type of the reflected function
(function) [edit]
Accessibility queries
checks if a member is accessible in a given context
(function) [edit]
checks if the reflected class has any inaccessible non-static data members
(function) [edit]
checks if the reflected class has any inaccessible direct base classes
(function) [edit]
checks if the reflected class has any inaccessible non-static data members or direct base classes
(function) [edit]
Scope identification
returns a reflection of the enclosing function
(function) [edit]
returns a reflection of the enclosing class
(function) [edit]
returns a reflection of the enclosing namespace
(function) [edit]
Reflection member queries
obtains the accessible direct members of the reflected class or namespace
(function) [edit]
(C++26)
obtains the accessible direct bases of the reflected class
(function) [edit]
obtains the accessible static data members of the reflected class
(function) [edit]
obtains the accessible non-static data members of the reflected class
(function) [edit]
obtains the accessible base class subobjects and non-static data members of the reflected class
(function) [edit]
obtains the enumerators of the reflected enum type
(function) [edit]
Reflection layout queries
(C++26)
returns the offset of a (member or base) subobject relative to its enclosing class
(function) [edit]
(C++26)
returns the size in bytes of the reflected object or type
(function) [edit]
returns the alignment of the reflected object or type
(function) [edit]
returns the size in bits of the reflected object or type
(function) [edit]
Annotation reflection
obtains the annotations applying to the reflected entity
(function) [edit]
obtains the annotations that apply to the reflected entity and have the specified type
(function) [edit]
Value extraction
(C++26)
extracts the value of the reflected entity
(function template) [edit]
Reflection substitution
checks whether the reflected arguments can be substituted in the reflected template
(function template) [edit]
substitutes reflected arguments in the reflected template
(function template) [edit]
Expression result reflection
returns a reflection representing a value or template parameter object, suitable for use as a constant template argument
(function template) [edit]
returns a reflection representing an object, suitable for use as a constant template argument
(function template) [edit]
returns a reflection representing a function, suitable for use as a constant template argument
(function template) [edit]
Class definition generation
creates a data member description for use with injected declarations
(function) [edit]
checks if reflection represents a data member description
(function) [edit]
defines an aggregate type from a sequence of data member descriptions
(function template) [edit]
Primary type categories
checks if reflected type is void
(function) [edit]
checks if reflected type is std::nullptr_t
(function) [edit]
checks if reflected type is an integral type
(function) [edit]
checks if reflected type is a floating-point type
(function) [edit]
checks if reflected type is an array type
(function) [edit]
checks if reflected type is a pointer type
(function) [edit]
checks if reflection represents an lvalue reference
(function) [edit]
checks if reflection represents an rvalue reference
(function) [edit]
checks if reflection represents a member object pointer type
(function) [edit]
checks if reflection represents a member function pointer type
(function) [edit]
checks if reflected type is an enumeration type
(function) [edit]
checks if reflected type is a union type
(function) [edit]
checks if reflected type is a non-union class type
(function) [edit]
checks if reflected type is a function type
(function) [edit]
checks if reflected type is std::meta::info
(function) [edit]
Composite type categories
checks if reflection represents either an lvalue reference or rvalue reference
(function) [edit]
checks if reflection represents an arithmetic type
(function) [edit]
checks if reflection represents a fundamental type
(function) [edit]
checks if reflected type is an object type
(function) [edit]
checks if reflected type is a scalar type
(function) [edit]
checks if reflected type is a compound type
(function) [edit]
checks if reflection represents a member pointer type
(function) [edit]
Type properties
checks if reflection represents a const-qualified type
(function) [edit]
checks if reflection represents a volatile-qualified type
(function) [edit]
checks if reflection represents a trivially copyable type
(function) [edit]
checks if reflected type is a standard-layout type
(function) [edit]
checks if reflected type is a class (but not union) type and has no non-static data members
(function) [edit]
checks if reflected type is a polymorphic class type
(function) [edit]
checks if reflected type is an abstract class type
(function) [edit]
checks if reflected type is a final class type
(function) [edit]
checks if reflected type is an aggregate type
(function) [edit]
checks if reflected type is a structural type
(function) [edit]
checks if reflection represents a signed arithmetic type
(function) [edit]
checks if reflection represents an unsigned arithmetic type
(function) [edit]
checks if reflection represents an array type of known bound
(function) [edit]
checks if reflection represents an array type of unknown bound
(function) [edit]
checks if reflection represents a scoped enumeration type
(function) [edit]
checks if reflected type has a constructor for specific arguments
(function template) [edit]
checks if reflected type has a default constructor
(function) [edit]
checks if reflected type has a copy constructor
(function) [edit]
checks if reflected type can be constructed from an rvalue reference
(function) [edit]
checks if reflected type has an assignment operator for a specific argument
(function) [edit]
checks if reflected type has a copy assignment operator
(function) [edit]
checks if reflected type has a move assignment operator
(function) [edit]
checks if objects of one reflected type can be swapped with objects of same or different other reflected type
(function) [edit]
checks if reflected type has a non-deleted destructor
(function) [edit]
checks if reflected type is an implicit-lifetime type
(function) [edit]
checks if reflected type has a virtual destructor
(function) [edit]
checks if every bit in reflected type's object representation contributes to its value
(function) [edit]
checks if a reference is bound to a temporary in direct-initialization
(function) [edit]
checks if a reference is bound to a temporary in copy-initialization
(function) [edit]
Type property queries
(C++26)
obtains the number of dimensions of reflected array type
(function) [edit]
(C++26)
obtains the size of reflected array type along a specified dimension
(function) [edit]
Type relations
checks if two reflections represent the same type
(function) [edit]
checks if two reflections represent types such that one type is a base of the other type
(function) [edit]
checks if two reflections represent types such that one type is a virtual base of the other type
(function) [edit]
checks if reflected type can be converted to the other type
(function) [edit]
checks if two reflections represent layout-compatible types
(function) [edit]
checks if reflected type is a pointer-interconvertible base of another type
(function) [edit]
checks if the reflected type can be invoked (as if by std::invoke) with the given argument types
(function template) [edit]
Const-volatile modifications
removes const and/or volatile qualifiers from reflected type
(function) [edit]
(C++26)(C++26)(C++26)
adds const and/or volatile qualifiers to reflected type
(function) [edit]
Reference modifications
removes a reference from reflected type
(function) [edit]
adds an lvalue or rvalue reference to reflected type
(function) [edit]
Sign modifications
returns the corresponding signed type for reflected integral type
(function) [edit]
returns the corresponding unsigned type for reflected integral type
(function) [edit]
Array modifications
removes one extent from reflected array type
(function) [edit]
removes all extents from reflected array type
(function) [edit]
Pointer modifications
removes a pointer from reflected type
(function) [edit]
adds a pointer to reflected type
(function) [edit]
Other transformations
combines meta::remove_cv and meta::remove_reference
(function) [edit]
(C++26)
applies type transformations as when passing a function argument by value
(function) [edit]
determines the common type of a sequence of reflected types
(function template) [edit]
determines the common reference type of a sequence of reflected types
(function template) [edit]
obtains the underlying integer type for reflected enumeration type
(function) [edit]
deduces the result type of invoking a callable object with a set of arguments
(function template) [edit]
get the reference type wrapped in std::reference_wrapper
(function) [edit]
obtains the size of reflected tuple
(function) [edit]
obtains the type of the specified element of reflected tuple
(function) [edit]
checks if the callable object can be invoked (as if by std::invoke) with a tuple of arguments
(function) [edit]
deduces the result type of invoking a callable object with a tuple of arguments
(function) [edit]
obtains the size of reflected variant's list of alternatives
(function) [edit]
obtains the type of reflected tuple's alternative specified by its index
(function) [edit]
performs three-way comparison on reflected types
(function) [edit]
Checking string literals
checks if a pointer points into a string literal
(function) [edit]

Synopsis

#include <compare>
#include <initializer_list>

namespace std {
  // checking string literals
  consteval bool is_string_literal(const char* p);
  consteval bool is_string_literal(const wchar_t* p);
  consteval bool is_string_literal(const char8_t* p);
  consteval bool is_string_literal(const char16_t* p);
  consteval bool is_string_literal(const char32_t* p);

  // promoting to static storage
  namespace meta {
    template<ranges::input_range R> consteval info reflect_constant_string(R&& r);
    template<ranges::input_range R> consteval info reflect_constant_array(R&& r);
  }
  template<ranges::input_range R>
  consteval const ranges::range_value_t<R>* define_static_string(R&& r);
  template<ranges::input_range R>
  consteval span<const ranges::range_value_t<R>, /* see description */>
  define_static_array(R&& r);
  template<class T> consteval const remove_cvref_t<T>* define_static_object(T&& r);
}

namespace std::meta {
  using info = decltype(^^::);

  // class exception
  class exception;

  // operator representations
  enum class operators
  {
    /* see description */;
  };
  using enum operators;
  consteval operators operator_of(info r);
  consteval string_view symbol_of(operators op);
  consteval u8string_view u8symbol_of(operators op);

  // reflection names and locations
  consteval bool has_identifier(info r);

  consteval string_view identifier_of(info r);
  consteval u8string_view u8identifier_of(info r);

  consteval string_view display_string_of(info r);
  consteval u8string_view u8display_string_of(info r);

  consteval source_location source_location_of(info r);

  // reflection queries
  consteval info type_of(info r);
  consteval info object_of(info r);
  consteval info constant_of(info r);

  consteval bool is_public(info r);
  consteval bool is_protected(info r);
  consteval bool is_private(info r);

  consteval bool is_virtual(info r);
  consteval bool is_pure_virtual(info r);
  consteval bool is_override(info r);
  consteval bool is_final(info r);

  consteval bool is_deleted(info r);
  consteval bool is_defaulted(info r);
  consteval bool is_user_provided(info r);
  consteval bool is_user_declared(info r);
  consteval bool is_explicit(info r);
  consteval bool is_noexcept(info r);

  consteval bool is_bit_field(info r);
  consteval bool is_enumerator(info r);
  consteval bool is_annotation(info r);

  consteval bool is_const(info r);
  consteval bool is_volatile(info r);
  consteval bool is_mutable_member(info r);
  consteval bool is_lvalue_reference_qualified(info r);
  consteval bool is_rvalue_reference_qualified(info r);

  consteval bool has_static_storage_duration(info r);
  consteval bool has_thread_storage_duration(info r);
  consteval bool has_automatic_storage_duration(info r);

  consteval bool has_internal_linkage(info r);
  consteval bool has_module_linkage(info r);
  consteval bool has_external_linkage(info r);
  consteval bool has_c_language_linkage(info r);
  consteval bool has_linkage(info r);

  consteval bool is_complete_type(info r);
  consteval bool is_enumerable_type(info r);

  consteval bool is_variable(info r);
  consteval bool is_type(info r);
  consteval bool is_namespace(info r);
  consteval bool is_type_alias(info r);
  consteval bool is_namespace_alias(info r);

  consteval bool is_function(info r);
  consteval bool is_conversion_function(info r);
  consteval bool is_operator_function(info r);
  consteval bool is_literal_operator(info r);
  consteval bool is_special_member_function(info r);
  consteval bool is_constructor(info r);
  consteval bool is_default_constructor(info r);
  consteval bool is_copy_constructor(info r);
  consteval bool is_move_constructor(info r);
  consteval bool is_assignment(info r);
  consteval bool is_copy_assignment(info r);
  consteval bool is_move_assignment(info r);
  consteval bool is_destructor(info r);

  consteval bool is_function_parameter(info r);
  consteval bool is_explicit_object_parameter(info r);
  consteval bool has_default_argument(info r);
  consteval bool is_vararg_function(info r);

  consteval bool is_template(info r);
  consteval bool is_function_template(info r);
  consteval bool is_variable_template(info r);
  consteval bool is_class_template(info r);
  consteval bool is_alias_template(info r);
  consteval bool is_conversion_function_template(info r);
  consteval bool is_operator_function_template(info r);
  consteval bool is_literal_operator_template(info r);
  consteval bool is_constructor_template(info r);
  consteval bool is_concept(info r);

  consteval bool is_value(info r);
  consteval bool is_object(info r);

  consteval bool is_structured_binding(info r);

  consteval bool is_class_member(info r);
  consteval bool is_namespace_member(info r);
  consteval bool is_nonstatic_data_member(info r);
  consteval bool is_static_member(info r);
  consteval bool is_base(info r);

  consteval bool has_default_member_initializer(info r);

  consteval bool has_parent(info r);
  consteval info parent_of(info r);

  consteval info dealias(info r);

  consteval bool has_template_arguments(info r);
  consteval info template_of(info r);
  consteval vector<info> template_arguments_of(info r);
  consteval vector<info> parameters_of(info r);
  consteval info variable_of(info r);
  consteval info return_type_of(info r);

  // access control context
  struct access_context;

  // member accessibility queries
  consteval bool is_accessible(info r, access_context ctx);
  consteval bool has_inaccessible_nonstatic_data_members(info r, access_context ctx);
  consteval bool has_inaccessible_bases(info r, access_context ctx);
  consteval bool has_inaccessible_subobjects(info r, access_context ctx);

  // scope identification
  consteval info current_function();
  consteval info current_class();
  consteval info current_namespace();

  // reflection member queries
  consteval vector<info> members_of(info r, access_context ctx);
  consteval vector<info> bases_of(info type, access_context ctx);
  consteval vector<info> static_data_members_of(info type, access_context ctx);
  consteval vector<info> nonstatic_data_members_of(info type, access_context ctx);
  consteval vector<info> subobjects_of(info type, access_context ctx);
  consteval vector<info> enumerators_of(info type_enum);

  // reflection layout queries
  struct member_offset;
  consteval member_offset offset_of(info r);
  consteval size_t size_of(info r);
  consteval size_t alignment_of(info r);
  consteval size_t bit_size_of(info r);

  // annotation reflection
  consteval vector<info> annotations_of(info item);
  consteval vector<info> annotations_of_with_type(info item, info type);

  // value extraction
  template<class T> consteval T extract(info r);

  // reflection substitution
  template<class R>
  concept reflection_range = /* see description */;

  template<reflection_range R = initializer_list<info>>
  consteval bool can_substitute(info templ, R&& arguments);
  template<reflection_range R = initializer_list<info>>
  consteval info substitute(info templ, R&& arguments);

  // expression result reflection
  template<class T> consteval info reflect_constant(T expr);
  template<class T> consteval info reflect_object(T& expr);
  template<class T> consteval info reflect_function(T& fn);

  // class definition generation
  struct data_member_options;
  consteval info data_member_spec(info type, data_member_options options);
  consteval bool is_data_member_spec(info r);
  template<reflection_range R = initializer_list<info>>
  consteval info define_aggregate(info type_class, R&& mdescrs);

  // primary type categories
  consteval bool is_void_type(info type);
  consteval bool is_null_pointer_type(info type);
  consteval bool is_integral_type(info type);
  consteval bool is_floating_point_type(info type);
  consteval bool is_array_type(info type);
  consteval bool is_pointer_type(info type);
  consteval bool is_lvalue_reference_type(info type);
  consteval bool is_rvalue_reference_type(info type);
  consteval bool is_member_object_pointer_type(info type);
  consteval bool is_member_function_pointer_type(info type);
  consteval bool is_enum_type(info type);
  consteval bool is_union_type(info type);
  consteval bool is_class_type(info type);
  consteval bool is_function_type(info type);
  consteval bool is_reflection_type(info type);

  // composite type categories
  consteval bool is_reference_type(info type);
  consteval bool is_arithmetic_type(info type);
  consteval bool is_fundamental_type(info type);
  consteval bool is_object_type(info type);
  consteval bool is_scalar_type(info type);
  consteval bool is_compound_type(info type);
  consteval bool is_member_pointer_type(info type);

  // type properties
  consteval bool is_const_type(info type);
  consteval bool is_volatile_type(info type);
  consteval bool is_trivially_copyable_type(info type);
  consteval bool is_standard_layout_type(info type);
  consteval bool is_empty_type(info type);
  consteval bool is_polymorphic_type(info type);
  consteval bool is_abstract_type(info type);
  consteval bool is_final_type(info type);
  consteval bool is_aggregate_type(info type);
  consteval bool is_structural_type(info type);
  consteval bool is_signed_type(info type);
  consteval bool is_unsigned_type(info type);
  consteval bool is_bounded_array_type(info type);
  consteval bool is_unbounded_array_type(info type);
  consteval bool is_scoped_enum_type(info type);

  template<reflection_range R = initializer_list<info>>
  consteval bool is_constructible_type(info type, R&& type_args);
  consteval bool is_default_constructible_type(info type);
  consteval bool is_copy_constructible_type(info type);
  consteval bool is_move_constructible_type(info type);

  consteval bool is_assignable_type(info type_dst, info type_src);
  consteval bool is_copy_assignable_type(info type);
  consteval bool is_move_assignable_type(info type);

  consteval bool is_swappable_with_type(info type1, info type2);
  consteval bool is_swappable_type(info type);

  consteval bool is_destructible_type(info type);

  template<reflection_range R = initializer_list<info>>
  consteval bool is_trivially_constructible_type(info type, R&& type_args);
  consteval bool is_trivially_default_constructible_type(info type);
  consteval bool is_trivially_copy_constructible_type(info type);
  consteval bool is_trivially_move_constructible_type(info type);

  consteval bool is_trivially_assignable_type(info type_dst, info type_src);
  consteval bool is_trivially_copy_assignable_type(info type);
  consteval bool is_trivially_move_assignable_type(info type);
  consteval bool is_trivially_destructible_type(info type);

  template<reflection_range R = initializer_list<info>>
  consteval bool is_nothrow_constructible_type(info type, R&& type_args);
  consteval bool is_nothrow_default_constructible_type(info type);
  consteval bool is_nothrow_copy_constructible_type(info type);
  consteval bool is_nothrow_move_constructible_type(info type);

  consteval bool is_nothrow_assignable_type(info type_dst, info type_src);
  consteval bool is_nothrow_copy_assignable_type(info type);
  consteval bool is_nothrow_move_assignable_type(info type);

  consteval bool is_nothrow_swappable_with_type(info type1, info type2);
  consteval bool is_nothrow_swappable_type(info type);

  consteval bool is_nothrow_destructible_type(info type);

  consteval bool is_implicit_lifetime_type(info type);

  consteval bool has_virtual_destructor(info type);

  consteval bool has_unique_object_representations(info type);

  consteval bool reference_constructs_from_temporary(info type_dst, info type_src);
  consteval bool reference_converts_from_temporary(info type_dst, info type_src);

  // type property queries
  consteval size_t rank(info type);
  consteval size_t extent(info type, unsigned i = 0);

  // type relations
  consteval bool is_same_type(info type1, info type2);
  consteval bool is_base_of_type(info type_base, info type_derived);
  consteval bool is_virtual_base_of_type(info type_base, info type_derived);
  consteval bool is_convertible_type(info type_src, info type_dst);
  consteval bool is_nothrow_convertible_type(info type_src, info type_dst);
  consteval bool is_layout_compatible_type(info type1, info type2);
  consteval bool is_pointer_interconvertible_base_of_type(info type_base,
                                                          info type_derived);

  template<reflection_range R = initializer_list<info>>
  consteval bool is_invocable_type(info type, R&& type_args);
  template<reflection_range R = initializer_list<info>>
  consteval bool is_invocable_r_type(info type_result, info type, R&& type_args);

  template<reflection_range R = initializer_list<info>>
  consteval bool is_nothrow_invocable_type(info type, R&& type_args);
  template<reflection_range R = initializer_list<info>>
  consteval bool is_nothrow_invocable_r_type(info type_result, info type, R&& type_args);

  // const-volatile modifications
  consteval info remove_const(info type);
  consteval info remove_volatile(info type);
  consteval info remove_cv(info type);
  consteval info add_const(info type);
  consteval info add_volatile(info type);
  consteval info add_cv(info type);

  // reference modifications
  consteval info remove_reference(info type);
  consteval info add_lvalue_reference(info type);
  consteval info add_rvalue_reference(info type);

  // sign modifications
  consteval info make_signed(info type);
  consteval info make_unsigned(info type);

  // array modifications
  consteval info remove_extent(info type);
  consteval info remove_all_extents(info type);

  // pointer modifications
  consteval info remove_pointer(info type);
  consteval info add_pointer(info type);

  // other transformations
  consteval info remove_cvref(info type);
  consteval info decay(info type);
  template<reflection_range R = initializer_list<info>>
  consteval info common_type(R&& type_args);
  template<reflection_range R = initializer_list<info>>
  consteval info common_reference(R&& type_args);
  consteval info underlying_type(info type);
  template<reflection_range R = initializer_list<info>>
  consteval info invoke_result(info type, R&& type_args);
  consteval info unwrap_reference(info type);
  consteval info unwrap_ref_decay(info type);

  consteval size_t tuple_size(info type);
  consteval info tuple_element(size_t index, info type);
  consteval bool is_applicable_type(info fn, info tuple);
  consteval bool is_nothrow_applicable_type(info fn, info tuple);
  consteval info apply_result(info fn, info tuple);

  consteval size_t variant_size(info type);
  consteval info variant_alternative(size_t index, info type);

  consteval strong_ordering type_order(info type_a, info type_b);
}

Class std::meta::exception

namespace std::meta {
  class exception : public std::exception
  {
  private:
    optional<string> /*what_*/; // exposition-only
    u8string /*u8what_*/;       // exposition-only
    info /*from_*/;             // exposition-only
    source_location /*where_*/; // exposition-only

  public:
    consteval exception(u8string_view what,
                        info from,
                        source_location where = source_location::current()) noexcept;

    consteval exception(string_view what,
                        info from,
                        source_location where = source_location::current()) noexcept;

    exception(const exception&) = default;
    exception(exception&&) = default;

    exception& operator=(const exception&) = default;
    exception& operator=(exception&&) = default;

    constexpr const char* what() const noexcept override;
    consteval u8string_view u8what() const noexcept;
    consteval info from() const noexcept;
    consteval source_location where() const noexcept;
  };
}

Class std::meta::access_context

namespace std::meta {
  struct access_context
  {
    access_context() = delete;

    consteval info scope() const;
    consteval info designating_class() const;

    static consteval access_context current() noexcept;
    static consteval access_context unprivileged() noexcept;
    static consteval access_context unchecked() noexcept;
    consteval access_context via(info cls) const;
  };
}

Class std::meta::member_offset

namespace std::meta {
  struct member_offset
  {
    ptrdiff_t bytes;
    ptrdiff_t bits;
    constexpr ptrdiff_t total_bits() const;
    auto operator<=>(const member_offset&) const = default;
  };
}

Class std::meta::data_member_options

namespace std::meta {
  struct data_member_options
  {
    struct /*name-type*/
    {                                         // exposition-only
      template<class T>
        requires constructible_from<u8string, T>
      consteval /*name-type*/(T&&);

      template<class T>
        requires constructible_from<string, T>
      consteval /*name-type*/(T&&);

    private:
      variant<u8string, string> /*contents*/; // exposition-only
    };

    optional</*name-type*/> name;
    optional<int> alignment;
    optional<int> bit_width;
    bool no_unique_address = false;
    vector<info> annotations;
  };
}