[meta.reflection.traits]

Every function and function template declared in this subclause throws an exception of type meta::exception unless the following conditions are met:

(2.1)
For every parameter p of type info, is_type(p) is true.
(2.2)
For every parameter r whose type is constrained on reflection_range, ranges::all_of(r, is_type) is true.

/ associated with [meta.unary.cat], 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); / associated with [meta.unary.comp], 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); / associated with [meta.unary.prop], 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_consteval_only_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); / associated with [meta.rel], 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); / associated with [meta.trans.cv], 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); / associated with [meta.trans.ref], reference modifications consteval info remove_reference(info type); consteval info add_lvalue_reference(info type); consteval info add_rvalue_reference(info type); / associated with [meta.trans.sign], sign modifications consteval info make_signed(info type); consteval info make_unsigned(info type); / associated with [meta.trans.arr], array modifications consteval info remove_extent(info type); consteval info remove_all_extents(info type); / associated with [meta.trans.ptr], pointer modifications consteval info remove_pointer(info type); consteval info add_pointer(info type); / associated with [meta.trans.other], 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);

Each function or function template declared above has the following behavior based on the signature and return type of that function or function template.

[Note 2:

The associated class template need not be instantiated.

— end note]

Table 64 — Reflection type traits [tab:meta.reflection.traits]

🔗 Signature and Return Type	*Returns*
🔗 bool meta::UNARY(info type); bool meta::UNARY_type(info type);	std::UNARY<T>::value, where T is the type or type alias represented by type
🔗 bool meta::BINARY(info t1, info t2); bool meta::BINARY_type(info t1, info t2);	std::BINARY< ${T 1, {T 2 > :: value, where {T 1 and {T 2 are the types or type aliases represented by t1 and t2, respectively}_{2 are the types or type aliases represented by t1 and t2, respectively}}_{1 and {T 2 are the types or type aliases represented by t1 and t2, respectively}_{2 are the types or type aliases represented by t1 and t2, respectively}}}_{2 > :: value}}_{1, {T 2 > :: value, where {T 1 and {T 2 are the types or type aliases represented by t1 and t2, respectively}_{2 are the types or type aliases represented by t1 and t2, respectively}}_{1 and {T 2 are the types or type aliases represented by t1 and t2, respectively}_{2 are the types or type aliases represented by t1 and t2, respectively}}}_{2 > :: value}}$
🔗 template<reflection_range R> bool meta::VARIADIC_type(info type, R&& args);	std::VARIADIC<T, U.>::value, where T is the type or type alias represented by type and U.. is the pack of types or type aliases whose elements are represented by the corresponding elements of args
🔗 template<reflection_range R> bool meta::VARIADIC_type(info t1, info t2, R&& args);	std::VARIADIC< ${T 1, {T 2, U . > :: value, where {T 1 and {T 2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}_{2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}}_{1 and {T 2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}_{2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}}}_{2, U . > :: value}}_{1, {T 2, U . > :: value, where {T 1 and {T 2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}_{2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}}_{1 and {T 2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}_{2 are the types or type aliases represented by t1 and t2, respectively, and U . is the pack of types or type aliases whose elements are represented by the corresponding elements of args}}}_{2, U . > :: value}}$
🔗 info meta::UNARY(info type);	A reflection representing the type denoted by std::UNARY<T>::type, where T is the type or type alias represented by type
🔗 template<reflection_range R> info meta::VARIADIC(R&& args);	A reflection representing the type denoted by std::VARIADIC<T.>::type, where T. is the pack of types or type aliases whose elements are represented by the corresponding elements of args
🔗 template<reflection_range R> info meta::VARIADIC(info type, R&& args);	A reflection representing the type denoted by std::VARIADIC<T, U.>::type, where T is the type or type alias represented by type and U. is the pack of types or type aliases whose elements are represented by the corresponding elements of args

[Note 3:

For those functions or function templates which return a reflection, that reflection always represents a type and never a type alias.

— end note]

[Note 4:

If t is a reflection of the type int and u is a reflection of an alias to the type int, then t == u is false but is_same_type(t, u) is true.

Also, t == dealias(u) is true.

— end note]

🔗

consteval size_t rank(info type);

Returns: std::rank<T>::value, where T is the type represented by dealias(type).

🔗

consteval size_t extent(info type, unsigned i = 0);

Returns: std::extent<T, I>::value, where T is the type represented by dealias(type) and I is a constant equal to i.

🔗

consteval size_t tuple_size(info type);

Returns: std::tuple_size<T>::value, where T is the type represented by dealias(type).

🔗

consteval info tuple_element(size_t index, info type);

Returns: A reflection representing the type denoted by std::tuple_element<I, T>::type, where T is the type represented by dealias(type) and I is a constant equal to index.

🔗

consteval size_t variant_size(info type);

Returns: std::variant_size<T>::value, where T is the type represented by dealias(type).

🔗

consteval info variant_alternative(size_t index, info type);

Returns: A reflection representing the type denoted by std::variant_alternative<I, T>::type, where T is the type represented by dealias(type) and I is a constant equal to index.

🔗

consteval strong_ordering type_order(info t1, info t2);

Returns: std::type_order<

{T 1, {T 2 > ​::​ value, where {T 1 and {T 2 are the types represented by dealias (​t1) and dealias (t2), respectively .}_{2 are the types represented by dealias (​t1) and dealias (t2), respectively .}}_{1 and {T 2 are the types represented by dealias (​t1) and dealias (t2), respectively .}_{2 are the types represented by dealias (​t1) and dealias (t2), respectively .}}}_{2 > ​::​ value}}_{1, {T 2 > ​::​ value, where {T 1 and {T 2 are the types represented by dealias (​t1) and dealias (t2), respectively .}_{2 are the types represented by dealias (​t1) and dealias (t2), respectively .}}_{1 and {T 2 are the types represented by dealias (​t1) and dealias (t2), respectively .}_{2 are the types represented by dealias (​t1) and dealias (t2), respectively .}}}_{2 > ​::​ value}}