[meta.reflection.annotation]

Constant When: item represents a type, type alias, variable, function, namespace, enumerator, direct base class relationship, or non-static data member.

2

#

Let E be

(2.1)
the corresponding base-specifier if item represents a direct base class relationship,
(2.2)
otherwise, the entity represented by item.

3

#

Returns: A vector containing all of the reflections R representing each annotation applying to each declaration of E that precedes either some point in the evaluation context ([expr.const]) or a point immediately following the class-specifier of the outermost class for which such a point is in a complete-class context.

For any two reflections

R_{1}

and

R_{2}

in the returned vector, if the annotation represented by

R_{1}

precedes the annotation represented by

R_{2}

, then

R_{1}

appears before

R_{2}

.

If

R_{1}

and

R_{2}

represent annotations from the same translation unit T, any element in the returned vector between

R_{1}

and

R_{2}

represents an annotation from T.

[Note 1:

The order in which two annotations appear is otherwise unspecified.

— end note]

[Example 1: [[=1]] void f(); [[=2, =3]] void g(); void g [[=4]] (); static_assert(annotations_of(^^f).size() == 1); static_assert(annotations_of(^^g).size() == 3); static_assert([: constant_of(annotations_of(^^g)[0]) :] == 2); static_assert(extract<int>(annotations_of(^^g)[1]) == 3); static_assert(extract<int>(annotations_of(^^g)[2]) == 4); struct Option { bool value; }; struct C { [[=Option{true}]] int a; [[=Option{false}]] int b; }; static_assert(extract<Option>(annotations_of(^^C::a)[0]).value); static_assert(!extract<Option>(annotations_of(^^C::b)[0]).value); template<class T> struct [[=42]] D { }; constexpr std::meta::info a1 = annotations_of(^^D<int>)[0]; constexpr std::meta::info a2 = annotations_of(^^D<char>)[0]; static_assert(a1 != a2); static_assert(constant_of(a1) == constant_of(a2)); [[=1]] int x, y; static_assert(annotations_of(^^x)[0] == annotations_of(^^y)[0]); — end example]

4

#

Constant When:

(4.1)
annotations_of(item) is a constant expression and
(4.2)
dealias(type) represents a type that is complete from some point in the evaluation context.

5

#

Returns: A vector containing each element e of annotations_of(item) where remove_const(type_of(e)) == remove_const(type) is true, preserving their order.

21 Metaprogramming library [meta]

21.4 Reflection [meta.reflection]

21.4.17 Annotation reflection [meta.reflection.annotation]