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// Examples from P1099R5
// { dg-do compile { target c++20 } }
namespace my_lib {
enum class errcode
{
SUCCESS = 0,
ENOMEM = 1,
EAGAIN = 2,
ETOOSLOW = 3
};
using enum errcode; // import enumerators into namespace
}
namespace NS {
my_lib::errcode get_widget() {
using namespace my_lib;
return ETOOSLOW; // works, and conversions to int don't.
int i = ETOOSLOW; // { dg-error "" }
}
}
enum class rgba_color_channel { red, green, blue, alpha};
const char * to_string(rgba_color_channel channel) {
switch (channel) {
using enum rgba_color_channel;
case red: return "red";
case green: return "green";
case blue: return "blue";
case alpha: return "alpha";
}
return nullptr;
}
namespace ns {
struct E_detail {
enum E { e1, e2 };
friend void swap(E&, E&); // adl-only swap in the only associated scope of the enum
};
using E = E_detail::E; // import E into ns
using enum E; // expose the enumerators of E in ns. Also note the direct reference to E.
}
int main() {
auto x = ns::e1;
auto y = ns::e2;
swap(x, y); // finds the swap in the associated struct
}
namespace N0 {
enum E { x };
struct S {
enum H { y };
enum class K { z };
using E::x; // OK, introduces x into S
using E::x; // { dg-error "" } redeclaration in class scope
using H::y; // { dg-error "" } redeclaration in class scope
using K::z; // OK, introduces z into S
};
namespace NS {
enum H { y };
enum class K { z };
using E::x; // OK, introduces x into NS
using E::x; // OK, just a redeclaration of the same entity
using H::y; // OK, redeclaration of the same entity
using K::z; // OK, introduces z into NS
};
}
namespace N1 {
struct S {
enum E { x };
enum class EC { y };
using EC::y;
};
void f() {
using S::x; // OK
x; // resolves to S::E::x;
using S::y; // OK
y; // resolves to S::EC::y;
}
}
namespace N2 {
enum class E { a, b, c };
using E::a, E::b, E::c; // OK, imports all three
auto x = (a,b,c);
}
namespace N3 {
struct B {
enum class E { x };
};
enum class H { y };
struct C : B {
using enum B::E; // OK, introduces E::x into C
using enum H; // OK, introduces y into C. Does not introduce H
};
auto i = C::y; // OK
C::H h; // { dg-error "" }
}
namespace N4 {
enum class button { up, down };
struct S {
using button::up;
button b = up; // OK
};
}
namespace N5 {
enum class fruit { orange, apple };
struct S {
using enum fruit; // OK, introduces orange and apple into S
};
void f() {
S s;
s.orange; // OK, names fruit::orange
S::orange; // OK, names fruit::orange
}
}
namespace N6 {
enum class fruit { orange, apple };
enum class color { red, orange };
void f() {
using enum fruit; // OK
using enum color; // { dg-error "" } color::orange and fruit::orange conflict
}
}
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