带有使用指令的模糊名称查找

It's not allowed to put a namespace and a class with the same name into one declarative region, i.e.

不允许将名称空间和名称相同的类放入一个声明性区域，例如。

namespace A {}
class A{};

is ill-formed (see §3.3.1/4). However, one can introduce the name of either one via a using-directive:

不规范的(见§3.3.1/4)。但是，可以通过使用指令来介绍其中任何一个的名称:

namespace N { namespace A {int i;} }

struct A {static int i;};

using namespace N;

int i = A::i; // The global struct, or namespace N::A?

Is this code ill-formed? VC++ thinks so, as well as Clang:

这是不规范的代码吗?VC++ +也这么认为，还有叮当声:

main.cpp:7:9: error: reference to 'A' is ambiguous
int i = A::i;
        ^
main.cpp:3:8: note: candidate found by name lookup is 'A'
struct A {static int i;};
       ^
main.cpp:1:25: note: candidate found by name lookup is 'N::A'
namespace N { namespace A {int i;} }
                        ^

However, GCC accepts it.

然而,GCC接受它。

Who is right?

谁是正确的?

1 个解决方案

#1

The code is ill-formed. When looking up A, §7.3.4/6 steps in:

不规范的代码。当查找,§7.3.4/6步骤:

If name lookup finds a declaration for a name in two different namespaces, and the declarations do not declare the same entity and do not declare functions, the use of the name is ill-formed.

如果名称查找在两个不同的名称空间中找到名称的声明，并且声明没有声明相同的实体，也没有声明函数，那么名称的使用是不恰当的。

Here, the namespaces are the global namespace and N, and the entities are the namespace N::A and the class ::A.

在这里，名称空间是全局名称空间和N，实体是名称空间N::A和类:::A。

#1