c – typedef并在相同范围内使用同名的声明

#include <iostream>
#include <typeinfo>


typedef int a_t;


namespace a_ns
{
class a_t {};
}


using a_ns::a_t;


int main()
{
    a_t a;
    std::cout << typeid(a).name() << std::endl;
    return 0;
}

建于：

clang -std=c++11 -pedantic -Wall -o a a.cpp -lstdc++
g++ -std=c++11 -pedantic -Wall -o a a.cpp -lstdc++
cl -EHsc -GR a.cpp

clang和g生成的可执行文件打印“i”,这似乎表明a是int类型,typedef占上风. cl生成可执行文件“class a_ns :: a_t”,这似乎表明Visual Studio更喜欢使用声明.

我希望代码不能按照以下标准摘录编译.我会期待一个类似于“已经在范围内使用声明冲突的声明”的错误.

7.1.3.6 Similarly,in a given scope,a class or enumeration shall not be declared with the same name as a typedef-name that is declared in
that scope and refers to a type other than the class or enumeration
itself.

7.3.3.1 A using-declaration introduces a name into the declarative region in which the using-declaration appears.

7.3.3.2 Every using-declaration is a declaration […]

可能有一些我在标准中缺少解释这个行为的东西(或者我太累了,看不清楚),但我似乎找不到.

谢谢.