c++ - 为什么编译代码 "foo::foo::foo::foob"？

Question

这个问题在这里已经有了答案:

Why is there an injected class name? (1 个回答)

关闭 5年前。

一位同事不小心写了这样的代码:

struct foo {
  foo() : baz(foobar) {}
  enum bar {foobar, fbar, foob};
  bar baz;
};

void f() {
  for( auto x : { foo::foobar,
                  foo::fbar,
                  foo::
                  foo::
                  foo::foob } );
    // ...
}

GCC 5.1.0 编译这个。

编译的规则是什么？

Answer 1

injected-class-name这里用到了，

the name of the class within its own definition acts as a public member type alias of itself for the purpose of lookup (except when used to name a constructor): this is known as injected-class-name

然后

foo::
foo::
foo::foob

即foo::foo::foo::foob 与 foo::foob 相同。

然后 for (auto x : {foo::foobar, foo::fbar, foo::foob }) 是 range-based for loop (since C++11) , 迭代 braced-init-list由 3 个枚举数组成。