c++11 - C++ 嵌套typedef的问题

Question

最近在写一个Tiny的STL库。可是出现了一点小问题。

如果一个typedef使用已定义过的typedef，如下列代码的
using value_type = T;
using reference = value_type&;
using const_reference = const reference;

template <typename T>
class allocator
{
public:
    using value_type      = T;
    using pointer         = value_type*;
    using const_pointer   = const pointer;
    using reference       = value_type&;
    using const_reference = const reference;
    using size_type       = std::size_t;
    using difference_type = std::ptrdiff_t;    
...

    const_pointer address(const_reference x) { return static_cast<const_pointer>(&x); }
...
};

但是编译时会出现以下问题：

其中61 行就是上面的address函数。
如果我把typedef 改为以下形式，

using value_type      = T;
using pointer         = T*;
using const_pointer   = const T*;
using reference       = T&;
using const_reference = const T&;
using size_type       = std::size_t;
using difference_type = std::ptrdiff_t;

编译报以下错误：

请问，
1、这两种定义方式都可以吗？如果可以，上述两种不同的报错方式该如何解释？
2、第二张图里的error该如何解决？

源代码太多，不大方便粘贴上来。
参见：https://github.com/MarinYoung4596/MySTL/tree/master/MySTL/MySTL

google了好久也没找到原因，因此也不知道该如何解答。
烦请大神们答疑解惑。

亦或者，能否告知这些错误可能是由于什么原因造成的？（或者我哪一块的语法理解不透彻），以便我查漏补缺？
非常感谢！

Answer 1

First correct two errors:

using value_type      = T;
using pointer         = value_type*;
using const_pointer   = const pointer;
using reference       = value_type&;
using const_reference = const reference;
using size_type       = std::size_t;
using difference_type = std::ptrdiff_t;    

const_pointer
== const pointer
== pointer const
== value_type* const
!= value_type const * // This is what you want
const_reference Same reason.

I don’t have 2015 at hand, I compiled it with 2013. After removing noexcept that does not exist in 2013, I also found that
myvector.insert(it, 2, 300)
in your test_vector.cpp actually calls this version:

template<typename InputIterator>
iterator insert(iterator position, InputIterator first, InputIterator second);

Then it took off. There are similar errors with constructors and assign functions.

In fact, this is easy to understand. The 2 and 300 types are the same. Why should we match the size_type and const_reference? The overloading of C++ is not in the order of declaration.

All errors are attributed to these two places. Because after I forced a dozen lines of code like this to correspond to the overload you want, I found that it was compiled. But I didn’t run it because it was not within the scope of the question, hahahaha.