Use of Union with reference
<p>At work I've been using linux and the GCC compiler for C++11 and C++14. In some of the code at work, I've used a union to store both a reference and a pointer, as so: (Simplified to just the important parts)</p>

<pre><code>struct MyStruct
{
    //Stuff
    union { double&amp; x; double* x_ptr; };
    MyStruct(double&amp; value) : x(value) {}
    //More stuff
};
</code></pre>

<p>I believe this code is clear, readable, unambiguous, and provides a convenient way to store references which can be shifted to something else. It provides easily understandable syntactic sugar without costing performance while improving readability. When I attempted to use code like this in visual studio 15, however, the code failed to compile due to "an illegal union member of type double&amp;".</p>

<ol>
<li>Is this code illegal under the standard, or just under Visual Studio 2015?</li>
<li>Can I MAKE it compile in Visual Studio 2015, or submit a bug report/change request/something?</li>
<li>Is use of a union in that way bad practice?</li>
</ol>

<p>Note: At my work, pretty much all code is written for Linux and compiled with GCC, and for my specific project, C++11 is guaranteed and GCC is the only compiler that's going to be used. </p>

<p><strong>Edit:</strong> Please don't tell me that putting a reference inside a union "has no meaning". When a reference is stored inside a struct, it takes up the same amount of space as a pointer. In addition, the following compiles with clang:</p>

<pre><code>struct MyStruct
{
    //This will compile
    union 
    { 
        struct { double&amp; x; }; 
        double* x_ptr; 
    };
    //This won't compile; WHY?
    /*union 
    { 
        double&amp; x;
        double* x_ptr; 
    };*/
    MyStruct(double&amp; val) : x(val){}
    void Repoint(double&amp; new_value) 
    { 
        x_ptr = &amp;new_value; 
    }
};
</code></pre>

<p>Why does it compile when the reference is wrapped in an anonymous struct, but not when it's just in the union?</p>

<p><kbd><a href="http://coliru.stacked-crooked.com/a/918a7b3d1652e112" rel="noreferrer">live example</a></kbd></p>