[Patch] Implement std::experimental::variant

[Jonathan Wakely]

On 5 August 2016 at 18:39, Tim Shen wrote:
>> There are
>> other variant implementations
>> written in C++17 that provide full conformance, so I think our variant
>> should do so too.
>
> Can you share a pointer to that implementation? I have tried to use
> union but still have questions with it.

I think Anthony Williams's implementation uses a union, but I don't
know if it supports the constexpr requirements.

https://bitbucket.org/anthonyw/variant

I think Agustín Bergé has a conforming implementation too, but I don't
know where that is.