How the following C++11 code should work?

The following code outputs different results on various compilers:

• 2,1,2 on Visual Studio 2013
• 2,2,2 on Visual Studio 2015
• 2,1,1 on GCC5/c++14
• 2,2,2 on Clang 3.7 with Microsoft Codegen
• 2,1,2 on Clang 3.6/c++11 under Ubuntu 14.04

Finally, how it should work according to C++ standard?

#include <iostream>
#include <vector>
#include <stdio.h>

using namespace std;

class Value;
using Array = std::vector<Value>;

class Value
{
public:
    Value(Array)
    {
    }

    Value(int)
    {
    }
};

void foo(Array const& a)
{
    printf("%d\n", (int)a.size());
}

int main()
{
    Array a1 = { 1, 2 };
    foo(a1);
    foo(Array{ a1 });
    foo(Array({ a1 }));
}