g++ 5.1.0 and current trunk 20150505 won't compile the following code with -std=c++1y:

constexpr auto fun(int n)
{
    switch(n) {
    case 0: return 0;
    default: return throw 42, 42;      
    }
}
    
int main()
{
    static_assert(fun(0) == 0, "");    
}

yielding the error: expression '<throw-expression>' is not a constant-expression

The same code compiles with -std=c++14 with all recent Clang versions (3.4.0 through SVN trunk).