Added cfg information about std::span

[Ashimaru]

Basic information about std::span type, I was not sure how to approach its std::dynamic_extent so I omitted it

[chrchr-github]

Thanks for contributing. Can you add a test case to show that it works? std.cpp should be the right location.

[chrchr-github]

Since std::span is C++20, you need to update the language standard, see edb0b63

With this change, will we warn for the code below?

int f() {
    std::span<int> s;
    {
        std::vector<int> v(1);
        s = v;
    }
    return s.back();
}

[Ashimaru]

Yeah, I already found it but thanks :) As for the snippet i will add it - I admit I missed that now I should provide such tests but I will add then in this PR

[Ashimaru]

I added tests for back/front/last/first operations and I started copying string_view tests since span sues similar process. During tests I also found that int example std::vector v{1} do not generate same issues, I suspect its caused that cfg defines that stdVector starts with std::vector< where as of c++17 '<' is optional.
Should I raise it in forum for adding ticket or just create another PR with needed tests and fix?

[Ashimaru]

Seems like c++20 flag is not supported for Ubuntu 20.04 (too old g++), should I change it to 2a or is there different way you guys are handing those issues?

[chrchr-github]

You could try if the 2a flag is sufficient for std::span. The standard was only recently raised to C++17.
Regarding the std::vector v{1} issue, you're welcome to open another PR. I'm not sure though if it can be solved with configuration alone.

[Ashimaru]

Could you aprprove test run here?

[chrchr-github]

Maybe @firewave can do that.