[cxx-interop] Add a basic test for using std::iterator_traits

[cabmeurer]

Add basic tests for using std::iterator_traits

Ref: #41166

[cabmeurer]

@hyp
@zoecarver
I thought I would give it a go and try to add some tests for iterator_traits

[hyp]

@swift-ci please test

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 265b8f229daded8609875d85d73f6fce60ac8920

[cabmeurer]

@swift-ci please test

[cabmeurer]

@zoecarver when you get a chance, could you merge this for me?

[zoecarver]

I'm sorry, I don't think that this really makes sense to test. If we are able to construct an object, it won't be nil. It might be interesting to see if we can import iterator_traits (a module interface test) but honestly, I'm not even sure how valuable that would be. I don't think people will be using traits like this very often in Swift.

What would be really helpful is some tests for std::next and std::prev (if you have time, std::distance, and std::advance might be interesting too) because I anticipate those will be used very frequently. Could you update this PR to test those instead (or make a new PR)?

I really appreciate you spending time writing tests! So, I'm sorry if this is disappointing :(

[zoecarver]

I should also mention that these tests look 100% correct, so really well done for your first PR! It's just the thing you're testing doesn't really make sense.

[cabmeurer]

I'm sorry, I don't think that this really makes sense to test. If we are able to construct an object, it won't be nil. It might be interesting to see if we can import iterator_traits (a module interface test) but honestly, I'm not even sure how valuable that would be. I don't think people will be using traits like this very often in Swift.

What would be really helpful is some tests for std::next and std::prev (if you have time, std::distance, and std::advance might be interesting too) because I anticipate those will be used very frequently. Could you update this PR to test those instead (or make a new PR)?

I really appreciate you spending time writing tests! So, I'm sorry if this is disappointing :(

Thank you! All good, excited that i can contribute and get feedback, it's the best way to learn. I completely follow and I will spend some time adding tests for std::next std::prev std::distance and std::advance. As thats also what we talked about on #41232

Thank you for taking the time to go over this stuff with me! I really appreciate it