integration_tests: added breaking template static function test

[SDAChess]

Adds a test for #1393

Please let me know if the test I wrote is correct.

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[adetaylor]

Thanks very much for this - I'm not ignoring it - I just need to get to the bottom of #1396 first

[adetaylor]

FWIW I consider this to be half-way between a bug and a feature request. The concrete types generated aren't exactly the same as "real" structs which are generated fully by autocxx, and so it's unsurprising to me that they lack static methods. I can see that it might be surprising to users, though, so I plan to look into how hard it would be to add that functionality. I suspect it will be hard, in which case I'm afraid I'm just going to close this, but I won't do so until I've made sure that it's not an easy addition.

[SDAChess]

Thank you for the work. If it's not an easy addition I'll try to take a stab at it :)

[adetaylor]

I did a bit of investigation building on your test, and it's not failing where I expected it to fail, it's failing earlier :)

Here's what I have been working with:

      class Boobar {
      public:
        static int test2() {
            return 1;
        }
      };
      
      template <typename T>
      class Toto
      {
      public:
      	static int test()
      	{
            return 1;
      	}
        T t;
      };
      

and with generate! directives fro Boobar and Toto along with your concrete! directive.

Results:

• Without the T t; field, autocxx refuses to generate anything for Toto because of the unused T. I have long term hopes to solve this by sneaking in extra PhantomData for each template param within bindgen, but I haven't done this yet.
• Even with the T t; and generate!("Toto") we still don't generate anything, because bindgen tells us nothing about Toto::test (but it does tell us about Boobar::test2).

So, I think at this point the first step is to figure out how to get bindgen to fess up about the existence of Toto::test in cases such as this. You can see the bindgen output in RUST_LOG=autocxx_engine=info cargo test test_cpp_static_template -- --nocapture.

What I expected was for bindgen to tell us about the various static functions in Toto but then for us to fail to attach them to the concrete type we generate.

If you think you might work on this, I'll leave it open for now.