[clang] [OpenACC] Implement 'var' parsing correctly, support array sections (PR #77617)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > @alexey-bataev : In particular I'd like to make you aware of what I've done here, since this is similar to the work you've done before/will affect it. It is currently my thought to make the OMPArraySectionExpr type a generic 'ArraySectionExpr' type in the not-so-distant future (PERHAPS with the OMP and OpenACC types inheriting from it? But perhaps those types aren't necessary), so I anticipate you'll be seeing stuff like this in the future.
> 
> Sure. I agree that better to reuse the existing implementation rather than add something new here. I don't have strong preferences, if it is better deriving OpenMP/OpenACC specific types or just have some "structural/functional" check. It depends on how many changes are required.

I think I agree, it'll come down to what the implementation looks like at the time.  From my current understanding, it is mostly just a 'limited' version of the OMP version, so I'm hopeful I can get away with a different 'build' function, and leave everything else alone in the AST besides perhaps a discriminator.

Thank you very much for your review and quick response!

https://github.com/llvm/llvm-project/pull/77617