[clang] [Clang][Parser] Report error when attribute missing ]] followed by ;; (PR #187580)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

> is a MUUUCH more interesting reproducer :)

This is an interesting case 😮

> I guess though: SHOULD we just move the consume-semi-and-exit on an error until after? OR just remove that whole branch? What happens if we just don't consume it ever?

If this branch is removed, we should report the correct error message because we will hit an error in Expect `R_square`. I'm not sure if there is a hidden edge case that can be problematic when we remove it. I will check that and run tests.

> I guess I wouldn't want us to give a weird answer for:
[[ErrorInSomeWay;]] to consume the semicolon then give a weird 'why are you saying ]]? type diagnostic.

That makes sense. I will check that and add the two cases to the tests.
Thanks

https://github.com/llvm/llvm-project/pull/187580