[clang] [Clang][Parser] Reject unbalanced unknown attribute arguments (PR #220259)

[Erich Keane via cfe-commits]

https://github.com/erichkeane requested changes to this pull request.

I think this is only acceptable if it doesn't have more than a very minor compile time impact.  You might have to contact someone to get this commit added to the compile time tracker.

Also, I don't really like this as a 'parsing' error like this.  IF were going to be doing it this way, it should be a pedantic warning, not an error on unbalanced token.  

https://github.com/llvm/llvm-project/pull/220259