[clang] [llvm] [WIP][Clang-Repl] Introduce Error Recovery for Clang-Repl. (PR #223305)

[via llvm-commits]

SahilPatidar wrote:

Yes, I need to polish `DeclStateReverter` since this is the class that acts as a bridge between Clang and our implementation. It gives us access to some decls, and right now I’m using some protected tricks to access the members. I still feel like I should do something to make this cleaner.

There are also a few cases where things mutate and Clang has a FIXME for the notifier, but we don’t have those notifications yet, like MSI mutation. Some cases are already covered, and in a few other places things mutate but we don’t have a clear path to know that this kind of decl needs to be added to the SweepTracker so I can know something modified.

But we can leave that aside for now. I can add or remove those cases later. Right now, I want to focus on `DeclStateReverter`.

https://github.com/llvm/llvm-project/pull/223305