[clang] [Clang] [Sema] Don't crash on unexpanded pack in invalid block literal (PR #110762)

[via cfe-commits]

Sirraide wrote:

> I don't think there's a deep reason blocks and lambdas don't use quite the same scope mechanics in the compiler, so if you wanted to pursue that, it seems reasonable. But this approach also seems viable.

Yeah, there is a comment about parameter packs in block arguments being a problem somewhere, but that’s from 2012, so that might no longer apply. I might look into this at some point if I have the time, but not for this pr (there are still other issues need to deal with first...)

https://github.com/llvm/llvm-project/pull/110762