[clang] [clang] Fix crash when declaring invalid lambda member (PR #74110)

[Aaron Ballman via cfe-commits]

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

Oooh, I see now, there's a new RUN line added to the test and that's where the new diagnostics are coming from.

The tests are unrelated to the patch and should be split out into a separate change, and you should add test coverage where we were crashing and we no longer do so. That may need to go into its own file which `// REQUIRES: asserts`.

https://github.com/llvm/llvm-project/pull/74110