[clang] [Clang][Sema] Diagnose type mismatch on redeclaration after redefinition error (PR #228212)

[Ambrose Leeb via cfe-commits]

Sirraide wrote:

> @Sirraide thank you for your patience and all the insights throughout this review, I learned a lot about how the redeclaration logic in Sema fits together, and I'm still working on developing an eye for these kinds of issues. This is my first OSS contribution after a few compiler projects, and I couldn't have asked for a better first review experience. Apologies if all the back-and-forth ended up adding to your workload!

np

https://github.com/llvm/llvm-project/pull/228212