[clang] [clang] Improve diagnostics with incompatible VLA types (PR #101261)

[Andrew Sukach via cfe-commits]

sookach wrote:

Sorry for taking so long, but the new commit handles the diagnostic a little differently. I store the text types in temporary strings and then append a message to the diagnostic if the texts are identical.

https://github.com/llvm/llvm-project/pull/101261